Auto merge of #3751 - rust-lang:rustup-2024-07-16, r=RalfJung

Automatic Rustup

10 files changed, 596 insertions, 226 deletions

diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
index 38f18022e3c..1123c31f551 100644
--- a/compiler/rustc_parse/src/parser/attr_wrapper.rs
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -103,11 +103,8 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl {
         // produce an empty `TokenStream` if no calls were made, and omit the
         // final token otherwise.
         let mut cursor_snapshot = self.cursor_snapshot.clone();
-        let tokens = iter::once((FlatToken::Token(self.start_token.0.clone()), self.start_token.1))
-            .chain(iter::repeat_with(|| {
-                let token = cursor_snapshot.next();
-                (FlatToken::Token(token.0), token.1)
-            }))
+        let tokens = iter::once(FlatToken::Token(self.start_token.clone()))
+            .chain(iter::repeat_with(|| FlatToken::Token(cursor_snapshot.next())))
             .take(self.num_calls as usize);
 
         if self.replace_ranges.is_empty() {
@@ -156,11 +153,8 @@ impl ToAttrTokenStream for LazyAttrTokenStreamImpl {
                     (range.start as usize)..(range.end as usize),
                     target
                         .into_iter()
-                        .map(|target| (FlatToken::AttrsTarget(target), Spacing::Alone))
-                        .chain(
-                            iter::repeat((FlatToken::Empty, Spacing::Alone))
-                                .take(range.len() - target_len),
-                        ),
+                        .map(|target| FlatToken::AttrsTarget(target))
+                        .chain(iter::repeat(FlatToken::Empty).take(range.len() - target_len)),
                 );
             }
             make_attr_token_stream(tokens.into_iter(), self.break_last_token)
@@ -301,21 +295,22 @@ impl<'a> Parser<'a> {
 
         let num_calls = end_pos - start_pos;
 
-        // If we have no attributes, then we will never need to
-        // use any replace ranges.
-        let replace_ranges: Box<[ReplaceRange]> = if ret.attrs().is_empty() && !self.capture_cfg {
-            Box::new([])
-        } else {
-            // Grab any replace ranges that occur *inside* the current AST node.
-            // We will perform the actual replacement when we convert the `LazyAttrTokenStream`
-            // to an `AttrTokenStream`.
-            self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end]
-                .iter()
-                .cloned()
-                .chain(inner_attr_replace_ranges.iter().cloned())
-                .map(|(range, data)| ((range.start - start_pos)..(range.end - start_pos), data))
-                .collect()
-        };
+        // This is hot enough for `deep-vector` that checking the conditions for an empty iterator
+        // is measurably faster than actually executing the iterator.
+        let replace_ranges: Box<[ReplaceRange]> =
+            if replace_ranges_start == replace_ranges_end && inner_attr_replace_ranges.is_empty() {
+                Box::new([])
+            } else {
+                // Grab any replace ranges that occur *inside* the current AST node.
+                // We will perform the actual replacement when we convert the `LazyAttrTokenStream`
+                // to an `AttrTokenStream`.
+                self.capture_state.replace_ranges[replace_ranges_start..replace_ranges_end]
+                    .iter()
+                    .cloned()
+                    .chain(inner_attr_replace_ranges.iter().cloned())
+                    .map(|(range, data)| ((range.start - start_pos)..(range.end - start_pos), data))
+                    .collect()
+            };
 
         let tokens = LazyAttrTokenStream::new(LazyAttrTokenStreamImpl {
             start_token,
@@ -325,12 +320,9 @@ impl<'a> Parser<'a> {
             replace_ranges,
         });
 
-        // If we support tokens at all
-        if let Some(target_tokens) = ret.tokens_mut() {
-            if target_tokens.is_none() {
-                // Store our newly captured tokens into the AST node.
-                *target_tokens = Some(tokens.clone());
-            }
+        // If we support tokens and don't already have them, store the newly captured tokens.
+        if let Some(target_tokens @ None) = ret.tokens_mut() {
+            *target_tokens = Some(tokens.clone());
         }
 
         let final_attrs = ret.attrs();
@@ -352,15 +344,10 @@ impl<'a> Parser<'a> {
             let target = AttrsTarget { attrs: final_attrs.iter().cloned().collect(), tokens };
             self.capture_state.replace_ranges.push((start_pos..end_pos, Some(target)));
             self.capture_state.replace_ranges.extend(inner_attr_replace_ranges);
-        }
-
-        // Only clear our `replace_ranges` when we're finished capturing entirely.
-        if matches!(self.capture_state.capturing, Capturing::No) {
+        } else if matches!(self.capture_state.capturing, Capturing::No) {
+            // Only clear the ranges once we've finished capturing entirely.
             self.capture_state.replace_ranges.clear();
-            // We don't clear `inner_attr_ranges`, as doing so repeatedly
-            // had a measurable performance impact. Most inner attributes that
-            // we insert will get removed - when we drop the parser, we'll free
-            // up the memory used by any attributes that we didn't remove from the map.
+            self.capture_state.inner_attr_ranges.clear();
         }
         Ok(ret)
     }
@@ -370,7 +357,7 @@ impl<'a> Parser<'a> {
 /// `AttrTokenStream`, creating an `AttrTokenTree::Delimited` for each matching pair of open and
 /// close delims.
 fn make_attr_token_stream(
-    mut iter: impl Iterator<Item = (FlatToken, Spacing)>,
+    iter: impl Iterator<Item = FlatToken>,
     break_last_token: bool,
 ) -> AttrTokenStream {
     #[derive(Debug)]
@@ -379,19 +366,19 @@ fn make_attr_token_stream(
         open_delim_sp: Option<(Delimiter, Span, Spacing)>,
         inner: Vec<AttrTokenTree>,
     }
-    let mut stack = vec![FrameData { open_delim_sp: None, inner: vec![] }];
-    let mut token_and_spacing = iter.next();
-    while let Some((token, spacing)) = token_and_spacing {
-        match token {
-            FlatToken::Token(Token { kind: TokenKind::OpenDelim(delim), span }) => {
-                stack
-                    .push(FrameData { open_delim_sp: Some((delim, span, spacing)), inner: vec![] });
+    // The stack always has at least one element. Storing it separately makes for shorter code.
+    let mut stack_top = FrameData { open_delim_sp: None, inner: vec![] };
+    let mut stack_rest = vec![];
+    for flat_token in iter {
+        match flat_token {
+            FlatToken::Token((Token { kind: TokenKind::OpenDelim(delim), span }, spacing)) => {
+                stack_rest.push(mem::replace(
+                    &mut stack_top,
+                    FrameData { open_delim_sp: Some((delim, span, spacing)), inner: vec![] },
+                ));
             }
-            FlatToken::Token(Token { kind: TokenKind::CloseDelim(delim), span }) => {
-                let frame_data = stack
-                    .pop()
-                    .unwrap_or_else(|| panic!("Token stack was empty for token: {token:?}"));
-
+            FlatToken::Token((Token { kind: TokenKind::CloseDelim(delim), span }, spacing)) => {
+                let frame_data = mem::replace(&mut stack_top, stack_rest.pop().unwrap());
                 let (open_delim, open_sp, open_spacing) = frame_data.open_delim_sp.unwrap();
                 assert_eq!(
                     open_delim, delim,
@@ -401,29 +388,20 @@ fn make_attr_token_stream(
                 let dspacing = DelimSpacing::new(open_spacing, spacing);
                 let stream = AttrTokenStream::new(frame_data.inner);
                 let delimited = AttrTokenTree::Delimited(dspan, dspacing, delim, stream);
-                stack
-                    .last_mut()
-                    .unwrap_or_else(|| panic!("Bottom token frame is missing for token: {token:?}"))
-                    .inner
-                    .push(delimited);
+                stack_top.inner.push(delimited);
+            }
+            FlatToken::Token((token, spacing)) => {
+                stack_top.inner.push(AttrTokenTree::Token(token, spacing))
+            }
+            FlatToken::AttrsTarget(target) => {
+                stack_top.inner.push(AttrTokenTree::AttrsTarget(target))
             }
-            FlatToken::Token(token) => stack
-                .last_mut()
-                .expect("Bottom token frame is missing!")
-                .inner
-                .push(AttrTokenTree::Token(token, spacing)),
-            FlatToken::AttrsTarget(target) => stack
-                .last_mut()
-                .expect("Bottom token frame is missing!")
-                .inner
-                .push(AttrTokenTree::AttrsTarget(target)),
             FlatToken::Empty => {}
         }
-        token_and_spacing = iter.next();
     }
-    let mut final_buf = stack.pop().expect("Missing final buf!");
+
     if break_last_token {
-        let last_token = final_buf.inner.pop().unwrap();
+        let last_token = stack_top.inner.pop().unwrap();
         if let AttrTokenTree::Token(last_token, spacing) = last_token {
             let unglued_first = last_token.kind.break_two_token_op().unwrap().0;
 
@@ -431,14 +409,14 @@ fn make_attr_token_stream(
             let mut first_span = last_token.span.shrink_to_lo();
             first_span = first_span.with_hi(first_span.lo() + rustc_span::BytePos(1));
 
-            final_buf
+            stack_top
                 .inner
                 .push(AttrTokenTree::Token(Token::new(unglued_first, first_span), spacing));
         } else {
             panic!("Unexpected last token {last_token:?}")
         }
     }
-    AttrTokenStream::new(final_buf.inner)
+    AttrTokenStream::new(stack_top.inner)
 }
 
 // Some types are used a lot. Make sure they don't unintentionally get bigger.
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 81d5f0fca0e..0da7fefe6ed 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -3,8 +3,8 @@ use super::{
     BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep, TokenType,
 };
 use crate::errors::{
-    AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, BadQPathStage2, BadTypePlus,
-    BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
+    AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, AwaitSuggestion,
+    BadQPathStage2, BadTypePlus, BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
     ComparisonOperatorsCannotBeChainedSugg, ConstGenericWithoutBraces,
     ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
     DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
@@ -566,7 +566,10 @@ impl<'a> Parser<'a> {
             && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Eq)))
         {
             // Likely typo: `=` → `==` in let expr or enum item
-            return Err(self.dcx().create_err(UseEqInstead { span: self.token.span }));
+            return Err(self.dcx().create_err(UseEqInstead {
+                span: self.token.span,
+                suggestion: self.token.span.with_lo(self.token.span.lo() + BytePos(1)),
+            }));
         }
 
         if self.token.is_keyword(kw::Move) && self.prev_token.is_keyword(kw::Async) {
@@ -1151,7 +1154,7 @@ impl<'a> Parser<'a> {
             // Eat from where we started until the end token so that parsing can continue
             // as if we didn't have those extra angle brackets.
             self.eat_to_tokens(end);
-            let span = lo.until(self.token.span);
+            let span = lo.to(self.prev_token.span);
 
             let num_extra_brackets = number_of_gt + number_of_shr * 2;
             return Some(self.dcx().emit_err(UnmatchedAngleBrackets { span, num_extra_brackets }));
@@ -1539,7 +1542,10 @@ impl<'a> Parser<'a> {
 
     pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
         if impl_dyn_multi {
-            self.dcx().emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(ty), span: ty.span });
+            self.dcx().emit_err(AmbiguousPlus {
+                span: ty.span,
+                suggestion: AddParen { lo: ty.span.shrink_to_lo(), hi: ty.span.shrink_to_hi() },
+            });
         }
     }
 
@@ -1604,25 +1610,14 @@ impl<'a> Parser<'a> {
         }
 
         self.bump(); // `+`
-        let bounds = self.parse_generic_bounds()?;
+        let _bounds = self.parse_generic_bounds()?;
         let sum_span = ty.span.to(self.prev_token.span);
 
         let sub = match &ty.kind {
-            TyKind::Ref(lifetime, mut_ty) => {
-                let sum_with_parens = pprust::to_string(|s| {
-                    s.s.word("&");
-                    s.print_opt_lifetime(lifetime);
-                    s.print_mutability(mut_ty.mutbl, false);
-                    s.popen();
-                    s.print_type(&mut_ty.ty);
-                    if !bounds.is_empty() {
-                        s.word(" + ");
-                        s.print_type_bounds(&bounds);
-                    }
-                    s.pclose()
-                });
-
-                BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
+            TyKind::Ref(_lifetime, mut_ty) => {
+                let lo = mut_ty.ty.span.shrink_to_lo();
+                let hi = self.prev_token.span.shrink_to_hi();
+                BadTypePlusSub::AddParen { suggestion: AddParen { lo, hi } }
             }
             TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
             _ => BadTypePlusSub::ExpectPath { span: sum_span },
@@ -1964,18 +1959,14 @@ impl<'a> Parser<'a> {
         is_question: bool,
     ) -> (Span, ErrorGuaranteed) {
         let span = lo.to(hi);
-        let applicability = match expr.kind {
-            ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
-            _ => Applicability::MachineApplicable,
-        };
-
         let guar = self.dcx().emit_err(IncorrectAwait {
             span,
-            sugg_span: (span, applicability),
-            expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(expr)),
-            question_mark: if is_question { "?" } else { "" },
+            suggestion: AwaitSuggestion {
+                removal: lo.until(expr.span),
+                dot_await: expr.span.shrink_to_hi(),
+                question_mark: if is_question { "?" } else { "" },
+            },
         });
-
         (span, guar)
     }
 
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index b2df9a14eb0..4bd20be4171 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -714,7 +714,7 @@ impl<'a> Parser<'a> {
                                 type_err.cancel();
                                 self.dcx().emit_err(errors::MalformedLoopLabel {
                                     span: label.ident.span,
-                                    correct_label: label.ident,
+                                    suggestion: label.ident.span.shrink_to_lo(),
                                 });
                                 return Ok(expr);
                             }
@@ -856,7 +856,7 @@ impl<'a> Parser<'a> {
         let hi = self.interpolated_or_expr_span(&expr);
         let span = lo.to(hi);
         if let Some(lt) = lifetime {
-            self.error_remove_borrow_lifetime(span, lt.ident.span);
+            self.error_remove_borrow_lifetime(span, lt.ident.span.until(expr.span));
         }
         Ok((span, ExprKind::AddrOf(borrow_kind, mutbl, expr)))
     }
@@ -1653,6 +1653,7 @@ impl<'a> Parser<'a> {
         let lo = label_.ident.span;
         let label = Some(label_);
         let ate_colon = self.eat(&token::Colon);
+        let tok_sp = self.token.span;
         let expr = if self.eat_keyword(kw::While) {
             self.parse_expr_while(label, lo)
         } else if self.eat_keyword(kw::For) {
@@ -1747,7 +1748,7 @@ impl<'a> Parser<'a> {
             self.dcx().emit_err(errors::RequireColonAfterLabeledExpression {
                 span: expr.span,
                 label: lo,
-                label_end: lo.shrink_to_hi(),
+                label_end: lo.between(tok_sp),
             });
         }
 
@@ -2106,7 +2107,7 @@ impl<'a> Parser<'a> {
                 self.bump();
                 self.dcx().emit_err(errors::FloatLiteralRequiresIntegerPart {
                     span: token.span,
-                    correct: pprust::token_to_string(token).into_owned(),
+                    suggestion: token.span.shrink_to_lo(),
                 });
             }
         }
@@ -2741,7 +2742,7 @@ impl<'a> Parser<'a> {
         if !attrs.is_empty()
             && let [x0 @ xn] | [x0, .., xn] = &*attrs.take_for_recovery(self.psess)
         {
-            let attributes = x0.span.to(xn.span);
+            let attributes = x0.span.until(branch_span);
             let last = xn.span;
             let ctx = if is_ctx_else { "else" } else { "if" };
             self.dcx().emit_err(errors::OuterAttributeNotAllowedOnIfElse {
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index abb6b51cebd..76857cb8504 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -239,6 +239,7 @@ impl<'a> Parser<'a> {
                 self.recover_const_impl(const_span, attrs, def_())?
             } else {
                 self.recover_const_mut(const_span);
+                self.recover_missing_kw_before_item()?;
                 let (ident, generics, ty, expr) = self.parse_const_item()?;
                 (
                     ident,
@@ -311,6 +312,9 @@ impl<'a> Parser<'a> {
                 Case::Insensitive,
             );
         } else if macros_allowed && self.check_path() {
+            if self.isnt_macro_invocation() {
+                self.recover_missing_kw_before_item()?;
+            }
             // MACRO INVOCATION ITEM
             (Ident::empty(), ItemKind::MacCall(P(self.parse_item_macro(vis)?)))
         } else {
@@ -374,25 +378,25 @@ impl<'a> Parser<'a> {
         self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::PathSep)
     }
 
-    /// Recover on encountering a struct or method definition where the user
-    /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
+    /// Recover on encountering a struct, enum, or method definition where the user
+    /// forgot to add the `struct`, `enum`, or `fn` keyword
     fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
-        // Space between `pub` keyword and the identifier
-        //
-        //     pub   S {}
-        //        ^^^ `sp` points here
-        let sp = self.prev_token.span.between(self.token.span);
-        let full_sp = self.prev_token.span.to(self.token.span);
-        let ident_sp = self.token.span;
-
-        let ident = if self.look_ahead(1, |t| {
-            [
-                token::Lt,
-                token::OpenDelim(Delimiter::Brace),
-                token::OpenDelim(Delimiter::Parenthesis),
-            ]
-            .contains(&t.kind)
-        }) {
+        let is_pub = self.prev_token.is_keyword(kw::Pub);
+        let is_const = self.prev_token.is_keyword(kw::Const);
+        let ident_span = self.token.span;
+        let span = if is_pub { self.prev_token.span.to(ident_span) } else { ident_span };
+        let insert_span = ident_span.shrink_to_lo();
+
+        let ident = if self.token.is_ident()
+            && (!is_const || self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Parenthesis)))
+            && self.look_ahead(1, |t| {
+                [
+                    token::Lt,
+                    token::OpenDelim(Delimiter::Brace),
+                    token::OpenDelim(Delimiter::Parenthesis),
+                ]
+                .contains(&t.kind)
+            }) {
             self.parse_ident().unwrap()
         } else {
             return Ok(());
@@ -406,46 +410,56 @@ impl<'a> Parser<'a> {
         }
 
         let err = if self.check(&token::OpenDelim(Delimiter::Brace)) {
-            // possible public struct definition where `struct` was forgotten
-            Some(errors::MissingKeywordForItemDefinition::Struct { span: sp, ident })
+            // possible struct or enum definition where `struct` or `enum` was forgotten
+            if self.look_ahead(1, |t| *t == token::CloseDelim(Delimiter::Brace)) {
+                // `S {}` could be unit enum or struct
+                Some(errors::MissingKeywordForItemDefinition::EnumOrStruct { span })
+            } else if self.look_ahead(2, |t| *t == token::Colon)
+                || self.look_ahead(3, |t| *t == token::Colon)
+            {
+                // `S { f:` or `S { pub f:`
+                Some(errors::MissingKeywordForItemDefinition::Struct { span, insert_span, ident })
+            } else {
+                Some(errors::MissingKeywordForItemDefinition::Enum { span, insert_span, ident })
+            }
         } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
-            // possible public function or tuple struct definition where `fn`/`struct` was
-            // forgotten
+            // possible function or tuple struct definition where `fn` or `struct` was forgotten
             self.bump(); // `(`
             let is_method = self.recover_self_param();
 
             self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::Yes);
 
-            let err =
-                if self.check(&token::RArrow) || self.check(&token::OpenDelim(Delimiter::Brace)) {
-                    self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
-                    self.bump(); // `{`
-                    self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
-                    if is_method {
-                        errors::MissingKeywordForItemDefinition::Method { span: sp, ident }
-                    } else {
-                        errors::MissingKeywordForItemDefinition::Function { span: sp, ident }
-                    }
-                } else if self.check(&token::Semi) {
-                    errors::MissingKeywordForItemDefinition::Struct { span: sp, ident }
+            let err = if self.check(&token::RArrow)
+                || self.check(&token::OpenDelim(Delimiter::Brace))
+            {
+                self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
+                self.bump(); // `{`
+                self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
+                if is_method {
+                    errors::MissingKeywordForItemDefinition::Method { span, insert_span, ident }
                 } else {
-                    errors::MissingKeywordForItemDefinition::Ambiguous {
-                        span: sp,
-                        subdiag: if found_generics {
-                            None
-                        } else if let Ok(snippet) = self.span_to_snippet(ident_sp) {
-                            Some(errors::AmbiguousMissingKwForItemSub::SuggestMacro {
-                                span: full_sp,
-                                snippet,
-                            })
-                        } else {
-                            Some(errors::AmbiguousMissingKwForItemSub::HelpMacro)
-                        },
-                    }
-                };
+                    errors::MissingKeywordForItemDefinition::Function { span, insert_span, ident }
+                }
+            } else if is_pub && self.check(&token::Semi) {
+                errors::MissingKeywordForItemDefinition::Struct { span, insert_span, ident }
+            } else {
+                errors::MissingKeywordForItemDefinition::Ambiguous {
+                    span,
+                    subdiag: if found_generics {
+                        None
+                    } else if let Ok(snippet) = self.span_to_snippet(ident_span) {
+                        Some(errors::AmbiguousMissingKwForItemSub::SuggestMacro {
+                            span: ident_span,
+                            snippet,
+                        })
+                    } else {
+                        Some(errors::AmbiguousMissingKwForItemSub::HelpMacro)
+                    },
+                }
+            };
             Some(err)
         } else if found_generics {
-            Some(errors::MissingKeywordForItemDefinition::Ambiguous { span: sp, subdiag: None })
+            Some(errors::MissingKeywordForItemDefinition::Ambiguous { span, subdiag: None })
         } else {
             None
         };
@@ -796,7 +810,7 @@ impl<'a> Parser<'a> {
                         self.dcx().struct_span_err(non_item_span, "non-item in item list");
                     self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
                     if is_let {
-                        err.span_suggestion(
+                        err.span_suggestion_verbose(
                             non_item_span,
                             "consider using `const` instead of `let` for associated const",
                             "const",
@@ -2227,9 +2241,13 @@ impl<'a> Parser<'a> {
             let kw_token = self.token.clone();
             let kw_str = pprust::token_to_string(&kw_token);
             let item = self.parse_item(ForceCollect::No)?;
+            let mut item = item.unwrap().span;
+            if self.token == token::Comma {
+                item = item.to(self.token.span);
+            }
             self.dcx().emit_err(errors::NestedAdt {
                 span: kw_token.span,
-                item: item.unwrap().span,
+                item,
                 kw_str,
                 keyword: keyword.as_str(),
             });
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 45ca267fe5d..958458eda9a 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1118,41 +1118,37 @@ impl<'a> Parser<'a> {
             return looker(&self.token);
         }
 
-        if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last()
-            && delim != Delimiter::Invisible
-        {
-            // We are not in the outermost token stream, and the token stream
-            // we are in has non-skipped delimiters. Look for skipped
-            // delimiters in the lookahead range.
-            let tree_cursor = &self.token_cursor.tree_cursor;
-            let all_normal = (0..dist).all(|i| {
-                let token = tree_cursor.look_ahead(i);
-                !matches!(token, Some(TokenTree::Delimited(.., Delimiter::Invisible, _)))
-            });
-            if all_normal {
-                // There were no skipped delimiters. Do lookahead by plain indexing.
-                return match tree_cursor.look_ahead(dist - 1) {
-                    Some(tree) => {
-                        // Indexing stayed within the current token stream.
-                        match tree {
-                            TokenTree::Token(token, _) => looker(token),
-                            TokenTree::Delimited(dspan, _, delim, _) => {
-                                looker(&Token::new(token::OpenDelim(*delim), dspan.open))
-                            }
+        // Typically around 98% of the `dist > 0` cases have `dist == 1`, so we
+        // have a fast special case for that.
+        if dist == 1 {
+            // The index is zero because the tree cursor's index always points
+            // to the next token to be gotten.
+            match self.token_cursor.tree_cursor.look_ahead(0) {
+                Some(tree) => {
+                    // Indexing stayed within the current token tree.
+                    return match tree {
+                        TokenTree::Token(token, _) => looker(token),
+                        TokenTree::Delimited(dspan, _, delim, _) => {
+                            looker(&Token::new(token::OpenDelim(*delim), dspan.open))
                         }
+                    };
+                }
+                None => {
+                    // The tree cursor lookahead went (one) past the end of the
+                    // current token tree. Try to return a close delimiter.
+                    if let Some(&(_, span, _, delim)) = self.token_cursor.stack.last()
+                        && delim != Delimiter::Invisible
+                    {
+                        // We are not in the outermost token stream, so we have
+                        // delimiters. Also, those delimiters are not skipped.
+                        return looker(&Token::new(token::CloseDelim(delim), span.close));
                     }
-                    None => {
-                        // Indexing went past the end of the current token
-                        // stream. Use the close delimiter, no matter how far
-                        // ahead `dist` went.
-                        looker(&Token::new(token::CloseDelim(delim), span.close))
-                    }
-                };
+                }
             }
         }
 
-        // We are in a more complex case. Just clone the token cursor and use
-        // `next`, skipping delimiters as necessary. Slow but simple.
+        // Just clone the token cursor and use `next`, skipping delimiters as
+        // necessary. Slow but simple.
         let mut cursor = self.token_cursor.clone();
         let mut i = 0;
         let mut token = Token::dummy();
@@ -1541,14 +1537,16 @@ impl<'a> Parser<'a> {
 
                 // we don't need N spans, but we want at least one, so print all of prev_token
                 dbg_fmt.field("prev_token", &parser.prev_token);
-                // make it easier to peek farther ahead by taking TokenKinds only until EOF
-                let tokens = (0..*lookahead)
-                    .map(|i| parser.look_ahead(i, |tok| tok.kind.clone()))
-                    .scan(parser.prev_token == TokenKind::Eof, |eof, tok| {
-                        let current = eof.then_some(tok.clone()); // include a trailing EOF token
-                        *eof |= &tok == &TokenKind::Eof;
-                        current
-                    });
+                let mut tokens = vec![];
+                for i in 0..*lookahead {
+                    let tok = parser.look_ahead(i, |tok| tok.kind.clone());
+                    let is_eof = tok == TokenKind::Eof;
+                    tokens.push(tok);
+                    if is_eof {
+                        // Don't look ahead past EOF.
+                        break;
+                    }
+                }
                 dbg_fmt.field_with("tokens", |field| field.debug_list().entries(tokens).finish());
                 dbg_fmt.field("approx_token_stream_pos", &parser.num_bump_calls);
 
@@ -1607,7 +1605,7 @@ pub(crate) fn make_unclosed_delims_error(
 enum FlatToken {
     /// A token - this holds both delimiter (e.g. '{' and '}')
     /// and non-delimiter tokens
-    Token(Token),
+    Token((Token, Spacing)),
     /// Holds the `AttrsTarget` for an AST node. The `AttrsTarget` is inserted
     /// directly into the constructed `AttrTokenStream` as an
     /// `AttrTokenTree::AttrsTarget`.
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 6f2b7177159..e4e89615d71 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -4,11 +4,11 @@ use crate::errors::{
     DotDotDotRestPattern, EnumPatternInsteadOfIdentifier, ExpectedBindingLeftOfAt,
     ExpectedCommaAfterPatternField, GenericArgsInPatRequireTurbofishSyntax,
     InclusiveRangeExtraEquals, InclusiveRangeMatchArrow, InclusiveRangeNoEnd, InvalidMutInPattern,
-    PatternOnWrongSideOfAt, RemoveLet, RepeatedMutInPattern, SwitchRefBoxOrder,
-    TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg, TrailingVertNotAllowed,
-    UnexpectedExpressionInPattern, UnexpectedLifetimeInPattern, UnexpectedParenInRangePat,
-    UnexpectedParenInRangePatSugg, UnexpectedVertVertBeforeFunctionParam,
-    UnexpectedVertVertInPattern,
+    ParenRangeSuggestion, PatternOnWrongSideOfAt, RemoveLet, RepeatedMutInPattern,
+    SwitchRefBoxOrder, TopLevelOrPatternNotAllowed, TopLevelOrPatternNotAllowedSugg,
+    TrailingVertNotAllowed, UnexpectedExpressionInPattern, UnexpectedLifetimeInPattern,
+    UnexpectedParenInRangePat, UnexpectedParenInRangePatSugg,
+    UnexpectedVertVertBeforeFunctionParam, UnexpectedVertVertInPattern, WrapInParens,
 };
 use crate::parser::expr::{could_be_unclosed_char_literal, LhsExpr};
 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
@@ -24,7 +24,7 @@ use rustc_errors::{Applicability, Diag, PResult};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_span::source_map::{respan, Spanned};
 use rustc_span::symbol::{kw, sym, Ident};
-use rustc_span::{ErrorGuaranteed, Span};
+use rustc_span::{BytePos, ErrorGuaranteed, Span};
 use thin_vec::{thin_vec, ThinVec};
 
 #[derive(PartialEq, Copy, Clone)]
@@ -236,11 +236,15 @@ impl<'a> Parser<'a> {
 
         if let PatKind::Or(pats) = &pat.kind {
             let span = pat.span;
-            let pat = pprust::pat_to_string(&pat);
             let sub = if pats.len() == 1 {
-                Some(TopLevelOrPatternNotAllowedSugg::RemoveLeadingVert { span, pat })
+                Some(TopLevelOrPatternNotAllowedSugg::RemoveLeadingVert {
+                    span: span.with_hi(span.lo() + BytePos(1)),
+                })
             } else {
-                Some(TopLevelOrPatternNotAllowedSugg::WrapInParens { span, pat })
+                Some(TopLevelOrPatternNotAllowedSugg::WrapInParens {
+                    span,
+                    suggestion: WrapInParens { lo: span.shrink_to_lo(), hi: span.shrink_to_hi() },
+                })
             };
 
             let err = self.dcx().create_err(match syntax_loc {
@@ -599,7 +603,10 @@ impl<'a> Parser<'a> {
         self.bump(); // `...`
 
         // The user probably mistook `...` for a rest pattern `..`.
-        self.dcx().emit_err(DotDotDotRestPattern { span: lo });
+        self.dcx().emit_err(DotDotDotRestPattern {
+            span: lo,
+            suggestion: lo.with_lo(lo.hi() - BytePos(1)),
+        });
         PatKind::Rest
     }
 
@@ -664,8 +671,13 @@ impl<'a> Parser<'a> {
             _ => return,
         }
 
-        self.dcx()
-            .emit_err(AmbiguousRangePattern { span: pat.span, pat: pprust::pat_to_string(pat) });
+        self.dcx().emit_err(AmbiguousRangePattern {
+            span: pat.span,
+            suggestion: ParenRangeSuggestion {
+                lo: pat.span.shrink_to_lo(),
+                hi: pat.span.shrink_to_hi(),
+            },
+        });
     }
 
     /// Parse `&pat` / `&mut pat`.
@@ -674,8 +686,11 @@ impl<'a> Parser<'a> {
         if let token::Lifetime(name) = self.token.kind {
             self.bump(); // `'a`
 
-            self.dcx()
-                .emit_err(UnexpectedLifetimeInPattern { span: self.prev_token.span, symbol: name });
+            self.dcx().emit_err(UnexpectedLifetimeInPattern {
+                span: self.prev_token.span,
+                symbol: name,
+                suggestion: self.prev_token.span.until(self.token.span),
+            });
         }
 
         let mutbl = self.parse_mutability();
@@ -913,10 +928,13 @@ impl<'a> Parser<'a> {
                 self.dcx().emit_err(InclusiveRangeExtraEquals { span: span_with_eq })
             }
             token::Gt if no_space => {
-                let after_pat = span.with_hi(span.hi() - rustc_span::BytePos(1)).shrink_to_hi();
+                let after_pat = span.with_hi(span.hi() - BytePos(1)).shrink_to_hi();
                 self.dcx().emit_err(InclusiveRangeMatchArrow { span, arrow: tok.span, after_pat })
             }
-            _ => self.dcx().emit_err(InclusiveRangeNoEnd { span }),
+            _ => self.dcx().emit_err(InclusiveRangeNoEnd {
+                span,
+                suggestion: span.with_lo(span.hi() - BytePos(1)),
+            }),
         }
     }
 
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 03c647dd527..b9014dea726 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -258,6 +258,7 @@ impl<'a> Parser<'a> {
                         self.bump(); // bump past the colon
                         self.dcx().emit_err(PathSingleColon {
                             span: self.prev_token.span,
+                            suggestion: self.prev_token.span.shrink_to_hi(),
                             type_ascription: self
                                 .psess
                                 .unstable_features
@@ -329,6 +330,7 @@ impl<'a> Parser<'a> {
                             err.cancel();
                             err = self.dcx().create_err(PathSingleColon {
                                 span: self.token.span,
+                                suggestion: self.prev_token.span.shrink_to_hi(),
                                 type_ascription: self
                                     .psess
                                     .unstable_features
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index d65f6ff68ee..70d41de00a7 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -430,8 +430,10 @@ impl<'a> Parser<'a> {
         let eq_consumed = match self.token.kind {
             token::BinOpEq(..) => {
                 // Recover `let x <op>= 1` as `let x = 1`
-                self.dcx()
-                    .emit_err(errors::CompoundAssignmentExpressionInLet { span: self.token.span });
+                self.dcx().emit_err(errors::CompoundAssignmentExpressionInLet {
+                    span: self.token.span,
+                    suggestion: self.token.span.with_hi(self.token.span.lo() + BytePos(1)),
+                });
                 self.bump();
                 true
             }
@@ -717,7 +719,7 @@ impl<'a> Parser<'a> {
                                                 e.cancel();
                                                 self.dcx().emit_err(MalformedLoopLabel {
                                                     span: label.ident.span,
-                                                    correct_label: label.ident,
+                                                    suggestion: label.ident.span.shrink_to_lo(),
                                                 });
                                                 *expr = labeled_expr;
                                                 break 'break_recover None;
diff --git a/compiler/rustc_parse/src/parser/tests.rs b/compiler/rustc_parse/src/parser/tests.rs
index 42392ad2163..cf791d332a2 100644
--- a/compiler/rustc_parse/src/parser/tests.rs
+++ b/compiler/rustc_parse/src/parser/tests.rs
@@ -1376,6 +1376,365 @@ fn ttdelim_span() {
     });
 }
 
+#[track_caller]
+fn look(p: &Parser<'_>, dist: usize, kind: rustc_ast::token::TokenKind) {
+    // Do the `assert_eq` outside the closure so that `track_caller` works.
+    // (`#![feature(closure_track_caller)]` + `#[track_caller]` on the closure
+    // doesn't give the line number in the test below if the assertion fails.)
+    let tok = p.look_ahead(dist, |tok| tok.clone());
+    assert_eq!(kind, tok.kind);
+}
+
+#[test]
+fn look_ahead() {
+    create_default_session_globals_then(|| {
+        let sym_f = Symbol::intern("f");
+        let sym_x = Symbol::intern("x");
+        #[allow(non_snake_case)]
+        let sym_S = Symbol::intern("S");
+        let raw_no = IdentIsRaw::No;
+
+        let psess = psess();
+        let mut p = string_to_parser(&psess, "fn f(x: u32) { x } struct S;".to_string());
+
+        // Current position is the `fn`.
+        look(&p, 0, token::Ident(kw::Fn, raw_no));
+        look(&p, 1, token::Ident(sym_f, raw_no));
+        look(&p, 2, token::OpenDelim(Delimiter::Parenthesis));
+        look(&p, 3, token::Ident(sym_x, raw_no));
+        look(&p, 4, token::Colon);
+        look(&p, 5, token::Ident(sym::u32, raw_no));
+        look(&p, 6, token::CloseDelim(Delimiter::Parenthesis));
+        look(&p, 7, token::OpenDelim(Delimiter::Brace));
+        look(&p, 8, token::Ident(sym_x, raw_no));
+        look(&p, 9, token::CloseDelim(Delimiter::Brace));
+        look(&p, 10, token::Ident(kw::Struct, raw_no));
+        look(&p, 11, token::Ident(sym_S, raw_no));
+        look(&p, 12, token::Semi);
+        // Any lookahead past the end of the token stream returns `Eof`.
+        look(&p, 13, token::Eof);
+        look(&p, 14, token::Eof);
+        look(&p, 15, token::Eof);
+        look(&p, 100, token::Eof);
+
+        // Move forward to the first `x`.
+        for _ in 0..3 {
+            p.bump();
+        }
+        look(&p, 0, token::Ident(sym_x, raw_no));
+        look(&p, 1, token::Colon);
+        look(&p, 2, token::Ident(sym::u32, raw_no));
+        look(&p, 3, token::CloseDelim(Delimiter::Parenthesis));
+        look(&p, 4, token::OpenDelim(Delimiter::Brace));
+        look(&p, 5, token::Ident(sym_x, raw_no));
+        look(&p, 6, token::CloseDelim(Delimiter::Brace));
+        look(&p, 7, token::Ident(kw::Struct, raw_no));
+        look(&p, 8, token::Ident(sym_S, raw_no));
+        look(&p, 9, token::Semi);
+        look(&p, 10, token::Eof);
+        look(&p, 11, token::Eof);
+        look(&p, 100, token::Eof);
+
+        // Move forward to the `;`.
+        for _ in 0..9 {
+            p.bump();
+        }
+        look(&p, 0, token::Semi);
+        // Any lookahead past the end of the token stream returns `Eof`.
+        look(&p, 1, token::Eof);
+        look(&p, 100, token::Eof);
+
+        // Move one past the `;`, i.e. past the end of the token stream.
+        p.bump();
+        look(&p, 0, token::Eof);
+        look(&p, 1, token::Eof);
+        look(&p, 100, token::Eof);
+
+        // Bumping after Eof is idempotent.
+        p.bump();
+        look(&p, 0, token::Eof);
+        look(&p, 1, token::Eof);
+        look(&p, 100, token::Eof);
+    });
+}
+
+/// There used to be some buggy behaviour when using `look_ahead` not within
+/// the outermost token stream, which this test covers.
+#[test]
+fn look_ahead_non_outermost_stream() {
+    create_default_session_globals_then(|| {
+        let sym_f = Symbol::intern("f");
+        let sym_x = Symbol::intern("x");
+        #[allow(non_snake_case)]
+        let sym_S = Symbol::intern("S");
+        let raw_no = IdentIsRaw::No;
+
+        let psess = psess();
+        let mut p = string_to_parser(&psess, "mod m { fn f(x: u32) { x } struct S; }".to_string());
+
+        // Move forward to the `fn`, which is not within the outermost token
+        // stream (because it's inside the `mod { ... }`).
+        for _ in 0..3 {
+            p.bump();
+        }
+        look(&p, 0, token::Ident(kw::Fn, raw_no));
+        look(&p, 1, token::Ident(sym_f, raw_no));
+        look(&p, 2, token::OpenDelim(Delimiter::Parenthesis));
+        look(&p, 3, token::Ident(sym_x, raw_no));
+        look(&p, 4, token::Colon);
+        look(&p, 5, token::Ident(sym::u32, raw_no));
+        look(&p, 6, token::CloseDelim(Delimiter::Parenthesis));
+        look(&p, 7, token::OpenDelim(Delimiter::Brace));
+        look(&p, 8, token::Ident(sym_x, raw_no));
+        look(&p, 9, token::CloseDelim(Delimiter::Brace));
+        look(&p, 10, token::Ident(kw::Struct, raw_no));
+        look(&p, 11, token::Ident(sym_S, raw_no));
+        look(&p, 12, token::Semi);
+        look(&p, 13, token::CloseDelim(Delimiter::Brace));
+        // Any lookahead past the end of the token stream returns `Eof`.
+        look(&p, 14, token::Eof);
+        look(&p, 15, token::Eof);
+        look(&p, 100, token::Eof);
+    });
+}
+
+// FIXME(nnethercote) All the output is currently wrong.
+#[test]
+fn debug_lookahead() {
+    create_default_session_globals_then(|| {
+        let psess = psess();
+        let mut p = string_to_parser(&psess, "fn f(x: u32) { x } struct S;".to_string());
+
+        // Current position is the `fn`.
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(0)),
+            "Parser {
+    prev_token: Token {
+        kind: Question,
+        span: Span {
+            lo: BytePos(
+                0,
+            ),
+            hi: BytePos(
+                0,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [],
+    approx_token_stream_pos: 1,
+    ..
+}"
+        );
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(7)),
+            "Parser {
+    prev_token: Token {
+        kind: Question,
+        span: Span {
+            lo: BytePos(
+                0,
+            ),
+            hi: BytePos(
+                0,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [
+        Ident(
+            \"fn\",
+            No,
+        ),
+        Ident(
+            \"f\",
+            No,
+        ),
+        OpenDelim(
+            Parenthesis,
+        ),
+        Ident(
+            \"x\",
+            No,
+        ),
+        Colon,
+        Ident(
+            \"u32\",
+            No,
+        ),
+        CloseDelim(
+            Parenthesis,
+        ),
+    ],
+    approx_token_stream_pos: 1,
+    ..
+}"
+        );
+        // There are 13 tokens. We request 15, get 14; the last one is `Eof`.
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(15)),
+            "Parser {
+    prev_token: Token {
+        kind: Question,
+        span: Span {
+            lo: BytePos(
+                0,
+            ),
+            hi: BytePos(
+                0,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [
+        Ident(
+            \"fn\",
+            No,
+        ),
+        Ident(
+            \"f\",
+            No,
+        ),
+        OpenDelim(
+            Parenthesis,
+        ),
+        Ident(
+            \"x\",
+            No,
+        ),
+        Colon,
+        Ident(
+            \"u32\",
+            No,
+        ),
+        CloseDelim(
+            Parenthesis,
+        ),
+        OpenDelim(
+            Brace,
+        ),
+        Ident(
+            \"x\",
+            No,
+        ),
+        CloseDelim(
+            Brace,
+        ),
+        Ident(
+            \"struct\",
+            No,
+        ),
+        Ident(
+            \"S\",
+            No,
+        ),
+        Semi,
+        Eof,
+    ],
+    approx_token_stream_pos: 1,
+    ..
+}"
+        );
+
+        // Move forward to the second `x`.
+        for _ in 0..8 {
+            p.bump();
+        }
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(1)),
+            "Parser {
+    prev_token: Token {
+        kind: OpenDelim(
+            Brace,
+        ),
+        span: Span {
+            lo: BytePos(
+                13,
+            ),
+            hi: BytePos(
+                14,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [
+        Ident(
+            \"x\",
+            No,
+        ),
+    ],
+    approx_token_stream_pos: 9,
+    ..
+}"
+        );
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(4)),
+            "Parser {
+    prev_token: Token {
+        kind: OpenDelim(
+            Brace,
+        ),
+        span: Span {
+            lo: BytePos(
+                13,
+            ),
+            hi: BytePos(
+                14,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [
+        Ident(
+            \"x\",
+            No,
+        ),
+        CloseDelim(
+            Brace,
+        ),
+        Ident(
+            \"struct\",
+            No,
+        ),
+        Ident(
+            \"S\",
+            No,
+        ),
+    ],
+    approx_token_stream_pos: 9,
+    ..
+}"
+        );
+
+        // Move two past the final token (the `;`).
+        for _ in 0..6 {
+            p.bump();
+        }
+        assert_eq!(
+            &format!("{:#?}", p.debug_lookahead(3)),
+            "Parser {
+    prev_token: Token {
+        kind: Eof,
+        span: Span {
+            lo: BytePos(
+                27,
+            ),
+            hi: BytePos(
+                28,
+            ),
+            ctxt: #0,
+        },
+    },
+    tokens: [
+        Eof,
+    ],
+    approx_token_stream_pos: 15,
+    ..
+}"
+        );
+    });
+}
+
 // This tests that when parsing a string (rather than a file) we don't try
 // and read in a file for a module declaration and just parse a stub.
 // See `recurse_into_file_modules` in the parser.
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 1e5b227aaa9..94321b1dddd 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -209,6 +209,7 @@ impl<'a> Parser<'a> {
         recover_qpath: RecoverQPath,
         recover_return_sign: RecoverReturnSign,
     ) -> PResult<'a, FnRetTy> {
+        let lo = self.prev_token.span;
         Ok(if self.eat(&token::RArrow) {
             // FIXME(Centril): Can we unconditionally `allow_plus`?
             let ty = self.parse_ty_common(
@@ -224,7 +225,10 @@ impl<'a> Parser<'a> {
             // Don't `eat` to prevent `=>` from being added as an expected token which isn't
             // actually expected and could only confuse users
             self.bump();
-            self.dcx().emit_err(ReturnTypesUseThinArrow { span: self.prev_token.span });
+            self.dcx().emit_err(ReturnTypesUseThinArrow {
+                span: self.prev_token.span,
+                suggestion: lo.between(self.token.span),
+            });
             let ty = self.parse_ty_common(
                 allow_plus,
                 AllowCVariadic::No,
@@ -794,8 +798,11 @@ impl<'a> Parser<'a> {
         {
             if self.token.is_keyword(kw::Dyn) {
                 // Account for `&dyn Trait + dyn Other`.
-                self.dcx().emit_err(InvalidDynKeyword { span: self.token.span });
                 self.bump();
+                self.dcx().emit_err(InvalidDynKeyword {
+                    span: self.prev_token.span,
+                    suggestion: self.prev_token.span.until(self.token.span),
+                });
             }
             bounds.push(self.parse_generic_bound()?);
             if allow_plus == AllowPlus::No || !self.eat_plus() {
@@ -861,7 +868,7 @@ impl<'a> Parser<'a> {
         if has_parens {
             // FIXME(Centril): Consider not erroring here and accepting `('lt)` instead,
             // possibly introducing `GenericBound::Paren(P<GenericBound>)`?
-            self.recover_paren_lifetime(lo, lt.ident.span)?;
+            self.recover_paren_lifetime(lo)?;
         }
         Ok(bound)
     }
@@ -909,16 +916,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Recover on `('lifetime)` with `(` already eaten.
-    fn recover_paren_lifetime(&mut self, lo: Span, lt_span: Span) -> PResult<'a, ()> {
+    fn recover_paren_lifetime(&mut self, lo: Span) -> PResult<'a, ()> {
         self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
         let span = lo.to(self.prev_token.span);
-        let (sugg, snippet) = if let Ok(snippet) = self.span_to_snippet(lt_span) {
-            (Some(span), snippet)
-        } else {
-            (None, String::new())
-        };
+        let sugg = errors::RemoveParens { lo, hi: self.prev_token.span };
 
-        self.dcx().emit_err(errors::ParenthesizedLifetime { span, sugg, snippet });
+        self.dcx().emit_err(errors::ParenthesizedLifetime { span, sugg });
         Ok(())
     }