move syntax::parse -> librustc_parse

also move MACRO_ARGUMENTS -> librustc_parse

11 files changed, 10572 insertions, 0 deletions

diff --git a/src/librustc_parse/parser/attr.rs b/src/librustc_parse/parser/attr.rs
new file mode 100644
index 00000000000..524b551e54c
--- /dev/null
+++ b/src/librustc_parse/parser/attr.rs
@@ -0,0 +1,351 @@
+use super::{SeqSep, Parser, TokenType, PathStyle};
+use syntax::attr;
+use syntax::ast;
+use syntax::util::comments;
+use syntax::token::{self, Nonterminal, DelimToken};
+use syntax::tokenstream::{TokenStream, TokenTree};
+use syntax_pos::{Span, Symbol};
+use errors::PResult;
+
+use log::debug;
+
+#[derive(Debug)]
+enum InnerAttributeParsePolicy<'a> {
+    Permitted,
+    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> {
+    /// Parses attributes that appear before an item.
+    pub(super) 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.kind {
+                token::Pound => {
+                    let inner_error_reason = if just_parsed_doc_comment {
+                        "an inner attribute is not permitted following an outer doc comment"
+                    } else if !attrs.is_empty() {
+                        "an inner attribute is not permitted following an outer attribute"
+                    } else {
+                        DEFAULT_UNEXPECTED_INNER_ATTR_ERR_MSG
+                    };
+                    let 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 = self.mk_doc_comment(s);
+                    if attr.style != ast::AttrStyle::Outer {
+                        let mut err = self.fatal("expected outer doc comment");
+                        err.note("inner doc comments like this (starting with \
+                                  `//!` or `/*!`) can only appear before items");
+                        return Err(err);
+                    }
+                    attrs.push(attr);
+                    self.bump();
+                    just_parsed_doc_comment = true;
+                }
+                _ => break,
+            }
+        }
+        Ok(attrs)
+    }
+
+    fn mk_doc_comment(&self, s: Symbol) -> ast::Attribute {
+        let style = comments::doc_comment_style(&s.as_str());
+        attr::mk_doc_comment(style, s, self.token.span)
+    }
+
+    /// Matches `attribute = # ! [ meta_item ]`.
+    ///
+    /// If `permit_inner` is `true`, then a leading `!` indicates an inner
+    /// attribute.
+    pub fn parse_attribute(&mut self, permit_inner: bool) -> PResult<'a, ast::Attribute> {
+        debug!("parse_attribute: permit_inner={:?} self.token={:?}",
+               permit_inner,
+               self.token);
+        let inner_parse_policy = if permit_inner {
+            InnerAttributeParsePolicy::Permitted
+        } else {
+            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)
+    }
+
+    /// The same as `parse_attribute`, except it takes in an `InnerAttributeParsePolicy`
+    /// that prescribes how to handle inner attributes.
+    fn parse_attribute_with_inner_parse_policy(
+        &mut self,
+        inner_parse_policy: InnerAttributeParsePolicy<'_>
+    ) -> PResult<'a, ast::Attribute> {
+        debug!("parse_attribute_with_inner_parse_policy: inner_parse_policy={:?} self.token={:?}",
+               inner_parse_policy,
+               self.token);
+        let (span, item, style) = match self.token.kind {
+            token::Pound => {
+                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();
+                    ast::AttrStyle::Inner
+                } else {
+                    ast::AttrStyle::Outer
+                };
+
+                self.expect(&token::OpenDelim(token::Bracket))?;
+                let item = self.parse_attr_item()?;
+                self.expect(&token::CloseDelim(token::Bracket))?;
+                let hi = self.prev_span;
+
+                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, item, style)
+            }
+            _ => {
+                let token_str = self.this_token_to_string();
+                return Err(self.fatal(&format!("expected `#`, found `{}`", token_str)));
+            }
+        };
+
+        Ok(attr::mk_attr_from_item(style, item, span))
+    }
+
+    /// Parses an inner part of an attribute (the path and following tokens).
+    /// The tokens must be either a delimited token stream, or empty token stream,
+    /// or the "legacy" key-value form.
+    ///     PATH `(` TOKEN_STREAM `)`
+    ///     PATH `[` TOKEN_STREAM `]`
+    ///     PATH `{` TOKEN_STREAM `}`
+    ///     PATH
+    ///     PATH `=` UNSUFFIXED_LIT
+    /// The delimiters or `=` are still put into the resulting token stream.
+    pub fn parse_attr_item(&mut self) -> PResult<'a, ast::AttrItem> {
+        let item = match self.token.kind {
+            token::Interpolated(ref nt) => match **nt {
+                Nonterminal::NtMeta(ref item) => Some(item.clone()),
+                _ => None,
+            },
+            _ => None,
+        };
+        Ok(if let Some(item) = item {
+            self.bump();
+            item
+        } else {
+            let path = self.parse_path(PathStyle::Mod)?;
+            let tokens = if self.check(&token::OpenDelim(DelimToken::Paren)) ||
+               self.check(&token::OpenDelim(DelimToken::Bracket)) ||
+               self.check(&token::OpenDelim(DelimToken::Brace)) {
+                   self.parse_token_tree().into()
+            } else if self.eat(&token::Eq) {
+                let eq = TokenTree::token(token::Eq, self.prev_span);
+                let mut is_interpolated_expr = false;
+                if let token::Interpolated(nt) = &self.token.kind {
+                    if let token::NtExpr(..) = **nt {
+                        is_interpolated_expr = true;
+                    }
+                }
+                let token_tree = if is_interpolated_expr {
+                    // We need to accept arbitrary interpolated expressions to continue
+                    // supporting things like `doc = $expr` that work on stable.
+                    // Non-literal interpolated expressions are rejected after expansion.
+                    self.parse_token_tree()
+                } else {
+                    self.parse_unsuffixed_lit()?.token_tree()
+                };
+                TokenStream::new(vec![eq.into(), token_tree.into()])
+            } else {
+                TokenStream::default()
+            };
+            ast::AttrItem { path, tokens }
+        })
+    }
+
+    /// Parses attributes that appear after the opening of an item. These should
+    /// be preceded by an exclamation mark, but we accept and warn about one
+    /// terminated by a semicolon.
+    ///
+    /// Matches `inner_attrs*`.
+    crate fn parse_inner_attributes(&mut self) -> PResult<'a, Vec<ast::Attribute>> {
+        let mut attrs: Vec<ast::Attribute> = vec![];
+        loop {
+            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) {
+                        break;
+                    }
+
+                    let attr = self.parse_attribute(true)?;
+                    assert_eq!(attr.style, ast::AttrStyle::Inner);
+                    attrs.push(attr);
+                }
+                token::DocComment(s) => {
+                    // We need to get the position of this token before we bump.
+                    let attr = self.mk_doc_comment(s);
+                    if attr.style == ast::AttrStyle::Inner {
+                        attrs.push(attr);
+                        self.bump();
+                    } else {
+                        break;
+                    }
+                }
+                _ => break,
+            }
+        }
+        Ok(attrs)
+    }
+
+    fn parse_unsuffixed_lit(&mut self) -> PResult<'a, ast::Lit> {
+        let lit = self.parse_lit()?;
+        debug!("checking if {:?} is unusuffixed", lit);
+
+        if !lit.kind.is_unsuffixed() {
+            let msg = "suffixed literals are not allowed in attributes";
+            self.diagnostic().struct_span_err(lit.span, msg)
+                             .help("instead of using a suffixed literal \
+                                    (1u8, 1.0f32, etc.), use an unsuffixed version \
+                                    (1, 1.0, etc.).")
+                             .emit()
+        }
+
+        Ok(lit)
+    }
+
+    /// Parses `cfg_attr(pred, attr_item_list)` where `attr_item_list` is comma-delimited.
+    pub fn parse_cfg_attr(&mut self) -> PResult<'a, (ast::MetaItem, Vec<(ast::AttrItem, Span)>)> {
+        self.expect(&token::OpenDelim(token::Paren))?;
+
+        let cfg_predicate = self.parse_meta_item()?;
+        self.expect(&token::Comma)?;
+
+        // Presumably, the majority of the time there will only be one attr.
+        let mut expanded_attrs = Vec::with_capacity(1);
+
+        while !self.check(&token::CloseDelim(token::Paren)) {
+            let lo = self.token.span.lo();
+            let item = self.parse_attr_item()?;
+            expanded_attrs.push((item, self.prev_span.with_lo(lo)));
+            self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Paren)])?;
+        }
+
+        self.expect(&token::CloseDelim(token::Paren))?;
+        Ok((cfg_predicate, expanded_attrs))
+    }
+
+    /// Matches the following grammar (per RFC 1559).
+    ///
+    ///     meta_item : PATH ( '=' 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.kind {
+            token::Interpolated(ref nt) => match **nt {
+                token::NtMeta(ref e) => Some(e.clone()),
+                _ => None,
+            },
+            _ => None,
+        };
+
+        if let Some(item) = nt_meta {
+            return match item.meta(item.path.span) {
+                Some(meta) => {
+                    self.bump();
+                    Ok(meta)
+                }
+                None => self.unexpected(),
+            }
+        }
+
+        let lo = self.token.span;
+        let path = self.parse_path(PathStyle::Mod)?;
+        let kind = self.parse_meta_item_kind()?;
+        let span = lo.to(self.prev_span);
+        Ok(ast::MetaItem { path, kind, span })
+    }
+
+    crate fn parse_meta_item_kind(&mut self) -> PResult<'a, ast::MetaItemKind> {
+        Ok(if self.eat(&token::Eq) {
+            ast::MetaItemKind::NameValue(self.parse_unsuffixed_lit()?)
+        } else if self.eat(&token::OpenDelim(token::Paren)) {
+            ast::MetaItemKind::List(self.parse_meta_seq()?)
+        } else {
+            ast::MetaItemKind::Word
+        })
+    }
+
+    /// Matches `meta_item_inner : (meta_item | UNSUFFIXED_LIT) ;`.
+    fn parse_meta_item_inner(&mut self) -> PResult<'a, ast::NestedMetaItem> {
+        match self.parse_unsuffixed_lit() {
+            Ok(lit) => {
+                return Ok(ast::NestedMetaItem::Literal(lit))
+            }
+            Err(ref mut err) => err.cancel(),
+        }
+
+        match self.parse_meta_item() {
+            Ok(mi) => {
+                return Ok(ast::NestedMetaItem::MetaItem(mi))
+            }
+            Err(ref mut err) => err.cancel(),
+        }
+
+        let found = self.this_token_to_string();
+        let msg = format!("expected unsuffixed literal or identifier, found `{}`", found);
+        Err(self.diagnostic().struct_span_err(self.token.span, &msg))
+    }
+
+    /// Matches `meta_seq = ( COMMASEP(meta_item_inner) )`.
+    fn parse_meta_seq(&mut self) -> PResult<'a, Vec<ast::NestedMetaItem>> {
+        self.parse_seq_to_end(&token::CloseDelim(token::Paren),
+                              SeqSep::trailing_allowed(token::Comma),
+                              |p: &mut Parser<'a>| p.parse_meta_item_inner())
+    }
+}
diff --git a/src/librustc_parse/parser/diagnostics.rs b/src/librustc_parse/parser/diagnostics.rs
new file mode 100644
index 00000000000..38eae008537
--- /dev/null
+++ b/src/librustc_parse/parser/diagnostics.rs
@@ -0,0 +1,1549 @@
+use super::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType, SeqSep, Parser};
+
+use syntax::ast::{
+    self, Param, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
+    Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind,
+};
+use syntax::token::{self, TokenKind, token_can_begin_expr};
+use syntax::print::pprust;
+use syntax::ptr::P;
+use syntax::symbol::{kw, sym};
+use syntax::ThinVec;
+use syntax::util::parser::AssocOp;
+use syntax::struct_span_err;
+
+use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, pluralize};
+use rustc_data_structures::fx::FxHashSet;
+use syntax_pos::{Span, DUMMY_SP, MultiSpan, SpanSnippetError};
+use log::{debug, trace};
+use std::mem;
+
+const TURBOFISH: &'static str = "use `::<...>` instead of `<...>` to specify type arguments";
+
+/// Creates a placeholder argument.
+pub(super) fn dummy_arg(ident: Ident) -> Param {
+    let pat = P(Pat {
+        id: ast::DUMMY_NODE_ID,
+        kind: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
+        span: ident.span,
+    });
+    let ty = Ty {
+        kind: TyKind::Err,
+        span: ident.span,
+        id: ast::DUMMY_NODE_ID
+    };
+    Param {
+        attrs: ThinVec::default(),
+        id: ast::DUMMY_NODE_ID,
+        pat,
+        span: ident.span,
+        ty: P(ty),
+        is_placeholder: false,
+    }
+}
+
+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(super) trait RecoverQPath: Sized + 'static {
+    const PATH_STYLE: PathStyle = PathStyle::Expr;
+    fn to_ty(&self) -> Option<P<Ty>>;
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
+}
+
+impl RecoverQPath for Ty {
+    const PATH_STYLE: PathStyle = PathStyle::Type;
+    fn to_ty(&self) -> Option<P<Ty>> {
+        Some(P(self.clone()))
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            kind: TyKind::Path(qself, path),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+impl RecoverQPath for Pat {
+    fn to_ty(&self) -> Option<P<Ty>> {
+        self.to_ty()
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            kind: PatKind::Path(qself, path),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+impl RecoverQPath for Expr {
+    fn to_ty(&self) -> Option<P<Ty>> {
+        self.to_ty()
+    }
+    fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
+        Self {
+            span: path.span,
+            kind: ExprKind::Path(qself, path),
+            attrs: ThinVec::new(),
+            id: ast::DUMMY_NODE_ID,
+        }
+    }
+}
+
+/// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
+crate enum ConsumeClosingDelim {
+    Yes,
+    No,
+}
+
+impl<'a> Parser<'a> {
+    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
+        self.span_fatal(self.token.span, m)
+    }
+
+    crate fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+        self.sess.span_diagnostic.struct_span_fatal(sp, m)
+    }
+
+    pub(super) fn span_fatal_err<S: Into<MultiSpan>>(
+        &self,
+        sp: S,
+        err: Error,
+    ) -> DiagnosticBuilder<'a> {
+        err.span_err(sp, self.diagnostic())
+    }
+
+    pub(super) fn bug(&self, m: &str) -> ! {
+        self.sess.span_diagnostic.span_bug(self.token.span, m)
+    }
+
+    pub(super) fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
+        self.sess.span_diagnostic.span_err(sp, m)
+    }
+
+    pub fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+        self.sess.span_diagnostic.struct_span_err(sp, m)
+    }
+
+    pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
+        self.sess.span_diagnostic.span_bug(sp, m)
+    }
+
+    pub(super) fn diagnostic(&self) -> &'a errors::Handler {
+        &self.sess.span_diagnostic
+    }
+
+    pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
+        self.sess.source_map().span_to_snippet(span)
+    }
+
+    pub(super) 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(super) 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_descr();
+        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 {}", 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 {}", 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 sm = self.sess.source_map();
+        if self.prev_span == 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, label_exp);
+        } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
+            // 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);
+        } else {
+            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(
+        &mut self,
+        err: &mut DiagnosticBuilder<'_>,
+        maybe_expected_semicolon: bool,
+    ) {
+        if let Some((sp, likely_path)) = self.last_type_ascription.take() {
+            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());
+
+            let allow_unstable = self.sess.unstable_features.is_nightly_build();
+
+            if likely_path {
+                err.span_suggestion(
+                    sp,
+                    "maybe write a path separator here",
+                    "::".to_string(),
+                    if allow_unstable {
+                        Applicability::MaybeIncorrect
+                    } else {
+                        Applicability::MachineApplicable
+                    },
+                );
+            } 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 allow_unstable {
+                err.span_label(sp, "tried to parse a type due to this type ascription");
+            } else {
+                err.span_label(sp, "tried to parse a type due to this");
+            }
+            if allow_unstable {
+                // Give extra information about type ascription only if it's a nightly compiler.
+                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.
+    pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
+        if let Err(ref mut err) = self.parse_seq_to_before_tokens(
+            kets,
+            SeqSep::none(),
+            TokenExpectType::Expect,
+            |p| Ok(p.parse_token_tree()),
+        ) {
+            err.cancel();
+        }
+    }
+
+    /// 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
+    /// ```
+    pub(super) 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 total_num_of_gt = number_of_gt + number_of_shr * 2;
+            self.diagnostic()
+                .struct_span_err(
+                    span,
+                    &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
+                )
+                .span_suggestion(
+                    span,
+                    &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
+                    String::new(),
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+    }
+
+    /// Produces an error if comparison operators are chained (RFC #558).
+    /// We only need to check the LHS, not the RHS, because all comparison ops have same
+    /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
+    ///
+    /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
+    /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
+    /// case.
+    ///
+    /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
+    /// associative we can infer that we have:
+    ///
+    ///           outer_op
+    ///           /   \
+    ///     inner_op   r2
+    ///        /  \
+    ///     l1    r1
+    pub(super) fn check_no_chained_comparison(
+        &mut self,
+        lhs: &Expr,
+        outer_op: &AssocOp,
+    ) -> PResult<'a, Option<P<Expr>>> {
+        debug_assert!(
+            outer_op.is_comparison(),
+            "check_no_chained_comparison: {:?} is not comparison",
+            outer_op,
+        );
+
+        let mk_err_expr = |this: &Self, span| {
+            Ok(Some(this.mk_expr(span, ExprKind::Err, ThinVec::new())))
+        };
+
+        match lhs.kind {
+            ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
+                // Respan to include both operators.
+                let op_span = op.span.to(self.prev_span);
+                let mut err = self.struct_span_err(
+                    op_span,
+                    "chained comparison operators require parentheses",
+                );
+
+                let suggest = |err: &mut DiagnosticBuilder<'_>| {
+                    err.span_suggestion_verbose(
+                        op_span.shrink_to_lo(),
+                        TURBOFISH,
+                        "::".to_string(),
+                        Applicability::MaybeIncorrect,
+                    );
+                };
+
+                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, ()>>>
+                    if *outer_op == AssocOp::Less {
+                        let snapshot = self.clone();
+                        self.bump();
+                        // So far we have parsed `foo<bar<`, consume the rest of the type args.
+                        let modifiers = [
+                            (token::Lt, 1),
+                            (token::Gt, -1),
+                            (token::BinOp(token::Shr), -2),
+                        ];
+                        self.consume_tts(1, &modifiers[..]);
+
+                        if !&[
+                            token::OpenDelim(token::Paren),
+                            token::ModSep,
+                        ].contains(&self.token.kind) {
+                            // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
+                            // parser and bail out.
+                            mem::replace(self, snapshot.clone());
+                        }
+                    }
+                    return if token::ModSep == self.token.kind {
+                        // We have some certainty that this was a bad turbofish at this point.
+                        // `foo< bar >::`
+                        suggest(&mut err);
+
+                        let snapshot = self.clone();
+                        self.bump(); // `::`
+
+                        // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
+                        match self.parse_expr() {
+                            Ok(_) => {
+                                // 99% certain that the suggestion is correct, continue parsing.
+                                err.emit();
+                                // FIXME: actually check that the two expressions in the binop are
+                                // paths and resynthesize new fn call expression instead of using
+                                // `ExprKind::Err` placeholder.
+                                mk_err_expr(self, lhs.span.to(self.prev_span))
+                            }
+                            Err(mut expr_err) => {
+                                expr_err.cancel();
+                                // Not entirely sure now, but we bubble the error up with the
+                                // suggestion.
+                                mem::replace(self, snapshot);
+                                Err(err)
+                            }
+                        }
+                    } else if token::OpenDelim(token::Paren) == self.token.kind {
+                        // We have high certainty that this was a bad turbofish at this point.
+                        // `foo< bar >(`
+                        suggest(&mut err);
+                        // Consume the fn call arguments.
+                        match self.consume_fn_args() {
+                            Err(()) => Err(err),
+                            Ok(()) => {
+                                err.emit();
+                                // FIXME: actually check that the two expressions in the binop are
+                                // paths and resynthesize new fn call expression instead of using
+                                // `ExprKind::Err` placeholder.
+                                mk_err_expr(self, lhs.span.to(self.prev_span))
+                            }
+                        }
+                    } else {
+                        // All we know is that this is `foo < bar >` and *nothing* else. Try to
+                        // be helpful, but don't attempt to recover.
+                        err.help(TURBOFISH);
+                        err.help("or use `(...)` if you meant to specify fn arguments");
+                        // These cases cause too many knock-down errors, bail out (#61329).
+                        Err(err)
+                    };
+                }
+                err.emit();
+            }
+            _ => {}
+        }
+        Ok(None)
+    }
+
+    fn consume_fn_args(&mut self) -> Result<(), ()> {
+        let snapshot = self.clone();
+        self.bump(); // `(`
+
+        // Consume the fn call arguments.
+        let modifiers = [
+            (token::OpenDelim(token::Paren), 1),
+            (token::CloseDelim(token::Paren), -1),
+        ];
+        self.consume_tts(1, &modifiers[..]);
+
+        if self.token.kind == token::Eof {
+            // Not entirely sure that what we consumed were fn arguments, rollback.
+            mem::replace(self, snapshot);
+            Err(())
+        } else {
+            // 99% certain that the suggestion is correct, continue parsing.
+            Ok(())
+        }
+    }
+
+    pub(super) fn maybe_report_ambiguous_plus(
+        &mut self,
+        allow_plus: bool,
+        impl_dyn_multi: bool,
+        ty: &Ty,
+    ) {
+        if !allow_plus && impl_dyn_multi {
+            let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
+            self.struct_span_err(ty.span, "ambiguous `+` in a type")
+                .span_suggestion(
+                    ty.span,
+                    "use parentheses to disambiguate",
+                    sum_with_parens,
+                    Applicability::MachineApplicable,
+                )
+                .emit();
+        }
+    }
+
+    pub(super) fn maybe_recover_from_bad_type_plus(
+        &mut self,
+        allow_plus: bool,
+        ty: &Ty,
+    ) -> PResult<'a, ()> {
+        // Do not add `+` to expected tokens.
+        if !allow_plus || !self.token.is_like_plus() {
+            return Ok(());
+        }
+
+        self.bump(); // `+`
+        let bounds = self.parse_generic_bounds(None)?;
+        let sum_span = ty.span.to(self.prev_span);
+
+        let mut err = struct_span_err!(
+            self.sess.span_diagnostic,
+            sum_span,
+            E0178,
+            "expected a path on the left-hand side of `+`, not `{}`",
+            pprust::ty_to_string(ty)
+        );
+
+        match ty.kind {
+            TyKind::Rptr(ref lifetime, ref mut_ty) => {
+                let sum_with_parens = pprust::to_string(|s| {
+                    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(
+                    sum_span,
+                    "try adding parentheses",
+                    sum_with_parens,
+                    Applicability::MachineApplicable,
+                );
+            }
+            TyKind::Ptr(..) | TyKind::BareFn(..) => {
+                err.span_label(sum_span, "perhaps you forgot parentheses?");
+            }
+            _ => {
+                err.span_label(sum_span, "expected a path");
+            }
+        }
+        err.emit();
+        Ok(())
+    }
+
+    /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
+    /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
+    /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
+    pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
+        &mut self,
+        base: P<T>,
+        allow_recovery: bool,
+    ) -> PResult<'a, P<T>> {
+        // Do not add `::` to expected tokens.
+        if allow_recovery && self.token == token::ModSep {
+            if let Some(ty) = base.to_ty() {
+                return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
+            }
+        }
+        Ok(base)
+    }
+
+    /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
+    /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
+    pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
+        &mut self,
+        ty_span: Span,
+        ty: P<Ty>,
+    ) -> PResult<'a, P<T>> {
+        self.expect(&token::ModSep)?;
+
+        let mut path = ast::Path {
+            segments: Vec::new(),
+            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
+            .span_to_snippet(ty_span)
+            .unwrap_or_else(|_| pprust::ty_to_string(&ty));
+        self.diagnostic()
+            .struct_span_err(path.span, "missing angle brackets in associated item path")
+            .span_suggestion(
+                // This is a best-effort recovery.
+                path.span,
+                "try",
+                format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
+                Applicability::MaybeIncorrect,
+            )
+            .emit();
+
+        let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
+        Ok(P(T::recovered(
+            Some(QSelf {
+                ty,
+                path_span,
+                position: 0,
+            }),
+            path,
+        )))
+    }
+
+    pub(super) fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
+        if self.eat(&token::Semi) {
+            let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
+            err.span_suggestion_short(
+                self.prev_span,
+                "remove this semicolon",
+                String::new(),
+                Applicability::MachineApplicable,
+            );
+            if !items.is_empty() {
+                let previous_item = &items[items.len() - 1];
+                let previous_item_kind_name = match previous_item.kind {
+                    // Say "braced struct" because tuple-structs and
+                    // braceless-empty-struct declarations do take a semicolon.
+                    ItemKind::Struct(..) => Some("braced struct"),
+                    ItemKind::Enum(..) => Some("enum"),
+                    ItemKind::Trait(..) => Some("trait"),
+                    ItemKind::Union(..) => Some("union"),
+                    _ => None,
+                };
+                if let Some(name) = previous_item_kind_name {
+                    err.help(&format!(
+                        "{} declarations are not followed by a semicolon",
+                        name
+                    ));
+                }
+            }
+            err.emit();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
+    /// closing delimiter.
+    pub(super) 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();
+        if !sm.is_multiline(prev_sp.until(sp)) {
+            // 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);
+        } else {
+            err.span_label(prev_sp, label_exp);
+            err.span_label(sp, "unexpected token");
+        }
+        Err(err)
+    }
+
+    pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
+        if self.eat(&token::Semi) {
+            return Ok(());
+        }
+        let sm = self.sess.source_map();
+        let msg = format!("expected `;`, found `{}`", self.this_token_descr());
+        let appl = Applicability::MachineApplicable;
+        if self.token.span == DUMMY_SP || self.prev_span == DUMMY_SP {
+            // Likely inside a macro, can't provide meaninful suggestions.
+            return self.expect(&token::Semi).map(|_| ());
+        } else if !sm.is_multiline(self.prev_span.until(self.token.span)) {
+            // The current token is in the same line as the prior token, not recoverable.
+        } else if self.look_ahead(1, |t| t == &token::CloseDelim(token::Brace)
+            || token_can_begin_expr(t) && t.kind != token::Colon
+        ) && [token::Comma, token::Colon].contains(&self.token.kind) {
+            // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
+            // either `,` or `:`, and the next token could either start a new statement or is a
+            // block close. For example:
+            //
+            //   let x = 32:
+            //   let y = 42;
+            self.bump();
+            let sp = self.prev_span;
+            self.struct_span_err(sp, &msg)
+                .span_suggestion(sp, "change this to `;`", ";".to_string(), appl)
+                .emit();
+            return Ok(())
+        } else if self.look_ahead(0, |t| t == &token::CloseDelim(token::Brace) || (
+                token_can_begin_expr(t)
+                && t != &token::Semi
+                && t != &token::Pound // Avoid triggering with too many trailing `#` in raw string.
+        )) {
+            // Missing semicolon typo. This is triggered if the next token could either start a
+            // new statement or is a block close. For example:
+            //
+            //   let x = 32
+            //   let y = 42;
+            let sp = self.prev_span.shrink_to_hi();
+            self.struct_span_err(sp, &msg)
+                .span_label(self.token.span, "unexpected token")
+                .span_suggestion_short(sp, "add `;` here", ";".to_string(), appl)
+                .emit();
+            return Ok(())
+        }
+        self.expect(&token::Semi).map(|_| ()) // Error unconditionally
+    }
+
+    pub(super) 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_semi()?;
+                }
+            }
+        } else {
+            self.bump();
+        }
+        Ok(())
+    }
+
+    /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
+    /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
+    pub(super) 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> }`.
+            // This needs to be handled separatedly from the next arm to avoid
+            // interpreting `await { <expr> }?` as `<expr>?.await`.
+            self.parse_block_expr(
+                None,
+                self.token.span,
+                BlockCheckMode::Default,
+                ThinVec::new(),
+            )
+        } else {
+            self.parse_expr()
+        }.map_err(|mut err| {
+            err.span_label(await_sp, "while parsing this incorrect await expression");
+            err
+        })?;
+        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(hi);
+        let app = match expr.kind {
+            ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
+            _ => Applicability::MachineApplicable,
+        };
+        self.struct_span_err(sp, "incorrect use of `await`")
+            .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
+            .emit();
+        sp
+    }
+
+    /// If encountering `future.await()`, consumes and emits an error.
+    pub(super) fn recover_from_await_method_call(&mut self) {
+        if self.token == token::OpenDelim(token::Paren) &&
+            self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
+        {
+            // future.await()
+            let lo = self.token.span;
+            self.bump(); // (
+            let sp = lo.to(self.token.span);
+            self.bump(); // )
+            self.struct_span_err(sp, "incorrect use of `await`")
+                .span_suggestion(
+                    sp,
+                    "`await` is not a method call, remove the parentheses",
+                    String::new(),
+                    Applicability::MachineApplicable,
+                ).emit()
+        }
+    }
+
+    /// Recovers a situation like `for ( $pat in $expr )`
+    /// and suggest writing `for $pat in $expr` instead.
+    ///
+    /// This should be called before parsing the `$block`.
+    pub(super) 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.kind {
+                    PatKind::Paren(pat) => pat,
+                    _ => P(pat),
+                })
+            }
+            _ => pat,
+        }
+    }
+
+    pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
+        (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
+            self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
+        ) ||
+            self.token.is_ident() &&
+            match node {
+                // `foo::` → `foo:` or `foo.bar::` → `foo.bar:`
+                ast::ExprKind::Path(..) | ast::ExprKind::Field(..) => true,
+                _ => false,
+            } &&
+            !self.token.is_reserved_ident() &&           // v `foo:bar(baz)`
+            self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren)) ||
+            self.look_ahead(1, |t| t == &token::Lt) &&     // `foo:bar<baz`
+            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) &&
+            (self.look_ahead(2, |t| t.is_ident()) ||   // `foo:bar::baz`
+             self.look_ahead(2, |t| t == &token::Lt))  // `foo:bar::<baz>`
+    }
+
+    pub(super) fn recover_seq_parse_error(
+        &mut self,
+        delim: token::DelimToken,
+        lo: Span,
+        result: PResult<'a, P<Expr>>,
+    ) -> P<Expr> {
+        match result {
+            Ok(x) => x,
+            Err(mut err) => {
+                err.emit();
+                // Recover from parse error, callers expect the closing delim to be consumed.
+                self.consume_block(delim, ConsumeClosingDelim::Yes);
+                self.mk_expr(lo.to(self.prev_span), ExprKind::Err, ThinVec::new())
+            }
+        }
+    }
+
+    pub(super) fn recover_closing_delimiter(
+        &mut self,
+        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.token.span) > unmatched.unclosed_span
+            {
+                pos = Some(i);
+            }
+        }
+        match pos {
+            Some(pos) => {
+                // Recover and assume that the detected unclosed delimiter was meant for
+                // this location. Emit the diagnostic and act as if the delimiter was
+                // present for the parser's sake.
+
+                 // Don't attempt to recover from this unclosed delimiter more than once.
+                let unmatched = self.unclosed_delims.remove(pos);
+                let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
+                if unmatched.found_delim.is_none() {
+                    // We encountered `Eof`, set this fact here to avoid complaining about missing
+                    // `fn main()` when we found place to suggest the closing brace.
+                    *self.sess.reached_eof.borrow_mut() = true;
+                }
+
+                // We want to suggest the inclusion of the closing delimiter where it makes
+                // the most sense, which is immediately after the last token:
+                //
+                //  {foo(bar {}}
+                //      -      ^
+                //      |      |
+                //      |      help: `)` may belong here
+                //      |
+                //      unclosed delimiter
+                if let Some(sp) = unmatched.unclosed_span {
+                    err.span_label(sp, "unclosed delimiter");
+                }
+                err.span_suggestion_short(
+                    self.sess.source_map().next_point(self.prev_span),
+                    &format!("{} may belong here", delim.to_string()),
+                    delim.to_string(),
+                    Applicability::MaybeIncorrect,
+                );
+                if unmatched.found_delim.is_none() {
+                    // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
+                    // errors which would be emitted elsewhere in the parser and let other error
+                    // recovery consume the rest of the file.
+                    Err(err)
+                } else {
+                    err.emit();
+                    self.expected_tokens.clear();  // Reduce the number of errors.
+                    Ok(true)
+                }
+            }
+            _ => Err(err),
+        }
+    }
+
+    /// Recovers from `pub` keyword in places where it seems _reasonable_ but isn't valid.
+    pub(super) fn eat_bad_pub(&mut self) {
+        // When `unclosed_delims` is populated, it means that the code being parsed is already
+        // quite malformed, which might mean that, for example, a pub struct definition could be
+        // parsed as being a trait item, which is invalid and this error would trigger
+        // unconditionally, resulting in misleading diagnostics. Because of this, we only attempt
+        // this nice to have recovery for code that is otherwise well formed.
+        if self.token.is_keyword(kw::Pub) && self.unclosed_delims.is_empty() {
+            match self.parse_visibility(false) {
+                Ok(vis) => {
+                    self.diagnostic()
+                        .struct_span_err(vis.span, "unnecessary visibility qualifier")
+                        .span_label(vis.span, "`pub` not permitted here")
+                        .emit();
+                }
+                Err(mut err) => err.emit(),
+            }
+        }
+    }
+
+    /// Eats tokens until we can be relatively sure we reached the end of the
+    /// statement. This is something of a best-effort heuristic.
+    ///
+    /// We terminate when we find an unmatched `}` (without consuming it).
+    pub(super) fn recover_stmt(&mut self) {
+        self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
+    }
+
+    /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
+    /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
+    /// approximate -- it can mean we break too early due to macros, but that
+    /// should only lead to sub-optimal recovery, not inaccurate parsing).
+    ///
+    /// If `break_on_block` is `Break`, then we will stop consuming tokens
+    /// after finding (and consuming) a brace-delimited block.
+    pub(super) fn recover_stmt_(
+        &mut self,
+        break_on_semi: SemiColonMode,
+        break_on_block: BlockMode,
+    ) {
+        let mut brace_depth = 0;
+        let mut bracket_depth = 0;
+        let mut in_block = false;
+        debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
+               break_on_semi, break_on_block);
+        loop {
+            debug!("recover_stmt_ loop {:?}", self.token);
+            match self.token.kind {
+                token::OpenDelim(token::DelimToken::Brace) => {
+                    brace_depth += 1;
+                    self.bump();
+                    if break_on_block == BlockMode::Break &&
+                       brace_depth == 1 &&
+                       bracket_depth == 0 {
+                        in_block = true;
+                    }
+                }
+                token::OpenDelim(token::DelimToken::Bracket) => {
+                    bracket_depth += 1;
+                    self.bump();
+                }
+                token::CloseDelim(token::DelimToken::Brace) => {
+                    if brace_depth == 0 {
+                        debug!("recover_stmt_ return - close delim {:?}", self.token);
+                        break;
+                    }
+                    brace_depth -= 1;
+                    self.bump();
+                    if in_block && bracket_depth == 0 && brace_depth == 0 {
+                        debug!("recover_stmt_ return - block end {:?}", self.token);
+                        break;
+                    }
+                }
+                token::CloseDelim(token::DelimToken::Bracket) => {
+                    bracket_depth -= 1;
+                    if bracket_depth < 0 {
+                        bracket_depth = 0;
+                    }
+                    self.bump();
+                }
+                token::Eof => {
+                    debug!("recover_stmt_ return - Eof");
+                    break;
+                }
+                token::Semi => {
+                    self.bump();
+                    if break_on_semi == SemiColonMode::Break &&
+                       brace_depth == 0 &&
+                       bracket_depth == 0 {
+                        debug!("recover_stmt_ return - Semi");
+                        break;
+                    }
+                }
+                token::Comma if break_on_semi == SemiColonMode::Comma &&
+                       brace_depth == 0 &&
+                       bracket_depth == 0 =>
+                {
+                    debug!("recover_stmt_ return - Semi");
+                    break;
+                }
+                _ => {
+                    self.bump()
+                }
+            }
+        }
+    }
+
+    pub(super) 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();
+        }
+    }
+
+    pub(super) fn expected_semi_or_open_brace<T>(&mut self) -> PResult<'a, T> {
+        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)
+    }
+
+    pub(super) fn eat_incorrect_doc_comment_for_param_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();
+        }
+    }
+
+    pub(super) fn parameter_without_type(
+        &mut self,
+        err: &mut DiagnosticBuilder<'_>,
+        pat: P<ast::Pat>,
+        require_name: bool,
+        is_self_allowed: 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.kind {
+            if require_name && (
+                is_trait_item ||
+                self.token == token::Comma ||
+                self.token == token::Lt ||
+                self.token == token::CloseDelim(token::Paren)
+            ) { // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
+                if is_self_allowed {
+                    err.span_suggestion(
+                        pat.span,
+                        "if this is a `self` type, give it a parameter name",
+                        format!("self: {}", ident),
+                        Applicability::MaybeIncorrect,
+                    );
+                }
+                // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
+                // `fn foo(HashMap: TypeName<u32>)`.
+                if self.token != token::Lt {
+                    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)");
+
+                // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
+                return if self.token == token::Lt { None } else { Some(ident) };
+            }
+        }
+        None
+    }
+
+    pub(super) 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 {
+            kind: PatKind::Wild,
+            span: pat.span,
+            id: ast::DUMMY_NODE_ID
+        });
+        Ok((pat, ty))
+    }
+
+    pub(super) fn recover_bad_self_param(
+        &mut self,
+        mut param: ast::Param,
+        is_trait_item: bool,
+    ) -> PResult<'a, ast::Param> {
+        let sp = param.pat.span;
+        param.ty.kind = 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(param)
+    }
+
+    pub(super) fn consume_block(
+        &mut self,
+        delim: token::DelimToken,
+        consume_close: ConsumeClosingDelim,
+    ) {
+        let mut brace_depth = 0;
+        loop {
+            if self.eat(&token::OpenDelim(delim)) {
+                brace_depth += 1;
+            } else if self.check(&token::CloseDelim(delim)) {
+                if brace_depth == 0 {
+                    if let ConsumeClosingDelim::Yes = consume_close {
+                        // Some of the callers of this method expect to be able to parse the
+                        // closing delimiter themselves, so we leave it alone. Otherwise we advance
+                        // the parser.
+                        self.bump();
+                    }
+                    return;
+                } else {
+                    self.bump();
+                    brace_depth -= 1;
+                    continue;
+                }
+            } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
+                return;
+            } else {
+                self.bump();
+            }
+        }
+    }
+
+    pub(super) 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
+    }
+
+    fn consume_tts(
+        &mut self,
+        mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
+        // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
+        modifier: &[(token::TokenKind, i64)],
+    ) {
+        while acc > 0 {
+            if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
+                acc += *val;
+            }
+            if self.token.kind == token::Eof {
+                break;
+            }
+            self.bump();
+        }
+    }
+
+    /// Replace duplicated recovered parameters with `_` pattern to avoid unecessary errors.
+    ///
+    /// This is necessary because at this point we don't know whether we parsed a function with
+    /// anonymous parameters or a function with names but no types. In order to minimize
+    /// unecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
+    /// the parameters 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 parameter names.
+    pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
+        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.kind, &input.ty.kind,
+            ) {
+                Some(*ident)
+            } else {
+                None
+            };
+            if let Some(ident) = opt_ident {
+                if seen_inputs.contains(&ident) {
+                    input.pat.kind = PatKind::Wild;
+                }
+                seen_inputs.insert(ident);
+            }
+        }
+    }
+}
diff --git a/src/librustc_parse/parser/expr.rs b/src/librustc_parse/parser/expr.rs
new file mode 100644
index 00000000000..dadb91f8b3c
--- /dev/null
+++ b/src/librustc_parse/parser/expr.rs
@@ -0,0 +1,1963 @@
+use super::{Parser, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode};
+use super::{SemiColonMode, SeqSep, TokenExpectType};
+use super::pat::{GateOr, PARAM_EXPECTED};
+use super::diagnostics::Error;
+use crate::maybe_recover_from_interpolated_ty_qpath;
+
+use syntax::ast::{
+    self, DUMMY_NODE_ID, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode,
+    Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm, Ty, TyKind,
+    FunctionRetTy, Param, FnDecl, BinOpKind, BinOp, UnOp, Mac, AnonConst, Field, Lit,
+};
+use syntax::token::{self, Token, TokenKind};
+use syntax::print::pprust;
+use syntax::ptr::P;
+use syntax::source_map::{self, Span};
+use syntax::util::classify;
+use syntax::util::literal::LitError;
+use syntax::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
+use syntax_pos::symbol::{kw, sym};
+use syntax_pos::Symbol;
+use errors::{PResult, Applicability};
+use std::mem;
+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 {
+    /// Converts `Some(attrs)` into `LhsExpr::AttributesParsed(attrs)`
+    /// and `None` into `LhsExpr::NotYetParsed`.
+    ///
+    /// This conversion does not allocate.
+    fn from(o: Option<ThinVec<Attribute>>) -> Self {
+        if let Some(attrs) = o {
+            LhsExpr::AttributesParsed(attrs)
+        } else {
+            LhsExpr::NotYetParsed
+        }
+    }
+}
+
+impl From<P<Expr>> for LhsExpr {
+    /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
+    ///
+    /// This conversion does not allocate.
+    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.kind) {
+                (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() {
+                if let Some(expr) = self.check_no_chained_comparison(&lhs, &op)? {
+                    return Ok(expr);
+                }
+            }
+            // 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.kind);
+                self.last_type_ascription = Some((self.prev_span, maybe_path));
+
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
+                self.sess.gated_spans.gate(sym::type_ascription, lhs.span);
+                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
+        }
+    }
+
+    /// Parses 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))
+    }
+
+    /// Parses 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 not",
+                        "!".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)?;
+                let span = lo.to(span);
+                self.sess.gated_spans.gate(sym::box_syntax, span);
+                (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 {}",
+                            pprust::path_to_string(&path),
+                            op_noun,
+                        );
+                        let span_after_type = parser_snapshot_after_type.token.span;
+                        let expr = mk_expr(self, P(Ty {
+                            span: path.span,
+                            kind: TyKind::Path(None, path),
+                            id: 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.kind {
+                    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) => {
+                        err.cancel();
+                        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_closure_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 {
+                    // Non-empty vector
+                    let first_expr = self.parse_expr()?;
+                    if self.eat(&token::Semi) {
+                        // Repeating array syntax: `[ 0; 512 ]`
+                        let count = AnonConst {
+                            id: 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.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);
+                    }
+
+                    let expr = self.mk_expr(lo.to(hi), ex, attrs);
+                    return self.maybe_recover_from_bad_qpath(expr, true);
+                }
+                if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
+                    return self.parse_closure_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_closure_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.gated_spans.gate(sym::generators, 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.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 = true | false | token_lit`.
+    pub(super) fn parse_lit(&mut self) -> PResult<'a, Lit> {
+        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) = &recovered {
+                self.bump();
+                self.struct_span_err(token.span, "float literals must have an integer part")
+                    .span_suggestion(
+                        token.span,
+                        "must have an integer part",
+                        pprust::token_to_string(token),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+            }
+        }
+
+        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 span = token.span;
+                let lit = match token.kind {
+                    token::Literal(lit) => lit,
+                    _ => unreachable!(),
+                };
+                self.bump();
+                self.error_literal_from_token(err, 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!())
+            }
+        }
+    }
+
+    fn error_literal_from_token(&self, err: LitError, lit: token::Lit, span: Span) {
+        // Checks if `s` looks like i32 or u1234 etc.
+        fn looks_like_width_suffix(first_chars: &[char], s: &str) -> bool {
+            s.len() > 1
+            && s.starts_with(first_chars)
+            && s[1..].chars().all(|c| c.is_ascii_digit())
+        }
+
+        let token::Lit { kind, suffix, .. } = lit;
+        match err {
+            // `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 => {
+                self.expect_no_suffix(
+                    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..]);
+                    self.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);
+                    self.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..]);
+                    self.struct_span_err(span, &msg)
+                        .help("valid widths are 32 and 64")
+                        .emit();
+                } else {
+                    let msg = format!("invalid suffix `{}` for float literal", suf);
+                    self.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!(),
+                };
+                self.struct_span_err(span, &format!("{} float literal is not supported", descr))
+                    .span_label(span, "not supported")
+                    .emit();
+            }
+            LitError::IntTooLarge => {
+                self.struct_span_err(span, "integer literal is too large")
+                    .emit();
+            }
+        }
+    }
+
+    pub(super) fn expect_no_suffix(&self, 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 = self.sess.span_diagnostic.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 {
+                self.struct_span_err(sp, &format!("suffixes on {} are invalid", kind))
+            };
+            err.span_label(sp, format!("invalid suffix `{}`", suf));
+            err.emit();
+        }
+    }
+
+    /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
+    pub 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.
+    pub(super) fn parse_block_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        lo: Span,
+        blk_mode: BlockCheckMode,
+        outer_attrs: ThinVec<Attribute>,
+    ) -> PResult<'a, P<Expr>> {
+        if let Some(label) = opt_label {
+            self.sess.gated_spans.gate(sym::label_break_value, label.ident.span);
+        }
+
+        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)?;
+        Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs))
+    }
+
+    /// Parses a closure expression (e.g., `move |args| expr`).
+    fn parse_closure_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.gated_spans.gate(sym::async_closure, 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))
+    }
+
+    /// Parses 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_param()
+                )?.0;
+                self.expect_or()?;
+                args
+            }
+        };
+        let output = self.parse_ret_ty(true)?;
+
+        Ok(P(FnDecl {
+            inputs: inputs_captures,
+            output,
+        }))
+    }
+
+    /// Parses a parameter in a closure header (e.g., `|arg, arg|`).
+    fn parse_fn_block_param(&mut self) -> PResult<'a, Param> {
+        let lo = self.token.span;
+        let attrs = self.parse_outer_attributes()?;
+        let pat = self.parse_pat(PARAM_EXPECTED)?;
+        let t = if self.eat(&token::Colon) {
+            self.parse_ty()?
+        } else {
+            P(Ty {
+                id: DUMMY_NODE_ID,
+                kind: TyKind::Infer,
+                span: self.prev_span,
+            })
+        };
+        let span = lo.to(self.token.span);
+        Ok(Param {
+            attrs: attrs.into(),
+            ty: t,
+            pat,
+            span,
+            id: DUMMY_NODE_ID,
+            is_placeholder: false,
+        })
+    }
+
+    /// 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))
+    }
+
+    /// Parses 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.kind {
+            // Remove the last feature gating of a `let` expression since it's stable.
+            self.sess.gated_spans.ungate_last(sym::let_chains, cond.span);
+        }
+
+        Ok(cond)
+    }
+
+    /// Parses a `let $pat = $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 pat = self.parse_top_pat(GateOr::No)?;
+        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.gated_spans.gate(sym::let_chains, span);
+        Ok(self.mk_expr(span, ExprKind::Let(pat, expr), attrs))
+    }
+
+    /// Parses an `else { ... }` expression (`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()));
+        }
+    }
+
+    /// Parses 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_pat(GateOr::Yes)?;
+        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))
+    }
+
+    /// Parses `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
+        }
+    }
+
+    /// Parses a `match ... { ... }` expression (`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));
+    }
+
+    pub(super) fn parse_arm(&mut self) -> PResult<'a, Arm> {
+        let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
+        let pat = self.parse_top_pat(GateOr::No)?;
+        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,
+            pat,
+            guard,
+            body: expr,
+            span: lo.to(hi),
+            id: DUMMY_NODE_ID,
+            is_placeholder: false,
+        })
+    }
+
+    /// 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 {
+            let span = span_lo.to(body.span);
+            self.sess.gated_spans.gate(sym::try_blocks, span);
+            Ok(self.mk_expr(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.
+    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, 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: DUMMY_NODE_ID,
+                        is_placeholder: false,
+                    });
+                }
+            }
+            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));
+    }
+
+    /// Parses `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: DUMMY_NODE_ID,
+            is_placeholder: false,
+        })
+    }
+
+    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, kind: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
+        P(Expr { kind, span, attrs, id: DUMMY_NODE_ID })
+    }
+
+    pub(super) fn mk_expr_err(&self, span: Span) -> P<Expr> {
+        self.mk_expr(span, ExprKind::Err, ThinVec::new())
+    }
+}
diff --git a/src/librustc_parse/parser/generics.rs b/src/librustc_parse/parser/generics.rs
new file mode 100644
index 00000000000..ba5eafc0ed7
--- /dev/null
+++ b/src/librustc_parse/parser/generics.rs
@@ -0,0 +1,308 @@
+use super::Parser;
+
+use syntax::ast::{self, WhereClause, GenericParam, GenericParamKind, GenericBounds, Attribute};
+use syntax::token;
+use syntax::source_map::DUMMY_SP;
+use syntax_pos::symbol::{kw, sym};
+
+use errors::PResult;
+
+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,
+            },
+            is_placeholder: false
+        })
+    }
+
+    fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
+        let lo = self.token.span;
+
+        self.expect_keyword(kw::Const)?;
+        let ident = self.parse_ident()?;
+        self.expect(&token::Colon)?;
+        let ty = self.parse_ty()?;
+
+        self.sess.gated_spans.gate(sym::const_generics, lo.to(self.prev_span));
+
+        Ok(GenericParam {
+            ident,
+            id: ast::DUMMY_NODE_ID,
+            attrs: preceding_attrs.into(),
+            bounds: Vec::new(),
+            kind: GenericParamKind::Const {
+                ty,
+            },
+            is_placeholder: false
+        })
+    }
+
+    /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
+    /// a trailing comma and erroneous trailing attributes.
+    pub(super) 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,
+                    is_placeholder: false
+                });
+            } 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 if self.token.can_begin_type() {
+                // Trying to write an associated type bound? (#26271)
+                let snapshot = self.clone();
+                match self.parse_ty_where_predicate() {
+                    Ok(where_predicate) => {
+                        self.struct_span_err(
+                            where_predicate.span(),
+                            "bounds on associated types do not belong here",
+                        )
+                        .span_label(where_predicate.span(), "belongs in `where` clause")
+                        .emit();
+                    }
+                    Err(mut err) => {
+                        err.cancel();
+                        std::mem::replace(self, snapshot);
+                        break
+                    }
+                }
+            } else {
+                // Check for trailing attributes and stop parsing.
+                if !attrs.is_empty() {
+                    if !params.is_empty() {
+                        self.struct_span_err(
+                            attrs[0].span,
+                            "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() {
+                where_clause.predicates.push(self.parse_ty_where_predicate()?);
+            } else {
+                break
+            }
+
+            if !self.eat(&token::Comma) {
+                break
+            }
+        }
+
+        where_clause.span = lo.to(self.prev_span);
+        Ok(where_clause)
+    }
+
+    fn parse_ty_where_predicate(&mut self) -> PResult<'a, ast::WherePredicate> {
+        let lo = self.token.span;
+        // 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))?;
+            Ok(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()?;
+            Ok(ast::WherePredicate::EqPredicate(
+                ast::WhereEqPredicate {
+                    span: lo.to(self.prev_span),
+                    lhs_ty: ty,
+                    rhs_ty,
+                    id: ast::DUMMY_NODE_ID,
+                }
+            ))
+        } else {
+            self.unexpected()
+        }
+    }
+
+    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/librustc_parse/parser/item.rs b/src/librustc_parse/parser/item.rs
new file mode 100644
index 00000000000..3e21436d313
--- /dev/null
+++ b/src/librustc_parse/parser/item.rs
@@ -0,0 +1,2238 @@
+use super::{Parser, PathStyle};
+use super::diagnostics::{Error, dummy_arg, ConsumeClosingDelim};
+
+use crate::maybe_whole;
+
+use syntax::ast::{self, Abi, DUMMY_NODE_ID, Ident, Attribute, AttrKind, AttrStyle, AnonConst, Item};
+use syntax::ast::{ItemKind, ImplItem, ImplItemKind, TraitItem, TraitItemKind, UseTree, UseTreeKind};
+use syntax::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness};
+use syntax::ast::{Visibility, VisibilityKind, Mutability, FnHeader, ForeignItem, ForeignItemKind};
+use syntax::ast::{Ty, TyKind, Generics, GenericBounds, TraitRef, EnumDef, VariantData, StructField};
+use syntax::ast::{Mac, MacDelimiter, Block, BindingMode, FnDecl, FnSig, SelfKind, Param};
+use syntax::ptr::P;
+use syntax::ThinVec;
+use syntax::token;
+use syntax::tokenstream::{TokenTree, TokenStream};
+use syntax::source_map::{self, respan, Span};
+use syntax_pos::BytePos;
+use syntax_pos::symbol::{kw, sym};
+
+use log::debug;
+use std::mem;
+use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, StashKey};
+
+/// Whether the type alias or associated type is a concrete type or an opaque type.
+#[derive(Debug)]
+pub(super) 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 vis = self.parse_visibility(false)?;
+
+        if self.eat_keyword(kw::Use) {
+            // USE ITEM
+            let item_ = ItemKind::Use(P(self.parse_use_tree()?));
+            self.expect_semi()?;
+
+            let span = lo.to(self.prev_span);
+            let item = self.mk_item(span, Ident::invalid(), item_, vis, 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, vis, attrs)?));
+            }
+
+            let abi = self.parse_opt_abi()?;
+
+            if self.eat_keyword(kw::Fn) {
+                // EXTERN FUNCTION ITEM
+                let fn_span = self.prev_span;
+                let header = FnHeader {
+                    unsafety: Unsafety::Normal,
+                    asyncness: respan(fn_span, IsAsync::NotAsync),
+                    constness: respan(fn_span, Constness::NotConst),
+                    abi,
+                };
+                return self.parse_item_fn(lo, vis, attrs, header);
+            } else if self.check(&token::OpenDelim(token::Brace)) {
+                return Ok(Some(
+                    self.parse_item_foreign_mod(lo, abi, vis, attrs, extern_sp)?,
+                ));
+            }
+
+            self.unexpected()?;
+        }
+
+        if self.is_static_global() {
+            self.bump();
+            // STATIC ITEM
+            let m = self.parse_mutability();
+            let info = self.parse_item_const(Some(m))?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if self.eat_keyword(kw::Const) {
+            let const_span = self.prev_span;
+            if [kw::Fn, kw::Unsafe, kw::Extern].iter().any(|k| self.check_keyword(*k)) {
+                // CONST FUNCTION ITEM
+                let unsafety = self.parse_unsafety();
+
+                if self.check_keyword(kw::Extern) {
+                    self.sess.gated_spans.gate(sym::const_extern_fn, lo.to(self.token.span));
+                }
+                let abi = self.parse_extern_abi()?;
+                self.bump(); // `fn`
+
+                let header = FnHeader {
+                    unsafety,
+                    asyncness: respan(const_span, IsAsync::NotAsync),
+                    constness: respan(const_span, Constness::Const),
+                    abi,
+                };
+                return self.parse_item_fn(lo, vis, attrs, header);
+            }
+
+            // 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 info = self.parse_item_const(None)?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        // Parses `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 asyncness = respan(async_span, IsAsync::Async {
+                    closure_id: DUMMY_NODE_ID,
+                    return_impl_trait_id: DUMMY_NODE_ID,
+                });
+                self.ban_async_in_2015(async_span);
+                let header = FnHeader {
+                    unsafety,
+                    asyncness,
+                    constness: respan(fn_span, Constness::NotConst),
+                    abi: Abi::new(sym::Rust, fn_span),
+                };
+                return self.parse_item_fn(lo, vis, attrs, header);
+            }
+        }
+
+        if self.check_keyword(kw::Unsafe) &&
+            self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
+        {
+            // UNSAFE TRAIT ITEM
+            self.bump(); // `unsafe`
+            let info = self.parse_item_trait(lo, Unsafety::Unsafe)?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        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 info = self.parse_item_impl(unsafety, defaultness)?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if self.check_keyword(kw::Fn) {
+            // FUNCTION ITEM
+            self.bump();
+            let fn_span = self.prev_span;
+            let header = FnHeader {
+                unsafety: Unsafety::Normal,
+                asyncness: respan(fn_span, IsAsync::NotAsync),
+                constness: respan(fn_span, Constness::NotConst),
+                abi: Abi::new(sym::Rust, fn_span),
+            };
+            return self.parse_item_fn(lo, vis, attrs, header);
+        }
+
+        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 = self.parse_extern_abi()?;
+            self.expect_keyword(kw::Fn)?;
+            let fn_span = self.prev_span;
+            let header = FnHeader {
+                unsafety: Unsafety::Unsafe,
+                asyncness: respan(fn_span, IsAsync::NotAsync),
+                constness: respan(fn_span, Constness::NotConst),
+                abi,
+            };
+            return self.parse_item_fn(lo, vis, attrs, header);
+        }
+
+        if self.eat_keyword(kw::Mod) {
+            // MODULE ITEM
+            let info = self.parse_item_mod(&attrs[..])?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        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 span = lo.to(self.prev_span);
+            return Ok(Some(self.mk_item(span, ident, item_, vis, attrs)));
+        }
+
+        if self.eat_keyword(kw::Enum) {
+            // ENUM ITEM
+            let info = self.parse_item_enum()?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if self.check_keyword(kw::Trait)
+            || (self.check_keyword(kw::Auto)
+                && self.is_keyword_ahead(1, &[kw::Trait]))
+        {
+            // TRAIT ITEM
+            let info = self.parse_item_trait(lo, Unsafety::Normal)?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if self.eat_keyword(kw::Struct) {
+            // STRUCT ITEM
+            let info = self.parse_item_struct()?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if self.is_union_item() {
+            // UNION ITEM
+            self.bump();
+            let info = self.parse_item_union()?;
+            return self.mk_item_with_info(attrs, lo, vis, info);
+        }
+
+        if let Some(macro_def) = self.eat_macro_def(&attrs, &vis, 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 vis.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 = self.recover_first_param();
+                self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
+                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, ConsumeClosingDelim::Yes);
+                    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)) {
+                    ("fn", self.recover_first_param(), 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, vis)
+    }
+
+    pub(super) fn mk_item_with_info(
+        &self,
+        attrs: Vec<Attribute>,
+        lo: Span,
+        vis: Visibility,
+        info: ItemInfo,
+    ) -> PResult<'a, Option<P<Item>>> {
+        let (ident, item, extra_attrs) = info;
+        let span = lo.to(self.prev_span);
+        let attrs = Self::maybe_append(attrs, extra_attrs);
+        Ok(Some(self.mk_item(span, ident, item, vis, attrs)))
+    }
+
+    fn maybe_append<T>(mut lhs: Vec<T>, mut rhs: Option<Vec<T>>) -> Vec<T> {
+        if let Some(ref mut rhs) = rhs {
+            lhs.append(rhs);
+        }
+        lhs
+    }
+
+    /// 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 { kind: AttrKind::DocComment(_), .. }) =>
+                "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_doc_comment() {
+            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_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 {
+            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 { kind: TyKind::Path(None, err_path(span)), span, id: 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(self.mk_ty(self.prev_span, TyKind::Err))
+        } 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.kind {
+                    // 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.consume_block(token::Brace, ConsumeClosingDelim::Yes);
+                        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, kind, 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() {
+            self.parse_impl_const()?
+        } else if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(&vis), at_end)? {
+            // FIXME: code copied from `parse_macro_use_or_failure` -- use abstraction!
+            (Ident::invalid(), ast::ImplItemKind::Macro(mac), Generics::default())
+        } else {
+            let (name, inner_attrs, generics, kind) = self.parse_impl_method(at_end)?;
+            attrs.extend(inner_attrs);
+            (name, kind, generics)
+        };
+
+        Ok(ImplItem {
+            id: DUMMY_NODE_ID,
+            span: lo.to(self.prev_span),
+            ident: name,
+            vis,
+            defaultness,
+            attrs,
+            generics,
+            kind,
+            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::Async,
+                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])
+    }
+
+    /// This parses the grammar:
+    ///     ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
+    fn parse_impl_const(&mut self) -> PResult<'a, (Ident, ImplItemKind, Generics)> {
+        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_semi()?;
+        Ok((name, ImplItemKind::Const(typ, expr), Generics::default()))
+    }
+
+    /// Parses `auto? trait Foo { ... }` or `trait Foo = Bar;`.
+    fn parse_item_trait(&mut self, lo: Span, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
+        // Parse optional `auto` prefix.
+        let is_auto = if self.eat_keyword(kw::Auto) {
+            IsAuto::Yes
+        } else {
+            IsAuto::No
+        };
+
+        self.expect_keyword(kw::Trait)?;
+        let ident = self.parse_ident()?;
+        let mut tps = self.parse_generics()?;
+
+        // Parse optional colon and supertrait bounds.
+        let had_colon = self.eat(&token::Colon);
+        let span_at_colon = self.prev_span;
+        let bounds = if had_colon {
+            self.parse_generic_bounds(Some(self.prev_span))?
+        } else {
+            Vec::new()
+        };
+
+        let span_before_eq = self.prev_span;
+        if self.eat(&token::Eq) {
+            // It's a trait alias.
+            if had_colon {
+                let span = span_at_colon.to(span_before_eq);
+                self.struct_span_err(span, "bounds are not allowed on trait aliases")
+                    .emit();
+            }
+
+            let bounds = self.parse_generic_bounds(None)?;
+            tps.where_clause = self.parse_where_clause()?;
+            self.expect_semi()?;
+
+            let whole_span = lo.to(self.prev_span);
+            if is_auto == IsAuto::Yes {
+                let msg = "trait aliases cannot be `auto`";
+                self.struct_span_err(whole_span, msg)
+                    .span_label(whole_span, msg)
+                    .emit();
+            }
+            if unsafety != Unsafety::Normal {
+                let msg = "trait aliases cannot be `unsafe`";
+                self.struct_span_err(whole_span, msg)
+                    .span_label(whole_span, msg)
+                    .emit();
+            }
+
+            self.sess.gated_spans.gate(sym::trait_alias, whole_span);
+
+            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.consume_block(token::Brace, ConsumeClosingDelim::Yes);
+                            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, kind, generics) = if self.eat_keyword(kw::Type) {
+            self.parse_trait_item_assoc_ty()?
+        } else if self.is_const_item() {
+            self.parse_trait_item_const()?
+        } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
+            // trait item macro.
+            (Ident::invalid(), TraitItemKind::Macro(mac), Generics::default())
+        } else {
+            self.parse_trait_item_method(at_end, &mut attrs)?
+        };
+
+        Ok(TraitItem {
+            id: DUMMY_NODE_ID,
+            ident: name,
+            attrs,
+            generics,
+            kind,
+            span: lo.to(self.prev_span),
+            tokens: None,
+        })
+    }
+
+    fn parse_trait_item_const(&mut self) -> PResult<'a, (Ident, TraitItemKind, Generics)> {
+        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) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+        self.expect_semi()?;
+        Ok((ident, TraitItemKind::Const(ty, default), Generics::default()))
+    }
+
+    /// Parses the following grammar:
+    ///
+    ///     TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
+    fn parse_trait_item_assoc_ty(&mut self) -> PResult<'a, (Ident, TraitItemKind, 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_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))
+                );
+            }
+
+            self.parse_use_tree_glob_or_nested()?
+        } 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) {
+                self.parse_use_tree_glob_or_nested()?
+            } else {
+                UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
+            }
+        };
+
+        Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
+    }
+
+    /// Parses `*` or `{...}`.
+    fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
+        Ok(if self.eat(&token::BinOp(token::Star)) {
+            UseTreeKind::Glob
+        } else {
+            UseTreeKind::Nested(self.parse_use_tree_list()?)
+        })
+    }
+
+    /// 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()?, 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_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_and_span(&fixed_name, 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 `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,
+        abi: Abi,
+        visibility: Visibility,
+        mut attrs: Vec<Attribute>,
+        extern_sp: Span,
+    ) -> PResult<'a, P<Item>> {
+        self.expect(&token::OpenDelim(token::Brace))?;
+
+        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.
+    pub 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) {
+                let mut err = self
+                    .struct_span_err(self.token.span, "extern items cannot be `const`");
+
+
+                // The user wrote 'const fn'
+                if self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe]) {
+                    err.emit();
+                    // Consume `const`
+                    self.bump();
+                    // Consume `unsafe` if present, since `extern` blocks
+                    // don't allow it. This will leave behind a plain 'fn'
+                    self.eat_keyword(kw::Unsafe);
+                    // Treat 'const fn` as a plain `fn` for error recovery purposes.
+                    // We've already emitted an error, so compilation is guaranteed
+                    // to fail
+                    return Ok(self.parse_item_foreign_fn(visibility, lo, attrs, extern_sp)?);
+                }
+                err.span_suggestion(
+                        self.token.span,
+                        "try using a static value",
+                        "static".to_owned(),
+                        Applicability::MachineApplicable
+                );
+                err.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: DUMMY_NODE_ID,
+                        attrs,
+                        vis: visibility,
+                        kind: ForeignItemKind::Macro(mac),
+                    }
+                )
+            }
+            None => {
+                if !attrs.is_empty()  {
+                    self.expected_item_err(&attrs)?;
+                }
+
+                self.unexpected()
+            }
+        }
+    }
+
+    /// 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_semi()?;
+        Ok(ForeignItem {
+            ident,
+            attrs,
+            kind: ForeignItemKind::Static(ty, mutbl),
+            id: 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_semi()?;
+        Ok(ast::ForeignItem {
+            ident,
+            attrs,
+            kind: ForeignItemKind::Ty,
+            id: 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
+        }
+    }
+
+    /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty = $expr` with
+    /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
+    ///
+    /// When `m` is `"const"`, `$ident` may also be `"_"`.
+    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() }?;
+
+        // Parse the type of a `const` or `static mut?` item.
+        // That is, the `":" $ty` fragment.
+        let ty = if self.token == token::Eq {
+            self.recover_missing_const_type(id, m)
+        } else {
+            // Not `=` so expect `":"" $ty` as usual.
+            self.expect(&token::Colon)?;
+            self.parse_ty()?
+        };
+
+        self.expect(&token::Eq)?;
+        let e = self.parse_expr()?;
+        self.expect_semi()?;
+        let item = match m {
+            Some(m) => ItemKind::Static(ty, m, e),
+            None => ItemKind::Const(ty, e),
+        };
+        Ok((id, item, None))
+    }
+
+    /// We were supposed to parse `:` but instead, we're already at `=`.
+    /// This means that the type is missing.
+    fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
+        // Construct the error and stash it away with the hope
+        // that typeck will later enrich the error with a type.
+        let kind = match m {
+            Some(Mutability::Mutable) => "static mut",
+            Some(Mutability::Immutable) => "static",
+            None => "const",
+        };
+        let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
+        err.span_suggestion(
+            id.span,
+            "provide a type for the item",
+            format!("{}: <type>", id),
+            Applicability::HasPlaceholders,
+        );
+        err.stash(id.span, StashKey::ItemNoType);
+
+        // The user intended that the type be inferred,
+        // so treat this as if the user wrote e.g. `const A: _ = expr;`.
+        P(Ty {
+            kind: TyKind::Infer,
+            span: id.span,
+            id: ast::DUMMY_NODE_ID,
+        })
+    }
+
+    /// Parses `type Foo = Bar;` or returns `None`
+    /// without modifying the parser state.
+    fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, 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, 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_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: &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()?,
+                    DUMMY_NODE_ID,
+                )
+            } else {
+                VariantData::Unit(DUMMY_NODE_ID)
+            };
+
+            let disr_expr = if self.eat(&token::Eq) {
+                Some(AnonConst {
+                    id: DUMMY_NODE_ID,
+                    value: self.parse_expr()?,
+                })
+            } else {
+                None
+            };
+
+            let vr = ast::Variant {
+                ident,
+                id: DUMMY_NODE_ID,
+                attrs: variant_attrs,
+                data: struct_def,
+                disr_expr,
+                span: vlo.to(self.prev_span),
+                is_placeholder: false,
+            };
+            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(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(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()?, DUMMY_NODE_ID);
+            generics.where_clause = self.parse_where_clause()?;
+            self.expect_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.consume_block(token::Brace, ConsumeClosingDelim::No);
+                    recovered = true;
+                    e
+                });
+                match field {
+                    Ok(field) => fields.push(field),
+                    Err(mut err) => {
+                        err.emit();
+                        break;
+                    }
+                }
+            }
+            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: DUMMY_NODE_ID,
+                ty,
+                attrs,
+                is_placeholder: false,
+            })
+        }).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: DUMMY_NODE_ID,
+            ty,
+            attrs,
+            is_placeholder: false,
+        })
+    }
+
+    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);
+
+        if !def.legacy {
+            self.sess.gated_spans.gate(sym::decl_macro, 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 report_invalid_macro_expansion_item(&self) {
+        self.struct_span_err(
+            self.prev_span,
+            "macros that expand to items must be delimited with braces or followed by a semicolon",
+        ).multipart_suggestion(
+            "change the delimiters to curly braces",
+            vec![
+                (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
+                (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
+            ],
+            Applicability::MaybeIncorrect,
+        ).span_suggestion(
+            self.sess.source_map().next_point(self.prev_span),
+            "add a semicolon",
+            ';'.to_string(),
+            Applicability::MaybeIncorrect,
+        ).emit();
+    }
+
+    fn mk_item(&self, span: Span, ident: Ident, kind: ItemKind, vis: Visibility,
+               attrs: Vec<Attribute>) -> P<Item> {
+        P(Item {
+            ident,
+            attrs,
+            id: DUMMY_NODE_ID,
+            kind,
+            vis,
+            span,
+            tokens: None,
+        })
+    }
+}
+
+/// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
+pub(super) struct ParamCfg {
+    /// Is `self` is allowed as the first parameter?
+    pub is_self_allowed: bool,
+    /// Is `...` allowed as the tail of the parameter list?
+    pub allow_c_variadic: bool,
+    /// `is_name_required` decides if, per-parameter,
+    /// the parameter must have a pattern or just a type.
+    pub is_name_required: fn(&token::Token) -> bool,
+}
+
+/// Parsing of functions and methods.
+impl<'a> Parser<'a> {
+    /// Parses an item-position function declaration.
+    fn parse_item_fn(
+        &mut self,
+        lo: Span,
+        vis: Visibility,
+        attrs: Vec<Attribute>,
+        header: FnHeader,
+    ) -> PResult<'a, Option<P<Item>>> {
+        let (ident, decl, generics) = self.parse_fn_sig(ParamCfg {
+            is_self_allowed: false,
+            allow_c_variadic: header.abi.symbol == sym::C && header.unsafety == Unsafety::Unsafe,
+            is_name_required: |_| true,
+        })?;
+        let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+        let kind = ItemKind::Fn(FnSig { decl, header }, generics, body);
+        self.mk_item_with_info(attrs, lo, vis, (ident, kind, Some(inner_attrs)))
+    }
+
+    /// 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, decl, generics) = self.parse_fn_sig(ParamCfg {
+            is_self_allowed: false,
+            allow_c_variadic: true,
+            is_name_required: |_| true,
+        })?;
+        let span = lo.to(self.token.span);
+        self.parse_semi_or_incorrect_foreign_fn_body(&ident, extern_sp)?;
+        Ok(ast::ForeignItem {
+            ident,
+            attrs,
+            kind: ForeignItemKind::Fn(decl, generics),
+            id: DUMMY_NODE_ID,
+            span,
+            vis,
+        })
+    }
+
+    /// Parses a method or a macro invocation in a trait impl.
+    fn parse_impl_method(
+        &mut self,
+        at_end: &mut bool,
+    ) -> PResult<'a, (Ident, Vec<Attribute>, Generics, ImplItemKind)> {
+        let (ident, sig, generics) = self.parse_method_sig(|_| true)?;
+        *at_end = true;
+        let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
+        Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(sig, body)))
+    }
+
+    fn parse_trait_item_method(
+        &mut self,
+        at_end: &mut bool,
+        attrs: &mut Vec<Attribute>,
+    ) -> PResult<'a, (Ident, TraitItemKind, Generics)> {
+        // 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 (ident, sig, generics) = self.parse_method_sig(|t| t.span.rust_2018())?;
+        let body = self.parse_trait_method_body(at_end, attrs)?;
+        Ok((ident, TraitItemKind::Method(sig, body), generics))
+    }
+
+    /// Parse the "body" of a method in a trait item definition.
+    /// This can either be `;` when there's no body,
+    /// or e.g. a block when the method is a provided one.
+    fn parse_trait_method_body(
+        &mut self,
+        at_end: &mut bool,
+        attrs: &mut Vec<Attribute>,
+    ) -> PResult<'a, Option<P<Block>>> {
+        Ok(match self.token.kind {
+            token::Semi => {
+                debug!("parse_trait_method_body(): parsing required method");
+                self.bump();
+                *at_end = true;
+                None
+            }
+            token::OpenDelim(token::Brace) => {
+                debug!("parse_trait_method_body(): 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(),
+        })
+    }
+
+    /// Parse the "signature", including the identifier, parameters, and generics
+    /// of a method. The body is not parsed as that differs between `trait`s and `impl`s.
+    fn parse_method_sig(
+        &mut self,
+        is_name_required: fn(&token::Token) -> bool,
+    ) -> PResult<'a, (Ident, FnSig, Generics)> {
+        let header = self.parse_fn_front_matter()?;
+        let (ident, decl, generics) = self.parse_fn_sig(ParamCfg {
+            is_self_allowed: true,
+            allow_c_variadic: false,
+            is_name_required,
+        })?;
+        Ok((ident, FnSig { header, decl }, generics))
+    }
+
+    /// 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, FnHeader> {
+        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::default())
+        } else {
+            let abi = self.parse_extern_abi()?;
+            (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(FnHeader { constness, unsafety, asyncness, abi })
+    }
+
+    /// Parse the "signature", including the identifier, parameters, and generics of a function.
+    fn parse_fn_sig(&mut self, cfg: ParamCfg) -> PResult<'a, (Ident, P<FnDecl>, Generics)> {
+        let ident = self.parse_ident()?;
+        let mut generics = self.parse_generics()?;
+        let decl = self.parse_fn_decl(cfg, true)?;
+        generics.where_clause = self.parse_where_clause()?;
+        Ok((ident, decl, generics))
+    }
+
+    /// Parses the parameter list and result type of a function declaration.
+    pub(super) fn parse_fn_decl(
+        &mut self,
+        cfg: ParamCfg,
+        ret_allow_plus: bool,
+    ) -> PResult<'a, P<FnDecl>> {
+        Ok(P(FnDecl {
+            inputs: self.parse_fn_params(cfg)?,
+            output: self.parse_ret_ty(ret_allow_plus)?,
+        }))
+    }
+
+    /// Parses the parameter list of a function, including the `(` and `)` delimiters.
+    fn parse_fn_params(&mut self, mut cfg: ParamCfg) -> PResult<'a, Vec<Param>> {
+        let sp = self.token.span;
+        let is_trait_item = cfg.is_self_allowed;
+        let mut c_variadic = false;
+        // Parse the arguments, starting out with `self` being possibly allowed...
+        let (params, _) = self.parse_paren_comma_seq(|p| {
+            let param = p.parse_param_general(&cfg, is_trait_item);
+            // ...now that we've parsed the first argument, `self` is no longer allowed.
+            cfg.is_self_allowed = false;
+
+            match param {
+                Ok(param) => Ok(
+                    if let TyKind::CVarArgs = param.ty.kind {
+                        c_variadic = true;
+                        if p.token != token::CloseDelim(token::Paren) {
+                            p.span_err(
+                                p.token.span,
+                                "`...` must be the last argument of a C-variadic function",
+                            );
+                            // FIXME(eddyb) this should probably still push `CVarArgs`.
+                            // Maybe AST validation/HIR lowering should emit the above error?
+                            None
+                        } else {
+                            Some(param)
+                        }
+                    } else {
+                        Some(param)
+                    }
+                ),
+                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))))
+                }
+            }
+        })?;
+
+        let mut params: Vec<_> = params.into_iter().filter_map(|x| x).collect();
+
+        // Replace duplicated recovered params with `_` pattern to avoid unecessary errors.
+        self.deduplicate_recovered_params_names(&mut params);
+
+        if c_variadic && params.len() <= 1 {
+            self.span_err(
+                sp,
+                "C-variadic function must be declared with at least one named argument",
+            );
+        }
+
+        Ok(params)
+    }
+
+    /// Skips unexpected attributes and doc comments in this position and emits an appropriate
+    /// error.
+    /// This version of parse param doesn't necessarily require identifier names.
+    fn parse_param_general(&mut self, cfg: &ParamCfg, is_trait_item: bool) -> PResult<'a, Param> {
+        let lo = self.token.span;
+        let attrs = self.parse_outer_attributes()?;
+
+        // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
+        if let Some(mut param) = self.parse_self_param()? {
+            param.attrs = attrs.into();
+            return if cfg.is_self_allowed {
+                Ok(param)
+            } else {
+                self.recover_bad_self_param(param, is_trait_item)
+            };
+        }
+
+        let is_name_required = match self.token.kind {
+            token::DotDotDot => false,
+            _ => (cfg.is_name_required)(&self.token),
+        };
+        let (pat, ty) = if is_name_required || self.is_named_param() {
+            debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
+
+            let pat = self.parse_fn_param_pat()?;
+            if let Err(mut err) = self.expect(&token::Colon) {
+                return if let Some(ident) = self.parameter_without_type(
+                    &mut err,
+                    pat,
+                    is_name_required,
+                    cfg.is_self_allowed,
+                    is_trait_item,
+                ) {
+                    err.emit();
+                    Ok(dummy_arg(ident))
+                } else {
+                    Err(err)
+                };
+            }
+
+            self.eat_incorrect_doc_comment_for_param_type();
+            (pat, self.parse_ty_common(true, true, cfg.allow_c_variadic)?)
+        } else {
+            debug!("parse_param_general ident_to_pat");
+            let parser_snapshot_before_ty = self.clone();
+            self.eat_incorrect_doc_comment_for_param_type();
+            let mut ty = self.parse_ty_common(true, true, cfg.allow_c_variadic);
+            if ty.is_ok() && self.token != token::Comma &&
+               self.token != token::CloseDelim(token::Paren) {
+                // This wasn't actually a type, but a pattern looking like a type,
+                // so we are going to rollback and re-parse for recovery.
+                ty = self.unexpected();
+            }
+            match ty {
+                Ok(ty) => {
+                    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)
+                }
+                // If this is a C-variadic argument and we hit an error, return the error.
+                Err(err) if self.token == token::DotDotDot => return Err(err),
+                // Recover from attempting to parse the argument as a type without pattern.
+                Err(mut err) => {
+                    err.cancel();
+                    mem::replace(self, parser_snapshot_before_ty);
+                    self.recover_arg_parse()?
+                }
+            }
+        };
+
+        let span = lo.to(self.token.span);
+
+        Ok(Param {
+            attrs: attrs.into(),
+            id: ast::DUMMY_NODE_ID,
+            is_placeholder: false,
+            pat,
+            span,
+            ty,
+        })
+    }
+
+    /// Returns the parsed optional self parameter and whether a self shortcut was used.
+    ///
+    /// See `parse_self_param_with_attrs` to collect attributes.
+    fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
+        // Extract an identifier *after* having confirmed that the token is one.
+        let expect_self_ident = |this: &mut Self| {
+            match this.token.kind {
+                // Preserve hygienic context.
+                token::Ident(name, _) => {
+                    let span = this.token.span;
+                    this.bump();
+                    Ident::new(name, span)
+                }
+                _ => unreachable!(),
+            }
+        };
+        // Is `self` `n` tokens ahead?
+        let is_isolated_self = |this: &Self, n| {
+            this.is_keyword_ahead(n, &[kw::SelfLower])
+            && this.look_ahead(n + 1, |t| t != &token::ModSep)
+        };
+        // Is `mut self` `n` tokens ahead?
+        let is_isolated_mut_self = |this: &Self, n| {
+            this.is_keyword_ahead(n, &[kw::Mut])
+            && is_isolated_self(this, n + 1)
+        };
+        // Parse `self` or `self: TYPE`. We already know the current token is `self`.
+        let parse_self_possibly_typed = |this: &mut Self, m| {
+            let eself_ident = expect_self_ident(this);
+            let eself_hi = this.prev_span;
+            let eself = if this.eat(&token::Colon) {
+                SelfKind::Explicit(this.parse_ty()?, m)
+            } else {
+                SelfKind::Value(m)
+            };
+            Ok((eself, eself_ident, eself_hi))
+        };
+        // Recover for the grammar `*self`, `*const self`, and `*mut self`.
+        let recover_self_ptr = |this: &mut Self| {
+            let msg = "cannot pass `self` by raw pointer";
+            let span = this.token.span;
+            this.struct_span_err(span, msg)
+                .span_label(span, msg)
+                .emit();
+
+            Ok((SelfKind::Value(Mutability::Immutable), expect_self_ident(this), this.prev_span))
+        };
+
+        // 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.token.span;
+        let (eself, eself_ident, eself_hi) = match self.token.kind {
+            token::BinOp(token::And) => {
+                let eself = if is_isolated_self(self, 1) {
+                    // `&self`
+                    self.bump();
+                    SelfKind::Region(None, Mutability::Immutable)
+                } else if is_isolated_mut_self(self, 1) {
+                    // `&mut self`
+                    self.bump();
+                    self.bump();
+                    SelfKind::Region(None, Mutability::Mutable)
+                } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
+                    // `&'lt self`
+                    self.bump();
+                    let lt = self.expect_lifetime();
+                    SelfKind::Region(Some(lt), Mutability::Immutable)
+                } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
+                    // `&'lt mut self`
+                    self.bump();
+                    let lt = self.expect_lifetime();
+                    self.bump();
+                    SelfKind::Region(Some(lt), Mutability::Mutable)
+                } else {
+                    // `&not_self`
+                    return Ok(None);
+                };
+                (eself, expect_self_ident(self), self.prev_span)
+            }
+            // `*self`
+            token::BinOp(token::Star) if is_isolated_self(self, 1) => {
+                self.bump();
+                recover_self_ptr(self)?
+            }
+            // `*mut self` and `*const self`
+            token::BinOp(token::Star) if
+                self.look_ahead(1, |t| t.is_mutability())
+                && is_isolated_self(self, 2) =>
+            {
+                self.bump();
+                self.bump();
+                recover_self_ptr(self)?
+            }
+            // `self` and `self: TYPE`
+            token::Ident(..) if is_isolated_self(self, 0) => {
+                parse_self_possibly_typed(self, Mutability::Immutable)?
+            }
+            // `mut self` and `mut self: TYPE`
+            token::Ident(..) if is_isolated_mut_self(self, 0) => {
+                self.bump();
+                parse_self_possibly_typed(self, Mutability::Mutable)?
+            }
+            _ => return Ok(None),
+        };
+
+        let eself = source_map::respan(eself_lo.to(eself_hi), eself);
+        Ok(Some(Param::from_self(ThinVec::default(), eself, eself_ident)))
+    }
+
+    fn is_named_param(&self) -> bool {
+        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(kw::Mut) => 1,
+            _ => 0,
+        };
+
+        self.look_ahead(offset, |t| t.is_ident()) &&
+        self.look_ahead(offset + 1, |t| t == &token::Colon)
+    }
+
+    fn recover_first_param(&mut self) -> &'static str {
+        match self.parse_outer_attributes()
+            .and_then(|_| self.parse_self_param())
+            .map_err(|mut e| e.cancel())
+        {
+            Ok(Some(_)) => "method",
+            _ => "function",
+        }
+    }
+}
diff --git a/src/librustc_parse/parser/mod.rs b/src/librustc_parse/parser/mod.rs
new file mode 100644
index 00000000000..a491d91e20f
--- /dev/null
+++ b/src/librustc_parse/parser/mod.rs
@@ -0,0 +1,1393 @@
+pub mod attr;
+mod expr;
+mod pat;
+mod item;
+mod module;
+mod ty;
+mod path;
+pub use path::PathStyle;
+mod stmt;
+mod generics;
+mod diagnostics;
+use diagnostics::Error;
+
+use crate::{Directory, DirectoryOwnership};
+use crate::lexer::UnmatchedBrace;
+
+use syntax::ast::{
+    self, Abi, DUMMY_NODE_ID, AttrStyle, Attribute, CrateSugar, Ident,
+    IsAsync, MacDelimiter, Mutability, StrStyle, Visibility, VisibilityKind, Unsafety,
+};
+
+use syntax::print::pprust;
+use syntax::ptr::P;
+use syntax::token::{self, Token, TokenKind, DelimToken};
+use syntax::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
+use syntax::sess::ParseSess;
+use syntax::source_map::respan;
+use syntax::struct_span_err;
+use syntax::util::comments::{doc_comment_style, strip_doc_comment_decoration};
+use syntax_pos::symbol::{kw, sym, Symbol};
+use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
+use rustc_data_structures::thin_vec::ThinVec;
+use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
+use log::debug;
+
+use std::borrow::Cow;
+use std::{cmp, mem, slice};
+use std::path::PathBuf;
+
+bitflags::bitflags! {
+    struct Restrictions: u8 {
+        const STMT_EXPR         = 1 << 0;
+        const NO_STRUCT_LITERAL = 1 << 1;
+    }
+}
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+enum SemiColonMode {
+    Break,
+    Ignore,
+    Comma,
+}
+
+#[derive(Clone, Copy, PartialEq, Debug)]
+enum BlockMode {
+    Break,
+    Ignore,
+}
+
+/// Like `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.kind {
+            if let token::$constructor(x) = &**nt {
+                let $x = x.clone();
+                $p.bump();
+                return Ok($e);
+            }
+        }
+    };
+}
+
+/// 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.kind {
+                if let token::NtTy(ty) = &**nt {
+                    let ty = ty.clone();
+                    $self.bump();
+                    return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
+                }
+            }
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq)]
+enum PrevTokenKind {
+    DocComment,
+    Comma,
+    Plus,
+    Interpolated,
+    Eof,
+    Ident,
+    BitOr,
+    Other,
+}
+
+// NOTE: `Ident`s are handled by `common.rs`.
+
+#[derive(Clone)]
+pub struct Parser<'a> {
+    pub sess: &'a ParseSess,
+    /// 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,
+    /// The span of the current non-normalized token.
+    meta_var_span: Option<Span>,
+    /// The span of the previous non-normalized token.
+    pub prev_span: Span,
+    /// The 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.
+    pub(super) directory: Directory<'a>,
+    /// `true` to parse sub-modules in other files.
+    pub(super) 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>,
+    expected_tokens: Vec<TokenType>,
+    token_cursor: TokenCursor,
+    desugar_doc_comments: bool,
+    /// `true` we should configure out of line modules as we parse.
+    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
+    /// appropriately.
+    ///
+    /// See the comments in the `parse_path_segment` function for more details.
+    unmatched_angle_bracket_count: u32,
+    max_angle_bracket_count: u32,
+    /// A list of all unclosed delimiters found by the lexer. If an entry is used for error recovery
+    /// it gets removed from here. Every entry left at the end gets emitted as an independent
+    /// error.
+    pub(super) unclosed_delims: Vec<UnmatchedBrace>,
+    last_unexpected_token_span: Option<Span>,
+    pub last_type_ascription: Option<(Span, bool /* likely path typo */)>,
+    /// If present, this `Parser` is not parsing Rust code but rather a macro call.
+    subparser_name: Option<&'static str>,
+}
+
+impl<'a> Drop for Parser<'a> {
+    fn drop(&mut self) {
+        emit_unclosed_delims(&mut self.unclosed_delims, &self.sess);
+    }
+}
+
+#[derive(Clone)]
+struct TokenCursor {
+    frame: TokenCursorFrame,
+    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,
+}
+
+/// This is used in `TokenCursorFrame` above to track tokens that are consumed
+/// by the parser, and then that's transitively used to record the tokens that
+/// each parse AST item is created with.
+///
+/// Right now this has two states, either collecting tokens or not collecting
+/// tokens. If we're collecting tokens we just save everything off into a local
+/// `Vec`. This should eventually though likely save tokens from the original
+/// token stream and just use slicing of token streams to avoid creation of a
+/// whole new vector.
+///
+/// The second state is where we're passively not recording tokens, but the last
+/// token is still tracked for when we want to start recording tokens. This
+/// "last token" means that when we start recording tokens we'll want to ensure
+/// that this, the first token, is included in the output.
+///
+/// You can find some more example usage of this in the `collect_tokens` method
+/// on the parser.
+#[derive(Clone)]
+enum LastToken {
+    Collecting(Vec<TreeAndJoint>),
+    Was(Option<TreeAndJoint>),
+}
+
+impl TokenCursorFrame {
+    fn new(span: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
+        TokenCursorFrame {
+            delim,
+            span,
+            open_delim: delim == token::NoDelim,
+            tree_cursor: tts.clone().into_trees(),
+            close_delim: delim == token::NoDelim,
+            last_token: LastToken::Was(None),
+        }
+    }
+}
+
+impl TokenCursor {
+    fn next(&mut self) -> Token {
+        loop {
+            let tree = if !self.frame.open_delim {
+                self.frame.open_delim = true;
+                TokenTree::open_tt(self.frame.span, self.frame.delim)
+            } else if let Some(tree) = self.frame.tree_cursor.next() {
+                tree
+            } else if !self.frame.close_delim {
+                self.frame.close_delim = true;
+                TokenTree::close_tt(self.frame.span, self.frame.delim)
+            } else if let Some(frame) = self.stack.pop() {
+                self.frame = frame;
+                continue
+            } else {
+                return Token::new(token::Eof, DUMMY_SP);
+            };
+
+            match self.frame.last_token {
+                LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
+                LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
+            }
+
+            match tree {
+                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));
+                }
+            }
+        }
+    }
+
+    fn next_desugared(&mut self) -> Token {
+        let (name, sp) = match self.next() {
+            Token { kind: token::DocComment(name), span } => (name, span),
+            tok => return tok,
+        };
+
+        let stripped = strip_doc_comment_decoration(&name.as_str());
+
+        // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
+        // required to wrap the text.
+        let mut num_of_hashes = 0;
+        let mut count = 0;
+        for ch in stripped.chars() {
+            count = match ch {
+                '"' => 1,
+                '#' if count > 0 => count + 1,
+                _ => 0,
+            };
+            num_of_hashes = cmp::max(num_of_hashes, count);
+        }
+
+        let delim_span = DelimSpan::from_single(sp);
+        let body = TokenTree::Delimited(
+            delim_span,
+            token::Bracket,
+            [
+                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(),
+        );
+
+        self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
+            delim_span,
+            token::NoDelim,
+            &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
+                [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
+                    .iter().cloned().collect::<TokenStream>()
+            } else {
+                [TokenTree::token(token::Pound, sp), body]
+                    .iter().cloned().collect::<TokenStream>()
+            },
+        )));
+
+        self.next()
+    }
+}
+
+#[derive(Clone, PartialEq)]
+enum TokenType {
+    Token(TokenKind),
+    Keyword(Symbol),
+    Operator,
+    Lifetime,
+    Ident,
+    Path,
+    Type,
+    Const,
+}
+
+impl TokenType {
+    fn to_string(&self) -> String {
+        match *self {
+            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(),
+            TokenType::Path => "path".to_string(),
+            TokenType::Type => "type".to_string(),
+            TokenType::Const => "const".to_string(),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+enum TokenExpectType {
+    Expect,
+    NoExpect,
+}
+
+/// A sequence separator.
+struct SeqSep {
+    /// The separator token.
+    sep: Option<TokenKind>,
+    /// `true` if a trailing separator is allowed.
+    trailing_sep_allowed: bool,
+}
+
+impl SeqSep {
+    fn trailing_allowed(t: TokenKind) -> SeqSep {
+        SeqSep {
+            sep: Some(t),
+            trailing_sep_allowed: true,
+        }
+    }
+
+    fn none() -> SeqSep {
+        SeqSep {
+            sep: None,
+            trailing_sep_allowed: false,
+        }
+    }
+}
+
+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,
+        subparser_name: Option<&'static str>,
+    ) -> Self {
+        let mut parser = Parser {
+            sess,
+            token: Token::dummy(),
+            prev_span: DUMMY_SP,
+            meta_var_span: None,
+            prev_token_kind: PrevTokenKind::Other,
+            restrictions: Restrictions::empty(),
+            recurse_into_file_modules,
+            directory: Directory {
+                path: Cow::from(PathBuf::new()),
+                ownership: DirectoryOwnership::Owned { relative: None }
+            },
+            root_module_name: None,
+            expected_tokens: Vec::new(),
+            token_cursor: TokenCursor {
+                frame: TokenCursorFrame::new(
+                    DelimSpan::dummy(),
+                    token::NoDelim,
+                    &tokens.into(),
+                ),
+                stack: Vec::new(),
+            },
+            desugar_doc_comments,
+            cfg_mods: true,
+            unmatched_angle_bracket_count: 0,
+            max_angle_bracket_count: 0,
+            unclosed_delims: Vec::new(),
+            last_unexpected_token_span: None,
+            last_type_ascription: None,
+            subparser_name,
+        };
+
+        parser.token = parser.next_tok();
+
+        if let Some(directory) = directory {
+            parser.directory = directory;
+        } else if !parser.token.span.is_dummy() {
+            if let Some(FileName::Real(path)) =
+                    &sess.source_map().lookup_char_pos(parser.token.span.lo()).file.unmapped_path {
+                if let Some(directory_path) = path.parent() {
+                    parser.directory.path = Cow::from(directory_path.to_path_buf());
+                }
+            }
+        }
+
+        parser.process_potential_macro_variable();
+        parser
+    }
+
+    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.span.is_dummy() {
+            // Tweak the location for better diagnostics, but keep syntactic context intact.
+            next.span = self.prev_span.with_ctxt(next.span.ctxt());
+        }
+        next
+    }
+
+    /// Converts the current token to a string using `self`'s reader.
+    pub fn this_token_to_string(&self) -> String {
+        pprust::token_to_string(&self.token)
+    }
+
+    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,
+        })
+    }
+
+    pub(super) fn this_token_descr(&self) -> String {
+        if let Some(prefix) = self.token_descr() {
+            format!("{} `{}`", prefix, self.this_token_to_string())
+        } else {
+            format!("`{}`", self.this_token_to_string())
+        }
+    }
+
+    crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
+        match self.expect_one_of(&[], &[]) {
+            Err(e) => Err(e),
+            Ok(_) => unreachable!(),
+        }
+    }
+
+    /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
+    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 {
+                self.unexpected_try_recover(t)
+            }
+        } else {
+            self.expect_one_of(slice::from_ref(t), &[])
+        }
+    }
+
+    /// Expect next token to be edible or inedible token.  If edible,
+    /// then consume it; if inedible, then return without consuming
+    /// anything.  Signal a fatal error if next token is unexpected.
+    pub fn expect_one_of(
+        &mut self,
+        edible: &[TokenKind],
+        inedible: &[TokenKind],
+    ) -> PResult<'a, bool /* recovered */> {
+        if edible.contains(&self.token.kind) {
+            self.bump();
+            Ok(false)
+        } else if inedible.contains(&self.token.kind) {
+            // leave it in the input
+            Ok(false)
+        } else if self.last_unexpected_token_span == Some(self.token.span) {
+            FatalError.raise();
+        } else {
+            self.expected_one_of_not_found(edible, inedible)
+        }
+    }
+
+    fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
+        self.parse_ident_common(true)
+    }
+
+    fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
+        match self.token.kind {
+            token::Ident(name, _) => {
+                if self.token.is_reserved_ident() {
+                    let mut err = self.expected_ident_found();
+                    if recover {
+                        err.emit();
+                    } else {
+                        return Err(err);
+                    }
+                }
+                let span = self.token.span;
+                self.bump();
+                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()
+                })
+            }
+        }
+    }
+
+    /// Checks if the next token is `tok`, and returns `true` if so.
+    ///
+    /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
+    /// encountered.
+    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: &TokenKind) -> bool {
+        let is_present = self.check(tok);
+        if is_present { self.bump() }
+        is_present
+    }
+
+    /// If the next token is the given keyword, returns `true` without eating it.
+    /// An expectation is also added for diagnostics purposes.
+    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`. An expectation is also added for diagnostics purposes.
+    fn eat_keyword(&mut self, kw: Symbol) -> bool {
+        if self.check_keyword(kw) {
+            self.bump();
+            true
+        } else {
+            false
+        }
+    }
+
+    fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
+        if self.token.is_keyword(kw) {
+            self.bump();
+            true
+        } else {
+            false
+        }
+    }
+
+    /// 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: Symbol) -> PResult<'a, ()> {
+        if !self.eat_keyword(kw) {
+            self.unexpected()
+        } else {
+            Ok(())
+        }
+    }
+
+    fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
+        if ok {
+            true
+        } else {
+            self.expected_tokens.push(typ);
+            false
+        }
+    }
+
+    fn check_ident(&mut self) -> bool {
+        self.check_or_expected(self.token.is_ident(), TokenType::Ident)
+    }
+
+    fn check_path(&mut self) -> bool {
+        self.check_or_expected(self.token.is_path_start(), TokenType::Path)
+    }
+
+    fn check_type(&mut self) -> bool {
+        self.check_or_expected(self.token.can_begin_type(), TokenType::Type)
+    }
+
+    fn check_const_arg(&mut self) -> bool {
+        self.check_or_expected(self.token.can_begin_const_arg(), TokenType::Const)
+    }
+
+    /// Checks to see if the next token is either `+` or `+=`.
+    /// Otherwise returns `false`.
+    fn check_plus(&mut self) -> bool {
+        self.check_or_expected(
+            self.token.is_like_plus(),
+            TokenType::Token(token::BinOp(token::Plus)),
+        )
+    }
+
+    /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
+    /// and continues. If a `+` is not seen, returns `false`.
+    ///
+    /// This is used when token-splitting `+=` into `+`.
+    /// 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.kind {
+            token::BinOp(token::Plus) => {
+                self.bump();
+                true
+            }
+            token::BinOpEq(token::Plus) => {
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                self.bump_with(token::Eq, span);
+                true
+            }
+            _ => false,
+        }
+    }
+
+    /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
+    /// `&` 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.kind {
+            token::BinOp(token::And) => {
+                self.bump();
+                Ok(())
+            }
+            token::AndAnd => {
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::BinOp(token::And), span))
+            }
+            _ => self.unexpected()
+        }
+    }
+
+    /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
+    /// `|` 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.kind {
+            token::BinOp(token::Or) => {
+                self.bump();
+                Ok(())
+            }
+            token::OrOr => {
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                Ok(self.bump_with(token::BinOp(token::Or), span))
+            }
+            _ => self.unexpected()
+        }
+    }
+
+    /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
+    /// `<` and continue. If `<-` is seen, replaces it with a single `<`
+    /// and continue. If a `<` is not seen, returns false.
+    ///
+    /// This is meant to be used when parsing generics on a path to get the
+    /// starting token.
+    fn eat_lt(&mut self) -> bool {
+        self.expected_tokens.push(TokenType::Token(token::Lt));
+        let ate = match self.token.kind {
+            token::Lt => {
+                self.bump();
+                true
+            }
+            token::BinOp(token::Shl) => {
+                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.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                self.bump_with(token::BinOp(token::Minus), span);
+                true
+            }
+            _ => false,
+        };
+
+        if ate {
+            // See doc comment for `unmatched_angle_bracket_count`.
+            self.unmatched_angle_bracket_count += 1;
+            self.max_angle_bracket_count += 1;
+            debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
+        }
+
+        ate
+    }
+
+    fn expect_lt(&mut self) -> PResult<'a, ()> {
+        if !self.eat_lt() {
+            self.unexpected()
+        } else {
+            Ok(())
+        }
+    }
+
+    /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
+    /// 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.kind {
+            token::Gt => {
+                self.bump();
+                Some(())
+            }
+            token::BinOp(token::Shr) => {
+                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.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                Some(self.bump_with(token::Ge, span))
+            }
+            token::Ge => {
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
+                Some(self.bump_with(token::Eq, span))
+            }
+            _ => None,
+        };
+
+        match ate {
+            Some(_) => {
+                // See doc comment for `unmatched_angle_bracket_count`.
+                if self.unmatched_angle_bracket_count > 0 {
+                    self.unmatched_angle_bracket_count -= 1;
+                    debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
+                }
+
+                Ok(())
+            },
+            None => self.unexpected(),
+        }
+    }
+
+    /// Parses a sequence, including the closing delimiter. The function
+    /// `f` must consume tokens until reaching the next separator or
+    /// closing bracket.
+    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();
+        }
+        Ok(val)
+    }
+
+    /// Parses a sequence, not including the closing delimiter. The function
+    /// `f` must consume tokens until reaching the next separator or
+    /// closing bracket.
+    fn parse_seq_to_before_end<T>(
+        &mut self,
+        ket: &TokenKind,
+        sep: SeqSep,
+        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 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,
+            }
+        })
+    }
+
+    fn parse_seq_to_before_tokens<T>(
+        &mut self,
+        kets: &[&TokenKind],
+        sep: SeqSep,
+        expect: TokenExpectType,
+        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 !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;
+                } else {
+                    match self.expect(t) {
+                        Ok(false) => {}
+                        Ok(true) => {
+                            recovered = true;
+                            break;
+                        }
+                        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.kind) {
+                                    self.bump();
+                                }
+                            }
+                            e.emit();
+                            // Attempt to keep parsing if it was an omitted separator.
+                            match f(self) {
+                                Ok(t) => {
+                                    v.push(t);
+                                    continue;
+                                },
+                                Err(mut e) => {
+                                    e.cancel();
+                                    break;
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+            if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) {
+                trailing = true;
+                break;
+            }
+
+            let t = f(self)?;
+            v.push(t);
+        }
+
+        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>(
+        &mut self,
+        bra: &TokenKind,
+        ket: &TokenKind,
+        sep: SeqSep,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
+        self.expect(bra)?;
+        let (result, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+        if !recovered {
+            self.eat(ket);
+        }
+        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.
+    pub fn bump(&mut self) {
+        if self.prev_token_kind == PrevTokenKind::Eof {
+            // Bumping after EOF is a bad sign, usually an infinite loop.
+            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.token.span);
+
+        // Record last token kind for possible error recovery.
+        self.prev_token_kind = match self.token.kind {
+            token::DocComment(..) => PrevTokenKind::DocComment,
+            token::Comma => PrevTokenKind::Comma,
+            token::BinOp(token::Plus) => PrevTokenKind::Plus,
+            token::BinOp(token::Or) => PrevTokenKind::BitOr,
+            token::Interpolated(..) => PrevTokenKind::Interpolated,
+            token::Eof => PrevTokenKind::Eof,
+            token::Ident(..) => PrevTokenKind::Ident,
+            _ => PrevTokenKind::Other,
+        };
+
+        self.token = self.next_tok();
+        self.expected_tokens.clear();
+        // Check after each token.
+        self.process_potential_macro_variable();
+    }
+
+    /// Advances 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: 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.token = Token::new(next, span);
+        self.expected_tokens.clear();
+    }
+
+    /// Look-ahead `dist` tokens of `self.token` and get access to that token there.
+    /// When `dist == 0` then the current token is looked at.
+    pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R {
+        if dist == 0 {
+            return looker(&self.token);
+        }
+
+        let frame = &self.token_cursor.frame;
+        looker(&match frame.tree_cursor.look_ahead(dist - 1) {
+            Some(tree) => match tree {
+                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)
+        })
+    }
+
+    /// 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(kw::Async) {
+            IsAsync::Async {
+                closure_id: DUMMY_NODE_ID,
+                return_impl_trait_id: DUMMY_NODE_ID,
+            }
+        } else {
+            IsAsync::NotAsync
+        }
+    }
+
+    /// Parses unsafety: `unsafe` or nothing.
+    fn parse_unsafety(&mut self) -> Unsafety {
+        if self.eat_keyword(kw::Unsafe) {
+            Unsafety::Unsafe
+        } else {
+            Unsafety::Normal
+        }
+    }
+
+    /// Parses mutability (`mut` or nothing).
+    fn parse_mutability(&mut self) -> Mutability {
+        if self.eat_keyword(kw::Mut) {
+            Mutability::Mutable
+        } else {
+            Mutability::Immutable
+        }
+    }
+
+    /// Possibly parses mutability (`const` or `mut`).
+    fn parse_const_or_mut(&mut self) -> Option<Mutability> {
+        if self.eat_keyword(kw::Mut) {
+            Some(Mutability::Mutable)
+        } else if self.eat_keyword(kw::Const) {
+            Some(Mutability::Immutable)
+        } else {
+            None
+        }
+    }
+
+    fn parse_field_name(&mut self) -> PResult<'a, Ident> {
+        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(symbol, self.prev_span))
+        } else {
+            self.parse_ident_common(false)
+        }
+    }
+
+    fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
+        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.token.span, msg);
+                return Err(err)
+            }
+        };
+        let tts = match self.parse_token_tree() {
+            TokenTree::Delimited(_, _, tts) => tts,
+            _ => unreachable!(),
+        };
+        let delim = match delim {
+            token::Paren => MacDelimiter::Parenthesis,
+            token::Bracket => MacDelimiter::Bracket,
+            token::Brace => MacDelimiter::Brace,
+            token::NoDelim => self.bug("unexpected no delimiter"),
+        };
+        Ok((delim, tts.into()))
+    }
+
+    fn parse_or_use_outer_attributes(
+        &mut self,
+        already_parsed_attrs: Option<ThinVec<Attribute>>,
+    ) -> PResult<'a, ThinVec<Attribute>> {
+        if let Some(attrs) = already_parsed_attrs {
+            Ok(attrs)
+        } else {
+            self.parse_outer_attributes().map(|a| a.into())
+        }
+    }
+
+    pub fn process_potential_macro_variable(&mut self) {
+        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.kind {
+                    token::Ident(name, _) => name,
+                    _ => unreachable!()
+                };
+                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.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::new(token::Ident(ident.name, is_raw), ident.span),
+                    token::NtLifetime(ident) =>
+                        Token::new(token::Lifetime(ident.name), ident.span),
+                    _ => return,
+                }
+            }
+            _ => return,
+        };
+    }
+
+    /// Parses a single token tree from the input.
+    pub fn parse_token_tree(&mut self) -> TokenTree {
+        match self.token.kind {
+            token::OpenDelim(..) => {
+                let frame = mem::replace(&mut self.token_cursor.frame,
+                                         self.token_cursor.stack.pop().unwrap());
+                self.token.span = frame.span.entire();
+                self.bump();
+                TokenTree::Delimited(
+                    frame.span,
+                    frame.delim,
+                    frame.tree_cursor.stream.into(),
+                )
+            },
+            token::CloseDelim(_) | token::Eof => unreachable!(),
+            _ => {
+                let token = self.token.take();
+                self.bump();
+                TokenTree::Token(token)
+            }
+        }
+    }
+
+    /// 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 {
+            tts.push(self.parse_token_tree());
+        }
+        Ok(tts)
+    }
+
+    pub fn parse_tokens(&mut self) -> TokenStream {
+        let mut result = Vec::new();
+        loop {
+            match self.token.kind {
+                token::Eof | token::CloseDelim(..) => break,
+                _ => result.push(self.parse_token_tree().into()),
+            }
+        }
+        TokenStream::new(result)
+    }
+
+    /// Evaluates the closure with restrictions in place.
+    ///
+    /// Afters the closure is evaluated, restrictions are reset.
+    fn with_res<T>(&mut self, res: Restrictions, f: impl FnOnce(&mut Self) -> T) -> T {
+        let old = self.restrictions;
+        self.restrictions = res;
+        let res = f(self);
+        self.restrictions = old;
+        res
+    }
+
+    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)`,
+    /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
+    /// If the following element can't be a tuple (i.e., it's a function definition), then
+    /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
+    /// so emit a proper diagnostic.
+    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(kw::Crate));
+        if self.is_crate_vis() {
+            self.bump(); // `crate`
+            self.sess.gated_spans.gate(sym::crate_visibility_modifier, self.prev_span);
+            return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
+        }
+
+        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.token.span.shrink_to_lo(), VisibilityKind::Inherited))
+        }
+        let lo = self.prev_span;
+
+        if self.check(&token::OpenDelim(token::Paren)) {
+            // We don't `self.bump()` the `(` yet because this might be a struct definition where
+            // `()` 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.is_keyword_ahead(1, &[kw::Crate])
+                && self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
+            {
+                // Parse `pub(crate)`.
+                self.bump(); // `(`
+                self.bump(); // `crate`
+                self.expect(&token::CloseDelim(token::Paren))?; // `)`
+                let vis = VisibilityKind::Crate(CrateSugar::PubCrate);
+                return Ok(respan(lo.to(self.prev_span), vis));
+            } else if self.is_keyword_ahead(1, &[kw::In]) {
+                // Parse `pub(in path)`.
+                self.bump(); // `(`
+                self.bump(); // `in`
+                let path = self.parse_path(PathStyle::Mod)?; // `path`
+                self.expect(&token::CloseDelim(token::Paren))?; // `)`
+                let vis = VisibilityKind::Restricted {
+                    path: P(path),
+                    id: ast::DUMMY_NODE_ID,
+                };
+                return Ok(respan(lo.to(self.prev_span), vis));
+            } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren))
+                && self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
+            {
+                // Parse `pub(self)` or `pub(super)`.
+                self.bump(); // `(`
+                let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
+                self.expect(&token::CloseDelim(token::Paren))?; // `)`
+                let vis = VisibilityKind::Restricted {
+                    path: P(path),
+                    id: ast::DUMMY_NODE_ID,
+                };
+                return Ok(respan(lo.to(self.prev_span), vis));
+            } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct.
+                self.recover_incorrect_vis_restriction()?;
+                // Emit diagnostic, but continue with public visibility.
+            }
+        }
+
+        Ok(respan(lo, VisibilityKind::Public))
+    }
+
+    /// Recovery for e.g. `pub(something) fn ...` or `struct X { pub(something) y: Z }`
+    fn recover_incorrect_vis_restriction(&mut self) -> PResult<'a, ()> {
+        self.bump(); // `(`
+        let path = self.parse_path(PathStyle::Mod)?;
+        self.expect(&token::CloseDelim(token::Paren))?;  // `)`
+
+        let msg = "incorrect visibility restriction";
+        let suggestion = r##"some possible visibility restrictions are:
+`pub(crate)`: visible only on the current crate
+`pub(super)`: visible only in the current module's parent
+`pub(in path::to::module)`: visible only on the specified path"##;
+
+        let path_str = pprust::path_to_string(&path);
+
+        struct_span_err!(self.sess.span_diagnostic, path.span, E0704, "{}", msg)
+            .help(suggestion)
+            .span_suggestion(
+                path.span,
+                &format!("make this visible only to module `{}` with `in`", path_str),
+                format!("in {}", path_str),
+                Applicability::MachineApplicable,
+            )
+            .emit();
+
+        Ok(())
+    }
+
+    /// Parses `extern string_literal?`.
+    /// If `extern` is not found, the Rust ABI is used.
+    /// If `extern` is found and a `string_literal` does not follow, the C ABI is used.
+    fn parse_extern_abi(&mut self) -> PResult<'a, Abi> {
+        Ok(if self.eat_keyword(kw::Extern) {
+            self.parse_opt_abi()?
+        } else {
+            Abi::default()
+        })
+    }
+
+    /// Parses a string literal as an ABI spec.
+    /// If one is not found, the "C" ABI is used.
+    fn parse_opt_abi(&mut self) -> PResult<'a, Abi> {
+        let span = if self.token.can_begin_literal_or_bool() {
+            let ast::Lit { span, kind, .. } = self.parse_lit()?;
+            match kind {
+                ast::LitKind::Str(symbol, _) => return Ok(Abi::new(symbol, span)),
+                ast::LitKind::Err(_) => {}
+                _ => {
+                    self.struct_span_err(span, "non-string ABI literal")
+                        .span_suggestion(
+                            span,
+                            "specify the ABI with a string literal",
+                            "\"C\"".to_string(),
+                            Applicability::MaybeIncorrect,
+                        )
+                        .emit();
+                }
+            }
+            span
+        } else {
+            self.prev_span
+        };
+        Ok(Abi::new(sym::C, span))
+    }
+
+    /// 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();
+        }
+    }
+
+    fn collect_tokens<R>(
+        &mut self,
+        f: impl FnOnce(&mut Self) -> PResult<'a, R>,
+    ) -> PResult<'a, (R, TokenStream)> {
+        // Record all tokens we parse when parsing this item.
+        let mut tokens = Vec::new();
+        let prev_collecting = match self.token_cursor.frame.last_token {
+            LastToken::Collecting(ref mut list) => {
+                Some(mem::take(list))
+            }
+            LastToken::Was(ref mut last) => {
+                tokens.extend(last.take());
+                None
+            }
+        };
+        self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
+        let prev = self.token_cursor.stack.len();
+        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::default()));
+        } 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::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::default()));
+            }
+        };
+
+        // If we're not at EOF our current token wasn't actually consumed by
+        // `f`, but it'll still be in our list that we pulled out. In that case
+        // put it back.
+        let extra_token = if self.token != token::Eof {
+            collected_tokens.pop()
+        } else {
+            None
+        };
+
+        // If we were previously collecting tokens, then this was a recursive
+        // call. In that case we need to record all the tokens we collected in
+        // our parent list as well. To do that we push a clone of our stream
+        // onto the previous list.
+        match prev_collecting {
+            Some(mut list) => {
+                list.extend(collected_tokens.iter().cloned());
+                list.extend(extra_token);
+                *last_token = LastToken::Collecting(list);
+            }
+            None => {
+                *last_token = LastToken::Was(extra_token);
+            }
+        }
+
+        Ok((ret?, TokenStream::new(collected_tokens)))
+    }
+
+    /// `::{` or `::*`
+    fn is_import_coupler(&mut self) -> bool {
+        self.check(&token::ModSep) &&
+            self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
+                                   *t == token::BinOp(token::Star))
+    }
+
+    fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
+        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();
+        Some(ret)
+    }
+
+    pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
+        match self.parse_optional_str() {
+            Some((s, style, suf)) => {
+                let sp = self.prev_span;
+                self.expect_no_suffix(sp, "a string literal", suf);
+                Ok((s, style))
+            }
+            _ => {
+                let msg = "expected string literal";
+                let mut err = self.fatal(msg);
+                err.span_label(self.token.span, msg);
+                Err(err)
+            }
+        }
+    }
+}
+
+crate fn make_unclosed_delims_error(
+    unmatched: UnmatchedBrace,
+    sess: &ParseSess,
+) -> Option<DiagnosticBuilder<'_>> {
+    // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
+    // `unmatched_braces` only for error recovery in the `Parser`.
+    let found_delim = unmatched.found_delim?;
+    let mut err = sess.span_diagnostic.struct_span_err(unmatched.found_span, &format!(
+        "incorrect close delimiter: `{}`",
+        pprust::token_kind_to_string(&token::CloseDelim(found_delim)),
+    ));
+    err.span_label(unmatched.found_span, "incorrect close delimiter");
+    if let Some(sp) = unmatched.candidate_span {
+        err.span_label(sp, "close delimiter possibly meant for this");
+    }
+    if let Some(sp) = unmatched.unclosed_span {
+        err.span_label(sp, "un-closed delimiter");
+    }
+    Some(err)
+}
+
+pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, sess: &ParseSess) {
+    *sess.reached_eof.borrow_mut() |= unclosed_delims.iter()
+        .any(|unmatched_delim| unmatched_delim.found_delim.is_none());
+    for unmatched in unclosed_delims.drain(..) {
+        make_unclosed_delims_error(unmatched, sess).map(|mut e| e.emit());
+    }
+}
diff --git a/src/librustc_parse/parser/module.rs b/src/librustc_parse/parser/module.rs
new file mode 100644
index 00000000000..3110f15e80b
--- /dev/null
+++ b/src/librustc_parse/parser/module.rs
@@ -0,0 +1,316 @@
+use super::Parser;
+use super::item::ItemInfo;
+use super::diagnostics::Error;
+
+use crate::{new_sub_parser_from_file, DirectoryOwnership};
+
+use syntax::attr;
+use syntax::ast::{self, Ident, Attribute, ItemKind, Mod, Crate};
+use syntax::token::{self, TokenKind};
+use syntax::source_map::{SourceMap, Span, DUMMY_SP, FileName};
+
+use syntax_pos::symbol::sym;
+use errors::PResult;
+
+use std::path::{self, Path, PathBuf};
+
+/// Information about the path to a module.
+pub(super) struct ModulePath {
+    name: String,
+    path_exists: bool,
+    pub result: Result<ModulePathSuccess, Error>,
+}
+
+pub(super) struct ModulePathSuccess {
+    pub path: PathBuf,
+    pub directory_ownership: DirectoryOwnership,
+}
+
+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
+    }
+
+    /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
+    pub(super) fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
+        // HACK(Centril): See documentation on `ParseSess::process_cfg_mod`.
+        let (in_cfg, outer_attrs) = (self.sess.process_cfg_mod)(
+            self.sess,
+            self.cfg_mods,
+            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 } =
+                    self.submod_path(id, &outer_attrs, id_span)?;
+                let (module, attrs) =
+                    self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
+                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,
+                },
+                path,
+            });
+        }
+
+        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 => {
+                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(super) 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(super) 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, 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),
+                },
+            }),
+            (false, true) => Ok(ModulePathSuccess {
+                path: secondary_path,
+                directory_ownership: DirectoryOwnership::Owned {
+                    relative: None,
+                },
+            }),
+            (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/librustc_parse/parser/pat.rs b/src/librustc_parse/parser/pat.rs
new file mode 100644
index 00000000000..b068a4f16a5
--- /dev/null
+++ b/src/librustc_parse/parser/pat.rs
@@ -0,0 +1,1015 @@
+use super::{Parser, PathStyle};
+use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
+use syntax::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
+use syntax::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
+use syntax::mut_visit::{noop_visit_pat, noop_visit_mac, MutVisitor};
+use syntax::ptr::P;
+use syntax::print::pprust;
+use syntax::ThinVec;
+use syntax::token;
+use syntax::source_map::{respan, Span, Spanned};
+use syntax_pos::symbol::{kw, sym};
+use errors::{PResult, Applicability, DiagnosticBuilder};
+
+type Expected = Option<&'static str>;
+
+/// `Expected` for function and lambda parameter patterns.
+pub(super) const PARAM_EXPECTED: Expected = Some("parameter name");
+
+const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here";
+
+/// Whether or not an or-pattern should be gated when occurring in the current context.
+#[derive(PartialEq)]
+pub(super) enum GateOr { Yes, No }
+
+/// Whether or not to recover a `,` when parsing or-patterns.
+#[derive(PartialEq, Copy, Clone)]
+enum RecoverComma { Yes, No }
+
+impl<'a> Parser<'a> {
+    /// Parses a pattern.
+    ///
+    /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
+    /// at the top level. Used when parsing the parameters of lambda expressions,
+    /// functions, function pointers, and `pat` macro fragments.
+    pub fn parse_pat(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
+        self.parse_pat_with_range_pat(true, expected)
+    }
+
+    /// Entry point to the main pattern parser.
+    /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
+    pub(super) fn parse_top_pat(&mut self, gate_or: GateOr) -> PResult<'a, P<Pat>> {
+        // Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
+        let gated_leading_vert = self.eat_or_separator(None) && gate_or == GateOr::Yes;
+        let leading_vert_span = self.prev_span;
+
+        // Parse the possibly-or-pattern.
+        let pat = self.parse_pat_with_or(None, gate_or, RecoverComma::Yes)?;
+
+        // If we parsed a leading `|` which should be gated,
+        // and no other gated or-pattern has been parsed thus far,
+        // then we should really gate the leading `|`.
+        // This complicated procedure is done purely for diagnostics UX.
+        if gated_leading_vert && self.sess.gated_spans.is_ungated(sym::or_patterns) {
+            self.sess.gated_spans.gate(sym::or_patterns, leading_vert_span);
+        }
+
+        Ok(pat)
+    }
+
+    /// Parse the pattern for a function or function pointer parameter.
+    /// Special recovery is provided for or-patterns and leading `|`.
+    pub(super) fn parse_fn_param_pat(&mut self) -> PResult<'a, P<Pat>> {
+        self.recover_leading_vert(None, "not allowed in a parameter pattern");
+        let pat = self.parse_pat_with_or(PARAM_EXPECTED, GateOr::No, RecoverComma::No)?;
+
+        if let PatKind::Or(..) = &pat.kind {
+            self.ban_illegal_fn_param_or_pat(&pat);
+        }
+
+        Ok(pat)
+    }
+
+    /// Ban `A | B` immediately in a parameter pattern and suggest wrapping in parens.
+    fn ban_illegal_fn_param_or_pat(&self, pat: &Pat) {
+        let msg = "wrap the pattern in parenthesis";
+        let fix = format!("({})", pprust::pat_to_string(pat));
+        self.struct_span_err(pat.span, "an or-pattern parameter must be wrapped in parenthesis")
+            .span_suggestion(pat.span, msg, fix, Applicability::MachineApplicable)
+            .emit();
+    }
+
+    /// Parses a pattern, that may be a or-pattern (e.g. `Foo | Bar` in `Some(Foo | Bar)`).
+    /// Corresponds to `pat<allow_top_alt>` in RFC 2535.
+    fn parse_pat_with_or(
+        &mut self,
+        expected: Expected,
+        gate_or: GateOr,
+        rc: RecoverComma,
+    ) -> PResult<'a, P<Pat>> {
+        // Parse the first pattern (`p_0`).
+        let first_pat = self.parse_pat(expected)?;
+        self.maybe_recover_unexpected_comma(first_pat.span, rc)?;
+
+        // 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)) && self.token != token::OrOr {
+            return Ok(first_pat)
+        }
+
+        // Parse the patterns `p_1 | ... | p_n` where `n > 0`.
+        let lo = first_pat.span;
+        let mut pats = vec![first_pat];
+        while self.eat_or_separator(Some(lo)) {
+            let pat = self.parse_pat(expected).map_err(|mut err| {
+                err.span_label(lo, WHILE_PARSING_OR_MSG);
+                err
+            })?;
+            self.maybe_recover_unexpected_comma(pat.span, rc)?;
+            pats.push(pat);
+        }
+        let or_pattern_span = lo.to(self.prev_span);
+
+        // Feature gate the or-pattern if instructed:
+        if gate_or == GateOr::Yes {
+            self.sess.gated_spans.gate(sym::or_patterns, or_pattern_span);
+        }
+
+        Ok(self.mk_pat(or_pattern_span, PatKind::Or(pats)))
+    }
+
+    /// Eat the or-pattern `|` separator.
+    /// If instead a `||` token is encountered, recover and pretend we parsed `|`.
+    fn eat_or_separator(&mut self, lo: Option<Span>) -> bool {
+        if self.recover_trailing_vert(lo) {
+            return false;
+        }
+
+        match self.token.kind {
+            token::OrOr => {
+                // Found `||`; Recover and pretend we parsed `|`.
+                self.ban_unexpected_or_or(lo);
+                self.bump();
+                true
+            }
+            _ => self.eat(&token::BinOp(token::Or)),
+        }
+    }
+
+    /// Recover if `|` or `||` is the current token and we have one of the
+    /// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us.
+    ///
+    /// These tokens all indicate that we reached the end of the or-pattern
+    /// list and can now reliably say that the `|` was an illegal trailing vert.
+    /// Note that there are more tokens such as `@` for which we know that the `|`
+    /// is an illegal parse. However, the user's intent is less clear in that case.
+    fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool {
+        let is_end_ahead = self.look_ahead(1, |token| match &token.kind {
+            token::FatArrow // e.g. `a | => 0,`.
+            | token::Ident(kw::If, false) // e.g. `a | if expr`.
+            | token::Eq // e.g. `let a | = 0`.
+            | token::Semi // e.g. `let a |;`.
+            | token::Colon // e.g. `let a | :`.
+            | token::Comma // e.g. `let (a |,)`.
+            | token::CloseDelim(token::Bracket) // e.g. `let [a | ]`.
+            | token::CloseDelim(token::Paren) // e.g. `let (a | )`.
+            | token::CloseDelim(token::Brace) => true, // e.g. `let A { f: a | }`.
+            _ => false,
+        });
+        match (is_end_ahead, &self.token.kind) {
+            (true, token::BinOp(token::Or)) | (true, token::OrOr) => {
+                self.ban_illegal_vert(lo, "trailing", "not allowed in an or-pattern");
+                self.bump();
+                true
+            }
+            _ => false,
+        }
+    }
+
+    /// We have parsed `||` instead of `|`. Error and suggest `|` instead.
+    fn ban_unexpected_or_or(&mut self, lo: Option<Span>) {
+        let mut err = self.struct_span_err(self.token.span, "unexpected token `||` after pattern");
+        err.span_suggestion(
+            self.token.span,
+            "use a single `|` to separate multiple alternative patterns",
+            "|".to_owned(),
+            Applicability::MachineApplicable
+        );
+        if let Some(lo) = lo {
+            err.span_label(lo, WHILE_PARSING_OR_MSG);
+        }
+        err.emit();
+    }
+
+    /// Some special error handling for the "top-level" patterns in a match arm,
+    /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
+    fn maybe_recover_unexpected_comma(&mut self, lo: Span, rc: RecoverComma) -> PResult<'a, ()> {
+        if rc == RecoverComma::No || self.token != token::Comma {
+            return Ok(());
+        }
+
+        // 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 = lo.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
+            );
+        }
+        Err(err)
+    }
+
+    /// 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(())
+    }
+
+    /// Recursive possibly-or-pattern parser with recovery for an erroneous leading `|`.
+    /// See `parse_pat_with_or` for details on parsing or-patterns.
+    fn parse_pat_with_or_inner(&mut self) -> PResult<'a, P<Pat>> {
+        self.recover_leading_vert(None, "only allowed in a top-level pattern");
+        self.parse_pat_with_or(None, GateOr::Yes, RecoverComma::No)
+    }
+
+    /// Recover if `|` or `||` is here.
+    /// The user is thinking that a leading `|` is allowed in this position.
+    fn recover_leading_vert(&mut self, lo: Option<Span>, ctx: &str) {
+        if let token::BinOp(token::Or) | token::OrOr = self.token.kind {
+            self.ban_illegal_vert(lo, "leading", ctx);
+            self.bump();
+        }
+    }
+
+    /// A `|` or possibly `||` token shouldn't be here. Ban it.
+    fn ban_illegal_vert(&mut self, lo: Option<Span>, pos: &str, ctx: &str) {
+        let span = self.token.span;
+        let mut err = self.struct_span_err(span, &format!("a {} `|` is {}", pos, ctx));
+        err.span_suggestion(
+            span,
+            &format!("remove the `{}`", pprust::token_to_string(&self.token)),
+            String::new(),
+            Applicability::MachineApplicable,
+        );
+        if let Some(lo) = lo {
+            err.span_label(lo, WHILE_PARSING_OR_MSG);
+        }
+        if let token::OrOr = self.token.kind {
+            err.note("alternatives in or-patterns are separated with `|`, not `||`");
+        }
+        err.emit();
+    }
+
+    /// 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: Expected,
+    ) -> 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.
+                let (pats, _) = self.parse_delim_comma_seq(
+                    token::Bracket,
+                    |p| p.parse_pat_with_or_inner(),
+                )?;
+                PatKind::Slice(pats)
+            }
+            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 != `&`, `&&`, `(`, `[`, `..`, `..=`, or `...`.
+            _ => if self.eat_keyword(kw::Underscore) {
+                // Parse _
+                PatKind::Wild
+            } else if self.eat_keyword(kw::Mut) {
+                self.parse_pat_ident_mut()?
+            } 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`
+                let pat = self.parse_pat_with_range_pat(false, None)?;
+                self.sess.gated_spans.gate(sym::box_patterns, lo.to(self.prev_span));
+                PatKind::Box(pat)
+            } else if self.can_be_ident_pat() {
+                // 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.is_start_of_pat_with_path() {
+                // 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)?;
+        let pat = self.recover_intersection_pat(pat)?;
+
+        if !allow_range_pat {
+            self.ban_pat_range_if_ambiguous(&pat)?
+        }
+
+        Ok(pat)
+    }
+
+    /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
+    ///
+    /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
+    /// should already have been parsed by now  at this point,
+    /// if the next token is `@` then we can try to parse the more general form.
+    ///
+    /// Consult `parse_pat_ident` for the `binding` grammar.
+    ///
+    /// The notion of intersection patterns are found in
+    /// e.g. [F#][and] where they are called AND-patterns.
+    ///
+    /// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching
+    fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> {
+        if self.token.kind != token::At {
+            // Next token is not `@` so it's not going to be an intersection pattern.
+            return Ok(lhs);
+        }
+
+        // At this point we attempt to parse `@ $pat_rhs` and emit an error.
+        self.bump(); // `@`
+        let mut rhs = self.parse_pat(None)?;
+        let sp = lhs.span.to(rhs.span);
+
+        if let PatKind::Ident(_, _, ref mut sub @ None) = rhs.kind {
+            // The user inverted the order, so help them fix that.
+            let mut applicability = Applicability::MachineApplicable;
+            lhs.walk(&mut |p| match p.kind {
+                // `check_match` is unhappy if the subpattern has a binding anywhere.
+                PatKind::Ident(..) => {
+                    applicability = Applicability::MaybeIncorrect;
+                    false // Short-circuit.
+                },
+                _ => true,
+            });
+
+            let lhs_span = lhs.span;
+            // Move the LHS into the RHS as a subpattern.
+            // The RHS is now the full pattern.
+            *sub = Some(lhs);
+
+            self.struct_span_err(sp, "pattern on wrong side of `@`")
+                .span_label(lhs_span, "pattern on the left, should be on the right")
+                .span_label(rhs.span, "binding on the right, should be on the left")
+                .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability)
+                .emit();
+        } else {
+            // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
+            rhs.kind = PatKind::Wild;
+            self.struct_span_err(sp, "left-hand side of `@` must be a binding")
+                .span_label(lhs.span, "interpreted as a pattern, not a binding")
+                .span_label(rhs.span, "also a pattern")
+                .note("bindings are `x`, `mut x`, `ref x`, and `ref mut x`")
+                .emit();
+        }
+
+        rhs.span = sp;
+        Ok(rhs)
+    }
+
+    /// Ban a range pattern if it has an ambiguous interpretation.
+    fn ban_pat_range_if_ambiguous(&self, pat: &Pat) -> PResult<'a, ()> {
+        match pat.kind {
+            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: Expected) -> 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_inner())?;
+
+        // 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)
+        })
+    }
+
+    /// Parse a mutable binding with the `mut` token already eaten.
+    fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
+        let mut_span = self.prev_span;
+
+        if self.eat_keyword(kw::Ref) {
+            return self.recover_mut_ref_ident(mut_span)
+        }
+
+        self.recover_additional_muts();
+
+        // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
+        if let token::Interpolated(ref nt) = self.token.kind {
+             if let token::NtPat(_) = **nt {
+                 self.expected_ident_found().emit();
+             }
+        }
+
+        // Parse the pattern we hope to be an identifier.
+        let mut pat = self.parse_pat(Some("identifier"))?;
+
+        // Add `mut` to any binding in the parsed pattern.
+        let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
+
+        // Unwrap; If we don't have `mut $ident`, error.
+        let pat = pat.into_inner();
+        match &pat.kind {
+            PatKind::Ident(..) => {}
+            _ => self.ban_mut_general_pat(mut_span, &pat, changed_any_binding),
+        }
+
+        Ok(pat.kind)
+    }
+
+    /// Recover on `mut ref? ident @ pat` and suggest
+    /// that the order of `mut` and `ref` is incorrect.
+    fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> {
+        let mutref_span = lo.to(self.prev_span);
+        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();
+
+        self.parse_pat_ident(BindingMode::ByRef(Mutability::Mutable))
+    }
+
+    /// Turn all by-value immutable bindings in a pattern into mutable bindings.
+    /// Returns `true` if any change was made.
+    fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
+        struct AddMut(bool);
+        impl MutVisitor for AddMut {
+            fn visit_mac(&mut self, mac: &mut Mac) {
+                noop_visit_mac(mac, self);
+            }
+
+            fn visit_pat(&mut self, pat: &mut P<Pat>) {
+                if let PatKind::Ident(BindingMode::ByValue(ref mut m @ Mutability::Immutable), ..)
+                    = pat.kind
+                {
+                    *m = Mutability::Mutable;
+                    self.0 = true;
+                }
+                noop_visit_pat(pat, self);
+            }
+        }
+
+        let mut add_mut = AddMut(false);
+        add_mut.visit_pat(pat);
+        add_mut.0
+    }
+
+    /// Error on `mut $pat` where `$pat` is not an ident.
+    fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
+        let span = lo.to(pat.span);
+        let fix = pprust::pat_to_string(&pat);
+        let (problem, suggestion) = if changed_any_binding {
+            ("`mut` must be attached to each individual binding", "add `mut` to each binding")
+        } else {
+            ("`mut` must be followed by a named binding", "remove the `mut` prefix")
+        };
+        self.struct_span_err(span, problem)
+            .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable)
+            .note("`mut` may be followed by `variable` and `variable @ pattern`")
+            .emit()
+    }
+
+    /// Eat any extraneous `mut`s and error + recover if we ate any.
+    fn recover_additional_muts(&mut self) {
+        let lo = self.token.span;
+        while self.eat_keyword(kw::Mut) {}
+        if lo == self.token.span {
+            return;
+        }
+
+        let span = lo.to(self.prev_span);
+        self.struct_span_err(span, "`mut` on a binding may not be repeated")
+            .span_suggestion(
+                span,
+                "remove the additional `mut`s",
+                String::new(),
+                Applicability::MachineApplicable,
+            )
+            .emit();
+    }
+
+    /// 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))
+    }
+
+    fn excluded_range_end(&self, span: Span) -> RangeEnd {
+        self.sess.gated_spans.gate(sym::exclusive_range_pattern, span);
+        RangeEnd::Excluded
+    }
+
+    /// 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 => (self.excluded_range_end(self.token.span), ".."),
+            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) {
+            (self.excluded_range_end(op_span), "..")
+        } 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: Expected,
+    ) -> PResult<'a, P<Pat>> {
+        err.cancel();
+
+        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)
+    }
+
+    /// 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()
+        }
+    }
+
+    /// Is this the start of a pattern beginning with a path?
+    fn is_start_of_pat_with_path(&mut self) -> bool {
+        self.check_path()
+        // Just for recovery (see `can_be_ident`).
+        || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
+    }
+
+    /// Would `parse_pat_ident` be appropriate here?
+    fn can_be_ident_pat(&mut self) -> bool {
+        self.check_ident()
+        && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
+        && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
+        // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
+        && !self.token.is_keyword(kw::In)
+        && self.look_ahead(1, |t| match t.kind { // Try to do something more complex?
+            token::OpenDelim(token::Paren) // A tuple struct pattern.
+            | token::OpenDelim(token::Brace) // A struct pattern.
+            | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
+            | token::ModSep // A tuple / struct variant pattern.
+            | token::Not => false, // A macro expanding to a pattern.
+            _ => true,
+        })
+    }
+
+    /// 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_inner())?;
+        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_inner()?;
+            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),
+            is_placeholder: false,
+        })
+    }
+
+    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, kind: PatKind) -> P<Pat> {
+        P(Pat { kind, span, id: ast::DUMMY_NODE_ID })
+    }
+}
diff --git a/src/librustc_parse/parser/path.rs b/src/librustc_parse/parser/path.rs
new file mode 100644
index 00000000000..68307440712
--- /dev/null
+++ b/src/librustc_parse/parser/path.rs
@@ -0,0 +1,497 @@
+use super::{Parser, TokenType};
+use crate::maybe_whole;
+use syntax::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
+use syntax::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
+use syntax::ThinVec;
+use syntax::token::{self, Token};
+use syntax::source_map::{Span, BytePos};
+use syntax_pos::symbol::{kw, sym};
+
+use std::mem;
+use log::debug;
+use errors::{PResult, Applicability, pluralize};
+
+/// 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.
+    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 item) => match item.tokens.is_empty() {
+                    true => Some(item.path.clone()),
+                    false => None,
+                },
+                _ => None,
+            },
+            _ => None,
+        };
+        if let Some(path) = meta_ident {
+            self.bump();
+            return Ok(path);
+        }
+        self.parse_path(style)
+    }
+
+    /// Parse a list of paths inside `#[derive(path_0, ..., path_n)]`.
+    pub fn parse_derive_paths(&mut self) -> PResult<'a, Vec<Path>> {
+        self.expect(&token::OpenDelim(token::Paren))?;
+        let mut list = Vec::new();
+        while !self.eat(&token::CloseDelim(token::Paren)) {
+            let path = self.parse_path_allowing_meta(PathStyle::Mod)?;
+            list.push(path);
+            if !self.eat(&token::Comma) {
+                self.expect(&token::CloseDelim(token::Paren))?;
+                break
+            }
+        }
+        Ok(list)
+    }
+
+    pub(super) 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 = ident.span.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)
+                );
+                self.diagnostic()
+                    .struct_span_err(
+                        span,
+                        &format!(
+                            "unmatched angle bracket{}",
+                            pluralize!(snapshot.unmatched_angle_bracket_count)
+                        ),
+                    )
+                    .span_suggestion(
+                        span,
+                        &format!(
+                            "remove extra angle bracket{}",
+                            pluralize!(snapshot.unmatched_angle_bracket_count)
+                        ),
+                        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);
+
+                // Gate associated type bounds, e.g., `Iterator<Item: Ord>`.
+                if let AssocTyConstraintKind::Bound { .. } = kind {
+                    self.sess.gated_spans.gate(sym::associated_type_bounds, 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_bool_lit() {
+                        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/librustc_parse/parser/stmt.rs b/src/librustc_parse/parser/stmt.rs
new file mode 100644
index 00000000000..a5f20691d07
--- /dev/null
+++ b/src/librustc_parse/parser/stmt.rs
@@ -0,0 +1,482 @@
+use super::{Parser, Restrictions, PrevTokenKind, SemiColonMode, BlockMode};
+use super::expr::LhsExpr;
+use super::path::PathStyle;
+use super::pat::GateOr;
+use super::diagnostics::Error;
+use crate::maybe_whole;
+use crate::DirectoryOwnership;
+
+use syntax::ThinVec;
+use syntax::ptr::P;
+use syntax::ast;
+use syntax::ast::{DUMMY_NODE_ID, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
+use syntax::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac, MacDelimiter};
+use syntax::util::classify;
+use syntax::token;
+use syntax::source_map::{respan, Span};
+use syntax::symbol::{kw, sym};
+
+use std::mem;
+use errors::{PResult, Applicability};
+
+impl<'a> Parser<'a> {
+    /// Parses 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: DUMMY_NODE_ID,
+                kind: 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: DUMMY_NODE_ID,
+                kind: 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: DUMMY_NODE_ID,
+                    kind: 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 kind = 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: DUMMY_NODE_ID,
+                span: lo.to(hi),
+                kind,
+            }
+        } 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: DUMMY_NODE_ID,
+                    span: lo.to(i.span),
+                    kind: 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: DUMMY_NODE_ID,
+                            span: lo.to(last_semi),
+                            kind: 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: DUMMY_NODE_ID,
+                        span: lo.to(e.span),
+                        kind: 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_pat(GateOr::Yes)?;
+
+        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: 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);
+                    e.cancel();
+                }
+                _ => ()
+            }
+            e.span_label(sp, "expected `{`");
+            return Err(e);
+        }
+
+        self.parse_block_tail(lo, BlockCheckMode::Default)
+    }
+
+    /// Parses a block. Inner attributes are allowed.
+    pub(super) 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) => {
+                    self.maybe_annotate_with_ascription(&mut err, false);
+                    err.emit();
+                    self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
+                    Some(Stmt {
+                        id: DUMMY_NODE_ID,
+                        kind: StmtKind::Expr(self.mk_expr_err(self.token.span)),
+                        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: DUMMY_NODE_ID,
+            rules: s,
+            span: lo.to(self.prev_span),
+        }))
+    }
+
+    /// Parses a statement, including the trailing semicolon.
+    pub 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),
+        };
+
+        let mut eat_semi = true;
+        match stmt.kind {
+            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.kind = StmtKind::Expr(self.mk_expr_err(sp));
+                    }
+                }
+            }
+            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_semi()?;
+                    eat_semi = false;
+                }
+            }
+            _ => {}
+        }
+
+        if eat_semi && 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/librustc_parse/parser/ty.rs b/src/librustc_parse/parser/ty.rs
new file mode 100644
index 00000000000..fccabee2404
--- /dev/null
+++ b/src/librustc_parse/parser/ty.rs
@@ -0,0 +1,460 @@
+use super::{Parser, PathStyle, PrevTokenKind, TokenType};
+use super::item::ParamCfg;
+
+use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
+
+use syntax::ptr::P;
+use syntax::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
+use syntax::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
+use syntax::ast::{Mutability, AnonConst, Mac};
+use syntax::token::{self, Token};
+use syntax::source_map::Span;
+use syntax::struct_span_fatal;
+use syntax_pos::symbol::kw;
+
+use errors::{PResult, Applicability, pluralize};
+
+/// 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 kind = 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.kind {
+                    // `(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(struct_span_fatal!(
+                    self.sess.span_diagnostic,
+                    self.token.span,
+                    E0743,
+                    "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 = self.mk_ty(span, kind);
+
+        // 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 = self.parse_const_or_mut().unwrap_or_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 = self.parse_extern_abi()?;
+        self.expect_keyword(kw::Fn)?;
+        let cfg = ParamCfg {
+            is_self_allowed: false,
+            allow_c_variadic: true,
+            is_name_required: |_| false,
+        };
+        let decl = self.parse_fn_decl(cfg, false)?;
+        Ok(TyKind::BareFn(P(BareFnTy {
+            abi,
+            unsafety,
+            generic_params,
+            decl,
+        })))
+    }
+
+    pub(super) 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 negative_bounds_len = negative_bounds.len();
+            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{}", pluralize!(negative_bounds_len)),
+                    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())
+        }
+    }
+
+    pub fn check_lifetime(&mut self) -> bool {
+        self.expected_tokens.push(TokenType::Lifetime);
+        self.token.is_lifetime()
+    }
+
+    /// Parses a single lifetime `'a` or panics.
+    pub 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")
+        }
+    }
+
+    pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
+        P(Ty { kind, span, id: ast::DUMMY_NODE_ID })
+    }
+}