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};
17 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
18 self.parse_pat_with_range_pat(true, expected)
21 /// Parses patterns, separated by '|' s.
22 pub(super) fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
23 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
24 self.eat(&token::BinOp(token::Or));
26 let mut pats = Vec::new();
28 pats.push(self.parse_top_level_pat()?);
30 if self.token == token::OrOr {
31 self.struct_span_err(self.token.span, "unexpected token `||` after pattern")
34 "use a single `|` to specify multiple patterns",
36 Applicability::MachineApplicable
40 } else if self.eat(&token::BinOp(token::Or)) {
41 // This is a No-op. Continue the loop to parse the next
49 /// A wrapper around `parse_pat` with some special error handling for the
50 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
51 /// to subpatterns within such).
52 pub(super) fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
53 let pat = self.parse_pat(None)?;
54 if self.token == token::Comma {
55 // An unexpected comma after a top-level pattern is a clue that the
56 // user (perhaps more accustomed to some other language) forgot the
57 // parentheses in what should have been a tuple pattern; return a
58 // suggestion-enhanced error here rather than choking on the comma
60 let comma_span = self.token.span;
62 if let Err(mut err) = self.skip_pat_list() {
63 // We didn't expect this to work anyway; we just wanted
64 // to advance to the end of the comma-sequence so we know
65 // the span to suggest parenthesizing
68 let seq_span = pat.span.to(self.prev_span);
69 let mut err = self.struct_span_err(comma_span, "unexpected `,` in pattern");
70 if let Ok(seq_snippet) = self.span_to_snippet(seq_span) {
73 "try adding parentheses to match on a tuple..",
74 format!("({})", seq_snippet),
75 Applicability::MachineApplicable
78 "..or a vertical bar to match on multiple alternatives",
79 format!("{}", seq_snippet.replace(",", " |")),
80 Applicability::MachineApplicable
88 /// Parse and throw away a parentesized comma separated
89 /// sequence of patterns until `)` is reached.
90 fn skip_pat_list(&mut self) -> PResult<'a, ()> {
91 while !self.check(&token::CloseDelim(token::Paren)) {
92 self.parse_pat(None)?;
93 if !self.eat(&token::Comma) {
100 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
102 fn parse_pat_with_range_pat(
104 allow_range_pat: bool,
105 expected: Option<&'static str>,
106 ) -> PResult<'a, P<Pat>> {
107 maybe_recover_from_interpolated_ty_qpath!(self, true);
108 maybe_whole!(self, NtPat, |x| x);
110 let lo = self.token.span;
111 let pat = match self.token.kind {
112 token::BinOp(token::And) | token::AndAnd => self.parse_pat_deref(expected)?,
113 token::OpenDelim(token::Paren) => self.parse_pat_tuple_or_parens()?,
114 token::OpenDelim(token::Bracket) => {
115 // Parse `[pat, pat,...]` as a slice pattern.
116 PatKind::Slice(self.parse_delim_comma_seq(token::Bracket, |p| p.parse_pat(None))?.0)
120 if self.is_pat_range_end_start() {
121 // Parse `..42` for recovery.
122 self.parse_pat_range_to(RangeEnd::Excluded, "..")?
124 // A rest pattern `..`.
129 // Parse `..=42` for recovery.
131 self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotEq), "..=")?
133 token::DotDotDot => {
134 // Parse `...42` for recovery.
136 self.parse_pat_range_to(RangeEnd::Included(RangeSyntax::DotDotDot), "...")?
138 // At this point, token != &, &&, (, [
139 _ => if self.eat_keyword(kw::Underscore) {
142 } else if self.eat_keyword(kw::Mut) {
143 self.recover_pat_ident_mut_first()?
144 } else if self.eat_keyword(kw::Ref) {
145 // Parse ref ident @ pat / ref mut ident @ pat
146 let mutbl = self.parse_mutability();
147 self.parse_pat_ident(BindingMode::ByRef(mutbl))?
148 } else if self.eat_keyword(kw::Box) {
150 PatKind::Box(self.parse_pat_with_range_pat(false, None)?)
151 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
152 self.parse_as_ident() {
153 // Parse `ident @ pat`
154 // This can give false positives and parse nullary enums,
155 // they are dealt with later in resolve.
156 self.parse_pat_ident(BindingMode::ByValue(Mutability::Immutable))?
157 } else if self.token.is_path_start() {
158 // Parse pattern starting with a path
159 let (qself, path) = if self.eat_lt() {
160 // Parse a qualified path
161 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
164 // Parse an unqualified path
165 (None, self.parse_path(PathStyle::Expr)?)
167 match self.token.kind {
168 token::Not if qself.is_none() => self.parse_pat_mac_invoc(lo, path)?,
169 token::DotDotDot | token::DotDotEq | token::DotDot => {
170 self.parse_pat_range_starting_with_path(lo, qself, path)?
172 token::OpenDelim(token::Brace) => self.parse_pat_struct(qself, path)?,
173 token::OpenDelim(token::Paren) => self.parse_pat_tuple_struct(qself, path)?,
174 _ => PatKind::Path(qself, path),
177 // Try to parse everything else as literal with optional minus
178 match self.parse_literal_maybe_minus() {
180 if self.check(&token::DotDot)
181 || self.check(&token::DotDotEq)
182 || self.check(&token::DotDotDot) =>
184 self.parse_pat_range_starting_with_lit(begin)?
186 Ok(begin) => PatKind::Lit(begin),
187 Err(err) => return self.fatal_unexpected_non_pat(err, expected),
192 let pat = self.mk_pat(lo.to(self.prev_span), pat);
193 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
195 if !allow_range_pat {
196 self.ban_pat_range_if_ambiguous(&pat)?
202 /// Ban a range pattern if it has an ambiguous interpretation.
203 fn ban_pat_range_if_ambiguous(&self, pat: &Pat) -> PResult<'a, ()> {
206 .., Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
208 PatKind::Range(..) => {}
212 let mut err = self.struct_span_err(
214 "the range pattern here has ambiguous interpretation",
218 "add parentheses to clarify the precedence",
219 format!("({})", pprust::pat_to_string(&pat)),
220 // "ambiguous interpretation" implies that we have to be guessing
221 Applicability::MaybeIncorrect
226 /// Parse `&pat` / `&mut pat`.
227 fn parse_pat_deref(&mut self, expected: Option<&'static str>) -> PResult<'a, PatKind> {
229 let mutbl = self.parse_mutability();
231 if let token::Lifetime(name) = self.token.kind {
232 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
233 err.span_label(self.token.span, "unexpected lifetime");
237 let subpat = self.parse_pat_with_range_pat(false, expected)?;
238 Ok(PatKind::Ref(subpat, mutbl))
241 /// Parse a tuple or parenthesis pattern.
242 fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
243 let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
245 // Here, `(pat,)` is a tuple pattern.
246 // For backward compatibility, `(..)` is a tuple pattern as well.
247 Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
248 PatKind::Paren(fields.into_iter().nth(0).unwrap())
250 PatKind::Tuple(fields)
254 /// Recover on `mut ref? ident @ pat` and suggest
255 /// that the order of `mut` and `ref` is incorrect.
256 fn recover_pat_ident_mut_first(&mut self) -> PResult<'a, PatKind> {
257 let mutref_span = self.prev_span.to(self.token.span);
258 let binding_mode = if self.eat_keyword(kw::Ref) {
259 self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
262 "try switching the order",
264 Applicability::MachineApplicable
267 BindingMode::ByRef(Mutability::Mutable)
269 BindingMode::ByValue(Mutability::Mutable)
271 self.parse_pat_ident(binding_mode)
274 /// Parse macro invocation
275 fn parse_pat_mac_invoc(&mut self, lo: Span, path: Path) -> PResult<'a, PatKind> {
277 let (delim, tts) = self.expect_delimited_token_tree()?;
282 span: lo.to(self.prev_span),
283 prior_type_ascription: self.last_type_ascription,
285 Ok(PatKind::Mac(mac))
288 /// Parse a range pattern `$path $form $end?` where `$form = ".." | "..." | "..=" ;`.
289 /// The `$path` has already been parsed and the next token is the `$form`.
290 fn parse_pat_range_starting_with_path(
293 qself: Option<QSelf>,
295 ) -> PResult<'a, PatKind> {
296 let (end_kind, form) = match self.token.kind {
297 token::DotDot => (RangeEnd::Excluded, ".."),
298 token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
299 token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
300 _ => panic!("can only parse `..`/`...`/`..=` for ranges (checked above)"),
302 let op_span = self.token.span;
304 let span = lo.to(self.prev_span);
305 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
307 let end = self.parse_pat_range_end_opt(&begin, form)?;
308 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
311 /// Parse a range pattern `$literal $form $end?` where `$form = ".." | "..." | "..=" ;`.
312 /// The `$path` has already been parsed and the next token is the `$form`.
313 fn parse_pat_range_starting_with_lit(&mut self, begin: P<Expr>) -> PResult<'a, PatKind> {
314 let op_span = self.token.span;
315 let (end_kind, form) = if self.eat(&token::DotDotDot) {
316 (RangeEnd::Included(RangeSyntax::DotDotDot), "...")
317 } else if self.eat(&token::DotDotEq) {
318 (RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
319 } else if self.eat(&token::DotDot) {
320 (RangeEnd::Excluded, "..")
322 panic!("impossible case: we already matched on a range-operator token")
324 let end = self.parse_pat_range_end_opt(&begin, form)?;
325 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
328 fn fatal_unexpected_non_pat(
330 mut err: DiagnosticBuilder<'a>,
331 expected: Option<&'static str>,
332 ) -> PResult<'a, P<Pat>> {
333 self.cancel(&mut err);
335 let expected = expected.unwrap_or("pattern");
336 let msg = format!("expected {}, found {}", expected, self.this_token_descr());
338 let mut err = self.fatal(&msg);
339 err.span_label(self.token.span, format!("expected {}", expected));
341 let sp = self.sess.source_map().start_point(self.token.span);
342 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
343 self.sess.expr_parentheses_needed(&mut err, *sp, None);
349 // Helper function to decide whether to parse as ident binding
350 // or to try to do something more complex like range patterns.
351 fn parse_as_ident(&mut self) -> bool {
352 self.look_ahead(1, |t| match t.kind {
353 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
354 token::DotDotDot | token::DotDotEq | token::DotDot |
355 token::ModSep | token::Not => false,
360 /// Is the current token suitable as the start of a range patterns end?
361 fn is_pat_range_end_start(&self) -> bool {
362 self.token.is_path_start() // e.g. `MY_CONST`;
363 || self.token == token::Dot // e.g. `.5` for recovery;
364 || self.token.can_begin_literal_or_bool() // e.g. `42`.
365 || self.token.is_whole_expr()
368 /// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
369 fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
370 let lo = self.prev_span;
371 let end = self.parse_pat_range_end()?;
372 let range_span = lo.to(end.span);
373 let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
376 .struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
379 "try using the minimum value for the type",
380 format!("MIN{}{}", form, pprust::expr_to_string(&end)),
381 Applicability::HasPlaceholders,
385 Ok(PatKind::Range(begin, end, respan(lo, re)))
388 /// Parse the end of a `X..Y`, `X..=Y`, or `X...Y` range pattern or recover
389 /// if that end is missing treating it as `X..`, `X..=`, or `X...` respectively.
390 fn parse_pat_range_end_opt(&mut self, begin: &Expr, form: &str) -> PResult<'a, P<Expr>> {
391 if self.is_pat_range_end_start() {
392 // Parsing e.g. `X..=Y`.
393 self.parse_pat_range_end()
395 // Parsing e.g. `X..`.
396 let range_span = begin.span.to(self.prev_span);
401 &format!("`X{}` range patterns are not supported", form),
405 "try using the maximum value for the type",
406 format!("{}{}MAX", pprust::expr_to_string(&begin), form),
407 Applicability::HasPlaceholders,
411 Ok(self.mk_expr(range_span, ExprKind::Err, ThinVec::new()))
415 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
416 if self.token.is_path_start() {
417 let lo = self.token.span;
418 let (qself, path) = if self.eat_lt() {
419 // Parse a qualified path
420 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
423 // Parse an unqualified path
424 (None, self.parse_path(PathStyle::Expr)?)
426 let hi = self.prev_span;
427 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
429 self.parse_literal_maybe_minus()
433 /// Parses `ident` or `ident @ pat`.
434 /// Used by the copy foo and ref foo patterns to give a good
435 /// error message when parsing mistakes like `ref foo(a, b)`.
436 fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
437 let ident = self.parse_ident()?;
438 let sub = if self.eat(&token::At) {
439 Some(self.parse_pat(Some("binding pattern"))?)
444 // Just to be friendly, if they write something like `ref Some(i)`,
445 // we end up here with `(` as the current token.
446 // This shortly leads to a parse error. Note that if there is no explicit
447 // binding mode then we do not end up here, because the lookahead
448 // will direct us over to `parse_enum_variant()`.
449 if self.token == token::OpenDelim(token::Paren) {
450 return Err(self.span_fatal(
452 "expected identifier, found enum pattern",
456 Ok(PatKind::Ident(binding_mode, ident, sub))
459 /// Parse a struct ("record") pattern (e.g. `Foo { ... }` or `Foo::Bar { ... }`).
460 fn parse_pat_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
462 let msg = "unexpected `{` after qualified path";
463 let mut err = self.fatal(msg);
464 err.span_label(self.token.span, msg);
469 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
475 Ok(PatKind::Struct(path, fields, etc))
478 /// Parse tuple struct or tuple variant pattern (e.g. `Foo(...)` or `Foo::Bar(...)`).
479 fn parse_pat_tuple_struct(&mut self, qself: Option<QSelf>, path: Path) -> PResult<'a, PatKind> {
481 let msg = "unexpected `(` after qualified path";
482 let mut err = self.fatal(msg);
483 err.span_label(self.token.span, msg);
486 let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
487 Ok(PatKind::TupleStruct(path, fields))
490 /// Parses the fields of a struct-like pattern.
491 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<FieldPat>, bool)> {
492 let mut fields = Vec::new();
494 let mut ate_comma = true;
495 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
496 let mut etc_span = None;
498 while self.token != token::CloseDelim(token::Brace) {
499 let attrs = match self.parse_outer_attributes() {
502 if let Some(mut delayed) = delayed_err {
508 let lo = self.token.span;
510 // check that a comma comes after every field
512 let err = self.struct_span_err(self.prev_span, "expected `,`");
513 if let Some(mut delayed) = delayed_err {
520 if self.check(&token::DotDot) || self.token == token::DotDotDot {
522 let mut etc_sp = self.token.span;
524 self.recover_one_fewer_dotdot();
525 self.bump(); // `..` || `...`
527 if self.token == token::CloseDelim(token::Brace) {
528 etc_span = Some(etc_sp);
531 let token_str = self.this_token_descr();
532 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
534 err.span_label(self.token.span, "expected `}`");
535 let mut comma_sp = None;
536 if self.token == token::Comma { // Issue #49257
537 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
538 etc_sp = etc_sp.to(nw_span);
539 err.span_label(etc_sp,
540 "`..` must be at the end and cannot have a trailing comma");
541 comma_sp = Some(self.token.span);
546 etc_span = Some(etc_sp.until(self.token.span));
547 if self.token == token::CloseDelim(token::Brace) {
548 // If the struct looks otherwise well formed, recover and continue.
549 if let Some(sp) = comma_sp {
550 err.span_suggestion_short(
554 Applicability::MachineApplicable,
559 } else if self.token.is_ident() && ate_comma {
560 // Accept fields coming after `..,`.
561 // This way we avoid "pattern missing fields" errors afterwards.
562 // We delay this error until the end in order to have a span for a
564 if let Some(mut delayed_err) = delayed_err {
568 delayed_err = Some(err);
571 if let Some(mut err) = delayed_err {
578 fields.push(match self.parse_pat_field(lo, attrs) {
581 if let Some(mut delayed_err) = delayed_err {
587 ate_comma = self.eat(&token::Comma);
590 if let Some(mut err) = delayed_err {
591 if let Some(etc_span) = etc_span {
592 err.multipart_suggestion(
593 "move the `..` to the end of the field list",
595 (etc_span, String::new()),
596 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
598 Applicability::MachineApplicable,
603 return Ok((fields, etc));
606 /// Recover on `...` as if it were `..` to avoid further errors.
607 /// See issue #46718.
608 fn recover_one_fewer_dotdot(&self) {
609 if self.token != token::DotDotDot {
613 self.struct_span_err(self.token.span, "expected field pattern, found `...`")
616 "to omit remaining fields, use one fewer `.`",
618 Applicability::MachineApplicable
623 fn parse_pat_field(&mut self, lo: Span, attrs: Vec<Attribute>) -> PResult<'a, FieldPat> {
624 // Check if a colon exists one ahead. This means we're parsing a fieldname.
626 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
627 // Parsing a pattern of the form "fieldname: pat"
628 let fieldname = self.parse_field_name()?;
630 let pat = self.parse_pat(None)?;
632 (pat, fieldname, false)
634 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
635 let is_box = self.eat_keyword(kw::Box);
636 let boxed_span = self.token.span;
637 let is_ref = self.eat_keyword(kw::Ref);
638 let is_mut = self.eat_keyword(kw::Mut);
639 let fieldname = self.parse_ident()?;
642 let bind_type = match (is_ref, is_mut) {
643 (true, true) => BindingMode::ByRef(Mutability::Mutable),
644 (true, false) => BindingMode::ByRef(Mutability::Immutable),
645 (false, true) => BindingMode::ByValue(Mutability::Mutable),
646 (false, false) => BindingMode::ByValue(Mutability::Immutable),
649 let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
650 let subpat = if is_box {
651 self.mk_pat(lo.to(hi), PatKind::Box(fieldpat))
655 (subpat, fieldname, true)
663 id: ast::DUMMY_NODE_ID,
668 pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
669 self.mk_pat(span, PatKind::Ident(bm, ident, None))
672 fn mk_pat(&self, span: Span, node: PatKind) -> P<Pat> {
673 P(Pat { node, span, id: ast::DUMMY_NODE_ID })