Merge pull request #1 from rust-lang/master

Pull from newest repo

24 files changed, 9816 insertions, 10716 deletions

diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index e99a86e807f..a42da112360 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -4,6 +4,7 @@ use crate::parse::{SeqSep, PResult};
 use crate::parse::token::{self, Nonterminal, DelimToken};
 use crate::parse::parser::{Parser, TokenType, PathStyle};
 use crate::tokenstream::{TokenStream, TokenTree};
+use crate::source_map::Span;
 
 use log::debug;
 use smallvec::smallvec;
@@ -11,20 +12,28 @@ use smallvec::smallvec;
 #[derive(Debug)]
 enum InnerAttributeParsePolicy<'a> {
     Permitted,
-    NotPermitted { reason: &'a str },
+    NotPermitted { reason: &'a str, saw_doc_comment: bool, prev_attr_sp: Option<Span> },
 }
 
 const DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG: &str = "an inner attribute is not \
                                                      permitted in this context";
 
 impl<'a> Parser<'a> {
+    crate fn parse_arg_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
+        let attrs = self.parse_outer_attributes()?;
+        attrs.iter().for_each(|a|
+            self.sess.param_attr_spans.borrow_mut().push(a.span)
+        );
+        Ok(attrs)
+    }
+
     /// Parse attributes that appear before an item
     crate fn parse_outer_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
         let mut attrs: Vec<ast::Attribute> = Vec::new();
         let mut just_parsed_doc_comment = false;
         loop {
             debug!("parse_outer_attributes: self.token={:?}", self.token);
-            match self.token {
+            match self.token.kind {
                 token::Pound => {
                     let inner_error_reason = if just_parsed_doc_comment {
                         "an inner attribute is not permitted following an outer doc comment"
@@ -34,12 +43,17 @@ impl<'a> Parser<'a> {
                         DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
                     };
                     let inner_parse_policy =
-                        InnerAttributeParsePolicy::NotPermitted { reason: inner_error_reason };
-                    attrs.push(self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?);
+                        InnerAttributeParsePolicy::NotPermitted {
+                            reason: inner_error_reason,
+                            saw_doc_comment: just_parsed_doc_comment,
+                            prev_attr_sp: attrs.last().and_then(|a| Some(a.span))
+                        };
+                    let attr = self.parse_attribute_with_inner_parse_policy(inner_parse_policy)?;
+                    attrs.push(attr);
                     just_parsed_doc_comment = false;
                 }
                 token::DocComment(s) => {
-                    let attr = attr::mk_sugared_doc_attr(attr::mk_attr_id(), s, self.span);
+                    let attr = attr::mk_sugared_doc_attr(s, self.token.span);
                     if attr.style != ast::AttrStyle::Outer {
                         let mut err = self.fatal("expected outer doc comment");
                         err.note("inner doc comments like this (starting with \
@@ -67,8 +81,11 @@ impl<'a> Parser<'a> {
         let inner_parse_policy = if permit_inner {
             InnerAttributeParsePolicy::Permitted
         } else {
-            InnerAttributeParsePolicy::NotPermitted
-                { reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG }
+            InnerAttributeParsePolicy::NotPermitted {
+                reason: DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG,
+                saw_doc_comment: false,
+                prev_attr_sp: None
+            }
         };
         self.parse_attribute_with_inner_parse_policy(inner_parse_policy)
     }
@@ -81,27 +98,17 @@ impl<'a> Parser<'a> {
         debug!("parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}",
                inner_parse_policy,
                self.token);
-        let (span, path, tokens, style) = match self.token {
+        let (span, path, tokens, style) = match self.token.kind {
             token::Pound => {
-                let lo = self.span;
+                let lo = self.token.span;
                 self.bump();
 
                 if let InnerAttributeParsePolicy::Permitted = inner_parse_policy {
                     self.expected_tokens.push(TokenType::Token(token::Not));
                 }
+
                 let style = if self.token == token::Not {
                     self.bump();
-                    if let InnerAttributeParsePolicy::NotPermitted { reason } = inner_parse_policy
-                    {
-                        let span = self.span;
-                        self.diagnostic()
-                            .struct_span_err(span, reason)
-                            .note("inner attributes, like `#![no_std]`, annotate the item \
-                                   enclosing them, and are usually found at the beginning of \
-                                   source files. Outer attributes, like `#[test]`, annotate the \
-                                   item following them.")
-                            .emit()
-                    }
                     ast::AttrStyle::Inner
                 } else {
                     ast::AttrStyle::Outer
@@ -112,7 +119,38 @@ impl<'a> Parser<'a> {
                 self.expect(&token::CloseDelim(token::Bracket))?;
                 let hi = self.prev_span;
 
-                (lo.to(hi), path, tokens, style)
+                let attr_sp = lo.to(hi);
+
+                // Emit error if inner attribute is encountered and not permitted
+                if style == ast::AttrStyle::Inner {
+                    if let InnerAttributeParsePolicy::NotPermitted { reason,
+                        saw_doc_comment, prev_attr_sp } = inner_parse_policy {
+                        let prev_attr_note = if saw_doc_comment {
+                            "previous doc comment"
+                        } else {
+                            "previous outer attribute"
+                        };
+
+                        let mut diagnostic = self
+                            .diagnostic()
+                            .struct_span_err(attr_sp, reason);
+
+                        if let Some(prev_attr_sp) = prev_attr_sp {
+                            diagnostic
+                                .span_label(attr_sp, "not permitted following an outer attibute")
+                                .span_label(prev_attr_sp, prev_attr_note);
+                        }
+
+                        diagnostic
+                            .note("inner attributes, like `#![no_std]`, annotate the item \
+                                   enclosing them, and are usually found at the beginning of \
+                                   source files. Outer attributes, like `#[test]`, annotate the \
+                                   item following them.")
+                            .emit()
+                    }
+                }
+
+                (attr_sp, path, tokens, style)
             }
             _ => {
                 let token_str = self.this_token_to_string();
@@ -140,7 +178,7 @@ impl<'a> Parser<'a> {
     /// PATH `=` TOKEN_TREE
     /// The delimiters or `=` are still put into the resulting token stream.
     crate fn parse_meta_item_unrestricted(&mut self) -> PResult<'a, (ast::Path, TokenStream)> {
-        let meta = match self.token {
+        let meta = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
                 Nonterminal::NtMeta(ref meta) => Some(meta.clone()),
                 _ => None,
@@ -157,9 +195,9 @@ impl<'a> Parser<'a> {
                self.check(&token::OpenDelim(DelimToken::Brace)) {
                    self.parse_token_tree().into()
             } else if self.eat(&token::Eq) {
-                let eq = TokenTree::Token(self.prev_span, token::Eq);
+                let eq = TokenTree::token(token::Eq, self.prev_span);
                 let mut is_interpolated_expr = false;
-                if let token::Interpolated(nt) = &self.token {
+                if let token::Interpolated(nt) = &self.token.kind {
                     if let token::NtExpr(..) = **nt {
                         is_interpolated_expr = true;
                     }
@@ -188,7 +226,7 @@ impl<'a> Parser<'a> {
     crate fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
         let mut attrs: Vec<ast::Attribute> = vec![];
         loop {
-            match self.token {
+            match self.token.kind {
                 token::Pound => {
                     // Don't even try to parse if it's not an inner attribute.
                     if !self.look_ahead(1, |t| t == &token::Not) {
@@ -201,7 +239,7 @@ impl<'a> Parser<'a> {
                 }
                 token::DocComment(s) => {
                     // we need to get the position of this token before we bump.
-                    let attr = attr::mk_sugared_doc_attr(attr::mk_attr_id(), s, self.span);
+                    let attr = attr::mk_sugared_doc_attr(s, self.token.span);
                     if attr.style == ast::AttrStyle::Inner {
                         attrs.push(attr);
                         self.bump();
@@ -217,7 +255,7 @@ impl<'a> Parser<'a> {
 
     fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
         let lit = self.parse_lit()?;
-        debug!("Checking if {:?} is unusuffixed.", lit);
+        debug!("checking if {:?} is unusuffixed", lit);
 
         if !lit.node.is_unsuffixed() {
             let msg = "suffixed literals are not allowed in attributes";
@@ -236,7 +274,7 @@ impl<'a> Parser<'a> {
     /// meta_item : IDENT ( '=' UNSUFFIXED_LIT | '(' meta_item_inner? ')' )? ;
     /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
     pub fn parse_meta_item(&mut self) -> PResult<'a, ast::MetaItem> {
-        let nt_meta = match self.token {
+        let nt_meta = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
                 token::NtMeta(ref e) => Some(e.clone()),
                 _ => None,
@@ -249,7 +287,7 @@ impl<'a> Parser<'a> {
             return Ok(meta);
         }
 
-        let lo = self.span;
+        let lo = self.token.span;
         let path = self.parse_path(PathStyle::Mod)?;
         let node = self.parse_meta_item_kind()?;
         let span = lo.to(self.prev_span);
@@ -284,7 +322,7 @@ impl<'a> Parser<'a> {
 
         let found = self.this_token_to_string();
         let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
-        Err(self.diagnostic().struct_span_err(self.span, &msg))
+        Err(self.diagnostic().struct_span_err(self.token.span, &msg))
     }
 
     /// matches meta_seq = ( COMMASEP(meta_item_inner) )
diff --git a/src/libsyntax/parse/classify.rs b/src/libsyntax/parse/classify.rs
index dfd6f451c28..6ebfab3a133 100644
--- a/src/libsyntax/parse/classify.rs
+++ b/src/libsyntax/parse/classify.rs
@@ -14,11 +14,9 @@ use crate::ast;
 pub fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
     match e.node {
         ast::ExprKind::If(..) |
-        ast::ExprKind::IfLet(..) |
         ast::ExprKind::Match(..) |
         ast::ExprKind::Block(..) |
         ast::ExprKind::While(..) |
-        ast::ExprKind::WhileLet(..) |
         ast::ExprKind::Loop(..) |
         ast::ExprKind::ForLoop(..) |
         ast::ExprKind::TryBlock(..) => false,
diff --git a/src/libsyntax/parse/diagnostics.rs b/src/libsyntax/parse/diagnostics.rs
index 1a2393be806..1fbf28fb830 100644
--- a/src/libsyntax/parse/diagnostics.rs
+++ b/src/libsyntax/parse/diagnostics.rs
@@ -1,16 +1,118 @@
-use crate::ast;
-use crate::ast::{BlockCheckMode, Expr, ExprKind, Item, ItemKind, Pat, PatKind, QSelf, Ty, TyKind};
-use crate::parse::parser::{BlockMode, PathStyle, TokenType, SemiColonMode};
-use crate::parse::token;
-use crate::parse::PResult;
-use crate::parse::Parser;
+use crate::ast::{
+    self, Arg, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
+    Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind, VariantData,
+};
+use crate::feature_gate::{feature_err, UnstableFeatures};
+use crate::parse::{SeqSep, PResult, Parser, ParseSess};
+use crate::parse::parser::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType};
+use crate::parse::token::{self, TokenKind};
 use crate::print::pprust;
 use crate::ptr::P;
-use crate::symbol::keywords;
+use crate::symbol::{kw, sym};
 use crate::ThinVec;
-use errors::{Applicability, DiagnosticBuilder};
-use syntax_pos::Span;
-use log::debug;
+use crate::util::parser::AssocOp;
+use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
+use rustc_data_structures::fx::FxHashSet;
+use syntax_pos::{Span, DUMMY_SP, MultiSpan, SpanSnippetError};
+use log::{debug, trace};
+use std::mem;
+
+/// Creates a placeholder argument.
+crate fn dummy_arg(ident: Ident) -> Arg {
+    let pat = P(Pat {
+        id: ast::DUMMY_NODE_ID,
+        node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
+        span: ident.span,
+    });
+    let ty = Ty {
+        node: TyKind::Err,
+        span: ident.span,
+        id: ast::DUMMY_NODE_ID
+    };
+    Arg { attrs: ThinVec::default(), id: ast::DUMMY_NODE_ID, pat, span: ident.span, ty: P(ty) }
+}
+
+pub enum Error {
+    FileNotFoundForModule {
+        mod_name: String,
+        default_path: String,
+        secondary_path: String,
+        dir_path: String,
+    },
+    DuplicatePaths {
+        mod_name: String,
+        default_path: String,
+        secondary_path: String,
+    },
+    UselessDocComment,
+    InclusiveRangeWithNoEnd,
+}
+
+impl Error {
+    fn span_err<S: Into<MultiSpan>>(
+        self,
+        sp: S,
+        handler: &errors::Handler,
+    ) -> DiagnosticBuilder<'_> {
+        match self {
+            Error::FileNotFoundForModule {
+                ref mod_name,
+                ref default_path,
+                ref secondary_path,
+                ref dir_path,
+            } => {
+                let mut err = struct_span_err!(
+                    handler,
+                    sp,
+                    E0583,
+                    "file not found for module `{}`",
+                    mod_name,
+                );
+                err.help(&format!(
+                    "name the file either {} or {} inside the directory \"{}\"",
+                    default_path,
+                    secondary_path,
+                    dir_path,
+                ));
+                err
+            }
+            Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
+                let mut err = struct_span_err!(
+                    handler,
+                    sp,
+                    E0584,
+                    "file for module `{}` found at both {} and {}",
+                    mod_name,
+                    default_path,
+                    secondary_path,
+                );
+                err.help("delete or rename one of them to remove the ambiguity");
+                err
+            }
+            Error::UselessDocComment => {
+                let mut err = struct_span_err!(
+                    handler,
+                    sp,
+                    E0585,
+                    "found a documentation comment that doesn't document anything",
+                );
+                err.help("doc comments must come before what they document, maybe a comment was \
+                          intended with `//`?");
+                err
+            }
+            Error::InclusiveRangeWithNoEnd => {
+                let mut err = struct_span_err!(
+                    handler,
+                    sp,
+                    E0586,
+                    "inclusive range with no end",
+                );
+                err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
+                err
+            }
+        }
+    }
+}
 
 pub trait RecoverQPath: Sized + 'static {
     const PATH_STYLE: PathStyle = PathStyle::Expr;
@@ -60,6 +162,414 @@ impl RecoverQPath for Expr {
 }
 
 impl<'a> Parser<'a> {
+    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
+        self.span_fatal(self.token.span, m)
+    }
+
+    pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+        self.sess.span_diagnostic.struct_span_fatal(sp, m)
+    }
+
+    pub fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
+        err.span_err(sp, self.diagnostic())
+    }
+
+    pub fn bug(&self, m: &str) -> ! {
+        self.sess.span_diagnostic.span_bug(self.token.span, m)
+    }
+
+    pub fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
+        self.sess.span_diagnostic.span_err(sp, m)
+    }
+
+    crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+        self.sess.span_diagnostic.struct_span_err(sp, m)
+    }
+
+    crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
+        self.sess.span_diagnostic.span_bug(sp, m)
+    }
+
+    crate fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
+        self.sess.span_diagnostic.cancel(err)
+    }
+
+    crate fn diagnostic(&self) -> &'a errors::Handler {
+        &self.sess.span_diagnostic
+    }
+
+    crate fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
+        self.sess.source_map().span_to_snippet(span)
+    }
+
+    crate fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
+        let mut err = self.struct_span_err(
+            self.token.span,
+            &format!("expected identifier, found {}", self.this_token_descr()),
+        );
+        if let token::Ident(name, false) = self.token.kind {
+            if Ident::new(name, self.token.span).is_raw_guess() {
+                err.span_suggestion(
+                    self.token.span,
+                    "you can escape reserved keywords to use them as identifiers",
+                    format!("r#{}", name),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+        }
+        if let Some(token_descr) = self.token_descr() {
+            err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
+        } else {
+            err.span_label(self.token.span, "expected identifier");
+            if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
+                err.span_suggestion(
+                    self.token.span,
+                    "remove this comma",
+                    String::new(),
+                    Applicability::MachineApplicable,
+                );
+            }
+        }
+        err
+    }
+
+    pub fn expected_one_of_not_found(
+        &mut self,
+        edible: &[TokenKind],
+        inedible: &[TokenKind],
+    ) -> PResult<'a, bool /* recovered */> {
+        fn tokens_to_string(tokens: &[TokenType]) -> String {
+            let mut i = tokens.iter();
+            // This might be a sign we need a connect method on Iterator.
+            let b = i.next()
+                     .map_or(String::new(), |t| t.to_string());
+            i.enumerate().fold(b, |mut b, (i, a)| {
+                if tokens.len() > 2 && i == tokens.len() - 2 {
+                    b.push_str(", or ");
+                } else if tokens.len() == 2 && i == tokens.len() - 2 {
+                    b.push_str(" or ");
+                } else {
+                    b.push_str(", ");
+                }
+                b.push_str(&a.to_string());
+                b
+            })
+        }
+
+        let mut expected = edible.iter()
+            .map(|x| TokenType::Token(x.clone()))
+            .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
+            .chain(self.expected_tokens.iter().cloned())
+            .collect::<Vec<_>>();
+        expected.sort_by_cached_key(|x| x.to_string());
+        expected.dedup();
+        let expect = tokens_to_string(&expected[..]);
+        let actual = self.this_token_to_string();
+        let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
+            let short_expect = if expected.len() > 6 {
+                format!("{} possible tokens", expected.len())
+            } else {
+                expect.clone()
+            };
+            (format!("expected one of {}, found `{}`", expect, actual),
+                (self.sess.source_map().next_point(self.prev_span),
+                format!("expected one of {} here", short_expect)))
+        } else if expected.is_empty() {
+            (format!("unexpected token: `{}`", actual),
+                (self.prev_span, "unexpected token after this".to_string()))
+        } else {
+            (format!("expected {}, found `{}`", expect, actual),
+                (self.sess.source_map().next_point(self.prev_span),
+                format!("expected {} here", expect)))
+        };
+        self.last_unexpected_token_span = Some(self.token.span);
+        let mut err = self.fatal(&msg_exp);
+        if self.token.is_ident_named(sym::and) {
+            err.span_suggestion_short(
+                self.token.span,
+                "use `&&` instead of `and` for the boolean operator",
+                "&&".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        if self.token.is_ident_named(sym::or) {
+            err.span_suggestion_short(
+                self.token.span,
+                "use `||` instead of `or` for the boolean operator",
+                "||".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        let sp = if self.token == token::Eof {
+            // This is EOF, don't want to point at the following char, but rather the last token
+            self.prev_span
+        } else {
+            label_sp
+        };
+        match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
+            TokenType::Token(t) => Some(t.clone()),
+            _ => None,
+        }).collect::<Vec<_>>(), err) {
+            Err(e) => err = e,
+            Ok(recovered) => {
+                return Ok(recovered);
+            }
+        }
+
+        let is_semi_suggestable = expected.iter().any(|t| match t {
+            TokenType::Token(token::Semi) => true, // we expect a `;` here
+            _ => false,
+        }) && ( // a `;` would be expected before the current keyword
+            self.token.is_keyword(kw::Break) ||
+            self.token.is_keyword(kw::Continue) ||
+            self.token.is_keyword(kw::For) ||
+            self.token.is_keyword(kw::If) ||
+            self.token.is_keyword(kw::Let) ||
+            self.token.is_keyword(kw::Loop) ||
+            self.token.is_keyword(kw::Match) ||
+            self.token.is_keyword(kw::Return) ||
+            self.token.is_keyword(kw::While)
+        );
+        let sm = self.sess.source_map();
+        match (sm.lookup_line(self.token.span.lo()), sm.lookup_line(sp.lo())) {
+            (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
+                // The spans are in different lines, expected `;` and found `let` or `return`.
+                // High likelihood that it is only a missing `;`.
+                err.span_suggestion_short(
+                    label_sp,
+                    "a semicolon may be missing here",
+                    ";".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+                err.emit();
+                return Ok(true);
+            }
+            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
+                // When the spans are in the same line, it means that the only content between
+                // them is whitespace, point at the found token in that case:
+                //
+                // X |     () => { syntax error };
+                //   |                    ^^^^^ expected one of 8 possible tokens here
+                //
+                // instead of having:
+                //
+                // X |     () => { syntax error };
+                //   |                   -^^^^^ unexpected token
+                //   |                   |
+                //   |                   expected one of 8 possible tokens here
+                err.span_label(self.token.span, label_exp);
+            }
+            _ if self.prev_span == syntax_pos::DUMMY_SP => {
+                // Account for macro context where the previous span might not be
+                // available to avoid incorrect output (#54841).
+                err.span_label(self.token.span, "unexpected token");
+            }
+            _ => {
+                err.span_label(sp, label_exp);
+                err.span_label(self.token.span, "unexpected token");
+            }
+        }
+        self.maybe_annotate_with_ascription(&mut err, false);
+        Err(err)
+    }
+
+    pub fn maybe_annotate_with_ascription(
+        &self,
+        err: &mut DiagnosticBuilder<'_>,
+        maybe_expected_semicolon: bool,
+    ) {
+        if let Some((sp, likely_path)) = self.last_type_ascription {
+            let sm = self.sess.source_map();
+            let next_pos = sm.lookup_char_pos(self.token.span.lo());
+            let op_pos = sm.lookup_char_pos(sp.hi());
+
+            if likely_path {
+                err.span_suggestion(
+                    sp,
+                    "maybe write a path separator here",
+                    "::".to_string(),
+                    match self.sess.unstable_features {
+                        UnstableFeatures::Disallow => Applicability::MachineApplicable,
+                        _ => Applicability::MaybeIncorrect,
+                    },
+                );
+            } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
+                err.span_suggestion(
+                    sp,
+                    "try using a semicolon",
+                    ";".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+            } else if let UnstableFeatures::Disallow = self.sess.unstable_features {
+                err.span_label(sp, "tried to parse a type due to this");
+            } else {
+                err.span_label(sp, "tried to parse a type due to this type ascription");
+            }
+            if let UnstableFeatures::Disallow = self.sess.unstable_features {
+                // Give extra information about type ascription only if it's a nightly compiler.
+            } else {
+                err.note("`#![feature(type_ascription)]` lets you annotate an expression with a \
+                          type: `<expr>: <type>`");
+                err.note("for more information, see \
+                          https://github.com/rust-lang/rust/issues/23416");
+            }
+        }
+    }
+
+    /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
+    /// passes through any errors encountered. Used for error recovery.
+    crate fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
+        let handler = self.diagnostic();
+
+        if let Err(ref mut err) = self.parse_seq_to_before_tokens(
+            kets,
+            SeqSep::none(),
+            TokenExpectType::Expect,
+            |p| Ok(p.parse_token_tree()),
+        ) {
+            handler.cancel(err);
+        }
+    }
+
+    /// This function checks if there are trailing angle brackets and produces
+    /// a diagnostic to suggest removing them.
+    ///
+    /// ```ignore (diagnostic)
+    /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
+    ///                                                        ^^ help: remove extra angle brackets
+    /// ```
+    crate fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: TokenKind) {
+        // This function is intended to be invoked after parsing a path segment where there are two
+        // cases:
+        //
+        // 1. A specific token is expected after the path segment.
+        //    eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
+        //        `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
+        // 2. No specific token is expected after the path segment.
+        //    eg. `x.foo` (field access)
+        //
+        // This function is called after parsing `.foo` and before parsing the token `end` (if
+        // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
+        // `Foo::<Bar>`.
+
+        // We only care about trailing angle brackets if we previously parsed angle bracket
+        // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
+        // removed in this case:
+        //
+        // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
+        //
+        // This case is particularly tricky as we won't notice it just looking at the tokens -
+        // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
+        // have already been parsed):
+        //
+        // `x.foo::<u32>>>(3)`
+        let parsed_angle_bracket_args = segment.args
+            .as_ref()
+            .map(|args| args.is_angle_bracketed())
+            .unwrap_or(false);
+
+        debug!(
+            "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
+            parsed_angle_bracket_args,
+        );
+        if !parsed_angle_bracket_args {
+            return;
+        }
+
+        // Keep the span at the start so we can highlight the sequence of `>` characters to be
+        // removed.
+        let lo = self.token.span;
+
+        // We need to look-ahead to see if we have `>` characters without moving the cursor forward
+        // (since we might have the field access case and the characters we're eating are
+        // actual operators and not trailing characters - ie `x.foo >> 3`).
+        let mut position = 0;
+
+        // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
+        // many of each (so we can correctly pluralize our error messages) and continue to
+        // advance.
+        let mut number_of_shr = 0;
+        let mut number_of_gt = 0;
+        while self.look_ahead(position, |t| {
+            trace!("check_trailing_angle_brackets: t={:?}", t);
+            if *t == token::BinOp(token::BinOpToken::Shr) {
+                number_of_shr += 1;
+                true
+            } else if *t == token::Gt {
+                number_of_gt += 1;
+                true
+            } else {
+                false
+            }
+        }) {
+            position += 1;
+        }
+
+        // If we didn't find any trailing `>` characters, then we have nothing to error about.
+        debug!(
+            "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
+            number_of_gt, number_of_shr,
+        );
+        if number_of_gt < 1 && number_of_shr < 1 {
+            return;
+        }
+
+        // Finally, double check that we have our end token as otherwise this is the
+        // second case.
+        if self.look_ahead(position, |t| {
+            trace!("check_trailing_angle_brackets: t={:?}", t);
+            *t == end
+        }) {
+            // Eat from where we started until the end token so that parsing can continue
+            // as if we didn't have those extra angle brackets.
+            self.eat_to_tokens(&[&end]);
+            let span = lo.until(self.token.span);
+
+            let plural = number_of_gt > 1 || number_of_shr >= 1;
+            self.diagnostic()
+                .struct_span_err(
+                    span,
+                    &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
+                )
+                .span_suggestion(
+                    span,
+                    &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
+                    String::new(),
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+    }
+
+    /// Produce an error if comparison operators are chained (RFC #558).
+    /// We only need to check lhs, not rhs, because all comparison ops
+    /// have same precedence and are left-associative
+    crate fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) {
+        debug_assert!(outer_op.is_comparison(),
+                      "check_no_chained_comparison: {:?} is not comparison",
+                      outer_op);
+        match lhs.node {
+            ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
+                // respan to include both operators
+                let op_span = op.span.to(self.token.span);
+                let mut err = self.struct_span_err(
+                    op_span,
+                    "chained comparison operators require parentheses",
+                );
+                if op.node == BinOpKind::Lt &&
+                    *outer_op == AssocOp::Less ||  // Include `<` to provide this recommendation
+                    *outer_op == AssocOp::Greater  // even in a case like the following:
+                {                                  //     Foo<Bar<Baz<Qux, ()>>>
+                    err.help(
+                        "use `::<...>` instead of `<...>` if you meant to specify type arguments");
+                    err.help("or use `(...)` if you meant to specify fn arguments");
+                }
+                err.emit();
+            }
+            _ => {}
+        }
+    }
+
     crate fn maybe_report_ambiguous_plus(
         &mut self,
         allow_plus: bool,
@@ -79,6 +589,54 @@ impl<'a> Parser<'a> {
         }
     }
 
+    crate fn maybe_report_invalid_custom_discriminants(
+        sess: &ParseSess,
+        variants: &[ast::Variant],
+    ) {
+        let has_fields = variants.iter().any(|variant| match variant.data {
+            VariantData::Tuple(..) | VariantData::Struct(..) => true,
+            VariantData::Unit(..) => false,
+        });
+
+        let discriminant_spans = variants.iter().filter(|variant| match variant.data {
+            VariantData::Tuple(..) | VariantData::Struct(..) => false,
+            VariantData::Unit(..) => true,
+        })
+        .filter_map(|variant| variant.disr_expr.as_ref().map(|c| c.value.span))
+        .collect::<Vec<_>>();
+
+        if !discriminant_spans.is_empty() && has_fields {
+            let mut err = feature_err(
+                sess,
+                sym::arbitrary_enum_discriminant,
+                discriminant_spans.clone(),
+                crate::feature_gate::GateIssue::Language,
+                "custom discriminant values are not allowed in enums with tuple or struct variants",
+            );
+            for sp in discriminant_spans {
+                err.span_label(sp, "disallowed custom discriminant");
+            }
+            for variant in variants.iter() {
+                match &variant.data {
+                    VariantData::Struct(..) => {
+                        err.span_label(
+                            variant.span,
+                            "struct variant defined here",
+                        );
+                    }
+                    VariantData::Tuple(..) => {
+                        err.span_label(
+                            variant.span,
+                            "tuple variant defined here",
+                        );
+                    }
+                    VariantData::Unit(..) => {}
+                }
+            }
+            err.emit();
+        }
+    }
+
     crate fn maybe_recover_from_bad_type_plus(
         &mut self,
         allow_plus: bool,
@@ -104,14 +662,12 @@ impl<'a> Parser<'a> {
         match ty.node {
             TyKind::Rptr(ref lifetime, ref mut_ty) => {
                 let sum_with_parens = pprust::to_string(|s| {
-                    use crate::print::pprust::PrintState;
-
-                    s.s.word("&")?;
-                    s.print_opt_lifetime(lifetime)?;
-                    s.print_mutability(mut_ty.mutbl)?;
-                    s.popen()?;
-                    s.print_type(&mut_ty.ty)?;
-                    s.print_type_bounds(" +", &bounds)?;
+                    s.s.word("&");
+                    s.print_opt_lifetime(lifetime);
+                    s.print_mutability(mut_ty.mutbl);
+                    s.popen();
+                    s.print_type(&mut_ty.ty);
+                    s.print_type_bounds(" +", &bounds);
                     s.pclose()
                 });
                 err.span_suggestion(
@@ -160,14 +716,12 @@ impl<'a> Parser<'a> {
 
         let mut path = ast::Path {
             segments: Vec::new(),
-            span: syntax_pos::DUMMY_SP,
+            span: DUMMY_SP,
         };
         self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
         path.span = ty_span.to(self.prev_span);
 
         let ty_str = self
-            .sess
-            .source_map()
             .span_to_snippet(ty_span)
             .unwrap_or_else(|_| pprust::ty_to_string(&ty));
         self.diagnostic()
@@ -226,13 +780,111 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Consume alternative await syntaxes like `await <expr>`, `await? <expr>`, `await(<expr>)`
-    /// and `await { <expr> }`.
+    /// Create a `DiagnosticBuilder` for an unexpected token `t` and try to recover if it is a
+    /// closing delimiter.
+    pub fn unexpected_try_recover(
+        &mut self,
+        t: &TokenKind,
+    ) -> PResult<'a, bool /* recovered */> {
+        let token_str = pprust::token_kind_to_string(t);
+        let this_token_str = self.this_token_descr();
+        let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
+            // Point at the end of the macro call when reaching end of macro arguments.
+            (token::Eof, Some(_)) => {
+                let sp = self.sess.source_map().next_point(self.token.span);
+                (sp, sp)
+            }
+            // We don't want to point at the following span after DUMMY_SP.
+            // This happens when the parser finds an empty TokenStream.
+            _ if self.prev_span == DUMMY_SP => (self.token.span, self.token.span),
+            // EOF, don't want to point at the following char, but rather the last token.
+            (token::Eof, None) => (self.prev_span, self.token.span),
+            _ => (self.sess.source_map().next_point(self.prev_span), self.token.span),
+        };
+        let msg = format!(
+            "expected `{}`, found {}",
+            token_str,
+            match (&self.token.kind, self.subparser_name) {
+                (token::Eof, Some(origin)) => format!("end of {}", origin),
+                _ => this_token_str,
+            },
+        );
+        let mut err = self.struct_span_err(sp, &msg);
+        let label_exp = format!("expected `{}`", token_str);
+        match self.recover_closing_delimiter(&[t.clone()], err) {
+            Err(e) => err = e,
+            Ok(recovered) => {
+                return Ok(recovered);
+            }
+        }
+        let sm = self.sess.source_map();
+        match (sm.lookup_line(prev_sp.lo()), sm.lookup_line(sp.lo())) {
+            (Ok(ref a), Ok(ref b)) if a.line == b.line => {
+                // When the spans are in the same line, it means that the only content
+                // between them is whitespace, point only at the found token.
+                err.span_label(sp, label_exp);
+            }
+            _ => {
+                err.span_label(prev_sp, label_exp);
+                err.span_label(sp, "unexpected token");
+            }
+        }
+        Err(err)
+    }
+
+    crate fn parse_semi_or_incorrect_foreign_fn_body(
+        &mut self,
+        ident: &Ident,
+        extern_sp: Span,
+    ) -> PResult<'a, ()> {
+        if self.token != token::Semi {
+            // this might be an incorrect fn definition (#62109)
+            let parser_snapshot = self.clone();
+            match self.parse_inner_attrs_and_block() {
+                Ok((_, body)) => {
+                    self.struct_span_err(ident.span, "incorrect `fn` inside `extern` block")
+                        .span_label(ident.span, "can't have a body")
+                        .span_label(body.span, "this body is invalid here")
+                        .span_label(
+                            extern_sp,
+                            "`extern` blocks define existing foreign functions and `fn`s \
+                             inside of them cannot have a body")
+                        .help("you might have meant to write a function accessible through ffi, \
+                               which can be done by writing `extern fn` outside of the \
+                               `extern` block")
+                        .note("for more information, visit \
+                               https://doc.rust-lang.org/std/keyword.extern.html")
+                        .emit();
+                }
+                Err(mut err) => {
+                    err.cancel();
+                    mem::replace(self, parser_snapshot);
+                    self.expect(&token::Semi)?;
+                }
+            }
+        } else {
+            self.bump();
+        }
+        Ok(())
+    }
+
+    /// Consume alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
+    /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
     crate fn parse_incorrect_await_syntax(
         &mut self,
         lo: Span,
         await_sp: Span,
     ) -> PResult<'a, (Span, ExprKind)> {
+        if self.token == token::Not {
+            // Handle `await!(<expr>)`.
+            self.expect(&token::Not)?;
+            self.expect(&token::OpenDelim(token::Paren))?;
+            let expr = self.parse_expr()?;
+            self.expect(&token::CloseDelim(token::Paren))?;
+            let sp = self.error_on_incorrect_await(lo, self.prev_span, &expr, false);
+            return Ok((sp, ExprKind::Await(expr)))
+        }
+
         let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
         let expr = if self.token == token::OpenDelim(token::Brace) {
             // Handle `await { <expr> }`.
@@ -240,7 +892,7 @@ impl<'a> Parser<'a> {
             // interpreting `await { <expr> }?` as `<expr>?.await`.
             self.parse_block_expr(
                 None,
-                self.span,
+                self.token.span,
                 BlockCheckMode::Default,
                 ThinVec::new(),
             )
@@ -250,10 +902,15 @@ impl<'a> Parser<'a> {
             err.span_label(await_sp, "while parsing this incorrect await expression");
             err
         })?;
-        let expr_str = self.sess.source_map().span_to_snippet(expr.span)
+        let sp = self.error_on_incorrect_await(lo, expr.span, &expr, is_question);
+        Ok((sp, ExprKind::Await(expr)))
+    }
+
+    fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
+        let expr_str = self.span_to_snippet(expr.span)
             .unwrap_or_else(|_| pprust::expr_to_string(&expr));
         let suggestion = format!("{}.await{}", expr_str, if is_question { "?" } else { "" });
-        let sp = lo.to(expr.span);
+        let sp = lo.to(hi);
         let app = match expr.node {
             ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
             _ => Applicability::MachineApplicable,
@@ -261,7 +918,7 @@ impl<'a> Parser<'a> {
         self.struct_span_err(sp, "incorrect use of `await`")
             .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
             .emit();
-        Ok((sp, ExprKind::Await(ast::AwaitOrigin::FieldLike, expr)))
+        sp
     }
 
     /// If encountering `future.await()`, consume and emit error.
@@ -270,9 +927,9 @@ impl<'a> Parser<'a> {
             self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
         {
             // future.await()
-            let lo = self.span;
+            let lo = self.token.span;
             self.bump(); // (
-            let sp = lo.to(self.span);
+            let sp = lo.to(self.token.span);
             self.bump(); // )
             self.struct_span_err(sp, "incorrect use of `await`")
                 .span_suggestion(
@@ -284,6 +941,48 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Recover a situation like `for ( $pat in $expr )`
+    /// and suggest writing `for $pat in $expr` instead.
+    ///
+    /// This should be called before parsing the `$block`.
+    crate fn recover_parens_around_for_head(
+        &mut self,
+        pat: P<Pat>,
+        expr: &Expr,
+        begin_paren: Option<Span>,
+    ) -> P<Pat> {
+        match (&self.token.kind, begin_paren) {
+            (token::CloseDelim(token::Paren), Some(begin_par_sp)) => {
+                self.bump();
+
+                let pat_str = self
+                    // Remove the `(` from the span of the pattern:
+                    .span_to_snippet(pat.span.trim_start(begin_par_sp).unwrap())
+                    .unwrap_or_else(|_| pprust::pat_to_string(&pat));
+
+                self.struct_span_err(self.prev_span, "unexpected closing `)`")
+                    .span_label(begin_par_sp, "opening `(`")
+                    .span_suggestion(
+                        begin_par_sp.to(self.prev_span),
+                        "remove parenthesis in `for` loop",
+                        format!("{} in {}", pat_str, pprust::expr_to_string(&expr)),
+                        // With e.g. `for (x) in y)` this would replace `(x) in y)`
+                        // with `x) in y)` which is syntactically invalid.
+                        // However, this is prevented before we get here.
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+
+                // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
+                pat.and_then(|pat| match pat.node {
+                    PatKind::Paren(pat) => pat,
+                    _ => P(pat),
+                })
+            }
+            _ => pat,
+        }
+    }
+
     crate fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
         self.token.is_ident() &&
             if let ast::ExprKind::Path(..) = node { true } else { false } &&
@@ -293,47 +992,9 @@ impl<'a> Parser<'a> {
             self.look_ahead(2, |t| t.is_ident()) ||
             self.look_ahead(1, |t| t == &token::Colon) &&  // `foo:bar:baz`
             self.look_ahead(2, |t| t.is_ident()) ||
-            self.look_ahead(1, |t| t == &token::ModSep) &&  // `foo:bar::baz`
-            self.look_ahead(2, |t| t.is_ident())
-    }
-
-    crate fn bad_type_ascription(
-        &self,
-        err: &mut DiagnosticBuilder<'a>,
-        lhs_span: Span,
-        cur_op_span: Span,
-        next_sp: Span,
-        maybe_path: bool,
-    ) {
-        err.span_label(self.span, "expecting a type here because of type ascription");
-        let cm = self.sess.source_map();
-        let next_pos = cm.lookup_char_pos(next_sp.lo());
-        let op_pos = cm.lookup_char_pos(cur_op_span.hi());
-        if op_pos.line != next_pos.line {
-            err.span_suggestion(
-                cur_op_span,
-                "try using a semicolon",
-                ";".to_string(),
-                Applicability::MaybeIncorrect,
-            );
-        } else {
-            if maybe_path {
-                err.span_suggestion(
-                    cur_op_span,
-                    "maybe you meant to write a path separator here",
-                    "::".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            } else {
-                err.note("type ascription is a nightly-only feature that lets \
-                          you annotate an expression with a type: `<expr>: <type>`")
-                    .span_note(
-                        lhs_span,
-                        "this expression expects an ascribed type after the colon",
-                    )
-                    .help("this might be indicative of a syntax error elsewhere");
-            }
-        }
+            self.look_ahead(1, |t| t == &token::ModSep) &&
+            (self.look_ahead(2, |t| t.is_ident()) ||   // `foo:bar::baz`
+             self.look_ahead(2, |t| t == &token::Lt))  // `foo:bar::<baz>`
     }
 
     crate fn recover_seq_parse_error(
@@ -355,14 +1016,14 @@ impl<'a> Parser<'a> {
 
     crate fn recover_closing_delimiter(
         &mut self,
-        tokens: &[token::Token],
+        tokens: &[TokenKind],
         mut err: DiagnosticBuilder<'a>,
     ) -> PResult<'a, bool> {
         let mut pos = None;
         // we want to use the last closing delim that would apply
         for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
             if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
-                && Some(self.span) > unmatched.unclosed_span
+                && Some(self.token.span) > unmatched.unclosed_span
             {
                 pos = Some(i);
             }
@@ -383,7 +1044,7 @@ impl<'a> Parser<'a> {
                 //  {foo(bar {}}
                 //      -      ^
                 //      |      |
-                //      |      help: `)` may belong here (FIXME: #58270)
+                //      |      help: `)` may belong here
                 //      |
                 //      unclosed delimiter
                 if let Some(sp) = unmatched.unclosed_span {
@@ -405,7 +1066,7 @@ impl<'a> Parser<'a> {
 
     /// Recover from `pub` keyword in places where it seems _reasonable_ but isn't valid.
     crate fn eat_bad_pub(&mut self) {
-        if self.token.is_keyword(keywords::Pub) {
+        if self.token.is_keyword(kw::Pub) {
             match self.parse_visibility(false) {
                 Ok(vis) => {
                     self.diagnostic()
@@ -441,7 +1102,7 @@ impl<'a> Parser<'a> {
                break_on_semi, break_on_block);
         loop {
             debug!("recover_stmt_ loop {:?}", self.token);
-            match self.token {
+            match self.token.kind {
                 token::OpenDelim(token::DelimToken::Brace) => {
                     brace_depth += 1;
                     self.bump();
@@ -501,6 +1162,148 @@ impl<'a> Parser<'a> {
         }
     }
 
+    crate fn check_for_for_in_in_typo(&mut self, in_span: Span) {
+        if self.eat_keyword(kw::In) {
+            // a common typo: `for _ in in bar {}`
+            self.struct_span_err(self.prev_span, "expected iterable, found keyword `in`")
+                .span_suggestion_short(
+                    in_span.until(self.prev_span),
+                    "remove the duplicated `in`",
+                    String::new(),
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+    }
+
+    crate fn expected_semi_or_open_brace(&mut self) -> PResult<'a, ast::TraitItem> {
+        let token_str = self.this_token_descr();
+        let mut err = self.fatal(&format!("expected `;` or `{{`, found {}", token_str));
+        err.span_label(self.token.span, "expected `;` or `{`");
+        Err(err)
+    }
+
+    crate fn eat_incorrect_doc_comment_for_arg_type(&mut self) {
+        if let token::DocComment(_) = self.token.kind {
+            self.struct_span_err(
+                self.token.span,
+                "documentation comments cannot be applied to a function parameter's type",
+            )
+            .span_label(self.token.span, "doc comments are not allowed here")
+            .emit();
+            self.bump();
+        } else if self.token == token::Pound && self.look_ahead(1, |t| {
+            *t == token::OpenDelim(token::Bracket)
+        }) {
+            let lo = self.token.span;
+            // Skip every token until next possible arg.
+            while self.token != token::CloseDelim(token::Bracket) {
+                self.bump();
+            }
+            let sp = lo.to(self.token.span);
+            self.bump();
+            self.struct_span_err(
+                sp,
+                "attributes cannot be applied to a function parameter's type",
+            )
+            .span_label(sp, "attributes are not allowed here")
+            .emit();
+        }
+    }
+
+    crate fn argument_without_type(
+        &mut self,
+        err: &mut DiagnosticBuilder<'_>,
+        pat: P<ast::Pat>,
+        require_name: bool,
+        is_trait_item: bool,
+    ) -> Option<Ident> {
+        // If we find a pattern followed by an identifier, it could be an (incorrect)
+        // C-style parameter declaration.
+        if self.check_ident() && self.look_ahead(1, |t| {
+            *t == token::Comma || *t == token::CloseDelim(token::Paren)
+        }) { // `fn foo(String s) {}`
+            let ident = self.parse_ident().unwrap();
+            let span = pat.span.with_hi(ident.span.hi());
+
+            err.span_suggestion(
+                span,
+                "declare the type after the parameter binding",
+                String::from("<identifier>: <type>"),
+                Applicability::HasPlaceholders,
+            );
+            return Some(ident);
+        } else if let PatKind::Ident(_, ident, _) = pat.node {
+            if require_name && (
+                is_trait_item ||
+                self.token == token::Comma ||
+                self.token == token::CloseDelim(token::Paren)
+            ) { // `fn foo(a, b) {}` or `fn foo(usize, usize) {}`
+                err.span_suggestion(
+                    pat.span,
+                    "if this was a parameter name, give it a type",
+                    format!("{}: TypeName", ident),
+                    Applicability::HasPlaceholders,
+                );
+                err.span_suggestion(
+                    pat.span,
+                    "if this is a type, explicitly ignore the parameter name",
+                    format!("_: {}", ident),
+                    Applicability::MachineApplicable,
+                );
+                err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
+                return Some(ident);
+            }
+        }
+        None
+    }
+
+    crate fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
+        let pat = self.parse_pat(Some("argument name"))?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+
+        self.diagnostic()
+            .struct_span_err_with_code(
+                pat.span,
+                "patterns aren't allowed in methods without bodies",
+                DiagnosticId::Error("E0642".into()),
+            )
+            .span_suggestion_short(
+                pat.span,
+                "give this argument a name or use an underscore to ignore it",
+                "_".to_owned(),
+                Applicability::MachineApplicable,
+            )
+            .emit();
+
+        // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
+        let pat = P(Pat {
+            node: PatKind::Wild,
+            span: pat.span,
+            id: ast::DUMMY_NODE_ID
+        });
+        Ok((pat, ty))
+    }
+
+    crate fn recover_bad_self_arg(
+        &mut self,
+        mut arg: ast::Arg,
+        is_trait_item: bool,
+    ) -> PResult<'a, ast::Arg> {
+        let sp = arg.pat.span;
+        arg.ty.node = TyKind::Err;
+        let mut err = self.struct_span_err(sp, "unexpected `self` parameter in function");
+        if is_trait_item {
+            err.span_label(sp, "must be the first associated function parameter");
+        } else {
+            err.span_label(sp, "not valid as function parameter");
+            err.note("`self` is only valid as the first parameter of an associated function");
+        }
+        err.emit();
+        Ok(arg)
+    }
+
     crate fn consume_block(&mut self, delim: token::DelimToken) {
         let mut brace_depth = 0;
         loop {
@@ -521,4 +1324,50 @@ impl<'a> Parser<'a> {
         }
     }
 
+    crate fn expected_expression_found(&self) -> DiagnosticBuilder<'a> {
+        let (span, msg) = match (&self.token.kind, self.subparser_name) {
+            (&token::Eof, Some(origin)) => {
+                let sp = self.sess.source_map().next_point(self.token.span);
+                (sp, format!("expected expression, found end of {}", origin))
+            }
+            _ => (self.token.span, format!(
+                "expected expression, found {}",
+                self.this_token_descr(),
+            )),
+        };
+        let mut err = self.struct_span_err(span, &msg);
+        let sp = self.sess.source_map().start_point(self.token.span);
+        if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
+            self.sess.expr_parentheses_needed(&mut err, *sp, None);
+        }
+        err.span_label(span, "expected expression");
+        err
+    }
+
+    /// Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
+    ///
+    /// This is necessary because at this point we don't know whether we parsed a function with
+    /// anonymous arguments or a function with names but no types. In order to minimize
+    /// unecessary errors, we assume the arguments are in the shape of `fn foo(a, b, c)` where
+    /// the arguments are *names* (so we don't emit errors about not being able to find `b` in
+    /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
+    /// we deduplicate them to not complain about duplicated argument names.
+    crate fn deduplicate_recovered_arg_names(&self, fn_inputs: &mut Vec<Arg>) {
+        let mut seen_inputs = FxHashSet::default();
+        for input in fn_inputs.iter_mut() {
+            let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) = (
+                &input.pat.node, &input.ty.node,
+            ) {
+                Some(*ident)
+            } else {
+                None
+            };
+            if let Some(ident) = opt_ident {
+                if seen_inputs.contains(&ident) {
+                    input.pat.node = PatKind::Wild;
+                }
+                seen_inputs.insert(ident);
+            }
+        }
+    }
 }
diff --git a/src/libsyntax/parse/lexer/comments.rs b/src/libsyntax/parse/lexer/comments.rs
index 97d3fc002e9..5121a9ef7b5 100644
--- a/src/libsyntax/parse/lexer/comments.rs
+++ b/src/libsyntax/parse/lexer/comments.rs
@@ -2,15 +2,16 @@ pub use CommentStyle::*;
 
 use crate::ast;
 use crate::source_map::SourceMap;
-use crate::parse::lexer::{is_block_doc_comment, is_pattern_whitespace};
-use crate::parse::lexer::{self, ParseSess, StringReader};
+use crate::parse::lexer::is_block_doc_comment;
+use crate::parse::lexer::ParseSess;
 
 use syntax_pos::{BytePos, CharPos, Pos, FileName};
-use log::debug;
 
-use std::io::Read;
 use std::usize;
 
+#[cfg(test)]
+mod tests;
+
 #[derive(Clone, Copy, PartialEq, Debug)]
 pub enum CommentStyle {
     /// No code on either side of each line of the comment
@@ -136,66 +137,6 @@ pub fn strip_doc_comment_decoration(comment: &str) -> String {
     panic!("not a doc-comment: {}", comment);
 }
 
-fn push_blank_line_comment(rdr: &StringReader<'_>, comments: &mut Vec<Comment>) {
-    debug!(">>> blank-line comment");
-    comments.push(Comment {
-        style: BlankLine,
-        lines: Vec::new(),
-        pos: rdr.pos,
-    });
-}
-
-fn consume_whitespace_counting_blank_lines(
-    rdr: &mut StringReader<'_>,
-    comments: &mut Vec<Comment>
-) {
-    while is_pattern_whitespace(rdr.ch) && !rdr.is_eof() {
-        if rdr.ch_is('\n') {
-            push_blank_line_comment(rdr, &mut *comments);
-        }
-        rdr.bump();
-    }
-}
-
-fn read_shebang_comment(rdr: &mut StringReader<'_>,
-                        code_to_the_left: bool,
-                        comments: &mut Vec<Comment>) {
-    debug!(">>> shebang comment");
-    let p = rdr.pos;
-    debug!("<<< shebang comment");
-    comments.push(Comment {
-        style: if code_to_the_left { Trailing } else { Isolated },
-        lines: vec![rdr.read_one_line_comment()],
-        pos: p,
-    });
-}
-
-fn read_line_comments(rdr: &mut StringReader<'_>,
-                      code_to_the_left: bool,
-                      comments: &mut Vec<Comment>) {
-    debug!(">>> line comments");
-    let p = rdr.pos;
-    let mut lines: Vec<String> = Vec::new();
-    while rdr.ch_is('/') && rdr.nextch_is('/') {
-        let line = rdr.read_one_line_comment();
-        debug!("{}", line);
-        // Doc comments are not put in comments.
-        if is_doc_comment(&line[..]) {
-            break;
-        }
-        lines.push(line);
-        rdr.consume_non_eol_whitespace();
-    }
-    debug!("<<< line comments");
-    if !lines.is_empty() {
-        comments.push(Comment {
-            style: if code_to_the_left { Trailing } else { Isolated },
-            lines,
-            pos: p,
-        });
-    }
-}
-
 /// Returns `None` if the first `col` chars of `s` contain a non-whitespace char.
 /// Otherwise returns `Some(k)` where `k` is first char offset after that leading
 /// whitespace. Note that `k` may be outside bounds of `s`.
@@ -210,224 +151,104 @@ fn all_whitespace(s: &str, col: CharPos) -> Option<usize> {
     Some(idx)
 }
 
-fn trim_whitespace_prefix_and_push_line(lines: &mut Vec<String>, s: String, col: CharPos) {
+fn trim_whitespace_prefix(s: &str, col: CharPos) -> &str {
     let len = s.len();
-    let s1 = match all_whitespace(&s[..], col) {
-        Some(col) => {
-            if col < len {
-                s[col..len].to_string()
-            } else {
-                String::new()
-            }
-        }
+    match all_whitespace(&s, col) {
+        Some(col) => if col < len { &s[col..] } else { "" },
         None => s,
-    };
-    debug!("pushing line: {}", s1);
-    lines.push(s1);
-}
-
-fn read_block_comment(rdr: &mut StringReader<'_>,
-                      code_to_the_left: bool,
-                      comments: &mut Vec<Comment>) {
-    debug!(">>> block comment");
-    let p = rdr.pos;
-    let mut lines: Vec<String> = Vec::new();
-
-    // Count the number of chars since the start of the line by rescanning.
-    let src_index = rdr.src_index(rdr.source_file.line_begin_pos(rdr.pos));
-    let end_src_index = rdr.src_index(rdr.pos);
-    assert!(src_index <= end_src_index,
-        "src_index={}, end_src_index={}, line_begin_pos={}",
-        src_index, end_src_index, rdr.source_file.line_begin_pos(rdr.pos).to_u32());
-
-    let col = CharPos(rdr.src[src_index..end_src_index].chars().count());
-
-    rdr.bump();
-    rdr.bump();
-
-    let mut curr_line = String::from("/*");
-
-    // doc-comments are not really comments, they are attributes
-    if (rdr.ch_is('*') && !rdr.nextch_is('*')) || rdr.ch_is('!') {
-        while !(rdr.ch_is('*') && rdr.nextch_is('/')) && !rdr.is_eof() {
-            curr_line.push(rdr.ch.unwrap());
-            rdr.bump();
-        }
-        if !rdr.is_eof() {
-            curr_line.push_str("*/");
-            rdr.bump();
-            rdr.bump();
-        }
-        if is_block_doc_comment(&curr_line[..]) {
-            return;
-        }
-        assert!(!curr_line.contains('\n'));
-        lines.push(curr_line);
-    } else {
-        let mut level: isize = 1;
-        while level > 0 {
-            debug!("=== block comment level {}", level);
-            if rdr.is_eof() {
-                rdr.fatal("unterminated block comment").raise();
-            }
-            if rdr.ch_is('\n') {
-                trim_whitespace_prefix_and_push_line(&mut lines, curr_line, col);
-                curr_line = String::new();
-                rdr.bump();
-            } else {
-                curr_line.push(rdr.ch.unwrap());
-                if rdr.ch_is('/') && rdr.nextch_is('*') {
-                    rdr.bump();
-                    rdr.bump();
-                    curr_line.push('*');
-                    level += 1;
-                } else {
-                    if rdr.ch_is('*') && rdr.nextch_is('/') {
-                        rdr.bump();
-                        rdr.bump();
-                        curr_line.push('/');
-                        level -= 1;
-                    } else {
-                        rdr.bump();
-                    }
-                }
-            }
-        }
-        if !curr_line.is_empty() {
-            trim_whitespace_prefix_and_push_line(&mut lines, curr_line, col);
-        }
     }
-
-    let mut style = if code_to_the_left {
-        Trailing
-    } else {
-        Isolated
-    };
-    rdr.consume_non_eol_whitespace();
-    if !rdr.is_eof() && !rdr.ch_is('\n') && lines.len() == 1 {
-        style = Mixed;
-    }
-    debug!("<<< block comment");
-    comments.push(Comment {
-        style,
-        lines,
-        pos: p,
-    });
 }
 
-
-fn consume_comment(rdr: &mut StringReader<'_>,
-                   comments: &mut Vec<Comment>,
-                   code_to_the_left: &mut bool,
-                   anything_to_the_left: &mut bool) {
-    debug!(">>> consume comment");
-    if rdr.ch_is('/') && rdr.nextch_is('/') {
-        read_line_comments(rdr, *code_to_the_left, comments);
-        *code_to_the_left = false;
-        *anything_to_the_left = false;
-    } else if rdr.ch_is('/') && rdr.nextch_is('*') {
-        read_block_comment(rdr, *code_to_the_left, comments);
-        *anything_to_the_left = true;
-    } else if rdr.ch_is('#') && rdr.nextch_is('!') {
-        read_shebang_comment(rdr, *code_to_the_left, comments);
-        *code_to_the_left = false;
-        *anything_to_the_left = false;
-    } else {
-        panic!();
-    }
-    debug!("<<< consume comment");
+fn split_block_comment_into_lines(
+    text: &str,
+    col: CharPos,
+) -> Vec<String> {
+    let mut res: Vec<String> = vec![];
+    let mut lines = text.lines();
+    // just push the first line
+    res.extend(lines.next().map(|it| it.to_string()));
+    // for other lines, strip common whitespace prefix
+    for line in lines {
+        res.push(trim_whitespace_prefix(line, col).to_string())
+    }
+    res
 }
 
 // it appears this function is called only from pprust... that's
 // probably not a good thing.
-pub fn gather_comments(sess: &ParseSess, path: FileName, srdr: &mut dyn Read) -> Vec<Comment>
-{
-    let mut src = String::new();
-    srdr.read_to_string(&mut src).unwrap();
+pub fn gather_comments(sess: &ParseSess, path: FileName, src: String) -> Vec<Comment> {
     let cm = SourceMap::new(sess.source_map().path_mapping().clone());
     let source_file = cm.new_source_file(path, src);
-    let mut rdr = lexer::StringReader::new_raw(sess, source_file, None);
+    let text = (*source_file.src.as_ref().unwrap()).clone();
 
+    let text: &str = text.as_str();
+    let start_bpos = source_file.start_pos;
+    let mut pos = 0;
     let mut comments: Vec<Comment> = Vec::new();
-    let mut code_to_the_left = false; // Only code
-    let mut anything_to_the_left = false; // Code or comments
+    let mut code_to_the_left = false;
 
-    while !rdr.is_eof() {
-        loop {
-            // Eat all the whitespace and count blank lines.
-            rdr.consume_non_eol_whitespace();
-            if rdr.ch_is('\n') {
-                if anything_to_the_left {
-                    rdr.bump(); // The line is not blank, do not count.
+    if let Some(shebang_len) = rustc_lexer::strip_shebang(text) {
+        comments.push(Comment {
+            style: Isolated,
+            lines: vec![text[..shebang_len].to_string()],
+            pos: start_bpos,
+        });
+        pos += shebang_len;
+    }
+
+    for token in rustc_lexer::tokenize(&text[pos..]) {
+        let token_text = &text[pos..pos + token.len];
+        match token.kind {
+            rustc_lexer::TokenKind::Whitespace => {
+                if let Some(mut idx) = token_text.find('\n') {
+                    code_to_the_left = false;
+                    while let Some(next_newline) = &token_text[idx + 1..].find('\n') {
+                        idx = idx + 1 + next_newline;
+                        comments.push(Comment {
+                            style: BlankLine,
+                            lines: vec![],
+                            pos: start_bpos + BytePos((pos + idx) as u32),
+                        });
+                    }
+                }
+            }
+            rustc_lexer::TokenKind::BlockComment { terminated: _ } => {
+                if !is_block_doc_comment(token_text) {
+                    let code_to_the_right = match text[pos + token.len..].chars().next() {
+                        Some('\r') | Some('\n') => false,
+                        _ => true,
+                    };
+                    let style = match (code_to_the_left, code_to_the_right) {
+                        (true, true) | (false, true) => Mixed,
+                        (false, false) => Isolated,
+                        (true, false) => Trailing,
+                    };
+
+                    // Count the number of chars since the start of the line by rescanning.
+                    let pos_in_file = start_bpos + BytePos(pos as u32);
+                    let line_begin_in_file = source_file.line_begin_pos(pos_in_file);
+                    let line_begin_pos = (line_begin_in_file - start_bpos).to_usize();
+                    let col = CharPos(text[line_begin_pos..pos].chars().count());
+
+                    let lines = split_block_comment_into_lines(token_text, col);
+                    comments.push(Comment { style, lines, pos: pos_in_file })
                 }
-                consume_whitespace_counting_blank_lines(&mut rdr, &mut comments);
-                code_to_the_left = false;
-                anything_to_the_left = false;
             }
-            // Eat one comment group
-            if rdr.peeking_at_comment() {
-                consume_comment(&mut rdr, &mut comments,
-                                &mut code_to_the_left, &mut anything_to_the_left);
-            } else {
-                break
+            rustc_lexer::TokenKind::LineComment => {
+                if !is_doc_comment(token_text) {
+                    comments.push(Comment {
+                        style: if code_to_the_left { Trailing } else { Isolated },
+                        lines: vec![token_text.to_string()],
+                        pos: start_bpos + BytePos(pos as u32),
+                    })
+                }
+            }
+            _ => {
+                code_to_the_left = true;
             }
         }
-
-        rdr.next_token();
-        code_to_the_left = true;
-        anything_to_the_left = true;
+        pos += token.len;
     }
 
     comments
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_block_doc_comment_1() {
-        let comment = "/**\n * Test \n **  Test\n *   Test\n*/";
-        let stripped = strip_doc_comment_decoration(comment);
-        assert_eq!(stripped, " Test \n*  Test\n   Test");
-    }
-
-    #[test]
-    fn test_block_doc_comment_2() {
-        let comment = "/**\n * Test\n *  Test\n*/";
-        let stripped = strip_doc_comment_decoration(comment);
-        assert_eq!(stripped, " Test\n  Test");
-    }
-
-    #[test]
-    fn test_block_doc_comment_3() {
-        let comment = "/**\n let a: *i32;\n *a = 5;\n*/";
-        let stripped = strip_doc_comment_decoration(comment);
-        assert_eq!(stripped, " let a: *i32;\n *a = 5;");
-    }
-
-    #[test]
-    fn test_block_doc_comment_4() {
-        let comment = "/*******************\n test\n *********************/";
-        let stripped = strip_doc_comment_decoration(comment);
-        assert_eq!(stripped, " test");
-    }
-
-    #[test]
-    fn test_line_doc_comment() {
-        let stripped = strip_doc_comment_decoration("/// test");
-        assert_eq!(stripped, " test");
-        let stripped = strip_doc_comment_decoration("///! test");
-        assert_eq!(stripped, " test");
-        let stripped = strip_doc_comment_decoration("// test");
-        assert_eq!(stripped, " test");
-        let stripped = strip_doc_comment_decoration("// test");
-        assert_eq!(stripped, " test");
-        let stripped = strip_doc_comment_decoration("///test");
-        assert_eq!(stripped, "test");
-        let stripped = strip_doc_comment_decoration("///!test");
-        assert_eq!(stripped, "test");
-        let stripped = strip_doc_comment_decoration("//test");
-        assert_eq!(stripped, "test");
-    }
-}
diff --git a/src/libsyntax/parse/lexer/comments/tests.rs b/src/libsyntax/parse/lexer/comments/tests.rs
new file mode 100644
index 00000000000..f9cd69fb50d
--- /dev/null
+++ b/src/libsyntax/parse/lexer/comments/tests.rs
@@ -0,0 +1,47 @@
+use super::*;
+
+#[test]
+fn test_block_doc_comment_1() {
+    let comment = "/**\n * Test \n **  Test\n *   Test\n*/";
+    let stripped = strip_doc_comment_decoration(comment);
+    assert_eq!(stripped, " Test \n*  Test\n   Test");
+}
+
+#[test]
+fn test_block_doc_comment_2() {
+    let comment = "/**\n * Test\n *  Test\n*/";
+    let stripped = strip_doc_comment_decoration(comment);
+    assert_eq!(stripped, " Test\n  Test");
+}
+
+#[test]
+fn test_block_doc_comment_3() {
+    let comment = "/**\n let a: *i32;\n *a = 5;\n*/";
+    let stripped = strip_doc_comment_decoration(comment);
+    assert_eq!(stripped, " let a: *i32;\n *a = 5;");
+}
+
+#[test]
+fn test_block_doc_comment_4() {
+    let comment = "/*******************\n test\n *********************/";
+    let stripped = strip_doc_comment_decoration(comment);
+    assert_eq!(stripped, " test");
+}
+
+#[test]
+fn test_line_doc_comment() {
+    let stripped = strip_doc_comment_decoration("/// test");
+    assert_eq!(stripped, " test");
+    let stripped = strip_doc_comment_decoration("///! test");
+    assert_eq!(stripped, " test");
+    let stripped = strip_doc_comment_decoration("// test");
+    assert_eq!(stripped, " test");
+    let stripped = strip_doc_comment_decoration("// test");
+    assert_eq!(stripped, " test");
+    let stripped = strip_doc_comment_decoration("///test");
+    assert_eq!(stripped, "test");
+    let stripped = strip_doc_comment_decoration("///!test");
+    assert_eq!(stripped, "test");
+    let stripped = strip_doc_comment_decoration("//test");
+    assert_eq!(stripped, "test");
+}
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 47da3ee6a6c..bdf468a52bb 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -1,40 +1,26 @@
-use crate::ast::{self, Ident};
-use crate::parse::{token, ParseSess};
-use crate::symbol::Symbol;
-use crate::parse::unescape;
+use crate::parse::ParseSess;
+use crate::parse::token::{self, Token, TokenKind};
+use crate::symbol::{sym, Symbol};
 use crate::parse::unescape_error_reporting::{emit_unescape_error, push_escaped_char};
 
-use errors::{FatalError, Diagnostic, DiagnosticBuilder};
-use syntax_pos::{BytePos, Pos, Span, NO_EXPANSION};
-use core::unicode::property::Pattern_White_Space;
+use errors::{FatalError, DiagnosticBuilder};
+use syntax_pos::{BytePos, Pos, Span};
+use rustc_lexer::Base;
+use rustc_lexer::unescape;
 
-use std::borrow::Cow;
 use std::char;
-use std::iter;
-use std::mem::replace;
+use std::convert::TryInto;
 use rustc_data_structures::sync::Lrc;
 use log::debug;
 
+#[cfg(test)]
+mod tests;
+
 pub mod comments;
 mod tokentrees;
 mod unicode_chars;
 
 #[derive(Clone, Debug)]
-pub struct TokenAndSpan {
-    pub tok: token::Token,
-    pub sp: Span,
-}
-
-impl Default for TokenAndSpan {
-    fn default() -> Self {
-        TokenAndSpan {
-            tok: token::Whitespace,
-            sp: syntax_pos::DUMMY_SP,
-        }
-    }
-}
-
-#[derive(Clone, Debug)]
 pub struct UnmatchedBrace {
     pub expected_delim: token::DelimToken,
     pub found_delim: token::DelimToken,
@@ -44,176 +30,22 @@ pub struct UnmatchedBrace {
 }
 
 pub struct StringReader<'a> {
-    crate sess: &'a ParseSess,
-    /// The absolute offset within the source_map of the next character to read
-    crate next_pos: BytePos,
-    /// The absolute offset within the source_map of the current character
-    crate pos: BytePos,
-    /// The current character (which has been read from self.pos)
-    crate ch: Option<char>,
-    crate source_file: Lrc<syntax_pos::SourceFile>,
+    sess: &'a ParseSess,
+    /// Initial position, read-only.
+    start_pos: BytePos,
+    /// The absolute offset within the source_map of the current character.
+    pos: BytePos,
     /// Stop reading src at this index.
-    crate end_src_index: usize,
-    // cached:
-    peek_tok: token::Token,
-    peek_span: Span,
-    peek_span_src_raw: Span,
-    fatal_errs: Vec<DiagnosticBuilder<'a>>,
-    // cache a direct reference to the source text, so that we don't have to
-    // retrieve it via `self.source_file.src.as_ref().unwrap()` all the time.
+    end_src_index: usize,
+    /// Source text to tokenize.
     src: Lrc<String>,
     override_span: Option<Span>,
 }
 
 impl<'a> StringReader<'a> {
-    fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
-        self.mk_sp_and_raw(lo, hi).0
-    }
-
-    fn mk_sp_and_raw(&self, lo: BytePos, hi: BytePos) -> (Span, Span) {
-        let raw = Span::new(lo, hi, NO_EXPANSION);
-        let real = self.override_span.unwrap_or(raw);
-
-        (real, raw)
-    }
-
-    fn mk_ident(&self, string: &str) -> Ident {
-        let mut ident = Ident::from_str(string);
-        if let Some(span) = self.override_span {
-            ident.span = span;
-        }
-
-        ident
-    }
-
-    fn unwrap_or_abort(&mut self, res: Result<TokenAndSpan, ()>) -> TokenAndSpan {
-        match res {
-            Ok(tok) => tok,
-            Err(_) => {
-                self.emit_fatal_errors();
-                FatalError.raise();
-            }
-        }
-    }
-
-    fn next_token(&mut self) -> TokenAndSpan where Self: Sized {
-        let res = self.try_next_token();
-        self.unwrap_or_abort(res)
-    }
-
-    /// Returns the next token. EFFECT: advances the string_reader.
-    pub fn try_next_token(&mut self) -> Result<TokenAndSpan, ()> {
-        assert!(self.fatal_errs.is_empty());
-        let ret_val = TokenAndSpan {
-            tok: replace(&mut self.peek_tok, token::Whitespace),
-            sp: self.peek_span,
-        };
-        self.advance_token()?;
-        Ok(ret_val)
-    }
-
-    /// Immutably extract string if found at current position with given delimiters
-    fn peek_delimited(&self, from_ch: char, to_ch: char) -> Option<String> {
-        let mut pos = self.pos;
-        let mut idx = self.src_index(pos);
-        let mut ch = char_at(&self.src, idx);
-        if ch != from_ch {
-            return None;
-        }
-        pos = pos + Pos::from_usize(ch.len_utf8());
-        let start_pos = pos;
-        idx = self.src_index(pos);
-        while idx < self.end_src_index {
-            ch = char_at(&self.src, idx);
-            if ch == to_ch {
-                return Some(self.src[self.src_index(start_pos)..self.src_index(pos)].to_string());
-            }
-            pos = pos + Pos::from_usize(ch.len_utf8());
-            idx = self.src_index(pos);
-        }
-        return None;
-    }
-
-    fn try_real_token(&mut self) -> Result<TokenAndSpan, ()> {
-        let mut t = self.try_next_token()?;
-        loop {
-            match t.tok {
-                token::Whitespace | token::Comment | token::Shebang(_) => {
-                    t = self.try_next_token()?;
-                }
-                _ => break,
-            }
-        }
-
-        Ok(t)
-    }
-
-    pub fn real_token(&mut self) -> TokenAndSpan {
-        let res = self.try_real_token();
-        self.unwrap_or_abort(res)
-    }
-
-    #[inline]
-    fn is_eof(&self) -> bool {
-        self.ch.is_none()
-    }
-
-    fn fail_unterminated_raw_string(&self, pos: BytePos, hash_count: u16) {
-        let mut err = self.struct_span_fatal(pos, pos, "unterminated raw string");
-        err.span_label(self.mk_sp(pos, pos), "unterminated raw string");
-
-        if hash_count > 0 {
-            err.note(&format!("this raw string should be terminated with `\"{}`",
-                              "#".repeat(hash_count as usize)));
-        }
-
-        err.emit();
-        FatalError.raise();
-    }
-
-    fn fatal(&self, m: &str) -> FatalError {
-        self.fatal_span(self.peek_span, m)
-    }
-
-    crate fn emit_fatal_errors(&mut self) {
-        for err in &mut self.fatal_errs {
-            err.emit();
-        }
-
-        self.fatal_errs.clear();
-    }
-
-    pub fn buffer_fatal_errors(&mut self) -> Vec<Diagnostic> {
-        let mut buffer = Vec::new();
-
-        for err in self.fatal_errs.drain(..) {
-            err.buffer(&mut buffer);
-        }
-
-        buffer
-    }
-
-    pub fn peek(&self) -> TokenAndSpan {
-        // FIXME(pcwalton): Bad copy!
-        TokenAndSpan {
-            tok: self.peek_tok.clone(),
-            sp: self.peek_span,
-        }
-    }
-
-    /// For comments.rs, which hackily pokes into next_pos and ch
-    fn new_raw(sess: &'a ParseSess,
+    pub fn new(sess: &'a ParseSess,
                source_file: Lrc<syntax_pos::SourceFile>,
                override_span: Option<Span>) -> Self {
-        let mut sr = StringReader::new_raw_internal(sess, source_file, override_span);
-        sr.bump();
-
-        sr
-    }
-
-    fn new_raw_internal(sess: &'a ParseSess, source_file: Lrc<syntax_pos::SourceFile>,
-        override_span: Option<Span>) -> Self
-    {
         if source_file.src.is_none() {
             sess.span_diagnostic.bug(&format!("Cannot lex source_file without source: {}",
                                               source_file.name));
@@ -223,32 +55,14 @@ impl<'a> StringReader<'a> {
 
         StringReader {
             sess,
-            next_pos: source_file.start_pos,
+            start_pos: source_file.start_pos,
             pos: source_file.start_pos,
-            ch: Some('\n'),
-            source_file,
             end_src_index: src.len(),
-            // dummy values; not read
-            peek_tok: token::Eof,
-            peek_span: syntax_pos::DUMMY_SP,
-            peek_span_src_raw: syntax_pos::DUMMY_SP,
             src,
-            fatal_errs: Vec::new(),
             override_span,
         }
     }
 
-    pub fn new_or_buffered_errs(sess: &'a ParseSess,
-                                source_file: Lrc<syntax_pos::SourceFile>,
-                                override_span: Option<Span>) -> Result<Self, Vec<Diagnostic>> {
-        let mut sr = StringReader::new_raw(sess, source_file, override_span);
-        if sr.advance_token().is_err() {
-            Err(sr.buffer_fatal_errors())
-        } else {
-            Ok(sr)
-        }
-    }
-
     pub fn retokenize(sess: &'a ParseSess, mut span: Span) -> Self {
         let begin = sess.source_map().lookup_byte_offset(span.lo());
         let end = sess.source_map().lookup_byte_offset(span.hi());
@@ -258,25 +72,61 @@ impl<'a> StringReader<'a> {
             span = span.shrink_to_lo();
         }
 
-        let mut sr = StringReader::new_raw_internal(sess, begin.sf, None);
+        let mut sr = StringReader::new(sess, begin.sf, None);
 
         // Seek the lexer to the right byte range.
-        sr.next_pos = span.lo();
         sr.end_src_index = sr.src_index(span.hi());
 
-        sr.bump();
+        sr
+    }
 
-        if sr.advance_token().is_err() {
-            sr.emit_fatal_errors();
-            FatalError.raise();
-        }
 
-        sr
+    fn mk_sp(&self, lo: BytePos, hi: BytePos) -> Span {
+        self.override_span.unwrap_or_else(|| Span::with_root_ctxt(lo, hi))
     }
 
-    #[inline]
-    fn ch_is(&self, c: char) -> bool {
-        self.ch == Some(c)
+    /// Returns the next token, including trivia like whitespace or comments.
+    ///
+    /// `Err(())` means that some errors were encountered, which can be
+    /// retrieved using `buffer_fatal_errors`.
+    pub fn next_token(&mut self) -> Token {
+        let start_src_index = self.src_index(self.pos);
+        let text: &str = &self.src[start_src_index..self.end_src_index];
+
+        if text.is_empty() {
+            let span = self.mk_sp(self.pos, self.pos);
+            return Token::new(token::Eof, span);
+        }
+
+        {
+            let is_beginning_of_file = self.pos == self.start_pos;
+            if is_beginning_of_file {
+                if let Some(shebang_len) = rustc_lexer::strip_shebang(text) {
+                    let start = self.pos;
+                    self.pos = self.pos + BytePos::from_usize(shebang_len);
+
+                    let sym = self.symbol_from(start + BytePos::from_usize("#!".len()));
+                    let kind = token::Shebang(sym);
+
+                    let span = self.mk_sp(start, self.pos);
+                    return Token::new(kind, span);
+                }
+            }
+        }
+
+        let token = rustc_lexer::first_token(text);
+
+        let start = self.pos;
+        self.pos = self.pos + BytePos::from_usize(token.len);
+
+        debug!("try_next_token: {:?}({:?})", token.kind, self.str_from(start));
+
+        // This could use `?`, but that makes code significantly (10-20%) slower.
+        // https://github.com/rust-lang/rust/issues/37939
+        let kind = self.cook_lexer_token(token.kind, start);
+
+        let span = self.mk_sp(start, self.pos);
+        Token::new(kind, span)
     }
 
     /// Report a fatal lexical error with a given span.
@@ -300,16 +150,6 @@ impl<'a> StringReader<'a> {
         self.err_span(self.mk_sp(from_pos, to_pos), m)
     }
 
-    /// Report a lexical error spanning [`from_pos`, `to_pos`), appending an
-    /// escaped character to the error message
-    fn fatal_span_char(&self, from_pos: BytePos, to_pos: BytePos, m: &str, c: char) -> FatalError {
-        let mut m = m.to_string();
-        m.push_str(": ");
-        push_escaped_char(&mut m, c);
-
-        self.fatal_span_(from_pos, to_pos, &m[..])
-    }
-
     fn struct_span_fatal(&self, from_pos: BytePos, to_pos: BytePos, m: &str)
         -> DiagnosticBuilder<'a>
     {
@@ -326,1186 +166,506 @@ impl<'a> StringReader<'a> {
         self.sess.span_diagnostic.struct_span_fatal(self.mk_sp(from_pos, to_pos), &m[..])
     }
 
-    /// Report a lexical error spanning [`from_pos`, `to_pos`), appending an
-    /// escaped character to the error message
-    fn err_span_char(&self, from_pos: BytePos, to_pos: BytePos, m: &str, c: char) {
-        let mut m = m.to_string();
-        m.push_str(": ");
-        push_escaped_char(&mut m, c);
-        self.err_span_(from_pos, to_pos, &m[..]);
-    }
-
-    /// Advance peek_tok and peek_span to refer to the next token, and
-    /// possibly update the interner.
-    fn advance_token(&mut self) -> Result<(), ()> {
-        match self.scan_whitespace_or_comment() {
-            Some(comment) => {
-                self.peek_span_src_raw = comment.sp;
-                self.peek_span = comment.sp;
-                self.peek_tok = comment.tok;
-            }
-            None => {
-                if self.is_eof() {
-                    self.peek_tok = token::Eof;
-                    let (real, raw) = self.mk_sp_and_raw(
-                        self.source_file.end_pos,
-                        self.source_file.end_pos,
-                    );
-                    self.peek_span = real;
-                    self.peek_span_src_raw = raw;
+    /// Turns simple `rustc_lexer::TokenKind` enum into a rich
+    /// `libsyntax::TokenKind`. This turns strings into interned
+    /// symbols and runs additional validation.
+    fn cook_lexer_token(
+        &self,
+        token: rustc_lexer::TokenKind,
+        start: BytePos,
+    ) -> TokenKind {
+        match token {
+            rustc_lexer::TokenKind::LineComment => {
+                let string = self.str_from(start);
+                // comments with only more "/"s are not doc comments
+                let tok = if is_doc_comment(string) {
+                    self.forbid_bare_cr(start, string, "bare CR not allowed in doc-comment");
+                    token::DocComment(Symbol::intern(string))
                 } else {
-                    let start_bytepos = self.pos;
-                    self.peek_tok = self.next_token_inner()?;
-                    let (real, raw) = self.mk_sp_and_raw(start_bytepos, self.pos);
-                    self.peek_span = real;
-                    self.peek_span_src_raw = raw;
+                    token::Comment
                 };
-            }
-        }
-
-        Ok(())
-    }
-
-    #[inline]
-    fn src_index(&self, pos: BytePos) -> usize {
-        (pos - self.source_file.start_pos).to_usize()
-    }
-
-    /// Calls `f` with a string slice of the source text spanning from `start`
-    /// up to but excluding `self.pos`, meaning the slice does not include
-    /// the character `self.ch`.
-    fn with_str_from<T, F>(&self, start: BytePos, f: F) -> T
-        where F: FnOnce(&str) -> T
-    {
-        self.with_str_from_to(start, self.pos, f)
-    }
 
-    /// Creates a Name from a given offset to the current offset.
-    fn name_from(&self, start: BytePos) -> ast::Name {
-        debug!("taking an ident from {:?} to {:?}", start, self.pos);
-        self.with_str_from(start, Symbol::intern)
-    }
-
-    /// As name_from, with an explicit endpoint.
-    fn name_from_to(&self, start: BytePos, end: BytePos) -> ast::Name {
-        debug!("taking an ident from {:?} to {:?}", start, end);
-        self.with_str_from_to(start, end, Symbol::intern)
-    }
-
-    /// Calls `f` with a string slice of the source text spanning from `start`
-    /// up to but excluding `end`.
-    fn with_str_from_to<T, F>(&self, start: BytePos, end: BytePos, f: F) -> T
-        where F: FnOnce(&str) -> T
-    {
-        f(&self.src[self.src_index(start)..self.src_index(end)])
-    }
-
-    /// Converts CRLF to LF in the given string, raising an error on bare CR.
-    fn translate_crlf<'b>(&self, start: BytePos, s: &'b str, errmsg: &'b str) -> Cow<'b, str> {
-        let mut chars = s.char_indices().peekable();
-        while let Some((i, ch)) = chars.next() {
-            if ch == '\r' {
-                if let Some((lf_idx, '\n')) = chars.peek() {
-                    return translate_crlf_(self, start, s, *lf_idx, chars, errmsg).into();
-                }
-                let pos = start + BytePos(i as u32);
-                let end_pos = start + BytePos((i + ch.len_utf8()) as u32);
-                self.err_span_(pos, end_pos, errmsg);
-            }
-        }
-        return s.into();
-
-        fn translate_crlf_(rdr: &StringReader<'_>,
-                           start: BytePos,
-                           s: &str,
-                           mut j: usize,
-                           mut chars: iter::Peekable<impl Iterator<Item = (usize, char)>>,
-                           errmsg: &str)
-                           -> String {
-            let mut buf = String::with_capacity(s.len());
-            // Skip first CR
-            buf.push_str(&s[.. j - 1]);
-            while let Some((i, ch)) = chars.next() {
-                if ch == '\r' {
-                    if j < i {
-                        buf.push_str(&s[j..i]);
-                    }
-                    let next = i + ch.len_utf8();
-                    j = next;
-                    if chars.peek().map(|(_, ch)| *ch) != Some('\n') {
-                        let pos = start + BytePos(i as u32);
-                        let end_pos = start + BytePos(next as u32);
-                        rdr.err_span_(pos, end_pos, errmsg);
-                    }
-                }
+                tok
             }
-            if j < s.len() {
-                buf.push_str(&s[j..]);
-            }
-            buf
-        }
-    }
+            rustc_lexer::TokenKind::BlockComment { terminated } => {
+                let string = self.str_from(start);
+                // block comments starting with "/**" or "/*!" are doc-comments
+                // but comments with only "*"s between two "/"s are not
+                let is_doc_comment = is_block_doc_comment(string);
 
-    /// Advance the StringReader by one character.
-    crate fn bump(&mut self) {
-        let next_src_index = self.src_index(self.next_pos);
-        if next_src_index < self.end_src_index {
-            let next_ch = char_at(&self.src, next_src_index);
-            let next_ch_len = next_ch.len_utf8();
-
-            self.ch = Some(next_ch);
-            self.pos = self.next_pos;
-            self.next_pos = self.next_pos + Pos::from_usize(next_ch_len);
-        } else {
-            self.ch = None;
-            self.pos = self.next_pos;
-        }
-    }
-
-    fn nextch(&self) -> Option<char> {
-        let next_src_index = self.src_index(self.next_pos);
-        if next_src_index < self.end_src_index {
-            Some(char_at(&self.src, next_src_index))
-        } else {
-            None
-        }
-    }
-
-    #[inline]
-    fn nextch_is(&self, c: char) -> bool {
-        self.nextch() == Some(c)
-    }
-
-    fn nextnextch(&self) -> Option<char> {
-        let next_src_index = self.src_index(self.next_pos);
-        if next_src_index < self.end_src_index {
-            let next_next_src_index =
-                next_src_index + char_at(&self.src, next_src_index).len_utf8();
-            if next_next_src_index < self.end_src_index {
-                return Some(char_at(&self.src, next_next_src_index));
-            }
-        }
-        None
-    }
-
-    #[inline]
-    fn nextnextch_is(&self, c: char) -> bool {
-        self.nextnextch() == Some(c)
-    }
-
-    /// Eats <XID_start><XID_continue>*, if possible.
-    fn scan_optional_raw_name(&mut self) -> Option<ast::Name> {
-        if !ident_start(self.ch) {
-            return None;
-        }
-
-        let start = self.pos;
-        self.bump();
-
-        while ident_continue(self.ch) {
-            self.bump();
-        }
-
-        self.with_str_from(start, |string| {
-            if string == "_" {
-                self.sess.span_diagnostic
-                    .struct_span_warn(self.mk_sp(start, self.pos),
-                                      "underscore literal suffix is not allowed")
-                    .warn("this was previously accepted by the compiler but is \
-                          being phased out; it will become a hard error in \
-                          a future release!")
-                    .note("for more information, see issue #42326 \
-                          <https://github.com/rust-lang/rust/issues/42326>")
-                    .emit();
-                None
-            } else {
-                Some(Symbol::intern(string))
-            }
-        })
-    }
-
-    /// PRECONDITION: self.ch is not whitespace
-    /// Eats any kind of comment.
-    fn scan_comment(&mut self) -> Option<TokenAndSpan> {
-        if let Some(c) = self.ch {
-            if c.is_whitespace() {
-                let msg = "called consume_any_line_comment, but there was whitespace";
-                self.sess.span_diagnostic.span_err(self.mk_sp(self.pos, self.pos), msg);
-            }
-        }
-
-        if self.ch_is('/') {
-            match self.nextch() {
-                Some('/') => {
-                    self.bump();
-                    self.bump();
-
-                    // line comments starting with "///" or "//!" are doc-comments
-                    let doc_comment = (self.ch_is('/') && !self.nextch_is('/')) || self.ch_is('!');
-                    let start_bpos = self.pos - BytePos(2);
-
-                    while !self.is_eof() {
-                        match self.ch.unwrap() {
-                            '\n' => break,
-                            '\r' => {
-                                if self.nextch_is('\n') {
-                                    // CRLF
-                                    break;
-                                } else if doc_comment {
-                                    self.err_span_(self.pos,
-                                                   self.next_pos,
-                                                   "bare CR not allowed in doc-comment");
-                                }
-                            }
-                            _ => (),
-                        }
-                        self.bump();
-                    }
-
-                    let tok = if doc_comment {
-                        self.with_str_from(start_bpos, |string| {
-                            token::DocComment(Symbol::intern(string))
-                        })
+                if !terminated {
+                    let msg = if is_doc_comment {
+                        "unterminated block doc-comment"
                     } else {
-                        token::Comment
+                        "unterminated block comment"
                     };
-                    Some(TokenAndSpan { tok, sp: self.mk_sp(start_bpos, self.pos) })
-                }
-                Some('*') => {
-                    self.bump();
-                    self.bump();
-                    self.scan_block_comment()
-                }
-                _ => None,
-            }
-        } else if self.ch_is('#') {
-            if self.nextch_is('!') {
-
-                // Parse an inner attribute.
-                if self.nextnextch_is('[') {
-                    return None;
-                }
-
-                let is_beginning_of_file = self.pos == self.source_file.start_pos;
-                if is_beginning_of_file {
-                    debug!("Skipping a shebang");
-                    let start = self.pos;
-                    while !self.ch_is('\n') && !self.is_eof() {
-                        self.bump();
-                    }
-                    return Some(TokenAndSpan {
-                        tok: token::Shebang(self.name_from(start)),
-                        sp: self.mk_sp(start, self.pos),
-                    });
-                }
-            }
-            None
-        } else {
-            None
-        }
-    }
-
-    /// If there is whitespace, shebang, or a comment, scan it. Otherwise,
-    /// return `None`.
-    fn scan_whitespace_or_comment(&mut self) -> Option<TokenAndSpan> {
-        match self.ch.unwrap_or('\0') {
-            // # to handle shebang at start of file -- this is the entry point
-            // for skipping over all "junk"
-            '/' | '#' => {
-                let c = self.scan_comment();
-                debug!("scanning a comment {:?}", c);
-                c
-            },
-            c if is_pattern_whitespace(Some(c)) => {
-                let start_bpos = self.pos;
-                while is_pattern_whitespace(self.ch) {
-                    self.bump();
-                }
-                let c = Some(TokenAndSpan {
-                    tok: token::Whitespace,
-                    sp: self.mk_sp(start_bpos, self.pos),
-                });
-                debug!("scanning whitespace: {:?}", c);
-                c
-            }
-            _ => None,
-        }
-    }
-
-    /// Might return a sugared-doc-attr
-    fn scan_block_comment(&mut self) -> Option<TokenAndSpan> {
-        // block comments starting with "/**" or "/*!" are doc-comments
-        let is_doc_comment = self.ch_is('*') || self.ch_is('!');
-        let start_bpos = self.pos - BytePos(2);
-
-        let mut level: isize = 1;
-        let mut has_cr = false;
-        while level > 0 {
-            if self.is_eof() {
-                let msg = if is_doc_comment {
-                    "unterminated block doc-comment"
-                } else {
-                    "unterminated block comment"
-                };
-                let last_bpos = self.pos;
-                self.fatal_span_(start_bpos, last_bpos, msg).raise();
-            }
-            let n = self.ch.unwrap();
-            match n {
-                '/' if self.nextch_is('*') => {
-                    level += 1;
-                    self.bump();
-                }
-                '*' if self.nextch_is('/') => {
-                    level -= 1;
-                    self.bump();
-                }
-                '\r' => {
-                    has_cr = true;
+                    let last_bpos = self.pos;
+                    self.fatal_span_(start, last_bpos, msg).raise();
                 }
-                _ => (),
-            }
-            self.bump();
-        }
 
-        self.with_str_from(start_bpos, |string| {
-            // but comments with only "*"s between two "/"s are not
-            let tok = if is_block_doc_comment(string) {
-                let string = if has_cr {
-                    self.translate_crlf(start_bpos,
+                let tok = if is_doc_comment {
+                    self.forbid_bare_cr(start,
                                         string,
-                                        "bare CR not allowed in block doc-comment")
+                                        "bare CR not allowed in block doc-comment");
+                    token::DocComment(Symbol::intern(string))
                 } else {
-                    string.into()
+                    token::Comment
                 };
-                token::DocComment(Symbol::intern(&string[..]))
-            } else {
-                token::Comment
-            };
-
-            Some(TokenAndSpan {
-                tok,
-                sp: self.mk_sp(start_bpos, self.pos),
-            })
-        })
-    }
-
-    /// Scan through any digits (base `scan_radix`) or underscores,
-    /// and return how many digits there were.
-    ///
-    /// `real_radix` represents the true radix of the number we're
-    /// interested in, and errors will be emitted for any digits
-    /// between `real_radix` and `scan_radix`.
-    fn scan_digits(&mut self, real_radix: u32, scan_radix: u32) -> usize {
-        assert!(real_radix <= scan_radix);
-        let mut len = 0;
-
-        loop {
-            let c = self.ch;
-            if c == Some('_') {
-                debug!("skipping a _");
-                self.bump();
-                continue;
-            }
-            match c.and_then(|cc| cc.to_digit(scan_radix)) {
-                Some(_) => {
-                    debug!("{:?} in scan_digits", c);
-                    // check that the hypothetical digit is actually
-                    // in range for the true radix
-                    if c.unwrap().to_digit(real_radix).is_none() {
-                        self.err_span_(self.pos,
-                                       self.next_pos,
-                                       &format!("invalid digit for a base {} literal", real_radix));
-                    }
-                    len += 1;
-                    self.bump();
-                }
-                _ => return len,
-            }
-        }
-    }
 
-    /// Lex a LIT_INTEGER or a LIT_FLOAT
-    fn scan_number(&mut self, c: char) -> token::Lit {
-        let mut base = 10;
-        let start_bpos = self.pos;
-        self.bump();
-
-        let num_digits = if c == '0' {
-            match self.ch.unwrap_or('\0') {
-                'b' => {
-                    self.bump();
-                    base = 2;
-                    self.scan_digits(2, 10)
-                }
-                'o' => {
-                    self.bump();
-                    base = 8;
-                    self.scan_digits(8, 10)
-                }
-                'x' => {
-                    self.bump();
-                    base = 16;
-                    self.scan_digits(16, 16)
-                }
-                '0'..='9' | '_' | '.' | 'e' | 'E' => {
-                    self.scan_digits(10, 10) + 1
-                }
-                _ => {
-                    // just a 0
-                    return token::Integer(self.name_from(start_bpos));
-                }
+                tok
             }
-        } else if c.is_digit(10) {
-            self.scan_digits(10, 10) + 1
-        } else {
-            0
-        };
-
-        if num_digits == 0 {
-            self.err_span_(start_bpos, self.pos, "no valid digits found for number");
-
-            return token::Integer(Symbol::intern("0"));
-        }
-
-        // might be a float, but don't be greedy if this is actually an
-        // integer literal followed by field/method access or a range pattern
-        // (`0..2` and `12.foo()`)
-        if self.ch_is('.') && !self.nextch_is('.') &&
-           !ident_start(self.nextch()) {
-            // might have stuff after the ., and if it does, it needs to start
-            // with a number
-            self.bump();
-            if self.ch.unwrap_or('\0').is_digit(10) {
-                self.scan_digits(10, 10);
-                self.scan_float_exponent();
-            }
-            let pos = self.pos;
-            self.check_float_base(start_bpos, pos, base);
-
-            token::Float(self.name_from(start_bpos))
-        } else {
-            // it might be a float if it has an exponent
-            if self.ch_is('e') || self.ch_is('E') {
-                self.scan_float_exponent();
-                let pos = self.pos;
-                self.check_float_base(start_bpos, pos, base);
-                return token::Float(self.name_from(start_bpos));
-            }
-            // but we certainly have an integer!
-            token::Integer(self.name_from(start_bpos))
-        }
-    }
-
-    /// Scan over a float exponent.
-    fn scan_float_exponent(&mut self) {
-        if self.ch_is('e') || self.ch_is('E') {
-            self.bump();
-
-            if self.ch_is('-') || self.ch_is('+') {
-                self.bump();
-            }
-
-            if self.scan_digits(10, 10) == 0 {
-                let mut err = self.struct_span_fatal(
-                    self.pos, self.next_pos,
-                    "expected at least one digit in exponent"
-                );
-                if let Some(ch) = self.ch {
-                    // check for e.g., Unicode minus '−' (Issue #49746)
-                    if unicode_chars::check_for_substitution(self, ch, &mut err) {
-                        self.bump();
-                        self.scan_digits(10, 10);
-                    }
-                }
-                err.emit();
-            }
-        }
-    }
-
-    /// Checks that a base is valid for a floating literal, emitting a nice
-    /// error if it isn't.
-    fn check_float_base(&mut self, start_bpos: BytePos, last_bpos: BytePos, base: usize) {
-        match base {
-            16 => {
-                self.err_span_(start_bpos,
-                               last_bpos,
-                               "hexadecimal float literal is not supported")
-            }
-            8 => {
-                self.err_span_(start_bpos,
-                               last_bpos,
-                               "octal float literal is not supported")
-            }
-            2 => {
-                self.err_span_(start_bpos,
-                               last_bpos,
-                               "binary float literal is not supported")
-            }
-            _ => (),
-        }
-    }
-
-    fn binop(&mut self, op: token::BinOpToken) -> token::Token {
-        self.bump();
-        if self.ch_is('=') {
-            self.bump();
-            token::BinOpEq(op)
-        } else {
-            token::BinOp(op)
-        }
-    }
-
-    /// Returns the next token from the string, advances the input past that
-    /// token, and updates the interner
-    fn next_token_inner(&mut self) -> Result<token::Token, ()> {
-        let c = self.ch;
-
-        if ident_start(c) {
-            let (is_ident_start, is_raw_ident) =
-                match (c.unwrap(), self.nextch(), self.nextnextch()) {
-                    // r# followed by an identifier starter is a raw identifier.
-                    // This is an exception to the r# case below.
-                    ('r', Some('#'), x) if ident_start(x) => (true, true),
-                    // r as in r" or r#" is part of a raw string literal.
-                    // b as in b' is part of a byte literal.
-                    // They are not identifiers, and are handled further down.
-                    ('r', Some('"'), _) |
-                    ('r', Some('#'), _) |
-                    ('b', Some('"'), _) |
-                    ('b', Some('\''), _) |
-                    ('b', Some('r'), Some('"')) |
-                    ('b', Some('r'), Some('#')) => (false, false),
-                    _ => (true, false),
-                };
-
-            if is_ident_start {
-                let raw_start = self.pos;
+            rustc_lexer::TokenKind::Whitespace => token::Whitespace,
+            rustc_lexer::TokenKind::Ident | rustc_lexer::TokenKind::RawIdent => {
+                let is_raw_ident = token == rustc_lexer::TokenKind::RawIdent;
+                let mut ident_start = start;
                 if is_raw_ident {
-                    // Consume the 'r#' characters.
-                    self.bump();
-                    self.bump();
-                }
-
-                let start = self.pos;
-                self.bump();
-
-                while ident_continue(self.ch) {
-                    self.bump();
+                    ident_start = ident_start + BytePos(2);
                 }
-
-                return Ok(self.with_str_from(start, |string| {
-                    // FIXME: perform NFKC normalization here. (Issue #2253)
-                    let ident = self.mk_ident(string);
-
-                    if is_raw_ident {
-                        let span = self.mk_sp(raw_start, self.pos);
-                        if !ident.can_be_raw() {
-                            self.err_span(span, &format!("`{}` cannot be a raw identifier", ident));
-                        }
-                        self.sess.raw_identifier_spans.borrow_mut().push(span);
+                // FIXME: perform NFKC normalization here. (Issue #2253)
+                let sym = self.symbol_from(ident_start);
+                if is_raw_ident {
+                    let span = self.mk_sp(start, self.pos);
+                    if !sym.can_be_raw() {
+                        self.err_span(span, &format!("`{}` cannot be a raw identifier", sym));
                     }
-
-                    token::Ident(ident, is_raw_ident)
-                }));
-            }
-        }
-
-        if is_dec_digit(c) {
-            let num = self.scan_number(c.unwrap());
-            let suffix = self.scan_optional_raw_name();
-            debug!("next_token_inner: scanned number {:?}, {:?}", num, suffix);
-            return Ok(token::Literal(num, suffix));
-        }
-
-        match c.expect("next_token_inner called at EOF") {
-            // One-byte tokens.
-            ';' => {
-                self.bump();
-                Ok(token::Semi)
-            }
-            ',' => {
-                self.bump();
-                Ok(token::Comma)
-            }
-            '.' => {
-                self.bump();
-                if self.ch_is('.') {
-                    self.bump();
-                    if self.ch_is('.') {
-                        self.bump();
-                        Ok(token::DotDotDot)
-                    } else if self.ch_is('=') {
-                        self.bump();
-                        Ok(token::DotDotEq)
+                    self.sess.raw_identifier_spans.borrow_mut().push(span);
+                }
+                token::Ident(sym, is_raw_ident)
+            }
+            rustc_lexer::TokenKind::Literal { kind, suffix_start } => {
+                let suffix_start = start + BytePos(suffix_start as u32);
+                let (kind, symbol) = self.cook_lexer_literal(start, suffix_start, kind);
+                let suffix = if suffix_start < self.pos {
+                    let string = self.str_from(suffix_start);
+                    if string == "_" {
+                        self.sess.span_diagnostic
+                            .struct_span_warn(self.mk_sp(suffix_start, self.pos),
+                                              "underscore literal suffix is not allowed")
+                            .warn("this was previously accepted by the compiler but is \
+                                   being phased out; it will become a hard error in \
+                                   a future release!")
+                            .note("for more information, see issue #42326 \
+                                   <https://github.com/rust-lang/rust/issues/42326>")
+                            .emit();
+                        None
                     } else {
-                        Ok(token::DotDot)
+                        Some(Symbol::intern(string))
                     }
                 } else {
-                    Ok(token::Dot)
-                }
-            }
-            '(' => {
-                self.bump();
-                Ok(token::OpenDelim(token::Paren))
-            }
-            ')' => {
-                self.bump();
-                Ok(token::CloseDelim(token::Paren))
-            }
-            '{' => {
-                self.bump();
-                Ok(token::OpenDelim(token::Brace))
-            }
-            '}' => {
-                self.bump();
-                Ok(token::CloseDelim(token::Brace))
-            }
-            '[' => {
-                self.bump();
-                Ok(token::OpenDelim(token::Bracket))
-            }
-            ']' => {
-                self.bump();
-                Ok(token::CloseDelim(token::Bracket))
-            }
-            '@' => {
-                self.bump();
-                Ok(token::At)
-            }
-            '#' => {
-                self.bump();
-                Ok(token::Pound)
-            }
-            '~' => {
-                self.bump();
-                Ok(token::Tilde)
-            }
-            '?' => {
-                self.bump();
-                Ok(token::Question)
-            }
-            ':' => {
-                self.bump();
-                if self.ch_is(':') {
-                    self.bump();
-                    Ok(token::ModSep)
-                } else {
-                    Ok(token::Colon)
+                    None
+                };
+                token::Literal(token::Lit { kind, symbol, suffix })
+            }
+            rustc_lexer::TokenKind::Lifetime { starts_with_number } => {
+                // Include the leading `'` in the real identifier, for macro
+                // expansion purposes. See #12512 for the gory details of why
+                // this is necessary.
+                let lifetime_name = self.str_from(start);
+                if starts_with_number {
+                    self.err_span_(
+                        start,
+                        self.pos,
+                        "lifetimes cannot start with a number",
+                    );
                 }
+                let ident = Symbol::intern(lifetime_name);
+                token::Lifetime(ident)
+            }
+            rustc_lexer::TokenKind::Semi => token::Semi,
+            rustc_lexer::TokenKind::Comma => token::Comma,
+            rustc_lexer::TokenKind::DotDotDot => token::DotDotDot,
+            rustc_lexer::TokenKind::DotDotEq => token::DotDotEq,
+            rustc_lexer::TokenKind::DotDot => token::DotDot,
+            rustc_lexer::TokenKind::Dot => token::Dot,
+            rustc_lexer::TokenKind::OpenParen => token::OpenDelim(token::Paren),
+            rustc_lexer::TokenKind::CloseParen => token::CloseDelim(token::Paren),
+            rustc_lexer::TokenKind::OpenBrace => token::OpenDelim(token::Brace),
+            rustc_lexer::TokenKind::CloseBrace => token::CloseDelim(token::Brace),
+            rustc_lexer::TokenKind::OpenBracket => token::OpenDelim(token::Bracket),
+            rustc_lexer::TokenKind::CloseBracket => token::CloseDelim(token::Bracket),
+            rustc_lexer::TokenKind::At => token::At,
+            rustc_lexer::TokenKind::Pound => token::Pound,
+            rustc_lexer::TokenKind::Tilde => token::Tilde,
+            rustc_lexer::TokenKind::Question => token::Question,
+            rustc_lexer::TokenKind::ColonColon => token::ModSep,
+            rustc_lexer::TokenKind::Colon => token::Colon,
+            rustc_lexer::TokenKind::Dollar => token::Dollar,
+            rustc_lexer::TokenKind::EqEq => token::EqEq,
+            rustc_lexer::TokenKind::Eq => token::Eq,
+            rustc_lexer::TokenKind::FatArrow => token::FatArrow,
+            rustc_lexer::TokenKind::Ne => token::Ne,
+            rustc_lexer::TokenKind::Not => token::Not,
+            rustc_lexer::TokenKind::Le => token::Le,
+            rustc_lexer::TokenKind::LArrow => token::LArrow,
+            rustc_lexer::TokenKind::Lt => token::Lt,
+            rustc_lexer::TokenKind::ShlEq => token::BinOpEq(token::Shl),
+            rustc_lexer::TokenKind::Shl => token::BinOp(token::Shl),
+            rustc_lexer::TokenKind::Ge => token::Ge,
+            rustc_lexer::TokenKind::Gt => token::Gt,
+            rustc_lexer::TokenKind::ShrEq => token::BinOpEq(token::Shr),
+            rustc_lexer::TokenKind::Shr => token::BinOp(token::Shr),
+            rustc_lexer::TokenKind::RArrow => token::RArrow,
+            rustc_lexer::TokenKind::Minus => token::BinOp(token::Minus),
+            rustc_lexer::TokenKind::MinusEq => token::BinOpEq(token::Minus),
+            rustc_lexer::TokenKind::And => token::BinOp(token::And),
+            rustc_lexer::TokenKind::AndEq => token::BinOpEq(token::And),
+            rustc_lexer::TokenKind::AndAnd => token::AndAnd,
+            rustc_lexer::TokenKind::Or => token::BinOp(token::Or),
+            rustc_lexer::TokenKind::OrEq => token::BinOpEq(token::Or),
+            rustc_lexer::TokenKind::OrOr => token::OrOr,
+            rustc_lexer::TokenKind::Plus => token::BinOp(token::Plus),
+            rustc_lexer::TokenKind::PlusEq => token::BinOpEq(token::Plus),
+            rustc_lexer::TokenKind::Star => token::BinOp(token::Star),
+            rustc_lexer::TokenKind::StarEq => token::BinOpEq(token::Star),
+            rustc_lexer::TokenKind::Slash => token::BinOp(token::Slash),
+            rustc_lexer::TokenKind::SlashEq => token::BinOpEq(token::Slash),
+            rustc_lexer::TokenKind::Caret => token::BinOp(token::Caret),
+            rustc_lexer::TokenKind::CaretEq => token::BinOpEq(token::Caret),
+            rustc_lexer::TokenKind::Percent => token::BinOp(token::Percent),
+            rustc_lexer::TokenKind::PercentEq => token::BinOpEq(token::Percent),
+
+            rustc_lexer::TokenKind::Unknown => {
+                let c = self.str_from(start).chars().next().unwrap();
+                let mut err = self.struct_fatal_span_char(start,
+                                                          self.pos,
+                                                          "unknown start of token",
+                                                          c);
+                // FIXME: the lexer could be used to turn the ASCII version of unicode homoglyphs,
+                // instead of keeping a table in `check_for_substitution`into the token. Ideally,
+                // this should be inside `rustc_lexer`. However, we should first remove compound
+                // tokens like `<<` from `rustc_lexer`, and then add fancier error recovery to it,
+                // as there will be less overall work to do this way.
+                let token = unicode_chars::check_for_substitution(self, start, c, &mut err)
+                    .unwrap_or_else(|| token::Unknown(self.symbol_from(start)));
+                err.emit();
+                token
             }
+        }
+    }
 
-            '$' => {
-                self.bump();
-                Ok(token::Dollar)
-            }
-
-            // Multi-byte tokens.
-            '=' => {
-                self.bump();
-                if self.ch_is('=') {
-                    self.bump();
-                    Ok(token::EqEq)
-                } else if self.ch_is('>') {
-                    self.bump();
-                    Ok(token::FatArrow)
-                } else {
-                    Ok(token::Eq)
+    fn cook_lexer_literal(
+        &self,
+        start: BytePos,
+        suffix_start: BytePos,
+        kind: rustc_lexer::LiteralKind
+    ) -> (token::LitKind, Symbol) {
+        match kind {
+            rustc_lexer::LiteralKind::Char { terminated } => {
+                if !terminated {
+                    self.fatal_span_(start, suffix_start,
+                                     "unterminated character literal".into())
+                        .raise()
                 }
-            }
-            '!' => {
-                self.bump();
-                if self.ch_is('=') {
-                    self.bump();
-                    Ok(token::Ne)
+                let content_start = start + BytePos(1);
+                let content_end = suffix_start - BytePos(1);
+                self.validate_char_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::Char, id)
+            },
+            rustc_lexer::LiteralKind::Byte { terminated } => {
+                if !terminated {
+                    self.fatal_span_(start + BytePos(1), suffix_start,
+                                     "unterminated byte constant".into())
+                        .raise()
+                }
+                let content_start = start + BytePos(2);
+                let content_end = suffix_start - BytePos(1);
+                self.validate_byte_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::Byte, id)
+            },
+            rustc_lexer::LiteralKind::Str { terminated } => {
+                if !terminated {
+                    self.fatal_span_(start, suffix_start,
+                                     "unterminated double quote string".into())
+                        .raise()
+                }
+                let content_start = start + BytePos(1);
+                let content_end = suffix_start - BytePos(1);
+                self.validate_str_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::Str, id)
+            }
+            rustc_lexer::LiteralKind::ByteStr { terminated } => {
+                if !terminated {
+                    self.fatal_span_(start + BytePos(1), suffix_start,
+                                     "unterminated double quote byte string".into())
+                        .raise()
+                }
+                let content_start = start + BytePos(2);
+                let content_end = suffix_start - BytePos(1);
+                self.validate_byte_str_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::ByteStr, id)
+            }
+            rustc_lexer::LiteralKind::RawStr { n_hashes, started, terminated } => {
+                if !started {
+                    self.report_non_started_raw_string(start);
+                }
+                if !terminated {
+                    self.report_unterminated_raw_string(start, n_hashes)
+                }
+                let n_hashes: u16 = self.restrict_n_hashes(start, n_hashes);
+                let n = u32::from(n_hashes);
+                let content_start = start + BytePos(2 + n);
+                let content_end = suffix_start - BytePos(1 + n);
+                self.validate_raw_str_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::StrRaw(n_hashes), id)
+            }
+            rustc_lexer::LiteralKind::RawByteStr { n_hashes, started, terminated } => {
+                if !started {
+                    self.report_non_started_raw_string(start);
+                }
+                if !terminated {
+                    self.report_unterminated_raw_string(start, n_hashes)
+                }
+                let n_hashes: u16 = self.restrict_n_hashes(start, n_hashes);
+                let n = u32::from(n_hashes);
+                let content_start = start + BytePos(3 + n);
+                let content_end = suffix_start - BytePos(1 + n);
+                self.validate_raw_byte_str_escape(content_start, content_end);
+                let id = self.symbol_from_to(content_start, content_end);
+                (token::ByteStrRaw(n_hashes), id)
+            }
+            rustc_lexer::LiteralKind::Int { base, empty_int } => {
+                if empty_int {
+                    self.err_span_(start, suffix_start, "no valid digits found for number");
+                    (token::Integer, sym::integer(0))
                 } else {
-                    Ok(token::Not)
-                }
-            }
-            '<' => {
-                self.bump();
-                match self.ch.unwrap_or('\x00') {
-                    '=' => {
-                        self.bump();
-                        Ok(token::Le)
-                    }
-                    '<' => {
-                        Ok(self.binop(token::Shl))
-                    }
-                    '-' => {
-                        self.bump();
-                        Ok(token::LArrow)
-                    }
-                    _ => {
-                        Ok(token::Lt)
-                    }
+                    self.validate_int_literal(base, start, suffix_start);
+                    (token::Integer, self.symbol_from_to(start, suffix_start))
                 }
-            }
-            '>' => {
-                self.bump();
-                match self.ch.unwrap_or('\x00') {
-                    '=' => {
-                        self.bump();
-                        Ok(token::Ge)
-                    }
-                    '>' => {
-                        Ok(self.binop(token::Shr))
-                    }
-                    _ => {
-                        Ok(token::Gt)
-                    }
-                }
-            }
-            '\'' => {
-                // Either a character constant 'a' OR a lifetime name 'abc
-                let start_with_quote = self.pos;
-                self.bump();
-                let start = self.pos;
-
-                // If the character is an ident start not followed by another single
-                // quote, then this is a lifetime name:
-                let starts_with_number = self.ch.unwrap_or('\x00').is_numeric();
-                if (ident_start(self.ch) || starts_with_number) && !self.nextch_is('\'') {
-                    self.bump();
-                    while ident_continue(self.ch) {
-                        self.bump();
-                    }
-                    // lifetimes shouldn't end with a single quote
-                    // if we find one, then this is an invalid character literal
-                    if self.ch_is('\'') {
-                        let id = self.name_from(start);
-                        self.bump();
-                        self.validate_char_escape(start_with_quote);
-                        return Ok(token::Literal(token::Char(id), None))
-                    }
-
-                    // Include the leading `'` in the real identifier, for macro
-                    // expansion purposes. See #12512 for the gory details of why
-                    // this is necessary.
-                    let ident = self.with_str_from(start_with_quote, |lifetime_name| {
-                        self.mk_ident(lifetime_name)
-                    });
-
-                    if starts_with_number {
-                        // this is a recovered lifetime written `'1`, error but accept it
-                        self.err_span_(
-                            start_with_quote,
-                            self.pos,
-                            "lifetimes cannot start with a number",
-                        );
-                    }
-
-                    return Ok(token::Lifetime(ident));
-                }
-                let msg = "unterminated character literal";
-                let id = self.scan_single_quoted_string(start_with_quote, msg);
-                self.validate_char_escape(start_with_quote);
-                let suffix = self.scan_optional_raw_name();
-                Ok(token::Literal(token::Char(id), suffix))
-            }
-            'b' => {
-                self.bump();
-                let lit = match self.ch {
-                    Some('\'') => {
-                        let start_with_quote = self.pos;
-                        self.bump();
-                        let msg = "unterminated byte constant";
-                        let id = self.scan_single_quoted_string(start_with_quote, msg);
-                        self.validate_byte_escape(start_with_quote);
-                        token::Byte(id)
-                    },
-                    Some('"') => {
-                        let start_with_quote = self.pos;
-                        let msg = "unterminated double quote byte string";
-                        let id = self.scan_double_quoted_string(msg);
-                        self.validate_byte_str_escape(start_with_quote);
-                        token::ByteStr(id)
-                    },
-                    Some('r') => self.scan_raw_byte_string(),
-                    _ => unreachable!(),  // Should have been a token::Ident above.
-                };
-                let suffix = self.scan_optional_raw_name();
-
-                Ok(token::Literal(lit, suffix))
-            }
-            '"' => {
-                let start_with_quote = self.pos;
-                let msg = "unterminated double quote string";
-                let id = self.scan_double_quoted_string(msg);
-                self.validate_str_escape(start_with_quote);
-                let suffix = self.scan_optional_raw_name();
-                Ok(token::Literal(token::Str_(id), suffix))
-            }
-            'r' => {
-                let start_bpos = self.pos;
-                self.bump();
-                let mut hash_count: u16 = 0;
-                while self.ch_is('#') {
-                    if hash_count == 65535 {
-                        let bpos = self.next_pos;
-                        self.fatal_span_(start_bpos,
-                                         bpos,
-                                         "too many `#` symbols: raw strings may be \
-                                         delimited by up to 65535 `#` symbols").raise();
-                    }
-                    self.bump();
-                    hash_count += 1;
+            },
+            rustc_lexer::LiteralKind::Float { base, empty_exponent } => {
+                if empty_exponent {
+                    let mut err = self.struct_span_fatal(
+                        start, self.pos,
+                        "expected at least one digit in exponent"
+                    );
+                    err.emit();
                 }
 
-                if self.is_eof() {
-                    self.fail_unterminated_raw_string(start_bpos, hash_count);
-                } else if !self.ch_is('"') {
-                    let last_bpos = self.pos;
-                    let curr_char = self.ch.unwrap();
-                    self.fatal_span_char(start_bpos,
-                                         last_bpos,
-                                         "found invalid character; only `#` is allowed \
-                                         in raw string delimitation",
-                                         curr_char).raise();
-                }
-                self.bump();
-                let content_start_bpos = self.pos;
-                let mut content_end_bpos;
-                let mut valid = true;
-                'outer: loop {
-                    if self.is_eof() {
-                        self.fail_unterminated_raw_string(start_bpos, hash_count);
+                match base {
+                    Base::Hexadecimal => {
+                        self.err_span_(start, suffix_start,
+                                       "hexadecimal float literal is not supported")
                     }
-                    // if self.ch_is('"') {
-                    // content_end_bpos = self.pos;
-                    // for _ in 0..hash_count {
-                    // self.bump();
-                    // if !self.ch_is('#') {
-                    // continue 'outer;
-                    let c = self.ch.unwrap();
-                    match c {
-                        '"' => {
-                            content_end_bpos = self.pos;
-                            for _ in 0..hash_count {
-                                self.bump();
-                                if !self.ch_is('#') {
-                                    continue 'outer;
-                                }
-                            }
-                            break;
-                        }
-                        '\r' => {
-                            if !self.nextch_is('\n') {
-                                let last_bpos = self.pos;
-                                self.err_span_(start_bpos,
-                                               last_bpos,
-                                               "bare CR not allowed in raw string, use \\r \
-                                                instead");
-                                valid = false;
-                            }
-                        }
-                        _ => (),
-                    }
-                    self.bump();
-                }
-
-                self.bump();
-                let id = if valid {
-                    self.name_from_to(content_start_bpos, content_end_bpos)
-                } else {
-                    Symbol::intern("??")
-                };
-                let suffix = self.scan_optional_raw_name();
-
-                Ok(token::Literal(token::StrRaw(id, hash_count), suffix))
-            }
-            '-' => {
-                if self.nextch_is('>') {
-                    self.bump();
-                    self.bump();
-                    Ok(token::RArrow)
-                } else {
-                    Ok(self.binop(token::Minus))
-                }
-            }
-            '&' => {
-                if self.nextch_is('&') {
-                    self.bump();
-                    self.bump();
-                    Ok(token::AndAnd)
-                } else {
-                    Ok(self.binop(token::And))
-                }
-            }
-            '|' => {
-                match self.nextch() {
-                    Some('|') => {
-                        self.bump();
-                        self.bump();
-                        Ok(token::OrOr)
+                    Base::Octal => {
+                        self.err_span_(start, suffix_start,
+                                       "octal float literal is not supported")
                     }
-                    _ => {
-                        Ok(self.binop(token::Or))
+                    Base::Binary => {
+                        self.err_span_(start, suffix_start,
+                                       "binary float literal is not supported")
                     }
+                    _ => ()
                 }
-            }
-            '+' => {
-                Ok(self.binop(token::Plus))
-            }
-            '*' => {
-                Ok(self.binop(token::Star))
-            }
-            '/' => {
-                Ok(self.binop(token::Slash))
-            }
-            '^' => {
-                Ok(self.binop(token::Caret))
-            }
-            '%' => {
-                Ok(self.binop(token::Percent))
-            }
-            c => {
-                let last_bpos = self.pos;
-                let bpos = self.next_pos;
-                let mut err = self.struct_fatal_span_char(last_bpos,
-                                                          bpos,
-                                                          "unknown start of token",
-                                                          c);
-                unicode_chars::check_for_substitution(self, c, &mut err);
-                self.fatal_errs.push(err);
 
-                Err(())
-            }
+                let id = self.symbol_from_to(start, suffix_start);
+                (token::Float, id)
+            },
         }
     }
 
-    fn read_to_eol(&mut self) -> String {
-        let mut val = String::new();
-        while !self.ch_is('\n') && !self.is_eof() {
-            val.push(self.ch.unwrap());
-            self.bump();
-        }
-
-        if self.ch_is('\n') {
-            self.bump();
-        }
+    #[inline]
+    fn src_index(&self, pos: BytePos) -> usize {
+        (pos - self.start_pos).to_usize()
+    }
 
-        val
+    /// Slice of the source text from `start` up to but excluding `self.pos`,
+    /// meaning the slice does not include the character `self.ch`.
+    fn str_from(&self, start: BytePos) -> &str
+    {
+        self.str_from_to(start, self.pos)
     }
 
-    fn read_one_line_comment(&mut self) -> String {
-        let val = self.read_to_eol();
-        assert!((val.as_bytes()[0] == b'/' && val.as_bytes()[1] == b'/') ||
-                (val.as_bytes()[0] == b'#' && val.as_bytes()[1] == b'!'));
-        val
+    /// Creates a Symbol from a given offset to the current offset.
+    fn symbol_from(&self, start: BytePos) -> Symbol {
+        debug!("taking an ident from {:?} to {:?}", start, self.pos);
+        Symbol::intern(self.str_from(start))
     }
 
-    fn consume_non_eol_whitespace(&mut self) {
-        while is_pattern_whitespace(self.ch) && !self.ch_is('\n') && !self.is_eof() {
-            self.bump();
-        }
+    /// As symbol_from, with an explicit endpoint.
+    fn symbol_from_to(&self, start: BytePos, end: BytePos) -> Symbol {
+        debug!("taking an ident from {:?} to {:?}", start, end);
+        Symbol::intern(self.str_from_to(start, end))
     }
 
-    fn peeking_at_comment(&self) -> bool {
-        (self.ch_is('/') && self.nextch_is('/')) || (self.ch_is('/') && self.nextch_is('*')) ||
-        // consider shebangs comments, but not inner attributes
-        (self.ch_is('#') && self.nextch_is('!') && !self.nextnextch_is('['))
+    /// Slice of the source text spanning from `start` up to but excluding `end`.
+    fn str_from_to(&self, start: BytePos, end: BytePos) -> &str
+    {
+        &self.src[self.src_index(start)..self.src_index(end)]
     }
 
-    fn scan_single_quoted_string(&mut self,
-                                 start_with_quote: BytePos,
-                                 unterminated_msg: &str) -> ast::Name {
-        // assumes that first `'` is consumed
-        let start = self.pos;
-        // lex `'''` as a single char, for recovery
-        if self.ch_is('\'') && self.nextch_is('\'') {
-            self.bump();
-        } else {
-            let mut first = true;
-            loop {
-                if self.ch_is('\'') {
-                    break;
-                }
-                if self.ch_is('\\') && (self.nextch_is('\'') || self.nextch_is('\\')) {
-                    self.bump();
-                    self.bump();
-                } else {
-                    // Only attempt to infer single line string literals. If we encounter
-                    // a slash, bail out in order to avoid nonsensical suggestion when
-                    // involving comments.
-                    if self.is_eof()
-                        || (self.ch_is('/') && !first)
-                        || (self.ch_is('\n') && !self.nextch_is('\'')) {
-
-                        self.fatal_span_(start_with_quote, self.pos, unterminated_msg.into())
-                            .raise()
-                    }
-                    self.bump();
-                }
-                first = false;
-            }
+    fn forbid_bare_cr(&self, start: BytePos, s: &str, errmsg: &str) {
+        let mut idx = 0;
+        loop {
+            idx = match s[idx..].find('\r') {
+                None => break,
+                Some(it) => idx + it + 1
+            };
+            self.err_span_(start + BytePos(idx as u32 - 1),
+                           start + BytePos(idx as u32),
+                           errmsg);
+        }
+    }
+
+    fn report_non_started_raw_string(&self, start: BytePos) -> ! {
+        let bad_char = self.str_from(start).chars().last().unwrap();
+        self
+            .struct_fatal_span_char(
+                start,
+                self.pos,
+                "found invalid character; only `#` is allowed \
+                 in raw string delimitation",
+                bad_char,
+            )
+            .emit();
+        FatalError.raise()
+    }
+
+    fn report_unterminated_raw_string(&self, start: BytePos, n_hashes: usize) -> ! {
+        let mut err = self.struct_span_fatal(
+            start, start,
+            "unterminated raw string",
+        );
+        err.span_label(
+            self.mk_sp(start, start),
+            "unterminated raw string",
+        );
+
+        if n_hashes > 0 {
+            err.note(&format!("this raw string should be terminated with `\"{}`",
+                                "#".repeat(n_hashes as usize)));
         }
 
-        let id = self.name_from(start);
-        self.bump();
-        id
+        err.emit();
+        FatalError.raise()
     }
 
-    fn scan_double_quoted_string(&mut self, unterminated_msg: &str) -> ast::Name {
-        debug_assert!(self.ch_is('\"'));
-        let start_with_quote = self.pos;
-        self.bump();
-        let start = self.pos;
-        while !self.ch_is('"') {
-            if self.is_eof() {
-                let pos = self.pos;
-                self.fatal_span_(start_with_quote, pos, unterminated_msg).raise();
-            }
-            if self.ch_is('\\') && (self.nextch_is('\\') || self.nextch_is('"')) {
-                self.bump();
+    fn restrict_n_hashes(&self, start: BytePos, n_hashes: usize) -> u16 {
+        match n_hashes.try_into() {
+            Ok(n_hashes) => n_hashes,
+            Err(_) => {
+                self.fatal_span_(start,
+                                 self.pos,
+                                 "too many `#` symbols: raw strings may be \
+                                  delimited by up to 65535 `#` symbols").raise();
             }
-            self.bump();
         }
-        let id = self.name_from(start);
-        self.bump();
-        id
     }
 
-    fn scan_raw_byte_string(&mut self) -> token::Lit {
-        let start_bpos = self.pos;
-        self.bump();
-        let mut hash_count = 0;
-        while self.ch_is('#') {
-            if hash_count == 65535 {
-                let bpos = self.next_pos;
-                self.fatal_span_(start_bpos,
-                                 bpos,
-                                 "too many `#` symbols: raw byte strings may be \
-                                 delimited by up to 65535 `#` symbols").raise();
-            }
-            self.bump();
-            hash_count += 1;
+    fn validate_char_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        if let Err((off, err)) = unescape::unescape_char(lit) {
+            emit_unescape_error(
+                &self.sess.span_diagnostic,
+                lit,
+                self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                unescape::Mode::Char,
+                0..off,
+                err,
+            )
         }
+    }
 
-        if self.is_eof() {
-            self.fail_unterminated_raw_string(start_bpos, hash_count);
-        } else if !self.ch_is('"') {
-            let pos = self.pos;
-            let ch = self.ch.unwrap();
-            self.fatal_span_char(start_bpos,
-                                        pos,
-                                        "found invalid character; only `#` is allowed in raw \
-                                         string delimitation",
-                                        ch).raise();
+    fn validate_byte_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        if let Err((off, err)) = unescape::unescape_byte(lit) {
+            emit_unescape_error(
+                &self.sess.span_diagnostic,
+                lit,
+                self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                unescape::Mode::Byte,
+                0..off,
+                err,
+            )
         }
-        self.bump();
-        let content_start_bpos = self.pos;
-        let mut content_end_bpos;
-        'outer: loop {
-            match self.ch {
-                None => {
-                    self.fail_unterminated_raw_string(start_bpos, hash_count);
-                }
-                Some('"') => {
-                    content_end_bpos = self.pos;
-                    for _ in 0..hash_count {
-                        self.bump();
-                        if !self.ch_is('#') {
-                            continue 'outer;
-                        }
-                    }
-                    break;
-                }
-                Some(c) => {
-                    if c > '\x7F' {
-                        let pos = self.pos;
-                        self.err_span_char(pos, pos, "raw byte string must be ASCII", c);
-                    }
-                }
-            }
-            self.bump();
-        }
-
-        self.bump();
-
-        token::ByteStrRaw(self.name_from_to(content_start_bpos, content_end_bpos), hash_count)
     }
 
-    fn validate_char_escape(&self, start_with_quote: BytePos) {
-        self.with_str_from_to(start_with_quote + BytePos(1), self.pos - BytePos(1), |lit| {
-            if let Err((off, err)) = unescape::unescape_char(lit) {
+    fn validate_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        unescape::unescape_str(lit, &mut |range, c| {
+            if let Err(err) = c {
                 emit_unescape_error(
                     &self.sess.span_diagnostic,
                     lit,
-                    self.mk_sp(start_with_quote, self.pos),
-                    unescape::Mode::Char,
-                    0..off,
+                    self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                    unescape::Mode::Str,
+                    range,
                     err,
                 )
             }
-        });
+        })
     }
 
-    fn validate_byte_escape(&self, start_with_quote: BytePos) {
-        self.with_str_from_to(start_with_quote + BytePos(1), self.pos - BytePos(1), |lit| {
-            if let Err((off, err)) = unescape::unescape_byte(lit) {
+    fn validate_raw_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        unescape::unescape_raw_str(lit, &mut |range, c| {
+            if let Err(err) = c {
                 emit_unescape_error(
                     &self.sess.span_diagnostic,
                     lit,
-                    self.mk_sp(start_with_quote, self.pos),
-                    unescape::Mode::Byte,
-                    0..off,
+                    self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                    unescape::Mode::Str,
+                    range,
                     err,
                 )
             }
-        });
+        })
     }
 
-    fn validate_str_escape(&self, start_with_quote: BytePos) {
-        self.with_str_from_to(start_with_quote + BytePos(1), self.pos - BytePos(1), |lit| {
-            unescape::unescape_str(lit, &mut |range, c| {
-                if let Err(err) = c {
-                    emit_unescape_error(
-                        &self.sess.span_diagnostic,
-                        lit,
-                        self.mk_sp(start_with_quote, self.pos),
-                        unescape::Mode::Str,
-                        range,
-                        err,
-                    )
-                }
-            })
-        });
+    fn validate_raw_byte_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        unescape::unescape_raw_byte_str(lit, &mut |range, c| {
+            if let Err(err) = c {
+                emit_unescape_error(
+                    &self.sess.span_diagnostic,
+                    lit,
+                    self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                    unescape::Mode::ByteStr,
+                    range,
+                    err,
+                )
+            }
+        })
     }
 
-    fn validate_byte_str_escape(&self, start_with_quote: BytePos) {
-        self.with_str_from_to(start_with_quote + BytePos(1), self.pos - BytePos(1), |lit| {
-            unescape::unescape_byte_str(lit, &mut |range, c| {
-                if let Err(err) = c {
-                    emit_unescape_error(
-                        &self.sess.span_diagnostic,
-                        lit,
-                        self.mk_sp(start_with_quote, self.pos),
-                        unescape::Mode::ByteStr,
-                        range,
-                        err,
-                    )
-                }
-            })
-        });
+    fn validate_byte_str_escape(&self, content_start: BytePos, content_end: BytePos) {
+        let lit = self.str_from_to(content_start, content_end);
+        unescape::unescape_byte_str(lit, &mut |range, c| {
+            if let Err(err) = c {
+                emit_unescape_error(
+                    &self.sess.span_diagnostic,
+                    lit,
+                    self.mk_sp(content_start - BytePos(1), content_end + BytePos(1)),
+                    unescape::Mode::ByteStr,
+                    range,
+                    err,
+                )
+            }
+        })
     }
-}
 
-// This tests the character for the unicode property 'PATTERN_WHITE_SPACE' which
-// is guaranteed to be forward compatible. http://unicode.org/reports/tr31/#R3
-#[inline]
-crate fn is_pattern_whitespace(c: Option<char>) -> bool {
-    c.map_or(false, Pattern_White_Space)
-}
-
-#[inline]
-fn in_range(c: Option<char>, lo: char, hi: char) -> bool {
-    c.map_or(false, |c| lo <= c && c <= hi)
-}
+    fn validate_int_literal(&self, base: Base, content_start: BytePos, content_end: BytePos) {
+        let base = match base {
+            Base::Binary => 2,
+            Base::Octal => 8,
+            _ => return,
+        };
+        let s = self.str_from_to(content_start + BytePos(2), content_end);
+        for (idx, c) in s.char_indices() {
+            let idx = idx as u32;
+            if c != '_' && c.to_digit(base).is_none() {
+                let lo = content_start + BytePos(2 + idx);
+                let hi = content_start + BytePos(2 + idx + c.len_utf8() as u32);
+                self.err_span_(lo, hi,
+                               &format!("invalid digit for a base {} literal", base));
 
-#[inline]
-fn is_dec_digit(c: Option<char>) -> bool {
-    in_range(c, '0', '9')
+            }
+        }
+    }
 }
 
 fn is_doc_comment(s: &str) -> bool {
@@ -1522,296 +682,3 @@ fn is_block_doc_comment(s: &str) -> bool {
     debug!("is {:?} a doc comment? {}", s, res);
     res
 }
-
-/// Determine whether `c` is a valid start for an ident.
-fn ident_start(c: Option<char>) -> bool {
-    let c = match c {
-        Some(c) => c,
-        None => return false,
-    };
-
-    (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_' || (c > '\x7f' && c.is_xid_start())
-}
-
-fn ident_continue(c: Option<char>) -> bool {
-    let c = match c {
-        Some(c) => c,
-        None => return false,
-    };
-
-    (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') || c == '_' ||
-    (c > '\x7f' && c.is_xid_continue())
-}
-
-#[inline]
-fn char_at(s: &str, byte: usize) -> char {
-    s[byte..].chars().next().unwrap()
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    use crate::ast::{Ident, CrateConfig};
-    use crate::symbol::Symbol;
-    use crate::source_map::{SourceMap, FilePathMapping};
-    use crate::feature_gate::UnstableFeatures;
-    use crate::parse::token;
-    use crate::diagnostics::plugin::ErrorMap;
-    use crate::with_globals;
-    use std::io;
-    use std::path::PathBuf;
-    use syntax_pos::{BytePos, Span, NO_EXPANSION};
-    use rustc_data_structures::fx::{FxHashSet, FxHashMap};
-    use rustc_data_structures::sync::Lock;
-
-    fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
-        let emitter = errors::emitter::EmitterWriter::new(Box::new(io::sink()),
-                                                          Some(sm.clone()),
-                                                          false,
-                                                          false,
-                                                          false);
-        ParseSess {
-            span_diagnostic: errors::Handler::with_emitter(true, None, Box::new(emitter)),
-            unstable_features: UnstableFeatures::from_environment(),
-            config: CrateConfig::default(),
-            included_mod_stack: Lock::new(Vec::new()),
-            source_map: sm,
-            missing_fragment_specifiers: Lock::new(FxHashSet::default()),
-            raw_identifier_spans: Lock::new(Vec::new()),
-            registered_diagnostics: Lock::new(ErrorMap::new()),
-            buffered_lints: Lock::new(vec![]),
-            ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
-        }
-    }
-
-    // open a string reader for the given string
-    fn setup<'a>(sm: &SourceMap,
-                 sess: &'a ParseSess,
-                 teststr: String)
-                 -> StringReader<'a> {
-        let sf = sm.new_source_file(PathBuf::from(teststr.clone()).into(), teststr);
-        let mut sr = StringReader::new_raw(sess, sf, None);
-        if sr.advance_token().is_err() {
-            sr.emit_fatal_errors();
-            FatalError.raise();
-        }
-        sr
-    }
-
-    #[test]
-    fn t1() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            let mut string_reader = setup(&sm,
-                                        &sh,
-                                        "/* my source file */ fn main() { println!(\"zebra\"); }\n"
-                                            .to_string());
-            let id = Ident::from_str("fn");
-            assert_eq!(string_reader.next_token().tok, token::Comment);
-            assert_eq!(string_reader.next_token().tok, token::Whitespace);
-            let tok1 = string_reader.next_token();
-            let tok2 = TokenAndSpan {
-                tok: token::Ident(id, false),
-                sp: Span::new(BytePos(21), BytePos(23), NO_EXPANSION),
-            };
-            assert_eq!(tok1.tok, tok2.tok);
-            assert_eq!(tok1.sp, tok2.sp);
-            assert_eq!(string_reader.next_token().tok, token::Whitespace);
-            // the 'main' id is already read:
-            assert_eq!(string_reader.pos.clone(), BytePos(28));
-            // read another token:
-            let tok3 = string_reader.next_token();
-            let tok4 = TokenAndSpan {
-                tok: mk_ident("main"),
-                sp: Span::new(BytePos(24), BytePos(28), NO_EXPANSION),
-            };
-            assert_eq!(tok3.tok, tok4.tok);
-            assert_eq!(tok3.sp, tok4.sp);
-            // the lparen is already read:
-            assert_eq!(string_reader.pos.clone(), BytePos(29))
-        })
-    }
-
-    // check that the given reader produces the desired stream
-    // of tokens (stop checking after exhausting the expected vec)
-    fn check_tokenization(mut string_reader: StringReader<'_>, expected: Vec<token::Token>) {
-        for expected_tok in &expected {
-            assert_eq!(&string_reader.next_token().tok, expected_tok);
-        }
-    }
-
-    // make the identifier by looking up the string in the interner
-    fn mk_ident(id: &str) -> token::Token {
-        token::Token::from_ast_ident(Ident::from_str(id))
-    }
-
-    #[test]
-    fn doublecolonparsing() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            check_tokenization(setup(&sm, &sh, "a b".to_string()),
-                            vec![mk_ident("a"), token::Whitespace, mk_ident("b")]);
-        })
-    }
-
-    #[test]
-    fn dcparsing_2() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            check_tokenization(setup(&sm, &sh, "a::b".to_string()),
-                            vec![mk_ident("a"), token::ModSep, mk_ident("b")]);
-        })
-    }
-
-    #[test]
-    fn dcparsing_3() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            check_tokenization(setup(&sm, &sh, "a ::b".to_string()),
-                            vec![mk_ident("a"), token::Whitespace, token::ModSep, mk_ident("b")]);
-        })
-    }
-
-    #[test]
-    fn dcparsing_4() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            check_tokenization(setup(&sm, &sh, "a:: b".to_string()),
-                            vec![mk_ident("a"), token::ModSep, token::Whitespace, mk_ident("b")]);
-        })
-    }
-
-    #[test]
-    fn character_a() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            assert_eq!(setup(&sm, &sh, "'a'".to_string()).next_token().tok,
-                    token::Literal(token::Char(Symbol::intern("a")), None));
-        })
-    }
-
-    #[test]
-    fn character_space() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            assert_eq!(setup(&sm, &sh, "' '".to_string()).next_token().tok,
-                    token::Literal(token::Char(Symbol::intern(" ")), None));
-        })
-    }
-
-    #[test]
-    fn character_escaped() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            assert_eq!(setup(&sm, &sh, "'\\n'".to_string()).next_token().tok,
-                    token::Literal(token::Char(Symbol::intern("\\n")), None));
-        })
-    }
-
-    #[test]
-    fn lifetime_name() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            assert_eq!(setup(&sm, &sh, "'abc".to_string()).next_token().tok,
-                    token::Lifetime(Ident::from_str("'abc")));
-        })
-    }
-
-    #[test]
-    fn raw_string() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            assert_eq!(setup(&sm, &sh, "r###\"\"#a\\b\x00c\"\"###".to_string())
-                        .next_token()
-                        .tok,
-                    token::Literal(token::StrRaw(Symbol::intern("\"#a\\b\x00c\""), 3), None));
-        })
-    }
-
-    #[test]
-    fn literal_suffixes() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            macro_rules! test {
-                ($input: expr, $tok_type: ident, $tok_contents: expr) => {{
-                    assert_eq!(setup(&sm, &sh, format!("{}suffix", $input)).next_token().tok,
-                            token::Literal(token::$tok_type(Symbol::intern($tok_contents)),
-                                            Some(Symbol::intern("suffix"))));
-                    // with a whitespace separator:
-                    assert_eq!(setup(&sm, &sh, format!("{} suffix", $input)).next_token().tok,
-                            token::Literal(token::$tok_type(Symbol::intern($tok_contents)),
-                                            None));
-                }}
-            }
-
-            test!("'a'", Char, "a");
-            test!("b'a'", Byte, "a");
-            test!("\"a\"", Str_, "a");
-            test!("b\"a\"", ByteStr, "a");
-            test!("1234", Integer, "1234");
-            test!("0b101", Integer, "0b101");
-            test!("0xABC", Integer, "0xABC");
-            test!("1.0", Float, "1.0");
-            test!("1.0e10", Float, "1.0e10");
-
-            assert_eq!(setup(&sm, &sh, "2us".to_string()).next_token().tok,
-                    token::Literal(token::Integer(Symbol::intern("2")),
-                                    Some(Symbol::intern("us"))));
-            assert_eq!(setup(&sm, &sh, "r###\"raw\"###suffix".to_string()).next_token().tok,
-                    token::Literal(token::StrRaw(Symbol::intern("raw"), 3),
-                                    Some(Symbol::intern("suffix"))));
-            assert_eq!(setup(&sm, &sh, "br###\"raw\"###suffix".to_string()).next_token().tok,
-                    token::Literal(token::ByteStrRaw(Symbol::intern("raw"), 3),
-                                    Some(Symbol::intern("suffix"))));
-        })
-    }
-
-    #[test]
-    fn line_doc_comments() {
-        assert!(is_doc_comment("///"));
-        assert!(is_doc_comment("/// blah"));
-        assert!(!is_doc_comment("////"));
-    }
-
-    #[test]
-    fn nested_block_comments() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            let mut lexer = setup(&sm, &sh, "/* /* */ */'a'".to_string());
-            match lexer.next_token().tok {
-                token::Comment => {}
-                _ => panic!("expected a comment!"),
-            }
-            assert_eq!(lexer.next_token().tok,
-                    token::Literal(token::Char(Symbol::intern("a")), None));
-        })
-    }
-
-    #[test]
-    fn crlf_comments() {
-        with_globals(|| {
-            let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
-            let sh = mk_sess(sm.clone());
-            let mut lexer = setup(&sm, &sh, "// test\r\n/// test\r\n".to_string());
-            let comment = lexer.next_token();
-            assert_eq!(comment.tok, token::Comment);
-            assert_eq!((comment.sp.lo(), comment.sp.hi()), (BytePos(0), BytePos(7)));
-            assert_eq!(lexer.next_token().tok, token::Whitespace);
-            assert_eq!(lexer.next_token().tok,
-                    token::DocComment(Symbol::intern("/// test")));
-        })
-    }
-}
diff --git a/src/libsyntax/parse/lexer/tests.rs b/src/libsyntax/parse/lexer/tests.rs
new file mode 100644
index 00000000000..94570140996
--- /dev/null
+++ b/src/libsyntax/parse/lexer/tests.rs
@@ -0,0 +1,231 @@
+use super::*;
+
+use crate::symbol::Symbol;
+use crate::source_map::{SourceMap, FilePathMapping};
+use crate::parse::token;
+use crate::with_default_globals;
+use std::io;
+use std::path::PathBuf;
+use errors::{Handler, emitter::EmitterWriter};
+use syntax_pos::{BytePos, Span};
+
+fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
+    let emitter = EmitterWriter::new(Box::new(io::sink()), Some(sm.clone()), false, false, false);
+    ParseSess::with_span_handler(Handler::with_emitter(true, None, Box::new(emitter)), sm)
+}
+
+// open a string reader for the given string
+fn setup<'a>(sm: &SourceMap,
+                sess: &'a ParseSess,
+                teststr: String)
+                -> StringReader<'a> {
+    let sf = sm.new_source_file(PathBuf::from(teststr.clone()).into(), teststr);
+    StringReader::new(sess, sf, None)
+}
+
+#[test]
+fn t1() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        let mut string_reader = setup(&sm,
+                                    &sh,
+                                    "/* my source file */ fn main() { println!(\"zebra\"); }\n"
+                                        .to_string());
+        assert_eq!(string_reader.next_token(), token::Comment);
+        assert_eq!(string_reader.next_token(), token::Whitespace);
+        let tok1 = string_reader.next_token();
+        let tok2 = Token::new(
+            mk_ident("fn"),
+            Span::with_root_ctxt(BytePos(21), BytePos(23)),
+        );
+        assert_eq!(tok1.kind, tok2.kind);
+        assert_eq!(tok1.span, tok2.span);
+        assert_eq!(string_reader.next_token(), token::Whitespace);
+        // read another token:
+        let tok3 = string_reader.next_token();
+        assert_eq!(string_reader.pos.clone(), BytePos(28));
+        let tok4 = Token::new(
+            mk_ident("main"),
+            Span::with_root_ctxt(BytePos(24), BytePos(28)),
+        );
+        assert_eq!(tok3.kind, tok4.kind);
+        assert_eq!(tok3.span, tok4.span);
+
+        assert_eq!(string_reader.next_token(), token::OpenDelim(token::Paren));
+        assert_eq!(string_reader.pos.clone(), BytePos(29))
+    })
+}
+
+// check that the given reader produces the desired stream
+// of tokens (stop checking after exhausting the expected vec)
+fn check_tokenization(mut string_reader: StringReader<'_>, expected: Vec<TokenKind>) {
+    for expected_tok in &expected {
+        assert_eq!(&string_reader.next_token(), expected_tok);
+    }
+}
+
+// make the identifier by looking up the string in the interner
+fn mk_ident(id: &str) -> TokenKind {
+    token::Ident(Symbol::intern(id), false)
+}
+
+fn mk_lit(kind: token::LitKind, symbol: &str, suffix: Option<&str>) -> TokenKind {
+    TokenKind::lit(kind, Symbol::intern(symbol), suffix.map(Symbol::intern))
+}
+
+#[test]
+fn doublecolonparsing() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        check_tokenization(setup(&sm, &sh, "a b".to_string()),
+                        vec![mk_ident("a"), token::Whitespace, mk_ident("b")]);
+    })
+}
+
+#[test]
+fn dcparsing_2() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        check_tokenization(setup(&sm, &sh, "a::b".to_string()),
+                        vec![mk_ident("a"), token::ModSep, mk_ident("b")]);
+    })
+}
+
+#[test]
+fn dcparsing_3() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        check_tokenization(setup(&sm, &sh, "a ::b".to_string()),
+                        vec![mk_ident("a"), token::Whitespace, token::ModSep, mk_ident("b")]);
+    })
+}
+
+#[test]
+fn dcparsing_4() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        check_tokenization(setup(&sm, &sh, "a:: b".to_string()),
+                        vec![mk_ident("a"), token::ModSep, token::Whitespace, mk_ident("b")]);
+    })
+}
+
+#[test]
+fn character_a() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        assert_eq!(setup(&sm, &sh, "'a'".to_string()).next_token(),
+                    mk_lit(token::Char, "a", None));
+    })
+}
+
+#[test]
+fn character_space() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        assert_eq!(setup(&sm, &sh, "' '".to_string()).next_token(),
+                    mk_lit(token::Char, " ", None));
+    })
+}
+
+#[test]
+fn character_escaped() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        assert_eq!(setup(&sm, &sh, "'\\n'".to_string()).next_token(),
+                    mk_lit(token::Char, "\\n", None));
+    })
+}
+
+#[test]
+fn lifetime_name() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        assert_eq!(setup(&sm, &sh, "'abc".to_string()).next_token(),
+                    token::Lifetime(Symbol::intern("'abc")));
+    })
+}
+
+#[test]
+fn raw_string() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        assert_eq!(setup(&sm, &sh, "r###\"\"#a\\b\x00c\"\"###".to_string()).next_token(),
+                    mk_lit(token::StrRaw(3), "\"#a\\b\x00c\"", None));
+    })
+}
+
+#[test]
+fn literal_suffixes() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        macro_rules! test {
+            ($input: expr, $tok_type: ident, $tok_contents: expr) => {{
+                assert_eq!(setup(&sm, &sh, format!("{}suffix", $input)).next_token(),
+                            mk_lit(token::$tok_type, $tok_contents, Some("suffix")));
+                // with a whitespace separator:
+                assert_eq!(setup(&sm, &sh, format!("{} suffix", $input)).next_token(),
+                            mk_lit(token::$tok_type, $tok_contents, None));
+            }}
+        }
+
+        test!("'a'", Char, "a");
+        test!("b'a'", Byte, "a");
+        test!("\"a\"", Str, "a");
+        test!("b\"a\"", ByteStr, "a");
+        test!("1234", Integer, "1234");
+        test!("0b101", Integer, "0b101");
+        test!("0xABC", Integer, "0xABC");
+        test!("1.0", Float, "1.0");
+        test!("1.0e10", Float, "1.0e10");
+
+        assert_eq!(setup(&sm, &sh, "2us".to_string()).next_token(),
+                    mk_lit(token::Integer, "2", Some("us")));
+        assert_eq!(setup(&sm, &sh, "r###\"raw\"###suffix".to_string()).next_token(),
+                    mk_lit(token::StrRaw(3), "raw", Some("suffix")));
+        assert_eq!(setup(&sm, &sh, "br###\"raw\"###suffix".to_string()).next_token(),
+                    mk_lit(token::ByteStrRaw(3), "raw", Some("suffix")));
+    })
+}
+
+#[test]
+fn line_doc_comments() {
+    assert!(is_doc_comment("///"));
+    assert!(is_doc_comment("/// blah"));
+    assert!(!is_doc_comment("////"));
+}
+
+#[test]
+fn nested_block_comments() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        let mut lexer = setup(&sm, &sh, "/* /* */ */'a'".to_string());
+        assert_eq!(lexer.next_token(), token::Comment);
+        assert_eq!(lexer.next_token(), mk_lit(token::Char, "a", None));
+    })
+}
+
+#[test]
+fn crlf_comments() {
+    with_default_globals(|| {
+        let sm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
+        let sh = mk_sess(sm.clone());
+        let mut lexer = setup(&sm, &sh, "// test\r\n/// test\r\n".to_string());
+        let comment = lexer.next_token();
+        assert_eq!(comment.kind, token::Comment);
+        assert_eq!((comment.span.lo(), comment.span.hi()), (BytePos(0), BytePos(7)));
+        assert_eq!(lexer.next_token(), token::Whitespace);
+        assert_eq!(lexer.next_token(), token::DocComment(Symbol::intern("/// test")));
+    })
+}
diff --git a/src/libsyntax/parse/lexer/tokentrees.rs b/src/libsyntax/parse/lexer/tokentrees.rs
index 4bfc5bb16c0..37e67a2729e 100644
--- a/src/libsyntax/parse/lexer/tokentrees.rs
+++ b/src/libsyntax/parse/lexer/tokentrees.rs
@@ -2,15 +2,16 @@ use syntax_pos::Span;
 
 use crate::print::pprust::token_to_string;
 use crate::parse::lexer::{StringReader, UnmatchedBrace};
-use crate::parse::{token, PResult};
-use crate::tokenstream::{DelimSpan, IsJoint::*, TokenStream, TokenTree, TreeAndJoint};
+use crate::parse::token::{self, Token};
+use crate::parse::PResult;
+use crate::tokenstream::{DelimSpan, IsJoint::{self, *}, TokenStream, TokenTree, TreeAndJoint};
 
 impl<'a> StringReader<'a> {
     crate fn into_token_trees(self) -> (PResult<'a, TokenStream>, Vec<UnmatchedBrace>) {
         let mut tt_reader = TokenTreesReader {
             string_reader: self,
-            token: token::Eof,
-            span: syntax_pos::DUMMY_SP,
+            token: Token::dummy(),
+            joint_to_prev: Joint,
             open_braces: Vec::new(),
             unmatched_braces: Vec::new(),
             matching_delim_spans: Vec::new(),
@@ -23,8 +24,8 @@ impl<'a> StringReader<'a> {
 
 struct TokenTreesReader<'a> {
     string_reader: StringReader<'a>,
-    token: token::Token,
-    span: Span,
+    token: Token,
+    joint_to_prev: IsJoint,
     /// Stack of open delimiters and their spans. Used for error message.
     open_braces: Vec<(token::DelimToken, Span)>,
     unmatched_braces: Vec<UnmatchedBrace>,
@@ -52,7 +53,7 @@ impl<'a> TokenTreesReader<'a> {
     fn parse_token_trees_until_close_delim(&mut self) -> TokenStream {
         let mut tts = vec![];
         loop {
-            if let token::CloseDelim(..) = self.token {
+            if let token::CloseDelim(..) = self.token.kind {
                 return TokenStream::new(tts);
             }
 
@@ -68,11 +69,11 @@ impl<'a> TokenTreesReader<'a> {
 
     fn parse_token_tree(&mut self) -> PResult<'a, TreeAndJoint> {
         let sm = self.string_reader.sess.source_map();
-        match self.token {
+        match self.token.kind {
             token::Eof => {
                 let msg = "this file contains an un-closed delimiter";
                 let mut err = self.string_reader.sess.span_diagnostic
-                    .struct_span_err(self.span, msg);
+                    .struct_span_err(self.token.span, msg);
                 for &(_, sp) in &self.open_braces {
                     err.span_label(sp, "un-closed delimiter");
                 }
@@ -102,10 +103,10 @@ impl<'a> TokenTreesReader<'a> {
             },
             token::OpenDelim(delim) => {
                 // The span for beginning of the delimited section
-                let pre_span = self.span;
+                let pre_span = self.token.span;
 
                 // Parse the open delimiter.
-                self.open_braces.push((delim, self.span));
+                self.open_braces.push((delim, self.token.span));
                 self.real_token();
 
                 // Parse the token trees within the delimiters.
@@ -114,9 +115,9 @@ impl<'a> TokenTreesReader<'a> {
                 let tts = self.parse_token_trees_until_close_delim();
 
                 // Expand to cover the entire delimited token tree
-                let delim_span = DelimSpan::from_pair(pre_span, self.span);
+                let delim_span = DelimSpan::from_pair(pre_span, self.token.span);
 
-                match self.token {
+                match self.token.kind {
                     // Correct delimiter.
                     token::CloseDelim(d) if d == delim => {
                         let (open_brace, open_brace_span) = self.open_braces.pop().unwrap();
@@ -126,7 +127,7 @@ impl<'a> TokenTreesReader<'a> {
                             self.matching_delim_spans.clear();
                         } else {
                             self.matching_delim_spans.push(
-                                (open_brace, open_brace_span, self.span),
+                                (open_brace, open_brace_span, self.token.span),
                             );
                         }
                         // Parse the close delimiter.
@@ -136,16 +137,16 @@ impl<'a> TokenTreesReader<'a> {
                     token::CloseDelim(other) => {
                         let mut unclosed_delimiter = None;
                         let mut candidate = None;
-                        if self.last_unclosed_found_span != Some(self.span) {
+                        if self.last_unclosed_found_span != Some(self.token.span) {
                             // do not complain about the same unclosed delimiter multiple times
-                            self.last_unclosed_found_span = Some(self.span);
+                            self.last_unclosed_found_span = Some(self.token.span);
                             // This is a conservative error: only report the last unclosed
                             // delimiter. The previous unclosed delimiters could actually be
                             // closed! The parser just hasn't gotten to them yet.
                             if let Some(&(_, sp)) = self.open_braces.last() {
                                 unclosed_delimiter = Some(sp);
                             };
-                            if let Some(current_padding) = sm.span_to_margin(self.span) {
+                            if let Some(current_padding) = sm.span_to_margin(self.token.span) {
                                 for (brace, brace_span) in &self.open_braces {
                                     if let Some(padding) = sm.span_to_margin(*brace_span) {
                                         // high likelihood of these two corresponding
@@ -159,7 +160,7 @@ impl<'a> TokenTreesReader<'a> {
                             self.unmatched_braces.push(UnmatchedBrace {
                                 expected_delim: tok,
                                 found_delim: other,
-                                found_span: self.span,
+                                found_span: self.token.span,
                                 unclosed_span: unclosed_delimiter,
                                 candidate_span: candidate,
                             });
@@ -198,29 +199,32 @@ impl<'a> TokenTreesReader<'a> {
                 let token_str = token_to_string(&self.token);
                 let msg = format!("unexpected close delimiter: `{}`", token_str);
                 let mut err = self.string_reader.sess.span_diagnostic
-                    .struct_span_err(self.span, &msg);
-                err.span_label(self.span, "unexpected close delimiter");
+                    .struct_span_err(self.token.span, &msg);
+                err.span_label(self.token.span, "unexpected close delimiter");
                 Err(err)
             },
             _ => {
-                let tt = TokenTree::Token(self.span, self.token.clone());
-                // Note that testing for joint-ness here is done via the raw
-                // source span as the joint-ness is a property of the raw source
-                // rather than wanting to take `override_span` into account.
-                // Additionally, we actually check if the *next* pair of tokens
-                // is joint, but this is equivalent to checking the current pair.
-                let raw = self.string_reader.peek_span_src_raw;
+                let tt = TokenTree::Token(self.token.take());
                 self.real_token();
-                let is_joint = raw.hi() == self.string_reader.peek_span_src_raw.lo()
-                    && token::is_op(&self.token);
+                let is_joint = self.joint_to_prev == Joint && self.token.is_op();
                 Ok((tt, if is_joint { Joint } else { NonJoint }))
             }
         }
     }
 
     fn real_token(&mut self) {
-        let t = self.string_reader.real_token();
-        self.token = t.tok;
-        self.span = t.sp;
+        self.joint_to_prev = Joint;
+        loop {
+            let token = self.string_reader.next_token();
+            match token.kind {
+                token::Whitespace | token::Comment | token::Shebang(_) | token::Unknown(_) => {
+                    self.joint_to_prev = NonJoint;
+                }
+                _ => {
+                    self.token = token;
+                    return;
+                },
+            }
+        }
     }
 }
diff --git a/src/libsyntax/parse/lexer/unicode_chars.rs b/src/libsyntax/parse/lexer/unicode_chars.rs
index 94ce6297fbe..525b4215aff 100644
--- a/src/libsyntax/parse/lexer/unicode_chars.rs
+++ b/src/libsyntax/parse/lexer/unicode_chars.rs
@@ -1,10 +1,12 @@
 // Characters and their corresponding confusables were collected from
 // http://www.unicode.org/Public/security/10.0.0/confusables.txt
 
-use syntax_pos::{Span, Pos, NO_EXPANSION};
-use errors::{Applicability, DiagnosticBuilder};
 use super::StringReader;
+use errors::{Applicability, DiagnosticBuilder};
+use syntax_pos::{BytePos, Pos, Span, symbol::kw};
+use crate::parse::token;
 
+#[rustfmt::skip] // for line breaks
 const UNICODE_ARRAY: &[(char, &str, char)] = &[
     ('
', "Line Separator", ' '),
     ('
', "Paragraph Separator", ' '),
@@ -49,7 +51,7 @@ const UNICODE_ARRAY: &[(char, &str, char)] = &[
     ('─', "Box Drawings Light Horizontal", '-'),
     ('━', "Box Drawings Heavy Horizontal", '-'),
     ('㇐', "CJK Stroke H", '-'),
-    ('ꟷ', "Latin Epigraphic Letter Dideways", '-'),
+    ('ꟷ', "Latin Epigraphic Letter Sideways I", '-'),
     ('ᅳ', "Hangul Jungseong Eu", '-'),
     ('ㅡ', "Hangul Letter Eu", '-'),
     ('一', "CJK Unified Ideograph-4E00", '-'),
@@ -293,74 +295,98 @@ const UNICODE_ARRAY: &[(char, &str, char)] = &[
     ('〉', "Right-Pointing Angle Bracket", '>'),
     ('〉', "Right Angle Bracket", '>'),
     ('》', "Right Double Angle Bracket", '>'),
-    ('＞', "Fullwidth Greater-Than Sign", '>'), ];
-
-
-const ASCII_ARRAY: &[(char, &str)] = &[
-    (' ', "Space"),
-    ('_', "Underscore"),
-    ('-', "Minus/Hyphen"),
-    (',', "Comma"),
-    (';', "Semicolon"),
-    (':', "Colon"),
-    ('!', "Exclamation Mark"),
-    ('?', "Question Mark"),
-    ('.', "Period"),
-    ('\'', "Single Quote"),
-    ('"', "Quotation Mark"),
-    ('(', "Left Parenthesis"),
-    (')', "Right Parenthesis"),
-    ('[', "Left Square Bracket"),
-    (']', "Right Square Bracket"),
-    ('{', "Left Curly Brace"),
-    ('}', "Right Curly Brace"),
-    ('*', "Asterisk"),
-    ('/', "Slash"),
-    ('\\', "Backslash"),
-    ('&', "Ampersand"),
-    ('+', "Plus Sign"),
-    ('<', "Less-Than Sign"),
-    ('=', "Equals Sign"),
-    ('>', "Greater-Than Sign"), ];
-
-crate fn check_for_substitution<'a>(reader: &StringReader<'a>,
-                                  ch: char,
-                                  err: &mut DiagnosticBuilder<'a>) -> bool {
-    UNICODE_ARRAY
-    .iter()
-    .find(|&&(c, _, _)| c == ch)
-    .map(|&(_, u_name, ascii_char)| {
-        let span = Span::new(reader.pos, reader.next_pos, NO_EXPANSION);
-        match ASCII_ARRAY.iter().find(|&&(c, _)| c == ascii_char) {
-            Some(&(ascii_char, ascii_name)) => {
-                // special help suggestion for "directed" double quotes
-                if let Some(s) = reader.peek_delimited('“', '”') {
-                    let msg = format!("Unicode characters '“' (Left Double Quotation Mark) and \
-                        '”' (Right Double Quotation Mark) look like '{}' ({}), but are not",
-                                ascii_char, ascii_name);
-                    err.span_suggestion(
-                        Span::new(reader.pos, reader.next_pos + Pos::from_usize(s.len()) +
-                            Pos::from_usize('”'.len_utf8()), NO_EXPANSION),
-                        &msg,
-                        format!("\"{}\"", s),
-                        Applicability::MaybeIncorrect);
-                } else {
-                    let msg =
-                        format!("Unicode character '{}' ({}) looks like '{}' ({}), but it is not",
-                                ch, u_name, ascii_char, ascii_name);
-                    err.span_suggestion(
-                        span,
-                        &msg,
-                        ascii_char.to_string(),
-                        Applicability::MaybeIncorrect);
-                }
-                true
-            },
-            None => {
-                let msg = format!("substitution character not found for '{}'", ch);
-                reader.sess.span_diagnostic.span_bug_no_panic(span, &msg);
-                false
-            }
+    ('＞', "Fullwidth Greater-Than Sign", '>'),
+];
+
+// FIXME: the lexer could be used to turn the ASCII version of unicode homoglyphs, instead of
+// keeping the substitution token in this table. Ideally, this should be inside `rustc_lexer`.
+// However, we should first remove compound tokens like `<<` from `rustc_lexer`, and then add
+// fancier error recovery to it, as there will be less overall work to do this way.
+const ASCII_ARRAY: &[(char, &str, Option<token::TokenKind>)] = &[
+    (' ', "Space", Some(token::Whitespace)),
+    ('_', "Underscore", Some(token::Ident(kw::Underscore, false))),
+    ('-', "Minus/Hyphen", Some(token::BinOp(token::Minus))),
+    (',', "Comma", Some(token::Comma)),
+    (';', "Semicolon", Some(token::Semi)),
+    (':', "Colon", Some(token::Colon)),
+    ('!', "Exclamation Mark", Some(token::Not)),
+    ('?', "Question Mark", Some(token::Question)),
+    ('.', "Period", Some(token::Dot)),
+    ('(', "Left Parenthesis", Some(token::OpenDelim(token::Paren))),
+    (')', "Right Parenthesis", Some(token::CloseDelim(token::Paren))),
+    ('[', "Left Square Bracket", Some(token::OpenDelim(token::Bracket))),
+    (']', "Right Square Bracket", Some(token::CloseDelim(token::Bracket))),
+    ('{', "Left Curly Brace", Some(token::OpenDelim(token::Brace))),
+    ('}', "Right Curly Brace", Some(token::CloseDelim(token::Brace))),
+    ('*', "Asterisk", Some(token::BinOp(token::Star))),
+    ('/', "Slash", Some(token::BinOp(token::Slash))),
+    ('\\', "Backslash", None),
+    ('&', "Ampersand", Some(token::BinOp(token::And))),
+    ('+', "Plus Sign", Some(token::BinOp(token::Plus))),
+    ('<', "Less-Than Sign", Some(token::Lt)),
+    ('=', "Equals Sign", Some(token::Eq)),
+    ('>', "Greater-Than Sign", Some(token::Gt)),
+    // FIXME: Literals are already lexed by this point, so we can't recover gracefully just by
+    // spitting the correct token out.
+    ('\'', "Single Quote", None),
+    ('"', "Quotation Mark", None),
+];
+
+crate fn check_for_substitution<'a>(
+    reader: &StringReader<'a>,
+    pos: BytePos,
+    ch: char,
+    err: &mut DiagnosticBuilder<'a>,
+) -> Option<token::TokenKind> {
+    let (u_name, ascii_char) = match UNICODE_ARRAY.iter().find(|&&(c, _, _)| c == ch) {
+        Some(&(_u_char, u_name, ascii_char)) => (u_name, ascii_char),
+        None => return None,
+    };
+
+    let span = Span::with_root_ctxt(pos, pos + Pos::from_usize(ch.len_utf8()));
+
+    let (ascii_name, token) = match ASCII_ARRAY.iter().find(|&&(c, _, _)| c == ascii_char) {
+        Some((_ascii_char, ascii_name, token)) => (ascii_name, token),
+        None => {
+            let msg = format!("substitution character not found for '{}'", ch);
+            reader.sess.span_diagnostic.span_bug_no_panic(span, &msg);
+            return None;
         }
-    }).unwrap_or(false)
+    };
+
+    // special help suggestion for "directed" double quotes
+    if let Some(s) = peek_delimited(&reader.src[reader.src_index(pos)..], '“', '”') {
+        let msg = format!(
+            "Unicode characters '“' (Left Double Quotation Mark) and \
+             '”' (Right Double Quotation Mark) look like '{}' ({}), but are not",
+            ascii_char, ascii_name
+        );
+        err.span_suggestion(
+            Span::with_root_ctxt(
+                pos,
+                pos + Pos::from_usize('“'.len_utf8() + s.len() + '”'.len_utf8()),
+            ),
+            &msg,
+            format!("\"{}\"", s),
+            Applicability::MaybeIncorrect,
+        );
+    } else {
+        let msg = format!(
+            "Unicode character '{}' ({}) looks like '{}' ({}), but it is not",
+            ch, u_name, ascii_char, ascii_name
+        );
+        err.span_suggestion(span, &msg, ascii_char.to_string(), Applicability::MaybeIncorrect);
+    }
+    token.clone()
+}
+
+/// Extract string if found at current position with given delimiters
+fn peek_delimited(text: &str, from_ch: char, to_ch: char) -> Option<&str> {
+    let mut chars = text.chars();
+    let first_char = chars.next()?;
+    if first_char != from_ch {
+        return None;
+    }
+    let last_char_idx = chars.as_str().find(to_ch)?;
+    Some(&chars.as_str()[..last_char_idx])
 }
diff --git a/src/libsyntax/parse/literal.rs b/src/libsyntax/parse/literal.rs
index 53195421ddc..6409acba573 100644
--- a/src/libsyntax/parse/literal.rs
+++ b/src/libsyntax/parse/literal.rs
@@ -1,487 +1,470 @@
 //! Code related to parsing literals.
 
-use crate::ast::{self, Ident, Lit, LitKind};
+use crate::ast::{self, Lit, LitKind};
 use crate::parse::parser::Parser;
 use crate::parse::PResult;
-use crate::parse::token::{self, Token};
-use crate::parse::unescape::{unescape_str, unescape_char, unescape_byte_str, unescape_byte};
+use crate::parse::token::{self, Token, TokenKind};
 use crate::print::pprust;
-use crate::symbol::{keywords, Symbol};
+use crate::symbol::{kw, sym, Symbol};
 use crate::tokenstream::{TokenStream, TokenTree};
 
 use errors::{Applicability, Handler};
 use log::debug;
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::Span;
+use rustc_lexer::unescape::{unescape_char, unescape_byte};
+use rustc_lexer::unescape::{unescape_str, unescape_byte_str};
+use rustc_lexer::unescape::{unescape_raw_str, unescape_raw_byte_str};
 
 use std::ascii;
 
-macro_rules! err {
-    ($opt_diag:expr, |$span:ident, $diag:ident| $($body:tt)*) => {
-        match $opt_diag {
-            Some(($span, $diag)) => { $($body)* }
-            None => return None,
+crate enum LitError {
+    NotLiteral,
+    LexerError,
+    InvalidSuffix,
+    InvalidIntSuffix,
+    InvalidFloatSuffix,
+    NonDecimalFloat(u32),
+    IntTooLarge,
+}
+
+impl LitError {
+    fn report(&self, diag: &Handler, lit: token::Lit, span: Span) {
+        let token::Lit { kind, suffix, .. } = lit;
+        match *self {
+            // `NotLiteral` is not an error by itself, so we don't report
+            // it and give the parser opportunity to try something else.
+            LitError::NotLiteral => {}
+            // `LexerError` *is* an error, but it was already reported
+            // by lexer, so here we don't report it the second time.
+            LitError::LexerError => {}
+            LitError::InvalidSuffix => {
+                expect_no_suffix(
+                    diag, span, &format!("{} {} literal", kind.article(), kind.descr()), suffix
+                );
+            }
+            LitError::InvalidIntSuffix => {
+                let suf = suffix.expect("suffix error with no suffix").as_str();
+                if looks_like_width_suffix(&['i', 'u'], &suf) {
+                    // If it looks like a width, try to be helpful.
+                    let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
+                    diag.struct_span_err(span, &msg)
+                        .help("valid widths are 8, 16, 32, 64 and 128")
+                        .emit();
+                } else {
+                    let msg = format!("invalid suffix `{}` for integer literal", suf);
+                    diag.struct_span_err(span, &msg)
+                        .span_label(span, format!("invalid suffix `{}`", suf))
+                        .help("the suffix must be one of the integral types (`u32`, `isize`, etc)")
+                        .emit();
+                }
+            }
+            LitError::InvalidFloatSuffix => {
+                let suf = suffix.expect("suffix error with no suffix").as_str();
+                if looks_like_width_suffix(&['f'], &suf) {
+                    // If it looks like a width, try to be helpful.
+                    let msg = format!("invalid width `{}` for float literal", &suf[1..]);
+                    diag.struct_span_err(span, &msg)
+                        .help("valid widths are 32 and 64")
+                        .emit();
+                } else {
+                    let msg = format!("invalid suffix `{}` for float literal", suf);
+                    diag.struct_span_err(span, &msg)
+                        .span_label(span, format!("invalid suffix `{}`", suf))
+                        .help("valid suffixes are `f32` and `f64`")
+                        .emit();
+                }
+            }
+            LitError::NonDecimalFloat(base) => {
+                let descr = match base {
+                    16 => "hexadecimal",
+                    8 => "octal",
+                    2 => "binary",
+                    _ => unreachable!(),
+                };
+                diag.struct_span_err(span, &format!("{} float literal is not supported", descr))
+                    .span_label(span, "not supported")
+                    .emit();
+            }
+            LitError::IntTooLarge => {
+                diag.struct_span_err(span, "integer literal is too large")
+                    .emit();
+            }
         }
     }
 }
 
 impl LitKind {
-    /// Converts literal token with a suffix into a semantic literal.
-    /// Works speculatively and may return `None` if diagnostic handler is not passed.
-    /// If diagnostic handler is passed, always returns `Some`,
-    /// possibly after reporting non-fatal errors and recovery.
-    fn from_lit_token(
-        lit: token::Lit,
-        suf: Option<Symbol>,
-        diag: Option<(Span, &Handler)>
-    ) -> Option<LitKind> {
-        if suf.is_some() && !lit.may_have_suffix() {
-            err!(diag, |span, diag| {
-                expect_no_suffix(span, diag, &format!("a {}", lit.literal_name()), suf)
-            });
+    /// Converts literal token into a semantic literal.
+    fn from_lit_token(lit: token::Lit) -> Result<LitKind, LitError> {
+        let token::Lit { kind, symbol, suffix } = lit;
+        if suffix.is_some() && !kind.may_have_suffix() {
+            return Err(LitError::InvalidSuffix);
         }
 
-        Some(match lit {
-            token::Bool(i) => {
-                assert!(i == keywords::True.name() || i == keywords::False.name());
-                LitKind::Bool(i == keywords::True.name())
+        Ok(match kind {
+            token::Bool => {
+                assert!(symbol == kw::True || symbol == kw::False);
+                LitKind::Bool(symbol == kw::True)
             }
-            token::Byte(i) => {
-                match unescape_byte(&i.as_str()) {
-                    Ok(c) => LitKind::Byte(c),
-                    Err(_) => LitKind::Err(i),
-                }
-            },
-            token::Char(i) => {
-                match unescape_char(&i.as_str()) {
-                    Ok(c) => LitKind::Char(c),
-                    Err(_) => LitKind::Err(i),
-                }
-            },
-            token::Err(i) => LitKind::Err(i),
+            token::Byte => return unescape_byte(&symbol.as_str())
+                .map(LitKind::Byte).map_err(|_| LitError::LexerError),
+            token::Char => return unescape_char(&symbol.as_str())
+                .map(LitKind::Char).map_err(|_| LitError::LexerError),
 
             // There are some valid suffixes for integer and float literals,
             // so all the handling is done internally.
-            token::Integer(s) => return integer_lit(&s.as_str(), suf, diag),
-            token::Float(s) => return float_lit(&s.as_str(), suf, diag),
+            token::Integer => return integer_lit(symbol, suffix),
+            token::Float => return float_lit(symbol, suffix),
 
-            token::Str_(mut sym) => {
+            token::Str => {
                 // If there are no characters requiring special treatment we can
-                // reuse the symbol from the Token. Otherwise, we must generate a
+                // reuse the symbol from the token. Otherwise, we must generate a
                 // new symbol because the string in the LitKind is different to the
-                // string in the Token.
-                let mut has_error = false;
-                let s = &sym.as_str();
-                if s.as_bytes().iter().any(|&c| c == b'\\' || c == b'\r') {
+                // string in the token.
+                let s = symbol.as_str();
+                let symbol = if s.contains(&['\\', '\r'][..]) {
                     let mut buf = String::with_capacity(s.len());
-                    unescape_str(s, &mut |_, unescaped_char| {
+                    let mut error = Ok(());
+                    unescape_str(&s, &mut |_, unescaped_char| {
                         match unescaped_char {
                             Ok(c) => buf.push(c),
-                            Err(_) => has_error = true,
+                            Err(_) => error = Err(LitError::LexerError),
                         }
                     });
-                    if has_error {
-                        return Some(LitKind::Err(sym));
-                    }
-                    sym = Symbol::intern(&buf)
-                }
-
-                LitKind::Str(sym, ast::StrStyle::Cooked)
+                    error?;
+                    Symbol::intern(&buf)
+                } else {
+                    symbol
+                };
+                LitKind::Str(symbol, ast::StrStyle::Cooked)
             }
-            token::StrRaw(mut sym, n) => {
+            token::StrRaw(n) => {
                 // Ditto.
-                let s = &sym.as_str();
-                if s.contains('\r') {
-                    sym = Symbol::intern(&raw_str_lit(s));
-                }
-                LitKind::Str(sym, ast::StrStyle::Raw(n))
+                let s = symbol.as_str();
+                let symbol = if s.contains('\r') {
+                    let mut buf = String::with_capacity(s.len());
+                    let mut error = Ok(());
+                    unescape_raw_str(&s, &mut |_, unescaped_char| {
+                        match unescaped_char {
+                            Ok(c) => buf.push(c),
+                            Err(_) => error = Err(LitError::LexerError),
+                        }
+                    });
+                    error?;
+                    buf.shrink_to_fit();
+                    Symbol::intern(&buf)
+                } else {
+                    symbol
+                };
+                LitKind::Str(symbol, ast::StrStyle::Raw(n))
             }
-            token::ByteStr(i) => {
-                let s = &i.as_str();
+            token::ByteStr => {
+                let s = symbol.as_str();
                 let mut buf = Vec::with_capacity(s.len());
-                let mut has_error = false;
-                unescape_byte_str(s, &mut |_, unescaped_byte| {
+                let mut error = Ok(());
+                unescape_byte_str(&s, &mut |_, unescaped_byte| {
                     match unescaped_byte {
                         Ok(c) => buf.push(c),
-                        Err(_) => has_error = true,
+                        Err(_) => error = Err(LitError::LexerError),
                     }
                 });
-                if has_error {
-                    return Some(LitKind::Err(i));
-                }
+                error?;
                 buf.shrink_to_fit();
                 LitKind::ByteStr(Lrc::new(buf))
             }
-            token::ByteStrRaw(i, _) => {
-                LitKind::ByteStr(Lrc::new(i.to_string().into_bytes()))
-            }
+            token::ByteStrRaw(_) => {
+                let s = symbol.as_str();
+                let bytes = if s.contains('\r') {
+                    let mut buf = Vec::with_capacity(s.len());
+                    let mut error = Ok(());
+                    unescape_raw_byte_str(&s, &mut |_, unescaped_byte| {
+                        match unescaped_byte {
+                            Ok(c) => buf.push(c),
+                            Err(_) => error = Err(LitError::LexerError),
+                        }
+                    });
+                    error?;
+                    buf.shrink_to_fit();
+                    buf
+                } else {
+                    symbol.to_string().into_bytes()
+                };
+
+                LitKind::ByteStr(Lrc::new(bytes))
+            },
+            token::Err => LitKind::Err(symbol),
         })
     }
 
     /// Attempts to recover a token from semantic literal.
     /// This function is used when the original token doesn't exist (e.g. the literal is created
     /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
-    pub fn to_lit_token(&self) -> (token::Lit, Option<Symbol>) {
-        match *self {
-            LitKind::Str(string, ast::StrStyle::Cooked) => {
-                let escaped = string.as_str().escape_default().to_string();
-                (token::Lit::Str_(Symbol::intern(&escaped)), None)
+    pub fn to_lit_token(&self) -> token::Lit {
+        let (kind, symbol, suffix) = match *self {
+            LitKind::Str(symbol, ast::StrStyle::Cooked) => {
+                // Don't re-intern unless the escaped string is different.
+                let s = &symbol.as_str();
+                let escaped = s.escape_default().to_string();
+                let symbol = if escaped == *s { symbol } else { Symbol::intern(&escaped) };
+                (token::Str, symbol, None)
             }
-            LitKind::Str(string, ast::StrStyle::Raw(n)) => {
-                (token::Lit::StrRaw(string, n), None)
+            LitKind::Str(symbol, ast::StrStyle::Raw(n)) => {
+                (token::StrRaw(n), symbol, None)
             }
             LitKind::ByteStr(ref bytes) => {
                 let string = bytes.iter().cloned().flat_map(ascii::escape_default)
                     .map(Into::<char>::into).collect::<String>();
-                (token::Lit::ByteStr(Symbol::intern(&string)), None)
+                (token::ByteStr, Symbol::intern(&string), None)
             }
             LitKind::Byte(byte) => {
                 let string: String = ascii::escape_default(byte).map(Into::<char>::into).collect();
-                (token::Lit::Byte(Symbol::intern(&string)), None)
+                (token::Byte, Symbol::intern(&string), None)
             }
             LitKind::Char(ch) => {
                 let string: String = ch.escape_default().map(Into::<char>::into).collect();
-                (token::Lit::Char(Symbol::intern(&string)), None)
+                (token::Char, Symbol::intern(&string), None)
             }
             LitKind::Int(n, ty) => {
                 let suffix = match ty {
-                    ast::LitIntType::Unsigned(ty) => Some(Symbol::intern(ty.ty_to_string())),
-                    ast::LitIntType::Signed(ty) => Some(Symbol::intern(ty.ty_to_string())),
+                    ast::LitIntType::Unsigned(ty) => Some(ty.to_symbol()),
+                    ast::LitIntType::Signed(ty) => Some(ty.to_symbol()),
                     ast::LitIntType::Unsuffixed => None,
                 };
-                (token::Lit::Integer(Symbol::intern(&n.to_string())), suffix)
+                (token::Integer, sym::integer(n), suffix)
             }
             LitKind::Float(symbol, ty) => {
-                (token::Lit::Float(symbol), Some(Symbol::intern(ty.ty_to_string())))
+                (token::Float, symbol, Some(ty.to_symbol()))
+            }
+            LitKind::FloatUnsuffixed(symbol) => {
+                (token::Float, symbol, None)
             }
-            LitKind::FloatUnsuffixed(symbol) => (token::Lit::Float(symbol), None),
             LitKind::Bool(value) => {
-                let kw = if value { keywords::True } else { keywords::False };
-                (token::Lit::Bool(kw.name()), None)
+                let symbol = if value { kw::True } else { kw::False };
+                (token::Bool, symbol, None)
             }
-            LitKind::Err(val) => (token::Lit::Err(val), None),
-        }
+            LitKind::Err(symbol) => {
+                (token::Err, symbol, None)
+            }
+        };
+
+        token::Lit::new(kind, symbol, suffix)
     }
 }
 
 impl Lit {
-    /// Converts literal token with a suffix into an AST literal.
-    /// Works speculatively and may return `None` if diagnostic handler is not passed.
-    /// If diagnostic handler is passed, may return `Some`,
-    /// possibly after reporting non-fatal errors and recovery, or `None` for irrecoverable errors.
-    crate fn from_token(
-        token: &token::Token,
-        span: Span,
-        diag: Option<(Span, &Handler)>,
-    ) -> Option<Lit> {
-        let (token, suffix) = match *token {
-            token::Ident(ident, false) if ident.name == keywords::True.name() ||
-                                          ident.name == keywords::False.name() =>
-                (token::Bool(ident.name), None),
-            token::Literal(token, suffix) =>
-                (token, suffix),
+    /// Converts literal token into an AST literal.
+    fn from_lit_token(token: token::Lit, span: Span) -> Result<Lit, LitError> {
+        Ok(Lit { token, node: LitKind::from_lit_token(token)?, span })
+    }
+
+    /// Converts arbitrary token into an AST literal.
+    crate fn from_token(token: &Token) -> Result<Lit, LitError> {
+        let lit = match token.kind {
+            token::Ident(name, false) if name == kw::True || name == kw::False =>
+                token::Lit::new(token::Bool, name, None),
+            token::Literal(lit) =>
+                lit,
             token::Interpolated(ref nt) => {
                 if let token::NtExpr(expr) | token::NtLiteral(expr) = &**nt {
                     if let ast::ExprKind::Lit(lit) = &expr.node {
-                        return Some(lit.clone());
+                        return Ok(lit.clone());
                     }
                 }
-                return None;
+                return Err(LitError::NotLiteral);
             }
-            _ => return None,
+            _ => return Err(LitError::NotLiteral)
         };
 
-        let node = LitKind::from_lit_token(token, suffix, diag)?;
-        Some(Lit { node, token, suffix, span })
+        Lit::from_lit_token(lit, token.span)
     }
 
     /// Attempts to recover an AST literal from semantic literal.
     /// This function is used when the original token doesn't exist (e.g. the literal is created
     /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
     pub fn from_lit_kind(node: LitKind, span: Span) -> Lit {
-        let (token, suffix) = node.to_lit_token();
-        Lit { node, token, suffix, span }
+        Lit { token: node.to_lit_token(), node, span }
     }
 
     /// Losslessly convert an AST literal into a token stream.
     crate fn tokens(&self) -> TokenStream {
-        let token = match self.token {
-            token::Bool(symbol) => Token::Ident(Ident::with_empty_ctxt(symbol), false),
-            token => Token::Literal(token, self.suffix),
+        let token = match self.token.kind {
+            token::Bool => token::Ident(self.token.symbol, false),
+            _ => token::Literal(self.token),
         };
-        TokenTree::Token(self.span, token).into()
+        TokenTree::token(token, self.span).into()
     }
 }
 
 impl<'a> Parser<'a> {
     /// Matches `lit = true | false | token_lit`.
     crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
-        let diag = Some((self.span, &self.sess.span_diagnostic));
-        if let Some(lit) = Lit::from_token(&self.token, self.span, diag) {
-            self.bump();
-            return Ok(lit);
-        } else if self.token == token::Dot {
-            // Recover `.4` as `0.4`.
-            let recovered = self.look_ahead(1, |t| {
-                if let token::Literal(token::Integer(val), suf) = *t {
-                    let next_span = self.look_ahead_span(1);
-                    if self.span.hi() == next_span.lo() {
-                        let sym = String::from("0.") + &val.as_str();
-                        let token = token::Literal(token::Float(Symbol::intern(&sym)), suf);
-                        return Some((token, self.span.to(next_span)));
+        let mut recovered = None;
+        if self.token == token::Dot {
+            // Attempt to recover `.4` as `0.4`.
+            recovered = self.look_ahead(1, |next_token| {
+                if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix })
+                        = next_token.kind {
+                    if self.token.span.hi() == next_token.span.lo() {
+                        let s = String::from("0.") + &symbol.as_str();
+                        let kind = TokenKind::lit(token::Float, Symbol::intern(&s), suffix);
+                        return Some(Token::new(kind, self.token.span.to(next_token.span)));
                     }
                 }
                 None
             });
-            if let Some((token, span)) = recovered {
+            if let Some(token) = &recovered {
+                self.bump();
                 self.diagnostic()
-                    .struct_span_err(span, "float literals must have an integer part")
+                    .struct_span_err(token.span, "float literals must have an integer part")
                     .span_suggestion(
-                        span,
+                        token.span,
                         "must have an integer part",
-                        pprust::token_to_string(&token),
+                        pprust::token_to_string(token),
                         Applicability::MachineApplicable,
                     )
                     .emit();
-                let diag = Some((span, &self.sess.span_diagnostic));
-                if let Some(lit) = Lit::from_token(&token, span, diag) {
-                    self.bump();
-                    self.bump();
-                    return Ok(lit);
-                }
             }
         }
 
-        Err(self.span_fatal(self.span, &format!("unexpected token: {}", self.this_token_descr())))
-    }
-}
-
-crate fn expect_no_suffix(sp: Span, diag: &Handler, kind: &str, suffix: Option<ast::Name>) {
-    match suffix {
-        None => {/* everything ok */}
-        Some(suf) => {
-            let text = suf.as_str();
-            if text.is_empty() {
-                diag.span_bug(sp, "found empty literal suffix in Some")
+        let token = recovered.as_ref().unwrap_or(&self.token);
+        match Lit::from_token(token) {
+            Ok(lit) => {
+                self.bump();
+                Ok(lit)
+            }
+            Err(LitError::NotLiteral) => {
+                let msg = format!("unexpected token: {}", self.this_token_descr());
+                Err(self.span_fatal(token.span, &msg))
+            }
+            Err(err) => {
+                let (lit, span) = (token.expect_lit(), token.span);
+                self.bump();
+                err.report(&self.sess.span_diagnostic, lit, span);
+                // Pack possible quotes and prefixes from the original literal into
+                // the error literal's symbol so they can be pretty-printed faithfully.
+                let suffixless_lit = token::Lit::new(lit.kind, lit.symbol, None);
+                let symbol = Symbol::intern(&suffixless_lit.to_string());
+                let lit = token::Lit::new(token::Err, symbol, lit.suffix);
+                Lit::from_lit_token(lit, span).map_err(|_| unreachable!())
             }
-            let mut err = if kind == "a tuple index" &&
-                ["i32", "u32", "isize", "usize"].contains(&text.to_string().as_str())
-            {
-                // #59553: warn instead of reject out of hand to allow the fix to percolate
-                // through the ecosystem when people fix their macros
-                let mut err = diag.struct_span_warn(
-                    sp,
-                    &format!("suffixes on {} are invalid", kind),
-                );
-                err.note(&format!(
-                    "`{}` is *temporarily* accepted on tuple index fields as it was \
-                        incorrectly accepted on stable for a few releases",
-                    text,
-                ));
-                err.help(
-                    "on proc macros, you'll want to use `syn::Index::from` or \
-                        `proc_macro::Literal::*_unsuffixed` for code that will desugar \
-                        to tuple field access",
-                );
-                err.note(
-                    "for more context, see https://github.com/rust-lang/rust/issues/60210",
-                );
-                err
-            } else {
-                diag.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
-            };
-            err.span_label(sp, format!("invalid suffix `{}`", text));
-            err.emit();
         }
     }
 }
 
-/// Parses a string representing a raw string literal into its final form. The
-/// only operation this does is convert embedded CRLF into a single LF.
-fn raw_str_lit(lit: &str) -> String {
-    debug!("raw_str_lit: given {}", lit.escape_default());
-    let mut res = String::with_capacity(lit.len());
-
-    let mut chars = lit.chars().peekable();
-    while let Some(c) = chars.next() {
-        if c == '\r' {
-            if *chars.peek().unwrap() != '\n' {
-                panic!("lexer accepted bare CR");
-            }
-            chars.next();
-            res.push('\n');
+crate fn expect_no_suffix(diag: &Handler, sp: Span, kind: &str, suffix: Option<Symbol>) {
+    if let Some(suf) = suffix {
+        let mut err = if kind == "a tuple index" &&
+                         [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suf) {
+            // #59553: warn instead of reject out of hand to allow the fix to percolate
+            // through the ecosystem when people fix their macros
+            let mut err = diag.struct_span_warn(
+                sp,
+                &format!("suffixes on {} are invalid", kind),
+            );
+            err.note(&format!(
+                "`{}` is *temporarily* accepted on tuple index fields as it was \
+                    incorrectly accepted on stable for a few releases",
+                suf,
+            ));
+            err.help(
+                "on proc macros, you'll want to use `syn::Index::from` or \
+                    `proc_macro::Literal::*_unsuffixed` for code that will desugar \
+                    to tuple field access",
+            );
+            err.note(
+                "for more context, see https://github.com/rust-lang/rust/issues/60210",
+            );
+            err
         } else {
-            res.push(c);
-        }
+            diag.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
+        };
+        err.span_label(sp, format!("invalid suffix `{}`", suf));
+        err.emit();
     }
-
-    res.shrink_to_fit();
-    res
 }
 
-// check if `s` looks like i32 or u1234 etc.
+// Checks if `s` looks like i32 or u1234 etc.
 fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
-    s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
+    s.len() > 1 && s.starts_with(first_chars) && s[1..].chars().all(|c| c.is_ascii_digit())
 }
 
-fn filtered_float_lit(data: Symbol, suffix: Option<Symbol>, diag: Option<(Span, &Handler)>)
-                      -> Option<LitKind> {
-    debug!("filtered_float_lit: {}, {:?}", data, suffix);
-    let suffix = match suffix {
-        Some(suffix) => suffix,
-        None => return Some(LitKind::FloatUnsuffixed(data)),
-    };
-
-    Some(match &*suffix.as_str() {
-        "f32" => LitKind::Float(data, ast::FloatTy::F32),
-        "f64" => LitKind::Float(data, ast::FloatTy::F64),
-        suf => {
-            err!(diag, |span, diag| {
-                if suf.len() >= 2 && looks_like_width_suffix(&['f'], suf) {
-                    // if it looks like a width, lets try to be helpful.
-                    let msg = format!("invalid width `{}` for float literal", &suf[1..]);
-                    diag.struct_span_err(span, &msg).help("valid widths are 32 and 64").emit()
-                } else {
-                    let msg = format!("invalid suffix `{}` for float literal", suf);
-                    diag.struct_span_err(span, &msg)
-                        .span_label(span, format!("invalid suffix `{}`", suf))
-                        .help("valid suffixes are `f32` and `f64`")
-                        .emit();
-                }
-            });
+fn strip_underscores(symbol: Symbol) -> Symbol {
+    // Do not allocate a new string unless necessary.
+    let s = symbol.as_str();
+    if s.contains('_') {
+        let mut s = s.to_string();
+        s.retain(|c| c != '_');
+        return Symbol::intern(&s);
+    }
+    symbol
+}
 
-            LitKind::FloatUnsuffixed(data)
+fn filtered_float_lit(symbol: Symbol, suffix: Option<Symbol>, base: u32)
+                      -> Result<LitKind, LitError> {
+    debug!("filtered_float_lit: {:?}, {:?}, {:?}", symbol, suffix, base);
+    if base != 10 {
+        return Err(LitError::NonDecimalFloat(base));
+    }
+    Ok(match suffix {
+        Some(suf) => match suf {
+            sym::f32 => LitKind::Float(symbol, ast::FloatTy::F32),
+            sym::f64 => LitKind::Float(symbol, ast::FloatTy::F64),
+            _ => return Err(LitError::InvalidFloatSuffix),
         }
+        None => LitKind::FloatUnsuffixed(symbol)
     })
 }
-fn float_lit(s: &str, suffix: Option<Symbol>, diag: Option<(Span, &Handler)>)
-                 -> Option<LitKind> {
-    debug!("float_lit: {:?}, {:?}", s, suffix);
-    // FIXME #2252: bounds checking float literals is deferred until trans
-
-    // Strip underscores without allocating a new String unless necessary.
-    let s2;
-    let s = if s.chars().any(|c| c == '_') {
-        s2 = s.chars().filter(|&c| c != '_').collect::<String>();
-        &s2
-    } else {
-        s
-    };
 
-    filtered_float_lit(Symbol::intern(s), suffix, diag)
+fn float_lit(symbol: Symbol, suffix: Option<Symbol>) -> Result<LitKind, LitError> {
+    debug!("float_lit: {:?}, {:?}", symbol, suffix);
+    filtered_float_lit(strip_underscores(symbol), suffix, 10)
 }
 
-fn integer_lit(s: &str, suffix: Option<Symbol>, diag: Option<(Span, &Handler)>)
-                   -> Option<LitKind> {
-    // s can only be ascii, byte indexing is fine
-
-    // Strip underscores without allocating a new String unless necessary.
-    let s2;
-    let mut s = if s.chars().any(|c| c == '_') {
-        s2 = s.chars().filter(|&c| c != '_').collect::<String>();
-        &s2
-    } else {
-        s
-    };
-
-    debug!("integer_lit: {}, {:?}", s, suffix);
+fn integer_lit(symbol: Symbol, suffix: Option<Symbol>) -> Result<LitKind, LitError> {
+    debug!("integer_lit: {:?}, {:?}", symbol, suffix);
+    let symbol = strip_underscores(symbol);
+    let s = symbol.as_str();
 
     let mut base = 10;
-    let orig = s;
-    let mut ty = ast::LitIntType::Unsuffixed;
-
-    if s.starts_with('0') && s.len() > 1 {
+    if s.len() > 1 && s.as_bytes()[0] == b'0' {
         match s.as_bytes()[1] {
             b'x' => base = 16,
             b'o' => base = 8,
             b'b' => base = 2,
-            _ => { }
-        }
-    }
-
-    // 1f64 and 2f32 etc. are valid float literals.
-    if let Some(suf) = suffix {
-        if looks_like_width_suffix(&['f'], &suf.as_str()) {
-            let err = match base {
-                16 => Some("hexadecimal float literal is not supported"),
-                8 => Some("octal float literal is not supported"),
-                2 => Some("binary float literal is not supported"),
-                _ => None,
-            };
-            if let Some(err) = err {
-                err!(diag, |span, diag| {
-                    diag.struct_span_err(span, err)
-                        .span_label(span, "not supported")
-                        .emit();
-                });
-            }
-            return filtered_float_lit(Symbol::intern(s), Some(suf), diag)
+            _ => {}
         }
     }
 
-    if base != 10 {
-        s = &s[2..];
-    }
-
-    if let Some(suf) = suffix {
-        if suf.as_str().is_empty() {
-            err!(diag, |span, diag| diag.span_bug(span, "found empty literal suffix in Some"));
+    let ty = match suffix {
+        Some(suf) => match suf {
+            sym::isize => ast::LitIntType::Signed(ast::IntTy::Isize),
+            sym::i8  => ast::LitIntType::Signed(ast::IntTy::I8),
+            sym::i16 => ast::LitIntType::Signed(ast::IntTy::I16),
+            sym::i32 => ast::LitIntType::Signed(ast::IntTy::I32),
+            sym::i64 => ast::LitIntType::Signed(ast::IntTy::I64),
+            sym::i128 => ast::LitIntType::Signed(ast::IntTy::I128),
+            sym::usize => ast::LitIntType::Unsigned(ast::UintTy::Usize),
+            sym::u8  => ast::LitIntType::Unsigned(ast::UintTy::U8),
+            sym::u16 => ast::LitIntType::Unsigned(ast::UintTy::U16),
+            sym::u32 => ast::LitIntType::Unsigned(ast::UintTy::U32),
+            sym::u64 => ast::LitIntType::Unsigned(ast::UintTy::U64),
+            sym::u128 => ast::LitIntType::Unsigned(ast::UintTy::U128),
+            // `1f64` and `2f32` etc. are valid float literals, and
+            // `fxxx` looks more like an invalid float literal than invalid integer literal.
+            _ if suf.as_str().starts_with('f') => return filtered_float_lit(symbol, suffix, base),
+            _ => return Err(LitError::InvalidIntSuffix),
         }
-        ty = match &*suf.as_str() {
-            "isize" => ast::LitIntType::Signed(ast::IntTy::Isize),
-            "i8"  => ast::LitIntType::Signed(ast::IntTy::I8),
-            "i16" => ast::LitIntType::Signed(ast::IntTy::I16),
-            "i32" => ast::LitIntType::Signed(ast::IntTy::I32),
-            "i64" => ast::LitIntType::Signed(ast::IntTy::I64),
-            "i128" => ast::LitIntType::Signed(ast::IntTy::I128),
-            "usize" => ast::LitIntType::Unsigned(ast::UintTy::Usize),
-            "u8"  => ast::LitIntType::Unsigned(ast::UintTy::U8),
-            "u16" => ast::LitIntType::Unsigned(ast::UintTy::U16),
-            "u32" => ast::LitIntType::Unsigned(ast::UintTy::U32),
-            "u64" => ast::LitIntType::Unsigned(ast::UintTy::U64),
-            "u128" => ast::LitIntType::Unsigned(ast::UintTy::U128),
-            suf => {
-                // i<digits> and u<digits> look like widths, so lets
-                // give an error message along those lines
-                err!(diag, |span, diag| {
-                    if looks_like_width_suffix(&['i', 'u'], suf) {
-                        let msg = format!("invalid width `{}` for integer literal", &suf[1..]);
-                        diag.struct_span_err(span, &msg)
-                            .help("valid widths are 8, 16, 32, 64 and 128")
-                            .emit();
-                    } else {
-                        let msg = format!("invalid suffix `{}` for numeric literal", suf);
-                        diag.struct_span_err(span, &msg)
-                            .span_label(span, format!("invalid suffix `{}`", suf))
-                            .help("the suffix must be one of the integral types \
-                                   (`u32`, `isize`, etc)")
-                            .emit();
-                    }
-                });
-
-                ty
-            }
-        }
-    }
-
-    debug!("integer_lit: the type is {:?}, base {:?}, the new string is {:?}, the original \
-           string was {:?}, the original suffix was {:?}", ty, base, s, orig, suffix);
-
-    Some(match u128::from_str_radix(s, base) {
-        Ok(r) => LitKind::Int(r, ty),
-        Err(_) => {
-            // small bases are lexed as if they were base 10, e.g, the string
-            // might be `0b10201`. This will cause the conversion above to fail,
-            // but these cases have errors in the lexer: we don't want to emit
-            // two errors, and we especially don't want to emit this error since
-            // it isn't necessarily true.
-            let already_errored = base < 10 &&
-                s.chars().any(|c| c.to_digit(10).map_or(false, |d| d >= base));
+        _ => ast::LitIntType::Unsuffixed
+    };
 
-            if !already_errored {
-                err!(diag, |span, diag| diag.span_err(span, "int literal is too large"));
-            }
-            LitKind::Int(0, ty)
-        }
+    let s = &s[if base != 10 { 2 } else { 0 } ..];
+    u128::from_str_radix(s, base).map(|i| LitKind::Int(i, ty)).map_err(|_| {
+        // Small bases are lexed as if they were base 10, e.g, the string
+        // might be `0b10201`. This will cause the conversion above to fail,
+        // but these kinds of errors are already reported by the lexer.
+        let from_lexer =
+            base < 10 && s.chars().any(|c| c.to_digit(10).map_or(false, |d| d >= base));
+        if from_lexer { LitError::LexerError } else { LitError::IntTooLarge }
     })
 }
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index 0611c1d9b42..b1f3612a839 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -5,21 +5,26 @@ use crate::early_buffered_lints::{BufferedEarlyLint, BufferedEarlyLintId};
 use crate::source_map::{SourceMap, FilePathMapping};
 use crate::feature_gate::UnstableFeatures;
 use crate::parse::parser::Parser;
-use crate::syntax::parse::parser::emit_unclosed_delims;
+use crate::parse::parser::emit_unclosed_delims;
+use crate::parse::token::TokenKind;
 use crate::tokenstream::{TokenStream, TokenTree};
 use crate::diagnostics::plugin::ErrorMap;
-use crate::print::pprust::token_to_string;
+use crate::print::pprust;
+use crate::symbol::Symbol;
 
 use errors::{Applicability, FatalError, Level, Handler, ColorConfig, Diagnostic, DiagnosticBuilder};
-use rustc_data_structures::sync::{Lrc, Lock};
+use rustc_data_structures::sync::{Lrc, Lock, Once};
 use syntax_pos::{Span, SourceFile, FileName, MultiSpan};
+use syntax_pos::edition::Edition;
+use syntax_pos::hygiene::ExpnId;
 
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use std::borrow::Cow;
 use std::path::{Path, PathBuf};
 use std::str;
 
-pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
+#[cfg(test)]
+mod tests;
 
 #[macro_use]
 pub mod parser;
@@ -30,14 +35,16 @@ pub mod token;
 crate mod classify;
 crate mod diagnostics;
 crate mod literal;
-crate mod unescape;
 crate mod unescape_error_reporting;
 
+pub type PResult<'a, T> = Result<T, DiagnosticBuilder<'a>>;
+
 /// Info about a parsing session.
 pub struct ParseSess {
     pub span_diagnostic: Handler,
     pub unstable_features: UnstableFeatures,
     pub config: CrateConfig,
+    pub edition: Edition,
     pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
     pub raw_identifier_spans: Lock<Vec<Span>>,
@@ -51,6 +58,16 @@ pub struct ParseSess {
     /// operation token that followed it, but that the parser cannot identify without further
     /// analysis.
     pub ambiguous_block_expr_parse: Lock<FxHashMap<Span, Span>>,
+    pub param_attr_spans: Lock<Vec<Span>>,
+    // Places where `let` exprs were used and should be feature gated according to `let_chains`.
+    pub let_chains_spans: Lock<Vec<Span>>,
+    // Places where `async || ..` exprs were used and should be feature gated.
+    pub async_closure_spans: Lock<Vec<Span>>,
+    // Places where `yield e?` exprs were used and should be feature gated.
+    pub yield_spans: Lock<Vec<Span>>,
+    pub injected_crate_name: Once<Symbol>,
+    // Places where or-patterns e.g. `Some(Foo | Bar)` were used and should be feature gated.
+    pub or_pattern_spans: Lock<Vec<Span>>,
 }
 
 impl ParseSess {
@@ -74,7 +91,14 @@ impl ParseSess {
             included_mod_stack: Lock::new(vec![]),
             source_map,
             buffered_lints: Lock::new(vec![]),
+            edition: ExpnId::root().expn_data().edition,
             ambiguous_block_expr_parse: Lock::new(FxHashMap::default()),
+            param_attr_spans: Lock::new(Vec::new()),
+            let_chains_spans: Lock::new(Vec::new()),
+            async_closure_spans: Lock::new(Vec::new()),
+            yield_spans: Lock::new(Vec::new()),
+            injected_crate_name: Once::new(),
+            or_pattern_spans: Lock::new(Vec::new()),
         }
     }
 
@@ -233,10 +257,10 @@ fn maybe_source_file_to_parser(
 ) -> Result<Parser<'_>, Vec<Diagnostic>> {
     let end_pos = source_file.end_pos;
     let (stream, unclosed_delims) = maybe_file_to_stream(sess, source_file, None)?;
-    let mut parser = stream_to_parser(sess, stream);
+    let mut parser = stream_to_parser(sess, stream, None);
     parser.unclosed_delims = unclosed_delims;
-    if parser.token == token::Eof && parser.span.is_dummy() {
-        parser.span = Span::new(end_pos, end_pos, parser.span.ctxt());
+    if parser.token == token::Eof && parser.token.span.is_dummy() {
+        parser.token.span = Span::new(end_pos, end_pos, parser.token.span.ctxt());
     }
 
     Ok(parser)
@@ -245,7 +269,7 @@ fn maybe_source_file_to_parser(
 // must preserve old name for now, because quote! from the *existing*
 // compiler expands into it
 pub fn new_parser_from_tts(sess: &ParseSess, tts: Vec<TokenTree>) -> Parser<'_> {
-    stream_to_parser(sess, tts.into_iter().collect())
+    stream_to_parser(sess, tts.into_iter().collect(), crate::MACRO_ARGUMENTS)
 }
 
 
@@ -296,7 +320,7 @@ pub fn maybe_file_to_stream(
     source_file: Lrc<SourceFile>,
     override_span: Option<Span>,
 ) -> Result<(TokenStream, Vec<lexer::UnmatchedBrace>), Vec<Diagnostic>> {
-    let srdr = lexer::StringReader::new_or_buffered_errs(sess, source_file, override_span)?;
+    let srdr = lexer::StringReader::new(sess, source_file, override_span);
     let (token_trees, unmatched_braces) = srdr.into_token_trees();
 
     match token_trees {
@@ -308,7 +332,7 @@ pub fn maybe_file_to_stream(
             for unmatched in unmatched_braces {
                 let mut db = sess.span_diagnostic.struct_span_err(unmatched.found_span, &format!(
                     "incorrect close delimiter: `{}`",
-                    token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
+                    pprust::token_kind_to_string(&token::CloseDelim(unmatched.found_delim)),
                 ));
                 db.span_label(unmatched.found_span, "incorrect close delimiter");
                 if let Some(sp) = unmatched.candidate_span {
@@ -325,20 +349,43 @@ pub fn maybe_file_to_stream(
 }
 
 /// Given stream and the `ParseSess`, produces a parser.
-pub fn stream_to_parser(sess: &ParseSess, stream: TokenStream) -> Parser<'_> {
-    Parser::new(sess, stream, None, true, false)
+pub fn stream_to_parser<'a>(
+    sess: &'a ParseSess,
+    stream: TokenStream,
+    subparser_name: Option<&'static str>,
+) -> Parser<'a> {
+    Parser::new(sess, stream, None, true, false, subparser_name)
+}
+
+/// Given stream, the `ParseSess` and the base directory, produces a parser.
+///
+/// Use this function when you are creating a parser from the token stream
+/// and also care about the current working directory of the parser (e.g.,
+/// you are trying to resolve modules defined inside a macro invocation).
+///
+/// # Note
+///
+/// The main usage of this function is outside of rustc, for those who uses
+/// libsyntax as a library. Please do not remove this function while refactoring
+/// just because it is not used in rustc codebase!
+pub fn stream_to_parser_with_base_dir<'a>(
+    sess: &'a ParseSess,
+    stream: TokenStream,
+    base_dir: Directory<'a>,
+) -> Parser<'a> {
+    Parser::new(sess, stream, Some(base_dir), true, false, None)
 }
 
 /// A sequence separator.
 pub struct SeqSep {
-    /// The seperator token.
-    pub sep: Option<token::Token>,
+    /// The separator token.
+    pub sep: Option<TokenKind>,
     /// `true` if a trailing separator is allowed.
     pub trailing_sep_allowed: bool,
 }
 
 impl SeqSep {
-    pub fn trailing_allowed(t: token::Token) -> SeqSep {
+    pub fn trailing_allowed(t: TokenKind) -> SeqSep {
         SeqSep {
             sep: Some(t),
             trailing_sep_allowed: true,
@@ -352,304 +399,3 @@ impl SeqSep {
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::ast::{self, Ident, PatKind};
-    use crate::attr::first_attr_value_str_by_name;
-    use crate::ptr::P;
-    use crate::print::pprust::item_to_string;
-    use crate::tokenstream::{DelimSpan, TokenTree};
-    use crate::util::parser_testing::string_to_stream;
-    use crate::util::parser_testing::{string_to_expr, string_to_item};
-    use crate::with_globals;
-    use syntax_pos::{Span, BytePos, Pos, NO_EXPANSION};
-
-    /// Parses an item.
-    ///
-    /// Returns `Ok(Some(item))` when successful, `Ok(None)` when no item was found, and `Err`
-    /// when a syntax error occurred.
-    fn parse_item_from_source_str(name: FileName, source: String, sess: &ParseSess)
-                                        -> PResult<'_, Option<P<ast::Item>>> {
-        new_parser_from_source_str(sess, name, source).parse_item()
-    }
-
-    // produce a syntax_pos::span
-    fn sp(a: u32, b: u32) -> Span {
-        Span::new(BytePos(a), BytePos(b), NO_EXPANSION)
-    }
-
-    #[should_panic]
-    #[test] fn bad_path_expr_1() {
-        with_globals(|| {
-            string_to_expr("::abc::def::return".to_string());
-        })
-    }
-
-    // check the token-tree-ization of macros
-    #[test]
-    fn string_to_tts_macro () {
-        with_globals(|| {
-            use crate::symbol::sym;
-
-            let tts: Vec<_> =
-                string_to_stream("macro_rules! zip (($a)=>($a))".to_string()).trees().collect();
-            let tts: &[TokenTree] = &tts[..];
-
-            match (tts.len(), tts.get(0), tts.get(1), tts.get(2), tts.get(3)) {
-                (
-                    4,
-                    Some(&TokenTree::Token(_, token::Ident(name_macro_rules, false))),
-                    Some(&TokenTree::Token(_, token::Not)),
-                    Some(&TokenTree::Token(_, token::Ident(name_zip, false))),
-                    Some(&TokenTree::Delimited(_, macro_delim, ref macro_tts)),
-                )
-                if name_macro_rules.name == sym::macro_rules
-                && name_zip.name.as_str() == "zip" => {
-                    let tts = &macro_tts.trees().collect::<Vec<_>>();
-                    match (tts.len(), tts.get(0), tts.get(1), tts.get(2)) {
-                        (
-                            3,
-                            Some(&TokenTree::Delimited(_, first_delim, ref first_tts)),
-                            Some(&TokenTree::Token(_, token::FatArrow)),
-                            Some(&TokenTree::Delimited(_, second_delim, ref second_tts)),
-                        )
-                        if macro_delim == token::Paren => {
-                            let tts = &first_tts.trees().collect::<Vec<_>>();
-                            match (tts.len(), tts.get(0), tts.get(1)) {
-                                (
-                                    2,
-                                    Some(&TokenTree::Token(_, token::Dollar)),
-                                    Some(&TokenTree::Token(_, token::Ident(ident, false))),
-                                )
-                                if first_delim == token::Paren && ident.name.as_str() == "a" => {},
-                                _ => panic!("value 3: {:?} {:?}", first_delim, first_tts),
-                            }
-                            let tts = &second_tts.trees().collect::<Vec<_>>();
-                            match (tts.len(), tts.get(0), tts.get(1)) {
-                                (
-                                    2,
-                                    Some(&TokenTree::Token(_, token::Dollar)),
-                                    Some(&TokenTree::Token(_, token::Ident(ident, false))),
-                                )
-                                if second_delim == token::Paren && ident.name.as_str() == "a" => {},
-                                _ => panic!("value 4: {:?} {:?}", second_delim, second_tts),
-                            }
-                        },
-                        _ => panic!("value 2: {:?} {:?}", macro_delim, macro_tts),
-                    }
-                },
-                _ => panic!("value: {:?}",tts),
-            }
-        })
-    }
-
-    #[test]
-    fn string_to_tts_1() {
-        with_globals(|| {
-            let tts = string_to_stream("fn a (b : i32) { b; }".to_string());
-
-            let expected = TokenStream::new(vec![
-                TokenTree::Token(sp(0, 2), token::Ident(Ident::from_str("fn"), false)).into(),
-                TokenTree::Token(sp(3, 4), token::Ident(Ident::from_str("a"), false)).into(),
-                TokenTree::Delimited(
-                    DelimSpan::from_pair(sp(5, 6), sp(13, 14)),
-                    token::DelimToken::Paren,
-                    TokenStream::new(vec![
-                        TokenTree::Token(sp(6, 7),
-                                         token::Ident(Ident::from_str("b"), false)).into(),
-                        TokenTree::Token(sp(8, 9), token::Colon).into(),
-                        TokenTree::Token(sp(10, 13),
-                                         token::Ident(Ident::from_str("i32"), false)).into(),
-                    ]).into(),
-                ).into(),
-                TokenTree::Delimited(
-                    DelimSpan::from_pair(sp(15, 16), sp(20, 21)),
-                    token::DelimToken::Brace,
-                    TokenStream::new(vec![
-                        TokenTree::Token(sp(17, 18),
-                                         token::Ident(Ident::from_str("b"), false)).into(),
-                        TokenTree::Token(sp(18, 19), token::Semi).into(),
-                    ]).into(),
-                ).into()
-            ]);
-
-            assert_eq!(tts, expected);
-        })
-    }
-
-    #[test] fn parse_use() {
-        with_globals(|| {
-            let use_s = "use foo::bar::baz;";
-            let vitem = string_to_item(use_s.to_string()).unwrap();
-            let vitem_s = item_to_string(&vitem);
-            assert_eq!(&vitem_s[..], use_s);
-
-            let use_s = "use foo::bar as baz;";
-            let vitem = string_to_item(use_s.to_string()).unwrap();
-            let vitem_s = item_to_string(&vitem);
-            assert_eq!(&vitem_s[..], use_s);
-        })
-    }
-
-    #[test] fn parse_extern_crate() {
-        with_globals(|| {
-            let ex_s = "extern crate foo;";
-            let vitem = string_to_item(ex_s.to_string()).unwrap();
-            let vitem_s = item_to_string(&vitem);
-            assert_eq!(&vitem_s[..], ex_s);
-
-            let ex_s = "extern crate foo as bar;";
-            let vitem = string_to_item(ex_s.to_string()).unwrap();
-            let vitem_s = item_to_string(&vitem);
-            assert_eq!(&vitem_s[..], ex_s);
-        })
-    }
-
-    fn get_spans_of_pat_idents(src: &str) -> Vec<Span> {
-        let item = string_to_item(src.to_string()).unwrap();
-
-        struct PatIdentVisitor {
-            spans: Vec<Span>
-        }
-        impl<'a> crate::visit::Visitor<'a> for PatIdentVisitor {
-            fn visit_pat(&mut self, p: &'a ast::Pat) {
-                match p.node {
-                    PatKind::Ident(_ , ref spannedident, _) => {
-                        self.spans.push(spannedident.span.clone());
-                    }
-                    _ => {
-                        crate::visit::walk_pat(self, p);
-                    }
-                }
-            }
-        }
-        let mut v = PatIdentVisitor { spans: Vec::new() };
-        crate::visit::walk_item(&mut v, &item);
-        return v.spans;
-    }
-
-    #[test] fn span_of_self_arg_pat_idents_are_correct() {
-        with_globals(|| {
-
-            let srcs = ["impl z { fn a (&self, &myarg: i32) {} }",
-                        "impl z { fn a (&mut self, &myarg: i32) {} }",
-                        "impl z { fn a (&'a self, &myarg: i32) {} }",
-                        "impl z { fn a (self, &myarg: i32) {} }",
-                        "impl z { fn a (self: Foo, &myarg: i32) {} }",
-                        ];
-
-            for &src in &srcs {
-                let spans = get_spans_of_pat_idents(src);
-                let (lo, hi) = (spans[0].lo(), spans[0].hi());
-                assert!("self" == &src[lo.to_usize()..hi.to_usize()],
-                        "\"{}\" != \"self\". src=\"{}\"",
-                        &src[lo.to_usize()..hi.to_usize()], src)
-            }
-        })
-    }
-
-    #[test] fn parse_exprs () {
-        with_globals(|| {
-            // just make sure that they parse....
-            string_to_expr("3 + 4".to_string());
-            string_to_expr("a::z.froob(b,&(987+3))".to_string());
-        })
-    }
-
-    #[test] fn attrs_fix_bug () {
-        with_globals(|| {
-            string_to_item("pub fn mk_file_writer(path: &Path, flags: &[FileFlag])
-                   -> Result<Box<Writer>, String> {
-    #[cfg(windows)]
-    fn wb() -> c_int {
-      (O_WRONLY | libc::consts::os::extra::O_BINARY) as c_int
-    }
-
-    #[cfg(unix)]
-    fn wb() -> c_int { O_WRONLY as c_int }
-
-    let mut fflags: c_int = wb();
-}".to_string());
-        })
-    }
-
-    #[test] fn crlf_doc_comments() {
-        with_globals(|| {
-            use crate::symbol::sym;
-
-            let sess = ParseSess::new(FilePathMapping::empty());
-
-            let name_1 = FileName::Custom("crlf_source_1".to_string());
-            let source = "/// doc comment\r\nfn foo() {}".to_string();
-            let item = parse_item_from_source_str(name_1, source, &sess)
-                .unwrap().unwrap();
-            let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
-            assert_eq!(doc.as_str(), "/// doc comment");
-
-            let name_2 = FileName::Custom("crlf_source_2".to_string());
-            let source = "/// doc comment\r\n/// line 2\r\nfn foo() {}".to_string();
-            let item = parse_item_from_source_str(name_2, source, &sess)
-                .unwrap().unwrap();
-            let docs = item.attrs.iter().filter(|a| a.path == sym::doc)
-                        .map(|a| a.value_str().unwrap().to_string()).collect::<Vec<_>>();
-            let b: &[_] = &["/// doc comment".to_string(), "/// line 2".to_string()];
-            assert_eq!(&docs[..], b);
-
-            let name_3 = FileName::Custom("clrf_source_3".to_string());
-            let source = "/** doc comment\r\n *  with CRLF */\r\nfn foo() {}".to_string();
-            let item = parse_item_from_source_str(name_3, source, &sess).unwrap().unwrap();
-            let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
-            assert_eq!(doc.as_str(), "/** doc comment\n *  with CRLF */");
-        });
-    }
-
-    #[test]
-    fn ttdelim_span() {
-        fn parse_expr_from_source_str(
-            name: FileName, source: String, sess: &ParseSess
-        ) -> PResult<'_, P<ast::Expr>> {
-            new_parser_from_source_str(sess, name, source).parse_expr()
-        }
-
-        with_globals(|| {
-            let sess = ParseSess::new(FilePathMapping::empty());
-            let expr = parse_expr_from_source_str(PathBuf::from("foo").into(),
-                "foo!( fn main() { body } )".to_string(), &sess).unwrap();
-
-            let tts: Vec<_> = match expr.node {
-                ast::ExprKind::Mac(ref mac) => mac.node.stream().trees().collect(),
-                _ => panic!("not a macro"),
-            };
-
-            let span = tts.iter().rev().next().unwrap().span();
-
-            match sess.source_map().span_to_snippet(span) {
-                Ok(s) => assert_eq!(&s[..], "{ body }"),
-                Err(_) => panic!("could not get snippet"),
-            }
-        });
-    }
-
-    // This tests that when parsing a string (rather than a file) we don't try
-    // and read in a file for a module declaration and just parse a stub.
-    // See `recurse_into_file_modules` in the parser.
-    #[test]
-    fn out_of_line_mod() {
-        with_globals(|| {
-            let sess = ParseSess::new(FilePathMapping::empty());
-            let item = parse_item_from_source_str(
-                PathBuf::from("foo").into(),
-                "mod foo { struct S; mod this_does_not_exist; }".to_owned(),
-                &sess,
-            ).unwrap().unwrap();
-
-            if let ast::ItemKind::Mod(ref m) = item.node {
-                assert!(m.items.len() == 2);
-            } else {
-                panic!();
-            }
-        });
-    }
-}
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 24d120376de..89725d8b339 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1,75 +1,40 @@
-// ignore-tidy-filelength
-
-use crate::ast::{AngleBracketedArgs, AsyncArgument, ParenthesizedArgs, AttrStyle, BareFnTy};
-use crate::ast::{GenericBound, TraitBoundModifier};
-use crate::ast::Unsafety;
-use crate::ast::{Mod, AnonConst, Arg, ArgSource, Arm, Guard, Attribute, BindingMode, TraitItemKind};
-use crate::ast::Block;
-use crate::ast::{BlockCheckMode, CaptureBy, Movability};
-use crate::ast::{Constness, Crate};
-use crate::ast::Defaultness;
-use crate::ast::EnumDef;
-use crate::ast::{Expr, ExprKind, RangeLimits};
-use crate::ast::{Field, FnDecl, FnHeader};
-use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
-use crate::ast::{GenericParam, GenericParamKind};
-use crate::ast::GenericArg;
-use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
-use crate::ast::{Label, Lifetime};
-use crate::ast::{Local, LocalSource};
-use crate::ast::MacStmtStyle;
-use crate::ast::{Mac, Mac_, MacDelimiter};
-use crate::ast::{MutTy, Mutability};
-use crate::ast::{Pat, PatKind, PathSegment};
-use crate::ast::{PolyTraitRef, QSelf};
-use crate::ast::{Stmt, StmtKind};
-use crate::ast::{VariantData, StructField};
-use crate::ast::StrStyle;
-use crate::ast::SelfKind;
-use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
-use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
-use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
-use crate::ast::{UseTree, UseTreeKind};
-use crate::ast::{BinOpKind, UnOp};
-use crate::ast::{RangeEnd, RangeSyntax};
-use crate::{ast, attr};
-use crate::ext::base::DummyResult;
-use crate::source_map::{self, SourceMap, Spanned, respan};
-use crate::parse::{SeqSep, classify, literal, token};
-use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
+mod expr;
+mod pat;
+mod item;
+pub use item::AliasKind;
+mod module;
+pub use module::{ModulePath, ModulePathSuccess};
+mod ty;
+mod path;
+pub use path::PathStyle;
+mod stmt;
+mod generics;
+
+use crate::ast::{self, AttrStyle, Attribute, Arg, BindingMode, StrStyle, SelfKind};
+use crate::ast::{FnDecl, Ident, IsAsync, MacDelimiter, Mutability, TyKind};
+use crate::ast::{Visibility, VisibilityKind, Unsafety, CrateSugar};
+use crate::source_map::{self, respan};
+use crate::parse::{SeqSep, literal, token};
+use crate::parse::lexer::UnmatchedBrace;
 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
-use crate::parse::token::DelimToken;
-use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
-use crate::util::parser::{AssocOp, Fixity};
+use crate::parse::token::{Token, TokenKind, DelimToken};
+use crate::parse::{ParseSess, Directory, DirectoryOwnership};
 use crate::print::pprust;
 use crate::ptr::P;
 use crate::parse::PResult;
 use crate::ThinVec;
 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
-use crate::symbol::{keywords, sym, Symbol};
+use crate::symbol::{kw, sym, Symbol};
+use crate::parse::diagnostics::{Error, dummy_arg};
 
-use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
+use errors::{Applicability, DiagnosticId, FatalError};
 use rustc_target::spec::abi::{self, Abi};
-use syntax_pos::{
-    Span, MultiSpan, BytePos, FileName,
-    hygiene::CompilerDesugaringKind,
-};
-use log::{debug, trace};
+use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
+use log::debug;
 
 use std::borrow::Cow;
-use std::cmp;
-use std::mem;
-use std::path::{self, Path, PathBuf};
-use std::slice;
-
-#[derive(Debug)]
-/// Whether the type alias or associated type is a concrete type or an existential type
-pub enum AliasKind {
-    /// Just a new name for the same type
-    Weak(P<Ty>),
-    /// Only trait impls of the type will be usable, not the actual type itself
-    Existential(GenericBounds),
-}
+use std::{cmp, mem, slice};
+use std::path::PathBuf;
 
 bitflags::bitflags! {
     struct Restrictions: u8 {
@@ -78,31 +43,6 @@ bitflags::bitflags! {
     }
 }
 
-type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
-
-/// Specifies how to parse a path.
-#[derive(Copy, Clone, PartialEq)]
-pub enum PathStyle {
-    /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
-    /// with something else. For example, in expressions `segment < ....` can be interpreted
-    /// as a comparison and `segment ( ....` can be interpreted as a function call.
-    /// In all such contexts the non-path interpretation is preferred by default for practical
-    /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
-    /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
-    Expr,
-    /// In other contexts, notably in types, no ambiguity exists and paths can be written
-    /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
-    /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
-    Type,
-    /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
-    /// visibilities or attributes.
-    /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
-    /// (paths in "mod" contexts have to be checked later for absence of generic arguments
-    /// anyway, due to macros), but it is used to avoid weird suggestions about expected
-    /// tokens when something goes wrong.
-    Mod,
-}
-
 #[derive(Clone, Copy, PartialEq, Debug)]
 crate enum SemiColonMode {
     Break,
@@ -116,40 +56,11 @@ crate enum BlockMode {
     Ignore,
 }
 
-/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
-/// dropped into the token stream, which happens while parsing the result of
-/// macro expansion). Placement of these is not as complex as I feared it would
-/// be. The important thing is to make sure that lookahead doesn't balk at
-/// `token::Interpolated` tokens.
-macro_rules! maybe_whole_expr {
-    ($p:expr) => {
-        if let token::Interpolated(nt) = &$p.token {
-            match &**nt {
-                token::NtExpr(e) | token::NtLiteral(e) => {
-                    let e = e.clone();
-                    $p.bump();
-                    return Ok(e);
-                }
-                token::NtPath(path) => {
-                    let path = path.clone();
-                    $p.bump();
-                    return Ok($p.mk_expr($p.span, ExprKind::Path(None, path), ThinVec::new()));
-                }
-                token::NtBlock(block) => {
-                    let block = block.clone();
-                    $p.bump();
-                    return Ok($p.mk_expr($p.span, ExprKind::Block(block, None), ThinVec::new()));
-                }
-                _ => {},
-            };
-        }
-    }
-}
-
 /// As maybe_whole_expr, but for things other than expressions
+#[macro_export]
 macro_rules! maybe_whole {
     ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
-        if let token::Interpolated(nt) = &$p.token {
+        if let token::Interpolated(nt) = &$p.token.kind {
             if let token::$constructor(x) = &**nt {
                 let $x = x.clone();
                 $p.bump();
@@ -160,10 +71,11 @@ macro_rules! maybe_whole {
 }
 
 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
+#[macro_export]
 macro_rules! maybe_recover_from_interpolated_ty_qpath {
     ($self: expr, $allow_qpath_recovery: expr) => {
         if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
-            if let token::Interpolated(nt) = &$self.token {
+            if let token::Interpolated(nt) = &$self.token.kind {
                 if let token::NtTy(ty) = &**nt {
                     let ty = ty.clone();
                     $self.bump();
@@ -193,33 +105,36 @@ enum PrevTokenKind {
     Other,
 }
 
-/* ident is handled by common.rs */
+// NOTE: `Ident`s are handled by `common.rs`.
 
 #[derive(Clone)]
 pub struct Parser<'a> {
     pub sess: &'a ParseSess,
-    /// the current token:
-    pub token: token::Token,
-    /// the span of the current token:
-    pub span: Span,
-    /// the span of the previous token:
+    /// The current normalized token.
+    /// "Normalized" means that some interpolated tokens
+    /// (`$i: ident` and `$l: lifetime` meta-variables) are replaced
+    /// with non-interpolated identifier and lifetime tokens they refer to.
+    /// Perhaps the normalized / non-normalized setup can be simplified somehow.
+    pub token: Token,
+    /// Span of the current non-normalized token.
     meta_var_span: Option<Span>,
+    /// Span of the previous non-normalized token.
     pub prev_span: Span,
-    /// the previous token kind
+    /// Kind of the previous normalized token (in simplified form).
     prev_token_kind: PrevTokenKind,
     restrictions: Restrictions,
-    /// Used to determine the path to externally loaded source files
+    /// Used to determine the path to externally loaded source files.
     crate directory: Directory<'a>,
-    /// Whether to parse sub-modules in other files.
+    /// `true` to parse sub-modules in other files.
     pub recurse_into_file_modules: bool,
     /// Name of the root module this parser originated from. If `None`, then the
     /// name is not known. This does not change while the parser is descending
     /// into modules, and sub-parsers have new values for this name.
     pub root_module_name: Option<String>,
     crate expected_tokens: Vec<TokenType>,
-    token_cursor: TokenCursor,
+    crate token_cursor: TokenCursor,
     desugar_doc_comments: bool,
-    /// Whether we should configure out of line modules as we parse.
+    /// `true` we should configure out of line modules as we parse.
     pub cfg_mods: bool,
     /// This field is used to keep track of how many left angle brackets we have seen. This is
     /// required in order to detect extra leading left angle brackets (`<` characters) and error
@@ -232,7 +147,10 @@ pub struct Parser<'a> {
     /// it gets removed from here. Every entry left at the end gets emitted as an independent
     /// error.
     crate unclosed_delims: Vec<UnmatchedBrace>,
-    last_unexpected_token_span: Option<Span>,
+    crate last_unexpected_token_span: Option<Span>,
+    crate last_type_ascription: Option<(Span, bool /* likely path typo */)>,
+    /// If present, this `Parser` is not parsing Rust code but rather a macro call.
+    crate subparser_name: Option<&'static str>,
 }
 
 impl<'a> Drop for Parser<'a> {
@@ -243,19 +161,19 @@ impl<'a> Drop for Parser<'a> {
 }
 
 #[derive(Clone)]
-struct TokenCursor {
-    frame: TokenCursorFrame,
-    stack: Vec<TokenCursorFrame>,
+crate struct TokenCursor {
+    crate frame: TokenCursorFrame,
+    crate stack: Vec<TokenCursorFrame>,
 }
 
 #[derive(Clone)]
-struct TokenCursorFrame {
-    delim: token::DelimToken,
-    span: DelimSpan,
-    open_delim: bool,
-    tree_cursor: tokenstream::Cursor,
-    close_delim: bool,
-    last_token: LastToken,
+crate struct TokenCursorFrame {
+    crate delim: token::DelimToken,
+    crate span: DelimSpan,
+    crate open_delim: bool,
+    crate tree_cursor: tokenstream::Cursor,
+    crate close_delim: bool,
+    crate last_token: LastToken,
 }
 
 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
@@ -276,16 +194,16 @@ struct TokenCursorFrame {
 /// You can find some more example usage of this in the `collect_tokens` method
 /// on the parser.
 #[derive(Clone)]
-enum LastToken {
+crate enum LastToken {
     Collecting(Vec<TreeAndJoint>),
     Was(Option<TreeAndJoint>),
 }
 
 impl TokenCursorFrame {
-    fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
+    fn new(span: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
         TokenCursorFrame {
-            delim: delim,
-            span: sp,
+            delim,
+            span,
             open_delim: delim == token::NoDelim,
             tree_cursor: tts.clone().into_trees(),
             close_delim: delim == token::NoDelim,
@@ -295,7 +213,7 @@ impl TokenCursorFrame {
 }
 
 impl TokenCursor {
-    fn next(&mut self) -> TokenAndSpan {
+    fn next(&mut self) -> Token {
         loop {
             let tree = if !self.frame.open_delim {
                 self.frame.open_delim = true;
@@ -309,7 +227,7 @@ impl TokenCursor {
                 self.frame = frame;
                 continue
             } else {
-                return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
+                return Token::new(token::Eof, DUMMY_SP);
             };
 
             match self.frame.last_token {
@@ -318,7 +236,7 @@ impl TokenCursor {
             }
 
             match tree {
-                TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
+                TokenTree::Token(token) => return token,
                 TokenTree::Delimited(sp, delim, tts) => {
                     let frame = TokenCursorFrame::new(sp, delim, &tts);
                     self.stack.push(mem::replace(&mut self.frame, frame));
@@ -327,9 +245,9 @@ impl TokenCursor {
         }
     }
 
-    fn next_desugared(&mut self) -> TokenAndSpan {
-        let (sp, name) = match self.next() {
-            TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
+    fn next_desugared(&mut self) -> Token {
+        let (name, sp) = match self.next() {
+            Token { kind: token::DocComment(name), span } => (name, span),
             tok => return tok,
         };
 
@@ -352,10 +270,12 @@ impl TokenCursor {
         let body = TokenTree::Delimited(
             delim_span,
             token::Bracket,
-            [TokenTree::Token(sp, token::Ident(ast::Ident::with_empty_ctxt(sym::doc), false)),
-             TokenTree::Token(sp, token::Eq),
-             TokenTree::Token(sp, token::Literal(
-                token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
+            [
+                TokenTree::token(token::Ident(sym::doc, false), sp),
+                TokenTree::token(token::Eq, sp),
+                TokenTree::token(TokenKind::lit(
+                    token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None
+                ), sp),
             ]
             .iter().cloned().collect::<TokenStream>().into(),
         );
@@ -364,10 +284,10 @@ impl TokenCursor {
             delim_span,
             token::NoDelim,
             &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
-                [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
+                [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
                     .iter().cloned().collect::<TokenStream>().into()
             } else {
-                [TokenTree::Token(sp, token::Pound), body]
+                [TokenTree::token(token::Pound, sp), body]
                     .iter().cloned().collect::<TokenStream>().into()
             },
         )));
@@ -378,8 +298,8 @@ impl TokenCursor {
 
 #[derive(Clone, PartialEq)]
 crate enum TokenType {
-    Token(token::Token),
-    Keyword(keywords::Keyword),
+    Token(TokenKind),
+    Keyword(Symbol),
     Operator,
     Lifetime,
     Ident,
@@ -391,8 +311,8 @@ crate enum TokenType {
 impl TokenType {
     crate fn to_string(&self) -> String {
         match *self {
-            TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
-            TokenType::Keyword(kw) => format!("`{}`", kw.name()),
+            TokenType::Token(ref t) => format!("`{}`", pprust::token_kind_to_string(t)),
+            TokenType::Keyword(kw) => format!("`{}`", kw),
             TokenType::Operator => "an operator".to_string(),
             TokenType::Lifetime => "lifetime".to_string(),
             TokenType::Ident => "identifier".to_string(),
@@ -403,145 +323,25 @@ impl TokenType {
     }
 }
 
-/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
-/// `IDENT<<u8 as Trait>::AssocTy>`.
-///
-/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
-/// that `IDENT` is not the ident of a fn trait.
-fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
-    t == &token::ModSep || t == &token::Lt ||
-    t == &token::BinOp(token::Shl)
-}
-
-/// Information about the path to a module.
-pub struct ModulePath {
-    name: String,
-    path_exists: bool,
-    pub result: Result<ModulePathSuccess, Error>,
-}
-
-pub struct ModulePathSuccess {
-    pub path: PathBuf,
-    pub directory_ownership: DirectoryOwnership,
-    warn: bool,
-}
-
-pub enum Error {
-    FileNotFoundForModule {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-        dir_path: String,
-    },
-    DuplicatePaths {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-    },
-    UselessDocComment,
-    InclusiveRangeWithNoEnd,
-}
-
-impl Error {
-    fn span_err<S: Into<MultiSpan>>(self,
-                                        sp: S,
-                                        handler: &errors::Handler) -> DiagnosticBuilder<'_> {
-        match self {
-            Error::FileNotFoundForModule { ref mod_name,
-                                           ref default_path,
-                                           ref secondary_path,
-                                           ref dir_path } => {
-                let mut err = struct_span_err!(handler, sp, E0583,
-                                               "file not found for module `{}`", mod_name);
-                err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
-                                  default_path,
-                                  secondary_path,
-                                  dir_path));
-                err
-            }
-            Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
-                let mut err = struct_span_err!(handler, sp, E0584,
-                                               "file for module `{}` found at both {} and {}",
-                                               mod_name,
-                                               default_path,
-                                               secondary_path);
-                err.help("delete or rename one of them to remove the ambiguity");
-                err
-            }
-            Error::UselessDocComment => {
-                let mut err = struct_span_err!(handler, sp, E0585,
-                                  "found a documentation comment that doesn't document anything");
-                err.help("doc comments must come before what they document, maybe a comment was \
-                          intended with `//`?");
-                err
-            }
-            Error::InclusiveRangeWithNoEnd => {
-                let mut err = struct_span_err!(handler, sp, E0586,
-                                               "inclusive range with no end");
-                err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
-                err
-            }
-        }
-    }
-}
-
-#[derive(Debug)]
-enum LhsExpr {
-    NotYetParsed,
-    AttributesParsed(ThinVec<Attribute>),
-    AlreadyParsed(P<Expr>),
-}
-
-impl From<Option<ThinVec<Attribute>>> for LhsExpr {
-    fn from(o: Option<ThinVec<Attribute>>) -> Self {
-        if let Some(attrs) = o {
-            LhsExpr::AttributesParsed(attrs)
-        } else {
-            LhsExpr::NotYetParsed
-        }
-    }
-}
-
-impl From<P<Expr>> for LhsExpr {
-    fn from(expr: P<Expr>) -> Self {
-        LhsExpr::AlreadyParsed(expr)
-    }
-}
-
-/// Creates a placeholder argument.
-fn dummy_arg(span: Span) -> Arg {
-    let ident = Ident::new(keywords::Invalid.name(), span);
-    let pat = P(Pat {
-        id: ast::DUMMY_NODE_ID,
-        node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
-        span,
-    });
-    let ty = Ty {
-        node: TyKind::Err,
-        span,
-        id: ast::DUMMY_NODE_ID
-    };
-    Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal }
-}
-
 #[derive(Copy, Clone, Debug)]
-enum TokenExpectType {
+crate enum TokenExpectType {
     Expect,
     NoExpect,
 }
 
 impl<'a> Parser<'a> {
-    pub fn new(sess: &'a ParseSess,
-               tokens: TokenStream,
-               directory: Option<Directory<'a>>,
-               recurse_into_file_modules: bool,
-               desugar_doc_comments: bool)
-               -> Self {
+    pub fn new(
+        sess: &'a ParseSess,
+        tokens: TokenStream,
+        directory: Option<Directory<'a>>,
+        recurse_into_file_modules: bool,
+        desugar_doc_comments: bool,
+        subparser_name: Option<&'static str>,
+    ) -> Self {
         let mut parser = Parser {
             sess,
-            token: token::Whitespace,
-            span: syntax_pos::DUMMY_SP,
-            prev_span: syntax_pos::DUMMY_SP,
+            token: Token::dummy(),
+            prev_span: DUMMY_SP,
             meta_var_span: None,
             prev_token_kind: PrevTokenKind::Other,
             restrictions: Restrictions::empty(),
@@ -566,16 +366,17 @@ impl<'a> Parser<'a> {
             max_angle_bracket_count: 0,
             unclosed_delims: Vec::new(),
             last_unexpected_token_span: None,
+            last_type_ascription: None,
+            subparser_name,
         };
 
-        let tok = parser.next_tok();
-        parser.token = tok.tok;
-        parser.span = tok.sp;
+        parser.token = parser.next_tok();
 
         if let Some(directory) = directory {
             parser.directory = directory;
-        } else if !parser.span.is_dummy() {
-            if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
+        } else if !parser.token.span.is_dummy() {
+            if let FileName::Real(mut path) =
+                    sess.source_map().span_to_unmapped_path(parser.token.span) {
                 path.pop();
                 parser.directory.path = Cow::from(path);
             }
@@ -585,15 +386,15 @@ impl<'a> Parser<'a> {
         parser
     }
 
-    fn next_tok(&mut self) -> TokenAndSpan {
+    fn next_tok(&mut self) -> Token {
         let mut next = if self.desugar_doc_comments {
             self.token_cursor.next_desugared()
         } else {
             self.token_cursor.next()
         };
-        if next.sp.is_dummy() {
+        if next.span.is_dummy() {
             // Tweak the location for better diagnostics, but keep syntactic context intact.
-            next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
+            next.span = self.prev_span.with_ctxt(next.span.ctxt());
         }
         next
     }
@@ -603,11 +404,11 @@ impl<'a> Parser<'a> {
         pprust::token_to_string(&self.token)
     }
 
-    fn token_descr(&self) -> Option<&'static str> {
-        Some(match &self.token {
-            t if t.is_special_ident() => "reserved identifier",
-            t if t.is_used_keyword() => "keyword",
-            t if t.is_unused_keyword() => "reserved keyword",
+    crate fn token_descr(&self) -> Option<&'static str> {
+        Some(match &self.token.kind {
+            _ if self.token.is_special_ident() => "reserved identifier",
+            _ if self.token.is_used_keyword() => "keyword",
+            _ if self.token.is_unused_keyword() => "reserved keyword",
             token::DocComment(..) => "doc comment",
             _ => return None,
         })
@@ -629,44 +430,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
-    pub fn expect(&mut self, t: &token::Token) -> PResult<'a,  bool /* recovered */> {
+    pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
         if self.expected_tokens.is_empty() {
             if self.token == *t {
                 self.bump();
                 Ok(false)
             } else {
-                let token_str = pprust::token_to_string(t);
-                let this_token_str = self.this_token_descr();
-                let mut err = self.fatal(&format!("expected `{}`, found {}",
-                                                  token_str,
-                                                  this_token_str));
-
-                let sp = if self.token == token::Token::Eof {
-                    // EOF, don't want to point at the following char, but rather the last token
-                    self.prev_span
-                } else {
-                    self.sess.source_map().next_point(self.prev_span)
-                };
-                let label_exp = format!("expected `{}`", token_str);
-                match self.recover_closing_delimiter(&[t.clone()], err) {
-                    Err(e) => err = e,
-                    Ok(recovered) => {
-                        return Ok(recovered);
-                    }
-                }
-                let cm = self.sess.source_map();
-                match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
-                    (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                        // When the spans are in the same line, it means that the only content
-                        // between them is whitespace, point only at the found token.
-                        err.span_label(self.span, label_exp);
-                    }
-                    _ => {
-                        err.span_label(sp, label_exp);
-                        err.span_label(self.span, "unexpected token");
-                    }
-                }
-                Err(err)
+                self.unexpected_try_recover(t)
             }
         } else {
             self.expect_one_of(slice::from_ref(t), &[])
@@ -678,193 +448,20 @@ impl<'a> Parser<'a> {
     /// anything.  Signal a fatal error if next token is unexpected.
     pub fn expect_one_of(
         &mut self,
-        edible: &[token::Token],
-        inedible: &[token::Token],
+        edible: &[TokenKind],
+        inedible: &[TokenKind],
     ) -> PResult<'a, bool /* recovered */> {
-        fn tokens_to_string(tokens: &[TokenType]) -> String {
-            let mut i = tokens.iter();
-            // This might be a sign we need a connect method on Iterator.
-            let b = i.next()
-                     .map_or(String::new(), |t| t.to_string());
-            i.enumerate().fold(b, |mut b, (i, a)| {
-                if tokens.len() > 2 && i == tokens.len() - 2 {
-                    b.push_str(", or ");
-                } else if tokens.len() == 2 && i == tokens.len() - 2 {
-                    b.push_str(" or ");
-                } else {
-                    b.push_str(", ");
-                }
-                b.push_str(&a.to_string());
-                b
-            })
-        }
-        if edible.contains(&self.token) {
+        if edible.contains(&self.token.kind) {
             self.bump();
             Ok(false)
-        } else if inedible.contains(&self.token) {
+        } else if inedible.contains(&self.token.kind) {
             // leave it in the input
             Ok(false)
-        } else if self.last_unexpected_token_span == Some(self.span) {
+        } else if self.last_unexpected_token_span == Some(self.token.span) {
             FatalError.raise();
         } else {
-            let mut expected = edible.iter()
-                .map(|x| TokenType::Token(x.clone()))
-                .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
-                .chain(self.expected_tokens.iter().cloned())
-                .collect::<Vec<_>>();
-            expected.sort_by_cached_key(|x| x.to_string());
-            expected.dedup();
-            let expect = tokens_to_string(&expected[..]);
-            let actual = self.this_token_to_string();
-            let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
-                let short_expect = if expected.len() > 6 {
-                    format!("{} possible tokens", expected.len())
-                } else {
-                    expect.clone()
-                };
-                (format!("expected one of {}, found `{}`", expect, actual),
-                 (self.sess.source_map().next_point(self.prev_span),
-                  format!("expected one of {} here", short_expect)))
-            } else if expected.is_empty() {
-                (format!("unexpected token: `{}`", actual),
-                 (self.prev_span, "unexpected token after this".to_string()))
-            } else {
-                (format!("expected {}, found `{}`", expect, actual),
-                 (self.sess.source_map().next_point(self.prev_span),
-                  format!("expected {} here", expect)))
-            };
-            self.last_unexpected_token_span = Some(self.span);
-            let mut err = self.fatal(&msg_exp);
-            if self.token.is_ident_named("and") {
-                err.span_suggestion_short(
-                    self.span,
-                    "use `&&` instead of `and` for the boolean operator",
-                    "&&".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-            if self.token.is_ident_named("or") {
-                err.span_suggestion_short(
-                    self.span,
-                    "use `||` instead of `or` for the boolean operator",
-                    "||".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-            let sp = if self.token == token::Token::Eof {
-                // This is EOF, don't want to point at the following char, but rather the last token
-                self.prev_span
-            } else {
-                label_sp
-            };
-            match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
-                TokenType::Token(t) => Some(t.clone()),
-                _ => None,
-            }).collect::<Vec<_>>(), err) {
-                Err(e) => err = e,
-                Ok(recovered) => {
-                    return Ok(recovered);
-                }
-            }
-
-            let is_semi_suggestable = expected.iter().any(|t| match t {
-                TokenType::Token(token::Semi) => true, // we expect a `;` here
-                _ => false,
-            }) && ( // a `;` would be expected before the current keyword
-                self.token.is_keyword(keywords::Break) ||
-                self.token.is_keyword(keywords::Continue) ||
-                self.token.is_keyword(keywords::For) ||
-                self.token.is_keyword(keywords::If) ||
-                self.token.is_keyword(keywords::Let) ||
-                self.token.is_keyword(keywords::Loop) ||
-                self.token.is_keyword(keywords::Match) ||
-                self.token.is_keyword(keywords::Return) ||
-                self.token.is_keyword(keywords::While)
-            );
-            let cm = self.sess.source_map();
-            match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
-                (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
-                    // The spans are in different lines, expected `;` and found `let` or `return`.
-                    // High likelihood that it is only a missing `;`.
-                    err.span_suggestion_short(
-                        label_sp,
-                        "a semicolon may be missing here",
-                        ";".to_string(),
-                        Applicability::MaybeIncorrect,
-                    );
-                    err.emit();
-                    return Ok(true);
-                }
-                (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                    // When the spans are in the same line, it means that the only content between
-                    // them is whitespace, point at the found token in that case:
-                    //
-                    // X |     () => { syntax error };
-                    //   |                    ^^^^^ expected one of 8 possible tokens here
-                    //
-                    // instead of having:
-                    //
-                    // X |     () => { syntax error };
-                    //   |                   -^^^^^ unexpected token
-                    //   |                   |
-                    //   |                   expected one of 8 possible tokens here
-                    err.span_label(self.span, label_exp);
-                }
-                _ if self.prev_span == syntax_pos::DUMMY_SP => {
-                    // Account for macro context where the previous span might not be
-                    // available to avoid incorrect output (#54841).
-                    err.span_label(self.span, "unexpected token");
-                }
-                _ => {
-                    err.span_label(sp, label_exp);
-                    err.span_label(self.span, "unexpected token");
-                }
-            }
-            Err(err)
-        }
-    }
-
-    /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
-    fn interpolated_or_expr_span(&self,
-                                 expr: PResult<'a, P<Expr>>)
-                                 -> PResult<'a, (Span, P<Expr>)> {
-        expr.map(|e| {
-            if self.prev_token_kind == PrevTokenKind::Interpolated {
-                (self.prev_span, e)
-            } else {
-                (e.span, e)
-            }
-        })
-    }
-
-    fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
-        let mut err = self.struct_span_err(self.span,
-                                           &format!("expected identifier, found {}",
-                                                    self.this_token_descr()));
-        if let token::Ident(ident, false) = &self.token {
-            if ident.is_raw_guess() {
-                err.span_suggestion(
-                    self.span,
-                    "you can escape reserved keywords to use them as identifiers",
-                    format!("r#{}", ident),
-                    Applicability::MaybeIncorrect,
-                );
-            }
+            self.expected_one_of_not_found(edible, inedible)
         }
-        if let Some(token_descr) = self.token_descr() {
-            err.span_label(self.span, format!("expected identifier, found {}", token_descr));
-        } else {
-            err.span_label(self.span, "expected identifier");
-            if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
-                err.span_suggestion(
-                    self.span,
-                    "remove this comma",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                );
-            }
-        }
-        err
     }
 
     pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
@@ -872,8 +469,8 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, _) => {
+        match self.token.kind {
+            token::Ident(name, _) => {
                 if self.token.is_reserved_ident() {
                     let mut err = self.expected_ident_found();
                     if recover {
@@ -882,16 +479,16 @@ impl<'a> Parser<'a> {
                         return Err(err);
                     }
                 }
-                let span = self.span;
+                let span = self.token.span;
                 self.bump();
-                Ok(Ident::new(ident.name, span))
+                Ok(Ident::new(name, span))
             }
             _ => {
                 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
-                        self.span_fatal_err(self.prev_span, Error::UselessDocComment)
-                    } else {
-                        self.expected_ident_found()
-                    })
+                    self.span_fatal_err(self.prev_span, Error::UselessDocComment)
+                } else {
+                    self.expected_ident_found()
+                })
             }
         }
     }
@@ -900,27 +497,27 @@ impl<'a> Parser<'a> {
     ///
     /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
     /// encountered.
-    crate fn check(&mut self, tok: &token::Token) -> bool {
+    crate fn check(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.token == *tok;
         if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
         is_present
     }
 
     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
-    pub fn eat(&mut self, tok: &token::Token) -> bool {
+    pub fn eat(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.check(tok);
         if is_present { self.bump() }
         is_present
     }
 
-    fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
+    fn check_keyword(&mut self, kw: Symbol) -> bool {
         self.expected_tokens.push(TokenType::Keyword(kw));
         self.token.is_keyword(kw)
     }
 
     /// If the next token is the given keyword, eats it and returns
     /// `true`. Otherwise, returns `false`.
-    pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
+    pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
         if self.check_keyword(kw) {
             self.bump();
             true
@@ -929,7 +526,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
+    fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
         if self.token.is_keyword(kw) {
             self.bump();
             true
@@ -941,7 +538,7 @@ impl<'a> Parser<'a> {
     /// If the given word is not a keyword, signals an error.
     /// If the next token is not the given word, signals an error.
     /// Otherwise, eats it.
-    fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
+    fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
         if !self.eat_keyword(kw) {
             self.unexpected()
         } else {
@@ -949,7 +546,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn check_ident(&mut self) -> bool {
+    crate fn check_ident(&mut self) -> bool {
         if self.token.is_ident() {
             true
         } else {
@@ -992,13 +589,13 @@ impl<'a> Parser<'a> {
     /// See issue #47856 for an example of when this may occur.
     fn eat_plus(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::Plus) => {
                 self.bump();
                 true
             }
             token::BinOpEq(token::Plus) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::Eq, span);
                 true
             }
@@ -1006,7 +603,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-
     /// Checks to see if the next token is either `+` or `+=`.
     /// Otherwise returns `false`.
     fn check_plus(&mut self) -> bool {
@@ -1023,13 +619,13 @@ impl<'a> Parser<'a> {
     /// `&` and continues. If an `&` is not seen, signals an error.
     fn expect_and(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::And) => {
                 self.bump();
                 Ok(())
             }
             token::AndAnd => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Ok(self.bump_with(token::BinOp(token::And), span))
             }
             _ => self.unexpected()
@@ -1040,13 +636,13 @@ impl<'a> Parser<'a> {
     /// `|` and continues. If an `|` is not seen, signals an error.
     fn expect_or(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::Or) => {
                 self.bump();
                 Ok(())
             }
             token::OrOr => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Ok(self.bump_with(token::BinOp(token::Or), span))
             }
             _ => self.unexpected()
@@ -1054,7 +650,7 @@ impl<'a> Parser<'a> {
     }
 
     fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
-        literal::expect_no_suffix(sp, &self.sess.span_diagnostic, kind, suffix)
+        literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
     }
 
     /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
@@ -1065,18 +661,18 @@ impl<'a> Parser<'a> {
     /// starting token.
     fn eat_lt(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Token(token::Lt));
-        let ate = match self.token {
+        let ate = match self.token.kind {
             token::Lt => {
                 self.bump();
                 true
             }
             token::BinOp(token::Shl) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::Lt, span);
                 true
             }
             token::LArrow => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::BinOp(token::Minus), span);
                 true
             }
@@ -1105,21 +701,21 @@ impl<'a> Parser<'a> {
     /// with a single `>` and continues. If a `>` is not seen, signals an error.
     fn expect_gt(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::Gt));
-        let ate = match self.token {
+        let ate = match self.token.kind {
             token::Gt => {
                 self.bump();
                 Some(())
             }
             token::BinOp(token::Shr) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Gt, span))
             }
             token::BinOpEq(token::Shr) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Ge, span))
             }
             token::Ge => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Eq, span))
             }
             _ => None,
@@ -1139,30 +735,16 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
-    /// passes through any errors encountered. Used for error recovery.
-    fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
-        let handler = self.diagnostic();
-
-        if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
-                                                                  SeqSep::none(),
-                                                                  TokenExpectType::Expect,
-                                                                  |p| Ok(p.parse_token_tree())) {
-            handler.cancel(err);
-        }
-    }
-
     /// Parses a sequence, including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_end<T, F>(&mut self,
-                                  ket: &token::Token,
-                                  sep: SeqSep,
-                                  f: F)
-                                  -> PResult<'a, Vec<T>> where
-        F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
-    {
-        let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+    pub fn parse_seq_to_end<T>(
+        &mut self,
+        ket: &TokenKind,
+        sep: SeqSep,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
+    ) -> PResult<'a, Vec<T>> {
+        let (val, _, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
         if !recovered {
             self.bump();
         }
@@ -1172,39 +754,39 @@ impl<'a> Parser<'a> {
     /// Parses a sequence, not including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_before_end<T, F>(
+    pub fn parse_seq_to_before_end<T>(
         &mut self,
-        ket: &token::Token,
+        ket: &TokenKind,
         sep: SeqSep,
-        f: F,
-    ) -> PResult<'a, (Vec<T>, bool)>
-        where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
-    {
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool, bool)> {
         self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
     }
 
-    fn parse_seq_to_before_tokens<T, F>(
+    fn expect_any_with_type(&mut self, kets: &[&TokenKind], expect: TokenExpectType) -> bool {
+        kets.iter().any(|k| {
+            match expect {
+                TokenExpectType::Expect => self.check(k),
+                TokenExpectType::NoExpect => self.token == **k,
+            }
+        })
+    }
+
+    crate fn parse_seq_to_before_tokens<T>(
         &mut self,
-        kets: &[&token::Token],
+        kets: &[&TokenKind],
         sep: SeqSep,
         expect: TokenExpectType,
-        mut f: F,
-    ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
-        where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
-    {
+        mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool /* trailing */, bool /* recovered */)> {
         let mut first = true;
         let mut recovered = false;
+        let mut trailing = false;
         let mut v = vec![];
-        while !kets.iter().any(|k| {
-                match expect {
-                    TokenExpectType::Expect => self.check(k),
-                    TokenExpectType::NoExpect => self.token == **k,
-                }
-            }) {
-            match self.token {
-                token::CloseDelim(..) | token::Eof => break,
-                _ => {}
-            };
+        while !self.expect_any_with_type(kets, expect) {
+            if let token::CloseDelim(..) | token::Eof = self.token.kind {
+                break
+            }
             if let Some(ref t) = sep.sep {
                 if first {
                     first = false;
@@ -1218,7 +800,7 @@ impl<'a> Parser<'a> {
                         Err(mut e) => {
                             // Attempt to keep parsing if it was a similar separator
                             if let Some(ref tokens) = t.similar_tokens() {
-                                if tokens.contains(&self.token) {
+                                if tokens.contains(&self.token.kind) {
                                     self.bump();
                                 }
                             }
@@ -1238,12 +820,8 @@ impl<'a> Parser<'a> {
                     }
                 }
             }
-            if sep.trailing_sep_allowed && kets.iter().any(|k| {
-                match expect {
-                    TokenExpectType::Expect => self.check(k),
-                    TokenExpectType::NoExpect => self.token == **k,
-                }
-            }) {
+            if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) {
+                trailing = true;
                 break;
             }
 
@@ -1251,27 +829,45 @@ impl<'a> Parser<'a> {
             v.push(t);
         }
 
-        Ok((v, recovered))
+        Ok((v, trailing, recovered))
     }
 
     /// Parses a sequence, including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    fn parse_unspanned_seq<T, F>(
+    fn parse_unspanned_seq<T>(
         &mut self,
-        bra: &token::Token,
-        ket: &token::Token,
+        bra: &TokenKind,
+        ket: &TokenKind,
         sep: SeqSep,
-        f: F,
-    ) -> PResult<'a, Vec<T>> where
-        F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
-    {
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
         self.expect(bra)?;
-        let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+        let (result, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
         if !recovered {
             self.eat(ket);
         }
-        Ok(result)
+        Ok((result, trailing))
+    }
+
+    fn parse_delim_comma_seq<T>(
+        &mut self,
+        delim: DelimToken,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
+        self.parse_unspanned_seq(
+            &token::OpenDelim(delim),
+            &token::CloseDelim(delim),
+            SeqSep::trailing_allowed(token::Comma),
+            f,
+        )
+    }
+
+    fn parse_paren_comma_seq<T>(
+        &mut self,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
+        self.parse_delim_comma_seq(token::Paren, f)
     }
 
     /// Advance the parser by one token
@@ -1281,10 +877,10 @@ impl<'a> Parser<'a> {
             self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
         }
 
-        self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
+        self.prev_span = self.meta_var_span.take().unwrap_or(self.token.span);
 
         // Record last token kind for possible error recovery.
-        self.prev_token_kind = match self.token {
+        self.prev_token_kind = match self.token.kind {
             token::DocComment(..) => PrevTokenKind::DocComment,
             token::Comma => PrevTokenKind::Comma,
             token::BinOp(token::Plus) => PrevTokenKind::Plus,
@@ -1295,9 +891,7 @@ impl<'a> Parser<'a> {
             _ => PrevTokenKind::Other,
         };
 
-        let next = self.next_tok();
-        self.span = next.sp;
-        self.token = next.tok;
+        self.token = self.next_tok();
         self.expected_tokens.clear();
         // check after each token
         self.process_potential_macro_variable();
@@ -1305,125 +899,45 @@ impl<'a> Parser<'a> {
 
     /// Advance the parser using provided token as a next one. Use this when
     /// consuming a part of a token. For example a single `<` from `<<`.
-    fn bump_with(&mut self, next: token::Token, span: Span) {
-        self.prev_span = self.span.with_hi(span.lo());
+    fn bump_with(&mut self, next: TokenKind, span: Span) {
+        self.prev_span = self.token.span.with_hi(span.lo());
         // It would be incorrect to record the kind of the current token, but
         // fortunately for tokens currently using `bump_with`, the
         // prev_token_kind will be of no use anyway.
         self.prev_token_kind = PrevTokenKind::Other;
-        self.span = span;
-        self.token = next;
+        self.token = Token::new(next, span);
         self.expected_tokens.clear();
     }
 
     pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
-        F: FnOnce(&token::Token) -> R,
+        F: FnOnce(&Token) -> R,
     {
         if dist == 0 {
-            return f(&self.token)
+            return f(&self.token);
         }
 
-        f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
+        let frame = &self.token_cursor.frame;
+        f(&match frame.tree_cursor.look_ahead(dist - 1) {
             Some(tree) => match tree {
-                TokenTree::Token(_, tok) => tok,
-                TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
-            },
-            None => token::CloseDelim(self.token_cursor.frame.delim),
+                TokenTree::Token(token) => token,
+                TokenTree::Delimited(dspan, delim, _) =>
+                    Token::new(token::OpenDelim(delim), dspan.open),
+            }
+            None => Token::new(token::CloseDelim(frame.delim), frame.span.close)
         })
     }
 
-    crate fn look_ahead_span(&self, dist: usize) -> Span {
-        if dist == 0 {
-            return self.span
-        }
-
-        match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
-            Some(TokenTree::Token(span, _)) => span,
-            Some(TokenTree::Delimited(span, ..)) => span.entire(),
-            None => self.look_ahead_span(dist - 1),
-        }
-    }
-    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(self.span, m)
-    }
-    pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(sp, m)
-    }
-    fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
-        err.span_err(sp, self.diagnostic())
-    }
-    fn bug(&self, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(self.span, m)
-    }
-    fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
-        self.sess.span_diagnostic.span_err(sp, m)
-    }
-    crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_err(sp, m)
-    }
-    crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(sp, m)
-    }
-
-    fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
-        self.sess.span_diagnostic.cancel(err)
-    }
-
-    crate fn diagnostic(&self) -> &'a errors::Handler {
-        &self.sess.span_diagnostic
-    }
-
-    /// Is the current token one of the keywords that signals a bare function type?
-    fn token_is_bare_fn_keyword(&mut self) -> bool {
-        self.check_keyword(keywords::Fn) ||
-            self.check_keyword(keywords::Unsafe) ||
-            self.check_keyword(keywords::Extern)
-    }
-
-    /// Parses a `TyKind::BareFn` type.
-    fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
-        /*
-
-        [unsafe] [extern "ABI"] fn (S) -> T
-         ^~~~^           ^~~~^     ^~^    ^
-           |               |        |     |
-           |               |        |   Return type
-           |               |      Argument types
-           |               |
-           |              ABI
-        Function Style
-        */
-
-        let unsafety = self.parse_unsafety();
-        let abi = if self.eat_keyword(keywords::Extern) {
-            self.parse_opt_abi()?.unwrap_or(Abi::C)
-        } else {
-            Abi::Rust
-        };
-
-        self.expect_keyword(keywords::Fn)?;
-        let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
-        let ret_ty = self.parse_ret_ty(false)?;
-        let decl = P(FnDecl {
-            inputs,
-            output: ret_ty,
-            c_variadic,
-        });
-        Ok(TyKind::BareFn(P(BareFnTy {
-            abi,
-            unsafety,
-            generic_params,
-            decl,
-        })))
+    /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
+    fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
+        self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
     }
 
     /// Parses asyncness: `async` or nothing.
     fn parse_asyncness(&mut self) -> IsAsync {
-        if self.eat_keyword(keywords::Async) {
+        if self.eat_keyword(kw::Async) {
             IsAsync::Async {
                 closure_id: ast::DUMMY_NODE_ID,
                 return_impl_trait_id: ast::DUMMY_NODE_ID,
-                arguments: Vec::new(),
             }
         } else {
             IsAsync::NotAsync
@@ -1432,365 +946,21 @@ impl<'a> Parser<'a> {
 
     /// Parses unsafety: `unsafe` or nothing.
     fn parse_unsafety(&mut self) -> Unsafety {
-        if self.eat_keyword(keywords::Unsafe) {
+        if self.eat_keyword(kw::Unsafe) {
             Unsafety::Unsafe
         } else {
             Unsafety::Normal
         }
     }
 
-    /// Parses the items in a trait declaration.
-    pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
-        maybe_whole!(self, NtTraitItem, |x| x);
-        let attrs = self.parse_outer_attributes()?;
-        let mut unclosed_delims = vec![];
-        let (mut item, tokens) = self.collect_tokens(|this| {
-            let item = this.parse_trait_item_(at_end, attrs);
-            unclosed_delims.append(&mut this.unclosed_delims);
-            item
-        })?;
-        self.unclosed_delims.append(&mut unclosed_delims);
-        // See `parse_item` for why this clause is here.
-        if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
-            item.tokens = Some(tokens);
-        }
-        Ok(item)
-    }
-
-    fn parse_trait_item_(&mut self,
-                         at_end: &mut bool,
-                         mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
-        let lo = self.span;
-        self.eat_bad_pub();
-        let (name, node, generics) = if self.eat_keyword(keywords::Type) {
-            self.parse_trait_item_assoc_ty()?
-        } else if self.is_const_item() {
-            self.expect_keyword(keywords::Const)?;
-            let ident = self.parse_ident()?;
-            self.expect(&token::Colon)?;
-            let ty = self.parse_ty()?;
-            let default = if self.eat(&token::Eq) {
-                let expr = self.parse_expr()?;
-                self.expect(&token::Semi)?;
-                Some(expr)
-            } else {
-                self.expect(&token::Semi)?;
-                None
-            };
-            (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
-        } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
-            // trait item macro.
-            (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
-        } else {
-            let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
-
-            let ident = self.parse_ident()?;
-            let mut generics = self.parse_generics()?;
-
-            let mut decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
-                // This is somewhat dubious; We don't want to allow
-                // argument names to be left off if there is a
-                // definition...
-
-                // We don't allow argument names to be left off in edition 2018.
-                p.parse_arg_general(p.span.rust_2018(), true, false)
-            })?;
-            generics.where_clause = self.parse_where_clause()?;
-            self.construct_async_arguments(&mut asyncness, &mut decl);
-
-            let sig = ast::MethodSig {
-                header: FnHeader {
-                    unsafety,
-                    constness,
-                    abi,
-                    asyncness,
-                },
-                decl,
-            };
-
-            let body = match self.token {
-                token::Semi => {
-                    self.bump();
-                    *at_end = true;
-                    debug!("parse_trait_methods(): parsing required method");
-                    None
-                }
-                token::OpenDelim(token::Brace) => {
-                    debug!("parse_trait_methods(): parsing provided method");
-                    *at_end = true;
-                    let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
-                    attrs.extend(inner_attrs.iter().cloned());
-                    Some(body)
-                }
-                token::Interpolated(ref nt) => {
-                    match **nt {
-                        token::NtBlock(..) => {
-                            *at_end = true;
-                            let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
-                            attrs.extend(inner_attrs.iter().cloned());
-                            Some(body)
-                        }
-                        _ => {
-                            let token_str = self.this_token_descr();
-                            let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
-                                                              token_str));
-                            err.span_label(self.span, "expected `;` or `{`");
-                            return Err(err);
-                        }
-                    }
-                }
-                _ => {
-                    let token_str = self.this_token_descr();
-                    let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
-                                                      token_str));
-                    err.span_label(self.span, "expected `;` or `{`");
-                    return Err(err);
-                }
-            };
-            (ident, ast::TraitItemKind::Method(sig, body), generics)
-        };
-
-        Ok(TraitItem {
-            id: ast::DUMMY_NODE_ID,
-            ident: name,
-            attrs,
-            generics,
-            node,
-            span: lo.to(self.prev_span),
-            tokens: None,
-        })
-    }
-
-    /// Parses an optional return type `[ -> TY ]` in a function declaration.
-    fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
-        if self.eat(&token::RArrow) {
-            Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
-        } else {
-            Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
-        }
-    }
-
-    /// Parses a type.
-    pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
-        self.parse_ty_common(true, true, false)
-    }
-
-    /// Parses a type in restricted contexts where `+` is not permitted.
-    ///
-    /// Example 1: `&'a TYPE`
-    ///     `+` is prohibited to maintain operator priority (P(+) < P(&)).
-    /// Example 2: `value1 as TYPE + value2`
-    ///     `+` is prohibited to avoid interactions with expression grammar.
-    fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
-        self.parse_ty_common(false, true, false)
-    }
-
-    fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
-                       allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
-        maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
-        maybe_whole!(self, NtTy, |x| x);
-
-        let lo = self.span;
-        let mut impl_dyn_multi = false;
-        let node = if self.eat(&token::OpenDelim(token::Paren)) {
-            // `(TYPE)` is a parenthesized type.
-            // `(TYPE,)` is a tuple with a single field of type TYPE.
-            let mut ts = vec![];
-            let mut last_comma = false;
-            while self.token != token::CloseDelim(token::Paren) {
-                ts.push(self.parse_ty()?);
-                if self.eat(&token::Comma) {
-                    last_comma = true;
-                } else {
-                    last_comma = false;
-                    break;
-                }
-            }
-            let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
-            self.expect(&token::CloseDelim(token::Paren))?;
-
-            if ts.len() == 1 && !last_comma {
-                let ty = ts.into_iter().nth(0).unwrap().into_inner();
-                let maybe_bounds = allow_plus && self.token.is_like_plus();
-                match ty.node {
-                    // `(TY_BOUND_NOPAREN) + BOUND + ...`.
-                    TyKind::Path(None, ref path) if maybe_bounds => {
-                        self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
-                    }
-                    TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
-                            if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
-                        let path = match bounds[0] {
-                            GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
-                            GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
-                        };
-                        self.parse_remaining_bounds(Vec::new(), path, lo, true)?
-                    }
-                    // `(TYPE)`
-                    _ => TyKind::Paren(P(ty))
-                }
-            } else {
-                TyKind::Tup(ts)
-            }
-        } else if self.eat(&token::Not) {
-            // Never type `!`
-            TyKind::Never
-        } else if self.eat(&token::BinOp(token::Star)) {
-            // Raw pointer
-            TyKind::Ptr(self.parse_ptr()?)
-        } else if self.eat(&token::OpenDelim(token::Bracket)) {
-            // Array or slice
-            let t = self.parse_ty()?;
-            // Parse optional `; EXPR` in `[TYPE; EXPR]`
-            let t = match self.maybe_parse_fixed_length_of_vec()? {
-                None => TyKind::Slice(t),
-                Some(length) => TyKind::Array(t, AnonConst {
-                    id: ast::DUMMY_NODE_ID,
-                    value: length,
-                }),
-            };
-            self.expect(&token::CloseDelim(token::Bracket))?;
-            t
-        } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
-            // Reference
-            self.expect_and()?;
-            self.parse_borrowed_pointee()?
-        } else if self.eat_keyword_noexpect(keywords::Typeof) {
-            // `typeof(EXPR)`
-            // In order to not be ambiguous, the type must be surrounded by parens.
-            self.expect(&token::OpenDelim(token::Paren))?;
-            let e = AnonConst {
-                id: ast::DUMMY_NODE_ID,
-                value: self.parse_expr()?,
-            };
-            self.expect(&token::CloseDelim(token::Paren))?;
-            TyKind::Typeof(e)
-        } else if self.eat_keyword(keywords::Underscore) {
-            // A type to be inferred `_`
-            TyKind::Infer
-        } else if self.token_is_bare_fn_keyword() {
-            // Function pointer type
-            self.parse_ty_bare_fn(Vec::new())?
-        } else if self.check_keyword(keywords::For) {
-            // Function pointer type or bound list (trait object type) starting with a poly-trait.
-            //   `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
-            //   `for<'lt> Trait1<'lt> + Trait2 + 'a`
-            let lo = self.span;
-            let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-            if self.token_is_bare_fn_keyword() {
-                self.parse_ty_bare_fn(lifetime_defs)?
-            } else {
-                let path = self.parse_path(PathStyle::Type)?;
-                let parse_plus = allow_plus && self.check_plus();
-                self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
-            }
-        } else if self.eat_keyword(keywords::Impl) {
-            // Always parse bounds greedily for better error recovery.
-            let bounds = self.parse_generic_bounds(None)?;
-            impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
-            TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
-        } else if self.check_keyword(keywords::Dyn) &&
-                  (self.span.rust_2018() ||
-                   self.look_ahead(1, |t| t.can_begin_bound() &&
-                                          !can_continue_type_after_non_fn_ident(t))) {
-            self.bump(); // `dyn`
-            // Always parse bounds greedily for better error recovery.
-            let bounds = self.parse_generic_bounds(None)?;
-            impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
-            TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
-        } else if self.check(&token::Question) ||
-                  self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
-            // Bound list (trait object type)
-            TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
-                                TraitObjectSyntax::None)
-        } else if self.eat_lt() {
-            // Qualified path
-            let (qself, path) = self.parse_qpath(PathStyle::Type)?;
-            TyKind::Path(Some(qself), path)
-        } else if self.token.is_path_start() {
-            // Simple path
-            let path = self.parse_path(PathStyle::Type)?;
-            if self.eat(&token::Not) {
-                // Macro invocation in type position
-                let (delim, tts) = self.expect_delimited_token_tree()?;
-                let node = Mac_ { path, tts, delim };
-                TyKind::Mac(respan(lo.to(self.prev_span), node))
-            } else {
-                // Just a type path or bound list (trait object type) starting with a trait.
-                //   `Type`
-                //   `Trait1 + Trait2 + 'a`
-                if allow_plus && self.check_plus() {
-                    self.parse_remaining_bounds(Vec::new(), path, lo, true)?
-                } else {
-                    TyKind::Path(None, path)
-                }
-            }
-        } else if self.check(&token::DotDotDot) {
-            if allow_c_variadic {
-                self.eat(&token::DotDotDot);
-                TyKind::CVarArgs
-            } else {
-                return Err(self.fatal(
-                    "only foreign functions are allowed to be C-variadic"
-                ));
-            }
-        } else {
-            let msg = format!("expected type, found {}", self.this_token_descr());
-            return Err(self.fatal(&msg));
-        };
-
-        let span = lo.to(self.prev_span);
-        let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
-
-        // Try to recover from use of `+` with incorrect priority.
-        self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
-        self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
-        self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
-    }
-
-    fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
-                              lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
-        let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
-        let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
-        if parse_plus {
-            self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
-            bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
-        }
-        Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
-    }
-
-    fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
-        let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
-        let mutbl = self.parse_mutability();
-        let ty = self.parse_ty_no_plus()?;
-        return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
-    }
-
-    fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
-        let mutbl = if self.eat_keyword(keywords::Mut) {
-            Mutability::Mutable
-        } else if self.eat_keyword(keywords::Const) {
-            Mutability::Immutable
-        } else {
-            let span = self.prev_span;
-            let msg = "expected mut or const in raw pointer type";
-            self.struct_span_err(span, msg)
-                .span_label(span, msg)
-                .help("use `*mut T` or `*const T` as appropriate")
-                .emit();
-            Mutability::Immutable
-        };
-        let t = self.parse_ty_no_plus()?;
-        Ok(MutTy { ty: t, mutbl: mutbl })
-    }
-
     fn is_named_argument(&self) -> bool {
-        let offset = match self.token {
+        let offset = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
                 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
                 _ => 0,
             }
             token::BinOp(token::And) | token::AndAnd => 1,
-            _ if self.token.is_keyword(keywords::Mut) => 1,
+            _ if self.token.is_keyword(kw::Mut) => 1,
             _ => 0,
         };
 
@@ -1800,88 +970,48 @@ impl<'a> Parser<'a> {
 
     /// Skips unexpected attributes and doc comments in this position and emits an appropriate
     /// error.
-    fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
-        if let token::DocComment(_) = self.token {
-            let mut err = self.diagnostic().struct_span_err(
-                self.span,
-                &format!("documentation comments cannot be applied to {}", applied_to),
-            );
-            err.span_label(self.span, "doc comments are not allowed here");
-            err.emit();
-            self.bump();
-        } else if self.token == token::Pound && self.look_ahead(1, |t| {
-            *t == token::OpenDelim(token::Bracket)
-        }) {
-            let lo = self.span;
-            // Skip every token until next possible arg.
-            while self.token != token::CloseDelim(token::Bracket) {
-                self.bump();
-            }
-            let sp = lo.to(self.span);
-            self.bump();
-            let mut err = self.diagnostic().struct_span_err(
-                sp,
-                &format!("attributes cannot be applied to {}", applied_to),
-            );
-            err.span_label(sp, "attributes are not allowed here");
-            err.emit();
-        }
-    }
-
     /// This version of parse arg doesn't necessarily require identifier names.
-    fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool,
-                         allow_c_variadic: bool) -> PResult<'a, Arg> {
-        if let Ok(Some(_)) = self.parse_self_arg() {
-            let mut err = self.struct_span_err(self.prev_span,
-                "unexpected `self` argument in function");
-            err.span_label(self.prev_span,
-                "`self` is only valid as the first argument of an associated function");
-            return Err(err);
+    fn parse_arg_general<F>(
+        &mut self,
+        is_trait_item: bool,
+        allow_c_variadic: bool,
+        is_name_required: F,
+    ) -> PResult<'a, Arg>
+    where
+        F: Fn(&token::Token) -> bool
+    {
+        let lo = self.token.span;
+        let attrs = self.parse_arg_attributes()?;
+        if let Some(mut arg) = self.parse_self_arg()? {
+            arg.attrs = attrs.into();
+            return self.recover_bad_self_arg(arg, is_trait_item);
         }
 
-        let (pat, ty) = if require_name || self.is_named_argument() {
-            debug!("parse_arg_general parse_pat (require_name:{})",
-                   require_name);
-            self.eat_incorrect_doc_comment("method arguments");
-            let pat = self.parse_pat(Some("argument name"))?;
+        let is_name_required = is_name_required(&self.token);
+        let (pat, ty) = if is_name_required || self.is_named_argument() {
+            debug!("parse_arg_general parse_pat (is_name_required:{})", is_name_required);
 
+            let pat = self.parse_pat(Some("argument name"))?;
             if let Err(mut err) = self.expect(&token::Colon) {
-                // If we find a pattern followed by an identifier, it could be an (incorrect)
-                // C-style parameter declaration.
-                if self.check_ident() && self.look_ahead(1, |t| {
-                    *t == token::Comma || *t == token::CloseDelim(token::Paren)
-                }) {
-                    let ident = self.parse_ident().unwrap();
-                    let span = pat.span.with_hi(ident.span.hi());
-
-                    err.span_suggestion(
-                        span,
-                        "declare the type after the parameter binding",
-                        String::from("<identifier>: <type>"),
-                        Applicability::HasPlaceholders,
-                    );
-                } else if require_name && is_trait_item {
-                    if let PatKind::Ident(_, ident, _) = pat.node {
-                        err.span_suggestion(
-                            pat.span,
-                            "explicitly ignore parameter",
-                            format!("_: {}", ident),
-                            Applicability::MachineApplicable,
-                        );
-                    }
-
-                    err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
+                if let Some(ident) = self.argument_without_type(
+                    &mut err,
+                    pat,
+                    is_name_required,
+                    is_trait_item,
+                ) {
+                    err.emit();
+                    return Ok(dummy_arg(ident));
+                } else {
+                    return Err(err);
                 }
-
-                return Err(err);
             }
 
-            self.eat_incorrect_doc_comment("a method argument's type");
+            self.eat_incorrect_doc_comment_for_arg_type();
             (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
         } else {
             debug!("parse_arg_general ident_to_pat");
             let parser_snapshot_before_ty = self.clone();
-            self.eat_incorrect_doc_comment("a method argument's type");
+            self.eat_incorrect_doc_comment_for_arg_type();
             let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
             if ty.is_ok() && self.token != token::Comma &&
                self.token != token::CloseDelim(token::Paren) {
@@ -1891,13 +1021,9 @@ impl<'a> Parser<'a> {
             }
             match ty {
                 Ok(ty) => {
-                    let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
-                    let pat = P(Pat {
-                        id: ast::DUMMY_NODE_ID,
-                        node: PatKind::Ident(
-                            BindingMode::ByValue(Mutability::Immutable), ident, None),
-                        span: ty.span,
-                    });
+                    let ident = Ident::new(kw::Invalid, self.prev_span);
+                    let bm = BindingMode::ByValue(Mutability::Immutable);
+                    let pat = self.mk_pat_ident(ty.span, bm, ident);
                     (pat, ty)
                 }
                 Err(mut err) => {
@@ -1909,331 +1035,19 @@ impl<'a> Parser<'a> {
                     // Recover from attempting to parse the argument as a type without pattern.
                     err.cancel();
                     mem::replace(self, parser_snapshot_before_ty);
-                    let pat = self.parse_pat(Some("argument name"))?;
-                    self.expect(&token::Colon)?;
-                    let ty = self.parse_ty()?;
-
-                    let mut err = self.diagnostic().struct_span_err_with_code(
-                        pat.span,
-                        "patterns aren't allowed in methods without bodies",
-                        DiagnosticId::Error("E0642".into()),
-                    );
-                    err.span_suggestion_short(
-                        pat.span,
-                        "give this argument a name or use an underscore to ignore it",
-                        "_".to_owned(),
-                        Applicability::MachineApplicable,
-                    );
-                    err.emit();
-
-                    // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
-                    let pat = P(Pat {
-                        node: PatKind::Wild,
-                        span: pat.span,
-                        id: ast::DUMMY_NODE_ID
-                    });
-                    (pat, ty)
+                    self.recover_arg_parse()?
                 }
             }
         };
 
-        Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal })
-    }
-
-    /// Parses a single function argument.
-    crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
-        self.parse_arg_general(true, false, false)
-    }
+        let span = lo.to(self.token.span);
 
-    /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
-    fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
-        let pat = self.parse_pat(Some("argument name"))?;
-        let t = if self.eat(&token::Colon) {
-            self.parse_ty()?
-        } else {
-            P(Ty {
-                id: ast::DUMMY_NODE_ID,
-                node: TyKind::Infer,
-                span: self.prev_span,
-            })
-        };
-        Ok(Arg {
-            ty: t,
-            pat,
-            id: ast::DUMMY_NODE_ID,
-            source: ast::ArgSource::Normal,
-        })
-    }
-
-    fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
-        if self.eat(&token::Semi) {
-            Ok(Some(self.parse_expr()?))
-        } else {
-            Ok(None)
-        }
-    }
-
-    /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
-    crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
-        maybe_whole_expr!(self);
-
-        let minus_lo = self.span;
-        let minus_present = self.eat(&token::BinOp(token::Minus));
-        let lo = self.span;
-        let literal = self.parse_lit()?;
-        let hi = self.prev_span;
-        let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
-
-        if minus_present {
-            let minus_hi = self.prev_span;
-            let unary = self.mk_unary(UnOp::Neg, expr);
-            Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
-        } else {
-            Ok(expr)
-        }
-    }
-
-    fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
-                let span = self.span;
-                self.bump();
-                Ok(Ident::new(ident.name, span))
-            }
-            _ => self.parse_ident(),
-        }
-    }
-
-    fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
-                let span = self.span;
-                self.bump();
-                Ok(Ident::new(ident.name, span))
-            }
-            _ => self.parse_ident(),
-        }
-    }
-
-    /// Parses a qualified path.
-    /// Assumes that the leading `<` has been parsed already.
-    ///
-    /// `qualified_path = <type [as trait_ref]>::path`
-    ///
-    /// # Examples
-    /// `<T>::default`
-    /// `<T as U>::a`
-    /// `<T as U>::F::a<S>` (without disambiguator)
-    /// `<T as U>::F::a::<S>` (with disambiguator)
-    fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
-        let lo = self.prev_span;
-        let ty = self.parse_ty()?;
-
-        // `path` will contain the prefix of the path up to the `>`,
-        // if any (e.g., `U` in the `<T as U>::*` examples
-        // above). `path_span` has the span of that path, or an empty
-        // span in the case of something like `<T>::Bar`.
-        let (mut path, path_span);
-        if self.eat_keyword(keywords::As) {
-            let path_lo = self.span;
-            path = self.parse_path(PathStyle::Type)?;
-            path_span = path_lo.to(self.prev_span);
-        } else {
-            path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
-            path_span = self.span.to(self.span);
-        }
-
-        // See doc comment for `unmatched_angle_bracket_count`.
-        self.expect(&token::Gt)?;
-        if self.unmatched_angle_bracket_count > 0 {
-            self.unmatched_angle_bracket_count -= 1;
-            debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
-        }
-
-        self.expect(&token::ModSep)?;
-
-        let qself = QSelf { ty, path_span, position: path.segments.len() };
-        self.parse_path_segments(&mut path.segments, style)?;
-
-        Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
-    }
-
-    /// Parses simple paths.
-    ///
-    /// `path = [::] segment+`
-    /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
-    ///
-    /// # Examples
-    /// `a::b::C<D>` (without disambiguator)
-    /// `a::b::C::<D>` (with disambiguator)
-    /// `Fn(Args)` (without disambiguator)
-    /// `Fn::(Args)` (with disambiguator)
-    pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
-        maybe_whole!(self, NtPath, |path| {
-            if style == PathStyle::Mod &&
-               path.segments.iter().any(|segment| segment.args.is_some()) {
-                self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
-            }
-            path
-        });
-
-        let lo = self.meta_var_span.unwrap_or(self.span);
-        let mut segments = Vec::new();
-        let mod_sep_ctxt = self.span.ctxt();
-        if self.eat(&token::ModSep) {
-            segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
-        }
-        self.parse_path_segments(&mut segments, style)?;
-
-        Ok(ast::Path { segments, span: lo.to(self.prev_span) })
-    }
-
-    /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
-    /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
-    /// attributes.
-    pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
-        let meta_ident = match self.token {
-            token::Interpolated(ref nt) => match **nt {
-                token::NtMeta(ref meta) => match meta.node {
-                    ast::MetaItemKind::Word => Some(meta.path.clone()),
-                    _ => None,
-                },
-                _ => None,
-            },
-            _ => None,
-        };
-        if let Some(path) = meta_ident {
-            self.bump();
-            return Ok(path);
-        }
-        self.parse_path(style)
-    }
-
-    crate fn parse_path_segments(&mut self,
-                           segments: &mut Vec<PathSegment>,
-                           style: PathStyle)
-                           -> PResult<'a, ()> {
-        loop {
-            let segment = self.parse_path_segment(style)?;
-            if style == PathStyle::Expr {
-                // In order to check for trailing angle brackets, we must have finished
-                // recursing (`parse_path_segment` can indirectly call this function),
-                // that is, the next token must be the highlighted part of the below example:
-                //
-                // `Foo::<Bar as Baz<T>>::Qux`
-                //                      ^ here
-                //
-                // As opposed to the below highlight (if we had only finished the first
-                // recursion):
-                //
-                // `Foo::<Bar as Baz<T>>::Qux`
-                //                     ^ here
-                //
-                // `PathStyle::Expr` is only provided at the root invocation and never in
-                // `parse_path_segment` to recurse and therefore can be checked to maintain
-                // this invariant.
-                self.check_trailing_angle_brackets(&segment, token::ModSep);
-            }
-            segments.push(segment);
-
-            if self.is_import_coupler() || !self.eat(&token::ModSep) {
-                return Ok(());
-            }
-        }
-    }
-
-    fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
-        let ident = self.parse_path_segment_ident()?;
-
-        let is_args_start = |token: &token::Token| match *token {
-            token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
-            | token::LArrow => true,
-            _ => false,
-        };
-        let check_args_start = |this: &mut Self| {
-            this.expected_tokens.extend_from_slice(
-                &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
-            );
-            is_args_start(&this.token)
-        };
-
-        Ok(if style == PathStyle::Type && check_args_start(self) ||
-              style != PathStyle::Mod && self.check(&token::ModSep)
-                                      && self.look_ahead(1, |t| is_args_start(t)) {
-            // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
-            // it isn't, then we reset the unmatched angle bracket count as we're about to start
-            // parsing a new path.
-            if style == PathStyle::Expr {
-                self.unmatched_angle_bracket_count = 0;
-                self.max_angle_bracket_count = 0;
-            }
-
-            // Generic arguments are found - `<`, `(`, `::<` or `::(`.
-            self.eat(&token::ModSep);
-            let lo = self.span;
-            let args = if self.eat_lt() {
-                // `<'a, T, A = U>`
-                let (args, bindings) =
-                    self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
-                self.expect_gt()?;
-                let span = lo.to(self.prev_span);
-                AngleBracketedArgs { args, bindings, span }.into()
-            } else {
-                // `(T, U) -> R`
-                self.bump(); // `(`
-                let (inputs, recovered) = self.parse_seq_to_before_tokens(
-                    &[&token::CloseDelim(token::Paren)],
-                    SeqSep::trailing_allowed(token::Comma),
-                    TokenExpectType::Expect,
-                    |p| p.parse_ty())?;
-                if !recovered {
-                    self.bump(); // `)`
-                }
-                let span = lo.to(self.prev_span);
-                let output = if self.eat(&token::RArrow) {
-                    Some(self.parse_ty_common(false, false, false)?)
-                } else {
-                    None
-                };
-                ParenthesizedArgs { inputs, output, span }.into()
-            };
-
-            PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
-        } else {
-            // Generic arguments are not found.
-            PathSegment::from_ident(ident)
-        })
-    }
-
-    crate fn check_lifetime(&mut self) -> bool {
-        self.expected_tokens.push(TokenType::Lifetime);
-        self.token.is_lifetime()
-    }
-
-    /// Parses a single lifetime `'a` or panics.
-    crate fn expect_lifetime(&mut self) -> Lifetime {
-        if let Some(ident) = self.token.lifetime() {
-            let span = self.span;
-            self.bump();
-            Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
-        } else {
-            self.span_bug(self.span, "not a lifetime")
-        }
-    }
-
-    fn eat_label(&mut self) -> Option<Label> {
-        if let Some(ident) = self.token.lifetime() {
-            let span = self.span;
-            self.bump();
-            Some(Label { ident: Ident::new(ident.name, span) })
-        } else {
-            None
-        }
+        Ok(Arg { attrs: attrs.into(), id: ast::DUMMY_NODE_ID, pat, span, ty })
     }
 
     /// Parses mutability (`mut` or nothing).
     fn parse_mutability(&mut self) -> Mutability {
-        if self.eat_keyword(keywords::Mut) {
+        if self.eat_keyword(kw::Mut) {
             Mutability::Mutable
         } else {
             Mutability::Immutable
@@ -2241,102 +1055,23 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_field_name(&mut self) -> PResult<'a, Ident> {
-        if let token::Literal(token::Integer(name), suffix) = self.token {
-            self.expect_no_suffix(self.span, "a tuple index", suffix);
+        if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
+                self.token.kind {
+            self.expect_no_suffix(self.token.span, "a tuple index", suffix);
             self.bump();
-            Ok(Ident::new(name, self.prev_span))
+            Ok(Ident::new(symbol, self.prev_span))
         } else {
             self.parse_ident_common(false)
         }
     }
 
-    /// Parse ident (COLON expr)?
-    fn parse_field(&mut self) -> PResult<'a, Field> {
-        let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
-
-        // Check if a colon exists one ahead. This means we're parsing a fieldname.
-        let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
-            t == &token::Colon || t == &token::Eq
-        }) {
-            let fieldname = self.parse_field_name()?;
-
-            // Check for an equals token. This means the source incorrectly attempts to
-            // initialize a field with an eq rather than a colon.
-            if self.token == token::Eq {
-                self.diagnostic()
-                    .struct_span_err(self.span, "expected `:`, found `=`")
-                    .span_suggestion(
-                        fieldname.span.shrink_to_hi().to(self.span),
-                        "replace equals symbol with a colon",
-                        ":".to_string(),
-                        Applicability::MachineApplicable,
-                    )
-                    .emit();
-            }
-            self.bump(); // `:`
-            (fieldname, self.parse_expr()?, false)
-        } else {
-            let fieldname = self.parse_ident_common(false)?;
-
-            // Mimic `x: x` for the `x` field shorthand.
-            let path = ast::Path::from_ident(fieldname);
-            let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
-            (fieldname, expr, true)
-        };
-        Ok(ast::Field {
-            ident: fieldname,
-            span: lo.to(expr.span),
-            expr,
-            is_shorthand,
-            attrs: attrs.into(),
-        })
-    }
-
-    crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
-        P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
-    }
-
-    fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
-        ExprKind::Unary(unop, expr)
-    }
-
-    fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
-        ExprKind::Binary(binop, lhs, rhs)
-    }
-
-    fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
-        ExprKind::Call(f, args)
-    }
-
-    fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
-        ExprKind::Index(expr, idx)
-    }
-
-    fn mk_range(&self,
-                    start: Option<P<Expr>>,
-                    end: Option<P<Expr>>,
-                    limits: RangeLimits)
-                    -> PResult<'a, ast::ExprKind> {
-        if end.is_none() && limits == RangeLimits::Closed {
-            Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
-        } else {
-            Ok(ExprKind::Range(start, end, limits))
-        }
-    }
-
-    fn mk_assign_op(&self, binop: ast::BinOp,
-                        lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
-        ExprKind::AssignOp(binop, lhs, rhs)
-    }
-
     fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
-        let delim = match self.token {
+        let delim = match self.token.kind {
             token::OpenDelim(delim) => delim,
             _ => {
                 let msg = "expected open delimiter";
                 let mut err = self.fatal(msg);
-                err.span_label(self.span, msg);
+                err.span_label(self.token.span, msg);
                 return Err(err)
             }
         };
@@ -2353,461 +1088,6 @@ impl<'a> Parser<'a> {
         Ok((delim, tts.into()))
     }
 
-    /// At the bottom (top?) of the precedence hierarchy,
-    /// Parses things like parenthesized exprs, macros, `return`, etc.
-    ///
-    /// N.B., this does not parse outer attributes, and is private because it only works
-    /// correctly if called from `parse_dot_or_call_expr()`.
-    fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
-        maybe_recover_from_interpolated_ty_qpath!(self, true);
-        maybe_whole_expr!(self);
-
-        // Outer attributes are already parsed and will be
-        // added to the return value after the fact.
-        //
-        // Therefore, prevent sub-parser from parsing
-        // attributes by giving them a empty "already parsed" list.
-        let mut attrs = ThinVec::new();
-
-        let lo = self.span;
-        let mut hi = self.span;
-
-        let ex: ExprKind;
-
-        // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
-        match self.token {
-            token::OpenDelim(token::Paren) => {
-                self.bump();
-
-                attrs.extend(self.parse_inner_attributes()?);
-
-                // (e) is parenthesized e
-                // (e,) is a tuple with only one field, e
-                let mut es = vec![];
-                let mut trailing_comma = false;
-                let mut recovered = false;
-                while self.token != token::CloseDelim(token::Paren) {
-                    es.push(match self.parse_expr() {
-                        Ok(es) => es,
-                        Err(err) => {
-                            // recover from parse error in tuple list
-                            return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
-                        }
-                    });
-                    recovered = self.expect_one_of(
-                        &[],
-                        &[token::Comma, token::CloseDelim(token::Paren)],
-                    )?;
-                    if self.eat(&token::Comma) {
-                        trailing_comma = true;
-                    } else {
-                        trailing_comma = false;
-                        break;
-                    }
-                }
-                if !recovered {
-                    self.bump();
-                }
-
-                hi = self.prev_span;
-                ex = if es.len() == 1 && !trailing_comma {
-                    ExprKind::Paren(es.into_iter().nth(0).unwrap())
-                } else {
-                    ExprKind::Tup(es)
-                };
-            }
-            token::OpenDelim(token::Brace) => {
-                return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
-            }
-            token::BinOp(token::Or) | token::OrOr => {
-                return self.parse_lambda_expr(attrs);
-            }
-            token::OpenDelim(token::Bracket) => {
-                self.bump();
-
-                attrs.extend(self.parse_inner_attributes()?);
-
-                if self.eat(&token::CloseDelim(token::Bracket)) {
-                    // Empty vector.
-                    ex = ExprKind::Array(Vec::new());
-                } else {
-                    // Nonempty vector.
-                    let first_expr = self.parse_expr()?;
-                    if self.eat(&token::Semi) {
-                        // Repeating array syntax: [ 0; 512 ]
-                        let count = AnonConst {
-                            id: ast::DUMMY_NODE_ID,
-                            value: self.parse_expr()?,
-                        };
-                        self.expect(&token::CloseDelim(token::Bracket))?;
-                        ex = ExprKind::Repeat(first_expr, count);
-                    } else if self.eat(&token::Comma) {
-                        // Vector with two or more elements.
-                        let remaining_exprs = self.parse_seq_to_end(
-                            &token::CloseDelim(token::Bracket),
-                            SeqSep::trailing_allowed(token::Comma),
-                            |p| Ok(p.parse_expr()?)
-                        )?;
-                        let mut exprs = vec![first_expr];
-                        exprs.extend(remaining_exprs);
-                        ex = ExprKind::Array(exprs);
-                    } else {
-                        // Vector with one element.
-                        self.expect(&token::CloseDelim(token::Bracket))?;
-                        ex = ExprKind::Array(vec![first_expr]);
-                    }
-                }
-                hi = self.prev_span;
-            }
-            _ => {
-                if self.eat_lt() {
-                    let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
-                    hi = path.span;
-                    return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
-                }
-                if self.span.rust_2018() && self.check_keyword(keywords::Async) {
-                    return if self.is_async_block() { // check for `async {` and `async move {`
-                        self.parse_async_block(attrs)
-                    } else {
-                        self.parse_lambda_expr(attrs)
-                    };
-                }
-                if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
-                    return self.parse_lambda_expr(attrs);
-                }
-                if self.eat_keyword(keywords::If) {
-                    return self.parse_if_expr(attrs);
-                }
-                if self.eat_keyword(keywords::For) {
-                    let lo = self.prev_span;
-                    return self.parse_for_expr(None, lo, attrs);
-                }
-                if self.eat_keyword(keywords::While) {
-                    let lo = self.prev_span;
-                    return self.parse_while_expr(None, lo, attrs);
-                }
-                if let Some(label) = self.eat_label() {
-                    let lo = label.ident.span;
-                    self.expect(&token::Colon)?;
-                    if self.eat_keyword(keywords::While) {
-                        return self.parse_while_expr(Some(label), lo, attrs)
-                    }
-                    if self.eat_keyword(keywords::For) {
-                        return self.parse_for_expr(Some(label), lo, attrs)
-                    }
-                    if self.eat_keyword(keywords::Loop) {
-                        return self.parse_loop_expr(Some(label), lo, attrs)
-                    }
-                    if self.token == token::OpenDelim(token::Brace) {
-                        return self.parse_block_expr(Some(label),
-                                                     lo,
-                                                     BlockCheckMode::Default,
-                                                     attrs);
-                    }
-                    let msg = "expected `while`, `for`, `loop` or `{` after a label";
-                    let mut err = self.fatal(msg);
-                    err.span_label(self.span, msg);
-                    return Err(err);
-                }
-                if self.eat_keyword(keywords::Loop) {
-                    let lo = self.prev_span;
-                    return self.parse_loop_expr(None, lo, attrs);
-                }
-                if self.eat_keyword(keywords::Continue) {
-                    let label = self.eat_label();
-                    let ex = ExprKind::Continue(label);
-                    let hi = self.prev_span;
-                    return Ok(self.mk_expr(lo.to(hi), ex, attrs));
-                }
-                if self.eat_keyword(keywords::Match) {
-                    let match_sp = self.prev_span;
-                    return self.parse_match_expr(attrs).map_err(|mut err| {
-                        err.span_label(match_sp, "while parsing this match expression");
-                        err
-                    });
-                }
-                if self.eat_keyword(keywords::Unsafe) {
-                    return self.parse_block_expr(
-                        None,
-                        lo,
-                        BlockCheckMode::Unsafe(ast::UserProvided),
-                        attrs);
-                }
-                if self.is_do_catch_block() {
-                    let mut db = self.fatal("found removed `do catch` syntax");
-                    db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
-                    return Err(db);
-                }
-                if self.is_try_block() {
-                    let lo = self.span;
-                    assert!(self.eat_keyword(keywords::Try));
-                    return self.parse_try_block(lo, attrs);
-                }
-                if self.eat_keyword(keywords::Return) {
-                    if self.token.can_begin_expr() {
-                        let e = self.parse_expr()?;
-                        hi = e.span;
-                        ex = ExprKind::Ret(Some(e));
-                    } else {
-                        ex = ExprKind::Ret(None);
-                    }
-                } else if self.eat_keyword(keywords::Break) {
-                    let label = self.eat_label();
-                    let e = if self.token.can_begin_expr()
-                               && !(self.token == token::OpenDelim(token::Brace)
-                                    && self.restrictions.contains(
-                                           Restrictions::NO_STRUCT_LITERAL)) {
-                        Some(self.parse_expr()?)
-                    } else {
-                        None
-                    };
-                    ex = ExprKind::Break(label, e);
-                    hi = self.prev_span;
-                } else if self.eat_keyword(keywords::Yield) {
-                    if self.token.can_begin_expr() {
-                        let e = self.parse_expr()?;
-                        hi = e.span;
-                        ex = ExprKind::Yield(Some(e));
-                    } else {
-                        ex = ExprKind::Yield(None);
-                    }
-                } else if self.token.is_keyword(keywords::Let) {
-                    // Catch this syntax error here, instead of in `parse_ident`, so
-                    // that we can explicitly mention that let is not to be used as an expression
-                    let mut db = self.fatal("expected expression, found statement (`let`)");
-                    db.span_label(self.span, "expected expression");
-                    db.note("variable declaration using `let` is a statement");
-                    return Err(db);
-                } else if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
-                    let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
-                    hi = await_hi;
-                    ex = e_kind;
-                } else if self.token.is_path_start() {
-                    let path = self.parse_path(PathStyle::Expr)?;
-
-                    // `!`, as an operator, is prefix, so we know this isn't that
-                    if self.eat(&token::Not) {
-                        // MACRO INVOCATION expression
-                        let (delim, tts) = self.expect_delimited_token_tree()?;
-                        hi = self.prev_span;
-                        ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
-                    } else if self.check(&token::OpenDelim(token::Brace)) {
-                        if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
-                            return expr;
-                        } else {
-                            hi = path.span;
-                            ex = ExprKind::Path(None, path);
-                        }
-                    } else {
-                        hi = path.span;
-                        ex = ExprKind::Path(None, path);
-                    }
-                } else {
-                    if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
-                        // Don't complain about bare semicolons after unclosed braces
-                        // recovery in order to keep the error count down. Fixing the
-                        // delimiters will possibly also fix the bare semicolon found in
-                        // expression context. For example, silence the following error:
-                        // ```
-                        // error: expected expression, found `;`
-                        //  --> file.rs:2:13
-                        //   |
-                        // 2 |     foo(bar(;
-                        //   |             ^ expected expression
-                        // ```
-                        self.bump();
-                        return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
-                    }
-                    match self.parse_literal_maybe_minus() {
-                        Ok(expr) => {
-                            hi = expr.span;
-                            ex = expr.node.clone();
-                        }
-                        Err(mut err) => {
-                            self.cancel(&mut err);
-                            let msg = format!("expected expression, found {}",
-                                              self.this_token_descr());
-                            let mut err = self.fatal(&msg);
-                            let sp = self.sess.source_map().start_point(self.span);
-                            if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow()
-                                .get(&sp)
-                            {
-                                self.sess.expr_parentheses_needed(&mut err, *sp, None);
-                            }
-                            err.span_label(self.span, "expected expression");
-                            return Err(err);
-                        }
-                    }
-                }
-            }
-        }
-
-        let expr = self.mk_expr(lo.to(hi), ex, attrs);
-        self.maybe_recover_from_bad_qpath(expr, true)
-    }
-
-    /// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
-    /// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
-    /// `await { <expr> }`.
-    fn parse_await_macro_or_alt(
-        &mut self,
-        lo: Span,
-        await_sp: Span,
-    ) -> PResult<'a, (Span, ExprKind)> {
-        if self.token == token::Not {
-            // Handle correct `await!(<expr>)`.
-            // FIXME: make this an error when `await!` is no longer supported
-            // https://github.com/rust-lang/rust/issues/60610
-            self.expect(&token::Not)?;
-            self.expect(&token::OpenDelim(token::Paren))?;
-            let expr = self.parse_expr().map_err(|mut err| {
-                err.span_label(await_sp, "while parsing this await macro call");
-                err
-            })?;
-            self.expect(&token::CloseDelim(token::Paren))?;
-            Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
-        } else { // Handle `await <expr>`.
-            self.parse_incorrect_await_syntax(lo, await_sp)
-        }
-    }
-
-    fn maybe_parse_struct_expr(
-        &mut self,
-        lo: Span,
-        path: &ast::Path,
-        attrs: &ThinVec<Attribute>,
-    ) -> Option<PResult<'a, P<Expr>>> {
-        let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
-        let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
-            // `{ ident, ` cannot start a block
-            self.look_ahead(2, |t| t == &token::Comma) ||
-            self.look_ahead(2, |t| t == &token::Colon) && (
-                // `{ ident: token, ` cannot start a block
-                self.look_ahead(4, |t| t == &token::Comma) ||
-                // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
-                self.look_ahead(3, |t| !t.can_begin_type())
-            )
-        );
-
-        if struct_allowed || certainly_not_a_block() {
-            // This is a struct literal, but we don't can't accept them here
-            let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
-            if let (Ok(expr), false) = (&expr, struct_allowed) {
-                let mut err = self.diagnostic().struct_span_err(
-                    expr.span,
-                    "struct literals are not allowed here",
-                );
-                err.multipart_suggestion(
-                    "surround the struct literal with parentheses",
-                    vec![
-                        (lo.shrink_to_lo(), "(".to_string()),
-                        (expr.span.shrink_to_hi(), ")".to_string()),
-                    ],
-                    Applicability::MachineApplicable,
-                );
-                err.emit();
-            }
-            return Some(expr);
-        }
-        None
-    }
-
-    fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
-                         -> PResult<'a, P<Expr>> {
-        let struct_sp = lo.to(self.prev_span);
-        self.bump();
-        let mut fields = Vec::new();
-        let mut base = None;
-
-        attrs.extend(self.parse_inner_attributes()?);
-
-        while self.token != token::CloseDelim(token::Brace) {
-            if self.eat(&token::DotDot) {
-                let exp_span = self.prev_span;
-                match self.parse_expr() {
-                    Ok(e) => {
-                        base = Some(e);
-                    }
-                    Err(mut e) => {
-                        e.emit();
-                        self.recover_stmt();
-                    }
-                }
-                if self.token == token::Comma {
-                    let mut err = self.sess.span_diagnostic.mut_span_err(
-                        exp_span.to(self.prev_span),
-                        "cannot use a comma after the base struct",
-                    );
-                    err.span_suggestion_short(
-                        self.span,
-                        "remove this comma",
-                        String::new(),
-                        Applicability::MachineApplicable
-                    );
-                    err.note("the base struct must always be the last field");
-                    err.emit();
-                    self.recover_stmt();
-                }
-                break;
-            }
-
-            let mut recovery_field = None;
-            if let token::Ident(ident, _) = self.token {
-                if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
-                    // Use in case of error after field-looking code: `S { foo: () with a }`
-                    let mut ident = ident.clone();
-                    ident.span = self.span;
-                    recovery_field = Some(ast::Field {
-                        ident,
-                        span: self.span,
-                        expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
-                        is_shorthand: false,
-                        attrs: ThinVec::new(),
-                    });
-                }
-            }
-            let mut parsed_field = None;
-            match self.parse_field() {
-                Ok(f) => parsed_field = Some(f),
-                Err(mut e) => {
-                    e.span_label(struct_sp, "while parsing this struct");
-                    e.emit();
-
-                    // If the next token is a comma, then try to parse
-                    // what comes next as additional fields, rather than
-                    // bailing out until next `}`.
-                    if self.token != token::Comma {
-                        self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
-                        if self.token != token::Comma {
-                            break;
-                        }
-                    }
-                }
-            }
-
-            match self.expect_one_of(&[token::Comma],
-                                     &[token::CloseDelim(token::Brace)]) {
-                Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
-                    // only include the field if there's no parse error for the field name
-                    fields.push(f);
-                }
-                Err(mut e) => {
-                    if let Some(f) = recovery_field {
-                        fields.push(f);
-                    }
-                    e.span_label(struct_sp, "while parsing this struct");
-                    e.emit();
-                    self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
-                    self.eat(&token::Comma);
-                }
-            }
-        }
-
-        let span = lo.to(self.span);
-        self.expect(&token::CloseDelim(token::Brace))?;
-        return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
-    }
-
     fn parse_or_use_outer_attributes(&mut self,
                                      already_parsed_attrs: Option<ThinVec<Attribute>>)
                                      -> PResult<'a, ThinVec<Attribute>> {
@@ -2818,351 +1098,46 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses a block or unsafe block.
-    crate fn parse_block_expr(
-        &mut self,
-        opt_label: Option<Label>,
-        lo: Span,
-        blk_mode: BlockCheckMode,
-        outer_attrs: ThinVec<Attribute>,
-    ) -> PResult<'a, P<Expr>> {
-        self.expect(&token::OpenDelim(token::Brace))?;
-
-        let mut attrs = outer_attrs;
-        attrs.extend(self.parse_inner_attributes()?);
-
-        let blk = self.parse_block_tail(lo, blk_mode)?;
-        return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
-    }
-
-    /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
-    fn parse_dot_or_call_expr(&mut self,
-                                  already_parsed_attrs: Option<ThinVec<Attribute>>)
-                                  -> PResult<'a, P<Expr>> {
-        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
-
-        let b = self.parse_bottom_expr();
-        let (span, b) = self.interpolated_or_expr_span(b)?;
-        self.parse_dot_or_call_expr_with(b, span, attrs)
-    }
-
-    fn parse_dot_or_call_expr_with(&mut self,
-                                       e0: P<Expr>,
-                                       lo: Span,
-                                       mut attrs: ThinVec<Attribute>)
-                                       -> PResult<'a, P<Expr>> {
-        // Stitch the list of outer attributes onto the return value.
-        // A little bit ugly, but the best way given the current code
-        // structure
-        self.parse_dot_or_call_expr_with_(e0, lo)
-        .map(|expr|
-            expr.map(|mut expr| {
-                attrs.extend::<Vec<_>>(expr.attrs.into());
-                expr.attrs = attrs;
-                match expr.node {
-                    ExprKind::If(..) | ExprKind::IfLet(..) => {
-                        if !expr.attrs.is_empty() {
-                            // Just point to the first attribute in there...
-                            let span = expr.attrs[0].span;
-
-                            self.span_err(span,
-                                "attributes are not yet allowed on `if` \
-                                expressions");
-                        }
-                    }
-                    _ => {}
-                }
-                expr
-            })
-        )
-    }
-
-    // Assuming we have just parsed `.`, continue parsing into an expression.
-    fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
-        if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
-            let span = lo.to(self.prev_span);
-            let await_expr = self.mk_expr(
-                span,
-                ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
-                ThinVec::new(),
-            );
-            self.recover_from_await_method_call();
-            return Ok(await_expr);
-        }
-        let segment = self.parse_path_segment(PathStyle::Expr)?;
-        self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
-
-        Ok(match self.token {
-            token::OpenDelim(token::Paren) => {
-                // Method call `expr.f()`
-                let mut args = self.parse_unspanned_seq(
-                    &token::OpenDelim(token::Paren),
-                    &token::CloseDelim(token::Paren),
-                    SeqSep::trailing_allowed(token::Comma),
-                    |p| Ok(p.parse_expr()?)
-                )?;
-                args.insert(0, self_arg);
-
-                let span = lo.to(self.prev_span);
-                self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
-            }
-            _ => {
-                // Field access `expr.f`
-                if let Some(args) = segment.args {
-                    self.span_err(args.span(),
-                                  "field expressions may not have generic arguments");
-                }
-
-                let span = lo.to(self.prev_span);
-                self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
-            }
-        })
-    }
-
-    /// This function checks if there are trailing angle brackets and produces
-    /// a diagnostic to suggest removing them.
-    ///
-    /// ```ignore (diagnostic)
-    /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
-    ///                                                        ^^ help: remove extra angle brackets
-    /// ```
-    fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
-        // This function is intended to be invoked after parsing a path segment where there are two
-        // cases:
-        //
-        // 1. A specific token is expected after the path segment.
-        //    eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
-        //        `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
-        // 2. No specific token is expected after the path segment.
-        //    eg. `x.foo` (field access)
-        //
-        // This function is called after parsing `.foo` and before parsing the token `end` (if
-        // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
-        // `Foo::<Bar>`.
-
-        // We only care about trailing angle brackets if we previously parsed angle bracket
-        // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
-        // removed in this case:
-        //
-        // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
-        //
-        // This case is particularly tricky as we won't notice it just looking at the tokens -
-        // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
-        // have already been parsed):
-        //
-        // `x.foo::<u32>>>(3)`
-        let parsed_angle_bracket_args = segment.args
-            .as_ref()
-            .map(|args| args.is_angle_bracketed())
-            .unwrap_or(false);
-
-        debug!(
-            "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
-            parsed_angle_bracket_args,
-        );
-        if !parsed_angle_bracket_args {
-            return;
-        }
-
-        // Keep the span at the start so we can highlight the sequence of `>` characters to be
-        // removed.
-        let lo = self.span;
-
-        // We need to look-ahead to see if we have `>` characters without moving the cursor forward
-        // (since we might have the field access case and the characters we're eating are
-        // actual operators and not trailing characters - ie `x.foo >> 3`).
-        let mut position = 0;
-
-        // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
-        // many of each (so we can correctly pluralize our error messages) and continue to
-        // advance.
-        let mut number_of_shr = 0;
-        let mut number_of_gt = 0;
-        while self.look_ahead(position, |t| {
-            trace!("check_trailing_angle_brackets: t={:?}", t);
-            if *t == token::BinOp(token::BinOpToken::Shr) {
-                number_of_shr += 1;
-                true
-            } else if *t == token::Gt {
-                number_of_gt += 1;
-                true
-            } else {
-                false
-            }
-        }) {
-            position += 1;
-        }
-
-        // If we didn't find any trailing `>` characters, then we have nothing to error about.
-        debug!(
-            "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
-            number_of_gt, number_of_shr,
-        );
-        if number_of_gt < 1 && number_of_shr < 1 {
-            return;
-        }
-
-        // Finally, double check that we have our end token as otherwise this is the
-        // second case.
-        if self.look_ahead(position, |t| {
-            trace!("check_trailing_angle_brackets: t={:?}", t);
-            *t == end
-        }) {
-            // Eat from where we started until the end token so that parsing can continue
-            // as if we didn't have those extra angle brackets.
-            self.eat_to_tokens(&[&end]);
-            let span = lo.until(self.span);
-
-            let plural = number_of_gt > 1 || number_of_shr >= 1;
-            self.diagnostic()
-                .struct_span_err(
-                    span,
-                    &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
-                )
-                .span_suggestion(
-                    span,
-                    &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
-        }
-    }
-
-    fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
-        let mut e = e0;
-        let mut hi;
-        loop {
-            // expr?
-            while self.eat(&token::Question) {
-                let hi = self.prev_span;
-                e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
-            }
-
-            // expr.f
-            if self.eat(&token::Dot) {
-                match self.token {
-                    token::Ident(..) => {
-                        e = self.parse_dot_suffix(e, lo)?;
-                    }
-                    token::Literal(token::Integer(name), suffix) => {
-                        let span = self.span;
-                        self.bump();
-                        let field = ExprKind::Field(e, Ident::new(name, span));
-                        e = self.mk_expr(lo.to(span), field, ThinVec::new());
-
-                        self.expect_no_suffix(span, "a tuple index", suffix);
-                    }
-                    token::Literal(token::Float(n), _suf) => {
-                      self.bump();
-                      let fstr = n.as_str();
-                      let mut err = self.diagnostic()
-                          .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
-                      err.span_label(self.prev_span, "unexpected token");
-                      if fstr.chars().all(|x| "0123456789.".contains(x)) {
-                          let float = match fstr.parse::<f64>().ok() {
-                              Some(f) => f,
-                              None => continue,
-                          };
-                          let sugg = pprust::to_string(|s| {
-                              use crate::print::pprust::PrintState;
-                              s.popen()?;
-                              s.print_expr(&e)?;
-                              s.s.word( ".")?;
-                              s.print_usize(float.trunc() as usize)?;
-                              s.pclose()?;
-                              s.s.word(".")?;
-                              s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
-                          });
-                          err.span_suggestion(
-                              lo.to(self.prev_span),
-                              "try parenthesizing the first index",
-                              sugg,
-                              Applicability::MachineApplicable
-                          );
-                      }
-                      return Err(err);
-
-                    }
-                    _ => {
-                        // FIXME Could factor this out into non_fatal_unexpected or something.
-                        let actual = self.this_token_to_string();
-                        self.span_err(self.span, &format!("unexpected token: `{}`", actual));
-                    }
-                }
-                continue;
-            }
-            if self.expr_is_complete(&e) { break; }
-            match self.token {
-                // expr(...)
-                token::OpenDelim(token::Paren) => {
-                    let seq = self.parse_unspanned_seq(
-                        &token::OpenDelim(token::Paren),
-                        &token::CloseDelim(token::Paren),
-                        SeqSep::trailing_allowed(token::Comma),
-                        |p| Ok(p.parse_expr()?)
-                    ).map(|es| {
-                        let nd = self.mk_call(e, es);
-                        let hi = self.prev_span;
-                        self.mk_expr(lo.to(hi), nd, ThinVec::new())
-                    });
-                    e = self.recover_seq_parse_error(token::Paren, lo, seq);
-                }
-
-                // expr[...]
-                // Could be either an index expression or a slicing expression.
-                token::OpenDelim(token::Bracket) => {
-                    self.bump();
-                    let ix = self.parse_expr()?;
-                    hi = self.span;
-                    self.expect(&token::CloseDelim(token::Bracket))?;
-                    let index = self.mk_index(e, ix);
-                    e = self.mk_expr(lo.to(hi), index, ThinVec::new())
-                }
-                _ => return Ok(e)
-            }
-        }
-        return Ok(e);
-    }
-
     crate fn process_potential_macro_variable(&mut self) {
-        let (token, span) = match self.token {
-            token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
+        self.token = match self.token.kind {
+            token::Dollar if self.token.span.from_expansion() &&
                              self.look_ahead(1, |t| t.is_ident()) => {
                 self.bump();
-                let name = match self.token {
-                    token::Ident(ident, _) => ident,
+                let name = match self.token.kind {
+                    token::Ident(name, _) => name,
                     _ => unreachable!()
                 };
-                let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
-                err.span_label(self.span, "unknown macro variable");
-                err.emit();
+                let span = self.prev_span.to(self.token.span);
+                self.diagnostic()
+                    .struct_span_fatal(span, &format!("unknown macro variable `{}`", name))
+                    .span_label(span, "unknown macro variable")
+                    .emit();
                 self.bump();
                 return
             }
             token::Interpolated(ref nt) => {
-                self.meta_var_span = Some(self.span);
+                self.meta_var_span = Some(self.token.span);
                 // Interpolated identifier and lifetime tokens are replaced with usual identifier
                 // and lifetime tokens, so the former are never encountered during normal parsing.
                 match **nt {
-                    token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
-                    token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
+                    token::NtIdent(ident, is_raw) =>
+                        Token::new(token::Ident(ident.name, is_raw), ident.span),
+                    token::NtLifetime(ident) =>
+                        Token::new(token::Lifetime(ident.name), ident.span),
                     _ => return,
                 }
             }
             _ => return,
         };
-        self.token = token;
-        self.span = span;
     }
 
     /// Parses a single token tree from the input.
     crate fn parse_token_tree(&mut self) -> TokenTree {
-        match self.token {
+        match self.token.kind {
             token::OpenDelim(..) => {
                 let frame = mem::replace(&mut self.token_cursor.frame,
                                          self.token_cursor.stack.pop().unwrap());
-                self.span = frame.span.entire();
+                self.token.span = frame.span.entire();
                 self.bump();
                 TokenTree::Delimited(
                     frame.span,
@@ -3172,15 +1147,14 @@ impl<'a> Parser<'a> {
             },
             token::CloseDelim(_) | token::Eof => unreachable!(),
             _ => {
-                let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
+                let token = self.token.take();
                 self.bump();
-                TokenTree::Token(span, token)
+                TokenTree::Token(token)
             }
         }
     }
 
-    // parse a stream of tokens into a list of TokenTree's,
-    // up to EOF.
+    /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
     pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
         let mut tts = Vec::new();
         while self.token != token::Eof {
@@ -3192,7 +1166,7 @@ impl<'a> Parser<'a> {
     pub fn parse_tokens(&mut self) -> TokenStream {
         let mut result = Vec::new();
         loop {
-            match self.token {
+            match self.token.kind {
                 token::Eof | token::CloseDelim(..) => break,
                 _ => result.push(self.parse_token_tree().into()),
             }
@@ -3200,823 +1174,6 @@ impl<'a> Parser<'a> {
         TokenStream::new(result)
     }
 
-    /// Parse a prefix-unary-operator expr
-    fn parse_prefix_expr(&mut self,
-                             already_parsed_attrs: Option<ThinVec<Attribute>>)
-                             -> PResult<'a, P<Expr>> {
-        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
-        let lo = self.span;
-        // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
-        let (hi, ex) = match self.token {
-            token::Not => {
-                self.bump();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                (lo.to(span), self.mk_unary(UnOp::Not, e))
-            }
-            // Suggest `!` for bitwise negation when encountering a `~`
-            token::Tilde => {
-                self.bump();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                let span_of_tilde = lo;
-                let mut err = self.diagnostic()
-                    .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
-                err.span_suggestion_short(
-                    span_of_tilde,
-                    "use `!` to perform bitwise negation",
-                    "!".to_owned(),
-                    Applicability::MachineApplicable
-                );
-                err.emit();
-                (lo.to(span), self.mk_unary(UnOp::Not, e))
-            }
-            token::BinOp(token::Minus) => {
-                self.bump();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                (lo.to(span), self.mk_unary(UnOp::Neg, e))
-            }
-            token::BinOp(token::Star) => {
-                self.bump();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                (lo.to(span), self.mk_unary(UnOp::Deref, e))
-            }
-            token::BinOp(token::And) | token::AndAnd => {
-                self.expect_and()?;
-                let m = self.parse_mutability();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                (lo.to(span), ExprKind::AddrOf(m, e))
-            }
-            token::Ident(..) if self.token.is_keyword(keywords::In) => {
-                self.bump();
-                let place = self.parse_expr_res(
-                    Restrictions::NO_STRUCT_LITERAL,
-                    None,
-                )?;
-                let blk = self.parse_block()?;
-                let span = blk.span;
-                let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
-                (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
-            }
-            token::Ident(..) if self.token.is_keyword(keywords::Box) => {
-                self.bump();
-                let e = self.parse_prefix_expr(None);
-                let (span, e) = self.interpolated_or_expr_span(e)?;
-                (lo.to(span), ExprKind::Box(e))
-            }
-            token::Ident(..) if self.token.is_ident_named("not") => {
-                // `not` is just an ordinary identifier in Rust-the-language,
-                // but as `rustc`-the-compiler, we can issue clever diagnostics
-                // for confused users who really want to say `!`
-                let token_cannot_continue_expr = |t: &token::Token| match *t {
-                    // These tokens can start an expression after `!`, but
-                    // can't continue an expression after an ident
-                    token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
-                    token::Literal(..) | token::Pound => true,
-                    token::Interpolated(ref nt) => match **nt {
-                        token::NtIdent(..) | token::NtExpr(..) |
-                        token::NtBlock(..) | token::NtPath(..) => true,
-                        _ => false,
-                    },
-                    _ => false
-                };
-                let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
-                if cannot_continue_expr {
-                    self.bump();
-                    // Emit the error ...
-                    let mut err = self.diagnostic()
-                        .struct_span_err(self.span,
-                                         &format!("unexpected {} after identifier",
-                                                  self.this_token_descr()));
-                    // span the `not` plus trailing whitespace to avoid
-                    // trailing whitespace after the `!` in our suggestion
-                    let to_replace = self.sess.source_map()
-                        .span_until_non_whitespace(lo.to(self.span));
-                    err.span_suggestion_short(
-                        to_replace,
-                        "use `!` to perform logical negation",
-                        "!".to_owned(),
-                        Applicability::MachineApplicable
-                    );
-                    err.emit();
-                    // —and recover! (just as if we were in the block
-                    // for the `token::Not` arm)
-                    let e = self.parse_prefix_expr(None);
-                    let (span, e) = self.interpolated_or_expr_span(e)?;
-                    (lo.to(span), self.mk_unary(UnOp::Not, e))
-                } else {
-                    return self.parse_dot_or_call_expr(Some(attrs));
-                }
-            }
-            _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
-        };
-        return Ok(self.mk_expr(lo.to(hi), ex, attrs));
-    }
-
-    /// Parses an associative expression.
-    ///
-    /// This parses an expression accounting for associativity and precedence of the operators in
-    /// the expression.
-    #[inline]
-    fn parse_assoc_expr(&mut self,
-                            already_parsed_attrs: Option<ThinVec<Attribute>>)
-                            -> PResult<'a, P<Expr>> {
-        self.parse_assoc_expr_with(0, already_parsed_attrs.into())
-    }
-
-    /// Parses an associative expression with operators of at least `min_prec` precedence.
-    fn parse_assoc_expr_with(&mut self,
-                                 min_prec: usize,
-                                 lhs: LhsExpr)
-                                 -> PResult<'a, P<Expr>> {
-        let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
-            expr
-        } else {
-            let attrs = match lhs {
-                LhsExpr::AttributesParsed(attrs) => Some(attrs),
-                _ => None,
-            };
-            if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
-                return self.parse_prefix_range_expr(attrs);
-            } else {
-                self.parse_prefix_expr(attrs)?
-            }
-        };
-
-        match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
-            (true, None) => {
-                // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
-                return Ok(lhs);
-            }
-            (false, _) => {} // continue parsing the expression
-            // An exhaustive check is done in the following block, but these are checked first
-            // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
-            // want to keep their span info to improve diagnostics in these cases in a later stage.
-            (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
-            (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
-            (true, Some(AssocOp::Add)) => { // `{ 42 } + 42
-                // These cases are ambiguous and can't be identified in the parser alone
-                let sp = self.sess.source_map().start_point(self.span);
-                self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
-                return Ok(lhs);
-            }
-            (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
-                return Ok(lhs);
-            }
-            (true, Some(_)) => {
-                // We've found an expression that would be parsed as a statement, but the next
-                // token implies this should be parsed as an expression.
-                // For example: `if let Some(x) = x { x } else { 0 } / 2`
-                let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
-                    "expected expression, found `{}`",
-                    pprust::token_to_string(&self.token),
-                ));
-                err.span_label(self.span, "expected expression");
-                self.sess.expr_parentheses_needed(
-                    &mut err,
-                    lhs.span,
-                    Some(pprust::expr_to_string(&lhs),
-                ));
-                err.emit();
-            }
-        }
-        self.expected_tokens.push(TokenType::Operator);
-        while let Some(op) = AssocOp::from_token(&self.token) {
-
-            // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
-            // it refers to. Interpolated identifiers are unwrapped early and never show up here
-            // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
-            // it as "interpolated", it doesn't change the answer for non-interpolated idents.
-            let lhs_span = match (self.prev_token_kind, &lhs.node) {
-                (PrevTokenKind::Interpolated, _) => self.prev_span,
-                (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
-                    if path.segments.len() == 1 => self.prev_span,
-                _ => lhs.span,
-            };
-
-            let cur_op_span = self.span;
-            let restrictions = if op.is_assign_like() {
-                self.restrictions & Restrictions::NO_STRUCT_LITERAL
-            } else {
-                self.restrictions
-            };
-            let prec = op.precedence();
-            if prec < min_prec {
-                break;
-            }
-            // Check for deprecated `...` syntax
-            if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
-                self.err_dotdotdot_syntax(self.span);
-            }
-
-            self.bump();
-            if op.is_comparison() {
-                self.check_no_chained_comparison(&lhs, &op);
-            }
-            // Special cases:
-            if op == AssocOp::As {
-                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
-                continue
-            } else if op == AssocOp::Colon {
-                let maybe_path = self.could_ascription_be_path(&lhs.node);
-                let next_sp = self.span;
-
-                lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
-                    Ok(lhs) => lhs,
-                    Err(mut err) => {
-                        self.bad_type_ascription(
-                            &mut err,
-                            lhs_span,
-                            cur_op_span,
-                            next_sp,
-                            maybe_path,
-                        );
-                        return Err(err);
-                    }
-                };
-                continue
-            } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
-                // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
-                // generalise it to the Fixity::None code.
-                //
-                // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
-                // two variants are handled with `parse_prefix_range_expr` call above.
-                let rhs = if self.is_at_start_of_range_notation_rhs() {
-                    Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
-                } else {
-                    None
-                };
-                let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
-                    x.span
-                } else {
-                    cur_op_span
-                });
-                let limits = if op == AssocOp::DotDot {
-                    RangeLimits::HalfOpen
-                } else {
-                    RangeLimits::Closed
-                };
-
-                let r = self.mk_range(Some(lhs), rhs, limits)?;
-                lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
-                break
-            }
-
-            let fixity = op.fixity();
-            let prec_adjustment = match fixity {
-                Fixity::Right => 0,
-                Fixity::Left => 1,
-                // We currently have no non-associative operators that are not handled above by
-                // the special cases. The code is here only for future convenience.
-                Fixity::None => 1,
-            };
-            let rhs = self.with_res(
-                restrictions - Restrictions::STMT_EXPR,
-                |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
-            )?;
-
-            // Make sure that the span of the parent node is larger than the span of lhs and rhs,
-            // including the attributes.
-            let lhs_span = lhs
-                .attrs
-                .iter()
-                .filter(|a| a.style == AttrStyle::Outer)
-                .next()
-                .map_or(lhs_span, |a| a.span);
-            let span = lhs_span.to(rhs.span);
-            lhs = match op {
-                AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
-                AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
-                AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
-                AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
-                AssocOp::Greater | AssocOp::GreaterEqual => {
-                    let ast_op = op.to_ast_binop().unwrap();
-                    let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
-                    self.mk_expr(span, binary, ThinVec::new())
-                }
-                AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
-                AssocOp::ObsoleteInPlace =>
-                    self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
-                AssocOp::AssignOp(k) => {
-                    let aop = match k {
-                        token::Plus =>    BinOpKind::Add,
-                        token::Minus =>   BinOpKind::Sub,
-                        token::Star =>    BinOpKind::Mul,
-                        token::Slash =>   BinOpKind::Div,
-                        token::Percent => BinOpKind::Rem,
-                        token::Caret =>   BinOpKind::BitXor,
-                        token::And =>     BinOpKind::BitAnd,
-                        token::Or =>      BinOpKind::BitOr,
-                        token::Shl =>     BinOpKind::Shl,
-                        token::Shr =>     BinOpKind::Shr,
-                    };
-                    let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
-                    self.mk_expr(span, aopexpr, ThinVec::new())
-                }
-                AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
-                    self.bug("AssocOp should have been handled by special case")
-                }
-            };
-
-            if let Fixity::None = fixity { break }
-        }
-        Ok(lhs)
-    }
-
-    fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
-                           expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
-                           -> PResult<'a, P<Expr>> {
-        let mk_expr = |this: &mut Self, rhs: P<Ty>| {
-            this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
-        };
-
-        // Save the state of the parser before parsing type normally, in case there is a
-        // LessThan comparison after this cast.
-        let parser_snapshot_before_type = self.clone();
-        match self.parse_ty_no_plus() {
-            Ok(rhs) => {
-                Ok(mk_expr(self, rhs))
-            }
-            Err(mut type_err) => {
-                // Rewind to before attempting to parse the type with generics, to recover
-                // from situations like `x as usize < y` in which we first tried to parse
-                // `usize < y` as a type with generic arguments.
-                let parser_snapshot_after_type = self.clone();
-                mem::replace(self, parser_snapshot_before_type);
-
-                match self.parse_path(PathStyle::Expr) {
-                    Ok(path) => {
-                        let (op_noun, op_verb) = match self.token {
-                            token::Lt => ("comparison", "comparing"),
-                            token::BinOp(token::Shl) => ("shift", "shifting"),
-                            _ => {
-                                // We can end up here even without `<` being the next token, for
-                                // example because `parse_ty_no_plus` returns `Err` on keywords,
-                                // but `parse_path` returns `Ok` on them due to error recovery.
-                                // Return original error and parser state.
-                                mem::replace(self, parser_snapshot_after_type);
-                                return Err(type_err);
-                            }
-                        };
-
-                        // Successfully parsed the type path leaving a `<` yet to parse.
-                        type_err.cancel();
-
-                        // Report non-fatal diagnostics, keep `x as usize` as an expression
-                        // in AST and continue parsing.
-                        let msg = format!("`<` is interpreted as a start of generic \
-                                           arguments for `{}`, not a {}", path, op_noun);
-                        let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
-                        err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
-                                       "interpreted as generic arguments");
-                        err.span_label(self.span, format!("not interpreted as {}", op_noun));
-
-                        let expr = mk_expr(self, P(Ty {
-                            span: path.span,
-                            node: TyKind::Path(None, path),
-                            id: ast::DUMMY_NODE_ID
-                        }));
-
-                        let expr_str = self.sess.source_map().span_to_snippet(expr.span)
-                                                .unwrap_or_else(|_| pprust::expr_to_string(&expr));
-                        err.span_suggestion(
-                            expr.span,
-                            &format!("try {} the cast value", op_verb),
-                            format!("({})", expr_str),
-                            Applicability::MachineApplicable
-                        );
-                        err.emit();
-
-                        Ok(expr)
-                    }
-                    Err(mut path_err) => {
-                        // Couldn't parse as a path, return original error and parser state.
-                        path_err.cancel();
-                        mem::replace(self, parser_snapshot_after_type);
-                        Err(type_err)
-                    }
-                }
-            }
-        }
-    }
-
-    /// Produce an error if comparison operators are chained (RFC #558).
-    /// We only need to check lhs, not rhs, because all comparison ops
-    /// have same precedence and are left-associative
-    fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) {
-        debug_assert!(outer_op.is_comparison(),
-                      "check_no_chained_comparison: {:?} is not comparison",
-                      outer_op);
-        match lhs.node {
-            ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
-                // respan to include both operators
-                let op_span = op.span.to(self.span);
-                let mut err = self.diagnostic().struct_span_err(op_span,
-                    "chained comparison operators require parentheses");
-                if op.node == BinOpKind::Lt &&
-                    *outer_op == AssocOp::Less ||  // Include `<` to provide this recommendation
-                    *outer_op == AssocOp::Greater  // even in a case like the following:
-                {                                  //     Foo<Bar<Baz<Qux, ()>>>
-                    err.help(
-                        "use `::<...>` instead of `<...>` if you meant to specify type arguments");
-                    err.help("or use `(...)` if you meant to specify fn arguments");
-                }
-                err.emit();
-            }
-            _ => {}
-        }
-    }
-
-    /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
-    fn parse_prefix_range_expr(&mut self,
-                               already_parsed_attrs: Option<ThinVec<Attribute>>)
-                               -> PResult<'a, P<Expr>> {
-        // Check for deprecated `...` syntax
-        if self.token == token::DotDotDot {
-            self.err_dotdotdot_syntax(self.span);
-        }
-
-        debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
-                      "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
-                      self.token);
-        let tok = self.token.clone();
-        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
-        let lo = self.span;
-        let mut hi = self.span;
-        self.bump();
-        let opt_end = if self.is_at_start_of_range_notation_rhs() {
-            // RHS must be parsed with more associativity than the dots.
-            let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
-            Some(self.parse_assoc_expr_with(next_prec,
-                                            LhsExpr::NotYetParsed)
-                .map(|x|{
-                    hi = x.span;
-                    x
-                })?)
-         } else {
-            None
-        };
-        let limits = if tok == token::DotDot {
-            RangeLimits::HalfOpen
-        } else {
-            RangeLimits::Closed
-        };
-
-        let r = self.mk_range(None, opt_end, limits)?;
-        Ok(self.mk_expr(lo.to(hi), r, attrs))
-    }
-
-    fn is_at_start_of_range_notation_rhs(&self) -> bool {
-        if self.token.can_begin_expr() {
-            // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
-            if self.token == token::OpenDelim(token::Brace) {
-                return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
-            }
-            true
-        } else {
-            false
-        }
-    }
-
-    /// Parses an `if` or `if let` expression (`if` token already eaten).
-    fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        if self.check_keyword(keywords::Let) {
-            return self.parse_if_let_expr(attrs);
-        }
-        let lo = self.prev_span;
-        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-
-        // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
-        // verify that the last statement is either an implicit return (no `;`) or an explicit
-        // return. This won't catch blocks with an explicit `return`, but that would be caught by
-        // the dead code lint.
-        if self.eat_keyword(keywords::Else) || !cond.returns() {
-            let sp = self.sess.source_map().next_point(lo);
-            let mut err = self.diagnostic()
-                .struct_span_err(sp, "missing condition for `if` statemement");
-            err.span_label(sp, "expected if condition here");
-            return Err(err)
-        }
-        let not_block = self.token != token::OpenDelim(token::Brace);
-        let thn = self.parse_block().map_err(|mut err| {
-            if not_block {
-                err.span_label(lo, "this `if` statement has a condition, but no block");
-            }
-            err
-        })?;
-        let mut els: Option<P<Expr>> = None;
-        let mut hi = thn.span;
-        if self.eat_keyword(keywords::Else) {
-            let elexpr = self.parse_else_expr()?;
-            hi = elexpr.span;
-            els = Some(elexpr);
-        }
-        Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
-    }
-
-    /// Parses an `if let` expression (`if` token already eaten).
-    fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
-                             -> PResult<'a, P<Expr>> {
-        let lo = self.prev_span;
-        self.expect_keyword(keywords::Let)?;
-        let pats = self.parse_pats()?;
-        self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let thn = self.parse_block()?;
-        let (hi, els) = if self.eat_keyword(keywords::Else) {
-            let expr = self.parse_else_expr()?;
-            (expr.span, Some(expr))
-        } else {
-            (thn.span, None)
-        };
-        Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
-    }
-
-    /// Parses `move |args| expr`.
-    fn parse_lambda_expr(&mut self,
-                             attrs: ThinVec<Attribute>)
-                             -> PResult<'a, P<Expr>>
-    {
-        let lo = self.span;
-        let movability = if self.eat_keyword(keywords::Static) {
-            Movability::Static
-        } else {
-            Movability::Movable
-        };
-        let asyncness = if self.span.rust_2018() {
-            self.parse_asyncness()
-        } else {
-            IsAsync::NotAsync
-        };
-        let capture_clause = if self.eat_keyword(keywords::Move) {
-            CaptureBy::Value
-        } else {
-            CaptureBy::Ref
-        };
-        let decl = self.parse_fn_block_decl()?;
-        let decl_hi = self.prev_span;
-        let body = match decl.output {
-            FunctionRetTy::Default(_) => {
-                let restrictions = self.restrictions - Restrictions::STMT_EXPR;
-                self.parse_expr_res(restrictions, None)?
-            },
-            _ => {
-                // If an explicit return type is given, require a
-                // block to appear (RFC 968).
-                let body_lo = self.span;
-                self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
-            }
-        };
-
-        Ok(self.mk_expr(
-            lo.to(body.span),
-            ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
-            attrs))
-    }
-
-    // `else` token already eaten
-    fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
-        if self.eat_keyword(keywords::If) {
-            return self.parse_if_expr(ThinVec::new());
-        } else {
-            let blk = self.parse_block()?;
-            return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
-        }
-    }
-
-    /// Parse a 'for' .. 'in' expression ('for' token already eaten)
-    fn parse_for_expr(&mut self, opt_label: Option<Label>,
-                          span_lo: Span,
-                          mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
-
-        let pat = self.parse_top_level_pat()?;
-        if !self.eat_keyword(keywords::In) {
-            let in_span = self.prev_span.between(self.span);
-            let mut err = self.sess.span_diagnostic
-                .struct_span_err(in_span, "missing `in` in `for` loop");
-            err.span_suggestion_short(
-                in_span, "try adding `in` here", " in ".into(),
-                // has been misleading, at least in the past (closed Issue #48492)
-                Applicability::MaybeIncorrect
-            );
-            err.emit();
-        }
-        let in_span = self.prev_span;
-        if self.eat_keyword(keywords::In) {
-            // a common typo: `for _ in in bar {}`
-            let mut err = self.sess.span_diagnostic.struct_span_err(
-                self.prev_span,
-                "expected iterable, found keyword `in`",
-            );
-            err.span_suggestion_short(
-                in_span.until(self.prev_span),
-                "remove the duplicated `in`",
-                String::new(),
-                Applicability::MachineApplicable,
-            );
-            err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
-            err.note("for more information on the status of emplacement syntax, see <\
-                      https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
-            err.emit();
-        }
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-
-        let hi = self.prev_span;
-        Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
-    }
-
-    /// Parses a `while` or `while let` expression (`while` token already eaten).
-    fn parse_while_expr(&mut self, opt_label: Option<Label>,
-                            span_lo: Span,
-                            mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        if self.token.is_keyword(keywords::Let) {
-            return self.parse_while_let_expr(opt_label, span_lo, attrs);
-        }
-        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        let span = span_lo.to(body.span);
-        return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
-    }
-
-    /// Parses a `while let` expression (`while` token already eaten).
-    fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
-                                span_lo: Span,
-                                mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        self.expect_keyword(keywords::Let)?;
-        let pats = self.parse_pats()?;
-        self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        let span = span_lo.to(body.span);
-        return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
-    }
-
-    // parse `loop {...}`, `loop` token already eaten
-    fn parse_loop_expr(&mut self, opt_label: Option<Label>,
-                           span_lo: Span,
-                           mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        let span = span_lo.to(body.span);
-        Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
-    }
-
-    /// Parses an `async move {...}` expression.
-    pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
-        -> PResult<'a, P<Expr>>
-    {
-        let span_lo = self.span;
-        self.expect_keyword(keywords::Async)?;
-        let capture_clause = if self.eat_keyword(keywords::Move) {
-            CaptureBy::Value
-        } else {
-            CaptureBy::Ref
-        };
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        Ok(self.mk_expr(
-            span_lo.to(body.span),
-            ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
-    }
-
-    /// Parses a `try {...}` expression (`try` token already eaten).
-    fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
-        -> PResult<'a, P<Expr>>
-    {
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        if self.eat_keyword(keywords::Catch) {
-            let mut error = self.struct_span_err(self.prev_span,
-                                                 "keyword `catch` cannot follow a `try` block");
-            error.help("try using `match` on the result of the `try` block instead");
-            error.emit();
-            Err(error)
-        } else {
-            Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
-        }
-    }
-
-    // `match` token already eaten
-    fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        let match_span = self.prev_span;
-        let lo = self.prev_span;
-        let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
-                                               None)?;
-        if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
-            if self.token == token::Token::Semi {
-                e.span_suggestion_short(
-                    match_span,
-                    "try removing this `match`",
-                    String::new(),
-                    Applicability::MaybeIncorrect // speculative
-                );
-            }
-            return Err(e)
-        }
-        attrs.extend(self.parse_inner_attributes()?);
-
-        let mut arms: Vec<Arm> = Vec::new();
-        while self.token != token::CloseDelim(token::Brace) {
-            match self.parse_arm() {
-                Ok(arm) => arms.push(arm),
-                Err(mut e) => {
-                    // Recover by skipping to the end of the block.
-                    e.emit();
-                    self.recover_stmt();
-                    let span = lo.to(self.span);
-                    if self.token == token::CloseDelim(token::Brace) {
-                        self.bump();
-                    }
-                    return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
-                }
-            }
-        }
-        let hi = self.span;
-        self.bump();
-        return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
-    }
-
-    crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
-        let attrs = self.parse_outer_attributes()?;
-        let pats = self.parse_pats()?;
-        let guard = if self.eat_keyword(keywords::If) {
-            Some(Guard::If(self.parse_expr()?))
-        } else {
-            None
-        };
-        let arrow_span = self.span;
-        self.expect(&token::FatArrow)?;
-        let arm_start_span = self.span;
-
-        let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
-            .map_err(|mut err| {
-                err.span_label(arrow_span, "while parsing the `match` arm starting here");
-                err
-            })?;
-
-        let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
-            && self.token != token::CloseDelim(token::Brace);
-
-        if require_comma {
-            let cm = self.sess.source_map();
-            self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
-                .map_err(|mut err| {
-                    match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
-                        (Ok(ref expr_lines), Ok(ref arm_start_lines))
-                        if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
-                            && expr_lines.lines.len() == 2
-                            && self.token == token::FatArrow => {
-                            // We check whether there's any trailing code in the parse span,
-                            // if there isn't, we very likely have the following:
-                            //
-                            // X |     &Y => "y"
-                            //   |        --    - missing comma
-                            //   |        |
-                            //   |        arrow_span
-                            // X |     &X => "x"
-                            //   |      - ^^ self.span
-                            //   |      |
-                            //   |      parsed until here as `"y" & X`
-                            err.span_suggestion_short(
-                                cm.next_point(arm_start_span),
-                                "missing a comma here to end this `match` arm",
-                                ",".to_owned(),
-                                Applicability::MachineApplicable
-                            );
-                        }
-                        _ => {
-                            err.span_label(arrow_span,
-                                           "while parsing the `match` arm starting here");
-                        }
-                    }
-                    err
-                })?;
-        } else {
-            self.eat(&token::Comma);
-        }
-
-        Ok(ast::Arm {
-            attrs,
-            pats,
-            guard,
-            body: expr,
-        })
-    }
-
-    /// Parses an expression.
-    #[inline]
-    pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
-        self.parse_expr_res(Restrictions::empty(), None)
-    }
-
     /// Evaluates the closure with restrictions in place.
     ///
     /// Afters the closure is evaluated, restrictions are reset.
@@ -4031,1963 +1188,54 @@ impl<'a> Parser<'a> {
 
     }
 
-    /// Parses an expression, subject to the given restrictions.
-    #[inline]
-    fn parse_expr_res(&mut self, r: Restrictions,
-                          already_parsed_attrs: Option<ThinVec<Attribute>>)
-                          -> PResult<'a, P<Expr>> {
-        self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
-    }
-
-    /// Parses the RHS of a local variable declaration (e.g., '= 14;').
-    fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
-        if self.eat(&token::Eq) {
-            Ok(Some(self.parse_expr()?))
-        } else if skip_eq {
-            Ok(Some(self.parse_expr()?))
-        } else {
-            Ok(None)
-        }
-    }
-
-    /// Parses patterns, separated by '|' s.
-    fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
-        // Allow a '|' before the pats (RFC 1925 + RFC 2530)
-        self.eat(&token::BinOp(token::Or));
-
-        let mut pats = Vec::new();
-        loop {
-            pats.push(self.parse_top_level_pat()?);
-
-            if self.token == token::OrOr {
-                let mut err = self.struct_span_err(self.span,
-                                                   "unexpected token `||` after pattern");
-                err.span_suggestion(
-                    self.span,
-                    "use a single `|` to specify multiple patterns",
-                    "|".to_owned(),
-                    Applicability::MachineApplicable
-                );
-                err.emit();
-                self.bump();
-            } else if self.eat(&token::BinOp(token::Or)) {
-                // This is a No-op. Continue the loop to parse the next
-                // pattern.
-            } else {
-                return Ok(pats);
-            }
-        };
-    }
-
-    // Parses a parenthesized list of patterns like
-    // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
-    // - a vector of the patterns that were parsed
-    // - an option indicating the index of the `..` element
-    // - a boolean indicating whether a trailing comma was present.
-    // Trailing commas are significant because (p) and (p,) are different patterns.
-    fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
-        self.expect(&token::OpenDelim(token::Paren))?;
-        let result = match self.parse_pat_list() {
-            Ok(result) => result,
-            Err(mut err) => { // recover from parse error in tuple pattern list
-                err.emit();
-                self.consume_block(token::Paren);
-                return Ok((vec![], Some(0), false));
-            }
-        };
-        self.expect(&token::CloseDelim(token::Paren))?;
-        Ok(result)
-    }
-
-    fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
-        let mut fields = Vec::new();
-        let mut ddpos = None;
-        let mut prev_dd_sp = None;
-        let mut trailing_comma = false;
-        loop {
-            if self.eat(&token::DotDot) {
-                if ddpos.is_none() {
-                    ddpos = Some(fields.len());
-                    prev_dd_sp = Some(self.prev_span);
-                } else {
-                    // Emit a friendly error, ignore `..` and continue parsing
-                    let mut err = self.struct_span_err(
-                        self.prev_span,
-                        "`..` can only be used once per tuple or tuple struct pattern",
-                    );
-                    err.span_label(self.prev_span, "can only be used once per pattern");
-                    if let Some(sp) = prev_dd_sp {
-                        err.span_label(sp, "previously present here");
-                    }
-                    err.emit();
-                }
-            } else if !self.check(&token::CloseDelim(token::Paren)) {
-                fields.push(self.parse_pat(None)?);
-            } else {
-                break
-            }
-
-            trailing_comma = self.eat(&token::Comma);
-            if !trailing_comma {
-                break
-            }
-        }
-
-        if ddpos == Some(fields.len()) && trailing_comma {
-            // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
-            let msg = "trailing comma is not permitted after `..`";
-            self.struct_span_err(self.prev_span, msg)
-                .span_label(self.prev_span, msg)
-                .emit();
-        }
-
-        Ok((fields, ddpos, trailing_comma))
-    }
-
-    fn parse_pat_vec_elements(
-        &mut self,
-    ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
-        let mut before = Vec::new();
-        let mut slice = None;
-        let mut after = Vec::new();
-        let mut first = true;
-        let mut before_slice = true;
-
-        while self.token != token::CloseDelim(token::Bracket) {
-            if first {
-                first = false;
-            } else {
-                self.expect(&token::Comma)?;
-
-                if self.token == token::CloseDelim(token::Bracket)
-                        && (before_slice || !after.is_empty()) {
-                    break
-                }
-            }
-
-            if before_slice {
-                if self.eat(&token::DotDot) {
-
-                    if self.check(&token::Comma) ||
-                            self.check(&token::CloseDelim(token::Bracket)) {
-                        slice = Some(P(Pat {
-                            id: ast::DUMMY_NODE_ID,
-                            node: PatKind::Wild,
-                            span: self.prev_span,
-                        }));
-                        before_slice = false;
-                    }
-                    continue
-                }
-            }
-
-            let subpat = self.parse_pat(None)?;
-            if before_slice && self.eat(&token::DotDot) {
-                slice = Some(subpat);
-                before_slice = false;
-            } else if before_slice {
-                before.push(subpat);
-            } else {
-                after.push(subpat);
-            }
-        }
-
-        Ok((before, slice, after))
-    }
-
-    fn parse_pat_field(
-        &mut self,
-        lo: Span,
-        attrs: Vec<Attribute>
-    ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
-        // Check if a colon exists one ahead. This means we're parsing a fieldname.
-        let hi;
-        let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
-            // Parsing a pattern of the form "fieldname: pat"
-            let fieldname = self.parse_field_name()?;
-            self.bump();
-            let pat = self.parse_pat(None)?;
-            hi = pat.span;
-            (pat, fieldname, false)
-        } else {
-            // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
-            let is_box = self.eat_keyword(keywords::Box);
-            let boxed_span = self.span;
-            let is_ref = self.eat_keyword(keywords::Ref);
-            let is_mut = self.eat_keyword(keywords::Mut);
-            let fieldname = self.parse_ident()?;
-            hi = self.prev_span;
-
-            let bind_type = match (is_ref, is_mut) {
-                (true, true) => BindingMode::ByRef(Mutability::Mutable),
-                (true, false) => BindingMode::ByRef(Mutability::Immutable),
-                (false, true) => BindingMode::ByValue(Mutability::Mutable),
-                (false, false) => BindingMode::ByValue(Mutability::Immutable),
-            };
-            let fieldpat = P(Pat {
-                id: ast::DUMMY_NODE_ID,
-                node: PatKind::Ident(bind_type, fieldname, None),
-                span: boxed_span.to(hi),
-            });
-
-            let subpat = if is_box {
-                P(Pat {
-                    id: ast::DUMMY_NODE_ID,
-                    node: PatKind::Box(fieldpat),
-                    span: lo.to(hi),
-                })
-            } else {
-                fieldpat
-            };
-            (subpat, fieldname, true)
-        };
-
-        Ok(source_map::Spanned {
-            span: lo.to(hi),
-            node: ast::FieldPat {
-                ident: fieldname,
-                pat: subpat,
-                is_shorthand,
-                attrs: attrs.into(),
-           }
-        })
-    }
-
-    /// Parses the fields of a struct-like pattern.
-    fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
-        let mut fields = Vec::new();
-        let mut etc = false;
-        let mut ate_comma = true;
-        let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
-        let mut etc_span = None;
-
-        while self.token != token::CloseDelim(token::Brace) {
-            let attrs = self.parse_outer_attributes()?;
-            let lo = self.span;
-
-            // check that a comma comes after every field
-            if !ate_comma {
-                let err = self.struct_span_err(self.prev_span, "expected `,`");
-                if let Some(mut delayed) = delayed_err {
-                    delayed.emit();
-                }
-                return Err(err);
-            }
-            ate_comma = false;
-
-            if self.check(&token::DotDot) || self.token == token::DotDotDot {
-                etc = true;
-                let mut etc_sp = self.span;
-
-                if self.token == token::DotDotDot { // Issue #46718
-                    // Accept `...` as if it were `..` to avoid further errors
-                    let mut err = self.struct_span_err(self.span,
-                                                       "expected field pattern, found `...`");
-                    err.span_suggestion(
-                        self.span,
-                        "to omit remaining fields, use one fewer `.`",
-                        "..".to_owned(),
-                        Applicability::MachineApplicable
-                    );
-                    err.emit();
-                }
-                self.bump();  // `..` || `...`
-
-                if self.token == token::CloseDelim(token::Brace) {
-                    etc_span = Some(etc_sp);
-                    break;
-                }
-                let token_str = self.this_token_descr();
-                let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
-
-                err.span_label(self.span, "expected `}`");
-                let mut comma_sp = None;
-                if self.token == token::Comma { // Issue #49257
-                    etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
-                    err.span_label(etc_sp,
-                                   "`..` must be at the end and cannot have a trailing comma");
-                    comma_sp = Some(self.span);
-                    self.bump();
-                    ate_comma = true;
-                }
-
-                etc_span = Some(etc_sp.until(self.span));
-                if self.token == token::CloseDelim(token::Brace) {
-                    // If the struct looks otherwise well formed, recover and continue.
-                    if let Some(sp) = comma_sp {
-                        err.span_suggestion_short(
-                            sp,
-                            "remove this comma",
-                            String::new(),
-                            Applicability::MachineApplicable,
-                        );
-                    }
-                    err.emit();
-                    break;
-                } else if self.token.is_ident() && ate_comma {
-                    // Accept fields coming after `..,`.
-                    // This way we avoid "pattern missing fields" errors afterwards.
-                    // We delay this error until the end in order to have a span for a
-                    // suggested fix.
-                    if let Some(mut delayed_err) = delayed_err {
-                        delayed_err.emit();
-                        return Err(err);
+    fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
+                     -> PResult<'a, (Vec<Arg> , bool)> {
+        let sp = self.token.span;
+        let mut c_variadic = false;
+        let (args, _): (Vec<Option<Arg>>, _) = self.parse_paren_comma_seq(|p| {
+            let do_not_enforce_named_arguments_for_c_variadic =
+                |token: &token::Token| -> bool {
+                    if token == &token::DotDotDot {
+                        false
                     } else {
-                        delayed_err = Some(err);
-                    }
-                } else {
-                    if let Some(mut err) = delayed_err {
-                        err.emit();
-                    }
-                    return Err(err);
-                }
-            }
-
-            fields.push(match self.parse_pat_field(lo, attrs) {
-                Ok(field) => field,
-                Err(err) => {
-                    if let Some(mut delayed_err) = delayed_err {
-                        delayed_err.emit();
+                        named_args
                     }
-                    return Err(err);
-                }
-            });
-            ate_comma = self.eat(&token::Comma);
-        }
-
-        if let Some(mut err) = delayed_err {
-            if let Some(etc_span) = etc_span {
-                err.multipart_suggestion(
-                    "move the `..` to the end of the field list",
-                    vec![
-                        (etc_span, String::new()),
-                        (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
-                    ],
-                    Applicability::MachineApplicable,
-                );
-            }
-            err.emit();
-        }
-        return Ok((fields, etc));
-    }
-
-    fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
-        if self.token.is_path_start() {
-            let lo = self.span;
-            let (qself, path) = if self.eat_lt() {
-                // Parse a qualified path
-                let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
-                (Some(qself), path)
-            } else {
-                // Parse an unqualified path
-                (None, self.parse_path(PathStyle::Expr)?)
-            };
-            let hi = self.prev_span;
-            Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
-        } else {
-            self.parse_literal_maybe_minus()
-        }
-    }
-
-    // helper function to decide whether to parse as ident binding or to try to do
-    // something more complex like range patterns
-    fn parse_as_ident(&mut self) -> bool {
-        self.look_ahead(1, |t| match *t {
-            token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
-            token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
-            // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
-            // range pattern branch
-            token::DotDot => None,
-            _ => Some(true),
-        }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
-            token::Comma | token::CloseDelim(token::Bracket) => true,
-            _ => false,
-        }))
-    }
-
-    /// A wrapper around `parse_pat` with some special error handling for the
-    /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
-    /// to subpatterns within such).
-    fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
-        let pat = self.parse_pat(None)?;
-        if self.token == token::Comma {
-            // An unexpected comma after a top-level pattern is a clue that the
-            // user (perhaps more accustomed to some other language) forgot the
-            // parentheses in what should have been a tuple pattern; return a
-            // suggestion-enhanced error here rather than choking on the comma
-            // later.
-            let comma_span = self.span;
-            self.bump();
-            if let Err(mut err) = self.parse_pat_list() {
-                // We didn't expect this to work anyway; we just wanted
-                // to advance to the end of the comma-sequence so we know
-                // the span to suggest parenthesizing
-                err.cancel();
-            }
-            let seq_span = pat.span.to(self.prev_span);
-            let mut err = self.struct_span_err(comma_span,
-                                               "unexpected `,` in pattern");
-            if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
-                err.span_suggestion(
-                    seq_span,
-                    "try adding parentheses to match on a tuple..",
-                    format!("({})", seq_snippet),
-                    Applicability::MachineApplicable
-                ).span_suggestion(
-                    seq_span,
-                    "..or a vertical bar to match on multiple alternatives",
-                    format!("{}", seq_snippet.replace(",", " |")),
-                    Applicability::MachineApplicable
-                );
-            }
-            return Err(err);
-        }
-        Ok(pat)
-    }
-
-    /// Parses a pattern.
-    pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
-        self.parse_pat_with_range_pat(true, expected)
-    }
-
-    /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
-    /// allowed).
-    fn parse_pat_with_range_pat(
-        &mut self,
-        allow_range_pat: bool,
-        expected: Option<&'static str>,
-    ) -> PResult<'a, P<Pat>> {
-        maybe_recover_from_interpolated_ty_qpath!(self, true);
-        maybe_whole!(self, NtPat, |x| x);
-
-        let lo = self.span;
-        let pat;
-        match self.token {
-            token::BinOp(token::And) | token::AndAnd => {
-                // Parse &pat / &mut pat
-                self.expect_and()?;
-                let mutbl = self.parse_mutability();
-                if let token::Lifetime(ident) = self.token {
-                    let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
-                                                      ident));
-                    err.span_label(self.span, "unexpected lifetime");
-                    return Err(err);
-                }
-                let subpat = self.parse_pat_with_range_pat(false, expected)?;
-                pat = PatKind::Ref(subpat, mutbl);
-            }
-            token::OpenDelim(token::Paren) => {
-                // Parse (pat,pat,pat,...) as tuple pattern
-                let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
-                pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
-                    PatKind::Paren(fields.into_iter().nth(0).unwrap())
-                } else {
-                    PatKind::Tuple(fields, ddpos)
-                };
-            }
-            token::OpenDelim(token::Bracket) => {
-                // Parse [pat,pat,...] as slice pattern
-                self.bump();
-                let (before, slice, after) = self.parse_pat_vec_elements()?;
-                self.expect(&token::CloseDelim(token::Bracket))?;
-                pat = PatKind::Slice(before, slice, after);
-            }
-            // At this point, token != &, &&, (, [
-            _ => if self.eat_keyword(keywords::Underscore) {
-                // Parse _
-                pat = PatKind::Wild;
-            } else if self.eat_keyword(keywords::Mut) {
-                // Parse mut ident @ pat / mut ref ident @ pat
-                let mutref_span = self.prev_span.to(self.span);
-                let binding_mode = if self.eat_keyword(keywords::Ref) {
-                    self.diagnostic()
-                        .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
-                        .span_suggestion(
-                            mutref_span,
-                            "try switching the order",
-                            "ref mut".into(),
-                            Applicability::MachineApplicable
-                        ).emit();
-                    BindingMode::ByRef(Mutability::Mutable)
-                } else {
-                    BindingMode::ByValue(Mutability::Mutable)
-                };
-                pat = self.parse_pat_ident(binding_mode)?;
-            } else if self.eat_keyword(keywords::Ref) {
-                // Parse ref ident @ pat / ref mut ident @ pat
-                let mutbl = self.parse_mutability();
-                pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
-            } else if self.eat_keyword(keywords::Box) {
-                // Parse box pat
-                let subpat = self.parse_pat_with_range_pat(false, None)?;
-                pat = PatKind::Box(subpat);
-            } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
-                      self.parse_as_ident() {
-                // Parse ident @ pat
-                // This can give false positives and parse nullary enums,
-                // they are dealt with later in resolve
-                let binding_mode = BindingMode::ByValue(Mutability::Immutable);
-                pat = self.parse_pat_ident(binding_mode)?;
-            } else if self.token.is_path_start() {
-                // Parse pattern starting with a path
-                let (qself, path) = if self.eat_lt() {
-                    // Parse a qualified path
-                    let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
-                    (Some(qself), path)
-                } else {
-                    // Parse an unqualified path
-                    (None, self.parse_path(PathStyle::Expr)?)
                 };
-                match self.token {
-                    token::Not if qself.is_none() => {
-                        // Parse macro invocation
-                        self.bump();
-                        let (delim, tts) = self.expect_delimited_token_tree()?;
-                        let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
-                        pat = PatKind::Mac(mac);
-                    }
-                    token::DotDotDot | token::DotDotEq | token::DotDot => {
-                        let end_kind = match self.token {
-                            token::DotDot => RangeEnd::Excluded,
-                            token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
-                            token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
-                            _ => panic!("can only parse `..`/`...`/`..=` for ranges \
-                                         (checked above)"),
-                        };
-                        let op_span = self.span;
-                        // Parse range
-                        let span = lo.to(self.prev_span);
-                        let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
-                        self.bump();
-                        let end = self.parse_pat_range_end()?;
-                        let op = Spanned { span: op_span, node: end_kind };
-                        pat = PatKind::Range(begin, end, op);
-                    }
-                    token::OpenDelim(token::Brace) => {
-                        if qself.is_some() {
-                            let msg = "unexpected `{` after qualified path";
-                            let mut err = self.fatal(msg);
-                            err.span_label(self.span, msg);
-                            return Err(err);
-                        }
-                        // Parse struct pattern
-                        self.bump();
-                        let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
-                            e.emit();
-                            self.recover_stmt();
-                            (vec![], true)
-                        });
-                        self.bump();
-                        pat = PatKind::Struct(path, fields, etc);
-                    }
-                    token::OpenDelim(token::Paren) => {
-                        if qself.is_some() {
-                            let msg = "unexpected `(` after qualified path";
-                            let mut err = self.fatal(msg);
-                            err.span_label(self.span, msg);
-                            return Err(err);
-                        }
-                        // Parse tuple struct or enum pattern
-                        let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
-                        pat = PatKind::TupleStruct(path, fields, ddpos)
-                    }
-                    _ => pat = PatKind::Path(qself, path),
-                }
-            } else {
-                // Try to parse everything else as literal with optional minus
-                match self.parse_literal_maybe_minus() {
-                    Ok(begin) => {
-                        let op_span = self.span;
-                        if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
-                                self.check(&token::DotDotDot) {
-                            let end_kind = if self.eat(&token::DotDotDot) {
-                                RangeEnd::Included(RangeSyntax::DotDotDot)
-                            } else if self.eat(&token::DotDotEq) {
-                                RangeEnd::Included(RangeSyntax::DotDotEq)
-                            } else if self.eat(&token::DotDot) {
-                                RangeEnd::Excluded
-                            } else {
-                                panic!("impossible case: we already matched \
-                                        on a range-operator token")
-                            };
-                            let end = self.parse_pat_range_end()?;
-                            let op = Spanned { span: op_span, node: end_kind };
-                            pat = PatKind::Range(begin, end, op);
+            match p.parse_arg_general(
+                false,
+                allow_c_variadic,
+                do_not_enforce_named_arguments_for_c_variadic
+            ) {
+                Ok(arg) => {
+                    if let TyKind::CVarArgs = arg.ty.node {
+                        c_variadic = true;
+                        if p.token != token::CloseDelim(token::Paren) {
+                            let span = p.token.span;
+                            p.span_err(span,
+                                "`...` must be the last argument of a C-variadic function");
+                            Ok(None)
                         } else {
-                            pat = PatKind::Lit(begin);
-                        }
-                    }
-                    Err(mut err) => {
-                        self.cancel(&mut err);
-                        let expected = expected.unwrap_or("pattern");
-                        let msg = format!(
-                            "expected {}, found {}",
-                            expected,
-                            self.this_token_descr(),
-                        );
-                        let mut err = self.fatal(&msg);
-                        err.span_label(self.span, format!("expected {}", expected));
-                        let sp = self.sess.source_map().start_point(self.span);
-                        if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
-                            self.sess.expr_parentheses_needed(&mut err, *sp, None);
-                        }
-                        return Err(err);
-                    }
-                }
-            }
-        }
-
-        let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
-        let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
-
-        if !allow_range_pat {
-            match pat.node {
-                PatKind::Range(
-                    _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
-                ) => {},
-                PatKind::Range(..) => {
-                    let mut err = self.struct_span_err(
-                        pat.span,
-                        "the range pattern here has ambiguous interpretation",
-                    );
-                    err.span_suggestion(
-                        pat.span,
-                        "add parentheses to clarify the precedence",
-                        format!("({})", pprust::pat_to_string(&pat)),
-                        // "ambiguous interpretation" implies that we have to be guessing
-                        Applicability::MaybeIncorrect
-                    );
-                    return Err(err);
-                }
-                _ => {}
-            }
-        }
-
-        Ok(pat)
-    }
-
-    /// Parses `ident` or `ident @ pat`.
-    /// used by the copy foo and ref foo patterns to give a good
-    /// error message when parsing mistakes like `ref foo(a, b)`.
-    fn parse_pat_ident(&mut self,
-                       binding_mode: ast::BindingMode)
-                       -> PResult<'a, PatKind> {
-        let ident = self.parse_ident()?;
-        let sub = if self.eat(&token::At) {
-            Some(self.parse_pat(Some("binding pattern"))?)
-        } else {
-            None
-        };
-
-        // just to be friendly, if they write something like
-        //   ref Some(i)
-        // we end up here with ( as the current token.  This shortly
-        // leads to a parse error.  Note that if there is no explicit
-        // binding mode then we do not end up here, because the lookahead
-        // will direct us over to parse_enum_variant()
-        if self.token == token::OpenDelim(token::Paren) {
-            return Err(self.span_fatal(
-                self.prev_span,
-                "expected identifier, found enum pattern"))
-        }
-
-        Ok(PatKind::Ident(binding_mode, ident, sub))
-    }
-
-    /// Parses a local variable declaration.
-    fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
-        let lo = self.prev_span;
-        let pat = self.parse_top_level_pat()?;
-
-        let (err, ty) = if self.eat(&token::Colon) {
-            // Save the state of the parser before parsing type normally, in case there is a `:`
-            // instead of an `=` typo.
-            let parser_snapshot_before_type = self.clone();
-            let colon_sp = self.prev_span;
-            match self.parse_ty() {
-                Ok(ty) => (None, Some(ty)),
-                Err(mut err) => {
-                    // Rewind to before attempting to parse the type and continue parsing
-                    let parser_snapshot_after_type = self.clone();
-                    mem::replace(self, parser_snapshot_before_type);
-
-                    let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
-                    err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
-                    (Some((parser_snapshot_after_type, colon_sp, err)), None)
-                }
-            }
-        } else {
-            (None, None)
-        };
-        let init = match (self.parse_initializer(err.is_some()), err) {
-            (Ok(init), None) => {  // init parsed, ty parsed
-                init
-            }
-            (Ok(init), Some((_, colon_sp, mut err))) => {  // init parsed, ty error
-                // Could parse the type as if it were the initializer, it is likely there was a
-                // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
-                err.span_suggestion_short(
-                    colon_sp,
-                    "use `=` if you meant to assign",
-                    "=".to_string(),
-                    Applicability::MachineApplicable
-                );
-                err.emit();
-                // As this was parsed successfully, continue as if the code has been fixed for the
-                // rest of the file. It will still fail due to the emitted error, but we avoid
-                // extra noise.
-                init
-            }
-            (Err(mut init_err), Some((snapshot, _, ty_err))) => {  // init error, ty error
-                init_err.cancel();
-                // Couldn't parse the type nor the initializer, only raise the type error and
-                // return to the parser state before parsing the type as the initializer.
-                // let x: <parse_error>;
-                mem::replace(self, snapshot);
-                return Err(ty_err);
-            }
-            (Err(err), None) => {  // init error, ty parsed
-                // Couldn't parse the initializer and we're not attempting to recover a failed
-                // parse of the type, return the error.
-                return Err(err);
-            }
-        };
-        let hi = if self.token == token::Semi {
-            self.span
-        } else {
-            self.prev_span
-        };
-        Ok(P(ast::Local {
-            ty,
-            pat,
-            init,
-            id: ast::DUMMY_NODE_ID,
-            span: lo.to(hi),
-            attrs,
-            source: LocalSource::Normal,
-        }))
-    }
-
-    /// Parses a structure field.
-    fn parse_name_and_ty(&mut self,
-                         lo: Span,
-                         vis: Visibility,
-                         attrs: Vec<Attribute>)
-                         -> PResult<'a, StructField> {
-        let name = self.parse_ident()?;
-        self.expect(&token::Colon)?;
-        let ty = self.parse_ty()?;
-        Ok(StructField {
-            span: lo.to(self.prev_span),
-            ident: Some(name),
-            vis,
-            id: ast::DUMMY_NODE_ID,
-            ty,
-            attrs,
-        })
-    }
-
-    /// Emits an expected-item-after-attributes error.
-    fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a,  ()> {
-        let message = match attrs.last() {
-            Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
-            _ => "expected item after attributes",
-        };
-
-        let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
-        if attrs.last().unwrap().is_sugared_doc {
-            err.span_label(self.prev_span, "this doc comment doesn't document anything");
-        }
-        Err(err)
-    }
-
-    /// Parse a statement. This stops just before trailing semicolons on everything but items.
-    /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
-    pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
-        Ok(self.parse_stmt_(true))
-    }
-
-    fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
-        self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
-            e.emit();
-            self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
-            None
-        })
-    }
-
-    fn is_async_block(&self) -> bool {
-        self.token.is_keyword(keywords::Async) &&
-        (
-            ( // `async move {`
-                self.look_ahead(1, |t| t.is_keyword(keywords::Move)) &&
-                self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
-            ) || ( // `async {`
-                self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
-            )
-        )
-    }
-
-    fn is_async_fn(&self) -> bool {
-        self.token.is_keyword(keywords::Async) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
-    }
-
-    fn is_do_catch_block(&self) -> bool {
-        self.token.is_keyword(keywords::Do) &&
-        self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
-        self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
-        !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
-    }
-
-    fn is_try_block(&self) -> bool {
-        self.token.is_keyword(keywords::Try) &&
-        self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
-        self.span.rust_2018() &&
-        // prevent `while try {} {}`, `if try {} {} else {}`, etc.
-        !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
-    }
-
-    fn is_union_item(&self) -> bool {
-        self.token.is_keyword(keywords::Union) &&
-        self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
-    }
-
-    fn is_crate_vis(&self) -> bool {
-        self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
-    }
-
-    fn is_existential_type_decl(&self) -> bool {
-        self.token.is_keyword(keywords::Existential) &&
-        self.look_ahead(1, |t| t.is_keyword(keywords::Type))
-    }
-
-    fn is_auto_trait_item(&self) -> bool {
-        // auto trait
-        (self.token.is_keyword(keywords::Auto)
-            && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
-        || // unsafe auto trait
-        (self.token.is_keyword(keywords::Unsafe) &&
-         self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
-         self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
-    }
-
-    fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
-                     -> PResult<'a, Option<P<Item>>> {
-        let token_lo = self.span;
-        let (ident, def) = match self.token {
-            token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
-                self.bump();
-                let ident = self.parse_ident()?;
-                let tokens = if self.check(&token::OpenDelim(token::Brace)) {
-                    match self.parse_token_tree() {
-                        TokenTree::Delimited(_, _, tts) => tts,
-                        _ => unreachable!(),
-                    }
-                } else if self.check(&token::OpenDelim(token::Paren)) {
-                    let args = self.parse_token_tree();
-                    let body = if self.check(&token::OpenDelim(token::Brace)) {
-                        self.parse_token_tree()
-                    } else {
-                        self.unexpected()?;
-                        unreachable!()
-                    };
-                    TokenStream::new(vec![
-                        args.into(),
-                        TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
-                        body.into(),
-                    ])
-                } else {
-                    self.unexpected()?;
-                    unreachable!()
-                };
-
-                (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
-            }
-            token::Ident(ident, _) if ident.name == sym::macro_rules &&
-                                   self.look_ahead(1, |t| *t == token::Not) => {
-                let prev_span = self.prev_span;
-                self.complain_if_pub_macro(&vis.node, prev_span);
-                self.bump();
-                self.bump();
-
-                let ident = self.parse_ident()?;
-                let (delim, tokens) = self.expect_delimited_token_tree()?;
-                if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
-                    self.report_invalid_macro_expansion_item();
-                }
-
-                (ident, ast::MacroDef { tokens: tokens, legacy: true })
-            }
-            _ => return Ok(None),
-        };
-
-        let span = lo.to(self.prev_span);
-        Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
-    }
-
-    fn parse_stmt_without_recovery(&mut self,
-                                   macro_legacy_warnings: bool)
-                                   -> PResult<'a, Option<Stmt>> {
-        maybe_whole!(self, NtStmt, |x| Some(x));
-
-        let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
-
-        Ok(Some(if self.eat_keyword(keywords::Let) {
-            Stmt {
-                id: ast::DUMMY_NODE_ID,
-                node: StmtKind::Local(self.parse_local(attrs.into())?),
-                span: lo.to(self.prev_span),
-            }
-        } else if let Some(macro_def) = self.eat_macro_def(
-            &attrs,
-            &source_map::respan(lo, VisibilityKind::Inherited),
-            lo,
-        )? {
-            Stmt {
-                id: ast::DUMMY_NODE_ID,
-                node: StmtKind::Item(macro_def),
-                span: lo.to(self.prev_span),
-            }
-        // Starts like a simple path, being careful to avoid contextual keywords
-        // such as a union items, item with `crate` visibility or auto trait items.
-        // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
-        // like a path (1 token), but it fact not a path.
-        // `union::b::c` - path, `union U { ... }` - not a path.
-        // `crate::b::c` - path, `crate struct S;` - not a path.
-        } else if self.token.is_path_start() &&
-                  !self.token.is_qpath_start() &&
-                  !self.is_union_item() &&
-                  !self.is_crate_vis() &&
-                  !self.is_existential_type_decl() &&
-                  !self.is_auto_trait_item() &&
-                  !self.is_async_fn() {
-            let pth = self.parse_path(PathStyle::Expr)?;
-
-            if !self.eat(&token::Not) {
-                let expr = if self.check(&token::OpenDelim(token::Brace)) {
-                    self.parse_struct_expr(lo, pth, ThinVec::new())?
-                } else {
-                    let hi = self.prev_span;
-                    self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
-                };
-
-                let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
-                    let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
-                    this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
-                })?;
-
-                return Ok(Some(Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    node: StmtKind::Expr(expr),
-                    span: lo.to(self.prev_span),
-                }));
-            }
-
-            // it's a macro invocation
-            let id = match self.token {
-                token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
-                _ => self.parse_ident()?,
-            };
-
-            // check that we're pointing at delimiters (need to check
-            // again after the `if`, because of `parse_ident`
-            // consuming more tokens).
-            match self.token {
-                token::OpenDelim(_) => {}
-                _ => {
-                    // we only expect an ident if we didn't parse one
-                    // above.
-                    let ident_str = if id.name == keywords::Invalid.name() {
-                        "identifier, "
-                    } else {
-                        ""
-                    };
-                    let tok_str = self.this_token_descr();
-                    let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
-                                                      ident_str,
-                                                      tok_str));
-                    err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
-                    return Err(err)
-                },
-            }
-
-            let (delim, tts) = self.expect_delimited_token_tree()?;
-            let hi = self.prev_span;
-
-            let style = if delim == MacDelimiter::Brace {
-                MacStmtStyle::Braces
-            } else {
-                MacStmtStyle::NoBraces
-            };
-
-            if id.name == keywords::Invalid.name() {
-                let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
-                let node = if delim == MacDelimiter::Brace ||
-                              self.token == token::Semi || self.token == token::Eof {
-                    StmtKind::Mac(P((mac, style, attrs.into())))
-                }
-                // We used to incorrectly stop parsing macro-expanded statements here.
-                // If the next token will be an error anyway but could have parsed with the
-                // earlier behavior, stop parsing here and emit a warning to avoid breakage.
-                else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
-                    // These can continue an expression, so we can't stop parsing and warn.
-                    token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
-                    token::BinOp(token::Minus) | token::BinOp(token::Star) |
-                    token::BinOp(token::And) | token::BinOp(token::Or) |
-                    token::AndAnd | token::OrOr |
-                    token::DotDot | token::DotDotDot | token::DotDotEq => false,
-                    _ => true,
-                } {
-                    self.warn_missing_semicolon();
-                    StmtKind::Mac(P((mac, style, attrs.into())))
-                } else {
-                    let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
-                    let e = self.maybe_recover_from_bad_qpath(e, true)?;
-                    let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
-                    let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
-                    StmtKind::Expr(e)
-                };
-                Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    span: lo.to(hi),
-                    node,
-                }
-            } else {
-                // if it has a special ident, it's definitely an item
-                //
-                // Require a semicolon or braces.
-                if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
-                    self.report_invalid_macro_expansion_item();
-                }
-                let span = lo.to(hi);
-                Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    span,
-                    node: StmtKind::Item({
-                        self.mk_item(
-                            span, id /*id is good here*/,
-                            ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
-                            respan(lo, VisibilityKind::Inherited),
-                            attrs)
-                    }),
-                }
-            }
-        } else {
-            // FIXME: Bad copy of attrs
-            let old_directory_ownership =
-                mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
-            let item = self.parse_item_(attrs.clone(), false, true)?;
-            self.directory.ownership = old_directory_ownership;
-
-            match item {
-                Some(i) => Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    span: lo.to(i.span),
-                    node: StmtKind::Item(i),
-                },
-                None => {
-                    let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
-                        if !attrs.is_empty() {
-                            if s.prev_token_kind == PrevTokenKind::DocComment {
-                                s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
-                            } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
-                                s.span_err(s.span, "expected statement after outer attribute");
-                            }
-                        }
-                    };
-
-                    // Do not attempt to parse an expression if we're done here.
-                    if self.token == token::Semi {
-                        unused_attrs(&attrs, self);
-                        self.bump();
-                        return Ok(None);
-                    }
-
-                    if self.token == token::CloseDelim(token::Brace) {
-                        unused_attrs(&attrs, self);
-                        return Ok(None);
-                    }
-
-                    // Remainder are line-expr stmts.
-                    let e = self.parse_expr_res(
-                        Restrictions::STMT_EXPR, Some(attrs.into()))?;
-                    Stmt {
-                        id: ast::DUMMY_NODE_ID,
-                        span: lo.to(e.span),
-                        node: StmtKind::Expr(e),
-                    }
-                }
-            }
-        }))
-    }
-
-    /// Checks if this expression is a successfully parsed statement.
-    fn expr_is_complete(&self, e: &Expr) -> bool {
-        self.restrictions.contains(Restrictions::STMT_EXPR) &&
-            !classify::expr_requires_semi_to_be_stmt(e)
-    }
-
-    /// Parses a block. No inner attributes are allowed.
-    pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
-        maybe_whole!(self, NtBlock, |x| x);
-
-        let lo = self.span;
-
-        if !self.eat(&token::OpenDelim(token::Brace)) {
-            let sp = self.span;
-            let tok = self.this_token_descr();
-            let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
-            let do_not_suggest_help =
-                self.token.is_keyword(keywords::In) || self.token == token::Colon;
-
-            if self.token.is_ident_named("and") {
-                e.span_suggestion_short(
-                    self.span,
-                    "use `&&` instead of `and` for the boolean operator",
-                    "&&".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-            if self.token.is_ident_named("or") {
-                e.span_suggestion_short(
-                    self.span,
-                    "use `||` instead of `or` for the boolean operator",
-                    "||".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-
-            // Check to see if the user has written something like
-            //
-            //    if (cond)
-            //      bar;
-            //
-            // Which is valid in other languages, but not Rust.
-            match self.parse_stmt_without_recovery(false) {
-                Ok(Some(stmt)) => {
-                    if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
-                        || do_not_suggest_help {
-                        // if the next token is an open brace (e.g., `if a b {`), the place-
-                        // inside-a-block suggestion would be more likely wrong than right
-                        e.span_label(sp, "expected `{`");
-                        return Err(e);
-                    }
-                    let mut stmt_span = stmt.span;
-                    // expand the span to include the semicolon, if it exists
-                    if self.eat(&token::Semi) {
-                        stmt_span = stmt_span.with_hi(self.prev_span.hi());
-                    }
-                    let sugg = pprust::to_string(|s| {
-                        use crate::print::pprust::{PrintState, INDENT_UNIT};
-                        s.ibox(INDENT_UNIT)?;
-                        s.bopen()?;
-                        s.print_stmt(&stmt)?;
-                        s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
-                    });
-                    e.span_suggestion(
-                        stmt_span,
-                        "try placing this code inside a block",
-                        sugg,
-                        // speculative, has been misleading in the past (closed Issue #46836)
-                        Applicability::MaybeIncorrect
-                    );
-                }
-                Err(mut e) => {
-                    self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
-                    self.cancel(&mut e);
-                }
-                _ => ()
-            }
-            e.span_label(sp, "expected `{`");
-            return Err(e);
-        }
-
-        self.parse_block_tail(lo, BlockCheckMode::Default)
-    }
-
-    /// Parses a block. Inner attributes are allowed.
-    fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
-        maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
-
-        let lo = self.span;
-        self.expect(&token::OpenDelim(token::Brace))?;
-        Ok((self.parse_inner_attributes()?,
-            self.parse_block_tail(lo, BlockCheckMode::Default)?))
-    }
-
-    /// Parses the rest of a block expression or function body.
-    /// Precondition: already parsed the '{'.
-    fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
-        let mut stmts = vec![];
-        while !self.eat(&token::CloseDelim(token::Brace)) {
-            let stmt = match self.parse_full_stmt(false) {
-                Err(mut err) => {
-                    err.emit();
-                    self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
-                    Some(Stmt {
-                        id: ast::DUMMY_NODE_ID,
-                        node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
-                        span: self.span,
-                    })
-                }
-                Ok(stmt) => stmt,
-            };
-            if let Some(stmt) = stmt {
-                stmts.push(stmt);
-            } else if self.token == token::Eof {
-                break;
-            } else {
-                // Found only `;` or `}`.
-                continue;
-            };
-        }
-        Ok(P(ast::Block {
-            stmts,
-            id: ast::DUMMY_NODE_ID,
-            rules: s,
-            span: lo.to(self.prev_span),
-        }))
-    }
-
-    /// Parses a statement, including the trailing semicolon.
-    crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
-        // skip looking for a trailing semicolon when we have an interpolated statement
-        maybe_whole!(self, NtStmt, |x| Some(x));
-
-        let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
-            Some(stmt) => stmt,
-            None => return Ok(None),
-        };
-
-        match stmt.node {
-            StmtKind::Expr(ref expr) if self.token != token::Eof => {
-                // expression without semicolon
-                if classify::expr_requires_semi_to_be_stmt(expr) {
-                    // Just check for errors and recover; do not eat semicolon yet.
-                    if let Err(mut e) =
-                        self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
-                    {
-                        e.emit();
-                        self.recover_stmt();
-                    }
-                }
-            }
-            StmtKind::Local(..) => {
-                // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
-                if macro_legacy_warnings && self.token != token::Semi {
-                    self.warn_missing_semicolon();
-                } else {
-                    self.expect_one_of(&[], &[token::Semi])?;
-                }
-            }
-            _ => {}
-        }
-
-        if self.eat(&token::Semi) {
-            stmt = stmt.add_trailing_semicolon();
-        }
-
-        stmt.span = stmt.span.with_hi(self.prev_span.hi());
-        Ok(Some(stmt))
-    }
-
-    fn warn_missing_semicolon(&self) {
-        self.diagnostic().struct_span_warn(self.span, {
-            &format!("expected `;`, found {}", self.this_token_descr())
-        }).note({
-            "This was erroneously allowed and will become a hard error in a future release"
-        }).emit();
-    }
-
-    fn err_dotdotdot_syntax(&self, span: Span) {
-        self.diagnostic().struct_span_err(span, {
-            "unexpected token: `...`"
-        }).span_suggestion(
-            span, "use `..` for an exclusive range", "..".to_owned(),
-            Applicability::MaybeIncorrect
-        ).span_suggestion(
-            span, "or `..=` for an inclusive range", "..=".to_owned(),
-            Applicability::MaybeIncorrect
-        ).emit();
-    }
-
-    /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
-    ///
-    /// ```
-    /// BOUND = TY_BOUND | LT_BOUND
-    /// LT_BOUND = LIFETIME (e.g., `'a`)
-    /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
-    /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
-    /// ```
-    fn parse_generic_bounds_common(&mut self,
-                                   allow_plus: bool,
-                                   colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
-        let mut bounds = Vec::new();
-        let mut negative_bounds = Vec::new();
-        let mut last_plus_span = None;
-        let mut was_negative = false;
-        loop {
-            // This needs to be synchronized with `Token::can_begin_bound`.
-            let is_bound_start = self.check_path() || self.check_lifetime() ||
-                                 self.check(&token::Not) || // used for error reporting only
-                                 self.check(&token::Question) ||
-                                 self.check_keyword(keywords::For) ||
-                                 self.check(&token::OpenDelim(token::Paren));
-            if is_bound_start {
-                let lo = self.span;
-                let has_parens = self.eat(&token::OpenDelim(token::Paren));
-                let inner_lo = self.span;
-                let is_negative = self.eat(&token::Not);
-                let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
-                if self.token.is_lifetime() {
-                    if let Some(question_span) = question {
-                        self.span_err(question_span,
-                                      "`?` may only modify trait bounds, not lifetime bounds");
-                    }
-                    bounds.push(GenericBound::Outlives(self.expect_lifetime()));
-                    if has_parens {
-                        let inner_span = inner_lo.to(self.prev_span);
-                        self.expect(&token::CloseDelim(token::Paren))?;
-                        let mut err = self.struct_span_err(
-                            lo.to(self.prev_span),
-                            "parenthesized lifetime bounds are not supported"
-                        );
-                        if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
-                            err.span_suggestion_short(
-                                lo.to(self.prev_span),
-                                "remove the parentheses",
-                                snippet.to_owned(),
-                                Applicability::MachineApplicable
-                            );
-                        }
-                        err.emit();
-                    }
-                } else {
-                    let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-                    let path = self.parse_path(PathStyle::Type)?;
-                    if has_parens {
-                        self.expect(&token::CloseDelim(token::Paren))?;
-                    }
-                    let poly_span = lo.to(self.prev_span);
-                    if is_negative {
-                        was_negative = true;
-                        if let Some(sp) = last_plus_span.or(colon_span) {
-                            negative_bounds.push(sp.to(poly_span));
+                            Ok(Some(arg))
                         }
                     } else {
-                        let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
-                        let modifier = if question.is_some() {
-                            TraitBoundModifier::Maybe
-                        } else {
-                            TraitBoundModifier::None
-                        };
-                        bounds.push(GenericBound::Trait(poly_trait, modifier));
+                        Ok(Some(arg))
                     }
-                }
-            } else {
-                break
-            }
-
-            if !allow_plus || !self.eat_plus() {
-                break
-            } else {
-                last_plus_span = Some(self.prev_span);
-            }
-        }
-
-        if !negative_bounds.is_empty() || was_negative {
-            let plural = negative_bounds.len() > 1;
-            let last_span = negative_bounds.last().map(|sp| *sp);
-            let mut err = self.struct_span_err(
-                negative_bounds,
-                "negative trait bounds are not supported",
-            );
-            if let Some(sp) = last_span {
-                err.span_label(sp, "negative trait bounds are not supported");
-            }
-            if let Some(bound_list) = colon_span {
-                let bound_list = bound_list.to(self.prev_span);
-                let mut new_bound_list = String::new();
-                if !bounds.is_empty() {
-                    let mut snippets = bounds.iter().map(|bound| bound.span())
-                        .map(|span| self.sess.source_map().span_to_snippet(span));
-                    while let Some(Ok(snippet)) = snippets.next() {
-                        new_bound_list.push_str(" + ");
-                        new_bound_list.push_str(&snippet);
-                    }
-                    new_bound_list = new_bound_list.replacen(" +", ":", 1);
-                }
-                err.span_suggestion_hidden(
-                    bound_list,
-                    &format!("remove the trait bound{}", if plural { "s" } else { "" }),
-                    new_bound_list,
-                    Applicability::MachineApplicable,
-                );
-            }
-            err.emit();
-        }
-
-        return Ok(bounds);
-    }
-
-    crate fn parse_generic_bounds(&mut self,
-                                  colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
-        self.parse_generic_bounds_common(true, colon_span)
-    }
-
-    /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
-    ///
-    /// ```
-    /// BOUND = LT_BOUND (e.g., `'a`)
-    /// ```
-    fn parse_lt_param_bounds(&mut self) -> GenericBounds {
-        let mut lifetimes = Vec::new();
-        while self.check_lifetime() {
-            lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
-
-            if !self.eat_plus() {
-                break
-            }
-        }
-        lifetimes
-    }
-
-    /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
-    fn parse_ty_param(&mut self,
-                      preceding_attrs: Vec<Attribute>)
-                      -> PResult<'a, GenericParam> {
-        let ident = self.parse_ident()?;
-
-        // Parse optional colon and param bounds.
-        let bounds = if self.eat(&token::Colon) {
-            self.parse_generic_bounds(Some(self.prev_span))?
-        } else {
-            Vec::new()
-        };
-
-        let default = if self.eat(&token::Eq) {
-            Some(self.parse_ty()?)
-        } else {
-            None
-        };
-
-        Ok(GenericParam {
-            ident,
-            id: ast::DUMMY_NODE_ID,
-            attrs: preceding_attrs.into(),
-            bounds,
-            kind: GenericParamKind::Type {
-                default,
-            }
-        })
-    }
-
-    /// Parses the following grammar:
-    ///
-    ///     TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
-    fn parse_trait_item_assoc_ty(&mut self)
-        -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
-        let ident = self.parse_ident()?;
-        let mut generics = self.parse_generics()?;
-
-        // Parse optional colon and param bounds.
-        let bounds = if self.eat(&token::Colon) {
-            self.parse_generic_bounds(None)?
-        } else {
-            Vec::new()
-        };
-        generics.where_clause = self.parse_where_clause()?;
-
-        let default = if self.eat(&token::Eq) {
-            Some(self.parse_ty()?)
-        } else {
-            None
-        };
-        self.expect(&token::Semi)?;
-
-        Ok((ident, TraitItemKind::Type(bounds, default), generics))
-    }
-
-    fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
-        self.expect_keyword(keywords::Const)?;
-        let ident = self.parse_ident()?;
-        self.expect(&token::Colon)?;
-        let ty = self.parse_ty()?;
-
-        Ok(GenericParam {
-            ident,
-            id: ast::DUMMY_NODE_ID,
-            attrs: preceding_attrs.into(),
-            bounds: Vec::new(),
-            kind: GenericParamKind::Const {
-                ty,
-            }
-        })
-    }
-
-    /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
-    /// a trailing comma and erroneous trailing attributes.
-    crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
-        let mut params = Vec::new();
-        loop {
-            let attrs = self.parse_outer_attributes()?;
-            if self.check_lifetime() {
-                let lifetime = self.expect_lifetime();
-                // Parse lifetime parameter.
-                let bounds = if self.eat(&token::Colon) {
-                    self.parse_lt_param_bounds()
-                } else {
-                    Vec::new()
-                };
-                params.push(ast::GenericParam {
-                    ident: lifetime.ident,
-                    id: lifetime.id,
-                    attrs: attrs.into(),
-                    bounds,
-                    kind: ast::GenericParamKind::Lifetime,
-                });
-            } else if self.check_keyword(keywords::Const) {
-                // Parse const parameter.
-                params.push(self.parse_const_param(attrs)?);
-            } else if self.check_ident() {
-                // Parse type parameter.
-                params.push(self.parse_ty_param(attrs)?);
-            } else {
-                // Check for trailing attributes and stop parsing.
-                if !attrs.is_empty() {
-                    if !params.is_empty() {
-                        self.struct_span_err(
-                            attrs[0].span,
-                            &format!("trailing attribute after generic parameter"),
-                        )
-                        .span_label(attrs[0].span, "attributes must go before parameters")
-                        .emit();
-                    } else {
-                        self.struct_span_err(
-                            attrs[0].span,
-                            &format!("attribute without generic parameters"),
-                        )
-                        .span_label(
-                            attrs[0].span,
-                            "attributes are only permitted when preceding parameters",
-                        )
-                        .emit();
-                    }
-                }
-                break
-            }
-
-            if !self.eat(&token::Comma) {
-                break
-            }
-        }
-        Ok(params)
-    }
-
-    /// Parses a set of optional generic type parameter declarations. Where
-    /// clauses are not parsed here, and must be added later via
-    /// `parse_where_clause()`.
-    ///
-    /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
-    ///                  | ( < lifetimes , typaramseq ( , )? > )
-    /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
-    fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
-        let span_lo = self.span;
-        if self.eat_lt() {
-            let params = self.parse_generic_params()?;
-            self.expect_gt()?;
-            Ok(ast::Generics {
-                params,
-                where_clause: WhereClause {
-                    id: ast::DUMMY_NODE_ID,
-                    predicates: Vec::new(),
-                    span: syntax_pos::DUMMY_SP,
                 },
-                span: span_lo.to(self.prev_span),
-            })
-        } else {
-            Ok(ast::Generics::default())
-        }
-    }
-
-    /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
-    /// For the purposes of understanding the parsing logic of generic arguments, this function
-    /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
-    /// had the correct amount of leading angle brackets.
-    ///
-    /// ```ignore (diagnostics)
-    /// bar::<<<<T as Foo>::Output>();
-    ///      ^^ help: remove extra angle brackets
-    /// ```
-    fn parse_generic_args_with_leaning_angle_bracket_recovery(
-        &mut self,
-        style: PathStyle,
-        lo: Span,
-    ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
-        // We need to detect whether there are extra leading left angle brackets and produce an
-        // appropriate error and suggestion. This cannot be implemented by looking ahead at
-        // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
-        // then there won't be matching `>` tokens to find.
-        //
-        // To explain how this detection works, consider the following example:
-        //
-        // ```ignore (diagnostics)
-        // bar::<<<<T as Foo>::Output>();
-        //      ^^ help: remove extra angle brackets
-        // ```
-        //
-        // Parsing of the left angle brackets starts in this function. We start by parsing the
-        // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
-        // `eat_lt`):
-        //
-        // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
-        // *Unmatched count:* 1
-        // *`parse_path_segment` calls deep:* 0
-        //
-        // This has the effect of recursing as this function is called if a `<` character
-        // is found within the expected generic arguments:
-        //
-        // *Upcoming tokens:* `<<<T as Foo>::Output>;`
-        // *Unmatched count:* 2
-        // *`parse_path_segment` calls deep:* 1
-        //
-        // Eventually we will have recursed until having consumed all of the `<` tokens and
-        // this will be reflected in the count:
-        //
-        // *Upcoming tokens:* `T as Foo>::Output>;`
-        // *Unmatched count:* 4
-        // `parse_path_segment` calls deep:* 3
-        //
-        // The parser will continue until reaching the first `>` - this will decrement the
-        // unmatched angle bracket count and return to the parent invocation of this function
-        // having succeeded in parsing:
-        //
-        // *Upcoming tokens:* `::Output>;`
-        // *Unmatched count:* 3
-        // *`parse_path_segment` calls deep:* 2
-        //
-        // This will continue until the next `>` character which will also return successfully
-        // to the parent invocation of this function and decrement the count:
-        //
-        // *Upcoming tokens:* `;`
-        // *Unmatched count:* 2
-        // *`parse_path_segment` calls deep:* 1
-        //
-        // At this point, this function will expect to find another matching `>` character but
-        // won't be able to and will return an error. This will continue all the way up the
-        // call stack until the first invocation:
-        //
-        // *Upcoming tokens:* `;`
-        // *Unmatched count:* 2
-        // *`parse_path_segment` calls deep:* 0
-        //
-        // In doing this, we have managed to work out how many unmatched leading left angle
-        // brackets there are, but we cannot recover as the unmatched angle brackets have
-        // already been consumed. To remedy this, we keep a snapshot of the parser state
-        // before we do the above. We can then inspect whether we ended up with a parsing error
-        // and unmatched left angle brackets and if so, restore the parser state before we
-        // consumed any `<` characters to emit an error and consume the erroneous tokens to
-        // recover by attempting to parse again.
-        //
-        // In practice, the recursion of this function is indirect and there will be other
-        // locations that consume some `<` characters - as long as we update the count when
-        // this happens, it isn't an issue.
-
-        let is_first_invocation = style == PathStyle::Expr;
-        // Take a snapshot before attempting to parse - we can restore this later.
-        let snapshot = if is_first_invocation {
-            Some(self.clone())
-        } else {
-            None
-        };
-
-        debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
-        match self.parse_generic_args() {
-            Ok(value) => Ok(value),
-            Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
-                // Cancel error from being unable to find `>`. We know the error
-                // must have been this due to a non-zero unmatched angle bracket
-                // count.
-                e.cancel();
-
-                // Swap `self` with our backup of the parser state before attempting to parse
-                // generic arguments.
-                let snapshot = mem::replace(self, snapshot.unwrap());
-
-                debug!(
-                    "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
-                     snapshot.count={:?}",
-                    snapshot.unmatched_angle_bracket_count,
-                );
-
-                // Eat the unmatched angle brackets.
-                for _ in 0..snapshot.unmatched_angle_bracket_count {
-                    self.eat_lt();
-                }
-
-                // Make a span over ${unmatched angle bracket count} characters.
-                let span = lo.with_hi(
-                    lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
-                );
-                let plural = snapshot.unmatched_angle_bracket_count > 1;
-                self.diagnostic()
-                    .struct_span_err(
-                        span,
-                        &format!(
-                            "unmatched angle bracket{}",
-                            if plural { "s" } else { "" }
-                        ),
-                    )
-                    .span_suggestion(
-                        span,
-                        &format!(
-                            "remove extra angle bracket{}",
-                            if plural { "s" } else { "" }
-                        ),
-                        String::new(),
-                        Applicability::MachineApplicable,
-                    )
-                    .emit();
-
-                // Try again without unmatched angle bracket characters.
-                self.parse_generic_args()
-            },
-            Err(e) => Err(e),
-        }
-    }
-
-    /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
-    /// possibly including trailing comma.
-    fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
-        let mut args = Vec::new();
-        let mut bindings = Vec::new();
-        let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
-        let mut assoc_ty_bindings: Vec<Span> = Vec::new();
-
-        let args_lo = self.span;
-
-        loop {
-            if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
-                // Parse lifetime argument.
-                args.push(GenericArg::Lifetime(self.expect_lifetime()));
-                misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
-            } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
-                // Parse associated type binding.
-                let lo = self.span;
-                let ident = self.parse_ident()?;
-                self.bump();
-                let ty = self.parse_ty()?;
-                let span = lo.to(self.prev_span);
-                bindings.push(TypeBinding {
-                    id: ast::DUMMY_NODE_ID,
-                    ident,
-                    ty,
-                    span,
-                });
-                assoc_ty_bindings.push(span);
-            } else if self.check_const_arg() {
-                // Parse const argument.
-                let expr = if let token::OpenDelim(token::Brace) = self.token {
-                    self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
-                } else if self.token.is_ident() {
-                    // FIXME(const_generics): to distinguish between idents for types and consts,
-                    // we should introduce a GenericArg::Ident in the AST and distinguish when
-                    // lowering to the HIR. For now, idents for const args are not permitted.
-                    return Err(
-                        self.fatal("identifiers may currently not be used for const generics")
-                    );
-                } else {
-                    self.parse_literal_maybe_minus()?
-                };
-                let value = AnonConst {
-                    id: ast::DUMMY_NODE_ID,
-                    value: expr,
-                };
-                args.push(GenericArg::Const(value));
-                misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
-            } else if self.check_type() {
-                // Parse type argument.
-                args.push(GenericArg::Type(self.parse_ty()?));
-                misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
-            } else {
-                break
-            }
-
-            if !self.eat(&token::Comma) {
-                break
-            }
-        }
-
-        // FIXME: we would like to report this in ast_validation instead, but we currently do not
-        // preserve ordering of generic parameters with respect to associated type binding, so we
-        // lose that information after parsing.
-        if misplaced_assoc_ty_bindings.len() > 0 {
-            let mut err = self.struct_span_err(
-                args_lo.to(self.prev_span),
-                "associated type bindings must be declared after generic parameters",
-            );
-            for span in misplaced_assoc_ty_bindings {
-                err.span_label(
-                    span,
-                    "this associated type binding should be moved after the generic parameters",
-                );
-            }
-            err.emit();
-        }
-
-        Ok((args, bindings))
-    }
-
-    /// Parses an optional where-clause and places it in `generics`.
-    ///
-    /// ```ignore (only-for-syntax-highlight)
-    /// where T : Trait<U, V> + 'b, 'a : 'b
-    /// ```
-    fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
-        let mut where_clause = WhereClause {
-            id: ast::DUMMY_NODE_ID,
-            predicates: Vec::new(),
-            span: syntax_pos::DUMMY_SP,
-        };
-
-        if !self.eat_keyword(keywords::Where) {
-            return Ok(where_clause);
-        }
-        let lo = self.prev_span;
-
-        // We are considering adding generics to the `where` keyword as an alternative higher-rank
-        // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
-        // change we parse those generics now, but report an error.
-        if self.choose_generics_over_qpath() {
-            let generics = self.parse_generics()?;
-            self.struct_span_err(
-                generics.span,
-                "generic parameters on `where` clauses are reserved for future use",
-            )
-                .span_label(generics.span, "currently unsupported")
-                .emit();
-        }
-
-        loop {
-            let lo = self.span;
-            if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
-                let lifetime = self.expect_lifetime();
-                // Bounds starting with a colon are mandatory, but possibly empty.
-                self.expect(&token::Colon)?;
-                let bounds = self.parse_lt_param_bounds();
-                where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
-                    ast::WhereRegionPredicate {
-                        span: lo.to(self.prev_span),
-                        lifetime,
-                        bounds,
-                    }
-                ));
-            } else if self.check_type() {
-                // Parse optional `for<'a, 'b>`.
-                // This `for` is parsed greedily and applies to the whole predicate,
-                // the bounded type can have its own `for` applying only to it.
-                // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
-                // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
-                // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
-                let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-
-                // Parse type with mandatory colon and (possibly empty) bounds,
-                // or with mandatory equality sign and the second type.
-                let ty = self.parse_ty()?;
-                if self.eat(&token::Colon) {
-                    let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
-                    where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
-                        ast::WhereBoundPredicate {
-                            span: lo.to(self.prev_span),
-                            bound_generic_params: lifetime_defs,
-                            bounded_ty: ty,
-                            bounds,
-                        }
-                    ));
-                // FIXME: Decide what should be used here, `=` or `==`.
-                // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
-                } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
-                    let rhs_ty = self.parse_ty()?;
-                    where_clause.predicates.push(ast::WherePredicate::EqPredicate(
-                        ast::WhereEqPredicate {
-                            span: lo.to(self.prev_span),
-                            lhs_ty: ty,
-                            rhs_ty,
-                            id: ast::DUMMY_NODE_ID,
-                        }
-                    ));
-                } else {
-                    return self.unexpected();
+                Err(mut e) => {
+                    e.emit();
+                    let lo = p.prev_span;
+                    // Skip every token until next possible arg or end.
+                    p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
+                    // Create a placeholder argument for proper arg count (issue #34264).
+                    let span = lo.to(p.prev_span);
+                    Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
                 }
-            } else {
-                break
             }
-
-            if !self.eat(&token::Comma) {
-                break
-            }
-        }
-
-        where_clause.span = lo.to(self.prev_span);
-        Ok(where_clause)
-    }
-
-    fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
-                     -> PResult<'a, (Vec<Arg> , bool)> {
-        self.expect(&token::OpenDelim(token::Paren))?;
-
-        let sp = self.span;
-        let mut c_variadic = false;
-        let (args, recovered): (Vec<Option<Arg>>, bool) =
-            self.parse_seq_to_before_end(
-                &token::CloseDelim(token::Paren),
-                SeqSep::trailing_allowed(token::Comma),
-                |p| {
-                    // If the argument is a C-variadic argument we should not
-                    // enforce named arguments.
-                    let enforce_named_args = if p.token == token::DotDotDot {
-                        false
-                    } else {
-                        named_args
-                    };
-                    match p.parse_arg_general(enforce_named_args, false,
-                                              allow_c_variadic) {
-                        Ok(arg) => {
-                            if let TyKind::CVarArgs = arg.ty.node {
-                                c_variadic = true;
-                                if p.token != token::CloseDelim(token::Paren) {
-                                    let span = p.span;
-                                    p.span_err(span,
-                                        "`...` must be the last argument of a C-variadic function");
-                                    Ok(None)
-                                } else {
-                                    Ok(Some(arg))
-                                }
-                            } else {
-                                Ok(Some(arg))
-                            }
-                        },
-                        Err(mut e) => {
-                            e.emit();
-                            let lo = p.prev_span;
-                            // Skip every token until next possible arg or end.
-                            p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
-                            // Create a placeholder argument for proper arg count (issue #34264).
-                            let span = lo.to(p.prev_span);
-                            Ok(Some(dummy_arg(span)))
-                        }
-                    }
-                }
-            )?;
-
-        if !recovered {
-            self.eat(&token::CloseDelim(token::Paren));
-        }
+        })?;
 
         let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
 
-        if c_variadic && args.is_empty() {
+        if c_variadic && args.len() <= 1 {
             self.span_err(sp,
                           "C-variadic function must be declared with at least one named argument");
         }
@@ -5995,47 +1243,36 @@ impl<'a> Parser<'a> {
         Ok((args, c_variadic))
     }
 
-    /// Parses the argument list and result type of a function declaration.
-    fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
-
-        let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
-        let ret_ty = self.parse_ret_ty(true)?;
-
-        Ok(P(FnDecl {
-            inputs: args,
-            output: ret_ty,
-            c_variadic,
-        }))
-    }
-
     /// Returns the parsed optional self argument and whether a self shortcut was used.
+    ///
+    /// See `parse_self_arg_with_attrs` to collect attributes.
     fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
-        let expect_ident = |this: &mut Self| match this.token {
+        let expect_ident = |this: &mut Self| match this.token.kind {
             // Preserve hygienic context.
-            token::Ident(ident, _) =>
-                { let span = this.span; this.bump(); Ident::new(ident.name, span) }
+            token::Ident(name, _) =>
+                { let span = this.token.span; this.bump(); Ident::new(name, span) }
             _ => unreachable!()
         };
         let isolated_self = |this: &mut Self, n| {
-            this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) &&
+            this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
             this.look_ahead(n + 1, |t| t != &token::ModSep)
         };
 
-        // Parse optional self parameter of a method.
-        // Only a limited set of initial token sequences is considered self parameters, anything
+        // Parse optional `self` parameter of a method.
+        // Only a limited set of initial token sequences is considered `self` parameters; anything
         // else is parsed as a normal function parameter list, so some lookahead is required.
-        let eself_lo = self.span;
-        let (eself, eself_ident, eself_hi) = match self.token {
+        let eself_lo = self.token.span;
+        let (eself, eself_ident, eself_hi) = match self.token.kind {
             token::BinOp(token::And) => {
-                // &self
-                // &mut self
-                // &'lt self
-                // &'lt mut self
-                // &not_self
+                // `&self`
+                // `&mut self`
+                // `&'lt self`
+                // `&'lt mut self`
+                // `&not_self`
                 (if isolated_self(self, 1) {
                     self.bump();
                     SelfKind::Region(None, Mutability::Immutable)
-                } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
+                } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
                           isolated_self(self, 2) {
                     self.bump();
                     self.bump();
@@ -6046,7 +1283,7 @@ impl<'a> Parser<'a> {
                     let lt = self.expect_lifetime();
                     SelfKind::Region(Some(lt), Mutability::Immutable)
                 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
-                          self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
+                          self.is_keyword_ahead(2, &[kw::Mut]) &&
                           isolated_self(self, 3) {
                     self.bump();
                     let lt = self.expect_lifetime();
@@ -6057,24 +1294,24 @@ impl<'a> Parser<'a> {
                 }, expect_ident(self), self.prev_span)
             }
             token::BinOp(token::Star) => {
-                // *self
-                // *const self
-                // *mut self
-                // *not_self
+                // `*self`
+                // `*const self`
+                // `*mut self`
+                // `*not_self`
                 // Emit special error for `self` cases.
                 let msg = "cannot pass `self` by raw pointer";
                 (if isolated_self(self, 1) {
                     self.bump();
-                    self.struct_span_err(self.span, msg)
-                        .span_label(self.span, msg)
+                    self.struct_span_err(self.token.span, msg)
+                        .span_label(self.token.span, msg)
                         .emit();
                     SelfKind::Value(Mutability::Immutable)
                 } else if self.look_ahead(1, |t| t.is_mutability()) &&
                           isolated_self(self, 2) {
                     self.bump();
                     self.bump();
-                    self.struct_span_err(self.span, msg)
-                        .span_label(self.span, msg)
+                    self.struct_span_err(self.token.span, msg)
+                        .span_label(self.token.span, msg)
                         .emit();
                     SelfKind::Value(Mutability::Immutable)
                 } else {
@@ -6083,8 +1320,8 @@ impl<'a> Parser<'a> {
             }
             token::Ident(..) => {
                 if isolated_self(self, 0) {
-                    // self
-                    // self: TYPE
+                    // `self`
+                    // `self: TYPE`
                     let eself_ident = expect_ident(self);
                     let eself_hi = self.prev_span;
                     (if self.eat(&token::Colon) {
@@ -6093,10 +1330,10 @@ impl<'a> Parser<'a> {
                     } else {
                         SelfKind::Value(Mutability::Immutable)
                     }, eself_ident, eself_hi)
-                } else if self.token.is_keyword(keywords::Mut) &&
+                } else if self.token.is_keyword(kw::Mut) &&
                           isolated_self(self, 1) {
-                    // mut self
-                    // mut self: TYPE
+                    // `mut self`
+                    // `mut self: TYPE`
                     self.bump();
                     let eself_ident = expect_ident(self);
                     let eself_hi = self.prev_span;
@@ -6114,7 +1351,18 @@ impl<'a> Parser<'a> {
         };
 
         let eself = source_map::respan(eself_lo.to(eself_hi), eself);
-        Ok(Some(Arg::from_self(eself, eself_ident)))
+        Ok(Some(Arg::from_self(ThinVec::default(), eself, eself_ident)))
+    }
+
+    /// Returns the parsed optional self argument with attributes and whether a self
+    /// shortcut was used.
+    fn parse_self_arg_with_attrs(&mut self) -> PResult<'a, Option<Arg>> {
+        let attrs = self.parse_arg_attributes()?;
+        let arg_opt = self.parse_self_arg()?;
+        Ok(arg_opt.map(|mut arg| {
+            arg.attrs = attrs.into();
+            arg
+        }))
     }
 
     /// Parses the parameter list and result type of a function that may have a `self` parameter.
@@ -6123,17 +1371,17 @@ impl<'a> Parser<'a> {
     {
         self.expect(&token::OpenDelim(token::Paren))?;
 
-        // Parse optional self argument
-        let self_arg = self.parse_self_arg()?;
+        // Parse optional self argument.
+        let self_arg = self.parse_self_arg_with_attrs()?;
 
         // Parse the rest of the function parameter list.
         let sep = SeqSep::trailing_allowed(token::Comma);
-        let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
+        let (mut fn_inputs, recovered) = if let Some(self_arg) = self_arg {
             if self.check(&token::CloseDelim(token::Paren)) {
                 (vec![self_arg], false)
             } else if self.eat(&token::Comma) {
                 let mut fn_inputs = vec![self_arg];
-                let (mut input, recovered) = self.parse_seq_to_before_end(
+                let (mut input, _, recovered) = self.parse_seq_to_before_end(
                     &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
                 fn_inputs.append(&mut input);
                 (fn_inputs, recovered)
@@ -6144,13 +1392,18 @@ impl<'a> Parser<'a> {
                 }
             }
         } else {
-            self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
+            let (input, _, recovered) =
+                self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
+            (input, recovered)
         };
 
         if !recovered {
             // Parse closing paren and return type.
             self.expect(&token::CloseDelim(token::Paren))?;
         }
+        // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
+        self.deduplicate_recovered_arg_names(&mut fn_inputs);
+
         Ok(P(FnDecl {
             inputs: fn_inputs,
             output: self.parse_ret_ty(true)?,
@@ -6158,682 +1411,8 @@ impl<'a> Parser<'a> {
         }))
     }
 
-    /// Parses the `|arg, arg|` header of a closure.
-    fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
-        let inputs_captures = {
-            if self.eat(&token::OrOr) {
-                Vec::new()
-            } else {
-                self.expect(&token::BinOp(token::Or))?;
-                let args = self.parse_seq_to_before_tokens(
-                    &[&token::BinOp(token::Or), &token::OrOr],
-                    SeqSep::trailing_allowed(token::Comma),
-                    TokenExpectType::NoExpect,
-                    |p| p.parse_fn_block_arg()
-                )?.0;
-                self.expect_or()?;
-                args
-            }
-        };
-        let output = self.parse_ret_ty(true)?;
-
-        Ok(P(FnDecl {
-            inputs: inputs_captures,
-            output,
-            c_variadic: false
-        }))
-    }
-
-    /// Parses the name and optional generic types of a function header.
-    fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
-        let id = self.parse_ident()?;
-        let generics = self.parse_generics()?;
-        Ok((id, generics))
-    }
-
-    fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
-               attrs: Vec<Attribute>) -> P<Item> {
-        P(Item {
-            ident,
-            attrs,
-            id: ast::DUMMY_NODE_ID,
-            node,
-            vis,
-            span,
-            tokens: None,
-        })
-    }
-
-    /// Parses an item-position function declaration.
-    fn parse_item_fn(&mut self,
-                     unsafety: Unsafety,
-                     mut asyncness: Spanned<IsAsync>,
-                     constness: Spanned<Constness>,
-                     abi: Abi)
-                     -> PResult<'a, ItemInfo> {
-        let (ident, mut generics) = self.parse_fn_header()?;
-        let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
-        let mut decl = self.parse_fn_decl(allow_c_variadic)?;
-        generics.where_clause = self.parse_where_clause()?;
-        let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
-        self.construct_async_arguments(&mut asyncness, &mut decl);
-        let header = FnHeader { unsafety, asyncness, constness, abi };
-        Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
-    }
-
-    /// Returns `true` if we are looking at `const ID`
-    /// (returns `false` for things like `const fn`, etc.).
-    fn is_const_item(&self) -> bool {
-        self.token.is_keyword(keywords::Const) &&
-            !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
-            !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
-    }
-
-    /// Parses all the "front matter" for a `fn` declaration, up to
-    /// and including the `fn` keyword:
-    ///
-    /// - `const fn`
-    /// - `unsafe fn`
-    /// - `const unsafe fn`
-    /// - `extern fn`
-    /// - etc.
-    fn parse_fn_front_matter(&mut self)
-        -> PResult<'a, (
-            Spanned<Constness>,
-            Unsafety,
-            Spanned<IsAsync>,
-            Abi
-        )>
-    {
-        let is_const_fn = self.eat_keyword(keywords::Const);
-        let const_span = self.prev_span;
-        let unsafety = self.parse_unsafety();
-        let asyncness = self.parse_asyncness();
-        let asyncness = respan(self.prev_span, asyncness);
-        let (constness, unsafety, abi) = if is_const_fn {
-            (respan(const_span, Constness::Const), unsafety, Abi::Rust)
-        } else {
-            let abi = if self.eat_keyword(keywords::Extern) {
-                self.parse_opt_abi()?.unwrap_or(Abi::C)
-            } else {
-                Abi::Rust
-            };
-            (respan(self.prev_span, Constness::NotConst), unsafety, abi)
-        };
-        if !self.eat_keyword(keywords::Fn) {
-            // It is possible for `expect_one_of` to recover given the contents of
-            // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
-            // account for this.
-            if !self.expect_one_of(&[], &[])? { unreachable!() }
-        }
-        Ok((constness, unsafety, asyncness, abi))
-    }
-
-    /// Parses an impl item.
-    pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
-        maybe_whole!(self, NtImplItem, |x| x);
-        let attrs = self.parse_outer_attributes()?;
-        let mut unclosed_delims = vec![];
-        let (mut item, tokens) = self.collect_tokens(|this| {
-            let item = this.parse_impl_item_(at_end, attrs);
-            unclosed_delims.append(&mut this.unclosed_delims);
-            item
-        })?;
-        self.unclosed_delims.append(&mut unclosed_delims);
-
-        // See `parse_item` for why this clause is here.
-        if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
-            item.tokens = Some(tokens);
-        }
-        Ok(item)
-    }
-
-    fn parse_impl_item_(&mut self,
-                        at_end: &mut bool,
-                        mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
-        let lo = self.span;
-        let vis = self.parse_visibility(false)?;
-        let defaultness = self.parse_defaultness();
-        let (name, node, generics) = if let Some(type_) = self.eat_type() {
-            let (name, alias, generics) = type_?;
-            let kind = match alias {
-                AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
-                AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
-            };
-            (name, kind, generics)
-        } else if self.is_const_item() {
-            // This parses the grammar:
-            //     ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
-            self.expect_keyword(keywords::Const)?;
-            let name = self.parse_ident()?;
-            self.expect(&token::Colon)?;
-            let typ = self.parse_ty()?;
-            self.expect(&token::Eq)?;
-            let expr = self.parse_expr()?;
-            self.expect(&token::Semi)?;
-            (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
-        } else {
-            let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
-            attrs.extend(inner_attrs);
-            (name, node, generics)
-        };
-
-        Ok(ImplItem {
-            id: ast::DUMMY_NODE_ID,
-            span: lo.to(self.prev_span),
-            ident: name,
-            vis,
-            defaultness,
-            attrs,
-            generics,
-            node,
-            tokens: None,
-        })
-    }
-
-    fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
-        match *vis {
-            VisibilityKind::Inherited => {}
-            _ => {
-                let is_macro_rules: bool = match self.token {
-                    token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
-                    _ => false,
-                };
-                let mut err = if is_macro_rules {
-                    let mut err = self.diagnostic()
-                        .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
-                    err.span_suggestion(
-                        sp,
-                        "try exporting the macro",
-                        "#[macro_export]".to_owned(),
-                        Applicability::MaybeIncorrect // speculative
-                    );
-                    err
-                } else {
-                    let mut err = self.diagnostic()
-                        .struct_span_err(sp, "can't qualify macro invocation with `pub`");
-                    err.help("try adjusting the macro to put `pub` inside the invocation");
-                    err
-                };
-                err.emit();
-            }
-        }
-    }
-
-    fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
-                                   -> DiagnosticBuilder<'a>
-    {
-        let expected_kinds = if item_type == "extern" {
-            "missing `fn`, `type`, or `static`"
-        } else {
-            "missing `fn`, `type`, or `const`"
-        };
-
-        // Given this code `path(`, it seems like this is not
-        // setting the visibility of a macro invocation, but rather
-        // a mistyped method declaration.
-        // Create a diagnostic pointing out that `fn` is missing.
-        //
-        // x |     pub path(&self) {
-        //   |        ^ missing `fn`, `type`, or `const`
-        //     pub  path(
-        //        ^^ `sp` below will point to this
-        let sp = prev_span.between(self.prev_span);
-        let mut err = self.diagnostic().struct_span_err(
-            sp,
-            &format!("{} for {}-item declaration",
-                     expected_kinds, item_type));
-        err.span_label(sp, expected_kinds);
-        err
-    }
-
-    /// Parse a method or a macro invocation in a trait impl.
-    fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
-                         -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
-                             ast::ImplItemKind)> {
-        // code copied from parse_macro_use_or_failure... abstraction!
-        if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
-            // method macro
-            Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
-                ast::ImplItemKind::Macro(mac)))
-        } else {
-            let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
-            let ident = self.parse_ident()?;
-            let mut generics = self.parse_generics()?;
-            let mut decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
-            generics.where_clause = self.parse_where_clause()?;
-            self.construct_async_arguments(&mut asyncness, &mut decl);
-            *at_end = true;
-            let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
-            let header = ast::FnHeader { abi, unsafety, constness, asyncness };
-            Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
-                ast::MethodSig { header, decl },
-                body
-            )))
-        }
-    }
-
-    /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
-    fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
-        let ident = self.parse_ident()?;
-        let mut tps = self.parse_generics()?;
-
-        // Parse optional colon and supertrait bounds.
-        let bounds = if self.eat(&token::Colon) {
-            self.parse_generic_bounds(Some(self.prev_span))?
-        } else {
-            Vec::new()
-        };
-
-        if self.eat(&token::Eq) {
-            // it's a trait alias
-            let bounds = self.parse_generic_bounds(None)?;
-            tps.where_clause = self.parse_where_clause()?;
-            self.expect(&token::Semi)?;
-            if is_auto == IsAuto::Yes {
-                let msg = "trait aliases cannot be `auto`";
-                self.struct_span_err(self.prev_span, msg)
-                    .span_label(self.prev_span, msg)
-                    .emit();
-            }
-            if unsafety != Unsafety::Normal {
-                let msg = "trait aliases cannot be `unsafe`";
-                self.struct_span_err(self.prev_span, msg)
-                    .span_label(self.prev_span, msg)
-                    .emit();
-            }
-            Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
-        } else {
-            // it's a normal trait
-            tps.where_clause = self.parse_where_clause()?;
-            self.expect(&token::OpenDelim(token::Brace))?;
-            let mut trait_items = vec![];
-            while !self.eat(&token::CloseDelim(token::Brace)) {
-                if let token::DocComment(_) = self.token {
-                    if self.look_ahead(1,
-                    |tok| tok == &token::Token::CloseDelim(token::Brace)) {
-                        let mut err = self.diagnostic().struct_span_err_with_code(
-                            self.span,
-                            "found a documentation comment that doesn't document anything",
-                            DiagnosticId::Error("E0584".into()),
-                        );
-                        err.help("doc comments must come before what they document, maybe a \
-                            comment was intended with `//`?",
-                        );
-                        err.emit();
-                        self.bump();
-                        continue;
-                    }
-                }
-                let mut at_end = false;
-                match self.parse_trait_item(&mut at_end) {
-                    Ok(item) => trait_items.push(item),
-                    Err(mut e) => {
-                        e.emit();
-                        if !at_end {
-                            self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
-                        }
-                    }
-                }
-            }
-            Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
-        }
-    }
-
-    fn choose_generics_over_qpath(&self) -> bool {
-        // There's an ambiguity between generic parameters and qualified paths in impls.
-        // If we see `<` it may start both, so we have to inspect some following tokens.
-        // The following combinations can only start generics,
-        // but not qualified paths (with one exception):
-        //     `<` `>` - empty generic parameters
-        //     `<` `#` - generic parameters with attributes
-        //     `<` (LIFETIME|IDENT) `>` - single generic parameter
-        //     `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
-        //     `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
-        //     `<` (LIFETIME|IDENT) `=` - generic parameter with a default
-        //     `<` const                - generic const parameter
-        // The only truly ambiguous case is
-        //     `<` IDENT `>` `::` IDENT ...
-        // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
-        // because this is what almost always expected in practice, qualified paths in impls
-        // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
-        self.token == token::Lt &&
-            (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
-             self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
-                self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
-                                       t == &token::Colon || t == &token::Eq) ||
-             self.look_ahead(1, |t| t.is_keyword(keywords::Const)))
-    }
-
-    fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
-        self.expect(&token::OpenDelim(token::Brace))?;
-        let attrs = self.parse_inner_attributes()?;
-
-        let mut impl_items = Vec::new();
-        while !self.eat(&token::CloseDelim(token::Brace)) {
-            let mut at_end = false;
-            match self.parse_impl_item(&mut at_end) {
-                Ok(impl_item) => impl_items.push(impl_item),
-                Err(mut err) => {
-                    err.emit();
-                    if !at_end {
-                        self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
-                    }
-                }
-            }
-        }
-        Ok((impl_items, attrs))
-    }
-
-    /// Parses an implementation item, `impl` keyword is already parsed.
-    ///
-    ///    impl<'a, T> TYPE { /* impl items */ }
-    ///    impl<'a, T> TRAIT for TYPE { /* impl items */ }
-    ///    impl<'a, T> !TRAIT for TYPE { /* impl items */ }
-    ///
-    /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
-    ///     `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
-    ///     `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
-    fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
-                       -> PResult<'a, ItemInfo> {
-        // First, parse generic parameters if necessary.
-        let mut generics = if self.choose_generics_over_qpath() {
-            self.parse_generics()?
-        } else {
-            ast::Generics::default()
-        };
-
-        // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
-        let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
-            self.bump(); // `!`
-            ast::ImplPolarity::Negative
-        } else {
-            ast::ImplPolarity::Positive
-        };
-
-        // Parse both types and traits as a type, then reinterpret if necessary.
-        let err_path = |span| ast::Path::from_ident(Ident::new(keywords::Invalid.name(), span));
-        let ty_first = if self.token.is_keyword(keywords::For) &&
-                          self.look_ahead(1, |t| t != &token::Lt) {
-            let span = self.prev_span.between(self.span);
-            self.struct_span_err(span, "missing trait in a trait impl").emit();
-            P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
-        } else {
-            self.parse_ty()?
-        };
-
-        // If `for` is missing we try to recover.
-        let has_for = self.eat_keyword(keywords::For);
-        let missing_for_span = self.prev_span.between(self.span);
-
-        let ty_second = if self.token == token::DotDot {
-            // We need to report this error after `cfg` expansion for compatibility reasons
-            self.bump(); // `..`, do not add it to expected tokens
-            Some(DummyResult::raw_ty(self.prev_span, true))
-        } else if has_for || self.token.can_begin_type() {
-            Some(self.parse_ty()?)
-        } else {
-            None
-        };
-
-        generics.where_clause = self.parse_where_clause()?;
-
-        let (impl_items, attrs) = self.parse_impl_body()?;
-
-        let item_kind = match ty_second {
-            Some(ty_second) => {
-                // impl Trait for Type
-                if !has_for {
-                    self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
-                        .span_suggestion_short(
-                            missing_for_span,
-                            "add `for` here",
-                            " for ".to_string(),
-                            Applicability::MachineApplicable,
-                        ).emit();
-                }
-
-                let ty_first = ty_first.into_inner();
-                let path = match ty_first.node {
-                    // This notably includes paths passed through `ty` macro fragments (#46438).
-                    TyKind::Path(None, path) => path,
-                    _ => {
-                        self.span_err(ty_first.span, "expected a trait, found type");
-                        err_path(ty_first.span)
-                    }
-                };
-                let trait_ref = TraitRef { path, ref_id: ty_first.id };
-
-                ItemKind::Impl(unsafety, polarity, defaultness,
-                               generics, Some(trait_ref), ty_second, impl_items)
-            }
-            None => {
-                // impl Type
-                ItemKind::Impl(unsafety, polarity, defaultness,
-                               generics, None, ty_first, impl_items)
-            }
-        };
-
-        Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
-    }
-
-    fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
-        if self.eat_keyword(keywords::For) {
-            self.expect_lt()?;
-            let params = self.parse_generic_params()?;
-            self.expect_gt()?;
-            // We rely on AST validation to rule out invalid cases: There must not be type
-            // parameters, and the lifetime parameters must not have bounds.
-            Ok(params)
-        } else {
-            Ok(Vec::new())
-        }
-    }
-
-    /// Parses `struct Foo { ... }`.
-    fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
-        let class_name = self.parse_ident()?;
-
-        let mut generics = self.parse_generics()?;
-
-        // There is a special case worth noting here, as reported in issue #17904.
-        // If we are parsing a tuple struct it is the case that the where clause
-        // should follow the field list. Like so:
-        //
-        // struct Foo<T>(T) where T: Copy;
-        //
-        // If we are parsing a normal record-style struct it is the case
-        // that the where clause comes before the body, and after the generics.
-        // So if we look ahead and see a brace or a where-clause we begin
-        // parsing a record style struct.
-        //
-        // Otherwise if we look ahead and see a paren we parse a tuple-style
-        // struct.
-
-        let vdata = if self.token.is_keyword(keywords::Where) {
-            generics.where_clause = self.parse_where_clause()?;
-            if self.eat(&token::Semi) {
-                // If we see a: `struct Foo<T> where T: Copy;` style decl.
-                VariantData::Unit(ast::DUMMY_NODE_ID)
-            } else {
-                // If we see: `struct Foo<T> where T: Copy { ... }`
-                let (fields, recovered) = self.parse_record_struct_body()?;
-                VariantData::Struct(fields, recovered)
-            }
-        // No `where` so: `struct Foo<T>;`
-        } else if self.eat(&token::Semi) {
-            VariantData::Unit(ast::DUMMY_NODE_ID)
-        // Record-style struct definition
-        } else if self.token == token::OpenDelim(token::Brace) {
-            let (fields, recovered) = self.parse_record_struct_body()?;
-            VariantData::Struct(fields, recovered)
-        // Tuple-style struct definition with optional where-clause.
-        } else if self.token == token::OpenDelim(token::Paren) {
-            let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
-            generics.where_clause = self.parse_where_clause()?;
-            self.expect(&token::Semi)?;
-            body
-        } else {
-            let token_str = self.this_token_descr();
-            let mut err = self.fatal(&format!(
-                "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
-                token_str
-            ));
-            err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
-            return Err(err);
-        };
-
-        Ok((class_name, ItemKind::Struct(vdata, generics), None))
-    }
-
-    /// Parses `union Foo { ... }`.
-    fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
-        let class_name = self.parse_ident()?;
-
-        let mut generics = self.parse_generics()?;
-
-        let vdata = if self.token.is_keyword(keywords::Where) {
-            generics.where_clause = self.parse_where_clause()?;
-            let (fields, recovered) = self.parse_record_struct_body()?;
-            VariantData::Struct(fields, recovered)
-        } else if self.token == token::OpenDelim(token::Brace) {
-            let (fields, recovered) = self.parse_record_struct_body()?;
-            VariantData::Struct(fields, recovered)
-        } else {
-            let token_str = self.this_token_descr();
-            let mut err = self.fatal(&format!(
-                "expected `where` or `{{` after union name, found {}", token_str));
-            err.span_label(self.span, "expected `where` or `{` after union name");
-            return Err(err);
-        };
-
-        Ok((class_name, ItemKind::Union(vdata, generics), None))
-    }
-
-    fn parse_record_struct_body(
-        &mut self,
-    ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
-        let mut fields = Vec::new();
-        let mut recovered = false;
-        if self.eat(&token::OpenDelim(token::Brace)) {
-            while self.token != token::CloseDelim(token::Brace) {
-                let field = self.parse_struct_decl_field().map_err(|e| {
-                    self.recover_stmt();
-                    recovered = true;
-                    e
-                });
-                match field {
-                    Ok(field) => fields.push(field),
-                    Err(mut err) => {
-                        err.emit();
-                    }
-                }
-            }
-            self.eat(&token::CloseDelim(token::Brace));
-        } else {
-            let token_str = self.this_token_descr();
-            let mut err = self.fatal(&format!(
-                    "expected `where`, or `{{` after struct name, found {}", token_str));
-            err.span_label(self.span, "expected `where`, or `{` after struct name");
-            return Err(err);
-        }
-
-        Ok((fields, recovered))
-    }
-
-    fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
-        // This is the case where we find `struct Foo<T>(T) where T: Copy;`
-        // Unit like structs are handled in parse_item_struct function
-        let fields = self.parse_unspanned_seq(
-            &token::OpenDelim(token::Paren),
-            &token::CloseDelim(token::Paren),
-            SeqSep::trailing_allowed(token::Comma),
-            |p| {
-                let attrs = p.parse_outer_attributes()?;
-                let lo = p.span;
-                let vis = p.parse_visibility(true)?;
-                let ty = p.parse_ty()?;
-                Ok(StructField {
-                    span: lo.to(ty.span),
-                    vis,
-                    ident: None,
-                    id: ast::DUMMY_NODE_ID,
-                    ty,
-                    attrs,
-                })
-            })?;
-
-        Ok(fields)
-    }
-
-    /// Parses a structure field declaration.
-    fn parse_single_struct_field(&mut self,
-                                     lo: Span,
-                                     vis: Visibility,
-                                     attrs: Vec<Attribute> )
-                                     -> PResult<'a, StructField> {
-        let mut seen_comma: bool = false;
-        let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
-        if self.token == token::Comma {
-            seen_comma = true;
-        }
-        match self.token {
-            token::Comma => {
-                self.bump();
-            }
-            token::CloseDelim(token::Brace) => {}
-            token::DocComment(_) => {
-                let previous_span = self.prev_span;
-                let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
-                self.bump(); // consume the doc comment
-                let comma_after_doc_seen = self.eat(&token::Comma);
-                // `seen_comma` is always false, because we are inside doc block
-                // condition is here to make code more readable
-                if seen_comma == false && comma_after_doc_seen == true {
-                    seen_comma = true;
-                }
-                if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
-                    err.emit();
-                } else {
-                    if seen_comma == false {
-                        let sp = self.sess.source_map().next_point(previous_span);
-                        err.span_suggestion(
-                            sp,
-                            "missing comma here",
-                            ",".into(),
-                            Applicability::MachineApplicable
-                        );
-                    }
-                    return Err(err);
-                }
-            }
-            _ => {
-                let sp = self.sess.source_map().next_point(self.prev_span);
-                let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
-                                                                self.this_token_descr()));
-                if self.token.is_ident() {
-                    // This is likely another field; emit the diagnostic and keep going
-                    err.span_suggestion(
-                        sp,
-                        "try adding a comma",
-                        ",".into(),
-                        Applicability::MachineApplicable,
-                    );
-                    err.emit();
-                } else {
-                    return Err(err)
-                }
-            }
-        }
-        Ok(a_var)
-    }
-
-    /// Parses an element of a struct declaration.
-    fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
-        let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
-        let vis = self.parse_visibility(false)?;
-        self.parse_single_struct_field(lo, vis, attrs)
+    fn is_crate_vis(&self) -> bool {
+        self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
     }
 
     /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
@@ -6844,17 +1423,17 @@ impl<'a> Parser<'a> {
     pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |x| x);
 
-        self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
+        self.expected_tokens.push(TokenType::Keyword(kw::Crate));
         if self.is_crate_vis() {
             self.bump(); // `crate`
             return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
         }
 
-        if !self.eat_keyword(keywords::Pub) {
+        if !self.eat_keyword(kw::Pub) {
             // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
             // keyword to grab a span from for inherited visibility; an empty span at the
             // beginning of the current token would seem to be the "Schelling span".
-            return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
+            return Ok(respan(self.token.span.shrink_to_lo(), VisibilityKind::Inherited))
         }
         let lo = self.prev_span;
 
@@ -6863,7 +1442,7 @@ impl<'a> Parser<'a> {
             // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
             // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
             // by the following tokens.
-            if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) &&
+            if self.is_keyword_ahead(1, &[kw::Crate]) &&
                 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
             {
                 // `pub(crate)`
@@ -6875,7 +1454,7 @@ impl<'a> Parser<'a> {
                     VisibilityKind::Crate(CrateSugar::PubCrate),
                 );
                 return Ok(vis)
-            } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
+            } else if self.is_keyword_ahead(1, &[kw::In]) {
                 // `pub(in path)`
                 self.bump(); // `(`
                 self.bump(); // `in`
@@ -6887,8 +1466,7 @@ impl<'a> Parser<'a> {
                 });
                 return Ok(vis)
             } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
-                      self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
-                                             t.is_keyword(keywords::SelfLower))
+                      self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
             {
                 // `pub(self)` or `pub(super)`
                 self.bump(); // `(`
@@ -6911,665 +1489,44 @@ impl<'a> Parser<'a> {
                 let sp = path.span;
                 let help_msg = format!("make this visible only to module `{}` with `in`", path);
                 self.expect(&token::CloseDelim(token::Paren))?;  // `)`
-                let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
-                err.help(suggestion);
-                err.span_suggestion(
-                    sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
-                );
-                err.emit();  // emit diagnostic, but continue with public visibility
-            }
-        }
-
-        Ok(respan(lo, VisibilityKind::Public))
-    }
-
-    /// Parses defaultness (i.e., `default` or nothing).
-    fn parse_defaultness(&mut self) -> Defaultness {
-        // `pub` is included for better error messages
-        if self.check_keyword(keywords::Default) &&
-           self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
-                                  t.is_keyword(keywords::Const) ||
-                                  t.is_keyword(keywords::Fn) ||
-                                  t.is_keyword(keywords::Unsafe) ||
-                                  t.is_keyword(keywords::Extern) ||
-                                  t.is_keyword(keywords::Type) ||
-                                  t.is_keyword(keywords::Pub)) {
-            self.bump(); // `default`
-            Defaultness::Default
-        } else {
-            Defaultness::Final
-        }
-    }
-
-    /// Given a termination token, parses all of the items in a module.
-    fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
-        let mut items = vec![];
-        while let Some(item) = self.parse_item()? {
-            items.push(item);
-            self.maybe_consume_incorrect_semicolon(&items);
-        }
-
-        if !self.eat(term) {
-            let token_str = self.this_token_descr();
-            if !self.maybe_consume_incorrect_semicolon(&items) {
-                let mut err = self.fatal(&format!("expected item, found {}", token_str));
-                err.span_label(self.span, "expected item");
-                return Err(err);
-            }
-        }
-
-        let hi = if self.span.is_dummy() {
-            inner_lo
-        } else {
-            self.prev_span
-        };
-
-        Ok(ast::Mod {
-            inner: inner_lo.to(hi),
-            items,
-            inline: true
-        })
-    }
-
-    fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
-        let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
-        self.expect(&token::Colon)?;
-        let ty = self.parse_ty()?;
-        self.expect(&token::Eq)?;
-        let e = self.parse_expr()?;
-        self.expect(&token::Semi)?;
-        let item = match m {
-            Some(m) => ItemKind::Static(ty, m, e),
-            None => ItemKind::Const(ty, e),
-        };
-        Ok((id, item, None))
-    }
-
-    /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
-    fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
-        let (in_cfg, outer_attrs) = {
-            let mut strip_unconfigured = crate::config::StripUnconfigured {
-                sess: self.sess,
-                features: None, // don't perform gated feature checking
-            };
-            let mut outer_attrs = outer_attrs.to_owned();
-            strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
-            (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
-        };
-
-        let id_span = self.span;
-        let id = self.parse_ident()?;
-        if self.eat(&token::Semi) {
-            if in_cfg && self.recurse_into_file_modules {
-                // This mod is in an external file. Let's go get it!
-                let ModulePathSuccess { path, directory_ownership, warn } =
-                    self.submod_path(id, &outer_attrs, id_span)?;
-                let (module, mut attrs) =
-                    self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
-                // Record that we fetched the mod from an external file
-                if warn {
-                    let attr = Attribute {
-                        id: attr::mk_attr_id(),
-                        style: ast::AttrStyle::Outer,
-                        path: ast::Path::from_ident(
-                            Ident::with_empty_ctxt(sym::warn_directory_ownership)),
-                        tokens: TokenStream::empty(),
-                        is_sugared_doc: false,
-                        span: syntax_pos::DUMMY_SP,
-                    };
-                    attr::mark_known(&attr);
-                    attrs.push(attr);
-                }
-                Ok((id, ItemKind::Mod(module), Some(attrs)))
-            } else {
-                let placeholder = ast::Mod {
-                    inner: syntax_pos::DUMMY_SP,
-                    items: Vec::new(),
-                    inline: false
-                };
-                Ok((id, ItemKind::Mod(placeholder), None))
-            }
-        } else {
-            let old_directory = self.directory.clone();
-            self.push_directory(id, &outer_attrs);
-
-            self.expect(&token::OpenDelim(token::Brace))?;
-            let mod_inner_lo = self.span;
-            let attrs = self.parse_inner_attributes()?;
-            let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
-
-            self.directory = old_directory;
-            Ok((id, ItemKind::Mod(module), Some(attrs)))
-        }
-    }
-
-    fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
-        if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
-            self.directory.path.to_mut().push(&path.as_str());
-            self.directory.ownership = DirectoryOwnership::Owned { relative: None };
-        } else {
-            // We have to push on the current module name in the case of relative
-            // paths in order to ensure that any additional module paths from inline
-            // `mod x { ... }` come after the relative extension.
-            //
-            // For example, a `mod z { ... }` inside `x/y.rs` should set the current
-            // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
-            if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
-                if let Some(ident) = relative.take() { // remove the relative offset
-                    self.directory.path.to_mut().push(ident.as_str());
-                }
-            }
-            self.directory.path.to_mut().push(&id.as_str());
-        }
-    }
-
-    pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
-        if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
-            let s = s.as_str();
-
-            // On windows, the base path might have the form
-            // `\\?\foo\bar` in which case it does not tolerate
-            // mixed `/` and `\` separators, so canonicalize
-            // `/` to `\`.
-            #[cfg(windows)]
-            let s = s.replace("/", "\\");
-            Some(dir_path.join(s))
-        } else {
-            None
-        }
-    }
-
-    /// Returns a path to a module.
-    pub fn default_submod_path(
-        id: ast::Ident,
-        relative: Option<ast::Ident>,
-        dir_path: &Path,
-        source_map: &SourceMap) -> ModulePath
-    {
-        // If we're in a foo.rs file instead of a mod.rs file,
-        // we need to look for submodules in
-        // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
-        // `./<id>.rs` and `./<id>/mod.rs`.
-        let relative_prefix_string;
-        let relative_prefix = if let Some(ident) = relative {
-            relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
-            &relative_prefix_string
-        } else {
-            ""
-        };
-
-        let mod_name = id.to_string();
-        let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
-        let secondary_path_str = format!("{}{}{}mod.rs",
-                                         relative_prefix, mod_name, path::MAIN_SEPARATOR);
-        let default_path = dir_path.join(&default_path_str);
-        let secondary_path = dir_path.join(&secondary_path_str);
-        let default_exists = source_map.file_exists(&default_path);
-        let secondary_exists = source_map.file_exists(&secondary_path);
-
-        let result = match (default_exists, secondary_exists) {
-            (true, false) => Ok(ModulePathSuccess {
-                path: default_path,
-                directory_ownership: DirectoryOwnership::Owned {
-                    relative: Some(id),
-                },
-                warn: false,
-            }),
-            (false, true) => Ok(ModulePathSuccess {
-                path: secondary_path,
-                directory_ownership: DirectoryOwnership::Owned {
-                    relative: None,
-                },
-                warn: false,
-            }),
-            (false, false) => Err(Error::FileNotFoundForModule {
-                mod_name: mod_name.clone(),
-                default_path: default_path_str,
-                secondary_path: secondary_path_str,
-                dir_path: dir_path.display().to_string(),
-            }),
-            (true, true) => Err(Error::DuplicatePaths {
-                mod_name: mod_name.clone(),
-                default_path: default_path_str,
-                secondary_path: secondary_path_str,
-            }),
-        };
-
-        ModulePath {
-            name: mod_name,
-            path_exists: default_exists || secondary_exists,
-            result,
-        }
-    }
-
-    fn submod_path(&mut self,
-                   id: ast::Ident,
-                   outer_attrs: &[Attribute],
-                   id_sp: Span)
-                   -> PResult<'a, ModulePathSuccess> {
-        if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
-            return Ok(ModulePathSuccess {
-                directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
-                    // All `#[path]` files are treated as though they are a `mod.rs` file.
-                    // This means that `mod foo;` declarations inside `#[path]`-included
-                    // files are siblings,
-                    //
-                    // Note that this will produce weirdness when a file named `foo.rs` is
-                    // `#[path]` included and contains a `mod foo;` declaration.
-                    // If you encounter this, it's your own darn fault :P
-                    Some(_) => DirectoryOwnership::Owned { relative: None },
-                    _ => DirectoryOwnership::UnownedViaMod(true),
-                },
-                path,
-                warn: false,
-            });
-        }
-
-        let relative = match self.directory.ownership {
-            DirectoryOwnership::Owned { relative } => relative,
-            DirectoryOwnership::UnownedViaBlock |
-            DirectoryOwnership::UnownedViaMod(_) => None,
-        };
-        let paths = Parser::default_submod_path(
-                        id, relative, &self.directory.path, self.sess.source_map());
-
-        match self.directory.ownership {
-            DirectoryOwnership::Owned { .. } => {
-                paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
-            },
-            DirectoryOwnership::UnownedViaBlock => {
-                let msg =
-                    "Cannot declare a non-inline module inside a block \
-                    unless it has a path attribute";
-                let mut err = self.diagnostic().struct_span_err(id_sp, msg);
-                if paths.path_exists {
-                    let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
-                                      paths.name);
-                    err.span_note(id_sp, &msg);
-                }
-                Err(err)
-            }
-            DirectoryOwnership::UnownedViaMod(warn) => {
-                if warn {
-                    if let Ok(result) = paths.result {
-                        return Ok(ModulePathSuccess { warn: true, ..result });
-                    }
-                }
-                let mut err = self.diagnostic().struct_span_err(id_sp,
-                    "cannot declare a new module at this location");
-                if !id_sp.is_dummy() {
-                    let src_path = self.sess.source_map().span_to_filename(id_sp);
-                    if let FileName::Real(src_path) = src_path {
-                        if let Some(stem) = src_path.file_stem() {
-                            let mut dest_path = src_path.clone();
-                            dest_path.set_file_name(stem);
-                            dest_path.push("mod.rs");
-                            err.span_note(id_sp,
-                                    &format!("maybe move this module `{}` to its own \
-                                                directory via `{}`", src_path.display(),
-                                            dest_path.display()));
-                        }
-                    }
-                }
-                if paths.path_exists {
-                    err.span_note(id_sp,
-                                  &format!("... or maybe `use` the module `{}` instead \
-                                            of possibly redeclaring it",
-                                           paths.name));
-                }
-                Err(err)
-            }
-        }
-    }
-
-    /// Reads a module from a source file.
-    fn eval_src_mod(&mut self,
-                    path: PathBuf,
-                    directory_ownership: DirectoryOwnership,
-                    name: String,
-                    id_sp: Span)
-                    -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
-        let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
-        if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
-            let mut err = String::from("circular modules: ");
-            let len = included_mod_stack.len();
-            for p in &included_mod_stack[i.. len] {
-                err.push_str(&p.to_string_lossy());
-                err.push_str(" -> ");
-            }
-            err.push_str(&path.to_string_lossy());
-            return Err(self.span_fatal(id_sp, &err[..]));
-        }
-        included_mod_stack.push(path.clone());
-        drop(included_mod_stack);
-
-        let mut p0 =
-            new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
-        p0.cfg_mods = self.cfg_mods;
-        let mod_inner_lo = p0.span;
-        let mod_attrs = p0.parse_inner_attributes()?;
-        let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
-        m0.inline = false;
-        self.sess.included_mod_stack.borrow_mut().pop();
-        Ok((m0, mod_attrs))
-    }
-
-    /// Parses a function declaration from a foreign module.
-    fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-                             -> PResult<'a, ForeignItem> {
-        self.expect_keyword(keywords::Fn)?;
-
-        let (ident, mut generics) = self.parse_fn_header()?;
-        let decl = self.parse_fn_decl(true)?;
-        generics.where_clause = self.parse_where_clause()?;
-        let hi = self.span;
-        self.expect(&token::Semi)?;
-        Ok(ast::ForeignItem {
-            ident,
-            attrs,
-            node: ForeignItemKind::Fn(decl, generics),
-            id: ast::DUMMY_NODE_ID,
-            span: lo.to(hi),
-            vis,
-        })
-    }
-
-    /// Parses a static item from a foreign module.
-    /// Assumes that the `static` keyword is already parsed.
-    fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-                                 -> PResult<'a, ForeignItem> {
-        let mutbl = self.parse_mutability();
-        let ident = self.parse_ident()?;
-        self.expect(&token::Colon)?;
-        let ty = self.parse_ty()?;
-        let hi = self.span;
-        self.expect(&token::Semi)?;
-        Ok(ForeignItem {
-            ident,
-            attrs,
-            node: ForeignItemKind::Static(ty, mutbl),
-            id: ast::DUMMY_NODE_ID,
-            span: lo.to(hi),
-            vis,
-        })
-    }
-
-    /// Parses a type from a foreign module.
-    fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-                             -> PResult<'a, ForeignItem> {
-        self.expect_keyword(keywords::Type)?;
-
-        let ident = self.parse_ident()?;
-        let hi = self.span;
-        self.expect(&token::Semi)?;
-        Ok(ast::ForeignItem {
-            ident: ident,
-            attrs: attrs,
-            node: ForeignItemKind::Ty,
-            id: ast::DUMMY_NODE_ID,
-            span: lo.to(hi),
-            vis: vis
-        })
-    }
-
-    fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
-        let error_msg = "crate name using dashes are not valid in `extern crate` statements";
-        let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
-                              in the code";
-        let mut ident = if self.token.is_keyword(keywords::SelfLower) {
-            self.parse_path_segment_ident()
-        } else {
-            self.parse_ident()
-        }?;
-        let mut idents = vec![];
-        let mut replacement = vec![];
-        let mut fixed_crate_name = false;
-        // Accept `extern crate name-like-this` for better diagnostics
-        let dash = token::Token::BinOp(token::BinOpToken::Minus);
-        if self.token == dash {  // Do not include `-` as part of the expected tokens list
-            while self.eat(&dash) {
-                fixed_crate_name = true;
-                replacement.push((self.prev_span, "_".to_string()));
-                idents.push(self.parse_ident()?);
-            }
-        }
-        if fixed_crate_name {
-            let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
-            let mut fixed_name = format!("{}", ident.name);
-            for part in idents {
-                fixed_name.push_str(&format!("_{}", part.name));
-            }
-            ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
-
-            let mut err = self.struct_span_err(fixed_name_sp, error_msg);
-            err.span_label(fixed_name_sp, "dash-separated idents are not valid");
-            err.multipart_suggestion(
-                suggestion_msg,
-                replacement,
-                Applicability::MachineApplicable,
-            );
-            err.emit();
-        }
-        Ok(ident)
-    }
-
-    /// Parses `extern crate` links.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// extern crate foo;
-    /// extern crate bar as foo;
-    /// ```
-    fn parse_item_extern_crate(&mut self,
-                               lo: Span,
-                               visibility: Visibility,
-                               attrs: Vec<Attribute>)
-                               -> PResult<'a, P<Item>> {
-        // Accept `extern crate name-like-this` for better diagnostics
-        let orig_name = self.parse_crate_name_with_dashes()?;
-        let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
-            (rename, Some(orig_name.name))
-        } else {
-            (orig_name, None)
-        };
-        self.expect(&token::Semi)?;
-
-        let span = lo.to(self.prev_span);
-        Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
-    }
-
-    /// Parses `extern` for foreign ABIs modules.
-    ///
-    /// `extern` is expected to have been
-    /// consumed before calling this method.
-    ///
-    /// # Examples
-    ///
-    /// ```ignore (only-for-syntax-highlight)
-    /// extern "C" {}
-    /// extern {}
-    /// ```
-    fn parse_item_foreign_mod(&mut self,
-                              lo: Span,
-                              opt_abi: Option<Abi>,
-                              visibility: Visibility,
-                              mut attrs: Vec<Attribute>)
-                              -> PResult<'a, P<Item>> {
-        self.expect(&token::OpenDelim(token::Brace))?;
-
-        let abi = opt_abi.unwrap_or(Abi::C);
-
-        attrs.extend(self.parse_inner_attributes()?);
-
-        let mut foreign_items = vec![];
-        while !self.eat(&token::CloseDelim(token::Brace)) {
-            foreign_items.push(self.parse_foreign_item()?);
-        }
-
-        let prev_span = self.prev_span;
-        let m = ast::ForeignMod {
-            abi,
-            items: foreign_items
-        };
-        let invalid = keywords::Invalid.ident();
-        Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
-    }
-
-    /// Parses `type Foo = Bar;`
-    /// or
-    /// `existential type Foo: Bar;`
-    /// or
-    /// `return `None``
-    /// without modifying the parser state.
-    fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
-        // This parses the grammar:
-        //     Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
-        if self.check_keyword(keywords::Type) ||
-           self.check_keyword(keywords::Existential) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
-            let existential = self.eat_keyword(keywords::Existential);
-            assert!(self.eat_keyword(keywords::Type));
-            Some(self.parse_existential_or_alias(existential))
-        } else {
-            None
-        }
-    }
-
-    /// Parses a type alias or existential type.
-    fn parse_existential_or_alias(
-        &mut self,
-        existential: bool,
-    ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
-        let ident = self.parse_ident()?;
-        let mut tps = self.parse_generics()?;
-        tps.where_clause = self.parse_where_clause()?;
-        let alias = if existential {
-            self.expect(&token::Colon)?;
-            let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
-            AliasKind::Existential(bounds)
-        } else {
-            self.expect(&token::Eq)?;
-            let ty = self.parse_ty()?;
-            AliasKind::Weak(ty)
-        };
-        self.expect(&token::Semi)?;
-        Ok((ident, alias, tps))
-    }
-
-    /// Parses the part of an enum declaration following the `{`.
-    fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
-        let mut variants = Vec::new();
-        let mut all_nullary = true;
-        let mut any_disr = vec![];
-        while self.token != token::CloseDelim(token::Brace) {
-            let variant_attrs = self.parse_outer_attributes()?;
-            let vlo = self.span;
-
-            let struct_def;
-            let mut disr_expr = None;
-            self.eat_bad_pub();
-            let ident = self.parse_ident()?;
-            if self.check(&token::OpenDelim(token::Brace)) {
-                // Parse a struct variant.
-                all_nullary = false;
-                let (fields, recovered) = self.parse_record_struct_body()?;
-                struct_def = VariantData::Struct(fields, recovered);
-            } else if self.check(&token::OpenDelim(token::Paren)) {
-                all_nullary = false;
-                struct_def = VariantData::Tuple(
-                    self.parse_tuple_struct_body()?,
-                    ast::DUMMY_NODE_ID,
-                );
-            } else if self.eat(&token::Eq) {
-                disr_expr = Some(AnonConst {
-                    id: ast::DUMMY_NODE_ID,
-                    value: self.parse_expr()?,
-                });
-                if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
-                    any_disr.push(sp);
-                }
-                struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
-            } else {
-                struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
-            }
-
-            let vr = ast::Variant_ {
-                ident,
-                id: ast::DUMMY_NODE_ID,
-                attrs: variant_attrs,
-                data: struct_def,
-                disr_expr,
-            };
-            variants.push(respan(vlo.to(self.prev_span), vr));
-
-            if !self.eat(&token::Comma) {
-                if self.token.is_ident() && !self.token.is_reserved_ident() {
-                    let sp = self.sess.source_map().next_point(self.prev_span);
-                    let mut err = self.struct_span_err(sp, "missing comma");
-                    err.span_suggestion_short(
+                struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg)
+                    .help(suggestion)
+                    .span_suggestion(
                         sp,
-                        "missing comma",
-                        ",".to_owned(),
-                        Applicability::MaybeIncorrect,
-                    );
-                    err.emit();
-                } else {
-                    break;
-                }
-            }
-        }
-        self.expect(&token::CloseDelim(token::Brace))?;
-        if !any_disr.is_empty() && !all_nullary {
-            let mut err = self.struct_span_err(
-                any_disr.clone(),
-                "discriminator values can only be used with a field-less enum",
-            );
-            for sp in any_disr {
-                err.span_label(sp, "only valid in field-less enums");
+                        &help_msg,
+                        format!("in {}", path),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();  // emit diagnostic, but continue with public visibility
             }
-            err.emit();
         }
 
-        Ok(ast::EnumDef { variants })
-    }
-
-    /// Parses an enum declaration.
-    fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
-        let id = self.parse_ident()?;
-        let mut generics = self.parse_generics()?;
-        generics.where_clause = self.parse_where_clause()?;
-        self.expect(&token::OpenDelim(token::Brace))?;
-
-        let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
-            self.recover_stmt();
-            self.eat(&token::CloseDelim(token::Brace));
-            e
-        })?;
-        Ok((id, ItemKind::Enum(enum_definition, generics), None))
+        Ok(respan(lo, VisibilityKind::Public))
     }
 
     /// Parses a string as an ABI spec on an extern type or module. Consumes
     /// the `extern` keyword, if one is found.
     fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
-        match self.token {
-            token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
-                let sp = self.span;
-                self.expect_no_suffix(sp, "an ABI spec", suf);
+        match self.token.kind {
+            token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
+            token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
+                let sp = self.token.span;
+                self.expect_no_suffix(sp, "an ABI spec", suffix);
                 self.bump();
-                match abi::lookup(&s.as_str()) {
+                match abi::lookup(&symbol.as_str()) {
                     Some(abi) => Ok(Some(abi)),
                     None => {
                         let prev_span = self.prev_span;
-                        let mut err = struct_span_err!(
+                        struct_span_err!(
                             self.sess.span_diagnostic,
                             prev_span,
                             E0703,
                             "invalid ABI: found `{}`",
-                            s);
-                        err.span_label(prev_span, "invalid ABI");
-                        err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
-                        err.emit();
+                            symbol
+                        )
+                        .span_label(prev_span, "invalid ABI")
+                        .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
+                        .emit();
                         Ok(None)
                     }
                 }
@@ -7579,640 +1536,16 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn is_static_global(&mut self) -> bool {
-        if self.check_keyword(keywords::Static) {
-            // Check if this could be a closure
-            !self.look_ahead(1, |token| {
-                if token.is_keyword(keywords::Move) {
-                    return true;
-                }
-                match *token {
-                    token::BinOp(token::Or) | token::OrOr => true,
-                    _ => false,
-                }
-            })
-        } else {
-            false
-        }
-    }
-
-    fn parse_item_(
-        &mut self,
-        attrs: Vec<Attribute>,
-        macros_allowed: bool,
-        attributes_allowed: bool,
-    ) -> PResult<'a, Option<P<Item>>> {
-        let mut unclosed_delims = vec![];
-        let (ret, tokens) = self.collect_tokens(|this| {
-            let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
-            unclosed_delims.append(&mut this.unclosed_delims);
-            item
-        })?;
-        self.unclosed_delims.append(&mut unclosed_delims);
-
-        // Once we've parsed an item and recorded the tokens we got while
-        // parsing we may want to store `tokens` into the item we're about to
-        // return. Note, though, that we specifically didn't capture tokens
-        // related to outer attributes. The `tokens` field here may later be
-        // used with procedural macros to convert this item back into a token
-        // stream, but during expansion we may be removing attributes as we go
-        // along.
-        //
-        // If we've got inner attributes then the `tokens` we've got above holds
-        // these inner attributes. If an inner attribute is expanded we won't
-        // actually remove it from the token stream, so we'll just keep yielding
-        // it (bad!). To work around this case for now we just avoid recording
-        // `tokens` if we detect any inner attributes. This should help keep
-        // expansion correct, but we should fix this bug one day!
-        Ok(ret.map(|item| {
-            item.map(|mut i| {
-                if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
-                    i.tokens = Some(tokens);
-                }
-                i
-            })
-        }))
-    }
-
-    /// Parses one of the items allowed by the flags.
-    fn parse_item_implementation(
-        &mut self,
-        attrs: Vec<Attribute>,
-        macros_allowed: bool,
-        attributes_allowed: bool,
-    ) -> PResult<'a, Option<P<Item>>> {
-        maybe_whole!(self, NtItem, |item| {
-            let mut item = item.into_inner();
-            let mut attrs = attrs;
-            mem::swap(&mut item.attrs, &mut attrs);
-            item.attrs.extend(attrs);
-            Some(P(item))
-        });
-
-        let lo = self.span;
-
-        let visibility = self.parse_visibility(false)?;
-
-        if self.eat_keyword(keywords::Use) {
-            // USE ITEM
-            let item_ = ItemKind::Use(P(self.parse_use_tree()?));
-            self.expect(&token::Semi)?;
-
-            let span = lo.to(self.prev_span);
-            let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
-            return Ok(Some(item));
-        }
-
-        if self.eat_keyword(keywords::Extern) {
-            if self.eat_keyword(keywords::Crate) {
-                return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
-            }
-
-            let opt_abi = self.parse_opt_abi()?;
-
-            if self.eat_keyword(keywords::Fn) {
-                // EXTERN FUNCTION ITEM
-                let fn_span = self.prev_span;
-                let abi = opt_abi.unwrap_or(Abi::C);
-                let (ident, item_, extra_attrs) =
-                    self.parse_item_fn(Unsafety::Normal,
-                                       respan(fn_span, IsAsync::NotAsync),
-                                       respan(fn_span, Constness::NotConst),
-                                       abi)?;
-                let prev_span = self.prev_span;
-                let item = self.mk_item(lo.to(prev_span),
-                                        ident,
-                                        item_,
-                                        visibility,
-                                        maybe_append(attrs, extra_attrs));
-                return Ok(Some(item));
-            } else if self.check(&token::OpenDelim(token::Brace)) {
-                return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
-            }
-
-            self.unexpected()?;
-        }
-
-        if self.is_static_global() {
-            self.bump();
-            // STATIC ITEM
-            let m = if self.eat_keyword(keywords::Mut) {
-                Mutability::Mutable
-            } else {
-                Mutability::Immutable
-            };
-            let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.eat_keyword(keywords::Const) {
-            let const_span = self.prev_span;
-            if self.check_keyword(keywords::Fn)
-                || (self.check_keyword(keywords::Unsafe)
-                    && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
-                // CONST FUNCTION ITEM
-                let unsafety = self.parse_unsafety();
-                self.bump();
-                let (ident, item_, extra_attrs) =
-                    self.parse_item_fn(unsafety,
-                                       respan(const_span, IsAsync::NotAsync),
-                                       respan(const_span, Constness::Const),
-                                       Abi::Rust)?;
-                let prev_span = self.prev_span;
-                let item = self.mk_item(lo.to(prev_span),
-                                        ident,
-                                        item_,
-                                        visibility,
-                                        maybe_append(attrs, extra_attrs));
-                return Ok(Some(item));
-            }
-
-            // CONST ITEM
-            if self.eat_keyword(keywords::Mut) {
-                let prev_span = self.prev_span;
-                let mut err = self.diagnostic()
-                    .struct_span_err(prev_span, "const globals cannot be mutable");
-                err.span_label(prev_span, "cannot be mutable");
-                err.span_suggestion(
-                    const_span,
-                    "you might want to declare a static instead",
-                    "static".to_owned(),
-                    Applicability::MaybeIncorrect,
-                );
-                err.emit();
-            }
-            let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-
-        // `unsafe async fn` or `async fn`
-        if (
-            self.check_keyword(keywords::Unsafe) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Async))
-        ) || (
-            self.check_keyword(keywords::Async) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
-        )
-        {
-            // ASYNC FUNCTION ITEM
-            let unsafety = self.parse_unsafety();
-            self.expect_keyword(keywords::Async)?;
-            let async_span = self.prev_span;
-            self.expect_keyword(keywords::Fn)?;
-            let fn_span = self.prev_span;
-            let (ident, item_, extra_attrs) =
-                self.parse_item_fn(unsafety,
-                                   respan(async_span, IsAsync::Async {
-                                       closure_id: ast::DUMMY_NODE_ID,
-                                       return_impl_trait_id: ast::DUMMY_NODE_ID,
-                                       arguments: Vec::new(),
-                                   }),
-                                   respan(fn_span, Constness::NotConst),
-                                   Abi::Rust)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            if self.span.rust_2015() {
-                self.diagnostic().struct_span_err_with_code(
+    /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
+    fn ban_async_in_2015(&self, async_span: Span) {
+        if async_span.rust_2015() {
+            self.diagnostic()
+                .struct_span_err_with_code(
                     async_span,
                     "`async fn` is not permitted in the 2015 edition",
                     DiagnosticId::Error("E0670".into())
-                ).emit();
-            }
-            return Ok(Some(item));
-        }
-        if self.check_keyword(keywords::Unsafe) &&
-            (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
-            self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
-        {
-            // UNSAFE TRAIT ITEM
-            self.bump(); // `unsafe`
-            let is_auto = if self.eat_keyword(keywords::Trait) {
-                IsAuto::No
-            } else {
-                self.expect_keyword(keywords::Auto)?;
-                self.expect_keyword(keywords::Trait)?;
-                IsAuto::Yes
-            };
-            let (ident, item_, extra_attrs) =
-                self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.check_keyword(keywords::Impl) ||
-           self.check_keyword(keywords::Unsafe) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
-           self.check_keyword(keywords::Default) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
-           self.check_keyword(keywords::Default) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
-            // IMPL ITEM
-            let defaultness = self.parse_defaultness();
-            let unsafety = self.parse_unsafety();
-            self.expect_keyword(keywords::Impl)?;
-            let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
-            let span = lo.to(self.prev_span);
-            return Ok(Some(self.mk_item(span, ident, item, visibility,
-                                        maybe_append(attrs, extra_attrs))));
-        }
-        if self.check_keyword(keywords::Fn) {
-            // FUNCTION ITEM
-            self.bump();
-            let fn_span = self.prev_span;
-            let (ident, item_, extra_attrs) =
-                self.parse_item_fn(Unsafety::Normal,
-                                   respan(fn_span, IsAsync::NotAsync),
-                                   respan(fn_span, Constness::NotConst),
-                                   Abi::Rust)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.check_keyword(keywords::Unsafe)
-            && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
-            // UNSAFE FUNCTION ITEM
-            self.bump(); // `unsafe`
-            // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
-            self.check(&token::OpenDelim(token::Brace));
-            let abi = if self.eat_keyword(keywords::Extern) {
-                self.parse_opt_abi()?.unwrap_or(Abi::C)
-            } else {
-                Abi::Rust
-            };
-            self.expect_keyword(keywords::Fn)?;
-            let fn_span = self.prev_span;
-            let (ident, item_, extra_attrs) =
-                self.parse_item_fn(Unsafety::Unsafe,
-                                   respan(fn_span, IsAsync::NotAsync),
-                                   respan(fn_span, Constness::NotConst),
-                                   abi)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.eat_keyword(keywords::Mod) {
-            // MODULE ITEM
-            let (ident, item_, extra_attrs) =
-                self.parse_item_mod(&attrs[..])?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if let Some(type_) = self.eat_type() {
-            let (ident, alias, generics) = type_?;
-            // TYPE ITEM
-            let item_ = match alias {
-                AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
-                AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
-            };
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    attrs);
-            return Ok(Some(item));
-        }
-        if self.eat_keyword(keywords::Enum) {
-            // ENUM ITEM
-            let (ident, item_, extra_attrs) = self.parse_item_enum()?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.check_keyword(keywords::Trait)
-            || (self.check_keyword(keywords::Auto)
-                && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
-        {
-            let is_auto = if self.eat_keyword(keywords::Trait) {
-                IsAuto::No
-            } else {
-                self.expect_keyword(keywords::Auto)?;
-                self.expect_keyword(keywords::Trait)?;
-                IsAuto::Yes
-            };
-            // TRAIT ITEM
-            let (ident, item_, extra_attrs) =
-                self.parse_item_trait(is_auto, Unsafety::Normal)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.eat_keyword(keywords::Struct) {
-            // STRUCT ITEM
-            let (ident, item_, extra_attrs) = self.parse_item_struct()?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if self.is_union_item() {
-            // UNION ITEM
-            self.bump();
-            let (ident, item_, extra_attrs) = self.parse_item_union()?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            return Ok(Some(item));
-        }
-        if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
-            return Ok(Some(macro_def));
-        }
-
-        // Verify whether we have encountered a struct or method definition where the user forgot to
-        // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
-        if visibility.node.is_pub() &&
-            self.check_ident() &&
-            self.look_ahead(1, |t| *t != token::Not)
-        {
-            // Space between `pub` keyword and the identifier
-            //
-            //     pub   S {}
-            //        ^^^ `sp` points here
-            let sp = self.prev_span.between(self.span);
-            let full_sp = self.prev_span.to(self.span);
-            let ident_sp = self.span;
-            if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
-                // possible public struct definition where `struct` was forgotten
-                let ident = self.parse_ident().unwrap();
-                let msg = format!("add `struct` here to parse `{}` as a public struct",
-                                  ident);
-                let mut err = self.diagnostic()
-                    .struct_span_err(sp, "missing `struct` for struct definition");
-                err.span_suggestion_short(
-                    sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
-                );
-                return Err(err);
-            } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
-                let ident = self.parse_ident().unwrap();
-                self.bump();  // `(`
-                let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
-                    "method"
-                } else {
-                    "function"
-                };
-                self.consume_block(token::Paren);
-                let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
-                    self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
-                    self.bump();  // `{`
-                    ("fn", kw_name, false)
-                } else if self.check(&token::OpenDelim(token::Brace)) {
-                    self.bump();  // `{`
-                    ("fn", kw_name, false)
-                } else if self.check(&token::Colon) {
-                    let kw = "struct";
-                    (kw, kw, false)
-                } else {
-                    ("fn` or `struct", "function or struct", true)
-                };
-
-                let msg = format!("missing `{}` for {} definition", kw, kw_name);
-                let mut err = self.diagnostic().struct_span_err(sp, &msg);
-                if !ambiguous {
-                    self.consume_block(token::Brace);
-                    let suggestion = format!("add `{}` here to parse `{}` as a public {}",
-                                             kw,
-                                             ident,
-                                             kw_name);
-                    err.span_suggestion_short(
-                        sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
-                    );
-                } else {
-                    if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
-                        err.span_suggestion(
-                            full_sp,
-                            "if you meant to call a macro, try",
-                            format!("{}!", snippet),
-                            // this is the `ambiguous` conditional branch
-                            Applicability::MaybeIncorrect
-                        );
-                    } else {
-                        err.help("if you meant to call a macro, remove the `pub` \
-                                  and add a trailing `!` after the identifier");
-                    }
-                }
-                return Err(err);
-            } else if self.look_ahead(1, |t| *t == token::Lt) {
-                let ident = self.parse_ident().unwrap();
-                self.eat_to_tokens(&[&token::Gt]);
-                self.bump();  // `>`
-                let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
-                    if let Ok(Some(_)) = self.parse_self_arg() {
-                        ("fn", "method", false)
-                    } else {
-                        ("fn", "function", false)
-                    }
-                } else if self.check(&token::OpenDelim(token::Brace)) {
-                    ("struct", "struct", false)
-                } else {
-                    ("fn` or `struct", "function or struct", true)
-                };
-                let msg = format!("missing `{}` for {} definition", kw, kw_name);
-                let mut err = self.diagnostic().struct_span_err(sp, &msg);
-                if !ambiguous {
-                    err.span_suggestion_short(
-                        sp,
-                        &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
-                        format!(" {} ", kw),
-                        Applicability::MachineApplicable,
-                    );
-                }
-                return Err(err);
-            }
-        }
-        self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
-    }
-
-    /// Parses a foreign item.
-    crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
-        maybe_whole!(self, NtForeignItem, |ni| ni);
-
-        let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
-        let visibility = self.parse_visibility(false)?;
-
-        // FOREIGN STATIC ITEM
-        // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
-        if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
-            if self.token.is_keyword(keywords::Const) {
-                self.diagnostic()
-                    .struct_span_err(self.span, "extern items cannot be `const`")
-                    .span_suggestion(
-                        self.span,
-                        "try using a static value",
-                        "static".to_owned(),
-                        Applicability::MachineApplicable
-                    ).emit();
-            }
-            self.bump(); // `static` or `const`
-            return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
-        }
-        // FOREIGN FUNCTION ITEM
-        if self.check_keyword(keywords::Fn) {
-            return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
-        }
-        // FOREIGN TYPE ITEM
-        if self.check_keyword(keywords::Type) {
-            return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
-        }
-
-        match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
-            Some(mac) => {
-                Ok(
-                    ForeignItem {
-                        ident: keywords::Invalid.ident(),
-                        span: lo.to(self.prev_span),
-                        id: ast::DUMMY_NODE_ID,
-                        attrs,
-                        vis: visibility,
-                        node: ForeignItemKind::Macro(mac),
-                    }
                 )
-            }
-            None => {
-                if !attrs.is_empty()  {
-                    self.expected_item_err(&attrs)?;
-                }
-
-                self.unexpected()
-            }
-        }
-    }
-
-    /// This is the fall-through for parsing items.
-    fn parse_macro_use_or_failure(
-        &mut self,
-        attrs: Vec<Attribute> ,
-        macros_allowed: bool,
-        attributes_allowed: bool,
-        lo: Span,
-        visibility: Visibility
-    ) -> PResult<'a, Option<P<Item>>> {
-        if macros_allowed && self.token.is_path_start() &&
-                !(self.is_async_fn() && self.span.rust_2015()) {
-            // MACRO INVOCATION ITEM
-
-            let prev_span = self.prev_span;
-            self.complain_if_pub_macro(&visibility.node, prev_span);
-
-            let mac_lo = self.span;
-
-            // item macro.
-            let pth = self.parse_path(PathStyle::Mod)?;
-            self.expect(&token::Not)?;
-
-            // a 'special' identifier (like what `macro_rules!` uses)
-            // is optional. We should eventually unify invoc syntax
-            // and remove this.
-            let id = if self.token.is_ident() {
-                self.parse_ident()?
-            } else {
-                keywords::Invalid.ident() // no special identifier
-            };
-            // eat a matched-delimiter token tree:
-            let (delim, tts) = self.expect_delimited_token_tree()?;
-            if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
-                self.report_invalid_macro_expansion_item();
-            }
-
-            let hi = self.prev_span;
-            let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
-            let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
-            return Ok(Some(item));
-        }
-
-        // FAILURE TO PARSE ITEM
-        match visibility.node {
-            VisibilityKind::Inherited => {}
-            _ => {
-                return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
-            }
-        }
-
-        if !attributes_allowed && !attrs.is_empty() {
-            self.expected_item_err(&attrs)?;
-        }
-        Ok(None)
-    }
-
-    /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
-    fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
-                               at_end: &mut bool) -> PResult<'a, Option<Mac>>
-    {
-        if self.token.is_path_start() &&
-                !(self.is_async_fn() && self.span.rust_2015()) {
-            let prev_span = self.prev_span;
-            let lo = self.span;
-            let pth = self.parse_path(PathStyle::Mod)?;
-
-            if pth.segments.len() == 1 {
-                if !self.eat(&token::Not) {
-                    return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
-                }
-            } else {
-                self.expect(&token::Not)?;
-            }
-
-            if let Some(vis) = vis {
-                self.complain_if_pub_macro(&vis.node, prev_span);
-            }
-
-            *at_end = true;
-
-            // eat a matched-delimiter token tree:
-            let (delim, tts) = self.expect_delimited_token_tree()?;
-            if delim != MacDelimiter::Brace {
-                self.expect(&token::Semi)?;
-            }
-
-            Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
-        } else {
-            Ok(None)
+                .emit();
         }
     }
 
@@ -8223,7 +1556,7 @@ impl<'a> Parser<'a> {
         let mut tokens = Vec::new();
         let prev_collecting = match self.token_cursor.frame.last_token {
             LastToken::Collecting(ref mut list) => {
-                Some(mem::replace(list, Vec::new()))
+                Some(mem::take(list))
             }
             LastToken::Was(ref mut last) => {
                 tokens.extend(last.take());
@@ -8235,14 +1568,27 @@ impl<'a> Parser<'a> {
         let ret = f(self);
         let last_token = if self.token_cursor.stack.len() == prev {
             &mut self.token_cursor.frame.last_token
+        } else if self.token_cursor.stack.get(prev).is_none() {
+            // This can happen due to a bad interaction of two unrelated recovery mechanisms with
+            // mismatched delimiters *and* recovery lookahead on the likely typo `pub ident(`
+            // (#62881).
+            return Ok((ret?, TokenStream::new(vec![])));
         } else {
             &mut self.token_cursor.stack[prev].last_token
         };
 
         // Pull out the tokens that we've collected from the call to `f` above.
         let mut collected_tokens = match *last_token {
-            LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
-            LastToken::Was(_) => panic!("our vector went away?"),
+            LastToken::Collecting(ref mut v) => mem::take(v),
+            LastToken::Was(ref was) => {
+                let msg = format!("our vector went away? - found Was({:?})", was);
+                debug!("collect_tokens: {}", msg);
+                self.sess.span_diagnostic.delay_span_bug(self.token.span, &msg);
+                // This can happen due to a bad interaction of two unrelated recovery mechanisms
+                // with mismatched delimiters *and* recovery lookahead on the likely typo
+                // `pub ident(` (#62895, different but similar to the case above).
+                return Ok((ret?, TokenStream::new(vec![])));
+            }
         };
 
         // If we're not at EOF our current token wasn't actually consumed by
@@ -8272,11 +1618,6 @@ impl<'a> Parser<'a> {
         Ok((ret?, TokenStream::new(collected_tokens)))
     }
 
-    pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
-        let attrs = self.parse_outer_attributes()?;
-        self.parse_item_(attrs, true, false)
-    }
-
     /// `::{` or `::*`
     fn is_import_coupler(&mut self) -> bool {
         self.check(&token::ModSep) &&
@@ -8284,89 +1625,12 @@ impl<'a> Parser<'a> {
                                    *t == token::BinOp(token::Star))
     }
 
-    /// Parses a `UseTree`.
-    ///
-    /// ```
-    /// USE_TREE = [`::`] `*` |
-    ///            [`::`] `{` USE_TREE_LIST `}` |
-    ///            PATH `::` `*` |
-    ///            PATH `::` `{` USE_TREE_LIST `}` |
-    ///            PATH [`as` IDENT]
-    /// ```
-    fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
-        let lo = self.span;
-
-        let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
-        let kind = if self.check(&token::OpenDelim(token::Brace)) ||
-                      self.check(&token::BinOp(token::Star)) ||
-                      self.is_import_coupler() {
-            // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
-            let mod_sep_ctxt = self.span.ctxt();
-            if self.eat(&token::ModSep) {
-                prefix.segments.push(
-                    PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
-                );
-            }
-
-            if self.eat(&token::BinOp(token::Star)) {
-                UseTreeKind::Glob
-            } else {
-                UseTreeKind::Nested(self.parse_use_tree_list()?)
-            }
-        } else {
-            // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
-            prefix = self.parse_path(PathStyle::Mod)?;
-
-            if self.eat(&token::ModSep) {
-                if self.eat(&token::BinOp(token::Star)) {
-                    UseTreeKind::Glob
-                } else {
-                    UseTreeKind::Nested(self.parse_use_tree_list()?)
-                }
-            } else {
-                UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
-            }
-        };
-
-        Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
-    }
-
-    /// Parses a `UseTreeKind::Nested(list)`.
-    ///
-    /// ```
-    /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
-    /// ```
-    fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
-        self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
-                                 &token::CloseDelim(token::Brace),
-                                 SeqSep::trailing_allowed(token::Comma), |this| {
-            Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
-        })
-    }
-
-    fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
-        if self.eat_keyword(keywords::As) {
-            self.parse_ident_or_underscore().map(Some)
-        } else {
-            Ok(None)
-        }
-    }
-
-    /// Parses a source module as a crate. This is the main entry point for the parser.
-    pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
-        let lo = self.span;
-        let krate = Ok(ast::Crate {
-            attrs: self.parse_inner_attributes()?,
-            module: self.parse_mod_items(&token::Eof, lo)?,
-            span: lo.to(self.span),
-        });
-        krate
-    }
-
     pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
-        let ret = match self.token {
-            token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
-            token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
+        let ret = match self.token.kind {
+            token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
+                (symbol, ast::StrStyle::Cooked, suffix),
+            token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
+                (symbol, ast::StrStyle::Raw(n), suffix),
             _ => return None
         };
         self.bump();
@@ -8383,7 +1647,7 @@ impl<'a> Parser<'a> {
             _ => {
                 let msg = "expected string literal";
                 let mut err = self.fatal(msg);
-                err.span_label(self.span, msg);
+                err.span_label(self.token.span, msg);
                 Err(err)
             }
         }
@@ -8407,122 +1671,13 @@ impl<'a> Parser<'a> {
             Applicability::MaybeIncorrect,
         ).emit();
     }
-
-    /// When lowering a `async fn` to the HIR, we need to move all of the arguments of the function
-    /// into the generated closure so that they are dropped when the future is polled and not when
-    /// it is created.
-    ///
-    /// The arguments of the function are replaced in HIR lowering with the arguments created by
-    /// this function and the statements created here are inserted at the top of the closure body.
-    fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
-        // FIXME(davidtwco): This function should really live in the HIR lowering but because
-        // the types constructed here need to be used in parts of resolve so that the correct
-        // locals are considered upvars, it is currently easier for it to live here in the parser,
-        // where it can be constructed once.
-        if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
-            for (index, input) in decl.inputs.iter_mut().enumerate() {
-                let id = ast::DUMMY_NODE_ID;
-                let span = input.pat.span;
-
-                // Construct a name for our temporary argument.
-                let name = format!("__arg{}", index);
-                let ident = Ident::from_str(&name).gensym();
-
-                // Check if this is a ident pattern, if so, we can optimize and avoid adding a
-                // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
-                // statement.
-                let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
-                    PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
-                        // Simple patterns like this don't have a generated argument, but they are
-                        // moved into the closure with a statement, so any `mut` bindings on the
-                        // argument will be unused. This binding mode can't be removed, because
-                        // this would affect the input to procedural macros, but they can have
-                        // their span marked as being the result of a compiler desugaring so
-                        // that they aren't linted against.
-                        input.pat.span = self.sess.source_map().mark_span_with_reason(
-                            CompilerDesugaringKind::Async, span, None);
-
-                        (binding_mode, ident, true)
-                    }
-                    _ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
-                };
-
-                // Construct an argument representing `__argN: <ty>` to replace the argument of the
-                // async function if it isn't a simple pattern.
-                let arg = if is_simple_pattern {
-                    None
-                } else {
-                    Some(Arg {
-                        ty: input.ty.clone(),
-                        id,
-                        pat: P(Pat {
-                            id,
-                            node: PatKind::Ident(
-                                BindingMode::ByValue(Mutability::Immutable), ident, None,
-                            ),
-                            span,
-                        }),
-                        source: ArgSource::AsyncFn(input.pat.clone()),
-                    })
-                };
-
-                // Construct a `let __argN = __argN;` statement to insert at the top of the
-                // async closure. This makes sure that the argument is captured by the closure and
-                // that the drop order is correct.
-                let move_local = Local {
-                    pat: P(Pat {
-                        id,
-                        node: PatKind::Ident(binding_mode, ident, None),
-                        span,
-                    }),
-                    // We explicitly do not specify the type for this statement. When the user's
-                    // argument type is `impl Trait` then this would require the
-                    // `impl_trait_in_bindings` feature to also be present for that same type to
-                    // be valid in this binding. At the time of writing (13 Mar 19),
-                    // `impl_trait_in_bindings` is not stable.
-                    ty: None,
-                    init: Some(P(Expr {
-                        id,
-                        node: ExprKind::Path(None, ast::Path {
-                            span,
-                            segments: vec![PathSegment { ident, id, args: None }],
-                        }),
-                        span,
-                        attrs: ThinVec::new(),
-                    })),
-                    id,
-                    span,
-                    attrs: ThinVec::new(),
-                    source: LocalSource::AsyncFn,
-                };
-
-                // Construct a `let <pat> = __argN;` statement to insert at the top of the
-                // async closure if this isn't a simple pattern.
-                let pat_stmt = if is_simple_pattern {
-                    None
-                } else {
-                    Some(Stmt {
-                        id,
-                        node: StmtKind::Local(P(Local {
-                            pat: input.pat.clone(),
-                            ..move_local.clone()
-                        })),
-                        span,
-                    })
-                };
-
-                let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
-                arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
-            }
-        }
-    }
 }
 
 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
     for unmatched in unclosed_delims.iter() {
         let mut err = handler.struct_span_err(unmatched.found_span, &format!(
             "incorrect close delimiter: `{}`",
-            pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
+            pprust::token_kind_to_string(&token::CloseDelim(unmatched.found_delim)),
         ));
         err.span_label(unmatched.found_span, "incorrect close delimiter");
         if let Some(sp) = unmatched.candidate_span {
diff --git a/src/libsyntax/parse/parser/expr.rs b/src/libsyntax/parse/parser/expr.rs
new file mode 100644
index 00000000000..ccc6bd15067
--- /dev/null
+++ b/src/libsyntax/parse/parser/expr.rs
@@ -0,0 +1,1772 @@
+use super::{Parser, PResult, Restrictions, PrevTokenKind, TokenType, PathStyle};
+use super::{BlockMode, SemiColonMode};
+use super::{SeqSep, TokenExpectType};
+
+use crate::maybe_recover_from_interpolated_ty_qpath;
+use crate::ptr::P;
+use crate::ast::{self, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode};
+use crate::ast::{Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm};
+use crate::ast::{Ty, TyKind, FunctionRetTy, Arg, FnDecl};
+use crate::ast::{BinOpKind, BinOp, UnOp};
+use crate::ast::{Mac, AnonConst, Field};
+
+use crate::parse::classify;
+use crate::parse::token::{self, Token};
+use crate::parse::diagnostics::{Error};
+use crate::print::pprust;
+use crate::source_map::{self, Span};
+use crate::symbol::{kw, sym};
+use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
+
+use std::mem;
+use errors::Applicability;
+use rustc_data_structures::thin_vec::ThinVec;
+
+/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
+/// dropped into the token stream, which happens while parsing the result of
+/// macro expansion). Placement of these is not as complex as I feared it would
+/// be. The important thing is to make sure that lookahead doesn't balk at
+/// `token::Interpolated` tokens.
+macro_rules! maybe_whole_expr {
+    ($p:expr) => {
+        if let token::Interpolated(nt) = &$p.token.kind {
+            match &**nt {
+                token::NtExpr(e) | token::NtLiteral(e) => {
+                    let e = e.clone();
+                    $p.bump();
+                    return Ok(e);
+                }
+                token::NtPath(path) => {
+                    let path = path.clone();
+                    $p.bump();
+                    return Ok($p.mk_expr(
+                        $p.token.span, ExprKind::Path(None, path), ThinVec::new()
+                    ));
+                }
+                token::NtBlock(block) => {
+                    let block = block.clone();
+                    $p.bump();
+                    return Ok($p.mk_expr(
+                        $p.token.span, ExprKind::Block(block, None), ThinVec::new()
+                    ));
+                }
+                // N.B: `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
+                _ => {},
+            };
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(super) enum LhsExpr {
+    NotYetParsed,
+    AttributesParsed(ThinVec<Attribute>),
+    AlreadyParsed(P<Expr>),
+}
+
+impl From<Option<ThinVec<Attribute>>> for LhsExpr {
+    fn from(o: Option<ThinVec<Attribute>>) -> Self {
+        if let Some(attrs) = o {
+            LhsExpr::AttributesParsed(attrs)
+        } else {
+            LhsExpr::NotYetParsed
+        }
+    }
+}
+
+impl From<P<Expr>> for LhsExpr {
+    fn from(expr: P<Expr>) -> Self {
+        LhsExpr::AlreadyParsed(expr)
+    }
+}
+
+impl<'a> Parser<'a> {
+    /// Parses an expression.
+    #[inline]
+    pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
+        self.parse_expr_res(Restrictions::empty(), None)
+    }
+
+    fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
+        self.parse_paren_comma_seq(|p| {
+            match p.parse_expr() {
+                Ok(expr) => Ok(expr),
+                Err(mut err) => match p.token.kind {
+                    token::Ident(name, false)
+                    if name == kw::Underscore && p.look_ahead(1, |t| {
+                        t == &token::Comma
+                    }) => {
+                        // Special-case handling of `foo(_, _, _)`
+                        err.emit();
+                        let sp = p.token.span;
+                        p.bump();
+                        Ok(p.mk_expr(sp, ExprKind::Err, ThinVec::new()))
+                    }
+                    _ => Err(err),
+                },
+            }
+        }).map(|(r, _)| r)
+    }
+
+    /// Parses an expression, subject to the given restrictions.
+    #[inline]
+    pub(super) fn parse_expr_res(
+        &mut self,
+        r: Restrictions,
+        already_parsed_attrs: Option<ThinVec<Attribute>>
+    ) -> PResult<'a, P<Expr>> {
+        self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
+    }
+
+    /// Parses an associative expression.
+    ///
+    /// This parses an expression accounting for associativity and precedence of the operators in
+    /// the expression.
+    #[inline]
+    fn parse_assoc_expr(
+        &mut self,
+        already_parsed_attrs: Option<ThinVec<Attribute>>,
+    ) -> PResult<'a, P<Expr>> {
+        self.parse_assoc_expr_with(0, already_parsed_attrs.into())
+    }
+
+    /// Parses an associative expression with operators of at least `min_prec` precedence.
+    pub(super) fn parse_assoc_expr_with(
+        &mut self,
+        min_prec: usize,
+        lhs: LhsExpr,
+    ) -> PResult<'a, P<Expr>> {
+        let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
+            expr
+        } else {
+            let attrs = match lhs {
+                LhsExpr::AttributesParsed(attrs) => Some(attrs),
+                _ => None,
+            };
+            if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
+                return self.parse_prefix_range_expr(attrs);
+            } else {
+                self.parse_prefix_expr(attrs)?
+            }
+        };
+        let last_type_ascription_set = self.last_type_ascription.is_some();
+
+        match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
+            (true, None) => {
+                self.last_type_ascription = None;
+                // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
+                return Ok(lhs);
+            }
+            (false, _) => {} // continue parsing the expression
+            // An exhaustive check is done in the following block, but these are checked first
+            // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
+            // want to keep their span info to improve diagnostics in these cases in a later stage.
+            (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
+            (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
+            (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
+            (true, Some(AssocOp::Add)) // `{ 42 } + 42
+            // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
+            // `if x { a } else { b } && if y { c } else { d }`
+            if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
+                self.last_type_ascription = None;
+                // These cases are ambiguous and can't be identified in the parser alone
+                let sp = self.sess.source_map().start_point(self.token.span);
+                self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
+                return Ok(lhs);
+            }
+            (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
+                self.last_type_ascription = None;
+                return Ok(lhs);
+            }
+            (true, Some(_)) => {
+                // We've found an expression that would be parsed as a statement, but the next
+                // token implies this should be parsed as an expression.
+                // For example: `if let Some(x) = x { x } else { 0 } / 2`
+                let mut err = self.struct_span_err(self.token.span, &format!(
+                    "expected expression, found `{}`",
+                    pprust::token_to_string(&self.token),
+                ));
+                err.span_label(self.token.span, "expected expression");
+                self.sess.expr_parentheses_needed(
+                    &mut err,
+                    lhs.span,
+                    Some(pprust::expr_to_string(&lhs),
+                ));
+                err.emit();
+            }
+        }
+        self.expected_tokens.push(TokenType::Operator);
+        while let Some(op) = AssocOp::from_token(&self.token) {
+
+            // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
+            // it refers to. Interpolated identifiers are unwrapped early and never show up here
+            // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
+            // it as "interpolated", it doesn't change the answer for non-interpolated idents.
+            let lhs_span = match (self.prev_token_kind, &lhs.node) {
+                (PrevTokenKind::Interpolated, _) => self.prev_span,
+                (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
+                    if path.segments.len() == 1 => self.prev_span,
+                _ => lhs.span,
+            };
+
+            let cur_op_span = self.token.span;
+            let restrictions = if op.is_assign_like() {
+                self.restrictions & Restrictions::NO_STRUCT_LITERAL
+            } else {
+                self.restrictions
+            };
+            let prec = op.precedence();
+            if prec < min_prec {
+                break;
+            }
+            // Check for deprecated `...` syntax
+            if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
+                self.err_dotdotdot_syntax(self.token.span);
+            }
+
+            if self.token == token::LArrow {
+                self.err_larrow_operator(self.token.span);
+            }
+
+            self.bump();
+            if op.is_comparison() {
+                self.check_no_chained_comparison(&lhs, &op);
+            }
+            // Special cases:
+            if op == AssocOp::As {
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
+                continue
+            } else if op == AssocOp::Colon {
+                let maybe_path = self.could_ascription_be_path(&lhs.node);
+                self.last_type_ascription = Some((self.prev_span, maybe_path));
+
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
+                continue
+            } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
+                // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
+                // generalise it to the Fixity::None code.
+                //
+                // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
+                // two variants are handled with `parse_prefix_range_expr` call above.
+                let rhs = if self.is_at_start_of_range_notation_rhs() {
+                    Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
+                } else {
+                    None
+                };
+                let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
+                    x.span
+                } else {
+                    cur_op_span
+                });
+                let limits = if op == AssocOp::DotDot {
+                    RangeLimits::HalfOpen
+                } else {
+                    RangeLimits::Closed
+                };
+
+                let r = self.mk_range(Some(lhs), rhs, limits)?;
+                lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
+                break
+            }
+
+            let fixity = op.fixity();
+            let prec_adjustment = match fixity {
+                Fixity::Right => 0,
+                Fixity::Left => 1,
+                // We currently have no non-associative operators that are not handled above by
+                // the special cases. The code is here only for future convenience.
+                Fixity::None => 1,
+            };
+            let rhs = self.with_res(
+                restrictions - Restrictions::STMT_EXPR,
+                |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
+            )?;
+
+            // Make sure that the span of the parent node is larger than the span of lhs and rhs,
+            // including the attributes.
+            let lhs_span = lhs
+                .attrs
+                .iter()
+                .filter(|a| a.style == AttrStyle::Outer)
+                .next()
+                .map_or(lhs_span, |a| a.span);
+            let span = lhs_span.to(rhs.span);
+            lhs = match op {
+                AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
+                AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
+                AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
+                AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
+                AssocOp::Greater | AssocOp::GreaterEqual => {
+                    let ast_op = op.to_ast_binop().unwrap();
+                    let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
+                    self.mk_expr(span, binary, ThinVec::new())
+                }
+                AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
+                AssocOp::AssignOp(k) => {
+                    let aop = match k {
+                        token::Plus =>    BinOpKind::Add,
+                        token::Minus =>   BinOpKind::Sub,
+                        token::Star =>    BinOpKind::Mul,
+                        token::Slash =>   BinOpKind::Div,
+                        token::Percent => BinOpKind::Rem,
+                        token::Caret =>   BinOpKind::BitXor,
+                        token::And =>     BinOpKind::BitAnd,
+                        token::Or =>      BinOpKind::BitOr,
+                        token::Shl =>     BinOpKind::Shl,
+                        token::Shr =>     BinOpKind::Shr,
+                    };
+                    let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
+                    self.mk_expr(span, aopexpr, ThinVec::new())
+                }
+                AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
+                    self.bug("AssocOp should have been handled by special case")
+                }
+            };
+
+            if let Fixity::None = fixity { break }
+        }
+        if last_type_ascription_set {
+            self.last_type_ascription = None;
+        }
+        Ok(lhs)
+    }
+
+    /// Checks if this expression is a successfully parsed statement.
+    fn expr_is_complete(&self, e: &Expr) -> bool {
+        self.restrictions.contains(Restrictions::STMT_EXPR) &&
+            !classify::expr_requires_semi_to_be_stmt(e)
+    }
+
+    fn is_at_start_of_range_notation_rhs(&self) -> bool {
+        if self.token.can_begin_expr() {
+            // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
+            if self.token == token::OpenDelim(token::Brace) {
+                return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+            }
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
+    fn parse_prefix_range_expr(
+        &mut self,
+        already_parsed_attrs: Option<ThinVec<Attribute>>
+    ) -> PResult<'a, P<Expr>> {
+        // Check for deprecated `...` syntax
+        if self.token == token::DotDotDot {
+            self.err_dotdotdot_syntax(self.token.span);
+        }
+
+        debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
+                      "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
+                      self.token);
+        let tok = self.token.clone();
+        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
+        let lo = self.token.span;
+        let mut hi = self.token.span;
+        self.bump();
+        let opt_end = if self.is_at_start_of_range_notation_rhs() {
+            // RHS must be parsed with more associativity than the dots.
+            let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
+            Some(self.parse_assoc_expr_with(next_prec, LhsExpr::NotYetParsed)
+                .map(|x| {
+                    hi = x.span;
+                    x
+                })?)
+        } else {
+            None
+        };
+        let limits = if tok == token::DotDot {
+            RangeLimits::HalfOpen
+        } else {
+            RangeLimits::Closed
+        };
+
+        let r = self.mk_range(None, opt_end, limits)?;
+        Ok(self.mk_expr(lo.to(hi), r, attrs))
+    }
+
+    /// Parse a prefix-unary-operator expr
+    fn parse_prefix_expr(
+        &mut self,
+        already_parsed_attrs: Option<ThinVec<Attribute>>
+    ) -> PResult<'a, P<Expr>> {
+        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
+        let lo = self.token.span;
+        // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
+        let (hi, ex) = match self.token.kind {
+            token::Not => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                (lo.to(span), self.mk_unary(UnOp::Not, e))
+            }
+            // Suggest `!` for bitwise negation when encountering a `~`
+            token::Tilde => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                let span_of_tilde = lo;
+                self.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator")
+                    .span_suggestion_short(
+                        span_of_tilde,
+                        "use `!` to perform bitwise negation",
+                        "!".to_owned(),
+                        Applicability::MachineApplicable
+                    )
+                    .emit();
+                (lo.to(span), self.mk_unary(UnOp::Not, e))
+            }
+            token::BinOp(token::Minus) => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                (lo.to(span), self.mk_unary(UnOp::Neg, e))
+            }
+            token::BinOp(token::Star) => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                (lo.to(span), self.mk_unary(UnOp::Deref, e))
+            }
+            token::BinOp(token::And) | token::AndAnd => {
+                self.expect_and()?;
+                let m = self.parse_mutability();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                (lo.to(span), ExprKind::AddrOf(m, e))
+            }
+            token::Ident(..) if self.token.is_keyword(kw::Box) => {
+                self.bump();
+                let e = self.parse_prefix_expr(None);
+                let (span, e) = self.interpolated_or_expr_span(e)?;
+                (lo.to(span), ExprKind::Box(e))
+            }
+            token::Ident(..) if self.token.is_ident_named(sym::not) => {
+                // `not` is just an ordinary identifier in Rust-the-language,
+                // but as `rustc`-the-compiler, we can issue clever diagnostics
+                // for confused users who really want to say `!`
+                let token_cannot_continue_expr = |t: &Token| match t.kind {
+                    // These tokens can start an expression after `!`, but
+                    // can't continue an expression after an ident
+                    token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
+                    token::Literal(..) | token::Pound => true,
+                    _ => t.is_whole_expr(),
+                };
+                let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
+                if cannot_continue_expr {
+                    self.bump();
+                    // Emit the error ...
+                    self.struct_span_err(
+                        self.token.span,
+                        &format!("unexpected {} after identifier",self.this_token_descr())
+                    )
+                    .span_suggestion_short(
+                        // Span the `not` plus trailing whitespace to avoid
+                        // trailing whitespace after the `!` in our suggestion
+                        self.sess.source_map()
+                            .span_until_non_whitespace(lo.to(self.token.span)),
+                        "use `!` to perform logical negation",
+                        "!".to_owned(),
+                        Applicability::MachineApplicable
+                    )
+                    .emit();
+                    // —and recover! (just as if we were in the block
+                    // for the `token::Not` arm)
+                    let e = self.parse_prefix_expr(None);
+                    let (span, e) = self.interpolated_or_expr_span(e)?;
+                    (lo.to(span), self.mk_unary(UnOp::Not, e))
+                } else {
+                    return self.parse_dot_or_call_expr(Some(attrs));
+                }
+            }
+            _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
+        };
+        return Ok(self.mk_expr(lo.to(hi), ex, attrs));
+    }
+
+    /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
+    fn interpolated_or_expr_span(
+        &self,
+        expr: PResult<'a, P<Expr>>,
+    ) -> PResult<'a, (Span, P<Expr>)> {
+        expr.map(|e| {
+            if self.prev_token_kind == PrevTokenKind::Interpolated {
+                (self.prev_span, e)
+            } else {
+                (e.span, e)
+            }
+        })
+    }
+
+    fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
+                           expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
+                           -> PResult<'a, P<Expr>> {
+        let mk_expr = |this: &mut Self, rhs: P<Ty>| {
+            this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
+        };
+
+        // Save the state of the parser before parsing type normally, in case there is a
+        // LessThan comparison after this cast.
+        let parser_snapshot_before_type = self.clone();
+        match self.parse_ty_no_plus() {
+            Ok(rhs) => {
+                Ok(mk_expr(self, rhs))
+            }
+            Err(mut type_err) => {
+                // Rewind to before attempting to parse the type with generics, to recover
+                // from situations like `x as usize < y` in which we first tried to parse
+                // `usize < y` as a type with generic arguments.
+                let parser_snapshot_after_type = self.clone();
+                mem::replace(self, parser_snapshot_before_type);
+
+                match self.parse_path(PathStyle::Expr) {
+                    Ok(path) => {
+                        let (op_noun, op_verb) = match self.token.kind {
+                            token::Lt => ("comparison", "comparing"),
+                            token::BinOp(token::Shl) => ("shift", "shifting"),
+                            _ => {
+                                // We can end up here even without `<` being the next token, for
+                                // example because `parse_ty_no_plus` returns `Err` on keywords,
+                                // but `parse_path` returns `Ok` on them due to error recovery.
+                                // Return original error and parser state.
+                                mem::replace(self, parser_snapshot_after_type);
+                                return Err(type_err);
+                            }
+                        };
+
+                        // Successfully parsed the type path leaving a `<` yet to parse.
+                        type_err.cancel();
+
+                        // Report non-fatal diagnostics, keep `x as usize` as an expression
+                        // in AST and continue parsing.
+                        let msg = format!("`<` is interpreted as a start of generic \
+                                           arguments for `{}`, not a {}", path, op_noun);
+                        let span_after_type = parser_snapshot_after_type.token.span;
+                        let expr = mk_expr(self, P(Ty {
+                            span: path.span,
+                            node: TyKind::Path(None, path),
+                            id: ast::DUMMY_NODE_ID
+                        }));
+
+                        let expr_str = self.span_to_snippet(expr.span)
+                            .unwrap_or_else(|_| pprust::expr_to_string(&expr));
+
+                        self.struct_span_err(self.token.span, &msg)
+                            .span_label(
+                                self.look_ahead(1, |t| t.span).to(span_after_type),
+                                "interpreted as generic arguments"
+                            )
+                            .span_label(self.token.span, format!("not interpreted as {}", op_noun))
+                            .span_suggestion(
+                                expr.span,
+                                &format!("try {} the cast value", op_verb),
+                                format!("({})", expr_str),
+                                Applicability::MachineApplicable
+                            )
+                            .emit();
+
+                        Ok(expr)
+                    }
+                    Err(mut path_err) => {
+                        // Couldn't parse as a path, return original error and parser state.
+                        path_err.cancel();
+                        mem::replace(self, parser_snapshot_after_type);
+                        Err(type_err)
+                    }
+                }
+            }
+        }
+    }
+
+    /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
+    fn parse_dot_or_call_expr(
+        &mut self,
+        already_parsed_attrs: Option<ThinVec<Attribute>>,
+    ) -> PResult<'a, P<Expr>> {
+        let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
+
+        let b = self.parse_bottom_expr();
+        let (span, b) = self.interpolated_or_expr_span(b)?;
+        self.parse_dot_or_call_expr_with(b, span, attrs)
+    }
+
+    pub(super) fn parse_dot_or_call_expr_with(
+        &mut self,
+        e0: P<Expr>,
+        lo: Span,
+        mut attrs: ThinVec<Attribute>,
+    ) -> PResult<'a, P<Expr>> {
+        // Stitch the list of outer attributes onto the return value.
+        // A little bit ugly, but the best way given the current code
+        // structure
+        self.parse_dot_or_call_expr_with_(e0, lo).map(|expr|
+            expr.map(|mut expr| {
+                attrs.extend::<Vec<_>>(expr.attrs.into());
+                expr.attrs = attrs;
+                match expr.node {
+                    ExprKind::If(..) if !expr.attrs.is_empty() => {
+                        // Just point to the first attribute in there...
+                        let span = expr.attrs[0].span;
+                        self.span_err(span, "attributes are not yet allowed on `if` expressions");
+                    }
+                    _ => {}
+                }
+                expr
+            })
+        )
+    }
+
+    fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+        let mut e = e0;
+        let mut hi;
+        loop {
+            // expr?
+            while self.eat(&token::Question) {
+                let hi = self.prev_span;
+                e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
+            }
+
+            // expr.f
+            if self.eat(&token::Dot) {
+                match self.token.kind {
+                    token::Ident(..) => {
+                        e = self.parse_dot_suffix(e, lo)?;
+                    }
+                    token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
+                        let span = self.token.span;
+                        self.bump();
+                        let field = ExprKind::Field(e, Ident::new(symbol, span));
+                        e = self.mk_expr(lo.to(span), field, ThinVec::new());
+
+                        self.expect_no_suffix(span, "a tuple index", suffix);
+                    }
+                    token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
+                      self.bump();
+                      let fstr = symbol.as_str();
+                      let msg = format!("unexpected token: `{}`", symbol);
+                      let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
+                      err.span_label(self.prev_span, "unexpected token");
+                      if fstr.chars().all(|x| "0123456789.".contains(x)) {
+                          let float = match fstr.parse::<f64>().ok() {
+                              Some(f) => f,
+                              None => continue,
+                          };
+                          let sugg = pprust::to_string(|s| {
+                              s.popen();
+                              s.print_expr(&e);
+                              s.s.word( ".");
+                              s.print_usize(float.trunc() as usize);
+                              s.pclose();
+                              s.s.word(".");
+                              s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
+                          });
+                          err.span_suggestion(
+                              lo.to(self.prev_span),
+                              "try parenthesizing the first index",
+                              sugg,
+                              Applicability::MachineApplicable
+                          );
+                      }
+                      return Err(err);
+
+                    }
+                    _ => {
+                        // FIXME Could factor this out into non_fatal_unexpected or something.
+                        let actual = self.this_token_to_string();
+                        self.span_err(self.token.span, &format!("unexpected token: `{}`", actual));
+                    }
+                }
+                continue;
+            }
+            if self.expr_is_complete(&e) { break; }
+            match self.token.kind {
+                // expr(...)
+                token::OpenDelim(token::Paren) => {
+                    let seq = self.parse_paren_expr_seq().map(|es| {
+                        let nd = self.mk_call(e, es);
+                        let hi = self.prev_span;
+                        self.mk_expr(lo.to(hi), nd, ThinVec::new())
+                    });
+                    e = self.recover_seq_parse_error(token::Paren, lo, seq);
+                }
+
+                // expr[...]
+                // Could be either an index expression or a slicing expression.
+                token::OpenDelim(token::Bracket) => {
+                    self.bump();
+                    let ix = self.parse_expr()?;
+                    hi = self.token.span;
+                    self.expect(&token::CloseDelim(token::Bracket))?;
+                    let index = self.mk_index(e, ix);
+                    e = self.mk_expr(lo.to(hi), index, ThinVec::new())
+                }
+                _ => return Ok(e)
+            }
+        }
+        return Ok(e);
+    }
+
+    /// Assuming we have just parsed `.`, continue parsing into an expression.
+    fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+        if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
+            return self.mk_await_expr(self_arg, lo);
+        }
+
+        let segment = self.parse_path_segment(PathStyle::Expr)?;
+        self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
+
+        Ok(match self.token.kind {
+            token::OpenDelim(token::Paren) => {
+                // Method call `expr.f()`
+                let mut args = self.parse_paren_expr_seq()?;
+                args.insert(0, self_arg);
+
+                let span = lo.to(self.prev_span);
+                self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
+            }
+            _ => {
+                // Field access `expr.f`
+                if let Some(args) = segment.args {
+                    self.span_err(args.span(),
+                                  "field expressions may not have generic arguments");
+                }
+
+                let span = lo.to(self.prev_span);
+                self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
+            }
+        })
+    }
+
+
+    /// At the bottom (top?) of the precedence hierarchy,
+    /// Parses things like parenthesized exprs, macros, `return`, etc.
+    ///
+    /// N.B., this does not parse outer attributes, and is private because it only works
+    /// correctly if called from `parse_dot_or_call_expr()`.
+    fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
+        maybe_recover_from_interpolated_ty_qpath!(self, true);
+        maybe_whole_expr!(self);
+
+        // Outer attributes are already parsed and will be
+        // added to the return value after the fact.
+        //
+        // Therefore, prevent sub-parser from parsing
+        // attributes by giving them a empty "already parsed" list.
+        let mut attrs = ThinVec::new();
+
+        let lo = self.token.span;
+        let mut hi = self.token.span;
+
+        let ex: ExprKind;
+
+        macro_rules! parse_lit {
+            () => {
+                match self.parse_lit() {
+                    Ok(literal) => {
+                        hi = self.prev_span;
+                        ex = ExprKind::Lit(literal);
+                    }
+                    Err(mut err) => {
+                        self.cancel(&mut err);
+                        return Err(self.expected_expression_found());
+                    }
+                }
+            }
+        }
+
+        // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
+        match self.token.kind {
+            // This match arm is a special-case of the `_` match arm below and
+            // could be removed without changing functionality, but it's faster
+            // to have it here, especially for programs with large constants.
+            token::Literal(_) => {
+                parse_lit!()
+            }
+            token::OpenDelim(token::Paren) => {
+                self.bump();
+
+                attrs.extend(self.parse_inner_attributes()?);
+
+                // (e) is parenthesized e
+                // (e,) is a tuple with only one field, e
+                let mut es = vec![];
+                let mut trailing_comma = false;
+                let mut recovered = false;
+                while self.token != token::CloseDelim(token::Paren) {
+                    es.push(match self.parse_expr() {
+                        Ok(es) => es,
+                        Err(mut err) => {
+                            // recover from parse error in tuple list
+                            match self.token.kind {
+                                token::Ident(name, false)
+                                if name == kw::Underscore && self.look_ahead(1, |t| {
+                                    t == &token::Comma
+                                }) => {
+                                    // Special-case handling of `Foo<(_, _, _)>`
+                                    err.emit();
+                                    let sp = self.token.span;
+                                    self.bump();
+                                    self.mk_expr(sp, ExprKind::Err, ThinVec::new())
+                                }
+                                _ => return Ok(
+                                    self.recover_seq_parse_error(token::Paren, lo, Err(err)),
+                                ),
+                            }
+                        }
+                    });
+                    recovered = self.expect_one_of(
+                        &[],
+                        &[token::Comma, token::CloseDelim(token::Paren)],
+                    )?;
+                    if self.eat(&token::Comma) {
+                        trailing_comma = true;
+                    } else {
+                        trailing_comma = false;
+                        break;
+                    }
+                }
+                if !recovered {
+                    self.bump();
+                }
+
+                hi = self.prev_span;
+                ex = if es.len() == 1 && !trailing_comma {
+                    ExprKind::Paren(es.into_iter().nth(0).unwrap())
+                } else {
+                    ExprKind::Tup(es)
+                };
+            }
+            token::OpenDelim(token::Brace) => {
+                return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
+            }
+            token::BinOp(token::Or) | token::OrOr => {
+                return self.parse_lambda_expr(attrs);
+            }
+            token::OpenDelim(token::Bracket) => {
+                self.bump();
+
+                attrs.extend(self.parse_inner_attributes()?);
+
+                if self.eat(&token::CloseDelim(token::Bracket)) {
+                    // Empty vector.
+                    ex = ExprKind::Array(Vec::new());
+                } else {
+                    // Nonempty vector.
+                    let first_expr = self.parse_expr()?;
+                    if self.eat(&token::Semi) {
+                        // Repeating array syntax: [ 0; 512 ]
+                        let count = AnonConst {
+                            id: ast::DUMMY_NODE_ID,
+                            value: self.parse_expr()?,
+                        };
+                        self.expect(&token::CloseDelim(token::Bracket))?;
+                        ex = ExprKind::Repeat(first_expr, count);
+                    } else if self.eat(&token::Comma) {
+                        // Vector with two or more elements.
+                        let remaining_exprs = self.parse_seq_to_end(
+                            &token::CloseDelim(token::Bracket),
+                            SeqSep::trailing_allowed(token::Comma),
+                            |p| Ok(p.parse_expr()?)
+                        )?;
+                        let mut exprs = vec![first_expr];
+                        exprs.extend(remaining_exprs);
+                        ex = ExprKind::Array(exprs);
+                    } else {
+                        // Vector with one element.
+                        self.expect(&token::CloseDelim(token::Bracket))?;
+                        ex = ExprKind::Array(vec![first_expr]);
+                    }
+                }
+                hi = self.prev_span;
+            }
+            _ => {
+                if self.eat_lt() {
+                    let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+                    hi = path.span;
+                    return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
+                }
+                if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
+                    return self.parse_lambda_expr(attrs);
+                }
+                if self.eat_keyword(kw::If) {
+                    return self.parse_if_expr(attrs);
+                }
+                if self.eat_keyword(kw::For) {
+                    let lo = self.prev_span;
+                    return self.parse_for_expr(None, lo, attrs);
+                }
+                if self.eat_keyword(kw::While) {
+                    let lo = self.prev_span;
+                    return self.parse_while_expr(None, lo, attrs);
+                }
+                if let Some(label) = self.eat_label() {
+                    let lo = label.ident.span;
+                    self.expect(&token::Colon)?;
+                    if self.eat_keyword(kw::While) {
+                        return self.parse_while_expr(Some(label), lo, attrs)
+                    }
+                    if self.eat_keyword(kw::For) {
+                        return self.parse_for_expr(Some(label), lo, attrs)
+                    }
+                    if self.eat_keyword(kw::Loop) {
+                        return self.parse_loop_expr(Some(label), lo, attrs)
+                    }
+                    if self.token == token::OpenDelim(token::Brace) {
+                        return self.parse_block_expr(Some(label),
+                                                     lo,
+                                                     BlockCheckMode::Default,
+                                                     attrs);
+                    }
+                    let msg = "expected `while`, `for`, `loop` or `{` after a label";
+                    let mut err = self.fatal(msg);
+                    err.span_label(self.token.span, msg);
+                    return Err(err);
+                }
+                if self.eat_keyword(kw::Loop) {
+                    let lo = self.prev_span;
+                    return self.parse_loop_expr(None, lo, attrs);
+                }
+                if self.eat_keyword(kw::Continue) {
+                    let label = self.eat_label();
+                    let ex = ExprKind::Continue(label);
+                    let hi = self.prev_span;
+                    return Ok(self.mk_expr(lo.to(hi), ex, attrs));
+                }
+                if self.eat_keyword(kw::Match) {
+                    let match_sp = self.prev_span;
+                    return self.parse_match_expr(attrs).map_err(|mut err| {
+                        err.span_label(match_sp, "while parsing this match expression");
+                        err
+                    });
+                }
+                if self.eat_keyword(kw::Unsafe) {
+                    return self.parse_block_expr(
+                        None,
+                        lo,
+                        BlockCheckMode::Unsafe(ast::UserProvided),
+                        attrs);
+                }
+                if self.is_do_catch_block() {
+                    let mut db = self.fatal("found removed `do catch` syntax");
+                    db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
+                    return Err(db);
+                }
+                if self.is_try_block() {
+                    let lo = self.token.span;
+                    assert!(self.eat_keyword(kw::Try));
+                    return self.parse_try_block(lo, attrs);
+                }
+
+                // Span::rust_2018() is somewhat expensive; don't get it repeatedly.
+                let is_span_rust_2018 = self.token.span.rust_2018();
+                if is_span_rust_2018 && self.check_keyword(kw::Async) {
+                    return if self.is_async_block() { // check for `async {` and `async move {`
+                        self.parse_async_block(attrs)
+                    } else {
+                        self.parse_lambda_expr(attrs)
+                    };
+                }
+                if self.eat_keyword(kw::Return) {
+                    if self.token.can_begin_expr() {
+                        let e = self.parse_expr()?;
+                        hi = e.span;
+                        ex = ExprKind::Ret(Some(e));
+                    } else {
+                        ex = ExprKind::Ret(None);
+                    }
+                } else if self.eat_keyword(kw::Break) {
+                    let label = self.eat_label();
+                    let e = if self.token.can_begin_expr()
+                               && !(self.token == token::OpenDelim(token::Brace)
+                                    && self.restrictions.contains(
+                                           Restrictions::NO_STRUCT_LITERAL)) {
+                        Some(self.parse_expr()?)
+                    } else {
+                        None
+                    };
+                    ex = ExprKind::Break(label, e);
+                    hi = self.prev_span;
+                } else if self.eat_keyword(kw::Yield) {
+                    if self.token.can_begin_expr() {
+                        let e = self.parse_expr()?;
+                        hi = e.span;
+                        ex = ExprKind::Yield(Some(e));
+                    } else {
+                        ex = ExprKind::Yield(None);
+                    }
+
+                    let span = lo.to(hi);
+                    self.sess.yield_spans.borrow_mut().push(span);
+                } else if self.eat_keyword(kw::Let) {
+                    return self.parse_let_expr(attrs);
+                } else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
+                    let (await_hi, e_kind) = self.parse_incorrect_await_syntax(lo, self.prev_span)?;
+                    hi = await_hi;
+                    ex = e_kind;
+                } else if self.token.is_path_start() {
+                    let path = self.parse_path(PathStyle::Expr)?;
+
+                    // `!`, as an operator, is prefix, so we know this isn't that
+                    if self.eat(&token::Not) {
+                        // MACRO INVOCATION expression
+                        let (delim, tts) = self.expect_delimited_token_tree()?;
+                        hi = self.prev_span;
+                        ex = ExprKind::Mac(Mac {
+                            path,
+                            tts,
+                            delim,
+                            span: lo.to(hi),
+                            prior_type_ascription: self.last_type_ascription,
+                        });
+                    } else if self.check(&token::OpenDelim(token::Brace)) {
+                        if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
+                            return expr;
+                        } else {
+                            hi = path.span;
+                            ex = ExprKind::Path(None, path);
+                        }
+                    } else {
+                        hi = path.span;
+                        ex = ExprKind::Path(None, path);
+                    }
+                } else {
+                    if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
+                        // Don't complain about bare semicolons after unclosed braces
+                        // recovery in order to keep the error count down. Fixing the
+                        // delimiters will possibly also fix the bare semicolon found in
+                        // expression context. For example, silence the following error:
+                        // ```
+                        // error: expected expression, found `;`
+                        //  --> file.rs:2:13
+                        //   |
+                        // 2 |     foo(bar(;
+                        //   |             ^ expected expression
+                        // ```
+                        self.bump();
+                        return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
+                    }
+                    parse_lit!()
+                }
+            }
+        }
+
+        let expr = self.mk_expr(lo.to(hi), ex, attrs);
+        self.maybe_recover_from_bad_qpath(expr, true)
+    }
+
+    /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
+    crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
+        maybe_whole_expr!(self);
+
+        let minus_lo = self.token.span;
+        let minus_present = self.eat(&token::BinOp(token::Minus));
+        let lo = self.token.span;
+        let literal = self.parse_lit()?;
+        let hi = self.prev_span;
+        let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
+
+        if minus_present {
+            let minus_hi = self.prev_span;
+            let unary = self.mk_unary(UnOp::Neg, expr);
+            Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
+        } else {
+            Ok(expr)
+        }
+    }
+
+    /// Parses a block or unsafe block.
+    crate fn parse_block_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        lo: Span,
+        blk_mode: BlockCheckMode,
+        outer_attrs: ThinVec<Attribute>,
+    ) -> PResult<'a, P<Expr>> {
+        self.expect(&token::OpenDelim(token::Brace))?;
+
+        let mut attrs = outer_attrs;
+        attrs.extend(self.parse_inner_attributes()?);
+
+        let blk = self.parse_block_tail(lo, blk_mode)?;
+        return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
+    }
+
+    /// Parses `move |args| expr`.
+    fn parse_lambda_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let lo = self.token.span;
+
+        let movability = if self.eat_keyword(kw::Static) {
+            Movability::Static
+        } else {
+            Movability::Movable
+        };
+
+        let asyncness = if self.token.span.rust_2018() {
+            self.parse_asyncness()
+        } else {
+            IsAsync::NotAsync
+        };
+        if asyncness.is_async() {
+            // Feature gate `async ||` closures.
+            self.sess.async_closure_spans.borrow_mut().push(self.prev_span);
+        }
+
+        let capture_clause = self.parse_capture_clause();
+        let decl = self.parse_fn_block_decl()?;
+        let decl_hi = self.prev_span;
+        let body = match decl.output {
+            FunctionRetTy::Default(_) => {
+                let restrictions = self.restrictions - Restrictions::STMT_EXPR;
+                self.parse_expr_res(restrictions, None)?
+            },
+            _ => {
+                // If an explicit return type is given, require a
+                // block to appear (RFC 968).
+                let body_lo = self.token.span;
+                self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
+            }
+        };
+
+        Ok(self.mk_expr(
+            lo.to(body.span),
+            ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
+            attrs))
+    }
+
+    /// Parse an optional `move` prefix to a closure lke construct.
+    fn parse_capture_clause(&mut self) -> CaptureBy {
+        if self.eat_keyword(kw::Move) {
+            CaptureBy::Value
+        } else {
+            CaptureBy::Ref
+        }
+    }
+
+    /// Parses the `|arg, arg|` header of a closure.
+    fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
+        let inputs_captures = {
+            if self.eat(&token::OrOr) {
+                Vec::new()
+            } else {
+                self.expect(&token::BinOp(token::Or))?;
+                let args = self.parse_seq_to_before_tokens(
+                    &[&token::BinOp(token::Or), &token::OrOr],
+                    SeqSep::trailing_allowed(token::Comma),
+                    TokenExpectType::NoExpect,
+                    |p| p.parse_fn_block_arg()
+                )?.0;
+                self.expect_or()?;
+                args
+            }
+        };
+        let output = self.parse_ret_ty(true)?;
+
+        Ok(P(FnDecl {
+            inputs: inputs_captures,
+            output,
+            c_variadic: false
+        }))
+    }
+
+    /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
+    fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
+        let lo = self.token.span;
+        let attrs = self.parse_arg_attributes()?;
+        let pat = self.parse_pat(Some("argument name"))?;
+        let t = if self.eat(&token::Colon) {
+            self.parse_ty()?
+        } else {
+            P(Ty {
+                id: ast::DUMMY_NODE_ID,
+                node: TyKind::Infer,
+                span: self.prev_span,
+            })
+        };
+        let span = lo.to(self.token.span);
+        Ok(Arg {
+            attrs: attrs.into(),
+            ty: t,
+            pat,
+            span,
+            id: ast::DUMMY_NODE_ID
+        })
+    }
+
+    /// Parses an `if` expression (`if` token already eaten).
+    fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let lo = self.prev_span;
+        let cond = self.parse_cond_expr()?;
+
+        // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
+        // verify that the last statement is either an implicit return (no `;`) or an explicit
+        // return. This won't catch blocks with an explicit `return`, but that would be caught by
+        // the dead code lint.
+        if self.eat_keyword(kw::Else) || !cond.returns() {
+            let sp = self.sess.source_map().next_point(lo);
+            let mut err = self.diagnostic()
+                .struct_span_err(sp, "missing condition for `if` expression");
+            err.span_label(sp, "expected if condition here");
+            return Err(err)
+        }
+        let not_block = self.token != token::OpenDelim(token::Brace);
+        let thn = self.parse_block().map_err(|mut err| {
+            if not_block {
+                err.span_label(lo, "this `if` statement has a condition, but no block");
+            }
+            err
+        })?;
+        let mut els: Option<P<Expr>> = None;
+        let mut hi = thn.span;
+        if self.eat_keyword(kw::Else) {
+            let elexpr = self.parse_else_expr()?;
+            hi = elexpr.span;
+            els = Some(elexpr);
+        }
+        Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
+    }
+
+    /// Parse the condition of a `if`- or `while`-expression
+    fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
+        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+        if let ExprKind::Let(..) = cond.node {
+            // Remove the last feature gating of a `let` expression since it's stable.
+            let last = self.sess.let_chains_spans.borrow_mut().pop();
+            debug_assert_eq!(cond.span, last.unwrap());
+        }
+
+        Ok(cond)
+    }
+
+    /// Parses a `let $pats = $expr` pseudo-expression.
+    /// The `let` token has already been eaten.
+    fn parse_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let lo = self.prev_span;
+        let pats = self.parse_pats()?;
+        self.expect(&token::Eq)?;
+        let expr = self.with_res(
+            Restrictions::NO_STRUCT_LITERAL,
+            |this| this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
+        )?;
+        let span = lo.to(expr.span);
+        self.sess.let_chains_spans.borrow_mut().push(span);
+        Ok(self.mk_expr(span, ExprKind::Let(pats, expr), attrs))
+    }
+
+    /// `else` token already eaten
+    fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
+        if self.eat_keyword(kw::If) {
+            return self.parse_if_expr(ThinVec::new());
+        } else {
+            let blk = self.parse_block()?;
+            return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
+        }
+    }
+
+    /// Parse a 'for' .. 'in' expression ('for' token already eaten)
+    fn parse_for_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        span_lo: Span,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
+        // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
+
+        // Record whether we are about to parse `for (`.
+        // This is used below for recovery in case of `for ( $stuff ) $block`
+        // in which case we will suggest `for $stuff $block`.
+        let begin_paren = match self.token.kind {
+            token::OpenDelim(token::Paren) => Some(self.token.span),
+            _ => None,
+        };
+
+        let pat = self.parse_top_level_pat()?;
+        if !self.eat_keyword(kw::In) {
+            let in_span = self.prev_span.between(self.token.span);
+            self.struct_span_err(in_span, "missing `in` in `for` loop")
+                .span_suggestion_short(
+                    in_span,
+                    "try adding `in` here", " in ".into(),
+                    // has been misleading, at least in the past (closed Issue #48492)
+                    Applicability::MaybeIncorrect
+                )
+                .emit();
+        }
+        let in_span = self.prev_span;
+        self.check_for_for_in_in_typo(in_span);
+        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+        let pat = self.recover_parens_around_for_head(pat, &expr, begin_paren);
+
+        let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
+        attrs.extend(iattrs);
+
+        let hi = self.prev_span;
+        Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
+    }
+
+    /// Parses a `while` or `while let` expression (`while` token already eaten).
+    fn parse_while_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        span_lo: Span,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
+        let cond = self.parse_cond_expr()?;
+        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+        attrs.extend(iattrs);
+        let span = span_lo.to(body.span);
+        Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs))
+    }
+
+    /// Parse `loop {...}`, `loop` token already eaten.
+    fn parse_loop_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        span_lo: Span,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
+        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+        attrs.extend(iattrs);
+        let span = span_lo.to(body.span);
+        Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
+    }
+
+    fn eat_label(&mut self) -> Option<Label> {
+        if let Some(ident) = self.token.lifetime() {
+            let span = self.token.span;
+            self.bump();
+            Some(Label { ident: Ident::new(ident.name, span) })
+        } else {
+            None
+        }
+    }
+
+    // `match` token already eaten
+    fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let match_span = self.prev_span;
+        let lo = self.prev_span;
+        let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
+            if self.token == token::Semi {
+                e.span_suggestion_short(
+                    match_span,
+                    "try removing this `match`",
+                    String::new(),
+                    Applicability::MaybeIncorrect // speculative
+                );
+            }
+            return Err(e)
+        }
+        attrs.extend(self.parse_inner_attributes()?);
+
+        let mut arms: Vec<Arm> = Vec::new();
+        while self.token != token::CloseDelim(token::Brace) {
+            match self.parse_arm() {
+                Ok(arm) => arms.push(arm),
+                Err(mut e) => {
+                    // Recover by skipping to the end of the block.
+                    e.emit();
+                    self.recover_stmt();
+                    let span = lo.to(self.token.span);
+                    if self.token == token::CloseDelim(token::Brace) {
+                        self.bump();
+                    }
+                    return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
+                }
+            }
+        }
+        let hi = self.token.span;
+        self.bump();
+        return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
+    }
+
+    crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+        let pats = self.parse_pats()?;
+        let guard = if self.eat_keyword(kw::If) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+        let arrow_span = self.token.span;
+        self.expect(&token::FatArrow)?;
+        let arm_start_span = self.token.span;
+
+        let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
+            .map_err(|mut err| {
+                err.span_label(arrow_span, "while parsing the `match` arm starting here");
+                err
+            })?;
+
+        let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
+            && self.token != token::CloseDelim(token::Brace);
+
+        let hi = self.token.span;
+
+        if require_comma {
+            let cm = self.sess.source_map();
+            self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
+                .map_err(|mut err| {
+                    match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
+                        (Ok(ref expr_lines), Ok(ref arm_start_lines))
+                        if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
+                            && expr_lines.lines.len() == 2
+                            && self.token == token::FatArrow => {
+                            // We check whether there's any trailing code in the parse span,
+                            // if there isn't, we very likely have the following:
+                            //
+                            // X |     &Y => "y"
+                            //   |        --    - missing comma
+                            //   |        |
+                            //   |        arrow_span
+                            // X |     &X => "x"
+                            //   |      - ^^ self.token.span
+                            //   |      |
+                            //   |      parsed until here as `"y" & X`
+                            err.span_suggestion_short(
+                                cm.next_point(arm_start_span),
+                                "missing a comma here to end this `match` arm",
+                                ",".to_owned(),
+                                Applicability::MachineApplicable
+                            );
+                        }
+                        _ => {
+                            err.span_label(arrow_span,
+                                           "while parsing the `match` arm starting here");
+                        }
+                    }
+                    err
+                })?;
+        } else {
+            self.eat(&token::Comma);
+        }
+
+        Ok(ast::Arm {
+            attrs,
+            pats,
+            guard,
+            body: expr,
+            span: lo.to(hi),
+            id: ast::DUMMY_NODE_ID,
+        })
+    }
+
+    /// Parses a `try {...}` expression (`try` token already eaten).
+    fn parse_try_block(
+        &mut self,
+        span_lo: Span,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
+        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+        attrs.extend(iattrs);
+        if self.eat_keyword(kw::Catch) {
+            let mut error = self.struct_span_err(self.prev_span,
+                                                 "keyword `catch` cannot follow a `try` block");
+            error.help("try using `match` on the result of the `try` block instead");
+            error.emit();
+            Err(error)
+        } else {
+            Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
+        }
+    }
+
+    fn is_do_catch_block(&self) -> bool {
+        self.token.is_keyword(kw::Do) &&
+        self.is_keyword_ahead(1, &[kw::Catch]) &&
+        self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
+        !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+    }
+
+    fn is_try_block(&self) -> bool {
+        self.token.is_keyword(kw::Try) &&
+        self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
+        self.token.span.rust_2018() &&
+        // prevent `while try {} {}`, `if try {} {} else {}`, etc.
+        !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
+    }
+
+    /// Parses an `async move? {...}` expression.
+    pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let span_lo = self.token.span;
+        self.expect_keyword(kw::Async)?;
+        let capture_clause = self.parse_capture_clause();
+        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
+        attrs.extend(iattrs);
+        Ok(self.mk_expr(
+            span_lo.to(body.span),
+            ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
+    }
+
+    fn is_async_block(&self) -> bool {
+        self.token.is_keyword(kw::Async) &&
+        (
+            ( // `async move {`
+                self.is_keyword_ahead(1, &[kw::Move]) &&
+                self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
+            ) || ( // `async {`
+                self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
+            )
+        )
+    }
+
+    fn maybe_parse_struct_expr(
+        &mut self,
+        lo: Span,
+        path: &ast::Path,
+        attrs: &ThinVec<Attribute>,
+    ) -> Option<PResult<'a, P<Expr>>> {
+        let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
+        let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
+            // `{ ident, ` cannot start a block
+            self.look_ahead(2, |t| t == &token::Comma) ||
+            self.look_ahead(2, |t| t == &token::Colon) && (
+                // `{ ident: token, ` cannot start a block
+                self.look_ahead(4, |t| t == &token::Comma) ||
+                // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
+                self.look_ahead(3, |t| !t.can_begin_type())
+            )
+        );
+
+        if struct_allowed || certainly_not_a_block() {
+            // This is a struct literal, but we don't can't accept them here
+            let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
+            if let (Ok(expr), false) = (&expr, struct_allowed) {
+                self.struct_span_err(
+                    expr.span,
+                    "struct literals are not allowed here",
+                )
+                .multipart_suggestion(
+                    "surround the struct literal with parentheses",
+                    vec![
+                        (lo.shrink_to_lo(), "(".to_string()),
+                        (expr.span.shrink_to_hi(), ")".to_string()),
+                    ],
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+            }
+            return Some(expr);
+        }
+        None
+    }
+
+    pub(super) fn parse_struct_expr(
+        &mut self,
+        lo: Span,
+        pth: ast::Path,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
+        let struct_sp = lo.to(self.prev_span);
+        self.bump();
+        let mut fields = Vec::new();
+        let mut base = None;
+
+        attrs.extend(self.parse_inner_attributes()?);
+
+        while self.token != token::CloseDelim(token::Brace) {
+            if self.eat(&token::DotDot) {
+                let exp_span = self.prev_span;
+                match self.parse_expr() {
+                    Ok(e) => {
+                        base = Some(e);
+                    }
+                    Err(mut e) => {
+                        e.emit();
+                        self.recover_stmt();
+                    }
+                }
+                if self.token == token::Comma {
+                    self.struct_span_err(
+                        exp_span.to(self.prev_span),
+                        "cannot use a comma after the base struct",
+                    )
+                    .span_suggestion_short(
+                        self.token.span,
+                        "remove this comma",
+                        String::new(),
+                        Applicability::MachineApplicable
+                    )
+                    .note("the base struct must always be the last field")
+                    .emit();
+                    self.recover_stmt();
+                }
+                break;
+            }
+
+            let mut recovery_field = None;
+            if let token::Ident(name, _) = self.token.kind {
+                if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
+                    // Use in case of error after field-looking code: `S { foo: () with a }`
+                    recovery_field = Some(ast::Field {
+                        ident: Ident::new(name, self.token.span),
+                        span: self.token.span,
+                        expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()),
+                        is_shorthand: false,
+                        attrs: ThinVec::new(),
+                        id: ast::DUMMY_NODE_ID,
+                    });
+                }
+            }
+            let mut parsed_field = None;
+            match self.parse_field() {
+                Ok(f) => parsed_field = Some(f),
+                Err(mut e) => {
+                    e.span_label(struct_sp, "while parsing this struct");
+                    e.emit();
+
+                    // If the next token is a comma, then try to parse
+                    // what comes next as additional fields, rather than
+                    // bailing out until next `}`.
+                    if self.token != token::Comma {
+                        self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+                        if self.token != token::Comma {
+                            break;
+                        }
+                    }
+                }
+            }
+
+            match self.expect_one_of(&[token::Comma],
+                                     &[token::CloseDelim(token::Brace)]) {
+                Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
+                    // only include the field if there's no parse error for the field name
+                    fields.push(f);
+                }
+                Err(mut e) => {
+                    if let Some(f) = recovery_field {
+                        fields.push(f);
+                    }
+                    e.span_label(struct_sp, "while parsing this struct");
+                    e.emit();
+                    self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
+                    self.eat(&token::Comma);
+                }
+            }
+        }
+
+        let span = lo.to(self.token.span);
+        self.expect(&token::CloseDelim(token::Brace))?;
+        return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
+    }
+
+    /// Parse ident (COLON expr)?
+    fn parse_field(&mut self) -> PResult<'a, Field> {
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+
+        // Check if a colon exists one ahead. This means we're parsing a fieldname.
+        let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
+            t == &token::Colon || t == &token::Eq
+        }) {
+            let fieldname = self.parse_field_name()?;
+
+            // Check for an equals token. This means the source incorrectly attempts to
+            // initialize a field with an eq rather than a colon.
+            if self.token == token::Eq {
+                self.diagnostic()
+                    .struct_span_err(self.token.span, "expected `:`, found `=`")
+                    .span_suggestion(
+                        fieldname.span.shrink_to_hi().to(self.token.span),
+                        "replace equals symbol with a colon",
+                        ":".to_string(),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+            }
+            self.bump(); // `:`
+            (fieldname, self.parse_expr()?, false)
+        } else {
+            let fieldname = self.parse_ident_common(false)?;
+
+            // Mimic `x: x` for the `x` field shorthand.
+            let path = ast::Path::from_ident(fieldname);
+            let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
+            (fieldname, expr, true)
+        };
+        Ok(ast::Field {
+            ident: fieldname,
+            span: lo.to(expr.span),
+            expr,
+            is_shorthand,
+            attrs: attrs.into(),
+            id: ast::DUMMY_NODE_ID,
+        })
+    }
+
+    fn err_dotdotdot_syntax(&self, span: Span) {
+        self.struct_span_err(span, "unexpected token: `...`")
+            .span_suggestion(
+                span,
+                "use `..` for an exclusive range", "..".to_owned(),
+                Applicability::MaybeIncorrect
+            )
+            .span_suggestion(
+                span,
+                "or `..=` for an inclusive range", "..=".to_owned(),
+                Applicability::MaybeIncorrect
+            )
+            .emit();
+    }
+
+    fn err_larrow_operator(&self, span: Span) {
+        self.struct_span_err(
+            span,
+            "unexpected token: `<-`"
+        ).span_suggestion(
+            span,
+            "if you meant to write a comparison against a negative value, add a \
+             space in between `<` and `-`",
+            "< -".to_string(),
+            Applicability::MaybeIncorrect
+        ).emit();
+    }
+
+    fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+        ExprKind::AssignOp(binop, lhs, rhs)
+    }
+
+    fn mk_range(
+        &self,
+        start: Option<P<Expr>>,
+        end: Option<P<Expr>>,
+        limits: RangeLimits
+    ) -> PResult<'a, ExprKind> {
+        if end.is_none() && limits == RangeLimits::Closed {
+            Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd))
+        } else {
+            Ok(ExprKind::Range(start, end, limits))
+        }
+    }
+
+    fn mk_unary(&self, unop: UnOp, expr: P<Expr>) -> ExprKind {
+        ExprKind::Unary(unop, expr)
+    }
+
+    fn mk_binary(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
+        ExprKind::Binary(binop, lhs, rhs)
+    }
+
+    fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ExprKind {
+        ExprKind::Index(expr, idx)
+    }
+
+    fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ExprKind {
+        ExprKind::Call(f, args)
+    }
+
+    fn mk_await_expr(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
+        let span = lo.to(self.prev_span);
+        let await_expr = self.mk_expr(span, ExprKind::Await(self_arg), ThinVec::new());
+        self.recover_from_await_method_call();
+        Ok(await_expr)
+    }
+
+    crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
+        P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
+    }
+}
diff --git a/src/libsyntax/parse/parser/generics.rs b/src/libsyntax/parse/parser/generics.rs
new file mode 100644
index 00000000000..54f24f8ef2b
--- /dev/null
+++ b/src/libsyntax/parse/parser/generics.rs
@@ -0,0 +1,276 @@
+use super::{Parser, PResult};
+
+use crate::ast::{self, WhereClause, GenericParam, GenericParamKind, GenericBounds, Attribute};
+use crate::parse::token;
+use crate::source_map::DUMMY_SP;
+use crate::symbol::kw;
+
+impl<'a> Parser<'a> {
+    /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
+    ///
+    /// ```
+    /// BOUND = LT_BOUND (e.g., `'a`)
+    /// ```
+    fn parse_lt_param_bounds(&mut self) -> GenericBounds {
+        let mut lifetimes = Vec::new();
+        while self.check_lifetime() {
+            lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
+
+            if !self.eat_plus() {
+                break
+            }
+        }
+        lifetimes
+    }
+
+    /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
+    fn parse_ty_param(&mut self,
+                      preceding_attrs: Vec<Attribute>)
+                      -> PResult<'a, GenericParam> {
+        let ident = self.parse_ident()?;
+
+        // Parse optional colon and param bounds.
+        let bounds = if self.eat(&token::Colon) {
+            self.parse_generic_bounds(Some(self.prev_span))?
+        } else {
+            Vec::new()
+        };
+
+        let default = if self.eat(&token::Eq) {
+            Some(self.parse_ty()?)
+        } else {
+            None
+        };
+
+        Ok(GenericParam {
+            ident,
+            id: ast::DUMMY_NODE_ID,
+            attrs: preceding_attrs.into(),
+            bounds,
+            kind: GenericParamKind::Type {
+                default,
+            }
+        })
+    }
+
+    fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
+        self.expect_keyword(kw::Const)?;
+        let ident = self.parse_ident()?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+
+        Ok(GenericParam {
+            ident,
+            id: ast::DUMMY_NODE_ID,
+            attrs: preceding_attrs.into(),
+            bounds: Vec::new(),
+            kind: GenericParamKind::Const {
+                ty,
+            }
+        })
+    }
+
+    /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
+    /// a trailing comma and erroneous trailing attributes.
+    crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
+        let mut params = Vec::new();
+        loop {
+            let attrs = self.parse_outer_attributes()?;
+            if self.check_lifetime() {
+                let lifetime = self.expect_lifetime();
+                // Parse lifetime parameter.
+                let bounds = if self.eat(&token::Colon) {
+                    self.parse_lt_param_bounds()
+                } else {
+                    Vec::new()
+                };
+                params.push(ast::GenericParam {
+                    ident: lifetime.ident,
+                    id: lifetime.id,
+                    attrs: attrs.into(),
+                    bounds,
+                    kind: ast::GenericParamKind::Lifetime,
+                });
+            } else if self.check_keyword(kw::Const) {
+                // Parse const parameter.
+                params.push(self.parse_const_param(attrs)?);
+            } else if self.check_ident() {
+                // Parse type parameter.
+                params.push(self.parse_ty_param(attrs)?);
+            } else {
+                // Check for trailing attributes and stop parsing.
+                if !attrs.is_empty() {
+                    if !params.is_empty() {
+                        self.struct_span_err(
+                            attrs[0].span,
+                            &format!("trailing attribute after generic parameter"),
+                        )
+                        .span_label(attrs[0].span, "attributes must go before parameters")
+                        .emit();
+                    } else {
+                        self.struct_span_err(
+                            attrs[0].span,
+                            &format!("attribute without generic parameters"),
+                        )
+                        .span_label(
+                            attrs[0].span,
+                            "attributes are only permitted when preceding parameters",
+                        )
+                        .emit();
+                    }
+                }
+                break
+            }
+
+            if !self.eat(&token::Comma) {
+                break
+            }
+        }
+        Ok(params)
+    }
+
+    /// Parses a set of optional generic type parameter declarations. Where
+    /// clauses are not parsed here, and must be added later via
+    /// `parse_where_clause()`.
+    ///
+    /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
+    ///                  | ( < lifetimes , typaramseq ( , )? > )
+    /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
+    pub(super) fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
+        let span_lo = self.token.span;
+        let (params, span) = if self.eat_lt() {
+            let params = self.parse_generic_params()?;
+            self.expect_gt()?;
+            (params, span_lo.to(self.prev_span))
+        } else {
+            (vec![], self.prev_span.between(self.token.span))
+        };
+        Ok(ast::Generics {
+            params,
+            where_clause: WhereClause {
+                predicates: Vec::new(),
+                span: DUMMY_SP,
+            },
+            span,
+        })
+    }
+
+    /// Parses an optional where-clause and places it in `generics`.
+    ///
+    /// ```ignore (only-for-syntax-highlight)
+    /// where T : Trait<U, V> + 'b, 'a : 'b
+    /// ```
+    pub(super) fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
+        let mut where_clause = WhereClause {
+            predicates: Vec::new(),
+            span: self.prev_span.to(self.prev_span),
+        };
+
+        if !self.eat_keyword(kw::Where) {
+            return Ok(where_clause);
+        }
+        let lo = self.prev_span;
+
+        // We are considering adding generics to the `where` keyword as an alternative higher-rank
+        // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
+        // change we parse those generics now, but report an error.
+        if self.choose_generics_over_qpath() {
+            let generics = self.parse_generics()?;
+            self.struct_span_err(
+                generics.span,
+                "generic parameters on `where` clauses are reserved for future use",
+            )
+                .span_label(generics.span, "currently unsupported")
+                .emit();
+        }
+
+        loop {
+            let lo = self.token.span;
+            if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
+                let lifetime = self.expect_lifetime();
+                // Bounds starting with a colon are mandatory, but possibly empty.
+                self.expect(&token::Colon)?;
+                let bounds = self.parse_lt_param_bounds();
+                where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
+                    ast::WhereRegionPredicate {
+                        span: lo.to(self.prev_span),
+                        lifetime,
+                        bounds,
+                    }
+                ));
+            } else if self.check_type() {
+                // Parse optional `for<'a, 'b>`.
+                // This `for` is parsed greedily and applies to the whole predicate,
+                // the bounded type can have its own `for` applying only to it.
+                // Examples:
+                // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
+                // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
+                // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
+                let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+
+                // Parse type with mandatory colon and (possibly empty) bounds,
+                // or with mandatory equality sign and the second type.
+                let ty = self.parse_ty()?;
+                if self.eat(&token::Colon) {
+                    let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
+                    where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
+                        ast::WhereBoundPredicate {
+                            span: lo.to(self.prev_span),
+                            bound_generic_params: lifetime_defs,
+                            bounded_ty: ty,
+                            bounds,
+                        }
+                    ));
+                // FIXME: Decide what should be used here, `=` or `==`.
+                // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
+                } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
+                    let rhs_ty = self.parse_ty()?;
+                    where_clause.predicates.push(ast::WherePredicate::EqPredicate(
+                        ast::WhereEqPredicate {
+                            span: lo.to(self.prev_span),
+                            lhs_ty: ty,
+                            rhs_ty,
+                            id: ast::DUMMY_NODE_ID,
+                        }
+                    ));
+                } else {
+                    return self.unexpected();
+                }
+            } else {
+                break
+            }
+
+            if !self.eat(&token::Comma) {
+                break
+            }
+        }
+
+        where_clause.span = lo.to(self.prev_span);
+        Ok(where_clause)
+    }
+
+    pub(super) fn choose_generics_over_qpath(&self) -> bool {
+        // There's an ambiguity between generic parameters and qualified paths in impls.
+        // If we see `<` it may start both, so we have to inspect some following tokens.
+        // The following combinations can only start generics,
+        // but not qualified paths (with one exception):
+        //     `<` `>` - empty generic parameters
+        //     `<` `#` - generic parameters with attributes
+        //     `<` (LIFETIME|IDENT) `>` - single generic parameter
+        //     `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
+        //     `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
+        //     `<` (LIFETIME|IDENT) `=` - generic parameter with a default
+        //     `<` const                - generic const parameter
+        // The only truly ambiguous case is
+        //     `<` IDENT `>` `::` IDENT ...
+        // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
+        // because this is what almost always expected in practice, qualified paths in impls
+        // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
+        self.token == token::Lt &&
+            (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
+             self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
+                self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
+                                       t == &token::Colon || t == &token::Eq) ||
+            self.is_keyword_ahead(1, &[kw::Const]))
+    }
+}
diff --git a/src/libsyntax/parse/parser/item.rs b/src/libsyntax/parse/parser/item.rs
new file mode 100644
index 00000000000..72819c99660
--- /dev/null
+++ b/src/libsyntax/parse/parser/item.rs
@@ -0,0 +1,1918 @@
+use super::{Parser, PResult, PathStyle, SemiColonMode, BlockMode};
+
+use crate::maybe_whole;
+use crate::ptr::P;
+use crate::ast::{self, Ident, Attribute, AttrStyle};
+use crate::ast::{Item, ItemKind, ImplItem, TraitItem, TraitItemKind};
+use crate::ast::{UseTree, UseTreeKind, PathSegment};
+use crate::ast::{IsAuto, Constness, IsAsync, Unsafety, Defaultness};
+use crate::ast::{Visibility, VisibilityKind, Mutability, FnDecl, FnHeader};
+use crate::ast::{ForeignItem, ForeignItemKind};
+use crate::ast::{Ty, TyKind, GenericBounds, TraitRef};
+use crate::ast::{EnumDef, VariantData, StructField, AnonConst};
+use crate::ast::{Mac, MacDelimiter};
+use crate::ext::base::DummyResult;
+use crate::parse::token;
+use crate::parse::parser::maybe_append;
+use crate::parse::diagnostics::{Error};
+use crate::tokenstream::{TokenTree, TokenStream};
+use crate::source_map::{respan, Span, Spanned};
+use crate::symbol::{kw, sym};
+
+use std::mem;
+use log::debug;
+use rustc_target::spec::abi::{Abi};
+use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
+
+/// Whether the type alias or associated type is a concrete type or an opaque type
+#[derive(Debug)]
+pub enum AliasKind {
+    /// Just a new name for the same type
+    Weak(P<Ty>),
+    /// Only trait impls of the type will be usable, not the actual type itself
+    OpaqueTy(GenericBounds),
+}
+
+pub(super) type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
+
+impl<'a> Parser<'a> {
+    pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
+        let attrs = self.parse_outer_attributes()?;
+        self.parse_item_(attrs, true, false)
+    }
+
+    pub(super) fn parse_item_(
+        &mut self,
+        attrs: Vec<Attribute>,
+        macros_allowed: bool,
+        attributes_allowed: bool,
+    ) -> PResult<'a, Option<P<Item>>> {
+        let mut unclosed_delims = vec![];
+        let (ret, tokens) = self.collect_tokens(|this| {
+            let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
+            unclosed_delims.append(&mut this.unclosed_delims);
+            item
+        })?;
+        self.unclosed_delims.append(&mut unclosed_delims);
+
+        // Once we've parsed an item and recorded the tokens we got while
+        // parsing we may want to store `tokens` into the item we're about to
+        // return. Note, though, that we specifically didn't capture tokens
+        // related to outer attributes. The `tokens` field here may later be
+        // used with procedural macros to convert this item back into a token
+        // stream, but during expansion we may be removing attributes as we go
+        // along.
+        //
+        // If we've got inner attributes then the `tokens` we've got above holds
+        // these inner attributes. If an inner attribute is expanded we won't
+        // actually remove it from the token stream, so we'll just keep yielding
+        // it (bad!). To work around this case for now we just avoid recording
+        // `tokens` if we detect any inner attributes. This should help keep
+        // expansion correct, but we should fix this bug one day!
+        Ok(ret.map(|item| {
+            item.map(|mut i| {
+                if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
+                    i.tokens = Some(tokens);
+                }
+                i
+            })
+        }))
+    }
+
+    /// Parses one of the items allowed by the flags.
+    fn parse_item_implementation(
+        &mut self,
+        attrs: Vec<Attribute>,
+        macros_allowed: bool,
+        attributes_allowed: bool,
+    ) -> PResult<'a, Option<P<Item>>> {
+        maybe_whole!(self, NtItem, |item| {
+            let mut item = item.into_inner();
+            let mut attrs = attrs;
+            mem::swap(&mut item.attrs, &mut attrs);
+            item.attrs.extend(attrs);
+            Some(P(item))
+        });
+
+        let lo = self.token.span;
+
+        let visibility = self.parse_visibility(false)?;
+
+        if self.eat_keyword(kw::Use) {
+            // USE ITEM
+            let item_ = ItemKind::Use(P(self.parse_use_tree()?));
+            self.expect(&token::Semi)?;
+
+            let span = lo.to(self.prev_span);
+            let item =
+                self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
+            return Ok(Some(item));
+        }
+
+        if self.eat_keyword(kw::Extern) {
+            let extern_sp = self.prev_span;
+            if self.eat_keyword(kw::Crate) {
+                return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
+            }
+
+            let opt_abi = self.parse_opt_abi()?;
+
+            if self.eat_keyword(kw::Fn) {
+                // EXTERN FUNCTION ITEM
+                let fn_span = self.prev_span;
+                let abi = opt_abi.unwrap_or(Abi::C);
+                let (ident, item_, extra_attrs) =
+                    self.parse_item_fn(Unsafety::Normal,
+                                       respan(fn_span, IsAsync::NotAsync),
+                                       respan(fn_span, Constness::NotConst),
+                                       abi)?;
+                let prev_span = self.prev_span;
+                let item = self.mk_item(lo.to(prev_span),
+                                        ident,
+                                        item_,
+                                        visibility,
+                                        maybe_append(attrs, extra_attrs));
+                return Ok(Some(item));
+            } else if self.check(&token::OpenDelim(token::Brace)) {
+                return Ok(Some(
+                    self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs, extern_sp)?,
+                ));
+            }
+
+            self.unexpected()?;
+        }
+
+        if self.is_static_global() {
+            self.bump();
+            // STATIC ITEM
+            let m = self.parse_mutability();
+            let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.eat_keyword(kw::Const) {
+            let const_span = self.prev_span;
+            if self.check_keyword(kw::Fn)
+                || (self.check_keyword(kw::Unsafe)
+                    && self.is_keyword_ahead(1, &[kw::Fn])) {
+                // CONST FUNCTION ITEM
+                let unsafety = self.parse_unsafety();
+                self.bump();
+                let (ident, item_, extra_attrs) =
+                    self.parse_item_fn(unsafety,
+                                       respan(const_span, IsAsync::NotAsync),
+                                       respan(const_span, Constness::Const),
+                                       Abi::Rust)?;
+                let prev_span = self.prev_span;
+                let item = self.mk_item(lo.to(prev_span),
+                                        ident,
+                                        item_,
+                                        visibility,
+                                        maybe_append(attrs, extra_attrs));
+                return Ok(Some(item));
+            }
+
+            // CONST ITEM
+            if self.eat_keyword(kw::Mut) {
+                let prev_span = self.prev_span;
+                self.struct_span_err(prev_span, "const globals cannot be mutable")
+                    .span_label(prev_span, "cannot be mutable")
+                    .span_suggestion(
+                        const_span,
+                        "you might want to declare a static instead",
+                        "static".to_owned(),
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
+            }
+            let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+
+        // Parse `async unsafe? fn`.
+        if self.check_keyword(kw::Async) {
+            let async_span = self.token.span;
+            if self.is_keyword_ahead(1, &[kw::Fn])
+                || self.is_keyword_ahead(2, &[kw::Fn])
+            {
+                // ASYNC FUNCTION ITEM
+                self.bump(); // `async`
+                let unsafety = self.parse_unsafety(); // `unsafe`?
+                self.expect_keyword(kw::Fn)?; // `fn`
+                let fn_span = self.prev_span;
+                let (ident, item_, extra_attrs) =
+                    self.parse_item_fn(unsafety,
+                                    respan(async_span, IsAsync::Async {
+                                        closure_id: ast::DUMMY_NODE_ID,
+                                        return_impl_trait_id: ast::DUMMY_NODE_ID,
+                                    }),
+                                    respan(fn_span, Constness::NotConst),
+                                    Abi::Rust)?;
+                let prev_span = self.prev_span;
+                let item = self.mk_item(lo.to(prev_span),
+                                        ident,
+                                        item_,
+                                        visibility,
+                                        maybe_append(attrs, extra_attrs));
+                self.ban_async_in_2015(async_span);
+                return Ok(Some(item));
+            }
+        }
+        if self.check_keyword(kw::Unsafe) &&
+            self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
+        {
+            // UNSAFE TRAIT ITEM
+            self.bump(); // `unsafe`
+            let is_auto = if self.eat_keyword(kw::Trait) {
+                IsAuto::No
+            } else {
+                self.expect_keyword(kw::Auto)?;
+                self.expect_keyword(kw::Trait)?;
+                IsAuto::Yes
+            };
+            let (ident, item_, extra_attrs) =
+                self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.check_keyword(kw::Impl) ||
+           self.check_keyword(kw::Unsafe) &&
+                self.is_keyword_ahead(1, &[kw::Impl]) ||
+           self.check_keyword(kw::Default) &&
+                self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
+            // IMPL ITEM
+            let defaultness = self.parse_defaultness();
+            let unsafety = self.parse_unsafety();
+            self.expect_keyword(kw::Impl)?;
+            let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
+            let span = lo.to(self.prev_span);
+            return Ok(Some(self.mk_item(span, ident, item, visibility,
+                                        maybe_append(attrs, extra_attrs))));
+        }
+        if self.check_keyword(kw::Fn) {
+            // FUNCTION ITEM
+            self.bump();
+            let fn_span = self.prev_span;
+            let (ident, item_, extra_attrs) =
+                self.parse_item_fn(Unsafety::Normal,
+                                   respan(fn_span, IsAsync::NotAsync),
+                                   respan(fn_span, Constness::NotConst),
+                                   Abi::Rust)?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.check_keyword(kw::Unsafe)
+            && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
+            // UNSAFE FUNCTION ITEM
+            self.bump(); // `unsafe`
+            // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
+            self.check(&token::OpenDelim(token::Brace));
+            let abi = if self.eat_keyword(kw::Extern) {
+                self.parse_opt_abi()?.unwrap_or(Abi::C)
+            } else {
+                Abi::Rust
+            };
+            self.expect_keyword(kw::Fn)?;
+            let fn_span = self.prev_span;
+            let (ident, item_, extra_attrs) =
+                self.parse_item_fn(Unsafety::Unsafe,
+                                   respan(fn_span, IsAsync::NotAsync),
+                                   respan(fn_span, Constness::NotConst),
+                                   abi)?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.eat_keyword(kw::Mod) {
+            // MODULE ITEM
+            let (ident, item_, extra_attrs) =
+                self.parse_item_mod(&attrs[..])?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if let Some(type_) = self.eat_type() {
+            let (ident, alias, generics) = type_?;
+            // TYPE ITEM
+            let item_ = match alias {
+                AliasKind::Weak(ty) => ItemKind::TyAlias(ty, generics),
+                AliasKind::OpaqueTy(bounds) => ItemKind::OpaqueTy(bounds, generics),
+            };
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    attrs);
+            return Ok(Some(item));
+        }
+        if self.eat_keyword(kw::Enum) {
+            // ENUM ITEM
+            let (ident, item_, extra_attrs) = self.parse_item_enum()?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.check_keyword(kw::Trait)
+            || (self.check_keyword(kw::Auto)
+                && self.is_keyword_ahead(1, &[kw::Trait]))
+        {
+            let is_auto = if self.eat_keyword(kw::Trait) {
+                IsAuto::No
+            } else {
+                self.expect_keyword(kw::Auto)?;
+                self.expect_keyword(kw::Trait)?;
+                IsAuto::Yes
+            };
+            // TRAIT ITEM
+            let (ident, item_, extra_attrs) =
+                self.parse_item_trait(is_auto, Unsafety::Normal)?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.eat_keyword(kw::Struct) {
+            // STRUCT ITEM
+            let (ident, item_, extra_attrs) = self.parse_item_struct()?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if self.is_union_item() {
+            // UNION ITEM
+            self.bump();
+            let (ident, item_, extra_attrs) = self.parse_item_union()?;
+            let prev_span = self.prev_span;
+            let item = self.mk_item(lo.to(prev_span),
+                                    ident,
+                                    item_,
+                                    visibility,
+                                    maybe_append(attrs, extra_attrs));
+            return Ok(Some(item));
+        }
+        if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
+            return Ok(Some(macro_def));
+        }
+
+        // Verify whether we have encountered a struct or method definition where the user forgot to
+        // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
+        if visibility.node.is_pub() &&
+            self.check_ident() &&
+            self.look_ahead(1, |t| *t != token::Not)
+        {
+            // Space between `pub` keyword and the identifier
+            //
+            //     pub   S {}
+            //        ^^^ `sp` points here
+            let sp = self.prev_span.between(self.token.span);
+            let full_sp = self.prev_span.to(self.token.span);
+            let ident_sp = self.token.span;
+            if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
+                // possible public struct definition where `struct` was forgotten
+                let ident = self.parse_ident().unwrap();
+                let msg = format!("add `struct` here to parse `{}` as a public struct",
+                                  ident);
+                let mut err = self.diagnostic()
+                    .struct_span_err(sp, "missing `struct` for struct definition");
+                err.span_suggestion_short(
+                    sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
+                );
+                return Err(err);
+            } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
+                let ident = self.parse_ident().unwrap();
+                self.bump();  // `(`
+                let kw_name = if let Ok(Some(_)) = self.parse_self_arg_with_attrs()
+                    .map_err(|mut e| e.cancel())
+                {
+                    "method"
+                } else {
+                    "function"
+                };
+                self.consume_block(token::Paren);
+                let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
+                    self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
+                    self.bump();  // `{`
+                    ("fn", kw_name, false)
+                } else if self.check(&token::OpenDelim(token::Brace)) {
+                    self.bump();  // `{`
+                    ("fn", kw_name, false)
+                } else if self.check(&token::Colon) {
+                    let kw = "struct";
+                    (kw, kw, false)
+                } else {
+                    ("fn` or `struct", "function or struct", true)
+                };
+
+                let msg = format!("missing `{}` for {} definition", kw, kw_name);
+                let mut err = self.diagnostic().struct_span_err(sp, &msg);
+                if !ambiguous {
+                    self.consume_block(token::Brace);
+                    let suggestion = format!("add `{}` here to parse `{}` as a public {}",
+                                             kw,
+                                             ident,
+                                             kw_name);
+                    err.span_suggestion_short(
+                        sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
+                    );
+                } else {
+                    if let Ok(snippet) = self.span_to_snippet(ident_sp) {
+                        err.span_suggestion(
+                            full_sp,
+                            "if you meant to call a macro, try",
+                            format!("{}!", snippet),
+                            // this is the `ambiguous` conditional branch
+                            Applicability::MaybeIncorrect
+                        );
+                    } else {
+                        err.help("if you meant to call a macro, remove the `pub` \
+                                  and add a trailing `!` after the identifier");
+                    }
+                }
+                return Err(err);
+            } else if self.look_ahead(1, |t| *t == token::Lt) {
+                let ident = self.parse_ident().unwrap();
+                self.eat_to_tokens(&[&token::Gt]);
+                self.bump();  // `>`
+                let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
+                    if let Ok(Some(_)) = self.parse_self_arg_with_attrs()
+                        .map_err(|mut e| e.cancel())
+                    {
+                        ("fn", "method", false)
+                    } else {
+                        ("fn", "function", false)
+                    }
+                } else if self.check(&token::OpenDelim(token::Brace)) {
+                    ("struct", "struct", false)
+                } else {
+                    ("fn` or `struct", "function or struct", true)
+                };
+                let msg = format!("missing `{}` for {} definition", kw, kw_name);
+                let mut err = self.diagnostic().struct_span_err(sp, &msg);
+                if !ambiguous {
+                    err.span_suggestion_short(
+                        sp,
+                        &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
+                        format!(" {} ", kw),
+                        Applicability::MachineApplicable,
+                    );
+                }
+                return Err(err);
+            }
+        }
+        self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
+    }
+
+    /// This is the fall-through for parsing items.
+    fn parse_macro_use_or_failure(
+        &mut self,
+        attrs: Vec<Attribute> ,
+        macros_allowed: bool,
+        attributes_allowed: bool,
+        lo: Span,
+        visibility: Visibility
+    ) -> PResult<'a, Option<P<Item>>> {
+        if macros_allowed && self.token.is_path_start() &&
+                !(self.is_async_fn() && self.token.span.rust_2015()) {
+            // MACRO INVOCATION ITEM
+
+            let prev_span = self.prev_span;
+            self.complain_if_pub_macro(&visibility.node, prev_span);
+
+            let mac_lo = self.token.span;
+
+            // item macro.
+            let path = self.parse_path(PathStyle::Mod)?;
+            self.expect(&token::Not)?;
+            let (delim, tts) = self.expect_delimited_token_tree()?;
+            if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
+                self.report_invalid_macro_expansion_item();
+            }
+
+            let hi = self.prev_span;
+            let mac = Mac {
+                path,
+                tts,
+                delim,
+                span: mac_lo.to(hi),
+                prior_type_ascription: self.last_type_ascription,
+            };
+            let item =
+                self.mk_item(lo.to(hi), Ident::invalid(), ItemKind::Mac(mac), visibility, attrs);
+            return Ok(Some(item));
+        }
+
+        // FAILURE TO PARSE ITEM
+        match visibility.node {
+            VisibilityKind::Inherited => {}
+            _ => {
+                return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
+            }
+        }
+
+        if !attributes_allowed && !attrs.is_empty() {
+            self.expected_item_err(&attrs)?;
+        }
+        Ok(None)
+    }
+
+    /// Emits an expected-item-after-attributes error.
+    fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a,  ()> {
+        let message = match attrs.last() {
+            Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
+            _ => "expected item after attributes",
+        };
+
+        let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
+        if attrs.last().unwrap().is_sugared_doc {
+            err.span_label(self.prev_span, "this doc comment doesn't document anything");
+        }
+        Err(err)
+    }
+
+    pub(super) fn is_async_fn(&self) -> bool {
+        self.token.is_keyword(kw::Async) &&
+            self.is_keyword_ahead(1, &[kw::Fn])
+    }
+
+    /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
+    fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
+                               at_end: &mut bool) -> PResult<'a, Option<Mac>>
+    {
+        if self.token.is_path_start() &&
+                !(self.is_async_fn() && self.token.span.rust_2015()) {
+            let prev_span = self.prev_span;
+            let lo = self.token.span;
+            let path = self.parse_path(PathStyle::Mod)?;
+
+            if path.segments.len() == 1 {
+                if !self.eat(&token::Not) {
+                    return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
+                }
+            } else {
+                self.expect(&token::Not)?;
+            }
+
+            if let Some(vis) = vis {
+                self.complain_if_pub_macro(&vis.node, prev_span);
+            }
+
+            *at_end = true;
+
+            // eat a matched-delimiter token tree:
+            let (delim, tts) = self.expect_delimited_token_tree()?;
+            if delim != MacDelimiter::Brace {
+                self.expect(&token::Semi)?;
+            }
+
+            Ok(Some(Mac {
+                path,
+                tts,
+                delim,
+                span: lo.to(self.prev_span),
+                prior_type_ascription: self.last_type_ascription,
+            }))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
+                                   -> DiagnosticBuilder<'a>
+    {
+        let expected_kinds = if item_type == "extern" {
+            "missing `fn`, `type`, or `static`"
+        } else {
+            "missing `fn`, `type`, or `const`"
+        };
+
+        // Given this code `path(`, it seems like this is not
+        // setting the visibility of a macro invocation, but rather
+        // a mistyped method declaration.
+        // Create a diagnostic pointing out that `fn` is missing.
+        //
+        // x |     pub path(&self) {
+        //   |        ^ missing `fn`, `type`, or `const`
+        //     pub  path(
+        //        ^^ `sp` below will point to this
+        let sp = prev_span.between(self.prev_span);
+        let mut err = self.diagnostic().struct_span_err(
+            sp,
+            &format!("{} for {}-item declaration",
+                     expected_kinds, item_type));
+        err.span_label(sp, expected_kinds);
+        err
+    }
+
+    /// Parses an implementation item, `impl` keyword is already parsed.
+    ///
+    ///    impl<'a, T> TYPE { /* impl items */ }
+    ///    impl<'a, T> TRAIT for TYPE { /* impl items */ }
+    ///    impl<'a, T> !TRAIT for TYPE { /* impl items */ }
+    ///
+    /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
+    ///     `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
+    ///     `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
+    fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
+                       -> PResult<'a, ItemInfo> {
+        // First, parse generic parameters if necessary.
+        let mut generics = if self.choose_generics_over_qpath() {
+            self.parse_generics()?
+        } else {
+            ast::Generics::default()
+        };
+
+        // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
+        let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
+            self.bump(); // `!`
+            ast::ImplPolarity::Negative
+        } else {
+            ast::ImplPolarity::Positive
+        };
+
+        // Parse both types and traits as a type, then reinterpret if necessary.
+        let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
+        let ty_first = if self.token.is_keyword(kw::For) &&
+                          self.look_ahead(1, |t| t != &token::Lt) {
+            let span = self.prev_span.between(self.token.span);
+            self.struct_span_err(span, "missing trait in a trait impl").emit();
+            P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
+        } else {
+            self.parse_ty()?
+        };
+
+        // If `for` is missing we try to recover.
+        let has_for = self.eat_keyword(kw::For);
+        let missing_for_span = self.prev_span.between(self.token.span);
+
+        let ty_second = if self.token == token::DotDot {
+            // We need to report this error after `cfg` expansion for compatibility reasons
+            self.bump(); // `..`, do not add it to expected tokens
+            Some(DummyResult::raw_ty(self.prev_span, true))
+        } else if has_for || self.token.can_begin_type() {
+            Some(self.parse_ty()?)
+        } else {
+            None
+        };
+
+        generics.where_clause = self.parse_where_clause()?;
+
+        let (impl_items, attrs) = self.parse_impl_body()?;
+
+        let item_kind = match ty_second {
+            Some(ty_second) => {
+                // impl Trait for Type
+                if !has_for {
+                    self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
+                        .span_suggestion_short(
+                            missing_for_span,
+                            "add `for` here",
+                            " for ".to_string(),
+                            Applicability::MachineApplicable,
+                        ).emit();
+                }
+
+                let ty_first = ty_first.into_inner();
+                let path = match ty_first.node {
+                    // This notably includes paths passed through `ty` macro fragments (#46438).
+                    TyKind::Path(None, path) => path,
+                    _ => {
+                        self.span_err(ty_first.span, "expected a trait, found type");
+                        err_path(ty_first.span)
+                    }
+                };
+                let trait_ref = TraitRef { path, ref_id: ty_first.id };
+
+                ItemKind::Impl(unsafety, polarity, defaultness,
+                               generics, Some(trait_ref), ty_second, impl_items)
+            }
+            None => {
+                // impl Type
+                ItemKind::Impl(unsafety, polarity, defaultness,
+                               generics, None, ty_first, impl_items)
+            }
+        };
+
+        Ok((Ident::invalid(), item_kind, Some(attrs)))
+    }
+
+    fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
+        self.expect(&token::OpenDelim(token::Brace))?;
+        let attrs = self.parse_inner_attributes()?;
+
+        let mut impl_items = Vec::new();
+        while !self.eat(&token::CloseDelim(token::Brace)) {
+            let mut at_end = false;
+            match self.parse_impl_item(&mut at_end) {
+                Ok(impl_item) => impl_items.push(impl_item),
+                Err(mut err) => {
+                    err.emit();
+                    if !at_end {
+                        self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
+                    }
+                }
+            }
+        }
+        Ok((impl_items, attrs))
+    }
+
+    /// Parses an impl item.
+    pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
+        maybe_whole!(self, NtImplItem, |x| x);
+        let attrs = self.parse_outer_attributes()?;
+        let mut unclosed_delims = vec![];
+        let (mut item, tokens) = self.collect_tokens(|this| {
+            let item = this.parse_impl_item_(at_end, attrs);
+            unclosed_delims.append(&mut this.unclosed_delims);
+            item
+        })?;
+        self.unclosed_delims.append(&mut unclosed_delims);
+
+        // See `parse_item` for why this clause is here.
+        if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
+            item.tokens = Some(tokens);
+        }
+        Ok(item)
+    }
+
+    fn parse_impl_item_(&mut self,
+                        at_end: &mut bool,
+                        mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
+        let lo = self.token.span;
+        let vis = self.parse_visibility(false)?;
+        let defaultness = self.parse_defaultness();
+        let (name, node, generics) = if let Some(type_) = self.eat_type() {
+            let (name, alias, generics) = type_?;
+            let kind = match alias {
+                AliasKind::Weak(typ) => ast::ImplItemKind::TyAlias(typ),
+                AliasKind::OpaqueTy(bounds) => ast::ImplItemKind::OpaqueTy(bounds),
+            };
+            (name, kind, generics)
+        } else if self.is_const_item() {
+            // This parses the grammar:
+            //     ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
+            self.expect_keyword(kw::Const)?;
+            let name = self.parse_ident()?;
+            self.expect(&token::Colon)?;
+            let typ = self.parse_ty()?;
+            self.expect(&token::Eq)?;
+            let expr = self.parse_expr()?;
+            self.expect(&token::Semi)?;
+            (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
+        } else {
+            let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
+            attrs.extend(inner_attrs);
+            (name, node, generics)
+        };
+
+        Ok(ImplItem {
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(self.prev_span),
+            ident: name,
+            vis,
+            defaultness,
+            attrs,
+            generics,
+            node,
+            tokens: None,
+        })
+    }
+
+    /// Parses defaultness (i.e., `default` or nothing).
+    fn parse_defaultness(&mut self) -> Defaultness {
+        // `pub` is included for better error messages
+        if self.check_keyword(kw::Default) &&
+            self.is_keyword_ahead(1, &[
+                kw::Impl,
+                kw::Const,
+                kw::Fn,
+                kw::Unsafe,
+                kw::Extern,
+                kw::Type,
+                kw::Pub,
+            ])
+        {
+            self.bump(); // `default`
+            Defaultness::Default
+        } else {
+            Defaultness::Final
+        }
+    }
+
+    /// Returns `true` if we are looking at `const ID`
+    /// (returns `false` for things like `const fn`, etc.).
+    fn is_const_item(&self) -> bool {
+        self.token.is_keyword(kw::Const) &&
+            !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
+    }
+
+    /// Parse a method or a macro invocation in a trait impl.
+    fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
+                         -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
+                             ast::ImplItemKind)> {
+        // code copied from parse_macro_use_or_failure... abstraction!
+        if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
+            // method macro
+            Ok((Ident::invalid(), vec![], ast::Generics::default(),
+                ast::ImplItemKind::Macro(mac)))
+        } else {
+            let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
+            let ident = self.parse_ident()?;
+            let mut generics = self.parse_generics()?;
+            let decl = self.parse_fn_decl_with_self(|p| {
+                p.parse_arg_general(true, false, |_| true)
+            })?;
+            generics.where_clause = self.parse_where_clause()?;
+            *at_end = true;
+            let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+            let header = ast::FnHeader { abi, unsafety, constness, asyncness };
+            Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
+                ast::MethodSig { header, decl },
+                body
+            )))
+        }
+    }
+
+    /// Parses all the "front matter" for a `fn` declaration, up to
+    /// and including the `fn` keyword:
+    ///
+    /// - `const fn`
+    /// - `unsafe fn`
+    /// - `const unsafe fn`
+    /// - `extern fn`
+    /// - etc.
+    fn parse_fn_front_matter(&mut self)
+        -> PResult<'a, (
+            Spanned<Constness>,
+            Unsafety,
+            Spanned<IsAsync>,
+            Abi
+        )>
+    {
+        let is_const_fn = self.eat_keyword(kw::Const);
+        let const_span = self.prev_span;
+        let asyncness = self.parse_asyncness();
+        if let IsAsync::Async { .. } = asyncness {
+            self.ban_async_in_2015(self.prev_span);
+        }
+        let asyncness = respan(self.prev_span, asyncness);
+        let unsafety = self.parse_unsafety();
+        let (constness, unsafety, abi) = if is_const_fn {
+            (respan(const_span, Constness::Const), unsafety, Abi::Rust)
+        } else {
+            let abi = if self.eat_keyword(kw::Extern) {
+                self.parse_opt_abi()?.unwrap_or(Abi::C)
+            } else {
+                Abi::Rust
+            };
+            (respan(self.prev_span, Constness::NotConst), unsafety, abi)
+        };
+        if !self.eat_keyword(kw::Fn) {
+            // It is possible for `expect_one_of` to recover given the contents of
+            // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
+            // account for this.
+            if !self.expect_one_of(&[], &[])? { unreachable!() }
+        }
+        Ok((constness, unsafety, asyncness, abi))
+    }
+
+    /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
+    fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
+        let ident = self.parse_ident()?;
+        let mut tps = self.parse_generics()?;
+
+        // Parse optional colon and supertrait bounds.
+        let bounds = if self.eat(&token::Colon) {
+            self.parse_generic_bounds(Some(self.prev_span))?
+        } else {
+            Vec::new()
+        };
+
+        if self.eat(&token::Eq) {
+            // it's a trait alias
+            let bounds = self.parse_generic_bounds(None)?;
+            tps.where_clause = self.parse_where_clause()?;
+            self.expect(&token::Semi)?;
+            if is_auto == IsAuto::Yes {
+                let msg = "trait aliases cannot be `auto`";
+                self.struct_span_err(self.prev_span, msg)
+                    .span_label(self.prev_span, msg)
+                    .emit();
+            }
+            if unsafety != Unsafety::Normal {
+                let msg = "trait aliases cannot be `unsafe`";
+                self.struct_span_err(self.prev_span, msg)
+                    .span_label(self.prev_span, msg)
+                    .emit();
+            }
+            Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
+        } else {
+            // it's a normal trait
+            tps.where_clause = self.parse_where_clause()?;
+            self.expect(&token::OpenDelim(token::Brace))?;
+            let mut trait_items = vec![];
+            while !self.eat(&token::CloseDelim(token::Brace)) {
+                if let token::DocComment(_) = self.token.kind {
+                    if self.look_ahead(1,
+                    |tok| tok == &token::CloseDelim(token::Brace)) {
+                        self.diagnostic().struct_span_err_with_code(
+                            self.token.span,
+                            "found a documentation comment that doesn't document anything",
+                            DiagnosticId::Error("E0584".into()),
+                        )
+                        .help(
+                            "doc comments must come before what they document, maybe a \
+                            comment was intended with `//`?",
+                        )
+                        .emit();
+                        self.bump();
+                        continue;
+                    }
+                }
+                let mut at_end = false;
+                match self.parse_trait_item(&mut at_end) {
+                    Ok(item) => trait_items.push(item),
+                    Err(mut e) => {
+                        e.emit();
+                        if !at_end {
+                            self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
+                        }
+                    }
+                }
+            }
+            Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
+        }
+    }
+
+    /// Parses the items in a trait declaration.
+    pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
+        maybe_whole!(self, NtTraitItem, |x| x);
+        let attrs = self.parse_outer_attributes()?;
+        let mut unclosed_delims = vec![];
+        let (mut item, tokens) = self.collect_tokens(|this| {
+            let item = this.parse_trait_item_(at_end, attrs);
+            unclosed_delims.append(&mut this.unclosed_delims);
+            item
+        })?;
+        self.unclosed_delims.append(&mut unclosed_delims);
+        // See `parse_item` for why this clause is here.
+        if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
+            item.tokens = Some(tokens);
+        }
+        Ok(item)
+    }
+
+    fn parse_trait_item_(&mut self,
+                         at_end: &mut bool,
+                         mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
+        let lo = self.token.span;
+        self.eat_bad_pub();
+        let (name, node, generics) = if self.eat_keyword(kw::Type) {
+            self.parse_trait_item_assoc_ty()?
+        } else if self.is_const_item() {
+            self.expect_keyword(kw::Const)?;
+            let ident = self.parse_ident()?;
+            self.expect(&token::Colon)?;
+            let ty = self.parse_ty()?;
+            let default = if self.eat(&token::Eq) {
+                let expr = self.parse_expr()?;
+                self.expect(&token::Semi)?;
+                Some(expr)
+            } else {
+                self.expect(&token::Semi)?;
+                None
+            };
+            (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
+        } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
+            // trait item macro.
+            (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
+        } else {
+            let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
+
+            let ident = self.parse_ident()?;
+            let mut generics = self.parse_generics()?;
+
+            let decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
+                // This is somewhat dubious; We don't want to allow
+                // argument names to be left off if there is a
+                // definition...
+
+                // We don't allow argument names to be left off in edition 2018.
+                let is_name_required = p.token.span.rust_2018();
+                p.parse_arg_general(true, false, |_| is_name_required)
+            })?;
+            generics.where_clause = self.parse_where_clause()?;
+
+            let sig = ast::MethodSig {
+                header: FnHeader {
+                    unsafety,
+                    constness,
+                    abi,
+                    asyncness,
+                },
+                decl,
+            };
+
+            let body = match self.token.kind {
+                token::Semi => {
+                    self.bump();
+                    *at_end = true;
+                    debug!("parse_trait_methods(): parsing required method");
+                    None
+                }
+                token::OpenDelim(token::Brace) => {
+                    debug!("parse_trait_methods(): parsing provided method");
+                    *at_end = true;
+                    let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+                    attrs.extend(inner_attrs.iter().cloned());
+                    Some(body)
+                }
+                token::Interpolated(ref nt) => {
+                    match **nt {
+                        token::NtBlock(..) => {
+                            *at_end = true;
+                            let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+                            attrs.extend(inner_attrs.iter().cloned());
+                            Some(body)
+                        }
+                        _ => {
+                            return self.expected_semi_or_open_brace();
+                        }
+                    }
+                }
+                _ => {
+                    return self.expected_semi_or_open_brace();
+                }
+            };
+            (ident, ast::TraitItemKind::Method(sig, body), generics)
+        };
+
+        Ok(TraitItem {
+            id: ast::DUMMY_NODE_ID,
+            ident: name,
+            attrs,
+            generics,
+            node,
+            span: lo.to(self.prev_span),
+            tokens: None,
+        })
+    }
+
+    /// Parses the following grammar:
+    ///
+    ///     TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
+    fn parse_trait_item_assoc_ty(&mut self)
+        -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
+        let ident = self.parse_ident()?;
+        let mut generics = self.parse_generics()?;
+
+        // Parse optional colon and param bounds.
+        let bounds = if self.eat(&token::Colon) {
+            self.parse_generic_bounds(None)?
+        } else {
+            Vec::new()
+        };
+        generics.where_clause = self.parse_where_clause()?;
+
+        let default = if self.eat(&token::Eq) {
+            Some(self.parse_ty()?)
+        } else {
+            None
+        };
+        self.expect(&token::Semi)?;
+
+        Ok((ident, TraitItemKind::Type(bounds, default), generics))
+    }
+
+    /// Parses a `UseTree`.
+    ///
+    /// ```
+    /// USE_TREE = [`::`] `*` |
+    ///            [`::`] `{` USE_TREE_LIST `}` |
+    ///            PATH `::` `*` |
+    ///            PATH `::` `{` USE_TREE_LIST `}` |
+    ///            PATH [`as` IDENT]
+    /// ```
+    fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
+        let lo = self.token.span;
+
+        let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
+        let kind = if self.check(&token::OpenDelim(token::Brace)) ||
+                      self.check(&token::BinOp(token::Star)) ||
+                      self.is_import_coupler() {
+            // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
+            let mod_sep_ctxt = self.token.span.ctxt();
+            if self.eat(&token::ModSep) {
+                prefix.segments.push(
+                    PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
+                );
+            }
+
+            if self.eat(&token::BinOp(token::Star)) {
+                UseTreeKind::Glob
+            } else {
+                UseTreeKind::Nested(self.parse_use_tree_list()?)
+            }
+        } else {
+            // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
+            prefix = self.parse_path(PathStyle::Mod)?;
+
+            if self.eat(&token::ModSep) {
+                if self.eat(&token::BinOp(token::Star)) {
+                    UseTreeKind::Glob
+                } else {
+                    UseTreeKind::Nested(self.parse_use_tree_list()?)
+                }
+            } else {
+                UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
+            }
+        };
+
+        Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
+    }
+
+    /// Parses a `UseTreeKind::Nested(list)`.
+    ///
+    /// ```
+    /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
+    /// ```
+    fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
+        self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, ast::DUMMY_NODE_ID)))
+            .map(|(r, _)| r)
+    }
+
+    fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
+        if self.eat_keyword(kw::As) {
+            self.parse_ident_or_underscore().map(Some)
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
+        match self.token.kind {
+            token::Ident(name, false) if name == kw::Underscore => {
+                let span = self.token.span;
+                self.bump();
+                Ok(Ident::new(name, span))
+            }
+            _ => self.parse_ident(),
+        }
+    }
+
+    /// Parses `extern crate` links.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// extern crate foo;
+    /// extern crate bar as foo;
+    /// ```
+    fn parse_item_extern_crate(
+        &mut self,
+        lo: Span,
+        visibility: Visibility,
+        attrs: Vec<Attribute>
+    ) -> PResult<'a, P<Item>> {
+        // Accept `extern crate name-like-this` for better diagnostics
+        let orig_name = self.parse_crate_name_with_dashes()?;
+        let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
+            (rename, Some(orig_name.name))
+        } else {
+            (orig_name, None)
+        };
+        self.expect(&token::Semi)?;
+
+        let span = lo.to(self.prev_span);
+        Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
+    }
+
+    fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
+        let error_msg = "crate name using dashes are not valid in `extern crate` statements";
+        let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
+                              in the code";
+        let mut ident = if self.token.is_keyword(kw::SelfLower) {
+            self.parse_path_segment_ident()
+        } else {
+            self.parse_ident()
+        }?;
+        let mut idents = vec![];
+        let mut replacement = vec![];
+        let mut fixed_crate_name = false;
+        // Accept `extern crate name-like-this` for better diagnostics
+        let dash = token::BinOp(token::BinOpToken::Minus);
+        if self.token == dash {  // Do not include `-` as part of the expected tokens list
+            while self.eat(&dash) {
+                fixed_crate_name = true;
+                replacement.push((self.prev_span, "_".to_string()));
+                idents.push(self.parse_ident()?);
+            }
+        }
+        if fixed_crate_name {
+            let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
+            let mut fixed_name = format!("{}", ident.name);
+            for part in idents {
+                fixed_name.push_str(&format!("_{}", part.name));
+            }
+            ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
+
+            self.struct_span_err(fixed_name_sp, error_msg)
+                .span_label(fixed_name_sp, "dash-separated idents are not valid")
+                .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
+                .emit();
+        }
+        Ok(ident)
+    }
+
+    /// Parses an item-position function declaration.
+    fn parse_item_fn(
+        &mut self,
+        unsafety: Unsafety,
+        asyncness: Spanned<IsAsync>,
+        constness: Spanned<Constness>,
+        abi: Abi
+    ) -> PResult<'a, ItemInfo> {
+        let (ident, mut generics) = self.parse_fn_header()?;
+        let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
+        let decl = self.parse_fn_decl(allow_c_variadic)?;
+        generics.where_clause = self.parse_where_clause()?;
+        let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+        let header = FnHeader { unsafety, asyncness, constness, abi };
+        Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
+    }
+
+    /// Parses the name and optional generic types of a function header.
+    fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
+        let id = self.parse_ident()?;
+        let generics = self.parse_generics()?;
+        Ok((id, generics))
+    }
+
+    /// Parses the argument list and result type of a function declaration.
+    fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
+        let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
+        let ret_ty = self.parse_ret_ty(true)?;
+
+        Ok(P(FnDecl {
+            inputs: args,
+            output: ret_ty,
+            c_variadic,
+        }))
+    }
+
+    /// Parses `extern` for foreign ABIs modules.
+    ///
+    /// `extern` is expected to have been
+    /// consumed before calling this method.
+    ///
+    /// # Examples
+    ///
+    /// ```ignore (only-for-syntax-highlight)
+    /// extern "C" {}
+    /// extern {}
+    /// ```
+    fn parse_item_foreign_mod(
+        &mut self,
+        lo: Span,
+        opt_abi: Option<Abi>,
+        visibility: Visibility,
+        mut attrs: Vec<Attribute>,
+        extern_sp: Span,
+    ) -> PResult<'a, P<Item>> {
+        self.expect(&token::OpenDelim(token::Brace))?;
+
+        let abi = opt_abi.unwrap_or(Abi::C);
+
+        attrs.extend(self.parse_inner_attributes()?);
+
+        let mut foreign_items = vec![];
+        while !self.eat(&token::CloseDelim(token::Brace)) {
+            foreign_items.push(self.parse_foreign_item(extern_sp)?);
+        }
+
+        let prev_span = self.prev_span;
+        let m = ast::ForeignMod {
+            abi,
+            items: foreign_items
+        };
+        let invalid = Ident::invalid();
+        Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
+    }
+
+    /// Parses a foreign item.
+    crate fn parse_foreign_item(&mut self, extern_sp: Span) -> PResult<'a, ForeignItem> {
+        maybe_whole!(self, NtForeignItem, |ni| ni);
+
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+        let visibility = self.parse_visibility(false)?;
+
+        // FOREIGN STATIC ITEM
+        // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
+        if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
+            if self.token.is_keyword(kw::Const) {
+                self.diagnostic()
+                    .struct_span_err(self.token.span, "extern items cannot be `const`")
+                    .span_suggestion(
+                        self.token.span,
+                        "try using a static value",
+                        "static".to_owned(),
+                        Applicability::MachineApplicable
+                    ).emit();
+            }
+            self.bump(); // `static` or `const`
+            return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
+        }
+        // FOREIGN FUNCTION ITEM
+        if self.check_keyword(kw::Fn) {
+            return Ok(self.parse_item_foreign_fn(visibility, lo, attrs, extern_sp)?);
+        }
+        // FOREIGN TYPE ITEM
+        if self.check_keyword(kw::Type) {
+            return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
+        }
+
+        match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
+            Some(mac) => {
+                Ok(
+                    ForeignItem {
+                        ident: Ident::invalid(),
+                        span: lo.to(self.prev_span),
+                        id: ast::DUMMY_NODE_ID,
+                        attrs,
+                        vis: visibility,
+                        node: ForeignItemKind::Macro(mac),
+                    }
+                )
+            }
+            None => {
+                if !attrs.is_empty()  {
+                    self.expected_item_err(&attrs)?;
+                }
+
+                self.unexpected()
+            }
+        }
+    }
+
+    /// Parses a function declaration from a foreign module.
+    fn parse_item_foreign_fn(
+        &mut self,
+        vis: ast::Visibility,
+        lo: Span,
+        attrs: Vec<Attribute>,
+        extern_sp: Span,
+    ) -> PResult<'a, ForeignItem> {
+        self.expect_keyword(kw::Fn)?;
+
+        let (ident, mut generics) = self.parse_fn_header()?;
+        let decl = self.parse_fn_decl(true)?;
+        generics.where_clause = self.parse_where_clause()?;
+        let hi = self.token.span;
+        self.parse_semi_or_incorrect_foreign_fn_body(&ident, extern_sp)?;
+        Ok(ast::ForeignItem {
+            ident,
+            attrs,
+            node: ForeignItemKind::Fn(decl, generics),
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(hi),
+            vis,
+        })
+    }
+
+    /// Parses a static item from a foreign module.
+    /// Assumes that the `static` keyword is already parsed.
+    fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
+                                 -> PResult<'a, ForeignItem> {
+        let mutbl = self.parse_mutability();
+        let ident = self.parse_ident()?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+        let hi = self.token.span;
+        self.expect(&token::Semi)?;
+        Ok(ForeignItem {
+            ident,
+            attrs,
+            node: ForeignItemKind::Static(ty, mutbl),
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(hi),
+            vis,
+        })
+    }
+
+    /// Parses a type from a foreign module.
+    fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
+                             -> PResult<'a, ForeignItem> {
+        self.expect_keyword(kw::Type)?;
+
+        let ident = self.parse_ident()?;
+        let hi = self.token.span;
+        self.expect(&token::Semi)?;
+        Ok(ast::ForeignItem {
+            ident,
+            attrs,
+            node: ForeignItemKind::Ty,
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(hi),
+            vis
+        })
+    }
+
+    fn is_static_global(&mut self) -> bool {
+        if self.check_keyword(kw::Static) {
+            // Check if this could be a closure
+            !self.look_ahead(1, |token| {
+                if token.is_keyword(kw::Move) {
+                    return true;
+                }
+                match token.kind {
+                    token::BinOp(token::Or) | token::OrOr => true,
+                    _ => false,
+                }
+            })
+        } else {
+            false
+        }
+    }
+
+    fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
+        let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+        self.expect(&token::Eq)?;
+        let e = self.parse_expr()?;
+        self.expect(&token::Semi)?;
+        let item = match m {
+            Some(m) => ItemKind::Static(ty, m, e),
+            None => ItemKind::Const(ty, e),
+        };
+        Ok((id, item, None))
+    }
+
+    /// Parses `type Foo = Bar;` or returns `None`
+    /// without modifying the parser state.
+    fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
+        // This parses the grammar:
+        //     Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
+        if self.eat_keyword(kw::Type) {
+            Some(self.parse_type_alias())
+        } else {
+            None
+        }
+    }
+
+    /// Parses a type alias or opaque type.
+    fn parse_type_alias(&mut self) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
+        let ident = self.parse_ident()?;
+        let mut tps = self.parse_generics()?;
+        tps.where_clause = self.parse_where_clause()?;
+        self.expect(&token::Eq)?;
+        let alias = if self.check_keyword(kw::Impl) {
+            self.bump();
+            let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
+            AliasKind::OpaqueTy(bounds)
+        } else {
+            let ty = self.parse_ty()?;
+            AliasKind::Weak(ty)
+        };
+        self.expect(&token::Semi)?;
+        Ok((ident, alias, tps))
+    }
+
+    /// Parses an enum declaration.
+    fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
+        let id = self.parse_ident()?;
+        let mut generics = self.parse_generics()?;
+        generics.where_clause = self.parse_where_clause()?;
+        self.expect(&token::OpenDelim(token::Brace))?;
+
+        let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
+            self.recover_stmt();
+            self.eat(&token::CloseDelim(token::Brace));
+            e
+        })?;
+        Ok((id, ItemKind::Enum(enum_definition, generics), None))
+    }
+
+    /// Parses the part of an enum declaration following the `{`.
+    fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
+        let mut variants = Vec::new();
+        while self.token != token::CloseDelim(token::Brace) {
+            let variant_attrs = self.parse_outer_attributes()?;
+            let vlo = self.token.span;
+
+            self.eat_bad_pub();
+            let ident = self.parse_ident()?;
+
+            let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
+                // Parse a struct variant.
+                let (fields, recovered) = self.parse_record_struct_body()?;
+                VariantData::Struct(fields, recovered)
+            } else if self.check(&token::OpenDelim(token::Paren)) {
+                VariantData::Tuple(
+                    self.parse_tuple_struct_body()?,
+                    ast::DUMMY_NODE_ID,
+                )
+            } else {
+                VariantData::Unit(ast::DUMMY_NODE_ID)
+            };
+
+            let disr_expr = if self.eat(&token::Eq) {
+                Some(AnonConst {
+                    id: ast::DUMMY_NODE_ID,
+                    value: self.parse_expr()?,
+                })
+            } else {
+                None
+            };
+
+            let vr = ast::Variant {
+                ident,
+                id: ast::DUMMY_NODE_ID,
+                attrs: variant_attrs,
+                data: struct_def,
+                disr_expr,
+                span: vlo.to(self.prev_span),
+            };
+            variants.push(vr);
+
+            if !self.eat(&token::Comma) {
+                if self.token.is_ident() && !self.token.is_reserved_ident() {
+                    let sp = self.sess.source_map().next_point(self.prev_span);
+                    self.struct_span_err(sp, "missing comma")
+                        .span_suggestion_short(
+                            sp,
+                            "missing comma",
+                            ",".to_owned(),
+                            Applicability::MaybeIncorrect,
+                        )
+                        .emit();
+                } else {
+                    break;
+                }
+            }
+        }
+        self.expect(&token::CloseDelim(token::Brace))?;
+
+        Ok(ast::EnumDef { variants })
+    }
+
+    /// Parses `struct Foo { ... }`.
+    fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
+        let class_name = self.parse_ident()?;
+
+        let mut generics = self.parse_generics()?;
+
+        // There is a special case worth noting here, as reported in issue #17904.
+        // If we are parsing a tuple struct it is the case that the where clause
+        // should follow the field list. Like so:
+        //
+        // struct Foo<T>(T) where T: Copy;
+        //
+        // If we are parsing a normal record-style struct it is the case
+        // that the where clause comes before the body, and after the generics.
+        // So if we look ahead and see a brace or a where-clause we begin
+        // parsing a record style struct.
+        //
+        // Otherwise if we look ahead and see a paren we parse a tuple-style
+        // struct.
+
+        let vdata = if self.token.is_keyword(kw::Where) {
+            generics.where_clause = self.parse_where_clause()?;
+            if self.eat(&token::Semi) {
+                // If we see a: `struct Foo<T> where T: Copy;` style decl.
+                VariantData::Unit(ast::DUMMY_NODE_ID)
+            } else {
+                // If we see: `struct Foo<T> where T: Copy { ... }`
+                let (fields, recovered) = self.parse_record_struct_body()?;
+                VariantData::Struct(fields, recovered)
+            }
+        // No `where` so: `struct Foo<T>;`
+        } else if self.eat(&token::Semi) {
+            VariantData::Unit(ast::DUMMY_NODE_ID)
+        // Record-style struct definition
+        } else if self.token == token::OpenDelim(token::Brace) {
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
+        // Tuple-style struct definition with optional where-clause.
+        } else if self.token == token::OpenDelim(token::Paren) {
+            let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
+            generics.where_clause = self.parse_where_clause()?;
+            self.expect(&token::Semi)?;
+            body
+        } else {
+            let token_str = self.this_token_descr();
+            let mut err = self.fatal(&format!(
+                "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
+                token_str
+            ));
+            err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
+            return Err(err);
+        };
+
+        Ok((class_name, ItemKind::Struct(vdata, generics), None))
+    }
+
+    /// Parses `union Foo { ... }`.
+    fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
+        let class_name = self.parse_ident()?;
+
+        let mut generics = self.parse_generics()?;
+
+        let vdata = if self.token.is_keyword(kw::Where) {
+            generics.where_clause = self.parse_where_clause()?;
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
+        } else if self.token == token::OpenDelim(token::Brace) {
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
+        } else {
+            let token_str = self.this_token_descr();
+            let mut err = self.fatal(&format!(
+                "expected `where` or `{{` after union name, found {}", token_str));
+            err.span_label(self.token.span, "expected `where` or `{` after union name");
+            return Err(err);
+        };
+
+        Ok((class_name, ItemKind::Union(vdata, generics), None))
+    }
+
+    pub(super) fn is_union_item(&self) -> bool {
+        self.token.is_keyword(kw::Union) &&
+        self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
+    }
+
+    fn parse_record_struct_body(
+        &mut self,
+    ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
+        let mut fields = Vec::new();
+        let mut recovered = false;
+        if self.eat(&token::OpenDelim(token::Brace)) {
+            while self.token != token::CloseDelim(token::Brace) {
+                let field = self.parse_struct_decl_field().map_err(|e| {
+                    self.recover_stmt();
+                    recovered = true;
+                    e
+                });
+                match field {
+                    Ok(field) => fields.push(field),
+                    Err(mut err) => {
+                        err.emit();
+                    }
+                }
+            }
+            self.eat(&token::CloseDelim(token::Brace));
+        } else {
+            let token_str = self.this_token_descr();
+            let mut err = self.fatal(&format!(
+                    "expected `where`, or `{{` after struct name, found {}", token_str));
+            err.span_label(self.token.span, "expected `where`, or `{` after struct name");
+            return Err(err);
+        }
+
+        Ok((fields, recovered))
+    }
+
+    fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
+        // This is the case where we find `struct Foo<T>(T) where T: Copy;`
+        // Unit like structs are handled in parse_item_struct function
+        self.parse_paren_comma_seq(|p| {
+            let attrs = p.parse_outer_attributes()?;
+            let lo = p.token.span;
+            let vis = p.parse_visibility(true)?;
+            let ty = p.parse_ty()?;
+            Ok(StructField {
+                span: lo.to(ty.span),
+                vis,
+                ident: None,
+                id: ast::DUMMY_NODE_ID,
+                ty,
+                attrs,
+            })
+        }).map(|(r, _)| r)
+    }
+
+    /// Parses an element of a struct declaration.
+    fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+        let vis = self.parse_visibility(false)?;
+        self.parse_single_struct_field(lo, vis, attrs)
+    }
+
+    /// Parses a structure field declaration.
+    fn parse_single_struct_field(&mut self,
+                                     lo: Span,
+                                     vis: Visibility,
+                                     attrs: Vec<Attribute> )
+                                     -> PResult<'a, StructField> {
+        let mut seen_comma: bool = false;
+        let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
+        if self.token == token::Comma {
+            seen_comma = true;
+        }
+        match self.token.kind {
+            token::Comma => {
+                self.bump();
+            }
+            token::CloseDelim(token::Brace) => {}
+            token::DocComment(_) => {
+                let previous_span = self.prev_span;
+                let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
+                self.bump(); // consume the doc comment
+                let comma_after_doc_seen = self.eat(&token::Comma);
+                // `seen_comma` is always false, because we are inside doc block
+                // condition is here to make code more readable
+                if seen_comma == false && comma_after_doc_seen == true {
+                    seen_comma = true;
+                }
+                if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
+                    err.emit();
+                } else {
+                    if seen_comma == false {
+                        let sp = self.sess.source_map().next_point(previous_span);
+                        err.span_suggestion(
+                            sp,
+                            "missing comma here",
+                            ",".into(),
+                            Applicability::MachineApplicable
+                        );
+                    }
+                    return Err(err);
+                }
+            }
+            _ => {
+                let sp = self.sess.source_map().next_point(self.prev_span);
+                let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
+                                                                self.this_token_descr()));
+                if self.token.is_ident() {
+                    // This is likely another field; emit the diagnostic and keep going
+                    err.span_suggestion(
+                        sp,
+                        "try adding a comma",
+                        ",".into(),
+                        Applicability::MachineApplicable,
+                    );
+                    err.emit();
+                } else {
+                    return Err(err)
+                }
+            }
+        }
+        Ok(a_var)
+    }
+
+    /// Parses a structure field.
+    fn parse_name_and_ty(
+        &mut self,
+        lo: Span,
+        vis: Visibility,
+        attrs: Vec<Attribute>
+    ) -> PResult<'a, StructField> {
+        let name = self.parse_ident()?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+        Ok(StructField {
+            span: lo.to(self.prev_span),
+            ident: Some(name),
+            vis,
+            id: ast::DUMMY_NODE_ID,
+            ty,
+            attrs,
+        })
+    }
+
+    pub(super) fn eat_macro_def(
+        &mut self,
+        attrs: &[Attribute],
+        vis: &Visibility,
+        lo: Span
+    ) -> PResult<'a, Option<P<Item>>> {
+        let token_lo = self.token.span;
+        let (ident, def) = if self.eat_keyword(kw::Macro) {
+            let ident = self.parse_ident()?;
+            let tokens = if self.check(&token::OpenDelim(token::Brace)) {
+                match self.parse_token_tree() {
+                    TokenTree::Delimited(_, _, tts) => tts,
+                    _ => unreachable!(),
+                }
+            } else if self.check(&token::OpenDelim(token::Paren)) {
+                let args = self.parse_token_tree();
+                let body = if self.check(&token::OpenDelim(token::Brace)) {
+                    self.parse_token_tree()
+                } else {
+                    self.unexpected()?;
+                    unreachable!()
+                };
+                TokenStream::new(vec![
+                    args.into(),
+                    TokenTree::token(token::FatArrow, token_lo.to(self.prev_span)).into(),
+                    body.into(),
+                ])
+            } else {
+                self.unexpected()?;
+                unreachable!()
+            };
+
+            (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
+        } else if self.check_keyword(sym::macro_rules) &&
+                  self.look_ahead(1, |t| *t == token::Not) &&
+                  self.look_ahead(2, |t| t.is_ident()) {
+            let prev_span = self.prev_span;
+            self.complain_if_pub_macro(&vis.node, prev_span);
+            self.bump();
+            self.bump();
+
+            let ident = self.parse_ident()?;
+            let (delim, tokens) = self.expect_delimited_token_tree()?;
+            if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
+                self.report_invalid_macro_expansion_item();
+            }
+
+            (ident, ast::MacroDef { tokens, legacy: true })
+        } else {
+            return Ok(None);
+        };
+
+        let span = lo.to(self.prev_span);
+        Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
+    }
+
+    fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
+        match *vis {
+            VisibilityKind::Inherited => {}
+            _ => {
+                let mut err = if self.token.is_keyword(sym::macro_rules) {
+                    let mut err = self.diagnostic()
+                        .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
+                    err.span_suggestion(
+                        sp,
+                        "try exporting the macro",
+                        "#[macro_export]".to_owned(),
+                        Applicability::MaybeIncorrect // speculative
+                    );
+                    err
+                } else {
+                    let mut err = self.diagnostic()
+                        .struct_span_err(sp, "can't qualify macro invocation with `pub`");
+                    err.help("try adjusting the macro to put `pub` inside the invocation");
+                    err
+                };
+                err.emit();
+            }
+        }
+    }
+
+    fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
+               attrs: Vec<Attribute>) -> P<Item> {
+        P(Item {
+            ident,
+            attrs,
+            id: ast::DUMMY_NODE_ID,
+            node,
+            vis,
+            span,
+            tokens: None,
+        })
+    }
+}
diff --git a/src/libsyntax/parse/parser/module.rs b/src/libsyntax/parse/parser/module.rs
new file mode 100644
index 00000000000..3f6f87b1c44
--- /dev/null
+++ b/src/libsyntax/parse/parser/module.rs
@@ -0,0 +1,332 @@
+use super::{Parser, PResult};
+use super::item::ItemInfo;
+
+use crate::attr;
+use crate::ast::{self, Ident, Attribute, ItemKind, Mod, Crate};
+use crate::parse::{new_sub_parser_from_file, DirectoryOwnership};
+use crate::parse::token::{self, TokenKind};
+use crate::parse::diagnostics::{Error};
+use crate::source_map::{SourceMap, Span, DUMMY_SP, FileName};
+use crate::symbol::sym;
+
+use std::path::{self, Path, PathBuf};
+
+/// Information about the path to a module.
+pub struct ModulePath {
+    name: String,
+    path_exists: bool,
+    pub result: Result<ModulePathSuccess, Error>,
+}
+
+pub struct ModulePathSuccess {
+    pub path: PathBuf,
+    pub directory_ownership: DirectoryOwnership,
+    warn: bool,
+}
+
+impl<'a> Parser<'a> {
+    /// Parses a source module as a crate. This is the main entry point for the parser.
+    pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
+        let lo = self.token.span;
+        let krate = Ok(ast::Crate {
+            attrs: self.parse_inner_attributes()?,
+            module: self.parse_mod_items(&token::Eof, lo)?,
+            span: lo.to(self.token.span),
+        });
+        krate
+    }
+
+    /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
+    pub(super) fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
+        let (in_cfg, outer_attrs) = {
+            let mut strip_unconfigured = crate::config::StripUnconfigured {
+                sess: self.sess,
+                features: None, // don't perform gated feature checking
+            };
+            let mut outer_attrs = outer_attrs.to_owned();
+            strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
+            (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
+        };
+
+        let id_span = self.token.span;
+        let id = self.parse_ident()?;
+        if self.eat(&token::Semi) {
+            if in_cfg && self.recurse_into_file_modules {
+                // This mod is in an external file. Let's go get it!
+                let ModulePathSuccess { path, directory_ownership, warn } =
+                    self.submod_path(id, &outer_attrs, id_span)?;
+                let (module, mut attrs) =
+                    self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
+                // Record that we fetched the mod from an external file
+                if warn {
+                    let attr = attr::mk_attr_outer(
+                        attr::mk_word_item(Ident::with_dummy_span(sym::warn_directory_ownership)));
+                    attr::mark_known(&attr);
+                    attrs.push(attr);
+                }
+                Ok((id, ItemKind::Mod(module), Some(attrs)))
+            } else {
+                let placeholder = ast::Mod {
+                    inner: DUMMY_SP,
+                    items: Vec::new(),
+                    inline: false
+                };
+                Ok((id, ItemKind::Mod(placeholder), None))
+            }
+        } else {
+            let old_directory = self.directory.clone();
+            self.push_directory(id, &outer_attrs);
+
+            self.expect(&token::OpenDelim(token::Brace))?;
+            let mod_inner_lo = self.token.span;
+            let attrs = self.parse_inner_attributes()?;
+            let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
+
+            self.directory = old_directory;
+            Ok((id, ItemKind::Mod(module), Some(attrs)))
+        }
+    }
+
+    /// Given a termination token, parses all of the items in a module.
+    fn parse_mod_items(&mut self, term: &TokenKind, inner_lo: Span) -> PResult<'a, Mod> {
+        let mut items = vec![];
+        while let Some(item) = self.parse_item()? {
+            items.push(item);
+            self.maybe_consume_incorrect_semicolon(&items);
+        }
+
+        if !self.eat(term) {
+            let token_str = self.this_token_descr();
+            if !self.maybe_consume_incorrect_semicolon(&items) {
+                let mut err = self.fatal(&format!("expected item, found {}", token_str));
+                err.span_label(self.token.span, "expected item");
+                return Err(err);
+            }
+        }
+
+        let hi = if self.token.span.is_dummy() {
+            inner_lo
+        } else {
+            self.prev_span
+        };
+
+        Ok(Mod {
+            inner: inner_lo.to(hi),
+            items,
+            inline: true
+        })
+    }
+
+    fn submod_path(
+        &mut self,
+        id: ast::Ident,
+        outer_attrs: &[Attribute],
+        id_sp: Span
+    ) -> PResult<'a, ModulePathSuccess> {
+        if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
+            return Ok(ModulePathSuccess {
+                directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
+                    // All `#[path]` files are treated as though they are a `mod.rs` file.
+                    // This means that `mod foo;` declarations inside `#[path]`-included
+                    // files are siblings,
+                    //
+                    // Note that this will produce weirdness when a file named `foo.rs` is
+                    // `#[path]` included and contains a `mod foo;` declaration.
+                    // If you encounter this, it's your own darn fault :P
+                    Some(_) => DirectoryOwnership::Owned { relative: None },
+                    _ => DirectoryOwnership::UnownedViaMod(true),
+                },
+                path,
+                warn: false,
+            });
+        }
+
+        let relative = match self.directory.ownership {
+            DirectoryOwnership::Owned { relative } => relative,
+            DirectoryOwnership::UnownedViaBlock |
+            DirectoryOwnership::UnownedViaMod(_) => None,
+        };
+        let paths = Parser::default_submod_path(
+                        id, relative, &self.directory.path, self.sess.source_map());
+
+        match self.directory.ownership {
+            DirectoryOwnership::Owned { .. } => {
+                paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
+            },
+            DirectoryOwnership::UnownedViaBlock => {
+                let msg =
+                    "Cannot declare a non-inline module inside a block \
+                    unless it has a path attribute";
+                let mut err = self.diagnostic().struct_span_err(id_sp, msg);
+                if paths.path_exists {
+                    let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
+                                      paths.name);
+                    err.span_note(id_sp, &msg);
+                }
+                Err(err)
+            }
+            DirectoryOwnership::UnownedViaMod(warn) => {
+                if warn {
+                    if let Ok(result) = paths.result {
+                        return Ok(ModulePathSuccess { warn: true, ..result });
+                    }
+                }
+                let mut err = self.diagnostic().struct_span_err(id_sp,
+                    "cannot declare a new module at this location");
+                if !id_sp.is_dummy() {
+                    let src_path = self.sess.source_map().span_to_filename(id_sp);
+                    if let FileName::Real(src_path) = src_path {
+                        if let Some(stem) = src_path.file_stem() {
+                            let mut dest_path = src_path.clone();
+                            dest_path.set_file_name(stem);
+                            dest_path.push("mod.rs");
+                            err.span_note(id_sp,
+                                    &format!("maybe move this module `{}` to its own \
+                                                directory via `{}`", src_path.display(),
+                                            dest_path.display()));
+                        }
+                    }
+                }
+                if paths.path_exists {
+                    err.span_note(id_sp,
+                                  &format!("... or maybe `use` the module `{}` instead \
+                                            of possibly redeclaring it",
+                                           paths.name));
+                }
+                Err(err)
+            }
+        }
+    }
+
+    pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
+        if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
+            let s = s.as_str();
+
+            // On windows, the base path might have the form
+            // `\\?\foo\bar` in which case it does not tolerate
+            // mixed `/` and `\` separators, so canonicalize
+            // `/` to `\`.
+            #[cfg(windows)]
+            let s = s.replace("/", "\\");
+            Some(dir_path.join(s))
+        } else {
+            None
+        }
+    }
+
+    /// Returns a path to a module.
+    pub fn default_submod_path(
+        id: ast::Ident,
+        relative: Option<ast::Ident>,
+        dir_path: &Path,
+        source_map: &SourceMap) -> ModulePath
+    {
+        // If we're in a foo.rs file instead of a mod.rs file,
+        // we need to look for submodules in
+        // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
+        // `./<id>.rs` and `./<id>/mod.rs`.
+        let relative_prefix_string;
+        let relative_prefix = if let Some(ident) = relative {
+            relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
+            &relative_prefix_string
+        } else {
+            ""
+        };
+
+        let mod_name = id.to_string();
+        let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
+        let secondary_path_str = format!("{}{}{}mod.rs",
+                                         relative_prefix, mod_name, path::MAIN_SEPARATOR);
+        let default_path = dir_path.join(&default_path_str);
+        let secondary_path = dir_path.join(&secondary_path_str);
+        let default_exists = source_map.file_exists(&default_path);
+        let secondary_exists = source_map.file_exists(&secondary_path);
+
+        let result = match (default_exists, secondary_exists) {
+            (true, false) => Ok(ModulePathSuccess {
+                path: default_path,
+                directory_ownership: DirectoryOwnership::Owned {
+                    relative: Some(id),
+                },
+                warn: false,
+            }),
+            (false, true) => Ok(ModulePathSuccess {
+                path: secondary_path,
+                directory_ownership: DirectoryOwnership::Owned {
+                    relative: None,
+                },
+                warn: false,
+            }),
+            (false, false) => Err(Error::FileNotFoundForModule {
+                mod_name: mod_name.clone(),
+                default_path: default_path_str,
+                secondary_path: secondary_path_str,
+                dir_path: dir_path.display().to_string(),
+            }),
+            (true, true) => Err(Error::DuplicatePaths {
+                mod_name: mod_name.clone(),
+                default_path: default_path_str,
+                secondary_path: secondary_path_str,
+            }),
+        };
+
+        ModulePath {
+            name: mod_name,
+            path_exists: default_exists || secondary_exists,
+            result,
+        }
+    }
+
+    /// Reads a module from a source file.
+    fn eval_src_mod(
+        &mut self,
+        path: PathBuf,
+        directory_ownership: DirectoryOwnership,
+        name: String,
+        id_sp: Span,
+    ) -> PResult<'a, (Mod, Vec<Attribute>)> {
+        let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
+        if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
+            let mut err = String::from("circular modules: ");
+            let len = included_mod_stack.len();
+            for p in &included_mod_stack[i.. len] {
+                err.push_str(&p.to_string_lossy());
+                err.push_str(" -> ");
+            }
+            err.push_str(&path.to_string_lossy());
+            return Err(self.span_fatal(id_sp, &err[..]));
+        }
+        included_mod_stack.push(path.clone());
+        drop(included_mod_stack);
+
+        let mut p0 =
+            new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
+        p0.cfg_mods = self.cfg_mods;
+        let mod_inner_lo = p0.token.span;
+        let mod_attrs = p0.parse_inner_attributes()?;
+        let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
+        m0.inline = false;
+        self.sess.included_mod_stack.borrow_mut().pop();
+        Ok((m0, mod_attrs))
+    }
+
+    fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
+        if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
+            self.directory.path.to_mut().push(&path.as_str());
+            self.directory.ownership = DirectoryOwnership::Owned { relative: None };
+        } else {
+            // We have to push on the current module name in the case of relative
+            // paths in order to ensure that any additional module paths from inline
+            // `mod x { ... }` come after the relative extension.
+            //
+            // For example, a `mod z { ... }` inside `x/y.rs` should set the current
+            // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
+            if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
+                if let Some(ident) = relative.take() { // remove the relative offset
+                    self.directory.path.to_mut().push(ident.as_str());
+                }
+            }
+            self.directory.path.to_mut().push(&id.as_str());
+        }
+    }
+}
diff --git a/src/libsyntax/parse/parser/pat.rs b/src/libsyntax/parse/parser/pat.rs
new file mode 100644
index 00000000000..fd458aec743
--- /dev/null
+++ b/src/libsyntax/parse/parser/pat.rs
@@ -0,0 +1,708 @@
+use super::{Parser, PResult, PathStyle};
+
+use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+use crate::ptr::P;
+use crate::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
+use crate::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
+use crate::parse::token::{self};
+use crate::print::pprust;
+use crate::source_map::{respan, Span, Spanned};
+use crate::symbol::kw;
+use crate::ThinVec;
+
+use errors::{Applicability, DiagnosticBuilder};
+
+impl<'a> Parser<'a> {
+    /// Parses a pattern.
+    pub fn parse_pat(
+        &mut self,
+        expected: Option<&'static str>
+    ) -> PResult<'a, P<Pat>> {
+        self.parse_pat_with_range_pat(true, expected)
+    }
+
+    /// Parses patterns, separated by '|' s.
+    pub(super) fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
+        // Allow a '|' before the pats (RFC 1925 + RFC 2530)
+        self.eat(&token::BinOp(token::Or));
+
+        let mut pats = Vec::new();
+        loop {
+            pats.push(self.parse_top_level_pat()?);
+
+            if self.token == token::OrOr {
+                self.struct_span_err(self.token.span, "unexpected token `||` after pattern")
+                    .span_suggestion(
+                        self.token.span,
+                        "use a single `|` to specify multiple patterns",
+                        "|".to_owned(),
+                        Applicability::MachineApplicable
+                    )
+                    .emit();
+                self.bump();
+            } else if self.eat(&token::BinOp(token::Or)) {
+                // This is a No-op. Continue the loop to parse the next
+                // pattern.
+            } else {
+                return Ok(pats);
+            }
+        };
+    }
+
+    /// A wrapper around `parse_pat` with some special error handling for the
+    /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
+    /// to subpatterns within such).
+    pub(super) fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
+        let pat = self.parse_pat(None)?;
+        if self.token == token::Comma {
+            // An unexpected comma after a top-level pattern is a clue that the
+            // user (perhaps more accustomed to some other language) forgot the
+            // parentheses in what should have been a tuple pattern; return a
+            // suggestion-enhanced error here rather than choking on the comma
+            // later.
+            let comma_span = self.token.span;
+            self.bump();
+            if let Err(mut err) = self.skip_pat_list() {
+                // We didn't expect this to work anyway; we just wanted
+                // to advance to the end of the comma-sequence so we know
+                // the span to suggest parenthesizing
+                err.cancel();
+            }
+            let seq_span = pat.span.to(self.prev_span);
+            let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
+            if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
+                err.span_suggestion(
+                    seq_span,
+                    "try adding parentheses to match on a tuple..",
+                    format!("({})", seq_snippet),
+                    Applicability::MachineApplicable
+                ).span_suggestion(
+                    seq_span,
+                    "..or a vertical bar to match on multiple alternatives",
+                    format!("{}", seq_snippet.replace(",", " |")),
+                    Applicability::MachineApplicable
+                );
+            }
+            return Err(err);
+        }
+        Ok(pat)
+    }
+
+    /// Parse and throw away a parentesized comma separated
+    /// sequence of patterns until `)` is reached.
+    fn skip_pat_list(&mut self) -> PResult<'a, ()> {
+        while !self.check(&token::CloseDelim(token::Paren)) {
+            self.parse_pat(None)?;
+            if !self.eat(&token::Comma) {
+                return Ok(())
+            }
+        }
+        Ok(())
+    }
+
+    /// Parses a pattern, that may be a or-pattern (e.g. `Some(Foo | Bar)`).
+    fn parse_pat_with_or(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
+        // Parse the first pattern.
+        let first_pat = self.parse_pat(expected)?;
+
+        // If the next token is not a `|`, this is not an or-pattern and
+        // we should exit here.
+        if !self.check(&token::BinOp(token::Or)) {
+            return Ok(first_pat)
+        }
+
+        let lo = first_pat.span;
+
+        let mut pats = vec![first_pat];
+
+        while self.eat(&token::BinOp(token::Or)) {
+            pats.push(self.parse_pat_with_range_pat(
+                true, expected
+            )?);
+        }
+
+        let or_pattern_span = lo.to(self.prev_span);
+
+        self.sess.or_pattern_spans.borrow_mut().push(or_pattern_span);
+
+        Ok(self.mk_pat(or_pattern_span, PatKind::Or(pats)))
+    }
+
+    /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
+    /// allowed).
+    fn parse_pat_with_range_pat(
+        &mut self,
+        allow_range_pat: bool,
+        expected: Option<&'static str>,
+    ) -> PResult<'a, P<Pat>> {
+        maybe_recover_from_interpolated_ty_qpath!(self, true);
+        maybe_whole!(self, NtPat, |x| x);
+
+        let lo = self.token.span;
+        let pat = match self.token.kind {
+            token::BinOp(token::And) | token::AndAnd => self.parse_pat_deref(expected)?,
+            token::OpenDelim(token::Paren) => self.parse_pat_tuple_or_parens()?,
+            token::OpenDelim(token::Bracket) => {
+                // Parse `[pat, pat,...]` as a slice pattern.
+                PatKind::Slice(self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat(None))?.0)
+            }
+            token::DotDot => {
+                self.bump();
+                if self.is_pat_range_end_start() {
+                    // Parse `..42` for recovery.
+                    self.parse_pat_range_to(RangeEnd::Excluded, "..")?
+                } else {
+                    // A rest pattern `..`.
+                    PatKind::Rest
+                }
+            }
+            token::DotDotEq => {
+                // Parse `..=42` for recovery.
+                self.bump();
+                self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?
+            }
+            token::DotDotDot => {
+                // Parse `...42` for recovery.
+                self.bump();
+                self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?
+            }
+            // At this point, token != &, &&, (, [
+            _ => if self.eat_keyword(kw::Underscore) {
+                // Parse _
+                PatKind::Wild
+            } else if self.eat_keyword(kw::Mut) {
+                self.recover_pat_ident_mut_first()?
+            } else if self.eat_keyword(kw::Ref) {
+                // Parse ref ident @ pat / ref mut ident @ pat
+                let mutbl = self.parse_mutability();
+                self.parse_pat_ident(BindingMode::ByRef(mutbl))?
+            } else if self.eat_keyword(kw::Box) {
+                // Parse `box pat`
+                PatKind::Box(self.parse_pat_with_range_pat(false, None)?)
+            } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
+                      self.parse_as_ident() {
+                // Parse `ident @ pat`
+                // This can give false positives and parse nullary enums,
+                // they are dealt with later in resolve.
+                self.parse_pat_ident(BindingMode::ByValue(Mutability::Immutable))?
+            } else if self.token.is_path_start() {
+                // Parse pattern starting with a path
+                let (qself, path) = if self.eat_lt() {
+                    // Parse a qualified path
+                    let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+                    (Some(qself), path)
+                } else {
+                    // Parse an unqualified path
+                    (None, self.parse_path(PathStyle::Expr)?)
+                };
+                match self.token.kind {
+                    token::Not if qself.is_none() => self.parse_pat_mac_invoc(lo, path)?,
+                    token::DotDotDot | token::DotDotEq | token::DotDot => {
+                        self.parse_pat_range_starting_with_path(lo, qself, path)?
+                    }
+                    token::OpenDelim(token::Brace) => self.parse_pat_struct(qself, path)?,
+                    token::OpenDelim(token::Paren) => self.parse_pat_tuple_struct(qself, path)?,
+                    _ => PatKind::Path(qself, path),
+                }
+            } else {
+                // Try to parse everything else as literal with optional minus
+                match self.parse_literal_maybe_minus() {
+                    Ok(begin)
+                        if self.check(&token::DotDot)
+                            || self.check(&token::DotDotEq)
+                            || self.check(&token::DotDotDot) =>
+                    {
+                        self.parse_pat_range_starting_with_lit(begin)?
+                    }
+                    Ok(begin) => PatKind::Lit(begin),
+                    Err(err) => return self.fatal_unexpected_non_pat(err, expected),
+                }
+            }
+        };
+
+        let pat = self.mk_pat(lo.to(self.prev_span), pat);
+        let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
+
+        if !allow_range_pat {
+            self.ban_pat_range_if_ambiguous(&pat)?
+        }
+
+        Ok(pat)
+    }
+
+    /// Ban a range pattern if it has an ambiguous interpretation.
+    fn ban_pat_range_if_ambiguous(&self, pat: &Pat) -> PResult<'a, ()> {
+        match pat.node {
+            PatKind::Range(
+                .., Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
+            ) => return Ok(()),
+            PatKind::Range(..) => {}
+            _ => return Ok(()),
+        }
+
+        let mut err = self.struct_span_err(
+            pat.span,
+            "the range pattern here has ambiguous interpretation",
+        );
+        err.span_suggestion(
+            pat.span,
+            "add parentheses to clarify the precedence",
+            format!("({})", pprust::pat_to_string(&pat)),
+            // "ambiguous interpretation" implies that we have to be guessing
+            Applicability::MaybeIncorrect
+        );
+        Err(err)
+    }
+
+    /// Parse `&pat` / `&mut pat`.
+    fn parse_pat_deref(&mut self, expected: Option<&'static str>) -> PResult<'a, PatKind> {
+        self.expect_and()?;
+        let mutbl = self.parse_mutability();
+
+        if let token::Lifetime(name) = self.token.kind {
+            let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
+            err.span_label(self.token.span, "unexpected lifetime");
+            return Err(err);
+        }
+
+        let subpat = self.parse_pat_with_range_pat(false, expected)?;
+        Ok(PatKind::Ref(subpat, mutbl))
+    }
+
+    /// Parse a tuple or parenthesis pattern.
+    fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
+        let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
+            p.parse_pat_with_or(None)
+        })?;
+
+        // Here, `(pat,)` is a tuple pattern.
+        // For backward compatibility, `(..)` is a tuple pattern as well.
+        Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
+            PatKind::Paren(fields.into_iter().nth(0).unwrap())
+        } else {
+            PatKind::Tuple(fields)
+        })
+    }
+
+    /// Recover on `mut ref? ident @ pat` and suggest
+    /// that the order of `mut` and `ref` is incorrect.
+    fn recover_pat_ident_mut_first(&mut self) -> PResult<'a, PatKind> {
+        let mutref_span = self.prev_span.to(self.token.span);
+        let binding_mode = if self.eat_keyword(kw::Ref) {
+            self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
+                .span_suggestion(
+                    mutref_span,
+                    "try switching the order",
+                    "ref mut".into(),
+                    Applicability::MachineApplicable
+                )
+                .emit();
+            BindingMode::ByRef(Mutability::Mutable)
+        } else {
+            BindingMode::ByValue(Mutability::Mutable)
+        };
+        self.parse_pat_ident(binding_mode)
+    }
+
+    /// Parse macro invocation
+    fn parse_pat_mac_invoc(&mut self, lo: Span, path: Path) -> PResult<'a, PatKind> {
+        self.bump();
+        let (delim, tts) = self.expect_delimited_token_tree()?;
+        let mac = Mac {
+            path,
+            tts,
+            delim,
+            span: lo.to(self.prev_span),
+            prior_type_ascription: self.last_type_ascription,
+        };
+        Ok(PatKind::Mac(mac))
+    }
+
+    /// Parse a range pattern `$path $form $end?` where `$form = ".." | "..." | "..=" ;`.
+    /// The `$path` has already been parsed and the next token is the `$form`.
+    fn parse_pat_range_starting_with_path(
+        &mut self,
+        lo: Span,
+        qself: Option<QSelf>,
+        path: Path
+    ) -> PResult<'a, PatKind> {
+        let (end_kind, form) = match self.token.kind {
+            token::DotDot => (RangeEnd::Excluded, ".."),
+            token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
+            token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
+            _ => panic!("can only parse `..`/`...`/`..=` for ranges (checked above)"),
+        };
+        let op_span = self.token.span;
+        // Parse range
+        let span = lo.to(self.prev_span);
+        let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
+        self.bump();
+        let end = self.parse_pat_range_end_opt(&begin, form)?;
+        Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
+    }
+
+    /// Parse a range pattern `$literal $form $end?` where `$form = ".." | "..." | "..=" ;`.
+    /// The `$path` has already been parsed and the next token is the `$form`.
+    fn parse_pat_range_starting_with_lit(&mut self, begin: P<Expr>) -> PResult<'a, PatKind> {
+        let op_span = self.token.span;
+        let (end_kind, form) = if self.eat(&token::DotDotDot) {
+            (RangeEnd::Included(RangeSyntax::DotDotDot), "...")
+        } else if self.eat(&token::DotDotEq) {
+            (RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
+        } else if self.eat(&token::DotDot) {
+            (RangeEnd::Excluded, "..")
+        } else {
+            panic!("impossible case: we already matched on a range-operator token")
+        };
+        let end = self.parse_pat_range_end_opt(&begin, form)?;
+        Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
+    }
+
+    fn fatal_unexpected_non_pat(
+        &mut self,
+        mut err: DiagnosticBuilder<'a>,
+        expected: Option<&'static str>,
+    ) -> PResult<'a, P<Pat>> {
+        self.cancel(&mut err);
+
+        let expected = expected.unwrap_or("pattern");
+        let msg = format!("expected {}, found {}", expected, self.this_token_descr());
+
+        let mut err = self.fatal(&msg);
+        err.span_label(self.token.span, format!("expected {}", expected));
+
+        let sp = self.sess.source_map().start_point(self.token.span);
+        if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
+            self.sess.expr_parentheses_needed(&mut err, *sp, None);
+        }
+
+        Err(err)
+    }
+
+    // Helper function to decide whether to parse as ident binding
+    // or to try to do something more complex like range patterns.
+    fn parse_as_ident(&mut self) -> bool {
+        self.look_ahead(1, |t| match t.kind {
+            token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
+            token::DotDotDot | token::DotDotEq | token::DotDot |
+            token::ModSep | token::Not => false,
+            _ => true,
+        })
+    }
+
+    /// Is the current token suitable as the start of a range patterns end?
+    fn is_pat_range_end_start(&self) -> bool {
+        self.token.is_path_start() // e.g. `MY_CONST`;
+            || self.token == token::Dot // e.g. `.5` for recovery;
+            || self.token.can_begin_literal_or_bool() // e.g. `42`.
+            || self.token.is_whole_expr()
+    }
+
+    /// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
+    fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
+        let lo = self.prev_span;
+        let end = self.parse_pat_range_end()?;
+        let range_span = lo.to(end.span);
+        let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
+
+        self.diagnostic()
+            .struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
+            .span_suggestion(
+                range_span,
+                "try using the minimum value for the type",
+                format!("MIN{}{}", form, pprust::expr_to_string(&end)),
+                Applicability::HasPlaceholders,
+            )
+            .emit();
+
+        Ok(PatKind::Range(begin, end, respan(lo, re)))
+    }
+
+    /// Parse the end of a `X..Y`, `X..=Y`, or `X...Y` range pattern  or recover
+    /// if that end is missing treating it as `X..`, `X..=`, or `X...` respectively.
+    fn parse_pat_range_end_opt(&mut self, begin: &Expr, form: &str) -> PResult<'a, P<Expr>> {
+        if self.is_pat_range_end_start() {
+            // Parsing e.g. `X..=Y`.
+            self.parse_pat_range_end()
+        } else {
+            // Parsing e.g. `X..`.
+            let range_span = begin.span.to(self.prev_span);
+
+            self.diagnostic()
+                .struct_span_err(
+                    range_span,
+                    &format!("`X{}` range patterns are not supported", form),
+                )
+                .span_suggestion(
+                    range_span,
+                    "try using the maximum value for the type",
+                    format!("{}{}MAX", pprust::expr_to_string(&begin), form),
+                    Applicability::HasPlaceholders,
+                )
+                .emit();
+
+            Ok(self.mk_expr(range_span, ExprKind::Err, ThinVec::new()))
+        }
+    }
+
+    fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
+        if self.token.is_path_start() {
+            let lo = self.token.span;
+            let (qself, path) = if self.eat_lt() {
+                // Parse a qualified path
+                let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
+                (Some(qself), path)
+            } else {
+                // Parse an unqualified path
+                (None, self.parse_path(PathStyle::Expr)?)
+            };
+            let hi = self.prev_span;
+            Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
+        } else {
+            self.parse_literal_maybe_minus()
+        }
+    }
+
+    /// Parses `ident` or `ident @ pat`.
+    /// Used by the copy foo and ref foo patterns to give a good
+    /// error message when parsing mistakes like `ref foo(a, b)`.
+    fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
+        let ident = self.parse_ident()?;
+        let sub = if self.eat(&token::At) {
+            Some(self.parse_pat(Some("binding pattern"))?)
+        } else {
+            None
+        };
+
+        // Just to be friendly, if they write something like `ref Some(i)`,
+        // we end up here with `(` as the current token.
+        // This shortly leads to a parse error. Note that if there is no explicit
+        // binding mode then we do not end up here, because the lookahead
+        // will direct us over to `parse_enum_variant()`.
+        if self.token == token::OpenDelim(token::Paren) {
+            return Err(self.span_fatal(
+                self.prev_span,
+                "expected identifier, found enum pattern",
+            ))
+        }
+
+        Ok(PatKind::Ident(binding_mode, ident, sub))
+    }
+
+    /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
+    fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
+        if qself.is_some() {
+            let msg = "unexpected `{` after qualified path";
+            let mut err = self.fatal(msg);
+            err.span_label(self.token.span, msg);
+            return Err(err);
+        }
+
+        self.bump();
+        let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
+            e.emit();
+            self.recover_stmt();
+            (vec![], true)
+        });
+        self.bump();
+        Ok(PatKind::Struct(path, fields, etc))
+    }
+
+    /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
+    fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
+        if qself.is_some() {
+            let msg = "unexpected `(` after qualified path";
+            let mut err = self.fatal(msg);
+            err.span_label(self.token.span, msg);
+            return Err(err);
+        }
+        let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat_with_or(None))?;
+        Ok(PatKind::TupleStruct(path, fields))
+    }
+
+    /// Parses the fields of a struct-like pattern.
+    fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<FieldPat>, bool)> {
+        let mut fields = Vec::new();
+        let mut etc = false;
+        let mut ate_comma = true;
+        let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
+        let mut etc_span = None;
+
+        while self.token != token::CloseDelim(token::Brace) {
+            let attrs = match self.parse_outer_attributes() {
+                Ok(attrs) => attrs,
+                Err(err) => {
+                    if let Some(mut delayed) = delayed_err {
+                        delayed.emit();
+                    }
+                    return Err(err);
+                },
+            };
+            let lo = self.token.span;
+
+            // check that a comma comes after every field
+            if !ate_comma {
+                let err = self.struct_span_err(self.prev_span, "expected `,`");
+                if let Some(mut delayed) = delayed_err {
+                    delayed.emit();
+                }
+                return Err(err);
+            }
+            ate_comma = false;
+
+            if self.check(&token::DotDot) || self.token == token::DotDotDot {
+                etc = true;
+                let mut etc_sp = self.token.span;
+
+                self.recover_one_fewer_dotdot();
+                self.bump();  // `..` || `...`
+
+                if self.token == token::CloseDelim(token::Brace) {
+                    etc_span = Some(etc_sp);
+                    break;
+                }
+                let token_str = self.this_token_descr();
+                let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
+
+                err.span_label(self.token.span, "expected `}`");
+                let mut comma_sp = None;
+                if self.token == token::Comma { // Issue #49257
+                    let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
+                    etc_sp = etc_sp.to(nw_span);
+                    err.span_label(etc_sp,
+                                   "`..` must be at the end and cannot have a trailing comma");
+                    comma_sp = Some(self.token.span);
+                    self.bump();
+                    ate_comma = true;
+                }
+
+                etc_span = Some(etc_sp.until(self.token.span));
+                if self.token == token::CloseDelim(token::Brace) {
+                    // If the struct looks otherwise well formed, recover and continue.
+                    if let Some(sp) = comma_sp {
+                        err.span_suggestion_short(
+                            sp,
+                            "remove this comma",
+                            String::new(),
+                            Applicability::MachineApplicable,
+                        );
+                    }
+                    err.emit();
+                    break;
+                } else if self.token.is_ident() && ate_comma {
+                    // Accept fields coming after `..,`.
+                    // This way we avoid "pattern missing fields" errors afterwards.
+                    // We delay this error until the end in order to have a span for a
+                    // suggested fix.
+                    if let Some(mut delayed_err) = delayed_err {
+                        delayed_err.emit();
+                        return Err(err);
+                    } else {
+                        delayed_err = Some(err);
+                    }
+                } else {
+                    if let Some(mut err) = delayed_err {
+                        err.emit();
+                    }
+                    return Err(err);
+                }
+            }
+
+            fields.push(match self.parse_pat_field(lo, attrs) {
+                Ok(field) => field,
+                Err(err) => {
+                    if let Some(mut delayed_err) = delayed_err {
+                        delayed_err.emit();
+                    }
+                    return Err(err);
+                }
+            });
+            ate_comma = self.eat(&token::Comma);
+        }
+
+        if let Some(mut err) = delayed_err {
+            if let Some(etc_span) = etc_span {
+                err.multipart_suggestion(
+                    "move the `..` to the end of the field list",
+                    vec![
+                        (etc_span, String::new()),
+                        (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
+                    ],
+                    Applicability::MachineApplicable,
+                );
+            }
+            err.emit();
+        }
+        return Ok((fields, etc));
+    }
+
+    /// Recover on `...` as if it were `..` to avoid further errors.
+    /// See issue #46718.
+    fn recover_one_fewer_dotdot(&self) {
+        if self.token != token::DotDotDot {
+            return;
+        }
+
+        self.struct_span_err(self.token.span, "expected field pattern, found `...`")
+            .span_suggestion(
+                self.token.span,
+                "to omit remaining fields, use one fewer `.`",
+                "..".to_owned(),
+                Applicability::MachineApplicable
+            )
+            .emit();
+    }
+
+    fn parse_pat_field(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, FieldPat> {
+        // Check if a colon exists one ahead. This means we're parsing a fieldname.
+        let hi;
+        let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
+            // Parsing a pattern of the form "fieldname: pat"
+            let fieldname = self.parse_field_name()?;
+            self.bump();
+            let pat = self.parse_pat_with_or(None)?;
+            hi = pat.span;
+            (pat, fieldname, false)
+        } else {
+            // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
+            let is_box = self.eat_keyword(kw::Box);
+            let boxed_span = self.token.span;
+            let is_ref = self.eat_keyword(kw::Ref);
+            let is_mut = self.eat_keyword(kw::Mut);
+            let fieldname = self.parse_ident()?;
+            hi = self.prev_span;
+
+            let bind_type = match (is_ref, is_mut) {
+                (true, true) => BindingMode::ByRef(Mutability::Mutable),
+                (true, false) => BindingMode::ByRef(Mutability::Immutable),
+                (false, true) => BindingMode::ByValue(Mutability::Mutable),
+                (false, false) => BindingMode::ByValue(Mutability::Immutable),
+            };
+
+            let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
+            let subpat = if is_box {
+                self.mk_pat(lo.to(hi), PatKind::Box(fieldpat))
+            } else {
+                fieldpat
+            };
+            (subpat, fieldname, true)
+        };
+
+        Ok(FieldPat {
+            ident: fieldname,
+            pat: subpat,
+            is_shorthand,
+            attrs: attrs.into(),
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(hi),
+        })
+    }
+
+    pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
+        self.mk_pat(span, PatKind::Ident(bm, ident, None))
+    }
+
+    fn mk_pat(&self, span: Span, node: PatKind) -> P<Pat> {
+        P(Pat { node, span, id: ast::DUMMY_NODE_ID })
+    }
+}
diff --git a/src/libsyntax/parse/parser/path.rs b/src/libsyntax/parse/parser/path.rs
new file mode 100644
index 00000000000..3eb4d45045a
--- /dev/null
+++ b/src/libsyntax/parse/parser/path.rs
@@ -0,0 +1,474 @@
+use super::{Parser, PResult, TokenType};
+
+use crate::{maybe_whole, ThinVec};
+use crate::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
+use crate::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
+use crate::parse::token::{self, Token};
+use crate::source_map::{Span, BytePos};
+use crate::symbol::kw;
+
+use std::mem;
+use log::debug;
+use errors::{Applicability};
+
+/// Specifies how to parse a path.
+#[derive(Copy, Clone, PartialEq)]
+pub enum PathStyle {
+    /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
+    /// with something else. For example, in expressions `segment < ....` can be interpreted
+    /// as a comparison and `segment ( ....` can be interpreted as a function call.
+    /// In all such contexts the non-path interpretation is preferred by default for practical
+    /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
+    /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
+    Expr,
+    /// In other contexts, notably in types, no ambiguity exists and paths can be written
+    /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
+    /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
+    Type,
+    /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
+    /// visibilities or attributes.
+    /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
+    /// (paths in "mod" contexts have to be checked later for absence of generic arguments
+    /// anyway, due to macros), but it is used to avoid weird suggestions about expected
+    /// tokens when something goes wrong.
+    Mod,
+}
+
+impl<'a> Parser<'a> {
+    /// Parses a qualified path.
+    /// Assumes that the leading `<` has been parsed already.
+    ///
+    /// `qualified_path = <type [as trait_ref]>::path`
+    ///
+    /// # Examples
+    /// `<T>::default`
+    /// `<T as U>::a`
+    /// `<T as U>::F::a<S>` (without disambiguator)
+    /// `<T as U>::F::a::<S>` (with disambiguator)
+    pub(super) fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, Path)> {
+        let lo = self.prev_span;
+        let ty = self.parse_ty()?;
+
+        // `path` will contain the prefix of the path up to the `>`,
+        // if any (e.g., `U` in the `<T as U>::*` examples
+        // above). `path_span` has the span of that path, or an empty
+        // span in the case of something like `<T>::Bar`.
+        let (mut path, path_span);
+        if self.eat_keyword(kw::As) {
+            let path_lo = self.token.span;
+            path = self.parse_path(PathStyle::Type)?;
+            path_span = path_lo.to(self.prev_span);
+        } else {
+            path_span = self.token.span.to(self.token.span);
+            path = ast::Path { segments: Vec::new(), span: path_span };
+        }
+
+        // See doc comment for `unmatched_angle_bracket_count`.
+        self.expect(&token::Gt)?;
+        if self.unmatched_angle_bracket_count > 0 {
+            self.unmatched_angle_bracket_count -= 1;
+            debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
+        }
+
+        self.expect(&token::ModSep)?;
+
+        let qself = QSelf { ty, path_span, position: path.segments.len() };
+        self.parse_path_segments(&mut path.segments, style)?;
+
+        Ok((qself, Path { segments: path.segments, span: lo.to(self.prev_span) }))
+    }
+
+    /// Parses simple paths.
+    ///
+    /// `path = [::] segment+`
+    /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
+    ///
+    /// # Examples
+    /// `a::b::C<D>` (without disambiguator)
+    /// `a::b::C::<D>` (with disambiguator)
+    /// `Fn(Args)` (without disambiguator)
+    /// `Fn::(Args)` (with disambiguator)
+    pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
+        maybe_whole!(self, NtPath, |path| {
+            if style == PathStyle::Mod &&
+               path.segments.iter().any(|segment| segment.args.is_some()) {
+                self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
+            }
+            path
+        });
+
+        let lo = self.meta_var_span.unwrap_or(self.token.span);
+        let mut segments = Vec::new();
+        let mod_sep_ctxt = self.token.span.ctxt();
+        if self.eat(&token::ModSep) {
+            segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
+        }
+        self.parse_path_segments(&mut segments, style)?;
+
+        Ok(Path { segments, span: lo.to(self.prev_span) })
+    }
+
+    /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
+    /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
+    /// attributes.
+    pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, Path> {
+        let meta_ident = match self.token.kind {
+            token::Interpolated(ref nt) => match **nt {
+                token::NtMeta(ref meta) => match meta.node {
+                    ast::MetaItemKind::Word => Some(meta.path.clone()),
+                    _ => None,
+                },
+                _ => None,
+            },
+            _ => None,
+        };
+        if let Some(path) = meta_ident {
+            self.bump();
+            return Ok(path);
+        }
+        self.parse_path(style)
+    }
+
+    crate fn parse_path_segments(&mut self,
+                           segments: &mut Vec<PathSegment>,
+                           style: PathStyle)
+                           -> PResult<'a, ()> {
+        loop {
+            let segment = self.parse_path_segment(style)?;
+            if style == PathStyle::Expr {
+                // In order to check for trailing angle brackets, we must have finished
+                // recursing (`parse_path_segment` can indirectly call this function),
+                // that is, the next token must be the highlighted part of the below example:
+                //
+                // `Foo::<Bar as Baz<T>>::Qux`
+                //                      ^ here
+                //
+                // As opposed to the below highlight (if we had only finished the first
+                // recursion):
+                //
+                // `Foo::<Bar as Baz<T>>::Qux`
+                //                     ^ here
+                //
+                // `PathStyle::Expr` is only provided at the root invocation and never in
+                // `parse_path_segment` to recurse and therefore can be checked to maintain
+                // this invariant.
+                self.check_trailing_angle_brackets(&segment, token::ModSep);
+            }
+            segments.push(segment);
+
+            if self.is_import_coupler() || !self.eat(&token::ModSep) {
+                return Ok(());
+            }
+        }
+    }
+
+    pub(super) fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
+        let ident = self.parse_path_segment_ident()?;
+
+        let is_args_start = |token: &Token| match token.kind {
+            token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
+            | token::LArrow => true,
+            _ => false,
+        };
+        let check_args_start = |this: &mut Self| {
+            this.expected_tokens.extend_from_slice(
+                &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
+            );
+            is_args_start(&this.token)
+        };
+
+        Ok(if style == PathStyle::Type && check_args_start(self) ||
+              style != PathStyle::Mod && self.check(&token::ModSep)
+                                      && self.look_ahead(1, |t| is_args_start(t)) {
+            // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
+            // it isn't, then we reset the unmatched angle bracket count as we're about to start
+            // parsing a new path.
+            if style == PathStyle::Expr {
+                self.unmatched_angle_bracket_count = 0;
+                self.max_angle_bracket_count = 0;
+            }
+
+            // Generic arguments are found - `<`, `(`, `::<` or `::(`.
+            self.eat(&token::ModSep);
+            let lo = self.token.span;
+            let args = if self.eat_lt() {
+                // `<'a, T, A = U>`
+                let (args, constraints) =
+                    self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
+                self.expect_gt()?;
+                let span = lo.to(self.prev_span);
+                AngleBracketedArgs { args, constraints, span }.into()
+            } else {
+                // `(T, U) -> R`
+                let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
+                let span = lo.to(self.prev_span);
+                let output = if self.eat(&token::RArrow) {
+                    Some(self.parse_ty_common(false, false, false)?)
+                } else {
+                    None
+                };
+                ParenthesizedArgs { inputs, output, span }.into()
+            };
+
+            PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
+        } else {
+            // Generic arguments are not found.
+            PathSegment::from_ident(ident)
+        })
+    }
+
+    pub(super) fn parse_path_segment_ident(&mut self) -> PResult<'a, Ident> {
+        match self.token.kind {
+            token::Ident(name, _) if name.is_path_segment_keyword() => {
+                let span = self.token.span;
+                self.bump();
+                Ok(Ident::new(name, span))
+            }
+            _ => self.parse_ident(),
+        }
+    }
+
+    /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
+    /// For the purposes of understanding the parsing logic of generic arguments, this function
+    /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
+    /// had the correct amount of leading angle brackets.
+    ///
+    /// ```ignore (diagnostics)
+    /// bar::<<<<T as Foo>::Output>();
+    ///      ^^ help: remove extra angle brackets
+    /// ```
+    fn parse_generic_args_with_leaning_angle_bracket_recovery(
+        &mut self,
+        style: PathStyle,
+        lo: Span,
+    ) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
+        // We need to detect whether there are extra leading left angle brackets and produce an
+        // appropriate error and suggestion. This cannot be implemented by looking ahead at
+        // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
+        // then there won't be matching `>` tokens to find.
+        //
+        // To explain how this detection works, consider the following example:
+        //
+        // ```ignore (diagnostics)
+        // bar::<<<<T as Foo>::Output>();
+        //      ^^ help: remove extra angle brackets
+        // ```
+        //
+        // Parsing of the left angle brackets starts in this function. We start by parsing the
+        // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
+        // `eat_lt`):
+        //
+        // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
+        // *Unmatched count:* 1
+        // *`parse_path_segment` calls deep:* 0
+        //
+        // This has the effect of recursing as this function is called if a `<` character
+        // is found within the expected generic arguments:
+        //
+        // *Upcoming tokens:* `<<<T as Foo>::Output>;`
+        // *Unmatched count:* 2
+        // *`parse_path_segment` calls deep:* 1
+        //
+        // Eventually we will have recursed until having consumed all of the `<` tokens and
+        // this will be reflected in the count:
+        //
+        // *Upcoming tokens:* `T as Foo>::Output>;`
+        // *Unmatched count:* 4
+        // `parse_path_segment` calls deep:* 3
+        //
+        // The parser will continue until reaching the first `>` - this will decrement the
+        // unmatched angle bracket count and return to the parent invocation of this function
+        // having succeeded in parsing:
+        //
+        // *Upcoming tokens:* `::Output>;`
+        // *Unmatched count:* 3
+        // *`parse_path_segment` calls deep:* 2
+        //
+        // This will continue until the next `>` character which will also return successfully
+        // to the parent invocation of this function and decrement the count:
+        //
+        // *Upcoming tokens:* `;`
+        // *Unmatched count:* 2
+        // *`parse_path_segment` calls deep:* 1
+        //
+        // At this point, this function will expect to find another matching `>` character but
+        // won't be able to and will return an error. This will continue all the way up the
+        // call stack until the first invocation:
+        //
+        // *Upcoming tokens:* `;`
+        // *Unmatched count:* 2
+        // *`parse_path_segment` calls deep:* 0
+        //
+        // In doing this, we have managed to work out how many unmatched leading left angle
+        // brackets there are, but we cannot recover as the unmatched angle brackets have
+        // already been consumed. To remedy this, we keep a snapshot of the parser state
+        // before we do the above. We can then inspect whether we ended up with a parsing error
+        // and unmatched left angle brackets and if so, restore the parser state before we
+        // consumed any `<` characters to emit an error and consume the erroneous tokens to
+        // recover by attempting to parse again.
+        //
+        // In practice, the recursion of this function is indirect and there will be other
+        // locations that consume some `<` characters - as long as we update the count when
+        // this happens, it isn't an issue.
+
+        let is_first_invocation = style == PathStyle::Expr;
+        // Take a snapshot before attempting to parse - we can restore this later.
+        let snapshot = if is_first_invocation {
+            Some(self.clone())
+        } else {
+            None
+        };
+
+        debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
+        match self.parse_generic_args() {
+            Ok(value) => Ok(value),
+            Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
+                // Cancel error from being unable to find `>`. We know the error
+                // must have been this due to a non-zero unmatched angle bracket
+                // count.
+                e.cancel();
+
+                // Swap `self` with our backup of the parser state before attempting to parse
+                // generic arguments.
+                let snapshot = mem::replace(self, snapshot.unwrap());
+
+                debug!(
+                    "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
+                     snapshot.count={:?}",
+                    snapshot.unmatched_angle_bracket_count,
+                );
+
+                // Eat the unmatched angle brackets.
+                for _ in 0..snapshot.unmatched_angle_bracket_count {
+                    self.eat_lt();
+                }
+
+                // Make a span over ${unmatched angle bracket count} characters.
+                let span = lo.with_hi(
+                    lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
+                );
+                let plural = snapshot.unmatched_angle_bracket_count > 1;
+                self.diagnostic()
+                    .struct_span_err(
+                        span,
+                        &format!(
+                            "unmatched angle bracket{}",
+                            if plural { "s" } else { "" }
+                        ),
+                    )
+                    .span_suggestion(
+                        span,
+                        &format!(
+                            "remove extra angle bracket{}",
+                            if plural { "s" } else { "" }
+                        ),
+                        String::new(),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+
+                // Try again without unmatched angle bracket characters.
+                self.parse_generic_args()
+            },
+            Err(e) => Err(e),
+        }
+    }
+
+    /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
+    /// possibly including trailing comma.
+    fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
+        let mut args = Vec::new();
+        let mut constraints = Vec::new();
+        let mut misplaced_assoc_ty_constraints: Vec<Span> = Vec::new();
+        let mut assoc_ty_constraints: Vec<Span> = Vec::new();
+
+        let args_lo = self.token.span;
+
+        loop {
+            if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
+                // Parse lifetime argument.
+                args.push(GenericArg::Lifetime(self.expect_lifetime()));
+                misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
+            } else if self.check_ident() && self.look_ahead(1,
+                    |t| t == &token::Eq || t == &token::Colon) {
+                // Parse associated type constraint.
+                let lo = self.token.span;
+                let ident = self.parse_ident()?;
+                let kind = if self.eat(&token::Eq) {
+                    AssocTyConstraintKind::Equality {
+                        ty: self.parse_ty()?,
+                    }
+                } else if self.eat(&token::Colon) {
+                    AssocTyConstraintKind::Bound {
+                        bounds: self.parse_generic_bounds(Some(self.prev_span))?,
+                    }
+                } else {
+                    unreachable!();
+                };
+                let span = lo.to(self.prev_span);
+                constraints.push(AssocTyConstraint {
+                    id: ast::DUMMY_NODE_ID,
+                    ident,
+                    kind,
+                    span,
+                });
+                assoc_ty_constraints.push(span);
+            } else if self.check_const_arg() {
+                // Parse const argument.
+                let expr = if let token::OpenDelim(token::Brace) = self.token.kind {
+                    self.parse_block_expr(
+                        None, self.token.span, BlockCheckMode::Default, ThinVec::new()
+                    )?
+                } else if self.token.is_ident() {
+                    // FIXME(const_generics): to distinguish between idents for types and consts,
+                    // we should introduce a GenericArg::Ident in the AST and distinguish when
+                    // lowering to the HIR. For now, idents for const args are not permitted.
+                    if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
+                        self.parse_literal_maybe_minus()?
+                    } else {
+                        return Err(
+                            self.fatal("identifiers may currently not be used for const generics")
+                        );
+                    }
+                } else {
+                    self.parse_literal_maybe_minus()?
+                };
+                let value = AnonConst {
+                    id: ast::DUMMY_NODE_ID,
+                    value: expr,
+                };
+                args.push(GenericArg::Const(value));
+                misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
+            } else if self.check_type() {
+                // Parse type argument.
+                args.push(GenericArg::Type(self.parse_ty()?));
+                misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
+            } else {
+                break
+            }
+
+            if !self.eat(&token::Comma) {
+                break
+            }
+        }
+
+        // FIXME: we would like to report this in ast_validation instead, but we currently do not
+        // preserve ordering of generic parameters with respect to associated type binding, so we
+        // lose that information after parsing.
+        if misplaced_assoc_ty_constraints.len() > 0 {
+            let mut err = self.struct_span_err(
+                args_lo.to(self.prev_span),
+                "associated type bindings must be declared after generic parameters",
+            );
+            for span in misplaced_assoc_ty_constraints {
+                err.span_label(
+                    span,
+                    "this associated type binding should be moved after the generic parameters",
+                );
+            }
+            err.emit();
+        }
+
+        Ok((args, constraints))
+    }
+}
diff --git a/src/libsyntax/parse/parser/stmt.rs b/src/libsyntax/parse/parser/stmt.rs
new file mode 100644
index 00000000000..c911caba4cd
--- /dev/null
+++ b/src/libsyntax/parse/parser/stmt.rs
@@ -0,0 +1,474 @@
+use super::{Parser, PResult, Restrictions, PrevTokenKind, SemiColonMode, BlockMode};
+use super::expr::LhsExpr;
+use super::path::PathStyle;
+
+use crate::ptr::P;
+use crate::{maybe_whole, ThinVec};
+use crate::ast::{self, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
+use crate::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac, MacDelimiter};
+use crate::ext::base::DummyResult;
+use crate::parse::{classify, DirectoryOwnership};
+use crate::parse::diagnostics::Error;
+use crate::parse::token::{self};
+use crate::source_map::{respan, Span};
+use crate::symbol::{kw, sym};
+
+use std::mem;
+use errors::Applicability;
+
+impl<'a> Parser<'a> {
+    /// Parse a statement. This stops just before trailing semicolons on everything but items.
+    /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
+    pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
+        Ok(self.parse_stmt_(true))
+    }
+
+    fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
+        self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
+            e.emit();
+            self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
+            None
+        })
+    }
+
+    fn parse_stmt_without_recovery(
+        &mut self,
+        macro_legacy_warnings: bool,
+    ) -> PResult<'a, Option<Stmt>> {
+        maybe_whole!(self, NtStmt, |x| Some(x));
+
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+
+        Ok(Some(if self.eat_keyword(kw::Let) {
+            Stmt {
+                id: ast::DUMMY_NODE_ID,
+                node: StmtKind::Local(self.parse_local(attrs.into())?),
+                span: lo.to(self.prev_span),
+            }
+        } else if let Some(macro_def) = self.eat_macro_def(
+            &attrs,
+            &respan(lo, VisibilityKind::Inherited),
+            lo,
+        )? {
+            Stmt {
+                id: ast::DUMMY_NODE_ID,
+                node: StmtKind::Item(macro_def),
+                span: lo.to(self.prev_span),
+            }
+        // Starts like a simple path, being careful to avoid contextual keywords
+        // such as a union items, item with `crate` visibility or auto trait items.
+        // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
+        // like a path (1 token), but it fact not a path.
+        // `union::b::c` - path, `union U { ... }` - not a path.
+        // `crate::b::c` - path, `crate struct S;` - not a path.
+        } else if self.token.is_path_start() &&
+                  !self.token.is_qpath_start() &&
+                  !self.is_union_item() &&
+                  !self.is_crate_vis() &&
+                  !self.is_auto_trait_item() &&
+                  !self.is_async_fn() {
+            let path = self.parse_path(PathStyle::Expr)?;
+
+            if !self.eat(&token::Not) {
+                let expr = if self.check(&token::OpenDelim(token::Brace)) {
+                    self.parse_struct_expr(lo, path, ThinVec::new())?
+                } else {
+                    let hi = self.prev_span;
+                    self.mk_expr(lo.to(hi), ExprKind::Path(None, path), ThinVec::new())
+                };
+
+                let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
+                    let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
+                    this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
+                })?;
+
+                return Ok(Some(Stmt {
+                    id: ast::DUMMY_NODE_ID,
+                    node: StmtKind::Expr(expr),
+                    span: lo.to(self.prev_span),
+                }));
+            }
+
+            let (delim, tts) = self.expect_delimited_token_tree()?;
+            let hi = self.prev_span;
+
+            let style = if delim == MacDelimiter::Brace {
+                MacStmtStyle::Braces
+            } else {
+                MacStmtStyle::NoBraces
+            };
+
+            let mac = Mac {
+                path,
+                tts,
+                delim,
+                span: lo.to(hi),
+                prior_type_ascription: self.last_type_ascription,
+            };
+            let node = if delim == MacDelimiter::Brace ||
+                          self.token == token::Semi || self.token == token::Eof {
+                StmtKind::Mac(P((mac, style, attrs.into())))
+            }
+            // We used to incorrectly stop parsing macro-expanded statements here.
+            // If the next token will be an error anyway but could have parsed with the
+            // earlier behavior, stop parsing here and emit a warning to avoid breakage.
+            else if macro_legacy_warnings &&
+                    self.token.can_begin_expr() &&
+                    match self.token.kind {
+                // These can continue an expression, so we can't stop parsing and warn.
+                token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
+                token::BinOp(token::Minus) | token::BinOp(token::Star) |
+                token::BinOp(token::And) | token::BinOp(token::Or) |
+                token::AndAnd | token::OrOr |
+                token::DotDot | token::DotDotDot | token::DotDotEq => false,
+                _ => true,
+            } {
+                self.warn_missing_semicolon();
+                StmtKind::Mac(P((mac, style, attrs.into())))
+            } else {
+                let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
+                let e = self.maybe_recover_from_bad_qpath(e, true)?;
+                let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
+                let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
+                StmtKind::Expr(e)
+            };
+            Stmt {
+                id: ast::DUMMY_NODE_ID,
+                span: lo.to(hi),
+                node,
+            }
+        } else {
+            // FIXME: Bad copy of attrs
+            let old_directory_ownership =
+                mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
+            let item = self.parse_item_(attrs.clone(), false, true)?;
+            self.directory.ownership = old_directory_ownership;
+
+            match item {
+                Some(i) => Stmt {
+                    id: ast::DUMMY_NODE_ID,
+                    span: lo.to(i.span),
+                    node: StmtKind::Item(i),
+                },
+                None => {
+                    let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
+                        if !attrs.is_empty() {
+                            if s.prev_token_kind == PrevTokenKind::DocComment {
+                                s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
+                            } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
+                                s.span_err(
+                                    s.token.span, "expected statement after outer attribute"
+                                );
+                            }
+                        }
+                    };
+
+                    // Do not attempt to parse an expression if we're done here.
+                    if self.token == token::Semi {
+                        unused_attrs(&attrs, self);
+                        self.bump();
+                        let mut last_semi = lo;
+                        while self.token == token::Semi {
+                            last_semi = self.token.span;
+                            self.bump();
+                        }
+                        // We are encoding a string of semicolons as an
+                        // an empty tuple that spans the excess semicolons
+                        // to preserve this info until the lint stage
+                        return Ok(Some(Stmt {
+                            id: ast::DUMMY_NODE_ID,
+                            span: lo.to(last_semi),
+                            node: StmtKind::Semi(self.mk_expr(lo.to(last_semi),
+                                ExprKind::Tup(Vec::new()),
+                                ThinVec::new()
+                            )),
+                        }));
+                    }
+
+                    if self.token == token::CloseDelim(token::Brace) {
+                        unused_attrs(&attrs, self);
+                        return Ok(None);
+                    }
+
+                    // Remainder are line-expr stmts.
+                    let e = self.parse_expr_res(
+                        Restrictions::STMT_EXPR, Some(attrs.into()))?;
+                    Stmt {
+                        id: ast::DUMMY_NODE_ID,
+                        span: lo.to(e.span),
+                        node: StmtKind::Expr(e),
+                    }
+                }
+            }
+        }))
+    }
+
+    /// Parses a local variable declaration.
+    fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
+        let lo = self.prev_span;
+        let pat = self.parse_top_level_pat()?;
+
+        let (err, ty) = if self.eat(&token::Colon) {
+            // Save the state of the parser before parsing type normally, in case there is a `:`
+            // instead of an `=` typo.
+            let parser_snapshot_before_type = self.clone();
+            let colon_sp = self.prev_span;
+            match self.parse_ty() {
+                Ok(ty) => (None, Some(ty)),
+                Err(mut err) => {
+                    // Rewind to before attempting to parse the type and continue parsing
+                    let parser_snapshot_after_type = self.clone();
+                    mem::replace(self, parser_snapshot_before_type);
+
+                    let snippet = self.span_to_snippet(pat.span).unwrap();
+                    err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
+                    (Some((parser_snapshot_after_type, colon_sp, err)), None)
+                }
+            }
+        } else {
+            (None, None)
+        };
+        let init = match (self.parse_initializer(err.is_some()), err) {
+            (Ok(init), None) => {  // init parsed, ty parsed
+                init
+            }
+            (Ok(init), Some((_, colon_sp, mut err))) => {  // init parsed, ty error
+                // Could parse the type as if it were the initializer, it is likely there was a
+                // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
+                err.span_suggestion_short(
+                    colon_sp,
+                    "use `=` if you meant to assign",
+                    "=".to_string(),
+                    Applicability::MachineApplicable
+                );
+                err.emit();
+                // As this was parsed successfully, continue as if the code has been fixed for the
+                // rest of the file. It will still fail due to the emitted error, but we avoid
+                // extra noise.
+                init
+            }
+            (Err(mut init_err), Some((snapshot, _, ty_err))) => {  // init error, ty error
+                init_err.cancel();
+                // Couldn't parse the type nor the initializer, only raise the type error and
+                // return to the parser state before parsing the type as the initializer.
+                // let x: <parse_error>;
+                mem::replace(self, snapshot);
+                return Err(ty_err);
+            }
+            (Err(err), None) => {  // init error, ty parsed
+                // Couldn't parse the initializer and we're not attempting to recover a failed
+                // parse of the type, return the error.
+                return Err(err);
+            }
+        };
+        let hi = if self.token == token::Semi {
+            self.token.span
+        } else {
+            self.prev_span
+        };
+        Ok(P(ast::Local {
+            ty,
+            pat,
+            init,
+            id: ast::DUMMY_NODE_ID,
+            span: lo.to(hi),
+            attrs,
+        }))
+    }
+
+    /// Parses the RHS of a local variable declaration (e.g., '= 14;').
+    fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
+        if self.eat(&token::Eq) {
+            Ok(Some(self.parse_expr()?))
+        } else if skip_eq {
+            Ok(Some(self.parse_expr()?))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn is_auto_trait_item(&self) -> bool {
+        // auto trait
+        (self.token.is_keyword(kw::Auto) &&
+            self.is_keyword_ahead(1, &[kw::Trait]))
+        || // unsafe auto trait
+        (self.token.is_keyword(kw::Unsafe) &&
+         self.is_keyword_ahead(1, &[kw::Auto]) &&
+         self.is_keyword_ahead(2, &[kw::Trait]))
+    }
+
+    /// Parses a block. No inner attributes are allowed.
+    pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
+        maybe_whole!(self, NtBlock, |x| x);
+
+        let lo = self.token.span;
+
+        if !self.eat(&token::OpenDelim(token::Brace)) {
+            let sp = self.token.span;
+            let tok = self.this_token_descr();
+            let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
+            let do_not_suggest_help =
+                self.token.is_keyword(kw::In) || self.token == token::Colon;
+
+            if self.token.is_ident_named(sym::and) {
+                e.span_suggestion_short(
+                    self.token.span,
+                    "use `&&` instead of `and` for the boolean operator",
+                    "&&".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+            if self.token.is_ident_named(sym::or) {
+                e.span_suggestion_short(
+                    self.token.span,
+                    "use `||` instead of `or` for the boolean operator",
+                    "||".to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+            }
+
+            // Check to see if the user has written something like
+            //
+            //    if (cond)
+            //      bar;
+            //
+            // Which is valid in other languages, but not Rust.
+            match self.parse_stmt_without_recovery(false) {
+                Ok(Some(stmt)) => {
+                    if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
+                        || do_not_suggest_help {
+                        // if the next token is an open brace (e.g., `if a b {`), the place-
+                        // inside-a-block suggestion would be more likely wrong than right
+                        e.span_label(sp, "expected `{`");
+                        return Err(e);
+                    }
+                    let mut stmt_span = stmt.span;
+                    // expand the span to include the semicolon, if it exists
+                    if self.eat(&token::Semi) {
+                        stmt_span = stmt_span.with_hi(self.prev_span.hi());
+                    }
+                    if let Ok(snippet) = self.span_to_snippet(stmt_span) {
+                        e.span_suggestion(
+                            stmt_span,
+                            "try placing this code inside a block",
+                            format!("{{ {} }}", snippet),
+                            // speculative, has been misleading in the past (#46836)
+                            Applicability::MaybeIncorrect,
+                        );
+                    }
+                }
+                Err(mut e) => {
+                    self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
+                    self.cancel(&mut e);
+                }
+                _ => ()
+            }
+            e.span_label(sp, "expected `{`");
+            return Err(e);
+        }
+
+        self.parse_block_tail(lo, BlockCheckMode::Default)
+    }
+
+    /// Parses a block. Inner attributes are allowed.
+    crate fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
+        maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
+
+        let lo = self.token.span;
+        self.expect(&token::OpenDelim(token::Brace))?;
+        Ok((self.parse_inner_attributes()?,
+            self.parse_block_tail(lo, BlockCheckMode::Default)?))
+    }
+
+    /// Parses the rest of a block expression or function body.
+    /// Precondition: already parsed the '{'.
+    pub(super) fn parse_block_tail(
+        &mut self,
+        lo: Span,
+        s: BlockCheckMode
+    ) -> PResult<'a, P<Block>> {
+        let mut stmts = vec![];
+        while !self.eat(&token::CloseDelim(token::Brace)) {
+            if self.token == token::Eof {
+                break;
+            }
+            let stmt = match self.parse_full_stmt(false) {
+                Err(mut err) => {
+                    err.emit();
+                    self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
+                    Some(Stmt {
+                        id: ast::DUMMY_NODE_ID,
+                        node: StmtKind::Expr(DummyResult::raw_expr(self.token.span, true)),
+                        span: self.token.span,
+                    })
+                }
+                Ok(stmt) => stmt,
+            };
+            if let Some(stmt) = stmt {
+                stmts.push(stmt);
+            } else {
+                // Found only `;` or `}`.
+                continue;
+            };
+        }
+        Ok(P(ast::Block {
+            stmts,
+            id: ast::DUMMY_NODE_ID,
+            rules: s,
+            span: lo.to(self.prev_span),
+        }))
+    }
+
+    /// Parses a statement, including the trailing semicolon.
+    crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
+        // skip looking for a trailing semicolon when we have an interpolated statement
+        maybe_whole!(self, NtStmt, |x| Some(x));
+
+        let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
+            Some(stmt) => stmt,
+            None => return Ok(None),
+        };
+
+        match stmt.node {
+            StmtKind::Expr(ref expr) if self.token != token::Eof => {
+                // expression without semicolon
+                if classify::expr_requires_semi_to_be_stmt(expr) {
+                    // Just check for errors and recover; do not eat semicolon yet.
+                    if let Err(mut e) =
+                        self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
+                    {
+                        e.emit();
+                        self.recover_stmt();
+                        // Don't complain about type errors in body tail after parse error (#57383).
+                        let sp = expr.span.to(self.prev_span);
+                        stmt.node = StmtKind::Expr(DummyResult::raw_expr(sp, true));
+                    }
+                }
+            }
+            StmtKind::Local(..) => {
+                // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
+                if macro_legacy_warnings && self.token != token::Semi {
+                    self.warn_missing_semicolon();
+                } else {
+                    self.expect_one_of(&[], &[token::Semi])?;
+                }
+            }
+            _ => {}
+        }
+
+        if self.eat(&token::Semi) {
+            stmt = stmt.add_trailing_semicolon();
+        }
+        stmt.span = stmt.span.to(self.prev_span);
+        Ok(Some(stmt))
+    }
+
+    fn warn_missing_semicolon(&self) {
+        self.diagnostic().struct_span_warn(self.token.span, {
+            &format!("expected `;`, found {}", self.this_token_descr())
+        }).note({
+            "This was erroneously allowed and will become a hard error in a future release"
+        }).emit();
+    }
+}
diff --git a/src/libsyntax/parse/parser/ty.rs b/src/libsyntax/parse/parser/ty.rs
new file mode 100644
index 00000000000..337702b8d30
--- /dev/null
+++ b/src/libsyntax/parse/parser/ty.rs
@@ -0,0 +1,462 @@
+use super::{Parser, PResult, PathStyle, PrevTokenKind, TokenType};
+
+use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
+use crate::ptr::P;
+use crate::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
+use crate::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
+use crate::ast::{Mutability, AnonConst, FnDecl, Mac};
+use crate::parse::token::{self, Token};
+use crate::source_map::Span;
+use crate::symbol::{kw};
+
+use rustc_target::spec::abi::Abi;
+
+use errors::{Applicability};
+
+/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
+/// `IDENT<<u8 as Trait>::AssocTy>`.
+///
+/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
+/// that `IDENT` is not the ident of a fn trait.
+fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
+    t == &token::ModSep || t == &token::Lt ||
+    t == &token::BinOp(token::Shl)
+}
+
+impl<'a> Parser<'a> {
+    /// Parses a type.
+    pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
+        self.parse_ty_common(true, true, false)
+    }
+
+    /// Parses a type in restricted contexts where `+` is not permitted.
+    ///
+    /// Example 1: `&'a TYPE`
+    ///     `+` is prohibited to maintain operator priority (P(+) < P(&)).
+    /// Example 2: `value1 as TYPE + value2`
+    ///     `+` is prohibited to avoid interactions with expression grammar.
+    pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
+        self.parse_ty_common(false, true, false)
+    }
+
+    /// Parses an optional return type `[ -> TY ]` in a function declaration.
+    pub(super) fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
+        if self.eat(&token::RArrow) {
+            Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
+        } else {
+            Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
+        }
+    }
+
+    pub(super) fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
+                       allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
+        maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
+        maybe_whole!(self, NtTy, |x| x);
+
+        let lo = self.token.span;
+        let mut impl_dyn_multi = false;
+        let node = if self.eat(&token::OpenDelim(token::Paren)) {
+            // `(TYPE)` is a parenthesized type.
+            // `(TYPE,)` is a tuple with a single field of type TYPE.
+            let mut ts = vec![];
+            let mut last_comma = false;
+            while self.token != token::CloseDelim(token::Paren) {
+                ts.push(self.parse_ty()?);
+                if self.eat(&token::Comma) {
+                    last_comma = true;
+                } else {
+                    last_comma = false;
+                    break;
+                }
+            }
+            let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
+            self.expect(&token::CloseDelim(token::Paren))?;
+
+            if ts.len() == 1 && !last_comma {
+                let ty = ts.into_iter().nth(0).unwrap().into_inner();
+                let maybe_bounds = allow_plus && self.token.is_like_plus();
+                match ty.node {
+                    // `(TY_BOUND_NOPAREN) + BOUND + ...`.
+                    TyKind::Path(None, ref path) if maybe_bounds => {
+                        self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
+                    }
+                    TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
+                            if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
+                        let path = match bounds[0] {
+                            GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
+                            GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
+                        };
+                        self.parse_remaining_bounds(Vec::new(), path, lo, true)?
+                    }
+                    // `(TYPE)`
+                    _ => TyKind::Paren(P(ty))
+                }
+            } else {
+                TyKind::Tup(ts)
+            }
+        } else if self.eat(&token::Not) {
+            // Never type `!`
+            TyKind::Never
+        } else if self.eat(&token::BinOp(token::Star)) {
+            // Raw pointer
+            TyKind::Ptr(self.parse_ptr()?)
+        } else if self.eat(&token::OpenDelim(token::Bracket)) {
+            // Array or slice
+            let t = self.parse_ty()?;
+            // Parse optional `; EXPR` in `[TYPE; EXPR]`
+            let t = match self.maybe_parse_fixed_length_of_vec()? {
+                None => TyKind::Slice(t),
+                Some(length) => TyKind::Array(t, AnonConst {
+                    id: ast::DUMMY_NODE_ID,
+                    value: length,
+                }),
+            };
+            self.expect(&token::CloseDelim(token::Bracket))?;
+            t
+        } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
+            // Reference
+            self.expect_and()?;
+            self.parse_borrowed_pointee()?
+        } else if self.eat_keyword_noexpect(kw::Typeof) {
+            // `typeof(EXPR)`
+            // In order to not be ambiguous, the type must be surrounded by parens.
+            self.expect(&token::OpenDelim(token::Paren))?;
+            let e = AnonConst {
+                id: ast::DUMMY_NODE_ID,
+                value: self.parse_expr()?,
+            };
+            self.expect(&token::CloseDelim(token::Paren))?;
+            TyKind::Typeof(e)
+        } else if self.eat_keyword(kw::Underscore) {
+            // A type to be inferred `_`
+            TyKind::Infer
+        } else if self.token_is_bare_fn_keyword() {
+            // Function pointer type
+            self.parse_ty_bare_fn(Vec::new())?
+        } else if self.check_keyword(kw::For) {
+            // Function pointer type or bound list (trait object type) starting with a poly-trait.
+            //   `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
+            //   `for<'lt> Trait1<'lt> + Trait2 + 'a`
+            let lo = self.token.span;
+            let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+            if self.token_is_bare_fn_keyword() {
+                self.parse_ty_bare_fn(lifetime_defs)?
+            } else {
+                let path = self.parse_path(PathStyle::Type)?;
+                let parse_plus = allow_plus && self.check_plus();
+                self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
+            }
+        } else if self.eat_keyword(kw::Impl) {
+            // Always parse bounds greedily for better error recovery.
+            let bounds = self.parse_generic_bounds(None)?;
+            impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
+            TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
+        } else if self.check_keyword(kw::Dyn) &&
+                  (self.token.span.rust_2018() ||
+                   self.look_ahead(1, |t| t.can_begin_bound() &&
+                                          !can_continue_type_after_non_fn_ident(t))) {
+            self.bump(); // `dyn`
+            // Always parse bounds greedily for better error recovery.
+            let bounds = self.parse_generic_bounds(None)?;
+            impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
+            TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
+        } else if self.check(&token::Question) ||
+                  self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
+            // Bound list (trait object type)
+            TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
+                                TraitObjectSyntax::None)
+        } else if self.eat_lt() {
+            // Qualified path
+            let (qself, path) = self.parse_qpath(PathStyle::Type)?;
+            TyKind::Path(Some(qself), path)
+        } else if self.token.is_path_start() {
+            // Simple path
+            let path = self.parse_path(PathStyle::Type)?;
+            if self.eat(&token::Not) {
+                // Macro invocation in type position
+                let (delim, tts) = self.expect_delimited_token_tree()?;
+                let mac = Mac {
+                    path,
+                    tts,
+                    delim,
+                    span: lo.to(self.prev_span),
+                    prior_type_ascription: self.last_type_ascription,
+                };
+                TyKind::Mac(mac)
+            } else {
+                // Just a type path or bound list (trait object type) starting with a trait.
+                //   `Type`
+                //   `Trait1 + Trait2 + 'a`
+                if allow_plus && self.check_plus() {
+                    self.parse_remaining_bounds(Vec::new(), path, lo, true)?
+                } else {
+                    TyKind::Path(None, path)
+                }
+            }
+        } else if self.check(&token::DotDotDot) {
+            if allow_c_variadic {
+                self.eat(&token::DotDotDot);
+                TyKind::CVarArgs
+            } else {
+                return Err(self.fatal(
+                    "only foreign functions are allowed to be C-variadic"
+                ));
+            }
+        } else {
+            let msg = format!("expected type, found {}", self.this_token_descr());
+            let mut err = self.fatal(&msg);
+            err.span_label(self.token.span, "expected type");
+            self.maybe_annotate_with_ascription(&mut err, true);
+            return Err(err);
+        };
+
+        let span = lo.to(self.prev_span);
+        let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
+
+        // Try to recover from use of `+` with incorrect priority.
+        self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
+        self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
+        self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
+    }
+
+    fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
+                              lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
+        let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
+        let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
+        if parse_plus {
+            self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
+            bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
+        }
+        Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
+    }
+
+    fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
+        let mutbl = if self.eat_keyword(kw::Mut) {
+            Mutability::Mutable
+        } else if self.eat_keyword(kw::Const) {
+            Mutability::Immutable
+        } else {
+            let span = self.prev_span;
+            let msg = "expected mut or const in raw pointer type";
+            self.struct_span_err(span, msg)
+                .span_label(span, msg)
+                .help("use `*mut T` or `*const T` as appropriate")
+                .emit();
+            Mutability::Immutable
+        };
+        let t = self.parse_ty_no_plus()?;
+        Ok(MutTy { ty: t, mutbl })
+    }
+
+    fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
+        if self.eat(&token::Semi) {
+            Ok(Some(self.parse_expr()?))
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
+        let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
+        let mutbl = self.parse_mutability();
+        let ty = self.parse_ty_no_plus()?;
+        return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }));
+    }
+
+    /// Is the current token one of the keywords that signals a bare function type?
+    fn token_is_bare_fn_keyword(&mut self) -> bool {
+        self.check_keyword(kw::Fn) ||
+            self.check_keyword(kw::Unsafe) ||
+            self.check_keyword(kw::Extern)
+    }
+
+    /// Parses a `TyKind::BareFn` type.
+    fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
+        /*
+
+        [unsafe] [extern "ABI"] fn (S) -> T
+         ^~~~^           ^~~~^     ^~^    ^
+           |               |        |     |
+           |               |        |   Return type
+           |               |      Argument types
+           |               |
+           |              ABI
+        Function Style
+        */
+
+        let unsafety = self.parse_unsafety();
+        let abi = if self.eat_keyword(kw::Extern) {
+            self.parse_opt_abi()?.unwrap_or(Abi::C)
+        } else {
+            Abi::Rust
+        };
+
+        self.expect_keyword(kw::Fn)?;
+        let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
+        let ret_ty = self.parse_ret_ty(false)?;
+        let decl = P(FnDecl {
+            inputs,
+            output: ret_ty,
+            c_variadic,
+        });
+        Ok(TyKind::BareFn(P(BareFnTy {
+            abi,
+            unsafety,
+            generic_params,
+            decl,
+        })))
+    }
+
+    crate fn parse_generic_bounds(&mut self,
+                                  colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
+        self.parse_generic_bounds_common(true, colon_span)
+    }
+
+    /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
+    ///
+    /// ```
+    /// BOUND = TY_BOUND | LT_BOUND
+    /// LT_BOUND = LIFETIME (e.g., `'a`)
+    /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
+    /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
+    /// ```
+    fn parse_generic_bounds_common(&mut self,
+                                   allow_plus: bool,
+                                   colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
+        let mut bounds = Vec::new();
+        let mut negative_bounds = Vec::new();
+        let mut last_plus_span = None;
+        let mut was_negative = false;
+        loop {
+            // This needs to be synchronized with `TokenKind::can_begin_bound`.
+            let is_bound_start = self.check_path() || self.check_lifetime() ||
+                                 self.check(&token::Not) || // used for error reporting only
+                                 self.check(&token::Question) ||
+                                 self.check_keyword(kw::For) ||
+                                 self.check(&token::OpenDelim(token::Paren));
+            if is_bound_start {
+                let lo = self.token.span;
+                let has_parens = self.eat(&token::OpenDelim(token::Paren));
+                let inner_lo = self.token.span;
+                let is_negative = self.eat(&token::Not);
+                let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
+                if self.token.is_lifetime() {
+                    if let Some(question_span) = question {
+                        self.span_err(question_span,
+                                      "`?` may only modify trait bounds, not lifetime bounds");
+                    }
+                    bounds.push(GenericBound::Outlives(self.expect_lifetime()));
+                    if has_parens {
+                        let inner_span = inner_lo.to(self.prev_span);
+                        self.expect(&token::CloseDelim(token::Paren))?;
+                        let mut err = self.struct_span_err(
+                            lo.to(self.prev_span),
+                            "parenthesized lifetime bounds are not supported"
+                        );
+                        if let Ok(snippet) = self.span_to_snippet(inner_span) {
+                            err.span_suggestion_short(
+                                lo.to(self.prev_span),
+                                "remove the parentheses",
+                                snippet.to_owned(),
+                                Applicability::MachineApplicable
+                            );
+                        }
+                        err.emit();
+                    }
+                } else {
+                    let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+                    let path = self.parse_path(PathStyle::Type)?;
+                    if has_parens {
+                        self.expect(&token::CloseDelim(token::Paren))?;
+                    }
+                    let poly_span = lo.to(self.prev_span);
+                    if is_negative {
+                        was_negative = true;
+                        if let Some(sp) = last_plus_span.or(colon_span) {
+                            negative_bounds.push(sp.to(poly_span));
+                        }
+                    } else {
+                        let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
+                        let modifier = if question.is_some() {
+                            TraitBoundModifier::Maybe
+                        } else {
+                            TraitBoundModifier::None
+                        };
+                        bounds.push(GenericBound::Trait(poly_trait, modifier));
+                    }
+                }
+            } else {
+                break
+            }
+
+            if !allow_plus || !self.eat_plus() {
+                break
+            } else {
+                last_plus_span = Some(self.prev_span);
+            }
+        }
+
+        if !negative_bounds.is_empty() || was_negative {
+            let plural = negative_bounds.len() > 1;
+            let last_span = negative_bounds.last().map(|sp| *sp);
+            let mut err = self.struct_span_err(
+                negative_bounds,
+                "negative trait bounds are not supported",
+            );
+            if let Some(sp) = last_span {
+                err.span_label(sp, "negative trait bounds are not supported");
+            }
+            if let Some(bound_list) = colon_span {
+                let bound_list = bound_list.to(self.prev_span);
+                let mut new_bound_list = String::new();
+                if !bounds.is_empty() {
+                    let mut snippets = bounds.iter().map(|bound| bound.span())
+                        .map(|span| self.span_to_snippet(span));
+                    while let Some(Ok(snippet)) = snippets.next() {
+                        new_bound_list.push_str(" + ");
+                        new_bound_list.push_str(&snippet);
+                    }
+                    new_bound_list = new_bound_list.replacen(" +", ":", 1);
+                }
+                err.span_suggestion_hidden(
+                    bound_list,
+                    &format!("remove the trait bound{}", if plural { "s" } else { "" }),
+                    new_bound_list,
+                    Applicability::MachineApplicable,
+                );
+            }
+            err.emit();
+        }
+
+        return Ok(bounds);
+    }
+
+    pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
+        if self.eat_keyword(kw::For) {
+            self.expect_lt()?;
+            let params = self.parse_generic_params()?;
+            self.expect_gt()?;
+            // We rely on AST validation to rule out invalid cases: There must not be type
+            // parameters, and the lifetime parameters must not have bounds.
+            Ok(params)
+        } else {
+            Ok(Vec::new())
+        }
+    }
+
+    crate fn check_lifetime(&mut self) -> bool {
+        self.expected_tokens.push(TokenType::Lifetime);
+        self.token.is_lifetime()
+    }
+
+    /// Parses a single lifetime `'a` or panics.
+    crate fn expect_lifetime(&mut self) -> Lifetime {
+        if let Some(ident) = self.token.lifetime() {
+            let span = self.token.span;
+            self.bump();
+            Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
+        } else {
+            self.span_bug(self.token.span, "not a lifetime")
+        }
+    }
+}
diff --git a/src/libsyntax/parse/tests.rs b/src/libsyntax/parse/tests.rs
new file mode 100644
index 00000000000..6a789ef99d6
--- /dev/null
+++ b/src/libsyntax/parse/tests.rs
@@ -0,0 +1,339 @@
+use super::*;
+
+use crate::ast::{self, Name, PatKind};
+use crate::attr::first_attr_value_str_by_name;
+use crate::parse::{ParseSess, PResult};
+use crate::parse::new_parser_from_source_str;
+use crate::parse::token::Token;
+use crate::print::pprust::item_to_string;
+use crate::ptr::P;
+use crate::source_map::FilePathMapping;
+use crate::symbol::{kw, sym};
+use crate::tests::{matches_codepattern, string_to_stream, with_error_checking_parse};
+use crate::tokenstream::{DelimSpan, TokenTree, TokenStream};
+use crate::with_default_globals;
+use syntax_pos::{Span, BytePos, Pos};
+
+use std::path::PathBuf;
+
+/// Parses an item.
+///
+/// Returns `Ok(Some(item))` when successful, `Ok(None)` when no item was found, and `Err`
+/// when a syntax error occurred.
+fn parse_item_from_source_str(name: FileName, source: String, sess: &ParseSess)
+                                    -> PResult<'_, Option<P<ast::Item>>> {
+    new_parser_from_source_str(sess, name, source).parse_item()
+}
+
+// produce a syntax_pos::span
+fn sp(a: u32, b: u32) -> Span {
+    Span::with_root_ctxt(BytePos(a), BytePos(b))
+}
+
+/// Parse a string, return an expr
+fn string_to_expr(source_str : String) -> P<ast::Expr> {
+    let ps = ParseSess::new(FilePathMapping::empty());
+    with_error_checking_parse(source_str, &ps, |p| {
+        p.parse_expr()
+    })
+}
+
+/// Parse a string, return an item
+fn string_to_item(source_str : String) -> Option<P<ast::Item>> {
+    let ps = ParseSess::new(FilePathMapping::empty());
+    with_error_checking_parse(source_str, &ps, |p| {
+        p.parse_item()
+    })
+}
+
+#[should_panic]
+#[test] fn bad_path_expr_1() {
+    with_default_globals(|| {
+        string_to_expr("::abc::def::return".to_string());
+    })
+}
+
+// check the token-tree-ization of macros
+#[test]
+fn string_to_tts_macro () {
+    with_default_globals(|| {
+        let tts: Vec<_> =
+            string_to_stream("macro_rules! zip (($a)=>($a))".to_string()).trees().collect();
+        let tts: &[TokenTree] = &tts[..];
+
+        match tts {
+            [
+                TokenTree::Token(Token { kind: token::Ident(name_macro_rules, false), .. }),
+                TokenTree::Token(Token { kind: token::Not, .. }),
+                TokenTree::Token(Token { kind: token::Ident(name_zip, false), .. }),
+                TokenTree::Delimited(_, macro_delim,  macro_tts)
+            ]
+            if name_macro_rules == &sym::macro_rules && name_zip.as_str() == "zip" => {
+                let tts = &macro_tts.trees().collect::<Vec<_>>();
+                match &tts[..] {
+                    [
+                        TokenTree::Delimited(_, first_delim, first_tts),
+                        TokenTree::Token(Token { kind: token::FatArrow, .. }),
+                        TokenTree::Delimited(_, second_delim, second_tts),
+                    ]
+                    if macro_delim == &token::Paren => {
+                        let tts = &first_tts.trees().collect::<Vec<_>>();
+                        match &tts[..] {
+                            [
+                                TokenTree::Token(Token { kind: token::Dollar, .. }),
+                                TokenTree::Token(Token { kind: token::Ident(name, false), .. }),
+                            ]
+                            if first_delim == &token::Paren && name.as_str() == "a" => {},
+                            _ => panic!("value 3: {:?} {:?}", first_delim, first_tts),
+                        }
+                        let tts = &second_tts.trees().collect::<Vec<_>>();
+                        match &tts[..] {
+                            [
+                                TokenTree::Token(Token { kind: token::Dollar, .. }),
+                                TokenTree::Token(Token { kind: token::Ident(name, false), .. }),
+                            ]
+                            if second_delim == &token::Paren && name.as_str() == "a" => {},
+                            _ => panic!("value 4: {:?} {:?}", second_delim, second_tts),
+                        }
+                    },
+                    _ => panic!("value 2: {:?} {:?}", macro_delim, macro_tts),
+                }
+            },
+            _ => panic!("value: {:?}",tts),
+        }
+    })
+}
+
+#[test]
+fn string_to_tts_1() {
+    with_default_globals(|| {
+        let tts = string_to_stream("fn a (b : i32) { b; }".to_string());
+
+        let expected = TokenStream::new(vec![
+            TokenTree::token(token::Ident(kw::Fn, false), sp(0, 2)).into(),
+            TokenTree::token(token::Ident(Name::intern("a"), false), sp(3, 4)).into(),
+            TokenTree::Delimited(
+                DelimSpan::from_pair(sp(5, 6), sp(13, 14)),
+                token::DelimToken::Paren,
+                TokenStream::new(vec![
+                    TokenTree::token(token::Ident(Name::intern("b"), false), sp(6, 7)).into(),
+                    TokenTree::token(token::Colon, sp(8, 9)).into(),
+                    TokenTree::token(token::Ident(sym::i32, false), sp(10, 13)).into(),
+                ]).into(),
+            ).into(),
+            TokenTree::Delimited(
+                DelimSpan::from_pair(sp(15, 16), sp(20, 21)),
+                token::DelimToken::Brace,
+                TokenStream::new(vec![
+                    TokenTree::token(token::Ident(Name::intern("b"), false), sp(17, 18)).into(),
+                    TokenTree::token(token::Semi, sp(18, 19)).into(),
+                ]).into(),
+            ).into()
+        ]);
+
+        assert_eq!(tts, expected);
+    })
+}
+
+#[test] fn parse_use() {
+    with_default_globals(|| {
+        let use_s = "use foo::bar::baz;";
+        let vitem = string_to_item(use_s.to_string()).unwrap();
+        let vitem_s = item_to_string(&vitem);
+        assert_eq!(&vitem_s[..], use_s);
+
+        let use_s = "use foo::bar as baz;";
+        let vitem = string_to_item(use_s.to_string()).unwrap();
+        let vitem_s = item_to_string(&vitem);
+        assert_eq!(&vitem_s[..], use_s);
+    })
+}
+
+#[test] fn parse_extern_crate() {
+    with_default_globals(|| {
+        let ex_s = "extern crate foo;";
+        let vitem = string_to_item(ex_s.to_string()).unwrap();
+        let vitem_s = item_to_string(&vitem);
+        assert_eq!(&vitem_s[..], ex_s);
+
+        let ex_s = "extern crate foo as bar;";
+        let vitem = string_to_item(ex_s.to_string()).unwrap();
+        let vitem_s = item_to_string(&vitem);
+        assert_eq!(&vitem_s[..], ex_s);
+    })
+}
+
+fn get_spans_of_pat_idents(src: &str) -> Vec<Span> {
+    let item = string_to_item(src.to_string()).unwrap();
+
+    struct PatIdentVisitor {
+        spans: Vec<Span>
+    }
+    impl<'a> crate::visit::Visitor<'a> for PatIdentVisitor {
+        fn visit_pat(&mut self, p: &'a ast::Pat) {
+            match p.node {
+                PatKind::Ident(_ , ref ident, _) => {
+                    self.spans.push(ident.span.clone());
+                }
+                _ => {
+                    crate::visit::walk_pat(self, p);
+                }
+            }
+        }
+    }
+    let mut v = PatIdentVisitor { spans: Vec::new() };
+    crate::visit::walk_item(&mut v, &item);
+    return v.spans;
+}
+
+#[test] fn span_of_self_arg_pat_idents_are_correct() {
+    with_default_globals(|| {
+
+        let srcs = ["impl z { fn a (&self, &myarg: i32) {} }",
+                    "impl z { fn a (&mut self, &myarg: i32) {} }",
+                    "impl z { fn a (&'a self, &myarg: i32) {} }",
+                    "impl z { fn a (self, &myarg: i32) {} }",
+                    "impl z { fn a (self: Foo, &myarg: i32) {} }",
+                    ];
+
+        for &src in &srcs {
+            let spans = get_spans_of_pat_idents(src);
+            let (lo, hi) = (spans[0].lo(), spans[0].hi());
+            assert!("self" == &src[lo.to_usize()..hi.to_usize()],
+                    "\"{}\" != \"self\". src=\"{}\"",
+                    &src[lo.to_usize()..hi.to_usize()], src)
+        }
+    })
+}
+
+#[test] fn parse_exprs () {
+    with_default_globals(|| {
+        // just make sure that they parse....
+        string_to_expr("3 + 4".to_string());
+        string_to_expr("a::z.froob(b,&(987+3))".to_string());
+    })
+}
+
+#[test] fn attrs_fix_bug () {
+    with_default_globals(|| {
+        string_to_item("pub fn mk_file_writer(path: &Path, flags: &[FileFlag])
+                -> Result<Box<Writer>, String> {
+#[cfg(windows)]
+fn wb() -> c_int {
+    (O_WRONLY | libc::consts::os::extra::O_BINARY) as c_int
+}
+
+#[cfg(unix)]
+fn wb() -> c_int { O_WRONLY as c_int }
+
+let mut fflags: c_int = wb();
+}".to_string());
+    })
+}
+
+#[test] fn crlf_doc_comments() {
+    with_default_globals(|| {
+        let sess = ParseSess::new(FilePathMapping::empty());
+
+        let name_1 = FileName::Custom("crlf_source_1".to_string());
+        let source = "/// doc comment\r\nfn foo() {}".to_string();
+        let item = parse_item_from_source_str(name_1, source, &sess)
+            .unwrap().unwrap();
+        let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
+        assert_eq!(doc.as_str(), "/// doc comment");
+
+        let name_2 = FileName::Custom("crlf_source_2".to_string());
+        let source = "/// doc comment\r\n/// line 2\r\nfn foo() {}".to_string();
+        let item = parse_item_from_source_str(name_2, source, &sess)
+            .unwrap().unwrap();
+        let docs = item.attrs.iter().filter(|a| a.path == sym::doc)
+                    .map(|a| a.value_str().unwrap().to_string()).collect::<Vec<_>>();
+        let b: &[_] = &["/// doc comment".to_string(), "/// line 2".to_string()];
+        assert_eq!(&docs[..], b);
+
+        let name_3 = FileName::Custom("clrf_source_3".to_string());
+        let source = "/** doc comment\r\n *  with CRLF */\r\nfn foo() {}".to_string();
+        let item = parse_item_from_source_str(name_3, source, &sess).unwrap().unwrap();
+        let doc = first_attr_value_str_by_name(&item.attrs, sym::doc).unwrap();
+        assert_eq!(doc.as_str(), "/** doc comment\n *  with CRLF */");
+    });
+}
+
+#[test]
+fn ttdelim_span() {
+    fn parse_expr_from_source_str(
+        name: FileName, source: String, sess: &ParseSess
+    ) -> PResult<'_, P<ast::Expr>> {
+        new_parser_from_source_str(sess, name, source).parse_expr()
+    }
+
+    with_default_globals(|| {
+        let sess = ParseSess::new(FilePathMapping::empty());
+        let expr = parse_expr_from_source_str(PathBuf::from("foo").into(),
+            "foo!( fn main() { body } )".to_string(), &sess).unwrap();
+
+        let tts: Vec<_> = match expr.node {
+            ast::ExprKind::Mac(ref mac) => mac.stream().trees().collect(),
+            _ => panic!("not a macro"),
+        };
+
+        let span = tts.iter().rev().next().unwrap().span();
+
+        match sess.source_map().span_to_snippet(span) {
+            Ok(s) => assert_eq!(&s[..], "{ body }"),
+            Err(_) => panic!("could not get snippet"),
+        }
+    });
+}
+
+// This tests that when parsing a string (rather than a file) we don't try
+// and read in a file for a module declaration and just parse a stub.
+// See `recurse_into_file_modules` in the parser.
+#[test]
+fn out_of_line_mod() {
+    with_default_globals(|| {
+        let sess = ParseSess::new(FilePathMapping::empty());
+        let item = parse_item_from_source_str(
+            PathBuf::from("foo").into(),
+            "mod foo { struct S; mod this_does_not_exist; }".to_owned(),
+            &sess,
+        ).unwrap().unwrap();
+
+        if let ast::ItemKind::Mod(ref m) = item.node {
+            assert!(m.items.len() == 2);
+        } else {
+            panic!();
+        }
+    });
+}
+
+#[test]
+fn eqmodws() {
+    assert_eq!(matches_codepattern("",""),true);
+    assert_eq!(matches_codepattern("","a"),false);
+    assert_eq!(matches_codepattern("a",""),false);
+    assert_eq!(matches_codepattern("a","a"),true);
+    assert_eq!(matches_codepattern("a b","a   \n\t\r  b"),true);
+    assert_eq!(matches_codepattern("a b ","a   \n\t\r  b"),true);
+    assert_eq!(matches_codepattern("a b","a   \n\t\r  b "),false);
+    assert_eq!(matches_codepattern("a   b","a b"),true);
+    assert_eq!(matches_codepattern("ab","a b"),false);
+    assert_eq!(matches_codepattern("a   b","ab"),true);
+    assert_eq!(matches_codepattern(" a   b","ab"),true);
+}
+
+#[test]
+fn pattern_whitespace() {
+    assert_eq!(matches_codepattern("","\x0C"), false);
+    assert_eq!(matches_codepattern("a b ","a   \u{0085}\n\t\r  b"),true);
+    assert_eq!(matches_codepattern("a b","a   \u{0085}\n\t\r  b "),false);
+}
+
+#[test]
+fn non_pattern_whitespace() {
+    // These have the property 'White_Space' but not 'Pattern_White_Space'
+    assert_eq!(matches_codepattern("a b","a\u{2002}b"), false);
+    assert_eq!(matches_codepattern("a   b","a\u{2002}b"), false);
+    assert_eq!(matches_codepattern("\u{205F}a   b","ab"), false);
+    assert_eq!(matches_codepattern("a  \u{3000}b","ab"), false);
+}
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 049fb6cb78b..be800b4de66 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -1,25 +1,24 @@
 pub use BinOpToken::*;
 pub use Nonterminal::*;
 pub use DelimToken::*;
-pub use Lit::*;
-pub use Token::*;
+pub use LitKind::*;
+pub use TokenKind::*;
 
 use crate::ast::{self};
-use crate::parse::ParseSess;
+use crate::parse::{parse_stream_from_source_str, ParseSess};
 use crate::print::pprust;
 use crate::ptr::P;
-use crate::symbol::keywords;
-use crate::syntax::parse::parse_stream_from_source_str;
+use crate::symbol::kw;
 use crate::tokenstream::{self, DelimSpan, TokenStream, TokenTree};
 
-use syntax_pos::symbol::{self, Symbol};
-use syntax_pos::{self, Span, FileName};
+use syntax_pos::symbol::Symbol;
+use syntax_pos::{self, Span, FileName, DUMMY_SP};
 use log::info;
 
 use std::fmt;
 use std::mem;
 #[cfg(target_arch = "x86_64")]
-use rustc_data_structures::static_assert;
+use rustc_data_structures::static_assert_size;
 use rustc_data_structures::sync::Lrc;
 
 #[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
@@ -59,101 +58,143 @@ impl DelimToken {
     }
 }
 
-#[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
-pub enum Lit {
-    Bool(ast::Name), // AST only, must never appear in a `Token`
-    Byte(ast::Name),
-    Char(ast::Name),
-    Err(ast::Name),
-    Integer(ast::Name),
-    Float(ast::Name),
-    Str_(ast::Name),
-    StrRaw(ast::Name, u16), /* raw str delimited by n hash symbols */
-    ByteStr(ast::Name),
-    ByteStrRaw(ast::Name, u16), /* raw byte str delimited by n hash symbols */
+#[derive(Clone, Copy, PartialEq, RustcEncodable, RustcDecodable, Debug)]
+pub enum LitKind {
+    Bool, // AST only, must never appear in a `Token`
+    Byte,
+    Char,
+    Integer,
+    Float,
+    Str,
+    StrRaw(u16), // raw string delimited by `n` hash symbols
+    ByteStr,
+    ByteStrRaw(u16), // raw byte string delimited by `n` hash symbols
+    Err,
 }
 
-#[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_LIT: mem::size_of::<Lit>() == 8);
+/// A literal token.
+#[derive(Clone, Copy, PartialEq, RustcEncodable, RustcDecodable, Debug)]
+pub struct Lit {
+    pub kind: LitKind,
+    pub symbol: Symbol,
+    pub suffix: Option<Symbol>,
+}
 
-impl Lit {
-    crate fn literal_name(&self) -> &'static str {
-        match *self {
-            Bool(_) => panic!("literal token contains `Lit::Bool`"),
-            Byte(_) => "byte literal",
-            Char(_) => "char literal",
-            Err(_) => "invalid literal",
-            Integer(_) => "integer literal",
-            Float(_) => "float literal",
-            Str_(_) | StrRaw(..) => "string literal",
-            ByteStr(_) | ByteStrRaw(..) => "byte string literal"
+impl fmt::Display for Lit {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let Lit { kind, symbol, suffix } = *self;
+        match kind {
+            Byte          => write!(f, "b'{}'", symbol)?,
+            Char          => write!(f, "'{}'", symbol)?,
+            Str           => write!(f, "\"{}\"", symbol)?,
+            StrRaw(n)     => write!(f, "r{delim}\"{string}\"{delim}",
+                                     delim="#".repeat(n as usize),
+                                     string=symbol)?,
+            ByteStr       => write!(f, "b\"{}\"", symbol)?,
+            ByteStrRaw(n) => write!(f, "br{delim}\"{string}\"{delim}",
+                                     delim="#".repeat(n as usize),
+                                     string=symbol)?,
+            Integer       |
+            Float         |
+            Bool          |
+            Err           => write!(f, "{}", symbol)?,
         }
+
+        if let Some(suffix) = suffix {
+            write!(f, "{}", suffix)?;
+        }
+
+        Ok(())
     }
+}
 
-    crate fn may_have_suffix(&self) -> bool {
-        match *self {
-            Integer(..) | Float(..) => true,
+impl LitKind {
+    /// An English article for the literal token kind.
+    crate fn article(self) -> &'static str {
+        match self {
+            Integer | Err => "an",
+            _ => "a",
+        }
+    }
+
+    crate fn descr(self) -> &'static str {
+        match self {
+            Bool => panic!("literal token contains `Lit::Bool`"),
+            Byte => "byte",
+            Char => "char",
+            Integer => "integer",
+            Float => "float",
+            Str | StrRaw(..) => "string",
+            ByteStr | ByteStrRaw(..) => "byte string",
+            Err => "error",
+        }
+    }
+
+    crate fn may_have_suffix(self) -> bool {
+        match self {
+            Integer | Float | Err => true,
             _ => false,
         }
     }
+}
 
-    // See comments in `Nonterminal::to_tokenstream` for why we care about
-    // *probably* equal here rather than actual equality
-    fn probably_equal_for_proc_macro(&self, other: &Lit) -> bool {
-        mem::discriminant(self) == mem::discriminant(other)
+impl Lit {
+    pub fn new(kind: LitKind, symbol: Symbol, suffix: Option<Symbol>) -> Lit {
+        Lit { kind, symbol, suffix }
     }
 }
 
-pub(crate) fn ident_can_begin_expr(ident: ast::Ident, is_raw: bool) -> bool {
-    let ident_token: Token = Ident(ident, is_raw);
+pub(crate) fn ident_can_begin_expr(name: ast::Name, span: Span, is_raw: bool) -> bool {
+    let ident_token = Token::new(Ident(name, is_raw), span);
 
     !ident_token.is_reserved_ident() ||
     ident_token.is_path_segment_keyword() ||
     [
-        keywords::Async.name(),
+        kw::Async,
 
         // FIXME: remove when `await!(..)` syntax is removed
         // https://github.com/rust-lang/rust/issues/60610
-        keywords::Await.name(),
-
-        keywords::Do.name(),
-        keywords::Box.name(),
-        keywords::Break.name(),
-        keywords::Continue.name(),
-        keywords::False.name(),
-        keywords::For.name(),
-        keywords::If.name(),
-        keywords::Loop.name(),
-        keywords::Match.name(),
-        keywords::Move.name(),
-        keywords::Return.name(),
-        keywords::True.name(),
-        keywords::Unsafe.name(),
-        keywords::While.name(),
-        keywords::Yield.name(),
-        keywords::Static.name(),
-    ].contains(&ident.name)
+        kw::Await,
+
+        kw::Do,
+        kw::Box,
+        kw::Break,
+        kw::Continue,
+        kw::False,
+        kw::For,
+        kw::If,
+        kw::Let,
+        kw::Loop,
+        kw::Match,
+        kw::Move,
+        kw::Return,
+        kw::True,
+        kw::Unsafe,
+        kw::While,
+        kw::Yield,
+        kw::Static,
+    ].contains(&name)
 }
 
-fn ident_can_begin_type(ident: ast::Ident, is_raw: bool) -> bool {
-    let ident_token: Token = Ident(ident, is_raw);
+fn ident_can_begin_type(name: ast::Name, span: Span, is_raw: bool) -> bool {
+    let ident_token = Token::new(Ident(name, is_raw), span);
 
     !ident_token.is_reserved_ident() ||
     ident_token.is_path_segment_keyword() ||
     [
-        keywords::Underscore.name(),
-        keywords::For.name(),
-        keywords::Impl.name(),
-        keywords::Fn.name(),
-        keywords::Unsafe.name(),
-        keywords::Extern.name(),
-        keywords::Typeof.name(),
-        keywords::Dyn.name(),
-    ].contains(&ident.name)
+        kw::Underscore,
+        kw::For,
+        kw::Impl,
+        kw::Fn,
+        kw::Unsafe,
+        kw::Extern,
+        kw::Typeof,
+        kw::Dyn,
+    ].contains(&name)
 }
 
-#[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Debug)]
-pub enum Token {
+#[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug)]
+pub enum TokenKind {
     /* Expression-operator symbols. */
     Eq,
     Lt,
@@ -193,11 +234,11 @@ pub enum Token {
     CloseDelim(DelimToken),
 
     /* Literals */
-    Literal(Lit, Option<ast::Name>),
+    Literal(Lit),
 
     /* Name components */
-    Ident(ast::Ident, /* is_raw */ bool),
-    Lifetime(ast::Ident),
+    Ident(ast::Name, /* is_raw */ bool),
+    Lifetime(ast::Name),
 
     Interpolated(Lrc<Nonterminal>),
 
@@ -214,22 +255,69 @@ pub enum Token {
     /// A comment.
     Comment,
     Shebang(ast::Name),
+    /// A completely invalid token which should be skipped.
+    Unknown(ast::Name),
 
     Eof,
 }
 
-// `Token` is used a lot. Make sure it doesn't unintentionally get bigger.
+// `TokenKind` is used a lot. Make sure it doesn't unintentionally get bigger.
 #[cfg(target_arch = "x86_64")]
-static_assert!(MEM_SIZE_OF_STATEMENT: mem::size_of::<Token>() == 16);
+static_assert_size!(TokenKind, 16);
+
+#[derive(Clone, PartialEq, RustcEncodable, RustcDecodable, Debug)]
+pub struct Token {
+    pub kind: TokenKind,
+    pub span: Span,
+}
+
+impl TokenKind {
+    pub fn lit(kind: LitKind, symbol: Symbol, suffix: Option<Symbol>) -> TokenKind {
+        Literal(Lit::new(kind, symbol, suffix))
+    }
+
+    /// Returns tokens that are likely to be typed accidentally instead of the current token.
+    /// Enables better error recovery when the wrong token is found.
+    crate fn similar_tokens(&self) -> Option<Vec<TokenKind>> {
+        match *self {
+            Comma => Some(vec![Dot, Lt, Semi]),
+            Semi => Some(vec![Colon, Comma]),
+            _ => None
+        }
+    }
+}
 
 impl Token {
+    crate fn new(kind: TokenKind, span: Span) -> Self {
+        Token { kind, span }
+    }
+
+    /// Some token that will be thrown away later.
+    crate fn dummy() -> Self {
+        Token::new(TokenKind::Whitespace, DUMMY_SP)
+    }
+
     /// Recovers a `Token` from an `ast::Ident`. This creates a raw identifier if necessary.
-    pub fn from_ast_ident(ident: ast::Ident) -> Token {
-        Ident(ident, ident.is_raw_guess())
+    crate fn from_ast_ident(ident: ast::Ident) -> Self {
+        Token::new(Ident(ident.name, ident.is_raw_guess()), ident.span)
+    }
+
+    /// Return this token by value and leave a dummy token in its place.
+    crate fn take(&mut self) -> Self {
+        mem::replace(self, Token::dummy())
+    }
+
+    crate fn is_op(&self) -> bool {
+        match self.kind {
+            OpenDelim(..) | CloseDelim(..) | Literal(..) | DocComment(..) |
+            Ident(..) | Lifetime(..) | Interpolated(..) |
+            Whitespace | Comment | Shebang(..) | Eof => false,
+            _ => true,
+        }
     }
 
     crate fn is_like_plus(&self) -> bool {
-        match *self {
+        match self.kind {
             BinOp(Plus) | BinOpEq(Plus) => true,
             _ => false,
         }
@@ -237,9 +325,9 @@ impl Token {
 
     /// Returns `true` if the token can appear at the start of an expression.
     crate fn can_begin_expr(&self) -> bool {
-        match *self {
-            Ident(ident, is_raw)              =>
-                ident_can_begin_expr(ident, is_raw), // value name or keyword
+        match self.kind {
+            Ident(name, is_raw)              =>
+                ident_can_begin_expr(name, self.span, is_raw), // value name or keyword
             OpenDelim(..)                     | // tuple, array or block
             Literal(..)                       | // literal
             Not                               | // operator not
@@ -269,9 +357,9 @@ impl Token {
 
     /// Returns `true` if the token can appear at the start of a type.
     crate fn can_begin_type(&self) -> bool {
-        match *self {
-            Ident(ident, is_raw)        =>
-                ident_can_begin_type(ident, is_raw), // type name or keyword
+        match self.kind {
+            Ident(name, is_raw)        =>
+                ident_can_begin_type(name, self.span, is_raw), // type name or keyword
             OpenDelim(Paren)            | // tuple
             OpenDelim(Bracket)          | // array
             Not                         | // never
@@ -291,8 +379,8 @@ impl Token {
     }
 
     /// Returns `true` if the token can appear at the start of a const param.
-    pub fn can_begin_const_arg(&self) -> bool {
-        match self {
+    crate fn can_begin_const_arg(&self) -> bool {
+        match self.kind {
             OpenDelim(Brace) => true,
             Interpolated(ref nt) => match **nt {
                 NtExpr(..) => true,
@@ -306,26 +394,33 @@ impl Token {
 
     /// Returns `true` if the token can appear at the start of a generic bound.
     crate fn can_begin_bound(&self) -> bool {
-        self.is_path_start() || self.is_lifetime() || self.is_keyword(keywords::For) ||
+        self.is_path_start() || self.is_lifetime() || self.is_keyword(kw::For) ||
         self == &Question || self == &OpenDelim(Paren)
     }
 
     /// Returns `true` if the token is any literal
     crate fn is_lit(&self) -> bool {
-        match *self {
+        match self.kind {
             Literal(..) => true,
             _           => false,
         }
     }
 
+    crate fn expect_lit(&self) -> Lit {
+        match self.kind {
+            Literal(lit) => lit,
+            _=> panic!("`expect_lit` called on non-literal"),
+        }
+    }
+
     /// Returns `true` if the token is any literal, a minus (which can prefix a literal,
     /// for example a '-42', or one of the boolean idents).
     crate fn can_begin_literal_or_bool(&self) -> bool {
-        match *self {
+        match self.kind {
             Literal(..)  => true,
             BinOp(Minus) => true,
-            Ident(ident, false) if ident.name == keywords::True.name() => true,
-            Ident(ident, false) if ident.name == keywords::False.name() => true,
+            Ident(name, false) if name == kw::True => true,
+            Ident(name, false) if name == kw::False => true,
             Interpolated(ref nt) => match **nt {
                 NtLiteral(..) => true,
                 _             => false,
@@ -336,8 +431,8 @@ impl Token {
 
     /// Returns an identifier if this token is an identifier.
     pub fn ident(&self) -> Option<(ast::Ident, /* is_raw */ bool)> {
-        match *self {
-            Ident(ident, is_raw) => Some((ident, is_raw)),
+        match self.kind {
+            Ident(name, is_raw) => Some((ast::Ident::new(name, self.span), is_raw)),
             Interpolated(ref nt) => match **nt {
                 NtIdent(ident, is_raw) => Some((ident, is_raw)),
                 _ => None,
@@ -345,10 +440,11 @@ impl Token {
             _ => None,
         }
     }
+
     /// Returns a lifetime identifier if this token is a lifetime.
     pub fn lifetime(&self) -> Option<ast::Ident> {
-        match *self {
-            Lifetime(ident) => Some(ident),
+        match self.kind {
+            Lifetime(name) => Some(ast::Ident::new(name, self.span)),
             Interpolated(ref nt) => match **nt {
                 NtLifetime(ident) => Some(ident),
                 _ => None,
@@ -356,6 +452,7 @@ impl Token {
             _ => None,
         }
     }
+
     /// Returns `true` if the token is an identifier.
     pub fn is_ident(&self) -> bool {
         self.ident().is_some()
@@ -367,16 +464,13 @@ impl Token {
 
     /// Returns `true` if the token is a identifier whose name is the given
     /// string slice.
-    crate fn is_ident_named(&self, name: &str) -> bool {
-        match self.ident() {
-            Some((ident, _)) => ident.as_str() == name,
-            None => false
-        }
+    crate fn is_ident_named(&self, name: Symbol) -> bool {
+        self.ident().map_or(false, |(ident, _)| ident.name == name)
     }
 
     /// Returns `true` if the token is an interpolated path.
     fn is_path(&self) -> bool {
-        if let Interpolated(ref nt) = *self {
+        if let Interpolated(ref nt) = self.kind {
             if let NtPath(..) = **nt {
                 return true;
             }
@@ -384,10 +478,23 @@ impl Token {
         false
     }
 
+    /// Would `maybe_whole_expr` in `parser.rs` return `Ok(..)`?
+    /// That is, is this a pre-parsed expression dropped into the token stream
+    /// (which happens while parsing the result of macro expansion)?
+    crate fn is_whole_expr(&self) -> bool {
+        if let Interpolated(ref nt) = self.kind {
+            if let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtIdent(..) | NtBlock(_) = **nt {
+                return true;
+            }
+        }
+
+        false
+    }
+
     /// Returns `true` if the token is either the `mut` or `const` keyword.
     crate fn is_mutability(&self) -> bool {
-        self.is_keyword(keywords::Mut) ||
-        self.is_keyword(keywords::Const)
+        self.is_keyword(kw::Mut) ||
+        self.is_keyword(kw::Const)
     }
 
     crate fn is_qpath_start(&self) -> bool {
@@ -400,11 +507,11 @@ impl Token {
     }
 
     /// Returns `true` if the token is a given keyword, `kw`.
-    pub fn is_keyword(&self, kw: keywords::Keyword) -> bool {
-        self.ident().map(|(ident, is_raw)| ident.name == kw.name() && !is_raw).unwrap_or(false)
+    pub fn is_keyword(&self, kw: Symbol) -> bool {
+        self.ident().map(|(id, is_raw)| id.name == kw && !is_raw).unwrap_or(false)
     }
 
-    pub fn is_path_segment_keyword(&self) -> bool {
+    crate fn is_path_segment_keyword(&self) -> bool {
         match self.ident() {
             Some((id, false)) => id.is_path_segment_keyword(),
             _ => false,
@@ -413,7 +520,7 @@ impl Token {
 
     // Returns true for reserved identifiers used internally for elided lifetimes,
     // unnamed method parameters, crate root module, error recovery etc.
-    pub fn is_special_ident(&self) -> bool {
+    crate fn is_special_ident(&self) -> bool {
         match self.ident() {
             Some((id, false)) => id.is_special(),
             _ => false,
@@ -445,58 +552,52 @@ impl Token {
     }
 
     crate fn glue(self, joint: Token) -> Option<Token> {
-        Some(match self {
-            Eq => match joint {
+        let kind = match self.kind {
+            Eq => match joint.kind {
                 Eq => EqEq,
                 Gt => FatArrow,
                 _ => return None,
             },
-            Lt => match joint {
+            Lt => match joint.kind {
                 Eq => Le,
                 Lt => BinOp(Shl),
                 Le => BinOpEq(Shl),
                 BinOp(Minus) => LArrow,
                 _ => return None,
             },
-            Gt => match joint {
+            Gt => match joint.kind {
                 Eq => Ge,
                 Gt => BinOp(Shr),
                 Ge => BinOpEq(Shr),
                 _ => return None,
             },
-            Not => match joint {
+            Not => match joint.kind {
                 Eq => Ne,
                 _ => return None,
             },
-            BinOp(op) => match joint {
+            BinOp(op) => match joint.kind {
                 Eq => BinOpEq(op),
                 BinOp(And) if op == And => AndAnd,
                 BinOp(Or) if op == Or => OrOr,
                 Gt if op == Minus => RArrow,
                 _ => return None,
             },
-            Dot => match joint {
+            Dot => match joint.kind {
                 Dot => DotDot,
                 DotDot => DotDotDot,
                 _ => return None,
             },
-            DotDot => match joint {
+            DotDot => match joint.kind {
                 Dot => DotDotDot,
                 Eq => DotDotEq,
                 _ => return None,
             },
-            Colon => match joint {
+            Colon => match joint.kind {
                 Colon => ModSep,
                 _ => return None,
             },
-            SingleQuote => match joint {
-                Ident(ident, false) => {
-                    let name = Symbol::intern(&format!("'{}", ident));
-                    Lifetime(symbol::Ident {
-                        name,
-                        span: ident.span,
-                    })
-                }
+            SingleQuote => match joint.kind {
+                Ident(name, false) => Lifetime(Symbol::intern(&format!("'{}", name))),
                 _ => return None,
             },
 
@@ -504,27 +605,19 @@ impl Token {
             DotDotEq | Comma | Semi | ModSep | RArrow | LArrow | FatArrow | Pound | Dollar |
             Question | OpenDelim(..) | CloseDelim(..) |
             Literal(..) | Ident(..) | Lifetime(..) | Interpolated(..) | DocComment(..) |
-            Whitespace | Comment | Shebang(..) | Eof => return None,
-        })
-    }
+            Whitespace | Comment | Shebang(..) | Unknown(..) | Eof => return None,
+        };
 
-    /// Returns tokens that are likely to be typed accidentally instead of the current token.
-    /// Enables better error recovery when the wrong token is found.
-    crate fn similar_tokens(&self) -> Option<Vec<Token>> {
-        match *self {
-            Comma => Some(vec![Dot, Lt, Semi]),
-            Semi => Some(vec![Colon, Comma]),
-            _ => None
-        }
+        Some(Token::new(kind, self.span.to(joint.span)))
     }
 
     // See comments in `Nonterminal::to_tokenstream` for why we care about
     // *probably* equal here rather than actual equality
     crate fn probably_equal_for_proc_macro(&self, other: &Token) -> bool {
-        if mem::discriminant(self) != mem::discriminant(other) {
+        if mem::discriminant(&self.kind) != mem::discriminant(&other.kind) {
             return false
         }
-        match (self, other) {
+        match (&self.kind, &other.kind) {
             (&Eq, &Eq) |
             (&Lt, &Lt) |
             (&Le, &Le) |
@@ -564,14 +657,12 @@ impl Token {
             (&DocComment(a), &DocComment(b)) |
             (&Shebang(a), &Shebang(b)) => a == b,
 
-            (&Lifetime(a), &Lifetime(b)) => a.name == b.name,
-            (&Ident(a, b), &Ident(c, d)) => b == d && (a.name == c.name ||
-                                                       a.name == keywords::DollarCrate.name() ||
-                                                       c.name == keywords::DollarCrate.name()),
+            (&Literal(a), &Literal(b)) => a == b,
 
-            (&Literal(ref a, b), &Literal(ref c, d)) => {
-                b == d && a.probably_equal_for_proc_macro(c)
-            }
+            (&Lifetime(a), &Lifetime(b)) => a == b,
+            (&Ident(a, b), &Ident(c, d)) => b == d && (a == c ||
+                                                       a == kw::DollarCrate ||
+                                                       c == kw::DollarCrate),
 
             (&Interpolated(_), &Interpolated(_)) => false,
 
@@ -580,6 +671,12 @@ impl Token {
     }
 }
 
+impl PartialEq<TokenKind> for Token {
+    fn eq(&self, rhs: &TokenKind) -> bool {
+        self.kind == *rhs
+    }
+}
+
 #[derive(Clone, RustcEncodable, RustcDecodable)]
 /// For interpolation during macro expansion.
 pub enum Nonterminal {
@@ -669,12 +766,10 @@ impl Nonterminal {
                 prepend_attrs(sess, &item.attrs, item.tokens.as_ref(), span)
             }
             Nonterminal::NtIdent(ident, is_raw) => {
-                let token = Token::Ident(ident, is_raw);
-                Some(TokenTree::Token(ident.span, token).into())
+                Some(TokenTree::token(Ident(ident.name, is_raw), ident.span).into())
             }
             Nonterminal::NtLifetime(ident) => {
-                let token = Token::Lifetime(ident);
-                Some(TokenTree::Token(ident.span, token).into())
+                Some(TokenTree::token(Lifetime(ident.name), ident.span).into())
             }
             Nonterminal::NtTT(ref tt) => {
                 Some(tt.clone().into())
@@ -721,15 +816,6 @@ impl Nonterminal {
     }
 }
 
-crate fn is_op(tok: &Token) -> bool {
-    match *tok {
-        OpenDelim(..) | CloseDelim(..) | Literal(..) | DocComment(..) |
-        Ident(..) | Lifetime(..) | Interpolated(..) |
-        Whitespace | Comment | Shebang(..) | Eof => false,
-        _ => true,
-    }
-}
-
 fn prepend_attrs(sess: &ParseSess,
                  attrs: &[ast::Attribute],
                  tokens: Option<&tokenstream::TokenStream>,
@@ -745,7 +831,7 @@ fn prepend_attrs(sess: &ParseSess,
         assert_eq!(attr.style, ast::AttrStyle::Outer,
                    "inner attributes should prevent cached tokens from existing");
 
-        let source = pprust::attr_to_string(attr);
+        let source = pprust::attribute_to_string(attr);
         let macro_filename = FileName::macro_expansion_source_code(&source);
         if attr.is_sugared_doc {
             let stream = parse_stream_from_source_str(macro_filename, source, sess, Some(span));
@@ -759,8 +845,8 @@ fn prepend_attrs(sess: &ParseSess,
         // For simple paths, push the identifier directly
         if attr.path.segments.len() == 1 && attr.path.segments[0].args.is_none() {
             let ident = attr.path.segments[0].ident;
-            let token = Ident(ident, ident.as_str().starts_with("r#"));
-            brackets.push(tokenstream::TokenTree::Token(ident.span, token));
+            let token = Ident(ident.name, ident.as_str().starts_with("r#"));
+            brackets.push(tokenstream::TokenTree::token(token, ident.span));
 
         // ... and for more complicated paths, fall back to a reparse hack that
         // should eventually be removed.
@@ -774,7 +860,7 @@ fn prepend_attrs(sess: &ParseSess,
         // The span we list here for `#` and for `[ ... ]` are both wrong in
         // that it encompasses more than each token, but it hopefully is "good
         // enough" for now at least.
-        builder.push(tokenstream::TokenTree::Token(attr.span, Pound));
+        builder.push(tokenstream::TokenTree::token(Pound, attr.span));
         let delim_span = DelimSpan::from_single(attr.span);
         builder.push(tokenstream::TokenTree::Delimited(
             delim_span, DelimToken::Bracket, brackets.build().into()));
diff --git a/src/libsyntax/parse/unescape.rs b/src/libsyntax/parse/unescape.rs
deleted file mode 100644
index 90ee549db01..00000000000
--- a/src/libsyntax/parse/unescape.rs
+++ /dev/null
@@ -1,515 +0,0 @@
-//! Utilities for validating  string and char literals and turning them into
-//! values they represent.
-
-use std::str::Chars;
-use std::ops::Range;
-
-#[derive(Debug, PartialEq, Eq)]
-pub(crate) enum EscapeError {
-    ZeroChars,
-    MoreThanOneChar,
-
-    LoneSlash,
-    InvalidEscape,
-    BareCarriageReturn,
-    EscapeOnlyChar,
-
-    TooShortHexEscape,
-    InvalidCharInHexEscape,
-    OutOfRangeHexEscape,
-
-    NoBraceInUnicodeEscape,
-    InvalidCharInUnicodeEscape,
-    EmptyUnicodeEscape,
-    UnclosedUnicodeEscape,
-    LeadingUnderscoreUnicodeEscape,
-    OverlongUnicodeEscape,
-    LoneSurrogateUnicodeEscape,
-    OutOfRangeUnicodeEscape,
-
-    UnicodeEscapeInByte,
-    NonAsciiCharInByte,
-}
-
-/// Takes a contents of a char literal (without quotes), and returns an
-/// unescaped char or an error
-pub(crate) fn unescape_char(literal_text: &str) -> Result<char, (usize, EscapeError)> {
-    let mut chars = literal_text.chars();
-    unescape_char_or_byte(&mut chars, Mode::Char)
-        .map_err(|err| (literal_text.len() - chars.as_str().len(), err))
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-pub(crate) fn unescape_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    unescape_str_or_byte_str(literal_text, Mode::Str, callback)
-}
-
-pub(crate) fn unescape_byte(literal_text: &str) -> Result<u8, (usize, EscapeError)> {
-    let mut chars = literal_text.chars();
-    unescape_char_or_byte(&mut chars, Mode::Byte)
-        .map(byte_from_char)
-        .map_err(|err| (literal_text.len() - chars.as_str().len(), err))
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-pub(crate) fn unescape_byte_str<F>(literal_text: &str, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<u8, EscapeError>),
-{
-    unescape_str_or_byte_str(literal_text, Mode::ByteStr, &mut |range, char| {
-        callback(range, char.map(byte_from_char))
-    })
-}
-
-#[derive(Debug, Clone, Copy)]
-pub(crate) enum Mode {
-    Char,
-    Str,
-    Byte,
-    ByteStr,
-}
-
-impl Mode {
-    fn in_single_quotes(self) -> bool {
-        match self {
-            Mode::Char | Mode::Byte => true,
-            Mode::Str | Mode::ByteStr => false,
-        }
-    }
-
-    pub(crate) fn in_double_quotes(self) -> bool {
-        !self.in_single_quotes()
-    }
-
-    pub(crate) fn is_bytes(self) -> bool {
-        match self {
-            Mode::Byte | Mode::ByteStr => true,
-            Mode::Char | Mode::Str => false,
-        }
-    }
-}
-
-
-fn scan_escape(first_char: char, chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
-    if first_char != '\\' {
-        return match first_char {
-            '\t' | '\n' => Err(EscapeError::EscapeOnlyChar),
-            '\r' => Err(if chars.clone().next() == Some('\n') {
-                EscapeError::EscapeOnlyChar
-            } else {
-                EscapeError::BareCarriageReturn
-            }),
-            '\'' if mode.in_single_quotes() => Err(EscapeError::EscapeOnlyChar),
-            '"' if mode.in_double_quotes() => Err(EscapeError::EscapeOnlyChar),
-            _ => {
-                if mode.is_bytes() && !first_char.is_ascii() {
-                    return Err(EscapeError::NonAsciiCharInByte);
-                }
-                Ok(first_char)
-            }
-        };
-    }
-
-    let second_char = chars.next().ok_or(EscapeError::LoneSlash)?;
-
-    let res = match second_char {
-        '"' => '"',
-        'n' => '\n',
-        'r' => '\r',
-        't' => '\t',
-        '\\' => '\\',
-        '\'' => '\'',
-        '0' => '\0',
-
-        'x' => {
-            let hi = chars.next().ok_or(EscapeError::TooShortHexEscape)?;
-            let hi = hi.to_digit(16).ok_or(EscapeError::InvalidCharInHexEscape)?;
-
-            let lo = chars.next().ok_or(EscapeError::TooShortHexEscape)?;
-            let lo = lo.to_digit(16).ok_or(EscapeError::InvalidCharInHexEscape)?;
-
-            let value = hi * 16 + lo;
-
-            if !mode.is_bytes() && !is_ascii(value) {
-                return Err(EscapeError::OutOfRangeHexEscape);
-            }
-            let value = value as u8;
-
-            value as char
-        }
-
-        'u' => {
-            if chars.next() != Some('{') {
-                return Err(EscapeError::NoBraceInUnicodeEscape);
-            }
-
-            let mut n_digits = 1;
-            let mut value: u32 = match chars.next().ok_or(EscapeError::UnclosedUnicodeEscape)? {
-                '_' => return Err(EscapeError::LeadingUnderscoreUnicodeEscape),
-                '}' => return Err(EscapeError::EmptyUnicodeEscape),
-                c => c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?,
-            };
-
-            loop {
-                match chars.next() {
-                    None => return Err(EscapeError::UnclosedUnicodeEscape),
-                    Some('_') => continue,
-                    Some('}') => {
-                        if n_digits > 6 {
-                            return Err(EscapeError::OverlongUnicodeEscape);
-                        }
-                        if mode.is_bytes() {
-                            return Err(EscapeError::UnicodeEscapeInByte);
-                        }
-
-                        break std::char::from_u32(value).ok_or_else(|| {
-                            if value > 0x10FFFF {
-                                EscapeError::OutOfRangeUnicodeEscape
-                            } else {
-                                EscapeError::LoneSurrogateUnicodeEscape
-                            }
-                        })?;
-                    }
-                    Some(c) => {
-                        let digit = c.to_digit(16).ok_or(EscapeError::InvalidCharInUnicodeEscape)?;
-                        n_digits += 1;
-                        if n_digits > 6 {
-                            continue;
-                        }
-                        let digit = digit as u32;
-                        value = value * 16 + digit;
-                    }
-                };
-            }
-        }
-        _ => return Err(EscapeError::InvalidEscape),
-    };
-    Ok(res)
-}
-
-fn unescape_char_or_byte(chars: &mut Chars<'_>, mode: Mode) -> Result<char, EscapeError> {
-    let first_char = chars.next().ok_or(EscapeError::ZeroChars)?;
-    let res = scan_escape(first_char, chars, mode)?;
-    if chars.next().is_some() {
-        return Err(EscapeError::MoreThanOneChar);
-    }
-    Ok(res)
-}
-
-/// Takes a contents of a string literal (without quotes) and produces a
-/// sequence of escaped characters or errors.
-fn unescape_str_or_byte_str<F>(src: &str, mode: Mode, callback: &mut F)
-where
-    F: FnMut(Range<usize>, Result<char, EscapeError>),
-{
-    assert!(mode.in_double_quotes());
-    let initial_len = src.len();
-    let mut chars = src.chars();
-    while let Some(first_char) = chars.next() {
-        let start = initial_len - chars.as_str().len() - first_char.len_utf8();
-
-        let unescaped_char = match first_char {
-            '\\' => {
-                let (second_char, third_char) = {
-                    let mut chars = chars.clone();
-                    (chars.next(), chars.next())
-                };
-                match (second_char, third_char) {
-                    (Some('\n'), _) | (Some('\r'), Some('\n')) => {
-                        skip_ascii_whitespace(&mut chars);
-                        continue;
-                    }
-                    _ => scan_escape(first_char, &mut chars, mode),
-                }
-            }
-            '\r' => {
-                let second_char = chars.clone().next();
-                if second_char == Some('\n') {
-                    chars.next();
-                    Ok('\n')
-                } else {
-                    scan_escape(first_char, &mut chars, mode)
-                }
-            }
-            '\n' => Ok('\n'),
-            '\t' => Ok('\t'),
-            _ => scan_escape(first_char, &mut chars, mode),
-        };
-        let end = initial_len - chars.as_str().len();
-        callback(start..end, unescaped_char);
-    }
-
-    fn skip_ascii_whitespace(chars: &mut Chars<'_>) {
-        let str = chars.as_str();
-        let first_non_space = str
-            .bytes()
-            .position(|b| b != b' ' && b != b'\t' && b != b'\n' && b != b'\r')
-            .unwrap_or(str.len());
-        *chars = str[first_non_space..].chars()
-    }
-}
-
-fn byte_from_char(c: char) -> u8 {
-    let res = c as u32;
-    assert!(res <= u8::max_value() as u32, "guaranteed because of Mode::Byte");
-    res as u8
-}
-
-fn is_ascii(x: u32) -> bool {
-    x <= 0x7F
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_unescape_char_bad() {
-        fn check(literal_text: &str, expected_error: EscapeError) {
-            let actual_result = unescape_char(literal_text).map_err(|(_offset, err)| err);
-            assert_eq!(actual_result, Err(expected_error));
-        }
-
-        check("", EscapeError::ZeroChars);
-        check(r"\", EscapeError::LoneSlash);
-
-        check("\n", EscapeError::EscapeOnlyChar);
-        check("\r\n", EscapeError::EscapeOnlyChar);
-        check("\t", EscapeError::EscapeOnlyChar);
-        check("'", EscapeError::EscapeOnlyChar);
-        check("\r", EscapeError::BareCarriageReturn);
-
-        check("spam", EscapeError::MoreThanOneChar);
-        check(r"\x0ff", EscapeError::MoreThanOneChar);
-        check(r#"\"a"#, EscapeError::MoreThanOneChar);
-        check(r"\na", EscapeError::MoreThanOneChar);
-        check(r"\ra", EscapeError::MoreThanOneChar);
-        check(r"\ta", EscapeError::MoreThanOneChar);
-        check(r"\\a", EscapeError::MoreThanOneChar);
-        check(r"\'a", EscapeError::MoreThanOneChar);
-        check(r"\0a", EscapeError::MoreThanOneChar);
-        check(r"\u{0}x", EscapeError::MoreThanOneChar);
-        check(r"\u{1F63b}}", EscapeError::MoreThanOneChar);
-
-        check(r"\v", EscapeError::InvalidEscape);
-        check(r"\💩", EscapeError::InvalidEscape);
-        check(r"\●", EscapeError::InvalidEscape);
-
-        check(r"\x", EscapeError::TooShortHexEscape);
-        check(r"\x0", EscapeError::TooShortHexEscape);
-        check(r"\xf", EscapeError::TooShortHexEscape);
-        check(r"\xa", EscapeError::TooShortHexEscape);
-        check(r"\xx", EscapeError::InvalidCharInHexEscape);
-        check(r"\xы", EscapeError::InvalidCharInHexEscape);
-        check(r"\x🦀", EscapeError::InvalidCharInHexEscape);
-        check(r"\xtt", EscapeError::InvalidCharInHexEscape);
-        check(r"\xff", EscapeError::OutOfRangeHexEscape);
-        check(r"\xFF", EscapeError::OutOfRangeHexEscape);
-        check(r"\x80", EscapeError::OutOfRangeHexEscape);
-
-        check(r"\u", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u[0123]", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u{0x}", EscapeError::InvalidCharInUnicodeEscape);
-        check(r"\u{", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{0000", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{}", EscapeError::EmptyUnicodeEscape);
-        check(r"\u{_0000}", EscapeError::LeadingUnderscoreUnicodeEscape);
-        check(r"\u{0000000}", EscapeError::OverlongUnicodeEscape);
-        check(r"\u{FFFFFF}", EscapeError::OutOfRangeUnicodeEscape);
-        check(r"\u{ffffff}", EscapeError::OutOfRangeUnicodeEscape);
-        check(r"\u{ffffff}", EscapeError::OutOfRangeUnicodeEscape);
-
-        check(r"\u{DC00}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DDDD}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DFFF}", EscapeError::LoneSurrogateUnicodeEscape);
-
-        check(r"\u{D800}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DAAA}", EscapeError::LoneSurrogateUnicodeEscape);
-        check(r"\u{DBFF}", EscapeError::LoneSurrogateUnicodeEscape);
-    }
-
-    #[test]
-    fn test_unescape_char_good() {
-        fn check(literal_text: &str, expected_char: char) {
-            let actual_result = unescape_char(literal_text);
-            assert_eq!(actual_result, Ok(expected_char));
-        }
-
-        check("a", 'a');
-        check("ы", 'ы');
-        check("🦀", '🦀');
-
-        check(r#"\""#, '"');
-        check(r"\n", '\n');
-        check(r"\r", '\r');
-        check(r"\t", '\t');
-        check(r"\\", '\\');
-        check(r"\'", '\'');
-        check(r"\0", '\0');
-
-        check(r"\x00", '\0');
-        check(r"\x5a", 'Z');
-        check(r"\x5A", 'Z');
-        check(r"\x7f", 127 as char);
-
-        check(r"\u{0}", '\0');
-        check(r"\u{000000}", '\0');
-        check(r"\u{41}", 'A');
-        check(r"\u{0041}", 'A');
-        check(r"\u{00_41}", 'A');
-        check(r"\u{4__1__}", 'A');
-        check(r"\u{1F63b}", '😻');
-    }
-
-    #[test]
-    fn test_unescape_str_good() {
-        fn check(literal_text: &str, expected: &str) {
-            let mut buf = Ok(String::with_capacity(literal_text.len()));
-            unescape_str(literal_text, &mut |range, c| {
-                if let Ok(b) = &mut buf {
-                    match c {
-                        Ok(c) => b.push(c),
-                        Err(e) => buf = Err((range, e)),
-                    }
-                }
-            });
-            let buf = buf.as_ref().map(|it| it.as_ref());
-            assert_eq!(buf, Ok(expected))
-        }
-
-        check("foo", "foo");
-        check("", "");
-        check(" \t\n\r\n", " \t\n\n");
-
-        check("hello \\\n     world", "hello world");
-        check("hello \\\r\n     world", "hello world");
-        check("thread's", "thread's")
-    }
-
-    #[test]
-    fn test_unescape_byte_bad() {
-        fn check(literal_text: &str, expected_error: EscapeError) {
-            let actual_result = unescape_byte(literal_text).map_err(|(_offset, err)| err);
-            assert_eq!(actual_result, Err(expected_error));
-        }
-
-        check("", EscapeError::ZeroChars);
-        check(r"\", EscapeError::LoneSlash);
-
-        check("\n", EscapeError::EscapeOnlyChar);
-        check("\r\n", EscapeError::EscapeOnlyChar);
-        check("\t", EscapeError::EscapeOnlyChar);
-        check("'", EscapeError::EscapeOnlyChar);
-        check("\r", EscapeError::BareCarriageReturn);
-
-        check("spam", EscapeError::MoreThanOneChar);
-        check(r"\x0ff", EscapeError::MoreThanOneChar);
-        check(r#"\"a"#, EscapeError::MoreThanOneChar);
-        check(r"\na", EscapeError::MoreThanOneChar);
-        check(r"\ra", EscapeError::MoreThanOneChar);
-        check(r"\ta", EscapeError::MoreThanOneChar);
-        check(r"\\a", EscapeError::MoreThanOneChar);
-        check(r"\'a", EscapeError::MoreThanOneChar);
-        check(r"\0a", EscapeError::MoreThanOneChar);
-
-        check(r"\v", EscapeError::InvalidEscape);
-        check(r"\💩", EscapeError::InvalidEscape);
-        check(r"\●", EscapeError::InvalidEscape);
-
-        check(r"\x", EscapeError::TooShortHexEscape);
-        check(r"\x0", EscapeError::TooShortHexEscape);
-        check(r"\xa", EscapeError::TooShortHexEscape);
-        check(r"\xf", EscapeError::TooShortHexEscape);
-        check(r"\xx", EscapeError::InvalidCharInHexEscape);
-        check(r"\xы", EscapeError::InvalidCharInHexEscape);
-        check(r"\x🦀", EscapeError::InvalidCharInHexEscape);
-        check(r"\xtt", EscapeError::InvalidCharInHexEscape);
-
-        check(r"\u", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u[0123]", EscapeError::NoBraceInUnicodeEscape);
-        check(r"\u{0x}", EscapeError::InvalidCharInUnicodeEscape);
-        check(r"\u{", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{0000", EscapeError::UnclosedUnicodeEscape);
-        check(r"\u{}", EscapeError::EmptyUnicodeEscape);
-        check(r"\u{_0000}", EscapeError::LeadingUnderscoreUnicodeEscape);
-        check(r"\u{0000000}", EscapeError::OverlongUnicodeEscape);
-
-        check("ы", EscapeError::NonAsciiCharInByte);
-        check("🦀", EscapeError::NonAsciiCharInByte);
-
-        check(r"\u{0}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{000000}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{41}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{0041}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{00_41}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{4__1__}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{1F63b}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{0}x", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{1F63b}}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{FFFFFF}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{ffffff}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{ffffff}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DC00}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DDDD}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DFFF}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{D800}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DAAA}", EscapeError::UnicodeEscapeInByte);
-        check(r"\u{DBFF}", EscapeError::UnicodeEscapeInByte);
-    }
-
-    #[test]
-    fn test_unescape_byte_good() {
-        fn check(literal_text: &str, expected_byte: u8) {
-            let actual_result = unescape_byte(literal_text);
-            assert_eq!(actual_result, Ok(expected_byte));
-        }
-
-        check("a", b'a');
-
-        check(r#"\""#, b'"');
-        check(r"\n", b'\n');
-        check(r"\r", b'\r');
-        check(r"\t", b'\t');
-        check(r"\\", b'\\');
-        check(r"\'", b'\'');
-        check(r"\0", b'\0');
-
-        check(r"\x00", b'\0');
-        check(r"\x5a", b'Z');
-        check(r"\x5A", b'Z');
-        check(r"\x7f", 127);
-        check(r"\x80", 128);
-        check(r"\xff", 255);
-        check(r"\xFF", 255);
-    }
-
-    #[test]
-    fn test_unescape_byte_str_good() {
-        fn check(literal_text: &str, expected: &[u8]) {
-            let mut buf = Ok(Vec::with_capacity(literal_text.len()));
-            unescape_byte_str(literal_text, &mut |range, c| {
-                if let Ok(b) = &mut buf {
-                    match c {
-                        Ok(c) => b.push(c),
-                        Err(e) => buf = Err((range, e)),
-                    }
-                }
-            });
-            let buf = buf.as_ref().map(|it| it.as_ref());
-            assert_eq!(buf, Ok(expected))
-        }
-
-        check("foo", b"foo");
-        check("", b"");
-        check(" \t\n\r\n", b" \t\n\n");
-
-        check("hello \\\n     world", b"hello world");
-        check("hello \\\r\n     world", b"hello world");
-        check("thread's", b"thread's")
-    }
-}
diff --git a/src/libsyntax/parse/unescape_error_reporting.rs b/src/libsyntax/parse/unescape_error_reporting.rs
index 22777c0884f..7eee07e61a9 100644
--- a/src/libsyntax/parse/unescape_error_reporting.rs
+++ b/src/libsyntax/parse/unescape_error_reporting.rs
@@ -3,12 +3,11 @@
 use std::ops::Range;
 use std::iter::once;
 
+use rustc_lexer::unescape::{EscapeError, Mode};
 use syntax_pos::{Span, BytePos};
 
 use crate::errors::{Handler, Applicability};
 
-use super::unescape::{EscapeError, Mode};
-
 pub(crate) fn emit_unescape_error(
     handler: &Handler,
     // interior part of the literal, without quotes
@@ -80,6 +79,11 @@ pub(crate) fn emit_unescape_error(
             };
             handler.span_err(span, msg);
         }
+        EscapeError::BareCarriageReturnInRawString => {
+            assert!(mode.in_double_quotes());
+            let msg = "bare CR not allowed in raw string";
+            handler.span_err(span, msg);
+        }
         EscapeError::InvalidEscape => {
             let (c, span) = last_char();
 
@@ -124,6 +128,11 @@ pub(crate) fn emit_unescape_error(
             handler.span_err(span, "byte constant must be ASCII. \
                                     Use a \\xHH escape for a non-ASCII byte")
         }
+        EscapeError::NonAsciiCharInByteString => {
+            assert!(mode.is_bytes());
+            let (_c, span) = last_char();
+            handler.span_err(span, "raw byte string must be ASCII")
+        }
         EscapeError::OutOfRangeHexEscape => {
             handler.span_err(span, "this form of character escape may only be used \
                                     with characters in the range [\\x00-\\x7f]")
@@ -181,7 +190,7 @@ pub(crate) fn emit_unescape_error(
             handler.span_err(span, "empty character literal")
         }
         EscapeError::LoneSlash => {
-            panic!("lexer accepted unterminated literal with trailing slash")
+            handler.span_err(span, "invalid trailing slash in literal")
         }
     }
 }