1 use super::{BlockMode, Parser, PathStyle, SemiColonMode, SeqSep, TokenExpectType, TokenType};
3 use rustc_data_structures::fx::FxHashSet;
4 use rustc_errors::{pluralize, struct_span_err};
5 use rustc_errors::{Applicability, DiagnosticBuilder, Handler, PResult};
6 use rustc_span::source_map::Spanned;
7 use rustc_span::symbol::kw;
8 use rustc_span::{MultiSpan, Span, SpanSnippetError, DUMMY_SP};
10 self, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, Param,
12 use syntax::ast::{AttrVec, ItemKind, Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind};
13 use syntax::print::pprust;
15 use syntax::token::{self, token_can_begin_expr, TokenKind};
16 use syntax::util::parser::AssocOp;
18 use log::{debug, trace};
21 const TURBOFISH: &'static str = "use `::<...>` instead of `<...>` to specify type arguments";
23 /// Creates a placeholder argument.
24 pub(super) fn dummy_arg(ident: Ident) -> Param {
26 id: ast::DUMMY_NODE_ID,
27 kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
30 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID };
32 attrs: AttrVec::default(),
33 id: ast::DUMMY_NODE_ID,
37 is_placeholder: false,
42 FileNotFoundForModule {
45 secondary_path: String,
51 secondary_path: String,
57 fn span_err(self, sp: impl Into<MultiSpan>, handler: &Handler) -> DiagnosticBuilder<'_> {
59 Error::FileNotFoundForModule {
65 let mut err = struct_span_err!(
69 "file not found for module `{}`",
73 "name the file either {} or {} inside the directory \"{}\"",
74 default_path, secondary_path, dir_path,
78 Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
79 let mut err = struct_span_err!(
83 "file for module `{}` found at both {} and {}",
88 err.help("delete or rename one of them to remove the ambiguity");
91 Error::UselessDocComment => {
92 let mut err = struct_span_err!(
96 "found a documentation comment that doesn't document anything",
99 "doc comments must come before what they document, maybe a comment was \
100 intended with `//`?",
108 pub(super) trait RecoverQPath: Sized + 'static {
109 const PATH_STYLE: PathStyle = PathStyle::Expr;
110 fn to_ty(&self) -> Option<P<Ty>>;
111 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
114 impl RecoverQPath for Ty {
115 const PATH_STYLE: PathStyle = PathStyle::Type;
116 fn to_ty(&self) -> Option<P<Ty>> {
117 Some(P(self.clone()))
119 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
120 Self { span: path.span, kind: TyKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
124 impl RecoverQPath for Pat {
125 fn to_ty(&self) -> Option<P<Ty>> {
128 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
129 Self { span: path.span, kind: PatKind::Path(qself, path), id: ast::DUMMY_NODE_ID }
133 impl RecoverQPath for Expr {
134 fn to_ty(&self) -> Option<P<Ty>> {
137 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
140 kind: ExprKind::Path(qself, path),
141 attrs: AttrVec::new(),
142 id: ast::DUMMY_NODE_ID,
147 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
148 crate enum ConsumeClosingDelim {
153 impl<'a> Parser<'a> {
154 pub(super) fn span_fatal_err<S: Into<MultiSpan>>(
158 ) -> DiagnosticBuilder<'a> {
159 err.span_err(sp, self.diagnostic())
162 pub fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
163 self.sess.span_diagnostic.struct_span_err(sp, m)
166 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
167 self.sess.span_diagnostic.span_bug(sp, m)
170 pub(super) fn diagnostic(&self) -> &'a Handler {
171 &self.sess.span_diagnostic
174 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
175 self.sess.source_map().span_to_snippet(span)
178 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
179 let mut err = self.struct_span_err(
181 &format!("expected identifier, found {}", super::token_descr(&self.token)),
183 let valid_follow = &[
189 TokenKind::OpenDelim(token::DelimToken::Brace),
190 TokenKind::OpenDelim(token::DelimToken::Paren),
191 TokenKind::CloseDelim(token::DelimToken::Brace),
192 TokenKind::CloseDelim(token::DelimToken::Paren),
194 if let token::Ident(name, false) = self.token.kind {
195 if Ident::new(name, self.token.span).is_raw_guess()
196 && self.look_ahead(1, |t| valid_follow.contains(&t.kind))
200 "you can escape reserved keywords to use them as identifiers",
201 format!("r#{}", name),
202 Applicability::MaybeIncorrect,
206 if let Some(token_descr) = super::token_descr_opt(&self.token) {
207 err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
209 err.span_label(self.token.span, "expected identifier");
210 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
215 Applicability::MachineApplicable,
222 pub(super) fn expected_one_of_not_found(
224 edible: &[TokenKind],
225 inedible: &[TokenKind],
226 ) -> PResult<'a, bool /* recovered */> {
227 fn tokens_to_string(tokens: &[TokenType]) -> String {
228 let mut i = tokens.iter();
229 // This might be a sign we need a connect method on `Iterator`.
230 let b = i.next().map_or(String::new(), |t| t.to_string());
231 i.enumerate().fold(b, |mut b, (i, a)| {
232 if tokens.len() > 2 && i == tokens.len() - 2 {
234 } else if tokens.len() == 2 && i == tokens.len() - 2 {
239 b.push_str(&a.to_string());
244 let mut expected = edible
246 .map(|x| TokenType::Token(x.clone()))
247 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
248 .chain(self.expected_tokens.iter().cloned())
249 .collect::<Vec<_>>();
250 expected.sort_by_cached_key(|x| x.to_string());
252 let expect = tokens_to_string(&expected[..]);
253 let actual = super::token_descr(&self.token);
254 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
255 let short_expect = if expected.len() > 6 {
256 format!("{} possible tokens", expected.len())
261 format!("expected one of {}, found {}", expect, actual),
262 (self.prev_span.shrink_to_hi(), format!("expected one of {}", short_expect)),
264 } else if expected.is_empty() {
266 format!("unexpected token: {}", actual),
267 (self.prev_span, "unexpected token after this".to_string()),
271 format!("expected {}, found {}", expect, actual),
272 (self.prev_span.shrink_to_hi(), format!("expected {}", expect)),
275 self.last_unexpected_token_span = Some(self.token.span);
276 let mut err = self.struct_span_err(self.token.span, &msg_exp);
277 let sp = if self.token == token::Eof {
278 // This is EOF; don't want to point at the following char, but rather the last token.
283 match self.recover_closing_delimiter(
286 .filter_map(|tt| match tt {
287 TokenType::Token(t) => Some(t.clone()),
290 .collect::<Vec<_>>(),
295 return Ok(recovered);
299 let sm = self.sess.source_map();
300 if self.prev_span == DUMMY_SP {
301 // Account for macro context where the previous span might not be
302 // available to avoid incorrect output (#54841).
303 err.span_label(self.token.span, label_exp);
304 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
305 // When the spans are in the same line, it means that the only content between
306 // them is whitespace, point at the found token in that case:
308 // X | () => { syntax error };
309 // | ^^^^^ expected one of 8 possible tokens here
311 // instead of having:
313 // X | () => { syntax error };
314 // | -^^^^^ unexpected token
316 // | expected one of 8 possible tokens here
317 err.span_label(self.token.span, label_exp);
319 err.span_label(sp, label_exp);
320 err.span_label(self.token.span, "unexpected token");
322 self.maybe_annotate_with_ascription(&mut err, false);
326 pub fn maybe_annotate_with_ascription(
328 err: &mut DiagnosticBuilder<'_>,
329 maybe_expected_semicolon: bool,
331 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
332 let sm = self.sess.source_map();
333 let next_pos = sm.lookup_char_pos(self.token.span.lo());
334 let op_pos = sm.lookup_char_pos(sp.hi());
336 let allow_unstable = self.sess.unstable_features.is_nightly_build();
341 "maybe write a path separator here",
344 Applicability::MaybeIncorrect
346 Applicability::MachineApplicable
349 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
352 "try using a semicolon",
354 Applicability::MaybeIncorrect,
356 } else if allow_unstable {
357 err.span_label(sp, "tried to parse a type due to this type ascription");
359 err.span_label(sp, "tried to parse a type due to this");
362 // Give extra information about type ascription only if it's a nightly compiler.
364 "`#![feature(type_ascription)]` lets you annotate an expression with a \
365 type: `<expr>: <type>`",
368 "for more information, see \
369 https://github.com/rust-lang/rust/issues/23416",
375 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
376 /// passes through any errors encountered. Used for error recovery.
377 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
378 if let Err(ref mut err) =
379 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
380 Ok(p.parse_token_tree())
387 /// This function checks if there are trailing angle brackets and produces
388 /// a diagnostic to suggest removing them.
390 /// ```ignore (diagnostic)
391 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
392 /// ^^ help: remove extra angle brackets
394 pub(super) fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: TokenKind) {
395 // This function is intended to be invoked after parsing a path segment where there are two
398 // 1. A specific token is expected after the path segment.
399 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
400 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
401 // 2. No specific token is expected after the path segment.
402 // eg. `x.foo` (field access)
404 // This function is called after parsing `.foo` and before parsing the token `end` (if
405 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
408 // We only care about trailing angle brackets if we previously parsed angle bracket
409 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
410 // removed in this case:
412 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
414 // This case is particularly tricky as we won't notice it just looking at the tokens -
415 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
416 // have already been parsed):
418 // `x.foo::<u32>>>(3)`
419 let parsed_angle_bracket_args =
420 segment.args.as_ref().map(|args| args.is_angle_bracketed()).unwrap_or(false);
423 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
424 parsed_angle_bracket_args,
426 if !parsed_angle_bracket_args {
430 // Keep the span at the start so we can highlight the sequence of `>` characters to be
432 let lo = self.token.span;
434 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
435 // (since we might have the field access case and the characters we're eating are
436 // actual operators and not trailing characters - ie `x.foo >> 3`).
437 let mut position = 0;
439 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
440 // many of each (so we can correctly pluralize our error messages) and continue to
442 let mut number_of_shr = 0;
443 let mut number_of_gt = 0;
444 while self.look_ahead(position, |t| {
445 trace!("check_trailing_angle_brackets: t={:?}", t);
446 if *t == token::BinOp(token::BinOpToken::Shr) {
449 } else if *t == token::Gt {
459 // If we didn't find any trailing `>` characters, then we have nothing to error about.
461 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
462 number_of_gt, number_of_shr,
464 if number_of_gt < 1 && number_of_shr < 1 {
468 // Finally, double check that we have our end token as otherwise this is the
470 if self.look_ahead(position, |t| {
471 trace!("check_trailing_angle_brackets: t={:?}", t);
474 // Eat from where we started until the end token so that parsing can continue
475 // as if we didn't have those extra angle brackets.
476 self.eat_to_tokens(&[&end]);
477 let span = lo.until(self.token.span);
479 let total_num_of_gt = number_of_gt + number_of_shr * 2;
480 self.struct_span_err(
482 &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
486 &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
488 Applicability::MachineApplicable,
494 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
495 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
496 /// parenthesising the leftmost comparison.
497 fn attempt_chained_comparison_suggestion(
499 err: &mut DiagnosticBuilder<'_>,
501 outer_op: &Spanned<AssocOp>,
503 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
504 match (op.node, &outer_op.node) {
505 // `x < y < z` and friends.
506 (BinOpKind::Lt, AssocOp::Less) | (BinOpKind::Lt, AssocOp::LessEqual) |
507 (BinOpKind::Le, AssocOp::LessEqual) | (BinOpKind::Le, AssocOp::Less) |
508 // `x > y > z` and friends.
509 (BinOpKind::Gt, AssocOp::Greater) | (BinOpKind::Gt, AssocOp::GreaterEqual) |
510 (BinOpKind::Ge, AssocOp::GreaterEqual) | (BinOpKind::Ge, AssocOp::Greater) => {
511 let expr_to_str = |e: &Expr| {
512 self.span_to_snippet(e.span)
513 .unwrap_or_else(|_| pprust::expr_to_string(&e))
516 inner_op.span.to(outer_op.span),
517 "split the comparison into two...",
524 outer_op.node.to_ast_binop().unwrap().to_string(),
526 Applicability::MaybeIncorrect,
529 inner_op.span.to(outer_op.span),
530 "...or parenthesize one of the comparisons",
536 outer_op.node.to_ast_binop().unwrap().to_string(),
538 Applicability::MaybeIncorrect,
546 /// Produces an error if comparison operators are chained (RFC #558).
547 /// We only need to check the LHS, not the RHS, because all comparison ops have same
548 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
550 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
551 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
554 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
555 /// associative we can infer that we have:
562 pub(super) fn check_no_chained_comparison(
565 outer_op: &Spanned<AssocOp>,
566 ) -> PResult<'a, Option<P<Expr>>> {
568 outer_op.node.is_comparison(),
569 "check_no_chained_comparison: {:?} is not comparison",
574 |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
576 match inner_op.kind {
577 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
578 // Respan to include both operators.
579 let op_span = op.span.to(self.prev_span);
581 self.struct_span_err(op_span, "comparison operators cannot be chained");
583 // If it looks like a genuine attempt to chain operators (as opposed to a
584 // misformatted turbofish, for instance), suggest a correct form.
585 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
587 let suggest = |err: &mut DiagnosticBuilder<'_>| {
588 err.span_suggestion_verbose(
589 op_span.shrink_to_lo(),
592 Applicability::MaybeIncorrect,
596 if op.node == BinOpKind::Lt &&
597 outer_op.node == AssocOp::Less || // Include `<` to provide this recommendation
598 outer_op.node == AssocOp::Greater
599 // even in a case like the following:
601 // Foo<Bar<Baz<Qux, ()>>>
602 if outer_op.node == AssocOp::Less {
603 let snapshot = self.clone();
605 // So far we have parsed `foo<bar<`, consume the rest of the type args.
607 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
608 self.consume_tts(1, &modifiers[..]);
610 if !&[token::OpenDelim(token::Paren), token::ModSep]
611 .contains(&self.token.kind)
613 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
614 // parser and bail out.
615 mem::replace(self, snapshot.clone());
618 return if token::ModSep == self.token.kind {
619 // We have some certainty that this was a bad turbofish at this point.
623 let snapshot = self.clone();
626 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
627 match self.parse_expr() {
629 // 99% certain that the suggestion is correct, continue parsing.
631 // FIXME: actually check that the two expressions in the binop are
632 // paths and resynthesize new fn call expression instead of using
633 // `ExprKind::Err` placeholder.
634 mk_err_expr(self, inner_op.span.to(self.prev_span))
636 Err(mut expr_err) => {
638 // Not entirely sure now, but we bubble the error up with the
640 mem::replace(self, snapshot);
644 } else if token::OpenDelim(token::Paren) == self.token.kind {
645 // We have high certainty that this was a bad turbofish at this point.
648 // Consume the fn call arguments.
649 match self.consume_fn_args() {
653 // FIXME: actually check that the two expressions in the binop are
654 // paths and resynthesize new fn call expression instead of using
655 // `ExprKind::Err` placeholder.
656 mk_err_expr(self, inner_op.span.to(self.prev_span))
660 // All we know is that this is `foo < bar >` and *nothing* else. Try to
661 // be helpful, but don't attempt to recover.
663 err.help("or use `(...)` if you meant to specify fn arguments");
664 // These cases cause too many knock-down errors, bail out (#61329).
675 fn consume_fn_args(&mut self) -> Result<(), ()> {
676 let snapshot = self.clone();
679 // Consume the fn call arguments.
681 [(token::OpenDelim(token::Paren), 1), (token::CloseDelim(token::Paren), -1)];
682 self.consume_tts(1, &modifiers[..]);
684 if self.token.kind == token::Eof {
685 // Not entirely sure that what we consumed were fn arguments, rollback.
686 mem::replace(self, snapshot);
689 // 99% certain that the suggestion is correct, continue parsing.
694 pub(super) fn maybe_report_ambiguous_plus(
697 impl_dyn_multi: bool,
700 if !allow_plus && impl_dyn_multi {
701 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
702 self.struct_span_err(ty.span, "ambiguous `+` in a type")
705 "use parentheses to disambiguate",
707 Applicability::MachineApplicable,
713 pub(super) fn maybe_recover_from_bad_type_plus(
717 ) -> PResult<'a, ()> {
718 // Do not add `+` to expected tokens.
719 if !allow_plus || !self.token.is_like_plus() {
724 let bounds = self.parse_generic_bounds(None)?;
725 let sum_span = ty.span.to(self.prev_span);
727 let mut err = struct_span_err!(
728 self.sess.span_diagnostic,
731 "expected a path on the left-hand side of `+`, not `{}`",
732 pprust::ty_to_string(ty)
736 TyKind::Rptr(ref lifetime, ref mut_ty) => {
737 let sum_with_parens = pprust::to_string(|s| {
739 s.print_opt_lifetime(lifetime);
740 s.print_mutability(mut_ty.mutbl, false);
742 s.print_type(&mut_ty.ty);
743 s.print_type_bounds(" +", &bounds);
748 "try adding parentheses",
750 Applicability::MachineApplicable,
753 TyKind::Ptr(..) | TyKind::BareFn(..) => {
754 err.span_label(sum_span, "perhaps you forgot parentheses?");
757 err.span_label(sum_span, "expected a path");
764 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
765 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
766 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
767 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
770 allow_recovery: bool,
771 ) -> PResult<'a, P<T>> {
772 // Do not add `::` to expected tokens.
773 if allow_recovery && self.token == token::ModSep {
774 if let Some(ty) = base.to_ty() {
775 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
781 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
782 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
783 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
787 ) -> PResult<'a, P<T>> {
788 self.expect(&token::ModSep)?;
790 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP };
791 self.parse_path_segments(&mut path.segments, T::PATH_STYLE)?;
792 path.span = ty_span.to(self.prev_span);
794 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
795 self.struct_span_err(path.span, "missing angle brackets in associated item path")
797 // This is a best-effort recovery.
800 format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
801 Applicability::MaybeIncorrect,
805 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
806 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
809 pub(super) fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
810 if self.eat(&token::Semi) {
811 let mut err = self.struct_span_err(self.prev_span, "expected item, found `;`");
812 err.span_suggestion_short(
814 "remove this semicolon",
816 Applicability::MachineApplicable,
818 if !items.is_empty() {
819 let previous_item = &items[items.len() - 1];
820 let previous_item_kind_name = match previous_item.kind {
821 // Say "braced struct" because tuple-structs and
822 // braceless-empty-struct declarations do take a semicolon.
823 ItemKind::Struct(..) => Some("braced struct"),
824 ItemKind::Enum(..) => Some("enum"),
825 ItemKind::Trait(..) => Some("trait"),
826 ItemKind::Union(..) => Some("union"),
829 if let Some(name) = previous_item_kind_name {
830 err.help(&format!("{} declarations are not followed by a semicolon", name));
840 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
841 /// closing delimiter.
842 pub(super) fn unexpected_try_recover(
845 ) -> PResult<'a, bool /* recovered */> {
846 let token_str = pprust::token_kind_to_string(t);
847 let this_token_str = super::token_descr(&self.token);
848 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
849 // Point at the end of the macro call when reaching end of macro arguments.
850 (token::Eof, Some(_)) => {
851 let sp = self.sess.source_map().next_point(self.token.span);
854 // We don't want to point at the following span after DUMMY_SP.
855 // This happens when the parser finds an empty TokenStream.
856 _ if self.prev_span == DUMMY_SP => (self.token.span, self.token.span),
857 // EOF, don't want to point at the following char, but rather the last token.
858 (token::Eof, None) => (self.prev_span, self.token.span),
859 _ => (self.prev_span.shrink_to_hi(), self.token.span),
862 "expected `{}`, found {}",
864 match (&self.token.kind, self.subparser_name) {
865 (token::Eof, Some(origin)) => format!("end of {}", origin),
869 let mut err = self.struct_span_err(sp, &msg);
870 let label_exp = format!("expected `{}`", token_str);
871 match self.recover_closing_delimiter(&[t.clone()], err) {
874 return Ok(recovered);
877 let sm = self.sess.source_map();
878 if !sm.is_multiline(prev_sp.until(sp)) {
879 // When the spans are in the same line, it means that the only content
880 // between them is whitespace, point only at the found token.
881 err.span_label(sp, label_exp);
883 err.span_label(prev_sp, label_exp);
884 err.span_label(sp, "unexpected token");
889 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
890 if self.eat(&token::Semi) {
893 let sm = self.sess.source_map();
894 let msg = format!("expected `;`, found `{}`", super::token_descr(&self.token));
895 let appl = Applicability::MachineApplicable;
896 if self.token.span == DUMMY_SP || self.prev_span == DUMMY_SP {
897 // Likely inside a macro, can't provide meaninful suggestions.
898 return self.expect(&token::Semi).map(drop);
899 } else if !sm.is_multiline(self.prev_span.until(self.token.span)) {
900 // The current token is in the same line as the prior token, not recoverable.
901 } else if self.look_ahead(1, |t| {
902 t == &token::CloseDelim(token::Brace)
903 || token_can_begin_expr(t) && t.kind != token::Colon
904 }) && [token::Comma, token::Colon].contains(&self.token.kind)
906 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
907 // either `,` or `:`, and the next token could either start a new statement or is a
908 // block close. For example:
913 let sp = self.prev_span;
914 self.struct_span_err(sp, &msg)
915 .span_suggestion(sp, "change this to `;`", ";".to_string(), appl)
918 } else if self.look_ahead(0, |t| {
919 t == &token::CloseDelim(token::Brace)
921 token_can_begin_expr(t) && t != &token::Semi && t != &token::Pound
922 // Avoid triggering with too many trailing `#` in raw string.
925 // Missing semicolon typo. This is triggered if the next token could either start a
926 // new statement or is a block close. For example:
930 let sp = self.prev_span.shrink_to_hi();
931 self.struct_span_err(sp, &msg)
932 .span_label(self.token.span, "unexpected token")
933 .span_suggestion_short(sp, "add `;` here", ";".to_string(), appl)
937 self.expect(&token::Semi).map(drop) // Error unconditionally
940 pub(super) fn parse_semi_or_incorrect_foreign_fn_body(
944 ) -> PResult<'a, ()> {
945 if self.token != token::Semi {
946 // This might be an incorrect fn definition (#62109).
947 let parser_snapshot = self.clone();
948 match self.parse_inner_attrs_and_block() {
950 self.struct_span_err(ident.span, "incorrect `fn` inside `extern` block")
951 .span_label(ident.span, "can't have a body")
952 .span_label(body.span, "this body is invalid here")
955 "`extern` blocks define existing foreign functions and `fn`s \
956 inside of them cannot have a body",
959 "you might have meant to write a function accessible through ffi, \
960 which can be done by writing `extern fn` outside of the \
964 "for more information, visit \
965 https://doc.rust-lang.org/std/keyword.extern.html",
971 mem::replace(self, parser_snapshot);
981 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
982 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
983 pub(super) fn recover_incorrect_await_syntax(
988 ) -> PResult<'a, P<Expr>> {
989 let (hi, expr, is_question) = if self.token == token::Not {
990 // Handle `await!(<expr>)`.
991 self.recover_await_macro()?
993 self.recover_await_prefix(await_sp)?
995 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
996 let expr = self.mk_expr(lo.to(sp), ExprKind::Await(expr), attrs);
997 self.maybe_recover_from_bad_qpath(expr, true)
1000 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1001 self.expect(&token::Not)?;
1002 self.expect(&token::OpenDelim(token::Paren))?;
1003 let expr = self.parse_expr()?;
1004 self.expect(&token::CloseDelim(token::Paren))?;
1005 Ok((self.prev_span, expr, false))
1008 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1009 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1010 let expr = if self.token == token::OpenDelim(token::Brace) {
1011 // Handle `await { <expr> }`.
1012 // This needs to be handled separatedly from the next arm to avoid
1013 // interpreting `await { <expr> }?` as `<expr>?.await`.
1014 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default, AttrVec::new())
1018 .map_err(|mut err| {
1019 err.span_label(await_sp, "while parsing this incorrect await expression");
1022 Ok((expr.span, expr, is_question))
1025 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1027 self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr));
1028 let suggestion = format!("{}.await{}", expr_str, if is_question { "?" } else { "" });
1030 let app = match expr.kind {
1031 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1032 _ => Applicability::MachineApplicable,
1034 self.struct_span_err(sp, "incorrect use of `await`")
1035 .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
1040 /// If encountering `future.await()`, consumes and emits an error.
1041 pub(super) fn recover_from_await_method_call(&mut self) {
1042 if self.token == token::OpenDelim(token::Paren)
1043 && self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
1046 let lo = self.token.span;
1048 let sp = lo.to(self.token.span);
1050 self.struct_span_err(sp, "incorrect use of `await`")
1053 "`await` is not a method call, remove the parentheses",
1055 Applicability::MachineApplicable,
1061 /// Recovers a situation like `for ( $pat in $expr )`
1062 /// and suggest writing `for $pat in $expr` instead.
1064 /// This should be called before parsing the `$block`.
1065 pub(super) fn recover_parens_around_for_head(
1069 begin_paren: Option<Span>,
1071 match (&self.token.kind, begin_paren) {
1072 (token::CloseDelim(token::Paren), Some(begin_par_sp)) => {
1076 // Remove the `(` from the span of the pattern:
1077 .span_to_snippet(pat.span.trim_start(begin_par_sp).unwrap())
1078 .unwrap_or_else(|_| pprust::pat_to_string(&pat));
1080 self.struct_span_err(self.prev_span, "unexpected closing `)`")
1081 .span_label(begin_par_sp, "opening `(`")
1083 begin_par_sp.to(self.prev_span),
1084 "remove parenthesis in `for` loop",
1085 format!("{} in {}", pat_str, pprust::expr_to_string(&expr)),
1086 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1087 // with `x) in y)` which is syntactically invalid.
1088 // However, this is prevented before we get here.
1089 Applicability::MachineApplicable,
1093 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1094 pat.and_then(|pat| match pat.kind {
1095 PatKind::Paren(pat) => pat,
1103 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1104 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1105 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1106 || self.token.is_ident() &&
1108 // `foo::` → `foo:` or `foo.bar::` → `foo.bar:`
1109 ast::ExprKind::Path(..) | ast::ExprKind::Field(..) => true,
1112 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1113 self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren))
1114 || self.look_ahead(1, |t| t == &token::Lt) && // `foo:bar<baz`
1115 self.look_ahead(2, |t| t.is_ident())
1116 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1117 self.look_ahead(2, |t| t.is_ident())
1118 || self.look_ahead(1, |t| t == &token::ModSep)
1119 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1120 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1123 pub(super) fn recover_seq_parse_error(
1125 delim: token::DelimToken,
1127 result: PResult<'a, P<Expr>>,
1133 // Recover from parse error, callers expect the closing delim to be consumed.
1134 self.consume_block(delim, ConsumeClosingDelim::Yes);
1135 self.mk_expr(lo.to(self.prev_span), ExprKind::Err, AttrVec::new())
1140 pub(super) fn recover_closing_delimiter(
1142 tokens: &[TokenKind],
1143 mut err: DiagnosticBuilder<'a>,
1144 ) -> PResult<'a, bool> {
1146 // We want to use the last closing delim that would apply.
1147 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1148 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1149 && Some(self.token.span) > unmatched.unclosed_span
1156 // Recover and assume that the detected unclosed delimiter was meant for
1157 // this location. Emit the diagnostic and act as if the delimiter was
1158 // present for the parser's sake.
1160 // Don't attempt to recover from this unclosed delimiter more than once.
1161 let unmatched = self.unclosed_delims.remove(pos);
1162 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1163 if unmatched.found_delim.is_none() {
1164 // We encountered `Eof`, set this fact here to avoid complaining about missing
1165 // `fn main()` when we found place to suggest the closing brace.
1166 *self.sess.reached_eof.borrow_mut() = true;
1169 // We want to suggest the inclusion of the closing delimiter where it makes
1170 // the most sense, which is immediately after the last token:
1175 // | help: `)` may belong here
1177 // unclosed delimiter
1178 if let Some(sp) = unmatched.unclosed_span {
1179 err.span_label(sp, "unclosed delimiter");
1181 err.span_suggestion_short(
1182 self.prev_span.shrink_to_hi(),
1183 &format!("{} may belong here", delim.to_string()),
1185 Applicability::MaybeIncorrect,
1187 if unmatched.found_delim.is_none() {
1188 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1189 // errors which would be emitted elsewhere in the parser and let other error
1190 // recovery consume the rest of the file.
1194 self.expected_tokens.clear(); // Reduce the number of errors.
1202 /// Eats tokens until we can be relatively sure we reached the end of the
1203 /// statement. This is something of a best-effort heuristic.
1205 /// We terminate when we find an unmatched `}` (without consuming it).
1206 pub(super) fn recover_stmt(&mut self) {
1207 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1210 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1211 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1212 /// approximate -- it can mean we break too early due to macros, but that
1213 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1215 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1216 /// after finding (and consuming) a brace-delimited block.
1217 pub(super) fn recover_stmt_(
1219 break_on_semi: SemiColonMode,
1220 break_on_block: BlockMode,
1222 let mut brace_depth = 0;
1223 let mut bracket_depth = 0;
1224 let mut in_block = false;
1225 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1227 debug!("recover_stmt_ loop {:?}", self.token);
1228 match self.token.kind {
1229 token::OpenDelim(token::DelimToken::Brace) => {
1232 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1237 token::OpenDelim(token::DelimToken::Bracket) => {
1241 token::CloseDelim(token::DelimToken::Brace) => {
1242 if brace_depth == 0 {
1243 debug!("recover_stmt_ return - close delim {:?}", self.token);
1248 if in_block && bracket_depth == 0 && brace_depth == 0 {
1249 debug!("recover_stmt_ return - block end {:?}", self.token);
1253 token::CloseDelim(token::DelimToken::Bracket) => {
1255 if bracket_depth < 0 {
1261 debug!("recover_stmt_ return - Eof");
1266 if break_on_semi == SemiColonMode::Break
1268 && bracket_depth == 0
1270 debug!("recover_stmt_ return - Semi");
1275 if break_on_semi == SemiColonMode::Comma
1277 && bracket_depth == 0 =>
1279 debug!("recover_stmt_ return - Semi");
1287 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1288 if self.eat_keyword(kw::In) {
1289 // a common typo: `for _ in in bar {}`
1290 self.struct_span_err(self.prev_span, "expected iterable, found keyword `in`")
1291 .span_suggestion_short(
1292 in_span.until(self.prev_span),
1293 "remove the duplicated `in`",
1295 Applicability::MachineApplicable,
1301 pub(super) fn expected_semi_or_open_brace<T>(&mut self) -> PResult<'a, T> {
1302 let token_str = super::token_descr(&self.token);
1303 let msg = &format!("expected `;` or `{{`, found {}", token_str);
1304 let mut err = self.struct_span_err(self.token.span, msg);
1305 err.span_label(self.token.span, "expected `;` or `{`");
1309 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1310 if let token::DocComment(_) = self.token.kind {
1311 self.struct_span_err(
1313 "documentation comments cannot be applied to a function parameter's type",
1315 .span_label(self.token.span, "doc comments are not allowed here")
1318 } else if self.token == token::Pound
1319 && self.look_ahead(1, |t| *t == token::OpenDelim(token::Bracket))
1321 let lo = self.token.span;
1322 // Skip every token until next possible arg.
1323 while self.token != token::CloseDelim(token::Bracket) {
1326 let sp = lo.to(self.token.span);
1328 self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
1329 .span_label(sp, "attributes are not allowed here")
1334 pub(super) fn parameter_without_type(
1336 err: &mut DiagnosticBuilder<'_>,
1339 is_self_allowed: bool,
1340 is_trait_item: bool,
1341 ) -> Option<Ident> {
1342 // If we find a pattern followed by an identifier, it could be an (incorrect)
1343 // C-style parameter declaration.
1344 if self.check_ident()
1345 && self.look_ahead(1, |t| *t == token::Comma || *t == token::CloseDelim(token::Paren))
1347 // `fn foo(String s) {}`
1348 let ident = self.parse_ident().unwrap();
1349 let span = pat.span.with_hi(ident.span.hi());
1351 err.span_suggestion(
1353 "declare the type after the parameter binding",
1354 String::from("<identifier>: <type>"),
1355 Applicability::HasPlaceholders,
1358 } else if let PatKind::Ident(_, ident, _) = pat.kind {
1361 || self.token == token::Comma
1362 || self.token == token::Lt
1363 || self.token == token::CloseDelim(token::Paren))
1365 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1366 if is_self_allowed {
1367 err.span_suggestion(
1369 "if this is a `self` type, give it a parameter name",
1370 format!("self: {}", ident),
1371 Applicability::MaybeIncorrect,
1374 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
1375 // `fn foo(HashMap: TypeName<u32>)`.
1376 if self.token != token::Lt {
1377 err.span_suggestion(
1379 "if this was a parameter name, give it a type",
1380 format!("{}: TypeName", ident),
1381 Applicability::HasPlaceholders,
1384 err.span_suggestion(
1386 "if this is a type, explicitly ignore the parameter name",
1387 format!("_: {}", ident),
1388 Applicability::MachineApplicable,
1390 err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
1392 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
1393 return if self.token == token::Lt { None } else { Some(ident) };
1399 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
1400 let pat = self.parse_pat(Some("argument name"))?;
1401 self.expect(&token::Colon)?;
1402 let ty = self.parse_ty()?;
1408 "patterns aren't allowed in methods without bodies",
1410 .span_suggestion_short(
1412 "give this argument a name or use an underscore to ignore it",
1414 Applicability::MachineApplicable,
1418 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
1419 let pat = P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID });
1423 pub(super) fn recover_bad_self_param(
1425 mut param: ast::Param,
1426 is_trait_item: bool,
1427 ) -> PResult<'a, ast::Param> {
1428 let sp = param.pat.span;
1429 param.ty.kind = TyKind::Err;
1430 let mut err = self.struct_span_err(sp, "unexpected `self` parameter in function");
1432 err.span_label(sp, "must be the first associated function parameter");
1434 err.span_label(sp, "not valid as function parameter");
1435 err.note("`self` is only valid as the first parameter of an associated function");
1441 pub(super) fn consume_block(
1443 delim: token::DelimToken,
1444 consume_close: ConsumeClosingDelim,
1446 let mut brace_depth = 0;
1448 if self.eat(&token::OpenDelim(delim)) {
1450 } else if self.check(&token::CloseDelim(delim)) {
1451 if brace_depth == 0 {
1452 if let ConsumeClosingDelim::Yes = consume_close {
1453 // Some of the callers of this method expect to be able to parse the
1454 // closing delimiter themselves, so we leave it alone. Otherwise we advance
1464 } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
1472 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a> {
1473 let (span, msg) = match (&self.token.kind, self.subparser_name) {
1474 (&token::Eof, Some(origin)) => {
1475 let sp = self.sess.source_map().next_point(self.token.span);
1476 (sp, format!("expected expression, found end of {}", origin))
1480 format!("expected expression, found {}", super::token_descr(&self.token),),
1483 let mut err = self.struct_span_err(span, &msg);
1484 let sp = self.sess.source_map().start_point(self.token.span);
1485 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
1486 self.sess.expr_parentheses_needed(&mut err, *sp, None);
1488 err.span_label(span, "expected expression");
1494 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
1495 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
1496 modifier: &[(token::TokenKind, i64)],
1499 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
1502 if self.token.kind == token::Eof {
1509 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
1511 /// This is necessary because at this point we don't know whether we parsed a function with
1512 /// anonymous parameters or a function with names but no types. In order to minimize
1513 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
1514 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
1515 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
1516 /// we deduplicate them to not complain about duplicated parameter names.
1517 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
1518 let mut seen_inputs = FxHashSet::default();
1519 for input in fn_inputs.iter_mut() {
1520 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
1521 (&input.pat.kind, &input.ty.kind)
1527 if let Some(ident) = opt_ident {
1528 if seen_inputs.contains(&ident) {
1529 input.pat.kind = PatKind::Wild;
1531 seen_inputs.insert(ident);