Auto merge of #2780 - RalfJung:rustup, r=RalfJung

Rustup

9 files changed, 250 insertions, 271 deletions

diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
index b97f22417cb..dbd3b76786f 100644
--- a/compiler/rustc_parse/src/parser/attr_wrapper.rs
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -469,6 +469,6 @@ mod size_asserts {
     use rustc_data_structures::static_assert_size;
     // tidy-alphabetical-start
     static_assert_size!(AttrWrapper, 16);
-    static_assert_size!(LazyAttrTokenStreamImpl, 144);
+    static_assert_size!(LazyAttrTokenStreamImpl, 120);
     // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 26274822ed8..cd9d85b1d91 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -2394,7 +2394,7 @@ impl<'a> Parser<'a> {
 
     /// Some special error handling for the "top-level" patterns in a match arm,
     /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
-    pub(crate) fn maybe_recover_colon_colon_in_pat_typo_or_anon_enum(
+    pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
         &mut self,
         mut first_pat: P<Pat>,
         expected: Option<Expected>,
@@ -2435,8 +2435,9 @@ impl<'a> Parser<'a> {
         // Create error for "unexpected `:`".
         match self.expected_one_of_not_found(&[], &[]) {
             Err(mut err) => {
-                snapshot_pat.bump(); // Skip the `:`.
-                snapshot_type.bump(); // Skip the `:`.
+                // Skip the `:`.
+                snapshot_pat.bump();
+                snapshot_type.bump();
                 match snapshot_pat.parse_pat_no_top_alt(expected) {
                     Err(inner_err) => {
                         inner_err.cancel();
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index b7a023868fc..c37808f8c3d 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -5,26 +5,7 @@ use super::{
     AttrWrapper, BlockMode, ClosureSpans, ForceCollect, Parser, PathStyle, Restrictions,
     SemiColonMode, SeqSep, TokenExpectType, TokenType, TrailingToken,
 };
-use crate::errors::{
-    ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncBlockIn2015,
-    AsyncMoveOrderIncorrect, BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct,
-    ComparisonInterpretedAsGeneric, ComparisonOrShiftInterpretedAsGenericSugg,
-    DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedEqForLetExpr,
-    ExpectedExpressionFoundLet, FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart,
-    FoundExprWouldBeStmt, HelpUseLatestEdition, IfExpressionLetSomeSub,
-    IfExpressionMissingCondition, IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub,
-    InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
-    InvalidInterpolatedExpression, InvalidLiteralSuffixOnTupleIndex, InvalidLogicalOperator,
-    InvalidLogicalOperatorSub, LabeledLoopInBreak, LeadingPlusNotSupported, LeftArrowOperator,
-    LifetimeInBorrowExpression, MacroInvocationWithQualifiedPath, MalformedLoopLabel,
-    MatchArmBodyWithoutBraces, MatchArmBodyWithoutBracesSugg, MissingCommaAfterMatchArm,
-    MissingDotDot, MissingInInForLoop, MissingInInForLoopSub, MissingSemicolonBeforeArray,
-    NoFieldsForFnCall, NotAsNegationOperator, NotAsNegationOperatorSub,
-    OuterAttributeNotAllowedOnIfElse, ParenthesesWithStructFields,
-    RequireColonAfterLabeledExpression, ShiftInterpretedAsGeneric, StructLiteralNotAllowedHere,
-    StructLiteralNotAllowedHereSugg, TildeAsUnaryOperator, UnexpectedIfWithIf,
-    UnexpectedTokenAfterLabel, UnexpectedTokenAfterLabelSugg, WrapExpressionInParentheses,
-};
+use crate::errors;
 use crate::maybe_recover_from_interpolated_ty_qpath;
 use core::mem;
 use rustc_ast::ptr::P;
@@ -244,10 +225,10 @@ impl<'a> Parser<'a> {
                 }
                 .into();
                 let invalid = format!("{}=", &sugg);
-                self.sess.emit_err(InvalidComparisonOperator {
+                self.sess.emit_err(errors::InvalidComparisonOperator {
                     span: sp,
                     invalid: invalid.clone(),
-                    sub: InvalidComparisonOperatorSub::Correctable {
+                    sub: errors::InvalidComparisonOperatorSub::Correctable {
                         span: sp,
                         invalid,
                         correct: sugg,
@@ -262,10 +243,10 @@ impl<'a> Parser<'a> {
                 && self.prev_token.span.hi() == self.token.span.lo()
             {
                 let sp = op.span.to(self.token.span);
-                self.sess.emit_err(InvalidComparisonOperator {
+                self.sess.emit_err(errors::InvalidComparisonOperator {
                     span: sp,
                     invalid: "<>".into(),
-                    sub: InvalidComparisonOperatorSub::Correctable {
+                    sub: errors::InvalidComparisonOperatorSub::Correctable {
                         span: sp,
                         invalid: "<>".into(),
                         correct: "!=".into(),
@@ -280,10 +261,10 @@ impl<'a> Parser<'a> {
                 && self.prev_token.span.hi() == self.token.span.lo()
             {
                 let sp = op.span.to(self.token.span);
-                self.sess.emit_err(InvalidComparisonOperator {
+                self.sess.emit_err(errors::InvalidComparisonOperator {
                     span: sp,
                     invalid: "<=>".into(),
-                    sub: InvalidComparisonOperatorSub::Spaceship(sp),
+                    sub: errors::InvalidComparisonOperatorSub::Spaceship(sp),
                 });
                 self.bump();
             }
@@ -420,7 +401,7 @@ impl<'a> Parser<'a> {
     /// but the next token implies this should be parsed as an expression.
     /// For example: `if let Some(x) = x { x } else { 0 } / 2`.
     fn error_found_expr_would_be_stmt(&self, lhs: &Expr) {
-        self.sess.emit_err(FoundExprWouldBeStmt {
+        self.sess.emit_err(errors::FoundExprWouldBeStmt {
             span: self.token.span,
             token: self.token.clone(),
             suggestion: ExprParenthesesNeeded::surrounding(lhs.span),
@@ -447,18 +428,18 @@ impl<'a> Parser<'a> {
             }
             (Some(op), _) => (op, self.token.span),
             (None, Some((Ident { name: sym::and, span }, false))) if self.may_recover() => {
-                self.sess.emit_err(InvalidLogicalOperator {
+                self.sess.emit_err(errors::InvalidLogicalOperator {
                     span: self.token.span,
                     incorrect: "and".into(),
-                    sub: InvalidLogicalOperatorSub::Conjunction(self.token.span),
+                    sub: errors::InvalidLogicalOperatorSub::Conjunction(self.token.span),
                 });
                 (AssocOp::LAnd, span)
             }
             (None, Some((Ident { name: sym::or, span }, false))) if self.may_recover() => {
-                self.sess.emit_err(InvalidLogicalOperator {
+                self.sess.emit_err(errors::InvalidLogicalOperator {
                     span: self.token.span,
                     incorrect: "or".into(),
-                    sub: InvalidLogicalOperatorSub::Disjunction(self.token.span),
+                    sub: errors::InvalidLogicalOperatorSub::Disjunction(self.token.span),
                 });
                 (AssocOp::LOr, span)
             }
@@ -581,8 +562,11 @@ impl<'a> Parser<'a> {
             }
             // `+lit`
             token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
-                let mut err =
-                    LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
+                let mut err = errors::LeadingPlusNotSupported {
+                    span: lo,
+                    remove_plus: None,
+                    add_parentheses: None,
+                };
 
                 // a block on the LHS might have been intended to be an expression instead
                 if let Some(sp) = this.sess.ambiguous_block_expr_parse.borrow().get(&lo) {
@@ -633,7 +617,7 @@ impl<'a> Parser<'a> {
 
     /// Recover on `~expr` in favor of `!expr`.
     fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
-        self.sess.emit_err(TildeAsUnaryOperator(lo));
+        self.sess.emit_err(errors::TildeAsUnaryOperator(lo));
 
         self.parse_unary_expr(lo, UnOp::Not)
     }
@@ -661,14 +645,14 @@ impl<'a> Parser<'a> {
         let negated_token = self.look_ahead(1, |t| t.clone());
 
         let sub_diag = if negated_token.is_numeric_lit() {
-            NotAsNegationOperatorSub::SuggestNotBitwise
+            errors::NotAsNegationOperatorSub::SuggestNotBitwise
         } else if negated_token.is_bool_lit() {
-            NotAsNegationOperatorSub::SuggestNotLogical
+            errors::NotAsNegationOperatorSub::SuggestNotLogical
         } else {
-            NotAsNegationOperatorSub::SuggestNotDefault
+            errors::NotAsNegationOperatorSub::SuggestNotDefault
         };
 
-        self.sess.emit_err(NotAsNegationOperator {
+        self.sess.emit_err(errors::NotAsNegationOperator {
             negated: negated_token.span,
             negated_desc: super::token_descr(&negated_token),
             // Span the `not` plus trailing whitespace to avoid
@@ -739,7 +723,7 @@ impl<'a> Parser<'a> {
                         match self.parse_labeled_expr(label, false) {
                             Ok(expr) => {
                                 type_err.cancel();
-                                self.sess.emit_err(MalformedLoopLabel {
+                                self.sess.emit_err(errors::MalformedLoopLabel {
                                     span: label.ident.span,
                                     correct_label: label.ident,
                                 });
@@ -764,20 +748,22 @@ impl<'a> Parser<'a> {
                         );
 
                         let args_span = self.look_ahead(1, |t| t.span).to(span_after_type);
-                        let suggestion = ComparisonOrShiftInterpretedAsGenericSugg {
+                        let suggestion = errors::ComparisonOrShiftInterpretedAsGenericSugg {
                             left: expr.span.shrink_to_lo(),
                             right: expr.span.shrink_to_hi(),
                         };
 
                         match self.token.kind {
-                            token::Lt => self.sess.emit_err(ComparisonInterpretedAsGeneric {
-                                comparison: self.token.span,
-                                r#type: path,
-                                args: args_span,
-                                suggestion,
-                            }),
+                            token::Lt => {
+                                self.sess.emit_err(errors::ComparisonInterpretedAsGeneric {
+                                    comparison: self.token.span,
+                                    r#type: path,
+                                    args: args_span,
+                                    suggestion,
+                                })
+                            }
                             token::BinOp(token::Shl) => {
-                                self.sess.emit_err(ShiftInterpretedAsGeneric {
+                                self.sess.emit_err(errors::ShiftInterpretedAsGeneric {
                                     shift: self.token.span,
                                     r#type: path,
                                     args: args_span,
@@ -918,7 +904,7 @@ impl<'a> Parser<'a> {
     }
 
     fn error_remove_borrow_lifetime(&self, span: Span, lt_span: Span) {
-        self.sess.emit_err(LifetimeInBorrowExpression { span, lifetime_span: lt_span });
+        self.sess.emit_err(errors::LifetimeInBorrowExpression { span, lifetime_span: lt_span });
     }
 
     /// Parse `mut?` or `raw [ const | mut ]`.
@@ -1212,14 +1198,14 @@ impl<'a> Parser<'a> {
                         let close_paren = self.prev_token.span;
                         let span = lo.to(self.prev_token.span);
                         if !fields.is_empty() {
-                            let mut replacement_err = ParenthesesWithStructFields {
+                            let mut replacement_err = errors::ParenthesesWithStructFields {
                                 span,
                                 r#type: path,
-                                braces_for_struct: BracesForStructLiteral {
+                                braces_for_struct: errors::BracesForStructLiteral {
                                     first: open_paren,
                                     second: close_paren,
                                 },
-                                no_fields_for_fn: NoFieldsForFnCall {
+                                no_fields_for_fn: errors::NoFieldsForFnCall {
                                     fields: fields
                                         .into_iter()
                                         .map(|field| field.span.until(field.expr.span))
@@ -1286,7 +1272,7 @@ impl<'a> Parser<'a> {
         } else {
             // Field access `expr.f`
             if let Some(args) = seg.args {
-                self.sess.emit_err(FieldExpressionWithGeneric(args.span()));
+                self.sess.emit_err(errors::FieldExpressionWithGeneric(args.span()));
             }
 
             let span = lo.to(self.prev_token.span);
@@ -1500,7 +1486,7 @@ impl<'a> Parser<'a> {
         let (span, kind) = if self.eat(&token::Not) {
             // MACRO INVOCATION expression
             if qself.is_some() {
-                self.sess.emit_err(MacroInvocationWithQualifiedPath(path.span));
+                self.sess.emit_err(errors::MacroInvocationWithQualifiedPath(path.span));
             }
             let lo = path.span;
             let mac = P(MacCall {
@@ -1550,7 +1536,7 @@ impl<'a> Parser<'a> {
         {
             let (lit, _) =
                 self.recover_unclosed_char(label_.ident, Parser::mk_token_lit_char, |self_| {
-                    self_.sess.create_err(UnexpectedTokenAfterLabel {
+                    self_.sess.create_err(errors::UnexpectedTokenAfterLabel {
                         span: self_.token.span,
                         remove_label: None,
                         enclose_in_block: None,
@@ -1562,7 +1548,7 @@ impl<'a> Parser<'a> {
             && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
         {
             // We're probably inside of a `Path<'a>` that needs a turbofish
-            self.sess.emit_err(UnexpectedTokenAfterLabel {
+            self.sess.emit_err(errors::UnexpectedTokenAfterLabel {
                 span: self.token.span,
                 remove_label: None,
                 enclose_in_block: None,
@@ -1570,7 +1556,7 @@ impl<'a> Parser<'a> {
             consume_colon = false;
             Ok(self.mk_expr_err(lo))
         } else {
-            let mut err = UnexpectedTokenAfterLabel {
+            let mut err = errors::UnexpectedTokenAfterLabel {
                 span: self.token.span,
                 remove_label: None,
                 enclose_in_block: None,
@@ -1606,7 +1592,7 @@ impl<'a> Parser<'a> {
                     return expr;
                 }
 
-                err.enclose_in_block = Some(UnexpectedTokenAfterLabelSugg {
+                err.enclose_in_block = Some(errors::UnexpectedTokenAfterLabelSugg {
                     left: span.shrink_to_lo(),
                     right: span.shrink_to_hi(),
                 });
@@ -1622,7 +1608,7 @@ impl<'a> Parser<'a> {
         }?;
 
         if !ate_colon && consume_colon {
-            self.sess.emit_err(RequireColonAfterLabeledExpression {
+            self.sess.emit_err(errors::RequireColonAfterLabeledExpression {
                 span: expr.span,
                 label: lo,
                 label_end: lo.shrink_to_hi(),
@@ -1671,7 +1657,7 @@ impl<'a> Parser<'a> {
         self.bump(); // `catch`
 
         let span = lo.to(self.prev_token.span);
-        self.sess.emit_err(DoCatchSyntaxRemoved { span });
+        self.sess.emit_err(errors::DoCatchSyntaxRemoved { span });
 
         self.parse_try_block(lo)
     }
@@ -1719,9 +1705,9 @@ impl<'a> Parser<'a> {
             // The value expression can be a labeled loop, see issue #86948, e.g.:
             // `loop { break 'label: loop { break 'label 42; }; }`
             let lexpr = self.parse_labeled_expr(label, true)?;
-            self.sess.emit_err(LabeledLoopInBreak {
+            self.sess.emit_err(errors::LabeledLoopInBreak {
                 span: lexpr.span,
-                sub: WrapExpressionInParentheses {
+                sub: errors::WrapExpressionInParentheses {
                     left: lexpr.span.shrink_to_lo(),
                     right: lexpr.span.shrink_to_hi(),
                 },
@@ -1841,7 +1827,7 @@ impl<'a> Parser<'a> {
             };
             if let Some(expr) = expr {
                 if matches!(expr.kind, ExprKind::Err) {
-                    let mut err = InvalidInterpolatedExpression { span: self.token.span }
+                    let mut err = errors::InvalidInterpolatedExpression { span: self.token.span }
                         .into_diagnostic(&self.sess.span_diagnostic);
                     err.downgrade_to_delayed_bug();
                     return Err(err);
@@ -1902,7 +1888,7 @@ impl<'a> Parser<'a> {
             });
             if let Some(token) = &recovered {
                 self.bump();
-                self.sess.emit_err(FloatLiteralRequiresIntegerPart {
+                self.sess.emit_err(errors::FloatLiteralRequiresIntegerPart {
                     span: token.span,
                     correct: pprust::token_to_string(token).into_owned(),
                 });
@@ -1963,13 +1949,17 @@ impl<'a> Parser<'a> {
         if [sym::i32, sym::u32, sym::isize, sym::usize].contains(&suffix) {
             // #59553: warn instead of reject out of hand to allow the fix to percolate
             // through the ecosystem when people fix their macros
-            self.sess.emit_warning(InvalidLiteralSuffixOnTupleIndex {
+            self.sess.emit_warning(errors::InvalidLiteralSuffixOnTupleIndex {
                 span,
                 suffix,
                 exception: Some(()),
             });
         } else {
-            self.sess.emit_err(InvalidLiteralSuffixOnTupleIndex { span, suffix, exception: None });
+            self.sess.emit_err(errors::InvalidLiteralSuffixOnTupleIndex {
+                span,
+                suffix,
+                exception: None,
+            });
         }
     }
 
@@ -2003,9 +1993,9 @@ impl<'a> Parser<'a> {
         let mut snapshot = self.create_snapshot_for_diagnostic();
         match snapshot.parse_array_or_repeat_expr(Delimiter::Brace) {
             Ok(arr) => {
-                self.sess.emit_err(ArrayBracketsInsteadOfSpaces {
+                self.sess.emit_err(errors::ArrayBracketsInsteadOfSpaces {
                     span: arr.span,
-                    sub: ArrayBracketsInsteadOfSpacesSugg {
+                    sub: errors::ArrayBracketsInsteadOfSpacesSugg {
                         left: lo,
                         right: snapshot.prev_token.span,
                     },
@@ -2051,7 +2041,7 @@ impl<'a> Parser<'a> {
                         .span_to_snippet(snapshot.token.span)
                         .map_or(false, |snippet| snippet == "]") =>
                 {
-                    return Err(MissingSemicolonBeforeArray {
+                    return Err(errors::MissingSemicolonBeforeArray {
                         open_delim: open_delim_span,
                         semicolon: prev_span.shrink_to_hi(),
                     }.into_diagnostic(&self.sess.span_diagnostic));
@@ -2077,7 +2067,7 @@ impl<'a> Parser<'a> {
         }
 
         if self.token.is_whole_block() {
-            self.sess.emit_err(InvalidBlockMacroSegment {
+            self.sess.emit_err(errors::InvalidBlockMacroSegment {
                 span: self.token.span,
                 context: lo.to(self.token.span),
             });
@@ -2109,7 +2099,7 @@ impl<'a> Parser<'a> {
             ClosureBinder::NotPresent
         };
 
-        let constness = self.parse_constness(Case::Sensitive);
+        let constness = self.parse_closure_constness(Case::Sensitive);
 
         let movability =
             if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
@@ -2141,7 +2131,7 @@ impl<'a> Parser<'a> {
         }
 
         if self.token.kind == TokenKind::Semi
-            && matches!(self.token_cursor.frame.delim_sp, Some((Delimiter::Parenthesis, _)))
+            && matches!(self.token_cursor.stack.last(), Some((_, Delimiter::Parenthesis, _)))
             && self.may_recover()
         {
             // It is likely that the closure body is a block but where the
@@ -2181,7 +2171,7 @@ impl<'a> Parser<'a> {
             // Check for `move async` and recover
             if self.check_keyword(kw::Async) {
                 let move_async_span = self.token.span.with_lo(self.prev_token.span.data().lo);
-                Err(AsyncMoveOrderIncorrect { span: move_async_span }
+                Err(errors::AsyncMoveOrderIncorrect { span: move_async_span }
                     .into_diagnostic(&self.sess.span_diagnostic))
             } else {
                 Ok(CaptureBy::Value)
@@ -2259,17 +2249,17 @@ impl<'a> Parser<'a> {
             let block = match &mut cond.kind {
                 ExprKind::Binary(Spanned { span: binop_span, .. }, _, right)
                     if let ExprKind::Block(_, None) = right.kind => {
-                        self.sess.emit_err(IfExpressionMissingThenBlock {
+                        self.sess.emit_err(errors::IfExpressionMissingThenBlock {
                             if_span: lo,
                             missing_then_block_sub:
-                                IfExpressionMissingThenBlockSub::UnfinishedCondition(cond_span.shrink_to_lo().to(*binop_span)),
+                                errors::IfExpressionMissingThenBlockSub::UnfinishedCondition(cond_span.shrink_to_lo().to(*binop_span)),
                                 let_else_sub: None,
 
                         });
                         std::mem::replace(right, this.mk_expr_err(binop_span.shrink_to_hi()))
                     },
                 ExprKind::Block(_, None) => {
-                    self.sess.emit_err(IfExpressionMissingCondition {
+                    self.sess.emit_err(errors::IfExpressionMissingCondition {
                         if_span: lo.shrink_to_hi(),
                         block_span: self.sess.source_map().start_point(cond_span),
                     });
@@ -2291,11 +2281,11 @@ impl<'a> Parser<'a> {
                 block
             } else {
                 let let_else_sub = matches!(cond.kind, ExprKind::Let(..))
-                    .then(|| IfExpressionLetSomeSub { if_span: lo.until(cond_span) });
+                    .then(|| errors::IfExpressionLetSomeSub { if_span: lo.until(cond_span) });
 
-                self.sess.emit_err(IfExpressionMissingThenBlock {
+                self.sess.emit_err(errors::IfExpressionMissingThenBlock {
                     if_span: lo,
-                    missing_then_block_sub: IfExpressionMissingThenBlockSub::AddThenBlock(
+                    missing_then_block_sub: errors::IfExpressionMissingThenBlockSub::AddThenBlock(
                         cond_span.shrink_to_hi(),
                     ),
                     let_else_sub,
@@ -2351,7 +2341,7 @@ impl<'a> Parser<'a> {
             TokenKind::AndAnd | TokenKind::Ident(kw::If, _) | TokenKind::Ident(kw::While, _)
         );
         if !self.restrictions.contains(Restrictions::ALLOW_LET) || not_in_chain {
-            self.sess.emit_err(ExpectedExpressionFoundLet { span: self.token.span });
+            self.sess.emit_err(errors::ExpectedExpressionFoundLet { span: self.token.span });
         }
 
         self.bump(); // Eat `let` token
@@ -2363,7 +2353,7 @@ impl<'a> Parser<'a> {
             CommaRecoveryMode::LikelyTuple,
         )?;
         if self.token == token::EqEq {
-            self.sess.emit_err(ExpectedEqForLetExpr {
+            self.sess.emit_err(errors::ExpectedEqForLetExpr {
                 span: self.token.span,
                 sugg_span: self.token.span,
             });
@@ -2398,7 +2388,7 @@ impl<'a> Parser<'a> {
                     if self.check(&TokenKind::OpenDelim(Delimiter::Brace))
                         && classify::expr_requires_semi_to_be_stmt(&cond) =>
                 {
-                    self.sess.emit_err(ExpectedElseBlock {
+                    self.sess.emit_err(errors::ExpectedElseBlock {
                         first_tok_span,
                         first_tok,
                         else_span,
@@ -2438,7 +2428,7 @@ impl<'a> Parser<'a> {
             [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
         };
         let ctx = if is_ctx_else { "else" } else { "if" };
-        self.sess.emit_err(OuterAttributeNotAllowedOnIfElse {
+        self.sess.emit_err(errors::OuterAttributeNotAllowedOnIfElse {
             last,
             branch_span,
             ctx_span,
@@ -2451,7 +2441,7 @@ impl<'a> Parser<'a> {
         if let ExprKind::Binary(Spanned { span: binop_span, node: binop}, _, right) = &cond.kind &&
             let BinOpKind::And = binop &&
             let ExprKind::If(cond, ..) = &right.kind {
-                    Err(self.sess.create_err(UnexpectedIfWithIf(binop_span.shrink_to_hi().to(cond.span.shrink_to_lo()))))
+                    Err(self.sess.create_err(errors::UnexpectedIfWithIf(binop_span.shrink_to_hi().to(cond.span.shrink_to_lo()))))
             } else {
                 Ok(())
             }
@@ -2481,6 +2471,21 @@ impl<'a> Parser<'a> {
 
         let pat = self.recover_parens_around_for_head(pat, begin_paren);
 
+        // Recover from missing expression in `for` loop
+        if matches!(expr.kind, ExprKind::Block(..))
+            && !matches!(self.token.kind, token::OpenDelim(token::Delimiter::Brace))
+            && self.may_recover()
+        {
+            self.sess
+                .emit_err(errors::MissingExpressionInForLoop { span: expr.span.shrink_to_lo() });
+            let err_expr = self.mk_expr(expr.span, ExprKind::Err);
+            let block = self.mk_block(vec![], BlockCheckMode::Default, self.prev_token.span);
+            return Ok(self.mk_expr(
+                lo.to(self.prev_token.span),
+                ExprKind::ForLoop(pat, err_expr, block, opt_label),
+            ));
+        }
+
         let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
 
         let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
@@ -2492,12 +2497,12 @@ impl<'a> Parser<'a> {
             // Possibly using JS syntax (#75311).
             let span = self.token.span;
             self.bump();
-            (span, MissingInInForLoopSub::InNotOf)
+            (span, errors::MissingInInForLoopSub::InNotOf)
         } else {
-            (self.prev_token.span.between(self.token.span), MissingInInForLoopSub::AddIn)
+            (self.prev_token.span.between(self.token.span), errors::MissingInInForLoopSub::AddIn)
         };
 
-        self.sess.emit_err(MissingInInForLoop { span, sub: sub(span) });
+        self.sess.emit_err(errors::MissingInInForLoop { span, sub: sub(span) });
     }
 
     /// Parses a `while` or `while let` expression (`while` token already eaten).
@@ -2601,17 +2606,17 @@ impl<'a> Parser<'a> {
         let err = |this: &Parser<'_>, stmts: Vec<ast::Stmt>| {
             let span = stmts[0].span.to(stmts[stmts.len() - 1].span);
 
-            this.sess.emit_err(MatchArmBodyWithoutBraces {
+            this.sess.emit_err(errors::MatchArmBodyWithoutBraces {
                 statements: span,
                 arrow: arrow_span,
                 num_statements: stmts.len(),
                 sub: if stmts.len() > 1 {
-                    MatchArmBodyWithoutBracesSugg::AddBraces {
+                    errors::MatchArmBodyWithoutBracesSugg::AddBraces {
                         left: span.shrink_to_lo(),
                         right: span.shrink_to_hi(),
                     }
                 } else {
-                    MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
+                    errors::MatchArmBodyWithoutBracesSugg::UseComma { semicolon: semi_sp }
                 },
             });
             this.mk_expr_err(span)
@@ -2717,6 +2722,14 @@ impl<'a> Parser<'a> {
                     );
                     err.emit();
                     this.bump();
+                } else if matches!(
+                    (&this.prev_token.kind, &this.token.kind),
+                    (token::DotDotEq, token::Gt)
+                ) {
+                    // `error_inclusive_range_match_arrow` handles cases like `0..=> {}`,
+                    // so we supress the error here
+                    err.delay_as_bug();
+                    this.bump();
                 } else {
                     return Err(err);
                 }
@@ -2794,7 +2807,7 @@ impl<'a> Parser<'a> {
                                 .is_ok();
                             if pattern_follows && snapshot.check(&TokenKind::FatArrow) {
                                 err.cancel();
-                                this.sess.emit_err(MissingCommaAfterMatchArm {
+                                this.sess.emit_err(errors::MissingCommaAfterMatchArm {
                                     span: hi.shrink_to_hi(),
                                 });
                                 return Ok(true);
@@ -2826,7 +2839,7 @@ impl<'a> Parser<'a> {
     fn parse_try_block(&mut self, span_lo: Span) -> PResult<'a, P<Expr>> {
         let (attrs, body) = self.parse_inner_attrs_and_block()?;
         if self.eat_keyword(kw::Catch) {
-            Err(CatchAfterTry { span: self.prev_token.span }
+            Err(errors::CatchAfterTry { span: self.prev_token.span }
                 .into_diagnostic(&self.sess.span_diagnostic))
         } else {
             let span = span_lo.to(body.span);
@@ -2902,9 +2915,9 @@ impl<'a> Parser<'a> {
             let expr = self.parse_struct_expr(qself.clone(), path.clone(), true);
             if let (Ok(expr), false) = (&expr, struct_allowed) {
                 // This is a struct literal, but we don't can't accept them here.
-                self.sess.emit_err(StructLiteralNotAllowedHere {
+                self.sess.emit_err(errors::StructLiteralNotAllowedHere {
                     span: expr.span,
-                    sub: StructLiteralNotAllowedHereSugg {
+                    sub: errors::StructLiteralNotAllowedHereSugg {
                         left: path.span.shrink_to_lo(),
                         right: expr.span.shrink_to_hi(),
                     },
@@ -2927,8 +2940,8 @@ impl<'a> Parser<'a> {
 
         let mut async_block_err = |e: &mut Diagnostic, span: Span| {
             recover_async = true;
-            AsyncBlockIn2015 { span }.add_to_diagnostic(e);
-            HelpUseLatestEdition::new().add_to_diagnostic(e);
+            errors::AsyncBlockIn2015 { span }.add_to_diagnostic(e);
+            errors::HelpUseLatestEdition::new().add_to_diagnostic(e);
         };
 
         while self.token != token::CloseDelim(close_delim) {
@@ -3072,7 +3085,7 @@ impl<'a> Parser<'a> {
         if self.token != token::Comma {
             return;
         }
-        self.sess.emit_err(CommaAfterBaseStruct {
+        self.sess.emit_err(errors::CommaAfterBaseStruct {
             span: span.to(self.prev_token.span),
             comma: self.token.span,
         });
@@ -3085,7 +3098,7 @@ impl<'a> Parser<'a> {
         {
             // recover from typo of `...`, suggest `..`
             let span = self.prev_token.span;
-            self.sess.emit_err(MissingDotDot { token_span: span, sugg_span: span });
+            self.sess.emit_err(errors::MissingDotDot { token_span: span, sugg_span: span });
             return true;
         }
         false
@@ -3153,18 +3166,18 @@ impl<'a> Parser<'a> {
             return;
         }
 
-        self.sess.emit_err(EqFieldInit {
+        self.sess.emit_err(errors::EqFieldInit {
             span: self.token.span,
             eq: field_name.span.shrink_to_hi().to(self.token.span),
         });
     }
 
     fn err_dotdotdot_syntax(&self, span: Span) {
-        self.sess.emit_err(DotDotDot { span });
+        self.sess.emit_err(errors::DotDotDot { span });
     }
 
     fn err_larrow_operator(&self, span: Span) {
-        self.sess.emit_err(LeftArrowOperator { span });
+        self.sess.emit_err(errors::LeftArrowOperator { span });
     }
 
     fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index 585dfc518b3..23f49ec55a1 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -1,5 +1,6 @@
 use crate::errors::{
-    MultipleWhereClauses, UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
+    MultipleWhereClauses, UnexpectedDefaultValueForLifetimeInGenericParameters,
+    UnexpectedSelfInGenericParameters, WhereClauseBeforeTupleStructBody,
     WhereClauseBeforeTupleStructBodySugg,
 };
 
@@ -145,6 +146,20 @@ impl<'a> Parser<'a> {
                         } else {
                             (None, Vec::new())
                         };
+
+                        if this.check_noexpect(&token::Eq)
+                            && this.look_ahead(1, |t| t.is_lifetime())
+                        {
+                            let lo = this.token.span;
+                            // Parse `= 'lifetime`.
+                            this.bump(); // `=`
+                            this.bump(); // `'lifetime`
+                            let span = lo.to(this.prev_token.span);
+                            this.sess.emit_err(
+                                UnexpectedDefaultValueForLifetimeInGenericParameters { span },
+                            );
+                        }
+
                         Some(ast::GenericParam {
                             ident: lifetime.ident,
                             id: lifetime.id,
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 81fd084ccb3..628e9d88cf1 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -2247,7 +2247,7 @@ impl<'a> Parser<'a> {
         let ext = self.parse_extern(case);
 
         if let Async::Yes { span, .. } = asyncness {
-            if span.rust_2015() {
+            if span.is_rust_2015() {
                 self.sess.emit_err(AsyncFnIn2015 { span, help: HelpUseLatestEdition::new() });
             }
         }
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index ffb23b50a16..0cb88f3c3a9 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -19,9 +19,8 @@ pub use path::PathStyle;
 
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Nonterminal, Token, TokenKind};
-use rustc_ast::tokenstream::AttributesData;
-use rustc_ast::tokenstream::{self, DelimSpan, Spacing};
-use rustc_ast::tokenstream::{TokenStream, TokenTree};
+use rustc_ast::tokenstream::{AttributesData, DelimSpan, Spacing};
+use rustc_ast::tokenstream::{TokenStream, TokenTree, TokenTreeCursor};
 use rustc_ast::util::case::Case;
 use rustc_ast::AttrId;
 use rustc_ast::DUMMY_NODE_ID;
@@ -168,7 +167,7 @@ pub struct Parser<'a> {
 // This type is used a lot, e.g. it's cloned when matching many declarative macro rules with nonterminals. Make sure
 // it doesn't unintentionally get bigger.
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-rustc_data_structures::static_assert_size!(Parser<'_>, 336);
+rustc_data_structures::static_assert_size!(Parser<'_>, 312);
 
 /// Stores span information about a closure.
 #[derive(Clone)]
@@ -221,18 +220,27 @@ impl<'a> Drop for Parser<'a> {
     }
 }
 
+/// Iterator over a `TokenStream` that produces `Token`s. It's a bit odd that
+/// we (a) lex tokens into a nice tree structure (`TokenStream`), and then (b)
+/// use this type to emit them as a linear sequence. But a linear sequence is
+/// what the parser expects, for the most part.
 #[derive(Clone)]
 struct TokenCursor {
-    // The current (innermost) frame. `frame` and `stack` could be combined,
-    // but it's faster to have them separately to access `frame` directly
-    // rather than via something like `stack.last().unwrap()` or
-    // `stack[stack.len() - 1]`.
-    frame: TokenCursorFrame,
-    // Additional frames that enclose `frame`.
-    stack: Vec<TokenCursorFrame>,
+    // Cursor for the current (innermost) token stream. The delimiters for this
+    // token stream are found in `self.stack.last()`; when that is `None` then
+    // we are in the outermost token stream which never has delimiters.
+    tree_cursor: TokenTreeCursor,
+
+    // Token streams surrounding the current one. The delimiters for stack[n]'s
+    // tokens are in `stack[n-1]`. `stack[0]` (when present) has no delimiters
+    // because it's the outermost token stream which never has delimiters.
+    stack: Vec<(TokenTreeCursor, Delimiter, DelimSpan)>,
+
     desugar_doc_comments: bool,
+
     // Counts the number of calls to `{,inlined_}next`.
     num_next_calls: usize,
+
     // During parsing, we may sometimes need to 'unglue' a
     // glued token into two component tokens
     // (e.g. '>>' into '>' and '>), so that the parser
@@ -257,18 +265,6 @@ struct TokenCursor {
     break_last_token: bool,
 }
 
-#[derive(Clone)]
-struct TokenCursorFrame {
-    delim_sp: Option<(Delimiter, DelimSpan)>,
-    tree_cursor: tokenstream::Cursor,
-}
-
-impl TokenCursorFrame {
-    fn new(delim_sp: Option<(Delimiter, DelimSpan)>, tts: TokenStream) -> Self {
-        TokenCursorFrame { delim_sp, tree_cursor: tts.into_trees() }
-    }
-}
-
 impl TokenCursor {
     fn next(&mut self, desugar_doc_comments: bool) -> (Token, Spacing) {
         self.inlined_next(desugar_doc_comments)
@@ -281,38 +277,47 @@ impl TokenCursor {
             // FIXME: we currently don't return `Delimiter` open/close delims. To fix #67062 we will
             // need to, whereupon the `delim != Delimiter::Invisible` conditions below can be
             // removed.
-            if let Some(tree) = self.frame.tree_cursor.next_ref() {
+            if let Some(tree) = self.tree_cursor.next_ref() {
                 match tree {
                     &TokenTree::Token(ref token, spacing) => match (desugar_doc_comments, token) {
                         (true, &Token { kind: token::DocComment(_, attr_style, data), span }) => {
-                            return self.desugar(attr_style, data, span);
+                            let desugared = self.desugar(attr_style, data, span);
+                            self.tree_cursor.replace_prev_and_rewind(desugared);
+                            // Continue to get the first token of the desugared doc comment.
+                        }
+                        _ => {
+                            debug_assert!(!matches!(
+                                token.kind,
+                                token::OpenDelim(_) | token::CloseDelim(_)
+                            ));
+                            return (token.clone(), spacing);
                         }
-                        _ => return (token.clone(), spacing),
                     },
                     &TokenTree::Delimited(sp, delim, ref tts) => {
-                        // Set `open_delim` to true here because we deal with it immediately.
-                        let frame = TokenCursorFrame::new(Some((delim, sp)), tts.clone());
-                        self.stack.push(mem::replace(&mut self.frame, frame));
+                        let trees = tts.clone().into_trees();
+                        self.stack.push((mem::replace(&mut self.tree_cursor, trees), delim, sp));
                         if delim != Delimiter::Invisible {
                             return (Token::new(token::OpenDelim(delim), sp.open), Spacing::Alone);
                         }
                         // No open delimiter to return; continue on to the next iteration.
                     }
                 };
-            } else if let Some(frame) = self.stack.pop() {
-                if let Some((delim, span)) = self.frame.delim_sp && delim != Delimiter::Invisible {
-                    self.frame = frame;
+            } else if let Some((tree_cursor, delim, span)) = self.stack.pop() {
+                // We have exhausted this token stream. Move back to its parent token stream.
+                self.tree_cursor = tree_cursor;
+                if delim != Delimiter::Invisible {
                     return (Token::new(token::CloseDelim(delim), span.close), Spacing::Alone);
                 }
-                self.frame = frame;
                 // No close delimiter to return; continue on to the next iteration.
             } else {
+                // We have exhausted the outermost token stream.
                 return (Token::new(token::Eof, DUMMY_SP), Spacing::Alone);
             }
         }
     }
 
-    fn desugar(&mut self, attr_style: AttrStyle, data: Symbol, span: Span) -> (Token, Spacing) {
+    // Desugar a doc comment into something like `#[doc = r"foo"]`.
+    fn desugar(&mut self, attr_style: AttrStyle, data: Symbol, span: Span) -> Vec<TokenTree> {
         // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
         // required to wrap the text. E.g.
         // - `abc d` is wrapped as `r"abc d"` (num_of_hashes = 0)
@@ -346,27 +351,15 @@ impl TokenCursor {
             .collect::<TokenStream>(),
         );
 
-        self.stack.push(mem::replace(
-            &mut self.frame,
-            TokenCursorFrame::new(
-                None,
-                if attr_style == AttrStyle::Inner {
-                    [
-                        TokenTree::token_alone(token::Pound, span),
-                        TokenTree::token_alone(token::Not, span),
-                        body,
-                    ]
-                    .into_iter()
-                    .collect::<TokenStream>()
-                } else {
-                    [TokenTree::token_alone(token::Pound, span), body]
-                        .into_iter()
-                        .collect::<TokenStream>()
-                },
-            ),
-        ));
-
-        self.next(/* desugar_doc_comments */ false)
+        if attr_style == AttrStyle::Inner {
+            vec![
+                TokenTree::token_alone(token::Pound, span),
+                TokenTree::token_alone(token::Not, span),
+                body,
+            ]
+        } else {
+            vec![TokenTree::token_alone(token::Pound, span), body]
+        }
     }
 }
 
@@ -475,7 +468,7 @@ impl<'a> Parser<'a> {
             restrictions: Restrictions::empty(),
             expected_tokens: Vec::new(),
             token_cursor: TokenCursor {
-                frame: TokenCursorFrame::new(None, tokens),
+                tree_cursor: tokens.into_trees(),
                 stack: Vec::new(),
                 num_next_calls: 0,
                 desugar_doc_comments,
@@ -739,9 +732,10 @@ impl<'a> Parser<'a> {
     fn check_const_closure(&self) -> bool {
         self.is_keyword_ahead(0, &[kw::Const])
             && self.look_ahead(1, |t| match &t.kind {
-                token::Ident(kw::Move | kw::Static | kw::Async, _)
-                | token::OrOr
-                | token::BinOp(token::Or) => true,
+                // async closures do not work with const closures, so we do not parse that here.
+                token::Ident(kw::Move | kw::Static, _) | token::OrOr | token::BinOp(token::Or) => {
+                    true
+                }
                 _ => false,
             })
     }
@@ -1142,14 +1136,16 @@ impl<'a> Parser<'a> {
             return looker(&self.token);
         }
 
-        let frame = &self.token_cursor.frame;
-        if let Some((delim, span)) = frame.delim_sp && delim != Delimiter::Invisible {
+        let tree_cursor = &self.token_cursor.tree_cursor;
+        if let Some(&(_, delim, span)) = self.token_cursor.stack.last()
+            && delim != Delimiter::Invisible
+        {
             let all_normal = (0..dist).all(|i| {
-                let token = frame.tree_cursor.look_ahead(i);
+                let token = tree_cursor.look_ahead(i);
                 !matches!(token, Some(TokenTree::Delimited(_, Delimiter::Invisible, _)))
             });
             if all_normal {
-                return match frame.tree_cursor.look_ahead(dist - 1) {
+                return match tree_cursor.look_ahead(dist - 1) {
                     Some(tree) => match tree {
                         TokenTree::Token(token, _) => looker(token),
                         TokenTree::Delimited(dspan, delim, _) => {
@@ -1203,8 +1199,18 @@ impl<'a> Parser<'a> {
 
     /// Parses constness: `const` or nothing.
     fn parse_constness(&mut self, case: Case) -> Const {
-        // Avoid const blocks to be parsed as const items
-        if self.look_ahead(1, |t| t != &token::OpenDelim(Delimiter::Brace))
+        self.parse_constness_(case, false)
+    }
+
+    /// Parses constness for closures
+    fn parse_closure_constness(&mut self, case: Case) -> Const {
+        self.parse_constness_(case, true)
+    }
+
+    fn parse_constness_(&mut self, case: Case, is_closure: bool) -> Const {
+        // Avoid const blocks and const closures to be parsed as const items
+        if (self.check_const_closure() == is_closure)
+            && self.look_ahead(1, |t| t != &token::OpenDelim(Delimiter::Brace))
             && self.eat_keyword_case(kw::Const, case)
         {
             Const::Yes(self.prev_token.uninterpolated_span())
@@ -1310,10 +1316,10 @@ impl<'a> Parser<'a> {
     pub(crate) fn parse_token_tree(&mut self) -> TokenTree {
         match self.token.kind {
             token::OpenDelim(..) => {
-                // Grab the tokens from this frame.
-                let frame = &self.token_cursor.frame;
-                let stream = frame.tree_cursor.stream.clone();
-                let (delim, span) = frame.delim_sp.unwrap();
+                // Grab the tokens within the delimiters.
+                let tree_cursor = &self.token_cursor.tree_cursor;
+                let stream = tree_cursor.stream.clone();
+                let (_, delim, span) = *self.token_cursor.stack.last().unwrap();
 
                 // Advance the token cursor through the entire delimited
                 // sequence. After getting the `OpenDelim` we are *within* the
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 88c75fd81e7..b054dc59a0c 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -148,8 +148,7 @@ impl<'a> Parser<'a> {
 
             // Check if the user wrote `foo:bar` instead of `foo::bar`.
             if ra == RecoverColon::Yes {
-                first_pat =
-                    self.maybe_recover_colon_colon_in_pat_typo_or_anon_enum(first_pat, expected);
+                first_pat = self.maybe_recover_colon_colon_in_pat_typo(first_pat, expected);
             }
 
             if let Some(leading_vert_span) = leading_vert_span {
@@ -744,7 +743,7 @@ impl<'a> Parser<'a> {
             }
             token::Gt if no_space => {
                 let after_pat = span.with_hi(span.hi() - rustc_span::BytePos(1)).shrink_to_hi();
-                self.sess.emit_err(InclusiveRangeMatchArrow { span, after_pat });
+                self.sess.emit_err(InclusiveRangeMatchArrow { span, arrow: tok.span, after_pat });
             }
             _ => {
                 self.sess.emit_err(InclusiveRangeNoEnd { span });
@@ -963,12 +962,15 @@ impl<'a> Parser<'a> {
             }
             ate_comma = false;
 
-            if self.check(&token::DotDot) || self.token == token::DotDotDot {
+            if self.check(&token::DotDot)
+                || self.check_noexpect(&token::DotDotDot)
+                || self.check_keyword(kw::Underscore)
+            {
                 etc = true;
                 let mut etc_sp = self.token.span;
 
-                self.recover_one_fewer_dotdot();
-                self.bump(); // `..` || `...`
+                self.recover_bad_dot_dot();
+                self.bump(); // `..` || `...` || `_`
 
                 if self.token == token::CloseDelim(Delimiter::Brace) {
                     etc_span = Some(etc_sp);
@@ -1061,14 +1063,15 @@ impl<'a> Parser<'a> {
         Ok((fields, etc))
     }
 
-    /// Recover on `...` as if it were `..` to avoid further errors.
+    /// Recover on `...` or `_` as if it were `..` to avoid further errors.
     /// See issue #46718.
-    fn recover_one_fewer_dotdot(&self) {
-        if self.token != token::DotDotDot {
+    fn recover_bad_dot_dot(&self) {
+        if self.token == token::DotDot {
             return;
         }
 
-        self.sess.emit_err(DotDotDotForRemainingFields { span: self.token.span });
+        let token_str = pprust::token_to_string(&self.token);
+        self.sess.emit_err(DotDotDotForRemainingFields { span: self.token.span, token_str });
     }
 
     fn parse_pat_field(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, PatField> {
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 647639b9b62..3afda5f69f0 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -7,12 +7,7 @@ use super::TrailingToken;
 use super::{
     AttrWrapper, BlockMode, FnParseMode, ForceCollect, Parser, Restrictions, SemiColonMode,
 };
-use crate::errors::{
-    AssignmentElseNotAllowed, CompoundAssignmentExpressionInLet, ConstLetMutuallyExclusive,
-    DocCommentDoesNotDocumentAnything, ExpectedStatementAfterOuterAttr, InvalidCurlyInLetElse,
-    InvalidExpressionInLetElse, InvalidIdentiferStartsWithNumber, InvalidVariableDeclaration,
-    InvalidVariableDeclarationSub, WrapExpressionInParentheses,
-};
+use crate::errors;
 use crate::maybe_whole;
 
 use rustc_ast as ast;
@@ -64,29 +59,33 @@ impl<'a> Parser<'a> {
         if self.token.is_keyword(kw::Mut) && self.is_keyword_ahead(1, &[kw::Let]) {
             self.bump();
             let mut_let_span = lo.to(self.token.span);
-            self.sess.emit_err(InvalidVariableDeclaration {
+            self.sess.emit_err(errors::InvalidVariableDeclaration {
                 span: mut_let_span,
-                sub: InvalidVariableDeclarationSub::SwitchMutLetOrder(mut_let_span),
+                sub: errors::InvalidVariableDeclarationSub::SwitchMutLetOrder(mut_let_span),
             });
         }
 
         Ok(Some(if self.token.is_keyword(kw::Let) {
             self.parse_local_mk(lo, attrs, capture_semi, force_collect)?
         } else if self.is_kw_followed_by_ident(kw::Mut) && self.may_recover() {
-            self.recover_stmt_local_after_let(lo, attrs, InvalidVariableDeclarationSub::MissingLet)?
+            self.recover_stmt_local_after_let(
+                lo,
+                attrs,
+                errors::InvalidVariableDeclarationSub::MissingLet,
+            )?
         } else if self.is_kw_followed_by_ident(kw::Auto) && self.may_recover() {
             self.bump(); // `auto`
             self.recover_stmt_local_after_let(
                 lo,
                 attrs,
-                InvalidVariableDeclarationSub::UseLetNotAuto,
+                errors::InvalidVariableDeclarationSub::UseLetNotAuto,
             )?
         } else if self.is_kw_followed_by_ident(sym::var) && self.may_recover() {
             self.bump(); // `var`
             self.recover_stmt_local_after_let(
                 lo,
                 attrs,
-                InvalidVariableDeclarationSub::UseLetNotVar,
+                errors::InvalidVariableDeclarationSub::UseLetNotVar,
             )?
         } else if self.check_path() && !self.token.is_qpath_start() && !self.is_path_start_item() {
             // We have avoided contextual keywords like `union`, items with `crate` visibility,
@@ -124,7 +123,7 @@ impl<'a> Parser<'a> {
                 let bl = self.parse_block()?;
                 // Destructuring assignment ... else.
                 // This is not allowed, but point it out in a nice way.
-                self.sess.emit_err(AssignmentElseNotAllowed { span: e.span.to(bl.span) });
+                self.sess.emit_err(errors::AssignmentElseNotAllowed { span: e.span.to(bl.span) });
             }
             self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
         } else {
@@ -217,12 +216,12 @@ impl<'a> Parser<'a> {
         && let attrs = attrs.take_for_recovery(self.sess)
         && let attrs @ [.., last] = &*attrs {
             if last.is_doc_comment() {
-                self.sess.emit_err(DocCommentDoesNotDocumentAnything {
+                self.sess.emit_err(errors::DocCommentDoesNotDocumentAnything {
                     span: last.span,
                     missing_comma: None,
                 });
             } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
-                self.sess.emit_err(ExpectedStatementAfterOuterAttr { span: last.span });
+                self.sess.emit_err(errors::ExpectedStatementAfterOuterAttr { span: last.span });
             }
         }
     }
@@ -231,7 +230,7 @@ impl<'a> Parser<'a> {
         &mut self,
         lo: Span,
         attrs: AttrWrapper,
-        subdiagnostic: fn(Span) -> InvalidVariableDeclarationSub,
+        subdiagnostic: fn(Span) -> errors::InvalidVariableDeclarationSub,
     ) -> PResult<'a, Stmt> {
         let stmt =
             self.collect_tokens_trailing_token(attrs, ForceCollect::Yes, |this, attrs| {
@@ -242,7 +241,7 @@ impl<'a> Parser<'a> {
                     TrailingToken::None,
                 ))
             })?;
-        self.sess.emit_err(InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
+        self.sess.emit_err(errors::InvalidVariableDeclaration { span: lo, sub: subdiagnostic(lo) });
         Ok(stmt)
     }
 
@@ -270,7 +269,7 @@ impl<'a> Parser<'a> {
         let lo = self.prev_token.span;
 
         if self.token.is_keyword(kw::Const) && self.look_ahead(1, |t| t.is_ident()) {
-            self.sess.emit_err(ConstLetMutuallyExclusive { span: lo.to(self.token.span) });
+            self.sess.emit_err(errors::ConstLetMutuallyExclusive { span: lo.to(self.token.span) });
             self.bump();
         }
 
@@ -373,7 +372,7 @@ impl<'a> Parser<'a> {
             rustc_ast::MetaItemLit::from_token(&self.token).is_none() &&
             (lit.kind == token::LitKind::Integer || lit.kind == token::LitKind::Float) &&
             self.look_ahead(1, |t| matches!(t.kind, token::Eq) || matches!(t.kind, token::Colon ) ) {
-                return Err(self.sess.create_err(InvalidIdentiferStartsWithNumber { span: self.token.span }));
+                return Err(self.sess.create_err(errors::InvalidIdentiferStartsWithNumber { span: self.token.span }));
         }
         Ok(())
     }
@@ -381,10 +380,10 @@ impl<'a> Parser<'a> {
     fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
         if let ast::ExprKind::Binary(op, ..) = init.kind {
             if op.node.lazy() {
-                self.sess.emit_err(InvalidExpressionInLetElse {
+                self.sess.emit_err(errors::InvalidExpressionInLetElse {
                     span: init.span,
                     operator: op.node.to_string(),
-                    sugg: WrapExpressionInParentheses {
+                    sugg: errors::WrapExpressionInParentheses {
                         left: init.span.shrink_to_lo(),
                         right: init.span.shrink_to_hi(),
                     },
@@ -395,9 +394,9 @@ impl<'a> Parser<'a> {
 
     fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
         if let Some(trailing) = classify::expr_trailing_brace(init) {
-            self.sess.emit_err(InvalidCurlyInLetElse {
+            self.sess.emit_err(errors::InvalidCurlyInLetElse {
                 span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
-                sugg: WrapExpressionInParentheses {
+                sugg: errors::WrapExpressionInParentheses {
                     left: trailing.span.shrink_to_lo(),
                     right: trailing.span.shrink_to_hi(),
                 },
@@ -410,7 +409,8 @@ impl<'a> Parser<'a> {
         let eq_consumed = match self.token.kind {
             token::BinOpEq(..) => {
                 // Recover `let x <op>= 1` as `let x = 1`
-                self.sess.emit_err(CompoundAssignmentExpressionInLet { span: self.token.span });
+                self.sess
+                    .emit_err(errors::CompoundAssignmentExpressionInLet { span: self.token.span });
                 self.bump();
                 true
             }
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 306cbcff149..a19ea04fa5e 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -17,7 +17,6 @@ use rustc_ast::{
     self as ast, BareFnTy, FnRetTy, GenericBound, GenericBounds, GenericParam, Generics, Lifetime,
     MacCall, MutTy, Mutability, PolyTraitRef, TraitBoundModifier, TraitObjectSyntax, Ty, TyKind,
 };
-use rustc_ast_pretty::pprust;
 use rustc_errors::{Applicability, PResult};
 use rustc_span::source_map::Span;
 use rustc_span::symbol::{kw, sym, Ident};
@@ -50,24 +49,17 @@ pub(super) enum AllowPlus {
     No,
 }
 
-#[derive(PartialEq, Clone, Copy)]
+#[derive(PartialEq)]
 pub(super) enum RecoverQPath {
     Yes,
     No,
 }
 
-#[derive(PartialEq, Clone, Copy)]
 pub(super) enum RecoverQuestionMark {
     Yes,
     No,
 }
 
-#[derive(PartialEq, Clone, Copy)]
-pub(super) enum RecoverAnonEnum {
-    Yes,
-    No,
-}
-
 /// Signals whether parsing a type should recover `->`.
 ///
 /// More specifically, when parsing a function like:
@@ -100,7 +92,7 @@ impl RecoverReturnSign {
 }
 
 // Is `...` (`CVarArgs`) legal at this level of type parsing?
-#[derive(PartialEq, Clone, Copy)]
+#[derive(PartialEq)]
 enum AllowCVariadic {
     Yes,
     No,
@@ -125,7 +117,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::Yes,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -140,7 +131,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             Some(ty_params),
             RecoverQuestionMark::Yes,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -155,7 +145,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::Yes,
-            RecoverAnonEnum::Yes,
         )
     }
 
@@ -173,7 +162,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::Yes,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -187,7 +175,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::No,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -199,7 +186,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::Yes,
             None,
             RecoverQuestionMark::No,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -212,7 +198,6 @@ impl<'a> Parser<'a> {
             RecoverReturnSign::OnlyFatArrow,
             None,
             RecoverQuestionMark::Yes,
-            RecoverAnonEnum::No,
         )
     }
 
@@ -232,7 +217,6 @@ impl<'a> Parser<'a> {
                 recover_return_sign,
                 None,
                 RecoverQuestionMark::Yes,
-                RecoverAnonEnum::Yes,
             )?;
             FnRetTy::Ty(ty)
         } else if recover_return_sign.can_recover(&self.token.kind) {
@@ -247,7 +231,6 @@ impl<'a> Parser<'a> {
                 recover_return_sign,
                 None,
                 RecoverQuestionMark::Yes,
-                RecoverAnonEnum::Yes,
             )?;
             FnRetTy::Ty(ty)
         } else {
@@ -263,7 +246,6 @@ impl<'a> Parser<'a> {
         recover_return_sign: RecoverReturnSign,
         ty_generics: Option<&Generics>,
         recover_question_mark: RecoverQuestionMark,
-        recover_anon_enum: RecoverAnonEnum,
     ) -> PResult<'a, P<Ty>> {
         let allow_qpath_recovery = recover_qpath == RecoverQPath::Yes;
         maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
@@ -347,50 +329,9 @@ impl<'a> Parser<'a> {
             AllowPlus::Yes => self.maybe_recover_from_bad_type_plus(&ty)?,
             AllowPlus::No => self.maybe_report_ambiguous_plus(impl_dyn_multi, &ty),
         }
-        if RecoverQuestionMark::Yes == recover_question_mark {
+        if let RecoverQuestionMark::Yes = recover_question_mark {
             ty = self.maybe_recover_from_question_mark(ty);
         }
-        if recover_anon_enum == RecoverAnonEnum::Yes
-            && self.check_noexpect(&token::BinOp(token::Or))
-            && self.look_ahead(1, |t| t.can_begin_type())
-        {
-            let mut pipes = vec![self.token.span];
-            let mut types = vec![ty];
-            loop {
-                if !self.eat(&token::BinOp(token::Or)) {
-                    break;
-                }
-                pipes.push(self.prev_token.span);
-                types.push(self.parse_ty_common(
-                    allow_plus,
-                    allow_c_variadic,
-                    recover_qpath,
-                    recover_return_sign,
-                    ty_generics,
-                    recover_question_mark,
-                    RecoverAnonEnum::No,
-                )?);
-            }
-            let mut err = self.struct_span_err(pipes, "anonymous enums are not supported");
-            for ty in &types {
-                err.span_label(ty.span, "");
-            }
-            err.help(&format!(
-                "create a named `enum` and use it here instead:\nenum Name {{\n{}\n}}",
-                types
-                    .iter()
-                    .enumerate()
-                    .map(|(i, t)| format!(
-                        "    Variant{}({}),",
-                        i + 1, // Lets not confuse people with zero-indexing :)
-                        pprust::to_string(|s| s.print_type(&t)),
-                    ))
-                    .collect::<Vec<_>>()
-                    .join("\n"),
-            ));
-            err.emit();
-            return Ok(self.mk_ty(lo.to(self.prev_token.span), TyKind::Err));
-        }
         if allow_qpath_recovery { self.maybe_recover_from_bad_qpath(ty) } else { Ok(ty) }
     }
 
@@ -673,7 +614,7 @@ impl<'a> Parser<'a> {
     /// Is a `dyn B0 + ... + Bn` type allowed here?
     fn is_explicit_dyn_type(&mut self) -> bool {
         self.check_keyword(kw::Dyn)
-            && (!self.token.uninterpolated_span().rust_2015()
+            && (self.token.uninterpolated_span().rust_2018()
                 || self.look_ahead(1, |t| {
                     (t.can_begin_bound() || t.kind == TokenKind::BinOp(token::Star))
                         && !can_continue_type_after_non_fn_ident(t)