1 use super::{ForceCollect, Parser, PathStyle, TrailingToken};
2 use crate::errors::RemoveLet;
3 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
4 use rustc_ast::mut_visit::{noop_visit_pat, MutVisitor};
6 use rustc_ast::token::{self, Delimiter};
8 self as ast, AttrVec, BindingAnnotation, ByRef, Expr, ExprKind, MacCall, Mutability, Pat,
9 PatField, PatKind, Path, QSelf, RangeEnd, RangeSyntax,
11 use rustc_ast_pretty::pprust;
12 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed, PResult};
13 use rustc_session::errors::ExprParenthesesNeeded;
14 use rustc_span::source_map::{respan, Span, Spanned};
15 use rustc_span::symbol::{kw, sym, Ident};
17 pub(super) type Expected = Option<&'static str>;
19 /// `Expected` for function and lambda parameter patterns.
20 pub(super) const PARAM_EXPECTED: Expected = Some("parameter name");
22 const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here";
24 /// Whether or not to recover a `,` when parsing or-patterns.
25 #[derive(PartialEq, Copy, Clone)]
26 pub enum RecoverComma {
31 /// Whether or not to recover a `:` when parsing patterns that were meant to be paths.
32 #[derive(PartialEq, Copy, Clone)]
33 pub enum RecoverColon {
38 /// Whether or not to recover a `a, b` when parsing patterns as `(a, b)` or that *and* `a | b`.
39 #[derive(PartialEq, Copy, Clone)]
40 pub enum CommaRecoveryMode {
45 /// The result of `eat_or_separator`. We want to distinguish which case we are in to avoid
46 /// emitting duplicate diagnostics.
47 #[derive(Debug, Clone, Copy)]
49 /// We recovered from a trailing vert.
51 /// We ate an `|` (or `||` and recovered).
53 /// We did not eat anything (i.e. the current token is not `|` or `||`).
60 /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
61 /// at the top level. Used when parsing the parameters of lambda expressions,
62 /// functions, function pointers, and `pat` macro fragments.
63 pub fn parse_pat_no_top_alt(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
64 self.parse_pat_with_range_pat(true, expected)
69 /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
70 /// Used for parsing patterns in all cases when `pat<no_top_alt>` is not used.
72 /// Note that after the FCP in <https://github.com/rust-lang/rust/issues/81415>,
73 /// a leading vert is allowed in nested or-patterns, too. This allows us to
74 /// simplify the grammar somewhat.
75 pub fn parse_pat_allow_top_alt(
80 rt: CommaRecoveryMode,
81 ) -> PResult<'a, P<Pat>> {
82 self.parse_pat_allow_top_alt_inner(expected, rc, ra, rt).map(|(pat, _)| pat)
85 /// Returns the pattern and a bool indicating whether we recovered from a trailing vert (true =
87 fn parse_pat_allow_top_alt_inner(
92 rt: CommaRecoveryMode,
93 ) -> PResult<'a, (P<Pat>, bool)> {
94 // Keep track of whether we recovered from a trailing vert so that we can avoid duplicated
95 // suggestions (which bothers rustfix).
97 // Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
98 let (leading_vert_span, mut trailing_vert) = match self.eat_or_separator(None) {
99 EatOrResult::AteOr => (Some(self.prev_token.span), false),
100 EatOrResult::TrailingVert => (None, true),
101 EatOrResult::None => (None, false),
104 // Parse the first pattern (`p_0`).
105 let mut first_pat = self.parse_pat_no_top_alt(expected)?;
106 if rc == RecoverComma::Yes {
107 self.maybe_recover_unexpected_comma(first_pat.span, rt)?;
110 // If the next token is not a `|`,
111 // this is not an or-pattern and we should exit here.
112 if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr {
113 // If we parsed a leading `|` which should be gated,
114 // then we should really gate the leading `|`.
115 // This complicated procedure is done purely for diagnostics UX.
117 // Check if the user wrote `foo:bar` instead of `foo::bar`.
118 if ra == RecoverColon::Yes {
119 first_pat = self.maybe_recover_colon_colon_in_pat_typo(first_pat, expected);
122 if let Some(leading_vert_span) = leading_vert_span {
123 // If there was a leading vert, treat this as an or-pattern. This improves
125 let span = leading_vert_span.to(self.prev_token.span);
126 return Ok((self.mk_pat(span, PatKind::Or(vec![first_pat])), trailing_vert));
129 return Ok((first_pat, trailing_vert));
132 // Parse the patterns `p_1 | ... | p_n` where `n > 0`.
133 let lo = leading_vert_span.unwrap_or(first_pat.span);
134 let mut pats = vec![first_pat];
136 match self.eat_or_separator(Some(lo)) {
137 EatOrResult::AteOr => {}
138 EatOrResult::None => break,
139 EatOrResult::TrailingVert => {
140 trailing_vert = true;
144 let pat = self.parse_pat_no_top_alt(expected).map_err(|mut err| {
145 err.span_label(lo, WHILE_PARSING_OR_MSG);
148 if rc == RecoverComma::Yes {
149 self.maybe_recover_unexpected_comma(pat.span, rt)?;
153 let or_pattern_span = lo.to(self.prev_token.span);
155 Ok((self.mk_pat(or_pattern_span, PatKind::Or(pats)), trailing_vert))
158 /// Parse a pattern and (maybe) a `Colon` in positions where a pattern may be followed by a
159 /// type annotation (e.g. for `let` bindings or `fn` params).
161 /// Generally, this corresponds to `pat_no_top_alt` followed by an optional `Colon`. It will
162 /// eat the `Colon` token if one is present.
164 /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
166 pub(super) fn parse_pat_before_ty(
171 ) -> PResult<'a, (P<Pat>, bool)> {
172 // We use `parse_pat_allow_top_alt` regardless of whether we actually want top-level
173 // or-patterns so that we can detect when a user tries to use it. This allows us to print a
174 // better error message.
175 let (pat, trailing_vert) = self.parse_pat_allow_top_alt_inner(
179 CommaRecoveryMode::LikelyTuple,
181 let colon = self.eat(&token::Colon);
183 if let PatKind::Or(pats) = &pat.kind {
184 let msg = format!("top-level or-patterns are not allowed in {}", syntax_loc);
185 let (help, fix) = if pats.len() == 1 {
186 // If all we have is a leading vert, then print a special message. This is the case
187 // if `parse_pat_allow_top_alt` returns an or-pattern with one variant.
188 let msg = "remove the `|`";
189 let fix = pprust::pat_to_string(&pat);
192 let msg = "wrap the pattern in parentheses";
193 let fix = format!("({})", pprust::pat_to_string(&pat));
198 // We already emitted an error and suggestion to remove the trailing vert. Don't
200 self.sess.span_diagnostic.delay_span_bug(pat.span, &msg);
202 self.struct_span_err(pat.span, &msg)
203 .span_suggestion(pat.span, help, fix, Applicability::MachineApplicable)
211 /// Parse the pattern for a function or function pointer parameter, followed by a colon.
213 /// The return value represents the parsed pattern and `true` if a `Colon` was parsed (`false`
215 pub(super) fn parse_fn_param_pat_colon(&mut self) -> PResult<'a, (P<Pat>, bool)> {
216 // In order to get good UX, we first recover in the case of a leading vert for an illegal
217 // top-level or-pat. Normally, this means recovering both `|` and `||`, but in this case,
218 // a leading `||` probably doesn't indicate an or-pattern attempt, so we handle that
220 if let token::OrOr = self.token.kind {
221 let span = self.token.span;
222 let mut err = self.struct_span_err(span, "unexpected `||` before function parameter");
223 err.span_suggestion(span, "remove the `||`", "", Applicability::MachineApplicable);
224 err.note("alternatives in or-patterns are separated with `|`, not `||`");
229 self.parse_pat_before_ty(PARAM_EXPECTED, RecoverComma::No, "function parameters")
232 /// Eat the or-pattern `|` separator.
233 /// If instead a `||` token is encountered, recover and pretend we parsed `|`.
234 fn eat_or_separator(&mut self, lo: Option<Span>) -> EatOrResult {
235 if self.recover_trailing_vert(lo) {
236 EatOrResult::TrailingVert
237 } else if matches!(self.token.kind, token::OrOr) {
238 // Found `||`; Recover and pretend we parsed `|`.
239 self.ban_unexpected_or_or(lo);
242 } else if self.eat(&token::BinOp(token::Or)) {
249 /// Recover if `|` or `||` is the current token and we have one of the
250 /// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us.
252 /// These tokens all indicate that we reached the end of the or-pattern
253 /// list and can now reliably say that the `|` was an illegal trailing vert.
254 /// Note that there are more tokens such as `@` for which we know that the `|`
255 /// is an illegal parse. However, the user's intent is less clear in that case.
256 fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool {
257 let is_end_ahead = self.look_ahead(1, |token| {
259 &token.uninterpolate().kind,
260 token::FatArrow // e.g. `a | => 0,`.
261 | token::Ident(kw::If, false) // e.g. `a | if expr`.
262 | token::Eq // e.g. `let a | = 0`.
263 | token::Semi // e.g. `let a |;`.
264 | token::Colon // e.g. `let a | :`.
265 | token::Comma // e.g. `let (a |,)`.
266 | token::CloseDelim(Delimiter::Bracket) // e.g. `let [a | ]`.
267 | token::CloseDelim(Delimiter::Parenthesis) // e.g. `let (a | )`.
268 | token::CloseDelim(Delimiter::Brace) // e.g. `let A { f: a | }`.
271 match (is_end_ahead, &self.token.kind) {
272 (true, token::BinOp(token::Or) | token::OrOr) => {
273 self.ban_illegal_vert(lo, "trailing", "not allowed in an or-pattern");
281 /// We have parsed `||` instead of `|`. Error and suggest `|` instead.
282 fn ban_unexpected_or_or(&mut self, lo: Option<Span>) {
283 let mut err = self.struct_span_err(self.token.span, "unexpected token `||` in pattern");
286 "use a single `|` to separate multiple alternative patterns",
288 Applicability::MachineApplicable,
290 if let Some(lo) = lo {
291 err.span_label(lo, WHILE_PARSING_OR_MSG);
296 /// A `|` or possibly `||` token shouldn't be here. Ban it.
297 fn ban_illegal_vert(&mut self, lo: Option<Span>, pos: &str, ctx: &str) {
298 let span = self.token.span;
299 let mut err = self.struct_span_err(span, &format!("a {} `|` is {}", pos, ctx));
302 &format!("remove the `{}`", pprust::token_to_string(&self.token)),
304 Applicability::MachineApplicable,
306 if let Some(lo) = lo {
307 err.span_label(lo, WHILE_PARSING_OR_MSG);
309 if let token::OrOr = self.token.kind {
310 err.note("alternatives in or-patterns are separated with `|`, not `||`");
315 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
317 fn parse_pat_with_range_pat(
319 allow_range_pat: bool,
321 ) -> PResult<'a, P<Pat>> {
322 maybe_recover_from_interpolated_ty_qpath!(self, true);
323 maybe_whole!(self, NtPat, |x| x);
325 let mut lo = self.token.span;
327 if self.token.is_keyword(kw::Let) && self.look_ahead(1, |tok| tok.can_begin_pattern()) {
329 self.sess.emit_err(RemoveLet { span: lo });
330 lo = self.token.span;
333 let pat = if self.check(&token::BinOp(token::And)) || self.token.kind == token::AndAnd {
334 self.parse_pat_deref(expected)?
335 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
336 self.parse_pat_tuple_or_parens()?
337 } else if self.check(&token::OpenDelim(Delimiter::Bracket)) {
338 // Parse `[pat, pat,...]` as a slice pattern.
339 let (pats, _) = self.parse_delim_comma_seq(Delimiter::Bracket, |p| {
340 p.parse_pat_allow_top_alt(
344 CommaRecoveryMode::EitherTupleOrPipe,
348 } else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
349 // A rest pattern `..`.
352 } else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) {
353 self.recover_dotdotdot_rest_pat(lo)
354 } else if let Some(form) = self.parse_range_end() {
355 self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
356 } else if self.eat_keyword(kw::Underscore) {
359 } else if self.eat_keyword(kw::Mut) {
360 self.parse_pat_ident_mut()?
361 } else if self.eat_keyword(kw::Ref) {
362 // Parse ref ident @ pat / ref mut ident @ pat
363 let mutbl = self.parse_mutability();
364 self.parse_pat_ident(BindingAnnotation(ByRef::Yes, mutbl))?
365 } else if self.eat_keyword(kw::Box) {
366 self.parse_pat_box()?
367 } else if self.check_inline_const(0) {
369 let const_expr = self.parse_const_block(lo.to(self.token.span), true)?;
371 if let Some(re) = self.parse_range_end() {
372 self.parse_pat_range_begin_with(const_expr, re)?
374 PatKind::Lit(const_expr)
376 } else if self.can_be_ident_pat() {
377 // Parse `ident @ pat`
378 // This can give false positives and parse nullary enums,
379 // they are dealt with later in resolve.
380 self.parse_pat_ident(BindingAnnotation::NONE)?
381 } else if self.is_start_of_pat_with_path() {
382 // Parse pattern starting with a path
383 let (qself, path) = if self.eat_lt() {
384 // Parse a qualified path
385 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
388 // Parse an unqualified path
389 (None, self.parse_path(PathStyle::Expr)?)
391 let span = lo.to(self.prev_token.span);
393 if qself.is_none() && self.check(&token::Not) {
394 self.parse_pat_mac_invoc(path)?
395 } else if let Some(form) = self.parse_range_end() {
396 let begin = self.mk_expr(span, ExprKind::Path(qself, path));
397 self.parse_pat_range_begin_with(begin, form)?
398 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
399 self.parse_pat_struct(qself, path)?
400 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
401 self.parse_pat_tuple_struct(qself, path)?
403 PatKind::Path(qself, path)
405 } else if matches!(self.token.kind, token::Lifetime(_))
406 // In pattern position, we're totally fine with using "next token isn't colon"
407 // as a heuristic. We could probably just always try to recover if it's a lifetime,
408 // because we never have `'a: label {}` in a pattern position anyways, but it does
409 // keep us from suggesting something like `let 'a: Ty = ..` => `let 'a': Ty = ..`
410 && !self.look_ahead(1, |token| matches!(token.kind, token::Colon))
412 // Recover a `'a` as a `'a'` literal
413 let lt = self.expect_lifetime();
414 let lit = self.recover_unclosed_char(lt.ident, |self_| {
415 let expected = expected.unwrap_or("pattern");
417 format!("expected {}, found {}", expected, super::token_descr(&self_.token));
419 let mut err = self_.struct_span_err(self_.token.span, &msg);
420 err.span_label(self_.token.span, format!("expected {}", expected));
423 PatKind::Lit(self.mk_expr(lo, ExprKind::Lit(lit.token_lit)))
425 // Try to parse everything else as literal with optional minus
426 match self.parse_literal_maybe_minus() {
427 Ok(begin) => match self.parse_range_end() {
428 Some(form) => self.parse_pat_range_begin_with(begin, form)?,
429 None => PatKind::Lit(begin),
431 Err(err) => return self.fatal_unexpected_non_pat(err, expected),
435 let pat = self.mk_pat(lo.to(self.prev_token.span), pat);
436 let pat = self.maybe_recover_from_bad_qpath(pat)?;
437 let pat = self.recover_intersection_pat(pat)?;
439 if !allow_range_pat {
440 self.ban_pat_range_if_ambiguous(&pat)
446 /// Recover from a typoed `...` pattern that was encountered
447 /// Ref: Issue #70388
448 fn recover_dotdotdot_rest_pat(&mut self, lo: Span) -> PatKind {
449 // A typoed rest pattern `...`.
450 self.bump(); // `...`
452 // The user probably mistook `...` for a rest pattern `..`.
453 self.struct_span_err(lo, "unexpected `...`")
454 .span_label(lo, "not a valid pattern")
455 .span_suggestion_short(
457 "for a rest pattern, use `..` instead of `...`",
459 Applicability::MachineApplicable,
465 /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
467 /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
468 /// should already have been parsed by now at this point,
469 /// if the next token is `@` then we can try to parse the more general form.
471 /// Consult `parse_pat_ident` for the `binding` grammar.
473 /// The notion of intersection patterns are found in
474 /// e.g. [F#][and] where they are called AND-patterns.
476 /// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching
477 fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> {
478 if self.token.kind != token::At {
479 // Next token is not `@` so it's not going to be an intersection pattern.
483 // At this point we attempt to parse `@ $pat_rhs` and emit an error.
485 let mut rhs = self.parse_pat_no_top_alt(None)?;
486 let sp = lhs.span.to(rhs.span);
488 if let PatKind::Ident(_, _, ref mut sub @ None) = rhs.kind {
489 // The user inverted the order, so help them fix that.
490 let mut applicability = Applicability::MachineApplicable;
491 // FIXME(bindings_after_at): Remove this code when stabilizing the feature.
492 lhs.walk(&mut |p| match p.kind {
493 // `check_match` is unhappy if the subpattern has a binding anywhere.
494 PatKind::Ident(..) => {
495 applicability = Applicability::MaybeIncorrect;
496 false // Short-circuit.
501 let lhs_span = lhs.span;
502 // Move the LHS into the RHS as a subpattern.
503 // The RHS is now the full pattern.
506 self.struct_span_err(sp, "pattern on wrong side of `@`")
507 .span_label(lhs_span, "pattern on the left, should be on the right")
508 .span_label(rhs.span, "binding on the right, should be on the left")
509 .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability)
512 // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
513 rhs.kind = PatKind::Wild;
514 self.struct_span_err(sp, "left-hand side of `@` must be a binding")
515 .span_label(lhs.span, "interpreted as a pattern, not a binding")
516 .span_label(rhs.span, "also a pattern")
517 .note("bindings are `x`, `mut x`, `ref x`, and `ref mut x`")
525 /// Ban a range pattern if it has an ambiguous interpretation.
526 fn ban_pat_range_if_ambiguous(&self, pat: &Pat) {
530 Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. },
532 PatKind::Range(..) => {}
536 self.struct_span_err(pat.span, "the range pattern here has ambiguous interpretation")
539 "add parentheses to clarify the precedence",
540 format!("({})", pprust::pat_to_string(&pat)),
541 // "ambiguous interpretation" implies that we have to be guessing
542 Applicability::MaybeIncorrect,
547 /// Parse `&pat` / `&mut pat`.
548 fn parse_pat_deref(&mut self, expected: Expected) -> PResult<'a, PatKind> {
550 self.recover_lifetime_in_deref_pat();
551 let mutbl = self.parse_mutability();
552 let subpat = self.parse_pat_with_range_pat(false, expected)?;
553 Ok(PatKind::Ref(subpat, mutbl))
556 fn recover_lifetime_in_deref_pat(&mut self) {
557 if let token::Lifetime(name) = self.token.kind {
560 let span = self.prev_token.span;
561 self.struct_span_err(span, &format!("unexpected lifetime `{}` in pattern", name))
562 .span_suggestion(span, "remove the lifetime", "", Applicability::MachineApplicable)
567 /// Parse a tuple or parenthesis pattern.
568 fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
569 let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
570 p.parse_pat_allow_top_alt(
574 CommaRecoveryMode::LikelyTuple,
578 // Here, `(pat,)` is a tuple pattern.
579 // For backward compatibility, `(..)` is a tuple pattern as well.
580 Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
581 PatKind::Paren(fields.into_iter().next().unwrap())
583 PatKind::Tuple(fields)
587 /// Parse a mutable binding with the `mut` token already eaten.
588 fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
589 let mut_span = self.prev_token.span;
591 if self.eat_keyword(kw::Ref) {
592 return self.recover_mut_ref_ident(mut_span);
595 self.recover_additional_muts();
597 // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
598 if let token::Interpolated(ref nt) = self.token.kind {
599 if let token::NtPat(_) = **nt {
600 self.expected_ident_found().emit();
604 // Parse the pattern we hope to be an identifier.
605 let mut pat = self.parse_pat_no_top_alt(Some("identifier"))?;
607 // If we don't have `mut $ident (@ pat)?`, error.
608 if let PatKind::Ident(BindingAnnotation(ByRef::No, m @ Mutability::Not), ..) = &mut pat.kind
610 // Don't recurse into the subpattern.
611 // `mut` on the outer binding doesn't affect the inner bindings.
612 *m = Mutability::Mut;
614 // Add `mut` to any binding in the parsed pattern.
615 let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
616 self.ban_mut_general_pat(mut_span, &pat, changed_any_binding);
619 Ok(pat.into_inner().kind)
622 /// Recover on `mut ref? ident @ pat` and suggest
623 /// that the order of `mut` and `ref` is incorrect.
624 fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> {
625 let mutref_span = lo.to(self.prev_token.span);
626 self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
629 "try switching the order",
631 Applicability::MachineApplicable,
635 self.parse_pat_ident(BindingAnnotation::REF_MUT)
638 /// Turn all by-value immutable bindings in a pattern into mutable bindings.
639 /// Returns `true` if any change was made.
640 fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
642 impl MutVisitor for AddMut {
643 fn visit_pat(&mut self, pat: &mut P<Pat>) {
644 if let PatKind::Ident(BindingAnnotation(ByRef::No, m @ Mutability::Not), ..) =
648 *m = Mutability::Mut;
650 noop_visit_pat(pat, self);
654 let mut add_mut = AddMut(false);
655 add_mut.visit_pat(pat);
659 /// Error on `mut $pat` where `$pat` is not an ident.
660 fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
661 let span = lo.to(pat.span);
662 let fix = pprust::pat_to_string(&pat);
663 let (problem, suggestion) = if changed_any_binding {
664 ("`mut` must be attached to each individual binding", "add `mut` to each binding")
666 ("`mut` must be followed by a named binding", "remove the `mut` prefix")
668 self.struct_span_err(span, problem)
669 .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable)
670 .note("`mut` may be followed by `variable` and `variable @ pattern`")
674 /// Eat any extraneous `mut`s and error + recover if we ate any.
675 fn recover_additional_muts(&mut self) {
676 let lo = self.token.span;
677 while self.eat_keyword(kw::Mut) {}
678 if lo == self.token.span {
682 let span = lo.to(self.prev_token.span);
683 self.struct_span_err(span, "`mut` on a binding may not be repeated")
686 "remove the additional `mut`s",
688 Applicability::MachineApplicable,
693 /// Parse macro invocation
694 fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
696 let args = self.parse_delim_args()?;
697 let mac = P(MacCall { path, args, prior_type_ascription: self.last_type_ascription });
698 Ok(PatKind::MacCall(mac))
701 fn fatal_unexpected_non_pat(
703 err: DiagnosticBuilder<'a, ErrorGuaranteed>,
705 ) -> PResult<'a, P<Pat>> {
708 let expected = expected.unwrap_or("pattern");
709 let msg = format!("expected {}, found {}", expected, super::token_descr(&self.token));
711 let mut err = self.struct_span_err(self.token.span, &msg);
712 err.span_label(self.token.span, format!("expected {}", expected));
714 let sp = self.sess.source_map().start_point(self.token.span);
715 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
716 err.subdiagnostic(ExprParenthesesNeeded::surrounding(*sp));
722 /// Parses the range pattern end form `".." | "..." | "..=" ;`.
723 fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> {
724 let re = if self.eat(&token::DotDotDot) {
725 RangeEnd::Included(RangeSyntax::DotDotDot)
726 } else if self.eat(&token::DotDotEq) {
727 RangeEnd::Included(RangeSyntax::DotDotEq)
728 } else if self.eat(&token::DotDot) {
733 Some(respan(self.prev_token.span, re))
736 /// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`.
737 /// `$begin $form` has already been parsed.
738 fn parse_pat_range_begin_with(
741 re: Spanned<RangeEnd>,
742 ) -> PResult<'a, PatKind> {
743 let end = if self.is_pat_range_end_start(0) {
744 // Parsing e.g. `X..=Y`.
745 Some(self.parse_pat_range_end()?)
747 // Parsing e.g. `X..`.
748 if let RangeEnd::Included(_) = re.node {
749 // FIXME(Centril): Consider semantic errors instead in `ast_validation`.
750 self.inclusive_range_with_incorrect_end(re.span);
754 Ok(PatKind::Range(Some(begin), end, re))
757 pub(super) fn inclusive_range_with_incorrect_end(&mut self, span: Span) {
758 let tok = &self.token;
760 // If the user typed "..==" instead of "..=", we want to give them
761 // a specific error message telling them to use "..=".
762 // Otherwise, we assume that they meant to type a half open exclusive
763 // range and give them an error telling them to do that instead.
764 if matches!(tok.kind, token::Eq) && tok.span.lo() == span.hi() {
765 let span_with_eq = span.to(tok.span);
767 // Ensure the user doesn't receive unhelpful unexpected token errors
769 if self.is_pat_range_end_start(0) {
770 let _ = self.parse_pat_range_end().map_err(|e| e.cancel());
773 self.error_inclusive_range_with_extra_equals(span_with_eq);
775 self.error_inclusive_range_with_no_end(span);
779 fn error_inclusive_range_with_extra_equals(&self, span: Span) {
780 self.struct_span_err(span, "unexpected `=` after inclusive range")
781 .span_suggestion_short(span, "use `..=` instead", "..=", Applicability::MaybeIncorrect)
782 .note("inclusive ranges end with a single equals sign (`..=`)")
786 fn error_inclusive_range_with_no_end(&self, span: Span) {
787 struct_span_err!(self.sess.span_diagnostic, span, E0586, "inclusive range with no end")
788 .span_suggestion_short(span, "use `..` instead", "..", Applicability::MachineApplicable)
789 .note("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)")
793 /// Parse a range-to pattern, `..X` or `..=X` where `X` remains to be parsed.
795 /// The form `...X` is prohibited to reduce confusion with the potential
796 /// expression syntax `...expr` for splatting in expressions.
797 fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> {
798 let end = self.parse_pat_range_end()?;
799 if let RangeEnd::Included(ref mut syn @ RangeSyntax::DotDotDot) = &mut re.node {
800 *syn = RangeSyntax::DotDotEq;
801 self.struct_span_err(re.span, "range-to patterns with `...` are not allowed")
802 .span_suggestion_short(
806 Applicability::MachineApplicable,
810 Ok(PatKind::Range(None, Some(end), re))
813 /// Is the token `dist` away from the current suitable as the start of a range patterns end?
814 fn is_pat_range_end_start(&self, dist: usize) -> bool {
815 self.check_inline_const(dist)
816 || self.look_ahead(dist, |t| {
817 t.is_path_start() // e.g. `MY_CONST`;
818 || t.kind == token::Dot // e.g. `.5` for recovery;
819 || t.can_begin_literal_maybe_minus() // e.g. `42`.
821 || t.is_lifetime() // recover `'a` instead of `'a'`
825 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
826 if self.check_inline_const(0) {
827 self.parse_const_block(self.token.span, true)
828 } else if self.check_path() {
829 let lo = self.token.span;
830 let (qself, path) = if self.eat_lt() {
831 // Parse a qualified path
832 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
835 // Parse an unqualified path
836 (None, self.parse_path(PathStyle::Expr)?)
838 let hi = self.prev_token.span;
839 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path)))
841 self.parse_literal_maybe_minus()
845 /// Is this the start of a pattern beginning with a path?
846 fn is_start_of_pat_with_path(&mut self) -> bool {
848 // Just for recovery (see `can_be_ident`).
849 || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
852 /// Would `parse_pat_ident` be appropriate here?
853 fn can_be_ident_pat(&mut self) -> bool {
855 && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
856 && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
857 // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
858 && !self.token.is_keyword(kw::In)
859 // Try to do something more complex?
860 && self.look_ahead(1, |t| !matches!(t.kind, token::OpenDelim(Delimiter::Parenthesis) // A tuple struct pattern.
861 | token::OpenDelim(Delimiter::Brace) // A struct pattern.
862 | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
863 | token::ModSep // A tuple / struct variant pattern.
864 | token::Not)) // A macro expanding to a pattern.
867 /// Parses `ident` or `ident @ pat`.
868 /// Used by the copy foo and ref foo patterns to give a good
869 /// error message when parsing mistakes like `ref foo(a, b)`.
870 fn parse_pat_ident(&mut self, binding_annotation: BindingAnnotation) -> PResult<'a, PatKind> {
871 let ident = self.parse_ident()?;
872 let sub = if self.eat(&token::At) {
873 Some(self.parse_pat_no_top_alt(Some("binding pattern"))?)
878 // Just to be friendly, if they write something like `ref Some(i)`,
879 // we end up here with `(` as the current token.
880 // This shortly leads to a parse error. Note that if there is no explicit
881 // binding mode then we do not end up here, because the lookahead
882 // will direct us over to `parse_enum_variant()`.
883 if self.token == token::OpenDelim(Delimiter::Parenthesis) {
885 .struct_span_err(self.prev_token.span, "expected identifier, found enum pattern"));
888 Ok(PatKind::Ident(binding_annotation, ident, sub))
891 /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
892 fn parse_pat_struct(&mut self, qself: Option<P<QSelf>>, path: Path) -> PResult<'a, PatKind> {
894 // Feature gate the use of qualified paths in patterns
895 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
898 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
899 e.span_label(path.span, "while parsing the fields for this pattern");
905 Ok(PatKind::Struct(qself, path, fields, etc))
908 /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
909 fn parse_pat_tuple_struct(
911 qself: Option<P<QSelf>>,
913 ) -> PResult<'a, PatKind> {
914 let (fields, _) = self.parse_paren_comma_seq(|p| {
915 p.parse_pat_allow_top_alt(
919 CommaRecoveryMode::EitherTupleOrPipe,
923 self.sess.gated_spans.gate(sym::more_qualified_paths, path.span);
925 Ok(PatKind::TupleStruct(qself, path, fields))
928 /// Are we sure this could not possibly be the start of a pattern?
930 /// Currently, this only accounts for tokens that can follow identifiers
931 /// in patterns, but this can be extended as necessary.
932 fn isnt_pattern_start(&self) -> bool {
939 token::OpenDelim(Delimiter::Brace),
940 token::CloseDelim(Delimiter::Brace),
941 token::CloseDelim(Delimiter::Parenthesis),
943 .contains(&self.token.kind)
947 fn parse_pat_box(&mut self) -> PResult<'a, PatKind> {
948 let box_span = self.prev_token.span;
950 if self.isnt_pattern_start() {
951 self.struct_span_err(
953 format!("expected pattern, found {}", super::token_descr(&self.token)),
955 .span_note(box_span, "`box` is a reserved keyword")
956 .span_suggestion_verbose(
957 box_span.shrink_to_lo(),
958 "escape `box` to use it as an identifier",
960 Applicability::MaybeIncorrect,
964 // We cannot use `parse_pat_ident()` since it will complain `box`
965 // is not an identifier.
966 let sub = if self.eat(&token::At) {
967 Some(self.parse_pat_no_top_alt(Some("binding pattern"))?)
972 Ok(PatKind::Ident(BindingAnnotation::NONE, Ident::new(kw::Box, box_span), sub))
974 let pat = self.parse_pat_with_range_pat(false, None)?;
975 self.sess.gated_spans.gate(sym::box_patterns, box_span.to(self.prev_token.span));
976 Ok(PatKind::Box(pat))
980 /// Parses the fields of a struct-like pattern.
981 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<PatField>, bool)> {
982 let mut fields = Vec::new();
984 let mut ate_comma = true;
985 let mut delayed_err: Option<DiagnosticBuilder<'a, ErrorGuaranteed>> = None;
986 let mut etc_span = None;
988 while self.token != token::CloseDelim(Delimiter::Brace) {
989 let attrs = match self.parse_outer_attributes() {
992 if let Some(mut delayed) = delayed_err {
998 let lo = self.token.span;
1000 // check that a comma comes after every field
1002 let err = self.struct_span_err(self.token.span, "expected `,`");
1003 if let Some(mut delayed) = delayed_err {
1010 if self.check(&token::DotDot) || self.token == token::DotDotDot {
1012 let mut etc_sp = self.token.span;
1014 self.recover_one_fewer_dotdot();
1015 self.bump(); // `..` || `...`
1017 if self.token == token::CloseDelim(Delimiter::Brace) {
1018 etc_span = Some(etc_sp);
1021 let token_str = super::token_descr(&self.token);
1022 let msg = &format!("expected `}}`, found {}", token_str);
1023 let mut err = self.struct_span_err(self.token.span, msg);
1025 err.span_label(self.token.span, "expected `}`");
1026 let mut comma_sp = None;
1027 if self.token == token::Comma {
1029 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
1030 etc_sp = etc_sp.to(nw_span);
1033 "`..` must be at the end and cannot have a trailing comma",
1035 comma_sp = Some(self.token.span);
1040 etc_span = Some(etc_sp.until(self.token.span));
1041 if self.token == token::CloseDelim(Delimiter::Brace) {
1042 // If the struct looks otherwise well formed, recover and continue.
1043 if let Some(sp) = comma_sp {
1044 err.span_suggestion_short(
1046 "remove this comma",
1048 Applicability::MachineApplicable,
1053 } else if self.token.is_ident() && ate_comma {
1054 // Accept fields coming after `..,`.
1055 // This way we avoid "pattern missing fields" errors afterwards.
1056 // We delay this error until the end in order to have a span for a
1058 if let Some(mut delayed_err) = delayed_err {
1062 delayed_err = Some(err);
1065 if let Some(mut err) = delayed_err {
1073 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
1074 let field = match this.parse_pat_field(lo, attrs) {
1075 Ok(field) => Ok(field),
1077 if let Some(mut delayed_err) = delayed_err.take() {
1083 ate_comma = this.eat(&token::Comma);
1084 // We just ate a comma, so there's no need to use
1085 // `TrailingToken::Comma`
1086 Ok((field, TrailingToken::None))
1092 if let Some(mut err) = delayed_err {
1093 if let Some(etc_span) = etc_span {
1094 err.multipart_suggestion(
1095 "move the `..` to the end of the field list",
1097 (etc_span, String::new()),
1098 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
1100 Applicability::MachineApplicable,
1108 /// Recover on `...` as if it were `..` to avoid further errors.
1109 /// See issue #46718.
1110 fn recover_one_fewer_dotdot(&self) {
1111 if self.token != token::DotDotDot {
1115 self.struct_span_err(self.token.span, "expected field pattern, found `...`")
1118 "to omit remaining fields, use one fewer `.`",
1120 Applicability::MachineApplicable,
1125 fn parse_pat_field(&mut self, lo: Span, attrs: AttrVec) -> PResult<'a, PatField> {
1126 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1128 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
1129 // Parsing a pattern of the form `fieldname: pat`.
1130 let fieldname = self.parse_field_name()?;
1132 let pat = self.parse_pat_allow_top_alt(
1136 CommaRecoveryMode::EitherTupleOrPipe,
1139 (pat, fieldname, false)
1141 // Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
1142 let is_box = self.eat_keyword(kw::Box);
1143 let boxed_span = self.token.span;
1144 let is_ref = self.eat_keyword(kw::Ref);
1145 let is_mut = self.eat_keyword(kw::Mut);
1146 let fieldname = self.parse_field_name()?;
1147 hi = self.prev_token.span;
1149 let mutability = match is_mut {
1150 false => Mutability::Not,
1151 true => Mutability::Mut,
1153 let ann = BindingAnnotation(ByRef::from(is_ref), mutability);
1154 let fieldpat = self.mk_pat_ident(boxed_span.to(hi), ann, fieldname);
1156 if is_box { self.mk_pat(lo.to(hi), PatKind::Box(fieldpat)) } else { fieldpat };
1157 (subpat, fieldname, true)
1165 id: ast::DUMMY_NODE_ID,
1167 is_placeholder: false,
1171 pub(super) fn mk_pat_ident(&self, span: Span, ann: BindingAnnotation, ident: Ident) -> P<Pat> {
1172 self.mk_pat(span, PatKind::Ident(ann, ident, None))
1175 pub(super) fn mk_pat(&self, span: Span, kind: PatKind) -> P<Pat> {
1176 P(Pat { kind, span, id: ast::DUMMY_NODE_ID, tokens: None })