1 use super::pat::Expected;
3 BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep,
4 TokenExpectType, TokenType,
7 AmbiguousPlus, AttributeOnParamType, BadQPathStage2, BadTypePlus, BadTypePlusSub,
8 ComparisonOperatorsCannotBeChained, ComparisonOperatorsCannotBeChainedSugg,
9 ConstGenericWithoutBraces, ConstGenericWithoutBracesSugg, DocCommentOnParamType,
10 DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
11 GenericParamsWithoutAngleBrackets, GenericParamsWithoutAngleBracketsSugg, InInTypo,
12 IncorrectAwait, IncorrectSemicolon, IncorrectUseOfAwait, ParenthesesInForHead,
13 ParenthesesInForHeadSugg, PatternMethodParamWithoutBody, QuestionMarkInType,
14 QuestionMarkInTypeSugg, SelfParamNotFirst, StructLiteralBodyWithoutPath,
15 StructLiteralBodyWithoutPathSugg, SuggEscapeToUseAsIdentifier, SuggRemoveComma,
16 UnexpectedConstInGenericParam, UnexpectedConstParamDeclaration,
17 UnexpectedConstParamDeclarationSugg, UnmatchedAngleBrackets, UseEqInstead,
20 use crate::lexer::UnmatchedBrace;
22 use rustc_ast::ptr::P;
23 use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
24 use rustc_ast::util::parser::AssocOp;
26 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingAnnotation, Block,
27 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Param, Pat, PatKind,
28 Path, PathSegment, QSelf, Ty, TyKind,
30 use rustc_ast_pretty::pprust;
31 use rustc_data_structures::fx::FxHashSet;
33 fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
35 use rustc_errors::{pluralize, Diagnostic, ErrorGuaranteed, IntoDiagnostic};
36 use rustc_session::errors::ExprParenthesesNeeded;
37 use rustc_span::source_map::Spanned;
38 use rustc_span::symbol::{kw, sym, Ident};
39 use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
40 use std::ops::{Deref, DerefMut};
46 /// Creates a placeholder argument.
47 pub(super) fn dummy_arg(ident: Ident) -> Param {
49 id: ast::DUMMY_NODE_ID,
50 kind: PatKind::Ident(BindingAnnotation::NONE, ident, None),
54 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
56 attrs: AttrVec::default(),
57 id: ast::DUMMY_NODE_ID,
61 is_placeholder: false,
65 pub(super) trait RecoverQPath: Sized + 'static {
66 const PATH_STYLE: PathStyle = PathStyle::Expr;
67 fn to_ty(&self) -> Option<P<Ty>>;
68 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
71 impl RecoverQPath for Ty {
72 const PATH_STYLE: PathStyle = PathStyle::Type;
73 fn to_ty(&self) -> Option<P<Ty>> {
76 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
79 kind: TyKind::Path(qself, path),
80 id: ast::DUMMY_NODE_ID,
86 impl RecoverQPath for Pat {
87 fn to_ty(&self) -> Option<P<Ty>> {
90 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
93 kind: PatKind::Path(qself, path),
94 id: ast::DUMMY_NODE_ID,
100 impl RecoverQPath for Expr {
101 fn to_ty(&self) -> Option<P<Ty>> {
104 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
107 kind: ExprKind::Path(qself, path),
108 attrs: AttrVec::new(),
109 id: ast::DUMMY_NODE_ID,
115 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
116 pub(crate) enum ConsumeClosingDelim {
121 #[derive(Clone, Copy)]
122 pub enum AttemptLocalParseRecovery {
127 impl AttemptLocalParseRecovery {
128 pub fn yes(&self) -> bool {
130 AttemptLocalParseRecovery::Yes => true,
131 AttemptLocalParseRecovery::No => false,
135 pub fn no(&self) -> bool {
137 AttemptLocalParseRecovery::Yes => false,
138 AttemptLocalParseRecovery::No => true,
143 /// Information for emitting suggestions and recovering from
144 /// C-style `i++`, `--i`, etc.
145 #[derive(Debug, Copy, Clone)]
146 struct IncDecRecovery {
147 /// Is this increment/decrement its own statement?
148 standalone: IsStandalone,
149 /// Is this an increment or decrement?
151 /// Is this pre- or postfix?
155 /// Is an increment or decrement expression its own statement?
156 #[derive(Debug, Copy, Clone)]
158 /// It's standalone, i.e., its own statement.
160 /// It's a subexpression, i.e., *not* standalone.
162 /// It's maybe standalone; we're not sure.
166 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
169 // FIXME: `i--` recovery isn't implemented yet
174 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
181 fn chr(&self) -> char {
188 fn name(&self) -> &'static str {
190 Self::Inc => "increment",
191 Self::Dec => "decrement",
196 impl std::fmt::Display for UnaryFixity {
197 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
199 Self::Pre => write!(f, "prefix"),
200 Self::Post => write!(f, "postfix"),
207 patches: Vec<(Span, String)>,
208 applicability: Applicability,
212 fn emit(self, err: &mut Diagnostic) {
213 err.multipart_suggestion(&self.msg, self.patches, self.applicability);
216 /// Overrides individual messages and applicabilities.
218 err: &mut Diagnostic,
220 applicability: Applicability,
221 suggestions: impl Iterator<Item = Self>,
223 err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
227 // SnapshotParser is used to create a snapshot of the parser
228 // without causing duplicate errors being emitted when the `Parser`
230 pub struct SnapshotParser<'a> {
232 unclosed_delims: Vec<UnmatchedBrace>,
235 impl<'a> Deref for SnapshotParser<'a> {
236 type Target = Parser<'a>;
238 fn deref(&self) -> &Self::Target {
243 impl<'a> DerefMut for SnapshotParser<'a> {
244 fn deref_mut(&mut self) -> &mut Self::Target {
249 impl<'a> Parser<'a> {
250 #[rustc_lint_diagnostics]
251 pub fn struct_span_err<S: Into<MultiSpan>>(
254 m: impl Into<DiagnosticMessage>,
255 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
256 self.sess.span_diagnostic.struct_span_err(sp, m)
259 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: impl Into<DiagnosticMessage>) -> ! {
260 self.sess.span_diagnostic.span_bug(sp, m)
263 pub(super) fn diagnostic(&self) -> &'a Handler {
264 &self.sess.span_diagnostic
267 /// Replace `self` with `snapshot.parser` and extend `unclosed_delims` with `snapshot.unclosed_delims`.
268 /// This is to avoid losing unclosed delims errors `create_snapshot_for_diagnostic` clears.
269 pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
270 *self = snapshot.parser;
271 self.unclosed_delims.extend(snapshot.unclosed_delims);
274 pub fn unclosed_delims(&self) -> &[UnmatchedBrace] {
275 &self.unclosed_delims
278 /// Create a snapshot of the `Parser`.
279 pub fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
280 let mut snapshot = self.clone();
281 let unclosed_delims = self.unclosed_delims.clone();
282 // Clear `unclosed_delims` in snapshot to avoid
283 // duplicate errors being emitted when the `Parser`
284 // is dropped (which may or may not happen, depending
285 // if the parsing the snapshot is created for is successful)
286 snapshot.unclosed_delims.clear();
287 SnapshotParser { parser: snapshot, unclosed_delims }
290 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
291 self.sess.source_map().span_to_snippet(span)
294 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
295 let valid_follow = &[
301 TokenKind::OpenDelim(Delimiter::Brace),
302 TokenKind::OpenDelim(Delimiter::Parenthesis),
303 TokenKind::CloseDelim(Delimiter::Brace),
304 TokenKind::CloseDelim(Delimiter::Parenthesis),
306 let suggest_raw = match self.token.ident() {
308 if ident.is_raw_guess()
309 && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
311 Some(SuggEscapeToUseAsIdentifier {
312 span: ident.span.shrink_to_lo(),
313 // `Symbol::to_string()` is different from `Symbol::into_diagnostic_arg()`,
314 // which uses `Symbol::to_ident_string()` and "helpfully" adds an implicit `r#`
315 ident_name: ident.name.to_string(),
321 let suggest_remove_comma =
322 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
323 Some(SuggRemoveComma { span: self.token.span })
328 let err = ExpectedIdentifier {
329 span: self.token.span,
330 token: self.token.clone(),
332 suggest_remove_comma,
334 err.into_diagnostic(&self.sess.span_diagnostic)
337 pub(super) fn expected_one_of_not_found(
339 edible: &[TokenKind],
340 inedible: &[TokenKind],
341 ) -> PResult<'a, bool /* recovered */> {
342 debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
343 fn tokens_to_string(tokens: &[TokenType]) -> String {
344 let mut i = tokens.iter();
345 // This might be a sign we need a connect method on `Iterator`.
346 let b = i.next().map_or_else(String::new, |t| t.to_string());
347 i.enumerate().fold(b, |mut b, (i, a)| {
348 if tokens.len() > 2 && i == tokens.len() - 2 {
350 } else if tokens.len() == 2 && i == tokens.len() - 2 {
355 b.push_str(&a.to_string());
360 let mut expected = edible
362 .map(|x| TokenType::Token(x.clone()))
363 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
364 .chain(self.expected_tokens.iter().cloned())
365 .filter_map(|token| {
366 // filter out suggestions which suggest the same token which was found and deemed incorrect
367 fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
368 if let TokenKind::Ident(current_sym, _) = found {
369 if let TokenType::Keyword(suggested_sym) = expected {
370 return current_sym == suggested_sym;
375 if token != parser::TokenType::Token(self.token.kind.clone()) {
376 let eq = is_ident_eq_keyword(&self.token.kind, &token);
377 // if the suggestion is a keyword and the found token is an ident,
378 // the content of which are equal to the suggestion's content,
379 // we can remove that suggestion (see the return None statement below)
381 // if this isn't the case however, and the suggestion is a token the
382 // content of which is the same as the found token's, we remove it as well
384 if let TokenType::Token(kind) = &token {
385 if kind == &self.token.kind {
394 .collect::<Vec<_>>();
395 expected.sort_by_cached_key(|x| x.to_string());
398 let sm = self.sess.source_map();
400 // Special-case "expected `;`" errors
401 if expected.contains(&TokenType::Token(token::Semi)) {
402 if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
403 // Likely inside a macro, can't provide meaningful suggestions.
404 } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
405 // The current token is in the same line as the prior token, not recoverable.
406 } else if [token::Comma, token::Colon].contains(&self.token.kind)
407 && self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis)
409 // Likely typo: The current token is on a new line and is expected to be
410 // `.`, `;`, `?`, or an operator after a close delimiter token.
412 // let a = std::process::Command::new("echo")
416 // https://github.com/rust-lang/rust/issues/72253
417 } else if self.look_ahead(1, |t| {
418 t == &token::CloseDelim(Delimiter::Brace)
419 || t.can_begin_expr() && t.kind != token::Colon
420 }) && [token::Comma, token::Colon].contains(&self.token.kind)
422 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
423 // either `,` or `:`, and the next token could either start a new statement or is a
424 // block close. For example:
428 self.sess.emit_err(ExpectedSemi {
429 span: self.token.span,
430 token: self.token.clone(),
431 unexpected_token_label: None,
432 sugg: ExpectedSemiSugg::ChangeToSemi(self.token.span),
436 } else if self.look_ahead(0, |t| {
437 t == &token::CloseDelim(Delimiter::Brace)
438 || ((t.can_begin_expr() || t.can_begin_item())
440 && t != &token::Pound)
441 // Avoid triggering with too many trailing `#` in raw string.
443 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
444 ) && t == &token::Pound)
445 }) && !expected.contains(&TokenType::Token(token::Comma))
447 // Missing semicolon typo. This is triggered if the next token could either start a
448 // new statement or is a block close. For example:
452 let span = self.prev_token.span.shrink_to_hi();
453 self.sess.emit_err(ExpectedSemi {
455 token: self.token.clone(),
456 unexpected_token_label: Some(self.token.span),
457 sugg: ExpectedSemiSugg::AddSemi(span),
463 if self.token.kind == TokenKind::EqEq
464 && self.prev_token.is_ident()
465 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Eq)))
467 // Likely typo: `=` → `==` in let expr or enum item
468 return Err(self.sess.create_err(UseEqInstead { span: self.token.span }));
471 let expect = tokens_to_string(&expected);
472 let actual = super::token_descr(&self.token);
473 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
474 let short_expect = if expected.len() > 6 {
475 format!("{} possible tokens", expected.len())
480 format!("expected one of {expect}, found {actual}"),
481 (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")),
483 } else if expected.is_empty() {
485 format!("unexpected token: {actual}"),
486 (self.prev_token.span, "unexpected token after this".to_string()),
490 format!("expected {expect}, found {actual}"),
491 (self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
494 self.last_unexpected_token_span = Some(self.token.span);
495 // FIXME: translation requires list formatting (for `expect`)
496 let mut err = self.struct_span_err(self.token.span, &msg_exp);
498 if let TokenKind::Ident(symbol, _) = &self.prev_token.kind {
499 if ["def", "fun", "func", "function"].contains(&symbol.as_str()) {
500 err.span_suggestion_short(
501 self.prev_token.span,
502 &format!("write `fn` instead of `{symbol}` to declare a function"),
504 Applicability::MachineApplicable,
509 // `pub` may be used for an item or `pub(crate)`
510 if self.prev_token.is_ident_named(sym::public)
511 && (self.token.can_begin_item()
512 || self.token.kind == TokenKind::OpenDelim(Delimiter::Parenthesis))
514 err.span_suggestion_short(
515 self.prev_token.span,
516 "write `pub` instead of `public` to make the item public",
518 Applicability::MachineApplicable,
522 // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
523 // there are unclosed angle brackets
524 if self.unmatched_angle_bracket_count > 0
525 && self.token.kind == TokenKind::Eq
526 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
528 err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
531 let sp = if self.token == token::Eof {
532 // This is EOF; don't want to point at the following char, but rather the last token.
537 match self.recover_closing_delimiter(
540 .filter_map(|tt| match tt {
541 TokenType::Token(t) => Some(t.clone()),
544 .collect::<Vec<_>>(),
549 return Ok(recovered);
553 if self.check_too_many_raw_str_terminators(&mut err) {
554 if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
562 if self.prev_token.span == DUMMY_SP {
563 // Account for macro context where the previous span might not be
564 // available to avoid incorrect output (#54841).
565 err.span_label(self.token.span, label_exp);
566 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
567 // When the spans are in the same line, it means that the only content between
568 // them is whitespace, point at the found token in that case:
570 // X | () => { syntax error };
571 // | ^^^^^ expected one of 8 possible tokens here
573 // instead of having:
575 // X | () => { syntax error };
576 // | -^^^^^ unexpected token
578 // | expected one of 8 possible tokens here
579 err.span_label(self.token.span, label_exp);
581 err.span_label(sp, label_exp);
582 err.span_label(self.token.span, "unexpected token");
584 self.maybe_annotate_with_ascription(&mut err, false);
588 fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
589 let sm = self.sess.source_map();
590 match (&self.prev_token.kind, &self.token.kind) {
592 TokenKind::Literal(Lit {
593 kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
597 ) if !sm.is_multiline(
598 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
601 let n_hashes: u8 = *n_hashes;
602 err.set_primary_message("too many `#` when terminating raw string");
603 let str_span = self.prev_token.span;
604 let mut span = self.token.span;
606 while self.token.kind == TokenKind::Pound
607 && !sm.is_multiline(span.shrink_to_hi().until(self.token.span.shrink_to_lo()))
609 span = span.with_hi(self.token.span.hi());
616 &format!("remove the extra `#`{}", pluralize!(count)),
618 Applicability::MachineApplicable,
622 &format!("this raw string started with {n_hashes} `#`{}", pluralize!(n_hashes)),
630 pub fn maybe_suggest_struct_literal(
634 ) -> Option<PResult<'a, P<Block>>> {
635 if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
636 // We might be having a struct literal where people forgot to include the path:
640 let mut snapshot = self.create_snapshot_for_diagnostic();
642 Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
643 let struct_expr = snapshot.parse_struct_expr(None, path, false);
644 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
645 return Some(match (struct_expr, block_tail) {
646 (Ok(expr), Err(mut err)) => {
647 // We have encountered the following:
652 // fn foo() -> Foo { Path {
656 self.sess.emit_err(StructLiteralBodyWithoutPath {
658 sugg: StructLiteralBodyWithoutPathSugg {
659 before: expr.span.shrink_to_lo(),
660 after: expr.span.shrink_to_hi(),
663 self.restore_snapshot(snapshot);
664 let mut tail = self.mk_block(
665 vec![self.mk_stmt_err(expr.span)],
667 lo.to(self.prev_token.span),
669 tail.could_be_bare_literal = true;
672 (Err(err), Ok(tail)) => {
673 // We have a block tail that contains a somehow valid type ascription expr.
677 (Err(snapshot_err), Err(err)) => {
678 // We don't know what went wrong, emit the normal error.
679 snapshot_err.cancel();
680 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
683 (Ok(_), Ok(mut tail)) => {
684 tail.could_be_bare_literal = true;
692 pub fn maybe_annotate_with_ascription(
694 err: &mut Diagnostic,
695 maybe_expected_semicolon: bool,
697 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
698 let sm = self.sess.source_map();
699 let next_pos = sm.lookup_char_pos(self.token.span.lo());
700 let op_pos = sm.lookup_char_pos(sp.hi());
702 let allow_unstable = self.sess.unstable_features.is_nightly_build();
707 "maybe write a path separator here",
710 Applicability::MaybeIncorrect
712 Applicability::MachineApplicable
715 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
716 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
719 "try using a semicolon",
721 Applicability::MaybeIncorrect,
723 } else if allow_unstable {
724 err.span_label(sp, "tried to parse a type due to this type ascription");
726 err.span_label(sp, "tried to parse a type due to this");
729 // Give extra information about type ascription only if it's a nightly compiler.
731 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
735 // Avoid giving too much info when it was likely an unrelated typo.
737 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
738 for more information",
745 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
746 /// passes through any errors encountered. Used for error recovery.
747 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
749 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
750 Ok(p.parse_token_tree())
757 /// This function checks if there are trailing angle brackets and produces
758 /// a diagnostic to suggest removing them.
760 /// ```ignore (diagnostic)
761 /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
762 /// ^^ help: remove extra angle brackets
765 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
766 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
767 pub(super) fn check_trailing_angle_brackets(
769 segment: &PathSegment,
772 // This function is intended to be invoked after parsing a path segment where there are two
775 // 1. A specific token is expected after the path segment.
776 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
777 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
778 // 2. No specific token is expected after the path segment.
779 // eg. `x.foo` (field access)
781 // This function is called after parsing `.foo` and before parsing the token `end` (if
782 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
785 // We only care about trailing angle brackets if we previously parsed angle bracket
786 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
787 // removed in this case:
789 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
791 // This case is particularly tricky as we won't notice it just looking at the tokens -
792 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
793 // have already been parsed):
795 // `x.foo::<u32>>>(3)`
796 let parsed_angle_bracket_args =
797 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
800 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
801 parsed_angle_bracket_args,
803 if !parsed_angle_bracket_args {
807 // Keep the span at the start so we can highlight the sequence of `>` characters to be
809 let lo = self.token.span;
811 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
812 // (since we might have the field access case and the characters we're eating are
813 // actual operators and not trailing characters - ie `x.foo >> 3`).
814 let mut position = 0;
816 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
817 // many of each (so we can correctly pluralize our error messages) and continue to
819 let mut number_of_shr = 0;
820 let mut number_of_gt = 0;
821 while self.look_ahead(position, |t| {
822 trace!("check_trailing_angle_brackets: t={:?}", t);
823 if *t == token::BinOp(token::BinOpToken::Shr) {
826 } else if *t == token::Gt {
836 // If we didn't find any trailing `>` characters, then we have nothing to error about.
838 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
839 number_of_gt, number_of_shr,
841 if number_of_gt < 1 && number_of_shr < 1 {
845 // Finally, double check that we have our end token as otherwise this is the
847 if self.look_ahead(position, |t| {
848 trace!("check_trailing_angle_brackets: t={:?}", t);
849 end.contains(&&t.kind)
851 // Eat from where we started until the end token so that parsing can continue
852 // as if we didn't have those extra angle brackets.
853 self.eat_to_tokens(end);
854 let span = lo.until(self.token.span);
856 let num_extra_brackets = number_of_gt + number_of_shr * 2;
857 self.sess.emit_err(UnmatchedAngleBrackets { span, num_extra_brackets });
863 /// Check if a method call with an intended turbofish has been written without surrounding
865 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
866 if token::ModSep == self.token.kind && segment.args.is_none() {
867 let snapshot = self.create_snapshot_for_diagnostic();
869 let lo = self.token.span;
870 match self.parse_angle_args(None) {
872 let span = lo.to(self.prev_token.span);
873 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
874 let mut trailing_span = self.prev_token.span.shrink_to_hi();
875 while self.token.kind == token::BinOp(token::Shr)
876 || self.token.kind == token::Gt
878 trailing_span = trailing_span.to(self.token.span);
881 if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
882 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
883 let args = AngleBracketedArgs { args, span }.into();
886 self.sess.emit_err(GenericParamsWithoutAngleBrackets {
888 sugg: GenericParamsWithoutAngleBracketsSugg {
889 left: span.shrink_to_lo(),
890 right: trailing_span,
894 // This doesn't look like an invalid turbofish, can't recover parse state.
895 self.restore_snapshot(snapshot);
899 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
900 // generic parse error instead.
902 self.restore_snapshot(snapshot);
908 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
909 /// encounter a parse error when encountering the first `,`.
910 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
912 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
914 ) -> PResult<'a, ()> {
915 if let ExprKind::Binary(binop, _, _) = &expr.kind
916 && let ast::BinOpKind::Lt = binop.node
917 && self.eat(&token::Comma)
919 let x = self.parse_seq_to_before_end(
921 SeqSep::trailing_allowed(token::Comma),
922 |p| p.parse_generic_arg(None),
925 Ok((_, _, false)) => {
926 if self.eat(&token::Gt) {
927 e.span_suggestion_verbose(
928 binop.span.shrink_to_lo(),
929 fluent::parser_sugg_turbofish_syntax,
931 Applicability::MaybeIncorrect,
934 match self.parse_expr() {
937 self.mk_expr_err(expr.span.to(self.prev_token.span));
941 *expr = self.mk_expr_err(expr.span);
956 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
957 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
958 /// parenthesising the leftmost comparison.
959 fn attempt_chained_comparison_suggestion(
961 err: &mut ComparisonOperatorsCannotBeChained,
963 outer_op: &Spanned<AssocOp>,
964 ) -> bool /* advanced the cursor */ {
965 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
966 if let ExprKind::Field(_, ident) = l1.kind
967 && ident.as_str().parse::<i32>().is_err()
968 && !matches!(r1.kind, ExprKind::Lit(_))
970 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
971 // suggestion being the only one to apply is high.
974 return match (op.node, &outer_op.node) {
976 (BinOpKind::Eq, AssocOp::Equal) |
977 // `x < y < z` and friends.
978 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
979 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
980 // `x > y > z` and friends.
981 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
982 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
983 let expr_to_str = |e: &Expr| {
984 self.span_to_snippet(e.span)
985 .unwrap_or_else(|_| pprust::expr_to_string(&e))
987 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::SplitComparison {
988 span: inner_op.span.shrink_to_hi(),
989 middle_term: expr_to_str(&r1),
991 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
994 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
995 // Consume `z`/outer-op-rhs.
996 let snapshot = self.create_snapshot_for_diagnostic();
997 match self.parse_expr() {
999 // We are sure that outer-op-rhs could be consumed, the suggestion is
1001 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1002 left: r1.span.shrink_to_lo(),
1003 right: r2.span.shrink_to_hi(),
1009 self.restore_snapshot(snapshot);
1015 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
1016 let snapshot = self.create_snapshot_for_diagnostic();
1017 // At this point it is always valid to enclose the lhs in parentheses, no
1018 // further checks are necessary.
1019 match self.parse_expr() {
1021 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1022 left: l1.span.shrink_to_lo(),
1023 right: r1.span.shrink_to_hi(),
1029 self.restore_snapshot(snapshot);
1040 /// Produces an error if comparison operators are chained (RFC #558).
1041 /// We only need to check the LHS, not the RHS, because all comparison ops have same
1042 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
1044 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
1045 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
1048 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
1049 /// associative we can infer that we have:
1058 pub(super) fn check_no_chained_comparison(
1061 outer_op: &Spanned<AssocOp>,
1062 ) -> PResult<'a, Option<P<Expr>>> {
1064 outer_op.node.is_comparison(),
1065 "check_no_chained_comparison: {:?} is not comparison",
1069 let mk_err_expr = |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err)));
1071 match inner_op.kind {
1072 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
1073 let mut err = ComparisonOperatorsCannotBeChained {
1074 span: vec![op.span, self.prev_token.span],
1075 suggest_turbofish: None,
1076 help_turbofish: None,
1077 chaining_sugg: None,
1080 // Include `<` to provide this recommendation even in a case like
1081 // `Foo<Bar<Baz<Qux, ()>>>`
1082 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
1083 || outer_op.node == AssocOp::Greater
1085 if outer_op.node == AssocOp::Less {
1086 let snapshot = self.create_snapshot_for_diagnostic();
1088 // So far we have parsed `foo<bar<`, consume the rest of the type args.
1090 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
1091 self.consume_tts(1, &modifiers);
1093 if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
1094 .contains(&self.token.kind)
1096 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
1097 // parser and bail out.
1098 self.restore_snapshot(snapshot);
1101 return if token::ModSep == self.token.kind {
1102 // We have some certainty that this was a bad turbofish at this point.
1104 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1106 let snapshot = self.create_snapshot_for_diagnostic();
1107 self.bump(); // `::`
1109 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
1110 match self.parse_expr() {
1112 // 99% certain that the suggestion is correct, continue parsing.
1113 self.sess.emit_err(err);
1114 // FIXME: actually check that the two expressions in the binop are
1115 // paths and resynthesize new fn call expression instead of using
1116 // `ExprKind::Err` placeholder.
1117 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1121 // Not entirely sure now, but we bubble the error up with the
1123 self.restore_snapshot(snapshot);
1124 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1127 } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
1128 // We have high certainty that this was a bad turbofish at this point.
1130 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1131 // Consume the fn call arguments.
1132 match self.consume_fn_args() {
1133 Err(()) => Err(err.into_diagnostic(&self.sess.span_diagnostic)),
1135 self.sess.emit_err(err);
1136 // FIXME: actually check that the two expressions in the binop are
1137 // paths and resynthesize new fn call expression instead of using
1138 // `ExprKind::Err` placeholder.
1139 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1143 if !matches!(l1.kind, ExprKind::Lit(_))
1144 && !matches!(r1.kind, ExprKind::Lit(_))
1146 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1147 // be helpful, but don't attempt to recover.
1148 err.help_turbofish = Some(());
1151 // If it looks like a genuine attempt to chain operators (as opposed to a
1152 // misformatted turbofish, for instance), suggest a correct form.
1153 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1155 self.sess.emit_err(err);
1156 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1158 // These cases cause too many knock-down errors, bail out (#61329).
1159 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1164 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1165 self.sess.emit_err(err);
1167 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1175 fn consume_fn_args(&mut self) -> Result<(), ()> {
1176 let snapshot = self.create_snapshot_for_diagnostic();
1179 // Consume the fn call arguments.
1181 (token::OpenDelim(Delimiter::Parenthesis), 1),
1182 (token::CloseDelim(Delimiter::Parenthesis), -1),
1184 self.consume_tts(1, &modifiers);
1186 if self.token.kind == token::Eof {
1187 // Not entirely sure that what we consumed were fn arguments, rollback.
1188 self.restore_snapshot(snapshot);
1191 // 99% certain that the suggestion is correct, continue parsing.
1196 pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
1198 self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
1202 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1203 pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
1204 if self.token == token::Question {
1206 self.sess.emit_err(QuestionMarkInType {
1207 span: self.prev_token.span,
1208 sugg: QuestionMarkInTypeSugg {
1209 left: ty.span.shrink_to_lo(),
1210 right: self.prev_token.span,
1213 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1219 pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
1220 // Do not add `+` to expected tokens.
1221 if !self.token.is_like_plus() {
1226 let bounds = self.parse_generic_bounds(None)?;
1227 let sum_span = ty.span.to(self.prev_token.span);
1229 let sub = match ty.kind {
1230 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1231 let sum_with_parens = pprust::to_string(|s| {
1233 s.print_opt_lifetime(lifetime);
1234 s.print_mutability(mut_ty.mutbl, false);
1236 s.print_type(&mut_ty.ty);
1237 if !bounds.is_empty() {
1239 s.print_type_bounds(&bounds);
1244 BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
1246 TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
1247 _ => BadTypePlusSub::ExpectPath { span: sum_span },
1250 self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
1255 pub(super) fn recover_from_prefix_increment(
1257 operand_expr: P<Expr>,
1260 ) -> PResult<'a, P<Expr>> {
1262 if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
1263 let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
1265 self.recover_from_inc_dec(operand_expr, kind, op_span)
1268 pub(super) fn recover_from_postfix_increment(
1270 operand_expr: P<Expr>,
1272 ) -> PResult<'a, P<Expr>> {
1273 let kind = IncDecRecovery {
1274 standalone: IsStandalone::Maybe,
1276 fixity: UnaryFixity::Post,
1279 self.recover_from_inc_dec(operand_expr, kind, op_span)
1282 fn recover_from_inc_dec(
1285 kind: IncDecRecovery,
1287 ) -> PResult<'a, P<Expr>> {
1288 let mut err = self.struct_span_err(
1290 &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
1292 err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
1294 let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
1295 err.help(&format!("use `{}= 1` instead", kind.op.chr()));
1301 let spans = match kind.fixity {
1302 UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
1303 UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
1306 match kind.standalone {
1307 IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
1308 IsStandalone::Subexpr => {
1309 let Ok(base_src) = self.span_to_snippet(base.span)
1310 else { return help_base_case(err, base) };
1312 UnaryFixity::Pre => {
1313 self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1315 UnaryFixity::Post => {
1316 self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1320 IsStandalone::Maybe => {
1321 let Ok(base_src) = self.span_to_snippet(base.span)
1322 else { return help_base_case(err, base) };
1323 let sugg1 = match kind.fixity {
1324 UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
1325 UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
1327 let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
1328 MultiSugg::emit_many(
1330 "use `+= 1` instead",
1331 Applicability::Unspecified,
1332 [sugg1, sugg2].into_iter(),
1339 fn prefix_inc_dec_suggest(
1342 kind: IncDecRecovery,
1343 (pre_span, post_span): (Span, Span),
1346 msg: format!("use `{}= 1` instead", kind.op.chr()),
1348 (pre_span, "{ ".to_string()),
1349 (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
1351 applicability: Applicability::MachineApplicable,
1355 fn postfix_inc_dec_suggest(
1358 kind: IncDecRecovery,
1359 (pre_span, post_span): (Span, Span),
1361 let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
1363 msg: format!("use `{}= 1` instead", kind.op.chr()),
1365 (pre_span, format!("{{ let {tmp_var} = ")),
1366 (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
1368 applicability: Applicability::HasPlaceholders,
1372 fn inc_dec_standalone_suggest(
1374 kind: IncDecRecovery,
1375 (pre_span, post_span): (Span, Span),
1377 let mut patches = Vec::new();
1379 if !pre_span.is_empty() {
1380 patches.push((pre_span, String::new()));
1383 patches.push((post_span, format!(" {}= 1", kind.op.chr())));
1386 msg: format!("use `{}= 1` instead", kind.op.chr()),
1388 applicability: Applicability::MachineApplicable,
1392 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1393 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1394 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1395 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1398 ) -> PResult<'a, P<T>> {
1399 // Do not add `::` to expected tokens.
1400 if self.token == token::ModSep {
1401 if let Some(ty) = base.to_ty() {
1402 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1408 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1409 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1410 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1414 ) -> PResult<'a, P<T>> {
1415 self.expect(&token::ModSep)?;
1417 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1418 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1419 path.span = ty_span.to(self.prev_token.span);
1421 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1422 self.sess.emit_err(BadQPathStage2 {
1424 ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1427 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1428 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1431 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1432 if self.token.kind == TokenKind::Semi {
1436 IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
1438 if !items.is_empty() {
1439 let previous_item = &items[items.len() - 1];
1440 let previous_item_kind_name = match previous_item.kind {
1441 // Say "braced struct" because tuple-structs and
1442 // braceless-empty-struct declarations do take a semicolon.
1443 ItemKind::Struct(..) => Some("braced struct"),
1444 ItemKind::Enum(..) => Some("enum"),
1445 ItemKind::Trait(..) => Some("trait"),
1446 ItemKind::Union(..) => Some("union"),
1449 if let Some(name) = previous_item_kind_name {
1450 err.opt_help = Some(());
1454 self.sess.emit_err(err);
1461 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1462 /// closing delimiter.
1463 pub(super) fn unexpected_try_recover(
1466 ) -> PResult<'a, bool /* recovered */> {
1467 let token_str = pprust::token_kind_to_string(t);
1468 let this_token_str = super::token_descr(&self.token);
1469 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1470 // Point at the end of the macro call when reaching end of macro arguments.
1471 (token::Eof, Some(_)) => {
1472 let sp = self.prev_token.span.shrink_to_hi();
1475 // We don't want to point at the following span after DUMMY_SP.
1476 // This happens when the parser finds an empty TokenStream.
1477 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1478 // EOF, don't want to point at the following char, but rather the last token.
1479 (token::Eof, None) => (self.prev_token.span, self.token.span),
1480 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1483 "expected `{}`, found {}",
1485 match (&self.token.kind, self.subparser_name) {
1486 (token::Eof, Some(origin)) => format!("end of {origin}"),
1487 _ => this_token_str,
1490 let mut err = self.struct_span_err(sp, &msg);
1491 let label_exp = format!("expected `{token_str}`");
1492 match self.recover_closing_delimiter(&[t.clone()], err) {
1495 return Ok(recovered);
1498 let sm = self.sess.source_map();
1499 if !sm.is_multiline(prev_sp.until(sp)) {
1500 // When the spans are in the same line, it means that the only content
1501 // between them is whitespace, point only at the found token.
1502 err.span_label(sp, label_exp);
1504 err.span_label(prev_sp, label_exp);
1505 err.span_label(sp, "unexpected token");
1510 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1511 if self.eat(&token::Semi) {
1514 self.expect(&token::Semi).map(drop) // Error unconditionally
1517 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1518 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1519 pub(super) fn recover_incorrect_await_syntax(
1523 ) -> PResult<'a, P<Expr>> {
1524 let (hi, expr, is_question) = if self.token == token::Not {
1525 // Handle `await!(<expr>)`.
1526 self.recover_await_macro()?
1528 self.recover_await_prefix(await_sp)?
1530 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1531 let kind = match expr.kind {
1532 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1533 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1534 ExprKind::Try(_) => ExprKind::Err,
1535 _ => ExprKind::Await(expr),
1537 let expr = self.mk_expr(lo.to(sp), kind);
1538 self.maybe_recover_from_bad_qpath(expr)
1541 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1542 self.expect(&token::Not)?;
1543 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1544 let expr = self.parse_expr()?;
1545 self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
1546 Ok((self.prev_token.span, expr, false))
1549 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1550 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1551 let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
1552 // Handle `await { <expr> }`.
1553 // This needs to be handled separately from the next arm to avoid
1554 // interpreting `await { <expr> }?` as `<expr>?.await`.
1555 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default)
1559 .map_err(|mut err| {
1560 err.span_label(await_sp, "while parsing this incorrect await expression");
1563 Ok((expr.span, expr, is_question))
1566 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1567 let span = lo.to(hi);
1568 let applicability = match expr.kind {
1569 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1570 _ => Applicability::MachineApplicable,
1573 self.sess.emit_err(IncorrectAwait {
1575 sugg_span: (span, applicability),
1576 expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
1577 question_mark: if is_question { "?" } else { "" },
1583 /// If encountering `future.await()`, consumes and emits an error.
1584 pub(super) fn recover_from_await_method_call(&mut self) {
1585 if self.token == token::OpenDelim(Delimiter::Parenthesis)
1586 && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
1589 let lo = self.token.span;
1591 let span = lo.to(self.token.span);
1594 self.sess.emit_err(IncorrectUseOfAwait { span });
1598 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1599 let is_try = self.token.is_keyword(kw::Try);
1600 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1601 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
1603 if is_try && is_questionmark && is_open {
1604 let lo = self.token.span;
1605 self.bump(); //remove try
1606 self.bump(); //remove !
1607 let try_span = lo.to(self.token.span); //we take the try!( span
1608 self.bump(); //remove (
1609 let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
1610 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
1611 let hi = self.token.span;
1612 self.bump(); //remove )
1613 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1614 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1615 let prefix = if is_empty { "" } else { "alternatively, " };
1617 err.multipart_suggestion(
1618 "you can use the `?` operator instead",
1619 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1620 Applicability::MachineApplicable,
1623 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);
1625 Ok(self.mk_expr_err(lo.to(hi)))
1627 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1631 /// Recovers a situation like `for ( $pat in $expr )`
1632 /// and suggest writing `for $pat in $expr` instead.
1634 /// This should be called before parsing the `$block`.
1635 pub(super) fn recover_parens_around_for_head(
1638 begin_paren: Option<Span>,
1640 match (&self.token.kind, begin_paren) {
1641 (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
1644 self.sess.emit_err(ParenthesesInForHead {
1645 span: vec![begin_par_sp, self.prev_token.span],
1646 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1647 // with `x) in y)` which is syntactically invalid.
1648 // However, this is prevented before we get here.
1649 sugg: ParenthesesInForHeadSugg {
1651 right: self.prev_token.span,
1655 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1656 pat.and_then(|pat| match pat.kind {
1657 PatKind::Paren(pat) => pat,
1665 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1666 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1667 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1668 || self.token.is_ident() &&
1669 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1670 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1671 self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
1672 || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
1673 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1674 self.look_ahead(2, |t| t == &token::Lt) &&
1675 self.look_ahead(3, |t| t.is_ident())
1676 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1677 self.look_ahead(2, |t| t.is_ident())
1678 || self.look_ahead(1, |t| t == &token::ModSep)
1679 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1680 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1683 pub(super) fn recover_seq_parse_error(
1687 result: PResult<'a, P<Expr>>,
1693 // Recover from parse error, callers expect the closing delim to be consumed.
1694 self.consume_block(delim, ConsumeClosingDelim::Yes);
1695 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err)
1700 pub(super) fn recover_closing_delimiter(
1702 tokens: &[TokenKind],
1703 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
1704 ) -> PResult<'a, bool> {
1706 // We want to use the last closing delim that would apply.
1707 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1708 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1709 && Some(self.token.span) > unmatched.unclosed_span
1716 // Recover and assume that the detected unclosed delimiter was meant for
1717 // this location. Emit the diagnostic and act as if the delimiter was
1718 // present for the parser's sake.
1720 // Don't attempt to recover from this unclosed delimiter more than once.
1721 let unmatched = self.unclosed_delims.remove(pos);
1722 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1723 if unmatched.found_delim.is_none() {
1724 // We encountered `Eof`, set this fact here to avoid complaining about missing
1725 // `fn main()` when we found place to suggest the closing brace.
1726 *self.sess.reached_eof.borrow_mut() = true;
1729 // We want to suggest the inclusion of the closing delimiter where it makes
1730 // the most sense, which is immediately after the last token:
1735 // | help: `)` may belong here
1737 // unclosed delimiter
1738 if let Some(sp) = unmatched.unclosed_span {
1739 let mut primary_span: Vec<Span> =
1740 err.span.primary_spans().iter().cloned().collect();
1741 primary_span.push(sp);
1742 let mut primary_span: MultiSpan = primary_span.into();
1743 for span_label in err.span.span_labels() {
1744 if let Some(label) = span_label.label {
1745 primary_span.push_span_label(span_label.span, label);
1748 err.set_span(primary_span);
1749 err.span_label(sp, "unclosed delimiter");
1751 // Backticks should be removed to apply suggestions.
1752 let mut delim = delim.to_string();
1753 delim.retain(|c| c != '`');
1754 err.span_suggestion_short(
1755 self.prev_token.span.shrink_to_hi(),
1756 &format!("`{delim}` may belong here"),
1758 Applicability::MaybeIncorrect,
1760 if unmatched.found_delim.is_none() {
1761 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1762 // errors which would be emitted elsewhere in the parser and let other error
1763 // recovery consume the rest of the file.
1767 self.expected_tokens.clear(); // Reduce the number of errors.
1775 /// Eats tokens until we can be relatively sure we reached the end of the
1776 /// statement. This is something of a best-effort heuristic.
1778 /// We terminate when we find an unmatched `}` (without consuming it).
1779 pub(super) fn recover_stmt(&mut self) {
1780 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1783 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1784 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1785 /// approximate -- it can mean we break too early due to macros, but that
1786 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1788 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1789 /// after finding (and consuming) a brace-delimited block.
1790 pub(super) fn recover_stmt_(
1792 break_on_semi: SemiColonMode,
1793 break_on_block: BlockMode,
1795 let mut brace_depth = 0;
1796 let mut bracket_depth = 0;
1797 let mut in_block = false;
1798 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1800 debug!("recover_stmt_ loop {:?}", self.token);
1801 match self.token.kind {
1802 token::OpenDelim(Delimiter::Brace) => {
1805 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1810 token::OpenDelim(Delimiter::Bracket) => {
1814 token::CloseDelim(Delimiter::Brace) => {
1815 if brace_depth == 0 {
1816 debug!("recover_stmt_ return - close delim {:?}", self.token);
1821 if in_block && bracket_depth == 0 && brace_depth == 0 {
1822 debug!("recover_stmt_ return - block end {:?}", self.token);
1826 token::CloseDelim(Delimiter::Bracket) => {
1828 if bracket_depth < 0 {
1834 debug!("recover_stmt_ return - Eof");
1839 if break_on_semi == SemiColonMode::Break
1841 && bracket_depth == 0
1843 debug!("recover_stmt_ return - Semi");
1848 if break_on_semi == SemiColonMode::Comma
1850 && bracket_depth == 0 =>
1852 debug!("recover_stmt_ return - Semi");
1860 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1861 if self.eat_keyword(kw::In) {
1862 // a common typo: `for _ in in bar {}`
1863 self.sess.emit_err(InInTypo {
1864 span: self.prev_token.span,
1865 sugg_span: in_span.until(self.prev_token.span),
1870 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1871 if let token::DocComment(..) = self.token.kind {
1872 self.sess.emit_err(DocCommentOnParamType { span: self.token.span });
1874 } else if self.token == token::Pound
1875 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
1877 let lo = self.token.span;
1878 // Skip every token until next possible arg.
1879 while self.token != token::CloseDelim(Delimiter::Bracket) {
1882 let sp = lo.to(self.token.span);
1884 self.sess.emit_err(AttributeOnParamType { span: sp });
1888 pub(super) fn parameter_without_type(
1890 err: &mut Diagnostic,
1894 ) -> Option<Ident> {
1895 // If we find a pattern followed by an identifier, it could be an (incorrect)
1896 // C-style parameter declaration.
1897 if self.check_ident()
1898 && self.look_ahead(1, |t| {
1899 *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
1902 // `fn foo(String s) {}`
1903 let ident = self.parse_ident().unwrap();
1904 let span = pat.span.with_hi(ident.span.hi());
1906 err.span_suggestion(
1908 "declare the type after the parameter binding",
1909 "<identifier>: <type>",
1910 Applicability::HasPlaceholders,
1913 } else if require_name
1914 && (self.token == token::Comma
1915 || self.token == token::Lt
1916 || self.token == token::CloseDelim(Delimiter::Parenthesis))
1918 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
1920 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
1922 PatKind::Ident(_, ident, _) => (
1925 ": TypeName".to_string(),
1927 pat.span.shrink_to_lo(),
1928 pat.span.shrink_to_hi(),
1929 pat.span.shrink_to_lo(),
1931 // Also catches `fn foo(&a)`.
1932 PatKind::Ref(ref inner_pat, mutab)
1933 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
1935 match inner_pat.clone().into_inner().kind {
1936 PatKind::Ident(_, ident, _) => {
1937 let mutab = mutab.prefix_str();
1941 format!("{ident}: &{mutab}TypeName"),
1943 pat.span.shrink_to_lo(),
1945 pat.span.shrink_to_lo(),
1948 _ => unreachable!(),
1952 // Otherwise, try to get a type and emit a suggestion.
1953 if let Some(ty) = pat.to_ty() {
1954 err.span_suggestion_verbose(
1956 "explicitly ignore the parameter name",
1957 format!("_: {}", pprust::ty_to_string(&ty)),
1958 Applicability::MachineApplicable,
1967 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1969 err.span_suggestion(
1971 "if this is a `self` type, give it a parameter name",
1973 Applicability::MaybeIncorrect,
1976 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
1977 // `fn foo(HashMap: TypeName<u32>)`.
1978 if self.token != token::Lt {
1979 err.span_suggestion(
1981 "if this is a parameter name, give it a type",
1983 Applicability::HasPlaceholders,
1986 err.span_suggestion(
1988 "if this is a type, explicitly ignore the parameter name",
1990 Applicability::MachineApplicable,
1994 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
1995 return if self.token == token::Lt { None } else { Some(ident) };
2000 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
2001 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
2002 self.expect(&token::Colon)?;
2003 let ty = self.parse_ty()?;
2005 self.sess.emit_err(PatternMethodParamWithoutBody { span: pat.span });
2007 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2009 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
2013 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
2014 let span = param.pat.span;
2015 param.ty.kind = TyKind::Err;
2016 self.sess.emit_err(SelfParamNotFirst { span });
2020 pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
2021 let mut brace_depth = 0;
2023 if self.eat(&token::OpenDelim(delim)) {
2025 } else if self.check(&token::CloseDelim(delim)) {
2026 if brace_depth == 0 {
2027 if let ConsumeClosingDelim::Yes = consume_close {
2028 // Some of the callers of this method expect to be able to parse the
2029 // closing delimiter themselves, so we leave it alone. Otherwise we advance
2039 } else if self.token == token::Eof {
2047 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2048 let (span, msg) = match (&self.token.kind, self.subparser_name) {
2049 (&token::Eof, Some(origin)) => {
2050 let sp = self.prev_token.span.shrink_to_hi();
2051 (sp, format!("expected expression, found end of {origin}"))
2055 format!("expected expression, found {}", super::token_descr(&self.token),),
2058 let mut err = self.struct_span_err(span, &msg);
2059 let sp = self.sess.source_map().start_point(self.token.span);
2060 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
2061 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
2063 err.span_label(span, "expected expression");
2069 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
2070 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
2071 modifier: &[(token::TokenKind, i64)],
2074 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
2077 if self.token.kind == token::Eof {
2084 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
2086 /// This is necessary because at this point we don't know whether we parsed a function with
2087 /// anonymous parameters or a function with names but no types. In order to minimize
2088 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
2089 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
2090 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
2091 /// we deduplicate them to not complain about duplicated parameter names.
2092 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
2093 let mut seen_inputs = FxHashSet::default();
2094 for input in fn_inputs.iter_mut() {
2095 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
2096 (&input.pat.kind, &input.ty.kind)
2102 if let Some(ident) = opt_ident {
2103 if seen_inputs.contains(&ident) {
2104 input.pat.kind = PatKind::Wild;
2106 seen_inputs.insert(ident);
2111 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
2112 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
2113 /// like the user has forgotten them.
2114 pub fn handle_ambiguous_unbraced_const_arg(
2116 args: &mut Vec<AngleBracketedArg>,
2117 ) -> PResult<'a, bool> {
2118 // If we haven't encountered a closing `>`, then the argument is malformed.
2119 // It's likely that the user has written a const expression without enclosing it
2120 // in braces, so we try to recover here.
2121 let arg = args.pop().unwrap();
2122 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
2123 // adverse side-effects to subsequent errors and seems to advance the parser.
2124 // We are causing this error here exclusively in case that a `const` expression
2125 // could be recovered from the current parser state, even if followed by more
2126 // arguments after a comma.
2127 let mut err = self.struct_span_err(
2129 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
2131 err.span_label(self.token.span, "expected one of `,` or `>`");
2132 match self.recover_const_arg(arg.span(), err) {
2134 args.push(AngleBracketedArg::Arg(arg));
2135 if self.eat(&token::Comma) {
2136 return Ok(true); // Continue
2141 // We will emit a more generic error later.
2145 return Ok(false); // Don't continue.
2148 /// Attempt to parse a generic const argument that has not been enclosed in braces.
2149 /// There are a limited number of expressions that are permitted without being encoded
2152 /// - Single-segment paths (i.e. standalone generic const parameters).
2153 /// All other expressions that can be parsed will emit an error suggesting the expression be
2154 /// wrapped in braces.
2155 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
2156 let start = self.token.span;
2157 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
2159 start.shrink_to_lo(),
2160 "while parsing a const generic argument starting here",
2164 if !self.expr_is_valid_const_arg(&expr) {
2165 self.sess.emit_err(ConstGenericWithoutBraces {
2167 sugg: ConstGenericWithoutBracesSugg {
2168 left: expr.span.shrink_to_lo(),
2169 right: expr.span.shrink_to_hi(),
2176 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2177 let snapshot = self.create_snapshot_for_diagnostic();
2178 let param = match self.parse_const_param(AttrVec::new()) {
2182 self.restore_snapshot(snapshot);
2187 let ident = param.ident.to_string();
2188 let sugg = match (ty_generics, self.sess.source_map().span_to_snippet(param.span())) {
2189 (Some(Generics { params, span: impl_generics, .. }), Ok(snippet)) => {
2190 Some(match ¶ms[..] {
2191 [] => UnexpectedConstParamDeclarationSugg::AddParam {
2192 impl_generics: *impl_generics,
2193 incorrect_decl: param.span(),
2197 [.., generic] => UnexpectedConstParamDeclarationSugg::AppendParam {
2198 impl_generics_end: generic.span().shrink_to_hi(),
2199 incorrect_decl: param.span(),
2207 self.sess.emit_err(UnexpectedConstParamDeclaration { span: param.span(), sugg });
2209 let value = self.mk_expr_err(param.span());
2210 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2213 pub fn recover_const_param_declaration(
2215 ty_generics: Option<&Generics>,
2216 ) -> PResult<'a, Option<GenericArg>> {
2217 // We have to check for a few different cases.
2218 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2219 return Ok(Some(arg));
2222 // We haven't consumed `const` yet.
2223 let start = self.token.span;
2224 self.bump(); // `const`
2226 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2227 let mut err = UnexpectedConstInGenericParam { span: start, to_remove: None };
2228 if self.check_const_arg() {
2229 err.to_remove = Some(start.until(self.token.span));
2230 self.sess.emit_err(err);
2231 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2233 let after_kw_const = self.token.span;
2234 self.recover_const_arg(after_kw_const, err.into_diagnostic(&self.sess.span_diagnostic))
2239 /// Try to recover from possible generic const argument without `{` and `}`.
2241 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2242 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2243 /// if we think that the resulting expression would be well formed.
2244 pub fn recover_const_arg(
2247 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2248 ) -> PResult<'a, GenericArg> {
2249 let is_op_or_dot = AssocOp::from_token(&self.token)
2251 if let AssocOp::Greater
2253 | AssocOp::ShiftRight
2254 | AssocOp::GreaterEqual
2255 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2256 // assign a value to a defaulted generic parameter.
2258 | AssocOp::AssignOp(_) = op
2266 || self.token.kind == TokenKind::Dot;
2267 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2268 // type params has been parsed.
2270 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2271 if !is_op_or_dot && !was_op {
2272 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2275 let snapshot = self.create_snapshot_for_diagnostic();
2279 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2281 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2282 if token::EqEq == snapshot.token.kind {
2283 err.span_suggestion(
2284 snapshot.token.span,
2285 "if you meant to use an associated type binding, replace `==` with `=`",
2287 Applicability::MaybeIncorrect,
2289 let value = self.mk_expr_err(start.to(expr.span));
2291 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2292 } else if token::Colon == snapshot.token.kind
2293 && expr.span.lo() == snapshot.token.span.hi()
2294 && matches!(expr.kind, ExprKind::Path(..))
2296 // Find a mistake like "foo::var:A".
2297 err.span_suggestion(
2298 snapshot.token.span,
2299 "write a path separator here",
2301 Applicability::MaybeIncorrect,
2304 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2305 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2307 // Avoid the following output by checking that we consumed a full const arg:
2308 // help: expressions must be enclosed in braces to be used as const generic
2311 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2313 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2320 self.restore_snapshot(snapshot);
2324 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2325 pub fn dummy_const_arg_needs_braces(
2327 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2330 err.multipart_suggestion(
2331 "expressions must be enclosed in braces to be used as const generic \
2333 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2334 Applicability::MaybeIncorrect,
2336 let value = self.mk_expr_err(span);
2338 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2341 /// Some special error handling for the "top-level" patterns in a match arm,
2342 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2343 pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
2345 mut first_pat: P<Pat>,
2348 if token::Colon != self.token.kind {
2351 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2352 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2356 // The pattern looks like it might be a path with a `::` -> `:` typo:
2357 // `match foo { bar:baz => {} }`
2358 let span = self.token.span;
2359 // We only emit "unexpected `:`" error here if we can successfully parse the
2360 // whole pattern correctly in that case.
2361 let snapshot = self.create_snapshot_for_diagnostic();
2363 // Create error for "unexpected `:`".
2364 match self.expected_one_of_not_found(&[], &[]) {
2366 self.bump(); // Skip the `:`.
2367 match self.parse_pat_no_top_alt(expected) {
2369 // Carry on as if we had not done anything, callers will emit a
2370 // reasonable error.
2373 self.restore_snapshot(snapshot);
2376 // We've parsed the rest of the pattern.
2377 let new_span = first_pat.span.to(pat.span);
2378 let mut show_sugg = false;
2379 // Try to construct a recovered pattern.
2380 match &mut pat.kind {
2381 PatKind::Struct(qself @ None, path, ..)
2382 | PatKind::TupleStruct(qself @ None, path, _)
2383 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2384 PatKind::Ident(_, ident, _) => {
2385 path.segments.insert(0, PathSegment::from_ident(*ident));
2386 path.span = new_span;
2390 PatKind::Path(old_qself, old_path) => {
2391 path.segments = old_path
2395 .chain(take(&mut path.segments))
2397 path.span = new_span;
2398 *qself = old_qself.clone();
2404 PatKind::Ident(BindingAnnotation::NONE, ident, None) => {
2405 match &first_pat.kind {
2406 PatKind::Ident(_, old_ident, _) => {
2407 let path = PatKind::Path(
2412 PathSegment::from_ident(*old_ident),
2413 PathSegment::from_ident(*ident),
2418 first_pat = self.mk_pat(new_span, path);
2421 PatKind::Path(old_qself, old_path) => {
2422 let mut segments = old_path.segments.clone();
2423 segments.push(PathSegment::from_ident(*ident));
2424 let path = PatKind::Path(
2426 Path { span: new_span, segments, tokens: None },
2428 first_pat = self.mk_pat(new_span, path);
2437 err.span_suggestion(
2439 "maybe write a path separator here",
2441 Applicability::MaybeIncorrect,
2444 first_pat = self.mk_pat(new_span, PatKind::Wild);
2451 // Carry on as if we had not done anything. This should be unreachable.
2452 self.restore_snapshot(snapshot);
2458 pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
2459 let Some(label) = self.eat_label().filter(|_| {
2460 self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
2464 let span = label.ident.span.to(self.prev_token.span);
2465 let mut err = self.struct_span_err(span, "block label not supported here");
2466 err.span_label(span, "not supported here");
2467 err.tool_only_span_suggestion(
2468 label.ident.span.until(self.token.span),
2469 "remove this block label",
2471 Applicability::MachineApplicable,
2477 /// Some special error handling for the "top-level" patterns in a match arm,
2478 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2479 pub(crate) fn maybe_recover_unexpected_comma(
2482 rt: CommaRecoveryMode,
2483 ) -> PResult<'a, ()> {
2484 if self.token != token::Comma {
2488 // An unexpected comma after a top-level pattern is a clue that the
2489 // user (perhaps more accustomed to some other language) forgot the
2490 // parentheses in what should have been a tuple pattern; return a
2491 // suggestion-enhanced error here rather than choking on the comma later.
2492 let comma_span = self.token.span;
2494 if let Err(err) = self.skip_pat_list() {
2495 // We didn't expect this to work anyway; we just wanted to advance to the
2496 // end of the comma-sequence so we know the span to suggest parenthesizing.
2499 let seq_span = lo.to(self.prev_token.span);
2500 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2501 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2502 err.multipart_suggestion(
2504 "try adding parentheses to match on a tuple{}",
2505 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
2508 (seq_span.shrink_to_lo(), "(".to_string()),
2509 (seq_span.shrink_to_hi(), ")".to_string()),
2511 Applicability::MachineApplicable,
2513 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
2514 err.span_suggestion(
2516 "...or a vertical bar to match on multiple alternatives",
2517 seq_snippet.replace(',', " |"),
2518 Applicability::MachineApplicable,
2525 pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
2526 let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
2527 let qself_position = qself.as_ref().map(|qself| qself.position);
2528 for (i, segments) in path.segments.windows(2).enumerate() {
2529 if qself_position.map(|pos| i < pos).unwrap_or(false) {
2532 if let [a, b] = segments {
2533 let (a_span, b_span) = (a.span(), b.span());
2534 let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
2535 if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
2536 return Err(DoubleColonInBound {
2537 span: path.span.shrink_to_hi(),
2538 between: between_span,
2540 .into_diagnostic(&self.sess.span_diagnostic));
2547 /// Parse and throw away a parenthesized comma separated
2548 /// sequence of patterns until `)` is reached.
2549 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2550 while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
2551 self.parse_pat_no_top_alt(None)?;
2552 if !self.eat(&token::Comma) {