1 use super::pat::Expected;
2 use super::ty::{AllowPlus, RecoverQuestionMark};
4 BlockMode, CommaRecoveryMode, Parser, PathStyle, RecoverColon, RecoverComma, Restrictions,
5 SemiColonMode, SeqSep, TokenExpectType, TokenType,
8 use crate::lexer::UnmatchedBrace;
10 use rustc_ast::ptr::P;
11 use rustc_ast::token::{self, Lit, LitKind, TokenKind};
12 use rustc_ast::util::parser::AssocOp;
14 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
15 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Mutability, Param, Pat,
16 PatKind, Path, PathSegment, QSelf, Ty, TyKind,
18 use rustc_ast_pretty::pprust;
19 use rustc_data_structures::fx::FxHashSet;
20 use rustc_errors::{pluralize, struct_span_err, Diagnostic, ErrorGuaranteed};
21 use rustc_errors::{Applicability, DiagnosticBuilder, Handler, PResult};
22 use rustc_span::source_map::Spanned;
23 use rustc_span::symbol::{kw, Ident};
24 use rustc_span::{MultiSpan, Span, SpanSnippetError, DUMMY_SP};
25 use std::ops::{Deref, DerefMut};
29 use tracing::{debug, trace};
31 const TURBOFISH_SUGGESTION_STR: &str =
32 "use `::<...>` instead of `<...>` to specify lifetime, type, or const arguments";
34 /// Creates a placeholder argument.
35 pub(super) fn dummy_arg(ident: Ident) -> Param {
37 id: ast::DUMMY_NODE_ID,
38 kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
42 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
44 attrs: AttrVec::default(),
45 id: ast::DUMMY_NODE_ID,
49 is_placeholder: false,
60 sp: impl Into<MultiSpan>,
62 ) -> DiagnosticBuilder<'_, ErrorGuaranteed> {
64 Error::UselessDocComment => {
65 let mut err = struct_span_err!(
69 "found a documentation comment that doesn't document anything",
72 "doc comments must come before what they document, maybe a comment was \
81 pub(super) trait RecoverQPath: Sized + 'static {
82 const PATH_STYLE: PathStyle = PathStyle::Expr;
83 fn to_ty(&self) -> Option<P<Ty>>;
84 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
87 impl RecoverQPath for Ty {
88 const PATH_STYLE: PathStyle = PathStyle::Type;
89 fn to_ty(&self) -> Option<P<Ty>> {
92 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
95 kind: TyKind::Path(qself, path),
96 id: ast::DUMMY_NODE_ID,
102 impl RecoverQPath for Pat {
103 fn to_ty(&self) -> Option<P<Ty>> {
106 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
109 kind: PatKind::Path(qself, path),
110 id: ast::DUMMY_NODE_ID,
116 impl RecoverQPath for Expr {
117 fn to_ty(&self) -> Option<P<Ty>> {
120 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
123 kind: ExprKind::Path(qself, path),
124 attrs: AttrVec::new(),
125 id: ast::DUMMY_NODE_ID,
131 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
132 crate enum ConsumeClosingDelim {
137 #[derive(Clone, Copy)]
138 pub enum AttemptLocalParseRecovery {
143 impl AttemptLocalParseRecovery {
144 pub fn yes(&self) -> bool {
146 AttemptLocalParseRecovery::Yes => true,
147 AttemptLocalParseRecovery::No => false,
151 pub fn no(&self) -> bool {
153 AttemptLocalParseRecovery::Yes => false,
154 AttemptLocalParseRecovery::No => true,
159 // SnapshotParser is used to create a snapshot of the parser
160 // without causing duplicate errors being emitted when the `Parser`
162 pub(super) struct SnapshotParser<'a> {
164 unclosed_delims: Vec<UnmatchedBrace>,
167 impl<'a> Deref for SnapshotParser<'a> {
168 type Target = Parser<'a>;
170 fn deref(&self) -> &Self::Target {
175 impl<'a> DerefMut for SnapshotParser<'a> {
176 fn deref_mut(&mut self) -> &mut Self::Target {
181 impl<'a> Parser<'a> {
182 pub(super) fn span_err<S: Into<MultiSpan>>(
186 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
187 err.span_err(sp, self.diagnostic())
190 pub fn struct_span_err<S: Into<MultiSpan>>(
194 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
195 self.sess.span_diagnostic.struct_span_err(sp, m)
198 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
199 self.sess.span_diagnostic.span_bug(sp, m)
202 pub(super) fn diagnostic(&self) -> &'a Handler {
203 &self.sess.span_diagnostic
206 /// Relace `self` with `snapshot.parser` and extend `unclosed_delims` with `snapshot.unclosed_delims`.
207 /// This is to avoid losing unclosed delims errors `create_snapshot_for_diagnostic` clears.
208 pub(super) fn restore_snapshot(&mut self, snapshot: SnapshotParser<'a>) {
209 *self = snapshot.parser;
210 self.unclosed_delims.extend(snapshot.unclosed_delims.clone());
213 /// Create a snapshot of the `Parser`.
214 pub(super) fn create_snapshot_for_diagnostic(&self) -> SnapshotParser<'a> {
215 let mut snapshot = self.clone();
216 let unclosed_delims = self.unclosed_delims.clone();
217 // Clear `unclosed_delims` in snapshot to avoid
218 // duplicate errors being emitted when the `Parser`
219 // is dropped (which may or may not happen, depending
220 // if the parsing the snapshot is created for is successful)
221 snapshot.unclosed_delims.clear();
222 SnapshotParser { parser: snapshot, unclosed_delims }
225 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
226 self.sess.source_map().span_to_snippet(span)
229 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
230 let mut err = self.struct_span_err(
232 &format!("expected identifier, found {}", super::token_descr(&self.token)),
234 let valid_follow = &[
240 TokenKind::OpenDelim(token::DelimToken::Brace),
241 TokenKind::OpenDelim(token::DelimToken::Paren),
242 TokenKind::CloseDelim(token::DelimToken::Brace),
243 TokenKind::CloseDelim(token::DelimToken::Paren),
245 match self.token.ident() {
247 if ident.is_raw_guess()
248 && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
250 err.span_suggestion_verbose(
251 ident.span.shrink_to_lo(),
252 &format!("escape `{}` to use it as an identifier", ident.name),
254 Applicability::MaybeIncorrect,
259 if let Some(token_descr) = super::token_descr_opt(&self.token) {
260 err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
262 err.span_label(self.token.span, "expected identifier");
263 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
268 Applicability::MachineApplicable,
275 pub(super) fn expected_one_of_not_found(
277 edible: &[TokenKind],
278 inedible: &[TokenKind],
279 ) -> PResult<'a, bool /* recovered */> {
280 debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
281 fn tokens_to_string(tokens: &[TokenType]) -> String {
282 let mut i = tokens.iter();
283 // This might be a sign we need a connect method on `Iterator`.
284 let b = i.next().map_or_else(String::new, |t| t.to_string());
285 i.enumerate().fold(b, |mut b, (i, a)| {
286 if tokens.len() > 2 && i == tokens.len() - 2 {
288 } else if tokens.len() == 2 && i == tokens.len() - 2 {
293 b.push_str(&a.to_string());
298 let mut expected = edible
300 .map(|x| TokenType::Token(x.clone()))
301 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
302 .chain(self.expected_tokens.iter().cloned())
303 .collect::<Vec<_>>();
304 expected.sort_by_cached_key(|x| x.to_string());
307 let sm = self.sess.source_map();
308 let msg = format!("expected `;`, found {}", super::token_descr(&self.token));
309 let appl = Applicability::MachineApplicable;
310 if expected.contains(&TokenType::Token(token::Semi)) {
311 if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
312 // Likely inside a macro, can't provide meaningful suggestions.
313 } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
314 // The current token is in the same line as the prior token, not recoverable.
315 } else if [token::Comma, token::Colon].contains(&self.token.kind)
316 && self.prev_token.kind == token::CloseDelim(token::Paren)
318 // Likely typo: The current token is on a new line and is expected to be
319 // `.`, `;`, `?`, or an operator after a close delimiter token.
321 // let a = std::process::Command::new("echo")
325 // https://github.com/rust-lang/rust/issues/72253
326 } else if self.look_ahead(1, |t| {
327 t == &token::CloseDelim(token::Brace)
328 || t.can_begin_expr() && t.kind != token::Colon
329 }) && [token::Comma, token::Colon].contains(&self.token.kind)
331 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
332 // either `,` or `:`, and the next token could either start a new statement or is a
333 // block close. For example:
338 let sp = self.prev_token.span;
339 self.struct_span_err(sp, &msg)
340 .span_suggestion_short(sp, "change this to `;`", ";".to_string(), appl)
343 } else if self.look_ahead(0, |t| {
344 t == &token::CloseDelim(token::Brace)
346 t.can_begin_expr() && t != &token::Semi && t != &token::Pound
347 // Avoid triggering with too many trailing `#` in raw string.
350 // Missing semicolon typo. This is triggered if the next token could either start a
351 // new statement or is a block close. For example:
355 let sp = self.prev_token.span.shrink_to_hi();
356 self.struct_span_err(sp, &msg)
357 .span_label(self.token.span, "unexpected token")
358 .span_suggestion_short(sp, "add `;` here", ";".to_string(), appl)
364 let expect = tokens_to_string(&expected);
365 let actual = super::token_descr(&self.token);
366 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
367 let short_expect = if expected.len() > 6 {
368 format!("{} possible tokens", expected.len())
373 format!("expected one of {expect}, found {actual}"),
374 (self.prev_token.span.shrink_to_hi(), format!("expected one of {short_expect}")),
376 } else if expected.is_empty() {
378 format!("unexpected token: {}", actual),
379 (self.prev_token.span, "unexpected token after this".to_string()),
383 format!("expected {expect}, found {actual}"),
384 (self.prev_token.span.shrink_to_hi(), format!("expected {expect}")),
387 self.last_unexpected_token_span = Some(self.token.span);
388 let mut err = self.struct_span_err(self.token.span, &msg_exp);
390 // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
391 // there are unclosed angle brackets
392 if self.unmatched_angle_bracket_count > 0
393 && self.token.kind == TokenKind::Eq
394 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
396 err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
399 let sp = if self.token == token::Eof {
400 // This is EOF; don't want to point at the following char, but rather the last token.
405 match self.recover_closing_delimiter(
408 .filter_map(|tt| match tt {
409 TokenType::Token(t) => Some(t.clone()),
412 .collect::<Vec<_>>(),
417 return Ok(recovered);
421 if self.check_too_many_raw_str_terminators(&mut err) {
425 if self.prev_token.span == DUMMY_SP {
426 // Account for macro context where the previous span might not be
427 // available to avoid incorrect output (#54841).
428 err.span_label(self.token.span, label_exp);
429 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
430 // When the spans are in the same line, it means that the only content between
431 // them is whitespace, point at the found token in that case:
433 // X | () => { syntax error };
434 // | ^^^^^ expected one of 8 possible tokens here
436 // instead of having:
438 // X | () => { syntax error };
439 // | -^^^^^ unexpected token
441 // | expected one of 8 possible tokens here
442 err.span_label(self.token.span, label_exp);
444 err.span_label(sp, label_exp);
445 err.span_label(self.token.span, "unexpected token");
447 self.maybe_annotate_with_ascription(&mut err, false);
451 fn check_too_many_raw_str_terminators(&mut self, err: &mut Diagnostic) -> bool {
452 match (&self.prev_token.kind, &self.token.kind) {
454 TokenKind::Literal(Lit {
455 kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
460 err.set_primary_message("too many `#` when terminating raw string");
463 "remove the extra `#`",
465 Applicability::MachineApplicable,
467 err.note(&format!("the raw string started with {n_hashes} `#`s"));
474 pub fn maybe_suggest_struct_literal(
478 ) -> Option<PResult<'a, P<Block>>> {
479 if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
480 // We might be having a struct literal where people forgot to include the path:
484 let mut snapshot = self.create_snapshot_for_diagnostic();
486 Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
487 let struct_expr = snapshot.parse_struct_expr(None, path, AttrVec::new(), false);
488 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
489 return Some(match (struct_expr, block_tail) {
490 (Ok(expr), Err(mut err)) => {
491 // We have encountered the following:
496 // fn foo() -> Foo { Path {
500 self.struct_span_err(expr.span, "struct literal body without path")
501 .multipart_suggestion(
502 "you might have forgotten to add the struct literal inside the block",
504 (expr.span.shrink_to_lo(), "{ SomeStruct ".to_string()),
505 (expr.span.shrink_to_hi(), " }".to_string()),
507 Applicability::MaybeIncorrect,
510 self.restore_snapshot(snapshot);
511 let mut tail = self.mk_block(
512 vec![self.mk_stmt_err(expr.span)],
514 lo.to(self.prev_token.span),
516 tail.could_be_bare_literal = true;
519 (Err(err), Ok(tail)) => {
520 // We have a block tail that contains a somehow valid type ascription expr.
524 (Err(snapshot_err), Err(err)) => {
525 // We don't know what went wrong, emit the normal error.
526 snapshot_err.cancel();
527 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
530 (Ok(_), Ok(mut tail)) => {
531 tail.could_be_bare_literal = true;
539 pub fn maybe_annotate_with_ascription(
541 err: &mut Diagnostic,
542 maybe_expected_semicolon: bool,
544 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
545 let sm = self.sess.source_map();
546 let next_pos = sm.lookup_char_pos(self.token.span.lo());
547 let op_pos = sm.lookup_char_pos(sp.hi());
549 let allow_unstable = self.sess.unstable_features.is_nightly_build();
554 "maybe write a path separator here",
557 Applicability::MaybeIncorrect
559 Applicability::MachineApplicable
562 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
563 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
566 "try using a semicolon",
568 Applicability::MaybeIncorrect,
570 } else if allow_unstable {
571 err.span_label(sp, "tried to parse a type due to this type ascription");
573 err.span_label(sp, "tried to parse a type due to this");
576 // Give extra information about type ascription only if it's a nightly compiler.
578 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
582 // Avoid giving too much info when it was likely an unrelated typo.
584 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
585 for more information",
592 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
593 /// passes through any errors encountered. Used for error recovery.
594 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
596 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
597 Ok(p.parse_token_tree())
604 /// This function checks if there are trailing angle brackets and produces
605 /// a diagnostic to suggest removing them.
607 /// ```ignore (diagnostic)
608 /// let _ = [1, 2, 3].into_iter().collect::<Vec<usize>>>>();
609 /// ^^ help: remove extra angle brackets
612 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
613 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
614 pub(super) fn check_trailing_angle_brackets(
616 segment: &PathSegment,
619 // This function is intended to be invoked after parsing a path segment where there are two
622 // 1. A specific token is expected after the path segment.
623 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
624 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
625 // 2. No specific token is expected after the path segment.
626 // eg. `x.foo` (field access)
628 // This function is called after parsing `.foo` and before parsing the token `end` (if
629 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
632 // We only care about trailing angle brackets if we previously parsed angle bracket
633 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
634 // removed in this case:
636 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
638 // This case is particularly tricky as we won't notice it just looking at the tokens -
639 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
640 // have already been parsed):
642 // `x.foo::<u32>>>(3)`
643 let parsed_angle_bracket_args =
644 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
647 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
648 parsed_angle_bracket_args,
650 if !parsed_angle_bracket_args {
654 // Keep the span at the start so we can highlight the sequence of `>` characters to be
656 let lo = self.token.span;
658 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
659 // (since we might have the field access case and the characters we're eating are
660 // actual operators and not trailing characters - ie `x.foo >> 3`).
661 let mut position = 0;
663 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
664 // many of each (so we can correctly pluralize our error messages) and continue to
666 let mut number_of_shr = 0;
667 let mut number_of_gt = 0;
668 while self.look_ahead(position, |t| {
669 trace!("check_trailing_angle_brackets: t={:?}", t);
670 if *t == token::BinOp(token::BinOpToken::Shr) {
673 } else if *t == token::Gt {
683 // If we didn't find any trailing `>` characters, then we have nothing to error about.
685 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
686 number_of_gt, number_of_shr,
688 if number_of_gt < 1 && number_of_shr < 1 {
692 // Finally, double check that we have our end token as otherwise this is the
694 if self.look_ahead(position, |t| {
695 trace!("check_trailing_angle_brackets: t={:?}", t);
696 end.contains(&&t.kind)
698 // Eat from where we started until the end token so that parsing can continue
699 // as if we didn't have those extra angle brackets.
700 self.eat_to_tokens(end);
701 let span = lo.until(self.token.span);
703 let total_num_of_gt = number_of_gt + number_of_shr * 2;
704 self.struct_span_err(
706 &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
710 &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
712 Applicability::MachineApplicable,
720 /// Check if a method call with an intended turbofish has been written without surrounding
722 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
723 if token::ModSep == self.token.kind && segment.args.is_none() {
724 let snapshot = self.create_snapshot_for_diagnostic();
726 let lo = self.token.span;
727 match self.parse_angle_args(None) {
729 let span = lo.to(self.prev_token.span);
730 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
731 let mut trailing_span = self.prev_token.span.shrink_to_hi();
732 while self.token.kind == token::BinOp(token::Shr)
733 || self.token.kind == token::Gt
735 trailing_span = trailing_span.to(self.token.span);
738 if self.token.kind == token::OpenDelim(token::Paren) {
739 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
740 let args = AngleBracketedArgs { args, span }.into();
743 self.struct_span_err(
745 "generic parameters without surrounding angle brackets",
747 .multipart_suggestion(
748 "surround the type parameters with angle brackets",
750 (span.shrink_to_lo(), "<".to_string()),
751 (trailing_span, ">".to_string()),
753 Applicability::MachineApplicable,
757 // This doesn't look like an invalid turbofish, can't recover parse state.
758 self.restore_snapshot(snapshot);
762 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
763 // generic parse error instead.
765 self.restore_snapshot(snapshot);
771 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
772 /// encounter a parse error when encountering the first `,`.
773 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
775 mut e: DiagnosticBuilder<'a, ErrorGuaranteed>,
777 ) -> PResult<'a, ()> {
778 if let ExprKind::Binary(binop, _, _) = &expr.kind
779 && let ast::BinOpKind::Lt = binop.node
780 && self.eat(&token::Comma)
782 let x = self.parse_seq_to_before_end(
784 SeqSep::trailing_allowed(token::Comma),
785 |p| p.parse_generic_arg(None),
788 Ok((_, _, false)) => {
789 if self.eat(&token::Gt) {
790 e.span_suggestion_verbose(
791 binop.span.shrink_to_lo(),
792 TURBOFISH_SUGGESTION_STR,
794 Applicability::MaybeIncorrect,
797 match self.parse_expr() {
800 self.mk_expr_err(expr.span.to(self.prev_token.span));
804 *expr = self.mk_expr_err(expr.span);
819 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
820 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
821 /// parenthesising the leftmost comparison.
822 fn attempt_chained_comparison_suggestion(
824 err: &mut Diagnostic,
826 outer_op: &Spanned<AssocOp>,
827 ) -> bool /* advanced the cursor */ {
828 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
829 if let ExprKind::Field(_, ident) = l1.kind
830 && ident.as_str().parse::<i32>().is_err()
831 && !matches!(r1.kind, ExprKind::Lit(_))
833 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
834 // suggestion being the only one to apply is high.
837 let mut enclose = |left: Span, right: Span| {
838 err.multipart_suggestion(
839 "parenthesize the comparison",
841 (left.shrink_to_lo(), "(".to_string()),
842 (right.shrink_to_hi(), ")".to_string()),
844 Applicability::MaybeIncorrect,
847 return match (op.node, &outer_op.node) {
849 (BinOpKind::Eq, AssocOp::Equal) |
850 // `x < y < z` and friends.
851 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
852 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
853 // `x > y > z` and friends.
854 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
855 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
856 let expr_to_str = |e: &Expr| {
857 self.span_to_snippet(e.span)
858 .unwrap_or_else(|_| pprust::expr_to_string(&e))
860 err.span_suggestion_verbose(
861 inner_op.span.shrink_to_hi(),
862 "split the comparison into two",
863 format!(" && {}", expr_to_str(&r1)),
864 Applicability::MaybeIncorrect,
866 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
869 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
870 // Consume `z`/outer-op-rhs.
871 let snapshot = self.create_snapshot_for_diagnostic();
872 match self.parse_expr() {
874 // We are sure that outer-op-rhs could be consumed, the suggestion is
876 enclose(r1.span, r2.span);
881 self.restore_snapshot(snapshot);
887 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
888 let snapshot = self.create_snapshot_for_diagnostic();
889 // At this point it is always valid to enclose the lhs in parentheses, no
890 // further checks are necessary.
891 match self.parse_expr() {
893 enclose(l1.span, r1.span);
898 self.restore_snapshot(snapshot);
909 /// Produces an error if comparison operators are chained (RFC #558).
910 /// We only need to check the LHS, not the RHS, because all comparison ops have same
911 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
913 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
914 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
917 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
918 /// associative we can infer that we have:
927 pub(super) fn check_no_chained_comparison(
930 outer_op: &Spanned<AssocOp>,
931 ) -> PResult<'a, Option<P<Expr>>> {
933 outer_op.node.is_comparison(),
934 "check_no_chained_comparison: {:?} is not comparison",
939 |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
941 match inner_op.kind {
942 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
943 let mut err = self.struct_span_err(
944 vec![op.span, self.prev_token.span],
945 "comparison operators cannot be chained",
948 let suggest = |err: &mut Diagnostic| {
949 err.span_suggestion_verbose(
950 op.span.shrink_to_lo(),
951 TURBOFISH_SUGGESTION_STR,
953 Applicability::MaybeIncorrect,
957 // Include `<` to provide this recommendation even in a case like
958 // `Foo<Bar<Baz<Qux, ()>>>`
959 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
960 || outer_op.node == AssocOp::Greater
962 if outer_op.node == AssocOp::Less {
963 let snapshot = self.create_snapshot_for_diagnostic();
965 // So far we have parsed `foo<bar<`, consume the rest of the type args.
967 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
968 self.consume_tts(1, &modifiers);
970 if !&[token::OpenDelim(token::Paren), token::ModSep]
971 .contains(&self.token.kind)
973 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
974 // parser and bail out.
975 self.restore_snapshot(snapshot);
978 return if token::ModSep == self.token.kind {
979 // We have some certainty that this was a bad turbofish at this point.
983 let snapshot = self.create_snapshot_for_diagnostic();
986 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
987 match self.parse_expr() {
989 // 99% certain that the suggestion is correct, continue parsing.
991 // FIXME: actually check that the two expressions in the binop are
992 // paths and resynthesize new fn call expression instead of using
993 // `ExprKind::Err` placeholder.
994 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
998 // Not entirely sure now, but we bubble the error up with the
1000 self.restore_snapshot(snapshot);
1004 } else if token::OpenDelim(token::Paren) == self.token.kind {
1005 // We have high certainty that this was a bad turbofish at this point.
1008 // Consume the fn call arguments.
1009 match self.consume_fn_args() {
1010 Err(()) => Err(err),
1013 // FIXME: actually check that the two expressions in the binop are
1014 // paths and resynthesize new fn call expression instead of using
1015 // `ExprKind::Err` placeholder.
1016 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1020 if !matches!(l1.kind, ExprKind::Lit(_))
1021 && !matches!(r1.kind, ExprKind::Lit(_))
1023 // All we know is that this is `foo < bar >` and *nothing* else. Try to
1024 // be helpful, but don't attempt to recover.
1025 err.help(TURBOFISH_SUGGESTION_STR);
1026 err.help("or use `(...)` if you meant to specify fn arguments");
1029 // If it looks like a genuine attempt to chain operators (as opposed to a
1030 // misformatted turbofish, for instance), suggest a correct form.
1031 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
1034 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
1036 // These cases cause too many knock-down errors, bail out (#61329).
1042 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
1045 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
1053 fn consume_fn_args(&mut self) -> Result<(), ()> {
1054 let snapshot = self.create_snapshot_for_diagnostic();
1057 // Consume the fn call arguments.
1059 [(token::OpenDelim(token::Paren), 1), (token::CloseDelim(token::Paren), -1)];
1060 self.consume_tts(1, &modifiers);
1062 if self.token.kind == token::Eof {
1063 // Not entirely sure that what we consumed were fn arguments, rollback.
1064 self.restore_snapshot(snapshot);
1067 // 99% certain that the suggestion is correct, continue parsing.
1072 pub(super) fn maybe_report_ambiguous_plus(
1074 allow_plus: AllowPlus,
1075 impl_dyn_multi: bool,
1078 if matches!(allow_plus, AllowPlus::No) && impl_dyn_multi {
1079 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
1080 self.struct_span_err(ty.span, "ambiguous `+` in a type")
1083 "use parentheses to disambiguate",
1085 Applicability::MachineApplicable,
1091 /// Swift lets users write `Ty?` to mean `Option<Ty>`. Parse the construct and recover from it.
1092 pub(super) fn maybe_recover_from_question_mark(
1095 recover_question_mark: RecoverQuestionMark,
1097 if let RecoverQuestionMark::No = recover_question_mark {
1100 if self.token == token::Question {
1102 self.struct_span_err(self.prev_token.span, "invalid `?` in type")
1103 .span_label(self.prev_token.span, "`?` is only allowed on expressions, not types")
1104 .multipart_suggestion(
1105 "if you meant to express that the type might not contain a value, use the `Option` wrapper type",
1107 (ty.span.shrink_to_lo(), "Option<".to_string()),
1108 (self.prev_token.span, ">".to_string()),
1110 Applicability::MachineApplicable,
1113 self.mk_ty(ty.span.to(self.prev_token.span), TyKind::Err)
1119 pub(super) fn maybe_recover_from_bad_type_plus(
1121 allow_plus: AllowPlus,
1123 ) -> PResult<'a, ()> {
1124 // Do not add `+` to expected tokens.
1125 if matches!(allow_plus, AllowPlus::No) || !self.token.is_like_plus() {
1130 let bounds = self.parse_generic_bounds(None)?;
1131 let sum_span = ty.span.to(self.prev_token.span);
1133 let mut err = struct_span_err!(
1134 self.sess.span_diagnostic,
1137 "expected a path on the left-hand side of `+`, not `{}`",
1138 pprust::ty_to_string(ty)
1142 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1143 let sum_with_parens = pprust::to_string(|s| {
1145 s.print_opt_lifetime(lifetime);
1146 s.print_mutability(mut_ty.mutbl, false);
1148 s.print_type(&mut_ty.ty);
1149 s.print_type_bounds(" +", &bounds);
1152 err.span_suggestion(
1154 "try adding parentheses",
1156 Applicability::MachineApplicable,
1159 TyKind::Ptr(..) | TyKind::BareFn(..) => {
1160 err.span_label(sum_span, "perhaps you forgot parentheses?");
1163 err.span_label(sum_span, "expected a path");
1170 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1171 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1172 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1173 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1176 allow_recovery: bool,
1177 ) -> PResult<'a, P<T>> {
1178 // Do not add `::` to expected tokens.
1179 if allow_recovery && self.token == token::ModSep {
1180 if let Some(ty) = base.to_ty() {
1181 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1187 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1188 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1189 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1193 ) -> PResult<'a, P<T>> {
1194 self.expect(&token::ModSep)?;
1196 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1197 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1198 path.span = ty_span.to(self.prev_token.span);
1200 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1201 self.struct_span_err(path.span, "missing angle brackets in associated item path")
1203 // This is a best-effort recovery.
1206 format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1207 Applicability::MaybeIncorrect,
1211 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1212 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1215 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1216 if self.token.kind == TokenKind::Semi {
1218 let mut err = self.struct_span_err(self.prev_token.span, "expected item, found `;`");
1219 err.span_suggestion_short(
1220 self.prev_token.span,
1221 "remove this semicolon",
1223 Applicability::MachineApplicable,
1225 if !items.is_empty() {
1226 let previous_item = &items[items.len() - 1];
1227 let previous_item_kind_name = match previous_item.kind {
1228 // Say "braced struct" because tuple-structs and
1229 // braceless-empty-struct declarations do take a semicolon.
1230 ItemKind::Struct(..) => Some("braced struct"),
1231 ItemKind::Enum(..) => Some("enum"),
1232 ItemKind::Trait(..) => Some("trait"),
1233 ItemKind::Union(..) => Some("union"),
1236 if let Some(name) = previous_item_kind_name {
1237 err.help(&format!("{name} declarations are not followed by a semicolon"));
1247 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1248 /// closing delimiter.
1249 pub(super) fn unexpected_try_recover(
1252 ) -> PResult<'a, bool /* recovered */> {
1253 let token_str = pprust::token_kind_to_string(t);
1254 let this_token_str = super::token_descr(&self.token);
1255 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1256 // Point at the end of the macro call when reaching end of macro arguments.
1257 (token::Eof, Some(_)) => {
1258 let sp = self.sess.source_map().next_point(self.prev_token.span);
1261 // We don't want to point at the following span after DUMMY_SP.
1262 // This happens when the parser finds an empty TokenStream.
1263 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1264 // EOF, don't want to point at the following char, but rather the last token.
1265 (token::Eof, None) => (self.prev_token.span, self.token.span),
1266 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1269 "expected `{}`, found {}",
1271 match (&self.token.kind, self.subparser_name) {
1272 (token::Eof, Some(origin)) => format!("end of {origin}"),
1273 _ => this_token_str,
1276 let mut err = self.struct_span_err(sp, &msg);
1277 let label_exp = format!("expected `{token_str}`");
1278 match self.recover_closing_delimiter(&[t.clone()], err) {
1281 return Ok(recovered);
1284 let sm = self.sess.source_map();
1285 if !sm.is_multiline(prev_sp.until(sp)) {
1286 // When the spans are in the same line, it means that the only content
1287 // between them is whitespace, point only at the found token.
1288 err.span_label(sp, label_exp);
1290 err.span_label(prev_sp, label_exp);
1291 err.span_label(sp, "unexpected token");
1296 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1297 if self.eat(&token::Semi) {
1300 self.expect(&token::Semi).map(drop) // Error unconditionally
1303 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1304 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1305 pub(super) fn recover_incorrect_await_syntax(
1310 ) -> PResult<'a, P<Expr>> {
1311 let (hi, expr, is_question) = if self.token == token::Not {
1312 // Handle `await!(<expr>)`.
1313 self.recover_await_macro()?
1315 self.recover_await_prefix(await_sp)?
1317 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1318 let kind = match expr.kind {
1319 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1320 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1321 ExprKind::Try(_) => ExprKind::Err,
1322 _ => ExprKind::Await(expr),
1324 let expr = self.mk_expr(lo.to(sp), kind, attrs);
1325 self.maybe_recover_from_bad_qpath(expr, true)
1328 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1329 self.expect(&token::Not)?;
1330 self.expect(&token::OpenDelim(token::Paren))?;
1331 let expr = self.parse_expr()?;
1332 self.expect(&token::CloseDelim(token::Paren))?;
1333 Ok((self.prev_token.span, expr, false))
1336 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1337 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1338 let expr = if self.token == token::OpenDelim(token::Brace) {
1339 // Handle `await { <expr> }`.
1340 // This needs to be handled separately from the next arm to avoid
1341 // interpreting `await { <expr> }?` as `<expr>?.await`.
1342 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default, AttrVec::new())
1346 .map_err(|mut err| {
1347 err.span_label(await_sp, "while parsing this incorrect await expression");
1350 Ok((expr.span, expr, is_question))
1353 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1355 self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr));
1356 let suggestion = format!("{}.await{}", expr_str, if is_question { "?" } else { "" });
1358 let app = match expr.kind {
1359 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1360 _ => Applicability::MachineApplicable,
1362 self.struct_span_err(sp, "incorrect use of `await`")
1363 .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
1368 /// If encountering `future.await()`, consumes and emits an error.
1369 pub(super) fn recover_from_await_method_call(&mut self) {
1370 if self.token == token::OpenDelim(token::Paren)
1371 && self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
1374 let lo = self.token.span;
1376 let sp = lo.to(self.token.span);
1378 self.struct_span_err(sp, "incorrect use of `await`")
1381 "`await` is not a method call, remove the parentheses",
1383 Applicability::MachineApplicable,
1389 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1390 let is_try = self.token.is_keyword(kw::Try);
1391 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1392 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(token::Paren)); //check for (
1394 if is_try && is_questionmark && is_open {
1395 let lo = self.token.span;
1396 self.bump(); //remove try
1397 self.bump(); //remove !
1398 let try_span = lo.to(self.token.span); //we take the try!( span
1399 self.bump(); //remove (
1400 let is_empty = self.token == token::CloseDelim(token::Paren); //check if the block is empty
1401 self.consume_block(token::Paren, ConsumeClosingDelim::No); //eat the block
1402 let hi = self.token.span;
1403 self.bump(); //remove )
1404 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1405 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1406 let prefix = if is_empty { "" } else { "alternatively, " };
1408 err.multipart_suggestion(
1409 "you can use the `?` operator instead",
1410 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1411 Applicability::MachineApplicable,
1414 err.span_suggestion(lo.shrink_to_lo(), &format!("{prefix}you can still access the deprecated `try!()` macro using the \"raw identifier\" syntax"), "r#".to_string(), Applicability::MachineApplicable);
1416 Ok(self.mk_expr_err(lo.to(hi)))
1418 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1422 /// Recovers a situation like `for ( $pat in $expr )`
1423 /// and suggest writing `for $pat in $expr` instead.
1425 /// This should be called before parsing the `$block`.
1426 pub(super) fn recover_parens_around_for_head(
1429 begin_paren: Option<Span>,
1431 match (&self.token.kind, begin_paren) {
1432 (token::CloseDelim(token::Paren), Some(begin_par_sp)) => {
1435 self.struct_span_err(
1436 MultiSpan::from_spans(vec![begin_par_sp, self.prev_token.span]),
1437 "unexpected parentheses surrounding `for` loop head",
1439 .multipart_suggestion(
1440 "remove parentheses in `for` loop",
1441 vec![(begin_par_sp, String::new()), (self.prev_token.span, String::new())],
1442 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1443 // with `x) in y)` which is syntactically invalid.
1444 // However, this is prevented before we get here.
1445 Applicability::MachineApplicable,
1449 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1450 pat.and_then(|pat| match pat.kind {
1451 PatKind::Paren(pat) => pat,
1459 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1460 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1461 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1462 || self.token.is_ident() &&
1463 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1464 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1465 self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren))
1466 || self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) // `foo:bar {`
1467 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1468 self.look_ahead(2, |t| t == &token::Lt) &&
1469 self.look_ahead(3, |t| t.is_ident())
1470 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1471 self.look_ahead(2, |t| t.is_ident())
1472 || self.look_ahead(1, |t| t == &token::ModSep)
1473 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1474 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1477 pub(super) fn recover_seq_parse_error(
1479 delim: token::DelimToken,
1481 result: PResult<'a, P<Expr>>,
1487 // Recover from parse error, callers expect the closing delim to be consumed.
1488 self.consume_block(delim, ConsumeClosingDelim::Yes);
1489 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err, AttrVec::new())
1494 pub(super) fn recover_closing_delimiter(
1496 tokens: &[TokenKind],
1497 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
1498 ) -> PResult<'a, bool> {
1500 // We want to use the last closing delim that would apply.
1501 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1502 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1503 && Some(self.token.span) > unmatched.unclosed_span
1510 // Recover and assume that the detected unclosed delimiter was meant for
1511 // this location. Emit the diagnostic and act as if the delimiter was
1512 // present for the parser's sake.
1514 // Don't attempt to recover from this unclosed delimiter more than once.
1515 let unmatched = self.unclosed_delims.remove(pos);
1516 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1517 if unmatched.found_delim.is_none() {
1518 // We encountered `Eof`, set this fact here to avoid complaining about missing
1519 // `fn main()` when we found place to suggest the closing brace.
1520 *self.sess.reached_eof.borrow_mut() = true;
1523 // We want to suggest the inclusion of the closing delimiter where it makes
1524 // the most sense, which is immediately after the last token:
1529 // | help: `)` may belong here
1531 // unclosed delimiter
1532 if let Some(sp) = unmatched.unclosed_span {
1533 let mut primary_span: Vec<Span> =
1534 err.span.primary_spans().iter().cloned().collect();
1535 primary_span.push(sp);
1536 let mut primary_span: MultiSpan = primary_span.into();
1537 for span_label in err.span.span_labels() {
1538 if let Some(label) = span_label.label {
1539 primary_span.push_span_label(span_label.span, label);
1542 err.set_span(primary_span);
1543 err.span_label(sp, "unclosed delimiter");
1545 // Backticks should be removed to apply suggestions.
1546 let mut delim = delim.to_string();
1547 delim.retain(|c| c != '`');
1548 err.span_suggestion_short(
1549 self.prev_token.span.shrink_to_hi(),
1550 &format!("`{delim}` may belong here"),
1552 Applicability::MaybeIncorrect,
1554 if unmatched.found_delim.is_none() {
1555 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1556 // errors which would be emitted elsewhere in the parser and let other error
1557 // recovery consume the rest of the file.
1561 self.expected_tokens.clear(); // Reduce the number of errors.
1569 /// Eats tokens until we can be relatively sure we reached the end of the
1570 /// statement. This is something of a best-effort heuristic.
1572 /// We terminate when we find an unmatched `}` (without consuming it).
1573 pub(super) fn recover_stmt(&mut self) {
1574 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1577 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1578 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1579 /// approximate -- it can mean we break too early due to macros, but that
1580 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1582 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1583 /// after finding (and consuming) a brace-delimited block.
1584 pub(super) fn recover_stmt_(
1586 break_on_semi: SemiColonMode,
1587 break_on_block: BlockMode,
1589 let mut brace_depth = 0;
1590 let mut bracket_depth = 0;
1591 let mut in_block = false;
1592 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1594 debug!("recover_stmt_ loop {:?}", self.token);
1595 match self.token.kind {
1596 token::OpenDelim(token::DelimToken::Brace) => {
1599 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1604 token::OpenDelim(token::DelimToken::Bracket) => {
1608 token::CloseDelim(token::DelimToken::Brace) => {
1609 if brace_depth == 0 {
1610 debug!("recover_stmt_ return - close delim {:?}", self.token);
1615 if in_block && bracket_depth == 0 && brace_depth == 0 {
1616 debug!("recover_stmt_ return - block end {:?}", self.token);
1620 token::CloseDelim(token::DelimToken::Bracket) => {
1622 if bracket_depth < 0 {
1628 debug!("recover_stmt_ return - Eof");
1633 if break_on_semi == SemiColonMode::Break
1635 && bracket_depth == 0
1637 debug!("recover_stmt_ return - Semi");
1642 if break_on_semi == SemiColonMode::Comma
1644 && bracket_depth == 0 =>
1646 debug!("recover_stmt_ return - Semi");
1654 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1655 if self.eat_keyword(kw::In) {
1656 // a common typo: `for _ in in bar {}`
1657 self.struct_span_err(self.prev_token.span, "expected iterable, found keyword `in`")
1658 .span_suggestion_short(
1659 in_span.until(self.prev_token.span),
1660 "remove the duplicated `in`",
1662 Applicability::MachineApplicable,
1668 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1669 if let token::DocComment(..) = self.token.kind {
1670 self.struct_span_err(
1672 "documentation comments cannot be applied to a function parameter's type",
1674 .span_label(self.token.span, "doc comments are not allowed here")
1677 } else if self.token == token::Pound
1678 && self.look_ahead(1, |t| *t == token::OpenDelim(token::Bracket))
1680 let lo = self.token.span;
1681 // Skip every token until next possible arg.
1682 while self.token != token::CloseDelim(token::Bracket) {
1685 let sp = lo.to(self.token.span);
1687 self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
1688 .span_label(sp, "attributes are not allowed here")
1693 pub(super) fn parameter_without_type(
1695 err: &mut Diagnostic,
1699 ) -> Option<Ident> {
1700 // If we find a pattern followed by an identifier, it could be an (incorrect)
1701 // C-style parameter declaration.
1702 if self.check_ident()
1703 && self.look_ahead(1, |t| *t == token::Comma || *t == token::CloseDelim(token::Paren))
1705 // `fn foo(String s) {}`
1706 let ident = self.parse_ident().unwrap();
1707 let span = pat.span.with_hi(ident.span.hi());
1709 err.span_suggestion(
1711 "declare the type after the parameter binding",
1712 String::from("<identifier>: <type>"),
1713 Applicability::HasPlaceholders,
1716 } else if require_name
1717 && (self.token == token::Comma
1718 || self.token == token::Lt
1719 || self.token == token::CloseDelim(token::Paren))
1721 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
1723 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
1725 PatKind::Ident(_, ident, _) => (
1727 "self: ".to_string(),
1728 ": TypeName".to_string(),
1730 pat.span.shrink_to_lo(),
1731 pat.span.shrink_to_hi(),
1732 pat.span.shrink_to_lo(),
1734 // Also catches `fn foo(&a)`.
1735 PatKind::Ref(ref inner_pat, mutab)
1736 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
1738 match inner_pat.clone().into_inner().kind {
1739 PatKind::Ident(_, ident, _) => {
1740 let mutab = mutab.prefix_str();
1743 "self: ".to_string(),
1744 format!("{ident}: &{mutab}TypeName"),
1746 pat.span.shrink_to_lo(),
1748 pat.span.shrink_to_lo(),
1751 _ => unreachable!(),
1755 // Otherwise, try to get a type and emit a suggestion.
1756 if let Some(ty) = pat.to_ty() {
1757 err.span_suggestion_verbose(
1759 "explicitly ignore the parameter name",
1760 format!("_: {}", pprust::ty_to_string(&ty)),
1761 Applicability::MachineApplicable,
1770 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1772 err.span_suggestion(
1774 "if this is a `self` type, give it a parameter name",
1776 Applicability::MaybeIncorrect,
1779 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
1780 // `fn foo(HashMap: TypeName<u32>)`.
1781 if self.token != token::Lt {
1782 err.span_suggestion(
1784 "if this is a parameter name, give it a type",
1786 Applicability::HasPlaceholders,
1789 err.span_suggestion(
1791 "if this is a type, explicitly ignore the parameter name",
1793 Applicability::MachineApplicable,
1797 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
1798 return if self.token == token::Lt { None } else { Some(ident) };
1803 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
1804 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
1805 self.expect(&token::Colon)?;
1806 let ty = self.parse_ty()?;
1812 "patterns aren't allowed in methods without bodies",
1814 .span_suggestion_short(
1816 "give this argument a name or use an underscore to ignore it",
1818 Applicability::MachineApplicable,
1822 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
1824 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
1828 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
1829 let sp = param.pat.span;
1830 param.ty.kind = TyKind::Err;
1831 self.struct_span_err(sp, "unexpected `self` parameter in function")
1832 .span_label(sp, "must be the first parameter of an associated function")
1837 pub(super) fn consume_block(
1839 delim: token::DelimToken,
1840 consume_close: ConsumeClosingDelim,
1842 let mut brace_depth = 0;
1844 if self.eat(&token::OpenDelim(delim)) {
1846 } else if self.check(&token::CloseDelim(delim)) {
1847 if brace_depth == 0 {
1848 if let ConsumeClosingDelim::Yes = consume_close {
1849 // Some of the callers of this method expect to be able to parse the
1850 // closing delimiter themselves, so we leave it alone. Otherwise we advance
1860 } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
1868 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
1869 let (span, msg) = match (&self.token.kind, self.subparser_name) {
1870 (&token::Eof, Some(origin)) => {
1871 let sp = self.sess.source_map().next_point(self.prev_token.span);
1872 (sp, format!("expected expression, found end of {origin}"))
1876 format!("expected expression, found {}", super::token_descr(&self.token),),
1879 let mut err = self.struct_span_err(span, &msg);
1880 let sp = self.sess.source_map().start_point(self.token.span);
1881 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
1882 self.sess.expr_parentheses_needed(&mut err, *sp);
1884 err.span_label(span, "expected expression");
1890 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
1891 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
1892 modifier: &[(token::TokenKind, i64)],
1895 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
1898 if self.token.kind == token::Eof {
1905 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
1907 /// This is necessary because at this point we don't know whether we parsed a function with
1908 /// anonymous parameters or a function with names but no types. In order to minimize
1909 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
1910 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
1911 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
1912 /// we deduplicate them to not complain about duplicated parameter names.
1913 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
1914 let mut seen_inputs = FxHashSet::default();
1915 for input in fn_inputs.iter_mut() {
1916 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
1917 (&input.pat.kind, &input.ty.kind)
1923 if let Some(ident) = opt_ident {
1924 if seen_inputs.contains(&ident) {
1925 input.pat.kind = PatKind::Wild;
1927 seen_inputs.insert(ident);
1932 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
1933 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
1934 /// like the user has forgotten them.
1935 pub fn handle_ambiguous_unbraced_const_arg(
1937 args: &mut Vec<AngleBracketedArg>,
1938 ) -> PResult<'a, bool> {
1939 // If we haven't encountered a closing `>`, then the argument is malformed.
1940 // It's likely that the user has written a const expression without enclosing it
1941 // in braces, so we try to recover here.
1942 let arg = args.pop().unwrap();
1943 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
1944 // adverse side-effects to subsequent errors and seems to advance the parser.
1945 // We are causing this error here exclusively in case that a `const` expression
1946 // could be recovered from the current parser state, even if followed by more
1947 // arguments after a comma.
1948 let mut err = self.struct_span_err(
1950 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
1952 err.span_label(self.token.span, "expected one of `,` or `>`");
1953 match self.recover_const_arg(arg.span(), err) {
1955 args.push(AngleBracketedArg::Arg(arg));
1956 if self.eat(&token::Comma) {
1957 return Ok(true); // Continue
1962 // We will emit a more generic error later.
1966 return Ok(false); // Don't continue.
1969 /// Attempt to parse a generic const argument that has not been enclosed in braces.
1970 /// There are a limited number of expressions that are permitted without being encoded
1973 /// - Single-segment paths (i.e. standalone generic const parameters).
1974 /// All other expressions that can be parsed will emit an error suggesting the expression be
1975 /// wrapped in braces.
1976 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
1977 let start = self.token.span;
1978 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
1980 start.shrink_to_lo(),
1981 "while parsing a const generic argument starting here",
1985 if !self.expr_is_valid_const_arg(&expr) {
1986 self.struct_span_err(
1988 "expressions must be enclosed in braces to be used as const generic \
1991 .multipart_suggestion(
1992 "enclose the `const` expression in braces",
1994 (expr.span.shrink_to_lo(), "{ ".to_string()),
1995 (expr.span.shrink_to_hi(), " }".to_string()),
1997 Applicability::MachineApplicable,
2004 fn recover_const_param_decl(&mut self, ty_generics: Option<&Generics>) -> Option<GenericArg> {
2005 let snapshot = self.create_snapshot_for_diagnostic();
2006 let param = match self.parse_const_param(vec![]) {
2010 self.restore_snapshot(snapshot);
2015 self.struct_span_err(param.span(), "unexpected `const` parameter declaration");
2016 err.span_label(param.span(), "expected a `const` expression, not a parameter declaration");
2017 if let (Some(generics), Ok(snippet)) =
2018 (ty_generics, self.sess.source_map().span_to_snippet(param.span()))
2020 let (span, sugg) = match &generics.params[..] {
2021 [] => (generics.span, format!("<{snippet}>")),
2022 [.., generic] => (generic.span().shrink_to_hi(), format!(", {snippet}")),
2024 err.multipart_suggestion(
2025 "`const` parameters must be declared for the `impl`",
2026 vec![(span, sugg), (param.span(), param.ident.to_string())],
2027 Applicability::MachineApplicable,
2030 let value = self.mk_expr_err(param.span());
2032 Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }))
2035 pub fn recover_const_param_declaration(
2037 ty_generics: Option<&Generics>,
2038 ) -> PResult<'a, Option<GenericArg>> {
2039 // We have to check for a few different cases.
2040 if let Some(arg) = self.recover_const_param_decl(ty_generics) {
2041 return Ok(Some(arg));
2044 // We haven't consumed `const` yet.
2045 let start = self.token.span;
2046 self.bump(); // `const`
2048 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
2050 .struct_span_err(start, "expected lifetime, type, or constant, found keyword `const`");
2051 if self.check_const_arg() {
2052 err.span_suggestion_verbose(
2053 start.until(self.token.span),
2054 "the `const` keyword is only needed in the definition of the type",
2056 Applicability::MaybeIncorrect,
2059 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
2061 let after_kw_const = self.token.span;
2062 self.recover_const_arg(after_kw_const, err).map(Some)
2066 /// Try to recover from possible generic const argument without `{` and `}`.
2068 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
2069 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
2070 /// if we think that that the resulting expression would be well formed.
2071 pub fn recover_const_arg(
2074 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2075 ) -> PResult<'a, GenericArg> {
2076 let is_op_or_dot = AssocOp::from_token(&self.token)
2078 if let AssocOp::Greater
2080 | AssocOp::ShiftRight
2081 | AssocOp::GreaterEqual
2082 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2083 // assign a value to a defaulted generic parameter.
2085 | AssocOp::AssignOp(_) = op
2093 || self.token.kind == TokenKind::Dot;
2094 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2095 // type params has been parsed.
2097 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2098 if !is_op_or_dot && !was_op {
2099 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2102 let snapshot = self.create_snapshot_for_diagnostic();
2106 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2108 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2109 if token::EqEq == snapshot.token.kind {
2110 err.span_suggestion(
2111 snapshot.token.span,
2112 "if you meant to use an associated type binding, replace `==` with `=`",
2114 Applicability::MaybeIncorrect,
2116 let value = self.mk_expr_err(start.to(expr.span));
2118 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2119 } else if token::Colon == snapshot.token.kind
2120 && expr.span.lo() == snapshot.token.span.hi()
2121 && matches!(expr.kind, ExprKind::Path(..))
2123 // Find a mistake like "foo::var:A".
2124 err.span_suggestion(
2125 snapshot.token.span,
2126 "write a path separator here",
2128 Applicability::MaybeIncorrect,
2131 return Ok(GenericArg::Type(self.mk_ty(start.to(expr.span), TyKind::Err)));
2132 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2134 // Avoid the following output by checking that we consumed a full const arg:
2135 // help: expressions must be enclosed in braces to be used as const generic
2138 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2140 return Ok(self.dummy_const_arg_needs_braces(err, start.to(expr.span)));
2147 self.restore_snapshot(snapshot);
2151 /// Creates a dummy const argument, and reports that the expression must be enclosed in braces
2152 pub fn dummy_const_arg_needs_braces(
2154 mut err: DiagnosticBuilder<'a, ErrorGuaranteed>,
2157 err.multipart_suggestion(
2158 "expressions must be enclosed in braces to be used as const generic \
2160 vec![(span.shrink_to_lo(), "{ ".to_string()), (span.shrink_to_hi(), " }".to_string())],
2161 Applicability::MaybeIncorrect,
2163 let value = self.mk_expr_err(span);
2165 GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })
2168 /// Get the diagnostics for the cases where `move async` is found.
2170 /// `move_async_span` starts at the 'm' of the move keyword and ends with the 'c' of the async keyword
2171 pub(super) fn incorrect_move_async_order_found(
2173 move_async_span: Span,
2174 ) -> DiagnosticBuilder<'a, ErrorGuaranteed> {
2176 self.struct_span_err(move_async_span, "the order of `move` and `async` is incorrect");
2177 err.span_suggestion_verbose(
2179 "try switching the order",
2180 "async move".to_owned(),
2181 Applicability::MaybeIncorrect,
2186 /// Some special error handling for the "top-level" patterns in a match arm,
2187 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2188 crate fn maybe_recover_colon_colon_in_pat_typo(
2190 mut first_pat: P<Pat>,
2194 if RecoverColon::Yes != ra || token::Colon != self.token.kind {
2197 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2198 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2202 // The pattern looks like it might be a path with a `::` -> `:` typo:
2203 // `match foo { bar:baz => {} }`
2204 let span = self.token.span;
2205 // We only emit "unexpected `:`" error here if we can successfully parse the
2206 // whole pattern correctly in that case.
2207 let snapshot = self.create_snapshot_for_diagnostic();
2209 // Create error for "unexpected `:`".
2210 match self.expected_one_of_not_found(&[], &[]) {
2212 self.bump(); // Skip the `:`.
2213 match self.parse_pat_no_top_alt(expected) {
2215 // Carry on as if we had not done anything, callers will emit a
2216 // reasonable error.
2219 self.restore_snapshot(snapshot);
2222 // We've parsed the rest of the pattern.
2223 let new_span = first_pat.span.to(pat.span);
2224 let mut show_sugg = false;
2225 // Try to construct a recovered pattern.
2226 match &mut pat.kind {
2227 PatKind::Struct(qself @ None, path, ..)
2228 | PatKind::TupleStruct(qself @ None, path, _)
2229 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2230 PatKind::Ident(_, ident, _) => {
2231 path.segments.insert(0, PathSegment::from_ident(*ident));
2232 path.span = new_span;
2236 PatKind::Path(old_qself, old_path) => {
2237 path.segments = old_path
2241 .chain(take(&mut path.segments))
2243 path.span = new_span;
2244 *qself = old_qself.clone();
2250 PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None) => {
2251 match &first_pat.kind {
2252 PatKind::Ident(_, old_ident, _) => {
2253 let path = PatKind::Path(
2258 PathSegment::from_ident(*old_ident),
2259 PathSegment::from_ident(*ident),
2264 first_pat = self.mk_pat(new_span, path);
2267 PatKind::Path(old_qself, old_path) => {
2268 let mut segments = old_path.segments.clone();
2269 segments.push(PathSegment::from_ident(*ident));
2270 let path = PatKind::Path(
2272 Path { span: new_span, segments, tokens: None },
2274 first_pat = self.mk_pat(new_span, path);
2283 err.span_suggestion(
2285 "maybe write a path separator here",
2287 Applicability::MaybeIncorrect,
2290 first_pat = self.mk_pat(new_span, PatKind::Wild);
2297 // Carry on as if we had not done anything. This should be unreachable.
2298 self.restore_snapshot(snapshot);
2304 crate fn maybe_recover_unexpected_block_label(&mut self) -> bool {
2305 let Some(label) = self.eat_label().filter(|_| {
2306 self.eat(&token::Colon) && self.token.kind == token::OpenDelim(token::Brace)
2310 let span = label.ident.span.to(self.prev_token.span);
2311 let mut err = self.struct_span_err(span, "block label not supported here");
2312 err.span_label(span, "not supported here");
2313 err.tool_only_span_suggestion(
2314 label.ident.span.until(self.token.span),
2315 "remove this block label",
2317 Applicability::MachineApplicable,
2323 /// Some special error handling for the "top-level" patterns in a match arm,
2324 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2325 crate fn maybe_recover_unexpected_comma(
2329 rt: CommaRecoveryMode,
2330 ) -> PResult<'a, ()> {
2331 if rc == RecoverComma::No || self.token != token::Comma {
2335 // An unexpected comma after a top-level pattern is a clue that the
2336 // user (perhaps more accustomed to some other language) forgot the
2337 // parentheses in what should have been a tuple pattern; return a
2338 // suggestion-enhanced error here rather than choking on the comma later.
2339 let comma_span = self.token.span;
2341 if let Err(err) = self.skip_pat_list() {
2342 // We didn't expect this to work anyway; we just wanted to advance to the
2343 // end of the comma-sequence so we know the span to suggest parenthesizing.
2346 let seq_span = lo.to(self.prev_token.span);
2347 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2348 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2349 err.multipart_suggestion(
2351 "try adding parentheses to match on a tuple{}",
2352 if let CommaRecoveryMode::LikelyTuple = rt { "" } else { "..." },
2355 (seq_span.shrink_to_lo(), "(".to_string()),
2356 (seq_span.shrink_to_hi(), ")".to_string()),
2358 Applicability::MachineApplicable,
2360 if let CommaRecoveryMode::EitherTupleOrPipe = rt {
2361 err.span_suggestion(
2363 "...or a vertical bar to match on multiple alternatives",
2364 seq_snippet.replace(',', " |"),
2365 Applicability::MachineApplicable,
2372 /// Parse and throw away a parenthesized comma separated
2373 /// sequence of patterns until `)` is reached.
2374 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2375 while !self.check(&token::CloseDelim(token::Paren)) {
2376 self.parse_pat_no_top_alt(None)?;
2377 if !self.eat(&token::Comma) {