1 use super::pat::Expected;
3 BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep,
4 TokenExpectType, TokenType,
7 use crate::lexer::UnmatchedBrace;
10 use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
11 use rustc_ast::util::parser::AssocOp;
13 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
14 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Mutability, Param, Pat,
15 PatKind, Path, PathSegment, QSelf, Ty, TyKind,
17 use rustc_ast_pretty::pprust;
18 use rustc_data_structures::fx::FxHashSet;
20 fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
22 use rustc_errors::{pluralize, struct_span_err, Diagnostic, EmissionGuarantee, ErrorGuaranteed};
23 use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
24 use rustc_span::source_map::Spanned;
25 use rustc_span::symbol::{kw, Ident};
26 use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
27 use std::ops::{Deref, DerefMut};
32 use tracing::{debug, trace};
34 const TURBOFISH_SUGGESTION_STR: &str =
35 "use `::<...>` instead of `<...>` to specify lifetime, type, or const arguments";
37 /// Creates a placeholder argument.
38 pub(super) fn dummy_arg(ident: Ident) -> Param {
40 id: ast::DUMMY_NODE_ID,
41 kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
45 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
47 attrs: AttrVec::default(),
48 id: ast::DUMMY_NODE_ID,
52 is_placeholder: false,
63 sp: impl Into<MultiSpan>,
65 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
67 Error::UselessDocComment => {
68 let mut err = struct_span_err!(
72 "found a documentation comment that doesn't document anything",
75 "doc comments must come before what they document, maybe a comment was \
84 pub(super) trait RecoverQPath: Sized + 'static {
85 const PATH_STYLE: PathStyle = PathStyle::Expr;
86 fn to_ty(&self) -> Option<P<Ty>>;
87 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
90 impl RecoverQPath for Ty {
91 const PATH_STYLE: PathStyle = PathStyle::Type;
92 fn to_ty(&self) -> Option<P<Ty>> {
95 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
98 kind: TyKind::Path(qself, path),
99 id: ast::DUMMY_NODE_ID,
105 impl RecoverQPath for Pat {
106 fn to_ty(&self) -> Option<P<Ty>> {
109 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
112 kind: PatKind::Path(qself, path),
113 id: ast::DUMMY_NODE_ID,
119 impl RecoverQPath for Expr {
120 fn to_ty(&self) -> Option<P<Ty>> {
123 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
126 kind: ExprKind::Path(qself, path),
127 attrs: AttrVec::new(),
128 id: ast::DUMMY_NODE_ID,
134 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
135 pub(crate) enum ConsumeClosingDelim {
140 #[derive(Clone, Copy)]
141 pub enum AttemptLocalParseRecovery {
146 impl AttemptLocalParseRecovery {
147 pub fn yes(&self) -> bool {
149 AttemptLocalParseRecovery::Yes => true,
150 AttemptLocalParseRecovery::No => false,
154 pub fn no(&self) -> bool {
156 AttemptLocalParseRecovery::Yes => false,
157 AttemptLocalParseRecovery::No => true,
162 /// Information for emitting suggestions and recovering from
163 /// C-style `i++`, `--i`, etc.
164 #[derive(Debug, Copy, Clone)]
165 struct IncDecRecovery {
166 /// Is this increment/decrement its own statement?
167 standalone: IsStandalone,
168 /// Is this an increment or decrement?
170 /// Is this pre- or postfix?
174 /// Is an increment or decrement expression its own statement?
175 #[derive(Debug, Copy, Clone)]
177 /// It's standalone, i.e., its own statement.
179 /// It's a subexpression, i.e., *not* standalone.
181 /// It's maybe standalone; we're not sure.
185 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
188 // FIXME: `i--` recovery isn't implemented yet
193 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
200 fn chr(&self) -> char {
207 fn name(&self) -> &'static str {
209 Self::Inc => "increment",
210 Self::Dec => "decrement",
215 impl std::fmt::Display for UnaryFixity {
216 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
218 Self::Pre => write!(f, "prefix"),
219 Self::Post => write!(f, "postfix"),
226 patches: Vec<(Span, String)>,
227 applicability: Applicability,
231 fn emit<G: EmissionGuarantee>(self, err: &mut DiagnosticBuilder<'_, G>) {
232 err.multipart_suggestion(&self.msg, self.patches, self.applicability);
235 /// Overrides individual messages and applicabilities.
236 fn emit_many<G: EmissionGuarantee>(
237 err: &mut DiagnosticBuilder<'_, G>,
239 applicability: Applicability,
240 suggestions: impl Iterator<Item = Self>,
242 err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
246 #[derive(SessionDiagnostic)]
247 #[error(parser::maybe_report_ambiguous_plus)]
248 struct AmbiguousPlus {
251 #[suggestion(code = "({sum_ty})")]
255 #[derive(SessionDiagnostic)]
256 #[error(parser::maybe_recover_from_bad_type_plus, code = "E0178")]
262 pub sub: BadTypePlusSub,
265 #[derive(SessionSubdiagnostic)]
266 pub enum BadTypePlusSub {
269 code = "{sum_with_parens}",
270 applicability = "machine-applicable"
273 sum_with_parens: String,
277 #[label(parser::forgot_paren)]
282 #[label(parser::expect_path)]
289 #[derive(SessionDiagnostic)]
290 #[error(parser::maybe_recover_from_bad_qpath_stage_2)]
291 struct BadQPathStage2 {
293 #[suggestion(applicability = "maybe-incorrect")]
298 #[derive(SessionDiagnostic)]
299 #[error(parser::incorrect_semicolon)]
300 struct IncorrectSemicolon<'a> {
302 #[suggestion_short(applicability = "machine-applicable")]
305 opt_help: Option<()>,
309 #[derive(SessionDiagnostic)]
310 #[error(parser::incorrect_use_of_await)]
311 struct IncorrectUseOfAwait {
313 #[suggestion(parser::parentheses_suggestion, applicability = "machine-applicable")]
317 #[derive(SessionDiagnostic)]
318 #[error(parser::incorrect_use_of_await)]
319 struct IncorrectAwait {
322 #[suggestion(parser::postfix_suggestion, code = "{expr}.await{question_mark}")]
323 sugg_span: (Span, Applicability),
325 question_mark: &'static str,
328 #[derive(SessionDiagnostic)]
329 #[error(parser::in_in_typo)]
333 #[suggestion(applicability = "machine-applicable")]
337 // SnapshotParser is used to create a snapshot of the parser
338 // without causing duplicate errors being emitted when the `Parser`
340 pub struct SnapshotParser<'a> {
342 unclosed_delims: Vec<UnmatchedBrace>,
345 impl<'a> Deref for SnapshotParser<'a> {
346 type Target = Parser<'a>;
348 fn deref(&self) -> &Self::Target {
353 impl<'a> DerefMut for SnapshotParser<'a> {
354 fn deref_mut(&mut self) -> &mut Self::Target {
359 impl<'a> Parser<'a> {
360 #[cfg_attr(not(bootstrap), rustc_lint_diagnostics)]
361 pub(super) fn span_err<S: Into<MultiSpan>>(
365 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
366 err.span_err(sp, self.diagnostic())
369 #[cfg_attr(not(bootstrap), rustc_lint_diagnostics)]
370 pub fn struct_span_err<S: Into<MultiSpan>>(
373 m: impl Into<DiagnosticMessage>,
374 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
375 self.sess.span_diagnostic.struct_span_err(sp, m)
378 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: impl Into<DiagnosticMessage>) -> ! {
379 self.sess.span_diagnostic.span_bug(sp, m)
382 pub(super) fn diagnostic(&self) -> &'a Handler {
383 &self.sess.span_diagnostic
386 /// Replace `self` with `snapshot.parser` and extend `unclosed_delims` with `snapshot.unclosed_delims`.
387 /// This is to avoid losing unclosed delims errors `create_snapshot_for_diagnostic` clears.
388 pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
389 *self = snapshot.parser;
390 self.unclosed_delims.extend(snapshot.unclosed_delims.clone());
393 pub fn unclosed_delims(&self) -> &[UnmatchedBrace] {
394 &self.unclosed_delims
397 /// Create a snapshot of the `Parser`.
398 pub fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
399 let mut snapshot = self.clone();
400 let unclosed_delims = self.unclosed_delims.clone();
401 // Clear `unclosed_delims` in snapshot to avoid
402 // duplicate errors being emitted when the `Parser`
403 // is dropped (which may or may not happen, depending
404 // if the parsing the snapshot is created for is successful)
405 snapshot.unclosed_delims.clear();
406 SnapshotParser { parser: snapshot, unclosed_delims }
409 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
410 self.sess.source_map().span_to_snippet(span)
413 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
414 let mut err = self.struct_span_err(
416 &format!("expected identifier, found {}", super::token_descr(&self.token)),
418 let valid_follow = &[
424 TokenKind::OpenDelim(Delimiter::Brace),
425 TokenKind::OpenDelim(Delimiter::Parenthesis),
426 TokenKind::CloseDelim(Delimiter::Brace),
427 TokenKind::CloseDelim(Delimiter::Parenthesis),
429 match self.token.ident() {
431 if ident.is_raw_guess()
432 && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
434 err.span_suggestion_verbose(
435 ident.span.shrink_to_lo(),
436 &format!("escape `{}` to use it as an identifier", ident.name),
438 Applicability::MaybeIncorrect,
443 if let Some(token_descr) = super::token_descr_opt(&self.token) {
444 err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
446 err.span_label(self.token.span, "expected identifier");
447 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
452 Applicability::MachineApplicable,
459 pub(super) fn expected_one_of_not_found(
461 edible: &[TokenKind],
462 inedible: &[TokenKind],
463 ) -> PResult<'a, bool /* recovered */> {
464 debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
465 fn tokens_to_string(tokens: &[TokenType]) -> String {
466 let mut i = tokens.iter();
467 // This might be a sign we need a connect method on `Iterator`.
468 let b = i.next().map_or_else(String::new, |t| t.to_string());
469 i.enumerate().fold(b, |mut b, (i, a)| {
470 if tokens.len() > 2 && i == tokens.len() - 2 {
472 } else if tokens.len() == 2 && i == tokens.len() - 2 {
477 b.push_str(&a.to_string());
482 let mut expected = edible
484 .map(|x| TokenType::Token(x.clone()))
485 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
486 .chain(self.expected_tokens.iter().cloned())
487 .filter_map(|token| {
488 // filter out suggestions which suggest the same token which was found and deemed incorrect
489 fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
490 if let TokenKind::Ident(current_sym, _) = found {
491 if let TokenType::Keyword(suggested_sym) = expected {
492 return current_sym == suggested_sym;
497 if token != parser::TokenType::Token(self.token.kind.clone()) {
498 let eq = is_ident_eq_keyword(&self.token.kind, &token);
499 // if the suggestion is a keyword and the found token is an ident,
500 // the content of which are equal to the suggestion's content,
501 // we can remove that suggestion (see the return None statement below)
503 // if this isn't the case however, and the suggestion is a token the
504 // content of which is the same as the found token's, we remove it as well
506 if let TokenType::Token(kind) = &token {
507 if kind == &self.token.kind {
516 .collect::<Vec<_>>();
517 expected.sort_by_cached_key(|x| x.to_string());
520 let sm = self.sess.source_map();
521 let msg = format!("expected `;`, found {}", super::token_descr(&self.token));
522 let appl = Applicability::MachineApplicable;
523 if expected.contains(&TokenType::Token(token::Semi)) {
524 if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
525 // Likely inside a macro, can't provide meaningful suggestions.
526 } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
527 // The current token is in the same line as the prior token, not recoverable.
528 } else if [token::Comma, token::Colon].contains(&self.token.kind)
529 && self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis)
531 // Likely typo: The current token is on a new line and is expected to be
532 // `.`, `;`, `?`, or an operator after a close delimiter token.
534 // let a = std::process::Command::new("echo")
538 // https://github.com/rust-lang/rust/issues/72253
539 } else if self.look_ahead(1, |t| {
540 t == &token::CloseDelim(Delimiter::Brace)
541 || t.can_begin_expr() && t.kind != token::Colon
542 }) && [token::Comma, token::Colon].contains(&self.token.kind)
544 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
545 // either `,` or `:`, and the next token could either start a new statement or is a
546 // block close. For example:
551 let sp = self.prev_token.span;
552 self.struct_span_err(sp, &msg)
553 .span_suggestion_short(sp, "change this to `;`", ";", appl)
556 } else if self.look_ahead(0, |t| {
557 t == &token::CloseDelim(Delimiter::Brace)
558 || (t.can_begin_expr() && t != &token::Semi && t != &token::Pound)
559 // Avoid triggering with too many trailing `#` in raw string.
561 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo())
562 ) && t == &token::Pound)
564 // Missing semicolon typo. This is triggered if the next token could either start a
565 // new statement or is a block close. For example:
569 let sp = self.prev_token.span.shrink_to_hi();
570 self.struct_span_err(sp, &msg)
571 .span_label(self.token.span, "unexpected token")
572 .span_suggestion_short(sp, "add `;` here", ";", appl)
578 let expect = tokens_to_string(&expected);
579 let actual = super::token_descr(&self.token);
580 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
581 let short_expect = if expected.len() > 6 {
582 format!("{} possible tokens", expected.len())
587 format!("expected one of {expect}, found {actual}"),
588 (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")),
590 } else if expected.is_empty() {
592 format!("unexpected token: {}", actual),
593 (self.prev_token.span, "unexpected token after this".to_string()),
597 format!("expected {expect}, found {actual}"),
598 (self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
601 self.last_unexpected_token_span = Some(self.token.span);
602 let mut err = self.struct_span_err(self.token.span, &msg_exp);
604 // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
605 // there are unclosed angle brackets
606 if self.unmatched_angle_bracket_count > 0
607 && self.token.kind == TokenKind::Eq
608 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
610 err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
613 let sp = if self.token == token::Eof {
614 // This is EOF; don't want to point at the following char, but rather the last token.
619 match self.recover_closing_delimiter(
622 .filter_map(|tt| match tt {
623 TokenType::Token(t) => Some(t.clone()),
626 .collect::<Vec<_>>(),
631 return Ok(recovered);
635 if self.check_too_many_raw_str_terminators(&mut err) {
636 if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
644 if self.prev_token.span == DUMMY_SP {
645 // Account for macro context where the previous span might not be
646 // available to avoid incorrect output (#54841).
647 err.span_label(self.token.span, label_exp);
648 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
649 // When the spans are in the same line, it means that the only content between
650 // them is whitespace, point at the found token in that case:
652 // X | () => { syntax error };
653 // | ^^^^^ expected one of 8 possible tokens here
655 // instead of having:
657 // X | () => { syntax error };
658 // | -^^^^^ unexpected token
660 // | expected one of 8 possible tokens here
661 err.span_label(self.token.span, label_exp);
663 err.span_label(sp, label_exp);
664 err.span_label(self.token.span, "unexpected token");
666 self.maybe_annotate_with_ascription(&mut err, false);
670 fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
671 let sm = self.sess.source_map();
672 match (&self.prev_token.kind, &self.token.kind) {
674 TokenKind::Literal(Lit {
675 kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
679 ) if !sm.is_multiline(
680 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
683 let n_hashes: u8 = *n_hashes;
684 err.set_primary_message("too many `#` when terminating raw string");
685 let str_span = self.prev_token.span;
686 let mut span = self.token.span;
688 while self.token.kind == TokenKind::Pound
689 && !sm.is_multiline(span.shrink_to_hi().until(self.token.span.shrink_to_lo()))
691 span = span.with_hi(self.token.span.hi());
698 &format!("remove the extra `#`{}", pluralize!(count)),
700 Applicability::MachineApplicable,
704 &format!("this raw string started with {n_hashes} `#`{}", pluralize!(n_hashes)),
712 pub fn maybe_suggest_struct_literal(
716 ) -> Option<PResult<'a, P<Block>>> {
717 if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
718 // We might be having a struct literal where people forgot to include the path:
722 let mut snapshot = self.create_snapshot_for_diagnostic();
724 Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
725 let struct_expr = snapshot.parse_struct_expr(None, path, AttrVec::new(), false);
726 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
727 return Some(match (struct_expr, block_tail) {
728 (Ok(expr), Err(mut err)) => {
729 // We have encountered the following:
734 // fn foo() -> Foo { Path {
738 self.struct_span_err(
740 fluent::parser::struct_literal_body_without_path,
742 .multipart_suggestion(
743 fluent::parser::suggestion,
745 (expr.span.shrink_to_lo(), "{ SomeStruct ".to_string()),
746 (expr.span.shrink_to_hi(), " }".to_string()),
748 Applicability::MaybeIncorrect,
751 self.restore_snapshot(snapshot);
752 let mut tail = self.mk_block(
753 vec![self.mk_stmt_err(expr.span)],
755 lo.to(self.prev_token.span),
757 tail.could_be_bare_literal = true;
760 (Err(err), Ok(tail)) => {
761 // We have a block tail that contains a somehow valid type ascription expr.
765 (Err(snapshot_err), Err(err)) => {
766 // We don't know what went wrong, emit the normal error.
767 snapshot_err.cancel();
768 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
771 (Ok(_), Ok(mut tail)) => {
772 tail.could_be_bare_literal = true;
780 pub fn maybe_annotate_with_ascription(
782 err: &mut Diagnostic,
783 maybe_expected_semicolon: bool,
785 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
786 let sm = self.sess.source_map();
787 let next_pos = sm.lookup_char_pos(self.token.span.lo());
788 let op_pos = sm.lookup_char_pos(sp.hi());
790 let allow_unstable = self.sess.unstable_features.is_nightly_build();
795 "maybe write a path separator here",
798 Applicability::MaybeIncorrect
800 Applicability::MachineApplicable
803 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
804 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
807 "try using a semicolon",
809 Applicability::MaybeIncorrect,
811 } else if allow_unstable {
812 err.span_label(sp, "tried to parse a type due to this type ascription");
814 err.span_label(sp, "tried to parse a type due to this");
817 // Give extra information about type ascription only if it's a nightly compiler.
819 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
823 // Avoid giving too much info when it was likely an unrelated typo.
825 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
826 for more information",
833 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
834 /// passes through any errors encountered. Used for error recovery.
835 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
837 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
838 Ok(p.parse_token_tree())
845 /// This function checks if there are trailing angle brackets and produces
846 /// a diagnostic to suggest removing them.
848 /// ```ignore (diagnostic)
849 /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
850 /// ^^ help: remove extra angle brackets
853 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
854 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
855 pub(super) fn check_trailing_angle_brackets(
857 segment: &PathSegment,
860 // This function is intended to be invoked after parsing a path segment where there are two
863 // 1. A specific token is expected after the path segment.
864 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
865 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
866 // 2. No specific token is expected after the path segment.
867 // eg. `x.foo` (field access)
869 // This function is called after parsing `.foo` and before parsing the token `end` (if
870 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
873 // We only care about trailing angle brackets if we previously parsed angle bracket
874 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
875 // removed in this case:
877 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
879 // This case is particularly tricky as we won't notice it just looking at the tokens -
880 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
881 // have already been parsed):
883 // `x.foo::<u32>>>(3)`
884 let parsed_angle_bracket_args =
885 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
888 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
889 parsed_angle_bracket_args,
891 if !parsed_angle_bracket_args {
895 // Keep the span at the start so we can highlight the sequence of `>` characters to be
897 let lo = self.token.span;
899 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
900 // (since we might have the field access case and the characters we're eating are
901 // actual operators and not trailing characters - ie `x.foo >> 3`).
902 let mut position = 0;
904 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
905 // many of each (so we can correctly pluralize our error messages) and continue to
907 let mut number_of_shr = 0;
908 let mut number_of_gt = 0;
909 while self.look_ahead(position, |t| {
910 trace!("check_trailing_angle_brackets: t={:?}", t);
911 if *t == token::BinOp(token::BinOpToken::Shr) {
914 } else if *t == token::Gt {
924 // If we didn't find any trailing `>` characters, then we have nothing to error about.
926 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
927 number_of_gt, number_of_shr,
929 if number_of_gt < 1 && number_of_shr < 1 {
933 // Finally, double check that we have our end token as otherwise this is the
935 if self.look_ahead(position, |t| {
936 trace!("check_trailing_angle_brackets: t={:?}", t);
937 end.contains(&&t.kind)
939 // Eat from where we started until the end token so that parsing can continue
940 // as if we didn't have those extra angle brackets.
941 self.eat_to_tokens(end);
942 let span = lo.until(self.token.span);
944 let total_num_of_gt = number_of_gt + number_of_shr * 2;
945 self.struct_span_err(
947 &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
951 &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
953 Applicability::MachineApplicable,
961 /// Check if a method call with an intended turbofish has been written without surrounding
963 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
964 if token::ModSep == self.token.kind && segment.args.is_none() {
965 let snapshot = self.create_snapshot_for_diagnostic();
967 let lo = self.token.span;
968 match self.parse_angle_args(None) {
970 let span = lo.to(self.prev_token.span);
971 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
972 let mut trailing_span = self.prev_token.span.shrink_to_hi();
973 while self.token.kind == token::BinOp(token::Shr)
974 || self.token.kind == token::Gt
976 trailing_span = trailing_span.to(self.token.span);
979 if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
980 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
981 let args = AngleBracketedArgs { args, span }.into();
984 self.struct_span_err(
986 "generic parameters without surrounding angle brackets",
988 .multipart_suggestion(
989 "surround the type parameters with angle brackets",
991 (span.shrink_to_lo(), "<".to_string()),
992 (trailing_span, ">".to_string()),
994 Applicability::MachineApplicable,
998 // This doesn't look like an invalid turbofish, can't recover parse state.
999 self.restore_snapshot(snapshot);
1003 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
1004 // generic parse error instead.
1006 self.restore_snapshot(snapshot);
1012 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
1013 /// encounter a parse error when encountering the first `,`.
1014 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
1016 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
1018 ) -> PResult<'a, ()> {
1019 if let ExprKind::Binary(binop, _, _) = &expr.kind
1020 && let ast::BinOpKind::Lt = binop.node
1021 && self.eat(&token::Comma)
1023 let x = self.parse_seq_to_before_end(
1025 SeqSep::trailing_allowed(token::Comma),
1026 |p| p.parse_generic_arg(None),
1029 Ok((_, _, false)) => {
1030 if self.eat(&token::Gt) {
1031 e.span_suggestion_verbose(
1032 binop.span.shrink_to_lo(),
1033 TURBOFISH_SUGGESTION_STR,
1035 Applicability::MaybeIncorrect,
1038 match self.parse_expr() {
1041 self.mk_expr_err(expr.span.to(self.prev_token.span));
1045 *expr = self.mk_expr_err(expr.span);
1060 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
1061 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
1062 /// parenthesising the leftmost comparison.
1063 fn attempt_chained_comparison_suggestion(
1065 err: &mut Diagnostic,
1067 outer_op: &Spanned<AssocOp>,
1068 ) -> bool /* advanced the cursor */ {
1069 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
1070 if let ExprKind::Field(_, ident) = l1.kind
1071 && ident.as_str().parse::<i32>().is_err()
1072 && !matches!(r1.kind, ExprKind::Lit(_))
1074 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
1075 // suggestion being the only one to apply is high.
1078 let mut enclose = |left: Span, right: Span| {
1079 err.multipart_suggestion(
1080 "parenthesize the comparison",
1082 (left.shrink_to_lo(), "(".to_string()),
1083 (right.shrink_to_hi(), ")".to_string()),
1085 Applicability::MaybeIncorrect,
1088 return match (op.node, &outer_op.node) {
1090 (BinOpKind::Eq, AssocOp::Equal) |
1091 // `x < y < z` and friends.
1092 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
1093 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
1094 // `x > y > z` and friends.
1095 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
1096 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
1097 let expr_to_str = |e: &Expr| {
1098 self.span_to_snippet(e.span)
1099 .unwrap_or_else(|_| pprust::expr_to_string(&e))
1101 err.span_suggestion_verbose(
1102 inner_op.span.shrink_to_hi(),
1103 "split the comparison into two",
1104 format!(" && {}", expr_to_str(&r1)),
1105 Applicability::MaybeIncorrect,
1107 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
1110 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
1111 // Consume `z`/outer-op-rhs.
1112 let snapshot = self.create_snapshot_for_diagnostic();
1113 match self.parse_expr() {
1115 // We are sure that outer-op-rhs could be consumed, the suggestion is
1117 enclose(r1.span, r2.span);
1122 self.restore_snapshot(snapshot);
1128 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
1129 let snapshot = self.create_snapshot_for_diagnostic();
1130 // At this point it is always valid to enclose the lhs in parentheses, no
1131 // further checks are necessary.
1132 match self.parse_expr() {
1134 enclose(l1.span, r1.span);
1139 self.restore_snapshot(snapshot);
1150 /// Produces an error if comparison operators are chained (RFC #558).
1151 /// We only need to check the LHS, not the RHS, because all comparison ops have same
1152 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
1154 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
1155 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
1158 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
1159 /// associative we can infer that we have:
1168 pub(super) fn check_no_chained_comparison(
1171 outer_op: &Spanned<AssocOp>,
1172 ) -> PResult<'a, Option<P<Expr>>> {
1174 outer_op.node.is_comparison(),
1175 "check_no_chained_comparison: {:?} is not comparison",
1180 |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
1182 match inner_op.kind {
1183 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
1184 let mut err = self.struct_span_err(
1185 vec![op.span, self.prev_token.span],
1186 "comparison operators cannot be chained",
1189 let suggest = |err: &mut Diagnostic| {
1190 err.span_suggestion_verbose(
1191 op.span.shrink_to_lo(),
1192 TURBOFISH_SUGGESTION_STR,
1194 Applicability::MaybeIncorrect,
1198 // Include `<` to provide this recommendation even in a case like
1199 // `Foo<Bar<Baz<Qux, ()>>>`
1200 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
1201 || outer_op.node == AssocOp::Greater
1203 if outer_op.node == AssocOp::Less {
1204 let snapshot = self.create_snapshot_for_diagnostic();
1206 // So far we have parsed `foo<bar<`, consume the rest of the type args.
1208 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
1209 self.consume_tts(1, &modifiers);
1211 if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
1212 .contains(&self.token.kind)
1214 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
1215 // parser and bail out.
1216 self.restore_snapshot(snapshot);
1219 return if token::ModSep == self.token.kind {
1220 // We have some certainty that this was a bad turbofish at this point.
1224 let snapshot = self.create_snapshot_for_diagnostic();
1225 self.bump(); // `::`
1227 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
1228 match self.parse_expr() {
1230 // 99% certain that the suggestion is correct, continue parsing.
1232 // FIXME: actually check that the two expressions in the binop are
1233 // paths and resynthesize new fn call expression instead of using
1234 // `ExprKind::Err` placeholder.
1235 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1239 // Not entirely sure now, but we bubble the error up with the
1241 self.restore_snapshot(snapshot);
1245 } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
1246 // We have high certainty that this was a bad turbofish at this point.
1249 // Consume the fn call arguments.
1250 match self.consume_fn_args() {
1251 Err(()) => Err(err),
1254 // FIXME: actually check that the two expressions in the binop are
1255 // paths and resynthesize new fn call expression instead of using
1256 // `ExprKind::Err` placeholder.
1257 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1261 if !matches!(l1.kind, ExprKind::Lit(_))
1262 && !matches!(r1.kind, ExprKind::Lit(_))
1264 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1265 // be helpful, but don't attempt to recover.
1266 err.help(TURBOFISH_SUGGESTION_STR);
1267 err.help("or use `(...)` if you meant to specify fn arguments");
1270 // If it looks like a genuine attempt to chain operators (as opposed to a
1271 // misformatted turbofish, for instance), suggest a correct form.
1272 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1275 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1277 // These cases cause too many knock-down errors, bail out (#61329).
1283 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1286 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1294 fn consume_fn_args(&mut self) -> Result<(), ()> {
1295 let snapshot = self.create_snapshot_for_diagnostic();
1298 // Consume the fn call arguments.
1300 (token::OpenDelim(Delimiter::Parenthesis), 1),
1301 (token::CloseDelim(Delimiter::Parenthesis), -1),
1303 self.consume_tts(1, &modifiers);
1305 if self.token.kind == token::Eof {
1306 // Not entirely sure that what we consumed were fn arguments, rollback.
1307 self.restore_snapshot(snapshot);
1310 // 99% certain that the suggestion is correct, continue parsing.
1315 pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
1317 self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
1321 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1322 pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
1323 if self.token == token::Question {
1325 self.struct_span_err(self.prev_token.span, "invalid `?` in type")
1326 .span_label(self.prev_token.span, "`?` is only allowed on expressions, not types")
1327 .multipart_suggestion(
1328 "if you meant to express that the type might not contain a value, use the `Option` wrapper type",
1330 (ty.span.shrink_to_lo(), "Option<".to_string()),
1331 (self.prev_token.span, ">".to_string()),
1333 Applicability::MachineApplicable,
1336 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1342 pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
1343 // Do not add `+` to expected tokens.
1344 if !self.token.is_like_plus() {
1349 let bounds = self.parse_generic_bounds(None)?;
1350 let sum_span = ty.span.to(self.prev_token.span);
1352 let sub = match ty.kind {
1353 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1354 let sum_with_parens = pprust::to_string(|s| {
1356 s.print_opt_lifetime(lifetime);
1357 s.print_mutability(mut_ty.mutbl, false);
1359 s.print_type(&mut_ty.ty);
1360 if !bounds.is_empty() {
1362 s.print_type_bounds(&bounds);
1367 BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
1369 TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
1370 _ => BadTypePlusSub::ExpectPath { span: sum_span },
1373 self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
1378 pub(super) fn recover_from_prefix_increment(
1380 operand_expr: P<Expr>,
1383 ) -> PResult<'a, P<Expr>> {
1385 if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
1386 let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
1388 self.recover_from_inc_dec(operand_expr, kind, op_span)
1391 pub(super) fn recover_from_postfix_increment(
1393 operand_expr: P<Expr>,
1395 ) -> PResult<'a, P<Expr>> {
1396 let kind = IncDecRecovery {
1397 standalone: IsStandalone::Maybe,
1399 fixity: UnaryFixity::Post,
1402 self.recover_from_inc_dec(operand_expr, kind, op_span)
1405 fn recover_from_inc_dec(
1408 kind: IncDecRecovery,
1410 ) -> PResult<'a, P<Expr>> {
1411 let mut err = self.struct_span_err(
1413 &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
1415 err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
1417 let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
1418 err.help(&format!("use `{}= 1` instead", kind.op.chr()));
1424 let spans = match kind.fixity {
1425 UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
1426 UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
1429 match kind.standalone {
1430 IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
1431 IsStandalone::Subexpr => {
1432 let Ok(base_src) = self.span_to_snippet(base.span)
1433 else { return help_base_case(err, base) };
1435 UnaryFixity::Pre => {
1436 self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1438 UnaryFixity::Post => {
1439 self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1443 IsStandalone::Maybe => {
1444 let Ok(base_src) = self.span_to_snippet(base.span)
1445 else { return help_base_case(err, base) };
1446 let sugg1 = match kind.fixity {
1447 UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
1448 UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
1450 let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
1451 MultiSugg::emit_many(
1453 "use `+= 1` instead",
1454 Applicability::Unspecified,
1455 [sugg1, sugg2].into_iter(),
1462 fn prefix_inc_dec_suggest(
1465 kind: IncDecRecovery,
1466 (pre_span, post_span): (Span, Span),
1469 msg: format!("use `{}= 1` instead", kind.op.chr()),
1471 (pre_span, "{ ".to_string()),
1472 (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
1474 applicability: Applicability::MachineApplicable,
1478 fn postfix_inc_dec_suggest(
1481 kind: IncDecRecovery,
1482 (pre_span, post_span): (Span, Span),
1484 let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
1486 msg: format!("use `{}= 1` instead", kind.op.chr()),
1488 (pre_span, format!("{{ let {} = ", tmp_var)),
1489 (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
1491 applicability: Applicability::HasPlaceholders,
1495 fn inc_dec_standalone_suggest(
1497 kind: IncDecRecovery,
1498 (pre_span, post_span): (Span, Span),
1501 msg: format!("use `{}= 1` instead", kind.op.chr()),
1502 patches: vec![(pre_span, String::new()), (post_span, format!(" {}= 1", kind.op.chr()))],
1503 applicability: Applicability::MachineApplicable,
1507 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1508 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1509 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1510 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1513 ) -> PResult<'a, P<T>> {
1514 // Do not add `::` to expected tokens.
1515 if self.token == token::ModSep {
1516 if let Some(ty) = base.to_ty() {
1517 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1523 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1524 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1525 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1529 ) -> PResult<'a, P<T>> {
1530 self.expect(&token::ModSep)?;
1532 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1533 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1534 path.span = ty_span.to(self.prev_token.span);
1536 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1537 self.sess.emit_err(BadQPathStage2 {
1539 ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1542 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1543 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1546 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1547 if self.token.kind == TokenKind::Semi {
1551 IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
1553 if !items.is_empty() {
1554 let previous_item = &items[items.len() - 1];
1555 let previous_item_kind_name = match previous_item.kind {
1556 // Say "braced struct" because tuple-structs and
1557 // braceless-empty-struct declarations do take a semicolon.
1558 ItemKind::Struct(..) => Some("braced struct"),
1559 ItemKind::Enum(..) => Some("enum"),
1560 ItemKind::Trait(..) => Some("trait"),
1561 ItemKind::Union(..) => Some("union"),
1564 if let Some(name) = previous_item_kind_name {
1565 err.opt_help = Some(());
1569 self.sess.emit_err(err);
1576 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1577 /// closing delimiter.
1578 pub(super) fn unexpected_try_recover(
1581 ) -> PResult<'a, bool /* recovered */> {
1582 let token_str = pprust::token_kind_to_string(t);
1583 let this_token_str = super::token_descr(&self.token);
1584 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1585 // Point at the end of the macro call when reaching end of macro arguments.
1586 (token::Eof, Some(_)) => {
1587 let sp = self.sess.source_map().next_point(self.prev_token.span);
1590 // We don't want to point at the following span after DUMMY_SP.
1591 // This happens when the parser finds an empty TokenStream.
1592 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1593 // EOF, don't want to point at the following char, but rather the last token.
1594 (token::Eof, None) => (self.prev_token.span, self.token.span),
1595 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1598 "expected `{}`, found {}",
1600 match (&self.token.kind, self.subparser_name) {
1601 (token::Eof, Some(origin)) => format!("end of {origin}"),
1602 _ => this_token_str,
1605 let mut err = self.struct_span_err(sp, &msg);
1606 let label_exp = format!("expected `{token_str}`");
1607 match self.recover_closing_delimiter(&[t.clone()], err) {
1610 return Ok(recovered);
1613 let sm = self.sess.source_map();
1614 if !sm.is_multiline(prev_sp.until(sp)) {
1615 // When the spans are in the same line, it means that the only content
1616 // between them is whitespace, point only at the found token.
1617 err.span_label(sp, label_exp);
1619 err.span_label(prev_sp, label_exp);
1620 err.span_label(sp, "unexpected token");
1625 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1626 if self.eat(&token::Semi) {
1629 self.expect(&token::Semi).map(drop) // Error unconditionally
1632 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1633 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1634 pub(super) fn recover_incorrect_await_syntax(
1639 ) -> PResult<'a, P<Expr>> {
1640 let (hi, expr, is_question) = if self.token == token::Not {
1641 // Handle `await!(<expr>)`.
1642 self.recover_await_macro()?
1644 self.recover_await_prefix(await_sp)?
1646 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1647 let kind = match expr.kind {
1648 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1649 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1650 ExprKind::Try(_) => ExprKind::Err,
1651 _ => ExprKind::Await(expr),
1653 let expr = self.mk_expr(lo.to(sp), kind, attrs);
1654 self.maybe_recover_from_bad_qpath(expr)
1657 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1658 self.expect(&token::Not)?;
1659 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1660 let expr = self.parse_expr()?;
1661 self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
1662 Ok((self.prev_token.span, expr, false))
1665 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1666 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1667 let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
1668 // Handle `await { <expr> }`.
1669 // This needs to be handled separately from the next arm to avoid
1670 // interpreting `await { <expr> }?` as `<expr>?.await`.
1671 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default, AttrVec::new())
1675 .map_err(|mut err| {
1676 err.span_label(await_sp, "while parsing this incorrect await expression");
1679 Ok((expr.span, expr, is_question))
1682 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1683 let span = lo.to(hi);
1684 let applicability = match expr.kind {
1685 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1686 _ => Applicability::MachineApplicable,
1689 self.sess.emit_err(IncorrectAwait {
1691 sugg_span: (span, applicability),
1692 expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
1693 question_mark: if is_question { "?" } else { "" },
1699 /// If encountering `future.await()`, consumes and emits an error.
1700 pub(super) fn recover_from_await_method_call(&mut self) {
1701 if self.token == token::OpenDelim(Delimiter::Parenthesis)
1702 && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
1705 let lo = self.token.span;
1707 let span = lo.to(self.token.span);
1710 self.sess.emit_err(IncorrectUseOfAwait { span });
1714 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1715 let is_try = self.token.is_keyword(kw::Try);
1716 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1717 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
1719 if is_try && is_questionmark && is_open {
1720 let lo = self.token.span;
1721 self.bump(); //remove try
1722 self.bump(); //remove !
1723 let try_span = lo.to(self.token.span); //we take the try!( span
1724 self.bump(); //remove (
1725 let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
1726 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
1727 let hi = self.token.span;
1728 self.bump(); //remove )
1729 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1730 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1731 let prefix = if is_empty { "" } else { "alternatively, " };
1733 err.multipart_suggestion(
1734 "you can use the `?` operator instead",
1735 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1736 Applicability::MachineApplicable,
1739 err.span_suggestion(lo.shrink_to_lo(), &format!("{prefix}you can still access the deprecated `try!()` macro using the \"raw identifier\" syntax"), "r#", Applicability::MachineApplicable);
1741 Ok(self.mk_expr_err(lo.to(hi)))
1743 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1747 /// Recovers a situation like `for ( $pat in $expr )`
1748 /// and suggest writing `for $pat in $expr` instead.
1750 /// This should be called before parsing the `$block`.
1751 pub(super) fn recover_parens_around_for_head(
1754 begin_paren: Option<Span>,
1756 match (&self.token.kind, begin_paren) {
1757 (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
1760 self.struct_span_err(
1761 MultiSpan::from_spans(vec![begin_par_sp, self.prev_token.span]),
1762 "unexpected parentheses surrounding `for` loop head",
1764 .multipart_suggestion(
1765 "remove parentheses in `for` loop",
1766 vec![(begin_par_sp, String::new()), (self.prev_token.span, String::new())],
1767 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1768 // with `x) in y)` which is syntactically invalid.
1769 // However, this is prevented before we get here.
1770 Applicability::MachineApplicable,
1774 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1775 pat.and_then(|pat| match pat.kind {
1776 PatKind::Paren(pat) => pat,
1784 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1785 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1786 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1787 || self.token.is_ident() &&
1788 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1789 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1790 self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
1791 || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
1792 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1793 self.look_ahead(2, |t| t == &token::Lt) &&
1794 self.look_ahead(3, |t| t.is_ident())
1795 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1796 self.look_ahead(2, |t| t.is_ident())
1797 || self.look_ahead(1, |t| t == &token::ModSep)
1798 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1799 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1802 pub(super) fn recover_seq_parse_error(
1806 result: PResult<'a, P<Expr>>,
1812 // Recover from parse error, callers expect the closing delim to be consumed.
1813 self.consume_block(delim, ConsumeClosingDelim::Yes);
1814 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err, AttrVec::new())
1819 pub(super) fn recover_closing_delimiter(
1821 tokens: &[TokenKind],
1822 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
1823 ) -> PResult<'a, bool> {
1825 // We want to use the last closing delim that would apply.
1826 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1827 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1828 && Some(self.token.span) > unmatched.unclosed_span
1835 // Recover and assume that the detected unclosed delimiter was meant for
1836 // this location. Emit the diagnostic and act as if the delimiter was
1837 // present for the parser's sake.
1839 // Don't attempt to recover from this unclosed delimiter more than once.
1840 let unmatched = self.unclosed_delims.remove(pos);
1841 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1842 if unmatched.found_delim.is_none() {
1843 // We encountered `Eof`, set this fact here to avoid complaining about missing
1844 // `fn main()` when we found place to suggest the closing brace.
1845 *self.sess.reached_eof.borrow_mut() = true;
1848 // We want to suggest the inclusion of the closing delimiter where it makes
1849 // the most sense, which is immediately after the last token:
1854 // | help: `)` may belong here
1856 // unclosed delimiter
1857 if let Some(sp) = unmatched.unclosed_span {
1858 let mut primary_span: Vec<Span> =
1859 err.span.primary_spans().iter().cloned().collect();
1860 primary_span.push(sp);
1861 let mut primary_span: MultiSpan = primary_span.into();
1862 for span_label in err.span.span_labels() {
1863 if let Some(label) = span_label.label {
1864 primary_span.push_span_label(span_label.span, label);
1867 err.set_span(primary_span);
1868 err.span_label(sp, "unclosed delimiter");
1870 // Backticks should be removed to apply suggestions.
1871 let mut delim = delim.to_string();
1872 delim.retain(|c| c != '`');
1873 err.span_suggestion_short(
1874 self.prev_token.span.shrink_to_hi(),
1875 &format!("`{delim}` may belong here"),
1877 Applicability::MaybeIncorrect,
1879 if unmatched.found_delim.is_none() {
1880 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1881 // errors which would be emitted elsewhere in the parser and let other error
1882 // recovery consume the rest of the file.
1886 self.expected_tokens.clear(); // Reduce the number of errors.
1894 /// Eats tokens until we can be relatively sure we reached the end of the
1895 /// statement. This is something of a best-effort heuristic.
1897 /// We terminate when we find an unmatched `}` (without consuming it).
1898 pub(super) fn recover_stmt(&mut self) {
1899 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1902 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1903 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1904 /// approximate -- it can mean we break too early due to macros, but that
1905 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1907 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1908 /// after finding (and consuming) a brace-delimited block.
1909 pub(super) fn recover_stmt_(
1911 break_on_semi: SemiColonMode,
1912 break_on_block: BlockMode,
1914 let mut brace_depth = 0;
1915 let mut bracket_depth = 0;
1916 let mut in_block = false;
1917 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1919 debug!("recover_stmt_ loop {:?}", self.token);
1920 match self.token.kind {
1921 token::OpenDelim(Delimiter::Brace) => {
1924 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1929 token::OpenDelim(Delimiter::Bracket) => {
1933 token::CloseDelim(Delimiter::Brace) => {
1934 if brace_depth == 0 {
1935 debug!("recover_stmt_ return - close delim {:?}", self.token);
1940 if in_block && bracket_depth == 0 && brace_depth == 0 {
1941 debug!("recover_stmt_ return - block end {:?}", self.token);
1945 token::CloseDelim(Delimiter::Bracket) => {
1947 if bracket_depth < 0 {
1953 debug!("recover_stmt_ return - Eof");
1958 if break_on_semi == SemiColonMode::Break
1960 && bracket_depth == 0
1962 debug!("recover_stmt_ return - Semi");
1967 if break_on_semi == SemiColonMode::Comma
1969 && bracket_depth == 0 =>
1971 debug!("recover_stmt_ return - Semi");
1979 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1980 if self.eat_keyword(kw::In) {
1981 // a common typo: `for _ in in bar {}`
1982 self.sess.emit_err(InInTypo {
1983 span: self.prev_token.span,
1984 sugg_span: in_span.until(self.prev_token.span),
1989 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1990 if let token::DocComment(..) = self.token.kind {
1991 self.struct_span_err(
1993 "documentation comments cannot be applied to a function parameter's type",
1995 .span_label(self.token.span, "doc comments are not allowed here")
1998 } else if self.token == token::Pound
1999 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
2001 let lo = self.token.span;
2002 // Skip every token until next possible arg.
2003 while self.token != token::CloseDelim(Delimiter::Bracket) {
2006 let sp = lo.to(self.token.span);
2008 self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
2009 .span_label(sp, "attributes are not allowed here")
2014 pub(super) fn parameter_without_type(
2016 err: &mut Diagnostic,
2020 ) -> Option<Ident> {
2021 // If we find a pattern followed by an identifier, it could be an (incorrect)
2022 // C-style parameter declaration.
2023 if self.check_ident()
2024 && self.look_ahead(1, |t| {
2025 *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
2028 // `fn foo(String s) {}`
2029 let ident = self.parse_ident().unwrap();
2030 let span = pat.span.with_hi(ident.span.hi());
2032 err.span_suggestion(
2034 "declare the type after the parameter binding",
2035 "<identifier>: <type>",
2036 Applicability::HasPlaceholders,
2039 } else if require_name
2040 && (self.token == token::Comma
2041 || self.token == token::Lt
2042 || self.token == token::CloseDelim(Delimiter::Parenthesis))
2044 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
2046 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
2048 PatKind::Ident(_, ident, _) => (
2051 ": TypeName".to_string(),
2053 pat.span.shrink_to_lo(),
2054 pat.span.shrink_to_hi(),
2055 pat.span.shrink_to_lo(),
2057 // Also catches `fn foo(&a)`.
2058 PatKind::Ref(ref inner_pat, mutab)
2059 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
2061 match inner_pat.clone().into_inner().kind {
2062 PatKind::Ident(_, ident, _) => {
2063 let mutab = mutab.prefix_str();
2067 format!("{ident}: &{mutab}TypeName"),
2069 pat.span.shrink_to_lo(),
2071 pat.span.shrink_to_lo(),
2074 _ => unreachable!(),
2078 // Otherwise, try to get a type and emit a suggestion.
2079 if let Some(ty) = pat.to_ty() {
2080 err.span_suggestion_verbose(
2082 "explicitly ignore the parameter name",
2083 format!("_: {}", pprust::ty_to_string(&ty)),
2084 Applicability::MachineApplicable,
2093 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
2095 err.span_suggestion(
2097 "if this is a `self` type, give it a parameter name",
2099 Applicability::MaybeIncorrect,
2102 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
2103 // `fn foo(HashMap: TypeName<u32>)`.
2104 if self.token != token::Lt {
2105 err.span_suggestion(
2107 "if this is a parameter name, give it a type",
2109 Applicability::HasPlaceholders,
2112 err.span_suggestion(
2114 "if this is a type, explicitly ignore the parameter name",
2116 Applicability::MachineApplicable,
2120 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
2121 return if self.token == token::Lt { None } else { Some(ident) };
2126 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
2127 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
2128 self.expect(&token::Colon)?;
2129 let ty = self.parse_ty()?;
2135 "patterns aren't allowed in methods without bodies",
2137 .span_suggestion_short(
2139 "give this argument a name or use an underscore to ignore it",
2141 Applicability::MachineApplicable,
2145 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2147 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
2151 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
2152 let sp = param.pat.span;
2153 param.ty.kind = TyKind::Err;
2154 self.struct_span_err(sp, "unexpected `self` parameter in function")
2155 .span_label(sp, "must be the first parameter of an associated function")
2160 pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
2161 let mut brace_depth = 0;
2163 if self.eat(&token::OpenDelim(delim)) {
2165 } else if self.check(&token::CloseDelim(delim)) {
2166 if brace_depth == 0 {
2167 if let ConsumeClosingDelim::Yes = consume_close {
2168 // Some of the callers of this method expect to be able to parse the
2169 // closing delimiter themselves, so we leave it alone. Otherwise we advance
2179 } else if self.token == token::Eof {
2187 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2188 let (span, msg) = match (&self.token.kind, self.subparser_name) {
2189 (&token::Eof, Some(origin)) => {
2190 let sp = self.sess.source_map().next_point(self.prev_token.span);
2191 (sp, format!("expected expression, found end of {origin}"))
2195 format!("expected expression, found {}", super::token_descr(&self.token),),
2198 let mut err = self.struct_span_err(span, &msg);
2199 let sp = self.sess.source_map().start_point(self.token.span);
2200 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
2201 self.sess.expr_parentheses_needed(&mut err, *sp);
2203 err.span_label(span, "expected expression");
2209 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
2210 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
2211 modifier: &[(token::TokenKind, i64)],
2214 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
2217 if self.token.kind == token::Eof {
2224 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
2226 /// This is necessary because at this point we don't know whether we parsed a function with
2227 /// anonymous parameters or a function with names but no types. In order to minimize
2228 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
2229 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
2230 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
2231 /// we deduplicate them to not complain about duplicated parameter names.
2232 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
2233 let mut seen_inputs = FxHashSet::default();
2234 for input in fn_inputs.iter_mut() {
2235 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
2236 (&input.pat.kind, &input.ty.kind)
2242 if let Some(ident) = opt_ident {
2243 if seen_inputs.contains(&ident) {
2244 input.pat.kind = PatKind::Wild;
2246 seen_inputs.insert(ident);
2251 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
2252 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
2253 /// like the user has forgotten them.
2254 pub fn handle_ambiguous_unbraced_const_arg(
2256 args: &mut Vec<AngleBracketedArg>,
2257 ) -> PResult<'a, bool> {
2258 // If we haven't encountered a closing `>`, then the argument is malformed.
2259 // It's likely that the user has written a const expression without enclosing it
2260 // in braces, so we try to recover here.
2261 let arg = args.pop().unwrap();
2262 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
2263 // adverse side-effects to subsequent errors and seems to advance the parser.
2264 // We are causing this error here exclusively in case that a `const` expression
2265 // could be recovered from the current parser state, even if followed by more
2266 // arguments after a comma.
2267 let mut err = self.struct_span_err(
2269 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
2271 err.span_label(self.token.span, "expected one of `,` or `>`");
2272 match self.recover_const_arg(arg.span(), err) {
2274 args.push(AngleBracketedArg::Arg(arg));
2275 if self.eat(&token::Comma) {
2276 return Ok(true); // Continue
2281 // We will emit a more generic error later.
2285 return Ok(false); // Don't continue.
2288 /// Attempt to parse a generic const argument that has not been enclosed in braces.
2289 /// There are a limited number of expressions that are permitted without being encoded
2292 /// - Single-segment paths (i.e. standalone generic const parameters).
2293 /// All other expressions that can be parsed will emit an error suggesting the expression be
2294 /// wrapped in braces.
2295 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
2296 let start = self.token.span;
2297 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
2299 start.shrink_to_lo(),
2300 "while parsing a const generic argument starting here",
2304 if !self.expr_is_valid_const_arg(&expr) {
2305 self.struct_span_err(
2307 "expressions must be enclosed in braces to be used as const generic \
2310 .multipart_suggestion(
2311 "enclose the `const` expression in braces",
2313 (expr.span.shrink_to_lo(), "{ ".to_string()),
2314 (expr.span.shrink_to_hi(), " }".to_string()),
2316 Applicability::MachineApplicable,
2323 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2324 let snapshot = self.create_snapshot_for_diagnostic();
2325 let param = match self.parse_const_param(vec![]) {
2329 self.restore_snapshot(snapshot);
2334 self.struct_span_err(param.span(), "unexpected `const` parameter declaration");
2335 err.span_label(param.span(), "expected a `const` expression, not a parameter declaration");
2336 if let (Some(generics), Ok(snippet)) =
2337 (ty_generics, self.sess.source_map().span_to_snippet(param.span()))
2339 let (span, sugg) = match &generics.params[..] {
2340 [] => (generics.span, format!("<{snippet}>")),
2341 [.., generic] => (generic.span().shrink_to_hi(), format!(", {snippet}")),
2343 err.multipart_suggestion(
2344 "`const` parameters must be declared for the `impl`",
2345 vec![(span, sugg), (param.span(), param.ident.to_string())],
2346 Applicability::MachineApplicable,
2349 let value = self.mk_expr_err(param.span());
2351 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2354 pub fn recover_const_param_declaration(
2356 ty_generics: Option<&Generics>,
2357 ) -> PResult<'a, Option<GenericArg>> {
2358 // We have to check for a few different cases.
2359 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2360 return Ok(Some(arg));
2363 // We haven't consumed `const` yet.
2364 let start = self.token.span;
2365 self.bump(); // `const`
2367 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2369 .struct_span_err(start, "expected lifetime, type, or constant, found keyword `const`");
2370 if self.check_const_arg() {
2371 err.span_suggestion_verbose(
2372 start.until(self.token.span),
2373 "the `const` keyword is only needed in the definition of the type",
2375 Applicability::MaybeIncorrect,
2378 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2380 let after_kw_const = self.token.span;
2381 self.recover_const_arg(after_kw_const, err).map(Some)
2385 /// Try to recover from possible generic const argument without `{` and `}`.
2387 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2388 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2389 /// if we think that that the resulting expression would be well formed.
2390 pub fn recover_const_arg(
2393 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2394 ) -> PResult<'a, GenericArg> {
2395 let is_op_or_dot = AssocOp::from_token(&self.token)
2397 if let AssocOp::Greater
2399 | AssocOp::ShiftRight
2400 | AssocOp::GreaterEqual
2401 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2402 // assign a value to a defaulted generic parameter.
2404 | AssocOp::AssignOp(_) = op
2412 || self.token.kind == TokenKind::Dot;
2413 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2414 // type params has been parsed.
2416 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2417 if !is_op_or_dot && !was_op {
2418 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2421 let snapshot = self.create_snapshot_for_diagnostic();
2425 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2427 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2428 if token::EqEq == snapshot.token.kind {
2429 err.span_suggestion(
2430 snapshot.token.span,
2431 "if you meant to use an associated type binding, replace `==` with `=`",
2433 Applicability::MaybeIncorrect,
2435 let value = self.mk_expr_err(start.to(expr.span));
2437 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2438 } else if token::Colon == snapshot.token.kind
2439 && expr.span.lo() == snapshot.token.span.hi()
2440 && matches!(expr.kind, ExprKind::Path(..))
2442 // Find a mistake like "foo::var:A".
2443 err.span_suggestion(
2444 snapshot.token.span,
2445 "write a path separator here",
2447 Applicability::MaybeIncorrect,
2450 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2451 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2453 // Avoid the following output by checking that we consumed a full const arg:
2454 // help: expressions must be enclosed in braces to be used as const generic
2457 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2459 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2466 self.restore_snapshot(snapshot);
2470 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2471 pub fn dummy_const_arg_needs_braces(
2473 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2476 err.multipart_suggestion(
2477 "expressions must be enclosed in braces to be used as const generic \
2479 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2480 Applicability::MaybeIncorrect,
2482 let value = self.mk_expr_err(span);
2484 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2487 /// Get the diagnostics for the cases where `move async` is found.
2489 /// `move_async_span` starts at the 'm' of the move keyword and ends with the 'c' of the async keyword
2490 pub(super) fn incorrect_move_async_order_found(
2492 move_async_span: Span,
2493 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2495 self.struct_span_err(move_async_span, "the order of `move` and `async` is incorrect");
2496 err.span_suggestion_verbose(
2498 "try switching the order",
2500 Applicability::MaybeIncorrect,
2505 /// Some special error handling for the "top-level" patterns in a match arm,
2506 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2507 pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
2509 mut first_pat: P<Pat>,
2512 if token::Colon != self.token.kind {
2515 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2516 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2520 // The pattern looks like it might be a path with a `::` -> `:` typo:
2521 // `match foo { bar:baz => {} }`
2522 let span = self.token.span;
2523 // We only emit "unexpected `:`" error here if we can successfully parse the
2524 // whole pattern correctly in that case.
2525 let snapshot = self.create_snapshot_for_diagnostic();
2527 // Create error for "unexpected `:`".
2528 match self.expected_one_of_not_found(&[], &[]) {
2530 self.bump(); // Skip the `:`.
2531 match self.parse_pat_no_top_alt(expected) {
2533 // Carry on as if we had not done anything, callers will emit a
2534 // reasonable error.
2537 self.restore_snapshot(snapshot);
2540 // We've parsed the rest of the pattern.
2541 let new_span = first_pat.span.to(pat.span);
2542 let mut show_sugg = false;
2543 // Try to construct a recovered pattern.
2544 match &mut pat.kind {
2545 PatKind::Struct(qself @ None, path, ..)
2546 | PatKind::TupleStruct(qself @ None, path, _)
2547 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2548 PatKind::Ident(_, ident, _) => {
2549 path.segments.insert(0, PathSegment::from_ident(*ident));
2550 path.span = new_span;
2554 PatKind::Path(old_qself, old_path) => {
2555 path.segments = old_path
2559 .chain(take(&mut path.segments))
2561 path.span = new_span;
2562 *qself = old_qself.clone();
2568 PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None) => {
2569 match &first_pat.kind {
2570 PatKind::Ident(_, old_ident, _) => {
2571 let path = PatKind::Path(
2576 PathSegment::from_ident(*old_ident),
2577 PathSegment::from_ident(*ident),
2582 first_pat = self.mk_pat(new_span, path);
2585 PatKind::Path(old_qself, old_path) => {
2586 let mut segments = old_path.segments.clone();
2587 segments.push(PathSegment::from_ident(*ident));
2588 let path = PatKind::Path(
2590 Path { span: new_span, segments, tokens: None },
2592 first_pat = self.mk_pat(new_span, path);
2601 err.span_suggestion(
2603 "maybe write a path separator here",
2605 Applicability::MaybeIncorrect,
2608 first_pat = self.mk_pat(new_span, PatKind::Wild);
2615 // Carry on as if we had not done anything. This should be unreachable.
2616 self.restore_snapshot(snapshot);
2622 pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
2623 let Some(label) = self.eat_label().filter(|_| {
2624 self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
2628 let span = label.ident.span.to(self.prev_token.span);
2629 let mut err = self.struct_span_err(span, "block label not supported here");
2630 err.span_label(span, "not supported here");
2631 err.tool_only_span_suggestion(
2632 label.ident.span.until(self.token.span),
2633 "remove this block label",
2635 Applicability::MachineApplicable,
2641 /// Some special error handling for the "top-level" patterns in a match arm,
2642 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2643 pub(crate) fn maybe_recover_unexpected_comma(
2646 rt: CommaRecoveryMode,
2647 ) -> PResult<'a, ()> {
2648 if self.token != token::Comma {
2652 // An unexpected comma after a top-level pattern is a clue that the
2653 // user (perhaps more accustomed to some other language) forgot the
2654 // parentheses in what should have been a tuple pattern; return a
2655 // suggestion-enhanced error here rather than choking on the comma later.
2656 let comma_span = self.token.span;
2658 if let Err(err) = self.skip_pat_list() {
2659 // We didn't expect this to work anyway; we just wanted to advance to the
2660 // end of the comma-sequence so we know the span to suggest parenthesizing.
2663 let seq_span = lo.to(self.prev_token.span);
2664 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2665 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2666 err.multipart_suggestion(
2668 "try adding parentheses to match on a tuple{}",
2669 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
2672 (seq_span.shrink_to_lo(), "(".to_string()),
2673 (seq_span.shrink_to_hi(), ")".to_string()),
2675 Applicability::MachineApplicable,
2677 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
2678 err.span_suggestion(
2680 "...or a vertical bar to match on multiple alternatives",
2681 seq_snippet.replace(',', " |"),
2682 Applicability::MachineApplicable,
2689 pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
2690 let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
2691 let qself_position = qself.as_ref().map(|qself| qself.position);
2692 for (i, segments) in path.segments.windows(2).enumerate() {
2693 if qself_position.map(|pos| i < pos).unwrap_or(false) {
2696 if let [a, b] = segments {
2697 let (a_span, b_span) = (a.span(), b.span());
2698 let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
2699 if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
2700 let mut err = self.struct_span_err(
2701 path.span.shrink_to_hi(),
2702 "expected `:` followed by trait or lifetime",
2704 err.span_suggestion(
2708 Applicability::MachineApplicable,
2717 /// Parse and throw away a parenthesized comma separated
2718 /// sequence of patterns until `)` is reached.
2719 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2720 while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
2721 self.parse_pat_no_top_alt(None)?;
2722 if !self.eat(&token::Comma) {