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) => {
174 let msg = "unexpected `{` after qualified path";
175 let mut err = self.fatal(msg);
176 err.span_label(self.token.span, msg);
179 // Parse struct pattern
181 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
187 PatKind::Struct(path, fields, etc)
189 token::OpenDelim(token::Paren) => {
191 let msg = "unexpected `(` after qualified path";
192 let mut err = self.fatal(msg);
193 err.span_label(self.token.span, msg);
196 // Parse tuple struct or enum pattern
197 let (fields, _) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
198 PatKind::TupleStruct(path, fields)
200 _ => PatKind::Path(qself, path),
203 // Try to parse everything else as literal with optional minus
204 match self.parse_literal_maybe_minus() {
206 if self.check(&token::DotDot)
207 || self.check(&token::DotDotEq)
208 || self.check(&token::DotDotDot) =>
210 self.parse_pat_range_starting_with_lit(begin)?
212 Ok(begin) => PatKind::Lit(begin),
213 Err(err) => return self.fatal_unexpected_non_pat(err, expected),
218 let pat = self.mk_pat(lo.to(self.prev_span), pat);
219 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
221 if !allow_range_pat {
222 self.ban_pat_range_if_ambiguous(&pat)?
228 /// Ban a range pattern if it has an ambiguous interpretation.
229 fn ban_pat_range_if_ambiguous(&self, pat: &Pat) -> PResult<'a, ()> {
232 .., Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
234 PatKind::Range(..) => {}
238 let mut err = self.struct_span_err(
240 "the range pattern here has ambiguous interpretation",
244 "add parentheses to clarify the precedence",
245 format!("({})", pprust::pat_to_string(&pat)),
246 // "ambiguous interpretation" implies that we have to be guessing
247 Applicability::MaybeIncorrect
252 /// Parse `&pat` / `&mut pat`.
253 fn parse_pat_deref(&mut self, expected: Option<&'static str>) -> PResult<'a, PatKind> {
255 let mutbl = self.parse_mutability();
257 if let token::Lifetime(name) = self.token.kind {
258 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
259 err.span_label(self.token.span, "unexpected lifetime");
263 let subpat = self.parse_pat_with_range_pat(false, expected)?;
264 Ok(PatKind::Ref(subpat, mutbl))
267 /// Parse a tuple or parenthesis pattern.
268 fn parse_pat_tuple_or_parens(&mut self) -> PResult<'a, PatKind> {
269 let (fields, trailing_comma) = self.parse_paren_comma_seq(|p| p.parse_pat(None))?;
271 // Here, `(pat,)` is a tuple pattern.
272 // For backward compatibility, `(..)` is a tuple pattern as well.
273 Ok(if fields.len() == 1 && !(trailing_comma || fields[0].is_rest()) {
274 PatKind::Paren(fields.into_iter().nth(0).unwrap())
276 PatKind::Tuple(fields)
280 /// Recover on `mut ref? ident @ pat` and suggest
281 /// that the order of `mut` and `ref` is incorrect.
282 fn recover_pat_ident_mut_first(&mut self) -> PResult<'a, PatKind> {
283 let mutref_span = self.prev_span.to(self.token.span);
284 let binding_mode = if self.eat_keyword(kw::Ref) {
285 self.struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
288 "try switching the order",
290 Applicability::MachineApplicable
293 BindingMode::ByRef(Mutability::Mutable)
295 BindingMode::ByValue(Mutability::Mutable)
297 self.parse_pat_ident(binding_mode)
300 /// Parse macro invocation
301 fn parse_pat_mac_invoc(&mut self, lo: Span, path: Path) -> PResult<'a, PatKind> {
303 let (delim, tts) = self.expect_delimited_token_tree()?;
304 let mac = respan(lo.to(self.prev_span), Mac_ {
308 prior_type_ascription: self.last_type_ascription,
310 Ok(PatKind::Mac(mac))
313 /// Parse a range pattern `$path $form $end?` where `$form = ".." | "..." | "..=" ;`.
314 /// The `$path` has already been parsed and the next token is the `$form`.
315 fn parse_pat_range_starting_with_path(
318 qself: Option<QSelf>,
320 ) -> PResult<'a, PatKind> {
321 let (end_kind, form) = match self.token.kind {
322 token::DotDot => (RangeEnd::Excluded, ".."),
323 token::DotDotDot => (RangeEnd::Included(RangeSyntax::DotDotDot), "..."),
324 token::DotDotEq => (RangeEnd::Included(RangeSyntax::DotDotEq), "..="),
325 _ => panic!("can only parse `..`/`...`/`..=` for ranges (checked above)"),
327 let op_span = self.token.span;
329 let span = lo.to(self.prev_span);
330 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
332 let end = self.parse_pat_range_end_opt(&begin, form)?;
333 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
336 /// Parse a range pattern `$literal $form $end?` where `$form = ".." | "..." | "..=" ;`.
337 /// The `$path` has already been parsed and the next token is the `$form`.
338 fn parse_pat_range_starting_with_lit(&mut self, begin: P<Expr>) -> PResult<'a, PatKind> {
339 let op_span = self.token.span;
340 let (end_kind, form) = if self.eat(&token::DotDotDot) {
341 (RangeEnd::Included(RangeSyntax::DotDotDot), "...")
342 } else if self.eat(&token::DotDotEq) {
343 (RangeEnd::Included(RangeSyntax::DotDotEq), "..=")
344 } else if self.eat(&token::DotDot) {
345 (RangeEnd::Excluded, "..")
347 panic!("impossible case: we already matched on a range-operator token")
349 let end = self.parse_pat_range_end_opt(&begin, form)?;
350 Ok(PatKind::Range(begin, end, respan(op_span, end_kind)))
353 fn fatal_unexpected_non_pat(
355 mut err: DiagnosticBuilder<'a>,
356 expected: Option<&'static str>,
357 ) -> PResult<'a, P<Pat>> {
358 self.cancel(&mut err);
360 let expected = expected.unwrap_or("pattern");
361 let msg = format!("expected {}, found {}", expected, self.this_token_descr());
363 let mut err = self.fatal(&msg);
364 err.span_label(self.token.span, format!("expected {}", expected));
366 let sp = self.sess.source_map().start_point(self.token.span);
367 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
368 self.sess.expr_parentheses_needed(&mut err, *sp, None);
374 // Helper function to decide whether to parse as ident binding
375 // or to try to do something more complex like range patterns.
376 fn parse_as_ident(&mut self) -> bool {
377 self.look_ahead(1, |t| match t.kind {
378 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
379 token::DotDotDot | token::DotDotEq | token::DotDot |
380 token::ModSep | token::Not => false,
385 /// Is the current token suitable as the start of a range patterns end?
386 fn is_pat_range_end_start(&self) -> bool {
387 self.token.is_path_start() // e.g. `MY_CONST`;
388 || self.token == token::Dot // e.g. `.5` for recovery;
389 || self.token.can_begin_literal_or_bool() // e.g. `42`.
390 || self.token.is_whole_expr()
393 /// Parse a range-to pattern, e.g. `..X` and `..=X` for recovery.
394 fn parse_pat_range_to(&mut self, re: RangeEnd, form: &str) -> PResult<'a, PatKind> {
395 let lo = self.prev_span;
396 let end = self.parse_pat_range_end()?;
397 let range_span = lo.to(end.span);
398 let begin = self.mk_expr(range_span, ExprKind::Err, ThinVec::new());
401 .struct_span_err(range_span, &format!("`{}X` range patterns are not supported", form))
404 "try using the minimum value for the type",
405 format!("MIN{}{}", form, pprust::expr_to_string(&end)),
406 Applicability::HasPlaceholders,
410 Ok(PatKind::Range(begin, end, respan(lo, re)))
413 /// Parse the end of a `X..Y`, `X..=Y`, or `X...Y` range pattern or recover
414 /// if that end is missing treating it as `X..`, `X..=`, or `X...` respectively.
415 fn parse_pat_range_end_opt(&mut self, begin: &Expr, form: &str) -> PResult<'a, P<Expr>> {
416 if self.is_pat_range_end_start() {
417 // Parsing e.g. `X..=Y`.
418 self.parse_pat_range_end()
420 // Parsing e.g. `X..`.
421 let range_span = begin.span.to(self.prev_span);
426 &format!("`X{}` range patterns are not supported", form),
430 "try using the maximum value for the type",
431 format!("{}{}MAX", pprust::expr_to_string(&begin), form),
432 Applicability::HasPlaceholders,
436 Ok(self.mk_expr(range_span, ExprKind::Err, ThinVec::new()))
440 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
441 if self.token.is_path_start() {
442 let lo = self.token.span;
443 let (qself, path) = if self.eat_lt() {
444 // Parse a qualified path
445 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
448 // Parse an unqualified path
449 (None, self.parse_path(PathStyle::Expr)?)
451 let hi = self.prev_span;
452 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
454 self.parse_literal_maybe_minus()
458 /// Parses `ident` or `ident @ pat`.
459 /// Used by the copy foo and ref foo patterns to give a good
460 /// error message when parsing mistakes like `ref foo(a, b)`.
461 fn parse_pat_ident(&mut self, binding_mode: BindingMode) -> PResult<'a, PatKind> {
462 let ident = self.parse_ident()?;
463 let sub = if self.eat(&token::At) {
464 Some(self.parse_pat(Some("binding pattern"))?)
469 // Just to be friendly, if they write something like `ref Some(i)`,
470 // we end up here with `(` as the current token.
471 // This shortly leads to a parse error. Note that if there is no explicit
472 // binding mode then we do not end up here, because the lookahead
473 // will direct us over to `parse_enum_variant()`.
474 if self.token == token::OpenDelim(token::Paren) {
475 return Err(self.span_fatal(
477 "expected identifier, found enum pattern",
481 Ok(PatKind::Ident(binding_mode, ident, sub))
484 /// Parses the fields of a struct-like pattern.
485 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<Spanned<FieldPat>>, bool)> {
486 let mut fields = Vec::new();
488 let mut ate_comma = true;
489 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
490 let mut etc_span = None;
492 while self.token != token::CloseDelim(token::Brace) {
493 let attrs = match self.parse_outer_attributes() {
496 if let Some(mut delayed) = delayed_err {
502 let lo = self.token.span;
504 // check that a comma comes after every field
506 let err = self.struct_span_err(self.prev_span, "expected `,`");
507 if let Some(mut delayed) = delayed_err {
514 if self.check(&token::DotDot) || self.token == token::DotDotDot {
516 let mut etc_sp = self.token.span;
518 if self.token == token::DotDotDot { // Issue #46718
519 // Accept `...` as if it were `..` to avoid further errors
520 self.struct_span_err(self.token.span, "expected field pattern, found `...`")
523 "to omit remaining fields, use one fewer `.`",
525 Applicability::MachineApplicable
529 self.bump(); // `..` || `...`
531 if self.token == token::CloseDelim(token::Brace) {
532 etc_span = Some(etc_sp);
535 let token_str = self.this_token_descr();
536 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
538 err.span_label(self.token.span, "expected `}`");
539 let mut comma_sp = None;
540 if self.token == token::Comma { // Issue #49257
541 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
542 etc_sp = etc_sp.to(nw_span);
543 err.span_label(etc_sp,
544 "`..` must be at the end and cannot have a trailing comma");
545 comma_sp = Some(self.token.span);
550 etc_span = Some(etc_sp.until(self.token.span));
551 if self.token == token::CloseDelim(token::Brace) {
552 // If the struct looks otherwise well formed, recover and continue.
553 if let Some(sp) = comma_sp {
554 err.span_suggestion_short(
558 Applicability::MachineApplicable,
563 } else if self.token.is_ident() && ate_comma {
564 // Accept fields coming after `..,`.
565 // This way we avoid "pattern missing fields" errors afterwards.
566 // We delay this error until the end in order to have a span for a
568 if let Some(mut delayed_err) = delayed_err {
572 delayed_err = Some(err);
575 if let Some(mut err) = delayed_err {
582 fields.push(match self.parse_pat_field(lo, attrs) {
585 if let Some(mut delayed_err) = delayed_err {
591 ate_comma = self.eat(&token::Comma);
594 if let Some(mut err) = delayed_err {
595 if let Some(etc_span) = etc_span {
596 err.multipart_suggestion(
597 "move the `..` to the end of the field list",
599 (etc_span, String::new()),
600 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
602 Applicability::MachineApplicable,
607 return Ok((fields, etc));
613 attrs: Vec<Attribute>
614 ) -> PResult<'a, Spanned<FieldPat>> {
615 // Check if a colon exists one ahead. This means we're parsing a fieldname.
617 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
618 // Parsing a pattern of the form "fieldname: pat"
619 let fieldname = self.parse_field_name()?;
621 let pat = self.parse_pat(None)?;
623 (pat, fieldname, false)
625 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
626 let is_box = self.eat_keyword(kw::Box);
627 let boxed_span = self.token.span;
628 let is_ref = self.eat_keyword(kw::Ref);
629 let is_mut = self.eat_keyword(kw::Mut);
630 let fieldname = self.parse_ident()?;
633 let bind_type = match (is_ref, is_mut) {
634 (true, true) => BindingMode::ByRef(Mutability::Mutable),
635 (true, false) => BindingMode::ByRef(Mutability::Immutable),
636 (false, true) => BindingMode::ByValue(Mutability::Mutable),
637 (false, false) => BindingMode::ByValue(Mutability::Immutable),
640 let fieldpat = self.mk_pat_ident(boxed_span.to(hi), bind_type, fieldname);
641 let subpat = if is_box {
642 self.mk_pat(lo.to(hi), PatKind::Box(fieldpat))
646 (subpat, fieldname, true)
660 pub(super) fn mk_pat_ident(&self, span: Span, bm: BindingMode, ident: Ident) -> P<Pat> {
661 self.mk_pat(span, PatKind::Ident(bm, ident, None))
664 fn mk_pat(&self, span: Span, node: PatKind) -> P<Pat> {
665 P(Pat { node, span, id: ast::DUMMY_NODE_ID })