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-rw-r--r--bench_data/glorious_old_parser8562
-rw-r--r--crates/ide/src/syntax_highlighting/tests.rs37
-rw-r--r--crates/syntax/src/tests.rs28
-rw-r--r--crates/test_utils/src/bench_fixture.rs9
4 files changed, 8628 insertions, 8 deletions
diff --git a/bench_data/glorious_old_parser b/bench_data/glorious_old_parser
new file mode 100644
index 000000000..7e900dfeb
--- /dev/null
+++ b/bench_data/glorious_old_parser
@@ -0,0 +1,8562 @@
1use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
2use crate::ast::{GenericBound, TraitBoundModifier};
3use crate::ast::Unsafety;
4use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
5use crate::ast::Block;
6use crate::ast::{BlockCheckMode, CaptureBy, Movability};
7use crate::ast::{Constness, Crate};
8use crate::ast::Defaultness;
9use crate::ast::EnumDef;
10use crate::ast::{Expr, ExprKind, RangeLimits};
11use crate::ast::{Field, FnDecl, FnHeader};
12use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
13use crate::ast::{GenericParam, GenericParamKind};
14use crate::ast::GenericArg;
15use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
16use crate::ast::{Label, Lifetime, Lit, LitKind};
17use crate::ast::Local;
18use crate::ast::MacStmtStyle;
19use crate::ast::{Mac, Mac_, MacDelimiter};
20use crate::ast::{MutTy, Mutability};
21use crate::ast::{Pat, PatKind, PathSegment};
22use crate::ast::{PolyTraitRef, QSelf};
23use crate::ast::{Stmt, StmtKind};
24use crate::ast::{VariantData, StructField};
25use crate::ast::StrStyle;
26use crate::ast::SelfKind;
27use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
28use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
29use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
30use crate::ast::{UseTree, UseTreeKind};
31use crate::ast::{BinOpKind, UnOp};
32use crate::ast::{RangeEnd, RangeSyntax};
33use crate::{ast, attr};
34use crate::ext::base::DummyResult;
35use crate::source_map::{self, SourceMap, Spanned, respan};
36use crate::parse::{self, SeqSep, classify, token};
37use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
38use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
39use crate::parse::token::DelimToken;
40use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
41use crate::util::parser::{AssocOp, Fixity};
42use crate::print::pprust;
43use crate::ptr::P;
44use crate::parse::PResult;
45use crate::ThinVec;
46use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
47use crate::symbol::{Symbol, keywords};
48
49use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
50use rustc_target::spec::abi::{self, Abi};
51use syntax_pos::{Span, MultiSpan, BytePos, FileName};
52use log::{debug, trace};
53
54use std::borrow::Cow;
55use std::cmp;
56use std::mem;
57use std::path::{self, Path, PathBuf};
58use std::slice;
59
60#[derive(Debug)]
61/// Whether the type alias or associated type is a concrete type or an existential type
62pub enum AliasKind {
63 /// Just a new name for the same type
64 Weak(P<Ty>),
65 /// Only trait impls of the type will be usable, not the actual type itself
66 Existential(GenericBounds),
67}
68
69bitflags::bitflags! {
70 struct Restrictions: u8 {
71 const STMT_EXPR = 1 << 0;
72 const NO_STRUCT_LITERAL = 1 << 1;
73 }
74}
75
76type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
77
78/// Specifies how to parse a path.
79#[derive(Copy, Clone, PartialEq)]
80pub enum PathStyle {
81 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
82 /// with something else. For example, in expressions `segment < ....` can be interpreted
83 /// as a comparison and `segment ( ....` can be interpreted as a function call.
84 /// In all such contexts the non-path interpretation is preferred by default for practical
85 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
86 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
87 Expr,
88 /// In other contexts, notably in types, no ambiguity exists and paths can be written
89 /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
90 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
91 Type,
92 /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
93 /// visibilities or attributes.
94 /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
95 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
96 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
97 /// tokens when something goes wrong.
98 Mod,
99}
100
101#[derive(Clone, Copy, PartialEq, Debug)]
102enum SemiColonMode {
103 Break,
104 Ignore,
105 Comma,
106}
107
108#[derive(Clone, Copy, PartialEq, Debug)]
109enum BlockMode {
110 Break,
111 Ignore,
112}
113
114/// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
115/// dropped into the token stream, which happens while parsing the result of
116/// macro expansion). Placement of these is not as complex as I feared it would
117/// be. The important thing is to make sure that lookahead doesn't balk at
118/// `token::Interpolated` tokens.
119macro_rules! maybe_whole_expr {
120 ($p:expr) => {
121 if let token::Interpolated(nt) = $p.token.clone() {
122 match *nt {
123 token::NtExpr(ref e) | token::NtLiteral(ref e) => {
124 $p.bump();
125 return Ok((*e).clone());
126 }
127 token::NtPath(ref path) => {
128 $p.bump();
129 let span = $p.span;
130 let kind = ExprKind::Path(None, (*path).clone());
131 return Ok($p.mk_expr(span, kind, ThinVec::new()));
132 }
133 token::NtBlock(ref block) => {
134 $p.bump();
135 let span = $p.span;
136 let kind = ExprKind::Block((*block).clone(), None);
137 return Ok($p.mk_expr(span, kind, ThinVec::new()));
138 }
139 _ => {},
140 };
141 }
142 }
143}
144
145/// As maybe_whole_expr, but for things other than expressions
146macro_rules! maybe_whole {
147 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
148 if let token::Interpolated(nt) = $p.token.clone() {
149 if let token::$constructor($x) = (*nt).clone() {
150 $p.bump();
151 return Ok($e);
152 }
153 }
154 };
155}
156
157fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
158 if let Some(ref mut rhs) = rhs {
159 lhs.append(rhs);
160 }
161 lhs
162}
163
164#[derive(Debug, Clone, Copy, PartialEq)]
165enum PrevTokenKind {
166 DocComment,
167 Comma,
168 Plus,
169 Interpolated,
170 Eof,
171 Ident,
172 Other,
173}
174
175trait RecoverQPath: Sized {
176 const PATH_STYLE: PathStyle = PathStyle::Expr;
177 fn to_ty(&self) -> Option<P<Ty>>;
178 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
179 fn to_string(&self) -> String;
180}
181
182impl RecoverQPath for Ty {
183 const PATH_STYLE: PathStyle = PathStyle::Type;
184 fn to_ty(&self) -> Option<P<Ty>> {
185 Some(P(self.clone()))
186 }
187 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
188 Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
189 }
190 fn to_string(&self) -> String {
191 pprust::ty_to_string(self)
192 }
193}
194
195impl RecoverQPath for Pat {
196 fn to_ty(&self) -> Option<P<Ty>> {
197 self.to_ty()
198 }
199 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
200 Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
201 }
202 fn to_string(&self) -> String {
203 pprust::pat_to_string(self)
204 }
205}
206
207impl RecoverQPath for Expr {
208 fn to_ty(&self) -> Option<P<Ty>> {
209 self.to_ty()
210 }
211 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
212 Self { span: path.span, node: ExprKind::Path(qself, path),
213 id: self.id, attrs: self.attrs.clone() }
214 }
215 fn to_string(&self) -> String {
216 pprust::expr_to_string(self)
217 }
218}
219
220/* ident is handled by common.rs */
221
222#[derive(Clone)]
223pub struct Parser<'a> {
224 pub sess: &'a ParseSess,
225 /// the current token:
226 pub token: token::Token,
227 /// the span of the current token:
228 pub span: Span,
229 /// the span of the previous token:
230 meta_var_span: Option<Span>,
231 pub prev_span: Span,
232 /// the previous token kind
233 prev_token_kind: PrevTokenKind,
234 restrictions: Restrictions,
235 /// Used to determine the path to externally loaded source files
236 crate directory: Directory<'a>,
237 /// Whether to parse sub-modules in other files.
238 pub recurse_into_file_modules: bool,
239 /// Name of the root module this parser originated from. If `None`, then the
240 /// name is not known. This does not change while the parser is descending
241 /// into modules, and sub-parsers have new values for this name.
242 pub root_module_name: Option<String>,
243 crate expected_tokens: Vec<TokenType>,
244 token_cursor: TokenCursor,
245 desugar_doc_comments: bool,
246 /// Whether we should configure out of line modules as we parse.
247 pub cfg_mods: bool,
248 /// This field is used to keep track of how many left angle brackets we have seen. This is
249 /// required in order to detect extra leading left angle brackets (`<` characters) and error
250 /// appropriately.
251 ///
252 /// See the comments in the `parse_path_segment` function for more details.
253 crate unmatched_angle_bracket_count: u32,
254 crate max_angle_bracket_count: u32,
255 /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
256 /// it gets removed from here. Every entry left at the end gets emitted as an independent
257 /// error.
258 crate unclosed_delims: Vec<UnmatchedBrace>,
259}
260
261
262#[derive(Clone)]
263struct TokenCursor {
264 frame: TokenCursorFrame,
265 stack: Vec<TokenCursorFrame>,
266}
267
268#[derive(Clone)]
269struct TokenCursorFrame {
270 delim: token::DelimToken,
271 span: DelimSpan,
272 open_delim: bool,
273 tree_cursor: tokenstream::Cursor,
274 close_delim: bool,
275 last_token: LastToken,
276}
277
278/// This is used in `TokenCursorFrame` above to track tokens that are consumed
279/// by the parser, and then that's transitively used to record the tokens that
280/// each parse AST item is created with.
281///
282/// Right now this has two states, either collecting tokens or not collecting
283/// tokens. If we're collecting tokens we just save everything off into a local
284/// `Vec`. This should eventually though likely save tokens from the original
285/// token stream and just use slicing of token streams to avoid creation of a
286/// whole new vector.
287///
288/// The second state is where we're passively not recording tokens, but the last
289/// token is still tracked for when we want to start recording tokens. This
290/// "last token" means that when we start recording tokens we'll want to ensure
291/// that this, the first token, is included in the output.
292///
293/// You can find some more example usage of this in the `collect_tokens` method
294/// on the parser.
295#[derive(Clone)]
296enum LastToken {
297 Collecting(Vec<TreeAndJoint>),
298 Was(Option<TreeAndJoint>),
299}
300
301impl TokenCursorFrame {
302 fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
303 TokenCursorFrame {
304 delim: delim,
305 span: sp,
306 open_delim: delim == token::NoDelim,
307 tree_cursor: tts.clone().into_trees(),
308 close_delim: delim == token::NoDelim,
309 last_token: LastToken::Was(None),
310 }
311 }
312}
313
314impl TokenCursor {
315 fn next(&mut self) -> TokenAndSpan {
316 loop {
317 let tree = if !self.frame.open_delim {
318 self.frame.open_delim = true;
319 TokenTree::open_tt(self.frame.span.open, self.frame.delim)
320 } else if let Some(tree) = self.frame.tree_cursor.next() {
321 tree
322 } else if !self.frame.close_delim {
323 self.frame.close_delim = true;
324 TokenTree::close_tt(self.frame.span.close, self.frame.delim)
325 } else if let Some(frame) = self.stack.pop() {
326 self.frame = frame;
327 continue
328 } else {
329 return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
330 };
331
332 match self.frame.last_token {
333 LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
334 LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
335 }
336
337 match tree {
338 TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
339 TokenTree::Delimited(sp, delim, tts) => {
340 let frame = TokenCursorFrame::new(sp, delim, &tts);
341 self.stack.push(mem::replace(&mut self.frame, frame));
342 }
343 }
344 }
345 }
346
347 fn next_desugared(&mut self) -> TokenAndSpan {
348 let (sp, name) = match self.next() {
349 TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
350 tok => return tok,
351 };
352
353 let stripped = strip_doc_comment_decoration(&name.as_str());
354
355 // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
356 // required to wrap the text.
357 let mut num_of_hashes = 0;
358 let mut count = 0;
359 for ch in stripped.chars() {
360 count = match ch {
361 '"' => 1,
362 '#' if count > 0 => count + 1,
363 _ => 0,
364 };
365 num_of_hashes = cmp::max(num_of_hashes, count);
366 }
367
368 let delim_span = DelimSpan::from_single(sp);
369 let body = TokenTree::Delimited(
370 delim_span,
371 token::Bracket,
372 [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
373 TokenTree::Token(sp, token::Eq),
374 TokenTree::Token(sp, token::Literal(
375 token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
376 ]
377 .iter().cloned().collect::<TokenStream>().into(),
378 );
379
380 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
381 delim_span,
382 token::NoDelim,
383 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
384 [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
385 .iter().cloned().collect::<TokenStream>().into()
386 } else {
387 [TokenTree::Token(sp, token::Pound), body]
388 .iter().cloned().collect::<TokenStream>().into()
389 },
390 )));
391
392 self.next()
393 }
394}
395
396#[derive(Clone, PartialEq)]
397crate enum TokenType {
398 Token(token::Token),
399 Keyword(keywords::Keyword),
400 Operator,
401 Lifetime,
402 Ident,
403 Path,
404 Type,
405 Const,
406}
407
408impl TokenType {
409 fn to_string(&self) -> String {
410 match *self {
411 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
412 TokenType::Keyword(kw) => format!("`{}`", kw.name()),
413 TokenType::Operator => "an operator".to_string(),
414 TokenType::Lifetime => "lifetime".to_string(),
415 TokenType::Ident => "identifier".to_string(),
416 TokenType::Path => "path".to_string(),
417 TokenType::Type => "type".to_string(),
418 TokenType::Const => "const".to_string(),
419 }
420 }
421}
422
423/// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
424/// `IDENT<<u8 as Trait>::AssocTy>`.
425///
426/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
427/// that `IDENT` is not the ident of a fn trait.
428fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
429 t == &token::ModSep || t == &token::Lt ||
430 t == &token::BinOp(token::Shl)
431}
432
433/// Information about the path to a module.
434pub struct ModulePath {
435 name: String,
436 path_exists: bool,
437 pub result: Result<ModulePathSuccess, Error>,
438}
439
440pub struct ModulePathSuccess {
441 pub path: PathBuf,
442 pub directory_ownership: DirectoryOwnership,
443 warn: bool,
444}
445
446pub enum Error {
447 FileNotFoundForModule {
448 mod_name: String,
449 default_path: String,
450 secondary_path: String,
451 dir_path: String,
452 },
453 DuplicatePaths {
454 mod_name: String,
455 default_path: String,
456 secondary_path: String,
457 },
458 UselessDocComment,
459 InclusiveRangeWithNoEnd,
460}
461
462impl Error {
463 fn span_err<S: Into<MultiSpan>>(self,
464 sp: S,
465 handler: &errors::Handler) -> DiagnosticBuilder<'_> {
466 match self {
467 Error::FileNotFoundForModule { ref mod_name,
468 ref default_path,
469 ref secondary_path,
470 ref dir_path } => {
471 let mut err = struct_span_err!(handler, sp, E0583,
472 "file not found for module `{}`", mod_name);
473 err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
474 default_path,
475 secondary_path,
476 dir_path));
477 err
478 }
479 Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
480 let mut err = struct_span_err!(handler, sp, E0584,
481 "file for module `{}` found at both {} and {}",
482 mod_name,
483 default_path,
484 secondary_path);
485 err.help("delete or rename one of them to remove the ambiguity");
486 err
487 }
488 Error::UselessDocComment => {
489 let mut err = struct_span_err!(handler, sp, E0585,
490 "found a documentation comment that doesn't document anything");
491 err.help("doc comments must come before what they document, maybe a comment was \
492 intended with `//`?");
493 err
494 }
495 Error::InclusiveRangeWithNoEnd => {
496 let mut err = struct_span_err!(handler, sp, E0586,
497 "inclusive range with no end");
498 err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
499 err
500 }
501 }
502 }
503}
504
505#[derive(Debug)]
506enum LhsExpr {
507 NotYetParsed,
508 AttributesParsed(ThinVec<Attribute>),
509 AlreadyParsed(P<Expr>),
510}
511
512impl From<Option<ThinVec<Attribute>>> for LhsExpr {
513 fn from(o: Option<ThinVec<Attribute>>) -> Self {
514 if let Some(attrs) = o {
515 LhsExpr::AttributesParsed(attrs)
516 } else {
517 LhsExpr::NotYetParsed
518 }
519 }
520}
521
522impl From<P<Expr>> for LhsExpr {
523 fn from(expr: P<Expr>) -> Self {
524 LhsExpr::AlreadyParsed(expr)
525 }
526}
527
528/// Creates a placeholder argument.
529fn dummy_arg(span: Span) -> Arg {
530 let ident = Ident::new(keywords::Invalid.name(), span);
531 let pat = P(Pat {
532 id: ast::DUMMY_NODE_ID,
533 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
534 span,
535 });
536 let ty = Ty {
537 node: TyKind::Err,
538 span,
539 id: ast::DUMMY_NODE_ID
540 };
541 Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
542}
543
544#[derive(Copy, Clone, Debug)]
545enum TokenExpectType {
546 Expect,
547 NoExpect,
548}
549
550impl<'a> Parser<'a> {
551 pub fn new(sess: &'a ParseSess,
552 tokens: TokenStream,
553 directory: Option<Directory<'a>>,
554 recurse_into_file_modules: bool,
555 desugar_doc_comments: bool)
556 -> Self {
557 let mut parser = Parser {
558 sess,
559 token: token::Whitespace,
560 span: syntax_pos::DUMMY_SP,
561 prev_span: syntax_pos::DUMMY_SP,
562 meta_var_span: None,
563 prev_token_kind: PrevTokenKind::Other,
564 restrictions: Restrictions::empty(),
565 recurse_into_file_modules,
566 directory: Directory {
567 path: Cow::from(PathBuf::new()),
568 ownership: DirectoryOwnership::Owned { relative: None }
569 },
570 root_module_name: None,
571 expected_tokens: Vec::new(),
572 token_cursor: TokenCursor {
573 frame: TokenCursorFrame::new(
574 DelimSpan::dummy(),
575 token::NoDelim,
576 &tokens.into(),
577 ),
578 stack: Vec::new(),
579 },
580 desugar_doc_comments,
581 cfg_mods: true,
582 unmatched_angle_bracket_count: 0,
583 max_angle_bracket_count: 0,
584 unclosed_delims: Vec::new(),
585 };
586
587 let tok = parser.next_tok();
588 parser.token = tok.tok;
589 parser.span = tok.sp;
590
591 if let Some(directory) = directory {
592 parser.directory = directory;
593 } else if !parser.span.is_dummy() {
594 if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
595 path.pop();
596 parser.directory.path = Cow::from(path);
597 }
598 }
599
600 parser.process_potential_macro_variable();
601 parser
602 }
603
604 fn next_tok(&mut self) -> TokenAndSpan {
605 let mut next = if self.desugar_doc_comments {
606 self.token_cursor.next_desugared()
607 } else {
608 self.token_cursor.next()
609 };
610 if next.sp.is_dummy() {
611 // Tweak the location for better diagnostics, but keep syntactic context intact.
612 next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
613 }
614 next
615 }
616
617 /// Converts the current token to a string using `self`'s reader.
618 pub fn this_token_to_string(&self) -> String {
619 pprust::token_to_string(&self.token)
620 }
621
622 fn token_descr(&self) -> Option<&'static str> {
623 Some(match &self.token {
624 t if t.is_special_ident() => "reserved identifier",
625 t if t.is_used_keyword() => "keyword",
626 t if t.is_unused_keyword() => "reserved keyword",
627 token::DocComment(..) => "doc comment",
628 _ => return None,
629 })
630 }
631
632 fn this_token_descr(&self) -> String {
633 if let Some(prefix) = self.token_descr() {
634 format!("{} `{}`", prefix, self.this_token_to_string())
635 } else {
636 format!("`{}`", self.this_token_to_string())
637 }
638 }
639
640 fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
641 let token_str = pprust::token_to_string(t);
642 Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
643 }
644
645 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
646 match self.expect_one_of(&[], &[]) {
647 Err(e) => Err(e),
648 Ok(_) => unreachable!(),
649 }
650 }
651
652 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
653 pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
654 if self.expected_tokens.is_empty() {
655 if self.token == *t {
656 self.bump();
657 Ok(false)
658 } else {
659 let token_str = pprust::token_to_string(t);
660 let this_token_str = self.this_token_descr();
661 let mut err = self.fatal(&format!("expected `{}`, found {}",
662 token_str,
663 this_token_str));
664
665 let sp = if self.token == token::Token::Eof {
666 // EOF, don't want to point at the following char, but rather the last token
667 self.prev_span
668 } else {
669 self.sess.source_map().next_point(self.prev_span)
670 };
671 let label_exp = format!("expected `{}`", token_str);
672 match self.recover_closing_delimiter(&[t.clone()], err) {
673 Err(e) => err = e,
674 Ok(recovered) => {
675 return Ok(recovered);
676 }
677 }
678 let cm = self.sess.source_map();
679 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
680 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
681 // When the spans are in the same line, it means that the only content
682 // between them is whitespace, point only at the found token.
683 err.span_label(self.span, label_exp);
684 }
685 _ => {
686 err.span_label(sp, label_exp);
687 err.span_label(self.span, "unexpected token");
688 }
689 }
690 Err(err)
691 }
692 } else {
693 self.expect_one_of(slice::from_ref(t), &[])
694 }
695 }
696
697 fn recover_closing_delimiter(
698 &mut self,
699 tokens: &[token::Token],
700 mut err: DiagnosticBuilder<'a>,
701 ) -> PResult<'a, bool> {
702 let mut pos = None;
703 // we want to use the last closing delim that would apply
704 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
705 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
706 && Some(self.span) > unmatched.unclosed_span
707 {
708 pos = Some(i);
709 }
710 }
711 match pos {
712 Some(pos) => {
713 // Recover and assume that the detected unclosed delimiter was meant for
714 // this location. Emit the diagnostic and act as if the delimiter was
715 // present for the parser's sake.
716
717 // Don't attempt to recover from this unclosed delimiter more than once.
718 let unmatched = self.unclosed_delims.remove(pos);
719 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
720
721 // We want to suggest the inclusion of the closing delimiter where it makes
722 // the most sense, which is immediately after the last token:
723 //
724 // {foo(bar {}}
725 // - ^
726 // | |
727 // | help: `)` may belong here (FIXME: #58270)
728 // |
729 // unclosed delimiter
730 if let Some(sp) = unmatched.unclosed_span {
731 err.span_label(sp, "unclosed delimiter");
732 }
733 err.span_suggestion_short(
734 self.sess.source_map().next_point(self.prev_span),
735 &format!("{} may belong here", delim.to_string()),
736 delim.to_string(),
737 Applicability::MaybeIncorrect,
738 );
739 err.emit();
740 self.expected_tokens.clear(); // reduce errors
741 Ok(true)
742 }
743 _ => Err(err),
744 }
745 }
746
747 /// Expect next token to be edible or inedible token. If edible,
748 /// then consume it; if inedible, then return without consuming
749 /// anything. Signal a fatal error if next token is unexpected.
750 pub fn expect_one_of(
751 &mut self,
752 edible: &[token::Token],
753 inedible: &[token::Token],
754 ) -> PResult<'a, bool /* recovered */> {
755 fn tokens_to_string(tokens: &[TokenType]) -> String {
756 let mut i = tokens.iter();
757 // This might be a sign we need a connect method on Iterator.
758 let b = i.next()
759 .map_or(String::new(), |t| t.to_string());
760 i.enumerate().fold(b, |mut b, (i, a)| {
761 if tokens.len() > 2 && i == tokens.len() - 2 {
762 b.push_str(", or ");
763 } else if tokens.len() == 2 && i == tokens.len() - 2 {
764 b.push_str(" or ");
765 } else {
766 b.push_str(", ");
767 }
768 b.push_str(&a.to_string());
769 b
770 })
771 }
772 if edible.contains(&self.token) {
773 self.bump();
774 Ok(false)
775 } else if inedible.contains(&self.token) {
776 // leave it in the input
777 Ok(false)
778 } else {
779 let mut expected = edible.iter()
780 .map(|x| TokenType::Token(x.clone()))
781 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
782 .chain(self.expected_tokens.iter().cloned())
783 .collect::<Vec<_>>();
784 expected.sort_by_cached_key(|x| x.to_string());
785 expected.dedup();
786 let expect = tokens_to_string(&expected[..]);
787 let actual = self.this_token_to_string();
788 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
789 let short_expect = if expected.len() > 6 {
790 format!("{} possible tokens", expected.len())
791 } else {
792 expect.clone()
793 };
794 (format!("expected one of {}, found `{}`", expect, actual),
795 (self.sess.source_map().next_point(self.prev_span),
796 format!("expected one of {} here", short_expect)))
797 } else if expected.is_empty() {
798 (format!("unexpected token: `{}`", actual),
799 (self.prev_span, "unexpected token after this".to_string()))
800 } else {
801 (format!("expected {}, found `{}`", expect, actual),
802 (self.sess.source_map().next_point(self.prev_span),
803 format!("expected {} here", expect)))
804 };
805 let mut err = self.fatal(&msg_exp);
806 if self.token.is_ident_named("and") {
807 err.span_suggestion_short(
808 self.span,
809 "use `&&` instead of `and` for the boolean operator",
810 "&&".to_string(),
811 Applicability::MaybeIncorrect,
812 );
813 }
814 if self.token.is_ident_named("or") {
815 err.span_suggestion_short(
816 self.span,
817 "use `||` instead of `or` for the boolean operator",
818 "||".to_string(),
819 Applicability::MaybeIncorrect,
820 );
821 }
822 let sp = if self.token == token::Token::Eof {
823 // This is EOF, don't want to point at the following char, but rather the last token
824 self.prev_span
825 } else {
826 label_sp
827 };
828 match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
829 TokenType::Token(t) => Some(t.clone()),
830 _ => None,
831 }).collect::<Vec<_>>(), err) {
832 Err(e) => err = e,
833 Ok(recovered) => {
834 return Ok(recovered);
835 }
836 }
837
838 let cm = self.sess.source_map();
839 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
840 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
841 // When the spans are in the same line, it means that the only content between
842 // them is whitespace, point at the found token in that case:
843 //
844 // X | () => { syntax error };
845 // | ^^^^^ expected one of 8 possible tokens here
846 //
847 // instead of having:
848 //
849 // X | () => { syntax error };
850 // | -^^^^^ unexpected token
851 // | |
852 // | expected one of 8 possible tokens here
853 err.span_label(self.span, label_exp);
854 }
855 _ if self.prev_span == syntax_pos::DUMMY_SP => {
856 // Account for macro context where the previous span might not be
857 // available to avoid incorrect output (#54841).
858 err.span_label(self.span, "unexpected token");
859 }
860 _ => {
861 err.span_label(sp, label_exp);
862 err.span_label(self.span, "unexpected token");
863 }
864 }
865 Err(err)
866 }
867 }
868
869 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
870 fn interpolated_or_expr_span(&self,
871 expr: PResult<'a, P<Expr>>)
872 -> PResult<'a, (Span, P<Expr>)> {
873 expr.map(|e| {
874 if self.prev_token_kind == PrevTokenKind::Interpolated {
875 (self.prev_span, e)
876 } else {
877 (e.span, e)
878 }
879 })
880 }
881
882 fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
883 let mut err = self.struct_span_err(self.span,
884 &format!("expected identifier, found {}",
885 self.this_token_descr()));
886 if let token::Ident(ident, false) = &self.token {
887 if ident.is_reserved() && !ident.is_path_segment_keyword() &&
888 ident.name != keywords::Underscore.name()
889 {
890 err.span_suggestion(
891 self.span,
892 "you can escape reserved keywords to use them as identifiers",
893 format!("r#{}", ident),
894 Applicability::MaybeIncorrect,
895 );
896 }
897 }
898 if let Some(token_descr) = self.token_descr() {
899 err.span_label(self.span, format!("expected identifier, found {}", token_descr));
900 } else {
901 err.span_label(self.span, "expected identifier");
902 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
903 err.span_suggestion(
904 self.span,
905 "remove this comma",
906 String::new(),
907 Applicability::MachineApplicable,
908 );
909 }
910 }
911 err
912 }
913
914 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
915 self.parse_ident_common(true)
916 }
917
918 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
919 match self.token {
920 token::Ident(ident, _) => {
921 if self.token.is_reserved_ident() {
922 let mut err = self.expected_ident_found();
923 if recover {
924 err.emit();
925 } else {
926 return Err(err);
927 }
928 }
929 let span = self.span;
930 self.bump();
931 Ok(Ident::new(ident.name, span))
932 }
933 _ => {
934 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
935 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
936 } else {
937 self.expected_ident_found()
938 })
939 }
940 }
941 }
942
943 /// Checks if the next token is `tok`, and returns `true` if so.
944 ///
945 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
946 /// encountered.
947 crate fn check(&mut self, tok: &token::Token) -> bool {
948 let is_present = self.token == *tok;
949 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
950 is_present
951 }
952
953 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
954 pub fn eat(&mut self, tok: &token::Token) -> bool {
955 let is_present = self.check(tok);
956 if is_present { self.bump() }
957 is_present
958 }
959
960 fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
961 self.expected_tokens.push(TokenType::Keyword(kw));
962 self.token.is_keyword(kw)
963 }
964
965 /// If the next token is the given keyword, eats it and returns
966 /// `true`. Otherwise, returns `false`.
967 pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
968 if self.check_keyword(kw) {
969 self.bump();
970 true
971 } else {
972 false
973 }
974 }
975
976 fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
977 if self.token.is_keyword(kw) {
978 self.bump();
979 true
980 } else {
981 false
982 }
983 }
984
985 /// If the given word is not a keyword, signals an error.
986 /// If the next token is not the given word, signals an error.
987 /// Otherwise, eats it.
988 fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
989 if !self.eat_keyword(kw) {
990 self.unexpected()
991 } else {
992 Ok(())
993 }
994 }
995
996 fn check_ident(&mut self) -> bool {
997 if self.token.is_ident() {
998 true
999 } else {
1000 self.expected_tokens.push(TokenType::Ident);
1001 false
1002 }
1003 }
1004
1005 fn check_path(&mut self) -> bool {
1006 if self.token.is_path_start() {
1007 true
1008 } else {
1009 self.expected_tokens.push(TokenType::Path);
1010 false
1011 }
1012 }
1013
1014 fn check_type(&mut self) -> bool {
1015 if self.token.can_begin_type() {
1016 true
1017 } else {
1018 self.expected_tokens.push(TokenType::Type);
1019 false
1020 }
1021 }
1022
1023 fn check_const_arg(&mut self) -> bool {
1024 if self.token.can_begin_const_arg() {
1025 true
1026 } else {
1027 self.expected_tokens.push(TokenType::Const);
1028 false
1029 }
1030 }
1031
1032 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
1033 /// and continues. If a `+` is not seen, returns `false`.
1034 ///
1035 /// This is used when token-splitting `+=` into `+`.
1036 /// See issue #47856 for an example of when this may occur.
1037 fn eat_plus(&mut self) -> bool {
1038 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1039 match self.token {
1040 token::BinOp(token::Plus) => {
1041 self.bump();
1042 true
1043 }
1044 token::BinOpEq(token::Plus) => {
1045 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1046 self.bump_with(token::Eq, span);
1047 true
1048 }
1049 _ => false,
1050 }
1051 }
1052
1053
1054 /// Checks to see if the next token is either `+` or `+=`.
1055 /// Otherwise returns `false`.
1056 fn check_plus(&mut self) -> bool {
1057 if self.token.is_like_plus() {
1058 true
1059 }
1060 else {
1061 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1062 false
1063 }
1064 }
1065
1066 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
1067 /// `&` and continues. If an `&` is not seen, signals an error.
1068 fn expect_and(&mut self) -> PResult<'a, ()> {
1069 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
1070 match self.token {
1071 token::BinOp(token::And) => {
1072 self.bump();
1073 Ok(())
1074 }
1075 token::AndAnd => {
1076 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1077 Ok(self.bump_with(token::BinOp(token::And), span))
1078 }
1079 _ => self.unexpected()
1080 }
1081 }
1082
1083 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
1084 /// `|` and continues. If an `|` is not seen, signals an error.
1085 fn expect_or(&mut self) -> PResult<'a, ()> {
1086 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
1087 match self.token {
1088 token::BinOp(token::Or) => {
1089 self.bump();
1090 Ok(())
1091 }
1092 token::OrOr => {
1093 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1094 Ok(self.bump_with(token::BinOp(token::Or), span))
1095 }
1096 _ => self.unexpected()
1097 }
1098 }
1099
1100 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
1101 match suffix {
1102 None => {/* everything ok */}
1103 Some(suf) => {
1104 let text = suf.as_str();
1105 if text.is_empty() {
1106 self.span_bug(sp, "found empty literal suffix in Some")
1107 }
1108 let msg = format!("{} with a suffix is invalid", kind);
1109 self.struct_span_err(sp, &msg)
1110 .span_label(sp, msg)
1111 .emit();
1112 }
1113 }
1114 }
1115
1116 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
1117 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
1118 /// and continue. If a `<` is not seen, returns false.
1119 ///
1120 /// This is meant to be used when parsing generics on a path to get the
1121 /// starting token.
1122 fn eat_lt(&mut self) -> bool {
1123 self.expected_tokens.push(TokenType::Token(token::Lt));
1124 let ate = match self.token {
1125 token::Lt => {
1126 self.bump();
1127 true
1128 }
1129 token::BinOp(token::Shl) => {
1130 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1131 self.bump_with(token::Lt, span);
1132 true
1133 }
1134 token::LArrow => {
1135 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1136 self.bump_with(token::BinOp(token::Minus), span);
1137 true
1138 }
1139 _ => false,
1140 };
1141
1142 if ate {
1143 // See doc comment for `unmatched_angle_bracket_count`.
1144 self.unmatched_angle_bracket_count += 1;
1145 self.max_angle_bracket_count += 1;
1146 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
1147 }
1148
1149 ate
1150 }
1151
1152 fn expect_lt(&mut self) -> PResult<'a, ()> {
1153 if !self.eat_lt() {
1154 self.unexpected()
1155 } else {
1156 Ok(())
1157 }
1158 }
1159
1160 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
1161 /// with a single `>` and continues. If a `>` is not seen, signals an error.
1162 fn expect_gt(&mut self) -> PResult<'a, ()> {
1163 self.expected_tokens.push(TokenType::Token(token::Gt));
1164 let ate = match self.token {
1165 token::Gt => {
1166 self.bump();
1167 Some(())
1168 }
1169 token::BinOp(token::Shr) => {
1170 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1171 Some(self.bump_with(token::Gt, span))
1172 }
1173 token::BinOpEq(token::Shr) => {
1174 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1175 Some(self.bump_with(token::Ge, span))
1176 }
1177 token::Ge => {
1178 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1179 Some(self.bump_with(token::Eq, span))
1180 }
1181 _ => None,
1182 };
1183
1184 match ate {
1185 Some(_) => {
1186 // See doc comment for `unmatched_angle_bracket_count`.
1187 if self.unmatched_angle_bracket_count > 0 {
1188 self.unmatched_angle_bracket_count -= 1;
1189 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1190 }
1191
1192 Ok(())
1193 },
1194 None => self.unexpected(),
1195 }
1196 }
1197
1198 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
1199 /// passes through any errors encountered. Used for error recovery.
1200 fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
1201 let handler = self.diagnostic();
1202
1203 if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
1204 SeqSep::none(),
1205 TokenExpectType::Expect,
1206 |p| Ok(p.parse_token_tree())) {
1207 handler.cancel(err);
1208 }
1209 }
1210
1211 /// Parses a sequence, including the closing delimiter. The function
1212 /// `f` must consume tokens until reaching the next separator or
1213 /// closing bracket.
1214 pub fn parse_seq_to_end<T, F>(&mut self,
1215 ket: &token::Token,
1216 sep: SeqSep,
1217 f: F)
1218 -> PResult<'a, Vec<T>> where
1219 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1220 {
1221 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1222 if !recovered {
1223 self.bump();
1224 }
1225 Ok(val)
1226 }
1227
1228 /// Parses a sequence, not including the closing delimiter. The function
1229 /// `f` must consume tokens until reaching the next separator or
1230 /// closing bracket.
1231 pub fn parse_seq_to_before_end<T, F>(
1232 &mut self,
1233 ket: &token::Token,
1234 sep: SeqSep,
1235 f: F,
1236 ) -> PResult<'a, (Vec<T>, bool)>
1237 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1238 {
1239 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
1240 }
1241
1242 fn parse_seq_to_before_tokens<T, F>(
1243 &mut self,
1244 kets: &[&token::Token],
1245 sep: SeqSep,
1246 expect: TokenExpectType,
1247 mut f: F,
1248 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
1249 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1250 {
1251 let mut first = true;
1252 let mut recovered = false;
1253 let mut v = vec![];
1254 while !kets.iter().any(|k| {
1255 match expect {
1256 TokenExpectType::Expect => self.check(k),
1257 TokenExpectType::NoExpect => self.token == **k,
1258 }
1259 }) {
1260 match self.token {
1261 token::CloseDelim(..) | token::Eof => break,
1262 _ => {}
1263 };
1264 if let Some(ref t) = sep.sep {
1265 if first {
1266 first = false;
1267 } else {
1268 match self.expect(t) {
1269 Ok(false) => {}
1270 Ok(true) => {
1271 recovered = true;
1272 break;
1273 }
1274 Err(mut e) => {
1275 // Attempt to keep parsing if it was a similar separator
1276 if let Some(ref tokens) = t.similar_tokens() {
1277 if tokens.contains(&self.token) {
1278 self.bump();
1279 }
1280 }
1281 e.emit();
1282 // Attempt to keep parsing if it was an omitted separator
1283 match f(self) {
1284 Ok(t) => {
1285 v.push(t);
1286 continue;
1287 },
1288 Err(mut e) => {
1289 e.cancel();
1290 break;
1291 }
1292 }
1293 }
1294 }
1295 }
1296 }
1297 if sep.trailing_sep_allowed && kets.iter().any(|k| {
1298 match expect {
1299 TokenExpectType::Expect => self.check(k),
1300 TokenExpectType::NoExpect => self.token == **k,
1301 }
1302 }) {
1303 break;
1304 }
1305
1306 let t = f(self)?;
1307 v.push(t);
1308 }
1309
1310 Ok((v, recovered))
1311 }
1312
1313 /// Parses a sequence, including the closing delimiter. The function
1314 /// `f` must consume tokens until reaching the next separator or
1315 /// closing bracket.
1316 fn parse_unspanned_seq<T, F>(
1317 &mut self,
1318 bra: &token::Token,
1319 ket: &token::Token,
1320 sep: SeqSep,
1321 f: F,
1322 ) -> PResult<'a, Vec<T>> where
1323 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1324 {
1325 self.expect(bra)?;
1326 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1327 if !recovered {
1328 self.eat(ket);
1329 }
1330 Ok(result)
1331 }
1332
1333 /// Advance the parser by one token
1334 pub fn bump(&mut self) {
1335 if self.prev_token_kind == PrevTokenKind::Eof {
1336 // Bumping after EOF is a bad sign, usually an infinite loop.
1337 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1338 }
1339
1340 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1341
1342 // Record last token kind for possible error recovery.
1343 self.prev_token_kind = match self.token {
1344 token::DocComment(..) => PrevTokenKind::DocComment,
1345 token::Comma => PrevTokenKind::Comma,
1346 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1347 token::Interpolated(..) => PrevTokenKind::Interpolated,
1348 token::Eof => PrevTokenKind::Eof,
1349 token::Ident(..) => PrevTokenKind::Ident,
1350 _ => PrevTokenKind::Other,
1351 };
1352
1353 let next = self.next_tok();
1354 self.span = next.sp;
1355 self.token = next.tok;
1356 self.expected_tokens.clear();
1357 // check after each token
1358 self.process_potential_macro_variable();
1359 }
1360
1361 /// Advance the parser using provided token as a next one. Use this when
1362 /// consuming a part of a token. For example a single `<` from `<<`.
1363 fn bump_with(&mut self, next: token::Token, span: Span) {
1364 self.prev_span = self.span.with_hi(span.lo());
1365 // It would be incorrect to record the kind of the current token, but
1366 // fortunately for tokens currently using `bump_with`, the
1367 // prev_token_kind will be of no use anyway.
1368 self.prev_token_kind = PrevTokenKind::Other;
1369 self.span = span;
1370 self.token = next;
1371 self.expected_tokens.clear();
1372 }
1373
1374 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1375 F: FnOnce(&token::Token) -> R,
1376 {
1377 if dist == 0 {
1378 return f(&self.token)
1379 }
1380
1381 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1382 Some(tree) => match tree {
1383 TokenTree::Token(_, tok) => tok,
1384 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1385 },
1386 None => token::CloseDelim(self.token_cursor.frame.delim),
1387 })
1388 }
1389
1390 fn look_ahead_span(&self, dist: usize) -> Span {
1391 if dist == 0 {
1392 return self.span
1393 }
1394
1395 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1396 Some(TokenTree::Token(span, _)) => span,
1397 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1398 None => self.look_ahead_span(dist - 1),
1399 }
1400 }
1401 pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
1402 self.sess.span_diagnostic.struct_span_fatal(self.span, m)
1403 }
1404 pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1405 self.sess.span_diagnostic.struct_span_fatal(sp, m)
1406 }
1407 fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
1408 err.span_err(sp, self.diagnostic())
1409 }
1410 fn bug(&self, m: &str) -> ! {
1411 self.sess.span_diagnostic.span_bug(self.span, m)
1412 }
1413 fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
1414 self.sess.span_diagnostic.span_err(sp, m)
1415 }
1416 fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1417 self.sess.span_diagnostic.struct_span_err(sp, m)
1418 }
1419 crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
1420 self.sess.span_diagnostic.span_bug(sp, m)
1421 }
1422
1423 fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
1424 self.sess.span_diagnostic.cancel(err)
1425 }
1426
1427 crate fn diagnostic(&self) -> &'a errors::Handler {
1428 &self.sess.span_diagnostic
1429 }
1430
1431 /// Is the current token one of the keywords that signals a bare function type?
1432 fn token_is_bare_fn_keyword(&mut self) -> bool {
1433 self.check_keyword(keywords::Fn) ||
1434 self.check_keyword(keywords::Unsafe) ||
1435 self.check_keyword(keywords::Extern)
1436 }
1437
1438 /// Parses a `TyKind::BareFn` type.
1439 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1440 /*
1441
1442 [unsafe] [extern "ABI"] fn (S) -> T
1443 ^~~~^ ^~~~^ ^~^ ^
1444 | | | |
1445 | | | Return type
1446 | | Argument types
1447 | |
1448 | ABI
1449 Function Style
1450 */
1451
1452 let unsafety = self.parse_unsafety();
1453 let abi = if self.eat_keyword(keywords::Extern) {
1454 self.parse_opt_abi()?.unwrap_or(Abi::C)
1455 } else {
1456 Abi::Rust
1457 };
1458
1459 self.expect_keyword(keywords::Fn)?;
1460 let (inputs, variadic) = self.parse_fn_args(false, true)?;
1461 let ret_ty = self.parse_ret_ty(false)?;
1462 let decl = P(FnDecl {
1463 inputs,
1464 output: ret_ty,
1465 variadic,
1466 });
1467 Ok(TyKind::BareFn(P(BareFnTy {
1468 abi,
1469 unsafety,
1470 generic_params,
1471 decl,
1472 })))
1473 }
1474
1475 /// Parses asyncness: `async` or nothing.
1476 fn parse_asyncness(&mut self) -> IsAsync {
1477 if self.eat_keyword(keywords::Async) {
1478 IsAsync::Async {
1479 closure_id: ast::DUMMY_NODE_ID,
1480 return_impl_trait_id: ast::DUMMY_NODE_ID,
1481 }
1482 } else {
1483 IsAsync::NotAsync
1484 }
1485 }
1486
1487 /// Parses unsafety: `unsafe` or nothing.
1488 fn parse_unsafety(&mut self) -> Unsafety {
1489 if self.eat_keyword(keywords::Unsafe) {
1490 Unsafety::Unsafe
1491 } else {
1492 Unsafety::Normal
1493 }
1494 }
1495
1496 /// Parses the items in a trait declaration.
1497 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1498 maybe_whole!(self, NtTraitItem, |x| x);
1499 let attrs = self.parse_outer_attributes()?;
1500 let (mut item, tokens) = self.collect_tokens(|this| {
1501 this.parse_trait_item_(at_end, attrs)
1502 })?;
1503 // See `parse_item` for why this clause is here.
1504 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1505 item.tokens = Some(tokens);
1506 }
1507 Ok(item)
1508 }
1509
1510 fn parse_trait_item_(&mut self,
1511 at_end: &mut bool,
1512 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1513 let lo = self.span;
1514
1515 let (name, node, generics) = if self.eat_keyword(keywords::Type) {
1516 self.parse_trait_item_assoc_ty()?
1517 } else if self.is_const_item() {
1518 self.expect_keyword(keywords::Const)?;
1519 let ident = self.parse_ident()?;
1520 self.expect(&token::Colon)?;
1521 let ty = self.parse_ty()?;
1522 let default = if self.eat(&token::Eq) {
1523 let expr = self.parse_expr()?;
1524 self.expect(&token::Semi)?;
1525 Some(expr)
1526 } else {
1527 self.expect(&token::Semi)?;
1528 None
1529 };
1530 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1531 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1532 // trait item macro.
1533 (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1534 } else {
1535 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
1536
1537 let ident = self.parse_ident()?;
1538 let mut generics = self.parse_generics()?;
1539
1540 let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1541 // This is somewhat dubious; We don't want to allow
1542 // argument names to be left off if there is a
1543 // definition...
1544
1545 // We don't allow argument names to be left off in edition 2018.
1546 p.parse_arg_general(p.span.rust_2018(), true)
1547 })?;
1548 generics.where_clause = self.parse_where_clause()?;
1549
1550 let sig = ast::MethodSig {
1551 header: FnHeader {
1552 unsafety,
1553 constness,
1554 abi,
1555 asyncness,
1556 },
1557 decl: d,
1558 };
1559
1560 let body = match self.token {
1561 token::Semi => {
1562 self.bump();
1563 *at_end = true;
1564 debug!("parse_trait_methods(): parsing required method");
1565 None
1566 }
1567 token::OpenDelim(token::Brace) => {
1568 debug!("parse_trait_methods(): parsing provided method");
1569 *at_end = true;
1570 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1571 attrs.extend(inner_attrs.iter().cloned());
1572 Some(body)
1573 }
1574 token::Interpolated(ref nt) => {
1575 match **nt {
1576 token::NtBlock(..) => {
1577 *at_end = true;
1578 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1579 attrs.extend(inner_attrs.iter().cloned());
1580 Some(body)
1581 }
1582 _ => {
1583 let token_str = self.this_token_descr();
1584 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1585 token_str));
1586 err.span_label(self.span, "expected `;` or `{`");
1587 return Err(err);
1588 }
1589 }
1590 }
1591 _ => {
1592 let token_str = self.this_token_descr();
1593 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1594 token_str));
1595 err.span_label(self.span, "expected `;` or `{`");
1596 return Err(err);
1597 }
1598 };
1599 (ident, ast::TraitItemKind::Method(sig, body), generics)
1600 };
1601
1602 Ok(TraitItem {
1603 id: ast::DUMMY_NODE_ID,
1604 ident: name,
1605 attrs,
1606 generics,
1607 node,
1608 span: lo.to(self.prev_span),
1609 tokens: None,
1610 })
1611 }
1612
1613 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1614 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1615 if self.eat(&token::RArrow) {
1616 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true)?))
1617 } else {
1618 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1619 }
1620 }
1621
1622 /// Parses a type.
1623 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1624 self.parse_ty_common(true, true)
1625 }
1626
1627 /// Parses a type in restricted contexts where `+` is not permitted.
1628 ///
1629 /// Example 1: `&'a TYPE`
1630 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1631 /// Example 2: `value1 as TYPE + value2`
1632 /// `+` is prohibited to avoid interactions with expression grammar.
1633 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1634 self.parse_ty_common(false, true)
1635 }
1636
1637 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool)
1638 -> PResult<'a, P<Ty>> {
1639 maybe_whole!(self, NtTy, |x| x);
1640
1641 let lo = self.span;
1642 let mut impl_dyn_multi = false;
1643 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1644 // `(TYPE)` is a parenthesized type.
1645 // `(TYPE,)` is a tuple with a single field of type TYPE.
1646 let mut ts = vec![];
1647 let mut last_comma = false;
1648 while self.token != token::CloseDelim(token::Paren) {
1649 ts.push(self.parse_ty()?);
1650 if self.eat(&token::Comma) {
1651 last_comma = true;
1652 } else {
1653 last_comma = false;
1654 break;
1655 }
1656 }
1657 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1658 self.expect(&token::CloseDelim(token::Paren))?;
1659
1660 if ts.len() == 1 && !last_comma {
1661 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1662 let maybe_bounds = allow_plus && self.token.is_like_plus();
1663 match ty.node {
1664 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1665 TyKind::Path(None, ref path) if maybe_bounds => {
1666 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1667 }
1668 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1669 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1670 let path = match bounds[0] {
1671 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1672 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1673 };
1674 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1675 }
1676 // `(TYPE)`
1677 _ => TyKind::Paren(P(ty))
1678 }
1679 } else {
1680 TyKind::Tup(ts)
1681 }
1682 } else if self.eat(&token::Not) {
1683 // Never type `!`
1684 TyKind::Never
1685 } else if self.eat(&token::BinOp(token::Star)) {
1686 // Raw pointer
1687 TyKind::Ptr(self.parse_ptr()?)
1688 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1689 // Array or slice
1690 let t = self.parse_ty()?;
1691 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1692 let t = match self.maybe_parse_fixed_length_of_vec()? {
1693 None => TyKind::Slice(t),
1694 Some(length) => TyKind::Array(t, AnonConst {
1695 id: ast::DUMMY_NODE_ID,
1696 value: length,
1697 }),
1698 };
1699 self.expect(&token::CloseDelim(token::Bracket))?;
1700 t
1701 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1702 // Reference
1703 self.expect_and()?;
1704 self.parse_borrowed_pointee()?
1705 } else if self.eat_keyword_noexpect(keywords::Typeof) {
1706 // `typeof(EXPR)`
1707 // In order to not be ambiguous, the type must be surrounded by parens.
1708 self.expect(&token::OpenDelim(token::Paren))?;
1709 let e = AnonConst {
1710 id: ast::DUMMY_NODE_ID,
1711 value: self.parse_expr()?,
1712 };
1713 self.expect(&token::CloseDelim(token::Paren))?;
1714 TyKind::Typeof(e)
1715 } else if self.eat_keyword(keywords::Underscore) {
1716 // A type to be inferred `_`
1717 TyKind::Infer
1718 } else if self.token_is_bare_fn_keyword() {
1719 // Function pointer type
1720 self.parse_ty_bare_fn(Vec::new())?
1721 } else if self.check_keyword(keywords::For) {
1722 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1723 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1724 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1725 let lo = self.span;
1726 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1727 if self.token_is_bare_fn_keyword() {
1728 self.parse_ty_bare_fn(lifetime_defs)?
1729 } else {
1730 let path = self.parse_path(PathStyle::Type)?;
1731 let parse_plus = allow_plus && self.check_plus();
1732 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1733 }
1734 } else if self.eat_keyword(keywords::Impl) {
1735 // Always parse bounds greedily for better error recovery.
1736 let bounds = self.parse_generic_bounds(None)?;
1737 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1738 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1739 } else if self.check_keyword(keywords::Dyn) &&
1740 (self.span.rust_2018() ||
1741 self.look_ahead(1, |t| t.can_begin_bound() &&
1742 !can_continue_type_after_non_fn_ident(t))) {
1743 self.bump(); // `dyn`
1744 // Always parse bounds greedily for better error recovery.
1745 let bounds = self.parse_generic_bounds(None)?;
1746 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1747 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1748 } else if self.check(&token::Question) ||
1749 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1750 // Bound list (trait object type)
1751 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1752 TraitObjectSyntax::None)
1753 } else if self.eat_lt() {
1754 // Qualified path
1755 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1756 TyKind::Path(Some(qself), path)
1757 } else if self.token.is_path_start() {
1758 // Simple path
1759 let path = self.parse_path(PathStyle::Type)?;
1760 if self.eat(&token::Not) {
1761 // Macro invocation in type position
1762 let (delim, tts) = self.expect_delimited_token_tree()?;
1763 let node = Mac_ { path, tts, delim };
1764 TyKind::Mac(respan(lo.to(self.prev_span), node))
1765 } else {
1766 // Just a type path or bound list (trait object type) starting with a trait.
1767 // `Type`
1768 // `Trait1 + Trait2 + 'a`
1769 if allow_plus && self.check_plus() {
1770 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1771 } else {
1772 TyKind::Path(None, path)
1773 }
1774 }
1775 } else {
1776 let msg = format!("expected type, found {}", self.this_token_descr());
1777 return Err(self.fatal(&msg));
1778 };
1779
1780 let span = lo.to(self.prev_span);
1781 let ty = Ty { node, span, id: ast::DUMMY_NODE_ID };
1782
1783 // Try to recover from use of `+` with incorrect priority.
1784 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1785 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1786 let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;
1787
1788 Ok(P(ty))
1789 }
1790
1791 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1792 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1793 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1794 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1795 if parse_plus {
1796 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1797 bounds.append(&mut self.parse_generic_bounds(None)?);
1798 }
1799 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1800 }
1801
1802 fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) {
1803 if !allow_plus && impl_dyn_multi {
1804 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
1805 self.struct_span_err(ty.span, "ambiguous `+` in a type")
1806 .span_suggestion(
1807 ty.span,
1808 "use parentheses to disambiguate",
1809 sum_with_parens,
1810 Applicability::MachineApplicable
1811 ).emit();
1812 }
1813 }
1814
1815 fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
1816 // Do not add `+` to expected tokens.
1817 if !allow_plus || !self.token.is_like_plus() {
1818 return Ok(())
1819 }
1820
1821 self.bump(); // `+`
1822 let bounds = self.parse_generic_bounds(None)?;
1823 let sum_span = ty.span.to(self.prev_span);
1824
1825 let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
1826 "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
1827
1828 match ty.node {
1829 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1830 let sum_with_parens = pprust::to_string(|s| {
1831 use crate::print::pprust::PrintState;
1832
1833 s.s.word("&")?;
1834 s.print_opt_lifetime(lifetime)?;
1835 s.print_mutability(mut_ty.mutbl)?;
1836 s.popen()?;
1837 s.print_type(&mut_ty.ty)?;
1838 s.print_type_bounds(" +", &bounds)?;
1839 s.pclose()
1840 });
1841 err.span_suggestion(
1842 sum_span,
1843 "try adding parentheses",
1844 sum_with_parens,
1845 Applicability::MachineApplicable
1846 );
1847 }
1848 TyKind::Ptr(..) | TyKind::BareFn(..) => {
1849 err.span_label(sum_span, "perhaps you forgot parentheses?");
1850 }
1851 _ => {
1852 err.span_label(sum_span, "expected a path");
1853 },
1854 }
1855 err.emit();
1856 Ok(())
1857 }
1858
1859 // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
1860 fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
1861 -> PResult<'a, T> {
1862 // Do not add `::` to expected tokens.
1863 if !allow_recovery || self.token != token::ModSep {
1864 return Ok(base);
1865 }
1866 let ty = match base.to_ty() {
1867 Some(ty) => ty,
1868 None => return Ok(base),
1869 };
1870
1871 self.bump(); // `::`
1872 let mut segments = Vec::new();
1873 self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
1874
1875 let span = ty.span.to(self.prev_span);
1876 let path_span = span.to(span); // use an empty path since `position` == 0
1877 let recovered = base.to_recovered(
1878 Some(QSelf { ty, path_span, position: 0 }),
1879 ast::Path { segments, span },
1880 );
1881
1882 self.diagnostic()
1883 .struct_span_err(span, "missing angle brackets in associated item path")
1884 .span_suggestion( // this is a best-effort recovery
1885 span, "try", recovered.to_string(), Applicability::MaybeIncorrect
1886 ).emit();
1887
1888 Ok(recovered)
1889 }
1890
1891 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1892 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1893 let mutbl = self.parse_mutability();
1894 let ty = self.parse_ty_no_plus()?;
1895 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1896 }
1897
1898 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1899 let mutbl = if self.eat_keyword(keywords::Mut) {
1900 Mutability::Mutable
1901 } else if self.eat_keyword(keywords::Const) {
1902 Mutability::Immutable
1903 } else {
1904 let span = self.prev_span;
1905 let msg = "expected mut or const in raw pointer type";
1906 self.struct_span_err(span, msg)
1907 .span_label(span, msg)
1908 .help("use `*mut T` or `*const T` as appropriate")
1909 .emit();
1910 Mutability::Immutable
1911 };
1912 let t = self.parse_ty_no_plus()?;
1913 Ok(MutTy { ty: t, mutbl: mutbl })
1914 }
1915
1916 fn is_named_argument(&mut self) -> bool {
1917 let offset = match self.token {
1918 token::Interpolated(ref nt) => match **nt {
1919 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1920 _ => 0,
1921 }
1922 token::BinOp(token::And) | token::AndAnd => 1,
1923 _ if self.token.is_keyword(keywords::Mut) => 1,
1924 _ => 0,
1925 };
1926
1927 self.look_ahead(offset, |t| t.is_ident()) &&
1928 self.look_ahead(offset + 1, |t| t == &token::Colon)
1929 }
1930
1931 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1932 /// error.
1933 fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
1934 if let token::DocComment(_) = self.token {
1935 let mut err = self.diagnostic().struct_span_err(
1936 self.span,
1937 &format!("documentation comments cannot be applied to {}", applied_to),
1938 );
1939 err.span_label(self.span, "doc comments are not allowed here");
1940 err.emit();
1941 self.bump();
1942 } else if self.token == token::Pound && self.look_ahead(1, |t| {
1943 *t == token::OpenDelim(token::Bracket)
1944 }) {
1945 let lo = self.span;
1946 // Skip every token until next possible arg.
1947 while self.token != token::CloseDelim(token::Bracket) {
1948 self.bump();
1949 }
1950 let sp = lo.to(self.span);
1951 self.bump();
1952 let mut err = self.diagnostic().struct_span_err(
1953 sp,
1954 &format!("attributes cannot be applied to {}", applied_to),
1955 );
1956 err.span_label(sp, "attributes are not allowed here");
1957 err.emit();
1958 }
1959 }
1960
1961 /// This version of parse arg doesn't necessarily require identifier names.
1962 fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool) -> PResult<'a, Arg> {
1963 maybe_whole!(self, NtArg, |x| x);
1964
1965 if let Ok(Some(_)) = self.parse_self_arg() {
1966 let mut err = self.struct_span_err(self.prev_span,
1967 "unexpected `self` argument in function");
1968 err.span_label(self.prev_span,
1969 "`self` is only valid as the first argument of an associated function");
1970 return Err(err);
1971 }
1972
1973 let (pat, ty) = if require_name || self.is_named_argument() {
1974 debug!("parse_arg_general parse_pat (require_name:{})",
1975 require_name);
1976 self.eat_incorrect_doc_comment("method arguments");
1977 let pat = self.parse_pat(Some("argument name"))?;
1978
1979 if let Err(mut err) = self.expect(&token::Colon) {
1980 // If we find a pattern followed by an identifier, it could be an (incorrect)
1981 // C-style parameter declaration.
1982 if self.check_ident() && self.look_ahead(1, |t| {
1983 *t == token::Comma || *t == token::CloseDelim(token::Paren)
1984 }) {
1985 let ident = self.parse_ident().unwrap();
1986 let span = pat.span.with_hi(ident.span.hi());
1987
1988 err.span_suggestion(
1989 span,
1990 "declare the type after the parameter binding",
1991 String::from("<identifier>: <type>"),
1992 Applicability::HasPlaceholders,
1993 );
1994 } else if require_name && is_trait_item {
1995 if let PatKind::Ident(_, ident, _) = pat.node {
1996 err.span_suggestion(
1997 pat.span,
1998 "explicitly ignore parameter",
1999 format!("_: {}", ident),
2000 Applicability::MachineApplicable,
2001 );
2002 }
2003
2004 err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
2005 }
2006
2007 return Err(err);
2008 }
2009
2010 self.eat_incorrect_doc_comment("a method argument's type");
2011 (pat, self.parse_ty()?)
2012 } else {
2013 debug!("parse_arg_general ident_to_pat");
2014 let parser_snapshot_before_ty = self.clone();
2015 self.eat_incorrect_doc_comment("a method argument's type");
2016 let mut ty = self.parse_ty();
2017 if ty.is_ok() && self.token != token::Comma &&
2018 self.token != token::CloseDelim(token::Paren) {
2019 // This wasn't actually a type, but a pattern looking like a type,
2020 // so we are going to rollback and re-parse for recovery.
2021 ty = self.unexpected();
2022 }
2023 match ty {
2024 Ok(ty) => {
2025 let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
2026 let pat = P(Pat {
2027 id: ast::DUMMY_NODE_ID,
2028 node: PatKind::Ident(
2029 BindingMode::ByValue(Mutability::Immutable), ident, None),
2030 span: ty.span,
2031 });
2032 (pat, ty)
2033 }
2034 Err(mut err) => {
2035 // Recover from attempting to parse the argument as a type without pattern.
2036 err.cancel();
2037 mem::replace(self, parser_snapshot_before_ty);
2038 let pat = self.parse_pat(Some("argument name"))?;
2039 self.expect(&token::Colon)?;
2040 let ty = self.parse_ty()?;
2041
2042 let mut err = self.diagnostic().struct_span_err_with_code(
2043 pat.span,
2044 "patterns aren't allowed in methods without bodies",
2045 DiagnosticId::Error("E0642".into()),
2046 );
2047 err.span_suggestion_short(
2048 pat.span,
2049 "give this argument a name or use an underscore to ignore it",
2050 "_".to_owned(),
2051 Applicability::MachineApplicable,
2052 );
2053 err.emit();
2054
2055 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
2056 let pat = P(Pat {
2057 node: PatKind::Wild,
2058 span: pat.span,
2059 id: ast::DUMMY_NODE_ID
2060 });
2061 (pat, ty)
2062 }
2063 }
2064 };
2065
2066 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
2067 }
2068
2069 /// Parses a single function argument.
2070 crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
2071 self.parse_arg_general(true, false)
2072 }
2073
2074 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
2075 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
2076 let pat = self.parse_pat(Some("argument name"))?;
2077 let t = if self.eat(&token::Colon) {
2078 self.parse_ty()?
2079 } else {
2080 P(Ty {
2081 id: ast::DUMMY_NODE_ID,
2082 node: TyKind::Infer,
2083 span: self.prev_span,
2084 })
2085 };
2086 Ok(Arg {
2087 ty: t,
2088 pat,
2089 id: ast::DUMMY_NODE_ID
2090 })
2091 }
2092
2093 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
2094 if self.eat(&token::Semi) {
2095 Ok(Some(self.parse_expr()?))
2096 } else {
2097 Ok(None)
2098 }
2099 }
2100
2101 /// Matches `token_lit = LIT_INTEGER | ...`.
2102 fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
2103 let out = match self.token {
2104 token::Interpolated(ref nt) => match **nt {
2105 token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node {
2106 ExprKind::Lit(ref lit) => { lit.node.clone() }
2107 _ => { return self.unexpected_last(&self.token); }
2108 },
2109 _ => { return self.unexpected_last(&self.token); }
2110 },
2111 token::Literal(lit, suf) => {
2112 let diag = Some((self.span, &self.sess.span_diagnostic));
2113 let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
2114
2115 if suffix_illegal {
2116 let sp = self.span;
2117 self.expect_no_suffix(sp, lit.literal_name(), suf)
2118 }
2119
2120 result.unwrap()
2121 }
2122 token::Dot if self.look_ahead(1, |t| match t {
2123 token::Literal(parse::token::Lit::Integer(_) , _) => true,
2124 _ => false,
2125 }) => { // recover from `let x = .4;`
2126 let lo = self.span;
2127 self.bump();
2128 if let token::Literal(
2129 parse::token::Lit::Integer(val),
2130 suffix,
2131 ) = self.token {
2132 let suffix = suffix.and_then(|s| {
2133 let s = s.as_str().get();
2134 if ["f32", "f64"].contains(&s) {
2135 Some(s)
2136 } else {
2137 None
2138 }
2139 }).unwrap_or("");
2140 self.bump();
2141 let sp = lo.to(self.prev_span);
2142 let mut err = self.diagnostic()
2143 .struct_span_err(sp, "float literals must have an integer part");
2144 err.span_suggestion(
2145 sp,
2146 "must have an integer part",
2147 format!("0.{}{}", val, suffix),
2148 Applicability::MachineApplicable,
2149 );
2150 err.emit();
2151 return Ok(match suffix {
2152 "f32" => ast::LitKind::Float(val, ast::FloatTy::F32),
2153 "f64" => ast::LitKind::Float(val, ast::FloatTy::F64),
2154 _ => ast::LitKind::FloatUnsuffixed(val),
2155 });
2156 } else {
2157 unreachable!();
2158 };
2159 }
2160 _ => { return self.unexpected_last(&self.token); }
2161 };
2162
2163 self.bump();
2164 Ok(out)
2165 }
2166
2167 /// Matches `lit = true | false | token_lit`.
2168 crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
2169 let lo = self.span;
2170 let lit = if self.eat_keyword(keywords::True) {
2171 LitKind::Bool(true)
2172 } else if self.eat_keyword(keywords::False) {
2173 LitKind::Bool(false)
2174 } else {
2175 let lit = self.parse_lit_token()?;
2176 lit
2177 };
2178 Ok(source_map::Spanned { node: lit, span: lo.to(self.prev_span) })
2179 }
2180
2181 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
2182 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
2183 maybe_whole_expr!(self);
2184
2185 let minus_lo = self.span;
2186 let minus_present = self.eat(&token::BinOp(token::Minus));
2187 let lo = self.span;
2188 let literal = self.parse_lit()?;
2189 let hi = self.prev_span;
2190 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
2191
2192 if minus_present {
2193 let minus_hi = self.prev_span;
2194 let unary = self.mk_unary(UnOp::Neg, expr);
2195 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
2196 } else {
2197 Ok(expr)
2198 }
2199 }
2200
2201 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
2202 match self.token {
2203 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
2204 let span = self.span;
2205 self.bump();
2206 Ok(Ident::new(ident.name, span))
2207 }
2208 _ => self.parse_ident(),
2209 }
2210 }
2211
2212 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
2213 match self.token {
2214 token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
2215 let span = self.span;
2216 self.bump();
2217 Ok(Ident::new(ident.name, span))
2218 }
2219 _ => self.parse_ident(),
2220 }
2221 }
2222
2223 /// Parses a qualified path.
2224 /// Assumes that the leading `<` has been parsed already.
2225 ///
2226 /// `qualified_path = <type [as trait_ref]>::path`
2227 ///
2228 /// # Examples
2229 /// `<T>::default`
2230 /// `<T as U>::a`
2231 /// `<T as U>::F::a<S>` (without disambiguator)
2232 /// `<T as U>::F::a::<S>` (with disambiguator)
2233 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
2234 let lo = self.prev_span;
2235 let ty = self.parse_ty()?;
2236
2237 // `path` will contain the prefix of the path up to the `>`,
2238 // if any (e.g., `U` in the `<T as U>::*` examples
2239 // above). `path_span` has the span of that path, or an empty
2240 // span in the case of something like `<T>::Bar`.
2241 let (mut path, path_span);
2242 if self.eat_keyword(keywords::As) {
2243 let path_lo = self.span;
2244 path = self.parse_path(PathStyle::Type)?;
2245 path_span = path_lo.to(self.prev_span);
2246 } else {
2247 path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
2248 path_span = self.span.to(self.span);
2249 }
2250
2251 // See doc comment for `unmatched_angle_bracket_count`.
2252 self.expect(&token::Gt)?;
2253 if self.unmatched_angle_bracket_count > 0 {
2254 self.unmatched_angle_bracket_count -= 1;
2255 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
2256 }
2257
2258 self.expect(&token::ModSep)?;
2259
2260 let qself = QSelf { ty, path_span, position: path.segments.len() };
2261 self.parse_path_segments(&mut path.segments, style, true)?;
2262
2263 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
2264 }
2265
2266 /// Parses simple paths.
2267 ///
2268 /// `path = [::] segment+`
2269 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
2270 ///
2271 /// # Examples
2272 /// `a::b::C<D>` (without disambiguator)
2273 /// `a::b::C::<D>` (with disambiguator)
2274 /// `Fn(Args)` (without disambiguator)
2275 /// `Fn::(Args)` (with disambiguator)
2276 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2277 self.parse_path_common(style, true)
2278 }
2279
2280 crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool)
2281 -> PResult<'a, ast::Path> {
2282 maybe_whole!(self, NtPath, |path| {
2283 if style == PathStyle::Mod &&
2284 path.segments.iter().any(|segment| segment.args.is_some()) {
2285 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
2286 }
2287 path
2288 });
2289
2290 let lo = self.meta_var_span.unwrap_or(self.span);
2291 let mut segments = Vec::new();
2292 let mod_sep_ctxt = self.span.ctxt();
2293 if self.eat(&token::ModSep) {
2294 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
2295 }
2296 self.parse_path_segments(&mut segments, style, enable_warning)?;
2297
2298 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
2299 }
2300
2301 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
2302 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
2303 /// attributes.
2304 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2305 let meta_ident = match self.token {
2306 token::Interpolated(ref nt) => match **nt {
2307 token::NtMeta(ref meta) => match meta.node {
2308 ast::MetaItemKind::Word => Some(meta.ident.clone()),
2309 _ => None,
2310 },
2311 _ => None,
2312 },
2313 _ => None,
2314 };
2315 if let Some(path) = meta_ident {
2316 self.bump();
2317 return Ok(path);
2318 }
2319 self.parse_path(style)
2320 }
2321
2322 fn parse_path_segments(&mut self,
2323 segments: &mut Vec<PathSegment>,
2324 style: PathStyle,
2325 enable_warning: bool)
2326 -> PResult<'a, ()> {
2327 loop {
2328 let segment = self.parse_path_segment(style, enable_warning)?;
2329 if style == PathStyle::Expr {
2330 // In order to check for trailing angle brackets, we must have finished
2331 // recursing (`parse_path_segment` can indirectly call this function),
2332 // that is, the next token must be the highlighted part of the below example:
2333 //
2334 // `Foo::<Bar as Baz<T>>::Qux`
2335 // ^ here
2336 //
2337 // As opposed to the below highlight (if we had only finished the first
2338 // recursion):
2339 //
2340 // `Foo::<Bar as Baz<T>>::Qux`
2341 // ^ here
2342 //
2343 // `PathStyle::Expr` is only provided at the root invocation and never in
2344 // `parse_path_segment` to recurse and therefore can be checked to maintain
2345 // this invariant.
2346 self.check_trailing_angle_brackets(&segment, token::ModSep);
2347 }
2348 segments.push(segment);
2349
2350 if self.is_import_coupler() || !self.eat(&token::ModSep) {
2351 return Ok(());
2352 }
2353 }
2354 }
2355
2356 fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool)
2357 -> PResult<'a, PathSegment> {
2358 let ident = self.parse_path_segment_ident()?;
2359
2360 let is_args_start = |token: &token::Token| match *token {
2361 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
2362 _ => false,
2363 };
2364 let check_args_start = |this: &mut Self| {
2365 this.expected_tokens.extend_from_slice(
2366 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
2367 );
2368 is_args_start(&this.token)
2369 };
2370
2371 Ok(if style == PathStyle::Type && check_args_start(self) ||
2372 style != PathStyle::Mod && self.check(&token::ModSep)
2373 && self.look_ahead(1, |t| is_args_start(t)) {
2374 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
2375 if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
2376 self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
2377 .span_label(self.prev_span, "try removing `::`").emit();
2378 }
2379 let lo = self.span;
2380
2381 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
2382 // it isn't, then we reset the unmatched angle bracket count as we're about to start
2383 // parsing a new path.
2384 if style == PathStyle::Expr {
2385 self.unmatched_angle_bracket_count = 0;
2386 self.max_angle_bracket_count = 0;
2387 }
2388
2389 let args = if self.eat_lt() {
2390 // `<'a, T, A = U>`
2391 let (args, bindings) =
2392 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
2393 self.expect_gt()?;
2394 let span = lo.to(self.prev_span);
2395 AngleBracketedArgs { args, bindings, span }.into()
2396 } else {
2397 // `(T, U) -> R`
2398 self.bump(); // `(`
2399 let (inputs, recovered) = self.parse_seq_to_before_tokens(
2400 &[&token::CloseDelim(token::Paren)],
2401 SeqSep::trailing_allowed(token::Comma),
2402 TokenExpectType::Expect,
2403 |p| p.parse_ty())?;
2404 if !recovered {
2405 self.bump(); // `)`
2406 }
2407 let span = lo.to(self.prev_span);
2408 let output = if self.eat(&token::RArrow) {
2409 Some(self.parse_ty_common(false, false)?)
2410 } else {
2411 None
2412 };
2413 ParenthesizedArgs { inputs, output, span }.into()
2414 };
2415
2416 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
2417 } else {
2418 // Generic arguments are not found.
2419 PathSegment::from_ident(ident)
2420 })
2421 }
2422
2423 crate fn check_lifetime(&mut self) -> bool {
2424 self.expected_tokens.push(TokenType::Lifetime);
2425 self.token.is_lifetime()
2426 }
2427
2428 /// Parses a single lifetime `'a` or panics.
2429 crate fn expect_lifetime(&mut self) -> Lifetime {
2430 if let Some(ident) = self.token.lifetime() {
2431 let span = self.span;
2432 self.bump();
2433 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
2434 } else {
2435 self.span_bug(self.span, "not a lifetime")
2436 }
2437 }
2438
2439 fn eat_label(&mut self) -> Option<Label> {
2440 if let Some(ident) = self.token.lifetime() {
2441 let span = self.span;
2442 self.bump();
2443 Some(Label { ident: Ident::new(ident.name, span) })
2444 } else {
2445 None
2446 }
2447 }
2448
2449 /// Parses mutability (`mut` or nothing).
2450 fn parse_mutability(&mut self) -> Mutability {
2451 if self.eat_keyword(keywords::Mut) {
2452 Mutability::Mutable
2453 } else {
2454 Mutability::Immutable
2455 }
2456 }
2457
2458 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
2459 if let token::Literal(token::Integer(name), None) = self.token {
2460 self.bump();
2461 Ok(Ident::new(name, self.prev_span))
2462 } else {
2463 self.parse_ident_common(false)
2464 }
2465 }
2466
2467 /// Parse ident (COLON expr)?
2468 fn parse_field(&mut self) -> PResult<'a, Field> {
2469 let attrs = self.parse_outer_attributes()?;
2470 let lo = self.span;
2471
2472 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2473 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
2474 t == &token::Colon || t == &token::Eq
2475 }) {
2476 let fieldname = self.parse_field_name()?;
2477
2478 // Check for an equals token. This means the source incorrectly attempts to
2479 // initialize a field with an eq rather than a colon.
2480 if self.token == token::Eq {
2481 self.diagnostic()
2482 .struct_span_err(self.span, "expected `:`, found `=`")
2483 .span_suggestion(
2484 fieldname.span.shrink_to_hi().to(self.span),
2485 "replace equals symbol with a colon",
2486 ":".to_string(),
2487 Applicability::MachineApplicable,
2488 )
2489 .emit();
2490 }
2491 self.bump(); // `:`
2492 (fieldname, self.parse_expr()?, false)
2493 } else {
2494 let fieldname = self.parse_ident_common(false)?;
2495
2496 // Mimic `x: x` for the `x` field shorthand.
2497 let path = ast::Path::from_ident(fieldname);
2498 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
2499 (fieldname, expr, true)
2500 };
2501 Ok(ast::Field {
2502 ident: fieldname,
2503 span: lo.to(expr.span),
2504 expr,
2505 is_shorthand,
2506 attrs: attrs.into(),
2507 })
2508 }
2509
2510 fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
2511 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
2512 }
2513
2514 fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
2515 ExprKind::Unary(unop, expr)
2516 }
2517
2518 fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2519 ExprKind::Binary(binop, lhs, rhs)
2520 }
2521
2522 fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
2523 ExprKind::Call(f, args)
2524 }
2525
2526 fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
2527 ExprKind::Index(expr, idx)
2528 }
2529
2530 fn mk_range(&mut self,
2531 start: Option<P<Expr>>,
2532 end: Option<P<Expr>>,
2533 limits: RangeLimits)
2534 -> PResult<'a, ast::ExprKind> {
2535 if end.is_none() && limits == RangeLimits::Closed {
2536 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
2537 } else {
2538 Ok(ExprKind::Range(start, end, limits))
2539 }
2540 }
2541
2542 fn mk_assign_op(&mut self, binop: ast::BinOp,
2543 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2544 ExprKind::AssignOp(binop, lhs, rhs)
2545 }
2546
2547 pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
2548 P(Expr {
2549 id: ast::DUMMY_NODE_ID,
2550 node: ExprKind::Mac(source_map::Spanned {node: m, span: span}),
2551 span,
2552 attrs,
2553 })
2554 }
2555
2556 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
2557 let delim = match self.token {
2558 token::OpenDelim(delim) => delim,
2559 _ => {
2560 let msg = "expected open delimiter";
2561 let mut err = self.fatal(msg);
2562 err.span_label(self.span, msg);
2563 return Err(err)
2564 }
2565 };
2566 let tts = match self.parse_token_tree() {
2567 TokenTree::Delimited(_, _, tts) => tts,
2568 _ => unreachable!(),
2569 };
2570 let delim = match delim {
2571 token::Paren => MacDelimiter::Parenthesis,
2572 token::Bracket => MacDelimiter::Bracket,
2573 token::Brace => MacDelimiter::Brace,
2574 token::NoDelim => self.bug("unexpected no delimiter"),
2575 };
2576 Ok((delim, tts.into()))
2577 }
2578
2579 /// At the bottom (top?) of the precedence hierarchy,
2580 /// Parses things like parenthesized exprs, macros, `return`, etc.
2581 ///
2582 /// N.B., this does not parse outer attributes, and is private because it only works
2583 /// correctly if called from `parse_dot_or_call_expr()`.
2584 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2585 maybe_whole_expr!(self);
2586
2587 // Outer attributes are already parsed and will be
2588 // added to the return value after the fact.
2589 //
2590 // Therefore, prevent sub-parser from parsing
2591 // attributes by giving them a empty "already parsed" list.
2592 let mut attrs = ThinVec::new();
2593
2594 let lo = self.span;
2595 let mut hi = self.span;
2596
2597 let ex: ExprKind;
2598
2599 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2600 match self.token {
2601 token::OpenDelim(token::Paren) => {
2602 self.bump();
2603
2604 attrs.extend(self.parse_inner_attributes()?);
2605
2606 // (e) is parenthesized e
2607 // (e,) is a tuple with only one field, e
2608 let mut es = vec![];
2609 let mut trailing_comma = false;
2610 let mut recovered = false;
2611 while self.token != token::CloseDelim(token::Paren) {
2612 es.push(self.parse_expr()?);
2613 recovered = self.expect_one_of(
2614 &[],
2615 &[token::Comma, token::CloseDelim(token::Paren)],
2616 )?;
2617 if self.eat(&token::Comma) {
2618 trailing_comma = true;
2619 } else {
2620 trailing_comma = false;
2621 break;
2622 }
2623 }
2624 if !recovered {
2625 self.bump();
2626 }
2627
2628 hi = self.prev_span;
2629 ex = if es.len() == 1 && !trailing_comma {
2630 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2631 } else {
2632 ExprKind::Tup(es)
2633 };
2634 }
2635 token::OpenDelim(token::Brace) => {
2636 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2637 }
2638 token::BinOp(token::Or) | token::OrOr => {
2639 return self.parse_lambda_expr(attrs);
2640 }
2641 token::OpenDelim(token::Bracket) => {
2642 self.bump();
2643
2644 attrs.extend(self.parse_inner_attributes()?);
2645
2646 if self.eat(&token::CloseDelim(token::Bracket)) {
2647 // Empty vector.
2648 ex = ExprKind::Array(Vec::new());
2649 } else {
2650 // Nonempty vector.
2651 let first_expr = self.parse_expr()?;
2652 if self.eat(&token::Semi) {
2653 // Repeating array syntax: [ 0; 512 ]
2654 let count = AnonConst {
2655 id: ast::DUMMY_NODE_ID,
2656 value: self.parse_expr()?,
2657 };
2658 self.expect(&token::CloseDelim(token::Bracket))?;
2659 ex = ExprKind::Repeat(first_expr, count);
2660 } else if self.eat(&token::Comma) {
2661 // Vector with two or more elements.
2662 let remaining_exprs = self.parse_seq_to_end(
2663 &token::CloseDelim(token::Bracket),
2664 SeqSep::trailing_allowed(token::Comma),
2665 |p| Ok(p.parse_expr()?)
2666 )?;
2667 let mut exprs = vec![first_expr];
2668 exprs.extend(remaining_exprs);
2669 ex = ExprKind::Array(exprs);
2670 } else {
2671 // Vector with one element.
2672 self.expect(&token::CloseDelim(token::Bracket))?;
2673 ex = ExprKind::Array(vec![first_expr]);
2674 }
2675 }
2676 hi = self.prev_span;
2677 }
2678 _ => {
2679 if self.eat_lt() {
2680 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2681 hi = path.span;
2682 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2683 }
2684 if self.span.rust_2018() && self.check_keyword(keywords::Async)
2685 {
2686 if self.is_async_block() { // check for `async {` and `async move {`
2687 return self.parse_async_block(attrs);
2688 } else {
2689 return self.parse_lambda_expr(attrs);
2690 }
2691 }
2692 if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
2693 return self.parse_lambda_expr(attrs);
2694 }
2695 if self.eat_keyword(keywords::If) {
2696 return self.parse_if_expr(attrs);
2697 }
2698 if self.eat_keyword(keywords::For) {
2699 let lo = self.prev_span;
2700 return self.parse_for_expr(None, lo, attrs);
2701 }
2702 if self.eat_keyword(keywords::While) {
2703 let lo = self.prev_span;
2704 return self.parse_while_expr(None, lo, attrs);
2705 }
2706 if let Some(label) = self.eat_label() {
2707 let lo = label.ident.span;
2708 self.expect(&token::Colon)?;
2709 if self.eat_keyword(keywords::While) {
2710 return self.parse_while_expr(Some(label), lo, attrs)
2711 }
2712 if self.eat_keyword(keywords::For) {
2713 return self.parse_for_expr(Some(label), lo, attrs)
2714 }
2715 if self.eat_keyword(keywords::Loop) {
2716 return self.parse_loop_expr(Some(label), lo, attrs)
2717 }
2718 if self.token == token::OpenDelim(token::Brace) {
2719 return self.parse_block_expr(Some(label),
2720 lo,
2721 BlockCheckMode::Default,
2722 attrs);
2723 }
2724 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2725 let mut err = self.fatal(msg);
2726 err.span_label(self.span, msg);
2727 return Err(err);
2728 }
2729 if self.eat_keyword(keywords::Loop) {
2730 let lo = self.prev_span;
2731 return self.parse_loop_expr(None, lo, attrs);
2732 }
2733 if self.eat_keyword(keywords::Continue) {
2734 let label = self.eat_label();
2735 let ex = ExprKind::Continue(label);
2736 let hi = self.prev_span;
2737 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2738 }
2739 if self.eat_keyword(keywords::Match) {
2740 let match_sp = self.prev_span;
2741 return self.parse_match_expr(attrs).map_err(|mut err| {
2742 err.span_label(match_sp, "while parsing this match expression");
2743 err
2744 });
2745 }
2746 if self.eat_keyword(keywords::Unsafe) {
2747 return self.parse_block_expr(
2748 None,
2749 lo,
2750 BlockCheckMode::Unsafe(ast::UserProvided),
2751 attrs);
2752 }
2753 if self.is_do_catch_block() {
2754 let mut db = self.fatal("found removed `do catch` syntax");
2755 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2756 return Err(db);
2757 }
2758 if self.is_try_block() {
2759 let lo = self.span;
2760 assert!(self.eat_keyword(keywords::Try));
2761 return self.parse_try_block(lo, attrs);
2762 }
2763 if self.eat_keyword(keywords::Return) {
2764 if self.token.can_begin_expr() {
2765 let e = self.parse_expr()?;
2766 hi = e.span;
2767 ex = ExprKind::Ret(Some(e));
2768 } else {
2769 ex = ExprKind::Ret(None);
2770 }
2771 } else if self.eat_keyword(keywords::Break) {
2772 let label = self.eat_label();
2773 let e = if self.token.can_begin_expr()
2774 && !(self.token == token::OpenDelim(token::Brace)
2775 && self.restrictions.contains(
2776 Restrictions::NO_STRUCT_LITERAL)) {
2777 Some(self.parse_expr()?)
2778 } else {
2779 None
2780 };
2781 ex = ExprKind::Break(label, e);
2782 hi = self.prev_span;
2783 } else if self.eat_keyword(keywords::Yield) {
2784 if self.token.can_begin_expr() {
2785 let e = self.parse_expr()?;
2786 hi = e.span;
2787 ex = ExprKind::Yield(Some(e));
2788 } else {
2789 ex = ExprKind::Yield(None);
2790 }
2791 } else if self.token.is_keyword(keywords::Let) {
2792 // Catch this syntax error here, instead of in `parse_ident`, so
2793 // that we can explicitly mention that let is not to be used as an expression
2794 let mut db = self.fatal("expected expression, found statement (`let`)");
2795 db.span_label(self.span, "expected expression");
2796 db.note("variable declaration using `let` is a statement");
2797 return Err(db);
2798 } else if self.token.is_path_start() {
2799 let pth = self.parse_path(PathStyle::Expr)?;
2800
2801 // `!`, as an operator, is prefix, so we know this isn't that
2802 if self.eat(&token::Not) {
2803 // MACRO INVOCATION expression
2804 let (delim, tts) = self.expect_delimited_token_tree()?;
2805 let hi = self.prev_span;
2806 let node = Mac_ { path: pth, tts, delim };
2807 return Ok(self.mk_mac_expr(lo.to(hi), node, attrs))
2808 }
2809 if self.check(&token::OpenDelim(token::Brace)) {
2810 // This is a struct literal, unless we're prohibited
2811 // from parsing struct literals here.
2812 let prohibited = self.restrictions.contains(
2813 Restrictions::NO_STRUCT_LITERAL
2814 );
2815 if !prohibited {
2816 return self.parse_struct_expr(lo, pth, attrs);
2817 }
2818 }
2819
2820 hi = pth.span;
2821 ex = ExprKind::Path(None, pth);
2822 } else {
2823 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2824 // Don't complain about bare semicolons after unclosed braces
2825 // recovery in order to keep the error count down. Fixing the
2826 // delimiters will possibly also fix the bare semicolon found in
2827 // expression context. For example, silence the following error:
2828 // ```
2829 // error: expected expression, found `;`
2830 // --> file.rs:2:13
2831 // |
2832 // 2 | foo(bar(;
2833 // | ^ expected expression
2834 // ```
2835 self.bump();
2836 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2837 }
2838 match self.parse_literal_maybe_minus() {
2839 Ok(expr) => {
2840 hi = expr.span;
2841 ex = expr.node.clone();
2842 }
2843 Err(mut err) => {
2844 self.cancel(&mut err);
2845 let msg = format!("expected expression, found {}",
2846 self.this_token_descr());
2847 let mut err = self.fatal(&msg);
2848 err.span_label(self.span, "expected expression");
2849 return Err(err);
2850 }
2851 }
2852 }
2853 }
2854 }
2855
2856 let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
2857 let expr = self.maybe_recover_from_bad_qpath(expr, true)?;
2858
2859 return Ok(P(expr));
2860 }
2861
2862 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2863 -> PResult<'a, P<Expr>> {
2864 let struct_sp = lo.to(self.prev_span);
2865 self.bump();
2866 let mut fields = Vec::new();
2867 let mut base = None;
2868
2869 attrs.extend(self.parse_inner_attributes()?);
2870
2871 while self.token != token::CloseDelim(token::Brace) {
2872 if self.eat(&token::DotDot) {
2873 let exp_span = self.prev_span;
2874 match self.parse_expr() {
2875 Ok(e) => {
2876 base = Some(e);
2877 }
2878 Err(mut e) => {
2879 e.emit();
2880 self.recover_stmt();
2881 }
2882 }
2883 if self.token == token::Comma {
2884 let mut err = self.sess.span_diagnostic.mut_span_err(
2885 exp_span.to(self.prev_span),
2886 "cannot use a comma after the base struct",
2887 );
2888 err.span_suggestion_short(
2889 self.span,
2890 "remove this comma",
2891 String::new(),
2892 Applicability::MachineApplicable
2893 );
2894 err.note("the base struct must always be the last field");
2895 err.emit();
2896 self.recover_stmt();
2897 }
2898 break;
2899 }
2900
2901 let mut recovery_field = None;
2902 if let token::Ident(ident, _) = self.token {
2903 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2904 // Use in case of error after field-looking code: `S { foo: () with a }`
2905 let mut ident = ident.clone();
2906 ident.span = self.span;
2907 recovery_field = Some(ast::Field {
2908 ident,
2909 span: self.span,
2910 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2911 is_shorthand: false,
2912 attrs: ThinVec::new(),
2913 });
2914 }
2915 }
2916 let mut parsed_field = None;
2917 match self.parse_field() {
2918 Ok(f) => parsed_field = Some(f),
2919 Err(mut e) => {
2920 e.span_label(struct_sp, "while parsing this struct");
2921 e.emit();
2922
2923 // If the next token is a comma, then try to parse
2924 // what comes next as additional fields, rather than
2925 // bailing out until next `}`.
2926 if self.token != token::Comma {
2927 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2928 if self.token != token::Comma {
2929 break;
2930 }
2931 }
2932 }
2933 }
2934
2935 match self.expect_one_of(&[token::Comma],
2936 &[token::CloseDelim(token::Brace)]) {
2937 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2938 // only include the field if there's no parse error for the field name
2939 fields.push(f);
2940 }
2941 Err(mut e) => {
2942 if let Some(f) = recovery_field {
2943 fields.push(f);
2944 }
2945 e.span_label(struct_sp, "while parsing this struct");
2946 e.emit();
2947 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2948 self.eat(&token::Comma);
2949 }
2950 }
2951 }
2952
2953 let span = lo.to(self.span);
2954 self.expect(&token::CloseDelim(token::Brace))?;
2955 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2956 }
2957
2958 fn parse_or_use_outer_attributes(&mut self,
2959 already_parsed_attrs: Option<ThinVec<Attribute>>)
2960 -> PResult<'a, ThinVec<Attribute>> {
2961 if let Some(attrs) = already_parsed_attrs {
2962 Ok(attrs)
2963 } else {
2964 self.parse_outer_attributes().map(|a| a.into())
2965 }
2966 }
2967
2968 /// Parses a block or unsafe block.
2969 fn parse_block_expr(&mut self, opt_label: Option<Label>,
2970 lo: Span, blk_mode: BlockCheckMode,
2971 outer_attrs: ThinVec<Attribute>)
2972 -> PResult<'a, P<Expr>> {
2973 self.expect(&token::OpenDelim(token::Brace))?;
2974
2975 let mut attrs = outer_attrs;
2976 attrs.extend(self.parse_inner_attributes()?);
2977
2978 let blk = self.parse_block_tail(lo, blk_mode)?;
2979 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2980 }
2981
2982 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2983 fn parse_dot_or_call_expr(&mut self,
2984 already_parsed_attrs: Option<ThinVec<Attribute>>)
2985 -> PResult<'a, P<Expr>> {
2986 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2987
2988 let b = self.parse_bottom_expr();
2989 let (span, b) = self.interpolated_or_expr_span(b)?;
2990 self.parse_dot_or_call_expr_with(b, span, attrs)
2991 }
2992
2993 fn parse_dot_or_call_expr_with(&mut self,
2994 e0: P<Expr>,
2995 lo: Span,
2996 mut attrs: ThinVec<Attribute>)
2997 -> PResult<'a, P<Expr>> {
2998 // Stitch the list of outer attributes onto the return value.
2999 // A little bit ugly, but the best way given the current code
3000 // structure
3001 self.parse_dot_or_call_expr_with_(e0, lo)
3002 .map(|expr|
3003 expr.map(|mut expr| {
3004 attrs.extend::<Vec<_>>(expr.attrs.into());
3005 expr.attrs = attrs;
3006 match expr.node {
3007 ExprKind::If(..) | ExprKind::IfLet(..) => {
3008 if !expr.attrs.is_empty() {
3009 // Just point to the first attribute in there...
3010 let span = expr.attrs[0].span;
3011
3012 self.span_err(span,
3013 "attributes are not yet allowed on `if` \
3014 expressions");
3015 }
3016 }
3017 _ => {}
3018 }
3019 expr
3020 })
3021 )
3022 }
3023
3024 // Assuming we have just parsed `.`, continue parsing into an expression.
3025 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3026 let segment = self.parse_path_segment(PathStyle::Expr, true)?;
3027 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
3028
3029 Ok(match self.token {
3030 token::OpenDelim(token::Paren) => {
3031 // Method call `expr.f()`
3032 let mut args = self.parse_unspanned_seq(
3033 &token::OpenDelim(token::Paren),
3034 &token::CloseDelim(token::Paren),
3035 SeqSep::trailing_allowed(token::Comma),
3036 |p| Ok(p.parse_expr()?)
3037 )?;
3038 args.insert(0, self_arg);
3039
3040 let span = lo.to(self.prev_span);
3041 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
3042 }
3043 _ => {
3044 // Field access `expr.f`
3045 if let Some(args) = segment.args {
3046 self.span_err(args.span(),
3047 "field expressions may not have generic arguments");
3048 }
3049
3050 let span = lo.to(self.prev_span);
3051 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
3052 }
3053 })
3054 }
3055
3056 /// This function checks if there are trailing angle brackets and produces
3057 /// a diagnostic to suggest removing them.
3058 ///
3059 /// ```ignore (diagnostic)
3060 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
3061 /// ^^ help: remove extra angle brackets
3062 /// ```
3063 fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
3064 // This function is intended to be invoked after parsing a path segment where there are two
3065 // cases:
3066 //
3067 // 1. A specific token is expected after the path segment.
3068 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
3069 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
3070 // 2. No specific token is expected after the path segment.
3071 // eg. `x.foo` (field access)
3072 //
3073 // This function is called after parsing `.foo` and before parsing the token `end` (if
3074 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
3075 // `Foo::<Bar>`.
3076
3077 // We only care about trailing angle brackets if we previously parsed angle bracket
3078 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
3079 // removed in this case:
3080 //
3081 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
3082 //
3083 // This case is particularly tricky as we won't notice it just looking at the tokens -
3084 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
3085 // have already been parsed):
3086 //
3087 // `x.foo::<u32>>>(3)`
3088 let parsed_angle_bracket_args = segment.args
3089 .as_ref()
3090 .map(|args| args.is_angle_bracketed())
3091 .unwrap_or(false);
3092
3093 debug!(
3094 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
3095 parsed_angle_bracket_args,
3096 );
3097 if !parsed_angle_bracket_args {
3098 return;
3099 }
3100
3101 // Keep the span at the start so we can highlight the sequence of `>` characters to be
3102 // removed.
3103 let lo = self.span;
3104
3105 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
3106 // (since we might have the field access case and the characters we're eating are
3107 // actual operators and not trailing characters - ie `x.foo >> 3`).
3108 let mut position = 0;
3109
3110 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
3111 // many of each (so we can correctly pluralize our error messages) and continue to
3112 // advance.
3113 let mut number_of_shr = 0;
3114 let mut number_of_gt = 0;
3115 while self.look_ahead(position, |t| {
3116 trace!("check_trailing_angle_brackets: t={:?}", t);
3117 if *t == token::BinOp(token::BinOpToken::Shr) {
3118 number_of_shr += 1;
3119 true
3120 } else if *t == token::Gt {
3121 number_of_gt += 1;
3122 true
3123 } else {
3124 false
3125 }
3126 }) {
3127 position += 1;
3128 }
3129
3130 // If we didn't find any trailing `>` characters, then we have nothing to error about.
3131 debug!(
3132 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
3133 number_of_gt, number_of_shr,
3134 );
3135 if number_of_gt < 1 && number_of_shr < 1 {
3136 return;
3137 }
3138
3139 // Finally, double check that we have our end token as otherwise this is the
3140 // second case.
3141 if self.look_ahead(position, |t| {
3142 trace!("check_trailing_angle_brackets: t={:?}", t);
3143 *t == end
3144 }) {
3145 // Eat from where we started until the end token so that parsing can continue
3146 // as if we didn't have those extra angle brackets.
3147 self.eat_to_tokens(&[&end]);
3148 let span = lo.until(self.span);
3149
3150 let plural = number_of_gt > 1 || number_of_shr >= 1;
3151 self.diagnostic()
3152 .struct_span_err(
3153 span,
3154 &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
3155 )
3156 .span_suggestion(
3157 span,
3158 &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
3159 String::new(),
3160 Applicability::MachineApplicable,
3161 )
3162 .emit();
3163 }
3164 }
3165
3166 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3167 let mut e = e0;
3168 let mut hi;
3169 loop {
3170 // expr?
3171 while self.eat(&token::Question) {
3172 let hi = self.prev_span;
3173 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
3174 }
3175
3176 // expr.f
3177 if self.eat(&token::Dot) {
3178 match self.token {
3179 token::Ident(..) => {
3180 e = self.parse_dot_suffix(e, lo)?;
3181 }
3182 token::Literal(token::Integer(name), _) => {
3183 let span = self.span;
3184 self.bump();
3185 let field = ExprKind::Field(e, Ident::new(name, span));
3186 e = self.mk_expr(lo.to(span), field, ThinVec::new());
3187 }
3188 token::Literal(token::Float(n), _suf) => {
3189 self.bump();
3190 let fstr = n.as_str();
3191 let mut err = self.diagnostic()
3192 .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
3193 err.span_label(self.prev_span, "unexpected token");
3194 if fstr.chars().all(|x| "0123456789.".contains(x)) {
3195 let float = match fstr.parse::<f64>().ok() {
3196 Some(f) => f,
3197 None => continue,
3198 };
3199 let sugg = pprust::to_string(|s| {
3200 use crate::print::pprust::PrintState;
3201 s.popen()?;
3202 s.print_expr(&e)?;
3203 s.s.word( ".")?;
3204 s.print_usize(float.trunc() as usize)?;
3205 s.pclose()?;
3206 s.s.word(".")?;
3207 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
3208 });
3209 err.span_suggestion(
3210 lo.to(self.prev_span),
3211 "try parenthesizing the first index",
3212 sugg,
3213 Applicability::MachineApplicable
3214 );
3215 }
3216 return Err(err);
3217
3218 }
3219 _ => {
3220 // FIXME Could factor this out into non_fatal_unexpected or something.
3221 let actual = self.this_token_to_string();
3222 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
3223 }
3224 }
3225 continue;
3226 }
3227 if self.expr_is_complete(&e) { break; }
3228 match self.token {
3229 // expr(...)
3230 token::OpenDelim(token::Paren) => {
3231 let es = self.parse_unspanned_seq(
3232 &token::OpenDelim(token::Paren),
3233 &token::CloseDelim(token::Paren),
3234 SeqSep::trailing_allowed(token::Comma),
3235 |p| Ok(p.parse_expr()?)
3236 )?;
3237 hi = self.prev_span;
3238
3239 let nd = self.mk_call(e, es);
3240 e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
3241 }
3242
3243 // expr[...]
3244 // Could be either an index expression or a slicing expression.
3245 token::OpenDelim(token::Bracket) => {
3246 self.bump();
3247 let ix = self.parse_expr()?;
3248 hi = self.span;
3249 self.expect(&token::CloseDelim(token::Bracket))?;
3250 let index = self.mk_index(e, ix);
3251 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
3252 }
3253 _ => return Ok(e)
3254 }
3255 }
3256 return Ok(e);
3257 }
3258
3259 crate fn process_potential_macro_variable(&mut self) {
3260 let (token, span) = match self.token {
3261 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
3262 self.look_ahead(1, |t| t.is_ident()) => {
3263 self.bump();
3264 let name = match self.token {
3265 token::Ident(ident, _) => ident,
3266 _ => unreachable!()
3267 };
3268 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
3269 err.span_label(self.span, "unknown macro variable");
3270 err.emit();
3271 self.bump();
3272 return
3273 }
3274 token::Interpolated(ref nt) => {
3275 self.meta_var_span = Some(self.span);
3276 // Interpolated identifier and lifetime tokens are replaced with usual identifier
3277 // and lifetime tokens, so the former are never encountered during normal parsing.
3278 match **nt {
3279 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
3280 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
3281 _ => return,
3282 }
3283 }
3284 _ => return,
3285 };
3286 self.token = token;
3287 self.span = span;
3288 }
3289
3290 /// Parses a single token tree from the input.
3291 crate fn parse_token_tree(&mut self) -> TokenTree {
3292 match self.token {
3293 token::OpenDelim(..) => {
3294 let frame = mem::replace(&mut self.token_cursor.frame,
3295 self.token_cursor.stack.pop().unwrap());
3296 self.span = frame.span.entire();
3297 self.bump();
3298 TokenTree::Delimited(
3299 frame.span,
3300 frame.delim,
3301 frame.tree_cursor.stream.into(),
3302 )
3303 },
3304 token::CloseDelim(_) | token::Eof => unreachable!(),
3305 _ => {
3306 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
3307 self.bump();
3308 TokenTree::Token(span, token)
3309 }
3310 }
3311 }
3312
3313 // parse a stream of tokens into a list of TokenTree's,
3314 // up to EOF.
3315 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
3316 let mut tts = Vec::new();
3317 while self.token != token::Eof {
3318 tts.push(self.parse_token_tree());
3319 }
3320 Ok(tts)
3321 }
3322
3323 pub fn parse_tokens(&mut self) -> TokenStream {
3324 let mut result = Vec::new();
3325 loop {
3326 match self.token {
3327 token::Eof | token::CloseDelim(..) => break,
3328 _ => result.push(self.parse_token_tree().into()),
3329 }
3330 }
3331 TokenStream::new(result)
3332 }
3333
3334 /// Parse a prefix-unary-operator expr
3335 fn parse_prefix_expr(&mut self,
3336 already_parsed_attrs: Option<ThinVec<Attribute>>)
3337 -> PResult<'a, P<Expr>> {
3338 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3339 let lo = self.span;
3340 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
3341 let (hi, ex) = match self.token {
3342 token::Not => {
3343 self.bump();
3344 let e = self.parse_prefix_expr(None);
3345 let (span, e) = self.interpolated_or_expr_span(e)?;
3346 (lo.to(span), self.mk_unary(UnOp::Not, e))
3347 }
3348 // Suggest `!` for bitwise negation when encountering a `~`
3349 token::Tilde => {
3350 self.bump();
3351 let e = self.parse_prefix_expr(None);
3352 let (span, e) = self.interpolated_or_expr_span(e)?;
3353 let span_of_tilde = lo;
3354 let mut err = self.diagnostic()
3355 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
3356 err.span_suggestion_short(
3357 span_of_tilde,
3358 "use `!` to perform bitwise negation",
3359 "!".to_owned(),
3360 Applicability::MachineApplicable
3361 );
3362 err.emit();
3363 (lo.to(span), self.mk_unary(UnOp::Not, e))
3364 }
3365 token::BinOp(token::Minus) => {
3366 self.bump();
3367 let e = self.parse_prefix_expr(None);
3368 let (span, e) = self.interpolated_or_expr_span(e)?;
3369 (lo.to(span), self.mk_unary(UnOp::Neg, e))
3370 }
3371 token::BinOp(token::Star) => {
3372 self.bump();
3373 let e = self.parse_prefix_expr(None);
3374 let (span, e) = self.interpolated_or_expr_span(e)?;
3375 (lo.to(span), self.mk_unary(UnOp::Deref, e))
3376 }
3377 token::BinOp(token::And) | token::AndAnd => {
3378 self.expect_and()?;
3379 let m = self.parse_mutability();
3380 let e = self.parse_prefix_expr(None);
3381 let (span, e) = self.interpolated_or_expr_span(e)?;
3382 (lo.to(span), ExprKind::AddrOf(m, e))
3383 }
3384 token::Ident(..) if self.token.is_keyword(keywords::In) => {
3385 self.bump();
3386 let place = self.parse_expr_res(
3387 Restrictions::NO_STRUCT_LITERAL,
3388 None,
3389 )?;
3390 let blk = self.parse_block()?;
3391 let span = blk.span;
3392 let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
3393 (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
3394 }
3395 token::Ident(..) if self.token.is_keyword(keywords::Box) => {
3396 self.bump();
3397 let e = self.parse_prefix_expr(None);
3398 let (span, e) = self.interpolated_or_expr_span(e)?;
3399 (lo.to(span), ExprKind::Box(e))
3400 }
3401 token::Ident(..) if self.token.is_ident_named("not") => {
3402 // `not` is just an ordinary identifier in Rust-the-language,
3403 // but as `rustc`-the-compiler, we can issue clever diagnostics
3404 // for confused users who really want to say `!`
3405 let token_cannot_continue_expr = |t: &token::Token| match *t {
3406 // These tokens can start an expression after `!`, but
3407 // can't continue an expression after an ident
3408 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
3409 token::Literal(..) | token::Pound => true,
3410 token::Interpolated(ref nt) => match **nt {
3411 token::NtIdent(..) | token::NtExpr(..) |
3412 token::NtBlock(..) | token::NtPath(..) => true,
3413 _ => false,
3414 },
3415 _ => false
3416 };
3417 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
3418 if cannot_continue_expr {
3419 self.bump();
3420 // Emit the error ...
3421 let mut err = self.diagnostic()
3422 .struct_span_err(self.span,
3423 &format!("unexpected {} after identifier",
3424 self.this_token_descr()));
3425 // span the `not` plus trailing whitespace to avoid
3426 // trailing whitespace after the `!` in our suggestion
3427 let to_replace = self.sess.source_map()
3428 .span_until_non_whitespace(lo.to(self.span));
3429 err.span_suggestion_short(
3430 to_replace,
3431 "use `!` to perform logical negation",
3432 "!".to_owned(),
3433 Applicability::MachineApplicable
3434 );
3435 err.emit();
3436 // —and recover! (just as if we were in the block
3437 // for the `token::Not` arm)
3438 let e = self.parse_prefix_expr(None);
3439 let (span, e) = self.interpolated_or_expr_span(e)?;
3440 (lo.to(span), self.mk_unary(UnOp::Not, e))
3441 } else {
3442 return self.parse_dot_or_call_expr(Some(attrs));
3443 }
3444 }
3445 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
3446 };
3447 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
3448 }
3449
3450 /// Parses an associative expression.
3451 ///
3452 /// This parses an expression accounting for associativity and precedence of the operators in
3453 /// the expression.
3454 #[inline]
3455 fn parse_assoc_expr(&mut self,
3456 already_parsed_attrs: Option<ThinVec<Attribute>>)
3457 -> PResult<'a, P<Expr>> {
3458 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
3459 }
3460
3461 /// Parses an associative expression with operators of at least `min_prec` precedence.
3462 fn parse_assoc_expr_with(&mut self,
3463 min_prec: usize,
3464 lhs: LhsExpr)
3465 -> PResult<'a, P<Expr>> {
3466 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
3467 expr
3468 } else {
3469 let attrs = match lhs {
3470 LhsExpr::AttributesParsed(attrs) => Some(attrs),
3471 _ => None,
3472 };
3473 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
3474 return self.parse_prefix_range_expr(attrs);
3475 } else {
3476 self.parse_prefix_expr(attrs)?
3477 }
3478 };
3479
3480 if self.expr_is_complete(&lhs) {
3481 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
3482 return Ok(lhs);
3483 }
3484 self.expected_tokens.push(TokenType::Operator);
3485 while let Some(op) = AssocOp::from_token(&self.token) {
3486
3487 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
3488 // it refers to. Interpolated identifiers are unwrapped early and never show up here
3489 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
3490 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
3491 let lhs_span = match (self.prev_token_kind, &lhs.node) {
3492 (PrevTokenKind::Interpolated, _) => self.prev_span,
3493 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
3494 if path.segments.len() == 1 => self.prev_span,
3495 _ => lhs.span,
3496 };
3497
3498 let cur_op_span = self.span;
3499 let restrictions = if op.is_assign_like() {
3500 self.restrictions & Restrictions::NO_STRUCT_LITERAL
3501 } else {
3502 self.restrictions
3503 };
3504 if op.precedence() < min_prec {
3505 break;
3506 }
3507 // Check for deprecated `...` syntax
3508 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
3509 self.err_dotdotdot_syntax(self.span);
3510 }
3511
3512 self.bump();
3513 if op.is_comparison() {
3514 self.check_no_chained_comparison(&lhs, &op);
3515 }
3516 // Special cases:
3517 if op == AssocOp::As {
3518 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
3519 continue
3520 } else if op == AssocOp::Colon {
3521 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
3522 Ok(lhs) => lhs,
3523 Err(mut err) => {
3524 err.span_label(self.span,
3525 "expecting a type here because of type ascription");
3526 let cm = self.sess.source_map();
3527 let cur_pos = cm.lookup_char_pos(self.span.lo());
3528 let op_pos = cm.lookup_char_pos(cur_op_span.hi());
3529 if cur_pos.line != op_pos.line {
3530 err.span_suggestion(
3531 cur_op_span,
3532 "try using a semicolon",
3533 ";".to_string(),
3534 Applicability::MaybeIncorrect // speculative
3535 );
3536 }
3537 return Err(err);
3538 }
3539 };
3540 continue
3541 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
3542 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
3543 // generalise it to the Fixity::None code.
3544 //
3545 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
3546 // two variants are handled with `parse_prefix_range_expr` call above.
3547 let rhs = if self.is_at_start_of_range_notation_rhs() {
3548 Some(self.parse_assoc_expr_with(op.precedence() + 1,
3549 LhsExpr::NotYetParsed)?)
3550 } else {
3551 None
3552 };
3553 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
3554 x.span
3555 } else {
3556 cur_op_span
3557 });
3558 let limits = if op == AssocOp::DotDot {
3559 RangeLimits::HalfOpen
3560 } else {
3561 RangeLimits::Closed
3562 };
3563
3564 let r = self.mk_range(Some(lhs), rhs, limits)?;
3565 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
3566 break
3567 }
3568
3569 let rhs = match op.fixity() {
3570 Fixity::Right => self.with_res(
3571 restrictions - Restrictions::STMT_EXPR,
3572 |this| {
3573 this.parse_assoc_expr_with(op.precedence(),
3574 LhsExpr::NotYetParsed)
3575 }),
3576 Fixity::Left => self.with_res(
3577 restrictions - Restrictions::STMT_EXPR,
3578 |this| {
3579 this.parse_assoc_expr_with(op.precedence() + 1,
3580 LhsExpr::NotYetParsed)
3581 }),
3582 // We currently have no non-associative operators that are not handled above by
3583 // the special cases. The code is here only for future convenience.
3584 Fixity::None => self.with_res(
3585 restrictions - Restrictions::STMT_EXPR,
3586 |this| {
3587 this.parse_assoc_expr_with(op.precedence() + 1,
3588 LhsExpr::NotYetParsed)
3589 }),
3590 }?;
3591
3592 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
3593 // including the attributes.
3594 let lhs_span = lhs
3595 .attrs
3596 .iter()
3597 .filter(|a| a.style == AttrStyle::Outer)
3598 .next()
3599 .map_or(lhs_span, |a| a.span);
3600 let span = lhs_span.to(rhs.span);
3601 lhs = match op {
3602 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
3603 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3604 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3605 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3606 AssocOp::Greater | AssocOp::GreaterEqual => {
3607 let ast_op = op.to_ast_binop().unwrap();
3608 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
3609 self.mk_expr(span, binary, ThinVec::new())
3610 }
3611 AssocOp::Assign =>
3612 self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3613 AssocOp::ObsoleteInPlace =>
3614 self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
3615 AssocOp::AssignOp(k) => {
3616 let aop = match k {
3617 token::Plus => BinOpKind::Add,
3618 token::Minus => BinOpKind::Sub,
3619 token::Star => BinOpKind::Mul,
3620 token::Slash => BinOpKind::Div,
3621 token::Percent => BinOpKind::Rem,
3622 token::Caret => BinOpKind::BitXor,
3623 token::And => BinOpKind::BitAnd,
3624 token::Or => BinOpKind::BitOr,
3625 token::Shl => BinOpKind::Shl,
3626 token::Shr => BinOpKind::Shr,
3627 };
3628 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3629 self.mk_expr(span, aopexpr, ThinVec::new())
3630 }
3631 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3632 self.bug("AssocOp should have been handled by special case")
3633 }
3634 };
3635
3636 if op.fixity() == Fixity::None { break }
3637 }
3638 Ok(lhs)
3639 }
3640
3641 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3642 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3643 -> PResult<'a, P<Expr>> {
3644 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3645 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3646 };
3647
3648 // Save the state of the parser before parsing type normally, in case there is a
3649 // LessThan comparison after this cast.
3650 let parser_snapshot_before_type = self.clone();
3651 match self.parse_ty_no_plus() {
3652 Ok(rhs) => {
3653 Ok(mk_expr(self, rhs))
3654 }
3655 Err(mut type_err) => {
3656 // Rewind to before attempting to parse the type with generics, to recover
3657 // from situations like `x as usize < y` in which we first tried to parse
3658 // `usize < y` as a type with generic arguments.
3659 let parser_snapshot_after_type = self.clone();
3660 mem::replace(self, parser_snapshot_before_type);
3661
3662 match self.parse_path(PathStyle::Expr) {
3663 Ok(path) => {
3664 let (op_noun, op_verb) = match self.token {
3665 token::Lt => ("comparison", "comparing"),
3666 token::BinOp(token::Shl) => ("shift", "shifting"),
3667 _ => {
3668 // We can end up here even without `<` being the next token, for
3669 // example because `parse_ty_no_plus` returns `Err` on keywords,
3670 // but `parse_path` returns `Ok` on them due to error recovery.
3671 // Return original error and parser state.
3672 mem::replace(self, parser_snapshot_after_type);
3673 return Err(type_err);
3674 }
3675 };
3676
3677 // Successfully parsed the type path leaving a `<` yet to parse.
3678 type_err.cancel();
3679
3680 // Report non-fatal diagnostics, keep `x as usize` as an expression
3681 // in AST and continue parsing.
3682 let msg = format!("`<` is interpreted as a start of generic \
3683 arguments for `{}`, not a {}", path, op_noun);
3684 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3685 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3686 "interpreted as generic arguments");
3687 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3688
3689 let expr = mk_expr(self, P(Ty {
3690 span: path.span,
3691 node: TyKind::Path(None, path),
3692 id: ast::DUMMY_NODE_ID
3693 }));
3694
3695 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3696 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3697 err.span_suggestion(
3698 expr.span,
3699 &format!("try {} the cast value", op_verb),
3700 format!("({})", expr_str),
3701 Applicability::MachineApplicable
3702 );
3703 err.emit();
3704
3705 Ok(expr)
3706 }
3707 Err(mut path_err) => {
3708 // Couldn't parse as a path, return original error and parser state.
3709 path_err.cancel();
3710 mem::replace(self, parser_snapshot_after_type);
3711 Err(type_err)
3712 }
3713 }
3714 }
3715 }
3716 }
3717
3718 /// Produce an error if comparison operators are chained (RFC #558).
3719 /// We only need to check lhs, not rhs, because all comparison ops
3720 /// have same precedence and are left-associative
3721 fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
3722 debug_assert!(outer_op.is_comparison(),
3723 "check_no_chained_comparison: {:?} is not comparison",
3724 outer_op);
3725 match lhs.node {
3726 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
3727 // respan to include both operators
3728 let op_span = op.span.to(self.span);
3729 let mut err = self.diagnostic().struct_span_err(op_span,
3730 "chained comparison operators require parentheses");
3731 if op.node == BinOpKind::Lt &&
3732 *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
3733 *outer_op == AssocOp::Greater // even in a case like the following:
3734 { // Foo<Bar<Baz<Qux, ()>>>
3735 err.help(
3736 "use `::<...>` instead of `<...>` if you meant to specify type arguments");
3737 err.help("or use `(...)` if you meant to specify fn arguments");
3738 }
3739 err.emit();
3740 }
3741 _ => {}
3742 }
3743 }
3744
3745 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3746 fn parse_prefix_range_expr(&mut self,
3747 already_parsed_attrs: Option<ThinVec<Attribute>>)
3748 -> PResult<'a, P<Expr>> {
3749 // Check for deprecated `...` syntax
3750 if self.token == token::DotDotDot {
3751 self.err_dotdotdot_syntax(self.span);
3752 }
3753
3754 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3755 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3756 self.token);
3757 let tok = self.token.clone();
3758 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3759 let lo = self.span;
3760 let mut hi = self.span;
3761 self.bump();
3762 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3763 // RHS must be parsed with more associativity than the dots.
3764 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3765 Some(self.parse_assoc_expr_with(next_prec,
3766 LhsExpr::NotYetParsed)
3767 .map(|x|{
3768 hi = x.span;
3769 x
3770 })?)
3771 } else {
3772 None
3773 };
3774 let limits = if tok == token::DotDot {
3775 RangeLimits::HalfOpen
3776 } else {
3777 RangeLimits::Closed
3778 };
3779
3780 let r = self.mk_range(None, opt_end, limits)?;
3781 Ok(self.mk_expr(lo.to(hi), r, attrs))
3782 }
3783
3784 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3785 if self.token.can_begin_expr() {
3786 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3787 if self.token == token::OpenDelim(token::Brace) {
3788 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3789 }
3790 true
3791 } else {
3792 false
3793 }
3794 }
3795
3796 /// Parses an `if` or `if let` expression (`if` token already eaten).
3797 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3798 if self.check_keyword(keywords::Let) {
3799 return self.parse_if_let_expr(attrs);
3800 }
3801 let lo = self.prev_span;
3802 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3803
3804 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3805 // verify that the last statement is either an implicit return (no `;`) or an explicit
3806 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3807 // the dead code lint.
3808 if self.eat_keyword(keywords::Else) || !cond.returns() {
3809 let sp = self.sess.source_map().next_point(lo);
3810 let mut err = self.diagnostic()
3811 .struct_span_err(sp, "missing condition for `if` statemement");
3812 err.span_label(sp, "expected if condition here");
3813 return Err(err)
3814 }
3815 let not_block = self.token != token::OpenDelim(token::Brace);
3816 let thn = self.parse_block().map_err(|mut err| {
3817 if not_block {
3818 err.span_label(lo, "this `if` statement has a condition, but no block");
3819 }
3820 err
3821 })?;
3822 let mut els: Option<P<Expr>> = None;
3823 let mut hi = thn.span;
3824 if self.eat_keyword(keywords::Else) {
3825 let elexpr = self.parse_else_expr()?;
3826 hi = elexpr.span;
3827 els = Some(elexpr);
3828 }
3829 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3830 }
3831
3832 /// Parses an `if let` expression (`if` token already eaten).
3833 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3834 -> PResult<'a, P<Expr>> {
3835 let lo = self.prev_span;
3836 self.expect_keyword(keywords::Let)?;
3837 let pats = self.parse_pats()?;
3838 self.expect(&token::Eq)?;
3839 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3840 let thn = self.parse_block()?;
3841 let (hi, els) = if self.eat_keyword(keywords::Else) {
3842 let expr = self.parse_else_expr()?;
3843 (expr.span, Some(expr))
3844 } else {
3845 (thn.span, None)
3846 };
3847 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3848 }
3849
3850 /// Parses `move |args| expr`.
3851 fn parse_lambda_expr(&mut self,
3852 attrs: ThinVec<Attribute>)
3853 -> PResult<'a, P<Expr>>
3854 {
3855 let lo = self.span;
3856 let movability = if self.eat_keyword(keywords::Static) {
3857 Movability::Static
3858 } else {
3859 Movability::Movable
3860 };
3861 let asyncness = if self.span.rust_2018() {
3862 self.parse_asyncness()
3863 } else {
3864 IsAsync::NotAsync
3865 };
3866 let capture_clause = if self.eat_keyword(keywords::Move) {
3867 CaptureBy::Value
3868 } else {
3869 CaptureBy::Ref
3870 };
3871 let decl = self.parse_fn_block_decl()?;
3872 let decl_hi = self.prev_span;
3873 let body = match decl.output {
3874 FunctionRetTy::Default(_) => {
3875 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3876 self.parse_expr_res(restrictions, None)?
3877 },
3878 _ => {
3879 // If an explicit return type is given, require a
3880 // block to appear (RFC 968).
3881 let body_lo = self.span;
3882 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3883 }
3884 };
3885
3886 Ok(self.mk_expr(
3887 lo.to(body.span),
3888 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3889 attrs))
3890 }
3891
3892 // `else` token already eaten
3893 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3894 if self.eat_keyword(keywords::If) {
3895 return self.parse_if_expr(ThinVec::new());
3896 } else {
3897 let blk = self.parse_block()?;
3898 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3899 }
3900 }
3901
3902 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3903 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3904 span_lo: Span,
3905 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3906 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3907
3908 let pat = self.parse_top_level_pat()?;
3909 if !self.eat_keyword(keywords::In) {
3910 let in_span = self.prev_span.between(self.span);
3911 let mut err = self.sess.span_diagnostic
3912 .struct_span_err(in_span, "missing `in` in `for` loop");
3913 err.span_suggestion_short(
3914 in_span, "try adding `in` here", " in ".into(),
3915 // has been misleading, at least in the past (closed Issue #48492)
3916 Applicability::MaybeIncorrect
3917 );
3918 err.emit();
3919 }
3920 let in_span = self.prev_span;
3921 if self.eat_keyword(keywords::In) {
3922 // a common typo: `for _ in in bar {}`
3923 let mut err = self.sess.span_diagnostic.struct_span_err(
3924 self.prev_span,
3925 "expected iterable, found keyword `in`",
3926 );
3927 err.span_suggestion_short(
3928 in_span.until(self.prev_span),
3929 "remove the duplicated `in`",
3930 String::new(),
3931 Applicability::MachineApplicable,
3932 );
3933 err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
3934 err.note("for more information on the status of emplacement syntax, see <\
3935 https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
3936 err.emit();
3937 }
3938 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3939 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3940 attrs.extend(iattrs);
3941
3942 let hi = self.prev_span;
3943 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3944 }
3945
3946 /// Parses a `while` or `while let` expression (`while` token already eaten).
3947 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3948 span_lo: Span,
3949 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3950 if self.token.is_keyword(keywords::Let) {
3951 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3952 }
3953 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3954 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3955 attrs.extend(iattrs);
3956 let span = span_lo.to(body.span);
3957 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3958 }
3959
3960 /// Parses a `while let` expression (`while` token already eaten).
3961 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3962 span_lo: Span,
3963 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3964 self.expect_keyword(keywords::Let)?;
3965 let pats = self.parse_pats()?;
3966 self.expect(&token::Eq)?;
3967 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3968 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3969 attrs.extend(iattrs);
3970 let span = span_lo.to(body.span);
3971 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3972 }
3973
3974 // parse `loop {...}`, `loop` token already eaten
3975 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3976 span_lo: Span,
3977 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3978 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3979 attrs.extend(iattrs);
3980 let span = span_lo.to(body.span);
3981 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3982 }
3983
3984 /// Parses an `async move {...}` expression.
3985 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3986 -> PResult<'a, P<Expr>>
3987 {
3988 let span_lo = self.span;
3989 self.expect_keyword(keywords::Async)?;
3990 let capture_clause = if self.eat_keyword(keywords::Move) {
3991 CaptureBy::Value
3992 } else {
3993 CaptureBy::Ref
3994 };
3995 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3996 attrs.extend(iattrs);
3997 Ok(self.mk_expr(
3998 span_lo.to(body.span),
3999 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
4000 }
4001
4002 /// Parses a `try {...}` expression (`try` token already eaten).
4003 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
4004 -> PResult<'a, P<Expr>>
4005 {
4006 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4007 attrs.extend(iattrs);
4008 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
4009 }
4010
4011 // `match` token already eaten
4012 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4013 let match_span = self.prev_span;
4014 let lo = self.prev_span;
4015 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
4016 None)?;
4017 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
4018 if self.token == token::Token::Semi {
4019 e.span_suggestion_short(
4020 match_span,
4021 "try removing this `match`",
4022 String::new(),
4023 Applicability::MaybeIncorrect // speculative
4024 );
4025 }
4026 return Err(e)
4027 }
4028 attrs.extend(self.parse_inner_attributes()?);
4029
4030 let mut arms: Vec<Arm> = Vec::new();
4031 while self.token != token::CloseDelim(token::Brace) {
4032 match self.parse_arm() {
4033 Ok(arm) => arms.push(arm),
4034 Err(mut e) => {
4035 // Recover by skipping to the end of the block.
4036 e.emit();
4037 self.recover_stmt();
4038 let span = lo.to(self.span);
4039 if self.token == token::CloseDelim(token::Brace) {
4040 self.bump();
4041 }
4042 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
4043 }
4044 }
4045 }
4046 let hi = self.span;
4047 self.bump();
4048 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
4049 }
4050
4051 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
4052 maybe_whole!(self, NtArm, |x| x);
4053
4054 let attrs = self.parse_outer_attributes()?;
4055 let pats = self.parse_pats()?;
4056 let guard = if self.eat_keyword(keywords::If) {
4057 Some(Guard::If(self.parse_expr()?))
4058 } else {
4059 None
4060 };
4061 let arrow_span = self.span;
4062 self.expect(&token::FatArrow)?;
4063 let arm_start_span = self.span;
4064
4065 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
4066 .map_err(|mut err| {
4067 err.span_label(arrow_span, "while parsing the `match` arm starting here");
4068 err
4069 })?;
4070
4071 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
4072 && self.token != token::CloseDelim(token::Brace);
4073
4074 if require_comma {
4075 let cm = self.sess.source_map();
4076 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
4077 .map_err(|mut err| {
4078 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
4079 (Ok(ref expr_lines), Ok(ref arm_start_lines))
4080 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
4081 && expr_lines.lines.len() == 2
4082 && self.token == token::FatArrow => {
4083 // We check whether there's any trailing code in the parse span,
4084 // if there isn't, we very likely have the following:
4085 //
4086 // X | &Y => "y"
4087 // | -- - missing comma
4088 // | |
4089 // | arrow_span
4090 // X | &X => "x"
4091 // | - ^^ self.span
4092 // | |
4093 // | parsed until here as `"y" & X`
4094 err.span_suggestion_short(
4095 cm.next_point(arm_start_span),
4096 "missing a comma here to end this `match` arm",
4097 ",".to_owned(),
4098 Applicability::MachineApplicable
4099 );
4100 }
4101 _ => {
4102 err.span_label(arrow_span,
4103 "while parsing the `match` arm starting here");
4104 }
4105 }
4106 err
4107 })?;
4108 } else {
4109 self.eat(&token::Comma);
4110 }
4111
4112 Ok(ast::Arm {
4113 attrs,
4114 pats,
4115 guard,
4116 body: expr,
4117 })
4118 }
4119
4120 /// Parses an expression.
4121 #[inline]
4122 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
4123 self.parse_expr_res(Restrictions::empty(), None)
4124 }
4125
4126 /// Evaluates the closure with restrictions in place.
4127 ///
4128 /// Afters the closure is evaluated, restrictions are reset.
4129 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
4130 where F: FnOnce(&mut Self) -> T
4131 {
4132 let old = self.restrictions;
4133 self.restrictions = r;
4134 let r = f(self);
4135 self.restrictions = old;
4136 return r;
4137
4138 }
4139
4140 /// Parses an expression, subject to the given restrictions.
4141 #[inline]
4142 fn parse_expr_res(&mut self, r: Restrictions,
4143 already_parsed_attrs: Option<ThinVec<Attribute>>)
4144 -> PResult<'a, P<Expr>> {
4145 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
4146 }
4147
4148 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
4149 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
4150 if self.eat(&token::Eq) {
4151 Ok(Some(self.parse_expr()?))
4152 } else if skip_eq {
4153 Ok(Some(self.parse_expr()?))
4154 } else {
4155 Ok(None)
4156 }
4157 }
4158
4159 /// Parses patterns, separated by '|' s.
4160 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
4161 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
4162 self.eat(&token::BinOp(token::Or));
4163
4164 let mut pats = Vec::new();
4165 loop {
4166 pats.push(self.parse_top_level_pat()?);
4167
4168 if self.token == token::OrOr {
4169 let mut err = self.struct_span_err(self.span,
4170 "unexpected token `||` after pattern");
4171 err.span_suggestion(
4172 self.span,
4173 "use a single `|` to specify multiple patterns",
4174 "|".to_owned(),
4175 Applicability::MachineApplicable
4176 );
4177 err.emit();
4178 self.bump();
4179 } else if self.eat(&token::BinOp(token::Or)) {
4180 // This is a No-op. Continue the loop to parse the next
4181 // pattern.
4182 } else {
4183 return Ok(pats);
4184 }
4185 };
4186 }
4187
4188 // Parses a parenthesized list of patterns like
4189 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
4190 // - a vector of the patterns that were parsed
4191 // - an option indicating the index of the `..` element
4192 // - a boolean indicating whether a trailing comma was present.
4193 // Trailing commas are significant because (p) and (p,) are different patterns.
4194 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4195 self.expect(&token::OpenDelim(token::Paren))?;
4196 let result = self.parse_pat_list()?;
4197 self.expect(&token::CloseDelim(token::Paren))?;
4198 Ok(result)
4199 }
4200
4201 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4202 let mut fields = Vec::new();
4203 let mut ddpos = None;
4204 let mut trailing_comma = false;
4205 loop {
4206 if self.eat(&token::DotDot) {
4207 if ddpos.is_none() {
4208 ddpos = Some(fields.len());
4209 } else {
4210 // Emit a friendly error, ignore `..` and continue parsing
4211 self.struct_span_err(
4212 self.prev_span,
4213 "`..` can only be used once per tuple or tuple struct pattern",
4214 )
4215 .span_label(self.prev_span, "can only be used once per pattern")
4216 .emit();
4217 }
4218 } else if !self.check(&token::CloseDelim(token::Paren)) {
4219 fields.push(self.parse_pat(None)?);
4220 } else {
4221 break
4222 }
4223
4224 trailing_comma = self.eat(&token::Comma);
4225 if !trailing_comma {
4226 break
4227 }
4228 }
4229
4230 if ddpos == Some(fields.len()) && trailing_comma {
4231 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
4232 let msg = "trailing comma is not permitted after `..`";
4233 self.struct_span_err(self.prev_span, msg)
4234 .span_label(self.prev_span, msg)
4235 .emit();
4236 }
4237
4238 Ok((fields, ddpos, trailing_comma))
4239 }
4240
4241 fn parse_pat_vec_elements(
4242 &mut self,
4243 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
4244 let mut before = Vec::new();
4245 let mut slice = None;
4246 let mut after = Vec::new();
4247 let mut first = true;
4248 let mut before_slice = true;
4249
4250 while self.token != token::CloseDelim(token::Bracket) {
4251 if first {
4252 first = false;
4253 } else {
4254 self.expect(&token::Comma)?;
4255
4256 if self.token == token::CloseDelim(token::Bracket)
4257 && (before_slice || !after.is_empty()) {
4258 break
4259 }
4260 }
4261
4262 if before_slice {
4263 if self.eat(&token::DotDot) {
4264
4265 if self.check(&token::Comma) ||
4266 self.check(&token::CloseDelim(token::Bracket)) {
4267 slice = Some(P(Pat {
4268 id: ast::DUMMY_NODE_ID,
4269 node: PatKind::Wild,
4270 span: self.prev_span,
4271 }));
4272 before_slice = false;
4273 }
4274 continue
4275 }
4276 }
4277
4278 let subpat = self.parse_pat(None)?;
4279 if before_slice && self.eat(&token::DotDot) {
4280 slice = Some(subpat);
4281 before_slice = false;
4282 } else if before_slice {
4283 before.push(subpat);
4284 } else {
4285 after.push(subpat);
4286 }
4287 }
4288
4289 Ok((before, slice, after))
4290 }
4291
4292 fn parse_pat_field(
4293 &mut self,
4294 lo: Span,
4295 attrs: Vec<Attribute>
4296 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
4297 // Check if a colon exists one ahead. This means we're parsing a fieldname.
4298 let hi;
4299 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
4300 // Parsing a pattern of the form "fieldname: pat"
4301 let fieldname = self.parse_field_name()?;
4302 self.bump();
4303 let pat = self.parse_pat(None)?;
4304 hi = pat.span;
4305 (pat, fieldname, false)
4306 } else {
4307 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
4308 let is_box = self.eat_keyword(keywords::Box);
4309 let boxed_span = self.span;
4310 let is_ref = self.eat_keyword(keywords::Ref);
4311 let is_mut = self.eat_keyword(keywords::Mut);
4312 let fieldname = self.parse_ident()?;
4313 hi = self.prev_span;
4314
4315 let bind_type = match (is_ref, is_mut) {
4316 (true, true) => BindingMode::ByRef(Mutability::Mutable),
4317 (true, false) => BindingMode::ByRef(Mutability::Immutable),
4318 (false, true) => BindingMode::ByValue(Mutability::Mutable),
4319 (false, false) => BindingMode::ByValue(Mutability::Immutable),
4320 };
4321 let fieldpat = P(Pat {
4322 id: ast::DUMMY_NODE_ID,
4323 node: PatKind::Ident(bind_type, fieldname, None),
4324 span: boxed_span.to(hi),
4325 });
4326
4327 let subpat = if is_box {
4328 P(Pat {
4329 id: ast::DUMMY_NODE_ID,
4330 node: PatKind::Box(fieldpat),
4331 span: lo.to(hi),
4332 })
4333 } else {
4334 fieldpat
4335 };
4336 (subpat, fieldname, true)
4337 };
4338
4339 Ok(source_map::Spanned {
4340 span: lo.to(hi),
4341 node: ast::FieldPat {
4342 ident: fieldname,
4343 pat: subpat,
4344 is_shorthand,
4345 attrs: attrs.into(),
4346 }
4347 })
4348 }
4349
4350 /// Parses the fields of a struct-like pattern.
4351 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
4352 let mut fields = Vec::new();
4353 let mut etc = false;
4354 let mut ate_comma = true;
4355 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
4356 let mut etc_span = None;
4357
4358 while self.token != token::CloseDelim(token::Brace) {
4359 let attrs = self.parse_outer_attributes()?;
4360 let lo = self.span;
4361
4362 // check that a comma comes after every field
4363 if !ate_comma {
4364 let err = self.struct_span_err(self.prev_span, "expected `,`");
4365 if let Some(mut delayed) = delayed_err {
4366 delayed.emit();
4367 }
4368 return Err(err);
4369 }
4370 ate_comma = false;
4371
4372 if self.check(&token::DotDot) || self.token == token::DotDotDot {
4373 etc = true;
4374 let mut etc_sp = self.span;
4375
4376 if self.token == token::DotDotDot { // Issue #46718
4377 // Accept `...` as if it were `..` to avoid further errors
4378 let mut err = self.struct_span_err(self.span,
4379 "expected field pattern, found `...`");
4380 err.span_suggestion(
4381 self.span,
4382 "to omit remaining fields, use one fewer `.`",
4383 "..".to_owned(),
4384 Applicability::MachineApplicable
4385 );
4386 err.emit();
4387 }
4388 self.bump(); // `..` || `...`
4389
4390 if self.token == token::CloseDelim(token::Brace) {
4391 etc_span = Some(etc_sp);
4392 break;
4393 }
4394 let token_str = self.this_token_descr();
4395 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
4396
4397 err.span_label(self.span, "expected `}`");
4398 let mut comma_sp = None;
4399 if self.token == token::Comma { // Issue #49257
4400 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
4401 err.span_label(etc_sp,
4402 "`..` must be at the end and cannot have a trailing comma");
4403 comma_sp = Some(self.span);
4404 self.bump();
4405 ate_comma = true;
4406 }
4407
4408 etc_span = Some(etc_sp.until(self.span));
4409 if self.token == token::CloseDelim(token::Brace) {
4410 // If the struct looks otherwise well formed, recover and continue.
4411 if let Some(sp) = comma_sp {
4412 err.span_suggestion_short(
4413 sp,
4414 "remove this comma",
4415 String::new(),
4416 Applicability::MachineApplicable,
4417 );
4418 }
4419 err.emit();
4420 break;
4421 } else if self.token.is_ident() && ate_comma {
4422 // Accept fields coming after `..,`.
4423 // This way we avoid "pattern missing fields" errors afterwards.
4424 // We delay this error until the end in order to have a span for a
4425 // suggested fix.
4426 if let Some(mut delayed_err) = delayed_err {
4427 delayed_err.emit();
4428 return Err(err);
4429 } else {
4430 delayed_err = Some(err);
4431 }
4432 } else {
4433 if let Some(mut err) = delayed_err {
4434 err.emit();
4435 }
4436 return Err(err);
4437 }
4438 }
4439
4440 fields.push(match self.parse_pat_field(lo, attrs) {
4441 Ok(field) => field,
4442 Err(err) => {
4443 if let Some(mut delayed_err) = delayed_err {
4444 delayed_err.emit();
4445 }
4446 return Err(err);
4447 }
4448 });
4449 ate_comma = self.eat(&token::Comma);
4450 }
4451
4452 if let Some(mut err) = delayed_err {
4453 if let Some(etc_span) = etc_span {
4454 err.multipart_suggestion(
4455 "move the `..` to the end of the field list",
4456 vec![
4457 (etc_span, String::new()),
4458 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
4459 ],
4460 Applicability::MachineApplicable,
4461 );
4462 }
4463 err.emit();
4464 }
4465 return Ok((fields, etc));
4466 }
4467
4468 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
4469 if self.token.is_path_start() {
4470 let lo = self.span;
4471 let (qself, path) = if self.eat_lt() {
4472 // Parse a qualified path
4473 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4474 (Some(qself), path)
4475 } else {
4476 // Parse an unqualified path
4477 (None, self.parse_path(PathStyle::Expr)?)
4478 };
4479 let hi = self.prev_span;
4480 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
4481 } else {
4482 self.parse_literal_maybe_minus()
4483 }
4484 }
4485
4486 // helper function to decide whether to parse as ident binding or to try to do
4487 // something more complex like range patterns
4488 fn parse_as_ident(&mut self) -> bool {
4489 self.look_ahead(1, |t| match *t {
4490 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
4491 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
4492 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
4493 // range pattern branch
4494 token::DotDot => None,
4495 _ => Some(true),
4496 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
4497 token::Comma | token::CloseDelim(token::Bracket) => true,
4498 _ => false,
4499 }))
4500 }
4501
4502 /// A wrapper around `parse_pat` with some special error handling for the
4503 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
4504 /// to subpatterns within such).
4505 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
4506 let pat = self.parse_pat(None)?;
4507 if self.token == token::Comma {
4508 // An unexpected comma after a top-level pattern is a clue that the
4509 // user (perhaps more accustomed to some other language) forgot the
4510 // parentheses in what should have been a tuple pattern; return a
4511 // suggestion-enhanced error here rather than choking on the comma
4512 // later.
4513 let comma_span = self.span;
4514 self.bump();
4515 if let Err(mut err) = self.parse_pat_list() {
4516 // We didn't expect this to work anyway; we just wanted
4517 // to advance to the end of the comma-sequence so we know
4518 // the span to suggest parenthesizing
4519 err.cancel();
4520 }
4521 let seq_span = pat.span.to(self.prev_span);
4522 let mut err = self.struct_span_err(comma_span,
4523 "unexpected `,` in pattern");
4524 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
4525 err.span_suggestion(
4526 seq_span,
4527 "try adding parentheses to match on a tuple..",
4528 format!("({})", seq_snippet),
4529 Applicability::MachineApplicable
4530 ).span_suggestion(
4531 seq_span,
4532 "..or a vertical bar to match on multiple alternatives",
4533 format!("{}", seq_snippet.replace(",", " |")),
4534 Applicability::MachineApplicable
4535 );
4536 }
4537 return Err(err);
4538 }
4539 Ok(pat)
4540 }
4541
4542 /// Parses a pattern.
4543 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
4544 self.parse_pat_with_range_pat(true, expected)
4545 }
4546
4547 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
4548 /// allowed).
4549 fn parse_pat_with_range_pat(
4550 &mut self,
4551 allow_range_pat: bool,
4552 expected: Option<&'static str>,
4553 ) -> PResult<'a, P<Pat>> {
4554 maybe_whole!(self, NtPat, |x| x);
4555
4556 let lo = self.span;
4557 let pat;
4558 match self.token {
4559 token::BinOp(token::And) | token::AndAnd => {
4560 // Parse &pat / &mut pat
4561 self.expect_and()?;
4562 let mutbl = self.parse_mutability();
4563 if let token::Lifetime(ident) = self.token {
4564 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
4565 ident));
4566 err.span_label(self.span, "unexpected lifetime");
4567 return Err(err);
4568 }
4569 let subpat = self.parse_pat_with_range_pat(false, expected)?;
4570 pat = PatKind::Ref(subpat, mutbl);
4571 }
4572 token::OpenDelim(token::Paren) => {
4573 // Parse (pat,pat,pat,...) as tuple pattern
4574 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
4575 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
4576 PatKind::Paren(fields.into_iter().nth(0).unwrap())
4577 } else {
4578 PatKind::Tuple(fields, ddpos)
4579 };
4580 }
4581 token::OpenDelim(token::Bracket) => {
4582 // Parse [pat,pat,...] as slice pattern
4583 self.bump();
4584 let (before, slice, after) = self.parse_pat_vec_elements()?;
4585 self.expect(&token::CloseDelim(token::Bracket))?;
4586 pat = PatKind::Slice(before, slice, after);
4587 }
4588 // At this point, token != &, &&, (, [
4589 _ => if self.eat_keyword(keywords::Underscore) {
4590 // Parse _
4591 pat = PatKind::Wild;
4592 } else if self.eat_keyword(keywords::Mut) {
4593 // Parse mut ident @ pat / mut ref ident @ pat
4594 let mutref_span = self.prev_span.to(self.span);
4595 let binding_mode = if self.eat_keyword(keywords::Ref) {
4596 self.diagnostic()
4597 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
4598 .span_suggestion(
4599 mutref_span,
4600 "try switching the order",
4601 "ref mut".into(),
4602 Applicability::MachineApplicable
4603 ).emit();
4604 BindingMode::ByRef(Mutability::Mutable)
4605 } else {
4606 BindingMode::ByValue(Mutability::Mutable)
4607 };
4608 pat = self.parse_pat_ident(binding_mode)?;
4609 } else if self.eat_keyword(keywords::Ref) {
4610 // Parse ref ident @ pat / ref mut ident @ pat
4611 let mutbl = self.parse_mutability();
4612 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
4613 } else if self.eat_keyword(keywords::Box) {
4614 // Parse box pat
4615 let subpat = self.parse_pat_with_range_pat(false, None)?;
4616 pat = PatKind::Box(subpat);
4617 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
4618 self.parse_as_ident() {
4619 // Parse ident @ pat
4620 // This can give false positives and parse nullary enums,
4621 // they are dealt with later in resolve
4622 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
4623 pat = self.parse_pat_ident(binding_mode)?;
4624 } else if self.token.is_path_start() {
4625 // Parse pattern starting with a path
4626 let (qself, path) = if self.eat_lt() {
4627 // Parse a qualified path
4628 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4629 (Some(qself), path)
4630 } else {
4631 // Parse an unqualified path
4632 (None, self.parse_path(PathStyle::Expr)?)
4633 };
4634 match self.token {
4635 token::Not if qself.is_none() => {
4636 // Parse macro invocation
4637 self.bump();
4638 let (delim, tts) = self.expect_delimited_token_tree()?;
4639 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4640 pat = PatKind::Mac(mac);
4641 }
4642 token::DotDotDot | token::DotDotEq | token::DotDot => {
4643 let end_kind = match self.token {
4644 token::DotDot => RangeEnd::Excluded,
4645 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4646 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4647 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4648 (checked above)"),
4649 };
4650 let op_span = self.span;
4651 // Parse range
4652 let span = lo.to(self.prev_span);
4653 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4654 self.bump();
4655 let end = self.parse_pat_range_end()?;
4656 let op = Spanned { span: op_span, node: end_kind };
4657 pat = PatKind::Range(begin, end, op);
4658 }
4659 token::OpenDelim(token::Brace) => {
4660 if qself.is_some() {
4661 let msg = "unexpected `{` after qualified path";
4662 let mut err = self.fatal(msg);
4663 err.span_label(self.span, msg);
4664 return Err(err);
4665 }
4666 // Parse struct pattern
4667 self.bump();
4668 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4669 e.emit();
4670 self.recover_stmt();
4671 (vec![], false)
4672 });
4673 self.bump();
4674 pat = PatKind::Struct(path, fields, etc);
4675 }
4676 token::OpenDelim(token::Paren) => {
4677 if qself.is_some() {
4678 let msg = "unexpected `(` after qualified path";
4679 let mut err = self.fatal(msg);
4680 err.span_label(self.span, msg);
4681 return Err(err);
4682 }
4683 // Parse tuple struct or enum pattern
4684 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4685 pat = PatKind::TupleStruct(path, fields, ddpos)
4686 }
4687 _ => pat = PatKind::Path(qself, path),
4688 }
4689 } else {
4690 // Try to parse everything else as literal with optional minus
4691 match self.parse_literal_maybe_minus() {
4692 Ok(begin) => {
4693 let op_span = self.span;
4694 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4695 self.check(&token::DotDotDot) {
4696 let end_kind = if self.eat(&token::DotDotDot) {
4697 RangeEnd::Included(RangeSyntax::DotDotDot)
4698 } else if self.eat(&token::DotDotEq) {
4699 RangeEnd::Included(RangeSyntax::DotDotEq)
4700 } else if self.eat(&token::DotDot) {
4701 RangeEnd::Excluded
4702 } else {
4703 panic!("impossible case: we already matched \
4704 on a range-operator token")
4705 };
4706 let end = self.parse_pat_range_end()?;
4707 let op = Spanned { span: op_span, node: end_kind };
4708 pat = PatKind::Range(begin, end, op);
4709 } else {
4710 pat = PatKind::Lit(begin);
4711 }
4712 }
4713 Err(mut err) => {
4714 self.cancel(&mut err);
4715 let expected = expected.unwrap_or("pattern");
4716 let msg = format!(
4717 "expected {}, found {}",
4718 expected,
4719 self.this_token_descr(),
4720 );
4721 let mut err = self.fatal(&msg);
4722 err.span_label(self.span, format!("expected {}", expected));
4723 return Err(err);
4724 }
4725 }
4726 }
4727 }
4728
4729 let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
4730 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4731
4732 if !allow_range_pat {
4733 match pat.node {
4734 PatKind::Range(
4735 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4736 ) => {},
4737 PatKind::Range(..) => {
4738 let mut err = self.struct_span_err(
4739 pat.span,
4740 "the range pattern here has ambiguous interpretation",
4741 );
4742 err.span_suggestion(
4743 pat.span,
4744 "add parentheses to clarify the precedence",
4745 format!("({})", pprust::pat_to_string(&pat)),
4746 // "ambiguous interpretation" implies that we have to be guessing
4747 Applicability::MaybeIncorrect
4748 );
4749 return Err(err);
4750 }
4751 _ => {}
4752 }
4753 }
4754
4755 Ok(P(pat))
4756 }
4757
4758 /// Parses `ident` or `ident @ pat`.
4759 /// used by the copy foo and ref foo patterns to give a good
4760 /// error message when parsing mistakes like `ref foo(a, b)`.
4761 fn parse_pat_ident(&mut self,
4762 binding_mode: ast::BindingMode)
4763 -> PResult<'a, PatKind> {
4764 let ident = self.parse_ident()?;
4765 let sub = if self.eat(&token::At) {
4766 Some(self.parse_pat(Some("binding pattern"))?)
4767 } else {
4768 None
4769 };
4770
4771 // just to be friendly, if they write something like
4772 // ref Some(i)
4773 // we end up here with ( as the current token. This shortly
4774 // leads to a parse error. Note that if there is no explicit
4775 // binding mode then we do not end up here, because the lookahead
4776 // will direct us over to parse_enum_variant()
4777 if self.token == token::OpenDelim(token::Paren) {
4778 return Err(self.span_fatal(
4779 self.prev_span,
4780 "expected identifier, found enum pattern"))
4781 }
4782
4783 Ok(PatKind::Ident(binding_mode, ident, sub))
4784 }
4785
4786 /// Parses a local variable declaration.
4787 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4788 let lo = self.prev_span;
4789 let pat = self.parse_top_level_pat()?;
4790
4791 let (err, ty) = if self.eat(&token::Colon) {
4792 // Save the state of the parser before parsing type normally, in case there is a `:`
4793 // instead of an `=` typo.
4794 let parser_snapshot_before_type = self.clone();
4795 let colon_sp = self.prev_span;
4796 match self.parse_ty() {
4797 Ok(ty) => (None, Some(ty)),
4798 Err(mut err) => {
4799 // Rewind to before attempting to parse the type and continue parsing
4800 let parser_snapshot_after_type = self.clone();
4801 mem::replace(self, parser_snapshot_before_type);
4802
4803 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4804 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4805 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4806 }
4807 }
4808 } else {
4809 (None, None)
4810 };
4811 let init = match (self.parse_initializer(err.is_some()), err) {
4812 (Ok(init), None) => { // init parsed, ty parsed
4813 init
4814 }
4815 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4816 // Could parse the type as if it were the initializer, it is likely there was a
4817 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4818 err.span_suggestion_short(
4819 colon_sp,
4820 "use `=` if you meant to assign",
4821 "=".to_string(),
4822 Applicability::MachineApplicable
4823 );
4824 err.emit();
4825 // As this was parsed successfully, continue as if the code has been fixed for the
4826 // rest of the file. It will still fail due to the emitted error, but we avoid
4827 // extra noise.
4828 init
4829 }
4830 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4831 init_err.cancel();
4832 // Couldn't parse the type nor the initializer, only raise the type error and
4833 // return to the parser state before parsing the type as the initializer.
4834 // let x: <parse_error>;
4835 mem::replace(self, snapshot);
4836 return Err(ty_err);
4837 }
4838 (Err(err), None) => { // init error, ty parsed
4839 // Couldn't parse the initializer and we're not attempting to recover a failed
4840 // parse of the type, return the error.
4841 return Err(err);
4842 }
4843 };
4844 let hi = if self.token == token::Semi {
4845 self.span
4846 } else {
4847 self.prev_span
4848 };
4849 Ok(P(ast::Local {
4850 ty,
4851 pat,
4852 init,
4853 id: ast::DUMMY_NODE_ID,
4854 span: lo.to(hi),
4855 attrs,
4856 }))
4857 }
4858
4859 /// Parses a structure field.
4860 fn parse_name_and_ty(&mut self,
4861 lo: Span,
4862 vis: Visibility,
4863 attrs: Vec<Attribute>)
4864 -> PResult<'a, StructField> {
4865 let name = self.parse_ident()?;
4866 self.expect(&token::Colon)?;
4867 let ty = self.parse_ty()?;
4868 Ok(StructField {
4869 span: lo.to(self.prev_span),
4870 ident: Some(name),
4871 vis,
4872 id: ast::DUMMY_NODE_ID,
4873 ty,
4874 attrs,
4875 })
4876 }
4877
4878 /// Emits an expected-item-after-attributes error.
4879 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4880 let message = match attrs.last() {
4881 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4882 _ => "expected item after attributes",
4883 };
4884
4885 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4886 if attrs.last().unwrap().is_sugared_doc {
4887 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4888 }
4889 Err(err)
4890 }
4891
4892 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4893 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4894 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4895 Ok(self.parse_stmt_(true))
4896 }
4897
4898 // Eat tokens until we can be relatively sure we reached the end of the
4899 // statement. This is something of a best-effort heuristic.
4900 //
4901 // We terminate when we find an unmatched `}` (without consuming it).
4902 fn recover_stmt(&mut self) {
4903 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
4904 }
4905
4906 // If `break_on_semi` is `Break`, then we will stop consuming tokens after
4907 // finding (and consuming)