1 use super::{Parser, PathStyle};
2 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
3 use rustc_ast::mut_visit::{noop_visit_mac, noop_visit_pat, MutVisitor};
6 use rustc_ast::{self as ast, AttrVec, Attribute, FieldPat, MacCall, Pat, PatKind, RangeEnd};
7 use rustc_ast::{BindingMode, Expr, ExprKind, Mutability, Path, QSelf, RangeSyntax};
8 use rustc_ast_pretty::pprust;
9 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, PResult};
10 use rustc_span::source_map::{respan, Span, Spanned};
11 use rustc_span::symbol::{kw, sym, Ident};
13 type Expected = Option<&'static str>;
15 /// `Expected` for function and lambda parameter patterns.
16 pub(super) const PARAM_EXPECTED: Expected = Some("parameter name");
18 const WHILE_PARSING_OR_MSG: &str = "while parsing this or-pattern starting here";
20 /// Whether or not an or-pattern should be gated when occurring in the current context.
22 pub(super) enum GateOr {
27 /// Whether or not to recover a `,` when parsing or-patterns.
28 #[derive(PartialEq, Copy, Clone)]
37 /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
38 /// at the top level. Used when parsing the parameters of lambda expressions,
39 /// functions, function pointers, and `pat` macro fragments.
40 pub fn parse_pat(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
41 self.parse_pat_with_range_pat(true, expected)
44 /// Entry point to the main pattern parser.
45 /// Corresponds to `top_pat` in RFC 2535 and allows or-pattern at the top level.
46 pub(super) fn parse_top_pat(&mut self, gate_or: GateOr) -> PResult<'a, P<Pat>> {
47 // Allow a '|' before the pats (RFCs 1925, 2530, and 2535).
48 let gated_leading_vert = self.eat_or_separator(None) && gate_or == GateOr::Yes;
49 let leading_vert_span = self.prev_token.span;
51 // Parse the possibly-or-pattern.
52 let pat = self.parse_pat_with_or(None, gate_or, RecoverComma::Yes)?;
54 // If we parsed a leading `|` which should be gated,
55 // and no other gated or-pattern has been parsed thus far,
56 // then we should really gate the leading `|`.
57 // This complicated procedure is done purely for diagnostics UX.
58 if gated_leading_vert && self.sess.gated_spans.is_ungated(sym::or_patterns) {
59 self.sess.gated_spans.gate(sym::or_patterns, leading_vert_span);
65 /// Parse the pattern for a function or function pointer parameter.
66 /// Special recovery is provided for or-patterns and leading `|`.
67 pub(super) fn parse_fn_param_pat(&mut self) -> PResult<'a, P<Pat>> {
68 self.recover_leading_vert(None, "not allowed in a parameter pattern");
69 let pat = self.parse_pat_with_or(PARAM_EXPECTED, GateOr::No, RecoverComma::No)?;
71 if let PatKind::Or(..) = &pat.kind {
72 self.ban_illegal_fn_param_or_pat(&pat);
78 /// Ban `A | B` immediately in a parameter pattern and suggest wrapping in parens.
79 fn ban_illegal_fn_param_or_pat(&self, pat: &Pat) {
80 let msg = "wrap the pattern in parenthesis";
81 let fix = format!("({})", pprust::pat_to_string(pat));
82 self.struct_span_err(pat.span, "an or-pattern parameter must be wrapped in parenthesis")
83 .span_suggestion(pat.span, msg, fix, Applicability::MachineApplicable)
87 /// Parses a pattern, that may be a or-pattern (e.g. `Foo | Bar` in `Some(Foo | Bar)`).
88 /// Corresponds to `pat<allow_top_alt>` in RFC 2535.
94 ) -> PResult<'a, P<Pat>> {
95 // Parse the first pattern (`p_0`).
96 let first_pat = self.parse_pat(expected)?;
97 self.maybe_recover_unexpected_comma(first_pat.span, rc)?;
99 // If the next token is not a `|`,
100 // this is not an or-pattern and we should exit here.
101 if !self.check(&token::BinOp(token::Or)) && self.token != token::OrOr {
102 return Ok(first_pat);
105 // Parse the patterns `p_1 | ... | p_n` where `n > 0`.
106 let lo = first_pat.span;
107 let mut pats = vec![first_pat];
108 while self.eat_or_separator(Some(lo)) {
109 let pat = self.parse_pat(expected).map_err(|mut err| {
110 err.span_label(lo, WHILE_PARSING_OR_MSG);
113 self.maybe_recover_unexpected_comma(pat.span, rc)?;
116 let or_pattern_span = lo.to(self.prev_token.span);
118 // Feature gate the or-pattern if instructed:
119 if gate_or == GateOr::Yes {
120 self.sess.gated_spans.gate(sym::or_patterns, or_pattern_span);
123 Ok(self.mk_pat(or_pattern_span, PatKind::Or(pats)))
126 /// Eat the or-pattern `|` separator.
127 /// If instead a `||` token is encountered, recover and pretend we parsed `|`.
128 fn eat_or_separator(&mut self, lo: Option<Span>) -> bool {
129 if self.recover_trailing_vert(lo) {
133 match self.token.kind {
135 // Found `||`; Recover and pretend we parsed `|`.
136 self.ban_unexpected_or_or(lo);
140 _ => self.eat(&token::BinOp(token::Or)),
144 /// Recover if `|` or `||` is the current token and we have one of the
145 /// tokens `=>`, `if`, `=`, `:`, `;`, `,`, `]`, `)`, or `}` ahead of us.
147 /// These tokens all indicate that we reached the end of the or-pattern
148 /// list and can now reliably say that the `|` was an illegal trailing vert.
149 /// Note that there are more tokens such as `@` for which we know that the `|`
150 /// is an illegal parse. However, the user's intent is less clear in that case.
151 fn recover_trailing_vert(&mut self, lo: Option<Span>) -> bool {
152 let is_end_ahead = self.look_ahead(1, |token| match &token.uninterpolate().kind {
153 token::FatArrow // e.g. `a | => 0,`.
154 | token::Ident(kw::If, false) // e.g. `a | if expr`.
155 | token::Eq // e.g. `let a | = 0`.
156 | token::Semi // e.g. `let a |;`.
157 | token::Colon // e.g. `let a | :`.
158 | token::Comma // e.g. `let (a |,)`.
159 | token::CloseDelim(token::Bracket) // e.g. `let [a | ]`.
160 | token::CloseDelim(token::Paren) // e.g. `let (a | )`.
161 | token::CloseDelim(token::Brace) => true, // e.g. `let A { f: a | }`.
164 match (is_end_ahead, &self.token.kind) {
165 (true, token::BinOp(token::Or) | token::OrOr) => {
166 self.ban_illegal_vert(lo, "trailing", "not allowed in an or-pattern");
174 /// We have parsed `||` instead of `|`. Error and suggest `|` instead.
175 fn ban_unexpected_or_or(&mut self, lo: Option<Span>) {
176 let mut err = self.struct_span_err(self.token.span, "unexpected token `||` after pattern");
179 "use a single `|` to separate multiple alternative patterns",
181 Applicability::MachineApplicable,
183 if let Some(lo) = lo {
184 err.span_label(lo, WHILE_PARSING_OR_MSG);
189 /// Some special error handling for the "top-level" patterns in a match arm,
190 /// `for` loop, `let`, &c. (in contrast to subpatterns within such).
191 fn maybe_recover_unexpected_comma(&mut self, lo: Span, rc: RecoverComma) -> PResult<'a, ()> {
192 if rc == RecoverComma::No || self.token != token::Comma {
196 // An unexpected comma after a top-level pattern is a clue that the
197 // user (perhaps more accustomed to some other language) forgot the
198 // parentheses in what should have been a tuple pattern; return a
199 // suggestion-enhanced error here rather than choking on the comma later.
200 let comma_span = self.token.span;
202 if let Err(mut err) = self.skip_pat_list() {
203 // We didn't expect this to work anyway; we just wanted to advance to the
204 // end of the comma-sequence so we know the span to suggest parenthesizing.
207 let seq_span = lo.to(self.prev_token.span);
208 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
209 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
212 "try adding parentheses to match on a tuple...",
213 format!("({})", seq_snippet),
214 Applicability::MachineApplicable,
218 "...or a vertical bar to match on multiple alternatives",
219 seq_snippet.replace(",", " |"),
220 Applicability::MachineApplicable,
226 /// Parse and throw away a parentesized comma separated
227 /// sequence of patterns until `)` is reached.
228 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
229 while !self.check(&token::CloseDelim(token::Paren)) {
230 self.parse_pat(None)?;
231 if !self.eat(&token::Comma) {
238 /// Recursive possibly-or-pattern parser with recovery for an erroneous leading `|`.
239 /// See `parse_pat_with_or` for details on parsing or-patterns.
240 fn parse_pat_with_or_inner(&mut self) -> PResult<'a, P<Pat>> {
241 self.recover_leading_vert(None, "only allowed in a top-level pattern");
242 self.parse_pat_with_or(None, GateOr::Yes, RecoverComma::No)
245 /// Recover if `|` or `||` is here.
246 /// The user is thinking that a leading `|` is allowed in this position.
247 fn recover_leading_vert(&mut self, lo: Option<Span>, ctx: &str) {
248 if let token::BinOp(token::Or) | token::OrOr = self.token.kind {
249 self.ban_illegal_vert(lo, "leading", ctx);
254 /// A `|` or possibly `||` token shouldn't be here. Ban it.
255 fn ban_illegal_vert(&mut self, lo: Option<Span>, pos: &str, ctx: &str) {
256 let span = self.token.span;
257 let mut err = self.struct_span_err(span, &format!("a {} `|` is {}", pos, ctx));
260 &format!("remove the `{}`", pprust::token_to_string(&self.token)),
262 Applicability::MachineApplicable,
264 if let Some(lo) = lo {
265 err.span_label(lo, WHILE_PARSING_OR_MSG);
267 if let token::OrOr = self.token.kind {
268 err.note("alternatives in or-patterns are separated with `|`, not `||`");
273 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
275 fn parse_pat_with_range_pat(
277 allow_range_pat: bool,
279 ) -> PResult<'a, P<Pat>> {
280 maybe_recover_from_interpolated_ty_qpath!(self, true);
281 maybe_whole!(self, NtPat, |x| x);
283 let lo = self.token.span;
285 let pat = if self.check(&token::BinOp(token::And)) || self.token.kind == token::AndAnd {
286 self.parse_pat_deref(expected)?
287 } else if self.check(&token::OpenDelim(token::Paren)) {
288 self.parse_pat_tuple_or_parens()?
289 } else if self.check(&token::OpenDelim(token::Bracket)) {
290 // Parse `[pat, pat,...]` as a slice pattern.
292 self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat_with_or_inner())?;
294 } else if self.check(&token::DotDot) && !self.is_pat_range_end_start(1) {
295 // A rest pattern `..`.
298 } else if self.check(&token::DotDotDot) && !self.is_pat_range_end_start(1) {
299 self.recover_dotdotdot_rest_pat(lo)
300 } else if let Some(form) = self.parse_range_end() {
301 self.parse_pat_range_to(form)? // `..=X`, `...X`, or `..X`.
302 } else if self.eat_keyword(kw::Underscore) {
305 } else if self.eat_keyword(kw::Mut) {
306 self.parse_pat_ident_mut()?
307 } else if self.eat_keyword(kw::Ref) {
308 // Parse ref ident @ pat / ref mut ident @ pat
309 let mutbl = self.parse_mutability();
310 self.parse_pat_ident(BindingMode::ByRef(mutbl))?
311 } else if self.eat_keyword(kw::Box) {
313 let pat = self.parse_pat_with_range_pat(false, None)?;
314 self.sess.gated_spans.gate(sym::box_patterns, lo.to(self.prev_token.span));
316 } else if self.can_be_ident_pat() {
317 // Parse `ident @ pat`
318 // This can give false positives and parse nullary enums,
319 // they are dealt with later in resolve.
320 self.parse_pat_ident(BindingMode::ByValue(Mutability::Not))?
321 } else if self.is_start_of_pat_with_path() {
322 // Parse pattern starting with a path
323 let (qself, path) = if self.eat_lt() {
324 // Parse a qualified path
325 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
328 // Parse an unqualified path
329 (None, self.parse_path(PathStyle::Expr)?)
331 let span = lo.to(self.prev_token.span);
333 if qself.is_none() && self.check(&token::Not) {
334 self.parse_pat_mac_invoc(path)?
335 } else if let Some(form) = self.parse_range_end() {
336 let begin = self.mk_expr(span, ExprKind::Path(qself, path), AttrVec::new());
337 self.parse_pat_range_begin_with(begin, form)?
338 } else if self.check(&token::OpenDelim(token::Brace)) {
339 self.parse_pat_struct(qself, path)?
340 } else if self.check(&token::OpenDelim(token::Paren)) {
341 self.parse_pat_tuple_struct(qself, path)?
343 PatKind::Path(qself, path)
346 // Try to parse everything else as literal with optional minus
347 match self.parse_literal_maybe_minus() {
348 Ok(begin) => match self.parse_range_end() {
349 Some(form) => self.parse_pat_range_begin_with(begin, form)?,
350 None => PatKind::Lit(begin),
352 Err(err) => return self.fatal_unexpected_non_pat(err, expected),
356 let pat = self.mk_pat(lo.to(self.prev_token.span), pat);
357 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
358 let pat = self.recover_intersection_pat(pat)?;
360 if !allow_range_pat {
361 self.ban_pat_range_if_ambiguous(&pat)
367 /// Recover from a typoed `...` pattern that was encountered
368 /// Ref: Issue #70388
369 fn recover_dotdotdot_rest_pat(&mut self, lo: Span) -> PatKind {
370 // A typoed rest pattern `...`.
371 self.bump(); // `...`
373 // The user probably mistook `...` for a rest pattern `..`.
374 self.struct_span_err(lo, "unexpected `...`")
375 .span_label(lo, "not a valid pattern")
376 .span_suggestion_short(
378 "for a rest pattern, use `..` instead of `...`",
380 Applicability::MachineApplicable,
386 /// Try to recover the more general form `intersect ::= $pat_lhs @ $pat_rhs`.
388 /// Allowed binding patterns generated by `binding ::= ref? mut? $ident @ $pat_rhs`
389 /// should already have been parsed by now at this point,
390 /// if the next token is `@` then we can try to parse the more general form.
392 /// Consult `parse_pat_ident` for the `binding` grammar.
394 /// The notion of intersection patterns are found in
395 /// e.g. [F#][and] where they are called AND-patterns.
397 /// [and]: https://docs.microsoft.com/en-us/dotnet/fsharp/language-reference/pattern-matching
398 fn recover_intersection_pat(&mut self, lhs: P<Pat>) -> PResult<'a, P<Pat>> {
399 if self.token.kind != token::At {
400 // Next token is not `@` so it's not going to be an intersection pattern.
404 // At this point we attempt to parse `@ $pat_rhs` and emit an error.
406 let mut rhs = self.parse_pat(None)?;
407 let sp = lhs.span.to(rhs.span);
409 if let PatKind::Ident(_, _, ref mut sub @ None) = rhs.kind {
410 // The user inverted the order, so help them fix that.
411 let mut applicability = Applicability::MachineApplicable;
412 // FIXME(bindings_after_at): Remove this code when stabilizing the feature.
413 lhs.walk(&mut |p| match p.kind {
414 // `check_match` is unhappy if the subpattern has a binding anywhere.
415 PatKind::Ident(..) => {
416 applicability = Applicability::MaybeIncorrect;
417 false // Short-circuit.
422 let lhs_span = lhs.span;
423 // Move the LHS into the RHS as a subpattern.
424 // The RHS is now the full pattern.
427 self.struct_span_err(sp, "pattern on wrong side of `@`")
428 .span_label(lhs_span, "pattern on the left, should be on the right")
429 .span_label(rhs.span, "binding on the right, should be on the left")
430 .span_suggestion(sp, "switch the order", pprust::pat_to_string(&rhs), applicability)
433 // The special case above doesn't apply so we may have e.g. `A(x) @ B(y)`.
434 rhs.kind = PatKind::Wild;
435 self.struct_span_err(sp, "left-hand side of `@` must be a binding")
436 .span_label(lhs.span, "interpreted as a pattern, not a binding")
437 .span_label(rhs.span, "also a pattern")
438 .note("bindings are `x`, `mut x`, `ref x`, and `ref mut x`")
446 /// Ban a range pattern if it has an ambiguous interpretation.
447 fn ban_pat_range_if_ambiguous(&self, pat: &Pat) {
451 Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. },
453 PatKind::Range(..) => {}
457 self.struct_span_err(pat.span, "the range pattern here has ambiguous interpretation")
460 "add parentheses to clarify the precedence",
461 format!("({})", pprust::pat_to_string(&pat)),
462 // "ambiguous interpretation" implies that we have to be guessing
463 Applicability::MaybeIncorrect,
468 /// Parse `&pat` / `&mut pat`.
469 fn parse_pat_deref(&mut self, expected: Expected) -> PResult<'a, PatKind> {
471 self.recover_lifetime_in_deref_pat();
472 let mutbl = self.parse_mutability();
473 let subpat = self.parse_pat_with_range_pat(false, expected)?;
474 Ok(PatKind::Ref(subpat, mutbl))
477 fn recover_lifetime_in_deref_pat(&mut self) {
478 if let token::Lifetime(name) = self.token.kind {
481 let span = self.prev_token.span;
482 self.struct_span_err(span, &format!("unexpected lifetime `{}` in pattern", name))
485 "remove the lifetime",
487 Applicability::MachineApplicable,
493 /// Parse a tuple or parenthesis pattern.
494 fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
495 let (fields, trailing_comma) =
496 self.parse_paren_comma_seq(|p| p.parse_pat_with_or_inner())?;
498 // Here, `(pat,)` is a tuple pattern.
499 // For backward compatibility, `(..)` is a tuple pattern as well.
500 Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
501 PatKind::Paren(fields.into_iter().next().unwrap())
503 PatKind::Tuple(fields)
507 /// Parse a mutable binding with the `mut` token already eaten.
508 fn parse_pat_ident_mut(&mut self) -> PResult<'a, PatKind> {
509 let mut_span = self.prev_token.span;
511 if self.eat_keyword(kw::Ref) {
512 return self.recover_mut_ref_ident(mut_span);
515 self.recover_additional_muts();
517 // Make sure we don't allow e.g. `let mut $p;` where `$p:pat`.
518 if let token::Interpolated(ref nt) = self.token.kind {
519 if let token::NtPat(_) = **nt {
520 self.expected_ident_found().emit();
524 // Parse the pattern we hope to be an identifier.
525 let mut pat = self.parse_pat(Some("identifier"))?;
527 // If we don't have `mut $ident (@ pat)?`, error.
528 if let PatKind::Ident(BindingMode::ByValue(m @ Mutability::Not), ..) = &mut pat.kind {
529 // Don't recurse into the subpattern.
530 // `mut` on the outer binding doesn't affect the inner bindings.
531 *m = Mutability::Mut;
533 // Add `mut` to any binding in the parsed pattern.
534 let changed_any_binding = Self::make_all_value_bindings_mutable(&mut pat);
535 self.ban_mut_general_pat(mut_span, &pat, changed_any_binding);
538 Ok(pat.into_inner().kind)
541 /// Recover on `mut ref? ident @ pat` and suggest
542 /// that the order of `mut` and `ref` is incorrect.
543 fn recover_mut_ref_ident(&mut self, lo: Span) -> PResult<'a, PatKind> {
544 let mutref_span = lo.to(self.prev_token.span);
545 self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
548 "try switching the order",
550 Applicability::MachineApplicable,
554 self.parse_pat_ident(BindingMode::ByRef(Mutability::Mut))
557 /// Turn all by-value immutable bindings in a pattern into mutable bindings.
558 /// Returns `true` if any change was made.
559 fn make_all_value_bindings_mutable(pat: &mut P<Pat>) -> bool {
561 impl MutVisitor for AddMut {
562 fn visit_mac(&mut self, mac: &mut MacCall) {
563 noop_visit_mac(mac, self);
566 fn visit_pat(&mut self, pat: &mut P<Pat>) {
567 if let PatKind::Ident(BindingMode::ByValue(m @ Mutability::Not), ..) = &mut pat.kind
570 *m = Mutability::Mut;
572 noop_visit_pat(pat, self);
576 let mut add_mut = AddMut(false);
577 add_mut.visit_pat(pat);
581 /// Error on `mut $pat` where `$pat` is not an ident.
582 fn ban_mut_general_pat(&self, lo: Span, pat: &Pat, changed_any_binding: bool) {
583 let span = lo.to(pat.span);
584 let fix = pprust::pat_to_string(&pat);
585 let (problem, suggestion) = if changed_any_binding {
586 ("`mut` must be attached to each individual binding", "add `mut` to each binding")
588 ("`mut` must be followed by a named binding", "remove the `mut` prefix")
590 self.struct_span_err(span, problem)
591 .span_suggestion(span, suggestion, fix, Applicability::MachineApplicable)
592 .note("`mut` may be followed by `variable` and `variable @ pattern`")
596 /// Eat any extraneous `mut`s and error + recover if we ate any.
597 fn recover_additional_muts(&mut self) {
598 let lo = self.token.span;
599 while self.eat_keyword(kw::Mut) {}
600 if lo == self.token.span {
604 let span = lo.to(self.prev_token.span);
605 self.struct_span_err(span, "`mut` on a binding may not be repeated")
608 "remove the additional `mut`s",
610 Applicability::MachineApplicable,
615 /// Parse macro invocation
616 fn parse_pat_mac_invoc(&mut self, path: Path) -> PResult<'a, PatKind> {
618 let args = self.parse_mac_args()?;
619 let mac = MacCall { path, args, prior_type_ascription: self.last_type_ascription };
620 Ok(PatKind::MacCall(mac))
623 fn fatal_unexpected_non_pat(
625 mut err: DiagnosticBuilder<'a>,
627 ) -> PResult<'a, P<Pat>> {
630 let expected = expected.unwrap_or("pattern");
631 let msg = format!("expected {}, found {}", expected, super::token_descr(&self.token));
633 let mut err = self.struct_span_err(self.token.span, &msg);
634 err.span_label(self.token.span, format!("expected {}", expected));
636 let sp = self.sess.source_map().start_point(self.token.span);
637 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
638 self.sess.expr_parentheses_needed(&mut err, *sp, None);
644 /// Parses the range pattern end form `".." | "..." | "..=" ;`.
645 fn parse_range_end(&mut self) -> Option<Spanned<RangeEnd>> {
646 let re = if self.eat(&token::DotDotDot) {
647 RangeEnd::Included(RangeSyntax::DotDotDot)
648 } else if self.eat(&token::DotDotEq) {
649 RangeEnd::Included(RangeSyntax::DotDotEq)
650 } else if self.eat(&token::DotDot) {
651 self.sess.gated_spans.gate(sym::exclusive_range_pattern, self.prev_token.span);
656 Some(respan(self.prev_token.span, re))
659 /// Parse a range pattern `$begin $form $end?` where `$form = ".." | "..." | "..=" ;`.
660 /// `$begin $form` has already been parsed.
661 fn parse_pat_range_begin_with(
664 re: Spanned<RangeEnd>,
665 ) -> PResult<'a, PatKind> {
666 let end = if self.is_pat_range_end_start(0) {
667 // Parsing e.g. `X..=Y`.
668 Some(self.parse_pat_range_end()?)
670 // Parsing e.g. `X..`.
671 self.sess.gated_spans.gate(sym::half_open_range_patterns, begin.span.to(re.span));
672 if let RangeEnd::Included(_) = re.node {
673 // FIXME(Centril): Consider semantic errors instead in `ast_validation`.
674 // Possibly also do this for `X..=` in *expression* contexts.
675 self.error_inclusive_range_with_no_end(re.span);
679 Ok(PatKind::Range(Some(begin), end, re))
682 pub(super) fn error_inclusive_range_with_no_end(&self, span: Span) {
683 struct_span_err!(self.sess.span_diagnostic, span, E0586, "inclusive range with no end")
684 .span_suggestion_short(
688 Applicability::MachineApplicable,
690 .note("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)")
694 /// Parse a range-to pattern, `..X` or `..=X` where `X` remains to be parsed.
696 /// The form `...X` is prohibited to reduce confusion with the potential
697 /// expression syntax `...expr` for splatting in expressions.
698 fn parse_pat_range_to(&mut self, mut re: Spanned<RangeEnd>) -> PResult<'a, PatKind> {
699 let end = self.parse_pat_range_end()?;
700 self.sess.gated_spans.gate(sym::half_open_range_patterns, re.span.to(self.prev_token.span));
701 if let RangeEnd::Included(ref mut syn @ RangeSyntax::DotDotDot) = &mut re.node {
702 *syn = RangeSyntax::DotDotEq;
703 self.struct_span_err(re.span, "range-to patterns with `...` are not allowed")
704 .span_suggestion_short(
708 Applicability::MachineApplicable,
712 Ok(PatKind::Range(None, Some(end), re))
715 /// Is the token `dist` away from the current suitable as the start of a range patterns end?
716 fn is_pat_range_end_start(&self, dist: usize) -> bool {
717 self.look_ahead(dist, |t| {
718 t.is_path_start() // e.g. `MY_CONST`;
719 || t.kind == token::Dot // e.g. `.5` for recovery;
720 || t.can_begin_literal_maybe_minus() // e.g. `42`.
725 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
726 if self.check_path() {
727 let lo = self.token.span;
728 let (qself, path) = if self.eat_lt() {
729 // Parse a qualified path
730 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
733 // Parse an unqualified path
734 (None, self.parse_path(PathStyle::Expr)?)
736 let hi = self.prev_token.span;
737 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), AttrVec::new()))
739 self.parse_literal_maybe_minus()
743 /// Is this the start of a pattern beginning with a path?
744 fn is_start_of_pat_with_path(&mut self) -> bool {
746 // Just for recovery (see `can_be_ident`).
747 || self.token.is_ident() && !self.token.is_bool_lit() && !self.token.is_keyword(kw::In)
750 /// Would `parse_pat_ident` be appropriate here?
751 fn can_be_ident_pat(&mut self) -> bool {
753 && !self.token.is_bool_lit() // Avoid `true` or `false` as a binding as it is a literal.
754 && !self.token.is_path_segment_keyword() // Avoid e.g. `Self` as it is a path.
755 // Avoid `in`. Due to recovery in the list parser this messes with `for ( $pat in $expr )`.
756 && !self.token.is_keyword(kw::In)
757 && self.look_ahead(1, |t| match t.kind { // Try to do something more complex?
758 token::OpenDelim(token::Paren) // A tuple struct pattern.
759 | token::OpenDelim(token::Brace) // A struct pattern.
760 | token::DotDotDot | token::DotDotEq | token::DotDot // A range pattern.
761 | token::ModSep // A tuple / struct variant pattern.
762 | token::Not => false, // A macro expanding to a pattern.
767 /// Parses `ident` or `ident @ pat`.
768 /// Used by the copy foo and ref foo patterns to give a good
769 /// error message when parsing mistakes like `ref foo(a, b)`.
770 fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
771 let ident = self.parse_ident()?;
772 let sub = if self.eat(&token::At) {
773 Some(self.parse_pat(Some("binding pattern"))?)
778 // Just to be friendly, if they write something like `ref Some(i)`,
779 // we end up here with `(` as the current token.
780 // This shortly leads to a parse error. Note that if there is no explicit
781 // binding mode then we do not end up here, because the lookahead
782 // will direct us over to `parse_enum_variant()`.
783 if self.token == token::OpenDelim(token::Paren) {
785 .struct_span_err(self.prev_token.span, "expected identifier, found enum pattern"));
788 Ok(PatKind::Ident(binding_mode, ident, sub))
791 /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
792 fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
794 return self.error_qpath_before_pat(&path, "{");
797 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
803 Ok(PatKind::Struct(path, fields, etc))
806 /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
807 fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
809 return self.error_qpath_before_pat(&path, "(");
811 let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat_with_or_inner())?;
812 Ok(PatKind::TupleStruct(path, fields))
815 /// Error when there's a qualified path, e.g. `<Foo as Bar>::Baz`
816 /// as the path of e.g., a tuple or record struct pattern.
817 fn error_qpath_before_pat(&mut self, path: &Path, token: &str) -> PResult<'a, PatKind> {
818 let msg = &format!("unexpected `{}` after qualified path", token);
819 let mut err = self.struct_span_err(self.token.span, msg);
820 err.span_label(self.token.span, msg);
821 err.span_label(path.span, "the qualified path");
825 /// Parses the fields of a struct-like pattern.
826 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<FieldPat>, bool)> {
827 let mut fields = Vec::new();
829 let mut ate_comma = true;
830 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
831 let mut etc_span = None;
833 while self.token != token::CloseDelim(token::Brace) {
834 let attrs = match self.parse_outer_attributes() {
837 if let Some(mut delayed) = delayed_err {
843 let lo = self.token.span;
845 // check that a comma comes after every field
847 let err = self.struct_span_err(self.prev_token.span, "expected `,`");
848 if let Some(mut delayed) = delayed_err {
855 if self.check(&token::DotDot) || self.token == token::DotDotDot {
857 let mut etc_sp = self.token.span;
859 self.recover_one_fewer_dotdot();
860 self.bump(); // `..` || `...`
862 if self.token == token::CloseDelim(token::Brace) {
863 etc_span = Some(etc_sp);
866 let token_str = super::token_descr(&self.token);
867 let msg = &format!("expected `}}`, found {}", token_str);
868 let mut err = self.struct_span_err(self.token.span, msg);
870 err.span_label(self.token.span, "expected `}`");
871 let mut comma_sp = None;
872 if self.token == token::Comma {
874 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
875 etc_sp = etc_sp.to(nw_span);
878 "`..` must be at the end and cannot have a trailing comma",
880 comma_sp = Some(self.token.span);
885 etc_span = Some(etc_sp.until(self.token.span));
886 if self.token == token::CloseDelim(token::Brace) {
887 // If the struct looks otherwise well formed, recover and continue.
888 if let Some(sp) = comma_sp {
889 err.span_suggestion_short(
893 Applicability::MachineApplicable,
898 } else if self.token.is_ident() && ate_comma {
899 // Accept fields coming after `..,`.
900 // This way we avoid "pattern missing fields" errors afterwards.
901 // We delay this error until the end in order to have a span for a
903 if let Some(mut delayed_err) = delayed_err {
907 delayed_err = Some(err);
910 if let Some(mut err) = delayed_err {
917 fields.push(match self.parse_pat_field(lo, attrs) {
920 if let Some(mut delayed_err) = delayed_err {
926 ate_comma = self.eat(&token::Comma);
929 if let Some(mut err) = delayed_err {
930 if let Some(etc_span) = etc_span {
931 err.multipart_suggestion(
932 "move the `..` to the end of the field list",
934 (etc_span, String::new()),
935 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
937 Applicability::MachineApplicable,
945 /// Recover on `...` as if it were `..` to avoid further errors.
946 /// See issue #46718.
947 fn recover_one_fewer_dotdot(&self) {
948 if self.token != token::DotDotDot {
952 self.struct_span_err(self.token.span, "expected field pattern, found `...`")
955 "to omit remaining fields, use one fewer `.`",
957 Applicability::MachineApplicable,
962 fn parse_pat_field(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, FieldPat> {
963 // Check if a colon exists one ahead. This means we're parsing a fieldname.
965 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
966 // Parsing a pattern of the form `fieldname: pat`.
967 let fieldname = self.parse_field_name()?;
969 let pat = self.parse_pat_with_or_inner()?;
971 (pat, fieldname, false)
973 // Parsing a pattern of the form `(box) (ref) (mut) fieldname`.
974 let is_box = self.eat_keyword(kw::Box);
975 let boxed_span = self.token.span;
976 let is_ref = self.eat_keyword(kw::Ref);
977 let is_mut = self.eat_keyword(kw::Mut);
978 let fieldname = self.parse_ident()?;
979 hi = self.prev_token.span;
981 let bind_type = match (is_ref, is_mut) {
982 (true, true) => BindingMode::ByRef(Mutability::Mut),
983 (true, false) => BindingMode::ByRef(Mutability::Not),
984 (false, true) => BindingMode::ByValue(Mutability::Mut),
985 (false, false) => BindingMode::ByValue(Mutability::Not),
988 let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
990 if is_box { self.mk_pat(lo.to(hi), PatKind::Box(fieldpat)) } else { fieldpat };
991 (subpat, fieldname, true)
999 id: ast::DUMMY_NODE_ID,
1001 is_placeholder: false,
1005 pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
1006 self.mk_pat(span, PatKind::Ident(bm, ident, None))
1009 fn mk_pat(&self, span: Span, kind: PatKind) -> P<Pat> {
1010 P(Pat { kind, span, id: ast::DUMMY_NODE_ID })