Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

17 files changed, 1294 insertions, 612 deletions

diff --git a/compiler/rustc_parse/src/errors.rs b/compiler/rustc_parse/src/errors.rs
index 9875cde4a..06b970ad9 100644
--- a/compiler/rustc_parse/src/errors.rs
+++ b/compiler/rustc_parse/src/errors.rs
@@ -971,6 +971,24 @@ pub(crate) struct StructLiteralBodyWithoutPathSugg {
 }
 
 #[derive(Diagnostic)]
+#[diag(parse_struct_literal_needing_parens)]
+pub(crate) struct StructLiteralNeedingParens {
+    #[primary_span]
+    pub span: Span,
+    #[subdiagnostic]
+    pub sugg: StructLiteralNeedingParensSugg,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(suggestion, applicability = "machine-applicable")]
+pub(crate) struct StructLiteralNeedingParensSugg {
+    #[suggestion_part(code = "(")]
+    pub before: Span,
+    #[suggestion_part(code = ")")]
+    pub after: Span,
+}
+
+#[derive(Diagnostic)]
 #[diag(parse_unmatched_angle_brackets)]
 pub(crate) struct UnmatchedAngleBrackets {
     #[primary_span]
@@ -1221,3 +1239,43 @@ pub(crate) struct UnexpectedIfWithIf(
     #[suggestion(applicability = "machine-applicable", code = " ", style = "verbose")]
     pub Span,
 );
+
+#[derive(Diagnostic)]
+#[diag(parse_maybe_fn_typo_with_impl)]
+pub(crate) struct FnTypoWithImpl {
+    #[primary_span]
+    #[suggestion(applicability = "maybe-incorrect", code = "impl", style = "verbose")]
+    pub fn_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_expected_fn_path_found_fn_keyword)]
+pub(crate) struct ExpectedFnPathFoundFnKeyword {
+    #[primary_span]
+    #[suggestion(applicability = "machine-applicable", code = "Fn", style = "verbose")]
+    pub fn_token_span: Span,
+}
+
+#[derive(Diagnostic)]
+#[diag(parse_where_clause_before_tuple_struct_body)]
+pub(crate) struct WhereClauseBeforeTupleStructBody {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    #[label(name_label)]
+    pub name: Span,
+    #[label(body_label)]
+    pub body: Span,
+    #[subdiagnostic]
+    pub sugg: Option<WhereClauseBeforeTupleStructBodySugg>,
+}
+
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(suggestion, applicability = "machine-applicable")]
+pub(crate) struct WhereClauseBeforeTupleStructBodySugg {
+    #[suggestion_part(code = "{snippet}")]
+    pub left: Span,
+    pub snippet: String,
+    #[suggestion_part(code = "")]
+    pub right: Span,
+}
diff --git a/compiler/rustc_parse/src/lexer/mod.rs b/compiler/rustc_parse/src/lexer/mod.rs
index f027843e6..9fe8d9836 100644
--- a/compiler/rustc_parse/src/lexer/mod.rs
+++ b/compiler/rustc_parse/src/lexer/mod.rs
@@ -52,8 +52,15 @@ pub(crate) fn parse_token_trees<'a>(
     }
 
     let cursor = Cursor::new(src);
-    let string_reader =
-        StringReader { sess, start_pos, pos: start_pos, src, cursor, override_span };
+    let string_reader = StringReader {
+        sess,
+        start_pos,
+        pos: start_pos,
+        src,
+        cursor,
+        override_span,
+        nbsp_is_whitespace: false,
+    };
     tokentrees::TokenTreesReader::parse_all_token_trees(string_reader)
 }
 
@@ -68,6 +75,10 @@ struct StringReader<'a> {
     /// Cursor for getting lexer tokens.
     cursor: Cursor<'a>,
     override_span: Option<Span>,
+    /// When a "unknown start of token: \u{a0}" has already been emitted earlier
+    /// in this file, it's safe to treat further occurrences of the non-breaking
+    /// space character as whitespace.
+    nbsp_is_whitespace: bool,
 }
 
 impl<'a> StringReader<'a> {
@@ -79,7 +90,7 @@ impl<'a> StringReader<'a> {
     /// preceded by whitespace.
     fn next_token(&mut self) -> (Token, bool) {
         let mut preceded_by_whitespace = false;
-
+        let mut swallow_next_invalid = 0;
         // Skip trivial (whitespace & comments) tokens
         loop {
             let token = self.cursor.advance_token();
@@ -232,19 +243,44 @@ impl<'a> StringReader<'a> {
                 rustc_lexer::TokenKind::Percent => token::BinOp(token::Percent),
 
                 rustc_lexer::TokenKind::Unknown | rustc_lexer::TokenKind::InvalidIdent => {
-                    let c = self.str_from(start).chars().next().unwrap();
+                    // Don't emit diagnostics for sequences of the same invalid token
+                    if swallow_next_invalid > 0 {
+                        swallow_next_invalid -= 1;
+                        continue;
+                    }
+                    let mut it = self.str_from_to_end(start).chars();
+                    let c = it.next().unwrap();
+                    if c == '\u{00a0}' {
+                        // If an error has already been reported on non-breaking
+                        // space characters earlier in the file, treat all
+                        // subsequent occurrences as whitespace.
+                        if self.nbsp_is_whitespace {
+                            preceded_by_whitespace = true;
+                            continue;
+                        }
+                        self.nbsp_is_whitespace = true;
+                    }
+                    let repeats = it.take_while(|c1| *c1 == c).count();
                     let mut err =
-                        self.struct_err_span_char(start, self.pos, "unknown start of token", c);
+                        self.struct_err_span_char(start, self.pos + Pos::from_usize(repeats * c.len_utf8()), "unknown start of token", c);
                     // FIXME: the lexer could be used to turn the ASCII version of unicode
                     // homoglyphs, instead of keeping a table in `check_for_substitution`into the
                     // token. Ideally, this should be inside `rustc_lexer`. However, we should
                     // first remove compound tokens like `<<` from `rustc_lexer`, and then add
                     // fancier error recovery to it, as there will be less overall work to do this
                     // way.
-                    let token = unicode_chars::check_for_substitution(self, start, c, &mut err);
+                    let token = unicode_chars::check_for_substitution(self, start, c, &mut err, repeats+1);
                     if c == '\x00' {
                         err.help("source files must contain UTF-8 encoded text, unexpected null bytes might occur when a different encoding is used");
                     }
+                    if repeats > 0 {
+                        if repeats == 1 {
+                            err.note(format!("character appears once more"));
+                        } else {
+                            err.note(format!("character appears {repeats} more times"));
+                        }
+                        swallow_next_invalid = repeats;
+                    }
                     err.emit();
                     if let Some(token) = token {
                         token
@@ -471,7 +507,7 @@ impl<'a> StringReader<'a> {
 
     /// Slice of the source text from `start` up to but excluding `self.pos`,
     /// meaning the slice does not include the character `self.ch`.
-    fn str_from(&self, start: BytePos) -> &str {
+    fn str_from(&self, start: BytePos) -> &'a str {
         self.str_from_to(start, self.pos)
     }
 
@@ -482,10 +518,15 @@ impl<'a> StringReader<'a> {
     }
 
     /// Slice of the source text spanning from `start` up to but excluding `end`.
-    fn str_from_to(&self, start: BytePos, end: BytePos) -> &str {
+    fn str_from_to(&self, start: BytePos, end: BytePos) -> &'a str {
         &self.src[self.src_index(start)..self.src_index(end)]
     }
 
+    /// Slice of the source text spanning from `start` until the end
+    fn str_from_to_end(&self, start: BytePos) -> &'a str {
+        &self.src[self.src_index(start)..]
+    }
+
     fn report_raw_str_error(&self, start: BytePos, prefix_len: u32) -> ! {
         match rustc_lexer::validate_raw_str(self.str_from(start), prefix_len) {
             Err(RawStrError::InvalidStarter { bad_char }) => {
diff --git a/compiler/rustc_parse/src/lexer/unicode_chars.rs b/compiler/rustc_parse/src/lexer/unicode_chars.rs
index f1b50296e..34d003ccf 100644
--- a/compiler/rustc_parse/src/lexer/unicode_chars.rs
+++ b/compiler/rustc_parse/src/lexer/unicode_chars.rs
@@ -7,329 +7,331 @@ use rustc_errors::{Applicability, Diagnostic};
 use rustc_span::{symbol::kw, BytePos, Pos, Span};
 
 #[rustfmt::skip] // for line breaks
-pub(crate) const UNICODE_ARRAY: &[(char, &str, char)] = &[
-    ('
', "Line Separator", ' '),
-    ('
', "Paragraph Separator", ' '),
-    (' ', "Ogham Space mark", ' '),
-    (' ', "En Quad", ' '),
-    (' ', "Em Quad", ' '),
-    (' ', "En Space", ' '),
-    (' ', "Em Space", ' '),
-    (' ', "Three-Per-Em Space", ' '),
-    (' ', "Four-Per-Em Space", ' '),
-    (' ', "Six-Per-Em Space", ' '),
-    (' ', "Punctuation Space", ' '),
-    (' ', "Thin Space", ' '),
-    (' ', "Hair Space", ' '),
-    (' ', "Medium Mathematical Space", ' '),
-    (' ', "No-Break Space", ' '),
-    (' ', "Figure Space", ' '),
-    (' ', "Narrow No-Break Space", ' '),
-    ('　', "Ideographic Space", ' '),
-
-    ('ߺ', "Nko Lajanyalan", '_'),
-    ('﹍', "Dashed Low Line", '_'),
-    ('﹎', "Centreline Low Line", '_'),
-    ('﹏', "Wavy Low Line", '_'),
-    ('＿', "Fullwidth Low Line", '_'),
-
-    ('‐', "Hyphen", '-'),
-    ('‑', "Non-Breaking Hyphen", '-'),
-    ('‒', "Figure Dash", '-'),
-    ('–', "En Dash", '-'),
-    ('—', "Em Dash", '-'),
-    ('﹘', "Small Em Dash", '-'),
-    ('۔', "Arabic Full Stop", '-'),
-    ('⁃', "Hyphen Bullet", '-'),
-    ('˗', "Modifier Letter Minus Sign", '-'),
-    ('−', "Minus Sign", '-'),
-    ('➖', "Heavy Minus Sign", '-'),
-    ('Ⲻ', "Coptic Letter Dialect-P Ni", '-'),
-    ('ー', "Katakana-Hiragana Prolonged Sound Mark", '-'),
-    ('－', "Fullwidth Hyphen-Minus", '-'),
-    ('―', "Horizontal Bar", '-'),
-    ('─', "Box Drawings Light Horizontal", '-'),
-    ('━', "Box Drawings Heavy Horizontal", '-'),
-    ('㇐', "CJK Stroke H", '-'),
-    ('ꟷ', "Latin Epigraphic Letter Sideways I", '-'),
-    ('ᅳ', "Hangul Jungseong Eu", '-'),
-    ('ㅡ', "Hangul Letter Eu", '-'),
-    ('一', "CJK Unified Ideograph-4E00", '-'),
-    ('⼀', "Kangxi Radical One", '-'),
-
-    ('؍', "Arabic Date Separator", ','),
-    ('٫', "Arabic Decimal Separator", ','),
-    ('‚', "Single Low-9 Quotation Mark", ','),
-    ('¸', "Cedilla", ','),
-    ('ꓹ', "Lisu Letter Tone Na Po", ','),
-    ('，', "Fullwidth Comma", ','),
-
-    (';', "Greek Question Mark", ';'),
-    ('；', "Fullwidth Semicolon", ';'),
-    ('︔', "Presentation Form For Vertical Semicolon", ';'),
-
-    ('ः', "Devanagari Sign Visarga", ':'),
-    ('ઃ', "Gujarati Sign Visarga", ':'),
-    ('：', "Fullwidth Colon", ':'),
-    ('։', "Armenian Full Stop", ':'),
-    ('܃', "Syriac Supralinear Colon", ':'),
-    ('܄', "Syriac Sublinear Colon", ':'),
-    ('᛬', "Runic Multiple Punctuation", ':'),
-    ('︰', "Presentation Form For Vertical Two Dot Leader", ':'),
-    ('᠃', "Mongolian Full Stop", ':'),
-    ('᠉', "Mongolian Manchu Full Stop", ':'),
-    ('⁚', "Two Dot Punctuation", ':'),
-    ('׃', "Hebrew Punctuation Sof Pasuq", ':'),
-    ('˸', "Modifier Letter Raised Colon", ':'),
-    ('꞉', "Modifier Letter Colon", ':'),
-    ('∶', "Ratio", ':'),
-    ('ː', "Modifier Letter Triangular Colon", ':'),
-    ('ꓽ', "Lisu Letter Tone Mya Jeu", ':'),
-    ('︓', "Presentation Form For Vertical Colon", ':'),
-
-    ('！', "Fullwidth Exclamation Mark", '!'),
-    ('ǃ', "Latin Letter Retroflex Click", '!'),
-    ('ⵑ', "Tifinagh Letter Tuareg Yang", '!'),
-    ('︕', "Presentation Form For Vertical Exclamation Mark", '!'),
-
-    ('ʔ', "Latin Letter Glottal Stop", '?'),
-    ('Ɂ', "Latin Capital Letter Glottal Stop", '?'),
-    ('ॽ', "Devanagari Letter Glottal Stop", '?'),
-    ('Ꭾ', "Cherokee Letter He", '?'),
-    ('ꛫ', "Bamum Letter Ntuu", '?'),
-    ('？', "Fullwidth Question Mark", '?'),
-    ('︖', "Presentation Form For Vertical Question Mark", '?'),
-
-    ('𝅭', "Musical Symbol Combining Augmentation Dot", '.'),
-    ('․', "One Dot Leader", '.'),
-    ('܁', "Syriac Supralinear Full Stop", '.'),
-    ('܂', "Syriac Sublinear Full Stop", '.'),
-    ('꘎', "Vai Full Stop", '.'),
-    ('𐩐', "Kharoshthi Punctuation Dot", '.'),
-    ('٠', "Arabic-Indic Digit Zero", '.'),
-    ('۰', "Extended Arabic-Indic Digit Zero", '.'),
-    ('ꓸ', "Lisu Letter Tone Mya Ti", '.'),
-    ('·', "Middle Dot", '.'),
-    ('・', "Katakana Middle Dot", '.'),
-    ('･', "Halfwidth Katakana Middle Dot", '.'),
-    ('᛫', "Runic Single Punctuation", '.'),
-    ('·', "Greek Ano Teleia", '.'),
-    ('⸱', "Word Separator Middle Dot", '.'),
-    ('𐄁', "Aegean Word Separator Dot", '.'),
-    ('•', "Bullet", '.'),
-    ('‧', "Hyphenation Point", '.'),
-    ('∙', "Bullet Operator", '.'),
-    ('⋅', "Dot Operator", '.'),
-    ('ꞏ', "Latin Letter Sinological Dot", '.'),
-    ('ᐧ', "Canadian Syllabics Final Middle Dot", '.'),
-    ('ᐧ', "Canadian Syllabics Final Middle Dot", '.'),
-    ('．', "Fullwidth Full Stop", '.'),
-    ('。', "Ideographic Full Stop", '.'),
-    ('︒', "Presentation Form For Vertical Ideographic Full Stop", '.'),
-
-    ('՝', "Armenian Comma", '\''),
-    ('＇', "Fullwidth Apostrophe", '\''),
-    ('‘', "Left Single Quotation Mark", '\''),
-    ('’', "Right Single Quotation Mark", '\''),
-    ('‛', "Single High-Reversed-9 Quotation Mark", '\''),
-    ('′', "Prime", '\''),
-    ('‵', "Reversed Prime", '\''),
-    ('՚', "Armenian Apostrophe", '\''),
-    ('׳', "Hebrew Punctuation Geresh", '\''),
-    ('`', "Grave Accent", '\''),
-    ('`', "Greek Varia", '\''),
-    ('｀', "Fullwidth Grave Accent", '\''),
-    ('´', "Acute Accent", '\''),
-    ('΄', "Greek Tonos", '\''),
-    ('´', "Greek Oxia", '\''),
-    ('᾽', "Greek Koronis", '\''),
-    ('᾿', "Greek Psili", '\''),
-    ('῾', "Greek Dasia", '\''),
-    ('ʹ', "Modifier Letter Prime", '\''),
-    ('ʹ', "Greek Numeral Sign", '\''),
-    ('ˈ', "Modifier Letter Vertical Line", '\''),
-    ('ˊ', "Modifier Letter Acute Accent", '\''),
-    ('ˋ', "Modifier Letter Grave Accent", '\''),
-    ('˴', "Modifier Letter Middle Grave Accent", '\''),
-    ('ʻ', "Modifier Letter Turned Comma", '\''),
-    ('ʽ', "Modifier Letter Reversed Comma", '\''),
-    ('ʼ', "Modifier Letter Apostrophe", '\''),
-    ('ʾ', "Modifier Letter Right Half Ring", '\''),
-    ('ꞌ', "Latin Small Letter Saltillo", '\''),
-    ('י', "Hebrew Letter Yod", '\''),
-    ('ߴ', "Nko High Tone Apostrophe", '\''),
-    ('ߵ', "Nko Low Tone Apostrophe", '\''),
-    ('ᑊ', "Canadian Syllabics West-Cree P", '\''),
-    ('ᛌ', "Runic Letter Short-Twig-Sol S", '\''),
-    ('𖽑', "Miao Sign Aspiration", '\''),
-    ('𖽒', "Miao Sign Reformed Voicing", '\''),
-
-    ('᳓', "Vedic Sign Nihshvasa", '"'),
-    ('＂', "Fullwidth Quotation Mark", '"'),
-    ('“', "Left Double Quotation Mark", '"'),
-    ('”', "Right Double Quotation Mark", '"'),
-    ('‟', "Double High-Reversed-9 Quotation Mark", '"'),
-    ('″', "Double Prime", '"'),
-    ('‶', "Reversed Double Prime", '"'),
-    ('〃', "Ditto Mark", '"'),
-    ('״', "Hebrew Punctuation Gershayim", '"'),
-    ('˝', "Double Acute Accent", '"'),
-    ('ʺ', "Modifier Letter Double Prime", '"'),
-    ('˶', "Modifier Letter Middle Double Acute Accent", '"'),
-    ('˵', "Modifier Letter Middle Double Grave Accent", '"'),
-    ('ˮ', "Modifier Letter Double Apostrophe", '"'),
-    ('ײ', "Hebrew Ligature Yiddish Double Yod", '"'),
-    ('❞', "Heavy Double Comma Quotation Mark Ornament", '"'),
-    ('❝', "Heavy Double Turned Comma Quotation Mark Ornament", '"'),
-
-    ('（', "Fullwidth Left Parenthesis", '('),
-    ('❨', "Medium Left Parenthesis Ornament", '('),
-    ('﴾', "Ornate Left Parenthesis", '('),
-
-    ('）', "Fullwidth Right Parenthesis", ')'),
-    ('❩', "Medium Right Parenthesis Ornament", ')'),
-    ('﴿', "Ornate Right Parenthesis", ')'),
-
-    ('［', "Fullwidth Left Square Bracket", '['),
-    ('❲', "Light Left Tortoise Shell Bracket Ornament", '['),
-    ('「', "Left Corner Bracket", '['),
-    ('『', "Left White Corner Bracket", '['),
-    ('【', "Left Black Lenticular Bracket", '['),
-    ('〔', "Left Tortoise Shell Bracket", '['),
-    ('〖', "Left White Lenticular Bracket", '['),
-    ('〘', "Left White Tortoise Shell Bracket", '['),
-    ('〚', "Left White Square Bracket", '['),
-
-    ('］', "Fullwidth Right Square Bracket", ']'),
-    ('❳', "Light Right Tortoise Shell Bracket Ornament", ']'),
-    ('」', "Right Corner Bracket", ']'),
-    ('』', "Right White Corner Bracket", ']'),
-    ('】', "Right Black Lenticular Bracket", ']'),
-    ('〕', "Right Tortoise Shell Bracket", ']'),
-    ('〗', "Right White Lenticular Bracket", ']'),
-    ('〙', "Right White Tortoise Shell Bracket", ']'),
-    ('〛', "Right White Square Bracket", ']'),
-
-    ('❴', "Medium Left Curly Bracket Ornament", '{'),
-    ('𝄔', "Musical Symbol Brace", '{'),
-    ('｛', "Fullwidth Left Curly Bracket", '{'),
-
-    ('❵', "Medium Right Curly Bracket Ornament", '}'),
-    ('｝', "Fullwidth Right Curly Bracket", '}'),
-
-    ('⁎', "Low Asterisk", '*'),
-    ('٭', "Arabic Five Pointed Star", '*'),
-    ('∗', "Asterisk Operator", '*'),
-    ('𐌟', "Old Italic Letter Ess", '*'),
-    ('＊', "Fullwidth Asterisk", '*'),
-
-    ('᜵', "Philippine Single Punctuation", '/'),
-    ('⁁', "Caret Insertion Point", '/'),
-    ('∕', "Division Slash", '/'),
-    ('⁄', "Fraction Slash", '/'),
-    ('╱', "Box Drawings Light Diagonal Upper Right To Lower Left", '/'),
-    ('⟋', "Mathematical Rising Diagonal", '/'),
-    ('⧸', "Big Solidus", '/'),
-    ('𝈺', "Greek Instrumental Notation Symbol-47", '/'),
-    ('㇓', "CJK Stroke Sp", '/'),
-    ('〳', "Vertical Kana Repeat Mark Upper Half", '/'),
-    ('Ⳇ', "Coptic Capital Letter Old Coptic Esh", '/'),
-    ('ノ', "Katakana Letter No", '/'),
-    ('丿', "CJK Unified Ideograph-4E3F", '/'),
-    ('⼃', "Kangxi Radical Slash", '/'),
-    ('／', "Fullwidth Solidus", '/'),
-
-    ('＼', "Fullwidth Reverse Solidus", '\\'),
-    ('﹨', "Small Reverse Solidus", '\\'),
-    ('∖', "Set Minus", '\\'),
-    ('⟍', "Mathematical Falling Diagonal", '\\'),
-    ('⧵', "Reverse Solidus Operator", '\\'),
-    ('⧹', "Big Reverse Solidus", '\\'),
-    ('⧹', "Greek Vocal Notation Symbol-16", '\\'),
-    ('⧹', "Greek Instrumental Symbol-48", '\\'),
-    ('㇔', "CJK Stroke D", '\\'),
-    ('丶', "CJK Unified Ideograph-4E36", '\\'),
-    ('⼂', "Kangxi Radical Dot", '\\'),
-    ('、', "Ideographic Comma", '\\'),
-    ('ヽ', "Katakana Iteration Mark", '\\'),
-
-    ('ꝸ', "Latin Small Letter Um", '&'),
-    ('＆', "Fullwidth Ampersand", '&'),
-
-    ('᛭', "Runic Cross Punctuation", '+'),
-    ('➕', "Heavy Plus Sign", '+'),
-    ('𐊛', "Lycian Letter H", '+'),
-    ('﬩', "Hebrew Letter Alternative Plus Sign", '+'),
-    ('＋', "Fullwidth Plus Sign", '+'),
-
-    ('‹', "Single Left-Pointing Angle Quotation Mark", '<'),
-    ('❮', "Heavy Left-Pointing Angle Quotation Mark Ornament", '<'),
-    ('˂', "Modifier Letter Left Arrowhead", '<'),
-    ('𝈶', "Greek Instrumental Symbol-40", '<'),
-    ('ᐸ', "Canadian Syllabics Pa", '<'),
-    ('ᚲ', "Runic Letter Kauna", '<'),
-    ('❬', "Medium Left-Pointing Angle Bracket Ornament", '<'),
-    ('⟨', "Mathematical Left Angle Bracket", '<'),
-    ('〈', "Left-Pointing Angle Bracket", '<'),
-    ('〈', "Left Angle Bracket", '<'),
-    ('㇛', "CJK Stroke Pd", '<'),
-    ('く', "Hiragana Letter Ku", '<'),
-    ('𡿨', "CJK Unified Ideograph-21FE8", '<'),
-    ('《', "Left Double Angle Bracket", '<'),
-    ('＜', "Fullwidth Less-Than Sign", '<'),
-
-    ('᐀', "Canadian Syllabics Hyphen", '='),
-    ('⹀', "Double Hyphen", '='),
-    ('゠', "Katakana-Hiragana Double Hyphen", '='),
-    ('꓿', "Lisu Punctuation Full Stop", '='),
-    ('＝', "Fullwidth Equals Sign", '='),
-
-    ('›', "Single Right-Pointing Angle Quotation Mark", '>'),
-    ('❯', "Heavy Right-Pointing Angle Quotation Mark Ornament", '>'),
-    ('˃', "Modifier Letter Right Arrowhead", '>'),
-    ('𝈷', "Greek Instrumental Symbol-42", '>'),
-    ('ᐳ', "Canadian Syllabics Po", '>'),
-    ('𖼿', "Miao Letter Archaic Zza", '>'),
-    ('❭', "Medium Right-Pointing Angle Bracket Ornament", '>'),
-    ('⟩', "Mathematical Right Angle Bracket", '>'),
-    ('〉', "Right-Pointing Angle Bracket", '>'),
-    ('〉', "Right Angle Bracket", '>'),
-    ('》', "Right Double Angle Bracket", '>'),
-    ('＞', "Fullwidth Greater-Than Sign", '>'),
+pub(crate) const UNICODE_ARRAY: &[(char, &str, &str)] = &[
+    ('
', "Line Separator", " "),
+    ('
', "Paragraph Separator", " "),
+    (' ', "Ogham Space mark", " "),
+    (' ', "En Quad", " "),
+    (' ', "Em Quad", " "),
+    (' ', "En Space", " "),
+    (' ', "Em Space", " "),
+    (' ', "Three-Per-Em Space", " "),
+    (' ', "Four-Per-Em Space", " "),
+    (' ', "Six-Per-Em Space", " "),
+    (' ', "Punctuation Space", " "),
+    (' ', "Thin Space", " "),
+    (' ', "Hair Space", " "),
+    (' ', "Medium Mathematical Space", " "),
+    (' ', "No-Break Space", " "),
+    (' ', "Figure Space", " "),
+    (' ', "Narrow No-Break Space", " "),
+    ('　', "Ideographic Space", " "),
+
+    ('ߺ', "Nko Lajanyalan", "_"),
+    ('﹍', "Dashed Low Line", "_"),
+    ('﹎', "Centreline Low Line", "_"),
+    ('﹏', "Wavy Low Line", "_"),
+    ('＿', "Fullwidth Low Line", "_"),
+
+    ('‐', "Hyphen", "-"),
+    ('‑', "Non-Breaking Hyphen", "-"),
+    ('‒', "Figure Dash", "-"),
+    ('–', "En Dash", "-"),
+    ('—', "Em Dash", "-"),
+    ('﹘', "Small Em Dash", "-"),
+    ('۔', "Arabic Full Stop", "-"),
+    ('⁃', "Hyphen Bullet", "-"),
+    ('˗', "Modifier Letter Minus Sign", "-"),
+    ('−', "Minus Sign", "-"),
+    ('➖', "Heavy Minus Sign", "-"),
+    ('Ⲻ', "Coptic Letter Dialect-P Ni", "-"),
+    ('ー', "Katakana-Hiragana Prolonged Sound Mark", "-"),
+    ('－', "Fullwidth Hyphen-Minus", "-"),
+    ('―', "Horizontal Bar", "-"),
+    ('─', "Box Drawings Light Horizontal", "-"),
+    ('━', "Box Drawings Heavy Horizontal", "-"),
+    ('㇐', "CJK Stroke H", "-"),
+    ('ꟷ', "Latin Epigraphic Letter Sideways I", "-"),
+    ('ᅳ', "Hangul Jungseong Eu", "-"),
+    ('ㅡ', "Hangul Letter Eu", "-"),
+    ('一', "CJK Unified Ideograph-4E00", "-"),
+    ('⼀', "Kangxi Radical One", "-"),
+
+    ('؍', "Arabic Date Separator", ","),
+    ('٫', "Arabic Decimal Separator", ","),
+    ('‚', "Single Low-9 Quotation Mark", ","),
+    ('¸', "Cedilla", ","),
+    ('ꓹ', "Lisu Letter Tone Na Po", ","),
+    ('，', "Fullwidth Comma", ","),
+
+    (';', "Greek Question Mark", ";"),
+    ('；', "Fullwidth Semicolon", ";"),
+    ('︔', "Presentation Form For Vertical Semicolon", ";"),
+
+    ('ः', "Devanagari Sign Visarga", ":"),
+    ('ઃ', "Gujarati Sign Visarga", ":"),
+    ('：', "Fullwidth Colon", ":"),
+    ('։', "Armenian Full Stop", ":"),
+    ('܃', "Syriac Supralinear Colon", ":"),
+    ('܄', "Syriac Sublinear Colon", ":"),
+    ('᛬', "Runic Multiple Punctuation", ":"),
+    ('︰', "Presentation Form For Vertical Two Dot Leader", ":"),
+    ('᠃', "Mongolian Full Stop", ":"),
+    ('᠉', "Mongolian Manchu Full Stop", ":"),
+    ('⁚', "Two Dot Punctuation", ":"),
+    ('׃', "Hebrew Punctuation Sof Pasuq", ":"),
+    ('˸', "Modifier Letter Raised Colon", ":"),
+    ('꞉', "Modifier Letter Colon", ":"),
+    ('∶', "Ratio", ":"),
+    ('ː', "Modifier Letter Triangular Colon", ":"),
+    ('ꓽ', "Lisu Letter Tone Mya Jeu", ":"),
+    ('︓', "Presentation Form For Vertical Colon", ":"),
+
+    ('！', "Fullwidth Exclamation Mark", "!"),
+    ('ǃ', "Latin Letter Retroflex Click", "!"),
+    ('ⵑ', "Tifinagh Letter Tuareg Yang", "!"),
+    ('︕', "Presentation Form For Vertical Exclamation Mark", "!"),
+
+    ('ʔ', "Latin Letter Glottal Stop", "?"),
+    ('Ɂ', "Latin Capital Letter Glottal Stop", "?"),
+    ('ॽ', "Devanagari Letter Glottal Stop", "?"),
+    ('Ꭾ', "Cherokee Letter He", "?"),
+    ('ꛫ', "Bamum Letter Ntuu", "?"),
+    ('？', "Fullwidth Question Mark", "?"),
+    ('︖', "Presentation Form For Vertical Question Mark", "?"),
+
+    ('𝅭', "Musical Symbol Combining Augmentation Dot", "."),
+    ('․', "One Dot Leader", "."),
+    ('܁', "Syriac Supralinear Full Stop", "."),
+    ('܂', "Syriac Sublinear Full Stop", "."),
+    ('꘎', "Vai Full Stop", "."),
+    ('𐩐', "Kharoshthi Punctuation Dot", "."),
+    ('٠', "Arabic-Indic Digit Zero", "."),
+    ('۰', "Extended Arabic-Indic Digit Zero", "."),
+    ('ꓸ', "Lisu Letter Tone Mya Ti", "."),
+    ('·', "Middle Dot", "."),
+    ('・', "Katakana Middle Dot", "."),
+    ('･', "Halfwidth Katakana Middle Dot", "."),
+    ('᛫', "Runic Single Punctuation", "."),
+    ('·', "Greek Ano Teleia", "."),
+    ('⸱', "Word Separator Middle Dot", "."),
+    ('𐄁', "Aegean Word Separator Dot", "."),
+    ('•', "Bullet", "."),
+    ('‧', "Hyphenation Point", "."),
+    ('∙', "Bullet Operator", "."),
+    ('⋅', "Dot Operator", "."),
+    ('ꞏ', "Latin Letter Sinological Dot", "."),
+    ('ᐧ', "Canadian Syllabics Final Middle Dot", "."),
+    ('ᐧ', "Canadian Syllabics Final Middle Dot", "."),
+    ('．', "Fullwidth Full Stop", "."),
+    ('。', "Ideographic Full Stop", "."),
+    ('︒', "Presentation Form For Vertical Ideographic Full Stop", "."),
+
+    ('՝', "Armenian Comma", "\'"),
+    ('＇', "Fullwidth Apostrophe", "\'"),
+    ('‘', "Left Single Quotation Mark", "\'"),
+    ('’', "Right Single Quotation Mark", "\'"),
+    ('‛', "Single High-Reversed-9 Quotation Mark", "\'"),
+    ('′', "Prime", "\'"),
+    ('‵', "Reversed Prime", "\'"),
+    ('՚', "Armenian Apostrophe", "\'"),
+    ('׳', "Hebrew Punctuation Geresh", "\'"),
+    ('`', "Grave Accent", "\'"),
+    ('`', "Greek Varia", "\'"),
+    ('｀', "Fullwidth Grave Accent", "\'"),
+    ('´', "Acute Accent", "\'"),
+    ('΄', "Greek Tonos", "\'"),
+    ('´', "Greek Oxia", "\'"),
+    ('᾽', "Greek Koronis", "\'"),
+    ('᾿', "Greek Psili", "\'"),
+    ('῾', "Greek Dasia", "\'"),
+    ('ʹ', "Modifier Letter Prime", "\'"),
+    ('ʹ', "Greek Numeral Sign", "\'"),
+    ('ˈ', "Modifier Letter Vertical Line", "\'"),
+    ('ˊ', "Modifier Letter Acute Accent", "\'"),
+    ('ˋ', "Modifier Letter Grave Accent", "\'"),
+    ('˴', "Modifier Letter Middle Grave Accent", "\'"),
+    ('ʻ', "Modifier Letter Turned Comma", "\'"),
+    ('ʽ', "Modifier Letter Reversed Comma", "\'"),
+    ('ʼ', "Modifier Letter Apostrophe", "\'"),
+    ('ʾ', "Modifier Letter Right Half Ring", "\'"),
+    ('ꞌ', "Latin Small Letter Saltillo", "\'"),
+    ('י', "Hebrew Letter Yod", "\'"),
+    ('ߴ', "Nko High Tone Apostrophe", "\'"),
+    ('ߵ', "Nko Low Tone Apostrophe", "\'"),
+    ('ᑊ', "Canadian Syllabics West-Cree P", "\'"),
+    ('ᛌ', "Runic Letter Short-Twig-Sol S", "\'"),
+    ('𖽑', "Miao Sign Aspiration", "\'"),
+    ('𖽒', "Miao Sign Reformed Voicing", "\'"),
+
+    ('᳓', "Vedic Sign Nihshvasa", "\""),
+    ('＂', "Fullwidth Quotation Mark", "\""),
+    ('“', "Left Double Quotation Mark", "\""),
+    ('”', "Right Double Quotation Mark", "\""),
+    ('‟', "Double High-Reversed-9 Quotation Mark", "\""),
+    ('″', "Double Prime", "\""),
+    ('‶', "Reversed Double Prime", "\""),
+    ('〃', "Ditto Mark", "\""),
+    ('״', "Hebrew Punctuation Gershayim", "\""),
+    ('˝', "Double Acute Accent", "\""),
+    ('ʺ', "Modifier Letter Double Prime", "\""),
+    ('˶', "Modifier Letter Middle Double Acute Accent", "\""),
+    ('˵', "Modifier Letter Middle Double Grave Accent", "\""),
+    ('ˮ', "Modifier Letter Double Apostrophe", "\""),
+    ('ײ', "Hebrew Ligature Yiddish Double Yod", "\""),
+    ('❞', "Heavy Double Comma Quotation Mark Ornament", "\""),
+    ('❝', "Heavy Double Turned Comma Quotation Mark Ornament", "\""),
+
+    ('（', "Fullwidth Left Parenthesis", "("),
+    ('❨', "Medium Left Parenthesis Ornament", "("),
+    ('﴾', "Ornate Left Parenthesis", "("),
+
+    ('）', "Fullwidth Right Parenthesis", ")"),
+    ('❩', "Medium Right Parenthesis Ornament", ")"),
+    ('﴿', "Ornate Right Parenthesis", ")"),
+
+    ('［', "Fullwidth Left Square Bracket", "["),
+    ('❲', "Light Left Tortoise Shell Bracket Ornament", "["),
+    ('「', "Left Corner Bracket", "["),
+    ('『', "Left White Corner Bracket", "["),
+    ('【', "Left Black Lenticular Bracket", "["),
+    ('〔', "Left Tortoise Shell Bracket", "["),
+    ('〖', "Left White Lenticular Bracket", "["),
+    ('〘', "Left White Tortoise Shell Bracket", "["),
+    ('〚', "Left White Square Bracket", "["),
+
+    ('］', "Fullwidth Right Square Bracket", "]"),
+    ('❳', "Light Right Tortoise Shell Bracket Ornament", "]"),
+    ('」', "Right Corner Bracket", "]"),
+    ('』', "Right White Corner Bracket", "]"),
+    ('】', "Right Black Lenticular Bracket", "]"),
+    ('〕', "Right Tortoise Shell Bracket", "]"),
+    ('〗', "Right White Lenticular Bracket", "]"),
+    ('〙', "Right White Tortoise Shell Bracket", "]"),
+    ('〛', "Right White Square Bracket", "]"),
+
+    ('❴', "Medium Left Curly Bracket Ornament", "{"),
+    ('𝄔', "Musical Symbol Brace", "{"),
+    ('｛', "Fullwidth Left Curly Bracket", "{"),
+
+    ('❵', "Medium Right Curly Bracket Ornament", "}"),
+    ('｝', "Fullwidth Right Curly Bracket", "}"),
+
+    ('⁎', "Low Asterisk", "*"),
+    ('٭', "Arabic Five Pointed Star", "*"),
+    ('∗', "Asterisk Operator", "*"),
+    ('𐌟', "Old Italic Letter Ess", "*"),
+    ('＊', "Fullwidth Asterisk", "*"),
+
+    ('᜵', "Philippine Single Punctuation", "/"),
+    ('⁁', "Caret Insertion Point", "/"),
+    ('∕', "Division Slash", "/"),
+    ('⁄', "Fraction Slash", "/"),
+    ('╱', "Box Drawings Light Diagonal Upper Right To Lower Left", "/"),
+    ('⟋', "Mathematical Rising Diagonal", "/"),
+    ('⧸', "Big Solidus", "/"),
+    ('𝈺', "Greek Instrumental Notation Symbol-47", "/"),
+    ('㇓', "CJK Stroke Sp", "/"),
+    ('〳', "Vertical Kana Repeat Mark Upper Half", "/"),
+    ('Ⳇ', "Coptic Capital Letter Old Coptic Esh", "/"),
+    ('ノ', "Katakana Letter No", "/"),
+    ('丿', "CJK Unified Ideograph-4E3F", "/"),
+    ('⼃', "Kangxi Radical Slash", "/"),
+    ('／', "Fullwidth Solidus", "/"),
+
+    ('＼', "Fullwidth Reverse Solidus", "\\"),
+    ('﹨', "Small Reverse Solidus", "\\"),
+    ('∖', "Set Minus", "\\"),
+    ('⟍', "Mathematical Falling Diagonal", "\\"),
+    ('⧵', "Reverse Solidus Operator", "\\"),
+    ('⧹', "Big Reverse Solidus", "\\"),
+    ('⧹', "Greek Vocal Notation Symbol-16", "\\"),
+    ('⧹', "Greek Instrumental Symbol-48", "\\"),
+    ('㇔', "CJK Stroke D", "\\"),
+    ('丶', "CJK Unified Ideograph-4E36", "\\"),
+    ('⼂', "Kangxi Radical Dot", "\\"),
+    ('、', "Ideographic Comma", "\\"),
+    ('ヽ', "Katakana Iteration Mark", "\\"),
+
+    ('ꝸ', "Latin Small Letter Um", "&"),
+    ('＆', "Fullwidth Ampersand", "&"),
+
+    ('᛭', "Runic Cross Punctuation", "+"),
+    ('➕', "Heavy Plus Sign", "+"),
+    ('𐊛', "Lycian Letter H", "+"),
+    ('﬩', "Hebrew Letter Alternative Plus Sign", "+"),
+    ('＋', "Fullwidth Plus Sign", "+"),
+
+    ('‹', "Single Left-Pointing Angle Quotation Mark", "<"),
+    ('❮', "Heavy Left-Pointing Angle Quotation Mark Ornament", "<"),
+    ('˂', "Modifier Letter Left Arrowhead", "<"),
+    ('𝈶', "Greek Instrumental Symbol-40", "<"),
+    ('ᐸ', "Canadian Syllabics Pa", "<"),
+    ('ᚲ', "Runic Letter Kauna", "<"),
+    ('❬', "Medium Left-Pointing Angle Bracket Ornament", "<"),
+    ('⟨', "Mathematical Left Angle Bracket", "<"),
+    ('〈', "Left-Pointing Angle Bracket", "<"),
+    ('〈', "Left Angle Bracket", "<"),
+    ('㇛', "CJK Stroke Pd", "<"),
+    ('く', "Hiragana Letter Ku", "<"),
+    ('𡿨', "CJK Unified Ideograph-21FE8", "<"),
+    ('《', "Left Double Angle Bracket", "<"),
+    ('＜', "Fullwidth Less-Than Sign", "<"),
+
+    ('᐀', "Canadian Syllabics Hyphen", "="),
+    ('⹀', "Double Hyphen", "="),
+    ('゠', "Katakana-Hiragana Double Hyphen", "="),
+    ('꓿', "Lisu Punctuation Full Stop", "="),
+    ('＝', "Fullwidth Equals Sign", "="),
+
+    ('›', "Single Right-Pointing Angle Quotation Mark", ">"),
+    ('❯', "Heavy Right-Pointing Angle Quotation Mark Ornament", ">"),
+    ('˃', "Modifier Letter Right Arrowhead", ">"),
+    ('𝈷', "Greek Instrumental Symbol-42", ">"),
+    ('ᐳ', "Canadian Syllabics Po", ">"),
+    ('𖼿', "Miao Letter Archaic Zza", ">"),
+    ('❭', "Medium Right-Pointing Angle Bracket Ornament", ">"),
+    ('⟩', "Mathematical Right Angle Bracket", ">"),
+    ('〉', "Right-Pointing Angle Bracket", ">"),
+    ('〉', "Right Angle Bracket", ">"),
+    ('》', "Right Double Angle Bracket", ">"),
+    ('＞', "Fullwidth Greater-Than Sign", ">"),
+    ('⩵', "Two Consecutive Equals Signs", "==")
 ];
 
 // FIXME: the lexer could be used to turn the ASCII version of unicode homoglyphs, instead of
 // keeping the substitution token in this table. Ideally, this should be inside `rustc_lexer`.
 // However, we should first remove compound tokens like `<<` from `rustc_lexer`, and then add
 // fancier error recovery to it, as there will be less overall work to do this way.
-const ASCII_ARRAY: &[(char, &str, Option<token::TokenKind>)] = &[
-    (' ', "Space", None),
-    ('_', "Underscore", Some(token::Ident(kw::Underscore, false))),
-    ('-', "Minus/Hyphen", Some(token::BinOp(token::Minus))),
-    (',', "Comma", Some(token::Comma)),
-    (';', "Semicolon", Some(token::Semi)),
-    (':', "Colon", Some(token::Colon)),
-    ('!', "Exclamation Mark", Some(token::Not)),
-    ('?', "Question Mark", Some(token::Question)),
-    ('.', "Period", Some(token::Dot)),
-    ('(', "Left Parenthesis", Some(token::OpenDelim(Delimiter::Parenthesis))),
-    (')', "Right Parenthesis", Some(token::CloseDelim(Delimiter::Parenthesis))),
-    ('[', "Left Square Bracket", Some(token::OpenDelim(Delimiter::Bracket))),
-    (']', "Right Square Bracket", Some(token::CloseDelim(Delimiter::Bracket))),
-    ('{', "Left Curly Brace", Some(token::OpenDelim(Delimiter::Brace))),
-    ('}', "Right Curly Brace", Some(token::CloseDelim(Delimiter::Brace))),
-    ('*', "Asterisk", Some(token::BinOp(token::Star))),
-    ('/', "Slash", Some(token::BinOp(token::Slash))),
-    ('\\', "Backslash", None),
-    ('&', "Ampersand", Some(token::BinOp(token::And))),
-    ('+', "Plus Sign", Some(token::BinOp(token::Plus))),
-    ('<', "Less-Than Sign", Some(token::Lt)),
-    ('=', "Equals Sign", Some(token::Eq)),
-    ('>', "Greater-Than Sign", Some(token::Gt)),
+const ASCII_ARRAY: &[(&str, &str, Option<token::TokenKind>)] = &[
+    (" ", "Space", None),
+    ("_", "Underscore", Some(token::Ident(kw::Underscore, false))),
+    ("-", "Minus/Hyphen", Some(token::BinOp(token::Minus))),
+    (",", "Comma", Some(token::Comma)),
+    (";", "Semicolon", Some(token::Semi)),
+    (":", "Colon", Some(token::Colon)),
+    ("!", "Exclamation Mark", Some(token::Not)),
+    ("?", "Question Mark", Some(token::Question)),
+    (".", "Period", Some(token::Dot)),
+    ("(", "Left Parenthesis", Some(token::OpenDelim(Delimiter::Parenthesis))),
+    (")", "Right Parenthesis", Some(token::CloseDelim(Delimiter::Parenthesis))),
+    ("[", "Left Square Bracket", Some(token::OpenDelim(Delimiter::Bracket))),
+    ("]", "Right Square Bracket", Some(token::CloseDelim(Delimiter::Bracket))),
+    ("{", "Left Curly Brace", Some(token::OpenDelim(Delimiter::Brace))),
+    ("}", "Right Curly Brace", Some(token::CloseDelim(Delimiter::Brace))),
+    ("*", "Asterisk", Some(token::BinOp(token::Star))),
+    ("/", "Slash", Some(token::BinOp(token::Slash))),
+    ("\\", "Backslash", None),
+    ("&", "Ampersand", Some(token::BinOp(token::And))),
+    ("+", "Plus Sign", Some(token::BinOp(token::Plus))),
+    ("<", "Less-Than Sign", Some(token::Lt)),
+    ("=", "Equals Sign", Some(token::Eq)),
+    ("==", "Double Equals Sign", Some(token::EqEq)),
+    (">", "Greater-Than Sign", Some(token::Gt)),
     // FIXME: Literals are already lexed by this point, so we can't recover gracefully just by
     // spitting the correct token out.
-    ('\'', "Single Quote", None),
-    ('"', "Quotation Mark", None),
+    ("\'", "Single Quote", None),
+    ("\"", "Quotation Mark", None),
 ];
 
 pub(super) fn check_for_substitution<'a>(
@@ -337,12 +339,13 @@ pub(super) fn check_for_substitution<'a>(
     pos: BytePos,
     ch: char,
     err: &mut Diagnostic,
+    count: usize,
 ) -> Option<token::TokenKind> {
-    let &(_u_char, u_name, ascii_char) = UNICODE_ARRAY.iter().find(|&&(c, _, _)| c == ch)?;
+    let &(_, u_name, ascii_str) = UNICODE_ARRAY.iter().find(|&&(c, _, _)| c == ch)?;
 
-    let span = Span::with_root_ctxt(pos, pos + Pos::from_usize(ch.len_utf8()));
+    let span = Span::with_root_ctxt(pos, pos + Pos::from_usize(ch.len_utf8() * count));
 
-    let Some((_ascii_char, ascii_name, token)) = ASCII_ARRAY.iter().find(|&&(c, _, _)| c == ascii_char) else {
+    let Some((_, ascii_name, token)) = ASCII_ARRAY.iter().find(|&&(s, _, _)| s == ascii_str) else {
         let msg = format!("substitution character not found for '{}'", ch);
         reader.sess.span_diagnostic.span_bug_no_panic(span, &msg);
         return None;
@@ -353,7 +356,7 @@ pub(super) fn check_for_substitution<'a>(
         let msg = format!(
             "Unicode characters '“' (Left Double Quotation Mark) and \
              '”' (Right Double Quotation Mark) look like '{}' ({}), but are not",
-            ascii_char, ascii_name
+            ascii_str, ascii_name
         );
         err.span_suggestion(
             Span::with_root_ctxt(
@@ -367,9 +370,14 @@ pub(super) fn check_for_substitution<'a>(
     } else {
         let msg = format!(
             "Unicode character '{}' ({}) looks like '{}' ({}), but it is not",
-            ch, u_name, ascii_char, ascii_name
+            ch, u_name, ascii_str, ascii_name
+        );
+        err.span_suggestion(
+            span,
+            &msg,
+            ascii_str.to_string().repeat(count),
+            Applicability::MaybeIncorrect,
         );
-        err.span_suggestion(span, &msg, ascii_char, Applicability::MaybeIncorrect);
     }
     token.clone()
 }
diff --git a/compiler/rustc_parse/src/parser/attr.rs b/compiler/rustc_parse/src/parser/attr.rs
index c7d239b64..686454a8f 100644
--- a/compiler/rustc_parse/src/parser/attr.rs
+++ b/compiler/rustc_parse/src/parser/attr.rs
@@ -6,7 +6,6 @@ use rustc_ast::attr;
 use rustc_ast::token::{self, Delimiter, Nonterminal};
 use rustc_errors::{error_code, fluent, Diagnostic, IntoDiagnostic, PResult};
 use rustc_span::{sym, BytePos, Span};
-use std::convert::TryInto;
 
 // Public for rustfmt usage
 #[derive(Debug)]
diff --git a/compiler/rustc_parse/src/parser/attr_wrapper.rs b/compiler/rustc_parse/src/parser/attr_wrapper.rs
index a084a7010..b97f22417 100644
--- a/compiler/rustc_parse/src/parser/attr_wrapper.rs
+++ b/compiler/rustc_parse/src/parser/attr_wrapper.rs
@@ -8,7 +8,6 @@ use rustc_errors::PResult;
 use rustc_session::parse::ParseSess;
 use rustc_span::{sym, Span, DUMMY_SP};
 
-use std::convert::TryInto;
 use std::ops::Range;
 
 /// A wrapper type to ensure that the parser handles outer attributes correctly.
diff --git a/compiler/rustc_parse/src/parser/diagnostics.rs b/compiler/rustc_parse/src/parser/diagnostics.rs
index c316a4dd6..4c918c670 100644
--- a/compiler/rustc_parse/src/parser/diagnostics.rs
+++ b/compiler/rustc_parse/src/parser/diagnostics.rs
@@ -12,9 +12,10 @@ use crate::errors::{
     IncorrectAwait, IncorrectSemicolon, IncorrectUseOfAwait, ParenthesesInForHead,
     ParenthesesInForHeadSugg, PatternMethodParamWithoutBody, QuestionMarkInType,
     QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
-    StructLiteralBodyWithoutPathSugg, SuggEscapeToUseAsIdentifier, SuggRemoveComma,
-    UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
-    UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead,
+    StructLiteralBodyWithoutPathSugg, StructLiteralNeedingParens, StructLiteralNeedingParensSugg,
+    SuggEscapeToUseAsIdentifier, SuggRemoveComma, UnexpectedConstInGenericParam,
+    UnexpectedConstParamDeclaration, UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets,
+    UseEqInstead,
 };
 
 use crate::lexer::UnmatchedBrace;
@@ -31,7 +32,8 @@ use rustc_ast::{
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{
-    fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
+    fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, FatalError, Handler, MultiSpan,
+    PResult,
 };
 use rustc_errors::{pluralize, Diagnostic, ErrorGuaranteed, IntoDiagnostic};
 use rustc_session::errors::ExprParenthesesNeeded;
@@ -41,7 +43,6 @@ use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
 use std::mem::take;
 use std::ops::{Deref, DerefMut};
 use thin_vec::{thin_vec, ThinVec};
-use tracing::{debug, trace};
 
 /// Creates a placeholder argument.
 pub(super) fn dummy_arg(ident: Ident) -> Param {
@@ -159,8 +160,6 @@ enum IsStandalone {
     Standalone,
     /// It's a subexpression, i.e., *not* standalone.
     Subexpr,
-    /// It's maybe standalone; we're not sure.
-    Maybe,
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
@@ -213,14 +212,8 @@ impl MultiSugg {
         err.multipart_suggestion(&self.msg, self.patches, self.applicability);
     }
 
-    /// Overrides individual messages and applicabilities.
-    fn emit_many(
-        err: &mut Diagnostic,
-        msg: &str,
-        applicability: Applicability,
-        suggestions: impl Iterator<Item = Self>,
-    ) {
-        err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
+    fn emit_verbose(self, err: &mut Diagnostic) {
+        err.multipart_suggestion_verbose(&self.msg, self.patches, self.applicability);
     }
 }
 
@@ -631,12 +624,15 @@ impl<'a> Parser<'a> {
         &mut self,
         lo: Span,
         s: BlockCheckMode,
+        maybe_struct_name: token::Token,
+        can_be_struct_literal: bool,
     ) -> Option<PResult<'a, P<Block>>> {
         if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
             // We might be having a struct literal where people forgot to include the path:
             // fn foo() -> Foo {
             //     field: value,
             // }
+            info!(?maybe_struct_name, ?self.token);
             let mut snapshot = self.create_snapshot_for_diagnostic();
             let path = Path {
                 segments: ThinVec::new(),
@@ -656,13 +652,6 @@ impl<'a> Parser<'a> {
                     //     field: value,
                     // } }
                     err.delay_as_bug();
-                    self.sess.emit_err(StructLiteralBodyWithoutPath {
-                        span: expr.span,
-                        sugg: StructLiteralBodyWithoutPathSugg {
-                            before: expr.span.shrink_to_lo(),
-                            after: expr.span.shrink_to_hi(),
-                        },
-                    });
                     self.restore_snapshot(snapshot);
                     let mut tail = self.mk_block(
                         vec![self.mk_stmt_err(expr.span)],
@@ -670,7 +659,25 @@ impl<'a> Parser<'a> {
                         lo.to(self.prev_token.span),
                     );
                     tail.could_be_bare_literal = true;
-                    Ok(tail)
+                    if maybe_struct_name.is_ident() && can_be_struct_literal {
+                        // Account for `if Example { a: one(), }.is_pos() {}`.
+                        Err(self.sess.create_err(StructLiteralNeedingParens {
+                            span: maybe_struct_name.span.to(expr.span),
+                            sugg: StructLiteralNeedingParensSugg {
+                                before: maybe_struct_name.span.shrink_to_lo(),
+                                after: expr.span.shrink_to_hi(),
+                            },
+                        }))
+                    } else {
+                        self.sess.emit_err(StructLiteralBodyWithoutPath {
+                            span: expr.span,
+                            sugg: StructLiteralBodyWithoutPathSugg {
+                                before: expr.span.shrink_to_lo(),
+                                after: expr.span.shrink_to_hi(),
+                            },
+                        });
+                        Ok(tail)
+                    }
                 }
                 (Err(err), Ok(tail)) => {
                     // We have a block tail that contains a somehow valid type ascription expr.
@@ -1112,7 +1119,11 @@ impl<'a> Parser<'a> {
                     return if token::ModSep == self.token.kind {
                         // We have some certainty that this was a bad turbofish at this point.
                         // `foo< bar >::`
-                        err.suggest_turbofish = Some(op.span.shrink_to_lo());
+                        if let ExprKind::Binary(o, ..) = inner_op.kind && o.node == BinOpKind::Lt {
+                            err.suggest_turbofish = Some(op.span.shrink_to_lo());
+                        } else {
+                            err.help_turbofish = Some(());
+                        }
 
                         let snapshot = self.create_snapshot_for_diagnostic();
                         self.bump(); // `::`
@@ -1138,7 +1149,11 @@ impl<'a> Parser<'a> {
                     } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
                         // We have high certainty that this was a bad turbofish at this point.
                         // `foo< bar >(`
-                        err.suggest_turbofish = Some(op.span.shrink_to_lo());
+                        if let ExprKind::Binary(o, ..) = inner_op.kind && o.node == BinOpKind::Lt {
+                            err.suggest_turbofish = Some(op.span.shrink_to_lo());
+                        } else {
+                            err.help_turbofish = Some(());
+                        }
                         // Consume the fn call arguments.
                         match self.consume_fn_args() {
                             Err(()) => Err(err.into_diagnostic(&self.sess.span_diagnostic)),
@@ -1238,7 +1253,7 @@ impl<'a> Parser<'a> {
         let sum_span = ty.span.to(self.prev_token.span);
 
         let sub = match &ty.kind {
-            TyKind::Rptr(lifetime, mut_ty) => {
+            TyKind::Ref(lifetime, mut_ty) => {
                 let sum_with_parens = pprust::to_string(|s| {
                     s.s.word("&");
                     s.print_opt_lifetime(lifetime);
@@ -1267,12 +1282,10 @@ impl<'a> Parser<'a> {
         &mut self,
         operand_expr: P<Expr>,
         op_span: Span,
-        prev_is_semi: bool,
+        start_stmt: bool,
     ) -> PResult<'a, P<Expr>> {
-        let standalone =
-            if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
+        let standalone = if start_stmt { IsStandalone::Standalone } else { IsStandalone::Subexpr };
         let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
-
         self.recover_from_inc_dec(operand_expr, kind, op_span)
     }
 
@@ -1280,13 +1293,13 @@ impl<'a> Parser<'a> {
         &mut self,
         operand_expr: P<Expr>,
         op_span: Span,
+        start_stmt: bool,
     ) -> PResult<'a, P<Expr>> {
         let kind = IncDecRecovery {
-            standalone: IsStandalone::Maybe,
+            standalone: if start_stmt { IsStandalone::Standalone } else { IsStandalone::Subexpr },
             op: IncOrDec::Inc,
             fixity: UnaryFixity::Post,
         };
-
         self.recover_from_inc_dec(operand_expr, kind, op_span)
     }
 
@@ -1315,34 +1328,25 @@ impl<'a> Parser<'a> {
         };
 
         match kind.standalone {
-            IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
+            IsStandalone::Standalone => {
+                self.inc_dec_standalone_suggest(kind, spans).emit_verbose(&mut err)
+            }
             IsStandalone::Subexpr => {
                 let Ok(base_src) = self.span_to_snippet(base.span)
-                    else { return help_base_case(err, base) };
+                else { return help_base_case(err, base) };
                 match kind.fixity {
                     UnaryFixity::Pre => {
                         self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
                     }
                     UnaryFixity::Post => {
-                        self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+                        // won't suggest since we can not handle the precedences
+                        // for example: `a + b++` has been parsed (a + b)++ and we can not suggest here
+                        if !matches!(base.kind, ExprKind::Binary(_, _, _)) {
+                            self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
+                        }
                     }
                 }
             }
-            IsStandalone::Maybe => {
-                let Ok(base_src) = self.span_to_snippet(base.span)
-                    else { return help_base_case(err, base) };
-                let sugg1 = match kind.fixity {
-                    UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
-                    UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
-                };
-                let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
-                MultiSugg::emit_many(
-                    &mut err,
-                    "use `+= 1` instead",
-                    Applicability::Unspecified,
-                    [sugg1, sugg2].into_iter(),
-                )
-            }
         }
         Err(err)
     }
@@ -1392,7 +1396,6 @@ impl<'a> Parser<'a> {
         }
 
         patches.push((post_span, format!(" {}= 1", kind.op.chr())));
-
         MultiSugg {
             msg: format!("use `{}= 1` instead", kind.op.chr()),
             patches,
@@ -2577,6 +2580,75 @@ impl<'a> Parser<'a> {
         Ok(())
     }
 
+    pub fn is_diff_marker(&mut self, long_kind: &TokenKind, short_kind: &TokenKind) -> bool {
+        (0..3).all(|i| self.look_ahead(i, |tok| tok == long_kind))
+            && self.look_ahead(3, |tok| tok == short_kind)
+    }
+
+    fn diff_marker(&mut self, long_kind: &TokenKind, short_kind: &TokenKind) -> Option<Span> {
+        if self.is_diff_marker(long_kind, short_kind) {
+            let lo = self.token.span;
+            for _ in 0..4 {
+                self.bump();
+            }
+            return Some(lo.to(self.prev_token.span));
+        }
+        None
+    }
+
+    pub fn recover_diff_marker(&mut self) {
+        let Some(start) = self.diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) else {
+            return;
+        };
+        let mut spans = Vec::with_capacity(3);
+        spans.push(start);
+        let mut middlediff3 = None;
+        let mut middle = None;
+        let mut end = None;
+        loop {
+            if self.token.kind == TokenKind::Eof {
+                break;
+            }
+            if let Some(span) = self.diff_marker(&TokenKind::OrOr, &TokenKind::BinOp(token::Or)) {
+                middlediff3 = Some(span);
+            }
+            if let Some(span) = self.diff_marker(&TokenKind::EqEq, &TokenKind::Eq) {
+                middle = Some(span);
+            }
+            if let Some(span) = self.diff_marker(&TokenKind::BinOp(token::Shr), &TokenKind::Gt) {
+                spans.push(span);
+                end = Some(span);
+                break;
+            }
+            self.bump();
+        }
+        let mut err = self.struct_span_err(spans, "encountered diff marker");
+        err.span_label(start, "after this is the code before the merge");
+        if let Some(middle) = middlediff3 {
+            err.span_label(middle, "");
+        }
+        if let Some(middle) = middle {
+            err.span_label(middle, "");
+        }
+        if let Some(end) = end {
+            err.span_label(end, "above this are the incoming code changes");
+        }
+        err.help(
+            "if you're having merge conflicts after pulling new code, the top section is the code \
+             you already had and the bottom section is the remote code",
+        );
+        err.help(
+            "if you're in the middle of a rebase, the top section is the code being rebased onto \
+             and the bottom section is the code coming from the current commit being rebased",
+        );
+        err.note(
+            "for an explanation on these markers from the `git` documentation, visit \
+             <https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging#_checking_out_conflicts>",
+        );
+        err.emit();
+        FatalError.raise()
+    }
+
     /// Parse and throw away a parenthesized comma separated
     /// sequence of patterns until `)` is reached.
     fn skip_pat_list(&mut self) -> PResult<'a, ()> {
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index f6a6ed379..bf93a89f0 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -83,7 +83,7 @@ macro_rules! maybe_whole_expr {
 pub(super) enum LhsExpr {
     NotYetParsed,
     AttributesParsed(AttrWrapper),
-    AlreadyParsed(P<Expr>),
+    AlreadyParsed { expr: P<Expr>, starts_statement: bool },
 }
 
 impl From<Option<AttrWrapper>> for LhsExpr {
@@ -97,11 +97,11 @@ impl From<Option<AttrWrapper>> for LhsExpr {
 }
 
 impl From<P<Expr>> for LhsExpr {
-    /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed(expr)`.
+    /// Converts the `expr: P<Expr>` into `LhsExpr::AlreadyParsed { expr, starts_statement: false }`.
     ///
     /// This conversion does not allocate.
     fn from(expr: P<Expr>) -> Self {
-        LhsExpr::AlreadyParsed(expr)
+        LhsExpr::AlreadyParsed { expr, starts_statement: false }
     }
 }
 
@@ -173,14 +173,16 @@ impl<'a> Parser<'a> {
         min_prec: usize,
         lhs: LhsExpr,
     ) -> PResult<'a, P<Expr>> {
-        let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
+        let mut starts_stmt = false;
+        let mut lhs = if let LhsExpr::AlreadyParsed { expr, starts_statement } = lhs {
+            starts_stmt = starts_statement;
             expr
         } else {
             let attrs = match lhs {
                 LhsExpr::AttributesParsed(attrs) => Some(attrs),
                 _ => None,
             };
-            if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind) {
+            if self.token.is_range_separator() {
                 return self.parse_prefix_range_expr(attrs);
             } else {
                 self.parse_prefix_expr(attrs)?
@@ -292,7 +294,7 @@ impl<'a> Parser<'a> {
                 let op_span = self.prev_token.span.to(self.token.span);
                 // Eat the second `+`
                 self.bump();
-                lhs = self.recover_from_postfix_increment(lhs, op_span)?;
+                lhs = self.recover_from_postfix_increment(lhs, op_span, starts_stmt)?;
                 continue;
             }
 
@@ -512,7 +514,7 @@ impl<'a> Parser<'a> {
         }
 
         debug_assert!(
-            [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token.kind),
+            self.token.is_range_separator(),
             "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
             self.token
         );
@@ -560,17 +562,23 @@ impl<'a> Parser<'a> {
 
         // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
         match this.token.uninterpolate().kind {
-            token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)), // `!expr`
-            token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)), // `~expr`
+            // `!expr`
+            token::Not => make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Not)),
+            // `~expr`
+            token::Tilde => make_it!(this, attrs, |this, _| this.recover_tilde_expr(lo)),
+            // `-expr`
             token::BinOp(token::Minus) => {
                 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Neg))
-            } // `-expr`
+            }
+            // `*expr`
             token::BinOp(token::Star) => {
                 make_it!(this, attrs, |this, _| this.parse_unary_expr(lo, UnOp::Deref))
-            } // `*expr`
+            }
+            // `&expr` and `&&expr`
             token::BinOp(token::And) | token::AndAnd => {
                 make_it!(this, attrs, |this, _| this.parse_borrow_expr(lo))
             }
+            // `+lit`
             token::BinOp(token::Plus) if this.look_ahead(1, |tok| tok.is_numeric_lit()) => {
                 let mut err =
                     LeadingPlusNotSupported { span: lo, remove_plus: None, add_parentheses: None };
@@ -585,19 +593,20 @@ impl<'a> Parser<'a> {
 
                 this.bump();
                 this.parse_prefix_expr(None)
-            } // `+expr`
+            }
             // Recover from `++x`:
             token::BinOp(token::Plus)
                 if this.look_ahead(1, |t| *t == token::BinOp(token::Plus)) =>
             {
-                let prev_is_semi = this.prev_token == token::Semi;
+                let starts_stmt = this.prev_token == token::Semi
+                    || this.prev_token == token::CloseDelim(Delimiter::Brace);
                 let pre_span = this.token.span.to(this.look_ahead(1, |t| t.span));
                 // Eat both `+`s.
                 this.bump();
                 this.bump();
 
                 let operand_expr = this.parse_dot_or_call_expr(Default::default())?;
-                this.recover_from_prefix_increment(operand_expr, pre_span, prev_is_semi)
+                this.recover_from_prefix_increment(operand_expr, pre_span, starts_stmt)
             }
             token::Ident(..) if this.token.is_keyword(kw::Box) => {
                 make_it!(this, attrs, |this, _| this.parse_box_expr(lo))
@@ -621,7 +630,7 @@ impl<'a> Parser<'a> {
         Ok((span, self.mk_unary(op, expr)))
     }
 
-    // Recover on `!` suggesting for bitwise negation instead.
+    /// Recover on `~expr` in favor of `!expr`.
     fn recover_tilde_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
         self.sess.emit_err(TildeAsUnaryOperator(lo));
 
@@ -648,7 +657,6 @@ impl<'a> Parser<'a> {
 
     /// Recover on `not expr` in favor of `!expr`.
     fn recover_not_expr(&mut self, lo: Span) -> PResult<'a, (Span, ExprKind)> {
-        // Emit the error...
         let negated_token = self.look_ahead(1, |t| t.clone());
 
         let sub_diag = if negated_token.is_numeric_lit() {
@@ -669,7 +677,6 @@ impl<'a> Parser<'a> {
             ),
         });
 
-        // ...and recover!
         self.parse_unary_expr(lo, UnOp::Not)
     }
 
@@ -896,7 +903,11 @@ impl<'a> Parser<'a> {
         let has_lifetime = self.token.is_lifetime() && self.look_ahead(1, |t| t != &token::Colon);
         let lifetime = has_lifetime.then(|| self.expect_lifetime()); // For recovery, see below.
         let (borrow_kind, mutbl) = self.parse_borrow_modifiers(lo);
-        let expr = self.parse_prefix_expr(None);
+        let expr = if self.token.is_range_separator() {
+            self.parse_prefix_range_expr(None)
+        } else {
+            self.parse_prefix_expr(None)
+        };
         let (hi, expr) = self.interpolated_or_expr_span(expr)?;
         let span = lo.to(hi);
         if let Some(lt) = lifetime {
@@ -1318,7 +1329,10 @@ impl<'a> Parser<'a> {
             self.parse_array_or_repeat_expr(Delimiter::Bracket)
         } else if self.check_path() {
             self.parse_path_start_expr()
-        } else if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
+        } else if self.check_keyword(kw::Move)
+            || self.check_keyword(kw::Static)
+            || self.check_const_closure()
+        {
             self.parse_closure_expr()
         } else if self.eat_keyword(kw::If) {
             self.parse_if_expr()
@@ -1339,9 +1353,6 @@ impl<'a> Parser<'a> {
                 err.span_label(sp, "while parsing this `loop` expression");
                 err
             })
-        } else if self.eat_keyword(kw::Continue) {
-            let kind = ExprKind::Continue(self.eat_label());
-            Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
         } else if self.eat_keyword(kw::Match) {
             let match_sp = self.prev_token.span;
             self.parse_match_expr().map_err(|mut err| {
@@ -1365,6 +1376,8 @@ impl<'a> Parser<'a> {
             self.parse_try_block(lo)
         } else if self.eat_keyword(kw::Return) {
             self.parse_return_expr()
+        } else if self.eat_keyword(kw::Continue) {
+            self.parse_continue_expr(lo)
         } else if self.eat_keyword(kw::Break) {
             self.parse_break_expr()
         } else if self.eat_keyword(kw::Yield) {
@@ -1461,9 +1474,8 @@ impl<'a> Parser<'a> {
             } else if self.eat(&token::Comma) {
                 // Vector with two or more elements.
                 let sep = SeqSep::trailing_allowed(token::Comma);
-                let (remaining_exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
-                let mut exprs = vec![first_expr];
-                exprs.extend(remaining_exprs);
+                let (mut exprs, _) = self.parse_seq_to_end(close, sep, |p| p.parse_expr())?;
+                exprs.insert(0, first_expr);
                 ExprKind::Array(exprs)
             } else {
                 // Vector with one element
@@ -1496,12 +1508,13 @@ impl<'a> Parser<'a> {
                 prior_type_ascription: self.last_type_ascription,
             });
             (lo.to(self.prev_token.span), ExprKind::MacCall(mac))
-        } else if self.check(&token::OpenDelim(Delimiter::Brace)) &&
-            let Some(expr) = self.maybe_parse_struct_expr(&qself, &path) {
-                if qself.is_some() {
-                    self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
-                }
-                return expr;
+        } else if self.check(&token::OpenDelim(Delimiter::Brace))
+            && let Some(expr) = self.maybe_parse_struct_expr(&qself, &path)
+        {
+            if qself.is_some() {
+                self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
+            }
+            return expr;
         } else {
             (path.span, ExprKind::Path(qself, path))
         };
@@ -1534,15 +1547,16 @@ impl<'a> Parser<'a> {
             && (matches!(self.token.kind, token::CloseDelim(_) | token::Comma)
                 || self.token.is_op())
         {
-            let lit = self.recover_unclosed_char(label_.ident, |self_| {
-                self_.sess.create_err(UnexpectedTokenAfterLabel {
-                    span: self_.token.span,
-                    remove_label: None,
-                    enclose_in_block: None,
-                })
-            });
+            let (lit, _) =
+                self.recover_unclosed_char(label_.ident, Parser::mk_token_lit_char, |self_| {
+                    self_.sess.create_err(UnexpectedTokenAfterLabel {
+                        span: self_.token.span,
+                        remove_label: None,
+                        enclose_in_block: None,
+                    })
+                });
             consume_colon = false;
-            Ok(self.mk_expr(lo, ExprKind::Lit(lit.token_lit)))
+            Ok(self.mk_expr(lo, ExprKind::Lit(lit)))
         } else if !ate_colon
             && (self.check_noexpect(&TokenKind::Comma) || self.check_noexpect(&TokenKind::Gt))
         {
@@ -1581,7 +1595,7 @@ impl<'a> Parser<'a> {
                     vis.0
                 };
 
-                // Suggestion involves adding a (as of time of writing this, unstable) labeled block.
+                // Suggestion involves adding a labeled block.
                 //
                 // If there are no breaks that may use this label, suggest removing the label and
                 // recover to the unmodified expression.
@@ -1617,12 +1631,13 @@ impl<'a> Parser<'a> {
         Ok(expr)
     }
 
-    /// Emit an error when a char is parsed as a lifetime because of a missing quote
-    pub(super) fn recover_unclosed_char(
+    /// Emit an error when a char is parsed as a lifetime because of a missing quote.
+    pub(super) fn recover_unclosed_char<L>(
         &self,
         lifetime: Ident,
+        mk_lit_char: impl FnOnce(Symbol, Span) -> L,
         err: impl FnOnce(&Self) -> DiagnosticBuilder<'a, ErrorGuaranteed>,
-    ) -> ast::MetaItemLit {
+    ) -> L {
         if let Some(mut diag) =
             self.sess.span_diagnostic.steal_diagnostic(lifetime.span, StashKey::LifetimeIsChar)
         {
@@ -1644,11 +1659,7 @@ impl<'a> Parser<'a> {
                 .emit();
         }
         let name = lifetime.without_first_quote().name;
-        ast::MetaItemLit {
-            token_lit: token::Lit::new(token::LitKind::Char, name, None),
-            kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
-            span: lifetime.span,
-        }
+        mk_lit_char(name, lifetime.span)
     }
 
     /// Recover on the syntax `do catch { ... }` suggesting `try { ... }` instead.
@@ -1703,10 +1714,10 @@ impl<'a> Parser<'a> {
     fn parse_break_expr(&mut self) -> PResult<'a, P<Expr>> {
         let lo = self.prev_token.span;
         let mut label = self.eat_label();
-        let kind = if label.is_some() && self.token == token::Colon {
+        let kind = if self.token == token::Colon && let Some(label) = label.take() {
             // The value expression can be a labeled loop, see issue #86948, e.g.:
             // `loop { break 'label: loop { break 'label 42; }; }`
-            let lexpr = self.parse_labeled_expr(label.take().unwrap(), true)?;
+            let lexpr = self.parse_labeled_expr(label, true)?;
             self.sess.emit_err(LabeledLoopInBreak {
                 span: lexpr.span,
                 sub: WrapExpressionInParentheses {
@@ -1718,8 +1729,8 @@ impl<'a> Parser<'a> {
         } else if self.token != token::OpenDelim(Delimiter::Brace)
             || !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
         {
-            let expr = self.parse_expr_opt()?;
-            if let Some(expr) = &expr {
+            let mut expr = self.parse_expr_opt()?;
+            if let Some(expr) = &mut expr {
                 if label.is_some()
                     && matches!(
                         expr.kind,
@@ -1737,7 +1748,19 @@ impl<'a> Parser<'a> {
                         BuiltinLintDiagnostics::BreakWithLabelAndLoop(expr.span),
                     );
                 }
+
+                // Recover `break label aaaaa`
+                if self.may_recover()
+                    && let ExprKind::Path(None, p) = &expr.kind
+                    && let [segment] = &*p.segments
+                    && let &ast::PathSegment { ident, args: None, .. } = segment
+                    && let Some(next) = self.parse_expr_opt()?
+                {
+                    label = Some(self.recover_ident_into_label(ident));
+                    *expr = next;
+                }
             }
+
             expr
         } else {
             None
@@ -1746,6 +1769,23 @@ impl<'a> Parser<'a> {
         self.maybe_recover_from_bad_qpath(expr)
     }
 
+    /// Parse `"continue" label?`.
+    fn parse_continue_expr(&mut self, lo: Span) -> PResult<'a, P<Expr>> {
+        let mut label = self.eat_label();
+
+        // Recover `continue label` -> `continue 'label`
+        if self.may_recover()
+            && label.is_none()
+            && let Some((ident, _)) = self.token.ident()
+        {
+            self.bump();
+            label = Some(self.recover_ident_into_label(ident));
+        }
+
+        let kind = ExprKind::Continue(label);
+        Ok(self.mk_expr(lo.to(self.prev_token.span), kind))
+    }
+
     /// Parse `"yield" expr?`.
     fn parse_yield_expr(&mut self) -> PResult<'a, P<Expr>> {
         let lo = self.prev_token.span;
@@ -1764,8 +1804,8 @@ impl<'a> Parser<'a> {
             Some(lit) => match lit.kind {
                 ast::LitKind::Str(symbol_unescaped, style) => Ok(ast::StrLit {
                     style,
-                    symbol: lit.token_lit.symbol,
-                    suffix: lit.token_lit.suffix,
+                    symbol: lit.symbol,
+                    suffix: lit.suffix,
                     span: lit.span,
                     symbol_unescaped,
                 }),
@@ -1775,7 +1815,23 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn handle_missing_lit(&mut self) -> PResult<'a, MetaItemLit> {
+    pub(crate) fn mk_token_lit_char(name: Symbol, span: Span) -> (token::Lit, Span) {
+        (token::Lit { symbol: name, suffix: None, kind: token::Char }, span)
+    }
+
+    fn mk_meta_item_lit_char(name: Symbol, span: Span) -> MetaItemLit {
+        ast::MetaItemLit {
+            symbol: name,
+            suffix: None,
+            kind: ast::LitKind::Char(name.as_str().chars().next().unwrap_or('_')),
+            span,
+        }
+    }
+
+    fn handle_missing_lit<L>(
+        &mut self,
+        mk_lit_char: impl FnOnce(Symbol, Span) -> L,
+    ) -> PResult<'a, L> {
         if let token::Interpolated(inner) = &self.token.kind {
             let expr = match inner.as_ref() {
                 token::NtExpr(expr) => Some(expr),
@@ -1799,7 +1855,7 @@ impl<'a> Parser<'a> {
         // On an error path, eagerly consider a lifetime to be an unclosed character lit
         if self.token.is_lifetime() {
             let lt = self.expect_lifetime();
-            Ok(self.recover_unclosed_char(lt.ident, err))
+            Ok(self.recover_unclosed_char(lt.ident, mk_lit_char, err))
         } else {
             Err(err(self))
         }
@@ -1808,11 +1864,13 @@ impl<'a> Parser<'a> {
     pub(super) fn parse_token_lit(&mut self) -> PResult<'a, (token::Lit, Span)> {
         self.parse_opt_token_lit()
             .ok_or(())
-            .or_else(|()| self.handle_missing_lit().map(|lit| (lit.token_lit, lit.span)))
+            .or_else(|()| self.handle_missing_lit(Parser::mk_token_lit_char))
     }
 
     pub(super) fn parse_meta_item_lit(&mut self) -> PResult<'a, MetaItemLit> {
-        self.parse_opt_meta_item_lit().ok_or(()).or_else(|()| self.handle_missing_lit())
+        self.parse_opt_meta_item_lit()
+            .ok_or(())
+            .or_else(|()| self.handle_missing_lit(Parser::mk_meta_item_lit_char))
     }
 
     fn recover_after_dot(&mut self) -> Option<Token> {
@@ -2015,7 +2073,7 @@ impl<'a> Parser<'a> {
             });
         }
 
-        let (attrs, blk) = self.parse_block_common(lo, blk_mode)?;
+        let (attrs, blk) = self.parse_block_common(lo, blk_mode, true)?;
         Ok(self.mk_expr_with_attrs(blk.span, ExprKind::Block(blk, opt_label), attrs))
     }
 
@@ -2041,6 +2099,8 @@ impl<'a> Parser<'a> {
             ClosureBinder::NotPresent
         };
 
+        let constness = self.parse_constness(Case::Sensitive);
+
         let movability =
             if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
 
@@ -2087,6 +2147,7 @@ impl<'a> Parser<'a> {
             ExprKind::Closure(Box::new(ast::Closure {
                 binder,
                 capture_clause,
+                constness,
                 asyncness,
                 movability,
                 fn_decl,
@@ -3013,9 +3074,29 @@ impl<'a> Parser<'a> {
         false
     }
 
+    /// Converts an ident into 'label and emits an "expected a label, found an identifier" error.
+    fn recover_ident_into_label(&mut self, ident: Ident) -> Label {
+        // Convert `label` -> `'label`,
+        // so that nameres doesn't complain about non-existing label
+        let label = format!("'{}", ident.name);
+        let ident = Ident { name: Symbol::intern(&label), span: ident.span };
+
+        self.struct_span_err(ident.span, "expected a label, found an identifier")
+            .span_suggestion(
+                ident.span,
+                "labels start with a tick",
+                label,
+                Applicability::MachineApplicable,
+            )
+            .emit();
+
+        Label { ident }
+    }
+
     /// Parses `ident (COLON expr)?`.
     fn parse_expr_field(&mut self) -> PResult<'a, ExprField> {
         let attrs = self.parse_outer_attributes()?;
+        self.recover_diff_marker();
         self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
             let lo = this.token.span;
 
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs
index fa75670b2..8ba811715 100644
--- a/compiler/rustc_parse/src/parser/generics.rs
+++ b/compiler/rustc_parse/src/parser/generics.rs
@@ -1,11 +1,20 @@
+use crate::errors::{WhereClauseBeforeTupleStructBody, WhereClauseBeforeTupleStructBodySugg};
+
 use super::{ForceCollect, Parser, TrailingToken};
 
+use ast::token::Delimiter;
 use rustc_ast::token;
 use rustc_ast::{
     self as ast, AttrVec, GenericBounds, GenericParam, GenericParamKind, TyKind, WhereClause,
 };
 use rustc_errors::{Applicability, PResult};
-use rustc_span::symbol::kw;
+use rustc_span::symbol::{kw, Ident};
+use rustc_span::Span;
+
+enum PredicateOrStructBody {
+    Predicate(ast::WherePredicate),
+    StructBody(Vec<ast::FieldDef>),
+}
 
 impl<'a> Parser<'a> {
     /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
@@ -240,23 +249,39 @@ impl<'a> Parser<'a> {
         })
     }
 
-    /// Parses an optional where-clause and places it in `generics`.
+    /// Parses an optional where-clause.
     ///
     /// ```ignore (only-for-syntax-highlight)
     /// where T : Trait<U, V> + 'b, 'a : 'b
     /// ```
     pub(super) fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
+        self.parse_where_clause_common(None).map(|(clause, _)| clause)
+    }
+
+    pub(super) fn parse_struct_where_clause(
+        &mut self,
+        struct_name: Ident,
+        body_insertion_point: Span,
+    ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> {
+        self.parse_where_clause_common(Some((struct_name, body_insertion_point)))
+    }
+
+    fn parse_where_clause_common(
+        &mut self,
+        struct_: Option<(Ident, Span)>,
+    ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> {
         let mut where_clause = WhereClause {
             has_where_token: false,
             predicates: Vec::new(),
             span: self.prev_token.span.shrink_to_hi(),
         };
+        let mut tuple_struct_body = None;
 
         if !self.eat_keyword(kw::Where) {
-            return Ok(where_clause);
+            return Ok((where_clause, None));
         }
         where_clause.has_where_token = true;
-        let lo = self.prev_token.span;
+        let where_lo = self.prev_token.span;
 
         // We are considering adding generics to the `where` keyword as an alternative higher-rank
         // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
@@ -272,7 +297,8 @@ impl<'a> Parser<'a> {
         }
 
         loop {
-            let lo = self.token.span;
+            let where_sp = where_lo.to(self.prev_token.span);
+            let pred_lo = self.token.span;
             if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
                 let lifetime = self.expect_lifetime();
                 // Bounds starting with a colon are mandatory, but possibly empty.
@@ -280,13 +306,21 @@ impl<'a> Parser<'a> {
                 let bounds = self.parse_lt_param_bounds();
                 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
                     ast::WhereRegionPredicate {
-                        span: lo.to(self.prev_token.span),
+                        span: pred_lo.to(self.prev_token.span),
                         lifetime,
                         bounds,
                     },
                 ));
             } else if self.check_type() {
-                where_clause.predicates.push(self.parse_ty_where_predicate()?);
+                match self.parse_ty_where_predicate_or_recover_tuple_struct_body(
+                    struct_, pred_lo, where_sp,
+                )? {
+                    PredicateOrStructBody::Predicate(pred) => where_clause.predicates.push(pred),
+                    PredicateOrStructBody::StructBody(body) => {
+                        tuple_struct_body = Some(body);
+                        break;
+                    }
+                }
             } else {
                 break;
             }
@@ -297,7 +331,7 @@ impl<'a> Parser<'a> {
             if self.eat_keyword_noexpect(kw::Where) {
                 let msg = "cannot define duplicate `where` clauses on an item";
                 let mut err = self.struct_span_err(self.token.span, msg);
-                err.span_label(lo, "previous `where` clause starts here");
+                err.span_label(pred_lo, "previous `where` clause starts here");
                 err.span_suggestion_verbose(
                     prev_token.shrink_to_hi().to(self.prev_token.span),
                     "consider joining the two `where` clauses into one",
@@ -310,8 +344,72 @@ impl<'a> Parser<'a> {
             }
         }
 
-        where_clause.span = lo.to(self.prev_token.span);
-        Ok(where_clause)
+        where_clause.span = where_lo.to(self.prev_token.span);
+        Ok((where_clause, tuple_struct_body))
+    }
+
+    fn parse_ty_where_predicate_or_recover_tuple_struct_body(
+        &mut self,
+        struct_: Option<(Ident, Span)>,
+        pred_lo: Span,
+        where_sp: Span,
+    ) -> PResult<'a, PredicateOrStructBody> {
+        let mut snapshot = None;
+
+        if let Some(struct_) = struct_
+            && self.may_recover()
+            && self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
+        {
+            snapshot = Some((struct_, self.create_snapshot_for_diagnostic()));
+        };
+
+        match self.parse_ty_where_predicate() {
+            Ok(pred) => Ok(PredicateOrStructBody::Predicate(pred)),
+            Err(type_err) => {
+                let Some(((struct_name, body_insertion_point), mut snapshot)) = snapshot else {
+                    return Err(type_err);
+                };
+
+                // Check if we might have encountered an out of place tuple struct body.
+                match snapshot.parse_tuple_struct_body() {
+                    // Since we don't know the exact reason why we failed to parse the
+                    // predicate (we might have stumbled upon something bogus like `(T): ?`),
+                    // employ a simple heuristic to weed out some pathological cases:
+                    // Look for a semicolon (strong indicator) or anything that might mark
+                    // the end of the item (weak indicator) following the body.
+                    Ok(body)
+                        if matches!(snapshot.token.kind, token::Semi | token::Eof)
+                            || snapshot.token.can_begin_item() =>
+                    {
+                        type_err.cancel();
+
+                        let body_sp = pred_lo.to(snapshot.prev_token.span);
+                        let map = self.sess.source_map();
+
+                        self.sess.emit_err(WhereClauseBeforeTupleStructBody {
+                            span: where_sp,
+                            name: struct_name.span,
+                            body: body_sp,
+                            sugg: map.span_to_snippet(body_sp).ok().map(|body| {
+                                WhereClauseBeforeTupleStructBodySugg {
+                                    left: body_insertion_point.shrink_to_hi(),
+                                    snippet: body,
+                                    right: map.end_point(where_sp).to(body_sp),
+                                }
+                            }),
+                        });
+
+                        self.restore_snapshot(snapshot);
+                        Ok(PredicateOrStructBody::StructBody(body))
+                    }
+                    Ok(_) => Err(type_err),
+                    Err(body_err) => {
+                        body_err.cancel();
+                        Err(type_err)
+                    }
+                }
+            }
+        }
     }
 
     fn parse_ty_where_predicate(&mut self) -> PResult<'a, ast::WherePredicate> {
diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 03f25392a..53680a82b 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -3,6 +3,7 @@ use crate::errors::{DocCommentDoesNotDocumentAnything, UseEmptyBlockNotSemi};
 use super::diagnostics::{dummy_arg, ConsumeClosingDelim};
 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
 use super::{AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, TrailingToken};
+use crate::errors::FnTypoWithImpl;
 use rustc_ast::ast::*;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, TokenKind};
@@ -21,10 +22,8 @@ use rustc_span::lev_distance::lev_distance;
 use rustc_span::source_map::{self, Span};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::DUMMY_SP;
-use std::convert::TryFrom;
 use std::mem;
 use thin_vec::ThinVec;
-use tracing::debug;
 
 impl<'a> Parser<'a> {
     /// Parses a source module as a crate. This is the main entry point for the parser.
@@ -99,7 +98,9 @@ impl<'a> Parser<'a> {
         fn_parse_mode: FnParseMode,
         force_collect: ForceCollect,
     ) -> PResult<'a, Option<Item>> {
+        self.recover_diff_marker();
         let attrs = self.parse_outer_attributes()?;
+        self.recover_diff_marker();
         self.parse_item_common(attrs, true, false, fn_parse_mode, force_collect)
     }
 
@@ -705,11 +706,12 @@ impl<'a> Parser<'a> {
             if self.recover_doc_comment_before_brace() {
                 continue;
             }
+            self.recover_diff_marker();
             match parse_item(self) {
                 Ok(None) => {
-                    let is_unnecessary_semicolon = !items.is_empty()
+                    let mut is_unnecessary_semicolon = !items.is_empty()
                         // When the close delim is `)` in a case like the following, `token.kind` is expected to be `token::CloseDelim(Delimiter::Parenthesis)`,
-                        // but the actual `token.kind` is `token::CloseDelim(Delimiter::Bracket)`.
+                        // but the actual `token.kind` is `token::CloseDelim(Delimiter::Brace)`.
                         // This is because the `token.kind` of the close delim is treated as the same as
                         // that of the open delim in `TokenTreesReader::parse_token_tree`, even if the delimiters of them are different.
                         // Therefore, `token.kind` should not be compared here.
@@ -728,7 +730,13 @@ impl<'a> Parser<'a> {
                             .span_to_snippet(self.prev_token.span)
                             .map_or(false, |snippet| snippet == "}")
                         && self.token.kind == token::Semi;
-                    let semicolon_span = self.token.span;
+                    let mut semicolon_span = self.token.span;
+                    if !is_unnecessary_semicolon {
+                        // #105369, Detect spurious `;` before assoc fn body
+                        is_unnecessary_semicolon = self.token == token::OpenDelim(Delimiter::Brace)
+                            && self.prev_token.kind == token::Semi;
+                        semicolon_span = self.prev_token.span;
+                    }
                     // We have to bail or we'll potentially never make progress.
                     let non_item_span = self.token.span;
                     let is_let = self.token.is_keyword(kw::Let);
@@ -1034,8 +1042,11 @@ impl<'a> Parser<'a> {
     /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
     /// ```
     fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
-        self.parse_delim_comma_seq(Delimiter::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
-            .map(|(r, _)| r)
+        self.parse_delim_comma_seq(Delimiter::Brace, |p| {
+            p.recover_diff_marker();
+            Ok((p.parse_use_tree()?, DUMMY_NODE_ID))
+        })
+        .map(|(r, _)| r)
     }
 
     fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
@@ -1374,7 +1385,9 @@ impl<'a> Parser<'a> {
     }
 
     fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
+        self.recover_diff_marker();
         let variant_attrs = self.parse_outer_attributes()?;
+        self.recover_diff_marker();
         self.collect_tokens_trailing_token(
             variant_attrs,
             ForceCollect::No,
@@ -1441,8 +1454,16 @@ impl<'a> Parser<'a> {
         // struct.
 
         let vdata = if self.token.is_keyword(kw::Where) {
-            generics.where_clause = self.parse_where_clause()?;
-            if self.eat(&token::Semi) {
+            let tuple_struct_body;
+            (generics.where_clause, tuple_struct_body) =
+                self.parse_struct_where_clause(class_name, generics.span)?;
+
+            if let Some(body) = tuple_struct_body {
+                // If we see a misplaced tuple struct body: `struct Foo<T> where T: Copy, (T);`
+                let body = VariantData::Tuple(body, DUMMY_NODE_ID);
+                self.expect_semi()?;
+                body
+            } else if self.eat(&token::Semi) {
                 // If we see a: `struct Foo<T> where T: Copy;` style decl.
                 VariantData::Unit(DUMMY_NODE_ID)
             } else {
@@ -1562,15 +1583,38 @@ impl<'a> Parser<'a> {
         Ok((fields, recovered))
     }
 
-    fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<FieldDef>> {
+    pub(super) fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<FieldDef>> {
         // This is the case where we find `struct Foo<T>(T) where T: Copy;`
         // Unit like structs are handled in parse_item_struct function
         self.parse_paren_comma_seq(|p| {
             let attrs = p.parse_outer_attributes()?;
             p.collect_tokens_trailing_token(attrs, ForceCollect::No, |p, attrs| {
+                let mut snapshot = None;
+                if p.is_diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) {
+                    // Account for `<<<<<<<` diff markers. We can't proactively error here because
+                    // that can be a valid type start, so we snapshot and reparse only we've
+                    // encountered another parse error.
+                    snapshot = Some(p.create_snapshot_for_diagnostic());
+                }
                 let lo = p.token.span;
-                let vis = p.parse_visibility(FollowedByType::Yes)?;
-                let ty = p.parse_ty()?;
+                let vis = match p.parse_visibility(FollowedByType::Yes) {
+                    Ok(vis) => vis,
+                    Err(err) => {
+                        if let Some(ref mut snapshot) = snapshot {
+                            snapshot.recover_diff_marker();
+                        }
+                        return Err(err);
+                    }
+                };
+                let ty = match p.parse_ty() {
+                    Ok(ty) => ty,
+                    Err(err) => {
+                        if let Some(ref mut snapshot) = snapshot {
+                            snapshot.recover_diff_marker();
+                        }
+                        return Err(err);
+                    }
+                };
 
                 Ok((
                     FieldDef {
@@ -1591,7 +1635,9 @@ impl<'a> Parser<'a> {
 
     /// Parses an element of a struct declaration.
     fn parse_field_def(&mut self, adt_ty: &str) -> PResult<'a, FieldDef> {
+        self.recover_diff_marker();
         let attrs = self.parse_outer_attributes()?;
+        self.recover_diff_marker();
         self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
             let lo = this.token.span;
             let vis = this.parse_visibility(FollowedByType::No)?;
@@ -2126,11 +2172,26 @@ impl<'a> Parser<'a> {
         vis: &Visibility,
         case: Case,
     ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
+        let fn_span = self.token.span;
         let header = self.parse_fn_front_matter(vis, case)?; // `const ... fn`
         let ident = self.parse_ident()?; // `foo`
         let mut generics = self.parse_generics()?; // `<'a, T, ...>`
-        let decl =
-            self.parse_fn_decl(fn_parse_mode.req_name, AllowPlus::Yes, RecoverReturnSign::Yes)?; // `(p: u8, ...)`
+        let decl = match self.parse_fn_decl(
+            fn_parse_mode.req_name,
+            AllowPlus::Yes,
+            RecoverReturnSign::Yes,
+        ) {
+            Ok(decl) => decl,
+            Err(old_err) => {
+                // If we see `for Ty ...` then user probably meant `impl` item.
+                if self.token.is_keyword(kw::For) {
+                    old_err.cancel();
+                    return Err(self.sess.create_err(FnTypoWithImpl { fn_span }));
+                } else {
+                    return Err(old_err);
+                }
+            }
+        };
         generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
 
         let mut sig_hi = self.prev_token.span;
@@ -2161,7 +2222,8 @@ impl<'a> Parser<'a> {
             *sig_hi = self.prev_token.span;
             (AttrVec::new(), None)
         } else if self.check(&token::OpenDelim(Delimiter::Brace)) || self.token.is_whole_block() {
-            self.parse_inner_attrs_and_block().map(|(attrs, body)| (attrs, Some(body)))?
+            self.parse_block_common(self.token.span, BlockCheckMode::Default, false)
+                .map(|(attrs, body)| (attrs, Some(body)))?
         } else if self.token.kind == token::Eq {
             // Recover `fn foo() = $expr;`.
             self.bump(); // `=`
@@ -2403,10 +2465,11 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses the parameter list of a function, including the `(` and `)` delimiters.
-    fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
+    pub(super) fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
         let mut first_param = true;
         // Parse the arguments, starting out with `self` being allowed...
         let (mut params, _) = self.parse_paren_comma_seq(|p| {
+            p.recover_diff_marker();
             let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
                 e.emit();
                 let lo = p.prev_token.span;
@@ -2444,7 +2507,6 @@ impl<'a> Parser<'a> {
             };
             let (pat, ty) = if is_name_required || this.is_named_param() {
                 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
-
                 let (pat, colon) = this.parse_fn_param_pat_colon()?;
                 if !colon {
                     let mut err = this.unexpected::<()>().unwrap_err();
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index bebb01266..ffb23b50a 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -25,7 +25,7 @@ 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, DelimArgs, Extern};
+use rustc_ast::{self as ast, AnonConst, AttrStyle, Const, DelimArgs, Extern};
 use rustc_ast::{Async, AttrArgs, AttrArgsEq, Expr, ExprKind, MacDelimiter, Mutability, StrLit};
 use rustc_ast::{HasAttrs, HasTokens, Unsafe, Visibility, VisibilityKind};
 use rustc_ast_pretty::pprust;
@@ -317,7 +317,7 @@ impl TokenCursor {
         // required to wrap the text. E.g.
         // - `abc d` is wrapped as `r"abc d"` (num_of_hashes = 0)
         // - `abc "d"` is wrapped as `r#"abc "d""#` (num_of_hashes = 1)
-        // - `abc "##d##"` is wrapped as `r###"abc "d""###` (num_of_hashes = 3)
+        // - `abc "##d##"` is wrapped as `r###"abc ##"d"##"###` (num_of_hashes = 3)
         let mut num_of_hashes = 0;
         let mut count = 0;
         for ch in data.as_str().chars() {
@@ -542,9 +542,9 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Expect next token to be edible or inedible token.  If edible,
+    /// Expect next token to be edible or inedible token. If edible,
     /// then consume it; if inedible, then return without consuming
-    /// anything.  Signal a fatal error if next token is unexpected.
+    /// anything. Signal a fatal error if next token is unexpected.
     pub fn expect_one_of(
         &mut self,
         edible: &[TokenKind],
@@ -736,6 +736,16 @@ impl<'a> Parser<'a> {
         self.check_or_expected(self.token.can_begin_const_arg(), TokenType::Const)
     }
 
+    fn check_const_closure(&self) -> bool {
+        self.is_keyword_ahead(0, &[kw::Const])
+            && self.look_ahead(1, |t| match &t.kind {
+                token::Ident(kw::Move | kw::Static | kw::Async, _)
+                | token::OrOr
+                | token::BinOp(token::Or) => true,
+                _ => false,
+            })
+    }
+
     fn check_inline_const(&self, dist: usize) -> bool {
         self.is_keyword_ahead(dist, &[kw::Const])
             && self.look_ahead(dist + 1, |t| match &t.kind {
@@ -1217,11 +1227,7 @@ impl<'a> Parser<'a> {
             value: self.mk_expr(blk.span, ExprKind::Block(blk, None)),
         };
         let blk_span = anon_const.value.span;
-        Ok(self.mk_expr_with_attrs(
-            span.to(blk_span),
-            ExprKind::ConstBlock(anon_const),
-            AttrVec::from(attrs),
-        ))
+        Ok(self.mk_expr_with_attrs(span.to(blk_span), ExprKind::ConstBlock(anon_const), attrs))
     }
 
     /// Parses mutability (`mut` or nothing).
@@ -1503,6 +1509,10 @@ impl<'a> Parser<'a> {
     pub fn clear_expected_tokens(&mut self) {
         self.expected_tokens.clear();
     }
+
+    pub fn approx_token_stream_pos(&self) -> usize {
+        self.token_cursor.num_next_calls
+    }
 }
 
 pub(crate) fn make_unclosed_delims_error(
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index cbeec951e..e73a17ced 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -411,16 +411,20 @@ impl<'a> Parser<'a> {
         {
             // Recover a `'a` as a `'a'` literal
             let lt = self.expect_lifetime();
-            let lit = self.recover_unclosed_char(lt.ident, |self_| {
-                let expected = expected.unwrap_or("pattern");
-                let msg =
-                    format!("expected {}, found {}", expected, super::token_descr(&self_.token));
+            let (lit, _) =
+                self.recover_unclosed_char(lt.ident, Parser::mk_token_lit_char, |self_| {
+                    let expected = expected.unwrap_or("pattern");
+                    let msg = format!(
+                        "expected {}, found {}",
+                        expected,
+                        super::token_descr(&self_.token)
+                    );
 
-                let mut err = self_.struct_span_err(self_.token.span, &msg);
-                err.span_label(self_.token.span, format!("expected {}", expected));
-                err
-            });
-            PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit.token_lit)))
+                    let mut err = self_.struct_span_err(self_.token.span, &msg);
+                    err.span_label(self_.token.span, format!("expected {}", expected));
+                    err
+                });
+            PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit)))
         } else {
             // Try to parse everything else as literal with optional minus
             match self.parse_literal_maybe_minus() {
@@ -465,7 +469,7 @@ impl<'a> Parser<'a> {
     /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
     ///
     /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
-    /// should already have been parsed by now  at this point,
+    /// should already have been parsed by now at this point,
     /// if the next token is `@` then we can try to parse the more general form.
     ///
     /// Consult `parse_pat_ident` for the `binding` grammar.
@@ -487,17 +491,6 @@ impl<'a> Parser<'a> {
 
         if let PatKind::Ident(_, _, sub @ None) = &mut rhs.kind {
             // The user inverted the order, so help them fix that.
-            let mut applicability = Applicability::MachineApplicable;
-            // FIXME(bindings_after_at): Remove this code when stabilizing the feature.
-            lhs.walk(&mut |p| match p.kind {
-                // `check_match` is unhappy if the subpattern has a binding anywhere.
-                PatKind::Ident(..) => {
-                    applicability = Applicability::MaybeIncorrect;
-                    false // Short-circuit.
-                }
-                _ => true,
-            });
-
             let lhs_span = lhs.span;
             // Move the LHS into the RHS as a subpattern.
             // The RHS is now the full pattern.
@@ -506,7 +499,12 @@ impl<'a> Parser<'a> {
             self.struct_span_err(sp, "pattern on wrong side of `@`")
                 .span_label(lhs_span, "pattern on the left, should be on the right")
                 .span_label(rhs.span, "binding on the right, should be on the left")
-                .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability)
+                .span_suggestion(
+                    sp,
+                    "switch the order",
+                    pprust::pat_to_string(&rhs),
+                    Applicability::MachineApplicable,
+                )
                 .emit();
         } else {
             // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs
index 2d432e3f5..5333d3b85 100644
--- a/compiler/rustc_parse/src/parser/path.rs
+++ b/compiler/rustc_parse/src/parser/path.rs
@@ -277,8 +277,7 @@ impl<'a> Parser<'a> {
                         if let Some(arg) = args
                             .iter()
                             .rev()
-                            .skip_while(|arg| matches!(arg, AngleBracketedArg::Constraint(_)))
-                            .next()
+                            .find(|arg| !matches!(arg, AngleBracketedArg::Constraint(_)))
                         {
                             err.span_suggestion_verbose(
                                 arg.span().shrink_to_hi(),
diff --git a/compiler/rustc_parse/src/parser/stmt.rs b/compiler/rustc_parse/src/parser/stmt.rs
index 42197e637..4ff9927aa 100644
--- a/compiler/rustc_parse/src/parser/stmt.rs
+++ b/compiler/rustc_parse/src/parser/stmt.rs
@@ -164,7 +164,10 @@ impl<'a> Parser<'a> {
             // Perform this outside of the `collect_tokens_trailing_token` closure,
             // since our outer attributes do not apply to this part of the expression
             let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
-                this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
+                this.parse_assoc_expr_with(
+                    0,
+                    LhsExpr::AlreadyParsed { expr, starts_statement: true },
+                )
             })?;
             Ok(self.mk_stmt(lo.to(self.prev_token.span), StmtKind::Expr(expr)))
         } else {
@@ -198,7 +201,10 @@ impl<'a> Parser<'a> {
             let e = self.mk_expr(lo.to(hi), ExprKind::MacCall(mac));
             let e = self.maybe_recover_from_bad_qpath(e)?;
             let e = self.parse_dot_or_call_expr_with(e, lo, attrs)?;
-            let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
+            let e = self.parse_assoc_expr_with(
+                0,
+                LhsExpr::AlreadyParsed { expr: e, starts_statement: false },
+            )?;
             StmtKind::Expr(e)
         };
         Ok(self.mk_stmt(lo.to(hi), kind))
@@ -498,7 +504,7 @@ impl<'a> Parser<'a> {
 
     /// Parses a block. Inner attributes are allowed.
     pub(super) fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (AttrVec, P<Block>)> {
-        self.parse_block_common(self.token.span, BlockCheckMode::Default)
+        self.parse_block_common(self.token.span, BlockCheckMode::Default, true)
     }
 
     /// Parses a block. Inner attributes are allowed.
@@ -506,16 +512,23 @@ impl<'a> Parser<'a> {
         &mut self,
         lo: Span,
         blk_mode: BlockCheckMode,
+        can_be_struct_literal: bool,
     ) -> PResult<'a, (AttrVec, P<Block>)> {
         maybe_whole!(self, NtBlock, |x| (AttrVec::new(), x));
 
+        let maybe_ident = self.prev_token.clone();
         self.maybe_recover_unexpected_block_label();
         if !self.eat(&token::OpenDelim(Delimiter::Brace)) {
             return self.error_block_no_opening_brace();
         }
 
         let attrs = self.parse_inner_attributes()?;
-        let tail = match self.maybe_suggest_struct_literal(lo, blk_mode) {
+        let tail = match self.maybe_suggest_struct_literal(
+            lo,
+            blk_mode,
+            maybe_ident,
+            can_be_struct_literal,
+        ) {
             Some(tail) => tail?,
             None => self.parse_block_tail(lo, blk_mode, AttemptLocalParseRecovery::Yes)?,
         };
@@ -531,13 +544,23 @@ impl<'a> Parser<'a> {
         recover: AttemptLocalParseRecovery,
     ) -> PResult<'a, P<Block>> {
         let mut stmts = vec![];
+        let mut snapshot = None;
         while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
             if self.token == token::Eof {
                 break;
             }
+            if self.is_diff_marker(&TokenKind::BinOp(token::Shl), &TokenKind::Lt) {
+                // Account for `<<<<<<<` diff markers. We can't proactively error here because
+                // that can be a valid path start, so we snapshot and reparse only we've
+                // encountered another parse error.
+                snapshot = Some(self.create_snapshot_for_diagnostic());
+            }
             let stmt = match self.parse_full_stmt(recover) {
                 Err(mut err) if recover.yes() => {
                     self.maybe_annotate_with_ascription(&mut err, false);
+                    if let Some(ref mut snapshot) = snapshot {
+                        snapshot.recover_diff_marker();
+                    }
                     err.emit();
                     self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
                     Some(self.mk_stmt_err(self.token.span))
diff --git a/compiler/rustc_parse/src/parser/ty.rs b/compiler/rustc_parse/src/parser/ty.rs
index b7206b576..867974672 100644
--- a/compiler/rustc_parse/src/parser/ty.rs
+++ b/compiler/rustc_parse/src/parser/ty.rs
@@ -1,8 +1,9 @@
 use super::{Parser, PathStyle, TokenType};
 
-use crate::errors::{FnPtrWithGenerics, FnPtrWithGenericsSugg};
+use crate::errors::{ExpectedFnPathFoundFnKeyword, FnPtrWithGenerics, FnPtrWithGenericsSugg};
 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
 
+use ast::DUMMY_NODE_ID;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Delimiter, Token, TokenKind};
 use rustc_ast::util::case::Case;
@@ -12,7 +13,9 @@ use rustc_ast::{
 };
 use rustc_errors::{pluralize, struct_span_err, Applicability, PResult};
 use rustc_span::source_map::Span;
-use rustc_span::symbol::{kw, sym};
+use rustc_span::symbol::{kw, sym, Ident};
+use rustc_span::Symbol;
+use thin_vec::thin_vec;
 
 /// Any `?` or `~const` modifiers that appear at the start of a bound.
 struct BoundModifiers {
@@ -501,7 +504,7 @@ impl<'a> Parser<'a> {
             self.bump_with((dyn_tok, dyn_tok_sp));
         }
         let ty = self.parse_ty_no_plus()?;
-        Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))
+        Ok(TyKind::Ref(opt_lifetime, MutTy { ty, mutbl }))
     }
 
     // Parses the `typeof(EXPR)`.
@@ -613,6 +616,25 @@ impl<'a> Parser<'a> {
     /// Parses an `impl B0 + ... + Bn` type.
     fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
         // Always parse bounds greedily for better error recovery.
+        if self.token.is_lifetime() {
+            self.look_ahead(1, |t| {
+                if let token::Ident(symname, _) = t.kind {
+                    // parse pattern with "'a Sized" we're supposed to give suggestion like
+                    // "'a + Sized"
+                    self.struct_span_err(
+                        self.token.span,
+                        &format!("expected `+` between lifetime and {}", symname),
+                    )
+                    .span_suggestion_verbose(
+                        self.token.span.shrink_to_hi(),
+                        "add `+`",
+                        " +",
+                        Applicability::MaybeIncorrect,
+                    )
+                    .emit();
+                }
+            })
+        }
         let bounds = self.parse_generic_bounds(None)?;
         *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus);
         Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
@@ -705,12 +727,15 @@ impl<'a> Parser<'a> {
         let mut bounds = Vec::new();
         let mut negative_bounds = Vec::new();
 
+        // In addition to looping while we find generic bounds:
+        // We continue even if we find a keyword. This is necessary for error recovery on,
+        // for example, `impl fn()`. The only keyword that can go after generic bounds is
+        // `where`, so stop if it's it.
+        // We also continue if we find types (not traits), again for error recovery.
         while self.can_begin_bound()
-            // Continue even if we find a keyword.
-            // This is necessary for error recover on, for example, `impl fn()`.
-            //
-            // The only keyword that can go after generic bounds is `where`, so stop if it's it.
-            || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))
+            || (self.may_recover()
+                && (self.token.can_begin_type()
+                    || (self.token.is_reserved_ident() && !self.token.is_keyword(kw::Where))))
         {
             if self.token.is_keyword(kw::Dyn) {
                 // Account for `&dyn Trait + dyn Other`.
@@ -911,8 +936,50 @@ impl<'a> Parser<'a> {
         has_parens: bool,
         modifiers: BoundModifiers,
     ) -> PResult<'a, GenericBound> {
-        let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
-        let path = self.parse_path(PathStyle::Type)?;
+        let mut lifetime_defs = self.parse_late_bound_lifetime_defs()?;
+        let mut path = if self.token.is_keyword(kw::Fn)
+            && self.look_ahead(1, |tok| tok.kind == TokenKind::OpenDelim(Delimiter::Parenthesis))
+            && let Some(path) = self.recover_path_from_fn()
+        {
+            path
+        } else if !self.token.is_path_start() && self.token.can_begin_type() {
+            let ty = self.parse_ty_no_plus()?;
+            // Instead of finding a path (a trait), we found a type.
+            let mut err = self.struct_span_err(ty.span, "expected a trait, found type");
+
+            // If we can recover, try to extract a path from the type. Note
+            // that we do not use the try operator when parsing the type because
+            // if it fails then we get a parser error which we don't want (we're trying
+            // to recover from errors, not make more).
+            let path = if self.may_recover()
+                && matches!(ty.kind, TyKind::Ptr(..) | TyKind::Ref(..))
+                && let TyKind::Path(_, path) = &ty.peel_refs().kind {
+                // Just get the indirection part of the type.
+                let span = ty.span.until(path.span);
+
+                err.span_suggestion_verbose(
+                    span,
+                    "consider removing the indirection",
+                    "",
+                    Applicability::MaybeIncorrect,
+                );
+
+                path.clone()
+            } else {
+                return Err(err);
+            };
+
+            err.emit();
+
+            path
+        } else {
+            self.parse_path(PathStyle::Type)?
+        };
+
+        if self.may_recover() && self.token == TokenKind::OpenDelim(Delimiter::Parenthesis) {
+            self.recover_fn_trait_with_lifetime_params(&mut path, &mut lifetime_defs)?;
+        }
+
         if has_parens {
             if self.token.is_like_plus() {
                 // Someone has written something like `&dyn (Trait + Other)`. The correct code
@@ -941,6 +1008,38 @@ impl<'a> Parser<'a> {
         Ok(GenericBound::Trait(poly_trait, modifier))
     }
 
+    // recovers a `Fn(..)` parenthesized-style path from `fn(..)`
+    fn recover_path_from_fn(&mut self) -> Option<ast::Path> {
+        let fn_token_span = self.token.span;
+        self.bump();
+        let args_lo = self.token.span;
+        let snapshot = self.create_snapshot_for_diagnostic();
+        match self.parse_fn_decl(|_| false, AllowPlus::No, RecoverReturnSign::OnlyFatArrow) {
+            Ok(decl) => {
+                self.sess.emit_err(ExpectedFnPathFoundFnKeyword { fn_token_span });
+                Some(ast::Path {
+                    span: fn_token_span.to(self.prev_token.span),
+                    segments: thin_vec![ast::PathSegment {
+                        ident: Ident::new(Symbol::intern("Fn"), fn_token_span),
+                        id: DUMMY_NODE_ID,
+                        args: Some(P(ast::GenericArgs::Parenthesized(ast::ParenthesizedArgs {
+                            span: args_lo.to(self.prev_token.span),
+                            inputs: decl.inputs.iter().map(|a| a.ty.clone()).collect(),
+                            inputs_span: args_lo.until(decl.output.span()),
+                            output: decl.output.clone(),
+                        }))),
+                    }],
+                    tokens: None,
+                })
+            }
+            Err(diag) => {
+                diag.cancel();
+                self.restore_snapshot(snapshot);
+                None
+            }
+        }
+    }
+
     /// Optionally parses `for<$generic_params>`.
     pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
         if self.eat_keyword(kw::For) {
@@ -955,6 +1054,92 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Recover from `Fn`-family traits (Fn, FnMut, FnOnce) with lifetime arguments
+    /// (e.g. `FnOnce<'a>(&'a str) -> bool`). Up to generic arguments have already
+    /// been eaten.
+    fn recover_fn_trait_with_lifetime_params(
+        &mut self,
+        fn_path: &mut ast::Path,
+        lifetime_defs: &mut Vec<GenericParam>,
+    ) -> PResult<'a, ()> {
+        let fn_path_segment = fn_path.segments.last_mut().unwrap();
+        let generic_args = if let Some(p_args) = &fn_path_segment.args {
+            p_args.clone().into_inner()
+        } else {
+            // Normally it wouldn't come here because the upstream should have parsed
+            // generic parameters (otherwise it's impossible to call this function).
+            return Ok(());
+        };
+        let lifetimes =
+            if let ast::GenericArgs::AngleBracketed(ast::AngleBracketedArgs { span: _, args }) =
+                &generic_args
+            {
+                args.into_iter()
+                    .filter_map(|arg| {
+                        if let ast::AngleBracketedArg::Arg(generic_arg) = arg
+                            && let ast::GenericArg::Lifetime(lifetime) = generic_arg {
+                            Some(lifetime)
+                        } else {
+                            None
+                        }
+                    })
+                    .collect()
+            } else {
+                Vec::new()
+            };
+        // Only try to recover if the trait has lifetime params.
+        if lifetimes.is_empty() {
+            return Ok(());
+        }
+
+        // Parse `(T, U) -> R`.
+        let inputs_lo = self.token.span;
+        let inputs: Vec<_> =
+            self.parse_fn_params(|_| false)?.into_iter().map(|input| input.ty).collect();
+        let inputs_span = inputs_lo.to(self.prev_token.span);
+        let output = self.parse_ret_ty(AllowPlus::No, RecoverQPath::No, RecoverReturnSign::No)?;
+        let args = ast::ParenthesizedArgs {
+            span: fn_path_segment.span().to(self.prev_token.span),
+            inputs,
+            inputs_span,
+            output,
+        }
+        .into();
+        *fn_path_segment =
+            ast::PathSegment { ident: fn_path_segment.ident, args, id: ast::DUMMY_NODE_ID };
+
+        // Convert parsed `<'a>` in `Fn<'a>` into `for<'a>`.
+        let mut generic_params = lifetimes
+            .iter()
+            .map(|lt| GenericParam {
+                id: lt.id,
+                ident: lt.ident,
+                attrs: ast::AttrVec::new(),
+                bounds: Vec::new(),
+                is_placeholder: false,
+                kind: ast::GenericParamKind::Lifetime,
+                colon_span: None,
+            })
+            .collect::<Vec<GenericParam>>();
+        lifetime_defs.append(&mut generic_params);
+
+        let generic_args_span = generic_args.span();
+        let mut err =
+            self.struct_span_err(generic_args_span, "`Fn` traits cannot take lifetime parameters");
+        let snippet = format!(
+            "for<{}> ",
+            lifetimes.iter().map(|lt| lt.ident.as_str()).intersperse(", ").collect::<String>(),
+        );
+        let before_fn_path = fn_path.span.shrink_to_lo();
+        err.multipart_suggestion(
+            "consider using a higher-ranked trait bound instead",
+            vec![(generic_args_span, "".to_owned()), (before_fn_path, snippet)],
+            Applicability::MaybeIncorrect,
+        )
+        .emit();
+        Ok(())
+    }
+
     pub(super) fn check_lifetime(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Lifetime);
         self.token.is_lifetime()
diff --git a/compiler/rustc_parse_format/Cargo.toml b/compiler/rustc_parse_format/Cargo.toml
index fcc68b3a2..72da398d3 100644
--- a/compiler/rustc_parse_format/Cargo.toml
+++ b/compiler/rustc_parse_format/Cargo.toml
@@ -5,3 +5,4 @@ edition = "2021"
 
 [dependencies]
 rustc_lexer = { path = "../rustc_lexer" }
+rustc_data_structures = { path = "../rustc_data_structures" }
diff --git a/compiler/rustc_parse_format/src/lib.rs b/compiler/rustc_parse_format/src/lib.rs
index 0113eb4e3..7b016cada 100644
--- a/compiler/rustc_parse_format/src/lib.rs
+++ b/compiler/rustc_parse_format/src/lib.rs
@@ -38,6 +38,31 @@ impl InnerSpan {
     }
 }
 
+/// The location and before/after width of a character whose width has changed from its source code
+/// representation
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub struct InnerWidthMapping {
+    /// Index of the character in the source
+    pub position: usize,
+    /// The inner width in characters
+    pub before: usize,
+    /// The transformed width in characters
+    pub after: usize,
+}
+
+impl InnerWidthMapping {
+    pub fn new(position: usize, before: usize, after: usize) -> InnerWidthMapping {
+        InnerWidthMapping { position, before, after }
+    }
+}
+
+/// Whether the input string is a literal. If yes, it contains the inner width mappings.
+#[derive(Clone, PartialEq, Eq)]
+enum InputStringKind {
+    NotALiteral,
+    Literal { width_mappings: Vec<InnerWidthMapping> },
+}
+
 /// The type of format string that we are parsing.
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
 pub enum ParseMode {
@@ -58,13 +83,13 @@ impl InnerOffset {
 
 /// A piece is a portion of the format string which represents the next part
 /// to emit. These are emitted as a stream by the `Parser` class.
-#[derive(Copy, Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq)]
 pub enum Piece<'a> {
     /// A literal string which should directly be emitted
     String(&'a str),
     /// This describes that formatting should process the next argument (as
     /// specified inside) for emission.
-    NextArgument(Argument<'a>),
+    NextArgument(Box<Argument<'a>>),
 }
 
 /// Representation of an argument specification.
@@ -200,8 +225,8 @@ pub struct Parser<'a> {
     style: Option<usize>,
     /// Start and end byte offset of every successfully parsed argument
     pub arg_places: Vec<InnerSpan>,
-    /// Characters that need to be shifted
-    skips: Vec<usize>,
+    /// Characters whose length has been changed from their in-code representation
+    width_map: Vec<InnerWidthMapping>,
     /// Span of the last opening brace seen, used for error reporting
     last_opening_brace: Option<InnerSpan>,
     /// Whether the source string is comes from `println!` as opposed to `format!` or `print!`
@@ -224,7 +249,7 @@ impl<'a> Iterator for Parser<'a> {
                 '{' => {
                     let curr_last_brace = self.last_opening_brace;
                     let byte_pos = self.to_span_index(pos);
-                    let lbrace_end = self.to_span_index(pos + 1);
+                    let lbrace_end = InnerOffset(byte_pos.0 + self.to_span_width(pos));
                     self.last_opening_brace = Some(byte_pos.to(lbrace_end));
                     self.cur.next();
                     if self.consume('{') {
@@ -233,18 +258,21 @@ impl<'a> Iterator for Parser<'a> {
                         Some(String(self.string(pos + 1)))
                     } else {
                         let arg = self.argument(lbrace_end);
-                        if let Some(rbrace_byte_idx) = self.must_consume('}') {
-                            let lbrace_inner_offset = self.to_span_index(pos);
-                            let rbrace_inner_offset = self.to_span_index(rbrace_byte_idx);
+                        if let Some(rbrace_pos) = self.must_consume('}') {
                             if self.is_literal {
+                                let lbrace_byte_pos = self.to_span_index(pos);
+                                let rbrace_byte_pos = self.to_span_index(rbrace_pos);
+
+                                let width = self.to_span_width(rbrace_pos);
+
                                 self.arg_places.push(
-                                    lbrace_inner_offset.to(InnerOffset(rbrace_inner_offset.0 + 1)),
+                                    lbrace_byte_pos.to(InnerOffset(rbrace_byte_pos.0 + width)),
                                 );
                             }
                         } else {
                             self.suggest_positional_arg_instead_of_captured_arg(arg);
                         }
-                        Some(NextArgument(arg))
+                        Some(NextArgument(Box::new(arg)))
                     }
                 }
                 '}' => {
@@ -285,7 +313,12 @@ impl<'a> Parser<'a> {
         append_newline: bool,
         mode: ParseMode,
     ) -> Parser<'a> {
-        let (skips, is_literal) = find_skips_from_snippet(snippet, style);
+        let input_string_kind = find_width_map_from_snippet(snippet, style);
+        let (width_map, is_literal) = match input_string_kind {
+            InputStringKind::Literal { width_mappings } => (width_mappings, true),
+            InputStringKind::NotALiteral => (Vec::new(), false),
+        };
+
         Parser {
             mode,
             input: s,
@@ -294,7 +327,7 @@ impl<'a> Parser<'a> {
             curarg: 0,
             style,
             arg_places: vec![],
-            skips,
+            width_map,
             last_opening_brace: None,
             append_newline,
             is_literal,
@@ -367,21 +400,34 @@ impl<'a> Parser<'a> {
         None
     }
 
+    fn remap_pos(&self, mut pos: usize) -> InnerOffset {
+        for width in &self.width_map {
+            if pos > width.position {
+                pos += width.before - width.after;
+            } else if pos == width.position && width.after == 0 {
+                pos += width.before;
+            } else {
+                break;
+            }
+        }
+
+        InnerOffset(pos)
+    }
+
     fn to_span_index(&self, pos: usize) -> InnerOffset {
-        let mut pos = pos;
         // This handles the raw string case, the raw argument is the number of #
         // in r###"..."### (we need to add one because of the `r`).
         let raw = self.style.map_or(0, |raw| raw + 1);
-        for skip in &self.skips {
-            if pos > *skip {
-                pos += 1;
-            } else if pos == *skip && raw == 0 {
-                pos += 1;
-            } else {
-                break;
-            }
+        let pos = self.remap_pos(pos);
+        InnerOffset(raw + pos.0 + 1)
+    }
+
+    fn to_span_width(&self, pos: usize) -> usize {
+        let pos = self.remap_pos(pos);
+        match self.width_map.iter().find(|w| w.position == pos.0) {
+            Some(w) => w.before,
+            None => 1,
         }
-        InnerOffset(raw + pos + 1)
     }
 
     fn span(&self, start_pos: usize, end_pos: usize) -> InnerSpan {
@@ -401,7 +447,7 @@ impl<'a> Parser<'a> {
                 Some(pos)
             } else {
                 let pos = self.to_span_index(pos);
-                let description = format!("expected `'}}'`, found `{:?}`", maybe);
+                let description = format!("expected `'}}'`, found `{maybe:?}`");
                 let label = "expected `}`".to_owned();
                 let (note, secondary_label) = if c == '}' {
                     (
@@ -425,12 +471,12 @@ impl<'a> Parser<'a> {
                 None
             }
         } else {
-            let description = format!("expected `{:?}` but string was terminated", c);
+            let description = format!("expected `{c:?}` but string was terminated");
             // point at closing `"`
             let pos = self.input.len() - if self.append_newline { 1 } else { 0 };
             let pos = self.to_span_index(pos);
             if c == '}' {
-                let label = format!("expected `{:?}`", c);
+                let label = format!("expected `{c:?}`");
                 let (note, secondary_label) = if c == '}' {
                     (
                         Some(
@@ -451,7 +497,7 @@ impl<'a> Parser<'a> {
                     should_be_replaced_with_positional_argument: false,
                 });
             } else {
-                self.err(description, format!("expected `{:?}`", c), pos.to(pos));
+                self.err(description, format!("expected `{c:?}`"), pos.to(pos));
             }
             None
         }
@@ -809,59 +855,55 @@ impl<'a> Parser<'a> {
 /// Finds the indices of all characters that have been processed and differ between the actual
 /// written code (code snippet) and the `InternedString` that gets processed in the `Parser`
 /// in order to properly synthesise the intra-string `Span`s for error diagnostics.
-fn find_skips_from_snippet(
+fn find_width_map_from_snippet(
     snippet: Option<string::String>,
     str_style: Option<usize>,
-) -> (Vec<usize>, bool) {
+) -> InputStringKind {
     let snippet = match snippet {
         Some(ref s) if s.starts_with('"') || s.starts_with("r\"") || s.starts_with("r#") => s,
-        _ => return (vec![], false),
+        _ => return InputStringKind::NotALiteral,
     };
 
     if str_style.is_some() {
-        return (vec![], true);
+        return InputStringKind::Literal { width_mappings: Vec::new() };
     }
 
     let snippet = &snippet[1..snippet.len() - 1];
 
     let mut s = snippet.char_indices();
-    let mut skips = vec![];
+    let mut width_mappings = vec![];
     while let Some((pos, c)) = s.next() {
         match (c, s.clone().next()) {
             // skip whitespace and empty lines ending in '\\'
-            ('\\', Some((next_pos, '\n'))) => {
-                skips.push(pos);
-                skips.push(next_pos);
+            ('\\', Some((_, '\n'))) => {
                 let _ = s.next();
+                let mut width = 2;
 
-                while let Some((pos, c)) = s.clone().next() {
+                while let Some((_, c)) = s.clone().next() {
                     if matches!(c, ' ' | '\n' | '\t') {
-                        skips.push(pos);
+                        width += 1;
                         let _ = s.next();
                     } else {
                         break;
                     }
                 }
+
+                width_mappings.push(InnerWidthMapping::new(pos, width, 0));
             }
-            ('\\', Some((next_pos, 'n' | 't' | 'r' | '0' | '\\' | '\'' | '\"'))) => {
-                skips.push(next_pos);
+            ('\\', Some((_, 'n' | 't' | 'r' | '0' | '\\' | '\'' | '\"'))) => {
+                width_mappings.push(InnerWidthMapping::new(pos, 2, 1));
                 let _ = s.next();
             }
             ('\\', Some((_, 'x'))) => {
-                for _ in 0..3 {
-                    // consume `\xAB` literal
-                    if let Some((pos, _)) = s.next() {
-                        skips.push(pos);
-                    } else {
-                        break;
-                    }
-                }
+                // consume `\xAB` literal
+                s.nth(2);
+                width_mappings.push(InnerWidthMapping::new(pos, 4, 1));
             }
             ('\\', Some((_, 'u'))) => {
-                if let Some((pos, _)) = s.next() {
-                    skips.push(pos);
-                }
-                if let Some((next_pos, next_c)) = s.next() {
+                let mut width = 2;
+                let _ = s.next();
+
+                if let Some((_, next_c)) = s.next() {
                     if next_c == '{' {
                         // consume up to 6 hexanumeric chars
                         let digits_len =
@@ -881,19 +923,18 @@ fn find_skips_from_snippet(
                         let required_skips = digits_len.saturating_sub(len_utf8.saturating_sub(1));
 
                         // skip '{' and '}' also
-                        for pos in (next_pos..).take(required_skips + 2) {
-                            skips.push(pos)
-                        }
+                        width += required_skips + 2;
 
                         s.nth(digits_len);
                     } else if next_c.is_digit(16) {
-                        skips.push(next_pos);
+                        width += 1;
+
                         // We suggest adding `{` and `}` when appropriate, accept it here as if
                         // it were correct
                         let mut i = 0; // consume up to 6 hexanumeric chars
-                        while let (Some((next_pos, c)), _) = (s.next(), i < 6) {
+                        while let (Some((_, c)), _) = (s.next(), i < 6) {
                             if c.is_digit(16) {
-                                skips.push(next_pos);
+                                width += 1;
                             } else {
                                 break;
                             }
@@ -901,12 +942,19 @@ fn find_skips_from_snippet(
                         }
                     }
                 }
+
+                width_mappings.push(InnerWidthMapping::new(pos, width, 1));
             }
             _ => {}
         }
     }
-    (skips, true)
+
+    InputStringKind::Literal { width_mappings }
 }
 
+// Assert a reasonable size for `Piece`
+#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
+rustc_data_structures::static_assert_size!(Piece<'_>, 16);
+
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_parse_format/src/tests.rs b/compiler/rustc_parse_format/src/tests.rs
index 3f9cb149b..2992ba845 100644
--- a/compiler/rustc_parse_format/src/tests.rs
+++ b/compiler/rustc_parse_format/src/tests.rs
@@ -76,51 +76,51 @@ fn invalid_precision() {
 fn format_nothing() {
     same(
         "{}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: fmtdflt(),
-        })],
+        }))],
     );
 }
 #[test]
 fn format_position() {
     same(
         "{3}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: fmtdflt(),
-        })],
+        }))],
     );
 }
 #[test]
 fn format_position_nothing_else() {
     same(
         "{3:}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: fmtdflt(),
-        })],
+        }))],
     );
 }
 #[test]
 fn format_named() {
     same(
         "{name}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentNamed("name"),
             position_span: InnerSpan { start: 2, end: 6 },
             format: fmtdflt(),
-        })],
+        }))],
     )
 }
 #[test]
 fn format_type() {
     same(
         "{3:x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: FormatSpec {
@@ -134,14 +134,14 @@ fn format_type() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
 }
 #[test]
 fn format_align_fill() {
     same(
         "{3:>}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: FormatSpec {
@@ -155,11 +155,11 @@ fn format_align_fill() {
                 ty: "",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{3:0<}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: FormatSpec {
@@ -173,11 +173,11 @@ fn format_align_fill() {
                 ty: "",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{3:*<abcd}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(3),
             position_span: InnerSpan { start: 2, end: 3 },
             format: FormatSpec {
@@ -191,14 +191,14 @@ fn format_align_fill() {
                 ty: "abcd",
                 ty_span: Some(InnerSpan::new(6, 10)),
             },
-        })],
+        }))],
     );
 }
 #[test]
 fn format_counts() {
     same(
         "{:10x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -212,11 +212,11 @@ fn format_counts() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:10$.10x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -230,11 +230,11 @@ fn format_counts() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{1:0$.10x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentIs(1),
             position_span: InnerSpan { start: 2, end: 3 },
             format: FormatSpec {
@@ -248,11 +248,11 @@ fn format_counts() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:.*x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(1),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -266,11 +266,11 @@ fn format_counts() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:.10$x}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -284,11 +284,11 @@ fn format_counts() {
                 ty: "x",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:a$.b$?}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -302,11 +302,11 @@ fn format_counts() {
                 ty: "?",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:.4}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -320,14 +320,14 @@ fn format_counts() {
                 ty: "",
                 ty_span: None,
             },
-        })],
+        }))],
     )
 }
 #[test]
 fn format_flags() {
     same(
         "{:-}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -341,11 +341,11 @@ fn format_flags() {
                 ty: "",
                 ty_span: None,
             },
-        })],
+        }))],
     );
     same(
         "{:+#}",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 2 },
             format: FormatSpec {
@@ -359,7 +359,7 @@ fn format_flags() {
                 ty: "",
                 ty_span: None,
             },
-        })],
+        }))],
     );
 }
 #[test]
@@ -368,7 +368,7 @@ fn format_mixture() {
         "abcd {3:x} efg",
         &[
             String("abcd "),
-            NextArgument(Argument {
+            NextArgument(Box::new(Argument {
                 position: ArgumentIs(3),
                 position_span: InnerSpan { start: 7, end: 8 },
                 format: FormatSpec {
@@ -382,7 +382,7 @@ fn format_mixture() {
                     ty: "x",
                     ty_span: None,
                 },
-            }),
+            })),
             String(" efg"),
         ],
     );
@@ -391,18 +391,18 @@ fn format_mixture() {
 fn format_whitespace() {
     same(
         "{ }",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 3 },
             format: fmtdflt(),
-        })],
+        }))],
     );
     same(
         "{  }",
-        &[NextArgument(Argument {
+        &[NextArgument(Box::new(Argument {
             position: ArgumentImplicitlyIs(0),
             position_span: InnerSpan { start: 2, end: 4 },
             format: fmtdflt(),
-        })],
+        }))],
     );
 }