1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use rustc_target::spec::abi::{self, Abi};
12 use ast::{AngleBracketedArgs, ParenthesisedArgs, AttrStyle, BareFnTy};
13 use ast::{GenericBound, TraitBoundModifier};
15 use ast::{Mod, AnonConst, Arg, Arm, Attribute, BindingMode, TraitItemKind};
17 use ast::{BlockCheckMode, CaptureBy, Movability};
18 use ast::{Constness, Crate};
21 use ast::{Expr, ExprKind, RangeLimits};
22 use ast::{Field, FnDecl, FnHeader};
23 use ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
24 use ast::{GenericParam, GenericParamKind};
26 use ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
27 use ast::{Label, Lifetime, Lit, LitKind};
29 use ast::MacStmtStyle;
30 use ast::{Mac, Mac_, MacDelimiter};
31 use ast::{MutTy, Mutability};
32 use ast::{Pat, PatKind, PathSegment};
33 use ast::{PolyTraitRef, QSelf};
34 use ast::{Stmt, StmtKind};
35 use ast::{VariantData, StructField};
38 use ast::{TraitItem, TraitRef, TraitObjectSyntax};
39 use ast::{Ty, TyKind, TypeBinding, GenericBounds};
40 use ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
41 use ast::{UseTree, UseTreeKind};
42 use ast::{BinOpKind, UnOp};
43 use ast::{RangeEnd, RangeSyntax};
45 use codemap::{self, CodeMap, Spanned, respan};
46 use syntax_pos::{self, Span, MultiSpan, BytePos, FileName, edition::Edition};
47 use errors::{self, Applicability, DiagnosticBuilder};
48 use parse::{self, SeqSep, classify, token};
49 use parse::lexer::TokenAndSpan;
50 use parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
51 use parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
52 use util::parser::{AssocOp, Fixity};
56 use tokenstream::{self, Delimited, ThinTokenStream, TokenTree, TokenStream};
57 use symbol::{Symbol, keywords};
63 use std::path::{self, Path, PathBuf};
67 /// Whether the type alias or associated type is a concrete type or an existential type
69 /// Just a new name for the same type
71 /// Only trait impls of the type will be usable, not the actual type itself
72 Existential(GenericBounds),
76 struct Restrictions: u8 {
77 const STMT_EXPR = 1 << 0;
78 const NO_STRUCT_LITERAL = 1 << 1;
82 type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
84 /// How to parse a path.
85 #[derive(Copy, Clone, PartialEq)]
87 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
88 /// with something else. For example, in expressions `segment < ....` can be interpreted
89 /// as a comparison and `segment ( ....` can be interpreted as a function call.
90 /// In all such contexts the non-path interpretation is preferred by default for practical
91 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
92 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
94 /// In other contexts, notably in types, no ambiguity exists and paths can be written
95 /// without the disambiguator, e.g. `x<y>` - unambiguously a path.
96 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
98 /// A path with generic arguments disallowed, e.g. `foo::bar::Baz`, used in imports,
99 /// visibilities or attributes.
100 /// Technically, this variant is unnecessary and e.g. `Expr` can be used instead
101 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
102 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
103 /// tokens when something goes wrong.
107 #[derive(Clone, Copy, PartialEq, Debug)]
113 #[derive(Clone, Copy, PartialEq, Debug)]
119 /// Possibly accept an `token::Interpolated` expression (a pre-parsed expression
120 /// dropped into the token stream, which happens while parsing the result of
121 /// macro expansion). Placement of these is not as complex as I feared it would
122 /// be. The important thing is to make sure that lookahead doesn't balk at
123 /// `token::Interpolated` tokens.
124 macro_rules! maybe_whole_expr {
126 if let token::Interpolated(nt) = $p.token.clone() {
128 token::NtExpr(ref e) | token::NtLiteral(ref e) => {
130 return Ok((*e).clone());
132 token::NtPath(ref path) => {
135 let kind = ExprKind::Path(None, (*path).clone());
136 return Ok($p.mk_expr(span, kind, ThinVec::new()));
138 token::NtBlock(ref block) => {
141 let kind = ExprKind::Block((*block).clone(), None);
142 return Ok($p.mk_expr(span, kind, ThinVec::new()));
150 /// As maybe_whole_expr, but for things other than expressions
151 macro_rules! maybe_whole {
152 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
153 if let token::Interpolated(nt) = $p.token.clone() {
154 if let token::$constructor($x) = nt.0.clone() {
162 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
163 if let Some(ref mut rhs) = rhs {
169 #[derive(Debug, Clone, Copy, PartialEq)]
180 trait RecoverQPath: Sized {
181 const PATH_STYLE: PathStyle = PathStyle::Expr;
182 fn to_ty(&self) -> Option<P<Ty>>;
183 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self;
184 fn to_string(&self) -> String;
187 impl RecoverQPath for Ty {
188 const PATH_STYLE: PathStyle = PathStyle::Type;
189 fn to_ty(&self) -> Option<P<Ty>> {
190 Some(P(self.clone()))
192 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
193 Self { span: path.span, node: TyKind::Path(qself, path), id: self.id }
195 fn to_string(&self) -> String {
196 pprust::ty_to_string(self)
200 impl RecoverQPath for Pat {
201 fn to_ty(&self) -> Option<P<Ty>> {
204 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
205 Self { span: path.span, node: PatKind::Path(qself, path), id: self.id }
207 fn to_string(&self) -> String {
208 pprust::pat_to_string(self)
212 impl RecoverQPath for Expr {
213 fn to_ty(&self) -> Option<P<Ty>> {
216 fn to_recovered(&self, qself: Option<QSelf>, path: ast::Path) -> Self {
217 Self { span: path.span, node: ExprKind::Path(qself, path),
218 id: self.id, attrs: self.attrs.clone() }
220 fn to_string(&self) -> String {
221 pprust::expr_to_string(self)
225 /* ident is handled by common.rs */
228 pub struct Parser<'a> {
229 pub sess: &'a ParseSess,
230 /// the current token:
231 pub token: token::Token,
232 /// the span of the current token:
234 /// the span of the previous token:
235 meta_var_span: Option<Span>,
237 /// the previous token kind
238 prev_token_kind: PrevTokenKind,
239 restrictions: Restrictions,
240 /// Used to determine the path to externally loaded source files
241 crate directory: Directory<'a>,
242 /// Whether to parse sub-modules in other files.
243 pub recurse_into_file_modules: bool,
244 /// Name of the root module this parser originated from. If `None`, then the
245 /// name is not known. This does not change while the parser is descending
246 /// into modules, and sub-parsers have new values for this name.
247 pub root_module_name: Option<String>,
248 crate expected_tokens: Vec<TokenType>,
249 token_cursor: TokenCursor,
250 desugar_doc_comments: bool,
251 /// Whether we should configure out of line modules as we parse.
258 frame: TokenCursorFrame,
259 stack: Vec<TokenCursorFrame>,
263 struct TokenCursorFrame {
264 delim: token::DelimToken,
267 tree_cursor: tokenstream::Cursor,
269 last_token: LastToken,
272 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
273 /// by the parser, and then that's transitively used to record the tokens that
274 /// each parse AST item is created with.
276 /// Right now this has two states, either collecting tokens or not collecting
277 /// tokens. If we're collecting tokens we just save everything off into a local
278 /// `Vec`. This should eventually though likely save tokens from the original
279 /// token stream and just use slicing of token streams to avoid creation of a
280 /// whole new vector.
282 /// The second state is where we're passively not recording tokens, but the last
283 /// token is still tracked for when we want to start recording tokens. This
284 /// "last token" means that when we start recording tokens we'll want to ensure
285 /// that this, the first token, is included in the output.
287 /// You can find some more example usage of this in the `collect_tokens` method
291 Collecting(Vec<TokenStream>),
292 Was(Option<TokenStream>),
295 impl TokenCursorFrame {
296 fn new(sp: Span, delimited: &Delimited) -> Self {
298 delim: delimited.delim,
300 open_delim: delimited.delim == token::NoDelim,
301 tree_cursor: delimited.stream().into_trees(),
302 close_delim: delimited.delim == token::NoDelim,
303 last_token: LastToken::Was(None),
309 fn next(&mut self) -> TokenAndSpan {
311 let tree = if !self.frame.open_delim {
312 self.frame.open_delim = true;
313 Delimited { delim: self.frame.delim, tts: TokenStream::empty().into() }
314 .open_tt(self.frame.span)
315 } else if let Some(tree) = self.frame.tree_cursor.next() {
317 } else if !self.frame.close_delim {
318 self.frame.close_delim = true;
319 Delimited { delim: self.frame.delim, tts: TokenStream::empty().into() }
320 .close_tt(self.frame.span)
321 } else if let Some(frame) = self.stack.pop() {
325 return TokenAndSpan { tok: token::Eof, sp: syntax_pos::DUMMY_SP }
328 match self.frame.last_token {
329 LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
330 LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
334 TokenTree::Token(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
335 TokenTree::Delimited(sp, ref delimited) => {
336 let frame = TokenCursorFrame::new(sp, delimited);
337 self.stack.push(mem::replace(&mut self.frame, frame));
343 fn next_desugared(&mut self) -> TokenAndSpan {
344 let (sp, name) = match self.next() {
345 TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, name),
349 let stripped = strip_doc_comment_decoration(&name.as_str());
351 // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
352 // required to wrap the text.
353 let mut num_of_hashes = 0;
355 for ch in stripped.chars() {
358 '#' if count > 0 => count + 1,
361 num_of_hashes = cmp::max(num_of_hashes, count);
364 let body = TokenTree::Delimited(sp, Delimited {
365 delim: token::Bracket,
366 tts: [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
367 TokenTree::Token(sp, token::Eq),
368 TokenTree::Token(sp, token::Literal(
369 token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))]
370 .iter().cloned().collect::<TokenStream>().into(),
373 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(sp, &Delimited {
374 delim: token::NoDelim,
375 tts: if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
376 [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
377 .iter().cloned().collect::<TokenStream>().into()
379 [TokenTree::Token(sp, token::Pound), body]
380 .iter().cloned().collect::<TokenStream>().into()
388 #[derive(Clone, PartialEq)]
389 crate enum TokenType {
391 Keyword(keywords::Keyword),
400 fn to_string(&self) -> String {
402 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
403 TokenType::Keyword(kw) => format!("`{}`", kw.name()),
404 TokenType::Operator => "an operator".to_string(),
405 TokenType::Lifetime => "lifetime".to_string(),
406 TokenType::Ident => "identifier".to_string(),
407 TokenType::Path => "path".to_string(),
408 TokenType::Type => "type".to_string(),
413 /// Returns true if `IDENT t` can start a type - `IDENT::a::b`, `IDENT<u8, u8>`,
414 /// `IDENT<<u8 as Trait>::AssocTy>`.
416 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
417 /// that IDENT is not the ident of a fn trait
418 fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
419 t == &token::ModSep || t == &token::Lt ||
420 t == &token::BinOp(token::Shl)
423 /// Information about the path to a module.
424 pub struct ModulePath {
427 pub result: Result<ModulePathSuccess, Error>,
430 pub struct ModulePathSuccess {
432 pub directory_ownership: DirectoryOwnership,
437 FileNotFoundForModule {
439 default_path: String,
440 secondary_path: String,
445 default_path: String,
446 secondary_path: String,
449 InclusiveRangeWithNoEnd,
453 fn span_err<S: Into<MultiSpan>>(self,
455 handler: &errors::Handler) -> DiagnosticBuilder {
457 Error::FileNotFoundForModule { ref mod_name,
461 let mut err = struct_span_err!(handler, sp, E0583,
462 "file not found for module `{}`", mod_name);
463 err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
469 Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
470 let mut err = struct_span_err!(handler, sp, E0584,
471 "file for module `{}` found at both {} and {}",
475 err.help("delete or rename one of them to remove the ambiguity");
478 Error::UselessDocComment => {
479 let mut err = struct_span_err!(handler, sp, E0585,
480 "found a documentation comment that doesn't document anything");
481 err.help("doc comments must come before what they document, maybe a comment was \
482 intended with `//`?");
485 Error::InclusiveRangeWithNoEnd => {
486 let mut err = struct_span_err!(handler, sp, E0586,
487 "inclusive range with no end");
488 err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
498 AttributesParsed(ThinVec<Attribute>),
499 AlreadyParsed(P<Expr>),
502 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
503 fn from(o: Option<ThinVec<Attribute>>) -> Self {
504 if let Some(attrs) = o {
505 LhsExpr::AttributesParsed(attrs)
507 LhsExpr::NotYetParsed
512 impl From<P<Expr>> for LhsExpr {
513 fn from(expr: P<Expr>) -> Self {
514 LhsExpr::AlreadyParsed(expr)
518 /// Create a placeholder argument.
519 fn dummy_arg(span: Span) -> Arg {
520 let ident = Ident::new(keywords::Invalid.name(), span);
522 id: ast::DUMMY_NODE_ID,
523 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
529 id: ast::DUMMY_NODE_ID
531 Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID }
534 #[derive(Copy, Clone, Debug)]
535 enum TokenExpectType {
540 impl<'a> Parser<'a> {
541 pub fn new(sess: &'a ParseSess,
543 directory: Option<Directory<'a>>,
544 recurse_into_file_modules: bool,
545 desugar_doc_comments: bool)
547 let mut parser = Parser {
549 token: token::Whitespace,
550 span: syntax_pos::DUMMY_SP,
551 prev_span: syntax_pos::DUMMY_SP,
553 prev_token_kind: PrevTokenKind::Other,
554 restrictions: Restrictions::empty(),
555 recurse_into_file_modules,
556 directory: Directory {
557 path: Cow::from(PathBuf::new()),
558 ownership: DirectoryOwnership::Owned { relative: None }
560 root_module_name: None,
561 expected_tokens: Vec::new(),
562 token_cursor: TokenCursor {
563 frame: TokenCursorFrame::new(syntax_pos::DUMMY_SP, &Delimited {
564 delim: token::NoDelim,
569 desugar_doc_comments,
573 let tok = parser.next_tok();
574 parser.token = tok.tok;
575 parser.span = tok.sp;
577 if let Some(directory) = directory {
578 parser.directory = directory;
579 } else if !parser.span.is_dummy() {
580 if let FileName::Real(mut path) = sess.codemap().span_to_unmapped_path(parser.span) {
582 parser.directory.path = Cow::from(path);
586 parser.process_potential_macro_variable();
590 fn next_tok(&mut self) -> TokenAndSpan {
591 let mut next = if self.desugar_doc_comments {
592 self.token_cursor.next_desugared()
594 self.token_cursor.next()
596 if next.sp.is_dummy() {
597 // Tweak the location for better diagnostics, but keep syntactic context intact.
598 next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
603 /// Convert the current token to a string using self's reader
604 pub fn this_token_to_string(&self) -> String {
605 pprust::token_to_string(&self.token)
608 fn token_descr(&self) -> Option<&'static str> {
609 Some(match &self.token {
610 t if t.is_special_ident() => "reserved identifier",
611 t if t.is_used_keyword() => "keyword",
612 t if t.is_unused_keyword() => "reserved keyword",
617 fn this_token_descr(&self) -> String {
618 if let Some(prefix) = self.token_descr() {
619 format!("{} `{}`", prefix, self.this_token_to_string())
621 format!("`{}`", self.this_token_to_string())
625 fn unexpected_last<T>(&self, t: &token::Token) -> PResult<'a, T> {
626 let token_str = pprust::token_to_string(t);
627 Err(self.span_fatal(self.prev_span, &format!("unexpected token: `{}`", token_str)))
630 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
631 match self.expect_one_of(&[], &[]) {
633 Ok(_) => unreachable!(),
637 /// Expect and consume the token t. Signal an error if
638 /// the next token is not t.
639 pub fn expect(&mut self, t: &token::Token) -> PResult<'a, ()> {
640 if self.expected_tokens.is_empty() {
641 if self.token == *t {
645 let token_str = pprust::token_to_string(t);
646 let this_token_str = self.this_token_to_string();
647 let mut err = self.fatal(&format!("expected `{}`, found `{}`",
651 let sp = if self.token == token::Token::Eof {
652 // EOF, don't want to point at the following char, but rather the last token
655 self.sess.codemap().next_point(self.prev_span)
657 let label_exp = format!("expected `{}`", token_str);
658 let cm = self.sess.codemap();
659 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
660 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
661 // When the spans are in the same line, it means that the only content
662 // between them is whitespace, point only at the found token.
663 err.span_label(self.span, label_exp);
666 err.span_label(sp, label_exp);
667 err.span_label(self.span, "unexpected token");
673 self.expect_one_of(slice::from_ref(t), &[])
677 /// Expect next token to be edible or inedible token. If edible,
678 /// then consume it; if inedible, then return without consuming
679 /// anything. Signal a fatal error if next token is unexpected.
680 fn expect_one_of(&mut self,
681 edible: &[token::Token],
682 inedible: &[token::Token]) -> PResult<'a, ()>{
683 fn tokens_to_string(tokens: &[TokenType]) -> String {
684 let mut i = tokens.iter();
685 // This might be a sign we need a connect method on Iterator.
687 .map_or("".to_string(), |t| t.to_string());
688 i.enumerate().fold(b, |mut b, (i, a)| {
689 if tokens.len() > 2 && i == tokens.len() - 2 {
691 } else if tokens.len() == 2 && i == tokens.len() - 2 {
696 b.push_str(&a.to_string());
700 if edible.contains(&self.token) {
703 } else if inedible.contains(&self.token) {
704 // leave it in the input
707 let mut expected = edible.iter()
708 .map(|x| TokenType::Token(x.clone()))
709 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
710 .chain(self.expected_tokens.iter().cloned())
711 .collect::<Vec<_>>();
712 expected.sort_by_cached_key(|x| x.to_string());
714 let expect = tokens_to_string(&expected[..]);
715 let actual = self.this_token_to_string();
716 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
717 let short_expect = if expected.len() > 6 {
718 format!("{} possible tokens", expected.len())
722 (format!("expected one of {}, found `{}`", expect, actual),
723 (self.sess.codemap().next_point(self.prev_span),
724 format!("expected one of {} here", short_expect)))
725 } else if expected.is_empty() {
726 (format!("unexpected token: `{}`", actual),
727 (self.prev_span, "unexpected token after this".to_string()))
729 (format!("expected {}, found `{}`", expect, actual),
730 (self.sess.codemap().next_point(self.prev_span),
731 format!("expected {} here", expect)))
733 let mut err = self.fatal(&msg_exp);
734 let sp = if self.token == token::Token::Eof {
735 // This is EOF, don't want to point at the following char, but rather the last token
741 let cm = self.sess.codemap();
742 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
743 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
744 // When the spans are in the same line, it means that the only content between
745 // them is whitespace, point at the found token in that case:
747 // X | () => { syntax error };
748 // | ^^^^^ expected one of 8 possible tokens here
750 // instead of having:
752 // X | () => { syntax error };
753 // | -^^^^^ unexpected token
755 // | expected one of 8 possible tokens here
756 err.span_label(self.span, label_exp);
759 err.span_label(sp, label_exp);
760 err.span_label(self.span, "unexpected token");
767 /// returns the span of expr, if it was not interpolated or the span of the interpolated token
768 fn interpolated_or_expr_span(&self,
769 expr: PResult<'a, P<Expr>>)
770 -> PResult<'a, (Span, P<Expr>)> {
772 if self.prev_token_kind == PrevTokenKind::Interpolated {
780 fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
781 let mut err = self.struct_span_err(self.span,
782 &format!("expected identifier, found {}",
783 self.this_token_descr()));
784 if let Some(token_descr) = self.token_descr() {
785 err.span_label(self.span, format!("expected identifier, found {}", token_descr));
787 err.span_label(self.span, "expected identifier");
788 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
789 err.span_suggestion(self.span, "remove this comma", "".into());
795 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
796 self.parse_ident_common(true)
799 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
801 token::Ident(ident, _) => {
802 if self.token.is_reserved_ident() {
803 let mut err = self.expected_ident_found();
810 let span = self.span;
812 Ok(Ident::new(ident.name, span))
815 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
816 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
818 self.expected_ident_found()
824 /// Check if the next token is `tok`, and return `true` if so.
826 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
828 fn check(&mut self, tok: &token::Token) -> bool {
829 let is_present = self.token == *tok;
830 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
834 /// Consume token 'tok' if it exists. Returns true if the given
835 /// token was present, false otherwise.
836 pub fn eat(&mut self, tok: &token::Token) -> bool {
837 let is_present = self.check(tok);
838 if is_present { self.bump() }
842 fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
843 self.expected_tokens.push(TokenType::Keyword(kw));
844 self.token.is_keyword(kw)
847 /// If the next token is the given keyword, eat it and return
848 /// true. Otherwise, return false.
849 pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
850 if self.check_keyword(kw) {
858 fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
859 if self.token.is_keyword(kw) {
867 /// If the given word is not a keyword, signal an error.
868 /// If the next token is not the given word, signal an error.
869 /// Otherwise, eat it.
870 fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
871 if !self.eat_keyword(kw) {
878 fn check_ident(&mut self) -> bool {
879 if self.token.is_ident() {
882 self.expected_tokens.push(TokenType::Ident);
887 fn check_path(&mut self) -> bool {
888 if self.token.is_path_start() {
891 self.expected_tokens.push(TokenType::Path);
896 fn check_type(&mut self) -> bool {
897 if self.token.can_begin_type() {
900 self.expected_tokens.push(TokenType::Type);
905 /// Expect and consume a `+`. if `+=` is seen, replace it with a `=`
906 /// and continue. If a `+` is not seen, return false.
908 /// This is using when token splitting += into +.
909 /// See issue 47856 for an example of when this may occur.
910 fn eat_plus(&mut self) -> bool {
911 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
913 token::BinOp(token::Plus) => {
917 token::BinOpEq(token::Plus) => {
918 let span = self.span.with_lo(self.span.lo() + BytePos(1));
919 self.bump_with(token::Eq, span);
927 /// Checks to see if the next token is either `+` or `+=`.
928 /// Otherwise returns false.
929 fn check_plus(&mut self) -> bool {
930 if self.token.is_like_plus() {
934 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
939 /// Expect and consume an `&`. If `&&` is seen, replace it with a single
940 /// `&` and continue. If an `&` is not seen, signal an error.
941 fn expect_and(&mut self) -> PResult<'a, ()> {
942 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
944 token::BinOp(token::And) => {
949 let span = self.span.with_lo(self.span.lo() + BytePos(1));
950 Ok(self.bump_with(token::BinOp(token::And), span))
952 _ => self.unexpected()
956 /// Expect and consume an `|`. If `||` is seen, replace it with a single
957 /// `|` and continue. If an `|` is not seen, signal an error.
958 fn expect_or(&mut self) -> PResult<'a, ()> {
959 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
961 token::BinOp(token::Or) => {
966 let span = self.span.with_lo(self.span.lo() + BytePos(1));
967 Ok(self.bump_with(token::BinOp(token::Or), span))
969 _ => self.unexpected()
973 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
975 None => {/* everything ok */}
977 let text = suf.as_str();
979 self.span_bug(sp, "found empty literal suffix in Some")
981 self.span_err(sp, &format!("{} with a suffix is invalid", kind));
986 /// Attempt to consume a `<`. If `<<` is seen, replace it with a single
987 /// `<` and continue. If a `<` is not seen, return false.
989 /// This is meant to be used when parsing generics on a path to get the
991 fn eat_lt(&mut self) -> bool {
992 self.expected_tokens.push(TokenType::Token(token::Lt));
998 token::BinOp(token::Shl) => {
999 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1000 self.bump_with(token::Lt, span);
1007 fn expect_lt(&mut self) -> PResult<'a, ()> {
1015 /// Expect and consume a GT. if a >> is seen, replace it
1016 /// with a single > and continue. If a GT is not seen,
1017 /// signal an error.
1018 fn expect_gt(&mut self) -> PResult<'a, ()> {
1019 self.expected_tokens.push(TokenType::Token(token::Gt));
1025 token::BinOp(token::Shr) => {
1026 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1027 Ok(self.bump_with(token::Gt, span))
1029 token::BinOpEq(token::Shr) => {
1030 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1031 Ok(self.bump_with(token::Ge, span))
1034 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1035 Ok(self.bump_with(token::Eq, span))
1037 _ => self.unexpected()
1041 /// Eat and discard tokens until one of `kets` is encountered. Respects token trees,
1042 /// passes through any errors encountered. Used for error recovery.
1043 fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
1044 let handler = self.diagnostic();
1046 if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
1048 TokenExpectType::Expect,
1049 |p| Ok(p.parse_token_tree())) {
1050 handler.cancel(err);
1054 /// Parse a sequence, including the closing delimiter. The function
1055 /// f must consume tokens until reaching the next separator or
1056 /// closing bracket.
1057 pub fn parse_seq_to_end<T, F>(&mut self,
1061 -> PResult<'a, Vec<T>> where
1062 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1064 let val = self.parse_seq_to_before_end(ket, sep, f)?;
1069 /// Parse a sequence, not including the closing delimiter. The function
1070 /// f must consume tokens until reaching the next separator or
1071 /// closing bracket.
1072 pub fn parse_seq_to_before_end<T, F>(&mut self,
1076 -> PResult<'a, Vec<T>>
1077 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1079 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
1082 fn parse_seq_to_before_tokens<T, F>(&mut self,
1083 kets: &[&token::Token],
1085 expect: TokenExpectType,
1087 -> PResult<'a, Vec<T>>
1088 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1090 let mut first: bool = true;
1092 while !kets.iter().any(|k| {
1094 TokenExpectType::Expect => self.check(k),
1095 TokenExpectType::NoExpect => self.token == **k,
1099 token::CloseDelim(..) | token::Eof => break,
1102 if let Some(ref t) = sep.sep {
1106 if let Err(mut e) = self.expect(t) {
1107 // Attempt to keep parsing if it was a similar separator
1108 if let Some(ref tokens) = t.similar_tokens() {
1109 if tokens.contains(&self.token) {
1114 // Attempt to keep parsing if it was an omitted separator
1128 if sep.trailing_sep_allowed && kets.iter().any(|k| {
1130 TokenExpectType::Expect => self.check(k),
1131 TokenExpectType::NoExpect => self.token == **k,
1144 /// Parse a sequence, including the closing delimiter. The function
1145 /// f must consume tokens until reaching the next separator or
1146 /// closing bracket.
1147 fn parse_unspanned_seq<T, F>(&mut self,
1152 -> PResult<'a, Vec<T>> where
1153 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1156 let result = self.parse_seq_to_before_end(ket, sep, f)?;
1157 if self.token == *ket {
1163 /// Advance the parser by one token
1164 pub fn bump(&mut self) {
1165 if self.prev_token_kind == PrevTokenKind::Eof {
1166 // Bumping after EOF is a bad sign, usually an infinite loop.
1167 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1170 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1172 // Record last token kind for possible error recovery.
1173 self.prev_token_kind = match self.token {
1174 token::DocComment(..) => PrevTokenKind::DocComment,
1175 token::Comma => PrevTokenKind::Comma,
1176 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1177 token::Interpolated(..) => PrevTokenKind::Interpolated,
1178 token::Eof => PrevTokenKind::Eof,
1179 token::Ident(..) => PrevTokenKind::Ident,
1180 _ => PrevTokenKind::Other,
1183 let next = self.next_tok();
1184 self.span = next.sp;
1185 self.token = next.tok;
1186 self.expected_tokens.clear();
1187 // check after each token
1188 self.process_potential_macro_variable();
1191 /// Advance the parser using provided token as a next one. Use this when
1192 /// consuming a part of a token. For example a single `<` from `<<`.
1193 fn bump_with(&mut self, next: token::Token, span: Span) {
1194 self.prev_span = self.span.with_hi(span.lo());
1195 // It would be incorrect to record the kind of the current token, but
1196 // fortunately for tokens currently using `bump_with`, the
1197 // prev_token_kind will be of no use anyway.
1198 self.prev_token_kind = PrevTokenKind::Other;
1201 self.expected_tokens.clear();
1204 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1205 F: FnOnce(&token::Token) -> R,
1208 return f(&self.token)
1211 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1212 Some(tree) => match tree {
1213 TokenTree::Token(_, tok) => tok,
1214 TokenTree::Delimited(_, delimited) => token::OpenDelim(delimited.delim),
1216 None => token::CloseDelim(self.token_cursor.frame.delim),
1220 fn look_ahead_span(&self, dist: usize) -> Span {
1225 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1226 Some(TokenTree::Token(span, _)) | Some(TokenTree::Delimited(span, _)) => span,
1227 None => self.look_ahead_span(dist - 1),
1230 pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
1231 self.sess.span_diagnostic.struct_span_fatal(self.span, m)
1233 pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1234 self.sess.span_diagnostic.struct_span_fatal(sp, m)
1236 fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
1237 err.span_err(sp, self.diagnostic())
1239 fn bug(&self, m: &str) -> ! {
1240 self.sess.span_diagnostic.span_bug(self.span, m)
1242 fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
1243 self.sess.span_diagnostic.span_err(sp, m)
1245 fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1246 self.sess.span_diagnostic.struct_span_err(sp, m)
1248 crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
1249 self.sess.span_diagnostic.span_bug(sp, m)
1251 crate fn abort_if_errors(&self) {
1252 self.sess.span_diagnostic.abort_if_errors();
1255 fn cancel(&self, err: &mut DiagnosticBuilder) {
1256 self.sess.span_diagnostic.cancel(err)
1259 crate fn diagnostic(&self) -> &'a errors::Handler {
1260 &self.sess.span_diagnostic
1263 /// Is the current token one of the keywords that signals a bare function
1265 fn token_is_bare_fn_keyword(&mut self) -> bool {
1266 self.check_keyword(keywords::Fn) ||
1267 self.check_keyword(keywords::Unsafe) ||
1268 self.check_keyword(keywords::Extern) && self.is_extern_non_path()
1271 /// parse a TyKind::BareFn type:
1272 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1275 [unsafe] [extern "ABI"] fn (S) -> T
1285 let unsafety = self.parse_unsafety();
1286 let abi = if self.eat_keyword(keywords::Extern) {
1287 self.parse_opt_abi()?.unwrap_or(Abi::C)
1292 self.expect_keyword(keywords::Fn)?;
1293 let (inputs, variadic) = self.parse_fn_args(false, true)?;
1294 let ret_ty = self.parse_ret_ty(false)?;
1295 let decl = P(FnDecl {
1300 Ok(TyKind::BareFn(P(BareFnTy {
1308 /// Parse asyncness: `async` or nothing
1309 fn parse_asyncness(&mut self) -> IsAsync {
1310 if self.eat_keyword(keywords::Async) {
1312 closure_id: ast::DUMMY_NODE_ID,
1313 return_impl_trait_id: ast::DUMMY_NODE_ID,
1320 /// Parse unsafety: `unsafe` or nothing.
1321 fn parse_unsafety(&mut self) -> Unsafety {
1322 if self.eat_keyword(keywords::Unsafe) {
1329 /// Parse the items in a trait declaration
1330 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1331 maybe_whole!(self, NtTraitItem, |x| x);
1332 let attrs = self.parse_outer_attributes()?;
1333 let (mut item, tokens) = self.collect_tokens(|this| {
1334 this.parse_trait_item_(at_end, attrs)
1336 // See `parse_item` for why this clause is here.
1337 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1338 item.tokens = Some(tokens);
1343 fn parse_trait_item_(&mut self,
1345 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1348 let (name, node, generics) = if self.eat_keyword(keywords::Type) {
1349 self.parse_trait_item_assoc_ty()?
1350 } else if self.is_const_item() {
1351 self.expect_keyword(keywords::Const)?;
1352 let ident = self.parse_ident()?;
1353 self.expect(&token::Colon)?;
1354 let ty = self.parse_ty()?;
1355 let default = if self.check(&token::Eq) {
1357 let expr = self.parse_expr()?;
1358 self.expect(&token::Semi)?;
1361 self.expect(&token::Semi)?;
1364 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1365 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1366 // trait item macro.
1367 (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1369 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
1371 let ident = self.parse_ident()?;
1372 let mut generics = self.parse_generics()?;
1374 let d = self.parse_fn_decl_with_self(|p: &mut Parser<'a>|{
1375 // This is somewhat dubious; We don't want to allow
1376 // argument names to be left off if there is a
1378 p.parse_arg_general(false)
1380 generics.where_clause = self.parse_where_clause()?;
1382 let sig = ast::MethodSig {
1392 let body = match self.token {
1396 debug!("parse_trait_methods(): parsing required method");
1399 token::OpenDelim(token::Brace) => {
1400 debug!("parse_trait_methods(): parsing provided method");
1402 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1403 attrs.extend(inner_attrs.iter().cloned());
1407 let token_str = self.this_token_to_string();
1408 let mut err = self.fatal(&format!("expected `;` or `{{`, found `{}`",
1410 err.span_label(self.span, "expected `;` or `{`");
1414 (ident, ast::TraitItemKind::Method(sig, body), generics)
1418 id: ast::DUMMY_NODE_ID,
1423 span: lo.to(self.prev_span),
1428 /// Parse optional return type [ -> TY ] in function decl
1429 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1430 if self.eat(&token::RArrow) {
1431 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true)?))
1433 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1438 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1439 self.parse_ty_common(true, true)
1442 /// Parse a type in restricted contexts where `+` is not permitted.
1443 /// Example 1: `&'a TYPE`
1444 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1445 /// Example 2: `value1 as TYPE + value2`
1446 /// `+` is prohibited to avoid interactions with expression grammar.
1447 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1448 self.parse_ty_common(false, true)
1451 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool)
1452 -> PResult<'a, P<Ty>> {
1453 maybe_whole!(self, NtTy, |x| x);
1456 let mut impl_dyn_multi = false;
1457 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1458 // `(TYPE)` is a parenthesized type.
1459 // `(TYPE,)` is a tuple with a single field of type TYPE.
1460 let mut ts = vec![];
1461 let mut last_comma = false;
1462 while self.token != token::CloseDelim(token::Paren) {
1463 ts.push(self.parse_ty()?);
1464 if self.eat(&token::Comma) {
1471 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1472 self.expect(&token::CloseDelim(token::Paren))?;
1474 if ts.len() == 1 && !last_comma {
1475 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1476 let maybe_bounds = allow_plus && self.token.is_like_plus();
1478 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1479 TyKind::Path(None, ref path) if maybe_bounds => {
1480 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1482 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1483 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1484 let path = match bounds[0] {
1485 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1486 _ => self.bug("unexpected lifetime bound"),
1488 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1491 _ => TyKind::Paren(P(ty))
1496 } else if self.eat(&token::Not) {
1499 } else if self.eat(&token::BinOp(token::Star)) {
1501 TyKind::Ptr(self.parse_ptr()?)
1502 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1504 let t = self.parse_ty()?;
1505 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1506 let t = match self.maybe_parse_fixed_length_of_vec()? {
1507 None => TyKind::Slice(t),
1508 Some(length) => TyKind::Array(t, AnonConst {
1509 id: ast::DUMMY_NODE_ID,
1513 self.expect(&token::CloseDelim(token::Bracket))?;
1515 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1518 self.parse_borrowed_pointee()?
1519 } else if self.eat_keyword_noexpect(keywords::Typeof) {
1521 // In order to not be ambiguous, the type must be surrounded by parens.
1522 self.expect(&token::OpenDelim(token::Paren))?;
1524 id: ast::DUMMY_NODE_ID,
1525 value: self.parse_expr()?,
1527 self.expect(&token::CloseDelim(token::Paren))?;
1529 } else if self.eat_keyword(keywords::Underscore) {
1530 // A type to be inferred `_`
1532 } else if self.token_is_bare_fn_keyword() {
1533 // Function pointer type
1534 self.parse_ty_bare_fn(Vec::new())?
1535 } else if self.check_keyword(keywords::For) {
1536 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1537 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1538 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1540 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1541 if self.token_is_bare_fn_keyword() {
1542 self.parse_ty_bare_fn(lifetime_defs)?
1544 let path = self.parse_path(PathStyle::Type)?;
1545 let parse_plus = allow_plus && self.check_plus();
1546 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1548 } else if self.eat_keyword(keywords::Impl) {
1549 // Always parse bounds greedily for better error recovery.
1550 let bounds = self.parse_generic_bounds()?;
1551 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1552 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1553 } else if self.check_keyword(keywords::Dyn) &&
1554 self.look_ahead(1, |t| t.can_begin_bound() &&
1555 !can_continue_type_after_non_fn_ident(t)) {
1556 self.bump(); // `dyn`
1557 // Always parse bounds greedily for better error recovery.
1558 let bounds = self.parse_generic_bounds()?;
1559 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1560 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1561 } else if self.check(&token::Question) ||
1562 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1563 // Bound list (trait object type)
1564 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus)?,
1565 TraitObjectSyntax::None)
1566 } else if self.eat_lt() {
1568 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1569 TyKind::Path(Some(qself), path)
1570 } else if self.token.is_path_start() {
1572 let path = self.parse_path(PathStyle::Type)?;
1573 if self.eat(&token::Not) {
1574 // Macro invocation in type position
1575 let (delim, tts) = self.expect_delimited_token_tree()?;
1576 let node = Mac_ { path, tts, delim };
1577 TyKind::Mac(respan(lo.to(self.prev_span), node))
1579 // Just a type path or bound list (trait object type) starting with a trait.
1581 // `Trait1 + Trait2 + 'a`
1582 if allow_plus && self.check_plus() {
1583 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1585 TyKind::Path(None, path)
1589 let msg = format!("expected type, found {}", self.this_token_descr());
1590 return Err(self.fatal(&msg));
1593 let span = lo.to(self.prev_span);
1594 let ty = Ty { node, span, id: ast::DUMMY_NODE_ID };
1596 // Try to recover from use of `+` with incorrect priority.
1597 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1598 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1599 let ty = self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)?;
1604 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1605 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1606 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1607 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1609 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1610 bounds.append(&mut self.parse_generic_bounds()?);
1612 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1615 fn maybe_report_ambiguous_plus(&mut self, allow_plus: bool, impl_dyn_multi: bool, ty: &Ty) {
1616 if !allow_plus && impl_dyn_multi {
1617 let sum_with_parens = format!("({})", pprust::ty_to_string(&ty));
1618 self.struct_span_err(ty.span, "ambiguous `+` in a type")
1619 .span_suggestion_with_applicability(
1621 "use parentheses to disambiguate",
1623 Applicability::MachineApplicable
1628 fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
1629 // Do not add `+` to expected tokens.
1630 if !allow_plus || !self.token.is_like_plus() {
1635 let bounds = self.parse_generic_bounds()?;
1636 let sum_span = ty.span.to(self.prev_span);
1638 let mut err = struct_span_err!(self.sess.span_diagnostic, sum_span, E0178,
1639 "expected a path on the left-hand side of `+`, not `{}`", pprust::ty_to_string(ty));
1642 TyKind::Rptr(ref lifetime, ref mut_ty) => {
1643 let sum_with_parens = pprust::to_string(|s| {
1644 use print::pprust::PrintState;
1647 s.print_opt_lifetime(lifetime)?;
1648 s.print_mutability(mut_ty.mutbl)?;
1650 s.print_type(&mut_ty.ty)?;
1651 s.print_type_bounds(" +", &bounds)?;
1654 err.span_suggestion_with_applicability(
1656 "try adding parentheses",
1658 Applicability::MachineApplicable
1661 TyKind::Ptr(..) | TyKind::BareFn(..) => {
1662 err.span_label(sum_span, "perhaps you forgot parentheses?");
1665 err.span_label(sum_span, "expected a path");
1672 // Try to recover from associated item paths like `[T]::AssocItem`/`(T, U)::AssocItem`.
1673 fn maybe_recover_from_bad_qpath<T: RecoverQPath>(&mut self, base: T, allow_recovery: bool)
1675 // Do not add `::` to expected tokens.
1676 if !allow_recovery || self.token != token::ModSep {
1679 let ty = match base.to_ty() {
1681 None => return Ok(base),
1684 self.bump(); // `::`
1685 let mut segments = Vec::new();
1686 self.parse_path_segments(&mut segments, T::PATH_STYLE, true)?;
1688 let span = ty.span.to(self.prev_span);
1689 let path_span = span.to(span); // use an empty path since `position` == 0
1690 let recovered = base.to_recovered(
1691 Some(QSelf { ty, path_span, position: 0 }),
1692 ast::Path { segments, span },
1696 .struct_span_err(span, "missing angle brackets in associated item path")
1697 .span_suggestion_with_applicability( // this is a best-effort recovery
1698 span, "try", recovered.to_string(), Applicability::MaybeIncorrect
1704 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1705 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1706 let mutbl = self.parse_mutability();
1707 let ty = self.parse_ty_no_plus()?;
1708 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1711 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1712 let mutbl = if self.eat_keyword(keywords::Mut) {
1714 } else if self.eat_keyword(keywords::Const) {
1715 Mutability::Immutable
1717 let span = self.prev_span;
1719 "expected mut or const in raw pointer type (use \
1720 `*mut T` or `*const T` as appropriate)");
1721 Mutability::Immutable
1723 let t = self.parse_ty_no_plus()?;
1724 Ok(MutTy { ty: t, mutbl: mutbl })
1727 fn is_named_argument(&mut self) -> bool {
1728 let offset = match self.token {
1729 token::Interpolated(ref nt) => match nt.0 {
1730 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1733 token::BinOp(token::And) | token::AndAnd => 1,
1734 _ if self.token.is_keyword(keywords::Mut) => 1,
1738 self.look_ahead(offset, |t| t.is_ident()) &&
1739 self.look_ahead(offset + 1, |t| t == &token::Colon)
1742 /// This version of parse arg doesn't necessarily require
1743 /// identifier names.
1744 fn parse_arg_general(&mut self, require_name: bool) -> PResult<'a, Arg> {
1745 maybe_whole!(self, NtArg, |x| x);
1747 let (pat, ty) = if require_name || self.is_named_argument() {
1748 debug!("parse_arg_general parse_pat (require_name:{})",
1750 let pat = self.parse_pat()?;
1752 self.expect(&token::Colon)?;
1753 (pat, self.parse_ty()?)
1755 debug!("parse_arg_general ident_to_pat");
1756 let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
1757 let ty = self.parse_ty()?;
1759 id: ast::DUMMY_NODE_ID,
1760 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
1769 id: ast::DUMMY_NODE_ID,
1773 /// Parse a single function argument
1774 crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
1775 self.parse_arg_general(true)
1778 /// Parse an argument in a lambda header e.g. |arg, arg|
1779 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1780 let pat = self.parse_pat()?;
1781 let t = if self.eat(&token::Colon) {
1785 id: ast::DUMMY_NODE_ID,
1786 node: TyKind::Infer,
1793 id: ast::DUMMY_NODE_ID
1797 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1798 if self.eat(&token::Semi) {
1799 Ok(Some(self.parse_expr()?))
1805 /// Matches token_lit = LIT_INTEGER | ...
1806 fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
1807 let out = match self.token {
1808 token::Interpolated(ref nt) => match nt.0 {
1809 token::NtExpr(ref v) | token::NtLiteral(ref v) => match v.node {
1810 ExprKind::Lit(ref lit) => { lit.node.clone() }
1811 _ => { return self.unexpected_last(&self.token); }
1813 _ => { return self.unexpected_last(&self.token); }
1815 token::Literal(lit, suf) => {
1816 let diag = Some((self.span, &self.sess.span_diagnostic));
1817 let (suffix_illegal, result) = parse::lit_token(lit, suf, diag);
1821 self.expect_no_suffix(sp, &format!("{} literal", lit.short_name()), suf)
1826 _ => { return self.unexpected_last(&self.token); }
1833 /// Matches lit = true | false | token_lit
1834 crate fn parse_lit(&mut self) -> PResult<'a, Lit> {
1836 let lit = if self.eat_keyword(keywords::True) {
1838 } else if self.eat_keyword(keywords::False) {
1839 LitKind::Bool(false)
1841 let lit = self.parse_lit_token()?;
1844 Ok(codemap::Spanned { node: lit, span: lo.to(self.prev_span) })
1847 /// matches '-' lit | lit (cf. ast_validation::AstValidator::check_expr_within_pat)
1848 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1849 maybe_whole_expr!(self);
1851 let minus_lo = self.span;
1852 let minus_present = self.eat(&token::BinOp(token::Minus));
1854 let literal = P(self.parse_lit()?);
1855 let hi = self.prev_span;
1856 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1859 let minus_hi = self.prev_span;
1860 let unary = self.mk_unary(UnOp::Neg, expr);
1861 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1867 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
1869 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
1870 let span = self.span;
1872 Ok(Ident::new(ident.name, span))
1874 _ => self.parse_ident(),
1878 /// Parses qualified path.
1879 /// Assumes that the leading `<` has been parsed already.
1881 /// `qualified_path = <type [as trait_ref]>::path`
1886 /// `<T as U>::F::a<S>` (without disambiguator)
1887 /// `<T as U>::F::a::<S>` (with disambiguator)
1888 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
1889 let lo = self.prev_span;
1890 let ty = self.parse_ty()?;
1892 // `path` will contain the prefix of the path up to the `>`,
1893 // if any (e.g., `U` in the `<T as U>::*` examples
1894 // above). `path_span` has the span of that path, or an empty
1895 // span in the case of something like `<T>::Bar`.
1896 let (mut path, path_span);
1897 if self.eat_keyword(keywords::As) {
1898 let path_lo = self.span;
1899 path = self.parse_path(PathStyle::Type)?;
1900 path_span = path_lo.to(self.prev_span);
1902 path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
1903 path_span = self.span.to(self.span);
1906 self.expect(&token::Gt)?;
1907 self.expect(&token::ModSep)?;
1909 let qself = QSelf { ty, path_span, position: path.segments.len() };
1910 self.parse_path_segments(&mut path.segments, style, true)?;
1912 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
1915 /// Parses simple paths.
1917 /// `path = [::] segment+`
1918 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
1921 /// `a::b::C<D>` (without disambiguator)
1922 /// `a::b::C::<D>` (with disambiguator)
1923 /// `Fn(Args)` (without disambiguator)
1924 /// `Fn::(Args)` (with disambiguator)
1925 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1926 self.parse_path_common(style, true)
1929 crate fn parse_path_common(&mut self, style: PathStyle, enable_warning: bool)
1930 -> PResult<'a, ast::Path> {
1931 maybe_whole!(self, NtPath, |path| {
1932 if style == PathStyle::Mod &&
1933 path.segments.iter().any(|segment| segment.args.is_some()) {
1934 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
1939 let lo = self.meta_var_span.unwrap_or(self.span);
1940 let mut segments = Vec::new();
1941 if self.eat(&token::ModSep) {
1942 segments.push(PathSegment::crate_root(lo.shrink_to_lo()));
1944 self.parse_path_segments(&mut segments, style, enable_warning)?;
1946 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
1949 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for back-compat.
1950 /// This is used when parsing derive macro paths in `#[derive]` attributes.
1951 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1952 let meta_ident = match self.token {
1953 token::Interpolated(ref nt) => match nt.0 {
1954 token::NtMeta(ref meta) => match meta.node {
1955 ast::MetaItemKind::Word => Some(meta.ident.clone()),
1962 if let Some(path) = meta_ident {
1966 self.parse_path(style)
1969 fn parse_path_segments(&mut self,
1970 segments: &mut Vec<PathSegment>,
1972 enable_warning: bool)
1973 -> PResult<'a, ()> {
1975 segments.push(self.parse_path_segment(style, enable_warning)?);
1977 if self.is_import_coupler() || !self.eat(&token::ModSep) {
1983 fn parse_path_segment(&mut self, style: PathStyle, enable_warning: bool)
1984 -> PResult<'a, PathSegment> {
1985 let ident = self.parse_path_segment_ident()?;
1987 let is_args_start = |token: &token::Token| match *token {
1988 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren) => true,
1991 let check_args_start = |this: &mut Self| {
1992 this.expected_tokens.extend_from_slice(
1993 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
1995 is_args_start(&this.token)
1998 Ok(if style == PathStyle::Type && check_args_start(self) ||
1999 style != PathStyle::Mod && self.check(&token::ModSep)
2000 && self.look_ahead(1, |t| is_args_start(t)) {
2001 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
2003 if self.eat(&token::ModSep) && style == PathStyle::Type && enable_warning {
2004 self.diagnostic().struct_span_warn(self.prev_span, "unnecessary path disambiguator")
2005 .span_label(self.prev_span, "try removing `::`").emit();
2008 let args = if self.eat_lt() {
2010 let (args, bindings) = self.parse_generic_args()?;
2012 let span = lo.to(self.prev_span);
2013 AngleBracketedArgs { args, bindings, span }.into()
2017 let inputs = self.parse_seq_to_before_tokens(
2018 &[&token::CloseDelim(token::Paren)],
2019 SeqSep::trailing_allowed(token::Comma),
2020 TokenExpectType::Expect,
2023 let output = if self.eat(&token::RArrow) {
2024 Some(self.parse_ty_common(false, false)?)
2028 let span = lo.to(self.prev_span);
2029 ParenthesisedArgs { inputs, output, span }.into()
2032 PathSegment { ident, args }
2034 // Generic arguments are not found.
2035 PathSegment::from_ident(ident)
2039 crate fn check_lifetime(&mut self) -> bool {
2040 self.expected_tokens.push(TokenType::Lifetime);
2041 self.token.is_lifetime()
2044 /// Parse single lifetime 'a or panic.
2045 crate fn expect_lifetime(&mut self) -> Lifetime {
2046 if let Some(ident) = self.token.lifetime() {
2047 let span = self.span;
2049 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
2051 self.span_bug(self.span, "not a lifetime")
2055 fn eat_label(&mut self) -> Option<Label> {
2056 if let Some(ident) = self.token.lifetime() {
2057 let span = self.span;
2059 Some(Label { ident: Ident::new(ident.name, span) })
2065 /// Parse mutability (`mut` or nothing).
2066 fn parse_mutability(&mut self) -> Mutability {
2067 if self.eat_keyword(keywords::Mut) {
2070 Mutability::Immutable
2074 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
2075 if let token::Literal(token::Integer(name), None) = self.token {
2077 Ok(Ident::new(name, self.prev_span))
2079 self.parse_ident_common(false)
2083 /// Parse ident (COLON expr)?
2084 fn parse_field(&mut self) -> PResult<'a, Field> {
2085 let attrs = self.parse_outer_attributes()?;
2088 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2089 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
2090 let fieldname = self.parse_field_name()?;
2092 (fieldname, self.parse_expr()?, false)
2094 let fieldname = self.parse_ident_common(false)?;
2096 // Mimic `x: x` for the `x` field shorthand.
2097 let path = ast::Path::from_ident(fieldname);
2098 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
2099 (fieldname, expr, true)
2103 span: lo.to(expr.span),
2106 attrs: attrs.into(),
2110 fn mk_expr(&mut self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
2111 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
2114 fn mk_unary(&mut self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
2115 ExprKind::Unary(unop, expr)
2118 fn mk_binary(&mut self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2119 ExprKind::Binary(binop, lhs, rhs)
2122 fn mk_call(&mut self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
2123 ExprKind::Call(f, args)
2126 fn mk_index(&mut self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
2127 ExprKind::Index(expr, idx)
2130 fn mk_range(&mut self,
2131 start: Option<P<Expr>>,
2132 end: Option<P<Expr>>,
2133 limits: RangeLimits)
2134 -> PResult<'a, ast::ExprKind> {
2135 if end.is_none() && limits == RangeLimits::Closed {
2136 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
2138 Ok(ExprKind::Range(start, end, limits))
2142 fn mk_assign_op(&mut self, binop: ast::BinOp,
2143 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2144 ExprKind::AssignOp(binop, lhs, rhs)
2147 pub fn mk_mac_expr(&mut self, span: Span, m: Mac_, attrs: ThinVec<Attribute>) -> P<Expr> {
2149 id: ast::DUMMY_NODE_ID,
2150 node: ExprKind::Mac(codemap::Spanned {node: m, span: span}),
2156 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, ThinTokenStream)> {
2157 let delim = match self.token {
2158 token::OpenDelim(delim) => delim,
2160 let msg = "expected open delimiter";
2161 let mut err = self.fatal(msg);
2162 err.span_label(self.span, msg);
2166 let delimited = match self.parse_token_tree() {
2167 TokenTree::Delimited(_, delimited) => delimited,
2168 _ => unreachable!(),
2170 let delim = match delim {
2171 token::Paren => MacDelimiter::Parenthesis,
2172 token::Bracket => MacDelimiter::Bracket,
2173 token::Brace => MacDelimiter::Brace,
2174 token::NoDelim => self.bug("unexpected no delimiter"),
2176 Ok((delim, delimited.stream().into()))
2179 /// At the bottom (top?) of the precedence hierarchy,
2180 /// parse things like parenthesized exprs,
2181 /// macros, return, etc.
2183 /// NB: This does not parse outer attributes,
2184 /// and is private because it only works
2185 /// correctly if called from parse_dot_or_call_expr().
2186 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2187 maybe_whole_expr!(self);
2189 // Outer attributes are already parsed and will be
2190 // added to the return value after the fact.
2192 // Therefore, prevent sub-parser from parsing
2193 // attributes by giving them a empty "already parsed" list.
2194 let mut attrs = ThinVec::new();
2197 let mut hi = self.span;
2201 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2203 token::OpenDelim(token::Paren) => {
2206 attrs.extend(self.parse_inner_attributes()?);
2208 // (e) is parenthesized e
2209 // (e,) is a tuple with only one field, e
2210 let mut es = vec![];
2211 let mut trailing_comma = false;
2212 while self.token != token::CloseDelim(token::Paren) {
2213 es.push(self.parse_expr()?);
2214 self.expect_one_of(&[], &[token::Comma, token::CloseDelim(token::Paren)])?;
2215 if self.check(&token::Comma) {
2216 trailing_comma = true;
2220 trailing_comma = false;
2226 hi = self.prev_span;
2227 ex = if es.len() == 1 && !trailing_comma {
2228 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2233 token::OpenDelim(token::Brace) => {
2234 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2236 token::BinOp(token::Or) | token::OrOr => {
2237 return self.parse_lambda_expr(attrs);
2239 token::OpenDelim(token::Bracket) => {
2242 attrs.extend(self.parse_inner_attributes()?);
2244 if self.check(&token::CloseDelim(token::Bracket)) {
2247 ex = ExprKind::Array(Vec::new());
2250 let first_expr = self.parse_expr()?;
2251 if self.check(&token::Semi) {
2252 // Repeating array syntax: [ 0; 512 ]
2254 let count = AnonConst {
2255 id: ast::DUMMY_NODE_ID,
2256 value: self.parse_expr()?,
2258 self.expect(&token::CloseDelim(token::Bracket))?;
2259 ex = ExprKind::Repeat(first_expr, count);
2260 } else if self.check(&token::Comma) {
2261 // Vector with two or more elements.
2263 let remaining_exprs = self.parse_seq_to_end(
2264 &token::CloseDelim(token::Bracket),
2265 SeqSep::trailing_allowed(token::Comma),
2266 |p| Ok(p.parse_expr()?)
2268 let mut exprs = vec![first_expr];
2269 exprs.extend(remaining_exprs);
2270 ex = ExprKind::Array(exprs);
2272 // Vector with one element.
2273 self.expect(&token::CloseDelim(token::Bracket))?;
2274 ex = ExprKind::Array(vec![first_expr]);
2277 hi = self.prev_span;
2281 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2283 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2285 if self.span.edition() >= Edition::Edition2018 &&
2286 self.check_keyword(keywords::Async)
2288 if self.is_async_block() { // check for `async {` and `async move {`
2289 return self.parse_async_block(attrs);
2291 return self.parse_lambda_expr(attrs);
2294 if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
2295 return self.parse_lambda_expr(attrs);
2297 if self.eat_keyword(keywords::If) {
2298 return self.parse_if_expr(attrs);
2300 if self.eat_keyword(keywords::For) {
2301 let lo = self.prev_span;
2302 return self.parse_for_expr(None, lo, attrs);
2304 if self.eat_keyword(keywords::While) {
2305 let lo = self.prev_span;
2306 return self.parse_while_expr(None, lo, attrs);
2308 if let Some(label) = self.eat_label() {
2309 let lo = label.ident.span;
2310 self.expect(&token::Colon)?;
2311 if self.eat_keyword(keywords::While) {
2312 return self.parse_while_expr(Some(label), lo, attrs)
2314 if self.eat_keyword(keywords::For) {
2315 return self.parse_for_expr(Some(label), lo, attrs)
2317 if self.eat_keyword(keywords::Loop) {
2318 return self.parse_loop_expr(Some(label), lo, attrs)
2320 if self.token == token::OpenDelim(token::Brace) {
2321 return self.parse_block_expr(Some(label),
2323 BlockCheckMode::Default,
2326 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2327 let mut err = self.fatal(msg);
2328 err.span_label(self.span, msg);
2331 if self.eat_keyword(keywords::Loop) {
2332 let lo = self.prev_span;
2333 return self.parse_loop_expr(None, lo, attrs);
2335 if self.eat_keyword(keywords::Continue) {
2336 let label = self.eat_label();
2337 let ex = ExprKind::Continue(label);
2338 let hi = self.prev_span;
2339 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2341 if self.eat_keyword(keywords::Match) {
2342 return self.parse_match_expr(attrs);
2344 if self.eat_keyword(keywords::Unsafe) {
2345 return self.parse_block_expr(
2348 BlockCheckMode::Unsafe(ast::UserProvided),
2351 if self.is_catch_expr() {
2353 assert!(self.eat_keyword(keywords::Do));
2354 assert!(self.eat_keyword(keywords::Catch));
2355 return self.parse_catch_expr(lo, attrs);
2357 if self.eat_keyword(keywords::Return) {
2358 if self.token.can_begin_expr() {
2359 let e = self.parse_expr()?;
2361 ex = ExprKind::Ret(Some(e));
2363 ex = ExprKind::Ret(None);
2365 } else if self.eat_keyword(keywords::Break) {
2366 let label = self.eat_label();
2367 let e = if self.token.can_begin_expr()
2368 && !(self.token == token::OpenDelim(token::Brace)
2369 && self.restrictions.contains(
2370 Restrictions::NO_STRUCT_LITERAL)) {
2371 Some(self.parse_expr()?)
2375 ex = ExprKind::Break(label, e);
2376 hi = self.prev_span;
2377 } else if self.eat_keyword(keywords::Yield) {
2378 if self.token.can_begin_expr() {
2379 let e = self.parse_expr()?;
2381 ex = ExprKind::Yield(Some(e));
2383 ex = ExprKind::Yield(None);
2385 } else if self.token.is_keyword(keywords::Let) {
2386 // Catch this syntax error here, instead of in `parse_ident`, so
2387 // that we can explicitly mention that let is not to be used as an expression
2388 let mut db = self.fatal("expected expression, found statement (`let`)");
2389 db.span_label(self.span, "expected expression");
2390 db.note("variable declaration using `let` is a statement");
2392 } else if self.token.is_path_start() {
2393 let pth = self.parse_path(PathStyle::Expr)?;
2395 // `!`, as an operator, is prefix, so we know this isn't that
2396 if self.eat(&token::Not) {
2397 // MACRO INVOCATION expression
2398 let (delim, tts) = self.expect_delimited_token_tree()?;
2399 let hi = self.prev_span;
2400 let node = Mac_ { path: pth, tts, delim };
2401 return Ok(self.mk_mac_expr(lo.to(hi), node, attrs))
2403 if self.check(&token::OpenDelim(token::Brace)) {
2404 // This is a struct literal, unless we're prohibited
2405 // from parsing struct literals here.
2406 let prohibited = self.restrictions.contains(
2407 Restrictions::NO_STRUCT_LITERAL
2410 return self.parse_struct_expr(lo, pth, attrs);
2415 ex = ExprKind::Path(None, pth);
2417 match self.parse_literal_maybe_minus() {
2420 ex = expr.node.clone();
2423 self.cancel(&mut err);
2424 let msg = format!("expected expression, found {}",
2425 self.this_token_descr());
2426 let mut err = self.fatal(&msg);
2427 err.span_label(self.span, "expected expression");
2435 let expr = Expr { node: ex, span: lo.to(hi), id: ast::DUMMY_NODE_ID, attrs };
2436 let expr = self.maybe_recover_from_bad_qpath(expr, true)?;
2441 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2442 -> PResult<'a, P<Expr>> {
2443 let struct_sp = lo.to(self.prev_span);
2445 let mut fields = Vec::new();
2446 let mut base = None;
2448 attrs.extend(self.parse_inner_attributes()?);
2450 while self.token != token::CloseDelim(token::Brace) {
2451 if self.eat(&token::DotDot) {
2452 let exp_span = self.prev_span;
2453 match self.parse_expr() {
2459 self.recover_stmt();
2462 if self.token == token::Comma {
2463 let mut err = self.sess.span_diagnostic.mut_span_err(
2464 exp_span.to(self.prev_span),
2465 "cannot use a comma after the base struct",
2467 err.span_suggestion_short_with_applicability(
2469 "remove this comma",
2471 Applicability::MachineApplicable
2473 err.note("the base struct must always be the last field");
2475 self.recover_stmt();
2480 match self.parse_field() {
2481 Ok(f) => fields.push(f),
2483 e.span_label(struct_sp, "while parsing this struct");
2486 // If the next token is a comma, then try to parse
2487 // what comes next as additional fields, rather than
2488 // bailing out until next `}`.
2489 if self.token != token::Comma {
2490 self.recover_stmt();
2496 match self.expect_one_of(&[token::Comma],
2497 &[token::CloseDelim(token::Brace)]) {
2501 self.recover_stmt();
2507 let span = lo.to(self.span);
2508 self.expect(&token::CloseDelim(token::Brace))?;
2509 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2512 fn parse_or_use_outer_attributes(&mut self,
2513 already_parsed_attrs: Option<ThinVec<Attribute>>)
2514 -> PResult<'a, ThinVec<Attribute>> {
2515 if let Some(attrs) = already_parsed_attrs {
2518 self.parse_outer_attributes().map(|a| a.into())
2522 /// Parse a block or unsafe block
2523 fn parse_block_expr(&mut self, opt_label: Option<Label>,
2524 lo: Span, blk_mode: BlockCheckMode,
2525 outer_attrs: ThinVec<Attribute>)
2526 -> PResult<'a, P<Expr>> {
2527 self.expect(&token::OpenDelim(token::Brace))?;
2529 let mut attrs = outer_attrs;
2530 attrs.extend(self.parse_inner_attributes()?);
2532 let blk = self.parse_block_tail(lo, blk_mode)?;
2533 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2536 /// parse a.b or a(13) or a[4] or just a
2537 fn parse_dot_or_call_expr(&mut self,
2538 already_parsed_attrs: Option<ThinVec<Attribute>>)
2539 -> PResult<'a, P<Expr>> {
2540 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2542 let b = self.parse_bottom_expr();
2543 let (span, b) = self.interpolated_or_expr_span(b)?;
2544 self.parse_dot_or_call_expr_with(b, span, attrs)
2547 fn parse_dot_or_call_expr_with(&mut self,
2550 mut attrs: ThinVec<Attribute>)
2551 -> PResult<'a, P<Expr>> {
2552 // Stitch the list of outer attributes onto the return value.
2553 // A little bit ugly, but the best way given the current code
2555 self.parse_dot_or_call_expr_with_(e0, lo)
2557 expr.map(|mut expr| {
2558 attrs.extend::<Vec<_>>(expr.attrs.into());
2561 ExprKind::If(..) | ExprKind::IfLet(..) => {
2562 if !expr.attrs.is_empty() {
2563 // Just point to the first attribute in there...
2564 let span = expr.attrs[0].span;
2567 "attributes are not yet allowed on `if` \
2578 // Assuming we have just parsed `.`, continue parsing into an expression.
2579 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2580 let segment = self.parse_path_segment(PathStyle::Expr, true)?;
2581 Ok(match self.token {
2582 token::OpenDelim(token::Paren) => {
2583 // Method call `expr.f()`
2584 let mut args = self.parse_unspanned_seq(
2585 &token::OpenDelim(token::Paren),
2586 &token::CloseDelim(token::Paren),
2587 SeqSep::trailing_allowed(token::Comma),
2588 |p| Ok(p.parse_expr()?)
2590 args.insert(0, self_arg);
2592 let span = lo.to(self.prev_span);
2593 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
2596 // Field access `expr.f`
2597 if let Some(args) = segment.args {
2598 self.span_err(args.span(),
2599 "field expressions may not have generic arguments");
2602 let span = lo.to(self.prev_span);
2603 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
2608 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2613 while self.eat(&token::Question) {
2614 let hi = self.prev_span;
2615 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
2619 if self.eat(&token::Dot) {
2621 token::Ident(..) => {
2622 e = self.parse_dot_suffix(e, lo)?;
2624 token::Literal(token::Integer(name), _) => {
2625 let span = self.span;
2627 let field = ExprKind::Field(e, Ident::new(name, span));
2628 e = self.mk_expr(lo.to(span), field, ThinVec::new());
2630 token::Literal(token::Float(n), _suf) => {
2632 let fstr = n.as_str();
2633 let mut err = self.diagnostic().struct_span_err(self.prev_span,
2634 &format!("unexpected token: `{}`", n));
2635 err.span_label(self.prev_span, "unexpected token");
2636 if fstr.chars().all(|x| "0123456789.".contains(x)) {
2637 let float = match fstr.parse::<f64>().ok() {
2641 let sugg = pprust::to_string(|s| {
2642 use print::pprust::PrintState;
2646 s.print_usize(float.trunc() as usize)?;
2649 s.s.word(fstr.splitn(2, ".").last().unwrap())
2651 err.span_suggestion_with_applicability(
2652 lo.to(self.prev_span),
2653 "try parenthesizing the first index",
2655 Applicability::MachineApplicable
2662 // FIXME Could factor this out into non_fatal_unexpected or something.
2663 let actual = self.this_token_to_string();
2664 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
2669 if self.expr_is_complete(&e) { break; }
2672 token::OpenDelim(token::Paren) => {
2673 let es = self.parse_unspanned_seq(
2674 &token::OpenDelim(token::Paren),
2675 &token::CloseDelim(token::Paren),
2676 SeqSep::trailing_allowed(token::Comma),
2677 |p| Ok(p.parse_expr()?)
2679 hi = self.prev_span;
2681 let nd = self.mk_call(e, es);
2682 e = self.mk_expr(lo.to(hi), nd, ThinVec::new());
2686 // Could be either an index expression or a slicing expression.
2687 token::OpenDelim(token::Bracket) => {
2689 let ix = self.parse_expr()?;
2691 self.expect(&token::CloseDelim(token::Bracket))?;
2692 let index = self.mk_index(e, ix);
2693 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
2701 crate fn process_potential_macro_variable(&mut self) {
2702 let (token, span) = match self.token {
2703 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
2704 self.look_ahead(1, |t| t.is_ident()) => {
2706 let name = match self.token {
2707 token::Ident(ident, _) => ident,
2710 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
2711 err.span_label(self.span, "unknown macro variable");
2715 token::Interpolated(ref nt) => {
2716 self.meta_var_span = Some(self.span);
2717 // Interpolated identifier and lifetime tokens are replaced with usual identifier
2718 // and lifetime tokens, so the former are never encountered during normal parsing.
2720 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
2721 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
2731 /// parse a single token tree from the input.
2732 crate fn parse_token_tree(&mut self) -> TokenTree {
2734 token::OpenDelim(..) => {
2735 let frame = mem::replace(&mut self.token_cursor.frame,
2736 self.token_cursor.stack.pop().unwrap());
2737 self.span = frame.span;
2739 TokenTree::Delimited(frame.span, Delimited {
2741 tts: frame.tree_cursor.original_stream().into(),
2744 token::CloseDelim(_) | token::Eof => unreachable!(),
2746 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
2748 TokenTree::Token(span, token)
2753 // parse a stream of tokens into a list of TokenTree's,
2755 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2756 let mut tts = Vec::new();
2757 while self.token != token::Eof {
2758 tts.push(self.parse_token_tree());
2763 pub fn parse_tokens(&mut self) -> TokenStream {
2764 let mut result = Vec::new();
2767 token::Eof | token::CloseDelim(..) => break,
2768 _ => result.push(self.parse_token_tree().into()),
2771 TokenStream::concat(result)
2774 /// Parse a prefix-unary-operator expr
2775 fn parse_prefix_expr(&mut self,
2776 already_parsed_attrs: Option<ThinVec<Attribute>>)
2777 -> PResult<'a, P<Expr>> {
2778 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2780 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
2781 let (hi, ex) = match self.token {
2784 let e = self.parse_prefix_expr(None);
2785 let (span, e) = self.interpolated_or_expr_span(e)?;
2786 (lo.to(span), self.mk_unary(UnOp::Not, e))
2788 // Suggest `!` for bitwise negation when encountering a `~`
2791 let e = self.parse_prefix_expr(None);
2792 let (span, e) = self.interpolated_or_expr_span(e)?;
2793 let span_of_tilde = lo;
2794 let mut err = self.diagnostic().struct_span_err(span_of_tilde,
2795 "`~` cannot be used as a unary operator");
2796 err.span_suggestion_short_with_applicability(
2798 "use `!` to perform bitwise negation",
2800 Applicability::MachineApplicable
2803 (lo.to(span), self.mk_unary(UnOp::Not, e))
2805 token::BinOp(token::Minus) => {
2807 let e = self.parse_prefix_expr(None);
2808 let (span, e) = self.interpolated_or_expr_span(e)?;
2809 (lo.to(span), self.mk_unary(UnOp::Neg, e))
2811 token::BinOp(token::Star) => {
2813 let e = self.parse_prefix_expr(None);
2814 let (span, e) = self.interpolated_or_expr_span(e)?;
2815 (lo.to(span), self.mk_unary(UnOp::Deref, e))
2817 token::BinOp(token::And) | token::AndAnd => {
2819 let m = self.parse_mutability();
2820 let e = self.parse_prefix_expr(None);
2821 let (span, e) = self.interpolated_or_expr_span(e)?;
2822 (lo.to(span), ExprKind::AddrOf(m, e))
2824 token::Ident(..) if self.token.is_keyword(keywords::In) => {
2826 let place = self.parse_expr_res(
2827 Restrictions::NO_STRUCT_LITERAL,
2830 let blk = self.parse_block()?;
2831 let span = blk.span;
2832 let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
2833 (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
2835 token::Ident(..) if self.token.is_keyword(keywords::Box) => {
2837 let e = self.parse_prefix_expr(None);
2838 let (span, e) = self.interpolated_or_expr_span(e)?;
2839 (lo.to(span), ExprKind::Box(e))
2841 token::Ident(..) if self.token.is_ident_named("not") => {
2842 // `not` is just an ordinary identifier in Rust-the-language,
2843 // but as `rustc`-the-compiler, we can issue clever diagnostics
2844 // for confused users who really want to say `!`
2845 let token_cannot_continue_expr = |t: &token::Token| match *t {
2846 // These tokens can start an expression after `!`, but
2847 // can't continue an expression after an ident
2848 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
2849 token::Literal(..) | token::Pound => true,
2850 token::Interpolated(ref nt) => match nt.0 {
2851 token::NtIdent(..) | token::NtExpr(..) |
2852 token::NtBlock(..) | token::NtPath(..) => true,
2857 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
2858 if cannot_continue_expr {
2860 // Emit the error ...
2861 let mut err = self.diagnostic()
2862 .struct_span_err(self.span,
2863 &format!("unexpected {} after identifier",
2864 self.this_token_descr()));
2865 // span the `not` plus trailing whitespace to avoid
2866 // trailing whitespace after the `!` in our suggestion
2867 let to_replace = self.sess.codemap()
2868 .span_until_non_whitespace(lo.to(self.span));
2869 err.span_suggestion_short_with_applicability(
2871 "use `!` to perform logical negation",
2873 Applicability::MachineApplicable
2876 // —and recover! (just as if we were in the block
2877 // for the `token::Not` arm)
2878 let e = self.parse_prefix_expr(None);
2879 let (span, e) = self.interpolated_or_expr_span(e)?;
2880 (lo.to(span), self.mk_unary(UnOp::Not, e))
2882 return self.parse_dot_or_call_expr(Some(attrs));
2885 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
2887 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2890 /// Parse an associative expression
2892 /// This parses an expression accounting for associativity and precedence of the operators in
2894 fn parse_assoc_expr(&mut self,
2895 already_parsed_attrs: Option<ThinVec<Attribute>>)
2896 -> PResult<'a, P<Expr>> {
2897 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2900 /// Parse an associative expression with operators of at least `min_prec` precedence
2901 fn parse_assoc_expr_with(&mut self,
2904 -> PResult<'a, P<Expr>> {
2905 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2908 let attrs = match lhs {
2909 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2912 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
2913 return self.parse_prefix_range_expr(attrs);
2915 self.parse_prefix_expr(attrs)?
2919 if self.expr_is_complete(&lhs) {
2920 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2923 self.expected_tokens.push(TokenType::Operator);
2924 while let Some(op) = AssocOp::from_token(&self.token) {
2926 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
2927 // it refers to. Interpolated identifiers are unwrapped early and never show up here
2928 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
2929 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
2930 let lhs_span = match (self.prev_token_kind, &lhs.node) {
2931 (PrevTokenKind::Interpolated, _) => self.prev_span,
2932 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
2933 if path.segments.len() == 1 => self.prev_span,
2937 let cur_op_span = self.span;
2938 let restrictions = if op.is_assign_like() {
2939 self.restrictions & Restrictions::NO_STRUCT_LITERAL
2943 if op.precedence() < min_prec {
2946 // Check for deprecated `...` syntax
2947 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
2948 self.err_dotdotdot_syntax(self.span);
2952 if op.is_comparison() {
2953 self.check_no_chained_comparison(&lhs, &op);
2956 if op == AssocOp::As {
2957 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
2959 } else if op == AssocOp::Colon {
2960 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
2963 err.span_label(self.span,
2964 "expecting a type here because of type ascription");
2965 let cm = self.sess.codemap();
2966 let cur_pos = cm.lookup_char_pos(self.span.lo());
2967 let op_pos = cm.lookup_char_pos(cur_op_span.hi());
2968 if cur_pos.line != op_pos.line {
2969 err.span_suggestion_with_applicability(
2971 "try using a semicolon",
2973 Applicability::MaybeIncorrect // speculative
2980 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
2981 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
2982 // generalise it to the Fixity::None code.
2984 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
2985 // two variants are handled with `parse_prefix_range_expr` call above.
2986 let rhs = if self.is_at_start_of_range_notation_rhs() {
2987 Some(self.parse_assoc_expr_with(op.precedence() + 1,
2988 LhsExpr::NotYetParsed)?)
2992 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2997 let limits = if op == AssocOp::DotDot {
2998 RangeLimits::HalfOpen
3003 let r = try!(self.mk_range(Some(lhs), rhs, limits));
3004 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
3008 let rhs = match op.fixity() {
3009 Fixity::Right => self.with_res(
3010 restrictions - Restrictions::STMT_EXPR,
3012 this.parse_assoc_expr_with(op.precedence(),
3013 LhsExpr::NotYetParsed)
3015 Fixity::Left => self.with_res(
3016 restrictions - Restrictions::STMT_EXPR,
3018 this.parse_assoc_expr_with(op.precedence() + 1,
3019 LhsExpr::NotYetParsed)
3021 // We currently have no non-associative operators that are not handled above by
3022 // the special cases. The code is here only for future convenience.
3023 Fixity::None => self.with_res(
3024 restrictions - Restrictions::STMT_EXPR,
3026 this.parse_assoc_expr_with(op.precedence() + 1,
3027 LhsExpr::NotYetParsed)
3031 let span = lhs_span.to(rhs.span);
3033 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
3034 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3035 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3036 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3037 AssocOp::Greater | AssocOp::GreaterEqual => {
3038 let ast_op = op.to_ast_binop().unwrap();
3039 let binary = self.mk_binary(codemap::respan(cur_op_span, ast_op), lhs, rhs);
3040 self.mk_expr(span, binary, ThinVec::new())
3043 self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3044 AssocOp::ObsoleteInPlace =>
3045 self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
3046 AssocOp::AssignOp(k) => {
3048 token::Plus => BinOpKind::Add,
3049 token::Minus => BinOpKind::Sub,
3050 token::Star => BinOpKind::Mul,
3051 token::Slash => BinOpKind::Div,
3052 token::Percent => BinOpKind::Rem,
3053 token::Caret => BinOpKind::BitXor,
3054 token::And => BinOpKind::BitAnd,
3055 token::Or => BinOpKind::BitOr,
3056 token::Shl => BinOpKind::Shl,
3057 token::Shr => BinOpKind::Shr,
3059 let aopexpr = self.mk_assign_op(codemap::respan(cur_op_span, aop), lhs, rhs);
3060 self.mk_expr(span, aopexpr, ThinVec::new())
3062 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3063 self.bug("AssocOp should have been handled by special case")
3067 if op.fixity() == Fixity::None { break }
3072 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3073 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3074 -> PResult<'a, P<Expr>> {
3075 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3076 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3079 // Save the state of the parser before parsing type normally, in case there is a
3080 // LessThan comparison after this cast.
3081 let parser_snapshot_before_type = self.clone();
3082 match self.parse_ty_no_plus() {
3084 Ok(mk_expr(self, rhs))
3086 Err(mut type_err) => {
3087 // Rewind to before attempting to parse the type with generics, to recover
3088 // from situations like `x as usize < y` in which we first tried to parse
3089 // `usize < y` as a type with generic arguments.
3090 let parser_snapshot_after_type = self.clone();
3091 mem::replace(self, parser_snapshot_before_type);
3093 match self.parse_path(PathStyle::Expr) {
3095 let (op_noun, op_verb) = match self.token {
3096 token::Lt => ("comparison", "comparing"),
3097 token::BinOp(token::Shl) => ("shift", "shifting"),
3099 // We can end up here even without `<` being the next token, for
3100 // example because `parse_ty_no_plus` returns `Err` on keywords,
3101 // but `parse_path` returns `Ok` on them due to error recovery.
3102 // Return original error and parser state.
3103 mem::replace(self, parser_snapshot_after_type);
3104 return Err(type_err);
3108 // Successfully parsed the type path leaving a `<` yet to parse.
3111 // Report non-fatal diagnostics, keep `x as usize` as an expression
3112 // in AST and continue parsing.
3113 let msg = format!("`<` is interpreted as a start of generic \
3114 arguments for `{}`, not a {}", path, op_noun);
3115 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3116 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3117 "interpreted as generic arguments");
3118 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3120 let expr = mk_expr(self, P(Ty {
3122 node: TyKind::Path(None, path),
3123 id: ast::DUMMY_NODE_ID
3126 let expr_str = self.sess.codemap().span_to_snippet(expr.span)
3127 .unwrap_or(pprust::expr_to_string(&expr));
3128 err.span_suggestion_with_applicability(
3130 &format!("try {} the cast value", op_verb),
3131 format!("({})", expr_str),
3132 Applicability::MachineApplicable
3138 Err(mut path_err) => {
3139 // Couldn't parse as a path, return original error and parser state.
3141 mem::replace(self, parser_snapshot_after_type);
3149 /// Produce an error if comparison operators are chained (RFC #558).
3150 /// We only need to check lhs, not rhs, because all comparison ops
3151 /// have same precedence and are left-associative
3152 fn check_no_chained_comparison(&mut self, lhs: &Expr, outer_op: &AssocOp) {
3153 debug_assert!(outer_op.is_comparison(),
3154 "check_no_chained_comparison: {:?} is not comparison",
3157 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
3158 // respan to include both operators
3159 let op_span = op.span.to(self.span);
3160 let mut err = self.diagnostic().struct_span_err(op_span,
3161 "chained comparison operators require parentheses");
3162 if op.node == BinOpKind::Lt &&
3163 *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
3164 *outer_op == AssocOp::Greater // even in a case like the following:
3165 { // Foo<Bar<Baz<Qux, ()>>>
3167 "use `::<...>` instead of `<...>` if you meant to specify type arguments");
3168 err.help("or use `(...)` if you meant to specify fn arguments");
3176 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3177 fn parse_prefix_range_expr(&mut self,
3178 already_parsed_attrs: Option<ThinVec<Attribute>>)
3179 -> PResult<'a, P<Expr>> {
3180 // Check for deprecated `...` syntax
3181 if self.token == token::DotDotDot {
3182 self.err_dotdotdot_syntax(self.span);
3185 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3186 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3188 let tok = self.token.clone();
3189 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3191 let mut hi = self.span;
3193 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3194 // RHS must be parsed with more associativity than the dots.
3195 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3196 Some(self.parse_assoc_expr_with(next_prec,
3197 LhsExpr::NotYetParsed)
3205 let limits = if tok == token::DotDot {
3206 RangeLimits::HalfOpen
3211 let r = try!(self.mk_range(None,
3214 Ok(self.mk_expr(lo.to(hi), r, attrs))
3217 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3218 if self.token.can_begin_expr() {
3219 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3220 if self.token == token::OpenDelim(token::Brace) {
3221 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3229 /// Parse an 'if' or 'if let' expression ('if' token already eaten)
3230 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3231 if self.check_keyword(keywords::Let) {
3232 return self.parse_if_let_expr(attrs);
3234 let lo = self.prev_span;
3235 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3237 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3238 // verify that the last statement is either an implicit return (no `;`) or an explicit
3239 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3240 // the dead code lint.
3241 if self.eat_keyword(keywords::Else) || !cond.returns() {
3242 let sp = self.sess.codemap().next_point(lo);
3243 let mut err = self.diagnostic()
3244 .struct_span_err(sp, "missing condition for `if` statemement");
3245 err.span_label(sp, "expected if condition here");
3248 let not_block = self.token != token::OpenDelim(token::Brace);
3249 let thn = self.parse_block().map_err(|mut err| {
3251 err.span_label(lo, "this `if` statement has a condition, but no block");
3255 let mut els: Option<P<Expr>> = None;
3256 let mut hi = thn.span;
3257 if self.eat_keyword(keywords::Else) {
3258 let elexpr = self.parse_else_expr()?;
3262 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3265 /// Parse an 'if let' expression ('if' token already eaten)
3266 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3267 -> PResult<'a, P<Expr>> {
3268 let lo = self.prev_span;
3269 self.expect_keyword(keywords::Let)?;
3270 let pats = self.parse_pats()?;
3271 self.expect(&token::Eq)?;
3272 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3273 let thn = self.parse_block()?;
3274 let (hi, els) = if self.eat_keyword(keywords::Else) {
3275 let expr = self.parse_else_expr()?;
3276 (expr.span, Some(expr))
3280 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3283 // `move |args| expr`
3284 fn parse_lambda_expr(&mut self,
3285 attrs: ThinVec<Attribute>)
3286 -> PResult<'a, P<Expr>>
3289 let movability = if self.eat_keyword(keywords::Static) {
3294 let asyncness = if self.span.edition() >= Edition::Edition2018 {
3295 self.parse_asyncness()
3299 let capture_clause = if self.eat_keyword(keywords::Move) {
3304 let decl = self.parse_fn_block_decl()?;
3305 let decl_hi = self.prev_span;
3306 let body = match decl.output {
3307 FunctionRetTy::Default(_) => {
3308 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3309 self.parse_expr_res(restrictions, None)?
3312 // If an explicit return type is given, require a
3313 // block to appear (RFC 968).
3314 let body_lo = self.span;
3315 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3321 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3325 // `else` token already eaten
3326 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3327 if self.eat_keyword(keywords::If) {
3328 return self.parse_if_expr(ThinVec::new());
3330 let blk = self.parse_block()?;
3331 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3335 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3336 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3338 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3339 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3341 let pat = self.parse_top_level_pat()?;
3342 if !self.eat_keyword(keywords::In) {
3343 let in_span = self.prev_span.between(self.span);
3344 let mut err = self.sess.span_diagnostic
3345 .struct_span_err(in_span, "missing `in` in `for` loop");
3346 err.span_suggestion_short_with_applicability(
3347 in_span, "try adding `in` here", " in ".into(),
3348 // has been misleading, at least in the past (closed Issue #48492)
3349 Applicability::MaybeIncorrect
3353 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3354 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3355 attrs.extend(iattrs);
3357 let hi = self.prev_span;
3358 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3361 /// Parse a 'while' or 'while let' expression ('while' token already eaten)
3362 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3364 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3365 if self.token.is_keyword(keywords::Let) {
3366 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3368 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3369 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3370 attrs.extend(iattrs);
3371 let span = span_lo.to(body.span);
3372 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3375 /// Parse a 'while let' expression ('while' token already eaten)
3376 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3378 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3379 self.expect_keyword(keywords::Let)?;
3380 let pats = self.parse_pats()?;
3381 self.expect(&token::Eq)?;
3382 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3383 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3384 attrs.extend(iattrs);
3385 let span = span_lo.to(body.span);
3386 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3389 // parse `loop {...}`, `loop` token already eaten
3390 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3392 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3393 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3394 attrs.extend(iattrs);
3395 let span = span_lo.to(body.span);
3396 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3399 /// Parse an `async move {...}` expression
3400 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3401 -> PResult<'a, P<Expr>>
3403 let span_lo = self.span;
3404 self.expect_keyword(keywords::Async)?;
3405 let capture_clause = if self.eat_keyword(keywords::Move) {
3410 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3411 attrs.extend(iattrs);
3413 span_lo.to(body.span),
3414 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3417 /// Parse a `do catch {...}` expression (`do catch` token already eaten)
3418 fn parse_catch_expr(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3419 -> PResult<'a, P<Expr>>
3421 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3422 attrs.extend(iattrs);
3423 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::Catch(body), attrs))
3426 // `match` token already eaten
3427 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3428 let match_span = self.prev_span;
3429 let lo = self.prev_span;
3430 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3432 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3433 if self.token == token::Token::Semi {
3434 e.span_suggestion_short_with_applicability(
3436 "try removing this `match`",
3438 Applicability::MaybeIncorrect // speculative
3443 attrs.extend(self.parse_inner_attributes()?);
3445 let mut arms: Vec<Arm> = Vec::new();
3446 while self.token != token::CloseDelim(token::Brace) {
3447 match self.parse_arm() {
3448 Ok(arm) => arms.push(arm),
3450 // Recover by skipping to the end of the block.
3452 self.recover_stmt();
3453 let span = lo.to(self.span);
3454 if self.token == token::CloseDelim(token::Brace) {
3457 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3463 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3466 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3467 maybe_whole!(self, NtArm, |x| x);
3469 let attrs = self.parse_outer_attributes()?;
3470 // Allow a '|' before the pats (RFC 1925)
3471 self.eat(&token::BinOp(token::Or));
3472 let pats = self.parse_pats()?;
3473 let guard = if self.eat_keyword(keywords::If) {
3474 Some(self.parse_expr()?)
3478 let arrow_span = self.span;
3479 self.expect(&token::FatArrow)?;
3480 let arm_start_span = self.span;
3482 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3483 .map_err(|mut err| {
3484 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3488 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3489 && self.token != token::CloseDelim(token::Brace);
3492 let cm = self.sess.codemap();
3493 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3494 .map_err(|mut err| {
3495 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3496 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3497 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3498 && expr_lines.lines.len() == 2
3499 && self.token == token::FatArrow => {
3500 // We check wether there's any trailing code in the parse span, if there
3501 // isn't, we very likely have the following:
3504 // | -- - missing comma
3510 // | parsed until here as `"y" & X`
3511 err.span_suggestion_short_with_applicability(
3512 cm.next_point(arm_start_span),
3513 "missing a comma here to end this `match` arm",
3515 Applicability::MachineApplicable
3519 err.span_label(arrow_span,
3520 "while parsing the `match` arm starting here");
3526 self.eat(&token::Comma);
3537 /// Parse an expression
3538 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3539 self.parse_expr_res(Restrictions::empty(), None)
3542 /// Evaluate the closure with restrictions in place.
3544 /// After the closure is evaluated, restrictions are reset.
3545 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
3546 where F: FnOnce(&mut Self) -> T
3548 let old = self.restrictions;
3549 self.restrictions = r;
3551 self.restrictions = old;
3556 /// Parse an expression, subject to the given restrictions
3557 fn parse_expr_res(&mut self, r: Restrictions,
3558 already_parsed_attrs: Option<ThinVec<Attribute>>)
3559 -> PResult<'a, P<Expr>> {
3560 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3563 /// Parse the RHS of a local variable declaration (e.g. '= 14;')
3564 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
3565 if self.check(&token::Eq) {
3567 Ok(Some(self.parse_expr()?))
3569 Ok(Some(self.parse_expr()?))
3575 /// Parse patterns, separated by '|' s
3576 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3577 let mut pats = Vec::new();
3579 pats.push(self.parse_top_level_pat()?);
3581 if self.token == token::OrOr {
3582 let mut err = self.struct_span_err(self.span,
3583 "unexpected token `||` after pattern");
3584 err.span_suggestion_with_applicability(
3586 "use a single `|` to specify multiple patterns",
3588 Applicability::MachineApplicable
3592 } else if self.check(&token::BinOp(token::Or)) {
3600 // Parses a parenthesized list of patterns like
3601 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
3602 // - a vector of the patterns that were parsed
3603 // - an option indicating the index of the `..` element
3604 // - a boolean indicating whether a trailing comma was present.
3605 // Trailing commas are significant because (p) and (p,) are different patterns.
3606 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3607 self.expect(&token::OpenDelim(token::Paren))?;
3608 let result = self.parse_pat_list()?;
3609 self.expect(&token::CloseDelim(token::Paren))?;
3613 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3614 let mut fields = Vec::new();
3615 let mut ddpos = None;
3616 let mut trailing_comma = false;
3618 if self.eat(&token::DotDot) {
3619 if ddpos.is_none() {
3620 ddpos = Some(fields.len());
3622 // Emit a friendly error, ignore `..` and continue parsing
3623 self.span_err(self.prev_span,
3624 "`..` can only be used once per tuple or tuple struct pattern");
3626 } else if !self.check(&token::CloseDelim(token::Paren)) {
3627 fields.push(self.parse_pat()?);
3632 trailing_comma = self.eat(&token::Comma);
3633 if !trailing_comma {
3638 if ddpos == Some(fields.len()) && trailing_comma {
3639 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
3640 self.span_err(self.prev_span, "trailing comma is not permitted after `..`");
3643 Ok((fields, ddpos, trailing_comma))
3646 fn parse_pat_vec_elements(
3648 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3649 let mut before = Vec::new();
3650 let mut slice = None;
3651 let mut after = Vec::new();
3652 let mut first = true;
3653 let mut before_slice = true;
3655 while self.token != token::CloseDelim(token::Bracket) {
3659 self.expect(&token::Comma)?;
3661 if self.token == token::CloseDelim(token::Bracket)
3662 && (before_slice || !after.is_empty()) {
3668 if self.eat(&token::DotDot) {
3670 if self.check(&token::Comma) ||
3671 self.check(&token::CloseDelim(token::Bracket)) {
3672 slice = Some(P(Pat {
3673 id: ast::DUMMY_NODE_ID,
3674 node: PatKind::Wild,
3675 span: self.prev_span,
3677 before_slice = false;
3683 let subpat = self.parse_pat()?;
3684 if before_slice && self.eat(&token::DotDot) {
3685 slice = Some(subpat);
3686 before_slice = false;
3687 } else if before_slice {
3688 before.push(subpat);
3694 Ok((before, slice, after))
3700 attrs: Vec<Attribute>
3701 ) -> PResult<'a, codemap::Spanned<ast::FieldPat>> {
3702 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3704 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3705 // Parsing a pattern of the form "fieldname: pat"
3706 let fieldname = self.parse_field_name()?;
3708 let pat = self.parse_pat()?;
3710 (pat, fieldname, false)
3712 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3713 let is_box = self.eat_keyword(keywords::Box);
3714 let boxed_span = self.span;
3715 let is_ref = self.eat_keyword(keywords::Ref);
3716 let is_mut = self.eat_keyword(keywords::Mut);
3717 let fieldname = self.parse_ident()?;
3718 hi = self.prev_span;
3720 let bind_type = match (is_ref, is_mut) {
3721 (true, true) => BindingMode::ByRef(Mutability::Mutable),
3722 (true, false) => BindingMode::ByRef(Mutability::Immutable),
3723 (false, true) => BindingMode::ByValue(Mutability::Mutable),
3724 (false, false) => BindingMode::ByValue(Mutability::Immutable),
3726 let fieldpat = P(Pat {
3727 id: ast::DUMMY_NODE_ID,
3728 node: PatKind::Ident(bind_type, fieldname, None),
3729 span: boxed_span.to(hi),
3732 let subpat = if is_box {
3734 id: ast::DUMMY_NODE_ID,
3735 node: PatKind::Box(fieldpat),
3741 (subpat, fieldname, true)
3744 Ok(codemap::Spanned {
3746 node: ast::FieldPat {
3750 attrs: attrs.into(),
3755 /// Parse the fields of a struct-like pattern
3756 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<codemap::Spanned<ast::FieldPat>>, bool)> {
3757 let mut fields = Vec::new();
3758 let mut etc = false;
3759 let mut ate_comma = true;
3760 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
3761 let mut etc_span = None;
3763 while self.token != token::CloseDelim(token::Brace) {
3764 let attrs = self.parse_outer_attributes()?;
3767 // check that a comma comes after every field
3769 let err = self.struct_span_err(self.prev_span, "expected `,`");
3774 if self.check(&token::DotDot) || self.token == token::DotDotDot {
3776 let mut etc_sp = self.span;
3778 if self.token == token::DotDotDot { // Issue #46718
3779 // Accept `...` as if it were `..` to avoid further errors
3780 let mut err = self.struct_span_err(self.span,
3781 "expected field pattern, found `...`");
3782 err.span_suggestion_with_applicability(
3784 "to omit remaining fields, use one fewer `.`",
3786 Applicability::MachineApplicable
3790 self.bump(); // `..` || `...`:w
3792 if self.token == token::CloseDelim(token::Brace) {
3793 etc_span = Some(etc_sp);
3796 let token_str = self.this_token_to_string();
3797 let mut err = self.fatal(&format!("expected `}}`, found `{}`", token_str));
3799 err.span_label(self.span, "expected `}`");
3800 let mut comma_sp = None;
3801 if self.token == token::Comma { // Issue #49257
3802 etc_sp = etc_sp.to(self.sess.codemap().span_until_non_whitespace(self.span));
3803 err.span_label(etc_sp,
3804 "`..` must be at the end and cannot have a trailing comma");
3805 comma_sp = Some(self.span);
3810 etc_span = Some(etc_sp);
3811 if self.token == token::CloseDelim(token::Brace) {
3812 // If the struct looks otherwise well formed, recover and continue.
3813 if let Some(sp) = comma_sp {
3814 err.span_suggestion_short(sp, "remove this comma", "".into());
3818 } else if self.token.is_ident() && ate_comma {
3819 // Accept fields coming after `..,`.
3820 // This way we avoid "pattern missing fields" errors afterwards.
3821 // We delay this error until the end in order to have a span for a
3823 if let Some(mut delayed_err) = delayed_err {
3827 delayed_err = Some(err);
3830 if let Some(mut err) = delayed_err {
3837 fields.push(match self.parse_pat_field(lo, attrs) {
3840 if let Some(mut delayed_err) = delayed_err {
3846 ate_comma = self.eat(&token::Comma);
3849 if let Some(mut err) = delayed_err {
3850 if let Some(etc_span) = etc_span {
3851 err.multipart_suggestion(
3852 "move the `..` to the end of the field list",
3854 (etc_span, "".into()),
3855 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
3861 return Ok((fields, etc));
3864 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3865 if self.token.is_path_start() {
3867 let (qself, path) = if self.eat_lt() {
3868 // Parse a qualified path
3869 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3872 // Parse an unqualified path
3873 (None, self.parse_path(PathStyle::Expr)?)
3875 let hi = self.prev_span;
3876 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
3878 self.parse_literal_maybe_minus()
3882 // helper function to decide whether to parse as ident binding or to try to do
3883 // something more complex like range patterns
3884 fn parse_as_ident(&mut self) -> bool {
3885 self.look_ahead(1, |t| match *t {
3886 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
3887 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
3888 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
3889 // range pattern branch
3890 token::DotDot => None,
3892 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
3893 token::Comma | token::CloseDelim(token::Bracket) => true,
3898 /// A wrapper around `parse_pat` with some special error handling for the
3899 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contast
3900 /// to subpatterns within such).
3901 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
3902 let pat = self.parse_pat()?;
3903 if self.token == token::Comma {
3904 // An unexpected comma after a top-level pattern is a clue that the
3905 // user (perhaps more accustomed to some other language) forgot the
3906 // parentheses in what should have been a tuple pattern; return a
3907 // suggestion-enhanced error here rather than choking on the comma
3909 let comma_span = self.span;
3911 if let Err(mut err) = self.parse_pat_list() {
3912 // We didn't expect this to work anyway; we just wanted
3913 // to advance to the end of the comma-sequence so we know
3914 // the span to suggest parenthesizing
3917 let seq_span = pat.span.to(self.prev_span);
3918 let mut err = self.struct_span_err(comma_span,
3919 "unexpected `,` in pattern");
3920 if let Ok(seq_snippet) = self.sess.codemap().span_to_snippet(seq_span) {
3921 err.span_suggestion_with_applicability(
3923 "try adding parentheses",
3924 format!("({})", seq_snippet),
3925 Applicability::MachineApplicable
3933 /// Parse a pattern.
3934 pub fn parse_pat(&mut self) -> PResult<'a, P<Pat>> {
3935 self.parse_pat_with_range_pat(true)
3938 /// Parse a pattern, with a setting whether modern range patterns e.g. `a..=b`, `a..b` are
3940 fn parse_pat_with_range_pat(&mut self, allow_range_pat: bool) -> PResult<'a, P<Pat>> {
3941 maybe_whole!(self, NtPat, |x| x);
3946 token::BinOp(token::And) | token::AndAnd => {
3947 // Parse &pat / &mut pat
3949 let mutbl = self.parse_mutability();
3950 if let token::Lifetime(ident) = self.token {
3951 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
3953 err.span_label(self.span, "unexpected lifetime");
3956 let subpat = self.parse_pat_with_range_pat(false)?;
3957 pat = PatKind::Ref(subpat, mutbl);
3959 token::OpenDelim(token::Paren) => {
3960 // Parse (pat,pat,pat,...) as tuple pattern
3961 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
3962 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
3963 PatKind::Paren(fields.into_iter().nth(0).unwrap())
3965 PatKind::Tuple(fields, ddpos)
3968 token::OpenDelim(token::Bracket) => {
3969 // Parse [pat,pat,...] as slice pattern
3971 let (before, slice, after) = self.parse_pat_vec_elements()?;
3972 self.expect(&token::CloseDelim(token::Bracket))?;
3973 pat = PatKind::Slice(before, slice, after);
3975 // At this point, token != &, &&, (, [
3976 _ => if self.eat_keyword(keywords::Underscore) {
3978 pat = PatKind::Wild;
3979 } else if self.eat_keyword(keywords::Mut) {
3980 // Parse mut ident @ pat / mut ref ident @ pat
3981 let mutref_span = self.prev_span.to(self.span);
3982 let binding_mode = if self.eat_keyword(keywords::Ref) {
3984 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
3985 .span_suggestion_with_applicability(
3987 "try switching the order",
3989 Applicability::MachineApplicable
3991 BindingMode::ByRef(Mutability::Mutable)
3993 BindingMode::ByValue(Mutability::Mutable)
3995 pat = self.parse_pat_ident(binding_mode)?;
3996 } else if self.eat_keyword(keywords::Ref) {
3997 // Parse ref ident @ pat / ref mut ident @ pat
3998 let mutbl = self.parse_mutability();
3999 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
4000 } else if self.eat_keyword(keywords::Box) {
4002 let subpat = self.parse_pat_with_range_pat(false)?;
4003 pat = PatKind::Box(subpat);
4004 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
4005 self.parse_as_ident() {
4006 // Parse ident @ pat
4007 // This can give false positives and parse nullary enums,
4008 // they are dealt with later in resolve
4009 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
4010 pat = self.parse_pat_ident(binding_mode)?;
4011 } else if self.token.is_path_start() {
4012 // Parse pattern starting with a path
4013 let (qself, path) = if self.eat_lt() {
4014 // Parse a qualified path
4015 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4018 // Parse an unqualified path
4019 (None, self.parse_path(PathStyle::Expr)?)
4022 token::Not if qself.is_none() => {
4023 // Parse macro invocation
4025 let (delim, tts) = self.expect_delimited_token_tree()?;
4026 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4027 pat = PatKind::Mac(mac);
4029 token::DotDotDot | token::DotDotEq | token::DotDot => {
4030 let end_kind = match self.token {
4031 token::DotDot => RangeEnd::Excluded,
4032 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4033 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4034 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4037 let op_span = self.span;
4039 let span = lo.to(self.prev_span);
4040 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4042 let end = self.parse_pat_range_end()?;
4043 let op = Spanned { span: op_span, node: end_kind };
4044 pat = PatKind::Range(begin, end, op);
4046 token::OpenDelim(token::Brace) => {
4047 if qself.is_some() {
4048 let msg = "unexpected `{` after qualified path";
4049 let mut err = self.fatal(msg);
4050 err.span_label(self.span, msg);
4053 // Parse struct pattern
4055 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4057 self.recover_stmt();
4061 pat = PatKind::Struct(path, fields, etc);
4063 token::OpenDelim(token::Paren) => {
4064 if qself.is_some() {
4065 let msg = "unexpected `(` after qualified path";
4066 let mut err = self.fatal(msg);
4067 err.span_label(self.span, msg);
4070 // Parse tuple struct or enum pattern
4071 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4072 pat = PatKind::TupleStruct(path, fields, ddpos)
4074 _ => pat = PatKind::Path(qself, path),
4077 // Try to parse everything else as literal with optional minus
4078 match self.parse_literal_maybe_minus() {
4080 let op_span = self.span;
4081 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4082 self.check(&token::DotDotDot) {
4083 let end_kind = if self.eat(&token::DotDotDot) {
4084 RangeEnd::Included(RangeSyntax::DotDotDot)
4085 } else if self.eat(&token::DotDotEq) {
4086 RangeEnd::Included(RangeSyntax::DotDotEq)
4087 } else if self.eat(&token::DotDot) {
4090 panic!("impossible case: we already matched \
4091 on a range-operator token")
4093 let end = self.parse_pat_range_end()?;
4094 let op = Spanned { span: op_span, node: end_kind };
4095 pat = PatKind::Range(begin, end, op);
4097 pat = PatKind::Lit(begin);
4101 self.cancel(&mut err);
4102 let msg = format!("expected pattern, found {}", self.this_token_descr());
4103 let mut err = self.fatal(&msg);
4104 err.span_label(self.span, "expected pattern");
4111 let pat = Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID };
4112 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4114 if !allow_range_pat {
4117 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4119 PatKind::Range(..) => {
4120 let mut err = self.struct_span_err(
4122 "the range pattern here has ambiguous interpretation",
4124 err.span_suggestion_with_applicability(
4126 "add parentheses to clarify the precedence",
4127 format!("({})", pprust::pat_to_string(&pat)),
4128 // "ambiguous interpretation" implies that we have to be guessing
4129 Applicability::MaybeIncorrect
4140 /// Parse ident or ident @ pat
4141 /// used by the copy foo and ref foo patterns to give a good
4142 /// error message when parsing mistakes like ref foo(a,b)
4143 fn parse_pat_ident(&mut self,
4144 binding_mode: ast::BindingMode)
4145 -> PResult<'a, PatKind> {
4146 let ident = self.parse_ident()?;
4147 let sub = if self.eat(&token::At) {
4148 Some(self.parse_pat()?)
4153 // just to be friendly, if they write something like
4155 // we end up here with ( as the current token. This shortly
4156 // leads to a parse error. Note that if there is no explicit
4157 // binding mode then we do not end up here, because the lookahead
4158 // will direct us over to parse_enum_variant()
4159 if self.token == token::OpenDelim(token::Paren) {
4160 return Err(self.span_fatal(
4162 "expected identifier, found enum pattern"))
4165 Ok(PatKind::Ident(binding_mode, ident, sub))
4168 /// Parse a local variable declaration
4169 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4170 let lo = self.prev_span;
4171 let pat = self.parse_top_level_pat()?;
4173 let (err, ty) = if self.eat(&token::Colon) {
4174 // Save the state of the parser before parsing type normally, in case there is a `:`
4175 // instead of an `=` typo.
4176 let parser_snapshot_before_type = self.clone();
4177 let colon_sp = self.prev_span;
4178 match self.parse_ty() {
4179 Ok(ty) => (None, Some(ty)),
4181 // Rewind to before attempting to parse the type and continue parsing
4182 let parser_snapshot_after_type = self.clone();
4183 mem::replace(self, parser_snapshot_before_type);
4185 let snippet = self.sess.codemap().span_to_snippet(pat.span).unwrap();
4186 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4187 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4193 let init = match (self.parse_initializer(err.is_some()), err) {
4194 (Ok(init), None) => { // init parsed, ty parsed
4197 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4198 // Could parse the type as if it were the initializer, it is likely there was a
4199 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4200 err.span_suggestion_short_with_applicability(
4202 "use `=` if you meant to assign",
4204 Applicability::MachineApplicable
4207 // As this was parsed successfully, continue as if the code has been fixed for the
4208 // rest of the file. It will still fail due to the emitted error, but we avoid
4212 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4214 // Couldn't parse the type nor the initializer, only raise the type error and
4215 // return to the parser state before parsing the type as the initializer.
4216 // let x: <parse_error>;
4217 mem::replace(self, snapshot);
4220 (Err(err), None) => { // init error, ty parsed
4221 // Couldn't parse the initializer and we're not attempting to recover a failed
4222 // parse of the type, return the error.
4226 let hi = if self.token == token::Semi {
4235 id: ast::DUMMY_NODE_ID,
4241 /// Parse a structure field
4242 fn parse_name_and_ty(&mut self,
4245 attrs: Vec<Attribute>)
4246 -> PResult<'a, StructField> {
4247 let name = self.parse_ident()?;
4248 self.expect(&token::Colon)?;
4249 let ty = self.parse_ty()?;
4251 span: lo.to(self.prev_span),
4254 id: ast::DUMMY_NODE_ID,
4260 /// Emit an expected item after attributes error.
4261 fn expected_item_err(&self, attrs: &[Attribute]) {
4262 let message = match attrs.last() {
4263 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4264 _ => "expected item after attributes",
4267 self.span_err(self.prev_span, message);
4270 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4271 /// e.g. a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4272 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4273 Ok(self.parse_stmt_(true))
4276 // Eat tokens until we can be relatively sure we reached the end of the
4277 // statement. This is something of a best-effort heuristic.
4279 // We terminate when we find an unmatched `}` (without consuming it).
4280 fn recover_stmt(&mut self) {
4281 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
4284 // If `break_on_semi` is `Break`, then we will stop consuming tokens after
4285 // finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
4286 // approximate - it can mean we break too early due to macros, but that
4287 // shoud only lead to sub-optimal recovery, not inaccurate parsing).
4289 // If `break_on_block` is `Break`, then we will stop consuming tokens
4290 // after finding (and consuming) a brace-delimited block.
4291 fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
4292 let mut brace_depth = 0;
4293 let mut bracket_depth = 0;
4294 let mut in_block = false;
4295 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
4296 break_on_semi, break_on_block);
4298 debug!("recover_stmt_ loop {:?}", self.token);
4300 token::OpenDelim(token::DelimToken::Brace) => {
4303 if break_on_block == BlockMode::Break &&
4305 bracket_depth == 0 {
4309 token::OpenDelim(token::DelimToken::Bracket) => {
4313 token::CloseDelim(token::DelimToken::Brace) => {
4314 if brace_depth == 0 {
4315 debug!("recover_stmt_ return - close delim {:?}", self.token);
4320 if in_block && bracket_depth == 0 && brace_depth == 0 {
4321 debug!("recover_stmt_ return - block end {:?}", self.token);
4325 token::CloseDelim(token::DelimToken::Bracket) => {
4327 if bracket_depth < 0 {
4333 debug!("recover_stmt_ return - Eof");
4338 if break_on_semi == SemiColonMode::Break &&
4340 bracket_depth == 0 {
4341 debug!("recover_stmt_ return - Semi");
4352 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4353 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4355 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4360 fn is_async_block(&mut self) -> bool {
4361 self.token.is_keyword(keywords::Async) &&
4364 self.look_ahead(1, |t| t.is_keyword(keywords::Move)) &&
4365 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4367 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4372 fn is_catch_expr(&mut self) -> bool {
4373 self.token.is_keyword(keywords::Do) &&
4374 self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
4375 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4377 // prevent `while catch {} {}`, `if catch {} {} else {}`, etc.
4378 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4381 fn is_union_item(&self) -> bool {
4382 self.token.is_keyword(keywords::Union) &&
4383 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4386 fn is_crate_vis(&self) -> bool {
4387 self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4390 fn is_extern_non_path(&self) -> bool {
4391 self.token.is_keyword(keywords::Extern) && self.look_ahead(1, |t| t != &token::ModSep)
4394 fn is_existential_type_decl(&self) -> bool {
4395 self.token.is_keyword(keywords::Existential) &&
4396 self.look_ahead(1, |t| t.is_keyword(keywords::Type))
4399 fn is_auto_trait_item(&mut self) -> bool {
4401 (self.token.is_keyword(keywords::Auto)
4402 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
4403 || // unsafe auto trait
4404 (self.token.is_keyword(keywords::Unsafe) &&
4405 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
4406 self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
4409 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4410 -> PResult<'a, Option<P<Item>>> {
4411 let token_lo = self.span;
4412 let (ident, def) = match self.token {
4413 token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
4415 let ident = self.parse_ident()?;
4416 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4417 match self.parse_token_tree() {
4418 TokenTree::Delimited(_, ref delimited) => delimited.stream(),
4419 _ => unreachable!(),
4421 } else if self.check(&token::OpenDelim(token::Paren)) {
4422 let args = self.parse_token_tree();
4423 let body = if self.check(&token::OpenDelim(token::Brace)) {
4424 self.parse_token_tree()
4429 TokenStream::concat(vec![
4431 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
4439 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4441 token::Ident(ident, _) if ident.name == "macro_rules" &&
4442 self.look_ahead(1, |t| *t == token::Not) => {
4443 let prev_span = self.prev_span;
4444 self.complain_if_pub_macro(&vis.node, prev_span);
4448 let ident = self.parse_ident()?;
4449 let (delim, tokens) = self.expect_delimited_token_tree()?;
4450 if delim != MacDelimiter::Brace {
4451 if !self.eat(&token::Semi) {
4452 let msg = "macros that expand to items must either \
4453 be surrounded with braces or followed by a semicolon";
4454 self.span_err(self.prev_span, msg);
4458 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4460 _ => return Ok(None),
4463 let span = lo.to(self.prev_span);
4464 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4467 fn parse_stmt_without_recovery(&mut self,
4468 macro_legacy_warnings: bool)
4469 -> PResult<'a, Option<Stmt>> {
4470 maybe_whole!(self, NtStmt, |x| Some(x));
4472 let attrs = self.parse_outer_attributes()?;
4475 Ok(Some(if self.eat_keyword(keywords::Let) {
4477 id: ast::DUMMY_NODE_ID,
4478 node: StmtKind::Local(self.parse_local(attrs.into())?),
4479 span: lo.to(self.prev_span),
4481 } else if let Some(macro_def) = self.eat_macro_def(
4483 &codemap::respan(lo, VisibilityKind::Inherited),
4487 id: ast::DUMMY_NODE_ID,
4488 node: StmtKind::Item(macro_def),
4489 span: lo.to(self.prev_span),
4491 // Starts like a simple path, being careful to avoid contextual keywords
4492 // such as a union items, item with `crate` visibility or auto trait items.
4493 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4494 // like a path (1 token), but it fact not a path.
4495 // `union::b::c` - path, `union U { ... }` - not a path.
4496 // `crate::b::c` - path, `crate struct S;` - not a path.
4497 // `extern::b::c` - path, `extern crate c;` - not a path.
4498 } else if self.token.is_path_start() &&
4499 !self.token.is_qpath_start() &&
4500 !self.is_union_item() &&
4501 !self.is_crate_vis() &&
4502 !self.is_extern_non_path() &&
4503 !self.is_existential_type_decl() &&
4504 !self.is_auto_trait_item() {
4505 let pth = self.parse_path(PathStyle::Expr)?;
4507 if !self.eat(&token::Not) {
4508 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4509 self.parse_struct_expr(lo, pth, ThinVec::new())?
4511 let hi = self.prev_span;
4512 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4515 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4516 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4517 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4520 return Ok(Some(Stmt {
4521 id: ast::DUMMY_NODE_ID,
4522 node: StmtKind::Expr(expr),
4523 span: lo.to(self.prev_span),
4527 // it's a macro invocation
4528 let id = match self.token {
4529 token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
4530 _ => self.parse_ident()?,
4533 // check that we're pointing at delimiters (need to check
4534 // again after the `if`, because of `parse_ident`
4535 // consuming more tokens).
4537 token::OpenDelim(_) => {}
4539 // we only expect an ident if we didn't parse one
4541 let ident_str = if id.name == keywords::Invalid.name() {
4546 let tok_str = self.this_token_to_string();
4547 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found `{}`",
4550 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
4555 let (delim, tts) = self.expect_delimited_token_tree()?;
4556 let hi = self.prev_span;
4558 let style = if delim == MacDelimiter::Brace {
4559 MacStmtStyle::Braces
4561 MacStmtStyle::NoBraces
4564 if id.name == keywords::Invalid.name() {
4565 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
4566 let node = if delim == MacDelimiter::Brace ||
4567 self.token == token::Semi || self.token == token::Eof {
4568 StmtKind::Mac(P((mac, style, attrs.into())))
4570 // We used to incorrectly stop parsing macro-expanded statements here.
4571 // If the next token will be an error anyway but could have parsed with the
4572 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
4573 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
4574 // These can continue an expression, so we can't stop parsing and warn.
4575 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
4576 token::BinOp(token::Minus) | token::BinOp(token::Star) |
4577 token::BinOp(token::And) | token::BinOp(token::Or) |
4578 token::AndAnd | token::OrOr |
4579 token::DotDot | token::DotDotDot | token::DotDotEq => false,
4582 self.warn_missing_semicolon();
4583 StmtKind::Mac(P((mac, style, attrs.into())))
4585 let e = self.mk_mac_expr(lo.to(hi), mac.node, ThinVec::new());
4586 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
4587 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
4591 id: ast::DUMMY_NODE_ID,
4596 // if it has a special ident, it's definitely an item
4598 // Require a semicolon or braces.
4599 if style != MacStmtStyle::Braces {
4600 if !self.eat(&token::Semi) {
4601 self.span_err(self.prev_span,
4602 "macros that expand to items must \
4603 either be surrounded with braces or \
4604 followed by a semicolon");
4607 let span = lo.to(hi);
4609 id: ast::DUMMY_NODE_ID,
4611 node: StmtKind::Item({
4613 span, id /*id is good here*/,
4614 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
4615 respan(lo, VisibilityKind::Inherited),
4621 // FIXME: Bad copy of attrs
4622 let old_directory_ownership =
4623 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
4624 let item = self.parse_item_(attrs.clone(), false, true)?;
4625 self.directory.ownership = old_directory_ownership;
4629 id: ast::DUMMY_NODE_ID,
4630 span: lo.to(i.span),
4631 node: StmtKind::Item(i),
4634 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
4635 if !attrs.is_empty() {
4636 if s.prev_token_kind == PrevTokenKind::DocComment {
4637 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
4638 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
4639 s.span_err(s.span, "expected statement after outer attribute");
4644 // Do not attempt to parse an expression if we're done here.
4645 if self.token == token::Semi {
4646 unused_attrs(&attrs, self);
4651 if self.token == token::CloseDelim(token::Brace) {
4652 unused_attrs(&attrs, self);
4656 // Remainder are line-expr stmts.
4657 let e = self.parse_expr_res(
4658 Restrictions::STMT_EXPR, Some(attrs.into()))?;
4660 id: ast::DUMMY_NODE_ID,
4661 span: lo.to(e.span),
4662 node: StmtKind::Expr(e),
4669 /// Is this expression a successfully-parsed statement?
4670 fn expr_is_complete(&mut self, e: &Expr) -> bool {
4671 self.restrictions.contains(Restrictions::STMT_EXPR) &&
4672 !classify::expr_requires_semi_to_be_stmt(e)
4675 /// Parse a block. No inner attrs are allowed.
4676 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
4677 maybe_whole!(self, NtBlock, |x| x);
4681 if !self.eat(&token::OpenDelim(token::Brace)) {
4683 let tok = self.this_token_to_string();
4684 let mut e = self.span_fatal(sp, &format!("expected `{{`, found `{}`", tok));
4686 // Check to see if the user has written something like
4691 // Which is valid in other languages, but not Rust.
4692 match self.parse_stmt_without_recovery(false) {
4694 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) {
4695 // if the next token is an open brace (e.g., `if a b {`), the place-
4696 // inside-a-block suggestion would be more likely wrong than right
4699 let mut stmt_span = stmt.span;
4700 // expand the span to include the semicolon, if it exists
4701 if self.eat(&token::Semi) {
4702 stmt_span = stmt_span.with_hi(self.prev_span.hi());
4704 let sugg = pprust::to_string(|s| {
4705 use print::pprust::{PrintState, INDENT_UNIT};
4706 s.ibox(INDENT_UNIT)?;
4708 s.print_stmt(&stmt)?;
4709 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
4711 e.span_suggestion_with_applicability(
4713 "try placing this code inside a block",
4715 // speculative, has been misleading in the past (closed Issue #46836)
4716 Applicability::MaybeIncorrect
4720 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4721 self.cancel(&mut e);
4728 self.parse_block_tail(lo, BlockCheckMode::Default)
4731 /// Parse a block. Inner attrs are allowed.
4732 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
4733 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
4736 self.expect(&token::OpenDelim(token::Brace))?;
4737 Ok((self.parse_inner_attributes()?,
4738 self.parse_block_tail(lo, BlockCheckMode::Default)?))
4741 /// Parse the rest of a block expression or function body
4742 /// Precondition: already parsed the '{'.
4743 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
4744 let mut stmts = vec![];
4745 let mut recovered = false;
4747 while !self.eat(&token::CloseDelim(token::Brace)) {
4748 let stmt = match self.parse_full_stmt(false) {
4751 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
4752 self.eat(&token::CloseDelim(token::Brace));
4758 if let Some(stmt) = stmt {
4760 } else if self.token == token::Eof {
4763 // Found only `;` or `}`.
4769 id: ast::DUMMY_NODE_ID,
4771 span: lo.to(self.prev_span),
4776 /// Parse a statement, including the trailing semicolon.
4777 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
4778 // skip looking for a trailing semicolon when we have an interpolated statement
4779 maybe_whole!(self, NtStmt, |x| Some(x));
4781 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
4783 None => return Ok(None),
4787 StmtKind::Expr(ref expr) if self.token != token::Eof => {
4788 // expression without semicolon
4789 if classify::expr_requires_semi_to_be_stmt(expr) {
4790 // Just check for errors and recover; do not eat semicolon yet.
4792 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
4795 self.recover_stmt();
4799 StmtKind::Local(..) => {
4800 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
4801 if macro_legacy_warnings && self.token != token::Semi {
4802 self.warn_missing_semicolon();
4804 self.expect_one_of(&[], &[token::Semi])?;
4810 if self.eat(&token::Semi) {
4811 stmt = stmt.add_trailing_semicolon();
4814 stmt.span = stmt.span.with_hi(self.prev_span.hi());
4818 fn warn_missing_semicolon(&self) {
4819 self.diagnostic().struct_span_warn(self.span, {
4820 &format!("expected `;`, found `{}`", self.this_token_to_string())
4822 "This was erroneously allowed and will become a hard error in a future release"
4826 fn err_dotdotdot_syntax(&self, span: Span) {
4827 self.diagnostic().struct_span_err(span, {
4828 "unexpected token: `...`"
4829 }).span_suggestion_with_applicability(
4830 span, "use `..` for an exclusive range", "..".to_owned(),
4831 Applicability::MaybeIncorrect
4832 ).span_suggestion_with_applicability(
4833 span, "or `..=` for an inclusive range", "..=".to_owned(),
4834 Applicability::MaybeIncorrect
4838 // Parse bounds of a type parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4839 // BOUND = TY_BOUND | LT_BOUND
4840 // LT_BOUND = LIFETIME (e.g. `'a`)
4841 // TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
4842 // TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g. `?for<'a: 'b> m::Trait<'a>`)
4843 fn parse_generic_bounds_common(&mut self, allow_plus: bool) -> PResult<'a, GenericBounds> {
4844 let mut bounds = Vec::new();
4846 // This needs to be syncronized with `Token::can_begin_bound`.
4847 let is_bound_start = self.check_path() || self.check_lifetime() ||
4848 self.check(&token::Question) ||
4849 self.check_keyword(keywords::For) ||
4850 self.check(&token::OpenDelim(token::Paren));
4853 let has_parens = self.eat(&token::OpenDelim(token::Paren));
4854 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
4855 if self.token.is_lifetime() {
4856 if let Some(question_span) = question {
4857 self.span_err(question_span,
4858 "`?` may only modify trait bounds, not lifetime bounds");
4860 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
4862 self.expect(&token::CloseDelim(token::Paren))?;
4863 self.span_err(self.prev_span,
4864 "parenthesized lifetime bounds are not supported");
4867 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
4868 let path = self.parse_path(PathStyle::Type)?;
4870 self.expect(&token::CloseDelim(token::Paren))?;
4872 let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
4873 let modifier = if question.is_some() {
4874 TraitBoundModifier::Maybe
4876 TraitBoundModifier::None
4878 bounds.push(GenericBound::Trait(poly_trait, modifier));
4884 if !allow_plus || !self.eat_plus() {
4892 fn parse_generic_bounds(&mut self) -> PResult<'a, GenericBounds> {
4893 self.parse_generic_bounds_common(true)
4896 // Parse bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4897 // BOUND = LT_BOUND (e.g. `'a`)
4898 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
4899 let mut lifetimes = Vec::new();
4900 while self.check_lifetime() {
4901 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
4903 if !self.eat_plus() {
4910 /// Matches typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?
4911 fn parse_ty_param(&mut self,
4912 preceding_attrs: Vec<Attribute>)
4913 -> PResult<'a, GenericParam> {
4914 let ident = self.parse_ident()?;
4916 // Parse optional colon and param bounds.
4917 let bounds = if self.eat(&token::Colon) {
4918 self.parse_generic_bounds()?
4923 let default = if self.eat(&token::Eq) {
4924 Some(self.parse_ty()?)
4931 id: ast::DUMMY_NODE_ID,
4932 attrs: preceding_attrs.into(),
4934 kind: GenericParamKind::Type {
4940 /// Parses the following grammar:
4941 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
4942 fn parse_trait_item_assoc_ty(&mut self)
4943 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
4944 let ident = self.parse_ident()?;
4945 let mut generics = self.parse_generics()?;
4947 // Parse optional colon and param bounds.
4948 let bounds = if self.eat(&token::Colon) {
4949 self.parse_generic_bounds()?
4953 generics.where_clause = self.parse_where_clause()?;
4955 let default = if self.eat(&token::Eq) {
4956 Some(self.parse_ty()?)
4960 self.expect(&token::Semi)?;
4962 Ok((ident, TraitItemKind::Type(bounds, default), generics))
4965 /// Parses (possibly empty) list of lifetime and type parameters, possibly including
4966 /// trailing comma and erroneous trailing attributes.
4967 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
4968 let mut params = Vec::new();
4969 let mut seen_ty_param = false;
4971 let attrs = self.parse_outer_attributes()?;
4972 if self.check_lifetime() {
4973 let lifetime = self.expect_lifetime();
4974 // Parse lifetime parameter.
4975 let bounds = if self.eat(&token::Colon) {
4976 self.parse_lt_param_bounds()
4980 params.push(ast::GenericParam {
4981 ident: lifetime.ident,
4983 attrs: attrs.into(),
4985 kind: ast::GenericParamKind::Lifetime,
4988 self.span_err(self.prev_span,
4989 "lifetime parameters must be declared prior to type parameters");
4991 } else if self.check_ident() {
4992 // Parse type parameter.
4993 params.push(self.parse_ty_param(attrs)?);
4994 seen_ty_param = true;
4996 // Check for trailing attributes and stop parsing.
4997 if !attrs.is_empty() {
4998 let param_kind = if seen_ty_param { "type" } else { "lifetime" };
4999 self.span_err(attrs[0].span,
5000 &format!("trailing attribute after {} parameters", param_kind));
5005 if !self.eat(&token::Comma) {
5012 /// Parse a set of optional generic type parameter declarations. Where
5013 /// clauses are not parsed here, and must be added later via
5014 /// `parse_where_clause()`.
5016 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5017 /// | ( < lifetimes , typaramseq ( , )? > )
5018 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5019 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5020 maybe_whole!(self, NtGenerics, |x| x);
5022 let span_lo = self.span;
5024 let params = self.parse_generic_params()?;
5028 where_clause: WhereClause {
5029 id: ast::DUMMY_NODE_ID,
5030 predicates: Vec::new(),
5031 span: syntax_pos::DUMMY_SP,
5033 span: span_lo.to(self.prev_span),
5036 Ok(ast::Generics::default())
5040 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5041 /// possibly including trailing comma.
5042 fn parse_generic_args(&mut self)
5043 -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5044 let mut args = Vec::new();
5045 let mut bindings = Vec::new();
5046 let mut seen_type = false;
5047 let mut seen_binding = false;
5049 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5050 // Parse lifetime argument.
5051 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5052 if seen_type || seen_binding {
5053 self.span_err(self.prev_span,
5054 "lifetime parameters must be declared prior to type parameters");
5056 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
5057 // Parse associated type binding.
5059 let ident = self.parse_ident()?;
5061 let ty = self.parse_ty()?;
5062 bindings.push(TypeBinding {
5063 id: ast::DUMMY_NODE_ID,
5066 span: lo.to(self.prev_span),
5068 seen_binding = true;
5069 } else if self.check_type() {
5070 // Parse type argument.
5071 let ty_param = self.parse_ty()?;
5073 self.span_err(ty_param.span,
5074 "type parameters must be declared prior to associated type bindings");
5076 args.push(GenericArg::Type(ty_param));
5082 if !self.eat(&token::Comma) {
5086 Ok((args, bindings))
5089 /// Parses an optional `where` clause and places it in `generics`.
5091 /// ```ignore (only-for-syntax-highlight)
5092 /// where T : Trait<U, V> + 'b, 'a : 'b
5094 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5095 maybe_whole!(self, NtWhereClause, |x| x);
5097 let mut where_clause = WhereClause {
5098 id: ast::DUMMY_NODE_ID,
5099 predicates: Vec::new(),
5100 span: syntax_pos::DUMMY_SP,
5103 if !self.eat_keyword(keywords::Where) {
5104 return Ok(where_clause);
5106 let lo = self.prev_span;
5108 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5109 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5110 // change we parse those generics now, but report an error.
5111 if self.choose_generics_over_qpath() {
5112 let generics = self.parse_generics()?;
5113 self.span_err(generics.span,
5114 "generic parameters on `where` clauses are reserved for future use");
5119 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5120 let lifetime = self.expect_lifetime();
5121 // Bounds starting with a colon are mandatory, but possibly empty.
5122 self.expect(&token::Colon)?;
5123 let bounds = self.parse_lt_param_bounds();
5124 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5125 ast::WhereRegionPredicate {
5126 span: lo.to(self.prev_span),
5131 } else if self.check_type() {
5132 // Parse optional `for<'a, 'b>`.
5133 // This `for` is parsed greedily and applies to the whole predicate,
5134 // the bounded type can have its own `for` applying only to it.
5135 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
5136 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
5137 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
5138 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5140 // Parse type with mandatory colon and (possibly empty) bounds,
5141 // or with mandatory equality sign and the second type.
5142 let ty = self.parse_ty()?;
5143 if self.eat(&token::Colon) {
5144 let bounds = self.parse_generic_bounds()?;
5145 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5146 ast::WhereBoundPredicate {
5147 span: lo.to(self.prev_span),
5148 bound_generic_params: lifetime_defs,
5153 // FIXME: Decide what should be used here, `=` or `==`.
5154 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5155 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5156 let rhs_ty = self.parse_ty()?;
5157 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5158 ast::WhereEqPredicate {
5159 span: lo.to(self.prev_span),
5162 id: ast::DUMMY_NODE_ID,
5166 return self.unexpected();
5172 if !self.eat(&token::Comma) {
5177 where_clause.span = lo.to(self.prev_span);
5181 fn parse_fn_args(&mut self, named_args: bool, allow_variadic: bool)
5182 -> PResult<'a, (Vec<Arg> , bool)> {
5184 let mut variadic = false;
5185 let args: Vec<Option<Arg>> =
5186 self.parse_unspanned_seq(
5187 &token::OpenDelim(token::Paren),
5188 &token::CloseDelim(token::Paren),
5189 SeqSep::trailing_allowed(token::Comma),
5191 if p.token == token::DotDotDot {
5195 if p.token != token::CloseDelim(token::Paren) {
5198 "`...` must be last in argument list for variadic function");
5202 let span = p.prev_span;
5203 if p.token == token::CloseDelim(token::Paren) {
5204 // continue parsing to present any further errors
5207 "only foreign functions are allowed to be variadic"
5209 Ok(Some(dummy_arg(span)))
5211 // this function definition looks beyond recovery, stop parsing
5213 "only foreign functions are allowed to be variadic");
5218 match p.parse_arg_general(named_args) {
5219 Ok(arg) => Ok(Some(arg)),
5222 let lo = p.prev_span;
5223 // Skip every token until next possible arg or end.
5224 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5225 // Create a placeholder argument for proper arg count (#34264).
5226 let span = lo.to(p.prev_span);
5227 Ok(Some(dummy_arg(span)))
5234 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5236 if variadic && args.is_empty() {
5238 "variadic function must be declared with at least one named argument");
5241 Ok((args, variadic))
5244 /// Parse the argument list and result type of a function declaration
5245 fn parse_fn_decl(&mut self, allow_variadic: bool) -> PResult<'a, P<FnDecl>> {
5247 let (args, variadic) = self.parse_fn_args(true, allow_variadic)?;
5248 let ret_ty = self.parse_ret_ty(true)?;
5257 /// Returns the parsed optional self argument and whether a self shortcut was used.
5258 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
5259 let expect_ident = |this: &mut Self| match this.token {
5260 // Preserve hygienic context.
5261 token::Ident(ident, _) =>
5262 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
5265 let isolated_self = |this: &mut Self, n| {
5266 this.look_ahead(n, |t| t.is_keyword(keywords::SelfValue)) &&
5267 this.look_ahead(n + 1, |t| t != &token::ModSep)
5270 // Parse optional self parameter of a method.
5271 // Only a limited set of initial token sequences is considered self parameters, anything
5272 // else is parsed as a normal function parameter list, so some lookahead is required.
5273 let eself_lo = self.span;
5274 let (eself, eself_ident, eself_hi) = match self.token {
5275 token::BinOp(token::And) => {
5281 (if isolated_self(self, 1) {
5283 SelfKind::Region(None, Mutability::Immutable)
5284 } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
5285 isolated_self(self, 2) {
5288 SelfKind::Region(None, Mutability::Mutable)
5289 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5290 isolated_self(self, 2) {
5292 let lt = self.expect_lifetime();
5293 SelfKind::Region(Some(lt), Mutability::Immutable)
5294 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5295 self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
5296 isolated_self(self, 3) {
5298 let lt = self.expect_lifetime();
5300 SelfKind::Region(Some(lt), Mutability::Mutable)
5303 }, expect_ident(self), self.prev_span)
5305 token::BinOp(token::Star) => {
5310 // Emit special error for `self` cases.
5311 (if isolated_self(self, 1) {
5313 self.span_err(self.span, "cannot pass `self` by raw pointer");
5314 SelfKind::Value(Mutability::Immutable)
5315 } else if self.look_ahead(1, |t| t.is_mutability()) &&
5316 isolated_self(self, 2) {
5319 self.span_err(self.span, "cannot pass `self` by raw pointer");
5320 SelfKind::Value(Mutability::Immutable)
5323 }, expect_ident(self), self.prev_span)
5325 token::Ident(..) => {
5326 if isolated_self(self, 0) {
5329 let eself_ident = expect_ident(self);
5330 let eself_hi = self.prev_span;
5331 (if self.eat(&token::Colon) {
5332 let ty = self.parse_ty()?;
5333 SelfKind::Explicit(ty, Mutability::Immutable)
5335 SelfKind::Value(Mutability::Immutable)
5336 }, eself_ident, eself_hi)
5337 } else if self.token.is_keyword(keywords::Mut) &&
5338 isolated_self(self, 1) {
5342 let eself_ident = expect_ident(self);
5343 let eself_hi = self.prev_span;
5344 (if self.eat(&token::Colon) {
5345 let ty = self.parse_ty()?;
5346 SelfKind::Explicit(ty, Mutability::Mutable)
5348 SelfKind::Value(Mutability::Mutable)
5349 }, eself_ident, eself_hi)
5354 _ => return Ok(None),
5357 let eself = codemap::respan(eself_lo.to(eself_hi), eself);
5358 Ok(Some(Arg::from_self(eself, eself_ident)))
5361 /// Parse the parameter list and result type of a function that may have a `self` parameter.
5362 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
5363 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
5365 self.expect(&token::OpenDelim(token::Paren))?;
5367 // Parse optional self argument
5368 let self_arg = self.parse_self_arg()?;
5370 // Parse the rest of the function parameter list.
5371 let sep = SeqSep::trailing_allowed(token::Comma);
5372 let fn_inputs = if let Some(self_arg) = self_arg {
5373 if self.check(&token::CloseDelim(token::Paren)) {
5375 } else if self.eat(&token::Comma) {
5376 let mut fn_inputs = vec![self_arg];
5377 fn_inputs.append(&mut self.parse_seq_to_before_end(
5378 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5382 return self.unexpected();
5385 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5388 // Parse closing paren and return type.
5389 self.expect(&token::CloseDelim(token::Paren))?;
5392 output: self.parse_ret_ty(true)?,
5397 // parse the |arg, arg| header on a lambda
5398 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
5399 let inputs_captures = {
5400 if self.eat(&token::OrOr) {
5403 self.expect(&token::BinOp(token::Or))?;
5404 let args = self.parse_seq_to_before_tokens(
5405 &[&token::BinOp(token::Or), &token::OrOr],
5406 SeqSep::trailing_allowed(token::Comma),
5407 TokenExpectType::NoExpect,
5408 |p| p.parse_fn_block_arg()
5414 let output = self.parse_ret_ty(true)?;
5417 inputs: inputs_captures,
5423 /// Parse the name and optional generic types of a function header.
5424 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
5425 let id = self.parse_ident()?;
5426 let generics = self.parse_generics()?;
5430 fn mk_item(&mut self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
5431 attrs: Vec<Attribute>) -> P<Item> {
5435 id: ast::DUMMY_NODE_ID,
5443 /// Parse an item-position function declaration.
5444 fn parse_item_fn(&mut self,
5447 constness: Spanned<Constness>,
5449 -> PResult<'a, ItemInfo> {
5450 let (ident, mut generics) = self.parse_fn_header()?;
5451 let decl = self.parse_fn_decl(false)?;
5452 generics.where_clause = self.parse_where_clause()?;
5453 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5454 let header = FnHeader { unsafety, asyncness, constness, abi };
5455 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
5458 /// true if we are looking at `const ID`, false for things like `const fn` etc
5459 fn is_const_item(&mut self) -> bool {
5460 self.token.is_keyword(keywords::Const) &&
5461 !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
5462 !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
5465 /// parses all the "front matter" for a `fn` declaration, up to
5466 /// and including the `fn` keyword:
5470 /// - `const unsafe fn`
5473 fn parse_fn_front_matter(&mut self)
5481 let is_const_fn = self.eat_keyword(keywords::Const);
5482 let const_span = self.prev_span;
5483 let unsafety = self.parse_unsafety();
5484 let asyncness = self.parse_asyncness();
5485 let (constness, unsafety, abi) = if is_const_fn {
5486 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
5488 let abi = if self.eat_keyword(keywords::Extern) {
5489 self.parse_opt_abi()?.unwrap_or(Abi::C)
5493 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
5495 self.expect_keyword(keywords::Fn)?;
5496 Ok((constness, unsafety, asyncness, abi))
5499 /// Parse an impl item.
5500 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
5501 maybe_whole!(self, NtImplItem, |x| x);
5502 let attrs = self.parse_outer_attributes()?;
5503 let (mut item, tokens) = self.collect_tokens(|this| {
5504 this.parse_impl_item_(at_end, attrs)
5507 // See `parse_item` for why this clause is here.
5508 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
5509 item.tokens = Some(tokens);
5514 fn parse_impl_item_(&mut self,
5516 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
5518 let vis = self.parse_visibility(false)?;
5519 let defaultness = self.parse_defaultness();
5520 let (name, node, generics) = if let Some(type_) = self.eat_type() {
5521 let (name, alias, generics) = type_?;
5522 let kind = match alias {
5523 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
5524 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
5526 (name, kind, generics)
5527 } else if self.is_const_item() {
5528 // This parses the grammar:
5529 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
5530 self.expect_keyword(keywords::Const)?;
5531 let name = self.parse_ident()?;
5532 self.expect(&token::Colon)?;
5533 let typ = self.parse_ty()?;
5534 self.expect(&token::Eq)?;
5535 let expr = self.parse_expr()?;
5536 self.expect(&token::Semi)?;
5537 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
5539 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
5540 attrs.extend(inner_attrs);
5541 (name, node, generics)
5545 id: ast::DUMMY_NODE_ID,
5546 span: lo.to(self.prev_span),
5557 fn complain_if_pub_macro(&mut self, vis: &VisibilityKind, sp: Span) {
5558 if let Err(mut err) = self.complain_if_pub_macro_diag(vis, sp) {
5563 fn complain_if_pub_macro_diag(&mut self, vis: &VisibilityKind, sp: Span) -> PResult<'a, ()> {
5565 VisibilityKind::Inherited => Ok(()),
5567 let is_macro_rules: bool = match self.token {
5568 token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
5572 let mut err = self.diagnostic()
5573 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
5574 err.span_suggestion_with_applicability(
5576 "try exporting the macro",
5577 "#[macro_export]".to_owned(),
5578 Applicability::MaybeIncorrect // speculative
5582 let mut err = self.diagnostic()
5583 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
5584 err.help("try adjusting the macro to put `pub` inside the invocation");
5591 fn missing_assoc_item_kind_err(&mut self, item_type: &str, prev_span: Span)
5592 -> DiagnosticBuilder<'a>
5594 let expected_kinds = if item_type == "extern" {
5595 "missing `fn`, `type`, or `static`"
5597 "missing `fn`, `type`, or `const`"
5600 // Given this code `path(`, it seems like this is not
5601 // setting the visibility of a macro invocation, but rather
5602 // a mistyped method declaration.
5603 // Create a diagnostic pointing out that `fn` is missing.
5605 // x | pub path(&self) {
5606 // | ^ missing `fn`, `type`, or `const`
5608 // ^^ `sp` below will point to this
5609 let sp = prev_span.between(self.prev_span);
5610 let mut err = self.diagnostic().struct_span_err(
5612 &format!("{} for {}-item declaration",
5613 expected_kinds, item_type));
5614 err.span_label(sp, expected_kinds);
5618 /// Parse a method or a macro invocation in a trait impl.
5619 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
5620 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
5621 ast::ImplItemKind)> {
5622 // code copied from parse_macro_use_or_failure... abstraction!
5623 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
5625 Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
5626 ast::ImplItemKind::Macro(mac)))
5628 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
5629 let ident = self.parse_ident()?;
5630 let mut generics = self.parse_generics()?;
5631 let decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
5632 generics.where_clause = self.parse_where_clause()?;
5634 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5635 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
5636 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
5637 ast::MethodSig { header, decl },
5643 /// Parse `trait Foo { ... }` or `trait Foo = Bar;`
5644 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
5645 let ident = self.parse_ident()?;
5646 let mut tps = self.parse_generics()?;
5648 // Parse optional colon and supertrait bounds.
5649 let bounds = if self.eat(&token::Colon) {
5650 self.parse_generic_bounds()?
5655 if self.eat(&token::Eq) {
5656 // it's a trait alias
5657 let bounds = self.parse_generic_bounds()?;
5658 tps.where_clause = self.parse_where_clause()?;
5659 self.expect(&token::Semi)?;
5660 if unsafety != Unsafety::Normal {
5661 self.span_err(self.prev_span, "trait aliases cannot be unsafe");
5663 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
5665 // it's a normal trait
5666 tps.where_clause = self.parse_where_clause()?;
5667 self.expect(&token::OpenDelim(token::Brace))?;
5668 let mut trait_items = vec![];
5669 while !self.eat(&token::CloseDelim(token::Brace)) {
5670 let mut at_end = false;
5671 match self.parse_trait_item(&mut at_end) {
5672 Ok(item) => trait_items.push(item),
5676 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5681 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
5685 fn choose_generics_over_qpath(&self) -> bool {
5686 // There's an ambiguity between generic parameters and qualified paths in impls.
5687 // If we see `<` it may start both, so we have to inspect some following tokens.
5688 // The following combinations can only start generics,
5689 // but not qualified paths (with one exception):
5690 // `<` `>` - empty generic parameters
5691 // `<` `#` - generic parameters with attributes
5692 // `<` (LIFETIME|IDENT) `>` - single generic parameter
5693 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
5694 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
5695 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
5696 // The only truly ambiguous case is
5697 // `<` IDENT `>` `::` IDENT ...
5698 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
5699 // because this is what almost always expected in practice, qualified paths in impls
5700 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
5701 self.token == token::Lt &&
5702 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
5703 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
5704 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
5705 t == &token::Colon || t == &token::Eq))
5708 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
5709 self.expect(&token::OpenDelim(token::Brace))?;
5710 let attrs = self.parse_inner_attributes()?;
5712 let mut impl_items = Vec::new();
5713 while !self.eat(&token::CloseDelim(token::Brace)) {
5714 let mut at_end = false;
5715 match self.parse_impl_item(&mut at_end) {
5716 Ok(impl_item) => impl_items.push(impl_item),
5720 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5725 Ok((impl_items, attrs))
5728 /// Parses an implementation item, `impl` keyword is already parsed.
5729 /// impl<'a, T> TYPE { /* impl items */ }
5730 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
5731 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
5732 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
5733 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
5734 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
5735 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
5736 -> PResult<'a, ItemInfo> {
5737 // First, parse generic parameters if necessary.
5738 let mut generics = if self.choose_generics_over_qpath() {
5739 self.parse_generics()?
5741 ast::Generics::default()
5744 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
5745 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
5747 ast::ImplPolarity::Negative
5749 ast::ImplPolarity::Positive
5752 // Parse both types and traits as a type, then reinterpret if necessary.
5753 let ty_first = self.parse_ty()?;
5755 // If `for` is missing we try to recover.
5756 let has_for = self.eat_keyword(keywords::For);
5757 let missing_for_span = self.prev_span.between(self.span);
5759 let ty_second = if self.token == token::DotDot {
5760 // We need to report this error after `cfg` expansion for compatibility reasons
5761 self.bump(); // `..`, do not add it to expected tokens
5762 Some(P(Ty { node: TyKind::Err, span: self.prev_span, id: ast::DUMMY_NODE_ID }))
5763 } else if has_for || self.token.can_begin_type() {
5764 Some(self.parse_ty()?)
5769 generics.where_clause = self.parse_where_clause()?;
5771 let (impl_items, attrs) = self.parse_impl_body()?;
5773 let item_kind = match ty_second {
5774 Some(ty_second) => {
5775 // impl Trait for Type
5777 self.span_err(missing_for_span, "missing `for` in a trait impl");
5780 let ty_first = ty_first.into_inner();
5781 let path = match ty_first.node {
5782 // This notably includes paths passed through `ty` macro fragments (#46438).
5783 TyKind::Path(None, path) => path,
5785 self.span_err(ty_first.span, "expected a trait, found type");
5786 ast::Path::from_ident(Ident::new(keywords::Invalid.name(), ty_first.span))
5789 let trait_ref = TraitRef { path, ref_id: ty_first.id };
5791 ItemKind::Impl(unsafety, polarity, defaultness,
5792 generics, Some(trait_ref), ty_second, impl_items)
5796 ItemKind::Impl(unsafety, polarity, defaultness,
5797 generics, None, ty_first, impl_items)
5801 Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
5804 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
5805 if self.eat_keyword(keywords::For) {
5807 let params = self.parse_generic_params()?;
5809 // We rely on AST validation to rule out invalid cases: There must not be type
5810 // parameters, and the lifetime parameters must not have bounds.
5817 /// Parse struct Foo { ... }
5818 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
5819 let class_name = self.parse_ident()?;
5821 let mut generics = self.parse_generics()?;
5823 // There is a special case worth noting here, as reported in issue #17904.
5824 // If we are parsing a tuple struct it is the case that the where clause
5825 // should follow the field list. Like so:
5827 // struct Foo<T>(T) where T: Copy;
5829 // If we are parsing a normal record-style struct it is the case
5830 // that the where clause comes before the body, and after the generics.
5831 // So if we look ahead and see a brace or a where-clause we begin
5832 // parsing a record style struct.
5834 // Otherwise if we look ahead and see a paren we parse a tuple-style
5837 let vdata = if self.token.is_keyword(keywords::Where) {
5838 generics.where_clause = self.parse_where_clause()?;
5839 if self.eat(&token::Semi) {
5840 // If we see a: `struct Foo<T> where T: Copy;` style decl.
5841 VariantData::Unit(ast::DUMMY_NODE_ID)
5843 // If we see: `struct Foo<T> where T: Copy { ... }`
5844 VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
5846 // No `where` so: `struct Foo<T>;`
5847 } else if self.eat(&token::Semi) {
5848 VariantData::Unit(ast::DUMMY_NODE_ID)
5849 // Record-style struct definition
5850 } else if self.token == token::OpenDelim(token::Brace) {
5851 VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
5852 // Tuple-style struct definition with optional where-clause.
5853 } else if self.token == token::OpenDelim(token::Paren) {
5854 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
5855 generics.where_clause = self.parse_where_clause()?;
5856 self.expect(&token::Semi)?;
5859 let token_str = self.this_token_to_string();
5860 let mut err = self.fatal(&format!(
5861 "expected `where`, `{{`, `(`, or `;` after struct name, found `{}`",
5864 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
5868 Ok((class_name, ItemKind::Struct(vdata, generics), None))
5871 /// Parse union Foo { ... }
5872 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
5873 let class_name = self.parse_ident()?;
5875 let mut generics = self.parse_generics()?;
5877 let vdata = if self.token.is_keyword(keywords::Where) {
5878 generics.where_clause = self.parse_where_clause()?;
5879 VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
5880 } else if self.token == token::OpenDelim(token::Brace) {
5881 VariantData::Struct(self.parse_record_struct_body()?, ast::DUMMY_NODE_ID)
5883 let token_str = self.this_token_to_string();
5884 let mut err = self.fatal(&format!(
5885 "expected `where` or `{{` after union name, found `{}`", token_str));
5886 err.span_label(self.span, "expected `where` or `{` after union name");
5890 Ok((class_name, ItemKind::Union(vdata, generics), None))
5893 fn consume_block(&mut self, delim: token::DelimToken) {
5894 let mut brace_depth = 0;
5895 if !self.eat(&token::OpenDelim(delim)) {
5899 if self.eat(&token::OpenDelim(delim)) {
5901 } else if self.eat(&token::CloseDelim(delim)) {
5902 if brace_depth == 0 {
5908 } else if self.eat(&token::Eof) || self.eat(&token::CloseDelim(token::NoDelim)) {
5916 fn parse_record_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
5917 let mut fields = Vec::new();
5918 if self.eat(&token::OpenDelim(token::Brace)) {
5919 while self.token != token::CloseDelim(token::Brace) {
5920 let field = self.parse_struct_decl_field().map_err(|e| {
5921 self.recover_stmt();
5925 Ok(field) => fields.push(field),
5931 self.eat(&token::CloseDelim(token::Brace));
5933 let token_str = self.this_token_to_string();
5934 let mut err = self.fatal(&format!(
5935 "expected `where`, or `{{` after struct name, found `{}`", token_str));
5936 err.span_label(self.span, "expected `where`, or `{` after struct name");
5943 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
5944 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
5945 // Unit like structs are handled in parse_item_struct function
5946 let fields = self.parse_unspanned_seq(
5947 &token::OpenDelim(token::Paren),
5948 &token::CloseDelim(token::Paren),
5949 SeqSep::trailing_allowed(token::Comma),
5951 let attrs = p.parse_outer_attributes()?;
5953 let vis = p.parse_visibility(true)?;
5954 let ty = p.parse_ty()?;
5956 span: lo.to(ty.span),
5959 id: ast::DUMMY_NODE_ID,
5968 /// Parse a structure field declaration
5969 fn parse_single_struct_field(&mut self,
5972 attrs: Vec<Attribute> )
5973 -> PResult<'a, StructField> {
5974 let mut seen_comma: bool = false;
5975 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
5976 if self.token == token::Comma {
5983 token::CloseDelim(token::Brace) => {}
5984 token::DocComment(_) => {
5985 let previous_span = self.prev_span;
5986 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
5987 self.bump(); // consume the doc comment
5988 let comma_after_doc_seen = self.eat(&token::Comma);
5989 // `seen_comma` is always false, because we are inside doc block
5990 // condition is here to make code more readable
5991 if seen_comma == false && comma_after_doc_seen == true {
5994 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
5997 if seen_comma == false {
5998 let sp = self.sess.codemap().next_point(previous_span);
5999 err.span_suggestion_with_applicability(
6001 "missing comma here",
6003 Applicability::MachineApplicable
6010 let sp = self.sess.codemap().next_point(self.prev_span);
6011 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found `{}`",
6012 self.this_token_to_string()));
6013 if self.token.is_ident() {
6014 // This is likely another field; emit the diagnostic and keep going
6015 err.span_suggestion(sp, "try adding a comma", ",".into());
6025 /// Parse an element of a struct definition
6026 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6027 let attrs = self.parse_outer_attributes()?;
6029 let vis = self.parse_visibility(false)?;
6030 self.parse_single_struct_field(lo, vis, attrs)
6033 /// Parse `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `pub(self)` for `pub(in self)`
6034 /// and `pub(super)` for `pub(in super)`. If the following element can't be a tuple (i.e. it's
6035 /// a function definition, it's not a tuple struct field) and the contents within the parens
6036 /// isn't valid, emit a proper diagnostic.
6037 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6038 maybe_whole!(self, NtVis, |x| x);
6040 self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
6041 if self.is_crate_vis() {
6042 self.bump(); // `crate`
6043 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6046 if !self.eat_keyword(keywords::Pub) {
6047 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6048 // keyword to grab a span from for inherited visibility; an empty span at the
6049 // beginning of the current token would seem to be the "Schelling span".
6050 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
6052 let lo = self.prev_span;
6054 if self.check(&token::OpenDelim(token::Paren)) {
6055 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6056 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6057 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6058 // by the following tokens.
6059 if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) {
6062 self.bump(); // `crate`
6063 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6065 lo.to(self.prev_span),
6066 VisibilityKind::Crate(CrateSugar::PubCrate),
6069 } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
6072 self.bump(); // `in`
6073 let path = self.parse_path(PathStyle::Mod)?; // `path`
6074 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6075 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6077 id: ast::DUMMY_NODE_ID,
6080 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6081 self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
6082 t.is_keyword(keywords::SelfValue))
6084 // `pub(self)` or `pub(super)`
6086 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6087 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6088 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6090 id: ast::DUMMY_NODE_ID,
6093 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6094 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6096 let msg = "incorrect visibility restriction";
6097 let suggestion = r##"some possible visibility restrictions are:
6098 `pub(crate)`: visible only on the current crate
6099 `pub(super)`: visible only in the current module's parent
6100 `pub(in path::to::module)`: visible only on the specified path"##;
6101 let path = self.parse_path(PathStyle::Mod)?;
6102 let sp = self.prev_span;
6103 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6104 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6105 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6106 err.help(suggestion);
6107 err.span_suggestion_with_applicability(
6108 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6110 err.emit(); // emit diagnostic, but continue with public visibility
6114 Ok(respan(lo, VisibilityKind::Public))
6117 /// Parse defaultness: `default` or nothing.
6118 fn parse_defaultness(&mut self) -> Defaultness {
6119 // `pub` is included for better error messages
6120 if self.check_keyword(keywords::Default) &&
6121 self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
6122 t.is_keyword(keywords::Const) ||
6123 t.is_keyword(keywords::Fn) ||
6124 t.is_keyword(keywords::Unsafe) ||
6125 t.is_keyword(keywords::Extern) ||
6126 t.is_keyword(keywords::Type) ||
6127 t.is_keyword(keywords::Pub)) {
6128 self.bump(); // `default`
6129 Defaultness::Default
6135 /// Given a termination token, parse all of the items in a module
6136 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
6137 let mut items = vec![];
6138 while let Some(item) = self.parse_item()? {
6142 if !self.eat(term) {
6143 let token_str = self.this_token_to_string();
6144 let mut err = self.fatal(&format!("expected item, found `{}`", token_str));
6145 if token_str == ";" {
6146 let msg = "consider removing this semicolon";
6147 err.span_suggestion_short_with_applicability(
6148 self.span, msg, "".to_string(), Applicability::MachineApplicable
6150 if !items.is_empty() { // Issue #51603
6151 let previous_item = &items[items.len()-1];
6152 let previous_item_kind_name = match previous_item.node {
6153 // say "braced struct" because tuple-structs and
6154 // braceless-empty-struct declarations do take a semicolon
6155 ItemKind::Struct(..) => Some("braced struct"),
6156 ItemKind::Enum(..) => Some("enum"),
6157 ItemKind::Trait(..) => Some("trait"),
6158 ItemKind::Union(..) => Some("union"),
6161 if let Some(name) = previous_item_kind_name {
6162 err.help(&format!("{} declarations are not followed by a semicolon",
6167 err.span_label(self.span, "expected item");
6172 let hi = if self.span.is_dummy() {
6179 inner: inner_lo.to(hi),
6184 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6185 let id = self.parse_ident()?;
6186 self.expect(&token::Colon)?;
6187 let ty = self.parse_ty()?;
6188 self.expect(&token::Eq)?;
6189 let e = self.parse_expr()?;
6190 self.expect(&token::Semi)?;
6191 let item = match m {
6192 Some(m) => ItemKind::Static(ty, m, e),
6193 None => ItemKind::Const(ty, e),
6195 Ok((id, item, None))
6198 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6199 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6200 let (in_cfg, outer_attrs) = {
6201 let mut strip_unconfigured = ::config::StripUnconfigured {
6203 should_test: false, // irrelevant
6204 features: None, // don't perform gated feature checking
6206 let outer_attrs = strip_unconfigured.process_cfg_attrs(outer_attrs.to_owned());
6207 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
6210 let id_span = self.span;
6211 let id = self.parse_ident()?;
6212 if self.check(&token::Semi) {
6214 if in_cfg && self.recurse_into_file_modules {
6215 // This mod is in an external file. Let's go get it!
6216 let ModulePathSuccess { path, directory_ownership, warn } =
6217 self.submod_path(id, &outer_attrs, id_span)?;
6218 let (module, mut attrs) =
6219 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
6221 let attr = Attribute {
6222 id: attr::mk_attr_id(),
6223 style: ast::AttrStyle::Outer,
6224 path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")),
6225 tokens: TokenStream::empty(),
6226 is_sugared_doc: false,
6227 span: syntax_pos::DUMMY_SP,
6229 attr::mark_known(&attr);
6232 Ok((id, module, Some(attrs)))
6234 let placeholder = ast::Mod { inner: syntax_pos::DUMMY_SP, items: Vec::new() };
6235 Ok((id, ItemKind::Mod(placeholder), None))
6238 let old_directory = self.directory.clone();
6239 self.push_directory(id, &outer_attrs);
6241 self.expect(&token::OpenDelim(token::Brace))?;
6242 let mod_inner_lo = self.span;
6243 let attrs = self.parse_inner_attributes()?;
6244 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
6246 self.directory = old_directory;
6247 Ok((id, ItemKind::Mod(module), Some(attrs)))
6251 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
6252 if let Some(path) = attr::first_attr_value_str_by_name(attrs, "path") {
6253 self.directory.path.to_mut().push(&path.as_str());
6254 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
6256 self.directory.path.to_mut().push(&id.as_str());
6260 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
6261 if let Some(s) = attr::first_attr_value_str_by_name(attrs, "path") {
6264 // On windows, the base path might have the form
6265 // `\\?\foo\bar` in which case it does not tolerate
6266 // mixed `/` and `\` separators, so canonicalize
6269 let s = s.replace("/", "\\");
6270 Some(dir_path.join(s))
6276 /// Returns either a path to a module, or .
6277 pub fn default_submod_path(
6279 relative: Option<ast::Ident>,
6281 codemap: &CodeMap) -> ModulePath
6283 // If we're in a foo.rs file instead of a mod.rs file,
6284 // we need to look for submodules in
6285 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
6286 // `./<id>.rs` and `./<id>/mod.rs`.
6287 let relative_prefix_string;
6288 let relative_prefix = if let Some(ident) = relative {
6289 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
6290 &relative_prefix_string
6295 let mod_name = id.to_string();
6296 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
6297 let secondary_path_str = format!("{}{}{}mod.rs",
6298 relative_prefix, mod_name, path::MAIN_SEPARATOR);
6299 let default_path = dir_path.join(&default_path_str);
6300 let secondary_path = dir_path.join(&secondary_path_str);
6301 let default_exists = codemap.file_exists(&default_path);
6302 let secondary_exists = codemap.file_exists(&secondary_path);
6304 let result = match (default_exists, secondary_exists) {
6305 (true, false) => Ok(ModulePathSuccess {
6307 directory_ownership: DirectoryOwnership::Owned {
6312 (false, true) => Ok(ModulePathSuccess {
6313 path: secondary_path,
6314 directory_ownership: DirectoryOwnership::Owned {
6319 (false, false) => Err(Error::FileNotFoundForModule {
6320 mod_name: mod_name.clone(),
6321 default_path: default_path_str,
6322 secondary_path: secondary_path_str,
6323 dir_path: format!("{}", dir_path.display()),
6325 (true, true) => Err(Error::DuplicatePaths {
6326 mod_name: mod_name.clone(),
6327 default_path: default_path_str,
6328 secondary_path: secondary_path_str,
6334 path_exists: default_exists || secondary_exists,
6339 fn submod_path(&mut self,
6341 outer_attrs: &[Attribute],
6343 -> PResult<'a, ModulePathSuccess> {
6344 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
6345 return Ok(ModulePathSuccess {
6346 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
6347 // All `#[path]` files are treated as though they are a `mod.rs` file.
6348 // This means that `mod foo;` declarations inside `#[path]`-included
6349 // files are siblings,
6351 // Note that this will produce weirdness when a file named `foo.rs` is
6352 // `#[path]` included and contains a `mod foo;` declaration.
6353 // If you encounter this, it's your own darn fault :P
6354 Some(_) => DirectoryOwnership::Owned { relative: None },
6355 _ => DirectoryOwnership::UnownedViaMod(true),
6362 let relative = match self.directory.ownership {
6363 DirectoryOwnership::Owned { relative } => {
6364 // Push the usage onto the list of non-mod.rs mod uses.
6365 // This is used later for feature-gate error reporting.
6366 if let Some(cur_file_ident) = relative {
6368 .non_modrs_mods.borrow_mut()
6369 .push((cur_file_ident, id_sp));
6373 DirectoryOwnership::UnownedViaBlock |
6374 DirectoryOwnership::UnownedViaMod(_) => None,
6376 let paths = Parser::default_submod_path(
6377 id, relative, &self.directory.path, self.sess.codemap());
6379 match self.directory.ownership {
6380 DirectoryOwnership::Owned { .. } => {
6381 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
6383 DirectoryOwnership::UnownedViaBlock => {
6385 "Cannot declare a non-inline module inside a block \
6386 unless it has a path attribute";
6387 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
6388 if paths.path_exists {
6389 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
6391 err.span_note(id_sp, &msg);
6395 DirectoryOwnership::UnownedViaMod(warn) => {
6397 if let Ok(result) = paths.result {
6398 return Ok(ModulePathSuccess { warn: true, ..result });
6401 let mut err = self.diagnostic().struct_span_err(id_sp,
6402 "cannot declare a new module at this location");
6403 if !id_sp.is_dummy() {
6404 let src_path = self.sess.codemap().span_to_filename(id_sp);
6405 if let FileName::Real(src_path) = src_path {
6406 if let Some(stem) = src_path.file_stem() {
6407 let mut dest_path = src_path.clone();
6408 dest_path.set_file_name(stem);
6409 dest_path.push("mod.rs");
6410 err.span_note(id_sp,
6411 &format!("maybe move this module `{}` to its own \
6412 directory via `{}`", src_path.display(),
6413 dest_path.display()));
6417 if paths.path_exists {
6418 err.span_note(id_sp,
6419 &format!("... or maybe `use` the module `{}` instead \
6420 of possibly redeclaring it",
6428 /// Read a module from a source file.
6429 fn eval_src_mod(&mut self,
6431 directory_ownership: DirectoryOwnership,
6434 -> PResult<'a, (ast::ItemKind, Vec<Attribute> )> {
6435 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
6436 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
6437 let mut err = String::from("circular modules: ");
6438 let len = included_mod_stack.len();
6439 for p in &included_mod_stack[i.. len] {
6440 err.push_str(&p.to_string_lossy());
6441 err.push_str(" -> ");
6443 err.push_str(&path.to_string_lossy());
6444 return Err(self.span_fatal(id_sp, &err[..]));
6446 included_mod_stack.push(path.clone());
6447 drop(included_mod_stack);
6450 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
6451 p0.cfg_mods = self.cfg_mods;
6452 let mod_inner_lo = p0.span;
6453 let mod_attrs = p0.parse_inner_attributes()?;
6454 let m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
6455 self.sess.included_mod_stack.borrow_mut().pop();
6456 Ok((ast::ItemKind::Mod(m0), mod_attrs))
6459 /// Parse a function declaration from a foreign module
6460 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6461 -> PResult<'a, ForeignItem> {
6462 self.expect_keyword(keywords::Fn)?;
6464 let (ident, mut generics) = self.parse_fn_header()?;
6465 let decl = self.parse_fn_decl(true)?;
6466 generics.where_clause = self.parse_where_clause()?;
6468 self.expect(&token::Semi)?;
6469 Ok(ast::ForeignItem {
6472 node: ForeignItemKind::Fn(decl, generics),
6473 id: ast::DUMMY_NODE_ID,
6479 /// Parse a static item from a foreign module.
6480 /// Assumes that the `static` keyword is already parsed.
6481 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6482 -> PResult<'a, ForeignItem> {
6483 let mutbl = self.eat_keyword(keywords::Mut);
6484 let ident = self.parse_ident()?;
6485 self.expect(&token::Colon)?;
6486 let ty = self.parse_ty()?;
6488 self.expect(&token::Semi)?;
6492 node: ForeignItemKind::Static(ty, mutbl),
6493 id: ast::DUMMY_NODE_ID,
6499 /// Parse a type from a foreign module
6500 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6501 -> PResult<'a, ForeignItem> {
6502 self.expect_keyword(keywords::Type)?;
6504 let ident = self.parse_ident()?;
6506 self.expect(&token::Semi)?;
6507 Ok(ast::ForeignItem {
6510 node: ForeignItemKind::Ty,
6511 id: ast::DUMMY_NODE_ID,
6517 /// Parse extern crate links
6521 /// extern crate foo;
6522 /// extern crate bar as foo;
6523 fn parse_item_extern_crate(&mut self,
6525 visibility: Visibility,
6526 attrs: Vec<Attribute>)
6527 -> PResult<'a, P<Item>> {
6528 let orig_name = self.parse_ident()?;
6529 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
6530 (rename, Some(orig_name.name))
6534 self.expect(&token::Semi)?;
6536 let span = lo.to(self.prev_span);
6537 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
6540 /// Parse `extern` for foreign ABIs
6543 /// `extern` is expected to have been
6544 /// consumed before calling this method
6550 fn parse_item_foreign_mod(&mut self,
6552 opt_abi: Option<Abi>,
6553 visibility: Visibility,
6554 mut attrs: Vec<Attribute>)
6555 -> PResult<'a, P<Item>> {
6556 self.expect(&token::OpenDelim(token::Brace))?;
6558 let abi = opt_abi.unwrap_or(Abi::C);
6560 attrs.extend(self.parse_inner_attributes()?);
6562 let mut foreign_items = vec![];
6563 while let Some(item) = self.parse_foreign_item()? {
6564 foreign_items.push(item);
6566 self.expect(&token::CloseDelim(token::Brace))?;
6568 let prev_span = self.prev_span;
6569 let m = ast::ForeignMod {
6571 items: foreign_items
6573 let invalid = keywords::Invalid.ident();
6574 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
6577 /// Parse type Foo = Bar;
6579 /// existential type Foo: Bar;
6581 /// return None without modifying the parser state
6582 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
6583 // This parses the grammar:
6584 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
6585 if self.check_keyword(keywords::Type) ||
6586 self.check_keyword(keywords::Existential) &&
6587 self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
6588 let existential = self.eat_keyword(keywords::Existential);
6589 assert!(self.eat_keyword(keywords::Type));
6590 Some(self.parse_existential_or_alias(existential))
6596 /// Parse type alias or existential type
6597 fn parse_existential_or_alias(
6600 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
6601 let ident = self.parse_ident()?;
6602 let mut tps = self.parse_generics()?;
6603 tps.where_clause = self.parse_where_clause()?;
6604 let alias = if existential {
6605 self.expect(&token::Colon)?;
6606 let bounds = self.parse_generic_bounds()?;
6607 AliasKind::Existential(bounds)
6609 self.expect(&token::Eq)?;
6610 let ty = self.parse_ty()?;
6613 self.expect(&token::Semi)?;
6614 Ok((ident, alias, tps))
6617 /// Parse the part of an "enum" decl following the '{'
6618 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
6619 let mut variants = Vec::new();
6620 let mut all_nullary = true;
6621 let mut any_disr = None;
6622 while self.token != token::CloseDelim(token::Brace) {
6623 let variant_attrs = self.parse_outer_attributes()?;
6624 let vlo = self.span;
6627 let mut disr_expr = None;
6628 let ident = self.parse_ident()?;
6629 if self.check(&token::OpenDelim(token::Brace)) {
6630 // Parse a struct variant.
6631 all_nullary = false;
6632 struct_def = VariantData::Struct(self.parse_record_struct_body()?,
6633 ast::DUMMY_NODE_ID);
6634 } else if self.check(&token::OpenDelim(token::Paren)) {
6635 all_nullary = false;
6636 struct_def = VariantData::Tuple(self.parse_tuple_struct_body()?,
6637 ast::DUMMY_NODE_ID);
6638 } else if self.eat(&token::Eq) {
6639 disr_expr = Some(AnonConst {
6640 id: ast::DUMMY_NODE_ID,
6641 value: self.parse_expr()?,
6643 any_disr = disr_expr.as_ref().map(|c| c.value.span);
6644 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6646 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6649 let vr = ast::Variant_ {
6651 attrs: variant_attrs,
6655 variants.push(respan(vlo.to(self.prev_span), vr));
6657 if !self.eat(&token::Comma) { break; }
6659 self.expect(&token::CloseDelim(token::Brace))?;
6661 Some(disr_span) if !all_nullary =>
6662 self.span_err(disr_span,
6663 "discriminator values can only be used with a field-less enum"),
6667 Ok(ast::EnumDef { variants: variants })
6670 /// Parse an "enum" declaration
6671 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
6672 let id = self.parse_ident()?;
6673 let mut generics = self.parse_generics()?;
6674 generics.where_clause = self.parse_where_clause()?;
6675 self.expect(&token::OpenDelim(token::Brace))?;
6677 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
6678 self.recover_stmt();
6679 self.eat(&token::CloseDelim(token::Brace));
6682 Ok((id, ItemKind::Enum(enum_definition, generics), None))
6685 /// Parses a string as an ABI spec on an extern type or module. Consumes
6686 /// the `extern` keyword, if one is found.
6687 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
6689 token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
6691 self.expect_no_suffix(sp, "ABI spec", suf);
6693 match abi::lookup(&s.as_str()) {
6694 Some(abi) => Ok(Some(abi)),
6696 let prev_span = self.prev_span;
6697 let mut err = struct_span_err!(
6698 self.sess.span_diagnostic,
6701 "invalid ABI: found `{}`",
6703 err.span_label(prev_span, "invalid ABI");
6704 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
6715 fn is_static_global(&mut self) -> bool {
6716 if self.check_keyword(keywords::Static) {
6717 // Check if this could be a closure
6718 !self.look_ahead(1, |token| {
6719 if token.is_keyword(keywords::Move) {
6723 token::BinOp(token::Or) | token::OrOr => true,
6734 attrs: Vec<Attribute>,
6735 macros_allowed: bool,
6736 attributes_allowed: bool,
6737 ) -> PResult<'a, Option<P<Item>>> {
6738 let (ret, tokens) = self.collect_tokens(|this| {
6739 this.parse_item_implementation(attrs, macros_allowed, attributes_allowed)
6742 // Once we've parsed an item and recorded the tokens we got while
6743 // parsing we may want to store `tokens` into the item we're about to
6744 // return. Note, though, that we specifically didn't capture tokens
6745 // related to outer attributes. The `tokens` field here may later be
6746 // used with procedural macros to convert this item back into a token
6747 // stream, but during expansion we may be removing attributes as we go
6750 // If we've got inner attributes then the `tokens` we've got above holds
6751 // these inner attributes. If an inner attribute is expanded we won't
6752 // actually remove it from the token stream, so we'll just keep yielding
6753 // it (bad!). To work around this case for now we just avoid recording
6754 // `tokens` if we detect any inner attributes. This should help keep
6755 // expansion correct, but we should fix this bug one day!
6758 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
6759 i.tokens = Some(tokens);
6766 /// Parse one of the items allowed by the flags.
6767 /// NB: this function no longer parses the items inside an
6769 fn parse_item_implementation(
6771 attrs: Vec<Attribute>,
6772 macros_allowed: bool,
6773 attributes_allowed: bool,
6774 ) -> PResult<'a, Option<P<Item>>> {
6775 maybe_whole!(self, NtItem, |item| {
6776 let mut item = item.into_inner();
6777 let mut attrs = attrs;
6778 mem::swap(&mut item.attrs, &mut attrs);
6779 item.attrs.extend(attrs);
6785 let visibility = self.parse_visibility(false)?;
6787 if self.eat_keyword(keywords::Use) {
6789 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
6790 self.expect(&token::Semi)?;
6792 let span = lo.to(self.prev_span);
6793 let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
6794 return Ok(Some(item));
6797 if self.check_keyword(keywords::Extern) && self.is_extern_non_path() {
6798 self.bump(); // `extern`
6799 if self.eat_keyword(keywords::Crate) {
6800 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
6803 let opt_abi = self.parse_opt_abi()?;
6805 if self.eat_keyword(keywords::Fn) {
6806 // EXTERN FUNCTION ITEM
6807 let fn_span = self.prev_span;
6808 let abi = opt_abi.unwrap_or(Abi::C);
6809 let (ident, item_, extra_attrs) =
6810 self.parse_item_fn(Unsafety::Normal,
6812 respan(fn_span, Constness::NotConst),
6814 let prev_span = self.prev_span;
6815 let item = self.mk_item(lo.to(prev_span),
6819 maybe_append(attrs, extra_attrs));
6820 return Ok(Some(item));
6821 } else if self.check(&token::OpenDelim(token::Brace)) {
6822 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
6828 if self.is_static_global() {
6831 let m = if self.eat_keyword(keywords::Mut) {
6834 Mutability::Immutable
6836 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
6837 let prev_span = self.prev_span;
6838 let item = self.mk_item(lo.to(prev_span),
6842 maybe_append(attrs, extra_attrs));
6843 return Ok(Some(item));
6845 if self.eat_keyword(keywords::Const) {
6846 let const_span = self.prev_span;
6847 if self.check_keyword(keywords::Fn)
6848 || (self.check_keyword(keywords::Unsafe)
6849 && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
6850 // CONST FUNCTION ITEM
6851 let unsafety = self.parse_unsafety();
6853 let (ident, item_, extra_attrs) =
6854 self.parse_item_fn(unsafety,
6856 respan(const_span, Constness::Const),
6858 let prev_span = self.prev_span;
6859 let item = self.mk_item(lo.to(prev_span),
6863 maybe_append(attrs, extra_attrs));
6864 return Ok(Some(item));
6868 if self.eat_keyword(keywords::Mut) {
6869 let prev_span = self.prev_span;
6870 self.diagnostic().struct_span_err(prev_span, "const globals cannot be mutable")
6871 .help("did you mean to declare a static?")
6874 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
6875 let prev_span = self.prev_span;
6876 let item = self.mk_item(lo.to(prev_span),
6880 maybe_append(attrs, extra_attrs));
6881 return Ok(Some(item));
6884 // `unsafe async fn` or `async fn`
6886 self.check_keyword(keywords::Unsafe) &&
6887 self.look_ahead(1, |t| t.is_keyword(keywords::Async))
6889 self.check_keyword(keywords::Async) &&
6890 self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
6893 // ASYNC FUNCTION ITEM
6894 let unsafety = self.parse_unsafety();
6895 self.expect_keyword(keywords::Async)?;
6896 self.expect_keyword(keywords::Fn)?;
6897 let fn_span = self.prev_span;
6898 let (ident, item_, extra_attrs) =
6899 self.parse_item_fn(unsafety,
6901 closure_id: ast::DUMMY_NODE_ID,
6902 return_impl_trait_id: ast::DUMMY_NODE_ID,
6904 respan(fn_span, Constness::NotConst),
6906 let prev_span = self.prev_span;
6907 let item = self.mk_item(lo.to(prev_span),
6911 maybe_append(attrs, extra_attrs));
6912 return Ok(Some(item));
6914 if self.check_keyword(keywords::Unsafe) &&
6915 (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
6916 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
6918 // UNSAFE TRAIT ITEM
6919 self.bump(); // `unsafe`
6920 let is_auto = if self.eat_keyword(keywords::Trait) {
6923 self.expect_keyword(keywords::Auto)?;
6924 self.expect_keyword(keywords::Trait)?;
6927 let (ident, item_, extra_attrs) =
6928 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
6929 let prev_span = self.prev_span;
6930 let item = self.mk_item(lo.to(prev_span),
6934 maybe_append(attrs, extra_attrs));
6935 return Ok(Some(item));
6937 if self.check_keyword(keywords::Impl) ||
6938 self.check_keyword(keywords::Unsafe) &&
6939 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
6940 self.check_keyword(keywords::Default) &&
6941 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
6942 self.check_keyword(keywords::Default) &&
6943 self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
6945 let defaultness = self.parse_defaultness();
6946 let unsafety = self.parse_unsafety();
6947 self.expect_keyword(keywords::Impl)?;
6948 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
6949 let span = lo.to(self.prev_span);
6950 return Ok(Some(self.mk_item(span, ident, item, visibility,
6951 maybe_append(attrs, extra_attrs))));
6953 if self.check_keyword(keywords::Fn) {
6956 let fn_span = self.prev_span;
6957 let (ident, item_, extra_attrs) =
6958 self.parse_item_fn(Unsafety::Normal,
6960 respan(fn_span, Constness::NotConst),
6962 let prev_span = self.prev_span;
6963 let item = self.mk_item(lo.to(prev_span),
6967 maybe_append(attrs, extra_attrs));
6968 return Ok(Some(item));
6970 if self.check_keyword(keywords::Unsafe)
6971 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
6972 // UNSAFE FUNCTION ITEM
6973 self.bump(); // `unsafe`
6974 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
6975 self.check(&token::OpenDelim(token::Brace));
6976 let abi = if self.eat_keyword(keywords::Extern) {
6977 self.parse_opt_abi()?.unwrap_or(Abi::C)
6981 self.expect_keyword(keywords::Fn)?;
6982 let fn_span = self.prev_span;
6983 let (ident, item_, extra_attrs) =
6984 self.parse_item_fn(Unsafety::Unsafe,
6986 respan(fn_span, Constness::NotConst),
6988 let prev_span = self.prev_span;
6989 let item = self.mk_item(lo.to(prev_span),
6993 maybe_append(attrs, extra_attrs));
6994 return Ok(Some(item));
6996 if self.eat_keyword(keywords::Mod) {
6998 let (ident, item_, extra_attrs) =
6999 self.parse_item_mod(&attrs[..])?;
7000 let prev_span = self.prev_span;
7001 let item = self.mk_item(lo.to(prev_span),
7005 maybe_append(attrs, extra_attrs));
7006 return Ok(Some(item));
7008 if let Some(type_) = self.eat_type() {
7009 let (ident, alias, generics) = type_?;
7011 let item_ = match alias {
7012 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7013 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7015 let prev_span = self.prev_span;
7016 let item = self.mk_item(lo.to(prev_span),
7021 return Ok(Some(item));
7023 if self.eat_keyword(keywords::Enum) {
7025 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7026 let prev_span = self.prev_span;
7027 let item = self.mk_item(lo.to(prev_span),
7031 maybe_append(attrs, extra_attrs));
7032 return Ok(Some(item));
7034 if self.check_keyword(keywords::Trait)
7035 || (self.check_keyword(keywords::Auto)
7036 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
7038 let is_auto = if self.eat_keyword(keywords::Trait) {
7041 self.expect_keyword(keywords::Auto)?;
7042 self.expect_keyword(keywords::Trait)?;
7046 let (ident, item_, extra_attrs) =
7047 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7048 let prev_span = self.prev_span;
7049 let item = self.mk_item(lo.to(prev_span),
7053 maybe_append(attrs, extra_attrs));
7054 return Ok(Some(item));
7056 if self.eat_keyword(keywords::Struct) {
7058 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7059 let prev_span = self.prev_span;
7060 let item = self.mk_item(lo.to(prev_span),
7064 maybe_append(attrs, extra_attrs));
7065 return Ok(Some(item));
7067 if self.is_union_item() {
7070 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7071 let prev_span = self.prev_span;
7072 let item = self.mk_item(lo.to(prev_span),
7076 maybe_append(attrs, extra_attrs));
7077 return Ok(Some(item));
7079 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7080 return Ok(Some(macro_def));
7083 // Verify whether we have encountered a struct or method definition where the user forgot to
7084 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7085 if visibility.node.is_pub() &&
7086 self.check_ident() &&
7087 self.look_ahead(1, |t| *t != token::Not)
7089 // Space between `pub` keyword and the identifier
7092 // ^^^ `sp` points here
7093 let sp = self.prev_span.between(self.span);
7094 let full_sp = self.prev_span.to(self.span);
7095 let ident_sp = self.span;
7096 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7097 // possible public struct definition where `struct` was forgotten
7098 let ident = self.parse_ident().unwrap();
7099 let msg = format!("add `struct` here to parse `{}` as a public struct",
7101 let mut err = self.diagnostic()
7102 .struct_span_err(sp, "missing `struct` for struct definition");
7103 err.span_suggestion_short_with_applicability(
7104 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7107 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7108 let ident = self.parse_ident().unwrap();
7109 self.consume_block(token::Paren);
7110 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) ||
7111 self.check(&token::OpenDelim(token::Brace))
7113 ("fn", "method", false)
7114 } else if self.check(&token::Colon) {
7118 ("fn` or `struct", "method or struct", true)
7121 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7122 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7124 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
7128 err.span_suggestion_short_with_applicability(
7129 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
7132 if let Ok(snippet) = self.sess.codemap().span_to_snippet(ident_sp) {
7133 err.span_suggestion_with_applicability(
7135 "if you meant to call a macro, try",
7136 format!("{}!", snippet),
7137 // this is the `ambiguous` conditional branch
7138 Applicability::MaybeIncorrect
7141 err.help("if you meant to call a macro, remove the `pub` \
7142 and add a trailing `!` after the identifier");
7148 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
7151 /// Parse a foreign item.
7152 crate fn parse_foreign_item(&mut self) -> PResult<'a, Option<ForeignItem>> {
7153 maybe_whole!(self, NtForeignItem, |ni| Some(ni));
7155 let attrs = self.parse_outer_attributes()?;
7157 let visibility = self.parse_visibility(false)?;
7159 // FOREIGN STATIC ITEM
7160 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
7161 if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
7162 if self.token.is_keyword(keywords::Const) {
7164 .struct_span_err(self.span, "extern items cannot be `const`")
7165 .span_suggestion_with_applicability(
7167 "try using a static value",
7168 "static".to_owned(),
7169 Applicability::MachineApplicable
7172 self.bump(); // `static` or `const`
7173 return Ok(Some(self.parse_item_foreign_static(visibility, lo, attrs)?));
7175 // FOREIGN FUNCTION ITEM
7176 if self.check_keyword(keywords::Fn) {
7177 return Ok(Some(self.parse_item_foreign_fn(visibility, lo, attrs)?));
7179 // FOREIGN TYPE ITEM
7180 if self.check_keyword(keywords::Type) {
7181 return Ok(Some(self.parse_item_foreign_type(visibility, lo, attrs)?));
7184 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
7188 ident: keywords::Invalid.ident(),
7189 span: lo.to(self.prev_span),
7190 id: ast::DUMMY_NODE_ID,
7193 node: ForeignItemKind::Macro(mac),
7198 if !attrs.is_empty() {
7199 self.expected_item_err(&attrs);
7207 /// This is the fall-through for parsing items.
7208 fn parse_macro_use_or_failure(
7210 attrs: Vec<Attribute> ,
7211 macros_allowed: bool,
7212 attributes_allowed: bool,
7214 visibility: Visibility
7215 ) -> PResult<'a, Option<P<Item>>> {
7216 if macros_allowed && self.token.is_path_start() {
7217 // MACRO INVOCATION ITEM
7219 let prev_span = self.prev_span;
7220 self.complain_if_pub_macro(&visibility.node, prev_span);
7222 let mac_lo = self.span;
7225 let pth = self.parse_path(PathStyle::Mod)?;
7226 self.expect(&token::Not)?;
7228 // a 'special' identifier (like what `macro_rules!` uses)
7229 // is optional. We should eventually unify invoc syntax
7231 let id = if self.token.is_ident() {
7234 keywords::Invalid.ident() // no special identifier
7236 // eat a matched-delimiter token tree:
7237 let (delim, tts) = self.expect_delimited_token_tree()?;
7238 if delim != MacDelimiter::Brace {
7239 if !self.eat(&token::Semi) {
7240 self.span_err(self.prev_span,
7241 "macros that expand to items must either \
7242 be surrounded with braces or followed by \
7247 let hi = self.prev_span;
7248 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
7249 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
7250 return Ok(Some(item));
7253 // FAILURE TO PARSE ITEM
7254 match visibility.node {
7255 VisibilityKind::Inherited => {}
7257 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
7261 if !attributes_allowed && !attrs.is_empty() {
7262 self.expected_item_err(&attrs);
7267 /// Parse a macro invocation inside a `trait`, `impl` or `extern` block
7268 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
7269 at_end: &mut bool) -> PResult<'a, Option<Mac>>
7271 if self.token.is_path_start() && !self.is_extern_non_path() {
7272 let prev_span = self.prev_span;
7274 let pth = self.parse_path(PathStyle::Mod)?;
7276 if pth.segments.len() == 1 {
7277 if !self.eat(&token::Not) {
7278 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
7281 self.expect(&token::Not)?;
7284 if let Some(vis) = vis {
7285 self.complain_if_pub_macro(&vis.node, prev_span);
7290 // eat a matched-delimiter token tree:
7291 let (delim, tts) = self.expect_delimited_token_tree()?;
7292 if delim != MacDelimiter::Brace {
7293 self.expect(&token::Semi)?
7296 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
7302 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
7303 where F: FnOnce(&mut Self) -> PResult<'a, R>
7305 // Record all tokens we parse when parsing this item.
7306 let mut tokens = Vec::new();
7307 let prev_collecting = match self.token_cursor.frame.last_token {
7308 LastToken::Collecting(ref mut list) => {
7309 Some(mem::replace(list, Vec::new()))
7311 LastToken::Was(ref mut last) => {
7312 tokens.extend(last.take());
7316 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
7317 let prev = self.token_cursor.stack.len();
7319 let last_token = if self.token_cursor.stack.len() == prev {
7320 &mut self.token_cursor.frame.last_token
7322 &mut self.token_cursor.stack[prev].last_token
7325 // Pull our the toekns that we've collected from the call to `f` above
7326 let mut collected_tokens = match *last_token {
7327 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
7328 LastToken::Was(_) => panic!("our vector went away?"),
7331 // If we're not at EOF our current token wasn't actually consumed by
7332 // `f`, but it'll still be in our list that we pulled out. In that case
7334 let extra_token = if self.token != token::Eof {
7335 collected_tokens.pop()
7340 // If we were previously collecting tokens, then this was a recursive
7341 // call. In that case we need to record all the tokens we collected in
7342 // our parent list as well. To do that we push a clone of our stream
7343 // onto the previous list.
7344 let stream = collected_tokens.into_iter().collect::<TokenStream>();
7345 match prev_collecting {
7347 list.push(stream.clone());
7348 list.extend(extra_token);
7349 *last_token = LastToken::Collecting(list);
7352 *last_token = LastToken::Was(extra_token);
7359 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
7360 let attrs = self.parse_outer_attributes()?;
7361 self.parse_item_(attrs, true, false)
7365 fn is_import_coupler(&mut self) -> bool {
7366 self.check(&token::ModSep) &&
7367 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
7368 *t == token::BinOp(token::Star))
7373 /// USE_TREE = [`::`] `*` |
7374 /// [`::`] `{` USE_TREE_LIST `}` |
7376 /// PATH `::` `{` USE_TREE_LIST `}` |
7377 /// PATH [`as` IDENT]
7378 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
7381 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
7382 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
7383 self.check(&token::BinOp(token::Star)) ||
7384 self.is_import_coupler() {
7385 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
7386 if self.eat(&token::ModSep) {
7387 prefix.segments.push(PathSegment::crate_root(lo.shrink_to_lo()));
7390 if self.eat(&token::BinOp(token::Star)) {
7393 UseTreeKind::Nested(self.parse_use_tree_list()?)
7396 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
7397 prefix = self.parse_path(PathStyle::Mod)?;
7399 if self.eat(&token::ModSep) {
7400 if self.eat(&token::BinOp(token::Star)) {
7403 UseTreeKind::Nested(self.parse_use_tree_list()?)
7406 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
7410 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
7413 /// Parse UseTreeKind::Nested(list)
7415 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
7416 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
7417 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
7418 &token::CloseDelim(token::Brace),
7419 SeqSep::trailing_allowed(token::Comma), |this| {
7420 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
7424 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
7425 if self.eat_keyword(keywords::As) {
7427 token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
7429 Ok(Some(ident.gensym()))
7431 _ => self.parse_ident().map(Some),
7438 /// Parses a source module as a crate. This is the main
7439 /// entry point for the parser.
7440 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
7443 attrs: self.parse_inner_attributes()?,
7444 module: self.parse_mod_items(&token::Eof, lo)?,
7445 span: lo.to(self.span),
7449 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
7450 let ret = match self.token {
7451 token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
7452 token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
7459 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
7460 match self.parse_optional_str() {
7461 Some((s, style, suf)) => {
7462 let sp = self.prev_span;
7463 self.expect_no_suffix(sp, "string literal", suf);
7467 let msg = "expected string literal";
7468 let mut err = self.fatal(msg);
7469 err.span_label(self.span, msg);