1 use super::pat::Expected;
3 BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep,
4 TokenExpectType, TokenType,
7 use crate::lexer::UnmatchedBrace;
10 use rustc_ast::token::{self, Delimiter, Lit, LitKind, TokenKind};
11 use rustc_ast::util::parser::AssocOp;
13 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
14 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Mutability, Param, Pat,
15 PatKind, Path, PathSegment, QSelf, Ty, TyKind,
17 use rustc_ast_pretty::pprust;
18 use rustc_data_structures::fx::FxHashSet;
20 fluent, Applicability, DiagnosticBuilder, DiagnosticMessage, Handler, MultiSpan, PResult,
22 use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed};
23 use rustc_macros::{SessionDiagnostic, SessionSubdiagnostic};
24 use rustc_span::source_map::Spanned;
25 use rustc_span::symbol::{kw, Ident};
26 use rustc_span::{Span, SpanSnippetError, DUMMY_SP};
27 use std::ops::{Deref, DerefMut};
32 use tracing::{debug, trace};
34 const TURBOFISH_SUGGESTION_STR: &str =
35 "use `::<...>` instead of `<...>` to specify lifetime, type, or const arguments";
37 /// Creates a placeholder argument.
38 pub(super) fn dummy_arg(ident: Ident) -> Param {
40 id: ast::DUMMY_NODE_ID,
41 kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
45 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
47 attrs: AttrVec::default(),
48 id: ast::DUMMY_NODE_ID,
52 is_placeholder: false,
63 sp: impl Into<MultiSpan>,
65 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
67 Error::UselessDocComment => {
68 let mut err = struct_span_err!(
72 "found a documentation comment that doesn't document anything",
75 "doc comments must come before what they document, maybe a comment was \
84 pub(super) trait RecoverQPath: Sized + 'static {
85 const PATH_STYLE: PathStyle = PathStyle::Expr;
86 fn to_ty(&self) -> Option<P<Ty>>;
87 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
90 impl RecoverQPath for Ty {
91 const PATH_STYLE: PathStyle = PathStyle::Type;
92 fn to_ty(&self) -> Option<P<Ty>> {
95 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
98 kind: TyKind::Path(qself, path),
99 id: ast::DUMMY_NODE_ID,
105 impl RecoverQPath for Pat {
106 fn to_ty(&self) -> Option<P<Ty>> {
109 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
112 kind: PatKind::Path(qself, path),
113 id: ast::DUMMY_NODE_ID,
119 impl RecoverQPath for Expr {
120 fn to_ty(&self) -> Option<P<Ty>> {
123 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
126 kind: ExprKind::Path(qself, path),
127 attrs: AttrVec::new(),
128 id: ast::DUMMY_NODE_ID,
134 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
135 pub(crate) enum ConsumeClosingDelim {
140 #[derive(Clone, Copy)]
141 pub enum AttemptLocalParseRecovery {
146 impl AttemptLocalParseRecovery {
147 pub fn yes(&self) -> bool {
149 AttemptLocalParseRecovery::Yes => true,
150 AttemptLocalParseRecovery::No => false,
154 pub fn no(&self) -> bool {
156 AttemptLocalParseRecovery::Yes => false,
157 AttemptLocalParseRecovery::No => true,
162 /// Information for emitting suggestions and recovering from
163 /// C-style `i++`, `--i`, etc.
164 #[derive(Debug, Copy, Clone)]
165 struct IncDecRecovery {
166 /// Is this increment/decrement its own statement?
167 standalone: IsStandalone,
168 /// Is this an increment or decrement?
170 /// Is this pre- or postfix?
174 /// Is an increment or decrement expression its own statement?
175 #[derive(Debug, Copy, Clone)]
177 /// It's standalone, i.e., its own statement.
179 /// It's a subexpression, i.e., *not* standalone.
181 /// It's maybe standalone; we're not sure.
185 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
188 // FIXME: `i--` recovery isn't implemented yet
193 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
200 fn chr(&self) -> char {
207 fn name(&self) -> &'static str {
209 Self::Inc => "increment",
210 Self::Dec => "decrement",
215 impl std::fmt::Display for UnaryFixity {
216 fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
218 Self::Pre => write!(f, "prefix"),
219 Self::Post => write!(f, "postfix"),
226 patches: Vec<(Span, String)>,
227 applicability: Applicability,
231 fn emit(self, err: &mut Diagnostic) {
232 err.multipart_suggestion(&self.msg, self.patches, self.applicability);
235 /// Overrides individual messages and applicabilities.
237 err: &mut Diagnostic,
239 applicability: Applicability,
240 suggestions: impl Iterator<Item = Self>,
242 err.multipart_suggestions(msg, suggestions.map(|s| s.patches), applicability);
246 #[derive(SessionDiagnostic)]
247 #[diag(parser::maybe_report_ambiguous_plus)]
248 struct AmbiguousPlus {
251 #[suggestion(code = "({sum_ty})")]
255 #[derive(SessionDiagnostic)]
256 #[diag(parser::maybe_recover_from_bad_type_plus, code = "E0178")]
262 pub sub: BadTypePlusSub,
265 #[derive(SessionSubdiagnostic)]
266 pub enum BadTypePlusSub {
269 code = "{sum_with_parens}",
270 applicability = "machine-applicable"
273 sum_with_parens: String,
277 #[label(parser::forgot_paren)]
282 #[label(parser::expect_path)]
289 #[derive(SessionDiagnostic)]
290 #[diag(parser::maybe_recover_from_bad_qpath_stage_2)]
291 struct BadQPathStage2 {
293 #[suggestion(applicability = "maybe-incorrect")]
298 #[derive(SessionDiagnostic)]
299 #[diag(parser::incorrect_semicolon)]
300 struct IncorrectSemicolon<'a> {
302 #[suggestion_short(applicability = "machine-applicable")]
305 opt_help: Option<()>,
309 #[derive(SessionDiagnostic)]
310 #[diag(parser::incorrect_use_of_await)]
311 struct IncorrectUseOfAwait {
313 #[suggestion(parser::parentheses_suggestion, applicability = "machine-applicable")]
317 #[derive(SessionDiagnostic)]
318 #[diag(parser::incorrect_use_of_await)]
319 struct IncorrectAwait {
322 #[suggestion(parser::postfix_suggestion, code = "{expr}.await{question_mark}")]
323 sugg_span: (Span, Applicability),
325 question_mark: &'static str,
328 #[derive(SessionDiagnostic)]
329 #[diag(parser::in_in_typo)]
333 #[suggestion(applicability = "machine-applicable")]
337 #[derive(SessionDiagnostic)]
338 #[diag(parser::invalid_variable_declaration)]
339 pub struct InvalidVariableDeclaration {
343 pub sub: InvalidVariableDeclarationSub,
346 #[derive(SessionSubdiagnostic)]
347 pub enum InvalidVariableDeclarationSub {
349 parser::switch_mut_let_order,
350 applicability = "maybe-incorrect",
353 SwitchMutLetOrder(#[primary_span] Span),
355 parser::missing_let_before_mut,
356 applicability = "machine-applicable",
359 MissingLet(#[primary_span] Span),
360 #[suggestion(parser::use_let_not_auto, applicability = "machine-applicable", code = "let")]
361 UseLetNotAuto(#[primary_span] Span),
362 #[suggestion(parser::use_let_not_var, applicability = "machine-applicable", code = "let")]
363 UseLetNotVar(#[primary_span] Span),
366 #[derive(SessionDiagnostic)]
367 #[diag(parser::invalid_comparison_operator)]
368 pub(crate) struct InvalidComparisonOperator {
373 pub sub: InvalidComparisonOperatorSub,
376 #[derive(SessionSubdiagnostic)]
377 pub(crate) enum InvalidComparisonOperatorSub {
380 applicability = "machine-applicable",
389 #[label(parser::spaceship_operator_invalid)]
390 Spaceship(#[primary_span] Span),
393 #[derive(SessionDiagnostic)]
394 #[diag(parser::invalid_logical_operator)]
396 pub(crate) struct InvalidLogicalOperator {
399 pub incorrect: String,
401 pub sub: InvalidLogicalOperatorSub,
404 #[derive(SessionSubdiagnostic)]
405 pub(crate) enum InvalidLogicalOperatorSub {
407 parser::use_amp_amp_for_conjunction,
408 applicability = "machine-applicable",
411 Conjunction(#[primary_span] Span),
413 parser::use_pipe_pipe_for_disjunction,
414 applicability = "machine-applicable",
417 Disjunction(#[primary_span] Span),
420 #[derive(SessionDiagnostic)]
421 #[diag(parser::tilde_is_not_unary_operator)]
422 pub(crate) struct TildeAsUnaryOperator(
424 #[suggestion_short(applicability = "machine-applicable", code = "!")]
428 #[derive(SessionDiagnostic)]
429 #[diag(parser::unexpected_token_after_not)]
430 pub(crate) struct NotAsNegationOperator {
433 pub negated_desc: String,
434 #[suggestion_short(applicability = "machine-applicable", code = "!")]
438 #[derive(SessionDiagnostic)]
439 #[diag(parser::malformed_loop_label)]
440 pub(crate) struct MalformedLoopLabel {
442 #[suggestion(applicability = "machine-applicable", code = "{correct_label}")]
444 pub correct_label: Ident,
447 #[derive(SessionDiagnostic)]
448 #[diag(parser::lifetime_in_borrow_expression)]
449 pub(crate) struct LifetimeInBorrowExpression {
452 #[suggestion(applicability = "machine-applicable", code = "")]
454 pub lifetime_span: Span,
457 #[derive(SessionDiagnostic)]
458 #[diag(parser::field_expression_with_generic)]
459 pub(crate) struct FieldExpressionWithGeneric(#[primary_span] pub Span);
461 #[derive(SessionDiagnostic)]
462 #[diag(parser::macro_invocation_with_qualified_path)]
463 pub(crate) struct MacroInvocationWithQualifiedPath(#[primary_span] pub Span);
465 #[derive(SessionDiagnostic)]
466 #[diag(parser::unexpected_token_after_label)]
467 pub(crate) struct UnexpectedTokenAfterLabel(
469 #[label(parser::unexpected_token_after_label)]
473 #[derive(SessionDiagnostic)]
474 #[diag(parser::require_colon_after_labeled_expression)]
476 pub(crate) struct RequireColonAfterLabeledExpression {
481 #[suggestion_short(applicability = "machine-applicable", code = ": ")]
485 #[derive(SessionDiagnostic)]
486 #[diag(parser::do_catch_syntax_removed)]
488 pub(crate) struct DoCatchSyntaxRemoved {
490 #[suggestion(applicability = "machine-applicable", code = "try")]
494 #[derive(SessionDiagnostic)]
495 #[diag(parser::float_literal_requires_integer_part)]
496 pub(crate) struct FloatLiteralRequiresIntegerPart {
498 #[suggestion(applicability = "machine-applicable", code = "{correct}")]
503 #[derive(SessionDiagnostic)]
504 #[diag(parser::invalid_int_literal_width)]
506 pub(crate) struct InvalidIntLiteralWidth {
512 #[derive(SessionDiagnostic)]
513 #[diag(parser::invalid_num_literal_base_prefix)]
515 pub(crate) struct InvalidNumLiteralBasePrefix {
517 #[suggestion(applicability = "maybe-incorrect", code = "{fixed}")]
522 #[derive(SessionDiagnostic)]
523 #[diag(parser::invalid_num_literal_suffix)]
525 pub(crate) struct InvalidNumLiteralSuffix {
532 #[derive(SessionDiagnostic)]
533 #[diag(parser::invalid_float_literal_width)]
535 pub(crate) struct InvalidFloatLiteralWidth {
541 #[derive(SessionDiagnostic)]
542 #[diag(parser::invalid_float_literal_suffix)]
544 pub(crate) struct InvalidFloatLiteralSuffix {
551 #[derive(SessionDiagnostic)]
552 #[diag(parser::int_literal_too_large)]
553 pub(crate) struct IntLiteralTooLarge {
558 #[derive(SessionDiagnostic)]
559 #[diag(parser::missing_semicolon_before_array)]
560 pub(crate) struct MissingSemicolonBeforeArray {
562 pub open_delim: Span,
563 #[suggestion_verbose(applicability = "maybe-incorrect", code = ";")]
567 #[derive(SessionDiagnostic)]
568 #[diag(parser::invalid_block_macro_segment)]
569 pub(crate) struct InvalidBlockMacroSegment {
576 #[derive(SessionDiagnostic)]
577 #[diag(parser::if_expression_missing_then_block)]
578 pub(crate) struct IfExpressionMissingThenBlock {
582 pub sub: IfExpressionMissingThenBlockSub,
585 #[derive(SessionSubdiagnostic)]
586 pub(crate) enum IfExpressionMissingThenBlockSub {
587 #[help(parser::condition_possibly_unfinished)]
588 UnfinishedCondition(#[primary_span] Span),
589 #[help(parser::add_then_block)]
590 AddThenBlock(#[primary_span] Span),
593 #[derive(SessionDiagnostic)]
594 #[diag(parser::if_expression_missing_condition)]
595 pub(crate) struct IfExpressionMissingCondition {
597 #[label(parser::condition_label)]
599 #[label(parser::block_label)]
600 pub block_span: Span,
603 #[derive(SessionDiagnostic)]
604 #[diag(parser::expected_expression_found_let)]
605 pub(crate) struct ExpectedExpressionFoundLet {
610 #[derive(SessionDiagnostic)]
611 #[diag(parser::expected_else_block)]
612 pub(crate) struct ExpectedElseBlock {
614 pub first_tok_span: Span,
615 pub first_tok: String,
618 #[suggestion(applicability = "maybe-incorrect", code = "if ")]
619 pub condition_start: Span,
622 #[derive(SessionDiagnostic)]
623 #[diag(parser::outer_attribute_not_allowed_on_if_else)]
624 pub(crate) struct OuterAttributeNotAllowedOnIfElse {
628 #[label(parser::branch_label)]
629 pub branch_span: Span,
631 #[label(parser::ctx_label)]
635 #[suggestion(applicability = "machine-applicable", code = "")]
636 pub attributes: Span,
639 #[derive(SessionDiagnostic)]
640 #[diag(parser::missing_in_in_for_loop)]
641 pub(crate) struct MissingInInForLoop {
645 pub sub: MissingInInForLoopSub,
648 #[derive(SessionSubdiagnostic)]
649 pub(crate) enum MissingInInForLoopSub {
650 // Has been misleading, at least in the past (closed Issue #48492), thus maybe-incorrect
651 #[suggestion_short(parser::use_in_not_of, applicability = "maybe-incorrect", code = "in")]
652 InNotOf(#[primary_span] Span),
653 #[suggestion_short(parser::add_in, applicability = "maybe-incorrect", code = " in ")]
654 AddIn(#[primary_span] Span),
657 #[derive(SessionDiagnostic)]
658 #[diag(parser::missing_comma_after_match_arm)]
659 pub(crate) struct MissingCommaAfterMatchArm {
661 #[suggestion(applicability = "machine-applicable", code = ",")]
665 #[derive(SessionDiagnostic)]
666 #[diag(parser::catch_after_try)]
668 pub(crate) struct CatchAfterTry {
673 #[derive(SessionDiagnostic)]
674 #[diag(parser::comma_after_base_struct)]
676 pub(crate) struct CommaAfterBaseStruct {
679 #[suggestion_short(applicability = "machine-applicable", code = "")]
683 #[derive(SessionDiagnostic)]
684 #[diag(parser::eq_field_init)]
685 pub(crate) struct EqFieldInit {
688 #[suggestion(applicability = "machine-applicable", code = ":")]
692 #[derive(SessionDiagnostic)]
693 #[diag(parser::dotdotdot)]
694 pub(crate) struct DotDotDot {
696 #[suggestion(parser::suggest_exclusive_range, applicability = "maybe-incorrect", code = "..")]
697 #[suggestion(parser::suggest_inclusive_range, applicability = "maybe-incorrect", code = "..=")]
701 #[derive(SessionDiagnostic)]
702 #[diag(parser::left_arrow_operator)]
703 pub(crate) struct LeftArrowOperator {
705 #[suggestion(applicability = "maybe-incorrect", code = "< -")]
709 // SnapshotParser is used to create a snapshot of the parser
710 // without causing duplicate errors being emitted when the `Parser`
712 pub struct SnapshotParser<'a> {
714 unclosed_delims: Vec<UnmatchedBrace>,
717 impl<'a> Deref for SnapshotParser<'a> {
718 type Target = Parser<'a>;
720 fn deref(&self) -> &Self::Target {
725 impl<'a> DerefMut for SnapshotParser<'a> {
726 fn deref_mut(&mut self) -> &mut Self::Target {
731 impl<'a> Parser<'a> {
732 #[rustc_lint_diagnostics]
733 pub(super) fn span_err<S: Into<MultiSpan>>(
737 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
738 err.span_err(sp, self.diagnostic())
741 #[rustc_lint_diagnostics]
742 pub fn struct_span_err<S: Into<MultiSpan>>(
745 m: impl Into<DiagnosticMessage>,
746 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
747 self.sess.span_diagnostic.struct_span_err(sp, m)
750 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: impl Into<DiagnosticMessage>) -> ! {
751 self.sess.span_diagnostic.span_bug(sp, m)
754 pub(super) fn diagnostic(&self) -> &'a Handler {
755 &self.sess.span_diagnostic
758 /// Replace `self` with `snapshot.parser` and extend `unclosed_delims` with `snapshot.unclosed_delims`.
759 /// This is to avoid losing unclosed delims errors `create_snapshot_for_diagnostic` clears.
760 pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
761 *self = snapshot.parser;
762 self.unclosed_delims.extend(snapshot.unclosed_delims.clone());
765 pub fn unclosed_delims(&self) -> &[UnmatchedBrace] {
766 &self.unclosed_delims
769 /// Create a snapshot of the `Parser`.
770 pub fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
771 let mut snapshot = self.clone();
772 let unclosed_delims = self.unclosed_delims.clone();
773 // Clear `unclosed_delims` in snapshot to avoid
774 // duplicate errors being emitted when the `Parser`
775 // is dropped (which may or may not happen, depending
776 // if the parsing the snapshot is created for is successful)
777 snapshot.unclosed_delims.clear();
778 SnapshotParser { parser: snapshot, unclosed_delims }
781 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
782 self.sess.source_map().span_to_snippet(span)
785 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
786 let mut err = self.struct_span_err(
788 &format!("expected identifier, found {}", super::token_descr(&self.token)),
790 let valid_follow = &[
796 TokenKind::OpenDelim(Delimiter::Brace),
797 TokenKind::OpenDelim(Delimiter::Parenthesis),
798 TokenKind::CloseDelim(Delimiter::Brace),
799 TokenKind::CloseDelim(Delimiter::Parenthesis),
801 match self.token.ident() {
803 if ident.is_raw_guess()
804 && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
806 err.span_suggestion_verbose(
807 ident.span.shrink_to_lo(),
808 &format!("escape `{}` to use it as an identifier", ident.name),
810 Applicability::MaybeIncorrect,
815 if let Some(token_descr) = super::token_descr_opt(&self.token) {
816 err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
818 err.span_label(self.token.span, "expected identifier");
819 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
824 Applicability::MachineApplicable,
831 pub(super) fn expected_one_of_not_found(
833 edible: &[TokenKind],
834 inedible: &[TokenKind],
835 ) -> PResult<'a, bool /* recovered */> {
836 debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
837 fn tokens_to_string(tokens: &[TokenType]) -> String {
838 let mut i = tokens.iter();
839 // This might be a sign we need a connect method on `Iterator`.
840 let b = i.next().map_or_else(String::new, |t| t.to_string());
841 i.enumerate().fold(b, |mut b, (i, a)| {
842 if tokens.len() > 2 && i == tokens.len() - 2 {
844 } else if tokens.len() == 2 && i == tokens.len() - 2 {
849 b.push_str(&a.to_string());
854 let mut expected = edible
856 .map(|x| TokenType::Token(x.clone()))
857 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
858 .chain(self.expected_tokens.iter().cloned())
859 .filter_map(|token| {
860 // filter out suggestions which suggest the same token which was found and deemed incorrect
861 fn is_ident_eq_keyword(found: &TokenKind, expected: &TokenType) -> bool {
862 if let TokenKind::Ident(current_sym, _) = found {
863 if let TokenType::Keyword(suggested_sym) = expected {
864 return current_sym == suggested_sym;
869 if token != parser::TokenType::Token(self.token.kind.clone()) {
870 let eq = is_ident_eq_keyword(&self.token.kind, &token);
871 // if the suggestion is a keyword and the found token is an ident,
872 // the content of which are equal to the suggestion's content,
873 // we can remove that suggestion (see the return None statement below)
875 // if this isn't the case however, and the suggestion is a token the
876 // content of which is the same as the found token's, we remove it as well
878 if let TokenType::Token(kind) = &token {
879 if kind == &self.token.kind {
888 .collect::<Vec<_>>();
889 expected.sort_by_cached_key(|x| x.to_string());
892 let sm = self.sess.source_map();
893 let msg = format!("expected `;`, found {}", super::token_descr(&self.token));
894 let appl = Applicability::MachineApplicable;
895 if expected.contains(&TokenType::Token(token::Semi)) {
896 if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
897 // Likely inside a macro, can't provide meaningful suggestions.
898 } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
899 // The current token is in the same line as the prior token, not recoverable.
900 } else if [token::Comma, token::Colon].contains(&self.token.kind)
901 && self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis)
903 // Likely typo: The current token is on a new line and is expected to be
904 // `.`, `;`, `?`, or an operator after a close delimiter token.
906 // let a = std::process::Command::new("echo")
910 // https://github.com/rust-lang/rust/issues/72253
911 } else if self.look_ahead(1, |t| {
912 t == &token::CloseDelim(Delimiter::Brace)
913 || t.can_begin_expr() && t.kind != token::Colon
914 }) && [token::Comma, token::Colon].contains(&self.token.kind)
916 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
917 // either `,` or `:`, and the next token could either start a new statement or is a
918 // block close. For example:
923 let sp = self.prev_token.span;
924 self.struct_span_err(sp, &msg)
925 .span_suggestion_short(sp, "change this to `;`", ";", appl)
928 } else if self.look_ahead(0, |t| {
929 t == &token::CloseDelim(Delimiter::Brace)
930 || (t.can_begin_expr() && t != &token::Semi && t != &token::Pound)
931 // Avoid triggering with too many trailing `#` in raw string.
933 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo())
934 ) && t == &token::Pound)
935 }) && !expected.contains(&TokenType::Token(token::Comma))
937 // Missing semicolon typo. This is triggered if the next token could either start a
938 // new statement or is a block close. For example:
942 let sp = self.prev_token.span.shrink_to_hi();
943 self.struct_span_err(sp, &msg)
944 .span_label(self.token.span, "unexpected token")
945 .span_suggestion_short(sp, "add `;` here", ";", appl)
951 let expect = tokens_to_string(&expected);
952 let actual = super::token_descr(&self.token);
953 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
954 let short_expect = if expected.len() > 6 {
955 format!("{} possible tokens", expected.len())
960 format!("expected one of {expect}, found {actual}"),
961 (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")),
963 } else if expected.is_empty() {
965 format!("unexpected token: {actual}"),
966 (self.prev_token.span, "unexpected token after this".to_string()),
970 format!("expected {expect}, found {actual}"),
971 (self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
974 self.last_unexpected_token_span = Some(self.token.span);
975 let mut err = self.struct_span_err(self.token.span, &msg_exp);
977 if let TokenKind::Ident(symbol, _) = &self.prev_token.kind {
978 if symbol.as_str() == "public" {
979 err.span_suggestion_short(
980 self.prev_token.span,
981 "write `pub` instead of `public` to make the item public",
987 if ["def", "fun", "func", "function"].contains(&symbol.as_str()) {
988 err.span_suggestion_short(
989 self.prev_token.span,
990 &format!("write `fn` instead of `{symbol}` to declare a function"),
997 // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
998 // there are unclosed angle brackets
999 if self.unmatched_angle_bracket_count > 0
1000 && self.token.kind == TokenKind::Eq
1001 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
1003 err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
1006 let sp = if self.token == token::Eof {
1007 // This is EOF; don't want to point at the following char, but rather the last token.
1008 self.prev_token.span
1012 match self.recover_closing_delimiter(
1015 .filter_map(|tt| match tt {
1016 TokenType::Token(t) => Some(t.clone()),
1019 .collect::<Vec<_>>(),
1024 return Ok(recovered);
1028 if self.check_too_many_raw_str_terminators(&mut err) {
1029 if expected.contains(&TokenType::Token(token::Semi)) && self.eat(&token::Semi) {
1037 if self.prev_token.span == DUMMY_SP {
1038 // Account for macro context where the previous span might not be
1039 // available to avoid incorrect output (#54841).
1040 err.span_label(self.token.span, label_exp);
1041 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
1042 // When the spans are in the same line, it means that the only content between
1043 // them is whitespace, point at the found token in that case:
1045 // X | () => { syntax error };
1046 // | ^^^^^ expected one of 8 possible tokens here
1048 // instead of having:
1050 // X | () => { syntax error };
1051 // | -^^^^^ unexpected token
1053 // | expected one of 8 possible tokens here
1054 err.span_label(self.token.span, label_exp);
1056 err.span_label(sp, label_exp);
1057 err.span_label(self.token.span, "unexpected token");
1059 self.maybe_annotate_with_ascription(&mut err, false);
1063 fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
1064 let sm = self.sess.source_map();
1065 match (&self.prev_token.kind, &self.token.kind) {
1067 TokenKind::Literal(Lit {
1068 kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
1072 ) if !sm.is_multiline(
1073 self.prev_token.span.shrink_to_hi().until(self.token.span.shrink_to_lo()),
1076 let n_hashes: u8 = *n_hashes;
1077 err.set_primary_message("too many `#` when terminating raw string");
1078 let str_span = self.prev_token.span;
1079 let mut span = self.token.span;
1081 while self.token.kind == TokenKind::Pound
1082 && !sm.is_multiline(span.shrink_to_hi().until(self.token.span.shrink_to_lo()))
1084 span = span.with_hi(self.token.span.hi());
1089 err.span_suggestion(
1091 &format!("remove the extra `#`{}", pluralize!(count)),
1093 Applicability::MachineApplicable,
1097 &format!("this raw string started with {n_hashes} `#`{}", pluralize!(n_hashes)),
1105 pub fn maybe_suggest_struct_literal(
1109 ) -> Option<PResult<'a, P<Block>>> {
1110 if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
1111 // We might be having a struct literal where people forgot to include the path:
1112 // fn foo() -> Foo {
1115 let mut snapshot = self.create_snapshot_for_diagnostic();
1117 Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
1118 let struct_expr = snapshot.parse_struct_expr(None, path, false);
1119 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
1120 return Some(match (struct_expr, block_tail) {
1121 (Ok(expr), Err(mut err)) => {
1122 // We have encountered the following:
1123 // fn foo() -> Foo {
1127 // fn foo() -> Foo { Path {
1131 self.struct_span_err(
1133 fluent::parser::struct_literal_body_without_path,
1135 .multipart_suggestion(
1136 fluent::parser::suggestion,
1138 (expr.span.shrink_to_lo(), "{ SomeStruct ".to_string()),
1139 (expr.span.shrink_to_hi(), " }".to_string()),
1141 Applicability::MaybeIncorrect,
1144 self.restore_snapshot(snapshot);
1145 let mut tail = self.mk_block(
1146 vec![self.mk_stmt_err(expr.span)],
1148 lo.to(self.prev_token.span),
1150 tail.could_be_bare_literal = true;
1153 (Err(err), Ok(tail)) => {
1154 // We have a block tail that contains a somehow valid type ascription expr.
1158 (Err(snapshot_err), Err(err)) => {
1159 // We don't know what went wrong, emit the normal error.
1160 snapshot_err.cancel();
1161 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
1164 (Ok(_), Ok(mut tail)) => {
1165 tail.could_be_bare_literal = true;
1173 pub fn maybe_annotate_with_ascription(
1175 err: &mut Diagnostic,
1176 maybe_expected_semicolon: bool,
1178 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
1179 let sm = self.sess.source_map();
1180 let next_pos = sm.lookup_char_pos(self.token.span.lo());
1181 let op_pos = sm.lookup_char_pos(sp.hi());
1183 let allow_unstable = self.sess.unstable_features.is_nightly_build();
1186 err.span_suggestion(
1188 "maybe write a path separator here",
1191 Applicability::MaybeIncorrect
1193 Applicability::MachineApplicable
1196 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
1197 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
1198 err.span_suggestion(
1200 "try using a semicolon",
1202 Applicability::MaybeIncorrect,
1204 } else if allow_unstable {
1205 err.span_label(sp, "tried to parse a type due to this type ascription");
1207 err.span_label(sp, "tried to parse a type due to this");
1210 // Give extra information about type ascription only if it's a nightly compiler.
1212 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
1216 // Avoid giving too much info when it was likely an unrelated typo.
1218 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
1219 for more information",
1226 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
1227 /// passes through any errors encountered. Used for error recovery.
1228 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
1230 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
1231 Ok(p.parse_token_tree())
1238 /// This function checks if there are trailing angle brackets and produces
1239 /// a diagnostic to suggest removing them.
1241 /// ```ignore (diagnostic)
1242 /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
1243 /// ^^ help: remove extra angle brackets
1246 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
1247 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
1248 pub(super) fn check_trailing_angle_brackets(
1250 segment: &PathSegment,
1253 // This function is intended to be invoked after parsing a path segment where there are two
1256 // 1. A specific token is expected after the path segment.
1257 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
1258 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
1259 // 2. No specific token is expected after the path segment.
1260 // eg. `x.foo` (field access)
1262 // This function is called after parsing `.foo` and before parsing the token `end` (if
1263 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
1266 // We only care about trailing angle brackets if we previously parsed angle bracket
1267 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
1268 // removed in this case:
1270 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
1272 // This case is particularly tricky as we won't notice it just looking at the tokens -
1273 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
1274 // have already been parsed):
1276 // `x.foo::<u32>>>(3)`
1277 let parsed_angle_bracket_args =
1278 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
1281 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
1282 parsed_angle_bracket_args,
1284 if !parsed_angle_bracket_args {
1288 // Keep the span at the start so we can highlight the sequence of `>` characters to be
1290 let lo = self.token.span;
1292 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
1293 // (since we might have the field access case and the characters we're eating are
1294 // actual operators and not trailing characters - ie `x.foo >> 3`).
1295 let mut position = 0;
1297 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
1298 // many of each (so we can correctly pluralize our error messages) and continue to
1300 let mut number_of_shr = 0;
1301 let mut number_of_gt = 0;
1302 while self.look_ahead(position, |t| {
1303 trace!("check_trailing_angle_brackets: t={:?}", t);
1304 if *t == token::BinOp(token::BinOpToken::Shr) {
1307 } else if *t == token::Gt {
1317 // If we didn't find any trailing `>` characters, then we have nothing to error about.
1319 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
1320 number_of_gt, number_of_shr,
1322 if number_of_gt < 1 && number_of_shr < 1 {
1326 // Finally, double check that we have our end token as otherwise this is the
1328 if self.look_ahead(position, |t| {
1329 trace!("check_trailing_angle_brackets: t={:?}", t);
1330 end.contains(&&t.kind)
1332 // Eat from where we started until the end token so that parsing can continue
1333 // as if we didn't have those extra angle brackets.
1334 self.eat_to_tokens(end);
1335 let span = lo.until(self.token.span);
1337 let total_num_of_gt = number_of_gt + number_of_shr * 2;
1338 self.struct_span_err(
1340 &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
1344 &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
1346 Applicability::MachineApplicable,
1354 /// Check if a method call with an intended turbofish has been written without surrounding
1356 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
1357 if token::ModSep == self.token.kind && segment.args.is_none() {
1358 let snapshot = self.create_snapshot_for_diagnostic();
1360 let lo = self.token.span;
1361 match self.parse_angle_args(None) {
1363 let span = lo.to(self.prev_token.span);
1364 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
1365 let mut trailing_span = self.prev_token.span.shrink_to_hi();
1366 while self.token.kind == token::BinOp(token::Shr)
1367 || self.token.kind == token::Gt
1369 trailing_span = trailing_span.to(self.token.span);
1372 if self.token.kind == token::OpenDelim(Delimiter::Parenthesis) {
1373 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
1374 let args = AngleBracketedArgs { args, span }.into();
1375 segment.args = args;
1377 self.struct_span_err(
1379 "generic parameters without surrounding angle brackets",
1381 .multipart_suggestion(
1382 "surround the type parameters with angle brackets",
1384 (span.shrink_to_lo(), "<".to_string()),
1385 (trailing_span, ">".to_string()),
1387 Applicability::MachineApplicable,
1391 // This doesn't look like an invalid turbofish, can't recover parse state.
1392 self.restore_snapshot(snapshot);
1396 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
1397 // generic parse error instead.
1399 self.restore_snapshot(snapshot);
1405 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
1406 /// encounter a parse error when encountering the first `,`.
1407 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
1409 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
1411 ) -> PResult<'a, ()> {
1412 if let ExprKind::Binary(binop, _, _) = &expr.kind
1413 && let ast::BinOpKind::Lt = binop.node
1414 && self.eat(&token::Comma)
1416 let x = self.parse_seq_to_before_end(
1418 SeqSep::trailing_allowed(token::Comma),
1419 |p| p.parse_generic_arg(None),
1422 Ok((_, _, false)) => {
1423 if self.eat(&token::Gt) {
1424 e.span_suggestion_verbose(
1425 binop.span.shrink_to_lo(),
1426 TURBOFISH_SUGGESTION_STR,
1428 Applicability::MaybeIncorrect,
1431 match self.parse_expr() {
1434 self.mk_expr_err(expr.span.to(self.prev_token.span));
1438 *expr = self.mk_expr_err(expr.span);
1453 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
1454 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
1455 /// parenthesising the leftmost comparison.
1456 fn attempt_chained_comparison_suggestion(
1458 err: &mut Diagnostic,
1460 outer_op: &Spanned<AssocOp>,
1461 ) -> bool /* advanced the cursor */ {
1462 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
1463 if let ExprKind::Field(_, ident) = l1.kind
1464 && ident.as_str().parse::<i32>().is_err()
1465 && !matches!(r1.kind, ExprKind::Lit(_))
1467 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
1468 // suggestion being the only one to apply is high.
1471 let mut enclose = |left: Span, right: Span| {
1472 err.multipart_suggestion(
1473 "parenthesize the comparison",
1475 (left.shrink_to_lo(), "(".to_string()),
1476 (right.shrink_to_hi(), ")".to_string()),
1478 Applicability::MaybeIncorrect,
1481 return match (op.node, &outer_op.node) {
1483 (BinOpKind::Eq, AssocOp::Equal) |
1484 // `x < y < z` and friends.
1485 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
1486 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
1487 // `x > y > z` and friends.
1488 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
1489 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
1490 let expr_to_str = |e: &Expr| {
1491 self.span_to_snippet(e.span)
1492 .unwrap_or_else(|_| pprust::expr_to_string(&e))
1494 err.span_suggestion_verbose(
1495 inner_op.span.shrink_to_hi(),
1496 "split the comparison into two",
1497 format!(" && {}", expr_to_str(&r1)),
1498 Applicability::MaybeIncorrect,
1500 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
1503 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
1504 // Consume `z`/outer-op-rhs.
1505 let snapshot = self.create_snapshot_for_diagnostic();
1506 match self.parse_expr() {
1508 // We are sure that outer-op-rhs could be consumed, the suggestion is
1510 enclose(r1.span, r2.span);
1515 self.restore_snapshot(snapshot);
1521 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
1522 let snapshot = self.create_snapshot_for_diagnostic();
1523 // At this point it is always valid to enclose the lhs in parentheses, no
1524 // further checks are necessary.
1525 match self.parse_expr() {
1527 enclose(l1.span, r1.span);
1532 self.restore_snapshot(snapshot);
1543 /// Produces an error if comparison operators are chained (RFC #558).
1544 /// We only need to check the LHS, not the RHS, because all comparison ops have same
1545 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
1547 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
1548 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
1551 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
1552 /// associative we can infer that we have:
1561 pub(super) fn check_no_chained_comparison(
1564 outer_op: &Spanned<AssocOp>,
1565 ) -> PResult<'a, Option<P<Expr>>> {
1567 outer_op.node.is_comparison(),
1568 "check_no_chained_comparison: {:?} is not comparison",
1572 let mk_err_expr = |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err)));
1574 match inner_op.kind {
1575 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
1576 let mut err = self.struct_span_err(
1577 vec![op.span, self.prev_token.span],
1578 "comparison operators cannot be chained",
1581 let suggest = |err: &mut Diagnostic| {
1582 err.span_suggestion_verbose(
1583 op.span.shrink_to_lo(),
1584 TURBOFISH_SUGGESTION_STR,
1586 Applicability::MaybeIncorrect,
1590 // Include `<` to provide this recommendation even in a case like
1591 // `Foo<Bar<Baz<Qux, ()>>>`
1592 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
1593 || outer_op.node == AssocOp::Greater
1595 if outer_op.node == AssocOp::Less {
1596 let snapshot = self.create_snapshot_for_diagnostic();
1598 // So far we have parsed `foo<bar<`, consume the rest of the type args.
1600 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
1601 self.consume_tts(1, &modifiers);
1603 if !&[token::OpenDelim(Delimiter::Parenthesis), token::ModSep]
1604 .contains(&self.token.kind)
1606 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
1607 // parser and bail out.
1608 self.restore_snapshot(snapshot);
1611 return if token::ModSep == self.token.kind {
1612 // We have some certainty that this was a bad turbofish at this point.
1616 let snapshot = self.create_snapshot_for_diagnostic();
1617 self.bump(); // `::`
1619 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
1620 match self.parse_expr() {
1622 // 99% certain that the suggestion is correct, continue parsing.
1624 // FIXME: actually check that the two expressions in the binop are
1625 // paths and resynthesize new fn call expression instead of using
1626 // `ExprKind::Err` placeholder.
1627 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1631 // Not entirely sure now, but we bubble the error up with the
1633 self.restore_snapshot(snapshot);
1637 } else if token::OpenDelim(Delimiter::Parenthesis) == self.token.kind {
1638 // We have high certainty that this was a bad turbofish at this point.
1641 // Consume the fn call arguments.
1642 match self.consume_fn_args() {
1643 Err(()) => Err(err),
1646 // FIXME: actually check that the two expressions in the binop are
1647 // paths and resynthesize new fn call expression instead of using
1648 // `ExprKind::Err` placeholder.
1649 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1653 if !matches!(l1.kind, ExprKind::Lit(_))
1654 && !matches!(r1.kind, ExprKind::Lit(_))
1656 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1657 // be helpful, but don't attempt to recover.
1658 err.help(TURBOFISH_SUGGESTION_STR);
1659 err.help("or use `(...)` if you meant to specify fn arguments");
1662 // If it looks like a genuine attempt to chain operators (as opposed to a
1663 // misformatted turbofish, for instance), suggest a correct form.
1664 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1667 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1669 // These cases cause too many knock-down errors, bail out (#61329).
1675 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1678 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1686 fn consume_fn_args(&mut self) -> Result<(), ()> {
1687 let snapshot = self.create_snapshot_for_diagnostic();
1690 // Consume the fn call arguments.
1692 (token::OpenDelim(Delimiter::Parenthesis), 1),
1693 (token::CloseDelim(Delimiter::Parenthesis), -1),
1695 self.consume_tts(1, &modifiers);
1697 if self.token.kind == token::Eof {
1698 // Not entirely sure that what we consumed were fn arguments, rollback.
1699 self.restore_snapshot(snapshot);
1702 // 99% certain that the suggestion is correct, continue parsing.
1707 pub(super) fn maybe_report_ambiguous_plus(&mut self, impl_dyn_multi: bool, ty: &Ty) {
1709 self.sess.emit_err(AmbiguousPlus { sum_ty: pprust::ty_to_string(&ty), span: ty.span });
1713 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1714 pub(super) fn maybe_recover_from_question_mark(&mut self, ty: P<Ty>) -> P<Ty> {
1715 if self.token == token::Question {
1717 self.struct_span_err(self.prev_token.span, "invalid `?` in type")
1718 .span_label(self.prev_token.span, "`?` is only allowed on expressions, not types")
1719 .multipart_suggestion(
1720 "if you meant to express that the type might not contain a value, use the `Option` wrapper type",
1722 (ty.span.shrink_to_lo(), "Option<".to_string()),
1723 (self.prev_token.span, ">".to_string()),
1725 Applicability::MachineApplicable,
1728 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1734 pub(super) fn maybe_recover_from_bad_type_plus(&mut self, ty: &Ty) -> PResult<'a, ()> {
1735 // Do not add `+` to expected tokens.
1736 if !self.token.is_like_plus() {
1741 let bounds = self.parse_generic_bounds(None)?;
1742 let sum_span = ty.span.to(self.prev_token.span);
1744 let sub = match ty.kind {
1745 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1746 let sum_with_parens = pprust::to_string(|s| {
1748 s.print_opt_lifetime(lifetime);
1749 s.print_mutability(mut_ty.mutbl, false);
1751 s.print_type(&mut_ty.ty);
1752 if !bounds.is_empty() {
1754 s.print_type_bounds(&bounds);
1759 BadTypePlusSub::AddParen { sum_with_parens, span: sum_span }
1761 TyKind::Ptr(..) | TyKind::BareFn(..) => BadTypePlusSub::ForgotParen { span: sum_span },
1762 _ => BadTypePlusSub::ExpectPath { span: sum_span },
1765 self.sess.emit_err(BadTypePlus { ty: pprust::ty_to_string(ty), span: sum_span, sub });
1770 pub(super) fn recover_from_prefix_increment(
1772 operand_expr: P<Expr>,
1775 ) -> PResult<'a, P<Expr>> {
1777 if prev_is_semi { IsStandalone::Standalone } else { IsStandalone::Subexpr };
1778 let kind = IncDecRecovery { standalone, op: IncOrDec::Inc, fixity: UnaryFixity::Pre };
1780 self.recover_from_inc_dec(operand_expr, kind, op_span)
1783 pub(super) fn recover_from_postfix_increment(
1785 operand_expr: P<Expr>,
1787 ) -> PResult<'a, P<Expr>> {
1788 let kind = IncDecRecovery {
1789 standalone: IsStandalone::Maybe,
1791 fixity: UnaryFixity::Post,
1794 self.recover_from_inc_dec(operand_expr, kind, op_span)
1797 fn recover_from_inc_dec(
1800 kind: IncDecRecovery,
1802 ) -> PResult<'a, P<Expr>> {
1803 let mut err = self.struct_span_err(
1805 &format!("Rust has no {} {} operator", kind.fixity, kind.op.name()),
1807 err.span_label(op_span, &format!("not a valid {} operator", kind.fixity));
1809 let help_base_case = |mut err: DiagnosticBuilder<'_, _>, base| {
1810 err.help(&format!("use `{}= 1` instead", kind.op.chr()));
1816 let spans = match kind.fixity {
1817 UnaryFixity::Pre => (op_span, base.span.shrink_to_hi()),
1818 UnaryFixity::Post => (base.span.shrink_to_lo(), op_span),
1821 match kind.standalone {
1822 IsStandalone::Standalone => self.inc_dec_standalone_suggest(kind, spans).emit(&mut err),
1823 IsStandalone::Subexpr => {
1824 let Ok(base_src) = self.span_to_snippet(base.span)
1825 else { return help_base_case(err, base) };
1827 UnaryFixity::Pre => {
1828 self.prefix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1830 UnaryFixity::Post => {
1831 self.postfix_inc_dec_suggest(base_src, kind, spans).emit(&mut err)
1835 IsStandalone::Maybe => {
1836 let Ok(base_src) = self.span_to_snippet(base.span)
1837 else { return help_base_case(err, base) };
1838 let sugg1 = match kind.fixity {
1839 UnaryFixity::Pre => self.prefix_inc_dec_suggest(base_src, kind, spans),
1840 UnaryFixity::Post => self.postfix_inc_dec_suggest(base_src, kind, spans),
1842 let sugg2 = self.inc_dec_standalone_suggest(kind, spans);
1843 MultiSugg::emit_many(
1845 "use `+= 1` instead",
1846 Applicability::Unspecified,
1847 [sugg1, sugg2].into_iter(),
1854 fn prefix_inc_dec_suggest(
1857 kind: IncDecRecovery,
1858 (pre_span, post_span): (Span, Span),
1861 msg: format!("use `{}= 1` instead", kind.op.chr()),
1863 (pre_span, "{ ".to_string()),
1864 (post_span, format!(" {}= 1; {} }}", kind.op.chr(), base_src)),
1866 applicability: Applicability::MachineApplicable,
1870 fn postfix_inc_dec_suggest(
1873 kind: IncDecRecovery,
1874 (pre_span, post_span): (Span, Span),
1876 let tmp_var = if base_src.trim() == "tmp" { "tmp_" } else { "tmp" };
1878 msg: format!("use `{}= 1` instead", kind.op.chr()),
1880 (pre_span, format!("{{ let {tmp_var} = ")),
1881 (post_span, format!("; {} {}= 1; {} }}", base_src, kind.op.chr(), tmp_var)),
1883 applicability: Applicability::HasPlaceholders,
1887 fn inc_dec_standalone_suggest(
1889 kind: IncDecRecovery,
1890 (pre_span, post_span): (Span, Span),
1893 msg: format!("use `{}= 1` instead", kind.op.chr()),
1894 patches: vec![(pre_span, String::new()), (post_span, format!(" {}= 1", kind.op.chr()))],
1895 applicability: Applicability::MachineApplicable,
1899 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1900 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1901 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1902 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1905 ) -> PResult<'a, P<T>> {
1906 // Do not add `::` to expected tokens.
1907 if self.token == token::ModSep {
1908 if let Some(ty) = base.to_ty() {
1909 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1915 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1916 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1917 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1921 ) -> PResult<'a, P<T>> {
1922 self.expect(&token::ModSep)?;
1924 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1925 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1926 path.span = ty_span.to(self.prev_token.span);
1928 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1929 self.sess.emit_err(BadQPathStage2 {
1931 ty: format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1934 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1935 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1938 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1939 if self.token.kind == TokenKind::Semi {
1943 IncorrectSemicolon { span: self.prev_token.span, opt_help: None, name: "" };
1945 if !items.is_empty() {
1946 let previous_item = &items[items.len() - 1];
1947 let previous_item_kind_name = match previous_item.kind {
1948 // Say "braced struct" because tuple-structs and
1949 // braceless-empty-struct declarations do take a semicolon.
1950 ItemKind::Struct(..) => Some("braced struct"),
1951 ItemKind::Enum(..) => Some("enum"),
1952 ItemKind::Trait(..) => Some("trait"),
1953 ItemKind::Union(..) => Some("union"),
1956 if let Some(name) = previous_item_kind_name {
1957 err.opt_help = Some(());
1961 self.sess.emit_err(err);
1968 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1969 /// closing delimiter.
1970 pub(super) fn unexpected_try_recover(
1973 ) -> PResult<'a, bool /* recovered */> {
1974 let token_str = pprust::token_kind_to_string(t);
1975 let this_token_str = super::token_descr(&self.token);
1976 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1977 // Point at the end of the macro call when reaching end of macro arguments.
1978 (token::Eof, Some(_)) => {
1979 let sp = self.sess.source_map().next_point(self.prev_token.span);
1982 // We don't want to point at the following span after DUMMY_SP.
1983 // This happens when the parser finds an empty TokenStream.
1984 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1985 // EOF, don't want to point at the following char, but rather the last token.
1986 (token::Eof, None) => (self.prev_token.span, self.token.span),
1987 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1990 "expected `{}`, found {}",
1992 match (&self.token.kind, self.subparser_name) {
1993 (token::Eof, Some(origin)) => format!("end of {origin}"),
1994 _ => this_token_str,
1997 let mut err = self.struct_span_err(sp, &msg);
1998 let label_exp = format!("expected `{token_str}`");
1999 match self.recover_closing_delimiter(&[t.clone()], err) {
2002 return Ok(recovered);
2005 let sm = self.sess.source_map();
2006 if !sm.is_multiline(prev_sp.until(sp)) {
2007 // When the spans are in the same line, it means that the only content
2008 // between them is whitespace, point only at the found token.
2009 err.span_label(sp, label_exp);
2011 err.span_label(prev_sp, label_exp);
2012 err.span_label(sp, "unexpected token");
2017 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
2018 if self.eat(&token::Semi) {
2021 self.expect(&token::Semi).map(drop) // Error unconditionally
2024 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
2025 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
2026 pub(super) fn recover_incorrect_await_syntax(
2030 ) -> PResult<'a, P<Expr>> {
2031 let (hi, expr, is_question) = if self.token == token::Not {
2032 // Handle `await!(<expr>)`.
2033 self.recover_await_macro()?
2035 self.recover_await_prefix(await_sp)?
2037 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
2038 let kind = match expr.kind {
2039 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
2040 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
2041 ExprKind::Try(_) => ExprKind::Err,
2042 _ => ExprKind::Await(expr),
2044 let expr = self.mk_expr(lo.to(sp), kind);
2045 self.maybe_recover_from_bad_qpath(expr)
2048 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
2049 self.expect(&token::Not)?;
2050 self.expect(&token::OpenDelim(Delimiter::Parenthesis))?;
2051 let expr = self.parse_expr()?;
2052 self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
2053 Ok((self.prev_token.span, expr, false))
2056 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
2057 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
2058 let expr = if self.token == token::OpenDelim(Delimiter::Brace) {
2059 // Handle `await { <expr> }`.
2060 // This needs to be handled separately from the next arm to avoid
2061 // interpreting `await { <expr> }?` as `<expr>?.await`.
2062 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default)
2066 .map_err(|mut err| {
2067 err.span_label(await_sp, "while parsing this incorrect await expression");
2070 Ok((expr.span, expr, is_question))
2073 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
2074 let span = lo.to(hi);
2075 let applicability = match expr.kind {
2076 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
2077 _ => Applicability::MachineApplicable,
2080 self.sess.emit_err(IncorrectAwait {
2082 sugg_span: (span, applicability),
2083 expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr)),
2084 question_mark: if is_question { "?" } else { "" },
2090 /// If encountering `future.await()`, consumes and emits an error.
2091 pub(super) fn recover_from_await_method_call(&mut self) {
2092 if self.token == token::OpenDelim(Delimiter::Parenthesis)
2093 && self.look_ahead(1, |t| t == &token::CloseDelim(Delimiter::Parenthesis))
2096 let lo = self.token.span;
2098 let span = lo.to(self.token.span);
2101 self.sess.emit_err(IncorrectUseOfAwait { span });
2105 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
2106 let is_try = self.token.is_keyword(kw::Try);
2107 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
2108 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(Delimiter::Parenthesis)); //check for (
2110 if is_try && is_questionmark && is_open {
2111 let lo = self.token.span;
2112 self.bump(); //remove try
2113 self.bump(); //remove !
2114 let try_span = lo.to(self.token.span); //we take the try!( span
2115 self.bump(); //remove (
2116 let is_empty = self.token == token::CloseDelim(Delimiter::Parenthesis); //check if the block is empty
2117 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::No); //eat the block
2118 let hi = self.token.span;
2119 self.bump(); //remove )
2120 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
2121 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
2122 let prefix = if is_empty { "" } else { "alternatively, " };
2124 err.multipart_suggestion(
2125 "you can use the `?` operator instead",
2126 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
2127 Applicability::MachineApplicable,
2130 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);
2132 Ok(self.mk_expr_err(lo.to(hi)))
2134 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
2138 /// Recovers a situation like `for ( $pat in $expr )`
2139 /// and suggest writing `for $pat in $expr` instead.
2141 /// This should be called before parsing the `$block`.
2142 pub(super) fn recover_parens_around_for_head(
2145 begin_paren: Option<Span>,
2147 match (&self.token.kind, begin_paren) {
2148 (token::CloseDelim(Delimiter::Parenthesis), Some(begin_par_sp)) => {
2151 self.struct_span_err(
2152 MultiSpan::from_spans(vec![begin_par_sp, self.prev_token.span]),
2153 "unexpected parentheses surrounding `for` loop head",
2155 .multipart_suggestion(
2156 "remove parentheses in `for` loop",
2157 vec![(begin_par_sp, String::new()), (self.prev_token.span, String::new())],
2158 // With e.g. `for (x) in y)` this would replace `(x) in y)`
2159 // with `x) in y)` which is syntactically invalid.
2160 // However, this is prevented before we get here.
2161 Applicability::MachineApplicable,
2165 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
2166 pat.and_then(|pat| match pat.kind {
2167 PatKind::Paren(pat) => pat,
2175 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
2176 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
2177 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
2178 || self.token.is_ident() &&
2179 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
2180 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
2181 self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Parenthesis))
2182 || self.look_ahead(1, |t| t == &token::OpenDelim(Delimiter::Brace)) // `foo:bar {`
2183 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
2184 self.look_ahead(2, |t| t == &token::Lt) &&
2185 self.look_ahead(3, |t| t.is_ident())
2186 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
2187 self.look_ahead(2, |t| t.is_ident())
2188 || self.look_ahead(1, |t| t == &token::ModSep)
2189 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
2190 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
2193 pub(super) fn recover_seq_parse_error(
2197 result: PResult<'a, P<Expr>>,
2203 // Recover from parse error, callers expect the closing delim to be consumed.
2204 self.consume_block(delim, ConsumeClosingDelim::Yes);
2205 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err)
2210 pub(super) fn recover_closing_delimiter(
2212 tokens: &[TokenKind],
2213 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2214 ) -> PResult<'a, bool> {
2216 // We want to use the last closing delim that would apply.
2217 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
2218 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
2219 && Some(self.token.span) > unmatched.unclosed_span
2226 // Recover and assume that the detected unclosed delimiter was meant for
2227 // this location. Emit the diagnostic and act as if the delimiter was
2228 // present for the parser's sake.
2230 // Don't attempt to recover from this unclosed delimiter more than once.
2231 let unmatched = self.unclosed_delims.remove(pos);
2232 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
2233 if unmatched.found_delim.is_none() {
2234 // We encountered `Eof`, set this fact here to avoid complaining about missing
2235 // `fn main()` when we found place to suggest the closing brace.
2236 *self.sess.reached_eof.borrow_mut() = true;
2239 // We want to suggest the inclusion of the closing delimiter where it makes
2240 // the most sense, which is immediately after the last token:
2245 // | help: `)` may belong here
2247 // unclosed delimiter
2248 if let Some(sp) = unmatched.unclosed_span {
2249 let mut primary_span: Vec<Span> =
2250 err.span.primary_spans().iter().cloned().collect();
2251 primary_span.push(sp);
2252 let mut primary_span: MultiSpan = primary_span.into();
2253 for span_label in err.span.span_labels() {
2254 if let Some(label) = span_label.label {
2255 primary_span.push_span_label(span_label.span, label);
2258 err.set_span(primary_span);
2259 err.span_label(sp, "unclosed delimiter");
2261 // Backticks should be removed to apply suggestions.
2262 let mut delim = delim.to_string();
2263 delim.retain(|c| c != '`');
2264 err.span_suggestion_short(
2265 self.prev_token.span.shrink_to_hi(),
2266 &format!("`{delim}` may belong here"),
2268 Applicability::MaybeIncorrect,
2270 if unmatched.found_delim.is_none() {
2271 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
2272 // errors which would be emitted elsewhere in the parser and let other error
2273 // recovery consume the rest of the file.
2277 self.expected_tokens.clear(); // Reduce the number of errors.
2285 /// Eats tokens until we can be relatively sure we reached the end of the
2286 /// statement. This is something of a best-effort heuristic.
2288 /// We terminate when we find an unmatched `}` (without consuming it).
2289 pub(super) fn recover_stmt(&mut self) {
2290 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
2293 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
2294 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
2295 /// approximate -- it can mean we break too early due to macros, but that
2296 /// should only lead to sub-optimal recovery, not inaccurate parsing).
2298 /// If `break_on_block` is `Break`, then we will stop consuming tokens
2299 /// after finding (and consuming) a brace-delimited block.
2300 pub(super) fn recover_stmt_(
2302 break_on_semi: SemiColonMode,
2303 break_on_block: BlockMode,
2305 let mut brace_depth = 0;
2306 let mut bracket_depth = 0;
2307 let mut in_block = false;
2308 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
2310 debug!("recover_stmt_ loop {:?}", self.token);
2311 match self.token.kind {
2312 token::OpenDelim(Delimiter::Brace) => {
2315 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
2320 token::OpenDelim(Delimiter::Bracket) => {
2324 token::CloseDelim(Delimiter::Brace) => {
2325 if brace_depth == 0 {
2326 debug!("recover_stmt_ return - close delim {:?}", self.token);
2331 if in_block && bracket_depth == 0 && brace_depth == 0 {
2332 debug!("recover_stmt_ return - block end {:?}", self.token);
2336 token::CloseDelim(Delimiter::Bracket) => {
2338 if bracket_depth < 0 {
2344 debug!("recover_stmt_ return - Eof");
2349 if break_on_semi == SemiColonMode::Break
2351 && bracket_depth == 0
2353 debug!("recover_stmt_ return - Semi");
2358 if break_on_semi == SemiColonMode::Comma
2360 && bracket_depth == 0 =>
2362 debug!("recover_stmt_ return - Semi");
2370 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
2371 if self.eat_keyword(kw::In) {
2372 // a common typo: `for _ in in bar {}`
2373 self.sess.emit_err(InInTypo {
2374 span: self.prev_token.span,
2375 sugg_span: in_span.until(self.prev_token.span),
2380 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
2381 if let token::DocComment(..) = self.token.kind {
2382 self.struct_span_err(
2384 "documentation comments cannot be applied to a function parameter's type",
2386 .span_label(self.token.span, "doc comments are not allowed here")
2389 } else if self.token == token::Pound
2390 && self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Bracket))
2392 let lo = self.token.span;
2393 // Skip every token until next possible arg.
2394 while self.token != token::CloseDelim(Delimiter::Bracket) {
2397 let sp = lo.to(self.token.span);
2399 self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
2400 .span_label(sp, "attributes are not allowed here")
2405 pub(super) fn parameter_without_type(
2407 err: &mut Diagnostic,
2411 ) -> Option<Ident> {
2412 // If we find a pattern followed by an identifier, it could be an (incorrect)
2413 // C-style parameter declaration.
2414 if self.check_ident()
2415 && self.look_ahead(1, |t| {
2416 *t == token::Comma || *t == token::CloseDelim(Delimiter::Parenthesis)
2419 // `fn foo(String s) {}`
2420 let ident = self.parse_ident().unwrap();
2421 let span = pat.span.with_hi(ident.span.hi());
2423 err.span_suggestion(
2425 "declare the type after the parameter binding",
2426 "<identifier>: <type>",
2427 Applicability::HasPlaceholders,
2430 } else if require_name
2431 && (self.token == token::Comma
2432 || self.token == token::Lt
2433 || self.token == token::CloseDelim(Delimiter::Parenthesis))
2435 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
2437 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
2439 PatKind::Ident(_, ident, _) => (
2442 ": TypeName".to_string(),
2444 pat.span.shrink_to_lo(),
2445 pat.span.shrink_to_hi(),
2446 pat.span.shrink_to_lo(),
2448 // Also catches `fn foo(&a)`.
2449 PatKind::Ref(ref inner_pat, mutab)
2450 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
2452 match inner_pat.clone().into_inner().kind {
2453 PatKind::Ident(_, ident, _) => {
2454 let mutab = mutab.prefix_str();
2458 format!("{ident}: &{mutab}TypeName"),
2460 pat.span.shrink_to_lo(),
2462 pat.span.shrink_to_lo(),
2465 _ => unreachable!(),
2469 // Otherwise, try to get a type and emit a suggestion.
2470 if let Some(ty) = pat.to_ty() {
2471 err.span_suggestion_verbose(
2473 "explicitly ignore the parameter name",
2474 format!("_: {}", pprust::ty_to_string(&ty)),
2475 Applicability::MachineApplicable,
2484 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
2486 err.span_suggestion(
2488 "if this is a `self` type, give it a parameter name",
2490 Applicability::MaybeIncorrect,
2493 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
2494 // `fn foo(HashMap: TypeName<u32>)`.
2495 if self.token != token::Lt {
2496 err.span_suggestion(
2498 "if this is a parameter name, give it a type",
2500 Applicability::HasPlaceholders,
2503 err.span_suggestion(
2505 "if this is a type, explicitly ignore the parameter name",
2507 Applicability::MachineApplicable,
2511 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
2512 return if self.token == token::Lt { None } else { Some(ident) };
2517 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
2518 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
2519 self.expect(&token::Colon)?;
2520 let ty = self.parse_ty()?;
2526 "patterns aren't allowed in methods without bodies",
2528 .span_suggestion_short(
2530 "give this argument a name or use an underscore to ignore it",
2532 Applicability::MachineApplicable,
2536 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2538 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
2542 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
2543 let sp = param.pat.span;
2544 param.ty.kind = TyKind::Err;
2545 self.struct_span_err(sp, "unexpected `self` parameter in function")
2546 .span_label(sp, "must be the first parameter of an associated function")
2551 pub(super) fn consume_block(&mut self, delim: Delimiter, consume_close: ConsumeClosingDelim) {
2552 let mut brace_depth = 0;
2554 if self.eat(&token::OpenDelim(delim)) {
2556 } else if self.check(&token::CloseDelim(delim)) {
2557 if brace_depth == 0 {
2558 if let ConsumeClosingDelim::Yes = consume_close {
2559 // Some of the callers of this method expect to be able to parse the
2560 // closing delimiter themselves, so we leave it alone. Otherwise we advance
2570 } else if self.token == token::Eof {
2578 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2579 let (span, msg) = match (&self.token.kind, self.subparser_name) {
2580 (&token::Eof, Some(origin)) => {
2581 let sp = self.sess.source_map().next_point(self.prev_token.span);
2582 (sp, format!("expected expression, found end of {origin}"))
2586 format!("expected expression, found {}", super::token_descr(&self.token),),
2589 let mut err = self.struct_span_err(span, &msg);
2590 let sp = self.sess.source_map().start_point(self.token.span);
2591 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
2592 self.sess.expr_parentheses_needed(&mut err, *sp);
2594 err.span_label(span, "expected expression");
2600 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
2601 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
2602 modifier: &[(token::TokenKind, i64)],
2605 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
2608 if self.token.kind == token::Eof {
2615 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
2617 /// This is necessary because at this point we don't know whether we parsed a function with
2618 /// anonymous parameters or a function with names but no types. In order to minimize
2619 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
2620 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
2621 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
2622 /// we deduplicate them to not complain about duplicated parameter names.
2623 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
2624 let mut seen_inputs = FxHashSet::default();
2625 for input in fn_inputs.iter_mut() {
2626 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
2627 (&input.pat.kind, &input.ty.kind)
2633 if let Some(ident) = opt_ident {
2634 if seen_inputs.contains(&ident) {
2635 input.pat.kind = PatKind::Wild;
2637 seen_inputs.insert(ident);
2642 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
2643 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
2644 /// like the user has forgotten them.
2645 pub fn handle_ambiguous_unbraced_const_arg(
2647 args: &mut Vec<AngleBracketedArg>,
2648 ) -> PResult<'a, bool> {
2649 // If we haven't encountered a closing `>`, then the argument is malformed.
2650 // It's likely that the user has written a const expression without enclosing it
2651 // in braces, so we try to recover here.
2652 let arg = args.pop().unwrap();
2653 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
2654 // adverse side-effects to subsequent errors and seems to advance the parser.
2655 // We are causing this error here exclusively in case that a `const` expression
2656 // could be recovered from the current parser state, even if followed by more
2657 // arguments after a comma.
2658 let mut err = self.struct_span_err(
2660 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
2662 err.span_label(self.token.span, "expected one of `,` or `>`");
2663 match self.recover_const_arg(arg.span(), err) {
2665 args.push(AngleBracketedArg::Arg(arg));
2666 if self.eat(&token::Comma) {
2667 return Ok(true); // Continue
2672 // We will emit a more generic error later.
2676 return Ok(false); // Don't continue.
2679 /// Attempt to parse a generic const argument that has not been enclosed in braces.
2680 /// There are a limited number of expressions that are permitted without being encoded
2683 /// - Single-segment paths (i.e. standalone generic const parameters).
2684 /// All other expressions that can be parsed will emit an error suggesting the expression be
2685 /// wrapped in braces.
2686 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
2687 let start = self.token.span;
2688 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
2690 start.shrink_to_lo(),
2691 "while parsing a const generic argument starting here",
2695 if !self.expr_is_valid_const_arg(&expr) {
2696 self.struct_span_err(
2698 "expressions must be enclosed in braces to be used as const generic \
2701 .multipart_suggestion(
2702 "enclose the `const` expression in braces",
2704 (expr.span.shrink_to_lo(), "{ ".to_string()),
2705 (expr.span.shrink_to_hi(), " }".to_string()),
2707 Applicability::MachineApplicable,
2714 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2715 let snapshot = self.create_snapshot_for_diagnostic();
2716 let param = match self.parse_const_param(vec![]) {
2720 self.restore_snapshot(snapshot);
2725 self.struct_span_err(param.span(), "unexpected `const` parameter declaration");
2726 err.span_label(param.span(), "expected a `const` expression, not a parameter declaration");
2727 if let (Some(generics), Ok(snippet)) =
2728 (ty_generics, self.sess.source_map().span_to_snippet(param.span()))
2730 let (span, sugg) = match &generics.params[..] {
2731 [] => (generics.span, format!("<{snippet}>")),
2732 [.., generic] => (generic.span().shrink_to_hi(), format!(", {snippet}")),
2734 err.multipart_suggestion(
2735 "`const` parameters must be declared for the `impl`",
2736 vec![(span, sugg), (param.span(), param.ident.to_string())],
2737 Applicability::MachineApplicable,
2740 let value = self.mk_expr_err(param.span());
2742 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2745 pub fn recover_const_param_declaration(
2747 ty_generics: Option<&Generics>,
2748 ) -> PResult<'a, Option<GenericArg>> {
2749 // We have to check for a few different cases.
2750 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2751 return Ok(Some(arg));
2754 // We haven't consumed `const` yet.
2755 let start = self.token.span;
2756 self.bump(); // `const`
2758 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2760 .struct_span_err(start, "expected lifetime, type, or constant, found keyword `const`");
2761 if self.check_const_arg() {
2762 err.span_suggestion_verbose(
2763 start.until(self.token.span),
2764 "the `const` keyword is only needed in the definition of the type",
2766 Applicability::MaybeIncorrect,
2769 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2771 let after_kw_const = self.token.span;
2772 self.recover_const_arg(after_kw_const, err).map(Some)
2776 /// Try to recover from possible generic const argument without `{` and `}`.
2778 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2779 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2780 /// if we think that that the resulting expression would be well formed.
2781 pub fn recover_const_arg(
2784 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2785 ) -> PResult<'a, GenericArg> {
2786 let is_op_or_dot = AssocOp::from_token(&self.token)
2788 if let AssocOp::Greater
2790 | AssocOp::ShiftRight
2791 | AssocOp::GreaterEqual
2792 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2793 // assign a value to a defaulted generic parameter.
2795 | AssocOp::AssignOp(_) = op
2803 || self.token.kind == TokenKind::Dot;
2804 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2805 // type params has been parsed.
2807 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2808 if !is_op_or_dot && !was_op {
2809 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2812 let snapshot = self.create_snapshot_for_diagnostic();
2816 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2818 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2819 if token::EqEq == snapshot.token.kind {
2820 err.span_suggestion(
2821 snapshot.token.span,
2822 "if you meant to use an associated type binding, replace `==` with `=`",
2824 Applicability::MaybeIncorrect,
2826 let value = self.mk_expr_err(start.to(expr.span));
2828 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2829 } else if token::Colon == snapshot.token.kind
2830 && expr.span.lo() == snapshot.token.span.hi()
2831 && matches!(expr.kind, ExprKind::Path(..))
2833 // Find a mistake like "foo::var:A".
2834 err.span_suggestion(
2835 snapshot.token.span,
2836 "write a path separator here",
2838 Applicability::MaybeIncorrect,
2841 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2842 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2844 // Avoid the following output by checking that we consumed a full const arg:
2845 // help: expressions must be enclosed in braces to be used as const generic
2848 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2850 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2857 self.restore_snapshot(snapshot);
2861 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2862 pub fn dummy_const_arg_needs_braces(
2864 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2867 err.multipart_suggestion(
2868 "expressions must be enclosed in braces to be used as const generic \
2870 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2871 Applicability::MaybeIncorrect,
2873 let value = self.mk_expr_err(span);
2875 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2878 /// Get the diagnostics for the cases where `move async` is found.
2880 /// `move_async_span` starts at the 'm' of the move keyword and ends with the 'c' of the async keyword
2881 pub(super) fn incorrect_move_async_order_found(
2883 move_async_span: Span,
2884 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2886 self.struct_span_err(move_async_span, "the order of `move` and `async` is incorrect");
2887 err.span_suggestion_verbose(
2889 "try switching the order",
2891 Applicability::MaybeIncorrect,
2896 /// Some special error handling for the "top-level" patterns in a match arm,
2897 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2898 pub(crate) fn maybe_recover_colon_colon_in_pat_typo(
2900 mut first_pat: P<Pat>,
2903 if token::Colon != self.token.kind {
2906 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2907 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2911 // The pattern looks like it might be a path with a `::` -> `:` typo:
2912 // `match foo { bar:baz => {} }`
2913 let span = self.token.span;
2914 // We only emit "unexpected `:`" error here if we can successfully parse the
2915 // whole pattern correctly in that case.
2916 let snapshot = self.create_snapshot_for_diagnostic();
2918 // Create error for "unexpected `:`".
2919 match self.expected_one_of_not_found(&[], &[]) {
2921 self.bump(); // Skip the `:`.
2922 match self.parse_pat_no_top_alt(expected) {
2924 // Carry on as if we had not done anything, callers will emit a
2925 // reasonable error.
2928 self.restore_snapshot(snapshot);
2931 // We've parsed the rest of the pattern.
2932 let new_span = first_pat.span.to(pat.span);
2933 let mut show_sugg = false;
2934 // Try to construct a recovered pattern.
2935 match &mut pat.kind {
2936 PatKind::Struct(qself @ None, path, ..)
2937 | PatKind::TupleStruct(qself @ None, path, _)
2938 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2939 PatKind::Ident(_, ident, _) => {
2940 path.segments.insert(0, PathSegment::from_ident(*ident));
2941 path.span = new_span;
2945 PatKind::Path(old_qself, old_path) => {
2946 path.segments = old_path
2950 .chain(take(&mut path.segments))
2952 path.span = new_span;
2953 *qself = old_qself.clone();
2959 PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None) => {
2960 match &first_pat.kind {
2961 PatKind::Ident(_, old_ident, _) => {
2962 let path = PatKind::Path(
2967 PathSegment::from_ident(*old_ident),
2968 PathSegment::from_ident(*ident),
2973 first_pat = self.mk_pat(new_span, path);
2976 PatKind::Path(old_qself, old_path) => {
2977 let mut segments = old_path.segments.clone();
2978 segments.push(PathSegment::from_ident(*ident));
2979 let path = PatKind::Path(
2981 Path { span: new_span, segments, tokens: None },
2983 first_pat = self.mk_pat(new_span, path);
2992 err.span_suggestion(
2994 "maybe write a path separator here",
2996 Applicability::MaybeIncorrect,
2999 first_pat = self.mk_pat(new_span, PatKind::Wild);
3006 // Carry on as if we had not done anything. This should be unreachable.
3007 self.restore_snapshot(snapshot);
3013 pub(crate) fn maybe_recover_unexpected_block_label(&mut self) -> bool {
3014 let Some(label) = self.eat_label().filter(|_| {
3015 self.eat(&token::Colon) && self.token.kind == token::OpenDelim(Delimiter::Brace)
3019 let span = label.ident.span.to(self.prev_token.span);
3020 let mut err = self.struct_span_err(span, "block label not supported here");
3021 err.span_label(span, "not supported here");
3022 err.tool_only_span_suggestion(
3023 label.ident.span.until(self.token.span),
3024 "remove this block label",
3026 Applicability::MachineApplicable,
3032 /// Some special error handling for the "top-level" patterns in a match arm,
3033 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
3034 pub(crate) fn maybe_recover_unexpected_comma(
3037 rt: CommaRecoveryMode,
3038 ) -> PResult<'a, ()> {
3039 if self.token != token::Comma {
3043 // An unexpected comma after a top-level pattern is a clue that the
3044 // user (perhaps more accustomed to some other language) forgot the
3045 // parentheses in what should have been a tuple pattern; return a
3046 // suggestion-enhanced error here rather than choking on the comma later.
3047 let comma_span = self.token.span;
3049 if let Err(err) = self.skip_pat_list() {
3050 // We didn't expect this to work anyway; we just wanted to advance to the
3051 // end of the comma-sequence so we know the span to suggest parenthesizing.
3054 let seq_span = lo.to(self.prev_token.span);
3055 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
3056 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
3057 err.multipart_suggestion(
3059 "try adding parentheses to match on a tuple{}",
3060 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
3063 (seq_span.shrink_to_lo(), "(".to_string()),
3064 (seq_span.shrink_to_hi(), ")".to_string()),
3066 Applicability::MachineApplicable,
3068 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
3069 err.span_suggestion(
3071 "...or a vertical bar to match on multiple alternatives",
3072 seq_snippet.replace(',', " |"),
3073 Applicability::MachineApplicable,
3080 pub(crate) fn maybe_recover_bounds_doubled_colon(&mut self, ty: &Ty) -> PResult<'a, ()> {
3081 let TyKind::Path(qself, path) = &ty.kind else { return Ok(()) };
3082 let qself_position = qself.as_ref().map(|qself| qself.position);
3083 for (i, segments) in path.segments.windows(2).enumerate() {
3084 if qself_position.map(|pos| i < pos).unwrap_or(false) {
3087 if let [a, b] = segments {
3088 let (a_span, b_span) = (a.span(), b.span());
3089 let between_span = a_span.shrink_to_hi().to(b_span.shrink_to_lo());
3090 if self.span_to_snippet(between_span).as_ref().map(|a| &a[..]) == Ok(":: ") {
3091 let mut err = self.struct_span_err(
3092 path.span.shrink_to_hi(),
3093 "expected `:` followed by trait or lifetime",
3095 err.span_suggestion(
3099 Applicability::MachineApplicable,
3108 /// Parse and throw away a parenthesized comma separated
3109 /// sequence of patterns until `)` is reached.
3110 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
3111 while !self.check(&token::CloseDelim(Delimiter::Parenthesis)) {
3112 self.parse_pat_no_top_alt(None)?;
3113 if !self.eat(&token::Comma) {