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 if !self.may_recover() {
776 // This function is intended to be invoked after parsing a path segment where there are two
779 // 1. A specific token is expected after the path segment.
780 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
781 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
782 // 2. No specific token is expected after the path segment.
783 // eg. `x.foo` (field access)
785 // This function is called after parsing `.foo` and before parsing the token `end` (if
786 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
789 // We only care about trailing angle brackets if we previously parsed angle bracket
790 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
791 // removed in this case:
793 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
795 // This case is particularly tricky as we won't notice it just looking at the tokens -
796 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
797 // have already been parsed):
799 // `x.foo::<u32>>>(3)`
800 let parsed_angle_bracket_args =
801 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
804 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
805 parsed_angle_bracket_args,
807 if !parsed_angle_bracket_args {
811 // Keep the span at the start so we can highlight the sequence of `>` characters to be
813 let lo = self.token.span;
815 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
816 // (since we might have the field access case and the characters we're eating are
817 // actual operators and not trailing characters - ie `x.foo >> 3`).
818 let mut position = 0;
820 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
821 // many of each (so we can correctly pluralize our error messages) and continue to
823 let mut number_of_shr = 0;
824 let mut number_of_gt = 0;
825 while self.look_ahead(position, |t| {
826 trace!("check_trailing_angle_brackets: t={:?}", t);
827 if *t == token::BinOp(token::BinOpToken::Shr) {
830 } else if *t == token::Gt {
840 // If we didn't find any trailing `>` characters, then we have nothing to error about.
842 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
843 number_of_gt, number_of_shr,
845 if number_of_gt < 1 && number_of_shr < 1 {
849 // Finally, double check that we have our end token as otherwise this is the
851 if self.look_ahead(position, |t| {
852 trace!("check_trailing_angle_brackets: t={:?}", t);
853 end.contains(&&t.kind)
855 // Eat from where we started until the end token so that parsing can continue
856 // as if we didn't have those extra angle brackets.
857 self.eat_to_tokens(end);
858 let span = lo.until(self.token.span);
860 let num_extra_brackets = number_of_gt + number_of_shr * 2;
861 self.sess.emit_err(UnmatchedAngleBrackets { span, num_extra_brackets });
867 /// Check if a method call with an intended turbofish has been written without surrounding
869 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
870 if !self.may_recover() {
874 if token::ModSep == self.token.kind && segment.args.is_none() {
875 let snapshot = self.create_snapshot_for_diagnostic();
877 let lo = self.token.span;
878 match self.parse_angle_args(None) {
880 let span = lo.to(self.prev_token.span);
881 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
882 let mut trailing_span = self.prev_token.span.shrink_to_hi();
883 while self.token.kind == token::BinOp(token::Shr)
884 || self.token.kind == token::Gt
886 trailing_span = trailing_span.to(self.token.span);
889 if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
890 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
891 let args = AngleBracketedArgs { args, span }.into();
894 self.sess.emit_err(GenericParamsWithoutAngleBrackets {
896 sugg: GenericParamsWithoutAngleBracketsSugg {
897 left: span.shrink_to_lo(),
898 right: trailing_span,
902 // This doesn't look like an invalid turbofish, can't recover parse state.
903 self.restore_snapshot(snapshot);
907 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
908 // generic parse error instead.
910 self.restore_snapshot(snapshot);
916 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
917 /// encounter a parse error when encountering the first `,`.
918 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
920 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
922 ) -> PResult<'a, ()> {
923 if let ExprKind::Binary(binop, _, _) = &expr.kind
924 && let ast::BinOpKind::Lt = binop.node
925 && self.eat(&token::Comma)
927 let x = self.parse_seq_to_before_end(
929 SeqSep::trailing_allowed(token::Comma),
930 |p| p.parse_generic_arg(None),
933 Ok((_, _, false)) => {
934 if self.eat(&token::Gt) {
935 e.span_suggestion_verbose(
936 binop.span.shrink_to_lo(),
937 fluent::parser_sugg_turbofish_syntax,
939 Applicability::MaybeIncorrect,
942 match self.parse_expr() {
945 self.mk_expr_err(expr.span.to(self.prev_token.span));
949 *expr = self.mk_expr_err(expr.span);
964 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
965 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
966 /// parenthesising the leftmost comparison.
967 fn attempt_chained_comparison_suggestion(
969 err: &mut ComparisonOperatorsCannotBeChained,
971 outer_op: &Spanned<AssocOp>,
972 ) -> bool /* advanced the cursor */ {
973 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
974 if let ExprKind::Field(_, ident) = l1.kind
975 && ident.as_str().parse::<i32>().is_err()
976 && !matches!(r1.kind, ExprKind::Lit(_))
978 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
979 // suggestion being the only one to apply is high.
982 return match (op.node, &outer_op.node) {
984 (BinOpKind::Eq, AssocOp::Equal) |
985 // `x < y < z` and friends.
986 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
987 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
988 // `x > y > z` and friends.
989 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
990 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
991 let expr_to_str = |e: &Expr| {
992 self.span_to_snippet(e.span)
993 .unwrap_or_else(|_| pprust::expr_to_string(&e))
995 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::SplitComparison {
996 span: inner_op.span.shrink_to_hi(),
997 middle_term: expr_to_str(&r1),
999 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
1002 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
1003 // Consume `z`/outer-op-rhs.
1004 let snapshot = self.create_snapshot_for_diagnostic();
1005 match self.parse_expr() {
1007 // We are sure that outer-op-rhs could be consumed, the suggestion is
1009 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1010 left: r1.span.shrink_to_lo(),
1011 right: r2.span.shrink_to_hi(),
1017 self.restore_snapshot(snapshot);
1023 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
1024 let snapshot = self.create_snapshot_for_diagnostic();
1025 // At this point it is always valid to enclose the lhs in parentheses, no
1026 // further checks are necessary.
1027 match self.parse_expr() {
1029 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1030 left: l1.span.shrink_to_lo(),
1031 right: r1.span.shrink_to_hi(),
1037 self.restore_snapshot(snapshot);
1048 /// Produces an error if comparison operators are chained (RFC #558).
1049 /// We only need to check the LHS, not the RHS, because all comparison ops have same
1050 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
1052 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
1053 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
1056 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
1057 /// associative we can infer that we have:
1066 pub(super) fn check_no_chained_comparison(
1069 outer_op: &Spanned<AssocOp>,
1070 ) -> PResult<'a, Option<P<Expr>>> {
1072 outer_op.node.is_comparison(),
1073 "check_no_chained_comparison: {:?} is not comparison",
1077 let mk_err_expr = |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err)));
1079 match inner_op.kind {
1080 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
1081 let mut err = ComparisonOperatorsCannotBeChained {
1082 span: vec![op.span, self.prev_token.span],
1083 suggest_turbofish: None,
1084 help_turbofish: None,
1085 chaining_sugg: None,
1088 // Include `<` to provide this recommendation even in a case like
1089 // `Foo<Bar<Baz<Qux, ()>>>`
1090 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
1091 || outer_op.node == AssocOp::Greater
1093 if outer_op.node == AssocOp::Less {
1094 let snapshot = self.create_snapshot_for_diagnostic();
1096 // So far we have parsed `foo<bar<`, consume the rest of the type args.
1098 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
1099 self.consume_tts(1, &modifiers);
1101 if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
1102 .contains(&self.token.kind)
1104 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
1105 // parser and bail out.
1106 self.restore_snapshot(snapshot);
1109 return if token::ModSep == self.token.kind {
1110 // We have some certainty that this was a bad turbofish at this point.
1112 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1114 let snapshot = self.create_snapshot_for_diagnostic();
1115 self.bump(); // `::`
1117 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
1118 match self.parse_expr() {
1120 // 99% certain that the suggestion is correct, continue parsing.
1121 self.sess.emit_err(err);
1122 // FIXME: actually check that the two expressions in the binop are
1123 // paths and resynthesize new fn call expression instead of using
1124 // `ExprKind::Err` placeholder.
1125 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1129 // Not entirely sure now, but we bubble the error up with the
1131 self.restore_snapshot(snapshot);
1132 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1135 } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
1136 // We have high certainty that this was a bad turbofish at this point.
1138 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1139 // Consume the fn call arguments.
1140 match self.consume_fn_args() {
1141 Err(()) => Err(err.into_diagnostic(&self.sess.span_diagnostic)),
1143 self.sess.emit_err(err);
1144 // FIXME: actually check that the two expressions in the binop are
1145 // paths and resynthesize new fn call expression instead of using
1146 // `ExprKind::Err` placeholder.
1147 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1151 if !matches!(l1.kind, ExprKind::Lit(_))
1152 && !matches!(r1.kind, ExprKind::Lit(_))
1154 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1155 // be helpful, but don't attempt to recover.
1156 err.help_turbofish = Some(());
1159 // If it looks like a genuine attempt to chain operators (as opposed to a
1160 // misformatted turbofish, for instance), suggest a correct form.
1161 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1163 self.sess.emit_err(err);
1164 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1166 // These cases cause too many knock-down errors, bail out (#61329).
1167 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1172 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1173 self.sess.emit_err(err);
1175 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1183 fn consume_fn_args(&mut self) -> Result<(), ()> {
1184 let snapshot = self.create_snapshot_for_diagnostic();
1187 // Consume the fn call arguments.
1189 (token::OpenDelim(Delimiter::Parenthesis), 1),
1190 (token::CloseDelim(Delimiter::Parenthesis), -1),
1192 self.consume_tts(1, &modifiers);
1194 if self.token.kind == token::Eof {
1195 // Not entirely sure that what we consumed were fn arguments, rollback.
1196 self.restore_snapshot(snapshot);
1199 // 99% certain that the suggestion is correct, continue parsing.
1204 pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
1206 self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
1210 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1211 pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
1212 if self.token == token::Question {
1214 self.sess.emit_err(QuestionMarkInType {
1215 span: self.prev_token.span,
1216 sugg: QuestionMarkInTypeSugg {
1217 left: ty.span.shrink_to_lo(),
1218 right: self.prev_token.span,
1221 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1227 pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
1228 // Do not add `+` to expected tokens.
1229 if !self.token.is_like_plus() {
1234 let bounds = self.parse_generic_bounds(None)?;
1235 let sum_span = ty.span.to(self.prev_token.span);
1237 let sub = match ty.kind {
1238 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1239 let sum_with_parens = pprust::to_string(|s| {
1241 s.print_opt_lifetime(lifetime);
1242 s.print_mutability(mut_ty.mutbl, false);
1244 s.print_type(&mut_ty.ty);
1245 if !bounds.is_empty() {
1247 s.print_type_bounds(&bounds);
1252 BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
1254 TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
1255 _ => BadTypePlusSub::ExpectPath { span: sum_span },
1258 self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
1263 pub(super) fn recover_from_prefix_increment(
1265 operand_expr: P<Expr>,
1268 ) -> PResult<'a, P<Expr>> {
1270 if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
1271 let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
1273 self.recover_from_inc_dec(operand_expr, kind, op_span)
1276 pub(super) fn recover_from_postfix_increment(
1278 operand_expr: P<Expr>,
1280 ) -> PResult<'a, P<Expr>> {
1281 let kind = IncDecRecovery {
1282 standalone: IsStandalone::Maybe,
1284 fixity: UnaryFixity::Post,
1287 self.recover_from_inc_dec(operand_expr, kind, op_span)
1290 fn recover_from_inc_dec(
1293 kind: IncDecRecovery,
1295 ) -> PResult<'a, P<Expr>> {
1296 let mut err = self.struct_span_err(
1298 &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
1300 err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
1302 let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
1303 err.help(&format!("use `{}= 1` instead", kind.op.chr()));
1309 let spans = match kind.fixity {
1310 UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
1311 UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
1314 match kind.standalone {
1315 IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
1316 IsStandalone::Subexpr => {
1317 let Ok(base_src) = self.span_to_snippet(base.span)
1318 else { return help_base_case(err, base) };
1320 UnaryFixity::Pre => {
1321 self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1323 UnaryFixity::Post => {
1324 self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1328 IsStandalone::Maybe => {
1329 let Ok(base_src) = self.span_to_snippet(base.span)
1330 else { return help_base_case(err, base) };
1331 let sugg1 = match kind.fixity {
1332 UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
1333 UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
1335 let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
1336 MultiSugg::emit_many(
1338 "use `+= 1` instead",
1339 Applicability::Unspecified,
1340 [sugg1, sugg2].into_iter(),
1347 fn prefix_inc_dec_suggest(
1350 kind: IncDecRecovery,
1351 (pre_span, post_span): (Span, Span),
1354 msg: format!("use `{}= 1` instead", kind.op.chr()),
1356 (pre_span, "{ ".to_string()),
1357 (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
1359 applicability: Applicability::MachineApplicable,
1363 fn postfix_inc_dec_suggest(
1366 kind: IncDecRecovery,
1367 (pre_span, post_span): (Span, Span),
1369 let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
1371 msg: format!("use `{}= 1` instead", kind.op.chr()),
1373 (pre_span, format!("{{ let {tmp_var} = ")),
1374 (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
1376 applicability: Applicability::HasPlaceholders,
1380 fn inc_dec_standalone_suggest(
1382 kind: IncDecRecovery,
1383 (pre_span, post_span): (Span, Span),
1385 let mut patches = Vec::new();
1387 if !pre_span.is_empty() {
1388 patches.push((pre_span, String::new()));
1391 patches.push((post_span, format!(" {}= 1", kind.op.chr())));
1394 msg: format!("use `{}= 1` instead", kind.op.chr()),
1396 applicability: Applicability::MachineApplicable,
1400 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1401 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1402 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1403 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1406 ) -> PResult<'a, P<T>> {
1407 if !self.may_recover() {
1411 // Do not add `::` to expected tokens.
1412 if self.token == token::ModSep {
1413 if let Some(ty) = base.to_ty() {
1414 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1420 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1421 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1422 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1426 ) -> PResult<'a, P<T>> {
1427 self.expect(&token::ModSep)?;
1429 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1430 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1431 path.span = ty_span.to(self.prev_token.span);
1433 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1434 self.sess.emit_err(BadQPathStage2 {
1436 ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1439 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1440 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1443 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1444 if self.token.kind == TokenKind::Semi {
1448 IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
1450 if !items.is_empty() {
1451 let previous_item = &items[items.len() - 1];
1452 let previous_item_kind_name = match previous_item.kind {
1453 // Say "braced struct" because tuple-structs and
1454 // braceless-empty-struct declarations do take a semicolon.
1455 ItemKind::Struct(..) => Some("braced struct"),
1456 ItemKind::Enum(..) => Some("enum"),
1457 ItemKind::Trait(..) => Some("trait"),
1458 ItemKind::Union(..) => Some("union"),
1461 if let Some(name) = previous_item_kind_name {
1462 err.opt_help = Some(());
1466 self.sess.emit_err(err);
1473 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1474 /// closing delimiter.
1475 pub(super) fn unexpected_try_recover(
1478 ) -> PResult<'a, bool /* recovered */> {
1479 let token_str = pprust::token_kind_to_string(t);
1480 let this_token_str = super::token_descr(&self.token);
1481 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1482 // Point at the end of the macro call when reaching end of macro arguments.
1483 (token::Eof, Some(_)) => {
1484 let sp = self.prev_token.span.shrink_to_hi();
1487 // We don't want to point at the following span after DUMMY_SP.
1488 // This happens when the parser finds an empty TokenStream.
1489 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1490 // EOF, don't want to point at the following char, but rather the last token.
1491 (token::Eof, None) => (self.prev_token.span, self.token.span),
1492 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1495 "expected `{}`, found {}",
1497 match (&self.token.kind, self.subparser_name) {
1498 (token::Eof, Some(origin)) => format!("end of {origin}"),
1499 _ => this_token_str,
1502 let mut err = self.struct_span_err(sp, &msg);
1503 let label_exp = format!("expected `{token_str}`");
1504 match self.recover_closing_delimiter(&[t.clone()], err) {
1507 return Ok(recovered);
1510 let sm = self.sess.source_map();
1511 if !sm.is_multiline(prev_sp.until(sp)) {
1512 // When the spans are in the same line, it means that the only content
1513 // between them is whitespace, point only at the found token.
1514 err.span_label(sp, label_exp);
1516 err.span_label(prev_sp, label_exp);
1517 err.span_label(sp, "unexpected token");
1522 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1523 if self.eat(&token::Semi) {
1526 self.expect(&token::Semi).map(drop) // Error unconditionally
1529 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1530 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1531 pub(super) fn recover_incorrect_await_syntax(
1535 ) -> PResult<'a, P<Expr>> {
1536 let (hi, expr, is_question) = if self.token == token::Not {
1537 // Handle `await!(<expr>)`.
1538 self.recover_await_macro()?
1540 self.recover_await_prefix(await_sp)?
1542 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1543 let kind = match expr.kind {
1544 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1545 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1546 ExprKind::Try(_) => ExprKind::Err,
1547 _ => ExprKind::Await(expr),
1549 let expr = self.mk_expr(lo.to(sp), kind);
1550 self.maybe_recover_from_bad_qpath(expr)
1553 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1554 self.expect(&token::Not)?;
1555 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1556 let expr = self.parse_expr()?;
1557 self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
1558 Ok((self.prev_token.span, expr, false))
1561 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1562 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1563 let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
1564 // Handle `await { <expr> }`.
1565 // This needs to be handled separately from the next arm to avoid
1566 // interpreting `await { <expr> }?` as `<expr>?.await`.
1567 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default)
1571 .map_err(|mut err| {
1572 err.span_label(await_sp, "while parsing this incorrect await expression");
1575 Ok((expr.span, expr, is_question))
1578 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1579 let span = lo.to(hi);
1580 let applicability = match expr.kind {
1581 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1582 _ => Applicability::MachineApplicable,
1585 self.sess.emit_err(IncorrectAwait {
1587 sugg_span: (span, applicability),
1588 expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
1589 question_mark: if is_question { "?" } else { "" },
1595 /// If encountering `future.await()`, consumes and emits an error.
1596 pub(super) fn recover_from_await_method_call(&mut self) {
1597 if self.token == token::OpenDelim(Delimiter::Parenthesis)
1598 && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
1601 let lo = self.token.span;
1603 let span = lo.to(self.token.span);
1606 self.sess.emit_err(IncorrectUseOfAwait { span });
1610 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1611 let is_try = self.token.is_keyword(kw::Try);
1612 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1613 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
1615 if is_try && is_questionmark && is_open {
1616 let lo = self.token.span;
1617 self.bump(); //remove try
1618 self.bump(); //remove !
1619 let try_span = lo.to(self.token.span); //we take the try!( span
1620 self.bump(); //remove (
1621 let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
1622 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
1623 let hi = self.token.span;
1624 self.bump(); //remove )
1625 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1626 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1627 let prefix = if is_empty { "" } else { "alternatively, " };
1629 err.multipart_suggestion(
1630 "you can use the `?` operator instead",
1631 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1632 Applicability::MachineApplicable,
1635 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);
1637 Ok(self.mk_expr_err(lo.to(hi)))
1639 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1643 /// Recovers a situation like `for ( $pat in $expr )`
1644 /// and suggest writing `for $pat in $expr` instead.
1646 /// This should be called before parsing the `$block`.
1647 pub(super) fn recover_parens_around_for_head(
1650 begin_paren: Option<Span>,
1652 match (&self.token.kind, begin_paren) {
1653 (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
1656 let sm = self.sess.source_map();
1657 let left = begin_par_sp;
1658 let right = self.prev_token.span;
1659 let left_snippet = if let Ok(snip) = sm.span_to_prev_source(left) &&
1660 !snip.ends_with(" ") {
1666 let right_snippet = if let Ok(snip) = sm.span_to_next_source(right) &&
1667 !snip.starts_with(" ") {
1673 self.sess.emit_err(ParenthesesInForHead {
1674 span: vec![left, right],
1675 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1676 // with `x) in y)` which is syntactically invalid.
1677 // However, this is prevented before we get here.
1678 sugg: ParenthesesInForHeadSugg { left, right, left_snippet, right_snippet },
1681 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1682 pat.and_then(|pat| match pat.kind {
1683 PatKind::Paren(pat) => pat,
1691 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1692 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1693 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1694 || self.token.is_ident() &&
1695 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1696 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1697 self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
1698 || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
1699 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1700 self.look_ahead(2, |t| t == &token::Lt) &&
1701 self.look_ahead(3, |t| t.is_ident())
1702 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1703 self.look_ahead(2, |t| t.is_ident())
1704 || self.look_ahead(1, |t| t == &token::ModSep)
1705 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1706 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1709 pub(super) fn recover_seq_parse_error(
1713 result: PResult<'a, P<Expr>>,
1719 // Recover from parse error, callers expect the closing delim to be consumed.
1720 self.consume_block(delim, ConsumeClosingDelim::Yes);
1721 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err)
1726 pub(super) fn recover_closing_delimiter(
1728 tokens: &[TokenKind],
1729 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
1730 ) -> PResult<'a, bool> {
1732 // We want to use the last closing delim that would apply.
1733 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1734 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1735 && Some(self.token.span) > unmatched.unclosed_span
1742 // Recover and assume that the detected unclosed delimiter was meant for
1743 // this location. Emit the diagnostic and act as if the delimiter was
1744 // present for the parser's sake.
1746 // Don't attempt to recover from this unclosed delimiter more than once.
1747 let unmatched = self.unclosed_delims.remove(pos);
1748 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1749 if unmatched.found_delim.is_none() {
1750 // We encountered `Eof`, set this fact here to avoid complaining about missing
1751 // `fn main()` when we found place to suggest the closing brace.
1752 *self.sess.reached_eof.borrow_mut() = true;
1755 // We want to suggest the inclusion of the closing delimiter where it makes
1756 // the most sense, which is immediately after the last token:
1761 // | help: `)` may belong here
1763 // unclosed delimiter
1764 if let Some(sp) = unmatched.unclosed_span {
1765 let mut primary_span: Vec<Span> =
1766 err.span.primary_spans().iter().cloned().collect();
1767 primary_span.push(sp);
1768 let mut primary_span: MultiSpan = primary_span.into();
1769 for span_label in err.span.span_labels() {
1770 if let Some(label) = span_label.label {
1771 primary_span.push_span_label(span_label.span, label);
1774 err.set_span(primary_span);
1775 err.span_label(sp, "unclosed delimiter");
1777 // Backticks should be removed to apply suggestions.
1778 let mut delim = delim.to_string();
1779 delim.retain(|c| c != '`');
1780 err.span_suggestion_short(
1781 self.prev_token.span.shrink_to_hi(),
1782 &format!("`{delim}` may belong here"),
1784 Applicability::MaybeIncorrect,
1786 if unmatched.found_delim.is_none() {
1787 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1788 // errors which would be emitted elsewhere in the parser and let other error
1789 // recovery consume the rest of the file.
1793 self.expected_tokens.clear(); // Reduce the number of errors.
1801 /// Eats tokens until we can be relatively sure we reached the end of the
1802 /// statement. This is something of a best-effort heuristic.
1804 /// We terminate when we find an unmatched `}` (without consuming it).
1805 pub(super) fn recover_stmt(&mut self) {
1806 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1809 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1810 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1811 /// approximate -- it can mean we break too early due to macros, but that
1812 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1814 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1815 /// after finding (and consuming) a brace-delimited block.
1816 pub(super) fn recover_stmt_(
1818 break_on_semi: SemiColonMode,
1819 break_on_block: BlockMode,
1821 let mut brace_depth = 0;
1822 let mut bracket_depth = 0;
1823 let mut in_block = false;
1824 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1826 debug!("recover_stmt_ loop {:?}", self.token);
1827 match self.token.kind {
1828 token::OpenDelim(Delimiter::Brace) => {
1831 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1836 token::OpenDelim(Delimiter::Bracket) => {
1840 token::CloseDelim(Delimiter::Brace) => {
1841 if brace_depth == 0 {
1842 debug!("recover_stmt_ return - close delim {:?}", self.token);
1847 if in_block && bracket_depth == 0 && brace_depth == 0 {
1848 debug!("recover_stmt_ return - block end {:?}", self.token);
1852 token::CloseDelim(Delimiter::Bracket) => {
1854 if bracket_depth < 0 {
1860 debug!("recover_stmt_ return - Eof");
1865 if break_on_semi == SemiColonMode::Break
1867 && bracket_depth == 0
1869 debug!("recover_stmt_ return - Semi");
1874 if break_on_semi == SemiColonMode::Comma
1876 && bracket_depth == 0 =>
1878 debug!("recover_stmt_ return - Semi");
1886 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1887 if self.eat_keyword(kw::In) {
1888 // a common typo: `for _ in in bar {}`
1889 self.sess.emit_err(InInTypo {
1890 span: self.prev_token.span,
1891 sugg_span: in_span.until(self.prev_token.span),
1896 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1897 if let token::DocComment(..) = self.token.kind {
1898 self.sess.emit_err(DocCommentOnParamType { span: self.token.span });
1900 } else if self.token == token::Pound
1901 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
1903 let lo = self.token.span;
1904 // Skip every token until next possible arg.
1905 while self.token != token::CloseDelim(Delimiter::Bracket) {
1908 let sp = lo.to(self.token.span);
1910 self.sess.emit_err(AttributeOnParamType { span: sp });
1914 pub(super) fn parameter_without_type(
1916 err: &mut Diagnostic,
1920 ) -> Option<Ident> {
1921 // If we find a pattern followed by an identifier, it could be an (incorrect)
1922 // C-style parameter declaration.
1923 if self.check_ident()
1924 && self.look_ahead(1, |t| {
1925 *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
1928 // `fn foo(String s) {}`
1929 let ident = self.parse_ident().unwrap();
1930 let span = pat.span.with_hi(ident.span.hi());
1932 err.span_suggestion(
1934 "declare the type after the parameter binding",
1935 "<identifier>: <type>",
1936 Applicability::HasPlaceholders,
1939 } else if require_name
1940 && (self.token == token::Comma
1941 || self.token == token::Lt
1942 || self.token == token::CloseDelim(Delimiter::Parenthesis))
1944 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
1946 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
1948 PatKind::Ident(_, ident, _) => (
1951 ": TypeName".to_string(),
1953 pat.span.shrink_to_lo(),
1954 pat.span.shrink_to_hi(),
1955 pat.span.shrink_to_lo(),
1957 // Also catches `fn foo(&a)`.
1958 PatKind::Ref(ref inner_pat, mutab)
1959 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
1961 match inner_pat.clone().into_inner().kind {
1962 PatKind::Ident(_, ident, _) => {
1963 let mutab = mutab.prefix_str();
1967 format!("{ident}: &{mutab}TypeName"),
1969 pat.span.shrink_to_lo(),
1971 pat.span.shrink_to_lo(),
1974 _ => unreachable!(),
1978 // Otherwise, try to get a type and emit a suggestion.
1979 if let Some(ty) = pat.to_ty() {
1980 err.span_suggestion_verbose(
1982 "explicitly ignore the parameter name",
1983 format!("_: {}", pprust::ty_to_string(&ty)),
1984 Applicability::MachineApplicable,
1993 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1995 err.span_suggestion(
1997 "if this is a `self` type, give it a parameter name",
1999 Applicability::MaybeIncorrect,
2002 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
2003 // `fn foo(HashMap: TypeName<u32>)`.
2004 if self.token != token::Lt {
2005 err.span_suggestion(
2007 "if this is a parameter name, give it a type",
2009 Applicability::HasPlaceholders,
2012 err.span_suggestion(
2014 "if this is a type, explicitly ignore the parameter name",
2016 Applicability::MachineApplicable,
2020 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
2021 return if self.token == token::Lt { None } else { Some(ident) };
2026 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
2027 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
2028 self.expect(&token::Colon)?;
2029 let ty = self.parse_ty()?;
2031 self.sess.emit_err(PatternMethodParamWithoutBody { span: pat.span });
2033 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2035 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
2039 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
2040 let span = param.pat.span;
2041 param.ty.kind = TyKind::Err;
2042 self.sess.emit_err(SelfParamNotFirst { span });
2046 pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
2047 let mut brace_depth = 0;
2049 if self.eat(&token::OpenDelim(delim)) {
2051 } else if self.check(&token::CloseDelim(delim)) {
2052 if brace_depth == 0 {
2053 if let ConsumeClosingDelim::Yes = consume_close {
2054 // Some of the callers of this method expect to be able to parse the
2055 // closing delimiter themselves, so we leave it alone. Otherwise we advance
2065 } else if self.token == token::Eof {
2073 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2074 let (span, msg) = match (&self.token.kind, self.subparser_name) {
2075 (&token::Eof, Some(origin)) => {
2076 let sp = self.prev_token.span.shrink_to_hi();
2077 (sp, format!("expected expression, found end of {origin}"))
2081 format!("expected expression, found {}", super::token_descr(&self.token),),
2084 let mut err = self.struct_span_err(span, &msg);
2085 let sp = self.sess.source_map().start_point(self.token.span);
2086 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
2087 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
2089 err.span_label(span, "expected expression");
2095 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
2096 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
2097 modifier: &[(token::TokenKind, i64)],
2100 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
2103 if self.token.kind == token::Eof {
2110 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
2112 /// This is necessary because at this point we don't know whether we parsed a function with
2113 /// anonymous parameters or a function with names but no types. In order to minimize
2114 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
2115 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
2116 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
2117 /// we deduplicate them to not complain about duplicated parameter names.
2118 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
2119 let mut seen_inputs = FxHashSet::default();
2120 for input in fn_inputs.iter_mut() {
2121 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
2122 (&input.pat.kind, &input.ty.kind)
2128 if let Some(ident) = opt_ident {
2129 if seen_inputs.contains(&ident) {
2130 input.pat.kind = PatKind::Wild;
2132 seen_inputs.insert(ident);
2137 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
2138 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
2139 /// like the user has forgotten them.
2140 pub fn handle_ambiguous_unbraced_const_arg(
2142 args: &mut Vec<AngleBracketedArg>,
2143 ) -> PResult<'a, bool> {
2144 // If we haven't encountered a closing `>`, then the argument is malformed.
2145 // It's likely that the user has written a const expression without enclosing it
2146 // in braces, so we try to recover here.
2147 let arg = args.pop().unwrap();
2148 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
2149 // adverse side-effects to subsequent errors and seems to advance the parser.
2150 // We are causing this error here exclusively in case that a `const` expression
2151 // could be recovered from the current parser state, even if followed by more
2152 // arguments after a comma.
2153 let mut err = self.struct_span_err(
2155 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
2157 err.span_label(self.token.span, "expected one of `,` or `>`");
2158 match self.recover_const_arg(arg.span(), err) {
2160 args.push(AngleBracketedArg::Arg(arg));
2161 if self.eat(&token::Comma) {
2162 return Ok(true); // Continue
2167 // We will emit a more generic error later.
2171 return Ok(false); // Don't continue.
2174 /// Attempt to parse a generic const argument that has not been enclosed in braces.
2175 /// There are a limited number of expressions that are permitted without being encoded
2178 /// - Single-segment paths (i.e. standalone generic const parameters).
2179 /// All other expressions that can be parsed will emit an error suggesting the expression be
2180 /// wrapped in braces.
2181 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
2182 let start = self.token.span;
2183 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
2185 start.shrink_to_lo(),
2186 "while parsing a const generic argument starting here",
2190 if !self.expr_is_valid_const_arg(&expr) {
2191 self.sess.emit_err(ConstGenericWithoutBraces {
2193 sugg: ConstGenericWithoutBracesSugg {
2194 left: expr.span.shrink_to_lo(),
2195 right: expr.span.shrink_to_hi(),
2202 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2203 let snapshot = self.create_snapshot_for_diagnostic();
2204 let param = match self.parse_const_param(AttrVec::new()) {
2208 self.restore_snapshot(snapshot);
2213 let ident = param.ident.to_string();
2214 let sugg = match (ty_generics, self.sess.source_map().span_to_snippet(param.span())) {
2215 (Some(Generics { params, span: impl_generics, .. }), Ok(snippet)) => {
2216 Some(match ¶ms[..] {
2217 [] => UnexpectedConstParamDeclarationSugg::AddParam {
2218 impl_generics: *impl_generics,
2219 incorrect_decl: param.span(),
2223 [.., generic] => UnexpectedConstParamDeclarationSugg::AppendParam {
2224 impl_generics_end: generic.span().shrink_to_hi(),
2225 incorrect_decl: param.span(),
2233 self.sess.emit_err(UnexpectedConstParamDeclaration { span: param.span(), sugg });
2235 let value = self.mk_expr_err(param.span());
2236 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2239 pub fn recover_const_param_declaration(
2241 ty_generics: Option<&Generics>,
2242 ) -> PResult<'a, Option<GenericArg>> {
2243 // We have to check for a few different cases.
2244 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2245 return Ok(Some(arg));
2248 // We haven't consumed `const` yet.
2249 let start = self.token.span;
2250 self.bump(); // `const`
2252 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2253 let mut err = UnexpectedConstInGenericParam { span: start, to_remove: None };
2254 if self.check_const_arg() {
2255 err.to_remove = Some(start.until(self.token.span));
2256 self.sess.emit_err(err);
2257 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2259 let after_kw_const = self.token.span;
2260 self.recover_const_arg(after_kw_const, err.into_diagnostic(&self.sess.span_diagnostic))
2265 /// Try to recover from possible generic const argument without `{` and `}`.
2267 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2268 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2269 /// if we think that the resulting expression would be well formed.
2270 pub fn recover_const_arg(
2273 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2274 ) -> PResult<'a, GenericArg> {
2275 let is_op_or_dot = AssocOp::from_token(&self.token)
2277 if let AssocOp::Greater
2279 | AssocOp::ShiftRight
2280 | AssocOp::GreaterEqual
2281 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2282 // assign a value to a defaulted generic parameter.
2284 | AssocOp::AssignOp(_) = op
2292 || self.token.kind == TokenKind::Dot;
2293 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2294 // type params has been parsed.
2296 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2297 if !is_op_or_dot && !was_op {
2298 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2301 let snapshot = self.create_snapshot_for_diagnostic();
2305 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2307 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2308 if token::EqEq == snapshot.token.kind {
2309 err.span_suggestion(
2310 snapshot.token.span,
2311 "if you meant to use an associated type binding, replace `==` with `=`",
2313 Applicability::MaybeIncorrect,
2315 let value = self.mk_expr_err(start.to(expr.span));
2317 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2318 } else if token::Colon == snapshot.token.kind
2319 && expr.span.lo() == snapshot.token.span.hi()
2320 && matches!(expr.kind, ExprKind::Path(..))
2322 // Find a mistake like "foo::var:A".
2323 err.span_suggestion(
2324 snapshot.token.span,
2325 "write a path separator here",
2327 Applicability::MaybeIncorrect,
2330 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2331 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2333 // Avoid the following output by checking that we consumed a full const arg:
2334 // help: expressions must be enclosed in braces to be used as const generic
2337 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2339 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2346 self.restore_snapshot(snapshot);
2350 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2351 pub fn dummy_const_arg_needs_braces(
2353 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2356 err.multipart_suggestion(
2357 "expressions must be enclosed in braces to be used as const generic \
2359 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2360 Applicability::MaybeIncorrect,
2362 let value = self.mk_expr_err(span);
2364 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2367 /// Some special error handling for the "top-level" patterns in a match arm,
2368 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2369 pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
2371 mut first_pat: P<Pat>,
2374 if token::Colon != self.token.kind {
2377 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2378 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2382 // The pattern looks like it might be a path with a `::` -> `:` typo:
2383 // `match foo { bar:baz => {} }`
2384 let span = self.token.span;
2385 // We only emit "unexpected `:`" error here if we can successfully parse the
2386 // whole pattern correctly in that case.
2387 let snapshot = self.create_snapshot_for_diagnostic();
2389 // Create error for "unexpected `:`".
2390 match self.expected_one_of_not_found(&[], &[]) {
2392 self.bump(); // Skip the `:`.
2393 match self.parse_pat_no_top_alt(expected) {
2395 // Carry on as if we had not done anything, callers will emit a
2396 // reasonable error.
2399 self.restore_snapshot(snapshot);
2402 // We've parsed the rest of the pattern.
2403 let new_span = first_pat.span.to(pat.span);
2404 let mut show_sugg = false;
2405 // Try to construct a recovered pattern.
2406 match &mut pat.kind {
2407 PatKind::Struct(qself @ None, path, ..)
2408 | PatKind::TupleStruct(qself @ None, path, _)
2409 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2410 PatKind::Ident(_, ident, _) => {
2411 path.segments.insert(0, PathSegment::from_ident(*ident));
2412 path.span = new_span;
2416 PatKind::Path(old_qself, old_path) => {
2417 path.segments = old_path
2421 .chain(take(&mut path.segments))
2423 path.span = new_span;
2424 *qself = old_qself.clone();
2430 PatKind::Ident(BindingAnnotation::NONE, ident, None) => {
2431 match &first_pat.kind {
2432 PatKind::Ident(_, old_ident, _) => {
2433 let path = PatKind::Path(
2438 PathSegment::from_ident(*old_ident),
2439 PathSegment::from_ident(*ident),
2444 first_pat = self.mk_pat(new_span, path);
2447 PatKind::Path(old_qself, old_path) => {
2448 let mut segments = old_path.segments.clone();
2449 segments.push(PathSegment::from_ident(*ident));
2450 let path = PatKind::Path(
2452 Path { span: new_span, segments, tokens: None },
2454 first_pat = self.mk_pat(new_span, path);
2463 err.span_suggestion(
2465 "maybe write a path separator here",
2467 Applicability::MaybeIncorrect,
2470 first_pat = self.mk_pat(new_span, PatKind::Wild);
2477 // Carry on as if we had not done anything. This should be unreachable.
2478 self.restore_snapshot(snapshot);
2484 pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
2485 // Check for `'a : {`
2486 if !(self.check_lifetime()
2487 && self.look_ahead(1, |tok| tok.kind == token::Colon)
2488 && self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Brace)))
2492 let label = self.eat_label().expect("just checked if a label exists");
2493 self.bump(); // eat `:`
2494 let span = label.ident.span.to(self.prev_token.span);
2495 let mut err = self.struct_span_err(span, "block label not supported here");
2496 err.span_label(span, "not supported here");
2497 err.tool_only_span_suggestion(
2498 label.ident.span.until(self.token.span),
2499 "remove this block label",
2501 Applicability::MachineApplicable,
2507 /// Some special error handling for the "top-level" patterns in a match arm,
2508 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2509 pub(crate) fn maybe_recover_unexpected_comma(
2512 rt: CommaRecoveryMode,
2513 ) -> PResult<'a, ()> {
2514 if self.token != token::Comma {
2518 // An unexpected comma after a top-level pattern is a clue that the
2519 // user (perhaps more accustomed to some other language) forgot the
2520 // parentheses in what should have been a tuple pattern; return a
2521 // suggestion-enhanced error here rather than choking on the comma later.
2522 let comma_span = self.token.span;
2524 if let Err(err) = self.skip_pat_list() {
2525 // We didn't expect this to work anyway; we just wanted to advance to the
2526 // end of the comma-sequence so we know the span to suggest parenthesizing.
2529 let seq_span = lo.to(self.prev_token.span);
2530 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2531 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2532 err.multipart_suggestion(
2534 "try adding parentheses to match on a tuple{}",
2535 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
2538 (seq_span.shrink_to_lo(), "(".to_string()),
2539 (seq_span.shrink_to_hi(), ")".to_string()),
2541 Applicability::MachineApplicable,
2543 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
2544 err.span_suggestion(
2546 "...or a vertical bar to match on multiple alternatives",
2547 seq_snippet.replace(',', " |"),
2548 Applicability::MachineApplicable,
2555 pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
2556 let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
2557 let qself_position = qself.as_ref().map(|qself| qself.position);
2558 for (i, segments) in path.segments.windows(2).enumerate() {
2559 if qself_position.map(|pos| i < pos).unwrap_or(false) {
2562 if let [a, b] = segments {
2563 let (a_span, b_span) = (a.span(), b.span());
2564 let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
2565 if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
2566 return Err(DoubleColonInBound {
2567 span: path.span.shrink_to_hi(),
2568 between: between_span,
2570 .into_diagnostic(&self.sess.span_diagnostic));
2577 /// Parse and throw away a parenthesized comma separated
2578 /// sequence of patterns until `)` is reached.
2579 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2580 while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
2581 self.parse_pat_no_top_alt(None)?;
2582 if !self.eat(&token::Comma) {