src/librustc_parse/parser/mod.rs

   1 pub mod attr;
   2 mod expr;
   3 mod item;
   4 mod pat;
   5 mod path;
   6 mod ty;
   7 pub use path::PathStyle;
   8 mod diagnostics;
   9 mod generics;
  10 mod stmt;
  11 use diagnostics::Error;
  12
  13 use crate::lexer::UnmatchedBrace;
  14
  15 use log::debug;
  16 use rustc_ast::ast::DUMMY_NODE_ID;
  17 use rustc_ast::ast::{self, AttrStyle, AttrVec, Const, CrateSugar, Extern, Unsafe};
  18 use rustc_ast::ast::{
  19     Async, MacArgs, MacDelimiter, Mutability, StrLit, Visibility, VisibilityKind,
  20 };
  21 use rustc_ast::ptr::P;
  22 use rustc_ast::token::{self, DelimToken, Token, TokenKind};
  23 use rustc_ast::tokenstream::{self, DelimSpan, TokenStream, TokenTree, TreeAndJoint};
  24 use rustc_ast::util::comments::{doc_comment_style, strip_doc_comment_decoration};
  25 use rustc_ast_pretty::pprust;
  26 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, FatalError, PResult};
  27 use rustc_session::parse::ParseSess;
  28 use rustc_span::source_map::{respan, Span, DUMMY_SP};
  29 use rustc_span::symbol::{kw, sym, Ident, Symbol};
  30
  31 use std::{cmp, mem, slice};
  32
  33 bitflags::bitflags! {
  34     struct Restrictions: u8 {
  35         const STMT_EXPR         = 1 << 0;
  36         const NO_STRUCT_LITERAL = 1 << 1;
  37     }
  38 }
  39
  40 #[derive(Clone, Copy, PartialEq, Debug)]
  41 enum SemiColonMode {
  42     Break,
  43     Ignore,
  44     Comma,
  45 }
  46
  47 #[derive(Clone, Copy, PartialEq, Debug)]
  48 enum BlockMode {
  49     Break,
  50     Ignore,
  51 }
  52
  53 /// Like `maybe_whole_expr`, but for things other than expressions.
  54 #[macro_export]
  55 macro_rules! maybe_whole {
  56     ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
  57         if let token::Interpolated(nt) = &$p.token.kind {
  58             if let token::$constructor(x) = &**nt {
  59                 let $x = x.clone();
  60                 $p.bump();
  61                 return Ok($e);
  62             }
  63         }
  64     };
  65 }
  66
  67 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
  68 #[macro_export]
  69 macro_rules! maybe_recover_from_interpolated_ty_qpath {
  70     ($self: expr, $allow_qpath_recovery: expr) => {
  71         if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
  72             if let token::Interpolated(nt) = &$self.token.kind {
  73                 if let token::NtTy(ty) = &**nt {
  74                     let ty = ty.clone();
  75                     $self.bump();
  76                     return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_token.span, ty);
  77                 }
  78             }
  79         }
  80     };
  81 }
  82
  83 #[derive(Clone)]
  84 pub struct Parser<'a> {
  85     pub sess: &'a ParseSess,
  86     /// The current token.
  87     pub token: Token,
  88     /// The previous token.
  89     pub prev_token: Token,
  90     restrictions: Restrictions,
  91     expected_tokens: Vec<TokenType>,
  92     token_cursor: TokenCursor,
  93     desugar_doc_comments: bool,
  94     /// This field is used to keep track of how many left angle brackets we have seen. This is
  95     /// required in order to detect extra leading left angle brackets (`<` characters) and error
  96     /// appropriately.
  97     ///
  98     /// See the comments in the `parse_path_segment` function for more details.
  99     unmatched_angle_bracket_count: u32,
 100     max_angle_bracket_count: u32,
 101     /// A list of all unclosed delimiters found by the lexer. If an entry is used for error recovery
 102     /// it gets removed from here. Every entry left at the end gets emitted as an independent
 103     /// error.
 104     pub(super) unclosed_delims: Vec<UnmatchedBrace>,
 105     last_unexpected_token_span: Option<Span>,
 106     pub last_type_ascription: Option<(Span, bool /* likely path typo */)>,
 107     /// If present, this `Parser` is not parsing Rust code but rather a macro call.
 108     subparser_name: Option<&'static str>,
 109 }
 110
 111 impl<'a> Drop for Parser<'a> {
 112     fn drop(&mut self) {
 113         emit_unclosed_delims(&mut self.unclosed_delims, &self.sess);
 114     }
 115 }
 116
 117 #[derive(Clone)]
 118 struct TokenCursor {
 119     frame: TokenCursorFrame,
 120     stack: Vec<TokenCursorFrame>,
 121     cur_token: Option<TreeAndJoint>,
 122     collecting: Option<Collecting>,
 123 }
 124
 125 #[derive(Clone)]
 126 struct TokenCursorFrame {
 127     delim: token::DelimToken,
 128     span: DelimSpan,
 129     open_delim: bool,
 130     tree_cursor: tokenstream::Cursor,
 131     close_delim: bool,
 132 }
 133
 134 /// Used to track additional state needed by `collect_tokens`
 135 #[derive(Clone, Debug)]
 136 struct Collecting {
 137     /// Holds the current tokens captured during the most
 138     /// recent call to `collect_tokens`
 139     buf: Vec<TreeAndJoint>,
 140     /// The depth of the `TokenCursor` stack at the time
 141     /// collection was started. When we encounter a `TokenTree::Delimited`,
 142     /// we want to record the `TokenTree::Delimited` itself,
 143     /// but *not* any of the inner tokens while we are inside
 144     /// the new frame (this would cause us to record duplicate tokens).
 145     ///
 146     /// This `depth` fields tracks stack depth we are recording tokens.
 147     /// Only tokens encountered at this depth will be recorded. See
 148     /// `TokenCursor::next` for more details.
 149     depth: usize,
 150 }
 151
 152 impl TokenCursorFrame {
 153     fn new(span: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
 154         TokenCursorFrame {
 155             delim,
 156             span,
 157             open_delim: delim == token::NoDelim,
 158             tree_cursor: tts.clone().into_trees(),
 159             close_delim: delim == token::NoDelim,
 160         }
 161     }
 162 }
 163
 164 impl TokenCursor {
 165     fn next(&mut self) -> Token {
 166         loop {
 167             let tree = if !self.frame.open_delim {
 168                 self.frame.open_delim = true;
 169                 TokenTree::open_tt(self.frame.span, self.frame.delim).into()
 170             } else if let Some(tree) = self.frame.tree_cursor.next_with_joint() {
 171                 tree
 172             } else if !self.frame.close_delim {
 173                 self.frame.close_delim = true;
 174                 TokenTree::close_tt(self.frame.span, self.frame.delim).into()
 175             } else if let Some(frame) = self.stack.pop() {
 176                 self.frame = frame;
 177                 continue;
 178             } else {
 179                 return Token::new(token::Eof, DUMMY_SP);
 180             };
 181
 182             // Don't set an open delimiter as our current token - we want
 183             // to leave it as the full `TokenTree::Delimited` from the previous
 184             // iteration of this loop
 185             if !matches!(tree.0, TokenTree::Token(Token { kind: TokenKind::OpenDelim(_), .. })) {
 186                 self.cur_token = Some(tree.clone());
 187             }
 188
 189             if let Some(collecting) = &mut self.collecting {
 190                 if collecting.depth == self.stack.len() {
 191                     debug!(
 192                         "TokenCursor::next():  collected {:?} at depth {:?}",
 193                         tree,
 194                         self.stack.len()
 195                     );
 196                     collecting.buf.push(tree.clone())
 197                 }
 198             }
 199
 200             match tree.0 {
 201                 TokenTree::Token(token) => return token,
 202                 TokenTree::Delimited(sp, delim, tts) => {
 203                     let frame = TokenCursorFrame::new(sp, delim, &tts);
 204                     self.stack.push(mem::replace(&mut self.frame, frame));
 205                 }
 206             }
 207         }
 208     }
 209
 210     fn next_desugared(&mut self) -> Token {
 211         let (name, sp) = match self.next() {
 212             Token { kind: token::DocComment(name), span } => (name, span),
 213             tok => return tok,
 214         };
 215
 216         let stripped = strip_doc_comment_decoration(&name.as_str());
 217
 218         // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
 219         // required to wrap the text.
 220         let mut num_of_hashes = 0;
 221         let mut count = 0;
 222         for ch in stripped.chars() {
 223             count = match ch {
 224                 '"' => 1,
 225                 '#' if count > 0 => count + 1,
 226                 _ => 0,
 227             };
 228             num_of_hashes = cmp::max(num_of_hashes, count);
 229         }
 230
 231         let delim_span = DelimSpan::from_single(sp);
 232         let body = TokenTree::Delimited(
 233             delim_span,
 234             token::Bracket,
 235             [
 236                 TokenTree::token(token::Ident(sym::doc, false), sp),
 237                 TokenTree::token(token::Eq, sp),
 238                 TokenTree::token(
 239                     TokenKind::lit(token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None),
 240                     sp,
 241                 ),
 242             ]
 243             .iter()
 244             .cloned()
 245             .collect::<TokenStream>(),
 246         );
 247
 248         self.stack.push(mem::replace(
 249             &mut self.frame,
 250             TokenCursorFrame::new(
 251                 delim_span,
 252                 token::NoDelim,
 253                 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
 254                     [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
 255                         .iter()
 256                         .cloned()
 257                         .collect::<TokenStream>()
 258                 } else {
 259                     [TokenTree::token(token::Pound, sp), body]
 260                         .iter()
 261                         .cloned()
 262                         .collect::<TokenStream>()
 263                 },
 264             ),
 265         ));
 266
 267         self.next()
 268     }
 269 }
 270
 271 #[derive(Clone, PartialEq)]
 272 enum TokenType {
 273     Token(TokenKind),
 274     Keyword(Symbol),
 275     Operator,
 276     Lifetime,
 277     Ident,
 278     Path,
 279     Type,
 280     Const,
 281 }
 282
 283 impl TokenType {
 284     fn to_string(&self) -> String {
 285         match *self {
 286             TokenType::Token(ref t) => format!("`{}`", pprust::token_kind_to_string(t)),
 287             TokenType::Keyword(kw) => format!("`{}`", kw),
 288             TokenType::Operator => "an operator".to_string(),
 289             TokenType::Lifetime => "lifetime".to_string(),
 290             TokenType::Ident => "identifier".to_string(),
 291             TokenType::Path => "path".to_string(),
 292             TokenType::Type => "type".to_string(),
 293             TokenType::Const => "const".to_string(),
 294         }
 295     }
 296 }
 297
 298 #[derive(Copy, Clone, Debug)]
 299 enum TokenExpectType {
 300     Expect,
 301     NoExpect,
 302 }
 303
 304 /// A sequence separator.
 305 struct SeqSep {
 306     /// The separator token.
 307     sep: Option<TokenKind>,
 308     /// `true` if a trailing separator is allowed.
 309     trailing_sep_allowed: bool,
 310 }
 311
 312 impl SeqSep {
 313     fn trailing_allowed(t: TokenKind) -> SeqSep {
 314         SeqSep { sep: Some(t), trailing_sep_allowed: true }
 315     }
 316
 317     fn none() -> SeqSep {
 318         SeqSep { sep: None, trailing_sep_allowed: false }
 319     }
 320 }
 321
 322 pub enum FollowedByType {
 323     Yes,
 324     No,
 325 }
 326
 327 fn token_descr_opt(token: &Token) -> Option<&'static str> {
 328     Some(match token.kind {
 329         _ if token.is_special_ident() => "reserved identifier",
 330         _ if token.is_used_keyword() => "keyword",
 331         _ if token.is_unused_keyword() => "reserved keyword",
 332         token::DocComment(..) => "doc comment",
 333         _ => return None,
 334     })
 335 }
 336
 337 pub(super) fn token_descr(token: &Token) -> String {
 338     let token_str = pprust::token_to_string(token);
 339     match token_descr_opt(token) {
 340         Some(prefix) => format!("{} `{}`", prefix, token_str),
 341         _ => format!("`{}`", token_str),
 342     }
 343 }
 344
 345 impl<'a> Parser<'a> {
 346     pub fn new(
 347         sess: &'a ParseSess,
 348         tokens: TokenStream,
 349         desugar_doc_comments: bool,
 350         subparser_name: Option<&'static str>,
 351     ) -> Self {
 352         let mut parser = Parser {
 353             sess,
 354             token: Token::dummy(),
 355             prev_token: Token::dummy(),
 356             restrictions: Restrictions::empty(),
 357             expected_tokens: Vec::new(),
 358             token_cursor: TokenCursor {
 359                 frame: TokenCursorFrame::new(DelimSpan::dummy(), token::NoDelim, &tokens),
 360                 stack: Vec::new(),
 361                 cur_token: None,
 362                 collecting: None,
 363             },
 364             desugar_doc_comments,
 365             unmatched_angle_bracket_count: 0,
 366             max_angle_bracket_count: 0,
 367             unclosed_delims: Vec::new(),
 368             last_unexpected_token_span: None,
 369             last_type_ascription: None,
 370             subparser_name,
 371         };
 372
 373         // Make parser point to the first token.
 374         parser.bump();
 375
 376         parser
 377     }
 378
 379     fn next_tok(&mut self, fallback_span: Span) -> Token {
 380         let mut next = if self.desugar_doc_comments {
 381             self.token_cursor.next_desugared()
 382         } else {
 383             self.token_cursor.next()
 384         };
 385         if next.span.is_dummy() {
 386             // Tweak the location for better diagnostics, but keep syntactic context intact.
 387             next.span = fallback_span.with_ctxt(next.span.ctxt());
 388         }
 389         next
 390     }
 391
 392     crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
 393         match self.expect_one_of(&[], &[]) {
 394             Err(e) => Err(e),
 395             // We can get `Ok(true)` from `recover_closing_delimiter`
 396             // which is called in `expected_one_of_not_found`.
 397             Ok(_) => FatalError.raise(),
 398         }
 399     }
 400
 401     /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
 402     pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
 403         if self.expected_tokens.is_empty() {
 404             if self.token == *t {
 405                 self.bump();
 406                 Ok(false)
 407             } else {
 408                 self.unexpected_try_recover(t)
 409             }
 410         } else {
 411             self.expect_one_of(slice::from_ref(t), &[])
 412         }
 413     }
 414
 415     /// Expect next token to be edible or inedible token.  If edible,
 416     /// then consume it; if inedible, then return without consuming
 417     /// anything.  Signal a fatal error if next token is unexpected.
 418     pub fn expect_one_of(
 419         &mut self,
 420         edible: &[TokenKind],
 421         inedible: &[TokenKind],
 422     ) -> PResult<'a, bool /* recovered */> {
 423         if edible.contains(&self.token.kind) {
 424             self.bump();
 425             Ok(false)
 426         } else if inedible.contains(&self.token.kind) {
 427             // leave it in the input
 428             Ok(false)
 429         } else if self.last_unexpected_token_span == Some(self.token.span) {
 430             FatalError.raise();
 431         } else {
 432             self.expected_one_of_not_found(edible, inedible)
 433         }
 434     }
 435
 436     // Public for rustfmt usage.
 437     pub fn parse_ident(&mut self) -> PResult<'a, Ident> {
 438         self.parse_ident_common(true)
 439     }
 440
 441     fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, Ident> {
 442         match self.token.ident() {
 443             Some((ident, is_raw)) => {
 444                 if !is_raw && ident.is_reserved() {
 445                     let mut err = self.expected_ident_found();
 446                     if recover {
 447                         err.emit();
 448                     } else {
 449                         return Err(err);
 450                     }
 451                 }
 452                 self.bump();
 453                 Ok(ident)
 454             }
 455             _ => Err(match self.prev_token.kind {
 456                 TokenKind::DocComment(..) => {
 457                     self.span_fatal_err(self.prev_token.span, Error::UselessDocComment)
 458                 }
 459                 _ => self.expected_ident_found(),
 460             }),
 461         }
 462     }
 463
 464     /// Checks if the next token is `tok`, and returns `true` if so.
 465     ///
 466     /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
 467     /// encountered.
 468     fn check(&mut self, tok: &TokenKind) -> bool {
 469         let is_present = self.token == *tok;
 470         if !is_present {
 471             self.expected_tokens.push(TokenType::Token(tok.clone()));
 472         }
 473         is_present
 474     }
 475
 476     /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
 477     pub fn eat(&mut self, tok: &TokenKind) -> bool {
 478         let is_present = self.check(tok);
 479         if is_present {
 480             self.bump()
 481         }
 482         is_present
 483     }
 484
 485     /// If the next token is the given keyword, returns `true` without eating it.
 486     /// An expectation is also added for diagnostics purposes.
 487     fn check_keyword(&mut self, kw: Symbol) -> bool {
 488         self.expected_tokens.push(TokenType::Keyword(kw));
 489         self.token.is_keyword(kw)
 490     }
 491
 492     /// If the next token is the given keyword, eats it and returns `true`.
 493     /// Otherwise, returns `false`. An expectation is also added for diagnostics purposes.
 494     // Public for rustfmt usage.
 495     pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
 496         if self.check_keyword(kw) {
 497             self.bump();
 498             true
 499         } else {
 500             false
 501         }
 502     }
 503
 504     fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
 505         if self.token.is_keyword(kw) {
 506             self.bump();
 507             true
 508         } else {
 509             false
 510         }
 511     }
 512
 513     /// If the given word is not a keyword, signals an error.
 514     /// If the next token is not the given word, signals an error.
 515     /// Otherwise, eats it.
 516     fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
 517         if !self.eat_keyword(kw) { self.unexpected() } else { Ok(()) }
 518     }
 519
 520     /// Is the given keyword `kw` followed by a non-reserved identifier?
 521     fn is_kw_followed_by_ident(&self, kw: Symbol) -> bool {
 522         self.token.is_keyword(kw) && self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
 523     }
 524
 525     fn check_or_expected(&mut self, ok: bool, typ: TokenType) -> bool {
 526         if ok {
 527             true
 528         } else {
 529             self.expected_tokens.push(typ);
 530             false
 531         }
 532     }
 533
 534     fn check_ident(&mut self) -> bool {
 535         self.check_or_expected(self.token.is_ident(), TokenType::Ident)
 536     }
 537
 538     fn check_path(&mut self) -> bool {
 539         self.check_or_expected(self.token.is_path_start(), TokenType::Path)
 540     }
 541
 542     fn check_type(&mut self) -> bool {
 543         self.check_or_expected(self.token.can_begin_type(), TokenType::Type)
 544     }
 545
 546     fn check_const_arg(&mut self) -> bool {
 547         self.check_or_expected(self.token.can_begin_const_arg(), TokenType::Const)
 548     }
 549
 550     /// Checks to see if the next token is either `+` or `+=`.
 551     /// Otherwise returns `false`.
 552     fn check_plus(&mut self) -> bool {
 553         self.check_or_expected(
 554             self.token.is_like_plus(),
 555             TokenType::Token(token::BinOp(token::Plus)),
 556         )
 557     }
 558
 559     /// Eats the expected token if it's present possibly breaking
 560     /// compound tokens like multi-character operators in process.
 561     /// Returns `true` if the token was eaten.
 562     fn break_and_eat(&mut self, expected: TokenKind) -> bool {
 563         if self.token.kind == expected {
 564             self.bump();
 565             return true;
 566         }
 567         match self.token.kind.break_two_token_op() {
 568             Some((first, second)) if first == expected => {
 569                 let first_span = self.sess.source_map().start_point(self.token.span);
 570                 let second_span = self.token.span.with_lo(first_span.hi());
 571                 self.token = Token::new(first, first_span);
 572                 self.bump_with(Token::new(second, second_span));
 573                 true
 574             }
 575             _ => {
 576                 self.expected_tokens.push(TokenType::Token(expected));
 577                 false
 578             }
 579         }
 580     }
 581
 582     /// Eats `+` possibly breaking tokens like `+=` in process.
 583     fn eat_plus(&mut self) -> bool {
 584         self.break_and_eat(token::BinOp(token::Plus))
 585     }
 586
 587     /// Eats `&` possibly breaking tokens like `&&` in process.
 588     /// Signals an error if `&` is not eaten.
 589     fn expect_and(&mut self) -> PResult<'a, ()> {
 590         if self.break_and_eat(token::BinOp(token::And)) { Ok(()) } else { self.unexpected() }
 591     }
 592
 593     /// Eats `|` possibly breaking tokens like `||` in process.
 594     /// Signals an error if `|` was not eaten.
 595     fn expect_or(&mut self) -> PResult<'a, ()> {
 596         if self.break_and_eat(token::BinOp(token::Or)) { Ok(()) } else { self.unexpected() }
 597     }
 598
 599     /// Eats `<` possibly breaking tokens like `<<` in process.
 600     fn eat_lt(&mut self) -> bool {
 601         let ate = self.break_and_eat(token::Lt);
 602         if ate {
 603             // See doc comment for `unmatched_angle_bracket_count`.
 604             self.unmatched_angle_bracket_count += 1;
 605             self.max_angle_bracket_count += 1;
 606             debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
 607         }
 608         ate
 609     }
 610
 611     /// Eats `<` possibly breaking tokens like `<<` in process.
 612     /// Signals an error if `<` was not eaten.
 613     fn expect_lt(&mut self) -> PResult<'a, ()> {
 614         if self.eat_lt() { Ok(()) } else { self.unexpected() }
 615     }
 616
 617     /// Eats `>` possibly breaking tokens like `>>` in process.
 618     /// Signals an error if `>` was not eaten.
 619     fn expect_gt(&mut self) -> PResult<'a, ()> {
 620         if self.break_and_eat(token::Gt) {
 621             // See doc comment for `unmatched_angle_bracket_count`.
 622             if self.unmatched_angle_bracket_count > 0 {
 623                 self.unmatched_angle_bracket_count -= 1;
 624                 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
 625             }
 626             Ok(())
 627         } else {
 628             self.unexpected()
 629         }
 630     }
 631
 632     fn expect_any_with_type(&mut self, kets: &[&TokenKind], expect: TokenExpectType) -> bool {
 633         kets.iter().any(|k| match expect {
 634             TokenExpectType::Expect => self.check(k),
 635             TokenExpectType::NoExpect => self.token == **k,
 636         })
 637     }
 638
 639     fn parse_seq_to_before_tokens<T>(
 640         &mut self,
 641         kets: &[&TokenKind],
 642         sep: SeqSep,
 643         expect: TokenExpectType,
 644         mut f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 645     ) -> PResult<'a, (Vec<T>, bool /* trailing */, bool /* recovered */)> {
 646         let mut first = true;
 647         let mut recovered = false;
 648         let mut trailing = false;
 649         let mut v = vec![];
 650         while !self.expect_any_with_type(kets, expect) {
 651             if let token::CloseDelim(..) | token::Eof = self.token.kind {
 652                 break;
 653             }
 654             if let Some(ref t) = sep.sep {
 655                 if first {
 656                     first = false;
 657                 } else {
 658                     match self.expect(t) {
 659                         Ok(false) => {}
 660                         Ok(true) => {
 661                             recovered = true;
 662                             break;
 663                         }
 664                         Err(mut expect_err) => {
 665                             let sp = self.prev_token.span.shrink_to_hi();
 666                             let token_str = pprust::token_kind_to_string(t);
 667
 668                             // Attempt to keep parsing if it was a similar separator.
 669                             if let Some(ref tokens) = t.similar_tokens() {
 670                                 if tokens.contains(&self.token.kind) {
 671                                     self.bump();
 672                                 }
 673                             }
 674
 675                             // If this was a missing `@` in a binding pattern
 676                             // bail with a suggestion
 677                             // https://github.com/rust-lang/rust/issues/72373
 678                             if self.prev_token.is_ident() && self.token.kind == token::DotDot {
 679                                 let msg = format!(
 680                                     "if you meant to bind the contents of \
 681                                     the rest of the array pattern into `{}`, use `@`",
 682                                     pprust::token_to_string(&self.prev_token)
 683                                 );
 684                                 expect_err
 685                                     .span_suggestion_verbose(
 686                                         self.prev_token.span.shrink_to_hi().until(self.token.span),
 687                                         &msg,
 688                                         " @ ".to_string(),
 689                                         Applicability::MaybeIncorrect,
 690                                     )
 691                                     .emit();
 692                                 break;
 693                             }
 694
 695                             // Attempt to keep parsing if it was an omitted separator.
 696                             match f(self) {
 697                                 Ok(t) => {
 698                                     // Parsed successfully, therefore most probably the code only
 699                                     // misses a separator.
 700                                     expect_err
 701                                         .span_suggestion_short(
 702                                             self.sess.source_map().next_point(sp),
 703                                             &format!("missing `{}`", token_str),
 704                                             token_str,
 705                                             Applicability::MaybeIncorrect,
 706                                         )
 707                                         .emit();
 708
 709                                     v.push(t);
 710                                     continue;
 711                                 }
 712                                 Err(mut e) => {
 713                                     // Parsing failed, therefore it must be something more serious
 714                                     // than just a missing separator.
 715                                     expect_err.emit();
 716
 717                                     e.cancel();
 718                                     break;
 719                                 }
 720                             }
 721                         }
 722                     }
 723                 }
 724             }
 725             if sep.trailing_sep_allowed && self.expect_any_with_type(kets, expect) {
 726                 trailing = true;
 727                 break;
 728             }
 729
 730             let t = f(self)?;
 731             v.push(t);
 732         }
 733
 734         Ok((v, trailing, recovered))
 735     }
 736
 737     /// Parses a sequence, not including the closing delimiter. The function
 738     /// `f` must consume tokens until reaching the next separator or
 739     /// closing bracket.
 740     fn parse_seq_to_before_end<T>(
 741         &mut self,
 742         ket: &TokenKind,
 743         sep: SeqSep,
 744         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 745     ) -> PResult<'a, (Vec<T>, bool, bool)> {
 746         self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
 747     }
 748
 749     /// Parses a sequence, including the closing delimiter. The function
 750     /// `f` must consume tokens until reaching the next separator or
 751     /// closing bracket.
 752     fn parse_seq_to_end<T>(
 753         &mut self,
 754         ket: &TokenKind,
 755         sep: SeqSep,
 756         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 757     ) -> PResult<'a, (Vec<T>, bool /* trailing */)> {
 758         let (val, trailing, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
 759         if !recovered {
 760             self.eat(ket);
 761         }
 762         Ok((val, trailing))
 763     }
 764
 765     /// Parses a sequence, including the closing delimiter. The function
 766     /// `f` must consume tokens until reaching the next separator or
 767     /// closing bracket.
 768     fn parse_unspanned_seq<T>(
 769         &mut self,
 770         bra: &TokenKind,
 771         ket: &TokenKind,
 772         sep: SeqSep,
 773         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 774     ) -> PResult<'a, (Vec<T>, bool)> {
 775         self.expect(bra)?;
 776         self.parse_seq_to_end(ket, sep, f)
 777     }
 778
 779     fn parse_delim_comma_seq<T>(
 780         &mut self,
 781         delim: DelimToken,
 782         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 783     ) -> PResult<'a, (Vec<T>, bool)> {
 784         self.parse_unspanned_seq(
 785             &token::OpenDelim(delim),
 786             &token::CloseDelim(delim),
 787             SeqSep::trailing_allowed(token::Comma),
 788             f,
 789         )
 790     }
 791
 792     fn parse_paren_comma_seq<T>(
 793         &mut self,
 794         f: impl FnMut(&mut Parser<'a>) -> PResult<'a, T>,
 795     ) -> PResult<'a, (Vec<T>, bool)> {
 796         self.parse_delim_comma_seq(token::Paren, f)
 797     }
 798
 799     /// Advance the parser by one token using provided token as the next one.
 800     fn bump_with(&mut self, next_token: Token) {
 801         // Bumping after EOF is a bad sign, usually an infinite loop.
 802         if self.prev_token.kind == TokenKind::Eof {
 803             let msg = "attempted to bump the parser past EOF (may be stuck in a loop)";
 804             self.span_bug(self.token.span, msg);
 805         }
 806
 807         // Update the current and previous tokens.
 808         self.prev_token = mem::replace(&mut self.token, next_token);
 809
 810         // Diagnostics.
 811         self.expected_tokens.clear();
 812     }
 813
 814     /// Advance the parser by one token.
 815     pub fn bump(&mut self) {
 816         let next_token = self.next_tok(self.token.span);
 817         self.bump_with(next_token);
 818     }
 819
 820     /// Look-ahead `dist` tokens of `self.token` and get access to that token there.
 821     /// When `dist == 0` then the current token is looked at.
 822     pub fn look_ahead<R>(&self, dist: usize, looker: impl FnOnce(&Token) -> R) -> R {
 823         if dist == 0 {
 824             return looker(&self.token);
 825         }
 826
 827         let frame = &self.token_cursor.frame;
 828         looker(&match frame.tree_cursor.look_ahead(dist - 1) {
 829             Some(tree) => match tree {
 830                 TokenTree::Token(token) => token,
 831                 TokenTree::Delimited(dspan, delim, _) => {
 832                     Token::new(token::OpenDelim(delim), dspan.open)
 833                 }
 834             },
 835             None => Token::new(token::CloseDelim(frame.delim), frame.span.close),
 836         })
 837     }
 838
 839     /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
 840     fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
 841         self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
 842     }
 843
 844     /// Parses asyncness: `async` or nothing.
 845     fn parse_asyncness(&mut self) -> Async {
 846         if self.eat_keyword(kw::Async) {
 847             let span = self.prev_token.uninterpolated_span();
 848             Async::Yes { span, closure_id: DUMMY_NODE_ID, return_impl_trait_id: DUMMY_NODE_ID }
 849         } else {
 850             Async::No
 851         }
 852     }
 853
 854     /// Parses unsafety: `unsafe` or nothing.
 855     fn parse_unsafety(&mut self) -> Unsafe {
 856         if self.eat_keyword(kw::Unsafe) {
 857             Unsafe::Yes(self.prev_token.uninterpolated_span())
 858         } else {
 859             Unsafe::No
 860         }
 861     }
 862
 863     /// Parses constness: `const` or nothing.
 864     fn parse_constness(&mut self) -> Const {
 865         if self.eat_keyword(kw::Const) {
 866             Const::Yes(self.prev_token.uninterpolated_span())
 867         } else {
 868             Const::No
 869         }
 870     }
 871
 872     /// Parses mutability (`mut` or nothing).
 873     fn parse_mutability(&mut self) -> Mutability {
 874         if self.eat_keyword(kw::Mut) { Mutability::Mut } else { Mutability::Not }
 875     }
 876
 877     /// Possibly parses mutability (`const` or `mut`).
 878     fn parse_const_or_mut(&mut self) -> Option<Mutability> {
 879         if self.eat_keyword(kw::Mut) {
 880             Some(Mutability::Mut)
 881         } else if self.eat_keyword(kw::Const) {
 882             Some(Mutability::Not)
 883         } else {
 884             None
 885         }
 886     }
 887
 888     fn parse_field_name(&mut self) -> PResult<'a, Ident> {
 889         if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token.kind
 890         {
 891             self.expect_no_suffix(self.token.span, "a tuple index", suffix);
 892             self.bump();
 893             Ok(Ident::new(symbol, self.prev_token.span))
 894         } else {
 895             self.parse_ident_common(false)
 896         }
 897     }
 898
 899     fn parse_mac_args(&mut self) -> PResult<'a, P<MacArgs>> {
 900         self.parse_mac_args_common(true).map(P)
 901     }
 902
 903     fn parse_attr_args(&mut self) -> PResult<'a, MacArgs> {
 904         self.parse_mac_args_common(false)
 905     }
 906
 907     fn parse_mac_args_common(&mut self, delimited_only: bool) -> PResult<'a, MacArgs> {
 908         Ok(
 909             if self.check(&token::OpenDelim(DelimToken::Paren))
 910                 || self.check(&token::OpenDelim(DelimToken::Bracket))
 911                 || self.check(&token::OpenDelim(DelimToken::Brace))
 912             {
 913                 match self.parse_token_tree() {
 914                     TokenTree::Delimited(dspan, delim, tokens) =>
 915                     // We've confirmed above that there is a delimiter so unwrapping is OK.
 916                     {
 917                         MacArgs::Delimited(dspan, MacDelimiter::from_token(delim).unwrap(), tokens)
 918                     }
 919                     _ => unreachable!(),
 920                 }
 921             } else if !delimited_only {
 922                 if self.eat(&token::Eq) {
 923                     let eq_span = self.prev_token.span;
 924                     let mut is_interpolated_expr = false;
 925                     if let token::Interpolated(nt) = &self.token.kind {
 926                         if let token::NtExpr(..) = **nt {
 927                             is_interpolated_expr = true;
 928                         }
 929                     }
 930                     let token_tree = if is_interpolated_expr {
 931                         // We need to accept arbitrary interpolated expressions to continue
 932                         // supporting things like `doc = $expr` that work on stable.
 933                         // Non-literal interpolated expressions are rejected after expansion.
 934                         self.parse_token_tree()
 935                     } else {
 936                         self.parse_unsuffixed_lit()?.token_tree()
 937                     };
 938
 939                     MacArgs::Eq(eq_span, token_tree.into())
 940                 } else {
 941                     MacArgs::Empty
 942                 }
 943             } else {
 944                 return self.unexpected();
 945             },
 946         )
 947     }
 948
 949     fn parse_or_use_outer_attributes(
 950         &mut self,
 951         already_parsed_attrs: Option<AttrVec>,
 952     ) -> PResult<'a, AttrVec> {
 953         if let Some(attrs) = already_parsed_attrs {
 954             Ok(attrs)
 955         } else {
 956             self.parse_outer_attributes().map(|a| a.into())
 957         }
 958     }
 959
 960     /// Parses a single token tree from the input.
 961     pub fn parse_token_tree(&mut self) -> TokenTree {
 962         match self.token.kind {
 963             token::OpenDelim(..) => {
 964                 let frame = mem::replace(
 965                     &mut self.token_cursor.frame,
 966                     self.token_cursor.stack.pop().unwrap(),
 967                 );
 968                 self.token = Token::new(TokenKind::CloseDelim(frame.delim), frame.span.close);
 969                 self.bump();
 970                 TokenTree::Delimited(frame.span, frame.delim, frame.tree_cursor.stream)
 971             }
 972             token::CloseDelim(_) | token::Eof => unreachable!(),
 973             _ => {
 974                 self.bump();
 975                 TokenTree::Token(self.prev_token.clone())
 976             }
 977         }
 978     }
 979
 980     /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
 981     pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
 982         let mut tts = Vec::new();
 983         while self.token != token::Eof {
 984             tts.push(self.parse_token_tree());
 985         }
 986         Ok(tts)
 987     }
 988
 989     pub fn parse_tokens(&mut self) -> TokenStream {
 990         let mut result = Vec::new();
 991         loop {
 992             match self.token.kind {
 993                 token::Eof | token::CloseDelim(..) => break,
 994                 _ => result.push(self.parse_token_tree().into()),
 995             }
 996         }
 997         TokenStream::new(result)
 998     }
 999
1000     /// Evaluates the closure with restrictions in place.
1001     ///
1002     /// Afters the closure is evaluated, restrictions are reset.
1003     fn with_res<T>(&mut self, res: Restrictions, f: impl FnOnce(&mut Self) -> T) -> T {
1004         let old = self.restrictions;
1005         self.restrictions = res;
1006         let res = f(self);
1007         self.restrictions = old;
1008         res
1009     }
1010
1011     fn is_crate_vis(&self) -> bool {
1012         self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
1013     }
1014
1015     /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
1016     /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
1017     /// If the following element can't be a tuple (i.e., it's a function definition), then
1018     /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
1019     /// so emit a proper diagnostic.
1020     pub fn parse_visibility(&mut self, fbt: FollowedByType) -> PResult<'a, Visibility> {
1021         maybe_whole!(self, NtVis, |x| x);
1022
1023         self.expected_tokens.push(TokenType::Keyword(kw::Crate));
1024         if self.is_crate_vis() {
1025             self.bump(); // `crate`
1026             self.sess.gated_spans.gate(sym::crate_visibility_modifier, self.prev_token.span);
1027             return Ok(respan(self.prev_token.span, VisibilityKind::Crate(CrateSugar::JustCrate)));
1028         }
1029
1030         if !self.eat_keyword(kw::Pub) {
1031             // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
1032             // keyword to grab a span from for inherited visibility; an empty span at the
1033             // beginning of the current token would seem to be the "Schelling span".
1034             return Ok(respan(self.token.span.shrink_to_lo(), VisibilityKind::Inherited));
1035         }
1036         let lo = self.prev_token.span;
1037
1038         if self.check(&token::OpenDelim(token::Paren)) {
1039             // We don't `self.bump()` the `(` yet because this might be a struct definition where
1040             // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
1041             // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
1042             // by the following tokens.
1043             if self.is_keyword_ahead(1, &[kw::Crate]) && self.look_ahead(2, |t| t != &token::ModSep)
1044             // account for `pub(crate::foo)`
1045             {
1046                 // Parse `pub(crate)`.
1047                 self.bump(); // `(`
1048                 self.bump(); // `crate`
1049                 self.expect(&token::CloseDelim(token::Paren))?; // `)`
1050                 let vis = VisibilityKind::Crate(CrateSugar::PubCrate);
1051                 return Ok(respan(lo.to(self.prev_token.span), vis));
1052             } else if self.is_keyword_ahead(1, &[kw::In]) {
1053                 // Parse `pub(in path)`.
1054                 self.bump(); // `(`
1055                 self.bump(); // `in`
1056                 let path = self.parse_path(PathStyle::Mod)?; // `path`
1057                 self.expect(&token::CloseDelim(token::Paren))?; // `)`
1058                 let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
1059                 return Ok(respan(lo.to(self.prev_token.span), vis));
1060             } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren))
1061                 && self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
1062             {
1063                 // Parse `pub(self)` or `pub(super)`.
1064                 self.bump(); // `(`
1065                 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
1066                 self.expect(&token::CloseDelim(token::Paren))?; // `)`
1067                 let vis = VisibilityKind::Restricted { path: P(path), id: ast::DUMMY_NODE_ID };
1068                 return Ok(respan(lo.to(self.prev_token.span), vis));
1069             } else if let FollowedByType::No = fbt {
1070                 // Provide this diagnostic if a type cannot follow;
1071                 // in particular, if this is not a tuple struct.
1072                 self.recover_incorrect_vis_restriction()?;
1073                 // Emit diagnostic, but continue with public visibility.
1074             }
1075         }
1076
1077         Ok(respan(lo, VisibilityKind::Public))
1078     }
1079
1080     /// Recovery for e.g. `pub(something) fn ...` or `struct X { pub(something) y: Z }`
1081     fn recover_incorrect_vis_restriction(&mut self) -> PResult<'a, ()> {
1082         self.bump(); // `(`
1083         let path = self.parse_path(PathStyle::Mod)?;
1084         self.expect(&token::CloseDelim(token::Paren))?; // `)`
1085
1086         let msg = "incorrect visibility restriction";
1087         let suggestion = r##"some possible visibility restrictions are:
1088 `pub(crate)`: visible only on the current crate
1089 `pub(super)`: visible only in the current module's parent
1090 `pub(in path::to::module)`: visible only on the specified path"##;
1091
1092         let path_str = pprust::path_to_string(&path);
1093
1094         struct_span_err!(self.sess.span_diagnostic, path.span, E0704, "{}", msg)
1095             .help(suggestion)
1096             .span_suggestion(
1097                 path.span,
1098                 &format!("make this visible only to module `{}` with `in`", path_str),
1099                 format!("in {}", path_str),
1100                 Applicability::MachineApplicable,
1101             )
1102             .emit();
1103
1104         Ok(())
1105     }
1106
1107     /// Parses `extern string_literal?`.
1108     fn parse_extern(&mut self) -> PResult<'a, Extern> {
1109         Ok(if self.eat_keyword(kw::Extern) {
1110             Extern::from_abi(self.parse_abi())
1111         } else {
1112             Extern::None
1113         })
1114     }
1115
1116     /// Parses a string literal as an ABI spec.
1117     fn parse_abi(&mut self) -> Option<StrLit> {
1118         match self.parse_str_lit() {
1119             Ok(str_lit) => Some(str_lit),
1120             Err(Some(lit)) => match lit.kind {
1121                 ast::LitKind::Err(_) => None,
1122                 _ => {
1123                     self.struct_span_err(lit.span, "non-string ABI literal")
1124                         .span_suggestion(
1125                             lit.span,
1126                             "specify the ABI with a string literal",
1127                             "\"C\"".to_string(),
1128                             Applicability::MaybeIncorrect,
1129                         )
1130                         .emit();
1131                     None
1132                 }
1133             },
1134             Err(None) => None,
1135         }
1136     }
1137
1138     /// Records all tokens consumed by the provided callback,
1139     /// including the current token. These tokens are collected
1140     /// into a `TokenStream`, and returned along with the result
1141     /// of the callback.
1142     ///
1143     /// Note: If your callback consumes an opening delimiter
1144     /// (including the case where you call `collect_tokens`
1145     /// when the current token is an opening delimeter),
1146     /// you must also consume the corresponding closing delimiter.
1147     ///
1148     /// That is, you can consume
1149     /// `something ([{ }])` or `([{}])`, but not `([{}]`
1150     ///
1151     /// This restriction shouldn't be an issue in practice,
1152     /// since this function is used to record the tokens for
1153     /// a parsed AST item, which always has matching delimiters.
1154     pub fn collect_tokens<R>(
1155         &mut self,
1156         f: impl FnOnce(&mut Self) -> PResult<'a, R>,
1157     ) -> PResult<'a, (R, TokenStream)> {
1158         // Record all tokens we parse when parsing this item.
1159         let tokens: Vec<TreeAndJoint> = self.token_cursor.cur_token.clone().into_iter().collect();
1160         debug!("collect_tokens: starting with {:?}", tokens);
1161
1162         // We need special handling for the case where `collect_tokens` is called
1163         // on an opening delimeter (e.g. '('). At this point, we have already pushed
1164         // a new frame - however, we want to record the original `TokenTree::Delimited`,
1165         // for consistency with the case where we start recording one token earlier.
1166         // See `TokenCursor::next` to see how `cur_token` is set up.
1167         let prev_depth =
1168             if matches!(self.token_cursor.cur_token, Some((TokenTree::Delimited(..), _))) {
1169                 if self.token_cursor.stack.is_empty() {
1170                     // There is nothing below us in the stack that
1171                     // the function could consume, so the only thing it can legally
1172                     // capture is the entire contents of the current frame.
1173                     return Ok((f(self)?, TokenStream::new(tokens)));
1174                 }
1175                 // We have already recorded the full `TokenTree::Delimited` when we created
1176                 // our `tokens` vector at the start of this function. We are now inside
1177                 // a new frame corresponding to the `TokenTree::Delimited` we already recoreded.
1178                 // We don't want to record any of the tokens inside this frame, since they
1179                 // will be duplicates of the tokens nested inside the `TokenTree::Delimited`.
1180                 // Therefore, we set our recording depth to the *previous* frame. This allows
1181                 // us to record a sequence like: `(foo).bar()`: the `(foo)` will be recored
1182                 // as our initial `cur_token`, while the `.bar()` will be recored after we
1183                 // pop the `(foo)` frame.
1184                 self.token_cursor.stack.len() - 1
1185             } else {
1186                 self.token_cursor.stack.len()
1187             };
1188         let prev_collecting =
1189             self.token_cursor.collecting.replace(Collecting { buf: tokens, depth: prev_depth });
1190
1191         let ret = f(self);
1192
1193         let mut collected_tokens = if let Some(collecting) = self.token_cursor.collecting.take() {
1194             collecting.buf
1195         } else {
1196             let msg = "our vector went away?";
1197             debug!("collect_tokens: {}", msg);
1198             self.sess.span_diagnostic.delay_span_bug(self.token.span, &msg);
1199             // This can happen due to a bad interaction of two unrelated recovery mechanisms
1200             // with mismatched delimiters *and* recovery lookahead on the likely typo
1201             // `pub ident(` (#62895, different but similar to the case above).
1202             return Ok((ret?, TokenStream::default()));
1203         };
1204
1205         debug!("collect_tokens: got raw tokens {:?}", collected_tokens);
1206
1207         // If we're not at EOF our current token wasn't actually consumed by
1208         // `f`, but it'll still be in our list that we pulled out. In that case
1209         // put it back.
1210         let extra_token = if self.token != token::Eof { collected_tokens.pop() } else { None };
1211
1212         if let Some(mut collecting) = prev_collecting {
1213             // If we were previously collecting at the same depth,
1214             // then the previous call to `collect_tokens` needs to see
1215             // the tokens we just recorded.
1216             //
1217             // If we were previously recording at an lower `depth`,
1218             // then the previous `collect_tokens` call already recorded
1219             // this entire frame in the form of a `TokenTree::Delimited`,
1220             // so there is nothing else for us to do.
1221             if collecting.depth == prev_depth {
1222                 collecting.buf.extend(collected_tokens.iter().cloned());
1223                 collecting.buf.extend(extra_token);
1224                 debug!("collect_tokens: updating previous buf to {:?}", collecting);
1225             }
1226             self.token_cursor.collecting = Some(collecting)
1227         }
1228
1229         Ok((ret?, TokenStream::new(collected_tokens)))
1230     }
1231
1232     /// `::{` or `::*`
1233     fn is_import_coupler(&mut self) -> bool {
1234         self.check(&token::ModSep)
1235             && self.look_ahead(1, |t| {
1236                 *t == token::OpenDelim(token::Brace) || *t == token::BinOp(token::Star)
1237             })
1238     }
1239 }
1240
1241 crate fn make_unclosed_delims_error(
1242     unmatched: UnmatchedBrace,
1243     sess: &ParseSess,
1244 ) -> Option<DiagnosticBuilder<'_>> {
1245     // `None` here means an `Eof` was found. We already emit those errors elsewhere, we add them to
1246     // `unmatched_braces` only for error recovery in the `Parser`.
1247     let found_delim = unmatched.found_delim?;
1248     let mut err = sess.span_diagnostic.struct_span_err(
1249         unmatched.found_span,
1250         &format!(
1251             "mismatched closing delimiter: `{}`",
1252             pprust::token_kind_to_string(&token::CloseDelim(found_delim)),
1253         ),
1254     );
1255     err.span_label(unmatched.found_span, "mismatched closing delimiter");
1256     if let Some(sp) = unmatched.candidate_span {
1257         err.span_label(sp, "closing delimiter possibly meant for this");
1258     }
1259     if let Some(sp) = unmatched.unclosed_span {
1260         err.span_label(sp, "unclosed delimiter");
1261     }
1262     Some(err)
1263 }
1264
1265 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, sess: &ParseSess) {
1266     *sess.reached_eof.borrow_mut() |=
1267         unclosed_delims.iter().any(|unmatched_delim| unmatched_delim.found_delim.is_none());
1268     for unmatched in unclosed_delims.drain(..) {
1269         if let Some(mut e) = make_unclosed_delims_error(unmatched, sess) {
1270             e.emit();
1271         }
1272     }
1273 }