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-rw-r--r--compiler/rustc_parse/src/errors.rs15
-rw-r--r--compiler/rustc_parse/src/lexer/mod.rs107
-rw-r--r--compiler/rustc_parse/src/lexer/unescape_error_reporting.rs42
-rw-r--r--compiler/rustc_parse/src/parser/attr_wrapper.rs12
-rw-r--r--compiler/rustc_parse/src/parser/diagnostics.rs36
-rw-r--r--compiler/rustc_parse/src/parser/expr.rs43
-rw-r--r--compiler/rustc_parse/src/parser/item.rs108
-rw-r--r--compiler/rustc_parse/src/parser/mod.rs58
-rw-r--r--compiler/rustc_parse/src/parser/path.rs4
-rw-r--r--compiler/rustc_parse/src/parser/stmt.rs12
-rw-r--r--compiler/rustc_parse/src/parser/ty.rs7
11 files changed, 282 insertions, 162 deletions
diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 0924c853715..d59982f7063 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -421,6 +421,15 @@ pub(crate) struct ExpectedExpressionFoundLet {
 }
 
 #[derive(Diagnostic)]
+#[diag(parser_expect_eq_instead_of_eqeq)]
+pub(crate) struct ExpectedEqForLetExpr {
+    #[primary_span]
+    pub span: Span,
+    #[suggestion(applicability = "maybe-incorrect", code = "=", style = "verbose")]
+    pub sugg_span: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parser_expected_else_block)]
 pub(crate) struct ExpectedElseBlock {
     #[primary_span]
@@ -1156,10 +1165,12 @@ pub(crate) struct ParenthesesInForHead {
 #[derive(Subdiagnostic)]
 #[multipart_suggestion(suggestion, applicability = "machine-applicable")]
 pub(crate) struct ParenthesesInForHeadSugg {
-    #[suggestion_part(code = "")]
+    #[suggestion_part(code = "{left_snippet}")]
     pub left: Span,
-    #[suggestion_part(code = "")]
+    pub left_snippet: String,
+    #[suggestion_part(code = "{right_snippet}")]
     pub right: Span,
+    pub right_snippet: String,
 }
 
 #[derive(Diagnostic)]
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index de8f1c00c12..645262bd2f1 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -353,55 +353,55 @@ impl<'a> StringReader<'a> {
     fn cook_lexer_literal(
         &self,
         start: BytePos,
-        suffix_start: BytePos,
+        end: BytePos,
         kind: rustc_lexer::LiteralKind,
     ) -> (token::LitKind, Symbol) {
-        // prefix means `"` or `br"` or `r###"`, ...
-        let (lit_kind, mode, prefix_len, postfix_len) = match kind {
+        match kind {
             rustc_lexer::LiteralKind::Char { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start, suffix_start),
+                        self.mk_sp(start, end),
                         "unterminated character literal",
                         error_code!(E0762),
                     )
                 }
-                (token::Char, Mode::Char, 1, 1) // ' '
+                self.cook_quoted(token::Char, Mode::Char, start, end, 1, 1) // ' '
             }
             rustc_lexer::LiteralKind::Byte { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start + BytePos(1), suffix_start),
+                        self.mk_sp(start + BytePos(1), end),
                         "unterminated byte constant",
                         error_code!(E0763),
                     )
                 }
-                (token::Byte, Mode::Byte, 2, 1) // b' '
+                self.cook_quoted(token::Byte, Mode::Byte, start, end, 2, 1) // b' '
             }
             rustc_lexer::LiteralKind::Str { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start, suffix_start),
+                        self.mk_sp(start, end),
                         "unterminated double quote string",
                         error_code!(E0765),
                     )
                 }
-                (token::Str, Mode::Str, 1, 1) // " "
+                self.cook_quoted(token::Str, Mode::Str, start, end, 1, 1) // " "
             }
             rustc_lexer::LiteralKind::ByteStr { terminated } => {
                 if !terminated {
                     self.sess.span_diagnostic.span_fatal_with_code(
-                        self.mk_sp(start + BytePos(1), suffix_start),
+                        self.mk_sp(start + BytePos(1), end),
                         "unterminated double quote byte string",
                         error_code!(E0766),
                     )
                 }
-                (token::ByteStr, Mode::ByteStr, 2, 1) // b" "
+                self.cook_quoted(token::ByteStr, Mode::ByteStr, start, end, 2, 1) // b" "
             }
             rustc_lexer::LiteralKind::RawStr { n_hashes } => {
                 if let Some(n_hashes) = n_hashes {
                     let n = u32::from(n_hashes);
-                    (token::StrRaw(n_hashes), Mode::RawStr, 2 + n, 1 + n) // r##" "##
+                    let kind = token::StrRaw(n_hashes);
+                    self.cook_quoted(kind, Mode::RawStr, start, end, 2 + n, 1 + n) // r##" "##
                 } else {
                     self.report_raw_str_error(start, 1);
                 }
@@ -409,56 +409,59 @@ impl<'a> StringReader<'a> {
             rustc_lexer::LiteralKind::RawByteStr { n_hashes } => {
                 if let Some(n_hashes) = n_hashes {
                     let n = u32::from(n_hashes);
-                    (token::ByteStrRaw(n_hashes), Mode::RawByteStr, 3 + n, 1 + n) // br##" "##
+                    let kind = token::ByteStrRaw(n_hashes);
+                    self.cook_quoted(kind, Mode::RawByteStr, start, end, 3 + n, 1 + n) // br##" "##
                 } else {
                     self.report_raw_str_error(start, 2);
                 }
             }
             rustc_lexer::LiteralKind::Int { base, empty_int } => {
-                return if empty_int {
+                if empty_int {
                     self.sess
                         .span_diagnostic
                         .struct_span_err_with_code(
-                            self.mk_sp(start, suffix_start),
+                            self.mk_sp(start, end),
                             "no valid digits found for number",
                             error_code!(E0768),
                         )
                         .emit();
                     (token::Integer, sym::integer(0))
                 } else {
-                    self.validate_int_literal(base, start, suffix_start);
-                    (token::Integer, self.symbol_from_to(start, suffix_start))
-                };
+                    if matches!(base, Base::Binary | Base::Octal) {
+                        let base = base as u32;
+                        let s = self.str_from_to(start + BytePos(2), end);
+                        for (idx, c) in s.char_indices() {
+                            if c != '_' && c.to_digit(base).is_none() {
+                                self.err_span_(
+                                    start + BytePos::from_usize(2 + idx),
+                                    start + BytePos::from_usize(2 + idx + c.len_utf8()),
+                                    &format!("invalid digit for a base {} literal", base),
+                                );
+                            }
+                        }
+                    }
+                    (token::Integer, self.symbol_from_to(start, end))
+                }
             }
             rustc_lexer::LiteralKind::Float { base, empty_exponent } => {
                 if empty_exponent {
                     self.err_span_(start, self.pos, "expected at least one digit in exponent");
                 }
-
                 match base {
-                    Base::Hexadecimal => self.err_span_(
-                        start,
-                        suffix_start,
-                        "hexadecimal float literal is not supported",
-                    ),
+                    Base::Hexadecimal => {
+                        self.err_span_(start, end, "hexadecimal float literal is not supported")
+                    }
                     Base::Octal => {
-                        self.err_span_(start, suffix_start, "octal float literal is not supported")
+                        self.err_span_(start, end, "octal float literal is not supported")
                     }
                     Base::Binary => {
-                        self.err_span_(start, suffix_start, "binary float literal is not supported")
+                        self.err_span_(start, end, "binary float literal is not supported")
                     }
-                    _ => (),
+                    _ => {}
                 }
-
-                let id = self.symbol_from_to(start, suffix_start);
-                return (token::Float, id);
+                (token::Float, self.symbol_from_to(start, end))
             }
-        };
-        let content_start = start + BytePos(prefix_len);
-        let content_end = suffix_start - BytePos(postfix_len);
-        let id = self.symbol_from_to(content_start, content_end);
-        self.validate_literal_escape(mode, content_start, content_end, prefix_len, postfix_len);
-        (lit_kind, id)
+        }
     }
 
     #[inline]
@@ -649,20 +652,22 @@ impl<'a> StringReader<'a> {
         )
     }
 
-    fn validate_literal_escape(
+    fn cook_quoted(
         &self,
+        kind: token::LitKind,
         mode: Mode,
-        content_start: BytePos,
-        content_end: BytePos,
+        start: BytePos,
+        end: BytePos,
         prefix_len: u32,
         postfix_len: u32,
-    ) {
+    ) -> (token::LitKind, Symbol) {
+        let content_start = start + BytePos(prefix_len);
+        let content_end = end - BytePos(postfix_len);
         let lit_content = self.str_from_to(content_start, content_end);
         unescape::unescape_literal(lit_content, mode, &mut |range, result| {
             // Here we only check for errors. The actual unescaping is done later.
             if let Err(err) = result {
-                let span_with_quotes = self
-                    .mk_sp(content_start - BytePos(prefix_len), content_end + BytePos(postfix_len));
+                let span_with_quotes = self.mk_sp(start, end);
                 let (start, end) = (range.start as u32, range.end as u32);
                 let lo = content_start + BytePos(start);
                 let hi = lo + BytePos(end - start);
@@ -678,23 +683,7 @@ impl<'a> StringReader<'a> {
                 );
             }
         });
-    }
-
-    fn validate_int_literal(&self, base: Base, content_start: BytePos, content_end: BytePos) {
-        let base = match base {
-            Base::Binary => 2,
-            Base::Octal => 8,
-            _ => return,
-        };
-        let s = self.str_from_to(content_start + BytePos(2), content_end);
-        for (idx, c) in s.char_indices() {
-            let idx = idx as u32;
-            if c != '_' && c.to_digit(base).is_none() {
-                let lo = content_start + BytePos(2 + idx);
-                let hi = content_start + BytePos(2 + idx + c.len_utf8() as u32);
-                self.err_span_(lo, hi, &format!("invalid digit for a base {} literal", base));
-            }
-        }
+        (kind, Symbol::intern(lit_content))
     }
 }
 
diff --git a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
index f075de71426..6373f5b4fd6 100644
--- a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
+++ b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
@@ -108,7 +108,7 @@ pub(crate) fn emit_unescape_error(
             }
 
             if !has_help {
-                let (prefix, msg) = if mode.is_bytes() {
+                let (prefix, msg) = if mode.is_byte() {
                     ("b", "if you meant to write a byte string literal, use double quotes")
                 } else {
                     ("", "if you meant to write a `str` literal, use double quotes")
@@ -142,7 +142,7 @@ pub(crate) fn emit_unescape_error(
         EscapeError::EscapeOnlyChar => {
             let (c, char_span) = last_char();
 
-            let msg = if mode.is_bytes() {
+            let msg = if mode.is_byte() {
                 "byte constant must be escaped"
             } else {
                 "character constant must be escaped"
@@ -182,11 +182,11 @@ pub(crate) fn emit_unescape_error(
             let (c, span) = last_char();
 
             let label =
-                if mode.is_bytes() { "unknown byte escape" } else { "unknown character escape" };
+                if mode.is_byte() { "unknown byte escape" } else { "unknown character escape" };
             let ec = escaped_char(c);
             let mut diag = handler.struct_span_err(span, &format!("{}: `{}`", label, ec));
             diag.span_label(span, label);
-            if c == '{' || c == '}' && !mode.is_bytes() {
+            if c == '{' || c == '}' && !mode.is_byte() {
                 diag.help(
                     "if used in a formatting string, curly braces are escaped with `{{` and `}}`",
                 );
@@ -196,7 +196,7 @@ pub(crate) fn emit_unescape_error(
                      version control settings",
                 );
             } else {
-                if !mode.is_bytes() {
+                if !mode.is_byte() {
                     diag.span_suggestion(
                         span_with_quotes,
                         "if you meant to write a literal backslash (perhaps escaping in a regular expression), consider a raw string literal",
@@ -231,16 +231,23 @@ pub(crate) fn emit_unescape_error(
                 .emit();
         }
         EscapeError::NonAsciiCharInByte => {
-            assert!(mode.is_bytes());
             let (c, span) = last_char();
-            let mut err = handler.struct_span_err(span, "non-ASCII character in byte constant");
+            let desc = match mode {
+                Mode::Byte => "byte literal",
+                Mode::ByteStr => "byte string literal",
+                Mode::RawByteStr => "raw byte string literal",
+                _ => panic!("non-is_byte literal paired with NonAsciiCharInByte"),
+            };
+            let mut err = handler.struct_span_err(span, format!("non-ASCII character in {}", desc));
             let postfix = if unicode_width::UnicodeWidthChar::width(c).unwrap_or(1) == 0 {
                 format!(" but is {:?}", c)
             } else {
                 String::new()
             };
-            err.span_label(span, &format!("byte constant must be ASCII{}", postfix));
-            if (c as u32) <= 0xFF {
+            err.span_label(span, &format!("must be ASCII{}", postfix));
+            // Note: the \\xHH suggestions are not given for raw byte string
+            // literals, because they are araw and so cannot use any escapes.
+            if (c as u32) <= 0xFF && mode != Mode::RawByteStr {
                 err.span_suggestion(
                     span,
                     &format!(
@@ -250,9 +257,9 @@ pub(crate) fn emit_unescape_error(
                     format!("\\x{:X}", c as u32),
                     Applicability::MaybeIncorrect,
                 );
-            } else if matches!(mode, Mode::Byte) {
+            } else if mode == Mode::Byte {
                 err.span_label(span, "this multibyte character does not fit into a single byte");
-            } else if matches!(mode, Mode::ByteStr) {
+            } else if mode != Mode::RawByteStr {
                 let mut utf8 = String::new();
                 utf8.push(c);
                 err.span_suggestion(
@@ -270,19 +277,6 @@ pub(crate) fn emit_unescape_error(
             }
             err.emit();
         }
-        EscapeError::NonAsciiCharInByteString => {
-            assert!(mode.is_bytes());
-            let (c, span) = last_char();
-            let postfix = if unicode_width::UnicodeWidthChar::width(c).unwrap_or(1) == 0 {
-                format!(" but is {:?}", c)
-            } else {
-                String::new()
-            };
-            handler
-                .struct_span_err(span, "raw byte string must be ASCII")
-                .span_label(span, &format!("must be ASCII{}", postfix))
-                .emit();
-        }
         EscapeError::OutOfRangeHexEscape => {
             handler
                 .struct_span_err(span, "out of range hex escape")
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
index 1b16ecb5ec2..c8160548763 100644
--- a/compiler/rustc_parse/src/parser/attr_wrapper.rs
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -5,7 +5,8 @@ use rustc_ast::tokenstream::{AttrTokenTree, DelimSpan, LazyAttrTokenStream, Spac
 use rustc_ast::{self as ast};
 use rustc_ast::{AttrVec, Attribute, HasAttrs, HasTokens};
 use rustc_errors::PResult;
-use rustc_span::{sym, Span};
+use rustc_session::parse::ParseSess;
+use rustc_span::{sym, Span, DUMMY_SP};
 
 use std::convert::TryInto;
 use std::ops::Range;
@@ -39,8 +40,13 @@ impl AttrWrapper {
     pub fn empty() -> AttrWrapper {
         AttrWrapper { attrs: AttrVec::new(), start_pos: usize::MAX }
     }
-    // FIXME: Delay span bug here?
-    pub(crate) fn take_for_recovery(self) -> AttrVec {
+
+    pub(crate) fn take_for_recovery(self, sess: &ParseSess) -> AttrVec {
+        sess.span_diagnostic.delay_span_bug(
+            self.attrs.get(0).map(|attr| attr.span).unwrap_or(DUMMY_SP),
+            "AttrVec is taken for recovery but no error is produced",
+        );
+
         self.attrs
     }
 
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index 7dc4fd0044f..0bbe073fe2a 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -1653,15 +1653,29 @@ impl<'a> Parser<'a> {
             (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
                 self.bump();
 
+                let sm = self.sess.source_map();
+                let left = begin_par_sp;
+                let right = self.prev_token.span;
+                let left_snippet = if let Ok(snip) = sm.span_to_prev_source(left) &&
+                        !snip.ends_with(" ") {
+                                " ".to_string()
+                            } else {
+                                "".to_string()
+                            };
+
+                let right_snippet = if let Ok(snip) = sm.span_to_next_source(right) &&
+                        !snip.starts_with(" ") {
+                                " ".to_string()
+                            } else {
+                                "".to_string()
+                        };
+
                 self.sess.emit_err(ParenthesesInForHead {
-                    span: vec![begin_par_sp, self.prev_token.span],
+                    span: vec![left, right],
                     // With e.g. `for (x) in y)` this would replace `(x) in y)`
                     // with `x) in y)` which is syntactically invalid.
                     // However, this is prevented before we get here.
-                    sugg: ParenthesesInForHeadSugg {
-                        left: begin_par_sp,
-                        right: self.prev_token.span,
-                    },
+                    sugg: ParenthesesInForHeadSugg { left, right, left_snippet, right_snippet },
                 });
 
                 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
@@ -2468,11 +2482,15 @@ impl<'a> Parser<'a> {
     }
 
     pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
-        let Some(label) = self.eat_label().filter(|_| {
-            self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
-        }) else {
+        // Check for `'a : {`
+        if !(self.check_lifetime()
+            && self.look_ahead(1, |tok| tok.kind == token::Colon)
+            && self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Brace)))
+        {
             return false;
-        };
+        }
+        let label = self.eat_label().expect("just checked if a label exists");
+        self.bump(); // eat `:`
         let span = label.ident.span.to(self.prev_token.span);
         let mut err = self.struct_span_err(span, "block label not supported here");
         err.span_label(span, "not supported here");
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 4a1162b9599..b072573af23 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -9,9 +9,9 @@ use crate::errors::{
     ArrayBracketsInsteadOfSpaces, ArrayBracketsInsteadOfSpacesSugg, AsyncMoveOrderIncorrect,
     BinaryFloatLiteralNotSupported, BracesForStructLiteral, CatchAfterTry, CommaAfterBaseStruct,
     ComparisonInterpretedAsGeneric, ComparisonOrShiftInterpretedAsGenericSugg,
-    DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedExpressionFoundLet,
-    FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart, FoundExprWouldBeStmt,
-    HexadecimalFloatLiteralNotSupported, IfExpressionMissingCondition,
+    DoCatchSyntaxRemoved, DotDotDot, EqFieldInit, ExpectedElseBlock, ExpectedEqForLetExpr,
+    ExpectedExpressionFoundLet, FieldExpressionWithGeneric, FloatLiteralRequiresIntegerPart,
+    FoundExprWouldBeStmt, HexadecimalFloatLiteralNotSupported, IfExpressionMissingCondition,
     IfExpressionMissingThenBlock, IfExpressionMissingThenBlockSub, IntLiteralTooLarge,
     InvalidBlockMacroSegment, InvalidComparisonOperator, InvalidComparisonOperatorSub,
     InvalidFloatLiteralSuffix, InvalidFloatLiteralWidth, InvalidIntLiteralWidth,
@@ -33,6 +33,7 @@ use core::mem;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
 use rustc_ast::tokenstream::Spacing;
+use rustc_ast::util::case::Case;
 use rustc_ast::util::classify;
 use rustc_ast::util::literal::LitError;
 use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
@@ -833,16 +834,11 @@ impl<'a> Parser<'a> {
                 ("cast", None)
             };
 
-        // Save the memory location of expr before parsing any following postfix operators.
-        // This will be compared with the memory location of the output expression.
-        // If they different we can assume we parsed another expression because the existing expression is not reallocated.
-        let addr_before = &*cast_expr as *const _ as usize;
         let with_postfix = self.parse_dot_or_call_expr_with_(cast_expr, span)?;
-        let changed = addr_before != &*with_postfix as *const _ as usize;
 
         // Check if an illegal postfix operator has been added after the cast.
-        // If the resulting expression is not a cast, or has a different memory location, it is an illegal postfix operator.
-        if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) || changed {
+        // If the resulting expression is not a cast, it is an illegal postfix operator.
+        if !matches!(with_postfix.kind, ExprKind::Cast(_, _) | ExprKind::Type(_, _)) {
             let msg = format!(
                 "{cast_kind} cannot be followed by {}",
                 match with_postfix.kind {
@@ -2095,7 +2091,7 @@ impl<'a> Parser<'a> {
             if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
 
         let asyncness = if self.token.uninterpolated_span().rust_2018() {
-            self.parse_asyncness()
+            self.parse_asyncness(Case::Sensitive)
         } else {
             Async::No
         };
@@ -2276,7 +2272,7 @@ impl<'a> Parser<'a> {
                 self.mk_block_err(cond_span.shrink_to_hi())
             }
         } else {
-            let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
+            let attrs = self.parse_outer_attributes()?; // For recovery.
             let block = if self.check(&token::OpenDelim(Delimiter::Brace)) {
                 self.parse_block()?
             } else {
@@ -2293,7 +2289,7 @@ impl<'a> Parser<'a> {
                     })?
                 }
             };
-            self.error_on_if_block_attrs(lo, false, block.span, &attrs);
+            self.error_on_if_block_attrs(lo, false, block.span, attrs);
             block
         };
         let els = if self.eat_keyword(kw::Else) { Some(self.parse_else_expr()?) } else { None };
@@ -2334,7 +2330,15 @@ impl<'a> Parser<'a> {
             RecoverColon::Yes,
             CommaRecoveryMode::LikelyTuple,
         )?;
-        self.expect(&token::Eq)?;
+        if self.token == token::EqEq {
+            self.sess.emit_err(ExpectedEqForLetExpr {
+                span: self.token.span,
+                sugg_span: self.token.span,
+            });
+            self.bump();
+        } else {
+            self.expect(&token::Eq)?;
+        }
         let expr = self.with_res(self.restrictions | Restrictions::NO_STRUCT_LITERAL, |this| {
             this.parse_assoc_expr_with(1 + prec_let_scrutinee_needs_par(), None.into())
         })?;
@@ -2346,7 +2350,7 @@ impl<'a> Parser<'a> {
     /// Parses an `else { ... }` expression (`else` token already eaten).
     fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
         let else_span = self.prev_token.span; // `else`
-        let attrs = self.parse_outer_attributes()?.take_for_recovery(); // For recovery.
+        let attrs = self.parse_outer_attributes()?; // For recovery.
         let expr = if self.eat_keyword(kw::If) {
             self.parse_if_expr()?
         } else if self.check(&TokenKind::OpenDelim(Delimiter::Brace)) {
@@ -2381,7 +2385,7 @@ impl<'a> Parser<'a> {
                 },
             }
         };
-        self.error_on_if_block_attrs(else_span, true, expr.span, &attrs);
+        self.error_on_if_block_attrs(else_span, true, expr.span, attrs);
         Ok(expr)
     }
 
@@ -2390,8 +2394,13 @@ impl<'a> Parser<'a> {
         ctx_span: Span,
         is_ctx_else: bool,
         branch_span: Span,
-        attrs: &[ast::Attribute],
+        attrs: AttrWrapper,
     ) {
+        if attrs.is_empty() {
+            return;
+        }
+
+        let attrs: &[ast::Attribute] = &attrs.take_for_recovery(self.sess);
         let (attributes, last) = match attrs {
             [] => return,
             [x0 @ xn] | [x0, .., xn] => (x0.span.to(xn.span), xn.span),
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index bda301c52e9..494f0cf56a8 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -8,6 +8,7 @@ use rustc_ast::ast::*;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, TokenKind};
 use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
+use rustc_ast::util::case::Case;
 use rustc_ast::{self as ast, AttrVec, Attribute, DUMMY_NODE_ID};
 use rustc_ast::{Async, Const, Defaultness, IsAuto, Mutability, Unsafe, UseTree, UseTreeKind};
 use rustc_ast::{BindingAnnotation, Block, FnDecl, FnSig, Param, SelfKind};
@@ -34,7 +35,7 @@ impl<'a> Parser<'a> {
 
     /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
     fn parse_item_mod(&mut self, attrs: &mut AttrVec) -> PResult<'a, ItemInfo> {
-        let unsafety = self.parse_unsafety();
+        let unsafety = self.parse_unsafety(Case::Sensitive);
         self.expect_keyword(kw::Mod)?;
         let id = self.parse_ident()?;
         let mod_kind = if self.eat(&token::Semi) {
@@ -143,8 +144,15 @@ impl<'a> Parser<'a> {
         let lo = self.token.span;
         let vis = self.parse_visibility(FollowedByType::No)?;
         let mut def = self.parse_defaultness();
-        let kind =
-            self.parse_item_kind(&mut attrs, mac_allowed, lo, &vis, &mut def, fn_parse_mode)?;
+        let kind = self.parse_item_kind(
+            &mut attrs,
+            mac_allowed,
+            lo,
+            &vis,
+            &mut def,
+            fn_parse_mode,
+            Case::Sensitive,
+        )?;
         if let Some((ident, kind)) = kind {
             self.error_on_unconsumed_default(def, &kind);
             let span = lo.to(self.prev_token.span);
@@ -205,16 +213,17 @@ impl<'a> Parser<'a> {
         vis: &Visibility,
         def: &mut Defaultness,
         fn_parse_mode: FnParseMode,
+        case: Case,
     ) -> PResult<'a, Option<ItemInfo>> {
         let def_final = def == &Defaultness::Final;
-        let mut def = || mem::replace(def, Defaultness::Final);
+        let mut def_ = || mem::replace(def, Defaultness::Final);
 
-        let info = if self.eat_keyword(kw::Use) {
+        let info = if self.eat_keyword_case(kw::Use, case) {
             self.parse_use_item()?
-        } else if self.check_fn_front_matter(def_final) {
+        } else if self.check_fn_front_matter(def_final, case) {
             // FUNCTION ITEM
             let (ident, sig, generics, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis)?;
-            (ident, ItemKind::Fn(Box::new(Fn { defaultness: def(), sig, generics, body })))
+            (ident, ItemKind::Fn(Box::new(Fn { defaultness: def_(), sig, generics, body })))
         } else if self.eat_keyword(kw::Extern) {
             if self.eat_keyword(kw::Crate) {
                 // EXTERN CRATE
@@ -225,7 +234,7 @@ impl<'a> Parser<'a> {
             }
         } else if self.is_unsafe_foreign_mod() {
             // EXTERN BLOCK
-            let unsafety = self.parse_unsafety();
+            let unsafety = self.parse_unsafety(Case::Sensitive);
             self.expect_keyword(kw::Extern)?;
             self.parse_item_foreign_mod(attrs, unsafety)?
         } else if self.is_static_global() {
@@ -234,15 +243,15 @@ impl<'a> Parser<'a> {
             let m = self.parse_mutability();
             let (ident, ty, expr) = self.parse_item_global(Some(m))?;
             (ident, ItemKind::Static(ty, m, expr))
-        } else if let Const::Yes(const_span) = self.parse_constness() {
+        } else if let Const::Yes(const_span) = self.parse_constness(Case::Sensitive) {
             // CONST ITEM
             if self.token.is_keyword(kw::Impl) {
                 // recover from `const impl`, suggest `impl const`
-                self.recover_const_impl(const_span, attrs, def())?
+                self.recover_const_impl(const_span, attrs, def_())?
             } else {
                 self.recover_const_mut(const_span);
                 let (ident, ty, expr) = self.parse_item_global(None)?;
-                (ident, ItemKind::Const(def(), ty, expr))
+                (ident, ItemKind::Const(def_(), ty, expr))
             }
         } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
             // TRAIT ITEM
@@ -251,7 +260,7 @@ impl<'a> Parser<'a> {
             || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
         {
             // IMPL ITEM
-            self.parse_item_impl(attrs, def())?
+            self.parse_item_impl(attrs, def_())?
         } else if self.check_keyword(kw::Mod)
             || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
         {
@@ -259,7 +268,7 @@ impl<'a> Parser<'a> {
             self.parse_item_mod(attrs)?
         } else if self.eat_keyword(kw::Type) {
             // TYPE ITEM
-            self.parse_type_alias(def())?
+            self.parse_type_alias(def_())?
         } else if self.eat_keyword(kw::Enum) {
             // ENUM ITEM
             self.parse_item_enum()?
@@ -286,6 +295,19 @@ impl<'a> Parser<'a> {
         } else if self.isnt_macro_invocation() && vis.kind.is_pub() {
             self.recover_missing_kw_before_item()?;
             return Ok(None);
+        } else if self.isnt_macro_invocation() && case == Case::Sensitive {
+            _ = def_;
+
+            // Recover wrong cased keywords
+            return self.parse_item_kind(
+                attrs,
+                macros_allowed,
+                lo,
+                vis,
+                def,
+                fn_parse_mode,
+                Case::Insensitive,
+            );
         } else if macros_allowed && self.check_path() {
             // MACRO INVOCATION ITEM
             (Ident::empty(), ItemKind::MacCall(P(self.parse_item_macro(vis)?)))
@@ -538,7 +560,7 @@ impl<'a> Parser<'a> {
         attrs: &mut AttrVec,
         defaultness: Defaultness,
     ) -> PResult<'a, ItemInfo> {
-        let unsafety = self.parse_unsafety();
+        let unsafety = self.parse_unsafety(Case::Sensitive);
         self.expect_keyword(kw::Impl)?;
 
         // First, parse generic parameters if necessary.
@@ -552,7 +574,7 @@ impl<'a> Parser<'a> {
             generics
         };
 
-        let constness = self.parse_constness();
+        let constness = self.parse_constness(Case::Sensitive);
         if let Const::Yes(span) = constness {
             self.sess.gated_spans.gate(sym::const_trait_impl, span);
         }
@@ -796,7 +818,7 @@ impl<'a> Parser<'a> {
 
     /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
     fn parse_item_trait(&mut self, attrs: &mut AttrVec, lo: Span) -> PResult<'a, ItemInfo> {
-        let unsafety = self.parse_unsafety();
+        let unsafety = self.parse_unsafety(Case::Sensitive);
         // Parse optional `auto` prefix.
         let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
 
@@ -971,6 +993,23 @@ impl<'a> Parser<'a> {
             if self.eat(&token::ModSep) {
                 self.parse_use_tree_glob_or_nested()?
             } else {
+                // Recover from using a colon as path separator.
+                while self.eat_noexpect(&token::Colon) {
+                    self.struct_span_err(self.prev_token.span, "expected `::`, found `:`")
+                        .span_suggestion_short(
+                            self.prev_token.span,
+                            "use double colon",
+                            "::",
+                            Applicability::MachineApplicable,
+                        )
+                        .note_once("import paths are delimited using `::`")
+                        .emit();
+
+                    // We parse the rest of the path and append it to the original prefix.
+                    self.parse_path_segments(&mut prefix.segments, PathStyle::Mod, None)?;
+                    prefix.span = lo.to(self.prev_token.span);
+                }
+
                 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
             }
         };
@@ -1745,7 +1784,7 @@ impl<'a> Parser<'a> {
         let (ident, is_raw) = self.ident_or_err()?;
         if !is_raw && ident.is_reserved() {
             let snapshot = self.create_snapshot_for_diagnostic();
-            let err = if self.check_fn_front_matter(false) {
+            let err = if self.check_fn_front_matter(false, Case::Sensitive) {
                 let inherited_vis = Visibility {
                     span: rustc_span::DUMMY_SP,
                     kind: VisibilityKind::Inherited,
@@ -2155,7 +2194,7 @@ impl<'a> Parser<'a> {
     ///
     /// `check_pub` adds additional `pub` to the checks in case users place it
     /// wrongly, can be used to ensure `pub` never comes after `default`.
-    pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
+    pub(super) fn check_fn_front_matter(&mut self, check_pub: bool, case: Case) -> bool {
         // We use an over-approximation here.
         // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
         // `pub` is added in case users got confused with the ordering like `async pub fn`,
@@ -2165,23 +2204,30 @@ impl<'a> Parser<'a> {
         } else {
             &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
         };
-        self.check_keyword(kw::Fn) // Definitely an `fn`.
+        self.check_keyword_case(kw::Fn, case) // Definitely an `fn`.
             // `$qual fn` or `$qual $qual`:
-            || quals.iter().any(|&kw| self.check_keyword(kw))
+            || quals.iter().any(|&kw| self.check_keyword_case(kw, case))
                 && self.look_ahead(1, |t| {
                     // `$qual fn`, e.g. `const fn` or `async fn`.
-                    t.is_keyword(kw::Fn)
+                    t.is_keyword_case(kw::Fn, case)
                     // Two qualifiers `$qual $qual` is enough, e.g. `async unsafe`.
-                    || t.is_non_raw_ident_where(|i| quals.contains(&i.name)
-                        // Rule out 2015 `const async: T = val`.
-                        && i.is_reserved()
+                    || (
+                        (
+                            t.is_non_raw_ident_where(|i|
+                                quals.contains(&i.name)
+                                    // Rule out 2015 `const async: T = val`.
+                                    && i.is_reserved()
+                            )
+                            || case == Case::Insensitive
+                                && t.is_non_raw_ident_where(|i| quals.iter().any(|qual| qual.as_str() == i.name.as_str().to_lowercase()))
+                        )
                         // Rule out unsafe extern block.
                         && !self.is_unsafe_foreign_mod())
                 })
             // `extern ABI fn`
-            || self.check_keyword(kw::Extern)
+            || self.check_keyword_case(kw::Extern, case)
                 && self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
-                && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
+                && self.look_ahead(2, |t| t.is_keyword_case(kw::Fn, case))
     }
 
     /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
@@ -2197,22 +2243,22 @@ impl<'a> Parser<'a> {
     /// `Visibility::Inherited` when no visibility is known.
     pub(super) fn parse_fn_front_matter(&mut self, orig_vis: &Visibility) -> PResult<'a, FnHeader> {
         let sp_start = self.token.span;
-        let constness = self.parse_constness();
+        let constness = self.parse_constness(Case::Insensitive);
 
         let async_start_sp = self.token.span;
-        let asyncness = self.parse_asyncness();
+        let asyncness = self.parse_asyncness(Case::Insensitive);
 
         let unsafe_start_sp = self.token.span;
-        let unsafety = self.parse_unsafety();
+        let unsafety = self.parse_unsafety(Case::Insensitive);
 
         let ext_start_sp = self.token.span;
-        let ext = self.parse_extern();
+        let ext = self.parse_extern(Case::Insensitive);
 
         if let Async::Yes { span, .. } = asyncness {
             self.ban_async_in_2015(span);
         }
 
-        if !self.eat_keyword(kw::Fn) {
+        if !self.eat_keyword_case(kw::Fn, Case::Insensitive) {
             // It is possible for `expect_one_of` to recover given the contents of
             // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
             // account for this.
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 2e59c005e31..14dc490fb02 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -22,6 +22,7 @@ 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::util::case::Case;
 use rustc_ast::AttrId;
 use rustc_ast::DUMMY_NODE_ID;
 use rustc_ast::{self as ast, AnonConst, AttrStyle, AttrVec, Const, Extern};
@@ -636,6 +637,20 @@ impl<'a> Parser<'a> {
         self.token.is_keyword(kw)
     }
 
+    fn check_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
+        if self.check_keyword(kw) {
+            return true;
+        }
+
+        if case == Case::Insensitive
+        && let Some((ident, /* is_raw */ false)) = self.token.ident()
+        && ident.as_str().to_lowercase() == kw.as_str().to_lowercase() {
+            true
+        } else {
+            false
+        }
+    }
+
     /// If the next token is the given keyword, eats it and returns `true`.
     /// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
     // Public for rustfmt usage.
@@ -648,6 +663,33 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Eats a keyword, optionally ignoring the case.
+    /// If the case differs (and is ignored) an error is issued.
+    /// This is useful for recovery.
+    fn eat_keyword_case(&mut self, kw: Symbol, case: Case) -> bool {
+        if self.eat_keyword(kw) {
+            return true;
+        }
+
+        if case == Case::Insensitive
+        && let Some((ident, /* is_raw */ false)) = self.token.ident()
+        && ident.as_str().to_lowercase() == kw.as_str().to_lowercase() {
+            self
+                .struct_span_err(ident.span, format!("keyword `{kw}` is written in a wrong case"))
+                .span_suggestion(
+                    ident.span,
+                    "write it in the correct case",
+                    kw,
+                    Applicability::MachineApplicable
+                ).emit();
+
+            self.bump();
+            return true;
+        }
+
+        false
+    }
+
     fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
         if self.token.is_keyword(kw) {
             self.bump();
@@ -1127,8 +1169,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses asyncness: `async` or nothing.
-    fn parse_asyncness(&mut self) -> Async {
-        if self.eat_keyword(kw::Async) {
+    fn parse_asyncness(&mut self, case: Case) -> Async {
+        if self.eat_keyword_case(kw::Async, case) {
             let span = self.prev_token.uninterpolated_span();
             Async::Yes { span, closure_id: DUMMY_NODE_ID, return_impl_trait_id: DUMMY_NODE_ID }
         } else {
@@ -1137,8 +1179,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses unsafety: `unsafe` or nothing.
-    fn parse_unsafety(&mut self) -> Unsafe {
-        if self.eat_keyword(kw::Unsafe) {
+    fn parse_unsafety(&mut self, case: Case) -> Unsafe {
+        if self.eat_keyword_case(kw::Unsafe, case) {
             Unsafe::Yes(self.prev_token.uninterpolated_span())
         } else {
             Unsafe::No
@@ -1146,10 +1188,10 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses constness: `const` or nothing.
-    fn parse_constness(&mut self) -> Const {
+    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.eat_keyword(kw::Const)
+            && self.eat_keyword_case(kw::Const, case)
         {
             Const::Yes(self.prev_token.uninterpolated_span())
         } else {
@@ -1404,8 +1446,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses `extern string_literal?`.
-    fn parse_extern(&mut self) -> Extern {
-        if self.eat_keyword(kw::Extern) {
+    fn parse_extern(&mut self, case: Case) -> Extern {
+        if self.eat_keyword_case(kw::Extern, case) {
             let mut extern_span = self.prev_token.span;
             let abi = self.parse_abi();
             if let Some(abi) = abi {
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index fdc1af27f82..d46565dea89 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -631,7 +631,9 @@ impl<'a> Parser<'a> {
     /// - A single-segment path.
     pub(super) fn expr_is_valid_const_arg(&self, expr: &P<rustc_ast::Expr>) -> bool {
         match &expr.kind {
-            ast::ExprKind::Block(_, _) | ast::ExprKind::Lit(_) => true,
+            ast::ExprKind::Block(_, _)
+            | ast::ExprKind::Lit(_)
+            | ast::ExprKind::IncludedBytes(..) => true,
             ast::ExprKind::Unary(ast::UnOp::Neg, expr) => {
                 matches!(expr.kind, ast::ExprKind::Lit(_))
             }
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 12753c6785c..9684145ad99 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -19,7 +19,7 @@ use rustc_ast as ast;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, TokenKind};
 use rustc_ast::util::classify;
-use rustc_ast::{AttrStyle, AttrVec, Attribute, LocalKind, MacCall, MacCallStmt, MacStmtStyle};
+use rustc_ast::{AttrStyle, AttrVec, LocalKind, MacCall, MacCallStmt, MacStmtStyle};
 use rustc_ast::{Block, BlockCheckMode, Expr, ExprKind, HasAttrs, Local, Stmt};
 use rustc_ast::{StmtKind, DUMMY_NODE_ID};
 use rustc_errors::{Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
@@ -101,7 +101,7 @@ impl<'a> Parser<'a> {
             self.mk_stmt(lo.to(item.span), StmtKind::Item(P(item)))
         } else if self.eat(&token::Semi) {
             // Do not attempt to parse an expression if we're done here.
-            self.error_outer_attrs(&attrs.take_for_recovery());
+            self.error_outer_attrs(attrs);
             self.mk_stmt(lo, StmtKind::Empty)
         } else if self.token != token::CloseDelim(Delimiter::Brace) {
             // Remainder are line-expr stmts.
@@ -120,7 +120,7 @@ impl<'a> Parser<'a> {
             }
             self.mk_stmt(lo.to(e.span), StmtKind::Expr(e))
         } else {
-            self.error_outer_attrs(&attrs.take_for_recovery());
+            self.error_outer_attrs(attrs);
             return Ok(None);
         }))
     }
@@ -199,8 +199,10 @@ impl<'a> Parser<'a> {
 
     /// Error on outer attributes in this context.
     /// Also error if the previous token was a doc comment.
-    fn error_outer_attrs(&self, attrs: &[Attribute]) {
-        if let [.., last] = attrs {
+    fn error_outer_attrs(&self, attrs: AttrWrapper) {
+        if !attrs.is_empty()
+        && let attrs = attrs.take_for_recovery(self.sess)
+        && let attrs @ [.., last] = &*attrs {
             if last.is_doc_comment() {
                 self.sess.emit_err(DocCommentDoesNotDocumentAnything {
                     span: last.span,
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index 2a8512acf8c..4d78c5bd0e2 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -4,6 +4,7 @@ use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
+use rustc_ast::util::case::Case;
 use rustc_ast::{
     self as ast, BareFnTy, FnRetTy, GenericBound, GenericBounds, GenericParam, Generics, Lifetime,
     MacCall, MutTy, Mutability, PolyTraitRef, TraitBoundModifier, TraitObjectSyntax, Ty, TyKind,
@@ -267,7 +268,7 @@ impl<'a> Parser<'a> {
         } else if self.eat_keyword(kw::Underscore) {
             // A type to be inferred `_`
             TyKind::Infer
-        } else if self.check_fn_front_matter(false) {
+        } else if self.check_fn_front_matter(false, Case::Sensitive) {
             // Function pointer type
             self.parse_ty_bare_fn(lo, Vec::new(), recover_return_sign)?
         } else if self.check_keyword(kw::For) {
@@ -275,7 +276,7 @@ impl<'a> Parser<'a> {
             //   `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
             //   `for<'lt> Trait1<'lt> + Trait2 + 'a`
             let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-            if self.check_fn_front_matter(false) {
+            if self.check_fn_front_matter(false, Case::Sensitive) {
                 self.parse_ty_bare_fn(lo, lifetime_defs, recover_return_sign)?
             } else {
                 let path = self.parse_path(PathStyle::Type)?;
@@ -401,7 +402,7 @@ impl<'a> Parser<'a> {
                 .span_suggestions(
                     span.shrink_to_hi(),
                     "add `mut` or `const` here",
-                    ["mut ".to_string(), "const ".to_string()].into_iter(),
+                    ["mut ".to_string(), "const ".to_string()],
                     Applicability::HasPlaceholders,
                 )
                 .emit();