Merge pull request #1 from rust-lang/master

Merge recent changes into master

1 files changed, 1797 insertions, 2587 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index fe31311094b..d85c2df16a3 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1,7 +1,9 @@
+// ignore-tidy-filelength
+
 use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
 use crate::ast::{GenericBound, TraitBoundModifier};
 use crate::ast::Unsafety;
-use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
+use crate::ast::{Mod, AnonConst, Arg, Arm, Attribute, BindingMode, TraitItemKind};
 use crate::ast::Block;
 use crate::ast::{BlockCheckMode, CaptureBy, Movability};
 use crate::ast::{Constness, Crate};
@@ -13,7 +15,7 @@ use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
 use crate::ast::{GenericParam, GenericParamKind};
 use crate::ast::GenericArg;
 use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
-use crate::ast::{Label, Lifetime, Lit, LitKind};
+use crate::ast::{Label, Lifetime};
 use crate::ast::Local;
 use crate::ast::MacStmtStyle;
 use crate::ast::{Mac, Mac_, MacDelimiter};
@@ -25,31 +27,33 @@ use crate::ast::{VariantData, StructField};
 use crate::ast::StrStyle;
 use crate::ast::SelfKind;
 use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
-use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
+use crate::ast::{Ty, TyKind, AssocTyConstraint, AssocTyConstraintKind, GenericBounds};
 use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
 use crate::ast::{UseTree, UseTreeKind};
 use crate::ast::{BinOpKind, UnOp};
 use crate::ast::{RangeEnd, RangeSyntax};
 use crate::{ast, attr};
 use crate::ext::base::DummyResult;
+use crate::ext::hygiene::SyntaxContext;
 use crate::source_map::{self, SourceMap, Spanned, respan};
-use crate::parse::{self, SeqSep, classify, token};
-use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
+use crate::parse::{SeqSep, classify, literal, token};
+use crate::parse::lexer::UnmatchedBrace;
 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
-use crate::parse::token::DelimToken;
+use crate::parse::token::{Token, TokenKind, DelimToken};
 use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
-use crate::util::parser::{AssocOp, Fixity};
+use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
 use crate::print::pprust;
 use crate::ptr::P;
 use crate::parse::PResult;
 use crate::ThinVec;
 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
-use crate::symbol::{Symbol, keywords};
+use crate::symbol::{kw, sym, Symbol};
+use crate::parse::diagnostics::{Error, dummy_arg};
 
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
 use rustc_target::spec::abi::{self, Abi};
-use syntax_pos::{Span, MultiSpan, BytePos, FileName};
-use log::{debug, trace};
+use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
+use log::debug;
 
 use std::borrow::Cow;
 use std::cmp;
@@ -58,12 +62,12 @@ use std::path::{self, Path, PathBuf};
 use std::slice;
 
 #[derive(Debug)]
-/// Whether the type alias or associated type is a concrete type or an existential type
+/// Whether the type alias or associated type is a concrete type or an opaque type
 pub enum AliasKind {
     /// Just a new name for the same type
     Weak(P<Ty>),
     /// Only trait impls of the type will be usable, not the actual type itself
-    Existential(GenericBounds),
+    OpaqueTy(GenericBounds),
 }
 
 bitflags::bitflags! {
@@ -99,14 +103,14 @@ pub enum PathStyle {
 }
 
 #[derive(Clone, Copy, PartialEq, Debug)]
-enum SemiColonMode {
+crate enum SemiColonMode {
     Break,
     Ignore,
     Comma,
 }
 
 #[derive(Clone, Copy, PartialEq, Debug)]
-enum BlockMode {
+crate enum BlockMode {
     Break,
     Ignore,
 }
@@ -118,24 +122,28 @@ enum BlockMode {
 /// `token::Interpolated` tokens.
 macro_rules! maybe_whole_expr {
     ($p:expr) => {
-        if let token::Interpolated(nt) = $p.token.clone() {
-            match *nt {
-                token::NtExpr(ref e) | token::NtLiteral(ref e) => {
+        if let token::Interpolated(nt) = &$p.token.kind {
+            match &**nt {
+                token::NtExpr(e) | token::NtLiteral(e) => {
+                    let e = e.clone();
                     $p.bump();
-                    return Ok((*e).clone());
+                    return Ok(e);
                 }
-                token::NtPath(ref path) => {
+                token::NtPath(path) => {
+                    let path = path.clone();
                     $p.bump();
-                    let span = $p.span;
-                    let kind = ExprKind::Path(None, (*path).clone());
-                    return Ok($p.mk_expr(span, kind, ThinVec::new()));
+                    return Ok($p.mk_expr(
+                        $p.token.span, ExprKind::Path(None, path), ThinVec::new()
+                    ));
                 }
-                token::NtBlock(ref block) => {
+                token::NtBlock(block) => {
+                    let block = block.clone();
                     $p.bump();
-                    let span = $p.span;
-                    let kind = ExprKind::Block((*block).clone(), None);
-                    return Ok($p.mk_expr(span, kind, ThinVec::new()));
+                    return Ok($p.mk_expr(
+                        $p.token.span, ExprKind::Block(block, None), ThinVec::new()
+                    ));
                 }
+                // N.B: `NtIdent(ident)` is normalized to `Ident` in `fn bump`.
                 _ => {},
             };
         }
@@ -145,8 +153,9 @@ macro_rules! maybe_whole_expr {
 /// As maybe_whole_expr, but for things other than expressions
 macro_rules! maybe_whole {
     ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
-        if let token::Interpolated(nt) = $p.token.clone() {
-            if let token::$constructor($x) = (*nt).clone() {
+        if let token::Interpolated(nt) = &$p.token.kind {
+            if let token::$constructor(x) = &**nt {
+                let $x = x.clone();
                 $p.bump();
                 return Ok($e);
             }
@@ -154,6 +163,21 @@ macro_rules! maybe_whole {
     };
 }
 
+/// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
+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);
+                }
+            }
+        }
+    }
+}
+
 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
     if let Some(ref mut rhs) = rhs {
         lhs.append(rhs);
@@ -169,81 +193,40 @@ enum PrevTokenKind {
     Interpolated,
     Eof,
     Ident,
+    BitOr,
     Other,
 }
 
-trait RecoverQPath: Sized {
-    const PATH_STYLE: PathStyle = PathStyle::Expr;
-    fn to_ty(&self) -> Option<P<Ty>>;
-    fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
-    fn to_string(&self) -> String;
-}
-
-impl RecoverQPath for Ty {
-    const PATH_STYLE: PathStyle = PathStyle::Type;
-    fn to_ty(&self) -> Option<P<Ty>> {
-        Some(P(self.clone()))
-    }
-    fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
-    }
-    fn to_string(&self) -> String {
-        pprust::ty_to_string(self)
-    }
-}
-
-impl RecoverQPath for Pat {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
-    }
-    fn to_string(&self) -> String {
-        pprust::pat_to_string(self)
-    }
-}
-
-impl RecoverQPath for Expr {
-    fn to_ty(&self) -> Option<P<Ty>> {
-        self.to_ty()
-    }
-    fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
-        Self { span: path.span, node: ExprKind::Path(qself, path),
-               id: self.id, attrs: self.attrs.clone() }
-    }
-    fn to_string(&self) -> String {
-        pprust::expr_to_string(self)
-    }
-}
-
-/* ident is handled by common.rs */
+// NOTE: `Ident`s are handled by `common.rs`.
 
 #[derive(Clone)]
 pub struct Parser<'a> {
     pub sess: &'a ParseSess,
-    /// the current token:
-    pub token: token::Token,
-    /// the span of the current token:
-    pub span: Span,
-    /// the span of the previous token:
+    /// The current normalized token.
+    /// "Normalized" means that some interpolated tokens
+    /// (`$i: ident` and `$l: lifetime` meta-variables) are replaced
+    /// with non-interpolated identifier and lifetime tokens they refer to.
+    /// Perhaps the normalized / non-normalized setup can be simplified somehow.
+    pub token: Token,
+    /// Span of the current non-normalized token.
     meta_var_span: Option<Span>,
+    /// Span of the previous non-normalized token.
     pub prev_span: Span,
-    /// the previous token kind
+    /// Kind of the previous normalized token (in simplified form).
     prev_token_kind: PrevTokenKind,
     restrictions: Restrictions,
-    /// Used to determine the path to externally loaded source files
+    /// Used to determine the path to externally loaded source files.
     crate directory: Directory<'a>,
-    /// Whether to parse sub-modules in other files.
+    /// `true` to parse sub-modules in other files.
     pub recurse_into_file_modules: bool,
     /// Name of the root module this parser originated from. If `None`, then the
     /// name is not known. This does not change while the parser is descending
     /// into modules, and sub-parsers have new values for this name.
     pub root_module_name: Option<String>,
     crate expected_tokens: Vec<TokenType>,
-    token_cursor: TokenCursor,
+    crate token_cursor: TokenCursor,
     desugar_doc_comments: bool,
-    /// Whether we should configure out of line modules as we parse.
+    /// `true` we should configure out of line modules as we parse.
     pub cfg_mods: bool,
     /// This field is used to keep track of how many left angle brackets we have seen. This is
     /// required in order to detect extra leading left angle brackets (`<` characters) and error
@@ -256,7 +239,10 @@ pub struct Parser<'a> {
     /// it gets removed from here. Every entry left at the end gets emitted as an independent
     /// error.
     crate unclosed_delims: Vec<UnmatchedBrace>,
-    last_unexpected_token_span: Option<Span>,
+    crate last_unexpected_token_span: Option<Span>,
+    crate last_type_ascription: Option<(Span, bool /* likely path typo */)>,
+    /// If present, this `Parser` is not parsing Rust code but rather a macro call.
+    crate subparser_name: Option<&'static str>,
 }
 
 impl<'a> Drop for Parser<'a> {
@@ -267,19 +253,19 @@ impl<'a> Drop for Parser<'a> {
 }
 
 #[derive(Clone)]
-struct TokenCursor {
-    frame: TokenCursorFrame,
-    stack: Vec<TokenCursorFrame>,
+crate struct TokenCursor {
+    crate frame: TokenCursorFrame,
+    crate stack: Vec<TokenCursorFrame>,
 }
 
 #[derive(Clone)]
-struct TokenCursorFrame {
-    delim: token::DelimToken,
-    span: DelimSpan,
-    open_delim: bool,
-    tree_cursor: tokenstream::Cursor,
-    close_delim: bool,
-    last_token: LastToken,
+crate struct TokenCursorFrame {
+    crate delim: token::DelimToken,
+    crate span: DelimSpan,
+    crate open_delim: bool,
+    crate tree_cursor: tokenstream::Cursor,
+    crate close_delim: bool,
+    crate last_token: LastToken,
 }
 
 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
@@ -300,16 +286,16 @@ struct TokenCursorFrame {
 /// You can find some more example usage of this in the `collect_tokens` method
 /// on the parser.
 #[derive(Clone)]
-enum LastToken {
+crate enum LastToken {
     Collecting(Vec<TreeAndJoint>),
     Was(Option<TreeAndJoint>),
 }
 
 impl TokenCursorFrame {
-    fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
+    fn new(span: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
         TokenCursorFrame {
-            delim: delim,
-            span: sp,
+            delim,
+            span,
             open_delim: delim == token::NoDelim,
             tree_cursor: tts.clone().into_trees(),
             close_delim: delim == token::NoDelim,
@@ -319,7 +305,7 @@ impl TokenCursorFrame {
 }
 
 impl TokenCursor {
-    fn next(&mut self) -> TokenAndSpan {
+    fn next(&mut self) -> Token {
         loop {
             let tree = if !self.frame.open_delim {
                 self.frame.open_delim = true;
@@ -333,7 +319,7 @@ impl TokenCursor {
                 self.frame = frame;
                 continue
             } else {
-                return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
+                return Token::new(token::Eof, DUMMY_SP);
             };
 
             match self.frame.last_token {
@@ -342,7 +328,7 @@ impl TokenCursor {
             }
 
             match tree {
-                TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
+                TokenTree::Token(token) => return token,
                 TokenTree::Delimited(sp, delim, tts) => {
                     let frame = TokenCursorFrame::new(sp, delim, &tts);
                     self.stack.push(mem::replace(&mut self.frame, frame));
@@ -351,9 +337,9 @@ impl TokenCursor {
         }
     }
 
-    fn next_desugared(&mut self) -> TokenAndSpan {
-        let (sp, name) = match self.next() {
-            TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
+    fn next_desugared(&mut self) -> Token {
+        let (name, sp) = match self.next() {
+            Token { kind: token::DocComment(name), span } => (name, span),
             tok => return tok,
         };
 
@@ -376,10 +362,12 @@ impl TokenCursor {
         let body = TokenTree::Delimited(
             delim_span,
             token::Bracket,
-            [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
-             TokenTree::Token(sp, token::Eq),
-             TokenTree::Token(sp, token::Literal(
-                token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
+            [
+                TokenTree::token(token::Ident(sym::doc, false), sp),
+                TokenTree::token(token::Eq, sp),
+                TokenTree::token(TokenKind::lit(
+                    token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None
+                ), sp),
             ]
             .iter().cloned().collect::<TokenStream>().into(),
         );
@@ -388,10 +376,10 @@ impl TokenCursor {
             delim_span,
             token::NoDelim,
             &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
-                [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
+                [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
                     .iter().cloned().collect::<TokenStream>().into()
             } else {
-                [TokenTree::Token(sp, token::Pound), body]
+                [TokenTree::token(token::Pound, sp), body]
                     .iter().cloned().collect::<TokenStream>().into()
             },
         )));
@@ -402,8 +390,8 @@ impl TokenCursor {
 
 #[derive(Clone, PartialEq)]
 crate enum TokenType {
-    Token(token::Token),
-    Keyword(keywords::Keyword),
+    Token(TokenKind),
+    Keyword(Symbol),
     Operator,
     Lifetime,
     Ident,
@@ -413,10 +401,10 @@ crate enum TokenType {
 }
 
 impl TokenType {
-    fn to_string(&self) -> String {
+    crate fn to_string(&self) -> String {
         match *self {
-            TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
-            TokenType::Keyword(kw) => format!("`{}`", kw.name()),
+            TokenType::Token(ref t) => format!("`{}`", pprust::token_kind_to_string(t)),
+            TokenType::Keyword(kw) => format!("`{}`", kw),
             TokenType::Operator => "an operator".to_string(),
             TokenType::Lifetime => "lifetime".to_string(),
             TokenType::Ident => "identifier".to_string(),
@@ -432,7 +420,7 @@ impl TokenType {
 ///
 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
 /// that `IDENT` is not the ident of a fn trait.
-fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
+fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
     t == &token::ModSep || t == &token::Lt ||
     t == &token::BinOp(token::Shl)
 }
@@ -450,65 +438,6 @@ pub struct ModulePathSuccess {
     warn: bool,
 }
 
-pub enum Error {
-    FileNotFoundForModule {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-        dir_path: String,
-    },
-    DuplicatePaths {
-        mod_name: String,
-        default_path: String,
-        secondary_path: String,
-    },
-    UselessDocComment,
-    InclusiveRangeWithNoEnd,
-}
-
-impl Error {
-    fn span_err<S: Into<MultiSpan>>(self,
-                                        sp: S,
-                                        handler: &errors::Handler) -> DiagnosticBuilder<'_> {
-        match self {
-            Error::FileNotFoundForModule { ref mod_name,
-                                           ref default_path,
-                                           ref secondary_path,
-                                           ref dir_path } => {
-                let mut err = struct_span_err!(handler, sp, E0583,
-                                               "file not found for module `{}`", mod_name);
-                err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
-                                  default_path,
-                                  secondary_path,
-                                  dir_path));
-                err
-            }
-            Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
-                let mut err = struct_span_err!(handler, sp, E0584,
-                                               "file for module `{}` found at both {} and {}",
-                                               mod_name,
-                                               default_path,
-                                               secondary_path);
-                err.help("delete or rename one of them to remove the ambiguity");
-                err
-            }
-            Error::UselessDocComment => {
-                let mut err = struct_span_err!(handler, sp, E0585,
-                                  "found a documentation comment that doesn't document anything");
-                err.help("doc comments must come before what they document, maybe a comment was \
-                          intended with `//`?");
-                err
-            }
-            Error::InclusiveRangeWithNoEnd => {
-                let mut err = struct_span_err!(handler, sp, E0586,
-                                               "inclusive range with no end");
-                err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
-                err
-            }
-        }
-    }
-}
-
 #[derive(Debug)]
 enum LhsExpr {
     NotYetParsed,
@@ -532,40 +461,25 @@ impl From<P<Expr>> for LhsExpr {
     }
 }
 
-/// Creates a placeholder argument.
-fn dummy_arg(span: Span) -> Arg {
-    let ident = Ident::new(keywords::Invalid.name(), span);
-    let pat = P(Pat {
-        id: ast::DUMMY_NODE_ID,
-        node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
-        span,
-    });
-    let ty = Ty {
-        node: TyKind::Err,
-        span,
-        id: ast::DUMMY_NODE_ID
-    };
-    Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
-}
-
 #[derive(Copy, Clone, Debug)]
-enum TokenExpectType {
+crate enum TokenExpectType {
     Expect,
     NoExpect,
 }
 
 impl<'a> Parser<'a> {
-    pub fn new(sess: &'a ParseSess,
-               tokens: TokenStream,
-               directory: Option<Directory<'a>>,
-               recurse_into_file_modules: bool,
-               desugar_doc_comments: bool)
-               -> Self {
+    pub fn new(
+        sess: &'a ParseSess,
+        tokens: TokenStream,
+        directory: Option<Directory<'a>>,
+        recurse_into_file_modules: bool,
+        desugar_doc_comments: bool,
+        subparser_name: Option<&'static str>,
+    ) -> Self {
         let mut parser = Parser {
             sess,
-            token: token::Whitespace,
-            span: syntax_pos::DUMMY_SP,
-            prev_span: syntax_pos::DUMMY_SP,
+            token: Token::dummy(),
+            prev_span: DUMMY_SP,
             meta_var_span: None,
             prev_token_kind: PrevTokenKind::Other,
             restrictions: Restrictions::empty(),
@@ -590,16 +504,17 @@ impl<'a> Parser<'a> {
             max_angle_bracket_count: 0,
             unclosed_delims: Vec::new(),
             last_unexpected_token_span: None,
+            last_type_ascription: None,
+            subparser_name,
         };
 
-        let tok = parser.next_tok();
-        parser.token = tok.tok;
-        parser.span = tok.sp;
+        parser.token = parser.next_tok();
 
         if let Some(directory) = directory {
             parser.directory = directory;
-        } else if !parser.span.is_dummy() {
-            if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
+        } else if !parser.token.span.is_dummy() {
+            if let FileName::Real(mut path) =
+                    sess.source_map().span_to_unmapped_path(parser.token.span) {
                 path.pop();
                 parser.directory.path = Cow::from(path);
             }
@@ -609,15 +524,15 @@ impl<'a> Parser<'a> {
         parser
     }
 
-    fn next_tok(&mut self) -> TokenAndSpan {
+    fn next_tok(&mut self) -> Token {
         let mut next = if self.desugar_doc_comments {
             self.token_cursor.next_desugared()
         } else {
             self.token_cursor.next()
         };
-        if next.sp.is_dummy() {
+        if next.span.is_dummy() {
             // Tweak the location for better diagnostics, but keep syntactic context intact.
-            next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
+            next.span = self.prev_span.with_ctxt(next.span.ctxt());
         }
         next
     }
@@ -627,17 +542,17 @@ impl<'a> Parser<'a> {
         pprust::token_to_string(&self.token)
     }
 
-    fn token_descr(&self) -> Option<&'static str> {
-        Some(match &self.token {
-            t if t.is_special_ident() => "reserved identifier",
-            t if t.is_used_keyword() => "keyword",
-            t if t.is_unused_keyword() => "reserved keyword",
+    crate fn token_descr(&self) -> Option<&'static str> {
+        Some(match &self.token.kind {
+            _ if self.token.is_special_ident() => "reserved identifier",
+            _ if self.token.is_used_keyword() => "keyword",
+            _ if self.token.is_unused_keyword() => "reserved keyword",
             token::DocComment(..) => "doc comment",
             _ => return None,
         })
     }
 
-    fn this_token_descr(&self) -> String {
+    crate fn this_token_descr(&self) -> String {
         if let Some(prefix) = self.token_descr() {
             format!("{} `{}`", prefix, self.this_token_to_string())
         } else {
@@ -645,11 +560,6 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
-        let token_str = pprust::token_to_string(t);
-        Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
-    }
-
     crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
         match self.expect_one_of(&[], &[]) {
             Err(e) => Err(e),
@@ -658,229 +568,45 @@ impl<'a> Parser<'a> {
     }
 
     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
-    pub fn expect(&mut self, t: &token::Token) -> PResult<'a,  bool /* recovered */> {
+    pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
         if self.expected_tokens.is_empty() {
             if self.token == *t {
                 self.bump();
                 Ok(false)
             } else {
-                let token_str = pprust::token_to_string(t);
-                let this_token_str = self.this_token_descr();
-                let mut err = self.fatal(&format!("expected `{}`, found {}",
-                                                  token_str,
-                                                  this_token_str));
-
-                let sp = if self.token == token::Token::Eof {
-                    // EOF, don't want to point at the following char, but rather the last token
-                    self.prev_span
-                } else {
-                    self.sess.source_map().next_point(self.prev_span)
-                };
-                let label_exp = format!("expected `{}`", token_str);
-                match self.recover_closing_delimiter(&[t.clone()], err) {
-                    Err(e) => err = e,
-                    Ok(recovered) => {
-                        return Ok(recovered);
-                    }
-                }
-                let cm = self.sess.source_map();
-                match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
-                    (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                        // When the spans are in the same line, it means that the only content
-                        // between them is whitespace, point only at the found token.
-                        err.span_label(self.span, label_exp);
-                    }
-                    _ => {
-                        err.span_label(sp, label_exp);
-                        err.span_label(self.span, "unexpected token");
-                    }
-                }
-                Err(err)
+                self.unexpected_try_recover(t)
             }
         } else {
             self.expect_one_of(slice::from_ref(t), &[])
         }
     }
 
-    fn recover_closing_delimiter(
-        &mut self,
-        tokens: &[token::Token],
-        mut err: DiagnosticBuilder<'a>,
-    ) -> PResult<'a, bool> {
-        let mut pos = None;
-        // we want to use the last closing delim that would apply
-        for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
-            if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
-                && Some(self.span) > unmatched.unclosed_span
-            {
-                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));
-
-                 // 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 (FIXME: #58270)
-                //      |
-                //      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,
-                );
-                err.emit();
-                self.expected_tokens.clear();  // reduce errors
-                Ok(true)
-            }
-            _ => Err(err),
-        }
-    }
-
     /// 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: &[token::Token],
-        inedible: &[token::Token],
+        edible: &[TokenKind],
+        inedible: &[TokenKind],
     ) -> PResult<'a, bool /* recovered */> {
-        fn tokens_to_string(tokens: &[TokenType]) -> String {
-            let mut i = tokens.iter();
-            // This might be a sign we need a connect method on Iterator.
-            let b = i.next()
-                     .map_or(String::new(), |t| t.to_string());
-            i.enumerate().fold(b, |mut b, (i, a)| {
-                if tokens.len() > 2 && i == tokens.len() - 2 {
-                    b.push_str(", or ");
-                } else if tokens.len() == 2 && i == tokens.len() - 2 {
-                    b.push_str(" or ");
-                } else {
-                    b.push_str(", ");
-                }
-                b.push_str(&a.to_string());
-                b
-            })
-        }
-        if edible.contains(&self.token) {
+        if edible.contains(&self.token.kind) {
             self.bump();
             Ok(false)
-        } else if inedible.contains(&self.token) {
+        } else if inedible.contains(&self.token.kind) {
             // leave it in the input
             Ok(false)
-        } else if self.last_unexpected_token_span == Some(self.span) {
+        } else if self.last_unexpected_token_span == Some(self.token.span) {
             FatalError.raise();
         } else {
-            let mut expected = edible.iter()
-                .map(|x| TokenType::Token(x.clone()))
-                .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
-                .chain(self.expected_tokens.iter().cloned())
-                .collect::<Vec<_>>();
-            expected.sort_by_cached_key(|x| x.to_string());
-            expected.dedup();
-            let expect = tokens_to_string(&expected[..]);
-            let actual = self.this_token_to_string();
-            let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
-                let short_expect = if expected.len() > 6 {
-                    format!("{} possible tokens", expected.len())
-                } else {
-                    expect.clone()
-                };
-                (format!("expected one of {}, found `{}`", expect, actual),
-                 (self.sess.source_map().next_point(self.prev_span),
-                  format!("expected one of {} here", short_expect)))
-            } else if expected.is_empty() {
-                (format!("unexpected token: `{}`", actual),
-                 (self.prev_span, "unexpected token after this".to_string()))
-            } else {
-                (format!("expected {}, found `{}`", expect, actual),
-                 (self.sess.source_map().next_point(self.prev_span),
-                  format!("expected {} here", expect)))
-            };
-            self.last_unexpected_token_span = Some(self.span);
-            let mut err = self.fatal(&msg_exp);
-            if self.token.is_ident_named("and") {
-                err.span_suggestion_short(
-                    self.span,
-                    "use `&&` instead of `and` for the boolean operator",
-                    "&&".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-            if self.token.is_ident_named("or") {
-                err.span_suggestion_short(
-                    self.span,
-                    "use `||` instead of `or` for the boolean operator",
-                    "||".to_string(),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-            let sp = if self.token == token::Token::Eof {
-                // This is EOF, don't want to point at the following char, but rather the last token
-                self.prev_span
-            } else {
-                label_sp
-            };
-            match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
-                TokenType::Token(t) => Some(t.clone()),
-                _ => None,
-            }).collect::<Vec<_>>(), err) {
-                Err(e) => err = e,
-                Ok(recovered) => {
-                    return Ok(recovered);
-                }
-            }
-
-            let cm = self.sess.source_map();
-            match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
-                (Ok(ref a), Ok(ref b)) if a.line == b.line => {
-                    // When the spans are in the same line, it means that the only content between
-                    // them is whitespace, point at the found token in that case:
-                    //
-                    // X |     () => { syntax error };
-                    //   |                    ^^^^^ expected one of 8 possible tokens here
-                    //
-                    // instead of having:
-                    //
-                    // X |     () => { syntax error };
-                    //   |                   -^^^^^ unexpected token
-                    //   |                   |
-                    //   |                   expected one of 8 possible tokens here
-                    err.span_label(self.span, label_exp);
-                }
-                _ if self.prev_span == syntax_pos::DUMMY_SP => {
-                    // Account for macro context where the previous span might not be
-                    // available to avoid incorrect output (#54841).
-                    err.span_label(self.span, "unexpected token");
-                }
-                _ => {
-                    err.span_label(sp, label_exp);
-                    err.span_label(self.span, "unexpected token");
-                }
-            }
-            Err(err)
+            self.expected_one_of_not_found(edible, inedible)
         }
     }
 
     /// 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>)> {
+    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)
@@ -890,45 +616,13 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
-        let mut err = self.struct_span_err(self.span,
-                                           &format!("expected identifier, found {}",
-                                                    self.this_token_descr()));
-        if let token::Ident(ident, false) = &self.token {
-            if ident.is_reserved() && !ident.is_path_segment_keyword() &&
-                ident.name != keywords::Underscore.name()
-            {
-                err.span_suggestion(
-                    self.span,
-                    "you can escape reserved keywords to use them as identifiers",
-                    format!("r#{}", ident),
-                    Applicability::MaybeIncorrect,
-                );
-            }
-        }
-        if let Some(token_descr) = self.token_descr() {
-            err.span_label(self.span, format!("expected identifier, found {}", token_descr));
-        } else {
-            err.span_label(self.span, "expected identifier");
-            if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
-                err.span_suggestion(
-                    self.span,
-                    "remove this comma",
-                    String::new(),
-                    Applicability::MachineApplicable,
-                );
-            }
-        }
-        err
-    }
-
     pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
         self.parse_ident_common(true)
     }
 
     fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, _) => {
+        match self.token.kind {
+            token::Ident(name, _) => {
                 if self.token.is_reserved_ident() {
                     let mut err = self.expected_ident_found();
                     if recover {
@@ -937,16 +631,16 @@ impl<'a> Parser<'a> {
                         return Err(err);
                     }
                 }
-                let span = self.span;
+                let span = self.token.span;
                 self.bump();
-                Ok(Ident::new(ident.name, span))
+                Ok(Ident::new(name, span))
             }
             _ => {
                 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
-                        self.span_fatal_err(self.prev_span, Error::UselessDocComment)
-                    } else {
-                        self.expected_ident_found()
-                    })
+                    self.span_fatal_err(self.prev_span, Error::UselessDocComment)
+                } else {
+                    self.expected_ident_found()
+                })
             }
         }
     }
@@ -955,27 +649,27 @@ impl<'a> Parser<'a> {
     ///
     /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
     /// encountered.
-    crate fn check(&mut self, tok: &token::Token) -> bool {
+    crate fn check(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.token == *tok;
         if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
         is_present
     }
 
     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
-    pub fn eat(&mut self, tok: &token::Token) -> bool {
+    pub fn eat(&mut self, tok: &TokenKind) -> bool {
         let is_present = self.check(tok);
         if is_present { self.bump() }
         is_present
     }
 
-    fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
+    fn check_keyword(&mut self, kw: Symbol) -> bool {
         self.expected_tokens.push(TokenType::Keyword(kw));
         self.token.is_keyword(kw)
     }
 
     /// If the next token is the given keyword, eats it and returns
     /// `true`. Otherwise, returns `false`.
-    pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
+    pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
         if self.check_keyword(kw) {
             self.bump();
             true
@@ -984,7 +678,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
+    fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
         if self.token.is_keyword(kw) {
             self.bump();
             true
@@ -996,7 +690,7 @@ impl<'a> Parser<'a> {
     /// If the given word is not a keyword, signals an error.
     /// If the next token is not the given word, signals an error.
     /// Otherwise, eats it.
-    fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
+    fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
         if !self.eat_keyword(kw) {
             self.unexpected()
         } else {
@@ -1004,7 +698,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn check_ident(&mut self) -> bool {
+    crate fn check_ident(&mut self) -> bool {
         if self.token.is_ident() {
             true
         } else {
@@ -1047,13 +741,13 @@ impl<'a> Parser<'a> {
     /// See issue #47856 for an example of when this may occur.
     fn eat_plus(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::Plus) => {
                 self.bump();
                 true
             }
             token::BinOpEq(token::Plus) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::Eq, span);
                 true
             }
@@ -1078,13 +772,13 @@ impl<'a> Parser<'a> {
     /// `&` and continues. If an `&` is not seen, signals an error.
     fn expect_and(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::And) => {
                 self.bump();
                 Ok(())
             }
             token::AndAnd => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Ok(self.bump_with(token::BinOp(token::And), span))
             }
             _ => self.unexpected()
@@ -1095,13 +789,13 @@ impl<'a> Parser<'a> {
     /// `|` and continues. If an `|` is not seen, signals an error.
     fn expect_or(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::Or) => {
                 self.bump();
                 Ok(())
             }
             token::OrOr => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Ok(self.bump_with(token::BinOp(token::Or), span))
             }
             _ => self.unexpected()
@@ -1109,19 +803,7 @@ impl<'a> Parser<'a> {
     }
 
     fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
-        match suffix {
-            None => {/* everything ok */}
-            Some(suf) => {
-                let text = suf.as_str();
-                if text.is_empty() {
-                    self.span_bug(sp, "found empty literal suffix in Some")
-                }
-                let msg = format!("{} with a suffix is invalid", kind);
-                self.struct_span_err(sp, &msg)
-                    .span_label(sp, msg)
-                    .emit();
-            }
-        }
+        literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
     }
 
     /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
@@ -1132,18 +814,18 @@ impl<'a> Parser<'a> {
     /// starting token.
     fn eat_lt(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Token(token::Lt));
-        let ate = match self.token {
+        let ate = match self.token.kind {
             token::Lt => {
                 self.bump();
                 true
             }
             token::BinOp(token::Shl) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::Lt, span);
                 true
             }
             token::LArrow => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 self.bump_with(token::BinOp(token::Minus), span);
                 true
             }
@@ -1172,21 +854,21 @@ impl<'a> Parser<'a> {
     /// with a single `>` and continues. If a `>` is not seen, signals an error.
     fn expect_gt(&mut self) -> PResult<'a, ()> {
         self.expected_tokens.push(TokenType::Token(token::Gt));
-        let ate = match self.token {
+        let ate = match self.token.kind {
             token::Gt => {
                 self.bump();
                 Some(())
             }
             token::BinOp(token::Shr) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Gt, span))
             }
             token::BinOpEq(token::Shr) => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Ge, span))
             }
             token::Ge => {
-                let span = self.span.with_lo(self.span.lo() + BytePos(1));
+                let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
                 Some(self.bump_with(token::Eq, span))
             }
             _ => None,
@@ -1206,30 +888,16 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
-    /// passes through any errors encountered. Used for error recovery.
-    fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
-        let handler = self.diagnostic();
-
-        if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
-                                                                  SeqSep::none(),
-                                                                  TokenExpectType::Expect,
-                                                                  |p| Ok(p.parse_token_tree())) {
-            handler.cancel(err);
-        }
-    }
-
     /// Parses a sequence, including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_end<T, F>(&mut self,
-                                  ket: &token::Token,
-                                  sep: SeqSep,
-                                  f: F)
-                                  -> PResult<'a, Vec<T>> where
-        F: FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
-    {
-        let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+    pub fn parse_seq_to_end<T>(
+        &mut self,
+        ket: &TokenKind,
+        sep: SeqSep,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a,  T>,
+    ) -> PResult<'a, Vec<T>> {
+        let (val, _, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
         if !recovered {
             self.bump();
         }
@@ -1239,39 +907,39 @@ impl<'a> Parser<'a> {
     /// Parses a sequence, not including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    pub fn parse_seq_to_before_end<T, F>(
+    pub fn parse_seq_to_before_end<T>(
         &mut self,
-        ket: &token::Token,
+        ket: &TokenKind,
         sep: SeqSep,
-        f: F,
-    ) -> PResult<'a, (Vec<T>, bool)>
-        where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
-    {
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool, bool)> {
         self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
     }
 
-    fn parse_seq_to_before_tokens<T, F>(
+    fn expect_any_with_type(&mut self, kets: &[&TokenKind], expect: TokenExpectType) -> bool {
+        kets.iter().any(|k| {
+            match expect {
+                TokenExpectType::Expect => self.check(k),
+                TokenExpectType::NoExpect => self.token == **k,
+            }
+        })
+    }
+
+    crate fn parse_seq_to_before_tokens<T>(
         &mut self,
-        kets: &[&token::Token],
+        kets: &[&TokenKind],
         sep: SeqSep,
         expect: TokenExpectType,
-        mut f: F,
-    ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
-        where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
-    {
+        mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool /* trailing */, bool /* recovered */)> {
         let mut first = true;
         let mut recovered = false;
+        let mut trailing = false;
         let mut v = vec![];
-        while !kets.iter().any(|k| {
-                match expect {
-                    TokenExpectType::Expect => self.check(k),
-                    TokenExpectType::NoExpect => self.token == **k,
-                }
-            }) {
-            match self.token {
-                token::CloseDelim(..) | token::Eof => break,
-                _ => {}
-            };
+        while !self.expect_any_with_type(kets, expect) {
+            if let token::CloseDelim(..) | token::Eof = self.token.kind {
+                break
+            }
             if let Some(ref t) = sep.sep {
                 if first {
                     first = false;
@@ -1285,7 +953,7 @@ impl<'a> Parser<'a> {
                         Err(mut e) => {
                             // Attempt to keep parsing if it was a similar separator
                             if let Some(ref tokens) = t.similar_tokens() {
-                                if tokens.contains(&self.token) {
+                                if tokens.contains(&self.token.kind) {
                                     self.bump();
                                 }
                             }
@@ -1305,12 +973,8 @@ impl<'a> Parser<'a> {
                     }
                 }
             }
-            if sep.trailing_sep_allowed && kets.iter().any(|k| {
-                match expect {
-                    TokenExpectType::Expect => self.check(k),
-                    TokenExpectType::NoExpect => self.token == **k,
-                }
-            }) {
+            if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) {
+                trailing = true;
                 break;
             }
 
@@ -1318,27 +982,45 @@ impl<'a> Parser<'a> {
             v.push(t);
         }
 
-        Ok((v, recovered))
+        Ok((v, trailing, recovered))
     }
 
     /// Parses a sequence, including the closing delimiter. The function
     /// `f` must consume tokens until reaching the next separator or
     /// closing bracket.
-    fn parse_unspanned_seq<T, F>(
+    fn parse_unspanned_seq<T>(
         &mut self,
-        bra: &token::Token,
-        ket: &token::Token,
+        bra: &TokenKind,
+        ket: &TokenKind,
         sep: SeqSep,
-        f: F,
-    ) -> PResult<'a, Vec<T>> where
-        F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
-    {
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
         self.expect(bra)?;
-        let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
+        let (result, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
         if !recovered {
             self.eat(ket);
         }
-        Ok(result)
+        Ok((result, trailing))
+    }
+
+    fn parse_delim_comma_seq<T>(
+        &mut self,
+        delim: DelimToken,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
+        self.parse_unspanned_seq(
+            &token::OpenDelim(delim),
+            &token::CloseDelim(delim),
+            SeqSep::trailing_allowed(token::Comma),
+            f,
+        )
+    }
+
+    fn parse_paren_comma_seq<T>(
+        &mut self,
+        f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
+    ) -> PResult<'a, (Vec<T>, bool)> {
+        self.parse_delim_comma_seq(token::Paren, f)
     }
 
     /// Advance the parser by one token
@@ -1348,22 +1030,21 @@ impl<'a> Parser<'a> {
             self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
         }
 
-        self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
+        self.prev_span = self.meta_var_span.take().unwrap_or(self.token.span);
 
         // Record last token kind for possible error recovery.
-        self.prev_token_kind = match self.token {
+        self.prev_token_kind = match self.token.kind {
             token::DocComment(..) => PrevTokenKind::DocComment,
             token::Comma => PrevTokenKind::Comma,
             token::BinOp(token::Plus) => PrevTokenKind::Plus,
+            token::BinOp(token::Or) => PrevTokenKind::BitOr,
             token::Interpolated(..) => PrevTokenKind::Interpolated,
             token::Eof => PrevTokenKind::Eof,
             token::Ident(..) => PrevTokenKind::Ident,
             _ => PrevTokenKind::Other,
         };
 
-        let next = self.next_tok();
-        self.span = next.sp;
-        self.token = next.tok;
+        self.token = self.next_tok();
         self.expected_tokens.clear();
         // check after each token
         self.process_potential_macro_variable();
@@ -1371,79 +1052,44 @@ impl<'a> Parser<'a> {
 
     /// Advance the parser using provided token as a next one. Use this when
     /// consuming a part of a token. For example a single `<` from `<<`.
-    fn bump_with(&mut self, next: token::Token, span: Span) {
-        self.prev_span = self.span.with_hi(span.lo());
+    fn bump_with(&mut self, next: TokenKind, span: Span) {
+        self.prev_span = self.token.span.with_hi(span.lo());
         // It would be incorrect to record the kind of the current token, but
         // fortunately for tokens currently using `bump_with`, the
         // prev_token_kind will be of no use anyway.
         self.prev_token_kind = PrevTokenKind::Other;
-        self.span = span;
-        self.token = next;
+        self.token = Token::new(next, span);
         self.expected_tokens.clear();
     }
 
     pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
-        F: FnOnce(&token::Token) -> R,
+        F: FnOnce(&Token) -> R,
     {
         if dist == 0 {
-            return f(&self.token)
+            return f(&self.token);
         }
 
-        f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
+        let frame = &self.token_cursor.frame;
+        f(&match frame.tree_cursor.look_ahead(dist - 1) {
             Some(tree) => match tree {
-                TokenTree::Token(_, tok) => tok,
-                TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
-            },
-            None => token::CloseDelim(self.token_cursor.frame.delim),
+                TokenTree::Token(token) => token,
+                TokenTree::Delimited(dspan, delim, _) =>
+                    Token::new(token::OpenDelim(delim), dspan.open),
+            }
+            None => Token::new(token::CloseDelim(frame.delim), frame.span.close)
         })
     }
 
-    fn look_ahead_span(&self, dist: usize) -> Span {
-        if dist == 0 {
-            return self.span
-        }
-
-        match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
-            Some(TokenTree::Token(span, _)) => span,
-            Some(TokenTree::Delimited(span, ..)) => span.entire(),
-            None => self.look_ahead_span(dist - 1),
-        }
-    }
-    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(self.span, m)
-    }
-    pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_fatal(sp, m)
-    }
-    fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
-        err.span_err(sp, self.diagnostic())
-    }
-    fn bug(&self, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(self.span, m)
-    }
-    fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
-        self.sess.span_diagnostic.span_err(sp, m)
-    }
-    fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
-        self.sess.span_diagnostic.struct_span_err(sp, m)
-    }
-    crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
-        self.sess.span_diagnostic.span_bug(sp, m)
-    }
-
-    fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
-        self.sess.span_diagnostic.cancel(err)
-    }
-
-    crate fn diagnostic(&self) -> &'a errors::Handler {
-        &self.sess.span_diagnostic
+    /// 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)))
     }
 
     /// Is the current token one of the keywords that signals a bare function type?
     fn token_is_bare_fn_keyword(&mut self) -> bool {
-        self.check_keyword(keywords::Fn) ||
-            self.check_keyword(keywords::Unsafe) ||
-            self.check_keyword(keywords::Extern)
+        self.check_keyword(kw::Fn) ||
+            self.check_keyword(kw::Unsafe) ||
+            self.check_keyword(kw::Extern)
     }
 
     /// Parses a `TyKind::BareFn` type.
@@ -1461,13 +1107,13 @@ impl<'a> Parser<'a> {
         */
 
         let unsafety = self.parse_unsafety();
-        let abi = if self.eat_keyword(keywords::Extern) {
+        let abi = if self.eat_keyword(kw::Extern) {
             self.parse_opt_abi()?.unwrap_or(Abi::C)
         } else {
             Abi::Rust
         };
 
-        self.expect_keyword(keywords::Fn)?;
+        self.expect_keyword(kw::Fn)?;
         let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
         let ret_ty = self.parse_ret_ty(false)?;
         let decl = P(FnDecl {
@@ -1485,7 +1131,7 @@ impl<'a> Parser<'a> {
 
     /// Parses asyncness: `async` or nothing.
     fn parse_asyncness(&mut self) -> IsAsync {
-        if self.eat_keyword(keywords::Async) {
+        if self.eat_keyword(kw::Async) {
             IsAsync::Async {
                 closure_id: ast::DUMMY_NODE_ID,
                 return_impl_trait_id: ast::DUMMY_NODE_ID,
@@ -1497,7 +1143,7 @@ impl<'a> Parser<'a> {
 
     /// Parses unsafety: `unsafe` or nothing.
     fn parse_unsafety(&mut self) -> Unsafety {
-        if self.eat_keyword(keywords::Unsafe) {
+        if self.eat_keyword(kw::Unsafe) {
             Unsafety::Unsafe
         } else {
             Unsafety::Normal
@@ -1525,12 +1171,12 @@ impl<'a> Parser<'a> {
     fn parse_trait_item_(&mut self,
                          at_end: &mut bool,
                          mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
-        let lo = self.span;
-
-        let (name, node, generics) = if self.eat_keyword(keywords::Type) {
+        let lo = self.token.span;
+        self.eat_bad_pub();
+        let (name, node, generics) = if self.eat_keyword(kw::Type) {
             self.parse_trait_item_assoc_ty()?
         } else if self.is_const_item() {
-            self.expect_keyword(keywords::Const)?;
+            self.expect_keyword(kw::Const)?;
             let ident = self.parse_ident()?;
             self.expect(&token::Colon)?;
             let ty = self.parse_ty()?;
@@ -1545,20 +1191,21 @@ impl<'a> Parser<'a> {
             (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
         } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
             // trait item macro.
-            (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
+            (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
         } else {
             let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
 
             let ident = self.parse_ident()?;
             let mut generics = self.parse_generics()?;
 
-            let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
+            let decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
                 // This is somewhat dubious; We don't want to allow
                 // argument names to be left off if there is a
                 // definition...
 
                 // We don't allow argument names to be left off in edition 2018.
-                p.parse_arg_general(p.span.rust_2018(), true, false)
+                let is_name_required = p.token.span.rust_2018();
+                p.parse_arg_general(true, false, |_| is_name_required)
             })?;
             generics.where_clause = self.parse_where_clause()?;
 
@@ -1569,10 +1216,10 @@ impl<'a> Parser<'a> {
                     abi,
                     asyncness,
                 },
-                decl: d,
+                decl,
             };
 
-            let body = match self.token {
+            let body = match self.token.kind {
                 token::Semi => {
                     self.bump();
                     *at_end = true;
@@ -1595,20 +1242,12 @@ impl<'a> Parser<'a> {
                             Some(body)
                         }
                         _ => {
-                            let token_str = self.this_token_descr();
-                            let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
-                                                              token_str));
-                            err.span_label(self.span, "expected `;` or `{`");
-                            return Err(err);
+                            return self.expected_semi_or_open_brace();
                         }
                     }
                 }
                 _ => {
-                    let token_str = self.this_token_descr();
-                    let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
-                                                      token_str));
-                    err.span_label(self.span, "expected `;` or `{`");
-                    return Err(err);
+                    return self.expected_semi_or_open_brace();
                 }
             };
             (ident, ast::TraitItemKind::Method(sig, body), generics)
@@ -1630,7 +1269,7 @@ impl<'a> Parser<'a> {
         if self.eat(&token::RArrow) {
             Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
         } else {
-            Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
+            Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
         }
     }
 
@@ -1651,9 +1290,10 @@ impl<'a> Parser<'a> {
 
     fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
                        allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
+        maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
         maybe_whole!(self, NtTy, |x| x);
 
-        let lo = self.span;
+        let lo = self.token.span;
         let mut impl_dyn_multi = false;
         let node = if self.eat(&token::OpenDelim(token::Paren)) {
             // `(TYPE)` is a parenthesized type.
@@ -1717,7 +1357,7 @@ impl<'a> Parser<'a> {
             // Reference
             self.expect_and()?;
             self.parse_borrowed_pointee()?
-        } else if self.eat_keyword_noexpect(keywords::Typeof) {
+        } 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))?;
@@ -1727,17 +1367,17 @@ impl<'a> Parser<'a> {
             };
             self.expect(&token::CloseDelim(token::Paren))?;
             TyKind::Typeof(e)
-        } else if self.eat_keyword(keywords::Underscore) {
+        } 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(keywords::For) {
+        } 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.span;
+            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)?
@@ -1746,13 +1386,13 @@ impl<'a> Parser<'a> {
                 let parse_plus = allow_plus && self.check_plus();
                 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
             }
-        } else if self.eat_keyword(keywords::Impl) {
+        } 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(keywords::Dyn) &&
-                  (self.span.rust_2018() ||
+        } 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`
@@ -1775,7 +1415,12 @@ impl<'a> Parser<'a> {
             if self.eat(&token::Not) {
                 // Macro invocation in type position
                 let (delim, tts) = self.expect_delimited_token_tree()?;
-                let node = Mac_ { path, tts, delim };
+                let node = Mac_ {
+                    path,
+                    tts,
+                    delim,
+                    prior_type_ascription: self.last_type_ascription,
+                };
                 TyKind::Mac(respan(lo.to(self.prev_span), node))
             } else {
                 // Just a type path or bound list (trait object type) starting with a trait.
@@ -1798,18 +1443,19 @@ impl<'a> Parser<'a> {
             }
         } else {
             let msg = format!("expected type, found {}", self.this_token_descr());
-            return Err(self.fatal(&msg));
+            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 = Ty { node, span, id: ast::DUMMY_NODE_ID };
+        let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
 
         // Try to recover from use of `+` with incorrect priority.
         self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
         self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
-        let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;
-
-        Ok(P(ty))
+        self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
     }
 
     fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
@@ -1823,106 +1469,17 @@ impl<'a> Parser<'a> {
         Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
     }
 
-    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();
-        }
-    }
-
-    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.node {
-            TyKind::Rptr(ref lifetime, ref mut_ty) => {
-                let sum_with_parens = pprust::to_string(|s| {
-                    use crate::print::pprust::PrintState;
-
-                    s.s.word("&")?;
-                    s.print_opt_lifetime(lifetime)?;
-                    s.print_mutability(mut_ty.mutbl)?;
-                    s.popen()?;
-                    s.print_type(&mut_ty.ty)?;
-                    s.print_type_bounds(" +", &bounds)?;
-                    s.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(())
-    }
-
-    // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
-    fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
-                                                     -> PResult<'a, T> {
-        // Do not add `::` to expected tokens.
-        if !allow_recovery || self.token != token::ModSep {
-            return Ok(base);
-        }
-        let ty = match base.to_ty() {
-            Some(ty) => ty,
-            None => return Ok(base),
-        };
-
-        self.bump(); // `::`
-        let mut segments = Vec::new();
-        self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
-
-        let span = ty.span.to(self.prev_span);
-        let path_span = span.to(span); // use an empty path since `position` == 0
-        let recovered = base.to_recovered(
-            Some(QSelf { ty, path_span, position: 0 }),
-            ast::Path { segments, span },
-        );
-
-        self.diagnostic()
-            .struct_span_err(span, "missing angle brackets in associated item path")
-            .span_suggestion( // this is a best-effort recovery
-                span, "try", recovered.to_string(), Applicability::MaybeIncorrect
-            ).emit();
-
-        Ok(recovered)
-    }
-
     fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
         let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
         let mutbl = self.parse_mutability();
         let ty = self.parse_ty_no_plus()?;
-        return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
+        return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }));
     }
 
     fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
-        let mutbl = if self.eat_keyword(keywords::Mut) {
+        let mutbl = if self.eat_keyword(kw::Mut) {
             Mutability::Mutable
-        } else if self.eat_keyword(keywords::Const) {
+        } else if self.eat_keyword(kw::Const) {
             Mutability::Immutable
         } else {
             let span = self.prev_span;
@@ -1934,17 +1491,17 @@ impl<'a> Parser<'a> {
             Mutability::Immutable
         };
         let t = self.parse_ty_no_plus()?;
-        Ok(MutTy { ty: t, mutbl: mutbl })
+        Ok(MutTy { ty: t, mutbl })
     }
 
-    fn is_named_argument(&mut self) -> bool {
-        let offset = match self.token {
+    fn is_named_argument(&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(keywords::Mut) => 1,
+            _ if self.token.is_keyword(kw::Mut) => 1,
             _ => 0,
         };
 
@@ -1954,90 +1511,48 @@ impl<'a> Parser<'a> {
 
     /// Skips unexpected attributes and doc comments in this position and emits an appropriate
     /// error.
-    fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
-        if let token::DocComment(_) = self.token {
-            let mut err = self.diagnostic().struct_span_err(
-                self.span,
-                &format!("documentation comments cannot be applied to {}", applied_to),
-            );
-            err.span_label(self.span, "doc comments are not allowed here");
-            err.emit();
-            self.bump();
-        } else if self.token == token::Pound && self.look_ahead(1, |t| {
-            *t == token::OpenDelim(token::Bracket)
-        }) {
-            let lo = self.span;
-            // Skip every token until next possible arg.
-            while self.token != token::CloseDelim(token::Bracket) {
-                self.bump();
-            }
-            let sp = lo.to(self.span);
-            self.bump();
-            let mut err = self.diagnostic().struct_span_err(
-                sp,
-                &format!("attributes cannot be applied to {}", applied_to),
-            );
-            err.span_label(sp, "attributes are not allowed here");
-            err.emit();
-        }
-    }
-
     /// This version of parse arg doesn't necessarily require identifier names.
-    fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool,
-                         allow_c_variadic: bool) -> PResult<'a, Arg> {
-        maybe_whole!(self, NtArg, |x| x);
-
-        if let Ok(Some(_)) = self.parse_self_arg() {
-            let mut err = self.struct_span_err(self.prev_span,
-                "unexpected `self` argument in function");
-            err.span_label(self.prev_span,
-                "`self` is only valid as the first argument of an associated function");
-            return Err(err);
+    fn parse_arg_general<F>(
+        &mut self,
+        is_trait_item: bool,
+        allow_c_variadic: bool,
+        is_name_required: F,
+    ) -> PResult<'a, Arg>
+    where
+        F: Fn(&token::Token) -> bool
+    {
+        let lo = self.token.span;
+        let attrs = self.parse_arg_attributes()?;
+        if let Some(mut arg) = self.parse_self_arg()? {
+            arg.attrs = attrs.into();
+            return self.recover_bad_self_arg(arg, is_trait_item);
         }
 
-        let (pat, ty) = if require_name || self.is_named_argument() {
-            debug!("parse_arg_general parse_pat (require_name:{})",
-                   require_name);
-            self.eat_incorrect_doc_comment("method arguments");
-            let pat = self.parse_pat(Some("argument name"))?;
+        let is_name_required = is_name_required(&self.token);
+        let (pat, ty) = if is_name_required || self.is_named_argument() {
+            debug!("parse_arg_general parse_pat (is_name_required:{})", is_name_required);
 
+            let pat = self.parse_pat(Some("argument name"))?;
             if let Err(mut err) = self.expect(&token::Colon) {
-                // If we find a pattern followed by an identifier, it could be an (incorrect)
-                // C-style parameter declaration.
-                if self.check_ident() && self.look_ahead(1, |t| {
-                    *t == token::Comma || *t == token::CloseDelim(token::Paren)
-                }) {
-                    let ident = self.parse_ident().unwrap();
-                    let span = pat.span.with_hi(ident.span.hi());
-
-                    err.span_suggestion(
-                        span,
-                        "declare the type after the parameter binding",
-                        String::from("<identifier>: <type>"),
-                        Applicability::HasPlaceholders,
-                    );
-                } else if require_name && is_trait_item {
-                    if let PatKind::Ident(_, ident, _) = pat.node {
-                        err.span_suggestion(
-                            pat.span,
-                            "explicitly ignore parameter",
-                            format!("_: {}", ident),
-                            Applicability::MachineApplicable,
-                        );
-                    }
-
-                    err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
+                if let Some(ident) = self.argument_without_type(
+                    &mut err,
+                    pat,
+                    is_name_required,
+                    is_trait_item,
+                ) {
+                    err.emit();
+                    return Ok(dummy_arg(ident));
+                } else {
+                    return Err(err);
                 }
-
-                return Err(err);
             }
 
-            self.eat_incorrect_doc_comment("a method argument's type");
+            self.eat_incorrect_doc_comment_for_arg_type();
             (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
         } else {
             debug!("parse_arg_general ident_to_pat");
             let parser_snapshot_before_ty = self.clone();
-            self.eat_incorrect_doc_comment("a method argument's type");
+            self.eat_incorrect_doc_comment_for_arg_type();
             let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
             if ty.is_ok() && self.token != token::Comma &&
                self.token != token::CloseDelim(token::Paren) {
@@ -2047,7 +1562,7 @@ impl<'a> Parser<'a> {
             }
             match ty {
                 Ok(ty) => {
-                    let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
+                    let ident = Ident::new(kw::Invalid, self.prev_span);
                     let pat = P(Pat {
                         id: ast::DUMMY_NODE_ID,
                         node: PatKind::Ident(
@@ -2065,44 +1580,20 @@ impl<'a> Parser<'a> {
                     // Recover from attempting to parse the argument as a type without pattern.
                     err.cancel();
                     mem::replace(self, parser_snapshot_before_ty);
-                    let pat = self.parse_pat(Some("argument name"))?;
-                    self.expect(&token::Colon)?;
-                    let ty = self.parse_ty()?;
-
-                    let mut err = self.diagnostic().struct_span_err_with_code(
-                        pat.span,
-                        "patterns aren't allowed in methods without bodies",
-                        DiagnosticId::Error("E0642".into()),
-                    );
-                    err.span_suggestion_short(
-                        pat.span,
-                        "give this argument a name or use an underscore to ignore it",
-                        "_".to_owned(),
-                        Applicability::MachineApplicable,
-                    );
-                    err.emit();
-
-                    // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
-                    let pat = P(Pat {
-                        node: PatKind::Wild,
-                        span: pat.span,
-                        id: ast::DUMMY_NODE_ID
-                    });
-                    (pat, ty)
+                    self.recover_arg_parse()?
                 }
             }
         };
 
-        Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
-    }
+        let span = lo.to(self.token.span);
 
-    /// Parses a single function argument.
-    crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
-        self.parse_arg_general(true, false, false)
+        Ok(Arg { attrs: attrs.into(), id: ast::DUMMY_NODE_ID, pat, span, ty })
     }
 
     /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
     fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
+        let lo = self.token.span;
+        let attrs = self.parse_arg_attributes()?;
         let pat = self.parse_pat(Some("argument name"))?;
         let t = if self.eat(&token::Colon) {
             self.parse_ty()?
@@ -2113,9 +1604,12 @@ impl<'a> Parser<'a> {
                 span: self.prev_span,
             })
         };
+        let span = lo.to(self.token.span);
         Ok(Arg {
+            attrs: attrs.into(),
             ty: t,
             pat,
+            span,
             id: ast::DUMMY_NODE_ID
         })
     }
@@ -2128,93 +1622,13 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Matches `token_lit = LIT_INTEGER | ...`.
-    fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
-        let out = match self.token {
-            token::Interpolated(ref nt) => match **nt {
-                token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node {
-                    ExprKind::Lit(ref lit) => { lit.node.clone() }
-                    _ => { return self.unexpected_last(&self.token); }
-                },
-                _ => { return self.unexpected_last(&self.token); }
-            },
-            token::Literal(lit, suf) => {
-                let diag = Some((self.span, &self.sess.span_diagnostic));
-                let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
-
-                if suffix_illegal {
-                    let sp = self.span;
-                    self.expect_no_suffix(sp, lit.literal_name(), suf)
-                }
-
-                result.unwrap()
-            }
-            token::Dot if self.look_ahead(1, |t| match t {
-                token::Literal(parse::token::Lit::Integer(_) , _) => true,
-                _ => false,
-            }) => { // recover from `let x = .4;`
-                let lo = self.span;
-                self.bump();
-                if let token::Literal(
-                    parse::token::Lit::Integer(val),
-                    suffix,
-                ) = self.token {
-                    let suffix = suffix.and_then(|s| {
-                        let s = s.as_str().get();
-                        if ["f32", "f64"].contains(&s) {
-                            Some(s)
-                        } else {
-                            None
-                        }
-                    }).unwrap_or("");
-                    self.bump();
-                    let sp = lo.to(self.prev_span);
-                    let mut err = self.diagnostic()
-                        .struct_span_err(sp, "float literals must have an integer part");
-                    err.span_suggestion(
-                        sp,
-                        "must have an integer part",
-                        format!("0.{}{}", val, suffix),
-                        Applicability::MachineApplicable,
-                    );
-                    err.emit();
-                    return Ok(match suffix {
-                        "f32" => ast::LitKind::Float(val, ast::FloatTy::F32),
-                        "f64" => ast::LitKind::Float(val, ast::FloatTy::F64),
-                        _ => ast::LitKind::FloatUnsuffixed(val),
-                    });
-                } else {
-                    unreachable!();
-                };
-            }
-            _ => { return self.unexpected_last(&self.token); }
-        };
-
-        self.bump();
-        Ok(out)
-    }
-
-    /// Matches `lit = true | false | token_lit`.
-    crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
-        let lo = self.span;
-        let lit = if self.eat_keyword(keywords::True) {
-            LitKind::Bool(true)
-        } else if self.eat_keyword(keywords::False) {
-            LitKind::Bool(false)
-        } else {
-            let lit = self.parse_lit_token()?;
-            lit
-        };
-        Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) })
-    }
-
     /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
     crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
         maybe_whole_expr!(self);
 
-        let minus_lo = self.span;
+        let minus_lo = self.token.span;
         let minus_present = self.eat(&token::BinOp(token::Minus));
-        let lo = self.span;
+        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());
@@ -2229,22 +1643,22 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
-                let span = self.span;
+        match self.token.kind {
+            token::Ident(name, _) if name.is_path_segment_keyword() => {
+                let span = self.token.span;
                 self.bump();
-                Ok(Ident::new(ident.name, span))
+                Ok(Ident::new(name, span))
             }
             _ => self.parse_ident(),
         }
     }
 
     fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
-        match self.token {
-            token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
-                let span = self.span;
+        match self.token.kind {
+            token::Ident(name, false) if name == kw::Underscore => {
+                let span = self.token.span;
                 self.bump();
-                Ok(Ident::new(ident.name, span))
+                Ok(Ident::new(name, span))
             }
             _ => self.parse_ident(),
         }
@@ -2269,13 +1683,13 @@ impl<'a> Parser<'a> {
         // above). `path_span` has the span of that path, or an empty
         // span in the case of something like `<T>::Bar`.
         let (mut path, path_span);
-        if self.eat_keyword(keywords::As) {
-            let path_lo = self.span;
+        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 = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
-            path_span = self.span.to(self.span);
+            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`.
@@ -2288,7 +1702,7 @@ impl<'a> Parser<'a> {
         self.expect(&token::ModSep)?;
 
         let qself = QSelf { ty, path_span, position: path.segments.len() };
-        self.parse_path_segments(&mut path.segments, style, true)?;
+        self.parse_path_segments(&mut path.segments, style)?;
 
         Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
     }
@@ -2304,11 +1718,6 @@ impl<'a> Parser<'a> {
     /// `Fn(Args)` (without disambiguator)
     /// `Fn::(Args)` (with disambiguator)
     pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
-        self.parse_path_common(style, true)
-    }
-
-    crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool)
-                             -> PResult<'a, ast::Path> {
         maybe_whole!(self, NtPath, |path| {
             if style == PathStyle::Mod &&
                path.segments.iter().any(|segment| segment.args.is_some()) {
@@ -2317,13 +1726,13 @@ impl<'a> Parser<'a> {
             path
         });
 
-        let lo = self.meta_var_span.unwrap_or(self.span);
+        let lo = self.meta_var_span.unwrap_or(self.token.span);
         let mut segments = Vec::new();
-        let mod_sep_ctxt = self.span.ctxt();
+        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, enable_warning)?;
+        self.parse_path_segments(&mut segments, style)?;
 
         Ok(ast::Path { segments, span: lo.to(self.prev_span) })
     }
@@ -2332,10 +1741,10 @@ impl<'a> Parser<'a> {
     /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
     /// attributes.
     pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
-        let meta_ident = match self.token {
+        let meta_ident = match self.token.kind {
             token::Interpolated(ref nt) => match **nt {
                 token::NtMeta(ref meta) => match meta.node {
-                    ast::MetaItemKind::Word => Some(meta.ident.clone()),
+                    ast::MetaItemKind::Word => Some(meta.path.clone()),
                     _ => None,
                 },
                 _ => None,
@@ -2349,13 +1758,12 @@ impl<'a> Parser<'a> {
         self.parse_path(style)
     }
 
-    fn parse_path_segments(&mut self,
+    crate fn parse_path_segments(&mut self,
                            segments: &mut Vec<PathSegment>,
-                           style: PathStyle,
-                           enable_warning: bool)
+                           style: PathStyle)
                            -> PResult<'a, ()> {
         loop {
-            let segment = self.parse_path_segment(style, enable_warning)?;
+            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),
@@ -2383,12 +1791,12 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool)
-                          -> PResult<'a, PathSegment> {
+    fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
         let ident = self.parse_path_segment_ident()?;
 
-        let is_args_start = |token: &token::Token| match *token {
-            token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
+        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| {
@@ -2401,13 +1809,6 @@ impl<'a> Parser<'a> {
         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)) {
-            // Generic arguments are found - `<`, `(`, `::<` or `::(`.
-            if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
-                self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
-                                 .span_label(self.prev_span, "try removing `::`").emit();
-            }
-            let lo = self.span;
-
             // 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.
@@ -2416,24 +1817,19 @@ impl<'a> Parser<'a> {
                 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, bindings) =
+                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, bindings, span }.into()
+                AngleBracketedArgs { args, constraints, span }.into()
             } else {
                 // `(T, U) -> R`
-                self.bump(); // `(`
-                let (inputs, recovered) = self.parse_seq_to_before_tokens(
-                    &[&token::CloseDelim(token::Paren)],
-                    SeqSep::trailing_allowed(token::Comma),
-                    TokenExpectType::Expect,
-                    |p| p.parse_ty())?;
-                if !recovered {
-                    self.bump(); // `)`
-                }
+                let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
                 let span = lo.to(self.prev_span);
                 let output = if self.eat(&token::RArrow) {
                     Some(self.parse_ty_common(false, false, false)?)
@@ -2458,17 +1854,17 @@ impl<'a> Parser<'a> {
     /// Parses a single lifetime `'a` or panics.
     crate fn expect_lifetime(&mut self) -> Lifetime {
         if let Some(ident) = self.token.lifetime() {
-            let span = self.span;
+            let span = self.token.span;
             self.bump();
             Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
         } else {
-            self.span_bug(self.span, "not a lifetime")
+            self.span_bug(self.token.span, "not a lifetime")
         }
     }
 
     fn eat_label(&mut self) -> Option<Label> {
         if let Some(ident) = self.token.lifetime() {
-            let span = self.span;
+            let span = self.token.span;
             self.bump();
             Some(Label { ident: Ident::new(ident.name, span) })
         } else {
@@ -2478,7 +1874,7 @@ impl<'a> Parser<'a> {
 
     /// Parses mutability (`mut` or nothing).
     fn parse_mutability(&mut self) -> Mutability {
-        if self.eat_keyword(keywords::Mut) {
+        if self.eat_keyword(kw::Mut) {
             Mutability::Mutable
         } else {
             Mutability::Immutable
@@ -2486,9 +1882,11 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_field_name(&mut self) -> PResult<'a, Ident> {
-        if let token::Literal(token::Integer(name), None) = self.token {
+        if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
+                self.token.kind {
+            self.expect_no_suffix(self.token.span, "a tuple index", suffix);
             self.bump();
-            Ok(Ident::new(name, self.prev_span))
+            Ok(Ident::new(symbol, self.prev_span))
         } else {
             self.parse_ident_common(false)
         }
@@ -2497,7 +1895,7 @@ impl<'a> Parser<'a> {
     /// Parse ident (COLON expr)?
     fn parse_field(&mut self) -> PResult<'a, Field> {
         let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
+        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| {
@@ -2509,9 +1907,9 @@ impl<'a> Parser<'a> {
             // initialize a field with an eq rather than a colon.
             if self.token == token::Eq {
                 self.diagnostic()
-                    .struct_span_err(self.span, "expected `:`, found `=`")
+                    .struct_span_err(self.token.span, "expected `:`, found `=`")
                     .span_suggestion(
-                        fieldname.span.shrink_to_hi().to(self.span),
+                        fieldname.span.shrink_to_hi().to(self.token.span),
                         "replace equals symbol with a colon",
                         ":".to_string(),
                         Applicability::MachineApplicable,
@@ -2537,59 +1935,50 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
+    crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
         P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
     }
 
-    fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
+    fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
         ExprKind::Unary(unop, expr)
     }
 
-    fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
+    fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
         ExprKind::Binary(binop, lhs, rhs)
     }
 
-    fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
+    fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
         ExprKind::Call(f, args)
     }
 
-    fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
+    fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
         ExprKind::Index(expr, idx)
     }
 
-    fn mk_range(&mut self,
+    fn mk_range(&self,
                     start: Option<P<Expr>>,
                     end: Option<P<Expr>>,
                     limits: RangeLimits)
                     -> PResult<'a, ast::ExprKind> {
         if end.is_none() && limits == RangeLimits::Closed {
-            Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
+            Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd))
         } else {
             Ok(ExprKind::Range(start, end, limits))
         }
     }
 
-    fn mk_assign_op(&mut self, binop: ast::BinOp,
+    fn mk_assign_op(&self, binop: ast::BinOp,
                         lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
         ExprKind::AssignOp(binop, lhs, rhs)
     }
 
-    pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
-        P(Expr {
-            id: ast::DUMMY_NODE_ID,
-            node: ExprKind::Mac(source_map::Spanned {node: m, span: span}),
-            span,
-            attrs,
-        })
-    }
-
     fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
-        let delim = match self.token {
+        let delim = match self.token.kind {
             token::OpenDelim(delim) => delim,
             _ => {
                 let msg = "expected open delimiter";
                 let mut err = self.fatal(msg);
-                err.span_label(self.span, msg);
+                err.span_label(self.token.span, msg);
                 return Err(err)
             }
         };
@@ -2612,6 +2001,7 @@ impl<'a> Parser<'a> {
     /// 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
@@ -2621,13 +2011,34 @@ impl<'a> Parser<'a> {
         // attributes by giving them a empty "already parsed" list.
         let mut attrs = ThinVec::new();
 
-        let lo = self.span;
-        let mut hi = self.span;
+        let lo = self.token.span;
+        let mut hi = self.token.span;
 
         let ex: ExprKind;
 
-        // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
-        match self.token {
+        macro_rules! parse_lit {
+            () => {
+                match self.parse_lit() {
+                    Ok(literal) => {
+                        hi = self.prev_span;
+                        ex = ExprKind::Lit(literal);
+                    }
+                    Err(mut err) => {
+                        self.cancel(&mut err);
+                        return Err(self.expected_expression_found());
+                    }
+                }
+            }
+        }
+
+        // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
+        match self.token.kind {
+            // This match arm is a special-case of the `_` match arm below and
+            // could be removed without changing functionality, but it's faster
+            // to have it here, especially for programs with large constants.
+            token::Literal(_) => {
+                parse_lit!()
+            }
             token::OpenDelim(token::Paren) => {
                 self.bump();
 
@@ -2639,7 +2050,13 @@ impl<'a> Parser<'a> {
                 let mut trailing_comma = false;
                 let mut recovered = false;
                 while self.token != token::CloseDelim(token::Paren) {
-                    es.push(self.parse_expr()?);
+                    es.push(match self.parse_expr() {
+                        Ok(es) => es,
+                        Err(err) => {
+                            // recover from parse error in tuple list
+                            return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
+                        }
+                    });
                     recovered = self.expect_one_of(
                         &[],
                         &[token::Comma, token::CloseDelim(token::Paren)],
@@ -2711,38 +2128,30 @@ impl<'a> Parser<'a> {
                     hi = path.span;
                     return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
                 }
-                if self.span.rust_2018() && self.check_keyword(keywords::Async)
-                {
-                    if self.is_async_block() { // check for `async {` and `async move {`
-                        return self.parse_async_block(attrs);
-                    } else {
-                        return self.parse_lambda_expr(attrs);
-                    }
-                }
-                if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
+                if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
                     return self.parse_lambda_expr(attrs);
                 }
-                if self.eat_keyword(keywords::If) {
+                if self.eat_keyword(kw::If) {
                     return self.parse_if_expr(attrs);
                 }
-                if self.eat_keyword(keywords::For) {
+                if self.eat_keyword(kw::For) {
                     let lo = self.prev_span;
                     return self.parse_for_expr(None, lo, attrs);
                 }
-                if self.eat_keyword(keywords::While) {
+                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(keywords::While) {
+                    if self.eat_keyword(kw::While) {
                         return self.parse_while_expr(Some(label), lo, attrs)
                     }
-                    if self.eat_keyword(keywords::For) {
+                    if self.eat_keyword(kw::For) {
                         return self.parse_for_expr(Some(label), lo, attrs)
                     }
-                    if self.eat_keyword(keywords::Loop) {
+                    if self.eat_keyword(kw::Loop) {
                         return self.parse_loop_expr(Some(label), lo, attrs)
                     }
                     if self.token == token::OpenDelim(token::Brace) {
@@ -2753,27 +2162,27 @@ impl<'a> Parser<'a> {
                     }
                     let msg = "expected `while`, `for`, `loop` or `{` after a label";
                     let mut err = self.fatal(msg);
-                    err.span_label(self.span, msg);
+                    err.span_label(self.token.span, msg);
                     return Err(err);
                 }
-                if self.eat_keyword(keywords::Loop) {
+                if self.eat_keyword(kw::Loop) {
                     let lo = self.prev_span;
                     return self.parse_loop_expr(None, lo, attrs);
                 }
-                if self.eat_keyword(keywords::Continue) {
+                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(keywords::Match) {
+                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(keywords::Unsafe) {
+                if self.eat_keyword(kw::Unsafe) {
                     return self.parse_block_expr(
                         None,
                         lo,
@@ -2786,11 +2195,21 @@ impl<'a> Parser<'a> {
                     return Err(db);
                 }
                 if self.is_try_block() {
-                    let lo = self.span;
-                    assert!(self.eat_keyword(keywords::Try));
+                    let lo = self.token.span;
+                    assert!(self.eat_keyword(kw::Try));
                     return self.parse_try_block(lo, attrs);
                 }
-                if self.eat_keyword(keywords::Return) {
+
+                // Span::rust_2018() is somewhat expensive; don't get it repeatedly.
+                let is_span_rust_2018 = self.token.span.rust_2018();
+                if is_span_rust_2018 && self.check_keyword(kw::Async) {
+                    return if self.is_async_block() { // check for `async {` and `async move {`
+                        self.parse_async_block(attrs)
+                    } else {
+                        self.parse_lambda_expr(attrs)
+                    };
+                }
+                if self.eat_keyword(kw::Return) {
                     if self.token.can_begin_expr() {
                         let e = self.parse_expr()?;
                         hi = e.span;
@@ -2798,7 +2217,7 @@ impl<'a> Parser<'a> {
                     } else {
                         ex = ExprKind::Ret(None);
                     }
-                } else if self.eat_keyword(keywords::Break) {
+                } 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)
@@ -2810,7 +2229,7 @@ impl<'a> Parser<'a> {
                     };
                     ex = ExprKind::Break(label, e);
                     hi = self.prev_span;
-                } else if self.eat_keyword(keywords::Yield) {
+                } else if self.eat_keyword(kw::Yield) {
                     if self.token.can_begin_expr() {
                         let e = self.parse_expr()?;
                         hi = e.span;
@@ -2818,37 +2237,37 @@ impl<'a> Parser<'a> {
                     } else {
                         ex = ExprKind::Yield(None);
                     }
-                } else if self.token.is_keyword(keywords::Let) {
-                    // Catch this syntax error here, instead of in `parse_ident`, so
-                    // that we can explicitly mention that let is not to be used as an expression
-                    let mut db = self.fatal("expected expression, found statement (`let`)");
-                    db.span_label(self.span, "expected expression");
-                    db.note("variable declaration using `let` is a statement");
-                    return Err(db);
+                } else if self.eat_keyword(kw::Let) {
+                    return self.parse_let_expr(attrs);
+                } else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
+                    let (await_hi, e_kind) = self.parse_incorrect_await_syntax(lo, self.prev_span)?;
+                    hi = await_hi;
+                    ex = e_kind;
                 } else if self.token.is_path_start() {
-                    let pth = self.parse_path(PathStyle::Expr)?;
+                    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()?;
-                        let hi = self.prev_span;
-                        let node = Mac_ { path: pth, tts, delim };
-                        return Ok(self.mk_mac_expr(lo.to(hi), node, attrs))
-                    }
-                    if self.check(&token::OpenDelim(token::Brace)) {
-                        // This is a struct literal, unless we're prohibited
-                        // from parsing struct literals here.
-                        let prohibited = self.restrictions.contains(
-                            Restrictions::NO_STRUCT_LITERAL
-                        );
-                        if !prohibited {
-                            return self.parse_struct_expr(lo, pth, attrs);
+                        hi = self.prev_span;
+                        ex = ExprKind::Mac(respan(lo.to(hi), Mac_ {
+                            path,
+                            tts,
+                            delim,
+                            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);
                     }
-
-                    hi = pth.span;
-                    ex = ExprKind::Path(None, pth);
                 } else {
                     if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
                         // Don't complain about bare semicolons after unclosed braces
@@ -2863,30 +2282,56 @@ impl<'a> Parser<'a> {
                         //   |             ^ expected expression
                         // ```
                         self.bump();
-                        return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
-                    }
-                    match self.parse_literal_maybe_minus() {
-                        Ok(expr) => {
-                            hi = expr.span;
-                            ex = expr.node.clone();
-                        }
-                        Err(mut err) => {
-                            self.cancel(&mut err);
-                            let msg = format!("expected expression, found {}",
-                                              self.this_token_descr());
-                            let mut err = self.fatal(&msg);
-                            err.span_label(self.span, "expected expression");
-                            return Err(err);
-                        }
+                        return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
                     }
+                    parse_lit!()
                 }
             }
         }
 
-        let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
-        let expr = self.maybe_recover_from_bad_qpath(expr, true)?;
+        let expr = self.mk_expr(lo.to(hi), ex, attrs);
+        self.maybe_recover_from_bad_qpath(expr, true)
+    }
 
-        return Ok(P(expr));
+    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
     }
 
     fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
@@ -2911,33 +2356,31 @@ impl<'a> Parser<'a> {
                     }
                 }
                 if self.token == token::Comma {
-                    let mut err = self.sess.span_diagnostic.mut_span_err(
+                    self.struct_span_err(
                         exp_span.to(self.prev_span),
                         "cannot use a comma after the base struct",
-                    );
-                    err.span_suggestion_short(
-                        self.span,
+                    )
+                    .span_suggestion_short(
+                        self.token.span,
                         "remove this comma",
                         String::new(),
                         Applicability::MachineApplicable
-                    );
-                    err.note("the base struct must always be the last field");
-                    err.emit();
+                    )
+                    .note("the base struct must always be the last field")
+                    .emit();
                     self.recover_stmt();
                 }
                 break;
             }
 
             let mut recovery_field = None;
-            if let token::Ident(ident, _) = self.token {
+            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 }`
-                    let mut ident = ident.clone();
-                    ident.span = self.span;
                     recovery_field = Some(ast::Field {
-                        ident,
-                        span: self.span,
-                        expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
+                        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(),
                     });
@@ -2980,7 +2423,7 @@ impl<'a> Parser<'a> {
             }
         }
 
-        let span = lo.to(self.span);
+        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));
     }
@@ -2996,10 +2439,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a block or unsafe block.
-    fn parse_block_expr(&mut self, opt_label: Option<Label>,
-                            lo: Span, blk_mode: BlockCheckMode,
-                            outer_attrs: ThinVec<Attribute>)
-                            -> PResult<'a, P<Expr>> {
+    crate fn parse_block_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        lo: Span,
+        blk_mode: BlockCheckMode,
+        outer_attrs: ThinVec<Attribute>,
+    ) -> PResult<'a, P<Expr>> {
         self.expect(&token::OpenDelim(token::Brace))?;
 
         let mut attrs = outer_attrs;
@@ -3034,15 +2480,13 @@ impl<'a> Parser<'a> {
                 attrs.extend::<Vec<_>>(expr.attrs.into());
                 expr.attrs = attrs;
                 match expr.node {
-                    ExprKind::If(..) | ExprKind::IfLet(..) => {
-                        if !expr.attrs.is_empty() {
-                            // Just point to the first attribute in there...
-                            let span = expr.attrs[0].span;
-
-                            self.span_err(span,
-                                "attributes are not yet allowed on `if` \
-                                expressions");
-                        }
+                    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");
                     }
                     _ => {}
                 }
@@ -3051,20 +2495,26 @@ impl<'a> Parser<'a> {
         )
     }
 
-    // Assuming we have just parsed `.`, continue parsing into an expression.
+    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)
+    }
+
+    /// 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>> {
-        let segment = self.parse_path_segment(PathStyle::Expr, true)?;
+        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 {
+        Ok(match self.token.kind {
             token::OpenDelim(token::Paren) => {
                 // Method call `expr.f()`
-                let mut args = self.parse_unspanned_seq(
-                    &token::OpenDelim(token::Paren),
-                    &token::CloseDelim(token::Paren),
-                    SeqSep::trailing_allowed(token::Comma),
-                    |p| Ok(p.parse_expr()?)
-                )?;
+                let mut args = self.parse_paren_expr_seq()?;
                 args.insert(0, self_arg);
 
                 let span = lo.to(self.prev_span);
@@ -3083,116 +2533,6 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// This function checks if there are trailing angle brackets and produces
-    /// a diagnostic to suggest removing them.
-    ///
-    /// ```ignore (diagnostic)
-    /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
-    ///                                                        ^^ help: remove extra angle brackets
-    /// ```
-    fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
-        // This function is intended to be invoked after parsing a path segment where there are two
-        // cases:
-        //
-        // 1. A specific token is expected after the path segment.
-        //    eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
-        //        `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
-        // 2. No specific token is expected after the path segment.
-        //    eg. `x.foo` (field access)
-        //
-        // This function is called after parsing `.foo` and before parsing the token `end` (if
-        // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
-        // `Foo::<Bar>`.
-
-        // We only care about trailing angle brackets if we previously parsed angle bracket
-        // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
-        // removed in this case:
-        //
-        // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
-        //
-        // This case is particularly tricky as we won't notice it just looking at the tokens -
-        // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
-        // have already been parsed):
-        //
-        // `x.foo::<u32>>>(3)`
-        let parsed_angle_bracket_args = segment.args
-            .as_ref()
-            .map(|args| args.is_angle_bracketed())
-            .unwrap_or(false);
-
-        debug!(
-            "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
-            parsed_angle_bracket_args,
-        );
-        if !parsed_angle_bracket_args {
-            return;
-        }
-
-        // Keep the span at the start so we can highlight the sequence of `>` characters to be
-        // removed.
-        let lo = self.span;
-
-        // We need to look-ahead to see if we have `>` characters without moving the cursor forward
-        // (since we might have the field access case and the characters we're eating are
-        // actual operators and not trailing characters - ie `x.foo >> 3`).
-        let mut position = 0;
-
-        // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
-        // many of each (so we can correctly pluralize our error messages) and continue to
-        // advance.
-        let mut number_of_shr = 0;
-        let mut number_of_gt = 0;
-        while self.look_ahead(position, |t| {
-            trace!("check_trailing_angle_brackets: t={:?}", t);
-            if *t == token::BinOp(token::BinOpToken::Shr) {
-                number_of_shr += 1;
-                true
-            } else if *t == token::Gt {
-                number_of_gt += 1;
-                true
-            } else {
-                false
-            }
-        }) {
-            position += 1;
-        }
-
-        // If we didn't find any trailing `>` characters, then we have nothing to error about.
-        debug!(
-            "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
-            number_of_gt, number_of_shr,
-        );
-        if number_of_gt < 1 && number_of_shr < 1 {
-            return;
-        }
-
-        // Finally, double check that we have our end token as otherwise this is the
-        // second case.
-        if self.look_ahead(position, |t| {
-            trace!("check_trailing_angle_brackets: t={:?}", t);
-            *t == end
-        }) {
-            // Eat from where we started until the end token so that parsing can continue
-            // as if we didn't have those extra angle brackets.
-            self.eat_to_tokens(&[&end]);
-            let span = lo.until(self.span);
-
-            let plural = number_of_gt > 1 || number_of_shr >= 1;
-            self.diagnostic()
-                .struct_span_err(
-                    span,
-                    &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
-                )
-                .span_suggestion(
-                    span,
-                    &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
-                    String::new(),
-                    Applicability::MachineApplicable,
-                )
-                .emit();
-        }
-    }
-
     fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
         let mut e = e0;
         let mut hi;
@@ -3205,125 +2545,128 @@ impl<'a> Parser<'a> {
 
             // expr.f
             if self.eat(&token::Dot) {
-                match self.token {
-                  token::Ident(..) => {
-                    e = self.parse_dot_suffix(e, lo)?;
-                  }
-                  token::Literal(token::Integer(name), _) => {
-                    let span = self.span;
-                    self.bump();
-                    let field = ExprKind::Field(e, Ident::new(name, span));
-                    e = self.mk_expr(lo.to(span), field, ThinVec::new());
-                  }
-                  token::Literal(token::Float(n), _suf) => {
-                    self.bump();
-                    let fstr = n.as_str();
-                    let mut err = self.diagnostic()
-                        .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
-                    err.span_label(self.prev_span, "unexpected token");
-                    if fstr.chars().all(|x| "0123456789.".contains(x)) {
-                        let float = match fstr.parse::<f64>().ok() {
-                            Some(f) => f,
-                            None => continue,
-                        };
-                        let sugg = pprust::to_string(|s| {
-                            use crate::print::pprust::PrintState;
-                            s.popen()?;
-                            s.print_expr(&e)?;
-                            s.s.word( ".")?;
-                            s.print_usize(float.trunc() as usize)?;
-                            s.pclose()?;
-                            s.s.word(".")?;
-                            s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
-                        });
-                        err.span_suggestion(
-                            lo.to(self.prev_span),
-                            "try parenthesizing the first index",
-                            sugg,
-                            Applicability::MachineApplicable
-                        );
+                match self.token.kind {
+                    token::Ident(..) => {
+                        e = self.parse_dot_suffix(e, lo)?;
                     }
-                    return Err(err);
+                    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.span, &format!("unexpected token: `{}`", actual));
-                  }
+                    }
+                    _ => {
+                        // 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 {
-              // expr(...)
-              token::OpenDelim(token::Paren) => {
-                let es = self.parse_unspanned_seq(
-                    &token::OpenDelim(token::Paren),
-                    &token::CloseDelim(token::Paren),
-                    SeqSep::trailing_allowed(token::Comma),
-                    |p| Ok(p.parse_expr()?)
-                )?;
-                hi = self.prev_span;
-
-                let nd = self.mk_call(e, es);
-                e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
-              }
+            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.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)
+                // 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);
     }
 
+    fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
+        self.parse_paren_comma_seq(|p| p.parse_expr()).map(|(r, _)| r)
+    }
+
     crate fn process_potential_macro_variable(&mut self) {
-        let (token, span) = match self.token {
-            token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
+        self.token = match self.token.kind {
+            token::Dollar if self.token.span.ctxt() != SyntaxContext::empty() &&
                              self.look_ahead(1, |t| t.is_ident()) => {
                 self.bump();
-                let name = match self.token {
-                    token::Ident(ident, _) => ident,
+                let name = match self.token.kind {
+                    token::Ident(name, _) => name,
                     _ => unreachable!()
                 };
-                let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
-                err.span_label(self.span, "unknown macro variable");
-                err.emit();
+                let span = self.prev_span.to(self.token.span);
+                self.diagnostic()
+                    .struct_span_fatal(span, &format!("unknown macro variable `{}`", name))
+                    .span_label(span, "unknown macro variable")
+                    .emit();
                 self.bump();
                 return
             }
             token::Interpolated(ref nt) => {
-                self.meta_var_span = Some(self.span);
+                self.meta_var_span = Some(self.token.span);
                 // Interpolated identifier and lifetime tokens are replaced with usual identifier
                 // and lifetime tokens, so the former are never encountered during normal parsing.
                 match **nt {
-                    token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
-                    token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
+                    token::NtIdent(ident, is_raw) =>
+                        Token::new(token::Ident(ident.name, is_raw), ident.span),
+                    token::NtLifetime(ident) =>
+                        Token::new(token::Lifetime(ident.name), ident.span),
                     _ => return,
                 }
             }
             _ => return,
         };
-        self.token = token;
-        self.span = span;
     }
 
     /// Parses a single token tree from the input.
     crate fn parse_token_tree(&mut self) -> TokenTree {
-        match self.token {
+        match self.token.kind {
             token::OpenDelim(..) => {
                 let frame = mem::replace(&mut self.token_cursor.frame,
                                          self.token_cursor.stack.pop().unwrap());
-                self.span = frame.span.entire();
+                self.token.span = frame.span.entire();
                 self.bump();
                 TokenTree::Delimited(
                     frame.span,
@@ -3333,15 +2676,14 @@ impl<'a> Parser<'a> {
             },
             token::CloseDelim(_) | token::Eof => unreachable!(),
             _ => {
-                let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
+                let token = self.token.take();
                 self.bump();
-                TokenTree::Token(span, token)
+                TokenTree::Token(token)
             }
         }
     }
 
-    // parse a stream of tokens into a list of TokenTree's,
-    // up to EOF.
+    /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
     pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
         let mut tts = Vec::new();
         while self.token != token::Eof {
@@ -3353,7 +2695,7 @@ impl<'a> Parser<'a> {
     pub fn parse_tokens(&mut self) -> TokenStream {
         let mut result = Vec::new();
         loop {
-            match self.token {
+            match self.token.kind {
                 token::Eof | token::CloseDelim(..) => break,
                 _ => result.push(self.parse_token_tree().into()),
             }
@@ -3366,9 +2708,9 @@ impl<'a> Parser<'a> {
                              already_parsed_attrs: Option<ThinVec<Attribute>>)
                              -> PResult<'a, P<Expr>> {
         let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
-        let lo = self.span;
-        // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
-        let (hi, ex) = match self.token {
+        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);
@@ -3381,15 +2723,14 @@ impl<'a> Parser<'a> {
                 let e = self.parse_prefix_expr(None);
                 let (span, e) = self.interpolated_or_expr_span(e)?;
                 let span_of_tilde = lo;
-                let mut err = self.diagnostic()
-                    .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
-                err.span_suggestion_short(
-                    span_of_tilde,
-                    "use `!` to perform bitwise negation",
-                    "!".to_owned(),
-                    Applicability::MachineApplicable
-                );
-                err.emit();
+                self.struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator")
+                    .span_suggestion_short(
+                        span_of_tilde,
+                        "use `!` to perform bitwise negation",
+                        "!".to_owned(),
+                        Applicability::MachineApplicable
+                    )
+                    .emit();
                 (lo.to(span), self.mk_unary(UnOp::Not, e))
             }
             token::BinOp(token::Minus) => {
@@ -3411,58 +2752,41 @@ impl<'a> Parser<'a> {
                 let (span, e) = self.interpolated_or_expr_span(e)?;
                 (lo.to(span), ExprKind::AddrOf(m, e))
             }
-            token::Ident(..) if self.token.is_keyword(keywords::In) => {
-                self.bump();
-                let place = self.parse_expr_res(
-                    Restrictions::NO_STRUCT_LITERAL,
-                    None,
-                )?;
-                let blk = self.parse_block()?;
-                let span = blk.span;
-                let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
-                (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
-            }
-            token::Ident(..) if self.token.is_keyword(keywords::Box) => {
+            token::Ident(..) if self.token.is_keyword(kw::Box) => {
                 self.bump();
                 let e = self.parse_prefix_expr(None);
                 let (span, e) = self.interpolated_or_expr_span(e)?;
                 (lo.to(span), ExprKind::Box(e))
             }
-            token::Ident(..) if self.token.is_ident_named("not") => {
+            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::Token| match *t {
+                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(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
+                    token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
                     token::Literal(..) | token::Pound => true,
-                    token::Interpolated(ref nt) => match **nt {
-                        token::NtIdent(..) | token::NtExpr(..) |
-                        token::NtBlock(..) | token::NtPath(..) => true,
-                        _ => false,
-                    },
-                    _ => false
+                    _ => 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 ...
-                    let mut err = self.diagnostic()
-                        .struct_span_err(self.span,
-                                         &format!("unexpected {} after identifier",
-                                                  self.this_token_descr()));
-                    // span the `not` plus trailing whitespace to avoid
-                    // trailing whitespace after the `!` in our suggestion
-                    let to_replace = self.sess.source_map()
-                        .span_until_non_whitespace(lo.to(self.span));
-                    err.span_suggestion_short(
-                        to_replace,
+                    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
-                    );
-                    err.emit();
+                    )
+                    .emit();
                     // —and recover! (just as if we were in the block
                     // for the `token::Not` arm)
                     let e = self.parse_prefix_expr(None);
@@ -3489,10 +2813,11 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses an associative expression with operators of at least `min_prec` precedence.
-    fn parse_assoc_expr_with(&mut self,
-                                 min_prec: usize,
-                                 lhs: LhsExpr)
-                                 -> PResult<'a, P<Expr>> {
+    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 {
@@ -3500,16 +2825,57 @@ impl<'a> Parser<'a> {
                 LhsExpr::AttributesParsed(attrs) => Some(attrs),
                 _ => None,
             };
-            if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
+            if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
                 return self.parse_prefix_range_expr(attrs);
             } else {
                 self.parse_prefix_expr(attrs)?
             }
         };
-
-        if self.expr_is_complete(&lhs) {
-            // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
-            return Ok(lhs);
+        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) {
@@ -3525,18 +2891,19 @@ impl<'a> Parser<'a> {
                 _ => lhs.span,
             };
 
-            let cur_op_span = self.span;
+            let cur_op_span = self.token.span;
             let restrictions = if op.is_assign_like() {
                 self.restrictions & Restrictions::NO_STRUCT_LITERAL
             } else {
                 self.restrictions
             };
-            if op.precedence() < min_prec {
+            let prec = op.precedence();
+            if prec < min_prec {
                 break;
             }
             // Check for deprecated `...` syntax
             if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
-                self.err_dotdotdot_syntax(self.span);
+                self.err_dotdotdot_syntax(self.token.span);
             }
 
             self.bump();
@@ -3548,25 +2915,10 @@ impl<'a> Parser<'a> {
                 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
                 continue
             } else if op == AssocOp::Colon {
-                lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
-                    Ok(lhs) => lhs,
-                    Err(mut err) => {
-                        err.span_label(self.span,
-                                       "expecting a type here because of type ascription");
-                        let cm = self.sess.source_map();
-                        let cur_pos = cm.lookup_char_pos(self.span.lo());
-                        let op_pos = cm.lookup_char_pos(cur_op_span.hi());
-                        if cur_pos.line != op_pos.line {
-                            err.span_suggestion(
-                                cur_op_span,
-                                "try using a semicolon",
-                                ";".to_string(),
-                                Applicability::MaybeIncorrect // speculative
-                            );
-                        }
-                        return Err(err);
-                    }
-                };
+                let maybe_path = self.could_ascription_be_path(&lhs.node);
+                self.last_type_ascription = Some((self.prev_span, maybe_path));
+
+                lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type)?;
                 continue
             } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
                 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
@@ -3575,8 +2927,7 @@ impl<'a> Parser<'a> {
                 // 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(op.precedence() + 1,
-                                                    LhsExpr::NotYetParsed)?)
+                    Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
                 } else {
                     None
                 };
@@ -3596,28 +2947,18 @@ impl<'a> Parser<'a> {
                 break
             }
 
-            let rhs = match op.fixity() {
-                Fixity::Right => self.with_res(
-                    restrictions - Restrictions::STMT_EXPR,
-                    |this| {
-                        this.parse_assoc_expr_with(op.precedence(),
-                            LhsExpr::NotYetParsed)
-                }),
-                Fixity::Left => self.with_res(
-                    restrictions - Restrictions::STMT_EXPR,
-                    |this| {
-                        this.parse_assoc_expr_with(op.precedence() + 1,
-                            LhsExpr::NotYetParsed)
-                }),
+            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 => self.with_res(
-                    restrictions - Restrictions::STMT_EXPR,
-                    |this| {
-                        this.parse_assoc_expr_with(op.precedence() + 1,
-                            LhsExpr::NotYetParsed)
-                }),
-            }?;
+                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.
@@ -3638,10 +2979,7 @@ impl<'a> Parser<'a> {
                     let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
                     self.mk_expr(span, binary, ThinVec::new())
                 }
-                AssocOp::Assign =>
-                    self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
-                AssocOp::ObsoleteInPlace =>
-                    self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
+                AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
                 AssocOp::AssignOp(k) => {
                     let aop = match k {
                         token::Plus =>    BinOpKind::Add,
@@ -3663,7 +3001,10 @@ impl<'a> Parser<'a> {
                 }
             };
 
-            if op.fixity() == Fixity::None { break }
+            if let Fixity::None = fixity { break }
+        }
+        if last_type_ascription_set {
+            self.last_type_ascription = None;
         }
         Ok(lhs)
     }
@@ -3691,7 +3032,7 @@ impl<'a> Parser<'a> {
 
                 match self.parse_path(PathStyle::Expr) {
                     Ok(path) => {
-                        let (op_noun, op_verb) = match self.token {
+                        let (op_noun, op_verb) = match self.token.kind {
                             token::Lt => ("comparison", "comparing"),
                             token::BinOp(token::Shl) => ("shift", "shifting"),
                             _ => {
@@ -3711,26 +3052,29 @@ impl<'a> Parser<'a> {
                         // in AST and continue parsing.
                         let msg = format!("`<` is interpreted as a start of generic \
                                            arguments for `{}`, not a {}", path, op_noun);
-                        let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
-                        err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
-                                       "interpreted as generic arguments");
-                        err.span_label(self.span, format!("not interpreted as {}", op_noun));
-
+                        let span_after_type = parser_snapshot_after_type.token.span;
                         let expr = mk_expr(self, P(Ty {
                             span: path.span,
                             node: TyKind::Path(None, path),
                             id: ast::DUMMY_NODE_ID
                         }));
 
-                        let expr_str = self.sess.source_map().span_to_snippet(expr.span)
-                                                .unwrap_or_else(|_| pprust::expr_to_string(&expr));
-                        err.span_suggestion(
-                            expr.span,
-                            &format!("try {} the cast value", op_verb),
-                            format!("({})", expr_str),
-                            Applicability::MachineApplicable
-                        );
-                        err.emit();
+                        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)
                     }
@@ -3745,49 +3089,22 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Produce an error if comparison operators are chained (RFC #558).
-    /// We only need to check lhs, not rhs, because all comparison ops
-    /// have same precedence and are left-associative
-    fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
-        debug_assert!(outer_op.is_comparison(),
-                      "check_no_chained_comparison: {:?} is not comparison",
-                      outer_op);
-        match lhs.node {
-            ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
-                // respan to include both operators
-                let op_span = op.span.to(self.span);
-                let mut err = self.diagnostic().struct_span_err(op_span,
-                    "chained comparison operators require parentheses");
-                if op.node == BinOpKind::Lt &&
-                    *outer_op == AssocOp::Less ||  // Include `<` to provide this recommendation
-                    *outer_op == AssocOp::Greater  // even in a case like the following:
-                {                                  //     Foo<Bar<Baz<Qux, ()>>>
-                    err.help(
-                        "use `::<...>` instead of `<...>` if you meant to specify type arguments");
-                    err.help("or use `(...)` if you meant to specify fn arguments");
-                }
-                err.emit();
-            }
-            _ => {}
-        }
-    }
-
     /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
     fn parse_prefix_range_expr(&mut self,
                                already_parsed_attrs: Option<ThinVec<Attribute>>)
                                -> PResult<'a, P<Expr>> {
         // Check for deprecated `...` syntax
         if self.token == token::DotDotDot {
-            self.err_dotdotdot_syntax(self.span);
+            self.err_dotdotdot_syntax(self.token.span);
         }
 
-        debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
+        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.span;
-        let mut hi = self.span;
+        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.
@@ -3798,7 +3115,7 @@ impl<'a> Parser<'a> {
                     hi = x.span;
                     x
                 })?)
-         } else {
+        } else {
             None
         };
         let limits = if tok == token::DotDot {
@@ -3823,19 +3140,16 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses an `if` or `if let` expression (`if` token already eaten).
+    /// Parses an `if` expression (`if` token already eaten).
     fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        if self.check_keyword(keywords::Let) {
-            return self.parse_if_let_expr(attrs);
-        }
         let lo = self.prev_span;
-        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        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(keywords::Else) || !cond.returns() {
+        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` statemement");
@@ -3851,7 +3165,7 @@ impl<'a> Parser<'a> {
         })?;
         let mut els: Option<P<Expr>> = None;
         let mut hi = thn.span;
-        if self.eat_keyword(keywords::Else) {
+        if self.eat_keyword(kw::Else) {
             let elexpr = self.parse_else_expr()?;
             hi = elexpr.span;
             els = Some(elexpr);
@@ -3859,22 +3173,32 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
     }
 
-    /// Parses an `if let` expression (`if` token already eaten).
-    fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
-                             -> PResult<'a, P<Expr>> {
+    /// Parse the condition of a `if`- or `while`-expression
+    fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
+        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+
+        if let ExprKind::Let(..) = cond.node {
+            // Remove the last feature gating of a `let` expression since it's stable.
+            let last = self.sess.let_chains_spans.borrow_mut().pop();
+            debug_assert_eq!(cond.span, last.unwrap());
+        }
+
+        Ok(cond)
+    }
+
+    /// Parses a `let $pats = $expr` pseudo-expression.
+    /// The `let` token has already been eaten.
+    fn parse_let_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
         let lo = self.prev_span;
-        self.expect_keyword(keywords::Let)?;
         let pats = self.parse_pats()?;
         self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let thn = self.parse_block()?;
-        let (hi, els) = if self.eat_keyword(keywords::Else) {
-            let expr = self.parse_else_expr()?;
-            (expr.span, Some(expr))
-        } else {
-            (thn.span, None)
-        };
-        Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
+        let expr = self.with_res(
+            Restrictions::NO_STRUCT_LITERAL,
+            |this| this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
+        )?;
+        let span = lo.to(expr.span);
+        self.sess.let_chains_spans.borrow_mut().push(span);
+        Ok(self.mk_expr(span, ExprKind::Let(pats, expr), attrs))
     }
 
     /// Parses `move |args| expr`.
@@ -3882,22 +3206,25 @@ impl<'a> Parser<'a> {
                              attrs: ThinVec<Attribute>)
                              -> PResult<'a, P<Expr>>
     {
-        let lo = self.span;
-        let movability = if self.eat_keyword(keywords::Static) {
+        let lo = self.token.span;
+
+        let movability = if self.eat_keyword(kw::Static) {
             Movability::Static
         } else {
             Movability::Movable
         };
-        let asyncness = if self.span.rust_2018() {
+
+        let asyncness = if self.token.span.rust_2018() {
             self.parse_asyncness()
         } else {
             IsAsync::NotAsync
         };
-        let capture_clause = if self.eat_keyword(keywords::Move) {
-            CaptureBy::Value
-        } else {
-            CaptureBy::Ref
-        };
+        if asyncness.is_async() {
+            // Feature gate `async ||` closures.
+            self.sess.async_closure_spans.borrow_mut().push(self.prev_span);
+        }
+
+        let capture_clause = self.parse_capture_clause();
         let decl = self.parse_fn_block_decl()?;
         let decl_hi = self.prev_span;
         let body = match decl.output {
@@ -3908,7 +3235,7 @@ impl<'a> Parser<'a> {
             _ => {
                 // If an explicit return type is given, require a
                 // block to appear (RFC 968).
-                let body_lo = self.span;
+                let body_lo = self.token.span;
                 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
             }
         };
@@ -3919,9 +3246,9 @@ impl<'a> Parser<'a> {
             attrs))
     }
 
-    // `else` token already eaten
+    /// `else` token already eaten
     fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
-        if self.eat_keyword(keywords::If) {
+        if self.eat_keyword(kw::If) {
             return self.parse_if_expr(ThinVec::new());
         } else {
             let blk = self.parse_block()?;
@@ -3930,42 +3257,40 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse a 'for' .. 'in' expression ('for' token already eaten)
-    fn parse_for_expr(&mut self, opt_label: Option<Label>,
-                          span_lo: Span,
-                          mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+    fn parse_for_expr(
+        &mut self,
+        opt_label: Option<Label>,
+        span_lo: Span,
+        mut attrs: ThinVec<Attribute>
+    ) -> PResult<'a, P<Expr>> {
         // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
 
+        // Record whether we are about to parse `for (`.
+        // This is used below for recovery in case of `for ( $stuff ) $block`
+        // in which case we will suggest `for $stuff $block`.
+        let begin_paren = match self.token.kind {
+            token::OpenDelim(token::Paren) => Some(self.token.span),
+            _ => None,
+        };
+
         let pat = self.parse_top_level_pat()?;
-        if !self.eat_keyword(keywords::In) {
-            let in_span = self.prev_span.between(self.span);
-            let mut err = self.sess.span_diagnostic
-                .struct_span_err(in_span, "missing `in` in `for` loop");
-            err.span_suggestion_short(
-                in_span, "try adding `in` here", " in ".into(),
-                // has been misleading, at least in the past (closed Issue #48492)
-                Applicability::MaybeIncorrect
-            );
-            err.emit();
+        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;
-        if self.eat_keyword(keywords::In) {
-            // a common typo: `for _ in in bar {}`
-            let mut err = self.sess.span_diagnostic.struct_span_err(
-                self.prev_span,
-                "expected iterable, found keyword `in`",
-            );
-            err.span_suggestion_short(
-                in_span.until(self.prev_span),
-                "remove the duplicated `in`",
-                String::new(),
-                Applicability::MachineApplicable,
-            );
-            err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
-            err.note("for more information on the status of emplacement syntax, see <\
-                      https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
-            err.emit();
-        }
+        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);
 
@@ -3977,31 +3302,14 @@ impl<'a> Parser<'a> {
     fn parse_while_expr(&mut self, opt_label: Option<Label>,
                             span_lo: Span,
                             mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        if self.token.is_keyword(keywords::Let) {
-            return self.parse_while_let_expr(opt_label, span_lo, attrs);
-        }
-        let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
+        let cond = self.parse_cond_expr()?;
         let (iattrs, body) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
         let span = span_lo.to(body.span);
-        return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
+        Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs))
     }
 
-    /// Parses a `while let` expression (`while` token already eaten).
-    fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
-                                span_lo: Span,
-                                mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
-        self.expect_keyword(keywords::Let)?;
-        let pats = self.parse_pats()?;
-        self.expect(&token::Eq)?;
-        let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
-        let (iattrs, body) = self.parse_inner_attrs_and_block()?;
-        attrs.extend(iattrs);
-        let span = span_lo.to(body.span);
-        return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
-    }
-
-    // parse `loop {...}`, `loop` token already eaten
+    /// Parse `loop {...}`, `loop` token already eaten.
     fn parse_loop_expr(&mut self, opt_label: Option<Label>,
                            span_lo: Span,
                            mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
@@ -4011,17 +3319,20 @@ impl<'a> Parser<'a> {
         Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
     }
 
-    /// Parses an `async move {...}` expression.
-    pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
-        -> PResult<'a, P<Expr>>
-    {
-        let span_lo = self.span;
-        self.expect_keyword(keywords::Async)?;
-        let capture_clause = if self.eat_keyword(keywords::Move) {
+    /// Parse an optional `move` prefix to a closure lke construct.
+    fn parse_capture_clause(&mut self) -> CaptureBy {
+        if self.eat_keyword(kw::Move) {
             CaptureBy::Value
         } else {
             CaptureBy::Ref
-        };
+        }
+    }
+
+    /// Parses an `async move? {...}` expression.
+    pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
+        let span_lo = self.token.span;
+        self.expect_keyword(kw::Async)?;
+        let capture_clause = self.parse_capture_clause();
         let (iattrs, body) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
         Ok(self.mk_expr(
@@ -4035,7 +3346,15 @@ impl<'a> Parser<'a> {
     {
         let (iattrs, body) = self.parse_inner_attrs_and_block()?;
         attrs.extend(iattrs);
-        Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
+        if self.eat_keyword(kw::Catch) {
+            let mut error = self.struct_span_err(self.prev_span,
+                                                 "keyword `catch` cannot follow a `try` block");
+            error.help("try using `match` on the result of the `try` block instead");
+            error.emit();
+            Err(error)
+        } else {
+            Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
+        }
     }
 
     // `match` token already eaten
@@ -4045,7 +3364,7 @@ impl<'a> Parser<'a> {
         let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
                                                None)?;
         if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
-            if self.token == token::Token::Semi {
+            if self.token == token::Semi {
                 e.span_suggestion_short(
                     match_span,
                     "try removing this `match`",
@@ -4065,7 +3384,7 @@ impl<'a> Parser<'a> {
                     // Recover by skipping to the end of the block.
                     e.emit();
                     self.recover_stmt();
-                    let span = lo.to(self.span);
+                    let span = lo.to(self.token.span);
                     if self.token == token::CloseDelim(token::Brace) {
                         self.bump();
                     }
@@ -4073,24 +3392,23 @@ impl<'a> Parser<'a> {
                 }
             }
         }
-        let hi = self.span;
+        let hi = self.token.span;
         self.bump();
         return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
     }
 
     crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
-        maybe_whole!(self, NtArm, |x| x);
-
         let attrs = self.parse_outer_attributes()?;
+        let lo = self.token.span;
         let pats = self.parse_pats()?;
-        let guard = if self.eat_keyword(keywords::If) {
-            Some(Guard::If(self.parse_expr()?))
+        let guard = if self.eat_keyword(kw::If) {
+            Some(self.parse_expr()?)
         } else {
             None
         };
-        let arrow_span = self.span;
+        let arrow_span = self.token.span;
         self.expect(&token::FatArrow)?;
-        let arm_start_span = self.span;
+        let arm_start_span = self.token.span;
 
         let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
             .map_err(|mut err| {
@@ -4101,6 +3419,8 @@ impl<'a> Parser<'a> {
         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)])
@@ -4118,7 +3438,7 @@ impl<'a> Parser<'a> {
                             //   |        |
                             //   |        arrow_span
                             // X |     &X => "x"
-                            //   |      - ^^ self.span
+                            //   |      - ^^ self.token.span
                             //   |      |
                             //   |      parsed until here as `"y" & X`
                             err.span_suggestion_short(
@@ -4144,6 +3464,7 @@ impl<'a> Parser<'a> {
             pats,
             guard,
             body: expr,
+            span: lo.to(hi),
         })
     }
 
@@ -4196,15 +3517,14 @@ impl<'a> Parser<'a> {
             pats.push(self.parse_top_level_pat()?);
 
             if self.token == token::OrOr {
-                let mut err = self.struct_span_err(self.span,
-                                                   "unexpected token `||` after pattern");
-                err.span_suggestion(
-                    self.span,
-                    "use a single `|` to specify multiple patterns",
-                    "|".to_owned(),
-                    Applicability::MachineApplicable
-                );
-                err.emit();
+                self.struct_span_err(self.token.span, "unexpected token `||` after pattern")
+                    .span_suggestion(
+                        self.token.span,
+                        "use a single `|` to specify multiple patterns",
+                        "|".to_owned(),
+                        Applicability::MachineApplicable
+                    )
+                    .emit();
                 self.bump();
             } else if self.eat(&token::BinOp(token::Or)) {
                 // This is a No-op. Continue the loop to parse the next
@@ -4215,110 +3535,6 @@ impl<'a> Parser<'a> {
         };
     }
 
-    // Parses a parenthesized list of patterns like
-    // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
-    // - a vector of the patterns that were parsed
-    // - an option indicating the index of the `..` element
-    // - a boolean indicating whether a trailing comma was present.
-    // Trailing commas are significant because (p) and (p,) are different patterns.
-    fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
-        self.expect(&token::OpenDelim(token::Paren))?;
-        let result = self.parse_pat_list()?;
-        self.expect(&token::CloseDelim(token::Paren))?;
-        Ok(result)
-    }
-
-    fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
-        let mut fields = Vec::new();
-        let mut ddpos = None;
-        let mut trailing_comma = false;
-        loop {
-            if self.eat(&token::DotDot) {
-                if ddpos.is_none() {
-                    ddpos = Some(fields.len());
-                } else {
-                    // Emit a friendly error, ignore `..` and continue parsing
-                    self.struct_span_err(
-                        self.prev_span,
-                        "`..` can only be used once per tuple or tuple struct pattern",
-                    )
-                        .span_label(self.prev_span, "can only be used once per pattern")
-                        .emit();
-                }
-            } else if !self.check(&token::CloseDelim(token::Paren)) {
-                fields.push(self.parse_pat(None)?);
-            } else {
-                break
-            }
-
-            trailing_comma = self.eat(&token::Comma);
-            if !trailing_comma {
-                break
-            }
-        }
-
-        if ddpos == Some(fields.len()) && trailing_comma {
-            // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
-            let msg = "trailing comma is not permitted after `..`";
-            self.struct_span_err(self.prev_span, msg)
-                .span_label(self.prev_span, msg)
-                .emit();
-        }
-
-        Ok((fields, ddpos, trailing_comma))
-    }
-
-    fn parse_pat_vec_elements(
-        &mut self,
-    ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
-        let mut before = Vec::new();
-        let mut slice = None;
-        let mut after = Vec::new();
-        let mut first = true;
-        let mut before_slice = true;
-
-        while self.token != token::CloseDelim(token::Bracket) {
-            if first {
-                first = false;
-            } else {
-                self.expect(&token::Comma)?;
-
-                if self.token == token::CloseDelim(token::Bracket)
-                        && (before_slice || !after.is_empty()) {
-                    break
-                }
-            }
-
-            if before_slice {
-                if self.eat(&token::DotDot) {
-
-                    if self.check(&token::Comma) ||
-                            self.check(&token::CloseDelim(token::Bracket)) {
-                        slice = Some(P(Pat {
-                            id: ast::DUMMY_NODE_ID,
-                            node: PatKind::Wild,
-                            span: self.prev_span,
-                        }));
-                        before_slice = false;
-                    }
-                    continue
-                }
-            }
-
-            let subpat = self.parse_pat(None)?;
-            if before_slice && self.eat(&token::DotDot) {
-                slice = Some(subpat);
-                before_slice = false;
-            } else if before_slice {
-                before.push(subpat);
-            } else {
-                after.push(subpat);
-            }
-        }
-
-        Ok((before, slice, after))
-    }
-
     fn parse_pat_field(
         &mut self,
         lo: Span,
@@ -4335,10 +3551,10 @@ impl<'a> Parser<'a> {
             (pat, fieldname, false)
         } else {
             // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
-            let is_box = self.eat_keyword(keywords::Box);
-            let boxed_span = self.span;
-            let is_ref = self.eat_keyword(keywords::Ref);
-            let is_mut = self.eat_keyword(keywords::Mut);
+            let 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;
 
@@ -4386,8 +3602,16 @@ impl<'a> Parser<'a> {
         let mut etc_span = None;
 
         while self.token != token::CloseDelim(token::Brace) {
-            let attrs = self.parse_outer_attributes()?;
-            let lo = self.span;
+            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 {
@@ -4401,19 +3625,18 @@ impl<'a> Parser<'a> {
 
             if self.check(&token::DotDot) || self.token == token::DotDotDot {
                 etc = true;
-                let mut etc_sp = self.span;
+                let mut etc_sp = self.token.span;
 
                 if self.token == token::DotDotDot { // Issue #46718
                     // Accept `...` as if it were `..` to avoid further errors
-                    let mut err = self.struct_span_err(self.span,
-                                                       "expected field pattern, found `...`");
-                    err.span_suggestion(
-                        self.span,
-                        "to omit remaining fields, use one fewer `.`",
-                        "..".to_owned(),
-                        Applicability::MachineApplicable
-                    );
-                    err.emit();
+                    self.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();
                 }
                 self.bump();  // `..` || `...`
 
@@ -4424,18 +3647,19 @@ impl<'a> Parser<'a> {
                 let token_str = self.this_token_descr();
                 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
 
-                err.span_label(self.span, "expected `}`");
+                err.span_label(self.token.span, "expected `}`");
                 let mut comma_sp = None;
                 if self.token == token::Comma { // Issue #49257
-                    etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
+                    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.span);
+                    comma_sp = Some(self.token.span);
                     self.bump();
                     ate_comma = true;
                 }
 
-                etc_span = Some(etc_sp.until(self.span));
+                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 {
@@ -4485,7 +3709,7 @@ impl<'a> Parser<'a> {
                     "move the `..` to the end of the field list",
                     vec![
                         (etc_span, String::new()),
-                        (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
+                        (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
                     ],
                     Applicability::MachineApplicable,
                 );
@@ -4497,7 +3721,7 @@ impl<'a> Parser<'a> {
 
     fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
         if self.token.is_path_start() {
-            let lo = self.span;
+            let lo = self.token.span;
             let (qself, path) = if self.eat_lt() {
                 // Parse a qualified path
                 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
@@ -4513,20 +3737,35 @@ impl<'a> Parser<'a> {
         }
     }
 
-    // helper function to decide whether to parse as ident binding or to try to do
-    // something more complex like range patterns
+    /// 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()
+    }
+
+    // Helper function to decide whether to parse as ident binding
+    // or to try to do something more complex like range patterns.
     fn parse_as_ident(&mut self) -> bool {
-        self.look_ahead(1, |t| match *t {
+        self.look_ahead(1, |t| match t.kind {
             token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
-            token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
-            // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
-            // range pattern branch
-            token::DotDot => None,
-            _ => Some(true),
-        }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
-            token::Comma | token::CloseDelim(token::Bracket) => true,
-            _ => false,
-        }))
+            token::DotDotDot | token::DotDotEq | token::DotDot |
+            token::ModSep | token::Not => false,
+            _ => true,
+        })
+    }
+
+    /// 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(())
     }
 
     /// A wrapper around `parse_pat` with some special error handling for the
@@ -4540,9 +3779,9 @@ impl<'a> Parser<'a> {
             // parentheses in what should have been a tuple pattern; return a
             // suggestion-enhanced error here rather than choking on the comma
             // later.
-            let comma_span = self.span;
+            let comma_span = self.token.span;
             self.bump();
-            if let Err(mut err) = self.parse_pat_list() {
+            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
@@ -4551,7 +3790,7 @@ impl<'a> Parser<'a> {
             let seq_span = pat.span.to(self.prev_span);
             let mut err = self.struct_span_err(comma_span,
                                                "unexpected `,` in pattern");
-            if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
+            if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
                 err.span_suggestion(
                     seq_span,
                     "try adding parentheses to match on a tuple..",
@@ -4574,6 +3813,53 @@ impl<'a> Parser<'a> {
         self.parse_pat_with_range_pat(true, expected)
     }
 
+    /// 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()))
+        }
+    }
+
     /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
     /// allowed).
     fn parse_pat_with_range_pat(
@@ -4581,48 +3867,69 @@ impl<'a> Parser<'a> {
         allow_range_pat: bool,
         expected: Option<&'static str>,
     ) -> PResult<'a, P<Pat>> {
+        maybe_recover_from_interpolated_ty_qpath!(self, true);
         maybe_whole!(self, NtPat, |x| x);
 
-        let lo = self.span;
+        let lo = self.token.span;
         let pat;
-        match self.token {
+        match self.token.kind {
             token::BinOp(token::And) | token::AndAnd => {
                 // Parse &pat / &mut pat
                 self.expect_and()?;
                 let mutbl = self.parse_mutability();
-                if let token::Lifetime(ident) = self.token {
-                    let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
-                                                      ident));
-                    err.span_label(self.span, "unexpected lifetime");
+                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)?;
                 pat = PatKind::Ref(subpat, mutbl);
             }
             token::OpenDelim(token::Paren) => {
-                // Parse (pat,pat,pat,...) as tuple pattern
-                let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
-                pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
+                // Parse a tuple or parenthesis pattern.
+                let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
+
+                // Here, `(pat,)` is a tuple pattern.
+                // For backward compatibility, `(..)` is a tuple pattern as well.
+                pat = if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
                     PatKind::Paren(fields.into_iter().nth(0).unwrap())
                 } else {
-                    PatKind::Tuple(fields, ddpos)
+                    PatKind::Tuple(fields)
                 };
             }
             token::OpenDelim(token::Bracket) => {
-                // Parse [pat,pat,...] as slice pattern
+                // Parse `[pat, pat,...]` as a slice pattern.
+                let (slice, _) = self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat(None))?;
+                pat = PatKind::Slice(slice);
+            }
+            token::DotDot => {
+                self.bump();
+                pat = 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();
+                pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?;
+            }
+            token::DotDotDot => {
+                // Parse `...42` for recovery.
                 self.bump();
-                let (before, slice, after) = self.parse_pat_vec_elements()?;
-                self.expect(&token::CloseDelim(token::Bracket))?;
-                pat = PatKind::Slice(before, slice, after);
+                pat = self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?;
             }
             // At this point, token != &, &&, (, [
-            _ => if self.eat_keyword(keywords::Underscore) {
+            _ => if self.eat_keyword(kw::Underscore) {
                 // Parse _
                 pat = PatKind::Wild;
-            } else if self.eat_keyword(keywords::Mut) {
+            } else if self.eat_keyword(kw::Mut) {
                 // Parse mut ident @ pat / mut ref ident @ pat
-                let mutref_span = self.prev_span.to(self.span);
-                let binding_mode = if self.eat_keyword(keywords::Ref) {
+                let mutref_span = self.prev_span.to(self.token.span);
+                let binding_mode = if self.eat_keyword(kw::Ref) {
                     self.diagnostic()
                         .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
                         .span_suggestion(
@@ -4636,11 +3943,11 @@ impl<'a> Parser<'a> {
                     BindingMode::ByValue(Mutability::Mutable)
                 };
                 pat = self.parse_pat_ident(binding_mode)?;
-            } else if self.eat_keyword(keywords::Ref) {
+            } else if self.eat_keyword(kw::Ref) {
                 // Parse ref ident @ pat / ref mut ident @ pat
                 let mutbl = self.parse_mutability();
                 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
-            } else if self.eat_keyword(keywords::Box) {
+            } else if self.eat_keyword(kw::Box) {
                 // Parse box pat
                 let subpat = self.parse_pat_with_range_pat(false, None)?;
                 pat = PatKind::Box(subpat);
@@ -4661,36 +3968,40 @@ impl<'a> Parser<'a> {
                     // Parse an unqualified path
                     (None, self.parse_path(PathStyle::Expr)?)
                 };
-                match self.token {
+                match self.token.kind {
                     token::Not if qself.is_none() => {
                         // Parse macro invocation
                         self.bump();
                         let (delim, tts) = self.expect_delimited_token_tree()?;
-                        let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
+                        let mac = respan(lo.to(self.prev_span), Mac_ {
+                            path,
+                            tts,
+                            delim,
+                            prior_type_ascription: self.last_type_ascription,
+                        });
                         pat = PatKind::Mac(mac);
                     }
                     token::DotDotDot | token::DotDotEq | token::DotDot => {
-                        let end_kind = match self.token {
-                            token::DotDot => RangeEnd::Excluded,
-                            token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
-                            token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
+                        let (end_kind, form) = match self.token.kind {
+                            token::DotDot => (RangeEnd::Excluded, ".."),
+                            token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
+                            token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
                             _ => panic!("can only parse `..`/`...`/`..=` for ranges \
                                          (checked above)"),
                         };
-                        let op_span = self.span;
+                        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()?;
-                        let op = Spanned { span: op_span, node: end_kind };
-                        pat = PatKind::Range(begin, end, op);
+                        let end = self.parse_pat_range_end_opt(&begin, form)?;
+                        pat = PatKind::Range(begin, end, respan(op_span, end_kind));
                     }
                     token::OpenDelim(token::Brace) => {
                         if qself.is_some() {
                             let msg = "unexpected `{` after qualified path";
                             let mut err = self.fatal(msg);
-                            err.span_label(self.span, msg);
+                            err.span_label(self.token.span, msg);
                             return Err(err);
                         }
                         // Parse struct pattern
@@ -4698,7 +4009,7 @@ impl<'a> Parser<'a> {
                         let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
                             e.emit();
                             self.recover_stmt();
-                            (vec![], false)
+                            (vec![], true)
                         });
                         self.bump();
                         pat = PatKind::Struct(path, fields, etc);
@@ -4707,12 +4018,12 @@ impl<'a> Parser<'a> {
                         if qself.is_some() {
                             let msg = "unexpected `(` after qualified path";
                             let mut err = self.fatal(msg);
-                            err.span_label(self.span, msg);
+                            err.span_label(self.token.span, msg);
                             return Err(err);
                         }
                         // Parse tuple struct or enum pattern
-                        let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
-                        pat = PatKind::TupleStruct(path, fields, ddpos)
+                        let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
+                        pat = PatKind::TupleStruct(path, fields)
                     }
                     _ => pat = PatKind::Path(qself, path),
                 }
@@ -4720,22 +4031,21 @@ impl<'a> Parser<'a> {
                 // Try to parse everything else as literal with optional minus
                 match self.parse_literal_maybe_minus() {
                     Ok(begin) => {
-                        let op_span = self.span;
+                        let op_span = self.token.span;
                         if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
                                 self.check(&token::DotDotDot) {
-                            let end_kind = if self.eat(&token::DotDotDot) {
-                                RangeEnd::Included(RangeSyntax::DotDotDot)
+                            let (end_kind, form) = if self.eat(&token::DotDotDot) {
+                                (RangeEnd::Included(RangeSyntax::DotDotDot), "...")
                             } else if self.eat(&token::DotDotEq) {
-                                RangeEnd::Included(RangeSyntax::DotDotEq)
+                                (RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
                             } else if self.eat(&token::DotDot) {
-                                RangeEnd::Excluded
+                                (RangeEnd::Excluded, "..")
                             } else {
                                 panic!("impossible case: we already matched \
                                         on a range-operator token")
                             };
-                            let end = self.parse_pat_range_end()?;
-                            let op = Spanned { span: op_span, node: end_kind };
-                            pat = PatKind::Range(begin, end, op);
+                            let end = self.parse_pat_range_end_opt(&begin, form)?;
+                            pat = PatKind::Range(begin, end, respan(op_span, end_kind))
                         } else {
                             pat = PatKind::Lit(begin);
                         }
@@ -4749,14 +4059,18 @@ impl<'a> Parser<'a> {
                             self.this_token_descr(),
                         );
                         let mut err = self.fatal(&msg);
-                        err.span_label(self.span, format!("expected {}", expected));
+                        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);
+                        }
                         return Err(err);
                     }
                 }
             }
         }
 
-        let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
+        let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
         let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
 
         if !allow_range_pat {
@@ -4782,7 +4096,7 @@ impl<'a> Parser<'a> {
             }
         }
 
-        Ok(P(pat))
+        Ok(pat)
     }
 
     /// Parses `ident` or `ident @ pat`.
@@ -4830,7 +4144,7 @@ impl<'a> Parser<'a> {
                     let parser_snapshot_after_type = self.clone();
                     mem::replace(self, parser_snapshot_before_type);
 
-                    let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
+                    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)
                 }
@@ -4872,7 +4186,7 @@ impl<'a> Parser<'a> {
             }
         };
         let hi = if self.token == token::Semi {
-            self.span
+            self.token.span
         } else {
             self.prev_span
         };
@@ -4925,92 +4239,6 @@ impl<'a> Parser<'a> {
         Ok(self.parse_stmt_(true))
     }
 
-    // Eat 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).
-    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.
-    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 {
-                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;
-                    } else {
-                        self.bump();
-                    }
-                }
-                _ => {
-                    self.bump()
-                }
-            }
-        }
-    }
-
     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();
@@ -5019,11 +4247,11 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn is_async_block(&mut self) -> bool {
-        self.token.is_keyword(keywords::Async) &&
+    fn is_async_block(&self) -> bool {
+        self.token.is_keyword(kw::Async) &&
         (
             ( // `async move {`
-                self.look_ahead(1, |t| t.is_keyword(keywords::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))
@@ -5031,117 +4259,107 @@ impl<'a> Parser<'a> {
         )
     }
 
-    fn is_async_fn(&mut self) -> bool {
-        self.token.is_keyword(keywords::Async) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
+    fn is_async_fn(&self) -> bool {
+        self.token.is_keyword(kw::Async) &&
+            self.is_keyword_ahead(1, &[kw::Fn])
     }
 
-    fn is_do_catch_block(&mut self) -> bool {
-        self.token.is_keyword(keywords::Do) &&
-        self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
+    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(&mut self) -> bool {
-        self.token.is_keyword(keywords::Try) &&
+    fn is_try_block(&self) -> bool {
+        self.token.is_keyword(kw::Try) &&
         self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
-        self.span.rust_2018() &&
+        self.token.span.rust_2018() &&
         // prevent `while try {} {}`, `if try {} {} else {}`, etc.
         !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
     }
 
     fn is_union_item(&self) -> bool {
-        self.token.is_keyword(keywords::Union) &&
+        self.token.is_keyword(kw::Union) &&
         self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
     }
 
     fn is_crate_vis(&self) -> bool {
-        self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
-    }
-
-    fn is_existential_type_decl(&self) -> bool {
-        self.token.is_keyword(keywords::Existential) &&
-        self.look_ahead(1, |t| t.is_keyword(keywords::Type))
+        self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
     }
 
-    fn is_auto_trait_item(&mut self) -> bool {
+    fn is_auto_trait_item(&self) -> bool {
         // auto trait
-        (self.token.is_keyword(keywords::Auto)
-            && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
+        (self.token.is_keyword(kw::Auto) &&
+            self.is_keyword_ahead(1, &[kw::Trait]))
         || // unsafe auto trait
-        (self.token.is_keyword(keywords::Unsafe) &&
-         self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
-         self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
+        (self.token.is_keyword(kw::Unsafe) &&
+         self.is_keyword_ahead(1, &[kw::Auto]) &&
+         self.is_keyword_ahead(2, &[kw::Trait]))
     }
 
     fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
                      -> PResult<'a, Option<P<Item>>> {
-        let token_lo = self.span;
-        let (ident, def) = match self.token {
-            token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
-                self.bump();
-                let ident = self.parse_ident()?;
-                let tokens = if self.check(&token::OpenDelim(token::Brace)) {
-                    match self.parse_token_tree() {
-                        TokenTree::Delimited(_, _, tts) => tts,
-                        _ => unreachable!(),
-                    }
-                } else if self.check(&token::OpenDelim(token::Paren)) {
-                    let args = self.parse_token_tree();
-                    let body = if self.check(&token::OpenDelim(token::Brace)) {
-                        self.parse_token_tree()
-                    } else {
-                        self.unexpected()?;
-                        unreachable!()
-                    };
-                    TokenStream::new(vec![
-                        args.into(),
-                        TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
-                        body.into(),
-                    ])
+        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 })
-            }
-            token::Ident(ident, _) if ident.name == "macro_rules" &&
-                                   self.look_ahead(1, |t| *t == token::Not) => {
-                let prev_span = self.prev_span;
-                self.complain_if_pub_macro(&vis.node, prev_span);
-                self.bump();
-                self.bump();
-
-                let ident = self.parse_ident()?;
-                let (delim, tokens) = self.expect_delimited_token_tree()?;
-                if delim != MacDelimiter::Brace {
-                    if !self.eat(&token::Semi) {
-                        let msg = "macros that expand to items must either \
-                                   be surrounded with braces or followed by a semicolon";
-                        self.span_err(self.prev_span, msg);
-                    }
-                }
+            (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();
 
-                (ident, ast::MacroDef { tokens: tokens, legacy: true })
+            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();
             }
-            _ => return Ok(None),
+
+            (ident, ast::MacroDef { tokens, legacy: true })
+        } else {
+            return Ok(None);
         };
 
         let span = lo.to(self.prev_span);
         Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
     }
 
-    fn parse_stmt_without_recovery(&mut self,
-                                   macro_legacy_warnings: bool)
-                                   -> PResult<'a, Option<Stmt>> {
+    fn parse_stmt_without_recovery(
+        &mut self,
+        macro_legacy_warnings: bool,
+    ) -> PResult<'a, Option<Stmt>> {
         maybe_whole!(self, NtStmt, |x| Some(x));
 
         let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
+        let lo = self.token.span;
 
-        Ok(Some(if self.eat_keyword(keywords::Let) {
+        Ok(Some(if self.eat_keyword(kw::Let) {
             Stmt {
                 id: ast::DUMMY_NODE_ID,
                 node: StmtKind::Local(self.parse_local(attrs.into())?),
@@ -5167,17 +4385,16 @@ impl<'a> Parser<'a> {
                   !self.token.is_qpath_start() &&
                   !self.is_union_item() &&
                   !self.is_crate_vis() &&
-                  !self.is_existential_type_decl() &&
                   !self.is_auto_trait_item() &&
                   !self.is_async_fn() {
-            let pth = self.parse_path(PathStyle::Expr)?;
+            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, pth, ThinVec::new())?
+                    self.parse_struct_expr(lo, path, ThinVec::new())?
                 } else {
                     let hi = self.prev_span;
-                    self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
+                    self.mk_expr(lo.to(hi), ExprKind::Path(None, path), ThinVec::new())
                 };
 
                 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
@@ -5192,34 +4409,6 @@ impl<'a> Parser<'a> {
                 }));
             }
 
-            // it's a macro invocation
-            let id = match self.token {
-                token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
-                _ => self.parse_ident()?,
-            };
-
-            // check that we're pointing at delimiters (need to check
-            // again after the `if`, because of `parse_ident`
-            // consuming more tokens).
-            match self.token {
-                token::OpenDelim(_) => {}
-                _ => {
-                    // we only expect an ident if we didn't parse one
-                    // above.
-                    let ident_str = if id.name == keywords::Invalid.name() {
-                        "identifier, "
-                    } else {
-                        ""
-                    };
-                    let tok_str = self.this_token_descr();
-                    let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
-                                                      ident_str,
-                                                      tok_str));
-                    err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
-                    return Err(err)
-                },
-            }
-
             let (delim, tts) = self.expect_delimited_token_tree()?;
             let hi = self.prev_span;
 
@@ -5229,61 +4418,43 @@ impl<'a> Parser<'a> {
                 MacStmtStyle::NoBraces
             };
 
-            if id.name == keywords::Invalid.name() {
-                let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
-                let node = if delim == MacDelimiter::Brace ||
-                              self.token == token::Semi || self.token == token::Eof {
-                    StmtKind::Mac(P((mac, style, attrs.into())))
-                }
-                // We used to incorrectly stop parsing macro-expanded statements here.
-                // If the next token will be an error anyway but could have parsed with the
-                // earlier behavior, stop parsing here and emit a warning to avoid breakage.
-                else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
-                    // These can continue an expression, so we can't stop parsing and warn.
-                    token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
-                    token::BinOp(token::Minus) | token::BinOp(token::Star) |
-                    token::BinOp(token::And) | token::BinOp(token::Or) |
-                    token::AndAnd | token::OrOr |
-                    token::DotDot | token::DotDotDot | token::DotDotEq => false,
-                    _ => true,
-                } {
-                    self.warn_missing_semicolon();
-                    StmtKind::Mac(P((mac, style, attrs.into())))
-                } else {
-                    let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new());
-                    let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
-                    let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
-                    StmtKind::Expr(e)
-                };
-                Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    span: lo.to(hi),
-                    node,
-                }
+            let mac = respan(lo.to(hi), Mac_ {
+                path,
+                tts,
+                delim,
+                prior_type_ascription: self.last_type_ascription,
+            });
+            let node = if delim == MacDelimiter::Brace ||
+                          self.token == token::Semi || self.token == token::Eof {
+                StmtKind::Mac(P((mac, style, attrs.into())))
+            }
+            // We used to incorrectly stop parsing macro-expanded statements here.
+            // If the next token will be an error anyway but could have parsed with the
+            // earlier behavior, stop parsing here and emit a warning to avoid breakage.
+            else if macro_legacy_warnings &&
+                    self.token.can_begin_expr() &&
+                    match self.token.kind {
+                // These can continue an expression, so we can't stop parsing and warn.
+                token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
+                token::BinOp(token::Minus) | token::BinOp(token::Star) |
+                token::BinOp(token::And) | token::BinOp(token::Or) |
+                token::AndAnd | token::OrOr |
+                token::DotDot | token::DotDotDot | token::DotDotEq => false,
+                _ => true,
+            } {
+                self.warn_missing_semicolon();
+                StmtKind::Mac(P((mac, style, attrs.into())))
             } else {
-                // if it has a special ident, it's definitely an item
-                //
-                // Require a semicolon or braces.
-                if style != MacStmtStyle::Braces {
-                    if !self.eat(&token::Semi) {
-                        self.span_err(self.prev_span,
-                                      "macros that expand to items must \
-                                       either be surrounded with braces or \
-                                       followed by a semicolon");
-                    }
-                }
-                let span = lo.to(hi);
-                Stmt {
-                    id: ast::DUMMY_NODE_ID,
-                    span,
-                    node: StmtKind::Item({
-                        self.mk_item(
-                            span, id /*id is good here*/,
-                            ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
-                            respan(lo, VisibilityKind::Inherited),
-                            attrs)
-                    }),
-                }
+                let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
+                let e = self.maybe_recover_from_bad_qpath(e, true)?;
+                let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
+                let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
+                StmtKind::Expr(e)
+            };
+            Stmt {
+                id: ast::DUMMY_NODE_ID,
+                span: lo.to(hi),
+                node,
             }
         } else {
             // FIXME: Bad copy of attrs
@@ -5304,7 +4475,9 @@ impl<'a> Parser<'a> {
                             if s.prev_token_kind == PrevTokenKind::DocComment {
                                 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
                             } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
-                                s.span_err(s.span, "expected statement after outer attribute");
+                                s.span_err(
+                                    s.token.span, "expected statement after outer attribute"
+                                );
                             }
                         }
                     };
@@ -5335,7 +4508,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Checks if this expression is a successfully parsed statement.
-    fn expr_is_complete(&mut self, e: &Expr) -> bool {
+    fn expr_is_complete(&self, e: &Expr) -> bool {
         self.restrictions.contains(Restrictions::STMT_EXPR) &&
             !classify::expr_requires_semi_to_be_stmt(e)
     }
@@ -5344,26 +4517,26 @@ impl<'a> Parser<'a> {
     pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
         maybe_whole!(self, NtBlock, |x| x);
 
-        let lo = self.span;
+        let lo = self.token.span;
 
         if !self.eat(&token::OpenDelim(token::Brace)) {
-            let sp = self.span;
+            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(keywords::In) || self.token == token::Colon;
+                self.token.is_keyword(kw::In) || self.token == token::Colon;
 
-            if self.token.is_ident_named("and") {
+            if self.token.is_ident_named(sym::and) {
                 e.span_suggestion_short(
-                    self.span,
+                    self.token.span,
                     "use `&&` instead of `and` for the boolean operator",
                     "&&".to_string(),
                     Applicability::MaybeIncorrect,
                 );
             }
-            if self.token.is_ident_named("or") {
+            if self.token.is_ident_named(sym::or) {
                 e.span_suggestion_short(
-                    self.span,
+                    self.token.span,
                     "use `||` instead of `or` for the boolean operator",
                     "||".to_string(),
                     Applicability::MaybeIncorrect,
@@ -5390,20 +4563,15 @@ impl<'a> Parser<'a> {
                     if self.eat(&token::Semi) {
                         stmt_span = stmt_span.with_hi(self.prev_span.hi());
                     }
-                    let sugg = pprust::to_string(|s| {
-                        use crate::print::pprust::{PrintState, INDENT_UNIT};
-                        s.ibox(INDENT_UNIT)?;
-                        s.bopen()?;
-                        s.print_stmt(&stmt)?;
-                        s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
-                    });
-                    e.span_suggestion(
-                        stmt_span,
-                        "try placing this code inside a block",
-                        sugg,
-                        // speculative, has been misleading in the past (closed Issue #46836)
-                        Applicability::MaybeIncorrect
-                    );
+                    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);
@@ -5419,10 +4587,10 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a block. Inner attributes are allowed.
-    fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
+    crate fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
         maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
 
-        let lo = self.span;
+        let lo = self.token.span;
         self.expect(&token::OpenDelim(token::Brace))?;
         Ok((self.parse_inner_attributes()?,
             self.parse_block_tail(lo, BlockCheckMode::Default)?))
@@ -5433,22 +4601,23 @@ impl<'a> Parser<'a> {
     fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
         let mut stmts = vec![];
         while !self.eat(&token::CloseDelim(token::Brace)) {
+            if self.token == token::Eof {
+                break;
+            }
             let stmt = match self.parse_full_stmt(false) {
                 Err(mut err) => {
                     err.emit();
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     Some(Stmt {
                         id: ast::DUMMY_NODE_ID,
-                        node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
-                        span: self.span,
+                        node: StmtKind::Expr(DummyResult::raw_expr(self.token.span, true)),
+                        span: self.token.span,
                     })
                 }
                 Ok(stmt) => stmt,
             };
             if let Some(stmt) = stmt {
                 stmts.push(stmt);
-            } else if self.token == token::Eof {
-                break;
             } else {
                 // Found only `;` or `}`.
                 continue;
@@ -5482,6 +4651,9 @@ impl<'a> Parser<'a> {
                     {
                         e.emit();
                         self.recover_stmt();
+                        // Don't complain about type errors in body tail after parse error (#57383).
+                        let sp = expr.span.to(self.prev_span);
+                        stmt.node = StmtKind::Expr(DummyResult::raw_expr(sp, true));
                     }
                 }
             }
@@ -5499,13 +4671,12 @@ impl<'a> Parser<'a> {
         if self.eat(&token::Semi) {
             stmt = stmt.add_trailing_semicolon();
         }
-
-        stmt.span = stmt.span.with_hi(self.prev_span.hi());
+        stmt.span = stmt.span.to(self.prev_span);
         Ok(Some(stmt))
     }
 
     fn warn_missing_semicolon(&self) {
-        self.diagnostic().struct_span_warn(self.span, {
+        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"
@@ -5540,16 +4711,16 @@ impl<'a> Parser<'a> {
         let mut last_plus_span = None;
         let mut was_negative = false;
         loop {
-            // This needs to be synchronized with `Token::can_begin_bound`.
+            // 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(keywords::For) ||
+                                 self.check_keyword(kw::For) ||
                                  self.check(&token::OpenDelim(token::Paren));
             if is_bound_start {
-                let lo = self.span;
+                let lo = self.token.span;
                 let has_parens = self.eat(&token::OpenDelim(token::Paren));
-                let inner_lo = self.span;
+                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() {
@@ -5565,7 +4736,7 @@ impl<'a> Parser<'a> {
                             lo.to(self.prev_span),
                             "parenthesized lifetime bounds are not supported"
                         );
-                        if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
+                        if let Ok(snippet) = self.span_to_snippet(inner_span) {
                             err.span_suggestion_short(
                                 lo.to(self.prev_span),
                                 "remove the parentheses",
@@ -5610,25 +4781,32 @@ impl<'a> Parser<'a> {
 
         if !negative_bounds.is_empty() || was_negative {
             let plural = negative_bounds.len() > 1;
-            let mut err = self.struct_span_err(negative_bounds,
-                                               "negative trait bounds are not supported");
+            let last_span = negative_bounds.last().map(|sp| *sp);
+            let mut err = self.struct_span_err(
+                negative_bounds,
+                "negative trait bounds are not supported",
+            );
+            if let Some(sp) = last_span {
+                err.span_label(sp, "negative trait bounds are not supported");
+            }
             if let Some(bound_list) = colon_span {
                 let bound_list = bound_list.to(self.prev_span);
                 let mut new_bound_list = String::new();
                 if !bounds.is_empty() {
                     let mut snippets = bounds.iter().map(|bound| bound.span())
-                        .map(|span| self.sess.source_map().span_to_snippet(span));
+                        .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_short(bound_list,
-                                        &format!("remove the trait bound{}",
-                                                if plural { "s" } else { "" }),
-                                        new_bound_list,
-                                        Applicability::MachineApplicable);
+                err.span_suggestion_hidden(
+                    bound_list,
+                    &format!("remove the trait bound{}", if plural { "s" } else { "" }),
+                    new_bound_list,
+                    Applicability::MachineApplicable,
+                );
             }
             err.emit();
         }
@@ -5636,7 +4814,8 @@ impl<'a> Parser<'a> {
         return Ok(bounds);
     }
 
-    fn parse_generic_bounds(&mut self, colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
+    crate fn parse_generic_bounds(&mut self,
+                                  colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
         self.parse_generic_bounds_common(true, colon_span)
     }
 
@@ -5714,7 +4893,7 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
-        self.expect_keyword(keywords::Const)?;
+        self.expect_keyword(kw::Const)?;
         let ident = self.parse_ident()?;
         self.expect(&token::Colon)?;
         let ty = self.parse_ty()?;
@@ -5751,7 +4930,7 @@ impl<'a> Parser<'a> {
                     bounds,
                     kind: ast::GenericParamKind::Lifetime,
                 });
-            } else if self.check_keyword(keywords::Const) {
+            } else if self.check_keyword(kw::Const) {
                 // Parse const parameter.
                 params.push(self.parse_const_param(attrs)?);
             } else if self.check_ident() {
@@ -5797,24 +4976,22 @@ impl<'a> Parser<'a> {
     ///                  | ( < lifetimes , typaramseq ( , )? > )
     /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
     fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
-        maybe_whole!(self, NtGenerics, |x| x);
-
-        let span_lo = self.span;
-        if self.eat_lt() {
+        let span_lo = self.token.span;
+        let (params, span) = if self.eat_lt() {
             let params = self.parse_generic_params()?;
             self.expect_gt()?;
-            Ok(ast::Generics {
-                params,
-                where_clause: WhereClause {
-                    id: ast::DUMMY_NODE_ID,
-                    predicates: Vec::new(),
-                    span: syntax_pos::DUMMY_SP,
-                },
-                span: span_lo.to(self.prev_span),
-            })
+            (params, span_lo.to(self.prev_span))
         } else {
-            Ok(ast::Generics::default())
-        }
+            (vec![], self.prev_span.between(self.token.span))
+        };
+        Ok(ast::Generics {
+            params,
+            where_clause: WhereClause {
+                predicates: Vec::new(),
+                span: DUMMY_SP,
+            },
+            span,
+        })
     }
 
     /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
@@ -5830,7 +5007,7 @@ impl<'a> Parser<'a> {
         &mut self,
         style: PathStyle,
         lo: Span,
-    ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
+    ) -> 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
@@ -5965,51 +5142,61 @@ impl<'a> Parser<'a> {
 
     /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
     /// possibly including trailing comma.
-    fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
+    fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
         let mut args = Vec::new();
-        let mut bindings = Vec::new();
-        let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
-        let mut assoc_ty_bindings: Vec<Span> = Vec::new();
+        let 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.span;
+        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_bindings.append(&mut assoc_ty_bindings);
-            } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
-                // Parse associated type binding.
-                let lo = self.span;
+                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()?;
-                self.bump();
-                let ty = self.parse_ty()?;
+                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);
-                bindings.push(TypeBinding {
+                constraints.push(AssocTyConstraint {
                     id: ast::DUMMY_NODE_ID,
                     ident,
-                    ty,
+                    kind,
                     span,
                 });
-                assoc_ty_bindings.push(span);
+                assoc_ty_constraints.push(span);
             } else if self.check_const_arg() {
-                // 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.
-
                 // Parse const argument.
-                let expr = if let token::OpenDelim(token::Brace) = self.token {
-                    self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
+                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.
-                    return Err(
-                        self.fatal("identifiers may currently not be used for const generics")
-                    );
+                    if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
+                        self.parse_literal_maybe_minus()?
+                    } else {
+                        return Err(
+                            self.fatal("identifiers may currently not be used for const generics")
+                        );
+                    }
                 } else {
-                    // FIXME(const_generics): this currently conflicts with emplacement syntax
-                    // with negative integer literals.
                     self.parse_literal_maybe_minus()?
                 };
                 let value = AnonConst {
@@ -6017,11 +5204,11 @@ impl<'a> Parser<'a> {
                     value: expr,
                 };
                 args.push(GenericArg::Const(value));
-                misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
+                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_bindings.append(&mut assoc_ty_bindings);
+                misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
             } else {
                 break
             }
@@ -6034,12 +5221,12 @@ impl<'a> Parser<'a> {
         // FIXME: we would like to report this in ast_validation instead, but we currently do not
         // preserve ordering of generic parameters with respect to associated type binding, so we
         // lose that information after parsing.
-        if misplaced_assoc_ty_bindings.len() > 0 {
+        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_bindings {
+            for span in misplaced_assoc_ty_constraints {
                 err.span_label(
                     span,
                     "this associated type binding should be moved after the generic parameters",
@@ -6048,7 +5235,7 @@ impl<'a> Parser<'a> {
             err.emit();
         }
 
-        Ok((args, bindings))
+        Ok((args, constraints))
     }
 
     /// Parses an optional where-clause and places it in `generics`.
@@ -6057,15 +5244,12 @@ impl<'a> Parser<'a> {
     /// where T : Trait<U, V> + 'b, 'a : 'b
     /// ```
     fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
-        maybe_whole!(self, NtWhereClause, |x| x);
-
         let mut where_clause = WhereClause {
-            id: ast::DUMMY_NODE_ID,
             predicates: Vec::new(),
-            span: syntax_pos::DUMMY_SP,
+            span: self.prev_span.to(self.prev_span),
         };
 
-        if !self.eat_keyword(keywords::Where) {
+        if !self.eat_keyword(kw::Where) {
             return Ok(where_clause);
         }
         let lo = self.prev_span;
@@ -6084,7 +5268,7 @@ impl<'a> Parser<'a> {
         }
 
         loop {
-            let lo = self.span;
+            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.
@@ -6101,9 +5285,10 @@ impl<'a> Parser<'a> {
                 // Parse optional `for<'a, 'b>`.
                 // This `for` is parsed greedily and applies to the whole predicate,
                 // the bounded type can have its own `for` applying only to it.
-                // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
-                // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
-                // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
+                // 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,
@@ -6149,55 +5334,48 @@ impl<'a> Parser<'a> {
 
     fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
                      -> PResult<'a, (Vec<Arg> , bool)> {
-        self.expect(&token::OpenDelim(token::Paren))?;
-
-        let sp = self.span;
+        let sp = self.token.span;
         let mut c_variadic = false;
-        let (args, recovered): (Vec<Option<Arg>>, bool) =
-            self.parse_seq_to_before_end(
-                &token::CloseDelim(token::Paren),
-                SeqSep::trailing_allowed(token::Comma),
-                |p| {
-                    // If the argument is a C-variadic argument we should not
-                    // enforce named arguments.
-                    let enforce_named_args = if p.token == token::DotDotDot {
+        let (args, _): (Vec<Option<Arg>>, _) = self.parse_paren_comma_seq(|p| {
+            let do_not_enforce_named_arguments_for_c_variadic =
+                |token: &token::Token| -> bool {
+                    if token == &token::DotDotDot {
                         false
                     } else {
                         named_args
-                    };
-                    match p.parse_arg_general(enforce_named_args, false,
-                                              allow_c_variadic) {
-                        Ok(arg) => {
-                            if let TyKind::CVarArgs = arg.ty.node {
-                                c_variadic = true;
-                                if p.token != token::CloseDelim(token::Paren) {
-                                    let span = p.span;
-                                    p.span_err(span,
-                                        "`...` must be the last argument of a C-variadic function");
-                                    Ok(None)
-                                } else {
-                                    Ok(Some(arg))
-                                }
-                            } else {
-                                Ok(Some(arg))
-                            }
-                        },
-                        Err(mut e) => {
-                            e.emit();
-                            let lo = p.prev_span;
-                            // Skip every token until next possible arg or end.
-                            p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
-                            // Create a placeholder argument for proper arg count (issue #34264).
-                            let span = lo.to(p.prev_span);
-                            Ok(Some(dummy_arg(span)))
+                    }
+                };
+            match p.parse_arg_general(
+                false,
+                allow_c_variadic,
+                do_not_enforce_named_arguments_for_c_variadic
+            ) {
+                Ok(arg) => {
+                    if let TyKind::CVarArgs = arg.ty.node {
+                        c_variadic = true;
+                        if p.token != token::CloseDelim(token::Paren) {
+                            let span = p.token.span;
+                            p.span_err(span,
+                                "`...` must be the last argument of a C-variadic function");
+                            Ok(None)
+                        } else {
+                            Ok(Some(arg))
                         }
+                    } else {
+                        Ok(Some(arg))
                     }
+                },
+                Err(mut e) => {
+                    e.emit();
+                    let lo = p.prev_span;
+                    // Skip every token until next possible arg or end.
+                    p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
+                    // Create a placeholder argument for proper arg count (issue #34264).
+                    let span = lo.to(p.prev_span);
+                    Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
                 }
-            )?;
-
-        if !recovered {
-            self.eat(&token::CloseDelim(token::Paren));
-        }
+            }
+        })?;
 
         let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
 
@@ -6211,7 +5389,6 @@ impl<'a> Parser<'a> {
 
     /// Parses the argument list and result type of a function declaration.
     fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
-
         let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
         let ret_ty = self.parse_ret_ty(true)?;
 
@@ -6223,33 +5400,35 @@ impl<'a> Parser<'a> {
     }
 
     /// Returns the parsed optional self argument and whether a self shortcut was used.
+    ///
+    /// See `parse_self_arg_with_attrs` to collect attributes.
     fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
-        let expect_ident = |this: &mut Self| match this.token {
+        let expect_ident = |this: &mut Self| match this.token.kind {
             // Preserve hygienic context.
-            token::Ident(ident, _) =>
-                { let span = this.span; this.bump(); Ident::new(ident.name, span) }
+            token::Ident(name, _) =>
+                { let span = this.token.span; this.bump(); Ident::new(name, span) }
             _ => unreachable!()
         };
         let isolated_self = |this: &mut Self, n| {
-            this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) &&
+            this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
             this.look_ahead(n + 1, |t| t != &token::ModSep)
         };
 
-        // Parse optional self parameter of a method.
-        // Only a limited set of initial token sequences is considered self parameters, anything
+        // Parse optional `self` parameter of a method.
+        // Only a limited set of initial token sequences is considered `self` parameters; anything
         // else is parsed as a normal function parameter list, so some lookahead is required.
-        let eself_lo = self.span;
-        let (eself, eself_ident, eself_hi) = match self.token {
+        let eself_lo = self.token.span;
+        let (eself, eself_ident, eself_hi) = match self.token.kind {
             token::BinOp(token::And) => {
-                // &self
-                // &mut self
-                // &'lt self
-                // &'lt mut self
-                // &not_self
+                // `&self`
+                // `&mut self`
+                // `&'lt self`
+                // `&'lt mut self`
+                // `&not_self`
                 (if isolated_self(self, 1) {
                     self.bump();
                     SelfKind::Region(None, Mutability::Immutable)
-                } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
+                } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
                           isolated_self(self, 2) {
                     self.bump();
                     self.bump();
@@ -6260,7 +5439,7 @@ impl<'a> Parser<'a> {
                     let lt = self.expect_lifetime();
                     SelfKind::Region(Some(lt), Mutability::Immutable)
                 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
-                          self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
+                          self.is_keyword_ahead(2, &[kw::Mut]) &&
                           isolated_self(self, 3) {
                     self.bump();
                     let lt = self.expect_lifetime();
@@ -6271,24 +5450,24 @@ impl<'a> Parser<'a> {
                 }, expect_ident(self), self.prev_span)
             }
             token::BinOp(token::Star) => {
-                // *self
-                // *const self
-                // *mut self
-                // *not_self
+                // `*self`
+                // `*const self`
+                // `*mut self`
+                // `*not_self`
                 // Emit special error for `self` cases.
                 let msg = "cannot pass `self` by raw pointer";
                 (if isolated_self(self, 1) {
                     self.bump();
-                    self.struct_span_err(self.span, msg)
-                        .span_label(self.span, msg)
+                    self.struct_span_err(self.token.span, msg)
+                        .span_label(self.token.span, msg)
                         .emit();
                     SelfKind::Value(Mutability::Immutable)
                 } else if self.look_ahead(1, |t| t.is_mutability()) &&
                           isolated_self(self, 2) {
                     self.bump();
                     self.bump();
-                    self.struct_span_err(self.span, msg)
-                        .span_label(self.span, msg)
+                    self.struct_span_err(self.token.span, msg)
+                        .span_label(self.token.span, msg)
                         .emit();
                     SelfKind::Value(Mutability::Immutable)
                 } else {
@@ -6297,8 +5476,8 @@ impl<'a> Parser<'a> {
             }
             token::Ident(..) => {
                 if isolated_self(self, 0) {
-                    // self
-                    // self: TYPE
+                    // `self`
+                    // `self: TYPE`
                     let eself_ident = expect_ident(self);
                     let eself_hi = self.prev_span;
                     (if self.eat(&token::Colon) {
@@ -6307,10 +5486,10 @@ impl<'a> Parser<'a> {
                     } else {
                         SelfKind::Value(Mutability::Immutable)
                     }, eself_ident, eself_hi)
-                } else if self.token.is_keyword(keywords::Mut) &&
+                } else if self.token.is_keyword(kw::Mut) &&
                           isolated_self(self, 1) {
-                    // mut self
-                    // mut self: TYPE
+                    // `mut self`
+                    // `mut self: TYPE`
                     self.bump();
                     let eself_ident = expect_ident(self);
                     let eself_hi = self.prev_span;
@@ -6328,7 +5507,18 @@ impl<'a> Parser<'a> {
         };
 
         let eself = source_map::respan(eself_lo.to(eself_hi), eself);
-        Ok(Some(Arg::from_self(eself, eself_ident)))
+        Ok(Some(Arg::from_self(ThinVec::default(), eself, eself_ident)))
+    }
+
+    /// Returns the parsed optional self argument with attributes and whether a self
+    /// shortcut was used.
+    fn parse_self_arg_with_attrs(&mut self) -> PResult<'a, Option<Arg>> {
+        let attrs = self.parse_arg_attributes()?;
+        let arg_opt = self.parse_self_arg()?;
+        Ok(arg_opt.map(|mut arg| {
+            arg.attrs = attrs.into();
+            arg
+        }))
     }
 
     /// Parses the parameter list and result type of a function that may have a `self` parameter.
@@ -6337,17 +5527,17 @@ impl<'a> Parser<'a> {
     {
         self.expect(&token::OpenDelim(token::Paren))?;
 
-        // Parse optional self argument
-        let self_arg = self.parse_self_arg()?;
+        // Parse optional self argument.
+        let self_arg = self.parse_self_arg_with_attrs()?;
 
         // Parse the rest of the function parameter list.
         let sep = SeqSep::trailing_allowed(token::Comma);
-        let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
+        let (mut fn_inputs, recovered) = if let Some(self_arg) = self_arg {
             if self.check(&token::CloseDelim(token::Paren)) {
                 (vec![self_arg], false)
             } else if self.eat(&token::Comma) {
                 let mut fn_inputs = vec![self_arg];
-                let (mut input, recovered) = self.parse_seq_to_before_end(
+                let (mut input, _, recovered) = self.parse_seq_to_before_end(
                     &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
                 fn_inputs.append(&mut input);
                 (fn_inputs, recovered)
@@ -6358,13 +5548,18 @@ impl<'a> Parser<'a> {
                 }
             }
         } else {
-            self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
+            let (input, _, recovered) =
+                self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
+            (input, recovered)
         };
 
         if !recovered {
             // Parse closing paren and return type.
             self.expect(&token::CloseDelim(token::Paren))?;
         }
+        // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
+        self.deduplicate_recovered_arg_names(&mut fn_inputs);
+
         Ok(P(FnDecl {
             inputs: fn_inputs,
             output: self.parse_ret_ty(true)?,
@@ -6405,7 +5600,7 @@ impl<'a> Parser<'a> {
         Ok((id, generics))
     }
 
-    fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
+    fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
                attrs: Vec<Attribute>) -> P<Item> {
         P(Item {
             ident,
@@ -6436,10 +5631,9 @@ impl<'a> Parser<'a> {
 
     /// Returns `true` if we are looking at `const ID`
     /// (returns `false` for things like `const fn`, etc.).
-    fn is_const_item(&mut self) -> bool {
-        self.token.is_keyword(keywords::Const) &&
-            !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
-            !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
+    fn is_const_item(&self) -> bool {
+        self.token.is_keyword(kw::Const) &&
+            !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
     }
 
     /// Parses all the "front matter" for a `fn` declaration, up to
@@ -6458,22 +5652,30 @@ impl<'a> Parser<'a> {
             Abi
         )>
     {
-        let is_const_fn = self.eat_keyword(keywords::Const);
+        let is_const_fn = self.eat_keyword(kw::Const);
         let const_span = self.prev_span;
-        let unsafety = self.parse_unsafety();
         let asyncness = self.parse_asyncness();
+        if let IsAsync::Async { .. } = asyncness {
+            self.ban_async_in_2015(self.prev_span);
+        }
         let asyncness = respan(self.prev_span, asyncness);
+        let unsafety = self.parse_unsafety();
         let (constness, unsafety, abi) = if is_const_fn {
             (respan(const_span, Constness::Const), unsafety, Abi::Rust)
         } else {
-            let abi = if self.eat_keyword(keywords::Extern) {
+            let abi = if self.eat_keyword(kw::Extern) {
                 self.parse_opt_abi()?.unwrap_or(Abi::C)
             } else {
                 Abi::Rust
             };
             (respan(self.prev_span, Constness::NotConst), unsafety, abi)
         };
-        self.expect_keyword(keywords::Fn)?;
+        if !self.eat_keyword(kw::Fn) {
+            // It is possible for `expect_one_of` to recover given the contents of
+            // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
+            // account for this.
+            if !self.expect_one_of(&[], &[])? { unreachable!() }
+        }
         Ok((constness, unsafety, asyncness, abi))
     }
 
@@ -6499,20 +5701,20 @@ impl<'a> Parser<'a> {
     fn parse_impl_item_(&mut self,
                         at_end: &mut bool,
                         mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
-        let lo = self.span;
+        let lo = self.token.span;
         let vis = self.parse_visibility(false)?;
         let defaultness = self.parse_defaultness();
         let (name, node, generics) = if let Some(type_) = self.eat_type() {
             let (name, alias, generics) = type_?;
             let kind = match alias {
-                AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
-                AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
+                AliasKind::Weak(typ) => ast::ImplItemKind::TyAlias(typ),
+                AliasKind::OpaqueTy(bounds) => ast::ImplItemKind::OpaqueTy(bounds),
             };
             (name, kind, generics)
         } else if self.is_const_item() {
             // This parses the grammar:
             //     ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
-            self.expect_keyword(keywords::Const)?;
+            self.expect_keyword(kw::Const)?;
             let name = self.parse_ident()?;
             self.expect(&token::Colon)?;
             let typ = self.parse_ty()?;
@@ -6539,15 +5741,11 @@ impl<'a> Parser<'a> {
         })
     }
 
-    fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) {
+    fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
         match *vis {
             VisibilityKind::Inherited => {}
             _ => {
-                let is_macro_rules: bool = match self.token {
-                    token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
-                    _ => false,
-                };
-                let mut err = if is_macro_rules {
+                let mut err = 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(
@@ -6568,7 +5766,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span)
+    fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
                                    -> DiagnosticBuilder<'a>
     {
         let expected_kinds = if item_type == "extern" {
@@ -6602,13 +5800,15 @@ impl<'a> Parser<'a> {
         // code copied from parse_macro_use_or_failure... abstraction!
         if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
             // method macro
-            Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
+            Ok((Ident::invalid(), vec![], ast::Generics::default(),
                 ast::ImplItemKind::Macro(mac)))
         } else {
             let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
             let ident = self.parse_ident()?;
             let mut generics = self.parse_generics()?;
-            let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
+            let decl = self.parse_fn_decl_with_self(|p| {
+                p.parse_arg_general(true, false, |_| true)
+            })?;
             generics.where_clause = self.parse_where_clause()?;
             *at_end = true;
             let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
@@ -6656,6 +5856,23 @@ impl<'a> Parser<'a> {
             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),
@@ -6693,7 +5910,7 @@ impl<'a> Parser<'a> {
              self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
                 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
                                        t == &token::Colon || t == &token::Eq) ||
-             self.look_ahead(1, |t| t.is_keyword(keywords::Const)))
+            self.is_keyword_ahead(1, &[kw::Const]))
     }
 
     fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
@@ -6743,16 +5960,24 @@ impl<'a> Parser<'a> {
         };
 
         // Parse both types and traits as a type, then reinterpret if necessary.
-        let ty_first = self.parse_ty()?;
+        let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
+        let ty_first = if self.token.is_keyword(kw::For) &&
+                          self.look_ahead(1, |t| t != &token::Lt) {
+            let span = self.prev_span.between(self.token.span);
+            self.struct_span_err(span, "missing trait in a trait impl").emit();
+            P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
+        } else {
+            self.parse_ty()?
+        };
 
         // If `for` is missing we try to recover.
-        let has_for = self.eat_keyword(keywords::For);
-        let missing_for_span = self.prev_span.between(self.span);
+        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(P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID }))
+            Some(DummyResult::raw_ty(self.prev_span, true))
         } else if has_for || self.token.can_begin_type() {
             Some(self.parse_ty()?)
         } else {
@@ -6782,7 +6007,7 @@ impl<'a> Parser<'a> {
                     TyKind::Path(None, path) => path,
                     _ => {
                         self.span_err(ty_first.span, "expected a trait, found type");
-                        ast::Path::from_ident(Ident::new(keywords::Invalid.name(), ty_first.span))
+                        err_path(ty_first.span)
                     }
                 };
                 let trait_ref = TraitRef { path, ref_id: ty_first.id };
@@ -6797,11 +6022,11 @@ impl<'a> Parser<'a> {
             }
         };
 
-        Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
+        Ok((Ident::invalid(), item_kind, Some(attrs)))
     }
 
     fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
-        if self.eat_keyword(keywords::For) {
+        if self.eat_keyword(kw::For) {
             self.expect_lt()?;
             let params = self.parse_generic_params()?;
             self.expect_gt()?;
@@ -6833,21 +6058,23 @@ impl<'a> Parser<'a> {
         // Otherwise if we look ahead and see a paren we parse a tuple-style
         // struct.
 
-        let vdata = if self.token.is_keyword(keywords::Where) {
+        let vdata = if self.token.is_keyword(kw::Where) {
             generics.where_clause = self.parse_where_clause()?;
             if self.eat(&token::Semi) {
                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
                 VariantData::Unit(ast::DUMMY_NODE_ID)
             } else {
                 // If we see: `struct Foo<T> where T: Copy { ... }`
-                VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
+                let (fields, recovered) = self.parse_record_struct_body()?;
+                VariantData::Struct(fields, recovered)
             }
         // No `where` so: `struct Foo<T>;`
         } else if self.eat(&token::Semi) {
             VariantData::Unit(ast::DUMMY_NODE_ID)
         // Record-style struct definition
         } else if self.token == token::OpenDelim(token::Brace) {
-            VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
         // Tuple-style struct definition with optional where-clause.
         } else if self.token == token::OpenDelim(token::Paren) {
             let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
@@ -6860,7 +6087,7 @@ impl<'a> Parser<'a> {
                 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
                 token_str
             ));
-            err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
+            err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
             return Err(err);
         };
 
@@ -6873,48 +6100,34 @@ impl<'a> Parser<'a> {
 
         let mut generics = self.parse_generics()?;
 
-        let vdata = if self.token.is_keyword(keywords::Where) {
+        let vdata = if self.token.is_keyword(kw::Where) {
             generics.where_clause = self.parse_where_clause()?;
-            VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
         } else if self.token == token::OpenDelim(token::Brace) {
-            VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
+            let (fields, recovered) = self.parse_record_struct_body()?;
+            VariantData::Struct(fields, recovered)
         } else {
             let token_str = self.this_token_descr();
             let mut err = self.fatal(&format!(
                 "expected `where` or `{{` after union name, found {}", token_str));
-            err.span_label(self.span, "expected `where` or `{` after union name");
+            err.span_label(self.token.span, "expected `where` or `{` after union name");
             return Err(err);
         };
 
         Ok((class_name, ItemKind::Union(vdata, generics), None))
     }
 
-    fn consume_block(&mut self, delim: token::DelimToken) {
-        let mut brace_depth = 0;
-        loop {
-            if self.eat(&token::OpenDelim(delim)) {
-                brace_depth += 1;
-            } else if self.eat(&token::CloseDelim(delim)) {
-                if brace_depth == 0 {
-                    return;
-                } else {
-                    brace_depth -= 1;
-                    continue;
-                }
-            } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
-                return;
-            } else {
-                self.bump();
-            }
-        }
-    }
-
-    fn parse_record_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
+    fn parse_record_struct_body(
+        &mut self,
+    ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
         let mut fields = Vec::new();
+        let mut recovered = false;
         if self.eat(&token::OpenDelim(token::Brace)) {
             while self.token != token::CloseDelim(token::Brace) {
                 let field = self.parse_struct_decl_field().map_err(|e| {
                     self.recover_stmt();
+                    recovered = true;
                     e
                 });
                 match field {
@@ -6929,36 +6142,30 @@ impl<'a> Parser<'a> {
             let token_str = self.this_token_descr();
             let mut err = self.fatal(&format!(
                     "expected `where`, or `{{` after struct name, found {}", token_str));
-            err.span_label(self.span, "expected `where`, or `{` after struct name");
+            err.span_label(self.token.span, "expected `where`, or `{` after struct name");
             return Err(err);
         }
 
-        Ok(fields)
+        Ok((fields, recovered))
     }
 
     fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
         // This is the case where we find `struct Foo<T>(T) where T: Copy;`
         // Unit like structs are handled in parse_item_struct function
-        let fields = self.parse_unspanned_seq(
-            &token::OpenDelim(token::Paren),
-            &token::CloseDelim(token::Paren),
-            SeqSep::trailing_allowed(token::Comma),
-            |p| {
-                let attrs = p.parse_outer_attributes()?;
-                let lo = p.span;
-                let vis = p.parse_visibility(true)?;
-                let ty = p.parse_ty()?;
-                Ok(StructField {
-                    span: lo.to(ty.span),
-                    vis,
-                    ident: None,
-                    id: ast::DUMMY_NODE_ID,
-                    ty,
-                    attrs,
-                })
-            })?;
-
-        Ok(fields)
+        self.parse_paren_comma_seq(|p| {
+            let attrs = p.parse_outer_attributes()?;
+            let lo = p.token.span;
+            let vis = p.parse_visibility(true)?;
+            let ty = p.parse_ty()?;
+            Ok(StructField {
+                span: lo.to(ty.span),
+                vis,
+                ident: None,
+                id: ast::DUMMY_NODE_ID,
+                ty,
+                attrs,
+            })
+        }).map(|(r, _)| r)
     }
 
     /// Parses a structure field declaration.
@@ -6972,14 +6179,14 @@ impl<'a> Parser<'a> {
         if self.token == token::Comma {
             seen_comma = true;
         }
-        match self.token {
+        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.span, Error::UselessDocComment);
+                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
@@ -7026,7 +6233,7 @@ impl<'a> Parser<'a> {
     /// Parses an element of a struct declaration.
     fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
         let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
+        let lo = self.token.span;
         let vis = self.parse_visibility(false)?;
         self.parse_single_struct_field(lo, vis, attrs)
     }
@@ -7039,17 +6246,17 @@ impl<'a> Parser<'a> {
     pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |x| x);
 
-        self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
+        self.expected_tokens.push(TokenType::Keyword(kw::Crate));
         if self.is_crate_vis() {
             self.bump(); // `crate`
             return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
         }
 
-        if !self.eat_keyword(keywords::Pub) {
+        if !self.eat_keyword(kw::Pub) {
             // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
             // keyword to grab a span from for inherited visibility; an empty span at the
             // beginning of the current token would seem to be the "Schelling span".
-            return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
+            return Ok(respan(self.token.span.shrink_to_lo(), VisibilityKind::Inherited))
         }
         let lo = self.prev_span;
 
@@ -7058,7 +6265,9 @@ impl<'a> Parser<'a> {
             // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
             // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
             // by the following tokens.
-            if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) {
+            if self.is_keyword_ahead(1, &[kw::Crate]) &&
+                self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
+            {
                 // `pub(crate)`
                 self.bump(); // `(`
                 self.bump(); // `crate`
@@ -7068,7 +6277,7 @@ impl<'a> Parser<'a> {
                     VisibilityKind::Crate(CrateSugar::PubCrate),
                 );
                 return Ok(vis)
-            } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
+            } else if self.is_keyword_ahead(1, &[kw::In]) {
                 // `pub(in path)`
                 self.bump(); // `(`
                 self.bump(); // `in`
@@ -7080,8 +6289,7 @@ impl<'a> Parser<'a> {
                 });
                 return Ok(vis)
             } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
-                      self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
-                                             t.is_keyword(keywords::SelfLower))
+                      self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
             {
                 // `pub(self)` or `pub(super)`
                 self.bump(); // `(`
@@ -7101,15 +6309,18 @@ impl<'a> Parser<'a> {
 `pub(super)`: visible only in the current module's parent
 `pub(in path::to::module)`: visible only on the specified path"##;
                 let path = self.parse_path(PathStyle::Mod)?;
-                let sp = self.prev_span;
+                let sp = path.span;
                 let help_msg = format!("make this visible only to module `{}` with `in`", path);
                 self.expect(&token::CloseDelim(token::Paren))?;  // `)`
-                let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
-                err.help(suggestion);
-                err.span_suggestion(
-                    sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
-                );
-                err.emit();  // emit diagnostic, but continue with public visibility
+                struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg)
+                    .help(suggestion)
+                    .span_suggestion(
+                        sp,
+                        &help_msg,
+                        format!("in {}", path),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();  // emit diagnostic, but continue with public visibility
             }
         }
 
@@ -7119,14 +6330,17 @@ impl<'a> Parser<'a> {
     /// Parses defaultness (i.e., `default` or nothing).
     fn parse_defaultness(&mut self) -> Defaultness {
         // `pub` is included for better error messages
-        if self.check_keyword(keywords::Default) &&
-           self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
-                                  t.is_keyword(keywords::Const) ||
-                                  t.is_keyword(keywords::Fn) ||
-                                  t.is_keyword(keywords::Unsafe) ||
-                                  t.is_keyword(keywords::Extern) ||
-                                  t.is_keyword(keywords::Type) ||
-                                  t.is_keyword(keywords::Pub)) {
+        if self.check_keyword(kw::Default) &&
+            self.is_keyword_ahead(1, &[
+                kw::Impl,
+                kw::Const,
+                kw::Fn,
+                kw::Unsafe,
+                kw::Extern,
+                kw::Type,
+                kw::Pub,
+            ])
+        {
             self.bump(); // `default`
             Defaultness::Default
         } else {
@@ -7134,39 +6348,8 @@ impl<'a> Parser<'a> {
         }
     }
 
-    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.node {
-                    // 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
-        }
-    }
-
     /// Given a termination token, parses all of the items in a module.
-    fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
+    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);
@@ -7177,12 +6360,12 @@ impl<'a> Parser<'a> {
             let token_str = self.this_token_descr();
             if !self.maybe_consume_incorrect_semicolon(&items) {
                 let mut err = self.fatal(&format!("expected item, found {}", token_str));
-                err.span_label(self.span, "expected item");
+                err.span_label(self.token.span, "expected item");
                 return Err(err);
             }
         }
 
-        let hi = if self.span.is_dummy() {
+        let hi = if self.token.span.is_dummy() {
             inner_lo
         } else {
             self.prev_span
@@ -7221,7 +6404,7 @@ impl<'a> Parser<'a> {
             (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
         };
 
-        let id_span = self.span;
+        let id_span = self.token.span;
         let id = self.parse_ident()?;
         if self.eat(&token::Semi) {
             if in_cfg && self.recurse_into_file_modules {
@@ -7232,21 +6415,15 @@ impl<'a> Parser<'a> {
                     self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
                 // Record that we fetched the mod from an external file
                 if warn {
-                    let attr = Attribute {
-                        id: attr::mk_attr_id(),
-                        style: ast::AttrStyle::Outer,
-                        path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")),
-                        tokens: TokenStream::empty(),
-                        is_sugared_doc: false,
-                        span: syntax_pos::DUMMY_SP,
-                    };
+                    let attr = attr::mk_attr_outer(
+                        attr::mk_word_item(Ident::with_empty_ctxt(sym::warn_directory_ownership)));
                     attr::mark_known(&attr);
                     attrs.push(attr);
                 }
                 Ok((id, ItemKind::Mod(module), Some(attrs)))
             } else {
                 let placeholder = ast::Mod {
-                    inner: syntax_pos::DUMMY_SP,
+                    inner: DUMMY_SP,
                     items: Vec::new(),
                     inline: false
                 };
@@ -7257,7 +6434,7 @@ impl<'a> Parser<'a> {
             self.push_directory(id, &outer_attrs);
 
             self.expect(&token::OpenDelim(token::Brace))?;
-            let mod_inner_lo = self.span;
+            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)?;
 
@@ -7267,7 +6444,7 @@ impl<'a> Parser<'a> {
     }
 
     fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
-        if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") {
+        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 {
@@ -7287,7 +6464,7 @@ impl<'a> Parser<'a> {
     }
 
     pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
-        if let Some(s) = attr::first_attr_value_str_by_name(attrs, "path") {
+        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
@@ -7446,12 +6623,13 @@ impl<'a> Parser<'a> {
     }
 
     /// Reads a module from a source file.
-    fn eval_src_mod(&mut self,
-                    path: PathBuf,
-                    directory_ownership: DirectoryOwnership,
-                    name: String,
-                    id_sp: Span)
-                    -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
+    fn eval_src_mod(
+        &mut self,
+        path: PathBuf,
+        directory_ownership: DirectoryOwnership,
+        name: String,
+        id_sp: Span,
+    ) -> PResult<'a, (ast::Mod, Vec<Attribute>)> {
         let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
         if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
             let mut err = String::from("circular modules: ");
@@ -7469,7 +6647,7 @@ impl<'a> Parser<'a> {
         let mut p0 =
             new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
         p0.cfg_mods = self.cfg_mods;
-        let mod_inner_lo = p0.span;
+        let mod_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;
@@ -7478,15 +6656,20 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a function declaration from a foreign module.
-    fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
-                             -> PResult<'a, ForeignItem> {
-        self.expect_keyword(keywords::Fn)?;
+    fn parse_item_foreign_fn(
+        &mut self,
+        vis: ast::Visibility,
+        lo: Span,
+        attrs: Vec<Attribute>,
+        extern_sp: Span,
+    ) -> PResult<'a, ForeignItem> {
+        self.expect_keyword(kw::Fn)?;
 
         let (ident, mut generics) = self.parse_fn_header()?;
         let decl = self.parse_fn_decl(true)?;
         generics.where_clause = self.parse_where_clause()?;
-        let hi = self.span;
-        self.expect(&token::Semi)?;
+        let hi = self.token.span;
+        self.parse_semi_or_incorrect_foreign_fn_body(&ident, extern_sp)?;
         Ok(ast::ForeignItem {
             ident,
             attrs,
@@ -7501,11 +6684,11 @@ impl<'a> Parser<'a> {
     /// 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.eat_keyword(keywords::Mut);
+        let mutbl = self.parse_mutability();
         let ident = self.parse_ident()?;
         self.expect(&token::Colon)?;
         let ty = self.parse_ty()?;
-        let hi = self.span;
+        let hi = self.token.span;
         self.expect(&token::Semi)?;
         Ok(ForeignItem {
             ident,
@@ -7520,18 +6703,18 @@ impl<'a> Parser<'a> {
     /// Parses a type from a foreign module.
     fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
                              -> PResult<'a, ForeignItem> {
-        self.expect_keyword(keywords::Type)?;
+        self.expect_keyword(kw::Type)?;
 
         let ident = self.parse_ident()?;
-        let hi = self.span;
+        let hi = self.token.span;
         self.expect(&token::Semi)?;
         Ok(ast::ForeignItem {
-            ident: ident,
-            attrs: attrs,
+            ident,
+            attrs,
             node: ForeignItemKind::Ty,
             id: ast::DUMMY_NODE_ID,
             span: lo.to(hi),
-            vis: vis
+            vis
         })
     }
 
@@ -7539,7 +6722,7 @@ impl<'a> Parser<'a> {
         let error_msg = "crate name using dashes are not valid in `extern crate` statements";
         let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
                               in the code";
-        let mut ident = if self.token.is_keyword(keywords::SelfLower) {
+        let mut ident = if self.token.is_keyword(kw::SelfLower) {
             self.parse_path_segment_ident()
         } else {
             self.parse_ident()
@@ -7548,7 +6731,7 @@ impl<'a> Parser<'a> {
         let mut replacement = vec![];
         let mut fixed_crate_name = false;
         // Accept `extern crate name-like-this` for better diagnostics
-        let dash = token::Token::BinOp(token::BinOpToken::Minus);
+        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;
@@ -7564,14 +6747,10 @@ impl<'a> Parser<'a> {
             }
             ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
 
-            let mut err = self.struct_span_err(fixed_name_sp, error_msg);
-            err.span_label(fixed_name_sp, "dash-separated idents are not valid");
-            err.multipart_suggestion(
-                suggestion_msg,
-                replacement,
-                Applicability::MachineApplicable,
-            );
-            err.emit();
+            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)
     }
@@ -7613,12 +6792,14 @@ impl<'a> Parser<'a> {
     /// extern "C" {}
     /// extern {}
     /// ```
-    fn parse_item_foreign_mod(&mut self,
-                              lo: Span,
-                              opt_abi: Option<Abi>,
-                              visibility: Visibility,
-                              mut attrs: Vec<Attribute>)
-                              -> PResult<'a, P<Item>> {
+    fn parse_item_foreign_mod(
+        &mut self,
+        lo: Span,
+        opt_abi: Option<Abi>,
+        visibility: Visibility,
+        mut attrs: Vec<Attribute>,
+        extern_sp: Span,
+    ) -> PResult<'a, P<Item>> {
         self.expect(&token::OpenDelim(token::Brace))?;
 
         let abi = opt_abi.unwrap_or(Abi::C);
@@ -7627,7 +6808,7 @@ impl<'a> Parser<'a> {
 
         let mut foreign_items = vec![];
         while !self.eat(&token::CloseDelim(token::Brace)) {
-            foreign_items.push(self.parse_foreign_item()?);
+            foreign_items.push(self.parse_foreign_item(extern_sp)?);
         }
 
         let prev_span = self.prev_span;
@@ -7635,44 +6816,33 @@ impl<'a> Parser<'a> {
             abi,
             items: foreign_items
         };
-        let invalid = keywords::Invalid.ident();
+        let invalid = Ident::invalid();
         Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
     }
 
-    /// Parses `type Foo = Bar;`
-    /// or
-    /// `existential type Foo: Bar;`
-    /// or
-    /// `return `None``
+    /// Parses `type Foo = Bar;` or returns `None`
     /// without modifying the parser state.
     fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
         // This parses the grammar:
         //     Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
-        if self.check_keyword(keywords::Type) ||
-           self.check_keyword(keywords::Existential) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
-            let existential = self.eat_keyword(keywords::Existential);
-            assert!(self.eat_keyword(keywords::Type));
-            Some(self.parse_existential_or_alias(existential))
+        if self.eat_keyword(kw::Type) {
+            Some(self.parse_type_alias())
         } else {
             None
         }
     }
 
-    /// Parses a type alias or existential type.
-    fn parse_existential_or_alias(
-        &mut self,
-        existential: bool,
-    ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
+    /// Parses a type alias or opaque type.
+    fn parse_type_alias(&mut self) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
         let ident = self.parse_ident()?;
         let mut tps = self.parse_generics()?;
         tps.where_clause = self.parse_where_clause()?;
-        let alias = if existential {
-            self.expect(&token::Colon)?;
+        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::Existential(bounds)
+            AliasKind::OpaqueTy(bounds)
         } else {
-            self.expect(&token::Eq)?;
             let ty = self.parse_ty()?;
             AliasKind::Weak(ty)
         };
@@ -7683,58 +6853,61 @@ impl<'a> Parser<'a> {
     /// Parses the part of an enum declaration following the `{`.
     fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
         let mut variants = Vec::new();
-        let mut all_nullary = true;
-        let mut any_disr = vec![];
         while self.token != token::CloseDelim(token::Brace) {
             let variant_attrs = self.parse_outer_attributes()?;
-            let vlo = self.span;
+            let vlo = self.token.span;
 
-            let struct_def;
-            let mut disr_expr = None;
+            self.eat_bad_pub();
             let ident = self.parse_ident()?;
-            if self.check(&token::OpenDelim(token::Brace)) {
+
+            let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
                 // Parse a struct variant.
-                all_nullary = false;
-                struct_def = VariantData::Struct(self.parse_record_struct_body()?,
-                                                 ast::DUMMY_NODE_ID);
+                let (fields, recovered) = self.parse_record_struct_body()?;
+                VariantData::Struct(fields, recovered)
             } else if self.check(&token::OpenDelim(token::Paren)) {
-                all_nullary = false;
-                struct_def = VariantData::Tuple(self.parse_tuple_struct_body()?,
-                                                ast::DUMMY_NODE_ID);
-            } else if self.eat(&token::Eq) {
-                disr_expr = Some(AnonConst {
+                VariantData::Tuple(
+                    self.parse_tuple_struct_body()?,
+                    ast::DUMMY_NODE_ID,
+                )
+            } else {
+                VariantData::Unit(ast::DUMMY_NODE_ID)
+            };
+
+            let disr_expr = if self.eat(&token::Eq) {
+                Some(AnonConst {
                     id: ast::DUMMY_NODE_ID,
                     value: self.parse_expr()?,
-                });
-                if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
-                    any_disr.push(sp);
-                }
-                struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
+                })
             } else {
-                struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
-            }
+                None
+            };
 
             let vr = ast::Variant_ {
                 ident,
+                id: ast::DUMMY_NODE_ID,
                 attrs: variant_attrs,
                 data: struct_def,
                 disr_expr,
             };
             variants.push(respan(vlo.to(self.prev_span), vr));
 
-            if !self.eat(&token::Comma) { break; }
-        }
-        self.expect(&token::CloseDelim(token::Brace))?;
-        if !any_disr.is_empty() && !all_nullary {
-            let mut err =self.struct_span_err(
-                any_disr.clone(),
-                "discriminator values can only be used with a field-less enum",
-            );
-            for sp in any_disr {
-                err.span_label(sp, "only valid in field-less enums");
+            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;
+                }
             }
-            err.emit();
         }
+        self.expect(&token::CloseDelim(token::Brace))?;
 
         Ok(ast::EnumDef { variants })
     }
@@ -7757,24 +6930,26 @@ impl<'a> Parser<'a> {
     /// Parses a string as an ABI spec on an extern type or module. Consumes
     /// the `extern` keyword, if one is found.
     fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
-        match self.token {
-            token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
-                let sp = self.span;
-                self.expect_no_suffix(sp, "ABI spec", suf);
+        match self.token.kind {
+            token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
+            token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
+                let sp = self.token.span;
+                self.expect_no_suffix(sp, "an ABI spec", suffix);
                 self.bump();
-                match abi::lookup(&s.as_str()) {
+                match abi::lookup(&symbol.as_str()) {
                     Some(abi) => Ok(Some(abi)),
                     None => {
                         let prev_span = self.prev_span;
-                        let mut err = struct_span_err!(
+                        struct_span_err!(
                             self.sess.span_diagnostic,
                             prev_span,
                             E0703,
                             "invalid ABI: found `{}`",
-                            s);
-                        err.span_label(prev_span, "invalid ABI");
-                        err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
-                        err.emit();
+                            symbol
+                        )
+                        .span_label(prev_span, "invalid ABI")
+                        .help(&format!("valid ABIs: {}", abi::all_names().join(", ")))
+                        .emit();
                         Ok(None)
                     }
                 }
@@ -7785,13 +6960,13 @@ impl<'a> Parser<'a> {
     }
 
     fn is_static_global(&mut self) -> bool {
-        if self.check_keyword(keywords::Static) {
+        if self.check_keyword(kw::Static) {
             // Check if this could be a closure
             !self.look_ahead(1, |token| {
-                if token.is_keyword(keywords::Move) {
+                if token.is_keyword(kw::Move) {
                     return true;
                 }
-                match *token {
+                match token.kind {
                     token::BinOp(token::Or) | token::OrOr => true,
                     _ => false,
                 }
@@ -7854,28 +7029,30 @@ impl<'a> Parser<'a> {
             Some(P(item))
         });
 
-        let lo = self.span;
+        let lo = self.token.span;
 
         let visibility = self.parse_visibility(false)?;
 
-        if self.eat_keyword(keywords::Use) {
+        if self.eat_keyword(kw::Use) {
             // USE ITEM
             let item_ = ItemKind::Use(P(self.parse_use_tree()?));
             self.expect(&token::Semi)?;
 
             let span = lo.to(self.prev_span);
-            let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
+            let item =
+                self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
             return Ok(Some(item));
         }
 
-        if self.eat_keyword(keywords::Extern) {
-            if self.eat_keyword(keywords::Crate) {
+        if self.eat_keyword(kw::Extern) {
+            let extern_sp = self.prev_span;
+            if self.eat_keyword(kw::Crate) {
                 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
             }
 
             let opt_abi = self.parse_opt_abi()?;
 
-            if self.eat_keyword(keywords::Fn) {
+            if self.eat_keyword(kw::Fn) {
                 // EXTERN FUNCTION ITEM
                 let fn_span = self.prev_span;
                 let abi = opt_abi.unwrap_or(Abi::C);
@@ -7892,7 +7069,9 @@ impl<'a> Parser<'a> {
                                         maybe_append(attrs, extra_attrs));
                 return Ok(Some(item));
             } else if self.check(&token::OpenDelim(token::Brace)) {
-                return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
+                return Ok(Some(
+                    self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs, extern_sp)?,
+                ));
             }
 
             self.unexpected()?;
@@ -7901,7 +7080,7 @@ impl<'a> Parser<'a> {
         if self.is_static_global() {
             self.bump();
             // STATIC ITEM
-            let m = if self.eat_keyword(keywords::Mut) {
+            let m = if self.eat_keyword(kw::Mut) {
                 Mutability::Mutable
             } else {
                 Mutability::Immutable
@@ -7915,11 +7094,11 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.eat_keyword(keywords::Const) {
+        if self.eat_keyword(kw::Const) {
             let const_span = self.prev_span;
-            if self.check_keyword(keywords::Fn)
-                || (self.check_keyword(keywords::Unsafe)
-                    && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
+            if self.check_keyword(kw::Fn)
+                || (self.check_keyword(kw::Unsafe)
+                    && self.is_keyword_ahead(1, &[kw::Fn])) {
                 // CONST FUNCTION ITEM
                 let unsafety = self.parse_unsafety();
                 self.bump();
@@ -7938,18 +7117,17 @@ impl<'a> Parser<'a> {
             }
 
             // CONST ITEM
-            if self.eat_keyword(keywords::Mut) {
+            if self.eat_keyword(kw::Mut) {
                 let prev_span = self.prev_span;
-                let mut err = self.diagnostic()
-                    .struct_span_err(prev_span, "const globals cannot be mutable");
-                err.span_label(prev_span, "cannot be mutable");
-                err.span_suggestion(
-                    const_span,
-                    "you might want to declare a static instead",
-                    "static".to_owned(),
-                    Applicability::MaybeIncorrect,
-                );
-                err.emit();
+                self.struct_span_err(prev_span, "const globals cannot be mutable")
+                    .span_label(prev_span, "cannot be mutable")
+                    .span_suggestion(
+                        const_span,
+                        "you might want to declare a static instead",
+                        "static".to_owned(),
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
             }
             let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
             let prev_span = self.prev_span;
@@ -7961,55 +7139,45 @@ impl<'a> Parser<'a> {
             return Ok(Some(item));
         }
 
-        // `unsafe async fn` or `async fn`
-        if (
-            self.check_keyword(keywords::Unsafe) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Async))
-        ) || (
-            self.check_keyword(keywords::Async) &&
-            self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
-        )
-        {
-            // ASYNC FUNCTION ITEM
-            let unsafety = self.parse_unsafety();
-            self.expect_keyword(keywords::Async)?;
-            let async_span = self.prev_span;
-            self.expect_keyword(keywords::Fn)?;
-            let fn_span = self.prev_span;
-            let (ident, item_, extra_attrs) =
-                self.parse_item_fn(unsafety,
-                                   respan(async_span, IsAsync::Async {
-                                       closure_id: ast::DUMMY_NODE_ID,
-                                       return_impl_trait_id: ast::DUMMY_NODE_ID,
-                                   }),
-                                   respan(fn_span, Constness::NotConst),
-                                   Abi::Rust)?;
-            let prev_span = self.prev_span;
-            let item = self.mk_item(lo.to(prev_span),
-                                    ident,
-                                    item_,
-                                    visibility,
-                                    maybe_append(attrs, extra_attrs));
-            if self.span.rust_2015() {
-                self.diagnostic().struct_span_err_with_code(
-                    async_span,
-                    "`async fn` is not permitted in the 2015 edition",
-                    DiagnosticId::Error("E0670".into())
-                ).emit();
+        // Parse `async unsafe? fn`.
+        if self.check_keyword(kw::Async) {
+            let async_span = self.token.span;
+            if self.is_keyword_ahead(1, &[kw::Fn])
+                || self.is_keyword_ahead(2, &[kw::Fn])
+            {
+                // ASYNC FUNCTION ITEM
+                self.bump(); // `async`
+                let unsafety = self.parse_unsafety(); // `unsafe`?
+                self.expect_keyword(kw::Fn)?; // `fn`
+                let fn_span = self.prev_span;
+                let (ident, item_, extra_attrs) =
+                    self.parse_item_fn(unsafety,
+                                    respan(async_span, IsAsync::Async {
+                                        closure_id: ast::DUMMY_NODE_ID,
+                                        return_impl_trait_id: ast::DUMMY_NODE_ID,
+                                    }),
+                                    respan(fn_span, Constness::NotConst),
+                                    Abi::Rust)?;
+                let prev_span = self.prev_span;
+                let item = self.mk_item(lo.to(prev_span),
+                                        ident,
+                                        item_,
+                                        visibility,
+                                        maybe_append(attrs, extra_attrs));
+                self.ban_async_in_2015(async_span);
+                return Ok(Some(item));
             }
-            return Ok(Some(item));
         }
-        if self.check_keyword(keywords::Unsafe) &&
-            (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
-            self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
+        if self.check_keyword(kw::Unsafe) &&
+            self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
         {
             // UNSAFE TRAIT ITEM
             self.bump(); // `unsafe`
-            let is_auto = if self.eat_keyword(keywords::Trait) {
+            let is_auto = if self.eat_keyword(kw::Trait) {
                 IsAuto::No
             } else {
-                self.expect_keyword(keywords::Auto)?;
-                self.expect_keyword(keywords::Trait)?;
+                self.expect_keyword(kw::Auto)?;
+                self.expect_keyword(kw::Trait)?;
                 IsAuto::Yes
             };
             let (ident, item_, extra_attrs) =
@@ -8022,23 +7190,21 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.check_keyword(keywords::Impl) ||
-           self.check_keyword(keywords::Unsafe) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
-           self.check_keyword(keywords::Default) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
-           self.check_keyword(keywords::Default) &&
-                self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
+        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(keywords::Impl)?;
+            self.expect_keyword(kw::Impl)?;
             let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
             let span = lo.to(self.prev_span);
             return Ok(Some(self.mk_item(span, ident, item, visibility,
                                         maybe_append(attrs, extra_attrs))));
         }
-        if self.check_keyword(keywords::Fn) {
+        if self.check_keyword(kw::Fn) {
             // FUNCTION ITEM
             self.bump();
             let fn_span = self.prev_span;
@@ -8055,18 +7221,18 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.check_keyword(keywords::Unsafe)
+        if self.check_keyword(kw::Unsafe)
             && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
             // UNSAFE FUNCTION ITEM
             self.bump(); // `unsafe`
             // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
             self.check(&token::OpenDelim(token::Brace));
-            let abi = if self.eat_keyword(keywords::Extern) {
+            let abi = if self.eat_keyword(kw::Extern) {
                 self.parse_opt_abi()?.unwrap_or(Abi::C)
             } else {
                 Abi::Rust
             };
-            self.expect_keyword(keywords::Fn)?;
+            self.expect_keyword(kw::Fn)?;
             let fn_span = self.prev_span;
             let (ident, item_, extra_attrs) =
                 self.parse_item_fn(Unsafety::Unsafe,
@@ -8081,7 +7247,7 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.eat_keyword(keywords::Mod) {
+        if self.eat_keyword(kw::Mod) {
             // MODULE ITEM
             let (ident, item_, extra_attrs) =
                 self.parse_item_mod(&attrs[..])?;
@@ -8097,8 +7263,8 @@ impl<'a> Parser<'a> {
             let (ident, alias, generics) = type_?;
             // TYPE ITEM
             let item_ = match alias {
-                AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
-                AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
+                AliasKind::Weak(ty) => ItemKind::TyAlias(ty, generics),
+                AliasKind::OpaqueTy(bounds) => ItemKind::OpaqueTy(bounds, generics),
             };
             let prev_span = self.prev_span;
             let item = self.mk_item(lo.to(prev_span),
@@ -8108,7 +7274,7 @@ impl<'a> Parser<'a> {
                                     attrs);
             return Ok(Some(item));
         }
-        if self.eat_keyword(keywords::Enum) {
+        if self.eat_keyword(kw::Enum) {
             // ENUM ITEM
             let (ident, item_, extra_attrs) = self.parse_item_enum()?;
             let prev_span = self.prev_span;
@@ -8119,15 +7285,15 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.check_keyword(keywords::Trait)
-            || (self.check_keyword(keywords::Auto)
-                && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
+        if self.check_keyword(kw::Trait)
+            || (self.check_keyword(kw::Auto)
+                && self.is_keyword_ahead(1, &[kw::Trait]))
         {
-            let is_auto = if self.eat_keyword(keywords::Trait) {
+            let is_auto = if self.eat_keyword(kw::Trait) {
                 IsAuto::No
             } else {
-                self.expect_keyword(keywords::Auto)?;
-                self.expect_keyword(keywords::Trait)?;
+                self.expect_keyword(kw::Auto)?;
+                self.expect_keyword(kw::Trait)?;
                 IsAuto::Yes
             };
             // TRAIT ITEM
@@ -8141,7 +7307,7 @@ impl<'a> Parser<'a> {
                                     maybe_append(attrs, extra_attrs));
             return Ok(Some(item));
         }
-        if self.eat_keyword(keywords::Struct) {
+        if self.eat_keyword(kw::Struct) {
             // STRUCT ITEM
             let (ident, item_, extra_attrs) = self.parse_item_struct()?;
             let prev_span = self.prev_span;
@@ -8178,9 +7344,9 @@ impl<'a> Parser<'a> {
             //
             //     pub   S {}
             //        ^^^ `sp` points here
-            let sp = self.prev_span.between(self.span);
-            let full_sp = self.prev_span.to(self.span);
-            let ident_sp = self.span;
+            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();
@@ -8195,7 +7361,9 @@ impl<'a> Parser<'a> {
             } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
                 let ident = self.parse_ident().unwrap();
                 self.bump();  // `(`
-                let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
+                let kw_name = if let Ok(Some(_)) = self.parse_self_arg_with_attrs()
+                    .map_err(|mut e| e.cancel())
+                {
                     "method"
                 } else {
                     "function"
@@ -8214,11 +7382,11 @@ impl<'a> Parser<'a> {
                 } else {
                     ("fn` or `struct", "function or struct", true)
                 };
-                self.consume_block(token::Brace);
 
                 let msg = format!("missing `{}` for {} definition", kw, kw_name);
                 let mut err = self.diagnostic().struct_span_err(sp, &msg);
                 if !ambiguous {
+                    self.consume_block(token::Brace);
                     let suggestion = format!("add `{}` here to parse `{}` as a public {}",
                                              kw,
                                              ident,
@@ -8227,7 +7395,7 @@ impl<'a> Parser<'a> {
                         sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
                     );
                 } else {
-                    if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
+                    if let Ok(snippet) = self.span_to_snippet(ident_sp) {
                         err.span_suggestion(
                             full_sp,
                             "if you meant to call a macro, try",
@@ -8246,7 +7414,9 @@ impl<'a> Parser<'a> {
                 self.eat_to_tokens(&[&token::Gt]);
                 self.bump();  // `>`
                 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
-                    if let Ok(Some(_)) = self.parse_self_arg() {
+                    if let Ok(Some(_)) = self.parse_self_arg_with_attrs()
+                        .map_err(|mut e| e.cancel())
+                    {
                         ("fn", "method", false)
                     } else {
                         ("fn", "function", false)
@@ -8272,22 +7442,35 @@ impl<'a> Parser<'a> {
         self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
     }
 
+    /// 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();
+        }
+    }
+
     /// Parses a foreign item.
-    crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
+    crate fn parse_foreign_item(&mut self, extern_sp: Span) -> PResult<'a, ForeignItem> {
         maybe_whole!(self, NtForeignItem, |ni| ni);
 
         let attrs = self.parse_outer_attributes()?;
-        let lo = self.span;
+        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(keywords::Static) || self.token.is_keyword(keywords::Const) {
-            if self.token.is_keyword(keywords::Const) {
+        if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
+            if self.token.is_keyword(kw::Const) {
                 self.diagnostic()
-                    .struct_span_err(self.span, "extern items cannot be `const`")
+                    .struct_span_err(self.token.span, "extern items cannot be `const`")
                     .span_suggestion(
-                        self.span,
+                        self.token.span,
                         "try using a static value",
                         "static".to_owned(),
                         Applicability::MachineApplicable
@@ -8297,11 +7480,11 @@ impl<'a> Parser<'a> {
             return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
         }
         // FOREIGN FUNCTION ITEM
-        if self.check_keyword(keywords::Fn) {
-            return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
+        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(keywords::Type) {
+        if self.check_keyword(kw::Type) {
             return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
         }
 
@@ -8309,7 +7492,7 @@ impl<'a> Parser<'a> {
             Some(mac) => {
                 Ok(
                     ForeignItem {
-                        ident: keywords::Invalid.ident(),
+                        ident: Ident::invalid(),
                         span: lo.to(self.prev_span),
                         id: ast::DUMMY_NODE_ID,
                         attrs,
@@ -8338,40 +7521,31 @@ impl<'a> Parser<'a> {
         visibility: Visibility
     ) -> PResult<'a, Option<P<Item>>> {
         if macros_allowed && self.token.is_path_start() &&
-                !(self.is_async_fn() && self.span.rust_2015()) {
+                !(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.span;
+            let mac_lo = self.token.span;
 
             // item macro.
-            let pth = self.parse_path(PathStyle::Mod)?;
+            let path = self.parse_path(PathStyle::Mod)?;
             self.expect(&token::Not)?;
-
-            // a 'special' identifier (like what `macro_rules!` uses)
-            // is optional. We should eventually unify invoc syntax
-            // and remove this.
-            let id = if self.token.is_ident() {
-                self.parse_ident()?
-            } else {
-                keywords::Invalid.ident() // no special identifier
-            };
-            // eat a matched-delimiter token tree:
             let (delim, tts) = self.expect_delimited_token_tree()?;
-            if delim != MacDelimiter::Brace {
-                if !self.eat(&token::Semi) {
-                    self.span_err(self.prev_span,
-                                  "macros that expand to items must either \
-                                   be surrounded with braces or followed by \
-                                   a semicolon");
-                }
+            if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
+                self.report_invalid_macro_expansion_item();
             }
 
             let hi = self.prev_span;
-            let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
-            let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
+            let mac = respan(mac_lo.to(hi), Mac_ {
+                path,
+                tts,
+                delim,
+                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));
         }
 
@@ -8394,12 +7568,12 @@ impl<'a> Parser<'a> {
                                at_end: &mut bool) -> PResult<'a, Option<Mac>>
     {
         if self.token.is_path_start() &&
-                !(self.is_async_fn() && self.span.rust_2015()) {
+                !(self.is_async_fn() && self.token.span.rust_2015()) {
             let prev_span = self.prev_span;
-            let lo = self.span;
-            let pth = self.parse_path(PathStyle::Mod)?;
+            let lo = self.token.span;
+            let path = self.parse_path(PathStyle::Mod)?;
 
-            if pth.segments.len() == 1 {
+            if path.segments.len() == 1 {
                 if !self.eat(&token::Not) {
                     return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
                 }
@@ -8419,7 +7593,12 @@ impl<'a> Parser<'a> {
                 self.expect(&token::Semi)?;
             }
 
-            Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
+            Ok(Some(respan(lo.to(self.prev_span), Mac_ {
+                path,
+                tts,
+                delim,
+                prior_type_ascription: self.last_type_ascription,
+            })))
         } else {
             Ok(None)
         }
@@ -8432,7 +7611,7 @@ impl<'a> Parser<'a> {
         let mut tokens = Vec::new();
         let prev_collecting = match self.token_cursor.frame.last_token {
             LastToken::Collecting(ref mut list) => {
-                Some(mem::replace(list, Vec::new()))
+                Some(mem::take(list))
             }
             LastToken::Was(ref mut last) => {
                 tokens.extend(last.take());
@@ -8444,14 +7623,27 @@ impl<'a> Parser<'a> {
         let ret = f(self);
         let last_token = if self.token_cursor.stack.len() == prev {
             &mut self.token_cursor.frame.last_token
+        } else if self.token_cursor.stack.get(prev).is_none() {
+            // This can happen due to a bad interaction of two unrelated recovery mechanisms with
+            // mismatched delimiters *and* recovery lookahead on the likely typo `pub ident(`
+            // (#62881).
+            return Ok((ret?, TokenStream::new(vec![])));
         } else {
             &mut self.token_cursor.stack[prev].last_token
         };
 
         // Pull out the tokens that we've collected from the call to `f` above.
         let mut collected_tokens = match *last_token {
-            LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
-            LastToken::Was(_) => panic!("our vector went away?"),
+            LastToken::Collecting(ref mut v) => mem::take(v),
+            LastToken::Was(ref was) => {
+                let msg = format!("our vector went away? - found Was({:?})", was);
+                debug!("collect_tokens: {}", msg);
+                self.sess.span_diagnostic.delay_span_bug(self.token.span, &msg);
+                // This can happen due to a bad interaction of two unrelated recovery mechanisms
+                // with mismatched delimiters *and* recovery lookahead on the likely typo
+                // `pub ident(` (#62895, different but similar to the case above).
+                return Ok((ret?, TokenStream::new(vec![])));
+            }
         };
 
         // If we're not at EOF our current token wasn't actually consumed by
@@ -8503,14 +7695,14 @@ impl<'a> Parser<'a> {
     ///            PATH [`as` IDENT]
     /// ```
     fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
-        let lo = self.span;
+        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.span.ctxt();
+            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))
@@ -8546,15 +7738,12 @@ impl<'a> Parser<'a> {
     /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
     /// ```
     fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
-        self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
-                                 &token::CloseDelim(token::Brace),
-                                 SeqSep::trailing_allowed(token::Comma), |this| {
-            Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
-        })
+        self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, ast::DUMMY_NODE_ID)))
+            .map(|(r, _)| r)
     }
 
     fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
-        if self.eat_keyword(keywords::As) {
+        if self.eat_keyword(kw::As) {
             self.parse_ident_or_underscore().map(Some)
         } else {
             Ok(None)
@@ -8563,19 +7752,21 @@ 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.span;
+        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.span),
+            span: lo.to(self.token.span),
         });
         krate
     }
 
     pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
-        let ret = match self.token {
-            token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
-            token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
+        let ret = match self.token.kind {
+            token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
+                (symbol, ast::StrStyle::Cooked, suffix),
+            token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
+                (symbol, ast::StrStyle::Raw(n), suffix),
             _ => return None
         };
         self.bump();
@@ -8586,24 +7777,43 @@ impl<'a> Parser<'a> {
         match self.parse_optional_str() {
             Some((s, style, suf)) => {
                 let sp = self.prev_span;
-                self.expect_no_suffix(sp, "string literal", suf);
+                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.span, msg);
+                err.span_label(self.token.span, msg);
                 Err(err)
             }
         }
     }
+
+    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();
+    }
 }
 
 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
     for unmatched in unclosed_delims.iter() {
         let mut err = handler.struct_span_err(unmatched.found_span, &format!(
             "incorrect close delimiter: `{}`",
-            pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
+            pprust::token_kind_to_string(&token::CloseDelim(unmatched.found_delim)),
         ));
         err.span_label(unmatched.found_span, "incorrect close delimiter");
         if let Some(sp) = unmatched.candidate_span {