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;
23 use rustc_ast::ptr::P;
24 use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
25 use rustc_ast::util::parser::AssocOp;
27 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingAnnotation, Block,
28 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Param, Pat, PatKind,
29 Path, PathSegment, QSelf, Ty, TyKind,
31 use rustc_ast_pretty::pprust;
32 use rustc_data_structures::fx::FxHashSet;
34 fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
36 use rustc_errors::{pluralize, Diagnostic, ErrorGuaranteed, IntoDiagnostic};
37 use rustc_session::errors::ExprParenthesesNeeded;
38 use rustc_span::source_map::Spanned;
39 use rustc_span::symbol::{kw, sym, Ident};
40 use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
42 use std::ops::{Deref, DerefMut};
43 use thin_vec::{thin_vec, ThinVec};
44 use tracing::{debug, trace};
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<P<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<P<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<P<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<P<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 segments: ThinVec::new(),
643 span: self.prev_token.span.shrink_to_lo(),
646 let struct_expr = snapshot.parse_struct_expr(None, path, false);
647 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
648 return Some(match (struct_expr, block_tail) {
649 (Ok(expr), Err(mut err)) => {
650 // We have encountered the following:
655 // fn foo() -> Foo { Path {
659 self.sess.emit_err(StructLiteralBodyWithoutPath {
661 sugg: StructLiteralBodyWithoutPathSugg {
662 before: expr.span.shrink_to_lo(),
663 after: expr.span.shrink_to_hi(),
666 self.restore_snapshot(snapshot);
667 let mut tail = self.mk_block(
668 vec![self.mk_stmt_err(expr.span)],
670 lo.to(self.prev_token.span),
672 tail.could_be_bare_literal = true;
675 (Err(err), Ok(tail)) => {
676 // We have a block tail that contains a somehow valid type ascription expr.
680 (Err(snapshot_err), Err(err)) => {
681 // We don't know what went wrong, emit the normal error.
682 snapshot_err.cancel();
683 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
686 (Ok(_), Ok(mut tail)) => {
687 tail.could_be_bare_literal = true;
695 pub fn maybe_annotate_with_ascription(
697 err: &mut Diagnostic,
698 maybe_expected_semicolon: bool,
700 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
701 let sm = self.sess.source_map();
702 let next_pos = sm.lookup_char_pos(self.token.span.lo());
703 let op_pos = sm.lookup_char_pos(sp.hi());
705 let allow_unstable = self.sess.unstable_features.is_nightly_build();
710 "maybe write a path separator here",
713 Applicability::MaybeIncorrect
715 Applicability::MachineApplicable
718 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
719 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
722 "try using a semicolon",
724 Applicability::MaybeIncorrect,
726 } else if allow_unstable {
727 err.span_label(sp, "tried to parse a type due to this type ascription");
729 err.span_label(sp, "tried to parse a type due to this");
732 // Give extra information about type ascription only if it's a nightly compiler.
734 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
738 // Avoid giving too much info when it was likely an unrelated typo.
740 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
741 for more information",
748 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
749 /// passes through any errors encountered. Used for error recovery.
750 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
752 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
753 Ok(p.parse_token_tree())
760 /// This function checks if there are trailing angle brackets and produces
761 /// a diagnostic to suggest removing them.
763 /// ```ignore (diagnostic)
764 /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
765 /// ^^ help: remove extra angle brackets
768 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
769 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
770 pub(super) fn check_trailing_angle_brackets(
772 segment: &PathSegment,
775 if !self.may_recover() {
779 // This function is intended to be invoked after parsing a path segment where there are two
782 // 1. A specific token is expected after the path segment.
783 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
784 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
785 // 2. No specific token is expected after the path segment.
786 // eg. `x.foo` (field access)
788 // This function is called after parsing `.foo` and before parsing the token `end` (if
789 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
792 // We only care about trailing angle brackets if we previously parsed angle bracket
793 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
794 // removed in this case:
796 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
798 // This case is particularly tricky as we won't notice it just looking at the tokens -
799 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
800 // have already been parsed):
802 // `x.foo::<u32>>>(3)`
803 let parsed_angle_bracket_args =
804 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
807 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
808 parsed_angle_bracket_args,
810 if !parsed_angle_bracket_args {
814 // Keep the span at the start so we can highlight the sequence of `>` characters to be
816 let lo = self.token.span;
818 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
819 // (since we might have the field access case and the characters we're eating are
820 // actual operators and not trailing characters - ie `x.foo >> 3`).
821 let mut position = 0;
823 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
824 // many of each (so we can correctly pluralize our error messages) and continue to
826 let mut number_of_shr = 0;
827 let mut number_of_gt = 0;
828 while self.look_ahead(position, |t| {
829 trace!("check_trailing_angle_brackets: t={:?}", t);
830 if *t == token::BinOp(token::BinOpToken::Shr) {
833 } else if *t == token::Gt {
843 // If we didn't find any trailing `>` characters, then we have nothing to error about.
845 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
846 number_of_gt, number_of_shr,
848 if number_of_gt < 1 && number_of_shr < 1 {
852 // Finally, double check that we have our end token as otherwise this is the
854 if self.look_ahead(position, |t| {
855 trace!("check_trailing_angle_brackets: t={:?}", t);
856 end.contains(&&t.kind)
858 // Eat from where we started until the end token so that parsing can continue
859 // as if we didn't have those extra angle brackets.
860 self.eat_to_tokens(end);
861 let span = lo.until(self.token.span);
863 let num_extra_brackets = number_of_gt + number_of_shr * 2;
864 self.sess.emit_err(UnmatchedAngleBrackets { span, num_extra_brackets });
870 /// Check if a method call with an intended turbofish has been written without surrounding
872 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
873 if !self.may_recover() {
877 if token::ModSep == self.token.kind && segment.args.is_none() {
878 let snapshot = self.create_snapshot_for_diagnostic();
880 let lo = self.token.span;
881 match self.parse_angle_args(None) {
883 let span = lo.to(self.prev_token.span);
884 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
885 let mut trailing_span = self.prev_token.span.shrink_to_hi();
886 while self.token.kind == token::BinOp(token::Shr)
887 || self.token.kind == token::Gt
889 trailing_span = trailing_span.to(self.token.span);
892 if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
893 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
894 let args = AngleBracketedArgs { args, span }.into();
897 self.sess.emit_err(GenericParamsWithoutAngleBrackets {
899 sugg: GenericParamsWithoutAngleBracketsSugg {
900 left: span.shrink_to_lo(),
901 right: trailing_span,
905 // This doesn't look like an invalid turbofish, can't recover parse state.
906 self.restore_snapshot(snapshot);
910 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
911 // generic parse error instead.
913 self.restore_snapshot(snapshot);
919 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
920 /// encounter a parse error when encountering the first `,`.
921 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
923 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
925 ) -> PResult<'a, ()> {
926 if let ExprKind::Binary(binop, _, _) = &expr.kind
927 && let ast::BinOpKind::Lt = binop.node
928 && self.eat(&token::Comma)
930 let x = self.parse_seq_to_before_end(
932 SeqSep::trailing_allowed(token::Comma),
933 |p| p.parse_generic_arg(None),
936 Ok((_, _, false)) => {
937 if self.eat(&token::Gt) {
938 e.span_suggestion_verbose(
939 binop.span.shrink_to_lo(),
940 fluent::parse_sugg_turbofish_syntax,
942 Applicability::MaybeIncorrect,
945 match self.parse_expr() {
948 self.mk_expr_err(expr.span.to(self.prev_token.span));
952 *expr = self.mk_expr_err(expr.span);
967 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
968 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
969 /// parenthesising the leftmost comparison.
970 fn attempt_chained_comparison_suggestion(
972 err: &mut ComparisonOperatorsCannotBeChained,
974 outer_op: &Spanned<AssocOp>,
975 ) -> bool /* advanced the cursor */ {
976 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
977 if let ExprKind::Field(_, ident) = l1.kind
978 && ident.as_str().parse::<i32>().is_err()
979 && !matches!(r1.kind, ExprKind::Lit(_))
981 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
982 // suggestion being the only one to apply is high.
985 return match (op.node, &outer_op.node) {
987 (BinOpKind::Eq, AssocOp::Equal) |
988 // `x < y < z` and friends.
989 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
990 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
991 // `x > y > z` and friends.
992 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
993 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
994 let expr_to_str = |e: &Expr| {
995 self.span_to_snippet(e.span)
996 .unwrap_or_else(|_| pprust::expr_to_string(&e))
998 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::SplitComparison {
999 span: inner_op.span.shrink_to_hi(),
1000 middle_term: expr_to_str(&r1),
1002 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
1005 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
1006 // Consume `z`/outer-op-rhs.
1007 let snapshot = self.create_snapshot_for_diagnostic();
1008 match self.parse_expr() {
1010 // We are sure that outer-op-rhs could be consumed, the suggestion is
1012 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1013 left: r1.span.shrink_to_lo(),
1014 right: r2.span.shrink_to_hi(),
1020 self.restore_snapshot(snapshot);
1026 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
1027 let snapshot = self.create_snapshot_for_diagnostic();
1028 // At this point it is always valid to enclose the lhs in parentheses, no
1029 // further checks are necessary.
1030 match self.parse_expr() {
1032 err.chaining_sugg = Some(ComparisonOperatorsCannotBeChainedSugg::Parenthesize {
1033 left: l1.span.shrink_to_lo(),
1034 right: r1.span.shrink_to_hi(),
1040 self.restore_snapshot(snapshot);
1051 /// Produces an error if comparison operators are chained (RFC #558).
1052 /// We only need to check the LHS, not the RHS, because all comparison ops have same
1053 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
1055 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
1056 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
1059 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
1060 /// associative we can infer that we have:
1069 pub(super) fn check_no_chained_comparison(
1072 outer_op: &Spanned<AssocOp>,
1073 ) -> PResult<'a, Option<P<Expr>>> {
1075 outer_op.node.is_comparison(),
1076 "check_no_chained_comparison: {:?} is not comparison",
1080 let mk_err_expr = |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err)));
1082 match inner_op.kind {
1083 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
1084 let mut err = ComparisonOperatorsCannotBeChained {
1085 span: vec![op.span, self.prev_token.span],
1086 suggest_turbofish: None,
1087 help_turbofish: None,
1088 chaining_sugg: None,
1091 // Include `<` to provide this recommendation even in a case like
1092 // `Foo<Bar<Baz<Qux, ()>>>`
1093 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
1094 || outer_op.node == AssocOp::Greater
1096 if outer_op.node == AssocOp::Less {
1097 let snapshot = self.create_snapshot_for_diagnostic();
1099 // So far we have parsed `foo<bar<`, consume the rest of the type args.
1101 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
1102 self.consume_tts(1, &modifiers);
1104 if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
1105 .contains(&self.token.kind)
1107 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
1108 // parser and bail out.
1109 self.restore_snapshot(snapshot);
1112 return if token::ModSep == self.token.kind {
1113 // We have some certainty that this was a bad turbofish at this point.
1115 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1117 let snapshot = self.create_snapshot_for_diagnostic();
1118 self.bump(); // `::`
1120 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
1121 match self.parse_expr() {
1123 // 99% certain that the suggestion is correct, continue parsing.
1124 self.sess.emit_err(err);
1125 // FIXME: actually check that the two expressions in the binop are
1126 // paths and resynthesize new fn call expression instead of using
1127 // `ExprKind::Err` placeholder.
1128 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1132 // Not entirely sure now, but we bubble the error up with the
1134 self.restore_snapshot(snapshot);
1135 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1138 } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
1139 // We have high certainty that this was a bad turbofish at this point.
1141 err.suggest_turbofish = Some(op.span.shrink_to_lo());
1142 // Consume the fn call arguments.
1143 match self.consume_fn_args() {
1144 Err(()) => Err(err.into_diagnostic(&self.sess.span_diagnostic)),
1146 self.sess.emit_err(err);
1147 // FIXME: actually check that the two expressions in the binop are
1148 // paths and resynthesize new fn call expression instead of using
1149 // `ExprKind::Err` placeholder.
1150 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1154 if !matches!(l1.kind, ExprKind::Lit(_))
1155 && !matches!(r1.kind, ExprKind::Lit(_))
1157 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1158 // be helpful, but don't attempt to recover.
1159 err.help_turbofish = Some(());
1162 // If it looks like a genuine attempt to chain operators (as opposed to a
1163 // misformatted turbofish, for instance), suggest a correct form.
1164 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1166 self.sess.emit_err(err);
1167 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1169 // These cases cause too many knock-down errors, bail out (#61329).
1170 Err(err.into_diagnostic(&self.sess.span_diagnostic))
1175 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1176 self.sess.emit_err(err);
1178 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1186 fn consume_fn_args(&mut self) -> Result<(), ()> {
1187 let snapshot = self.create_snapshot_for_diagnostic();
1190 // Consume the fn call arguments.
1192 (token::OpenDelim(Delimiter::Parenthesis), 1),
1193 (token::CloseDelim(Delimiter::Parenthesis), -1),
1195 self.consume_tts(1, &modifiers);
1197 if self.token.kind == token::Eof {
1198 // Not entirely sure that what we consumed were fn arguments, rollback.
1199 self.restore_snapshot(snapshot);
1202 // 99% certain that the suggestion is correct, continue parsing.
1207 pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
1209 self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
1213 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1214 pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
1215 if self.token == token::Question {
1217 self.sess.emit_err(QuestionMarkInType {
1218 span: self.prev_token.span,
1219 sugg: QuestionMarkInTypeSugg {
1220 left: ty.span.shrink_to_lo(),
1221 right: self.prev_token.span,
1224 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1230 pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
1231 // Do not add `+` to expected tokens.
1232 if !self.token.is_like_plus() {
1237 let bounds = self.parse_generic_bounds(None)?;
1238 let sum_span = ty.span.to(self.prev_token.span);
1240 let sub = match ty.kind {
1241 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1242 let sum_with_parens = pprust::to_string(|s| {
1244 s.print_opt_lifetime(lifetime);
1245 s.print_mutability(mut_ty.mutbl, false);
1247 s.print_type(&mut_ty.ty);
1248 if !bounds.is_empty() {
1250 s.print_type_bounds(&bounds);
1255 BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
1257 TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
1258 _ => BadTypePlusSub::ExpectPath { span: sum_span },
1261 self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
1266 pub(super) fn recover_from_prefix_increment(
1268 operand_expr: P<Expr>,
1271 ) -> PResult<'a, P<Expr>> {
1273 if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
1274 let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
1276 self.recover_from_inc_dec(operand_expr, kind, op_span)
1279 pub(super) fn recover_from_postfix_increment(
1281 operand_expr: P<Expr>,
1283 ) -> PResult<'a, P<Expr>> {
1284 let kind = IncDecRecovery {
1285 standalone: IsStandalone::Maybe,
1287 fixity: UnaryFixity::Post,
1290 self.recover_from_inc_dec(operand_expr, kind, op_span)
1293 fn recover_from_inc_dec(
1296 kind: IncDecRecovery,
1298 ) -> PResult<'a, P<Expr>> {
1299 let mut err = self.struct_span_err(
1301 &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
1303 err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
1305 let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
1306 err.help(&format!("use `{}= 1` instead", kind.op.chr()));
1312 let spans = match kind.fixity {
1313 UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
1314 UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
1317 match kind.standalone {
1318 IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
1319 IsStandalone::Subexpr => {
1320 let Ok(base_src) = self.span_to_snippet(base.span)
1321 else { return help_base_case(err, base) };
1323 UnaryFixity::Pre => {
1324 self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1326 UnaryFixity::Post => {
1327 self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1331 IsStandalone::Maybe => {
1332 let Ok(base_src) = self.span_to_snippet(base.span)
1333 else { return help_base_case(err, base) };
1334 let sugg1 = match kind.fixity {
1335 UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
1336 UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
1338 let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
1339 MultiSugg::emit_many(
1341 "use `+= 1` instead",
1342 Applicability::Unspecified,
1343 [sugg1, sugg2].into_iter(),
1350 fn prefix_inc_dec_suggest(
1353 kind: IncDecRecovery,
1354 (pre_span, post_span): (Span, Span),
1357 msg: format!("use `{}= 1` instead", kind.op.chr()),
1359 (pre_span, "{ ".to_string()),
1360 (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
1362 applicability: Applicability::MachineApplicable,
1366 fn postfix_inc_dec_suggest(
1369 kind: IncDecRecovery,
1370 (pre_span, post_span): (Span, Span),
1372 let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
1374 msg: format!("use `{}= 1` instead", kind.op.chr()),
1376 (pre_span, format!("{{ let {tmp_var} = ")),
1377 (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
1379 applicability: Applicability::HasPlaceholders,
1383 fn inc_dec_standalone_suggest(
1385 kind: IncDecRecovery,
1386 (pre_span, post_span): (Span, Span),
1388 let mut patches = Vec::new();
1390 if !pre_span.is_empty() {
1391 patches.push((pre_span, String::new()));
1394 patches.push((post_span, format!(" {}= 1", kind.op.chr())));
1397 msg: format!("use `{}= 1` instead", kind.op.chr()),
1399 applicability: Applicability::MachineApplicable,
1403 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1404 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1405 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1406 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1409 ) -> PResult<'a, P<T>> {
1410 if !self.may_recover() {
1414 // Do not add `::` to expected tokens.
1415 if self.token == token::ModSep {
1416 if let Some(ty) = base.to_ty() {
1417 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1423 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1424 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1425 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1429 ) -> PResult<'a, P<T>> {
1430 self.expect(&token::ModSep)?;
1432 let mut path = ast::Path { segments: ThinVec::new(), span: DUMMY_SP, tokens: None };
1433 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1434 path.span = ty_span.to(self.prev_token.span);
1436 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1437 self.sess.emit_err(BadQPathStage2 {
1439 ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1442 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1443 Ok(P(T::recovered(Some(P(QSelf { ty, path_span, position: 0 })), path)))
1446 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1447 if self.token.kind == TokenKind::Semi {
1451 IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
1453 if !items.is_empty() {
1454 let previous_item = &items[items.len() - 1];
1455 let previous_item_kind_name = match previous_item.kind {
1456 // Say "braced struct" because tuple-structs and
1457 // braceless-empty-struct declarations do take a semicolon.
1458 ItemKind::Struct(..) => Some("braced struct"),
1459 ItemKind::Enum(..) => Some("enum"),
1460 ItemKind::Trait(..) => Some("trait"),
1461 ItemKind::Union(..) => Some("union"),
1464 if let Some(name) = previous_item_kind_name {
1465 err.opt_help = Some(());
1469 self.sess.emit_err(err);
1476 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1477 /// closing delimiter.
1478 pub(super) fn unexpected_try_recover(
1481 ) -> PResult<'a, bool /* recovered */> {
1482 let token_str = pprust::token_kind_to_string(t);
1483 let this_token_str = super::token_descr(&self.token);
1484 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1485 // Point at the end of the macro call when reaching end of macro arguments.
1486 (token::Eof, Some(_)) => {
1487 let sp = self.prev_token.span.shrink_to_hi();
1490 // We don't want to point at the following span after DUMMY_SP.
1491 // This happens when the parser finds an empty TokenStream.
1492 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1493 // EOF, don't want to point at the following char, but rather the last token.
1494 (token::Eof, None) => (self.prev_token.span, self.token.span),
1495 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1498 "expected `{}`, found {}",
1500 match (&self.token.kind, self.subparser_name) {
1501 (token::Eof, Some(origin)) => format!("end of {origin}"),
1502 _ => this_token_str,
1505 let mut err = self.struct_span_err(sp, &msg);
1506 let label_exp = format!("expected `{token_str}`");
1507 match self.recover_closing_delimiter(&[t.clone()], err) {
1510 return Ok(recovered);
1513 let sm = self.sess.source_map();
1514 if !sm.is_multiline(prev_sp.until(sp)) {
1515 // When the spans are in the same line, it means that the only content
1516 // between them is whitespace, point only at the found token.
1517 err.span_label(sp, label_exp);
1519 err.span_label(prev_sp, label_exp);
1520 err.span_label(sp, "unexpected token");
1525 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1526 if self.eat(&token::Semi) {
1529 self.expect(&token::Semi).map(drop) // Error unconditionally
1532 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1533 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1534 pub(super) fn recover_incorrect_await_syntax(
1538 ) -> PResult<'a, P<Expr>> {
1539 let (hi, expr, is_question) = if self.token == token::Not {
1540 // Handle `await!(<expr>)`.
1541 self.recover_await_macro()?
1543 self.recover_await_prefix(await_sp)?
1545 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1546 let kind = match expr.kind {
1547 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1548 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1549 ExprKind::Try(_) => ExprKind::Err,
1550 _ => ExprKind::Await(expr),
1552 let expr = self.mk_expr(lo.to(sp), kind);
1553 self.maybe_recover_from_bad_qpath(expr)
1556 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1557 self.expect(&token::Not)?;
1558 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
1559 let expr = self.parse_expr()?;
1560 self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
1561 Ok((self.prev_token.span, expr, false))
1564 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1565 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1566 let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
1567 // Handle `await { <expr> }`.
1568 // This needs to be handled separately from the next arm to avoid
1569 // interpreting `await { <expr> }?` as `<expr>?.await`.
1570 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default)
1574 .map_err(|mut err| {
1575 err.span_label(await_sp, "while parsing this incorrect await expression");
1578 Ok((expr.span, expr, is_question))
1581 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1582 let span = lo.to(hi);
1583 let applicability = match expr.kind {
1584 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1585 _ => Applicability::MachineApplicable,
1588 self.sess.emit_err(IncorrectAwait {
1590 sugg_span: (span, applicability),
1591 expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
1592 question_mark: if is_question { "?" } else { "" },
1598 /// If encountering `future.await()`, consumes and emits an error.
1599 pub(super) fn recover_from_await_method_call(&mut self) {
1600 if self.token == token::OpenDelim(Delimiter::Parenthesis)
1601 && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
1604 let lo = self.token.span;
1606 let span = lo.to(self.token.span);
1609 self.sess.emit_err(IncorrectUseOfAwait { span });
1613 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1614 let is_try = self.token.is_keyword(kw::Try);
1615 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1616 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
1618 if is_try && is_questionmark && is_open {
1619 let lo = self.token.span;
1620 self.bump(); //remove try
1621 self.bump(); //remove !
1622 let try_span = lo.to(self.token.span); //we take the try!( span
1623 self.bump(); //remove (
1624 let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
1625 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
1626 let hi = self.token.span;
1627 self.bump(); //remove )
1628 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1629 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1630 let prefix = if is_empty { "" } else { "alternatively, " };
1632 err.multipart_suggestion(
1633 "you can use the `?` operator instead",
1634 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1635 Applicability::MachineApplicable,
1638 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);
1640 Ok(self.mk_expr_err(lo.to(hi)))
1642 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1646 /// Recovers a situation like `for ( $pat in $expr )`
1647 /// and suggest writing `for $pat in $expr` instead.
1649 /// This should be called before parsing the `$block`.
1650 pub(super) fn recover_parens_around_for_head(
1653 begin_paren: Option<Span>,
1655 match (&self.token.kind, begin_paren) {
1656 (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
1659 let sm = self.sess.source_map();
1660 let left = begin_par_sp;
1661 let right = self.prev_token.span;
1662 let left_snippet = if let Ok(snip) = sm.span_to_prev_source(left) &&
1663 !snip.ends_with(' ') {
1669 let right_snippet = if let Ok(snip) = sm.span_to_next_source(right) &&
1670 !snip.starts_with(' ') {
1676 self.sess.emit_err(ParenthesesInForHead {
1677 span: vec![left, right],
1678 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1679 // with `x) in y)` which is syntactically invalid.
1680 // However, this is prevented before we get here.
1681 sugg: ParenthesesInForHeadSugg { left, right, left_snippet, right_snippet },
1684 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1685 pat.and_then(|pat| match pat.kind {
1686 PatKind::Paren(pat) => pat,
1694 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1695 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1696 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1697 || self.token.is_ident() &&
1698 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1699 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1700 self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
1701 || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
1702 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1703 self.look_ahead(2, |t| t == &token::Lt) &&
1704 self.look_ahead(3, |t| t.is_ident())
1705 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1706 self.look_ahead(2, |t| t.is_ident())
1707 || self.look_ahead(1, |t| t == &token::ModSep)
1708 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1709 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1712 pub(super) fn recover_seq_parse_error(
1716 result: PResult<'a, P<Expr>>,
1722 // Recover from parse error, callers expect the closing delim to be consumed.
1723 self.consume_block(delim, ConsumeClosingDelim::Yes);
1724 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err)
1729 pub(super) fn recover_closing_delimiter(
1731 tokens: &[TokenKind],
1732 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
1733 ) -> PResult<'a, bool> {
1735 // We want to use the last closing delim that would apply.
1736 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1737 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1738 && Some(self.token.span) > unmatched.unclosed_span
1745 // Recover and assume that the detected unclosed delimiter was meant for
1746 // this location. Emit the diagnostic and act as if the delimiter was
1747 // present for the parser's sake.
1749 // Don't attempt to recover from this unclosed delimiter more than once.
1750 let unmatched = self.unclosed_delims.remove(pos);
1751 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1752 if unmatched.found_delim.is_none() {
1753 // We encountered `Eof`, set this fact here to avoid complaining about missing
1754 // `fn main()` when we found place to suggest the closing brace.
1755 *self.sess.reached_eof.borrow_mut() = true;
1758 // We want to suggest the inclusion of the closing delimiter where it makes
1759 // the most sense, which is immediately after the last token:
1764 // | help: `)` may belong here
1766 // unclosed delimiter
1767 if let Some(sp) = unmatched.unclosed_span {
1768 let mut primary_span: Vec<Span> =
1769 err.span.primary_spans().iter().cloned().collect();
1770 primary_span.push(sp);
1771 let mut primary_span: MultiSpan = primary_span.into();
1772 for span_label in err.span.span_labels() {
1773 if let Some(label) = span_label.label {
1774 primary_span.push_span_label(span_label.span, label);
1777 err.set_span(primary_span);
1778 err.span_label(sp, "unclosed delimiter");
1780 // Backticks should be removed to apply suggestions.
1781 let mut delim = delim.to_string();
1782 delim.retain(|c| c != '`');
1783 err.span_suggestion_short(
1784 self.prev_token.span.shrink_to_hi(),
1785 &format!("`{delim}` may belong here"),
1787 Applicability::MaybeIncorrect,
1789 if unmatched.found_delim.is_none() {
1790 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1791 // errors which would be emitted elsewhere in the parser and let other error
1792 // recovery consume the rest of the file.
1796 self.expected_tokens.clear(); // Reduce the number of errors.
1804 /// Eats tokens until we can be relatively sure we reached the end of the
1805 /// statement. This is something of a best-effort heuristic.
1807 /// We terminate when we find an unmatched `}` (without consuming it).
1808 pub(super) fn recover_stmt(&mut self) {
1809 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1812 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1813 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1814 /// approximate -- it can mean we break too early due to macros, but that
1815 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1817 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1818 /// after finding (and consuming) a brace-delimited block.
1819 pub(super) fn recover_stmt_(
1821 break_on_semi: SemiColonMode,
1822 break_on_block: BlockMode,
1824 let mut brace_depth = 0;
1825 let mut bracket_depth = 0;
1826 let mut in_block = false;
1827 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1829 debug!("recover_stmt_ loop {:?}", self.token);
1830 match self.token.kind {
1831 token::OpenDelim(Delimiter::Brace) => {
1834 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1839 token::OpenDelim(Delimiter::Bracket) => {
1843 token::CloseDelim(Delimiter::Brace) => {
1844 if brace_depth == 0 {
1845 debug!("recover_stmt_ return - close delim {:?}", self.token);
1850 if in_block && bracket_depth == 0 && brace_depth == 0 {
1851 debug!("recover_stmt_ return - block end {:?}", self.token);
1855 token::CloseDelim(Delimiter::Bracket) => {
1857 if bracket_depth < 0 {
1863 debug!("recover_stmt_ return - Eof");
1868 if break_on_semi == SemiColonMode::Break
1870 && bracket_depth == 0
1872 debug!("recover_stmt_ return - Semi");
1877 if break_on_semi == SemiColonMode::Comma
1879 && bracket_depth == 0 =>
1881 debug!("recover_stmt_ return - Semi");
1889 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1890 if self.eat_keyword(kw::In) {
1891 // a common typo: `for _ in in bar {}`
1892 self.sess.emit_err(InInTypo {
1893 span: self.prev_token.span,
1894 sugg_span: in_span.until(self.prev_token.span),
1899 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1900 if let token::DocComment(..) = self.token.kind {
1901 self.sess.emit_err(DocCommentOnParamType { span: self.token.span });
1903 } else if self.token == token::Pound
1904 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
1906 let lo = self.token.span;
1907 // Skip every token until next possible arg.
1908 while self.token != token::CloseDelim(Delimiter::Bracket) {
1911 let sp = lo.to(self.token.span);
1913 self.sess.emit_err(AttributeOnParamType { span: sp });
1917 pub(super) fn parameter_without_type(
1919 err: &mut Diagnostic,
1923 ) -> Option<Ident> {
1924 // If we find a pattern followed by an identifier, it could be an (incorrect)
1925 // C-style parameter declaration.
1926 if self.check_ident()
1927 && self.look_ahead(1, |t| {
1928 *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
1931 // `fn foo(String s) {}`
1932 let ident = self.parse_ident().unwrap();
1933 let span = pat.span.with_hi(ident.span.hi());
1935 err.span_suggestion(
1937 "declare the type after the parameter binding",
1938 "<identifier>: <type>",
1939 Applicability::HasPlaceholders,
1942 } else if require_name
1943 && (self.token == token::Comma
1944 || self.token == token::Lt
1945 || self.token == token::CloseDelim(Delimiter::Parenthesis))
1947 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
1949 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
1951 PatKind::Ident(_, ident, _) => (
1954 ": TypeName".to_string(),
1956 pat.span.shrink_to_lo(),
1957 pat.span.shrink_to_hi(),
1958 pat.span.shrink_to_lo(),
1960 // Also catches `fn foo(&a)`.
1961 PatKind::Ref(ref inner_pat, mutab)
1962 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
1964 match inner_pat.clone().into_inner().kind {
1965 PatKind::Ident(_, ident, _) => {
1966 let mutab = mutab.prefix_str();
1970 format!("{ident}: &{mutab}TypeName"),
1972 pat.span.shrink_to_lo(),
1974 pat.span.shrink_to_lo(),
1977 _ => unreachable!(),
1981 // Otherwise, try to get a type and emit a suggestion.
1982 if let Some(ty) = pat.to_ty() {
1983 err.span_suggestion_verbose(
1985 "explicitly ignore the parameter name",
1986 format!("_: {}", pprust::ty_to_string(&ty)),
1987 Applicability::MachineApplicable,
1996 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1998 err.span_suggestion(
2000 "if this is a `self` type, give it a parameter name",
2002 Applicability::MaybeIncorrect,
2005 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
2006 // `fn foo(HashMap: TypeName<u32>)`.
2007 if self.token != token::Lt {
2008 err.span_suggestion(
2010 "if this is a parameter name, give it a type",
2012 Applicability::HasPlaceholders,
2015 err.span_suggestion(
2017 "if this is a type, explicitly ignore the parameter name",
2019 Applicability::MachineApplicable,
2023 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
2024 return if self.token == token::Lt { None } else { Some(ident) };
2029 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
2030 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
2031 self.expect(&token::Colon)?;
2032 let ty = self.parse_ty()?;
2034 self.sess.emit_err(PatternMethodParamWithoutBody { span: pat.span });
2036 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2038 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
2042 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
2043 let span = param.pat.span;
2044 param.ty.kind = TyKind::Err;
2045 self.sess.emit_err(SelfParamNotFirst { span });
2049 pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
2050 let mut brace_depth = 0;
2052 if self.eat(&token::OpenDelim(delim)) {
2054 } else if self.check(&token::CloseDelim(delim)) {
2055 if brace_depth == 0 {
2056 if let ConsumeClosingDelim::Yes = consume_close {
2057 // Some of the callers of this method expect to be able to parse the
2058 // closing delimiter themselves, so we leave it alone. Otherwise we advance
2068 } else if self.token == token::Eof {
2076 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2077 let (span, msg) = match (&self.token.kind, self.subparser_name) {
2078 (&token::Eof, Some(origin)) => {
2079 let sp = self.prev_token.span.shrink_to_hi();
2080 (sp, format!("expected expression, found end of {origin}"))
2084 format!("expected expression, found {}", super::token_descr(&self.token),),
2087 let mut err = self.struct_span_err(span, &msg);
2088 let sp = self.sess.source_map().start_point(self.token.span);
2089 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
2090 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
2092 err.span_label(span, "expected expression");
2098 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
2099 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
2100 modifier: &[(token::TokenKind, i64)],
2103 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
2106 if self.token.kind == token::Eof {
2113 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
2115 /// This is necessary because at this point we don't know whether we parsed a function with
2116 /// anonymous parameters or a function with names but no types. In order to minimize
2117 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
2118 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
2119 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
2120 /// we deduplicate them to not complain about duplicated parameter names.
2121 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
2122 let mut seen_inputs = FxHashSet::default();
2123 for input in fn_inputs.iter_mut() {
2124 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
2125 (&input.pat.kind, &input.ty.kind)
2131 if let Some(ident) = opt_ident {
2132 if seen_inputs.contains(&ident) {
2133 input.pat.kind = PatKind::Wild;
2135 seen_inputs.insert(ident);
2140 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
2141 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
2142 /// like the user has forgotten them.
2143 pub fn handle_ambiguous_unbraced_const_arg(
2145 args: &mut Vec<AngleBracketedArg>,
2146 ) -> PResult<'a, bool> {
2147 // If we haven't encountered a closing `>`, then the argument is malformed.
2148 // It's likely that the user has written a const expression without enclosing it
2149 // in braces, so we try to recover here.
2150 let arg = args.pop().unwrap();
2151 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
2152 // adverse side-effects to subsequent errors and seems to advance the parser.
2153 // We are causing this error here exclusively in case that a `const` expression
2154 // could be recovered from the current parser state, even if followed by more
2155 // arguments after a comma.
2156 let mut err = self.struct_span_err(
2158 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
2160 err.span_label(self.token.span, "expected one of `,` or `>`");
2161 match self.recover_const_arg(arg.span(), err) {
2163 args.push(AngleBracketedArg::Arg(arg));
2164 if self.eat(&token::Comma) {
2165 return Ok(true); // Continue
2170 // We will emit a more generic error later.
2174 return Ok(false); // Don't continue.
2177 /// Attempt to parse a generic const argument that has not been enclosed in braces.
2178 /// There are a limited number of expressions that are permitted without being encoded
2181 /// - Single-segment paths (i.e. standalone generic const parameters).
2182 /// All other expressions that can be parsed will emit an error suggesting the expression be
2183 /// wrapped in braces.
2184 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
2185 let start = self.token.span;
2186 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
2188 start.shrink_to_lo(),
2189 "while parsing a const generic argument starting here",
2193 if !self.expr_is_valid_const_arg(&expr) {
2194 self.sess.emit_err(ConstGenericWithoutBraces {
2196 sugg: ConstGenericWithoutBracesSugg {
2197 left: expr.span.shrink_to_lo(),
2198 right: expr.span.shrink_to_hi(),
2205 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2206 let snapshot = self.create_snapshot_for_diagnostic();
2207 let param = match self.parse_const_param(AttrVec::new()) {
2211 self.restore_snapshot(snapshot);
2216 let ident = param.ident.to_string();
2217 let sugg = match (ty_generics, self.sess.source_map().span_to_snippet(param.span())) {
2218 (Some(Generics { params, span: impl_generics, .. }), Ok(snippet)) => {
2219 Some(match ¶ms[..] {
2220 [] => UnexpectedConstParamDeclarationSugg::AddParam {
2221 impl_generics: *impl_generics,
2222 incorrect_decl: param.span(),
2226 [.., generic] => UnexpectedConstParamDeclarationSugg::AppendParam {
2227 impl_generics_end: generic.span().shrink_to_hi(),
2228 incorrect_decl: param.span(),
2236 self.sess.emit_err(UnexpectedConstParamDeclaration { span: param.span(), sugg });
2238 let value = self.mk_expr_err(param.span());
2239 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2242 pub fn recover_const_param_declaration(
2244 ty_generics: Option<&Generics>,
2245 ) -> PResult<'a, Option<GenericArg>> {
2246 // We have to check for a few different cases.
2247 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2248 return Ok(Some(arg));
2251 // We haven't consumed `const` yet.
2252 let start = self.token.span;
2253 self.bump(); // `const`
2255 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2256 let mut err = UnexpectedConstInGenericParam { span: start, to_remove: None };
2257 if self.check_const_arg() {
2258 err.to_remove = Some(start.until(self.token.span));
2259 self.sess.emit_err(err);
2260 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2262 let after_kw_const = self.token.span;
2263 self.recover_const_arg(after_kw_const, err.into_diagnostic(&self.sess.span_diagnostic))
2268 /// Try to recover from possible generic const argument without `{` and `}`.
2270 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2271 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2272 /// if we think that the resulting expression would be well formed.
2273 pub fn recover_const_arg(
2276 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2277 ) -> PResult<'a, GenericArg> {
2278 let is_op_or_dot = AssocOp::from_token(&self.token)
2280 if let AssocOp::Greater
2282 | AssocOp::ShiftRight
2283 | AssocOp::GreaterEqual
2284 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2285 // assign a value to a defaulted generic parameter.
2287 | AssocOp::AssignOp(_) = op
2295 || self.token.kind == TokenKind::Dot;
2296 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2297 // type params has been parsed.
2299 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2300 if !is_op_or_dot && !was_op {
2301 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2304 let snapshot = self.create_snapshot_for_diagnostic();
2308 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2310 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2311 if token::EqEq == snapshot.token.kind {
2312 err.span_suggestion(
2313 snapshot.token.span,
2314 "if you meant to use an associated type binding, replace `==` with `=`",
2316 Applicability::MaybeIncorrect,
2318 let value = self.mk_expr_err(start.to(expr.span));
2320 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2321 } else if token::Colon == snapshot.token.kind
2322 && expr.span.lo() == snapshot.token.span.hi()
2323 && matches!(expr.kind, ExprKind::Path(..))
2325 // Find a mistake like "foo::var:A".
2326 err.span_suggestion(
2327 snapshot.token.span,
2328 "write a path separator here",
2330 Applicability::MaybeIncorrect,
2333 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2334 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2336 // Avoid the following output by checking that we consumed a full const arg:
2337 // help: expressions must be enclosed in braces to be used as const generic
2340 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2342 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2349 self.restore_snapshot(snapshot);
2353 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2354 pub fn dummy_const_arg_needs_braces(
2356 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2359 err.multipart_suggestion(
2360 "expressions must be enclosed in braces to be used as const generic \
2362 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2363 Applicability::MaybeIncorrect,
2365 let value = self.mk_expr_err(span);
2367 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2370 /// Some special error handling for the "top-level" patterns in a match arm,
2371 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2372 pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
2374 mut first_pat: P<Pat>,
2377 if token::Colon != self.token.kind {
2380 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2381 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2385 // The pattern looks like it might be a path with a `::` -> `:` typo:
2386 // `match foo { bar:baz => {} }`
2387 let span = self.token.span;
2388 // We only emit "unexpected `:`" error here if we can successfully parse the
2389 // whole pattern correctly in that case.
2390 let snapshot = self.create_snapshot_for_diagnostic();
2392 // Create error for "unexpected `:`".
2393 match self.expected_one_of_not_found(&[], &[]) {
2395 self.bump(); // Skip the `:`.
2396 match self.parse_pat_no_top_alt(expected) {
2398 // Carry on as if we had not done anything, callers will emit a
2399 // reasonable error.
2402 self.restore_snapshot(snapshot);
2405 // We've parsed the rest of the pattern.
2406 let new_span = first_pat.span.to(pat.span);
2407 let mut show_sugg = false;
2408 // Try to construct a recovered pattern.
2409 match &mut pat.kind {
2410 PatKind::Struct(qself @ None, path, ..)
2411 | PatKind::TupleStruct(qself @ None, path, _)
2412 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2413 PatKind::Ident(_, ident, _) => {
2414 path.segments.insert(0, PathSegment::from_ident(*ident));
2415 path.span = new_span;
2419 PatKind::Path(old_qself, old_path) => {
2420 path.segments = old_path
2424 .chain(take(&mut path.segments))
2426 path.span = new_span;
2427 *qself = old_qself.clone();
2433 PatKind::Ident(BindingAnnotation::NONE, ident, None) => {
2434 match &first_pat.kind {
2435 PatKind::Ident(_, old_ident, _) => {
2436 let path = PatKind::Path(
2440 segments: thin_vec![
2441 PathSegment::from_ident(*old_ident),
2442 PathSegment::from_ident(*ident),
2447 first_pat = self.mk_pat(new_span, path);
2450 PatKind::Path(old_qself, old_path) => {
2451 let mut segments = old_path.segments.clone();
2452 segments.push(PathSegment::from_ident(*ident));
2453 let path = PatKind::Path(
2455 Path { span: new_span, segments, tokens: None },
2457 first_pat = self.mk_pat(new_span, path);
2466 err.span_suggestion(
2468 "maybe write a path separator here",
2470 Applicability::MaybeIncorrect,
2473 first_pat = self.mk_pat(new_span, PatKind::Wild);
2480 // Carry on as if we had not done anything. This should be unreachable.
2481 self.restore_snapshot(snapshot);
2487 pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
2488 // Check for `'a : {`
2489 if !(self.check_lifetime()
2490 && self.look_ahead(1, |tok| tok.kind == token::Colon)
2491 && self.look_ahead(2, |tok| tok.kind == token::OpenDelim(Delimiter::Brace)))
2495 let label = self.eat_label().expect("just checked if a label exists");
2496 self.bump(); // eat `:`
2497 let span = label.ident.span.to(self.prev_token.span);
2498 let mut err = self.struct_span_err(span, "block label not supported here");
2499 err.span_label(span, "not supported here");
2500 err.tool_only_span_suggestion(
2501 label.ident.span.until(self.token.span),
2502 "remove this block label",
2504 Applicability::MachineApplicable,
2510 /// Some special error handling for the "top-level" patterns in a match arm,
2511 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2512 pub(crate) fn maybe_recover_unexpected_comma(
2515 rt: CommaRecoveryMode,
2516 ) -> PResult<'a, ()> {
2517 if self.token != token::Comma {
2521 // An unexpected comma after a top-level pattern is a clue that the
2522 // user (perhaps more accustomed to some other language) forgot the
2523 // parentheses in what should have been a tuple pattern; return a
2524 // suggestion-enhanced error here rather than choking on the comma later.
2525 let comma_span = self.token.span;
2527 if let Err(err) = self.skip_pat_list() {
2528 // We didn't expect this to work anyway; we just wanted to advance to the
2529 // end of the comma-sequence so we know the span to suggest parenthesizing.
2532 let seq_span = lo.to(self.prev_token.span);
2533 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2534 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2535 err.multipart_suggestion(
2537 "try adding parentheses to match on a tuple{}",
2538 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
2541 (seq_span.shrink_to_lo(), "(".to_string()),
2542 (seq_span.shrink_to_hi(), ")".to_string()),
2544 Applicability::MachineApplicable,
2546 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
2547 err.span_suggestion(
2549 "...or a vertical bar to match on multiple alternatives",
2550 seq_snippet.replace(',', " |"),
2551 Applicability::MachineApplicable,
2558 pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
2559 let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
2560 let qself_position = qself.as_ref().map(|qself| qself.position);
2561 for (i, segments) in path.segments.windows(2).enumerate() {
2562 if qself_position.map(|pos| i < pos).unwrap_or(false) {
2565 if let [a, b] = segments {
2566 let (a_span, b_span) = (a.span(), b.span());
2567 let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
2568 if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
2569 return Err(DoubleColonInBound {
2570 span: path.span.shrink_to_hi(),
2571 between: between_span,
2573 .into_diagnostic(&self.sess.span_diagnostic));
2580 /// Parse and throw away a parenthesized comma separated
2581 /// sequence of patterns until `)` is reached.
2582 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2583 while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
2584 self.parse_pat_no_top_alt(None)?;
2585 if !self.eat(&token::Comma) {