1 use super::pat::Expected;
2 use super::ty::AllowPlus;
4 BlockMode, Parser, PathStyle, RecoverColon, RecoverComma, Restrictions, SemiColonMode, SeqSep,
5 TokenExpectType, TokenType,
10 use rustc_ast::token::{self, Lit, LitKind, TokenKind};
11 use rustc_ast::util::parser::AssocOp;
13 AngleBracketedArg, AngleBracketedArgs, AnonConst, AttrVec, BinOpKind, BindingMode, Block,
14 BlockCheckMode, Expr, ExprKind, GenericArg, Generics, Item, ItemKind, Mutability, Param, Pat,
15 PatKind, Path, PathSegment, QSelf, Ty, TyKind,
17 use rustc_ast_pretty::pprust;
18 use rustc_data_structures::fx::FxHashSet;
19 use rustc_errors::{pluralize, struct_span_err};
20 use rustc_errors::{Applicability, DiagnosticBuilder, Handler, PResult};
21 use rustc_span::source_map::Spanned;
22 use rustc_span::symbol::{kw, Ident};
23 use rustc_span::{MultiSpan, Span, SpanSnippetError, DUMMY_SP};
27 use tracing::{debug, trace};
29 const TURBOFISH_SUGGESTION_STR: &str =
30 "use `::<...>` instead of `<...>` to specify type or const arguments";
32 /// Creates a placeholder argument.
33 pub(super) fn dummy_arg(ident: Ident) -> Param {
35 id: ast::DUMMY_NODE_ID,
36 kind: PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None),
40 let ty = Ty { kind: TyKind::Err, span: ident.span, id: ast::DUMMY_NODE_ID, tokens: None };
42 attrs: AttrVec::default(),
43 id: ast::DUMMY_NODE_ID,
47 is_placeholder: false,
56 fn span_err(self, sp: impl Into<MultiSpan>, handler: &Handler) -> DiagnosticBuilder<'_> {
58 Error::UselessDocComment => {
59 let mut err = struct_span_err!(
63 "found a documentation comment that doesn't document anything",
66 "doc comments must come before what they document, maybe a comment was \
75 pub(super) trait RecoverQPath: Sized + 'static {
76 const PATH_STYLE: PathStyle = PathStyle::Expr;
77 fn to_ty(&self) -> Option<P<Ty>>;
78 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self;
81 impl RecoverQPath for Ty {
82 const PATH_STYLE: PathStyle = PathStyle::Type;
83 fn to_ty(&self) -> Option<P<Ty>> {
86 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
89 kind: TyKind::Path(qself, path),
90 id: ast::DUMMY_NODE_ID,
96 impl RecoverQPath for Pat {
97 fn to_ty(&self) -> Option<P<Ty>> {
100 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
103 kind: PatKind::Path(qself, path),
104 id: ast::DUMMY_NODE_ID,
110 impl RecoverQPath for Expr {
111 fn to_ty(&self) -> Option<P<Ty>> {
114 fn recovered(qself: Option<QSelf>, path: ast::Path) -> Self {
117 kind: ExprKind::Path(qself, path),
118 attrs: AttrVec::new(),
119 id: ast::DUMMY_NODE_ID,
125 /// Control whether the closing delimiter should be consumed when calling `Parser::consume_block`.
126 crate enum ConsumeClosingDelim {
131 #[derive(Clone, Copy)]
132 pub enum AttemptLocalParseRecovery {
137 impl AttemptLocalParseRecovery {
138 pub fn yes(&self) -> bool {
140 AttemptLocalParseRecovery::Yes => true,
141 AttemptLocalParseRecovery::No => false,
145 pub fn no(&self) -> bool {
147 AttemptLocalParseRecovery::Yes => false,
148 AttemptLocalParseRecovery::No => true,
153 impl<'a> Parser<'a> {
154 pub(super) fn span_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
155 err.span_err(sp, self.diagnostic())
158 pub fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
159 self.sess.span_diagnostic.struct_span_err(sp, m)
162 pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
163 self.sess.span_diagnostic.span_bug(sp, m)
166 pub(super) fn diagnostic(&self) -> &'a Handler {
167 &self.sess.span_diagnostic
170 pub(super) fn span_to_snippet(&self, span: Span) -> Result<String, SpanSnippetError> {
171 self.sess.source_map().span_to_snippet(span)
174 pub(super) fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
175 let mut err = self.struct_span_err(
177 &format!("expected identifier, found {}", super::token_descr(&self.token)),
179 let valid_follow = &[
185 TokenKind::OpenDelim(token::DelimToken::Brace),
186 TokenKind::OpenDelim(token::DelimToken::Paren),
187 TokenKind::CloseDelim(token::DelimToken::Brace),
188 TokenKind::CloseDelim(token::DelimToken::Paren),
190 match self.token.ident() {
192 if ident.is_raw_guess()
193 && self.look_ahead(1, |t| valid_follow.contains(&t.kind)) =>
197 "you can escape reserved keywords to use them as identifiers",
198 format!("r#{}", ident.name),
199 Applicability::MaybeIncorrect,
204 if let Some(token_descr) = super::token_descr_opt(&self.token) {
205 err.span_label(self.token.span, format!("expected identifier, found {}", token_descr));
207 err.span_label(self.token.span, "expected identifier");
208 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
213 Applicability::MachineApplicable,
220 pub(super) fn expected_one_of_not_found(
222 edible: &[TokenKind],
223 inedible: &[TokenKind],
224 ) -> PResult<'a, bool /* recovered */> {
225 debug!("expected_one_of_not_found(edible: {:?}, inedible: {:?})", edible, inedible);
226 fn tokens_to_string(tokens: &[TokenType]) -> String {
227 let mut i = tokens.iter();
228 // This might be a sign we need a connect method on `Iterator`.
229 let b = i.next().map_or_else(String::new, |t| t.to_string());
230 i.enumerate().fold(b, |mut b, (i, a)| {
231 if tokens.len() > 2 && i == tokens.len() - 2 {
233 } else if tokens.len() == 2 && i == tokens.len() - 2 {
238 b.push_str(&a.to_string());
243 let mut expected = edible
245 .map(|x| TokenType::Token(x.clone()))
246 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
247 .chain(self.expected_tokens.iter().cloned())
248 .collect::<Vec<_>>();
249 expected.sort_by_cached_key(|x| x.to_string());
252 let sm = self.sess.source_map();
253 let msg = format!("expected `;`, found {}", super::token_descr(&self.token));
254 let appl = Applicability::MachineApplicable;
255 if expected.contains(&TokenType::Token(token::Semi)) {
256 if self.token.span == DUMMY_SP || self.prev_token.span == DUMMY_SP {
257 // Likely inside a macro, can't provide meaningful suggestions.
258 } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) {
259 // The current token is in the same line as the prior token, not recoverable.
260 } else if [token::Comma, token::Colon].contains(&self.token.kind)
261 && self.prev_token.kind == token::CloseDelim(token::Paren)
263 // Likely typo: The current token is on a new line and is expected to be
264 // `.`, `;`, `?`, or an operator after a close delimiter token.
266 // let a = std::process::Command::new("echo")
270 // https://github.com/rust-lang/rust/issues/72253
271 } else if self.look_ahead(1, |t| {
272 t == &token::CloseDelim(token::Brace)
273 || t.can_begin_expr() && t.kind != token::Colon
274 }) && [token::Comma, token::Colon].contains(&self.token.kind)
276 // Likely typo: `,` → `;` or `:` → `;`. This is triggered if the current token is
277 // either `,` or `:`, and the next token could either start a new statement or is a
278 // block close. For example:
283 let sp = self.prev_token.span;
284 self.struct_span_err(sp, &msg)
285 .span_suggestion_short(sp, "change this to `;`", ";".to_string(), appl)
288 } else if self.look_ahead(0, |t| {
289 t == &token::CloseDelim(token::Brace)
291 t.can_begin_expr() && t != &token::Semi && t != &token::Pound
292 // Avoid triggering with too many trailing `#` in raw string.
295 // Missing semicolon typo. This is triggered if the next token could either start a
296 // new statement or is a block close. For example:
300 let sp = self.prev_token.span.shrink_to_hi();
301 self.struct_span_err(sp, &msg)
302 .span_label(self.token.span, "unexpected token")
303 .span_suggestion_short(sp, "add `;` here", ";".to_string(), appl)
309 let expect = tokens_to_string(&expected);
310 let actual = super::token_descr(&self.token);
311 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
312 let short_expect = if expected.len() > 6 {
313 format!("{} possible tokens", expected.len())
318 format!("expected one of {}, found {}", expect, actual),
319 (self.prev_token.span.shrink_to_hi(), format!("expected one of {}", short_expect)),
321 } else if expected.is_empty() {
323 format!("unexpected token: {}", actual),
324 (self.prev_token.span, "unexpected token after this".to_string()),
328 format!("expected {}, found {}", expect, actual),
329 (self.prev_token.span.shrink_to_hi(), format!("expected {}", expect)),
332 self.last_unexpected_token_span = Some(self.token.span);
333 let mut err = self.struct_span_err(self.token.span, &msg_exp);
335 // Add suggestion for a missing closing angle bracket if '>' is included in expected_tokens
336 // there are unclosed angle brackets
337 if self.unmatched_angle_bracket_count > 0
338 && self.token.kind == TokenKind::Eq
339 && expected.iter().any(|tok| matches!(tok, TokenType::Token(TokenKind::Gt)))
341 err.span_label(self.prev_token.span, "maybe try to close unmatched angle bracket");
344 let sp = if self.token == token::Eof {
345 // This is EOF; don't want to point at the following char, but rather the last token.
350 match self.recover_closing_delimiter(
353 .filter_map(|tt| match tt {
354 TokenType::Token(t) => Some(t.clone()),
357 .collect::<Vec<_>>(),
362 return Ok(recovered);
366 if self.check_too_many_raw_str_terminators(&mut err) {
370 if self.prev_token.span == DUMMY_SP {
371 // Account for macro context where the previous span might not be
372 // available to avoid incorrect output (#54841).
373 err.span_label(self.token.span, label_exp);
374 } else if !sm.is_multiline(self.token.span.shrink_to_hi().until(sp.shrink_to_lo())) {
375 // When the spans are in the same line, it means that the only content between
376 // them is whitespace, point at the found token in that case:
378 // X | () => { syntax error };
379 // | ^^^^^ expected one of 8 possible tokens here
381 // instead of having:
383 // X | () => { syntax error };
384 // | -^^^^^ unexpected token
386 // | expected one of 8 possible tokens here
387 err.span_label(self.token.span, label_exp);
389 err.span_label(sp, label_exp);
390 err.span_label(self.token.span, "unexpected token");
392 self.maybe_annotate_with_ascription(&mut err, false);
396 fn check_too_many_raw_str_terminators(&mut self, err: &mut DiagnosticBuilder<'_>) -> bool {
397 match (&self.prev_token.kind, &self.token.kind) {
399 TokenKind::Literal(Lit {
400 kind: LitKind::StrRaw(n_hashes) | LitKind::ByteStrRaw(n_hashes),
405 err.set_primary_message("too many `#` when terminating raw string");
408 "remove the extra `#`",
410 Applicability::MachineApplicable,
412 err.note(&format!("the raw string started with {} `#`s", n_hashes));
419 pub fn maybe_suggest_struct_literal(
423 ) -> Option<PResult<'a, P<Block>>> {
424 if self.token.is_ident() && self.look_ahead(1, |t| t == &token::Colon) {
425 // We might be having a struct literal where people forgot to include the path:
429 let mut snapshot = self.clone();
431 Path { segments: vec![], span: self.prev_token.span.shrink_to_lo(), tokens: None };
432 let struct_expr = snapshot.parse_struct_expr(None, path, AttrVec::new(), false);
433 let block_tail = self.parse_block_tail(lo, s, AttemptLocalParseRecovery::No);
434 return Some(match (struct_expr, block_tail) {
435 (Ok(expr), Err(mut err)) => {
436 // We have encountered the following:
441 // fn foo() -> Foo { Path {
445 self.struct_span_err(expr.span, "struct literal body without path")
446 .multipart_suggestion(
447 "you might have forgotten to add the struct literal inside the block",
449 (expr.span.shrink_to_lo(), "{ SomeStruct ".to_string()),
450 (expr.span.shrink_to_hi(), " }".to_string()),
452 Applicability::MaybeIncorrect,
456 let mut tail = self.mk_block(
457 vec![self.mk_stmt_err(expr.span)],
459 lo.to(self.prev_token.span),
461 tail.could_be_bare_literal = true;
464 (Err(mut err), Ok(tail)) => {
465 // We have a block tail that contains a somehow valid type ascription expr.
469 (Err(mut snapshot_err), Err(err)) => {
470 // We don't know what went wrong, emit the normal error.
471 snapshot_err.cancel();
472 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
475 (Ok(_), Ok(mut tail)) => {
476 tail.could_be_bare_literal = true;
484 pub fn maybe_annotate_with_ascription(
486 err: &mut DiagnosticBuilder<'_>,
487 maybe_expected_semicolon: bool,
489 if let Some((sp, likely_path)) = self.last_type_ascription.take() {
490 let sm = self.sess.source_map();
491 let next_pos = sm.lookup_char_pos(self.token.span.lo());
492 let op_pos = sm.lookup_char_pos(sp.hi());
494 let allow_unstable = self.sess.unstable_features.is_nightly_build();
499 "maybe write a path separator here",
502 Applicability::MaybeIncorrect
504 Applicability::MachineApplicable
507 self.sess.type_ascription_path_suggestions.borrow_mut().insert(sp);
508 } else if op_pos.line != next_pos.line && maybe_expected_semicolon {
511 "try using a semicolon",
513 Applicability::MaybeIncorrect,
515 } else if allow_unstable {
516 err.span_label(sp, "tried to parse a type due to this type ascription");
518 err.span_label(sp, "tried to parse a type due to this");
521 // Give extra information about type ascription only if it's a nightly compiler.
523 "`#![feature(type_ascription)]` lets you annotate an expression with a type: \
527 // Avoid giving too much info when it was likely an unrelated typo.
529 "see issue #23416 <https://github.com/rust-lang/rust/issues/23416> \
530 for more information",
537 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
538 /// passes through any errors encountered. Used for error recovery.
539 pub(super) fn eat_to_tokens(&mut self, kets: &[&TokenKind]) {
540 if let Err(ref mut err) =
541 self.parse_seq_to_before_tokens(kets, SeqSep::none(), TokenExpectType::Expect, |p| {
542 Ok(p.parse_token_tree())
549 /// This function checks if there are trailing angle brackets and produces
550 /// a diagnostic to suggest removing them.
552 /// ```ignore (diagnostic)
553 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
554 /// ^^ help: remove extra angle brackets
557 /// If `true` is returned, then trailing brackets were recovered, tokens were consumed
558 /// up until one of the tokens in 'end' was encountered, and an error was emitted.
559 pub(super) fn check_trailing_angle_brackets(
561 segment: &PathSegment,
564 // This function is intended to be invoked after parsing a path segment where there are two
567 // 1. A specific token is expected after the path segment.
568 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
569 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
570 // 2. No specific token is expected after the path segment.
571 // eg. `x.foo` (field access)
573 // This function is called after parsing `.foo` and before parsing the token `end` (if
574 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
577 // We only care about trailing angle brackets if we previously parsed angle bracket
578 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
579 // removed in this case:
581 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
583 // This case is particularly tricky as we won't notice it just looking at the tokens -
584 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
585 // have already been parsed):
587 // `x.foo::<u32>>>(3)`
588 let parsed_angle_bracket_args =
589 segment.args.as_ref().map_or(false, |args| args.is_angle_bracketed());
592 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
593 parsed_angle_bracket_args,
595 if !parsed_angle_bracket_args {
599 // Keep the span at the start so we can highlight the sequence of `>` characters to be
601 let lo = self.token.span;
603 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
604 // (since we might have the field access case and the characters we're eating are
605 // actual operators and not trailing characters - ie `x.foo >> 3`).
606 let mut position = 0;
608 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
609 // many of each (so we can correctly pluralize our error messages) and continue to
611 let mut number_of_shr = 0;
612 let mut number_of_gt = 0;
613 while self.look_ahead(position, |t| {
614 trace!("check_trailing_angle_brackets: t={:?}", t);
615 if *t == token::BinOp(token::BinOpToken::Shr) {
618 } else if *t == token::Gt {
628 // If we didn't find any trailing `>` characters, then we have nothing to error about.
630 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
631 number_of_gt, number_of_shr,
633 if number_of_gt < 1 && number_of_shr < 1 {
637 // Finally, double check that we have our end token as otherwise this is the
639 if self.look_ahead(position, |t| {
640 trace!("check_trailing_angle_brackets: t={:?}", t);
641 end.contains(&&t.kind)
643 // Eat from where we started until the end token so that parsing can continue
644 // as if we didn't have those extra angle brackets.
645 self.eat_to_tokens(end);
646 let span = lo.until(self.token.span);
648 let total_num_of_gt = number_of_gt + number_of_shr * 2;
649 self.struct_span_err(
651 &format!("unmatched angle bracket{}", pluralize!(total_num_of_gt)),
655 &format!("remove extra angle bracket{}", pluralize!(total_num_of_gt)),
657 Applicability::MachineApplicable,
665 /// Check if a method call with an intended turbofish has been written without surrounding
667 pub(super) fn check_turbofish_missing_angle_brackets(&mut self, segment: &mut PathSegment) {
668 if token::ModSep == self.token.kind && segment.args.is_none() {
669 let snapshot = self.clone();
671 let lo = self.token.span;
672 match self.parse_angle_args(None) {
674 let span = lo.to(self.prev_token.span);
675 // Detect trailing `>` like in `x.collect::Vec<_>>()`.
676 let mut trailing_span = self.prev_token.span.shrink_to_hi();
677 while self.token.kind == token::BinOp(token::Shr)
678 || self.token.kind == token::Gt
680 trailing_span = trailing_span.to(self.token.span);
683 if self.token.kind == token::OpenDelim(token::Paren) {
684 // Recover from bad turbofish: `foo.collect::Vec<_>()`.
685 let args = AngleBracketedArgs { args, span }.into();
688 self.struct_span_err(
690 "generic parameters without surrounding angle brackets",
692 .multipart_suggestion(
693 "surround the type parameters with angle brackets",
695 (span.shrink_to_lo(), "<".to_string()),
696 (trailing_span, ">".to_string()),
698 Applicability::MachineApplicable,
702 // This doesn't look like an invalid turbofish, can't recover parse state.
707 // We couldn't parse generic parameters, unlikely to be a turbofish. Rely on
708 // generic parse error instead.
716 /// When writing a turbofish with multiple type parameters missing the leading `::`, we will
717 /// encounter a parse error when encountering the first `,`.
718 pub(super) fn check_mistyped_turbofish_with_multiple_type_params(
720 mut e: DiagnosticBuilder<'a>,
722 ) -> PResult<'a, ()> {
723 if let ExprKind::Binary(binop, _, _) = &expr.kind {
724 if let ast::BinOpKind::Lt = binop.node {
725 if self.eat(&token::Comma) {
726 let x = self.parse_seq_to_before_end(
728 SeqSep::trailing_allowed(token::Comma),
729 |p| p.parse_generic_arg(None),
732 Ok((_, _, false)) => {
733 if self.eat(&token::Gt) {
734 match self.parse_expr() {
736 e.span_suggestion_verbose(
737 binop.span.shrink_to_lo(),
738 TURBOFISH_SUGGESTION_STR,
740 Applicability::MaybeIncorrect,
744 self.mk_expr_err(expr.span.to(self.prev_token.span));
764 /// Check to see if a pair of chained operators looks like an attempt at chained comparison,
765 /// e.g. `1 < x <= 3`. If so, suggest either splitting the comparison into two, or
766 /// parenthesising the leftmost comparison.
767 fn attempt_chained_comparison_suggestion(
769 err: &mut DiagnosticBuilder<'_>,
771 outer_op: &Spanned<AssocOp>,
772 ) -> bool /* advanced the cursor */ {
773 if let ExprKind::Binary(op, ref l1, ref r1) = inner_op.kind {
774 if let ExprKind::Field(_, ident) = l1.kind {
775 if ident.as_str().parse::<i32>().is_err() && !matches!(r1.kind, ExprKind::Lit(_)) {
776 // The parser has encountered `foo.bar<baz`, the likelihood of the turbofish
777 // suggestion being the only one to apply is high.
781 let mut enclose = |left: Span, right: Span| {
782 err.multipart_suggestion(
783 "parenthesize the comparison",
785 (left.shrink_to_lo(), "(".to_string()),
786 (right.shrink_to_hi(), ")".to_string()),
788 Applicability::MaybeIncorrect,
791 return match (op.node, &outer_op.node) {
793 (BinOpKind::Eq, AssocOp::Equal) |
794 // `x < y < z` and friends.
795 (BinOpKind::Lt, AssocOp::Less | AssocOp::LessEqual) |
796 (BinOpKind::Le, AssocOp::LessEqual | AssocOp::Less) |
797 // `x > y > z` and friends.
798 (BinOpKind::Gt, AssocOp::Greater | AssocOp::GreaterEqual) |
799 (BinOpKind::Ge, AssocOp::GreaterEqual | AssocOp::Greater) => {
800 let expr_to_str = |e: &Expr| {
801 self.span_to_snippet(e.span)
802 .unwrap_or_else(|_| pprust::expr_to_string(&e))
804 err.span_suggestion_verbose(
805 inner_op.span.shrink_to_hi(),
806 "split the comparison into two",
807 format!(" && {}", expr_to_str(&r1)),
808 Applicability::MaybeIncorrect,
810 false // Keep the current parse behavior, where the AST is `(x < y) < z`.
813 (BinOpKind::Eq, AssocOp::Less | AssocOp::LessEqual | AssocOp::Greater | AssocOp::GreaterEqual) => {
814 // Consume `z`/outer-op-rhs.
815 let snapshot = self.clone();
816 match self.parse_expr() {
818 // We are sure that outer-op-rhs could be consumed, the suggestion is
820 enclose(r1.span, r2.span);
823 Err(mut expr_err) => {
831 (BinOpKind::Lt | BinOpKind::Le | BinOpKind::Gt | BinOpKind::Ge, AssocOp::Equal) => {
832 let snapshot = self.clone();
833 // At this point it is always valid to enclose the lhs in parentheses, no
834 // further checks are necessary.
835 match self.parse_expr() {
837 enclose(l1.span, r1.span);
840 Err(mut expr_err) => {
853 /// Produces an error if comparison operators are chained (RFC #558).
854 /// We only need to check the LHS, not the RHS, because all comparison ops have same
855 /// precedence (see `fn precedence`) and are left-associative (see `fn fixity`).
857 /// This can also be hit if someone incorrectly writes `foo<bar>()` when they should have used
858 /// the turbofish (`foo::<bar>()`) syntax. We attempt some heuristic recovery if that is the
861 /// Keep in mind that given that `outer_op.is_comparison()` holds and comparison ops are left
862 /// associative we can infer that we have:
871 pub(super) fn check_no_chained_comparison(
874 outer_op: &Spanned<AssocOp>,
875 ) -> PResult<'a, Option<P<Expr>>> {
877 outer_op.node.is_comparison(),
878 "check_no_chained_comparison: {:?} is not comparison",
883 |this: &Self, span| Ok(Some(this.mk_expr(span, ExprKind::Err, AttrVec::new())));
885 match inner_op.kind {
886 ExprKind::Binary(op, ref l1, ref r1) if op.node.is_comparison() => {
887 let mut err = self.struct_span_err(
888 vec![op.span, self.prev_token.span],
889 "comparison operators cannot be chained",
892 let suggest = |err: &mut DiagnosticBuilder<'_>| {
893 err.span_suggestion_verbose(
894 op.span.shrink_to_lo(),
895 TURBOFISH_SUGGESTION_STR,
897 Applicability::MaybeIncorrect,
901 // Include `<` to provide this recommendation even in a case like
902 // `Foo<Bar<Baz<Qux, ()>>>`
903 if op.node == BinOpKind::Lt && outer_op.node == AssocOp::Less
904 || outer_op.node == AssocOp::Greater
906 if outer_op.node == AssocOp::Less {
907 let snapshot = self.clone();
909 // So far we have parsed `foo<bar<`, consume the rest of the type args.
911 [(token::Lt, 1), (token::Gt, -1), (token::BinOp(token::Shr), -2)];
912 self.consume_tts(1, &modifiers);
914 if !&[token::OpenDelim(token::Paren), token::ModSep]
915 .contains(&self.token.kind)
917 // We don't have `foo< bar >(` or `foo< bar >::`, so we rewind the
918 // parser and bail out.
919 *self = snapshot.clone();
922 return if token::ModSep == self.token.kind {
923 // We have some certainty that this was a bad turbofish at this point.
927 let snapshot = self.clone();
930 // Consume the rest of the likely `foo<bar>::new()` or return at `foo<bar>`.
931 match self.parse_expr() {
933 // 99% certain that the suggestion is correct, continue parsing.
935 // FIXME: actually check that the two expressions in the binop are
936 // paths and resynthesize new fn call expression instead of using
937 // `ExprKind::Err` placeholder.
938 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
940 Err(mut expr_err) => {
942 // Not entirely sure now, but we bubble the error up with the
948 } else if token::OpenDelim(token::Paren) == self.token.kind {
949 // We have high certainty that this was a bad turbofish at this point.
952 // Consume the fn call arguments.
953 match self.consume_fn_args() {
957 // FIXME: actually check that the two expressions in the binop are
958 // paths and resynthesize new fn call expression instead of using
959 // `ExprKind::Err` placeholder.
960 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
964 if !matches!(l1.kind, ExprKind::Lit(_))
965 && !matches!(r1.kind, ExprKind::Lit(_))
967 // All we know is that this is `foo < bar >` and *nothing* else. Try to
968 // be helpful, but don't attempt to recover.
969 err.help(TURBOFISH_SUGGESTION_STR);
970 err.help("or use `(...)` if you meant to specify fn arguments");
973 // If it looks like a genuine attempt to chain operators (as opposed to a
974 // misformatted turbofish, for instance), suggest a correct form.
975 if self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op)
978 mk_err_expr(self, inner_op.span.to(self.prev_token.span))
980 // These cases cause too many knock-down errors, bail out (#61329).
986 self.attempt_chained_comparison_suggestion(&mut err, inner_op, outer_op);
989 return mk_err_expr(self, inner_op.span.to(self.prev_token.span));
997 fn consume_fn_args(&mut self) -> Result<(), ()> {
998 let snapshot = self.clone();
1001 // Consume the fn call arguments.
1003 [(token::OpenDelim(token::Paren), 1), (token::CloseDelim(token::Paren), -1)];
1004 self.consume_tts(1, &modifiers);
1006 if self.token.kind == token::Eof {
1007 // Not entirely sure that what we consumed were fn arguments, rollback.
1011 // 99% certain that the suggestion is correct, continue parsing.
1016 pub(super) fn maybe_report_ambiguous_plus(
1018 allow_plus: AllowPlus,
1019 impl_dyn_multi: bool,
1022 if matches!(allow_plus, AllowPlus::No) && impl_dyn_multi {
1023 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
1024 self.struct_span_err(ty.span, "ambiguous `+` in a type")
1027 "use parentheses to disambiguate",
1029 Applicability::MachineApplicable,
1035 pub(super) fn maybe_recover_from_bad_type_plus(
1037 allow_plus: AllowPlus,
1039 ) -> PResult<'a, ()> {
1040 // Do not add `+` to expected tokens.
1041 if matches!(allow_plus, AllowPlus::No) || !self.token.is_like_plus() {
1046 let bounds = self.parse_generic_bounds(None)?;
1047 let sum_span = ty.span.to(self.prev_token.span);
1049 let mut err = struct_span_err!(
1050 self.sess.span_diagnostic,
1053 "expected a path on the left-hand side of `+`, not `{}`",
1054 pprust::ty_to_string(ty)
1058 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1059 let sum_with_parens = pprust::to_string(|s| {
1061 s.print_opt_lifetime(lifetime);
1062 s.print_mutability(mut_ty.mutbl, false);
1064 s.print_type(&mut_ty.ty);
1065 s.print_type_bounds(" +", &bounds);
1068 err.span_suggestion(
1070 "try adding parentheses",
1072 Applicability::MachineApplicable,
1075 TyKind::Ptr(..) | TyKind::BareFn(..) => {
1076 err.span_label(sum_span, "perhaps you forgot parentheses?");
1079 err.span_label(sum_span, "expected a path");
1086 /// Tries to recover from associated item paths like `[T]::AssocItem` / `(T, U)::AssocItem`.
1087 /// Attempts to convert the base expression/pattern/type into a type, parses the `::AssocItem`
1088 /// tail, and combines them into a `<Ty>::AssocItem` expression/pattern/type.
1089 pub(super) fn maybe_recover_from_bad_qpath<T: RecoverQPath>(
1092 allow_recovery: bool,
1093 ) -> PResult<'a, P<T>> {
1094 // Do not add `::` to expected tokens.
1095 if allow_recovery && self.token == token::ModSep {
1096 if let Some(ty) = base.to_ty() {
1097 return self.maybe_recover_from_bad_qpath_stage_2(ty.span, ty);
1103 /// Given an already parsed `Ty`, parses the `::AssocItem` tail and
1104 /// combines them into a `<Ty>::AssocItem` expression/pattern/type.
1105 pub(super) fn maybe_recover_from_bad_qpath_stage_2<T: RecoverQPath>(
1109 ) -> PResult<'a, P<T>> {
1110 self.expect(&token::ModSep)?;
1112 let mut path = ast::Path { segments: Vec::new(), span: DUMMY_SP, tokens: None };
1113 self.parse_path_segments(&mut path.segments, T::PATH_STYLE, None)?;
1114 path.span = ty_span.to(self.prev_token.span);
1116 let ty_str = self.span_to_snippet(ty_span).unwrap_or_else(|_| pprust::ty_to_string(&ty));
1117 self.struct_span_err(path.span, "missing angle brackets in associated item path")
1119 // This is a best-effort recovery.
1122 format!("<{}>::{}", ty_str, pprust::path_to_string(&path)),
1123 Applicability::MaybeIncorrect,
1127 let path_span = ty_span.shrink_to_hi(); // Use an empty path since `position == 0`.
1128 Ok(P(T::recovered(Some(QSelf { ty, path_span, position: 0 }), path)))
1131 pub fn maybe_consume_incorrect_semicolon(&mut self, items: &[P<Item>]) -> bool {
1132 if self.token.kind == TokenKind::Semi {
1134 let mut err = self.struct_span_err(self.prev_token.span, "expected item, found `;`");
1135 err.span_suggestion_short(
1136 self.prev_token.span,
1137 "remove this semicolon",
1139 Applicability::MachineApplicable,
1141 if !items.is_empty() {
1142 let previous_item = &items[items.len() - 1];
1143 let previous_item_kind_name = match previous_item.kind {
1144 // Say "braced struct" because tuple-structs and
1145 // braceless-empty-struct declarations do take a semicolon.
1146 ItemKind::Struct(..) => Some("braced struct"),
1147 ItemKind::Enum(..) => Some("enum"),
1148 ItemKind::Trait(..) => Some("trait"),
1149 ItemKind::Union(..) => Some("union"),
1152 if let Some(name) = previous_item_kind_name {
1153 err.help(&format!("{} declarations are not followed by a semicolon", name));
1163 /// Creates a `DiagnosticBuilder` for an unexpected token `t` and tries to recover if it is a
1164 /// closing delimiter.
1165 pub(super) fn unexpected_try_recover(
1168 ) -> PResult<'a, bool /* recovered */> {
1169 let token_str = pprust::token_kind_to_string(t);
1170 let this_token_str = super::token_descr(&self.token);
1171 let (prev_sp, sp) = match (&self.token.kind, self.subparser_name) {
1172 // Point at the end of the macro call when reaching end of macro arguments.
1173 (token::Eof, Some(_)) => {
1174 let sp = self.sess.source_map().next_point(self.prev_token.span);
1177 // We don't want to point at the following span after DUMMY_SP.
1178 // This happens when the parser finds an empty TokenStream.
1179 _ if self.prev_token.span == DUMMY_SP => (self.token.span, self.token.span),
1180 // EOF, don't want to point at the following char, but rather the last token.
1181 (token::Eof, None) => (self.prev_token.span, self.token.span),
1182 _ => (self.prev_token.span.shrink_to_hi(), self.token.span),
1185 "expected `{}`, found {}",
1187 match (&self.token.kind, self.subparser_name) {
1188 (token::Eof, Some(origin)) => format!("end of {}", origin),
1189 _ => this_token_str,
1192 let mut err = self.struct_span_err(sp, &msg);
1193 let label_exp = format!("expected `{}`", token_str);
1194 match self.recover_closing_delimiter(&[t.clone()], err) {
1197 return Ok(recovered);
1200 let sm = self.sess.source_map();
1201 if !sm.is_multiline(prev_sp.until(sp)) {
1202 // When the spans are in the same line, it means that the only content
1203 // between them is whitespace, point only at the found token.
1204 err.span_label(sp, label_exp);
1206 err.span_label(prev_sp, label_exp);
1207 err.span_label(sp, "unexpected token");
1212 pub(super) fn expect_semi(&mut self) -> PResult<'a, ()> {
1213 if self.eat(&token::Semi) {
1216 self.expect(&token::Semi).map(drop) // Error unconditionally
1219 /// Consumes alternative await syntaxes like `await!(<expr>)`, `await <expr>`,
1220 /// `await? <expr>`, `await(<expr>)`, and `await { <expr> }`.
1221 pub(super) fn recover_incorrect_await_syntax(
1226 ) -> PResult<'a, P<Expr>> {
1227 let (hi, expr, is_question) = if self.token == token::Not {
1228 // Handle `await!(<expr>)`.
1229 self.recover_await_macro()?
1231 self.recover_await_prefix(await_sp)?
1233 let sp = self.error_on_incorrect_await(lo, hi, &expr, is_question);
1234 let kind = match expr.kind {
1235 // Avoid knock-down errors as we don't know whether to interpret this as `foo().await?`
1236 // or `foo()?.await` (the very reason we went with postfix syntax 😅).
1237 ExprKind::Try(_) => ExprKind::Err,
1238 _ => ExprKind::Await(expr),
1240 let expr = self.mk_expr(lo.to(sp), kind, attrs);
1241 self.maybe_recover_from_bad_qpath(expr, true)
1244 fn recover_await_macro(&mut self) -> PResult<'a, (Span, P<Expr>, bool)> {
1245 self.expect(&token::Not)?;
1246 self.expect(&token::OpenDelim(token::Paren))?;
1247 let expr = self.parse_expr()?;
1248 self.expect(&token::CloseDelim(token::Paren))?;
1249 Ok((self.prev_token.span, expr, false))
1252 fn recover_await_prefix(&mut self, await_sp: Span) -> PResult<'a, (Span, P<Expr>, bool)> {
1253 let is_question = self.eat(&token::Question); // Handle `await? <expr>`.
1254 let expr = if self.token == token::OpenDelim(token::Brace) {
1255 // Handle `await { <expr> }`.
1256 // This needs to be handled separately from the next arm to avoid
1257 // interpreting `await { <expr> }?` as `<expr>?.await`.
1258 self.parse_block_expr(None, self.token.span, BlockCheckMode::Default, AttrVec::new())
1262 .map_err(|mut err| {
1263 err.span_label(await_sp, "while parsing this incorrect await expression");
1266 Ok((expr.span, expr, is_question))
1269 fn error_on_incorrect_await(&self, lo: Span, hi: Span, expr: &Expr, is_question: bool) -> Span {
1271 self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(&expr));
1272 let suggestion = format!("{}.await{}", expr_str, if is_question { "?" } else { "" });
1274 let app = match expr.kind {
1275 ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
1276 _ => Applicability::MachineApplicable,
1278 self.struct_span_err(sp, "incorrect use of `await`")
1279 .span_suggestion(sp, "`await` is a postfix operation", suggestion, app)
1284 /// If encountering `future.await()`, consumes and emits an error.
1285 pub(super) fn recover_from_await_method_call(&mut self) {
1286 if self.token == token::OpenDelim(token::Paren)
1287 && self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
1290 let lo = self.token.span;
1292 let sp = lo.to(self.token.span);
1294 self.struct_span_err(sp, "incorrect use of `await`")
1297 "`await` is not a method call, remove the parentheses",
1299 Applicability::MachineApplicable,
1305 pub(super) fn try_macro_suggestion(&mut self) -> PResult<'a, P<Expr>> {
1306 let is_try = self.token.is_keyword(kw::Try);
1307 let is_questionmark = self.look_ahead(1, |t| t == &token::Not); //check for !
1308 let is_open = self.look_ahead(2, |t| t == &token::OpenDelim(token::Paren)); //check for (
1310 if is_try && is_questionmark && is_open {
1311 let lo = self.token.span;
1312 self.bump(); //remove try
1313 self.bump(); //remove !
1314 let try_span = lo.to(self.token.span); //we take the try!( span
1315 self.bump(); //remove (
1316 let is_empty = self.token == token::CloseDelim(token::Paren); //check if the block is empty
1317 self.consume_block(token::Paren, ConsumeClosingDelim::No); //eat the block
1318 let hi = self.token.span;
1319 self.bump(); //remove )
1320 let mut err = self.struct_span_err(lo.to(hi), "use of deprecated `try` macro");
1321 err.note("in the 2018 edition `try` is a reserved keyword, and the `try!()` macro is deprecated");
1322 let prefix = if is_empty { "" } else { "alternatively, " };
1324 err.multipart_suggestion(
1325 "you can use the `?` operator instead",
1326 vec![(try_span, "".to_owned()), (hi, "?".to_owned())],
1327 Applicability::MachineApplicable,
1330 err.span_suggestion(lo.shrink_to_lo(), &format!("{}you can still access the deprecated `try!()` macro using the \"raw identifier\" syntax", prefix), "r#".to_string(), Applicability::MachineApplicable);
1332 Ok(self.mk_expr_err(lo.to(hi)))
1334 Err(self.expected_expression_found()) // The user isn't trying to invoke the try! macro
1338 /// Recovers a situation like `for ( $pat in $expr )`
1339 /// and suggest writing `for $pat in $expr` instead.
1341 /// This should be called before parsing the `$block`.
1342 pub(super) fn recover_parens_around_for_head(
1345 begin_paren: Option<Span>,
1347 match (&self.token.kind, begin_paren) {
1348 (token::CloseDelim(token::Paren), Some(begin_par_sp)) => {
1351 self.struct_span_err(
1352 MultiSpan::from_spans(vec![begin_par_sp, self.prev_token.span]),
1353 "unexpected parentheses surrounding `for` loop head",
1355 .multipart_suggestion(
1356 "remove parentheses in `for` loop",
1357 vec![(begin_par_sp, String::new()), (self.prev_token.span, String::new())],
1358 // With e.g. `for (x) in y)` this would replace `(x) in y)`
1359 // with `x) in y)` which is syntactically invalid.
1360 // However, this is prevented before we get here.
1361 Applicability::MachineApplicable,
1365 // Unwrap `(pat)` into `pat` to avoid the `unused_parens` lint.
1366 pat.and_then(|pat| match pat.kind {
1367 PatKind::Paren(pat) => pat,
1375 pub(super) fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
1376 (self.token == token::Lt && // `foo:<bar`, likely a typoed turbofish.
1377 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident()))
1378 || self.token.is_ident() &&
1379 matches!(node, ast::ExprKind::Path(..) | ast::ExprKind::Field(..)) &&
1380 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
1381 self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren))
1382 || self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) // `foo:bar {`
1383 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar::<baz`
1384 self.look_ahead(2, |t| t == &token::Lt) &&
1385 self.look_ahead(3, |t| t.is_ident())
1386 || self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
1387 self.look_ahead(2, |t| t.is_ident())
1388 || self.look_ahead(1, |t| t == &token::ModSep)
1389 && (self.look_ahead(2, |t| t.is_ident()) || // `foo:bar::baz`
1390 self.look_ahead(2, |t| t == &token::Lt)) // `foo:bar::<baz>`
1393 pub(super) fn recover_seq_parse_error(
1395 delim: token::DelimToken,
1397 result: PResult<'a, P<Expr>>,
1403 // Recover from parse error, callers expect the closing delim to be consumed.
1404 self.consume_block(delim, ConsumeClosingDelim::Yes);
1405 self.mk_expr(lo.to(self.prev_token.span), ExprKind::Err, AttrVec::new())
1410 pub(super) fn recover_closing_delimiter(
1412 tokens: &[TokenKind],
1413 mut err: DiagnosticBuilder<'a>,
1414 ) -> PResult<'a, bool> {
1416 // We want to use the last closing delim that would apply.
1417 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
1418 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
1419 && Some(self.token.span) > unmatched.unclosed_span
1426 // Recover and assume that the detected unclosed delimiter was meant for
1427 // this location. Emit the diagnostic and act as if the delimiter was
1428 // present for the parser's sake.
1430 // Don't attempt to recover from this unclosed delimiter more than once.
1431 let unmatched = self.unclosed_delims.remove(pos);
1432 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
1433 if unmatched.found_delim.is_none() {
1434 // We encountered `Eof`, set this fact here to avoid complaining about missing
1435 // `fn main()` when we found place to suggest the closing brace.
1436 *self.sess.reached_eof.borrow_mut() = true;
1439 // We want to suggest the inclusion of the closing delimiter where it makes
1440 // the most sense, which is immediately after the last token:
1445 // | help: `)` may belong here
1447 // unclosed delimiter
1448 if let Some(sp) = unmatched.unclosed_span {
1449 let mut primary_span: Vec<Span> =
1450 err.span.primary_spans().iter().cloned().collect();
1451 primary_span.push(sp);
1452 let mut primary_span: MultiSpan = primary_span.into();
1453 for span_label in err.span.span_labels() {
1454 if let Some(label) = span_label.label {
1455 primary_span.push_span_label(span_label.span, label);
1458 err.set_span(primary_span);
1459 err.span_label(sp, "unclosed delimiter");
1461 // Backticks should be removed to apply suggestions.
1462 let mut delim = delim.to_string();
1463 delim.retain(|c| c != '`');
1464 err.span_suggestion_short(
1465 self.prev_token.span.shrink_to_hi(),
1466 &format!("`{}` may belong here", delim),
1468 Applicability::MaybeIncorrect,
1470 if unmatched.found_delim.is_none() {
1471 // Encountered `Eof` when lexing blocks. Do not recover here to avoid knockdown
1472 // errors which would be emitted elsewhere in the parser and let other error
1473 // recovery consume the rest of the file.
1477 self.expected_tokens.clear(); // Reduce the number of errors.
1485 /// Eats tokens until we can be relatively sure we reached the end of the
1486 /// statement. This is something of a best-effort heuristic.
1488 /// We terminate when we find an unmatched `}` (without consuming it).
1489 pub(super) fn recover_stmt(&mut self) {
1490 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
1493 /// If `break_on_semi` is `Break`, then we will stop consuming tokens after
1494 /// finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
1495 /// approximate -- it can mean we break too early due to macros, but that
1496 /// should only lead to sub-optimal recovery, not inaccurate parsing).
1498 /// If `break_on_block` is `Break`, then we will stop consuming tokens
1499 /// after finding (and consuming) a brace-delimited block.
1500 pub(super) fn recover_stmt_(
1502 break_on_semi: SemiColonMode,
1503 break_on_block: BlockMode,
1505 let mut brace_depth = 0;
1506 let mut bracket_depth = 0;
1507 let mut in_block = false;
1508 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})", break_on_semi, break_on_block);
1510 debug!("recover_stmt_ loop {:?}", self.token);
1511 match self.token.kind {
1512 token::OpenDelim(token::DelimToken::Brace) => {
1515 if break_on_block == BlockMode::Break && brace_depth == 1 && bracket_depth == 0
1520 token::OpenDelim(token::DelimToken::Bracket) => {
1524 token::CloseDelim(token::DelimToken::Brace) => {
1525 if brace_depth == 0 {
1526 debug!("recover_stmt_ return - close delim {:?}", self.token);
1531 if in_block && bracket_depth == 0 && brace_depth == 0 {
1532 debug!("recover_stmt_ return - block end {:?}", self.token);
1536 token::CloseDelim(token::DelimToken::Bracket) => {
1538 if bracket_depth < 0 {
1544 debug!("recover_stmt_ return - Eof");
1549 if break_on_semi == SemiColonMode::Break
1551 && bracket_depth == 0
1553 debug!("recover_stmt_ return - Semi");
1558 if break_on_semi == SemiColonMode::Comma
1560 && bracket_depth == 0 =>
1562 debug!("recover_stmt_ return - Semi");
1570 pub(super) fn check_for_for_in_in_typo(&mut self, in_span: Span) {
1571 if self.eat_keyword(kw::In) {
1572 // a common typo: `for _ in in bar {}`
1573 self.struct_span_err(self.prev_token.span, "expected iterable, found keyword `in`")
1574 .span_suggestion_short(
1575 in_span.until(self.prev_token.span),
1576 "remove the duplicated `in`",
1578 Applicability::MachineApplicable,
1584 pub(super) fn eat_incorrect_doc_comment_for_param_type(&mut self) {
1585 if let token::DocComment(..) = self.token.kind {
1586 self.struct_span_err(
1588 "documentation comments cannot be applied to a function parameter's type",
1590 .span_label(self.token.span, "doc comments are not allowed here")
1593 } else if self.token == token::Pound
1594 && self.look_ahead(1, |t| *t == token::OpenDelim(token::Bracket))
1596 let lo = self.token.span;
1597 // Skip every token until next possible arg.
1598 while self.token != token::CloseDelim(token::Bracket) {
1601 let sp = lo.to(self.token.span);
1603 self.struct_span_err(sp, "attributes cannot be applied to a function parameter's type")
1604 .span_label(sp, "attributes are not allowed here")
1609 pub(super) fn parameter_without_type(
1611 err: &mut DiagnosticBuilder<'_>,
1615 ) -> Option<Ident> {
1616 // If we find a pattern followed by an identifier, it could be an (incorrect)
1617 // C-style parameter declaration.
1618 if self.check_ident()
1619 && self.look_ahead(1, |t| *t == token::Comma || *t == token::CloseDelim(token::Paren))
1621 // `fn foo(String s) {}`
1622 let ident = self.parse_ident().unwrap();
1623 let span = pat.span.with_hi(ident.span.hi());
1625 err.span_suggestion(
1627 "declare the type after the parameter binding",
1628 String::from("<identifier>: <type>"),
1629 Applicability::HasPlaceholders,
1632 } else if require_name
1633 && (self.token == token::Comma
1634 || self.token == token::Lt
1635 || self.token == token::CloseDelim(token::Paren))
1637 let rfc_note = "anonymous parameters are removed in the 2018 edition (see RFC 1685)";
1639 let (ident, self_sugg, param_sugg, type_sugg, self_span, param_span, type_span) =
1641 PatKind::Ident(_, ident, _) => (
1643 "self: ".to_string(),
1644 ": TypeName".to_string(),
1646 pat.span.shrink_to_lo(),
1647 pat.span.shrink_to_hi(),
1648 pat.span.shrink_to_lo(),
1650 // Also catches `fn foo(&a)`.
1651 PatKind::Ref(ref inner_pat, mutab)
1652 if matches!(inner_pat.clone().into_inner().kind, PatKind::Ident(..)) =>
1654 match inner_pat.clone().into_inner().kind {
1655 PatKind::Ident(_, ident, _) => {
1656 let mutab = mutab.prefix_str();
1659 "self: ".to_string(),
1660 format!("{}: &{}TypeName", ident, mutab),
1662 pat.span.shrink_to_lo(),
1664 pat.span.shrink_to_lo(),
1667 _ => unreachable!(),
1671 // Otherwise, try to get a type and emit a suggestion.
1672 if let Some(ty) = pat.to_ty() {
1673 err.span_suggestion_verbose(
1675 "explicitly ignore the parameter name",
1676 format!("_: {}", pprust::ty_to_string(&ty)),
1677 Applicability::MachineApplicable,
1686 // `fn foo(a, b) {}`, `fn foo(a<x>, b<y>) {}` or `fn foo(usize, usize) {}`
1688 err.span_suggestion(
1690 "if this is a `self` type, give it a parameter name",
1692 Applicability::MaybeIncorrect,
1695 // Avoid suggesting that `fn foo(HashMap<u32>)` is fixed with a change to
1696 // `fn foo(HashMap: TypeName<u32>)`.
1697 if self.token != token::Lt {
1698 err.span_suggestion(
1700 "if this is a parameter name, give it a type",
1702 Applicability::HasPlaceholders,
1705 err.span_suggestion(
1707 "if this is a type, explicitly ignore the parameter name",
1709 Applicability::MachineApplicable,
1713 // Don't attempt to recover by using the `X` in `X<Y>` as the parameter name.
1714 return if self.token == token::Lt { None } else { Some(ident) };
1719 pub(super) fn recover_arg_parse(&mut self) -> PResult<'a, (P<ast::Pat>, P<ast::Ty>)> {
1720 let pat = self.parse_pat_no_top_alt(Some("argument name"))?;
1721 self.expect(&token::Colon)?;
1722 let ty = self.parse_ty()?;
1728 "patterns aren't allowed in methods without bodies",
1730 .span_suggestion_short(
1732 "give this argument a name or use an underscore to ignore it",
1734 Applicability::MachineApplicable,
1738 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
1740 P(Pat { kind: PatKind::Wild, span: pat.span, id: ast::DUMMY_NODE_ID, tokens: None });
1744 pub(super) fn recover_bad_self_param(&mut self, mut param: Param) -> PResult<'a, Param> {
1745 let sp = param.pat.span;
1746 param.ty.kind = TyKind::Err;
1747 self.struct_span_err(sp, "unexpected `self` parameter in function")
1748 .span_label(sp, "must be the first parameter of an associated function")
1753 pub(super) fn consume_block(
1755 delim: token::DelimToken,
1756 consume_close: ConsumeClosingDelim,
1758 let mut brace_depth = 0;
1760 if self.eat(&token::OpenDelim(delim)) {
1762 } else if self.check(&token::CloseDelim(delim)) {
1763 if brace_depth == 0 {
1764 if let ConsumeClosingDelim::Yes = consume_close {
1765 // Some of the callers of this method expect to be able to parse the
1766 // closing delimiter themselves, so we leave it alone. Otherwise we advance
1776 } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
1784 pub(super) fn expected_expression_found(&self) -> DiagnosticBuilder<'a> {
1785 let (span, msg) = match (&self.token.kind, self.subparser_name) {
1786 (&token::Eof, Some(origin)) => {
1787 let sp = self.sess.source_map().next_point(self.prev_token.span);
1788 (sp, format!("expected expression, found end of {}", origin))
1792 format!("expected expression, found {}", super::token_descr(&self.token),),
1795 let mut err = self.struct_span_err(span, &msg);
1796 let sp = self.sess.source_map().start_point(self.token.span);
1797 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
1798 self.sess.expr_parentheses_needed(&mut err, *sp);
1800 err.span_label(span, "expected expression");
1806 mut acc: i64, // `i64` because malformed code can have more closing delims than opening.
1807 // Not using `FxHashMap` due to `token::TokenKind: !Eq + !Hash`.
1808 modifier: &[(token::TokenKind, i64)],
1811 if let Some((_, val)) = modifier.iter().find(|(t, _)| *t == self.token.kind) {
1814 if self.token.kind == token::Eof {
1821 /// Replace duplicated recovered parameters with `_` pattern to avoid unnecessary errors.
1823 /// This is necessary because at this point we don't know whether we parsed a function with
1824 /// anonymous parameters or a function with names but no types. In order to minimize
1825 /// unnecessary errors, we assume the parameters are in the shape of `fn foo(a, b, c)` where
1826 /// the parameters are *names* (so we don't emit errors about not being able to find `b` in
1827 /// the local scope), but if we find the same name multiple times, like in `fn foo(i8, i8)`,
1828 /// we deduplicate them to not complain about duplicated parameter names.
1829 pub(super) fn deduplicate_recovered_params_names(&self, fn_inputs: &mut Vec<Param>) {
1830 let mut seen_inputs = FxHashSet::default();
1831 for input in fn_inputs.iter_mut() {
1832 let opt_ident = if let (PatKind::Ident(_, ident, _), TyKind::Err) =
1833 (&input.pat.kind, &input.ty.kind)
1839 if let Some(ident) = opt_ident {
1840 if seen_inputs.contains(&ident) {
1841 input.pat.kind = PatKind::Wild;
1843 seen_inputs.insert(ident);
1848 /// Handle encountering a symbol in a generic argument list that is not a `,` or `>`. In this
1849 /// case, we emit an error and try to suggest enclosing a const argument in braces if it looks
1850 /// like the user has forgotten them.
1851 pub fn handle_ambiguous_unbraced_const_arg(
1853 args: &mut Vec<AngleBracketedArg>,
1854 ) -> PResult<'a, bool> {
1855 // If we haven't encountered a closing `>`, then the argument is malformed.
1856 // It's likely that the user has written a const expression without enclosing it
1857 // in braces, so we try to recover here.
1858 let arg = args.pop().unwrap();
1859 // FIXME: for some reason using `unexpected` or `expected_one_of_not_found` has
1860 // adverse side-effects to subsequent errors and seems to advance the parser.
1861 // We are causing this error here exclusively in case that a `const` expression
1862 // could be recovered from the current parser state, even if followed by more
1863 // arguments after a comma.
1864 let mut err = self.struct_span_err(
1866 &format!("expected one of `,` or `>`, found {}", super::token_descr(&self.token)),
1868 err.span_label(self.token.span, "expected one of `,` or `>`");
1869 match self.recover_const_arg(arg.span(), err) {
1871 args.push(AngleBracketedArg::Arg(arg));
1872 if self.eat(&token::Comma) {
1873 return Ok(true); // Continue
1878 // We will emit a more generic error later.
1882 return Ok(false); // Don't continue.
1885 /// Attempt to parse a generic const argument that has not been enclosed in braces.
1886 /// There are a limited number of expressions that are permitted without being encoded
1889 /// - Single-segment paths (i.e. standalone generic const parameters).
1890 /// All other expressions that can be parsed will emit an error suggesting the expression be
1891 /// wrapped in braces.
1892 pub fn handle_unambiguous_unbraced_const_arg(&mut self) -> PResult<'a, P<Expr>> {
1893 let start = self.token.span;
1894 let expr = self.parse_expr_res(Restrictions::CONST_EXPR, None).map_err(|mut err| {
1896 start.shrink_to_lo(),
1897 "while parsing a const generic argument starting here",
1901 if !self.expr_is_valid_const_arg(&expr) {
1902 self.struct_span_err(
1904 "expressions must be enclosed in braces to be used as const generic \
1907 .multipart_suggestion(
1908 "enclose the `const` expression in braces",
1910 (expr.span.shrink_to_lo(), "{ ".to_string()),
1911 (expr.span.shrink_to_hi(), " }".to_string()),
1913 Applicability::MachineApplicable,
1920 fn recover_const_param_decl(
1922 ty_generics: Option<&Generics>,
1923 ) -> PResult<'a, Option<GenericArg>> {
1924 let snapshot = self.clone();
1925 let param = match self.parse_const_param(vec![]) {
1934 self.struct_span_err(param.span(), "unexpected `const` parameter declaration");
1935 err.span_label(param.span(), "expected a `const` expression, not a parameter declaration");
1936 if let (Some(generics), Ok(snippet)) =
1937 (ty_generics, self.sess.source_map().span_to_snippet(param.span()))
1939 let (span, sugg) = match &generics.params[..] {
1940 [] => (generics.span, format!("<{}>", snippet)),
1941 [.., generic] => (generic.span().shrink_to_hi(), format!(", {}", snippet)),
1943 err.multipart_suggestion(
1944 "`const` parameters must be declared for the `impl`",
1945 vec![(span, sugg), (param.span(), param.ident.to_string())],
1946 Applicability::MachineApplicable,
1949 let value = self.mk_expr_err(param.span());
1951 return Ok(Some(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value })));
1954 pub fn recover_const_param_declaration(
1956 ty_generics: Option<&Generics>,
1957 ) -> PResult<'a, Option<GenericArg>> {
1958 // We have to check for a few different cases.
1959 if let Ok(arg) = self.recover_const_param_decl(ty_generics) {
1963 // We haven't consumed `const` yet.
1964 let start = self.token.span;
1965 self.bump(); // `const`
1967 // Detect and recover from the old, pre-RFC2000 syntax for const generics.
1969 .struct_span_err(start, "expected lifetime, type, or constant, found keyword `const`");
1970 if self.check_const_arg() {
1971 err.span_suggestion_verbose(
1972 start.until(self.token.span),
1973 "the `const` keyword is only needed in the definition of the type",
1975 Applicability::MaybeIncorrect,
1978 Ok(Some(GenericArg::Const(self.parse_const_arg()?)))
1980 let after_kw_const = self.token.span;
1981 self.recover_const_arg(after_kw_const, err).map(Some)
1985 /// Try to recover from possible generic const argument without `{` and `}`.
1987 /// When encountering code like `foo::< bar + 3 >` or `foo::< bar - baz >` we suggest
1988 /// `foo::<{ bar + 3 }>` and `foo::<{ bar - baz }>`, respectively. We only provide a suggestion
1989 /// if we think that that the resulting expression would be well formed.
1990 pub fn recover_const_arg(
1993 mut err: DiagnosticBuilder<'a>,
1994 ) -> PResult<'a, GenericArg> {
1995 let is_op = AssocOp::from_token(&self.token)
1997 if let AssocOp::Greater
1999 | AssocOp::ShiftRight
2000 | AssocOp::GreaterEqual
2001 // Don't recover from `foo::<bar = baz>`, because this could be an attempt to
2002 // assign a value to a defaulted generic parameter.
2004 | AssocOp::AssignOp(_) = op
2012 // This will be true when a trait object type `Foo +` or a path which was a `const fn` with
2013 // type params has been parsed.
2015 matches!(self.prev_token.kind, token::BinOp(token::Plus | token::Shr) | token::Gt);
2016 if !is_op && !was_op {
2017 // We perform these checks and early return to avoid taking a snapshot unnecessarily.
2020 let snapshot = self.clone();
2024 match self.parse_expr_res(Restrictions::CONST_EXPR, None) {
2026 // Find a mistake like `MyTrait<Assoc == S::Assoc>`.
2027 if token::EqEq == snapshot.token.kind {
2028 err.span_suggestion(
2029 snapshot.token.span,
2030 "if you meant to use an associated type binding, replace `==` with `=`",
2032 Applicability::MaybeIncorrect,
2034 let value = self.mk_expr_err(start.to(expr.span));
2036 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2037 } else if token::Comma == self.token.kind || self.token.kind.should_end_const_arg()
2039 // Avoid the following output by checking that we consumed a full const arg:
2040 // help: expressions must be enclosed in braces to be used as const generic
2043 // LL | let sr: Vec<{ (u32, _, _) = vec![] };
2045 err.multipart_suggestion(
2046 "expressions must be enclosed in braces to be used as const generic \
2049 (start.shrink_to_lo(), "{ ".to_string()),
2050 (expr.span.shrink_to_hi(), " }".to_string()),
2052 Applicability::MaybeIncorrect,
2054 let value = self.mk_expr_err(start.to(expr.span));
2056 return Ok(GenericArg::Const(AnonConst { id: ast::DUMMY_NODE_ID, value }));
2067 /// Get the diagnostics for the cases where `move async` is found.
2069 /// `move_async_span` starts at the 'm' of the move keyword and ends with the 'c' of the async keyword
2070 pub(super) fn incorrect_move_async_order_found(
2072 move_async_span: Span,
2073 ) -> DiagnosticBuilder<'a> {
2075 self.struct_span_err(move_async_span, "the order of `move` and `async` is incorrect");
2076 err.span_suggestion_verbose(
2078 "try switching the order",
2079 "async move".to_owned(),
2080 Applicability::MaybeIncorrect,
2085 /// Some special error handling for the "top-level" patterns in a match arm,
2086 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2087 crate fn maybe_recover_colon_colon_in_pat_typo(
2089 mut first_pat: P<Pat>,
2093 if RecoverColon::Yes != ra || token::Colon != self.token.kind {
2096 if !matches!(first_pat.kind, PatKind::Ident(_, _, None) | PatKind::Path(..))
2097 || !self.look_ahead(1, |token| token.is_ident() && !token.is_reserved_ident())
2101 // The pattern looks like it might be a path with a `::` -> `:` typo:
2102 // `match foo { bar:baz => {} }`
2103 let span = self.token.span;
2104 // We only emit "unexpected `:`" error here if we can successfully parse the
2105 // whole pattern correctly in that case.
2106 let snapshot = self.clone();
2108 // Create error for "unexpected `:`".
2109 match self.expected_one_of_not_found(&[], &[]) {
2111 self.bump(); // Skip the `:`.
2112 match self.parse_pat_no_top_alt(expected) {
2113 Err(mut inner_err) => {
2114 // Carry on as if we had not done anything, callers will emit a
2115 // reasonable error.
2121 // We've parsed the rest of the pattern.
2122 let new_span = first_pat.span.to(pat.span);
2123 let mut show_sugg = false;
2124 // Try to construct a recovered pattern.
2125 match &mut pat.kind {
2126 PatKind::Struct(qself @ None, path, ..)
2127 | PatKind::TupleStruct(qself @ None, path, _)
2128 | PatKind::Path(qself @ None, path) => match &first_pat.kind {
2129 PatKind::Ident(_, ident, _) => {
2130 path.segments.insert(0, PathSegment::from_ident(ident.clone()));
2131 path.span = new_span;
2135 PatKind::Path(old_qself, old_path) => {
2136 path.segments = old_path
2140 .chain(take(&mut path.segments))
2142 path.span = new_span;
2143 *qself = old_qself.clone();
2149 PatKind::Ident(BindingMode::ByValue(Mutability::Not), ident, None) => {
2150 match &first_pat.kind {
2151 PatKind::Ident(_, old_ident, _) => {
2152 let path = PatKind::Path(
2157 PathSegment::from_ident(old_ident.clone()),
2158 PathSegment::from_ident(ident.clone()),
2163 first_pat = self.mk_pat(new_span, path);
2166 PatKind::Path(old_qself, old_path) => {
2167 let mut segments = old_path.segments.clone();
2168 segments.push(PathSegment::from_ident(ident.clone()));
2169 let path = PatKind::Path(
2171 Path { span: new_span, segments, tokens: None },
2173 first_pat = self.mk_pat(new_span, path);
2182 err.span_suggestion(
2184 "maybe write a path separator here",
2186 Applicability::MaybeIncorrect,
2189 first_pat = self.mk_pat(new_span, PatKind::Wild);
2196 // Carry on as if we had not done anything. This should be unreachable.
2203 /// Some special error handling for the "top-level" patterns in a match arm,
2204 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
2205 crate fn maybe_recover_unexpected_comma(
2209 ) -> PResult<'a, ()> {
2210 if rc == RecoverComma::No || self.token != token::Comma {
2214 // An unexpected comma after a top-level pattern is a clue that the
2215 // user (perhaps more accustomed to some other language) forgot the
2216 // parentheses in what should have been a tuple pattern; return a
2217 // suggestion-enhanced error here rather than choking on the comma later.
2218 let comma_span = self.token.span;
2220 if let Err(mut err) = self.skip_pat_list() {
2221 // We didn't expect this to work anyway; we just wanted to advance to the
2222 // end of the comma-sequence so we know the span to suggest parenthesizing.
2225 let seq_span = lo.to(self.prev_token.span);
2226 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
2227 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
2228 const MSG: &str = "try adding parentheses to match on a tuple...";
2230 err.span_suggestion(
2233 format!("({})", seq_snippet),
2234 Applicability::MachineApplicable,
2236 err.span_suggestion(
2238 "...or a vertical bar to match on multiple alternatives",
2239 seq_snippet.replace(",", " |"),
2240 Applicability::MachineApplicable,
2246 /// Parse and throw away a parenthesized comma separated
2247 /// sequence of patterns until `)` is reached.
2248 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
2249 while !self.check(&token::CloseDelim(token::Paren)) {
2250 self.parse_pat_no_top_alt(None)?;
2251 if !self.eat(&token::Comma) {