1 use super::{Parser, PResult, PathStyle};
3 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
5 use crate::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
6 use crate::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
7 use crate::parse::token::{self};
8 use crate::print::pprust;
9 use crate::source_map::{respan, Span, Spanned};
10 use crate::symbol::kw;
13 use errors::{Applicability, DiagnosticBuilder};
15 type Expected = Option<&'static str>;
19 pub fn parse_pat(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
20 self.parse_pat_with_range_pat(true, expected)
23 /// Parses patterns, separated by '|' s.
24 pub(super) fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
25 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
26 self.eat(&token::BinOp(token::Or));
28 let mut pats = Vec::new();
30 pats.push(self.parse_top_level_pat()?);
32 if self.token == token::OrOr {
33 self.ban_unexpected_or_or();
35 } else if self.eat(&token::BinOp(token::Or)) {
36 // This is a No-op. Continue the loop to parse the next
44 fn ban_unexpected_or_or(&mut self) {
45 self.struct_span_err(self.token.span, "unexpected token `||` after pattern")
48 "use a single `|` to specify multiple patterns",
50 Applicability::MachineApplicable
55 /// A wrapper around `parse_pat` with some special error handling for the
56 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
57 /// to subpatterns within such).
58 pub(super) fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
59 let pat = self.parse_pat(None)?;
60 if self.token == token::Comma {
61 // An unexpected comma after a top-level pattern is a clue that the
62 // user (perhaps more accustomed to some other language) forgot the
63 // parentheses in what should have been a tuple pattern; return a
64 // suggestion-enhanced error here rather than choking on the comma
66 let comma_span = self.token.span;
68 if let Err(mut err) = self.skip_pat_list() {
69 // We didn't expect this to work anyway; we just wanted
70 // to advance to the end of the comma-sequence so we know
71 // the span to suggest parenthesizing
74 let seq_span = pat.span.to(self.prev_span);
75 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
76 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
79 "try adding parentheses to match on a tuple..",
80 format!("({})", seq_snippet),
81 Applicability::MachineApplicable
84 "..or a vertical bar to match on multiple alternatives",
85 format!("{}", seq_snippet.replace(",", " |")),
86 Applicability::MachineApplicable
94 /// Parse and throw away a parentesized comma separated
95 /// sequence of patterns until `)` is reached.
96 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
97 while !self.check(&token::CloseDelim(token::Paren)) {
98 self.parse_pat(None)?;
99 if !self.eat(&token::Comma) {
106 /// Parses a pattern, that may be a or-pattern (e.g. `Some(Foo | Bar)`).
107 fn parse_pat_with_or(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
108 // Parse the first pattern.
109 let first_pat = self.parse_pat(expected)?;
111 // If the next token is not a `|`, this is not an or-pattern and
112 // we should exit here.
113 if !self.check(&token::BinOp(token::Or)) {
117 let lo = first_pat.span;
119 let mut pats = vec![first_pat];
121 while self.eat(&token::BinOp(token::Or)) {
122 pats.push(self.parse_pat_with_range_pat(true, expected)?);
125 let or_pattern_span = lo.to(self.prev_span);
127 self.sess.gated_spans.or_patterns.borrow_mut().push(or_pattern_span);
129 Ok(self.mk_pat(or_pattern_span, PatKind::Or(pats)))
132 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
134 fn parse_pat_with_range_pat(
136 allow_range_pat: bool,
138 ) -> PResult<'a, P<Pat>> {
139 maybe_recover_from_interpolated_ty_qpath!(self, true);
140 maybe_whole!(self, NtPat, |x| x);
142 let lo = self.token.span;
143 let pat = match self.token.kind {
144 token::BinOp(token::And) | token::AndAnd => self.parse_pat_deref(expected)?,
145 token::OpenDelim(token::Paren) => self.parse_pat_tuple_or_parens()?,
146 token::OpenDelim(token::Bracket) => {
147 // Parse `[pat, pat,...]` as a slice pattern.
148 PatKind::Slice(self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat(None))?.0)
152 if self.is_pat_range_end_start() {
153 // Parse `..42` for recovery.
154 self.parse_pat_range_to(RangeEnd::Excluded, "..")?
156 // A rest pattern `..`.
161 // Parse `..=42` for recovery.
163 self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?
165 token::DotDotDot => {
166 // Parse `...42` for recovery.
168 self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?
170 // At this point, token != &, &&, (, [
171 _ => if self.eat_keyword(kw::Underscore) {
174 } else if self.eat_keyword(kw::Mut) {
175 self.recover_pat_ident_mut_first()?
176 } else if self.eat_keyword(kw::Ref) {
177 // Parse ref ident @ pat / ref mut ident @ pat
178 let mutbl = self.parse_mutability();
179 self.parse_pat_ident(BindingMode::ByRef(mutbl))?
180 } else if self.eat_keyword(kw::Box) {
182 PatKind::Box(self.parse_pat_with_range_pat(false, None)?)
183 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
184 self.parse_as_ident() {
185 // Parse `ident @ pat`
186 // This can give false positives and parse nullary enums,
187 // they are dealt with later in resolve.
188 self.parse_pat_ident(BindingMode::ByValue(Mutability::Immutable))?
189 } else if self.token.is_path_start() {
190 // Parse pattern starting with a path
191 let (qself, path) = if self.eat_lt() {
192 // Parse a qualified path
193 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
196 // Parse an unqualified path
197 (None, self.parse_path(PathStyle::Expr)?)
199 match self.token.kind {
200 token::Not if qself.is_none() => self.parse_pat_mac_invoc(lo, path)?,
201 token::DotDotDot | token::DotDotEq | token::DotDot => {
202 self.parse_pat_range_starting_with_path(lo, qself, path)?
204 token::OpenDelim(token::Brace) => self.parse_pat_struct(qself, path)?,
205 token::OpenDelim(token::Paren) => self.parse_pat_tuple_struct(qself, path)?,
206 _ => PatKind::Path(qself, path),
209 // Try to parse everything else as literal with optional minus
210 match self.parse_literal_maybe_minus() {
212 if self.check(&token::DotDot)
213 || self.check(&token::DotDotEq)
214 || self.check(&token::DotDotDot) =>
216 self.parse_pat_range_starting_with_lit(begin)?
218 Ok(begin) => PatKind::Lit(begin),
219 Err(err) => return self.fatal_unexpected_non_pat(err, expected),
224 let pat = self.mk_pat(lo.to(self.prev_span), pat);
225 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
227 if !allow_range_pat {
228 self.ban_pat_range_if_ambiguous(&pat)?
234 /// Ban a range pattern if it has an ambiguous interpretation.
235 fn ban_pat_range_if_ambiguous(&self, pat: &Pat) -> PResult<'a, ()> {
238 .., Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
240 PatKind::Range(..) => {}
244 let mut err = self.struct_span_err(
246 "the range pattern here has ambiguous interpretation",
250 "add parentheses to clarify the precedence",
251 format!("({})", pprust::pat_to_string(&pat)),
252 // "ambiguous interpretation" implies that we have to be guessing
253 Applicability::MaybeIncorrect
258 /// Parse `&pat` / `&mut pat`.
259 fn parse_pat_deref(&mut self, expected: Expected) -> PResult<'a, PatKind> {
261 let mutbl = self.parse_mutability();
263 if let token::Lifetime(name) = self.token.kind {
264 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
265 err.span_label(self.token.span, "unexpected lifetime");
269 let subpat = self.parse_pat_with_range_pat(false, expected)?;
270 Ok(PatKind::Ref(subpat, mutbl))
273 /// Parse a tuple or parenthesis pattern.
274 fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
275 let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| {
276 p.parse_pat_with_or(None)
279 // Here, `(pat,)` is a tuple pattern.
280 // For backward compatibility, `(..)` is a tuple pattern as well.
281 Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
282 PatKind::Paren(fields.into_iter().nth(0).unwrap())
284 PatKind::Tuple(fields)
288 /// Recover on `mut ref? ident @ pat` and suggest
289 /// that the order of `mut` and `ref` is incorrect.
290 fn recover_pat_ident_mut_first(&mut self) -> PResult<'a, PatKind> {
291 let mutref_span = self.prev_span.to(self.token.span);
292 let binding_mode = if self.eat_keyword(kw::Ref) {
293 self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
296 "try switching the order",
298 Applicability::MachineApplicable
301 BindingMode::ByRef(Mutability::Mutable)
303 BindingMode::ByValue(Mutability::Mutable)
305 self.parse_pat_ident(binding_mode)
308 /// Parse macro invocation
309 fn parse_pat_mac_invoc(&mut self, lo: Span, path: Path) -> PResult<'a, PatKind> {
311 let (delim, tts) = self.expect_delimited_token_tree()?;
316 span: lo.to(self.prev_span),
317 prior_type_ascription: self.last_type_ascription,
319 Ok(PatKind::Mac(mac))
322 /// Parse a range pattern `$path $form $end?` where `$form = ".." | "..." | "..=" ;`.
323 /// The `$path` has already been parsed and the next token is the `$form`.
324 fn parse_pat_range_starting_with_path(
327 qself: Option<QSelf>,
329 ) -> PResult<'a, PatKind> {
330 let (end_kind, form) = match self.token.kind {
331 token::DotDot => (RangeEnd::Excluded, ".."),
332 token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
333 token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
334 _ => panic!("can only parse `..`/`...`/`..=` for ranges (checked above)"),
336 let op_span = self.token.span;
338 let span = lo.to(self.prev_span);
339 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
341 let end = self.parse_pat_range_end_opt(&begin, form)?;
342 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
345 /// Parse a range pattern `$literal $form $end?` where `$form = ".." | "..." | "..=" ;`.
346 /// The `$path` has already been parsed and the next token is the `$form`.
347 fn parse_pat_range_starting_with_lit(&mut self, begin: P<Expr>) -> PResult<'a, PatKind> {
348 let op_span = self.token.span;
349 let (end_kind, form) = if self.eat(&token::DotDotDot) {
350 (RangeEnd::Included(RangeSyntax::DotDotDot), "...")
351 } else if self.eat(&token::DotDotEq) {
352 (RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
353 } else if self.eat(&token::DotDot) {
354 (RangeEnd::Excluded, "..")
356 panic!("impossible case: we already matched on a range-operator token")
358 let end = self.parse_pat_range_end_opt(&begin, form)?;
359 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
362 fn fatal_unexpected_non_pat(
364 mut err: DiagnosticBuilder<'a>,
366 ) -> PResult<'a, P<Pat>> {
367 self.cancel(&mut err);
369 let expected = expected.unwrap_or("pattern");
370 let msg = format!("expected {}, found {}", expected, self.this_token_descr());
372 let mut err = self.fatal(&msg);
373 err.span_label(self.token.span, format!("expected {}", expected));
375 let sp = self.sess.source_map().start_point(self.token.span);
376 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
377 self.sess.expr_parentheses_needed(&mut err, *sp, None);
383 // Helper function to decide whether to parse as ident binding
384 // or to try to do something more complex like range patterns.
385 fn parse_as_ident(&mut self) -> bool {
386 self.look_ahead(1, |t| match t.kind {
387 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
388 token::DotDotDot | token::DotDotEq | token::DotDot |
389 token::ModSep | token::Not => false,
394 /// Is the current token suitable as the start of a range patterns end?
395 fn is_pat_range_end_start(&self) -> bool {
396 self.token.is_path_start() // e.g. `MY_CONST`;
397 || self.token == token::Dot // e.g. `.5` for recovery;
398 || self.token.can_begin_literal_or_bool() // e.g. `42`.
399 || self.token.is_whole_expr()
402 /// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
403 fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
404 let lo = self.prev_span;
405 let end = self.parse_pat_range_end()?;
406 let range_span = lo.to(end.span);
407 let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
410 .struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
413 "try using the minimum value for the type",
414 format!("MIN{}{}", form, pprust::expr_to_string(&end)),
415 Applicability::HasPlaceholders,
419 Ok(PatKind::Range(begin, end, respan(lo, re)))
422 /// Parse the end of a `X..Y`, `X..=Y`, or `X...Y` range pattern or recover
423 /// if that end is missing treating it as `X..`, `X..=`, or `X...` respectively.
424 fn parse_pat_range_end_opt(&mut self, begin: &Expr, form: &str) -> PResult<'a, P<Expr>> {
425 if self.is_pat_range_end_start() {
426 // Parsing e.g. `X..=Y`.
427 self.parse_pat_range_end()
429 // Parsing e.g. `X..`.
430 let range_span = begin.span.to(self.prev_span);
435 &format!("`X{}` range patterns are not supported", form),
439 "try using the maximum value for the type",
440 format!("{}{}MAX", pprust::expr_to_string(&begin), form),
441 Applicability::HasPlaceholders,
445 Ok(self.mk_expr(range_span, ExprKind::Err, ThinVec::new()))
449 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
450 if self.token.is_path_start() {
451 let lo = self.token.span;
452 let (qself, path) = if self.eat_lt() {
453 // Parse a qualified path
454 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
457 // Parse an unqualified path
458 (None, self.parse_path(PathStyle::Expr)?)
460 let hi = self.prev_span;
461 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
463 self.parse_literal_maybe_minus()
467 /// Parses `ident` or `ident @ pat`.
468 /// Used by the copy foo and ref foo patterns to give a good
469 /// error message when parsing mistakes like `ref foo(a, b)`.
470 fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
471 let ident = self.parse_ident()?;
472 let sub = if self.eat(&token::At) {
473 Some(self.parse_pat(Some("binding pattern"))?)
478 // Just to be friendly, if they write something like `ref Some(i)`,
479 // we end up here with `(` as the current token.
480 // This shortly leads to a parse error. Note that if there is no explicit
481 // binding mode then we do not end up here, because the lookahead
482 // will direct us over to `parse_enum_variant()`.
483 if self.token == token::OpenDelim(token::Paren) {
484 return Err(self.span_fatal(
486 "expected identifier, found enum pattern",
490 Ok(PatKind::Ident(binding_mode, ident, sub))
493 /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
494 fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
496 let msg = "unexpected `{` after qualified path";
497 let mut err = self.fatal(msg);
498 err.span_label(self.token.span, msg);
503 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
509 Ok(PatKind::Struct(path, fields, etc))
512 /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
513 fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
515 let msg = "unexpected `(` after qualified path";
516 let mut err = self.fatal(msg);
517 err.span_label(self.token.span, msg);
520 let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat_with_or(None))?;
521 Ok(PatKind::TupleStruct(path, fields))
524 /// Parses the fields of a struct-like pattern.
525 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<FieldPat>, bool)> {
526 let mut fields = Vec::new();
528 let mut ate_comma = true;
529 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
530 let mut etc_span = None;
532 while self.token != token::CloseDelim(token::Brace) {
533 let attrs = match self.parse_outer_attributes() {
536 if let Some(mut delayed) = delayed_err {
542 let lo = self.token.span;
544 // check that a comma comes after every field
546 let err = self.struct_span_err(self.prev_span, "expected `,`");
547 if let Some(mut delayed) = delayed_err {
554 if self.check(&token::DotDot) || self.token == token::DotDotDot {
556 let mut etc_sp = self.token.span;
558 self.recover_one_fewer_dotdot();
559 self.bump(); // `..` || `...`
561 if self.token == token::CloseDelim(token::Brace) {
562 etc_span = Some(etc_sp);
565 let token_str = self.this_token_descr();
566 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
568 err.span_label(self.token.span, "expected `}`");
569 let mut comma_sp = None;
570 if self.token == token::Comma { // Issue #49257
571 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
572 etc_sp = etc_sp.to(nw_span);
573 err.span_label(etc_sp,
574 "`..` must be at the end and cannot have a trailing comma");
575 comma_sp = Some(self.token.span);
580 etc_span = Some(etc_sp.until(self.token.span));
581 if self.token == token::CloseDelim(token::Brace) {
582 // If the struct looks otherwise well formed, recover and continue.
583 if let Some(sp) = comma_sp {
584 err.span_suggestion_short(
588 Applicability::MachineApplicable,
593 } else if self.token.is_ident() && ate_comma {
594 // Accept fields coming after `..,`.
595 // This way we avoid "pattern missing fields" errors afterwards.
596 // We delay this error until the end in order to have a span for a
598 if let Some(mut delayed_err) = delayed_err {
602 delayed_err = Some(err);
605 if let Some(mut err) = delayed_err {
612 fields.push(match self.parse_pat_field(lo, attrs) {
615 if let Some(mut delayed_err) = delayed_err {
621 ate_comma = self.eat(&token::Comma);
624 if let Some(mut err) = delayed_err {
625 if let Some(etc_span) = etc_span {
626 err.multipart_suggestion(
627 "move the `..` to the end of the field list",
629 (etc_span, String::new()),
630 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
632 Applicability::MachineApplicable,
637 return Ok((fields, etc));
640 /// Recover on `...` as if it were `..` to avoid further errors.
641 /// See issue #46718.
642 fn recover_one_fewer_dotdot(&self) {
643 if self.token != token::DotDotDot {
647 self.struct_span_err(self.token.span, "expected field pattern, found `...`")
650 "to omit remaining fields, use one fewer `.`",
652 Applicability::MachineApplicable
657 fn parse_pat_field(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, FieldPat> {
658 // Check if a colon exists one ahead. This means we're parsing a fieldname.
660 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
661 // Parsing a pattern of the form "fieldname: pat"
662 let fieldname = self.parse_field_name()?;
664 let pat = self.parse_pat_with_or(None)?;
666 (pat, fieldname, false)
668 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
669 let is_box = self.eat_keyword(kw::Box);
670 let boxed_span = self.token.span;
671 let is_ref = self.eat_keyword(kw::Ref);
672 let is_mut = self.eat_keyword(kw::Mut);
673 let fieldname = self.parse_ident()?;
676 let bind_type = match (is_ref, is_mut) {
677 (true, true) => BindingMode::ByRef(Mutability::Mutable),
678 (true, false) => BindingMode::ByRef(Mutability::Immutable),
679 (false, true) => BindingMode::ByValue(Mutability::Mutable),
680 (false, false) => BindingMode::ByValue(Mutability::Immutable),
683 let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
684 let subpat = if is_box {
685 self.mk_pat(lo.to(hi), PatKind::Box(fieldpat))
689 (subpat, fieldname, true)
697 id: ast::DUMMY_NODE_ID,
702 pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
703 self.mk_pat(span, PatKind::Ident(bm, ident, None))
706 fn mk_pat(&self, span: Span, node: PatKind) -> P<Pat> {
707 P(Pat { node, span, id: ast::DUMMY_NODE_ID })