1 // ignore-tidy-filelength
3 use crate::ast::{AngleBracketedArgs, ParenthesizedArgs, AttrStyle, BareFnTy};
4 use crate::ast::{GenericBound, TraitBoundModifier};
5 use crate::ast::Unsafety;
6 use crate::ast::{Mod, AnonConst, Arg, Arm, Guard, Attribute, BindingMode, TraitItemKind};
8 use crate::ast::{BlockCheckMode, CaptureBy, Movability};
9 use crate::ast::{Constness, Crate};
10 use crate::ast::Defaultness;
11 use crate::ast::EnumDef;
12 use crate::ast::{Expr, ExprKind, RangeLimits};
13 use crate::ast::{Field, FnDecl, FnHeader};
14 use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
15 use crate::ast::{GenericParam, GenericParamKind};
16 use crate::ast::GenericArg;
17 use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
18 use crate::ast::{Label, Lifetime};
19 use crate::ast::Local;
20 use crate::ast::MacStmtStyle;
21 use crate::ast::{Mac, Mac_, MacDelimiter};
22 use crate::ast::{MutTy, Mutability};
23 use crate::ast::{Pat, PatKind, PathSegment};
24 use crate::ast::{PolyTraitRef, QSelf};
25 use crate::ast::{Stmt, StmtKind};
26 use crate::ast::{VariantData, StructField};
27 use crate::ast::StrStyle;
28 use crate::ast::SelfKind;
29 use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
30 use crate::ast::{Ty, TyKind, AssocTyConstraint, AssocTyConstraintKind, GenericBounds};
31 use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
32 use crate::ast::{UseTree, UseTreeKind};
33 use crate::ast::{BinOpKind, UnOp};
34 use crate::ast::{RangeEnd, RangeSyntax};
35 use crate::{ast, attr};
36 use crate::ext::base::DummyResult;
37 use crate::ext::hygiene::SyntaxContext;
38 use crate::source_map::{self, SourceMap, Spanned, respan};
39 use crate::parse::{SeqSep, classify, literal, token};
40 use crate::parse::lexer::UnmatchedBrace;
41 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
42 use crate::parse::token::{Token, TokenKind, DelimToken};
43 use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
44 use crate::util::parser::{AssocOp, Fixity};
45 use crate::print::pprust;
47 use crate::parse::PResult;
49 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
50 use crate::symbol::{kw, sym, Symbol};
51 use crate::parse::diagnostics::{Error, dummy_arg};
53 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
54 use rustc_target::spec::abi::{self, Abi};
55 use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
62 use std::path::{self, Path, PathBuf};
66 /// Whether the type alias or associated type is a concrete type or an existential type
68 /// Just a new name for the same type
70 /// Only trait impls of the type will be usable, not the actual type itself
71 Existential(GenericBounds),
75 struct Restrictions: u8 {
76 const STMT_EXPR = 1 << 0;
77 const NO_STRUCT_LITERAL = 1 << 1;
81 type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
83 /// Specifies how to parse a path.
84 #[derive(Copy, Clone, PartialEq)]
86 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
87 /// with something else. For example, in expressions `segment < ....` can be interpreted
88 /// as a comparison and `segment ( ....` can be interpreted as a function call.
89 /// In all such contexts the non-path interpretation is preferred by default for practical
90 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
91 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
93 /// In other contexts, notably in types, no ambiguity exists and paths can be written
94 /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
95 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
97 /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
98 /// visibilities or attributes.
99 /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
100 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
101 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
102 /// tokens when something goes wrong.
106 #[derive(Clone, Copy, PartialEq, Debug)]
107 crate enum SemiColonMode {
113 #[derive(Clone, Copy, PartialEq, Debug)]
114 crate enum BlockMode {
119 /// Possibly accepts 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) = &$p.token.kind {
128 token::NtExpr(e) | token::NtLiteral(e) => {
133 token::NtPath(path) => {
134 let path = path.clone();
136 return Ok($p.mk_expr(
137 $p.token.span, ExprKind::Path(None, path), ThinVec::new()
140 token::NtBlock(block) => {
141 let block = block.clone();
143 return Ok($p.mk_expr(
144 $p.token.span, ExprKind::Block(block, None), ThinVec::new()
153 /// As maybe_whole_expr, but for things other than expressions
154 macro_rules! maybe_whole {
155 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
156 if let token::Interpolated(nt) = &$p.token.kind {
157 if let token::$constructor(x) = &**nt {
166 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
167 macro_rules! maybe_recover_from_interpolated_ty_qpath {
168 ($self: expr, $allow_qpath_recovery: expr) => {
169 if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
170 if let token::Interpolated(nt) = &$self.token.kind {
171 if let token::NtTy(ty) = &**nt {
174 return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
181 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
182 if let Some(ref mut rhs) = rhs {
188 #[derive(Debug, Clone, Copy, PartialEq)]
200 // NOTE: `Ident`s are handled by `common.rs`.
203 pub struct Parser<'a> {
204 pub sess: &'a ParseSess,
205 /// The current normalized token.
206 /// "Normalized" means that some interpolated tokens
207 /// (`$i: ident` and `$l: lifetime` meta-variables) are replaced
208 /// with non-interpolated identifier and lifetime tokens they refer to.
209 /// Perhaps the normalized / non-normalized setup can be simplified somehow.
211 /// Span of the current non-normalized token.
212 meta_var_span: Option<Span>,
213 /// Span of the previous non-normalized token.
215 /// Kind of the previous normalized token (in simplified form).
216 prev_token_kind: PrevTokenKind,
217 restrictions: Restrictions,
218 /// Used to determine the path to externally loaded source files.
219 crate directory: Directory<'a>,
220 /// `true` to parse sub-modules in other files.
221 pub recurse_into_file_modules: bool,
222 /// Name of the root module this parser originated from. If `None`, then the
223 /// name is not known. This does not change while the parser is descending
224 /// into modules, and sub-parsers have new values for this name.
225 pub root_module_name: Option<String>,
226 crate expected_tokens: Vec<TokenType>,
227 crate token_cursor: TokenCursor,
228 desugar_doc_comments: bool,
229 /// `true` we should configure out of line modules as we parse.
231 /// This field is used to keep track of how many left angle brackets we have seen. This is
232 /// required in order to detect extra leading left angle brackets (`<` characters) and error
235 /// See the comments in the `parse_path_segment` function for more details.
236 crate unmatched_angle_bracket_count: u32,
237 crate max_angle_bracket_count: u32,
238 /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
239 /// it gets removed from here. Every entry left at the end gets emitted as an independent
241 crate unclosed_delims: Vec<UnmatchedBrace>,
242 crate last_unexpected_token_span: Option<Span>,
243 /// If present, this `Parser` is not parsing Rust code but rather a macro call.
244 crate subparser_name: Option<&'static str>,
247 impl<'a> Drop for Parser<'a> {
249 let diag = self.diagnostic();
250 emit_unclosed_delims(&mut self.unclosed_delims, diag);
254 // FIXME: Parser uses `self.span` all the time.
255 // Remove this impl if you think that using `self.token.span` instead is acceptable.
256 impl Deref for Parser<'_> {
258 fn deref(&self) -> &Self::Target {
264 crate struct TokenCursor {
265 crate frame: TokenCursorFrame,
266 crate stack: Vec<TokenCursorFrame>,
270 crate struct TokenCursorFrame {
271 crate delim: token::DelimToken,
272 crate span: DelimSpan,
273 crate open_delim: bool,
274 crate tree_cursor: tokenstream::Cursor,
275 crate close_delim: bool,
276 crate last_token: LastToken,
279 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
280 /// by the parser, and then that's transitively used to record the tokens that
281 /// each parse AST item is created with.
283 /// Right now this has two states, either collecting tokens or not collecting
284 /// tokens. If we're collecting tokens we just save everything off into a local
285 /// `Vec`. This should eventually though likely save tokens from the original
286 /// token stream and just use slicing of token streams to avoid creation of a
287 /// whole new vector.
289 /// The second state is where we're passively not recording tokens, but the last
290 /// token is still tracked for when we want to start recording tokens. This
291 /// "last token" means that when we start recording tokens we'll want to ensure
292 /// that this, the first token, is included in the output.
294 /// You can find some more example usage of this in the `collect_tokens` method
297 crate enum LastToken {
298 Collecting(Vec<TreeAndJoint>),
299 Was(Option<TreeAndJoint>),
302 impl TokenCursorFrame {
303 fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
307 open_delim: delim == token::NoDelim,
308 tree_cursor: tts.clone().into_trees(),
309 close_delim: delim == token::NoDelim,
310 last_token: LastToken::Was(None),
316 fn next(&mut self) -> Token {
318 let tree = if !self.frame.open_delim {
319 self.frame.open_delim = true;
320 TokenTree::open_tt(self.frame.span.open, self.frame.delim)
321 } else if let Some(tree) = self.frame.tree_cursor.next() {
323 } else if !self.frame.close_delim {
324 self.frame.close_delim = true;
325 TokenTree::close_tt(self.frame.span.close, self.frame.delim)
326 } else if let Some(frame) = self.stack.pop() {
330 return Token::new(token::Eof, DUMMY_SP);
333 match self.frame.last_token {
334 LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
335 LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
339 TokenTree::Token(token) => return token,
340 TokenTree::Delimited(sp, delim, tts) => {
341 let frame = TokenCursorFrame::new(sp, delim, &tts);
342 self.stack.push(mem::replace(&mut self.frame, frame));
348 fn next_desugared(&mut self) -> Token {
349 let (name, sp) = match self.next() {
350 Token { kind: token::DocComment(name), span } => (name, span),
354 let stripped = strip_doc_comment_decoration(&name.as_str());
356 // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
357 // required to wrap the text.
358 let mut num_of_hashes = 0;
360 for ch in stripped.chars() {
363 '#' if count > 0 => count + 1,
366 num_of_hashes = cmp::max(num_of_hashes, count);
369 let delim_span = DelimSpan::from_single(sp);
370 let body = TokenTree::Delimited(
374 TokenTree::token(token::Ident(sym::doc, false), sp),
375 TokenTree::token(token::Eq, sp),
376 TokenTree::token(TokenKind::lit(
377 token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None
380 .iter().cloned().collect::<TokenStream>().into(),
383 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
386 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
387 [TokenTree::token(token::Pound, sp), TokenTree::token(token::Not, sp), body]
388 .iter().cloned().collect::<TokenStream>().into()
390 [TokenTree::token(token::Pound, sp), body]
391 .iter().cloned().collect::<TokenStream>().into()
399 #[derive(Clone, PartialEq)]
400 crate enum TokenType {
412 crate fn to_string(&self) -> String {
414 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
415 TokenType::Keyword(kw) => format!("`{}`", kw),
416 TokenType::Operator => "an operator".to_string(),
417 TokenType::Lifetime => "lifetime".to_string(),
418 TokenType::Ident => "identifier".to_string(),
419 TokenType::Path => "path".to_string(),
420 TokenType::Type => "type".to_string(),
421 TokenType::Const => "const".to_string(),
426 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
427 /// `IDENT<<u8 as Trait>::AssocTy>`.
429 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
430 /// that `IDENT` is not the ident of a fn trait.
431 fn can_continue_type_after_non_fn_ident(t: &TokenKind) -> bool {
432 t == &token::ModSep || t == &token::Lt ||
433 t == &token::BinOp(token::Shl)
436 /// Information about the path to a module.
437 pub struct ModulePath {
440 pub result: Result<ModulePathSuccess, Error>,
443 pub struct ModulePathSuccess {
445 pub directory_ownership: DirectoryOwnership,
452 AttributesParsed(ThinVec<Attribute>),
453 AlreadyParsed(P<Expr>),
456 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
457 fn from(o: Option<ThinVec<Attribute>>) -> Self {
458 if let Some(attrs) = o {
459 LhsExpr::AttributesParsed(attrs)
461 LhsExpr::NotYetParsed
466 impl From<P<Expr>> for LhsExpr {
467 fn from(expr: P<Expr>) -> Self {
468 LhsExpr::AlreadyParsed(expr)
472 #[derive(Copy, Clone, Debug)]
473 crate enum TokenExpectType {
478 impl<'a> Parser<'a> {
482 directory: Option<Directory<'a>>,
483 recurse_into_file_modules: bool,
484 desugar_doc_comments: bool,
485 subparser_name: Option<&'static str>,
487 let mut parser = Parser {
489 token: Token::dummy(),
492 prev_token_kind: PrevTokenKind::Other,
493 restrictions: Restrictions::empty(),
494 recurse_into_file_modules,
495 directory: Directory {
496 path: Cow::from(PathBuf::new()),
497 ownership: DirectoryOwnership::Owned { relative: None }
499 root_module_name: None,
500 expected_tokens: Vec::new(),
501 token_cursor: TokenCursor {
502 frame: TokenCursorFrame::new(
509 desugar_doc_comments,
511 unmatched_angle_bracket_count: 0,
512 max_angle_bracket_count: 0,
513 unclosed_delims: Vec::new(),
514 last_unexpected_token_span: None,
518 parser.token = parser.next_tok();
520 if let Some(directory) = directory {
521 parser.directory = directory;
522 } else if !parser.token.span.is_dummy() {
523 if let FileName::Real(mut path) =
524 sess.source_map().span_to_unmapped_path(parser.token.span) {
526 parser.directory.path = Cow::from(path);
530 parser.process_potential_macro_variable();
534 fn next_tok(&mut self) -> Token {
535 let mut next = if self.desugar_doc_comments {
536 self.token_cursor.next_desugared()
538 self.token_cursor.next()
540 if next.span.is_dummy() {
541 // Tweak the location for better diagnostics, but keep syntactic context intact.
542 next.span = self.prev_span.with_ctxt(next.span.ctxt());
547 /// Converts the current token to a string using `self`'s reader.
548 pub fn this_token_to_string(&self) -> String {
549 pprust::token_to_string(&self.token)
552 crate fn token_descr(&self) -> Option<&'static str> {
553 Some(match &self.token.kind {
554 _ if self.token.is_special_ident() => "reserved identifier",
555 _ if self.token.is_used_keyword() => "keyword",
556 _ if self.token.is_unused_keyword() => "reserved keyword",
557 token::DocComment(..) => "doc comment",
562 crate fn this_token_descr(&self) -> String {
563 if let Some(prefix) = self.token_descr() {
564 format!("{} `{}`", prefix, self.this_token_to_string())
566 format!("`{}`", self.this_token_to_string())
570 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
571 match self.expect_one_of(&[], &[]) {
573 Ok(_) => unreachable!(),
577 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
578 pub fn expect(&mut self, t: &TokenKind) -> PResult<'a, bool /* recovered */> {
579 if self.expected_tokens.is_empty() {
580 if self.token == *t {
584 self.unexpected_try_recover(t)
587 self.expect_one_of(slice::from_ref(t), &[])
591 /// Expect next token to be edible or inedible token. If edible,
592 /// then consume it; if inedible, then return without consuming
593 /// anything. Signal a fatal error if next token is unexpected.
594 pub fn expect_one_of(
596 edible: &[TokenKind],
597 inedible: &[TokenKind],
598 ) -> PResult<'a, bool /* recovered */> {
599 if edible.contains(&self.token) {
602 } else if inedible.contains(&self.token) {
603 // leave it in the input
605 } else if self.last_unexpected_token_span == Some(self.token.span) {
608 self.expected_one_of_not_found(edible, inedible)
612 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
613 fn interpolated_or_expr_span(
615 expr: PResult<'a, P<Expr>>,
616 ) -> PResult<'a, (Span, P<Expr>)> {
618 if self.prev_token_kind == PrevTokenKind::Interpolated {
626 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
627 self.parse_ident_common(true)
630 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
631 match self.token.kind {
632 token::Ident(name, _) => {
633 if self.token.is_reserved_ident() {
634 let mut err = self.expected_ident_found();
641 let span = self.token.span;
643 Ok(Ident::new(name, span))
646 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
647 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
649 self.expected_ident_found()
655 /// Checks if the next token is `tok`, and returns `true` if so.
657 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
659 crate fn check(&mut self, tok: &TokenKind) -> bool {
660 let is_present = self.token == *tok;
661 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
665 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
666 pub fn eat(&mut self, tok: &TokenKind) -> bool {
667 let is_present = self.check(tok);
668 if is_present { self.bump() }
672 fn check_keyword(&mut self, kw: Symbol) -> bool {
673 self.expected_tokens.push(TokenType::Keyword(kw));
674 self.token.is_keyword(kw)
677 /// If the next token is the given keyword, eats it and returns
678 /// `true`. Otherwise, returns `false`.
679 pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
680 if self.check_keyword(kw) {
688 fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
689 if self.token.is_keyword(kw) {
697 /// If the given word is not a keyword, signals an error.
698 /// If the next token is not the given word, signals an error.
699 /// Otherwise, eats it.
700 fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
701 if !self.eat_keyword(kw) {
708 crate fn check_ident(&mut self) -> bool {
709 if self.token.is_ident() {
712 self.expected_tokens.push(TokenType::Ident);
717 fn check_path(&mut self) -> bool {
718 if self.token.is_path_start() {
721 self.expected_tokens.push(TokenType::Path);
726 fn check_type(&mut self) -> bool {
727 if self.token.can_begin_type() {
730 self.expected_tokens.push(TokenType::Type);
735 fn check_const_arg(&mut self) -> bool {
736 if self.token.can_begin_const_arg() {
739 self.expected_tokens.push(TokenType::Const);
744 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
745 /// and continues. If a `+` is not seen, returns `false`.
747 /// This is used when token-splitting `+=` into `+`.
748 /// See issue #47856 for an example of when this may occur.
749 fn eat_plus(&mut self) -> bool {
750 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
751 match self.token.kind {
752 token::BinOp(token::Plus) => {
756 token::BinOpEq(token::Plus) => {
757 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
758 self.bump_with(token::Eq, span);
766 /// Checks to see if the next token is either `+` or `+=`.
767 /// Otherwise returns `false`.
768 fn check_plus(&mut self) -> bool {
769 if self.token.is_like_plus() {
773 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
778 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
779 /// `&` and continues. If an `&` is not seen, signals an error.
780 fn expect_and(&mut self) -> PResult<'a, ()> {
781 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
782 match self.token.kind {
783 token::BinOp(token::And) => {
788 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
789 Ok(self.bump_with(token::BinOp(token::And), span))
791 _ => self.unexpected()
795 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
796 /// `|` and continues. If an `|` is not seen, signals an error.
797 fn expect_or(&mut self) -> PResult<'a, ()> {
798 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
799 match self.token.kind {
800 token::BinOp(token::Or) => {
805 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
806 Ok(self.bump_with(token::BinOp(token::Or), span))
808 _ => self.unexpected()
812 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
813 literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
816 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
817 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
818 /// and continue. If a `<` is not seen, returns false.
820 /// This is meant to be used when parsing generics on a path to get the
822 fn eat_lt(&mut self) -> bool {
823 self.expected_tokens.push(TokenType::Token(token::Lt));
824 let ate = match self.token.kind {
829 token::BinOp(token::Shl) => {
830 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
831 self.bump_with(token::Lt, span);
835 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
836 self.bump_with(token::BinOp(token::Minus), span);
843 // See doc comment for `unmatched_angle_bracket_count`.
844 self.unmatched_angle_bracket_count += 1;
845 self.max_angle_bracket_count += 1;
846 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
852 fn expect_lt(&mut self) -> PResult<'a, ()> {
860 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
861 /// with a single `>` and continues. If a `>` is not seen, signals an error.
862 fn expect_gt(&mut self) -> PResult<'a, ()> {
863 self.expected_tokens.push(TokenType::Token(token::Gt));
864 let ate = match self.token.kind {
869 token::BinOp(token::Shr) => {
870 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
871 Some(self.bump_with(token::Gt, span))
873 token::BinOpEq(token::Shr) => {
874 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
875 Some(self.bump_with(token::Ge, span))
878 let span = self.token.span.with_lo(self.token.span.lo() + BytePos(1));
879 Some(self.bump_with(token::Eq, span))
886 // See doc comment for `unmatched_angle_bracket_count`.
887 if self.unmatched_angle_bracket_count > 0 {
888 self.unmatched_angle_bracket_count -= 1;
889 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
894 None => self.unexpected(),
898 /// Parses a sequence, including the closing delimiter. The function
899 /// `f` must consume tokens until reaching the next separator or
901 pub fn parse_seq_to_end<T, F>(&mut self,
905 -> PResult<'a, Vec<T>> where
906 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
908 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
915 /// Parses a sequence, not including the closing delimiter. The function
916 /// `f` must consume tokens until reaching the next separator or
918 pub fn parse_seq_to_before_end<T, F>(
923 ) -> PResult<'a, (Vec<T>, bool)>
924 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
926 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
929 crate fn parse_seq_to_before_tokens<T, F>(
933 expect: TokenExpectType,
935 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
936 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
938 let mut first = true;
939 let mut recovered = false;
941 while !kets.iter().any(|k| {
943 TokenExpectType::Expect => self.check(k),
944 TokenExpectType::NoExpect => self.token == **k,
947 match self.token.kind {
948 token::CloseDelim(..) | token::Eof => break,
951 if let Some(ref t) = sep.sep {
955 match self.expect(t) {
962 // Attempt to keep parsing if it was a similar separator
963 if let Some(ref tokens) = t.similar_tokens() {
964 if tokens.contains(&self.token) {
969 // Attempt to keep parsing if it was an omitted separator
984 if sep.trailing_sep_allowed && kets.iter().any(|k| {
986 TokenExpectType::Expect => self.check(k),
987 TokenExpectType::NoExpect => self.token == **k,
1000 /// Parses a sequence, including the closing delimiter. The function
1001 /// `f` must consume tokens until reaching the next separator or
1002 /// closing bracket.
1003 fn parse_unspanned_seq<T, F>(
1009 ) -> PResult<'a, Vec<T>> where
1010 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1013 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1020 /// Advance the parser by one token
1021 pub fn bump(&mut self) {
1022 if self.prev_token_kind == PrevTokenKind::Eof {
1023 // Bumping after EOF is a bad sign, usually an infinite loop.
1024 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1027 self.prev_span = self.meta_var_span.take().unwrap_or(self.token.span);
1029 // Record last token kind for possible error recovery.
1030 self.prev_token_kind = match self.token.kind {
1031 token::DocComment(..) => PrevTokenKind::DocComment,
1032 token::Comma => PrevTokenKind::Comma,
1033 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1034 token::BinOp(token::Or) => PrevTokenKind::BitOr,
1035 token::Interpolated(..) => PrevTokenKind::Interpolated,
1036 token::Eof => PrevTokenKind::Eof,
1037 token::Ident(..) => PrevTokenKind::Ident,
1038 _ => PrevTokenKind::Other,
1041 self.token = self.next_tok();
1042 self.expected_tokens.clear();
1043 // check after each token
1044 self.process_potential_macro_variable();
1047 /// Advance the parser using provided token as a next one. Use this when
1048 /// consuming a part of a token. For example a single `<` from `<<`.
1049 fn bump_with(&mut self, next: TokenKind, span: Span) {
1050 self.prev_span = self.token.span.with_hi(span.lo());
1051 // It would be incorrect to record the kind of the current token, but
1052 // fortunately for tokens currently using `bump_with`, the
1053 // prev_token_kind will be of no use anyway.
1054 self.prev_token_kind = PrevTokenKind::Other;
1055 self.token = Token::new(next, span);
1056 self.expected_tokens.clear();
1059 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1060 F: FnOnce(&Token) -> R,
1063 return f(&self.token);
1066 let frame = &self.token_cursor.frame;
1067 f(&match frame.tree_cursor.look_ahead(dist - 1) {
1068 Some(tree) => match tree {
1069 TokenTree::Token(token) => token,
1070 TokenTree::Delimited(dspan, delim, _) =>
1071 Token::new(token::OpenDelim(delim), dspan.open),
1073 None => Token::new(token::CloseDelim(frame.delim), frame.span.close)
1077 crate fn look_ahead_span(&self, dist: usize) -> Span {
1079 return self.token.span
1082 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1083 Some(TokenTree::Token(token)) => token.span,
1084 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1085 None => self.look_ahead_span(dist - 1),
1089 /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
1090 fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
1091 self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
1094 /// Is the current token one of the keywords that signals a bare function type?
1095 fn token_is_bare_fn_keyword(&mut self) -> bool {
1096 self.check_keyword(kw::Fn) ||
1097 self.check_keyword(kw::Unsafe) ||
1098 self.check_keyword(kw::Extern)
1101 /// Parses a `TyKind::BareFn` type.
1102 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1105 [unsafe] [extern "ABI"] fn (S) -> T
1115 let unsafety = self.parse_unsafety();
1116 let abi = if self.eat_keyword(kw::Extern) {
1117 self.parse_opt_abi()?.unwrap_or(Abi::C)
1122 self.expect_keyword(kw::Fn)?;
1123 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1124 let ret_ty = self.parse_ret_ty(false)?;
1125 let decl = P(FnDecl {
1130 Ok(TyKind::BareFn(P(BareFnTy {
1138 /// Parses asyncness: `async` or nothing.
1139 fn parse_asyncness(&mut self) -> IsAsync {
1140 if self.eat_keyword(kw::Async) {
1142 closure_id: ast::DUMMY_NODE_ID,
1143 return_impl_trait_id: ast::DUMMY_NODE_ID,
1150 /// Parses unsafety: `unsafe` or nothing.
1151 fn parse_unsafety(&mut self) -> Unsafety {
1152 if self.eat_keyword(kw::Unsafe) {
1159 /// Parses the items in a trait declaration.
1160 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1161 maybe_whole!(self, NtTraitItem, |x| x);
1162 let attrs = self.parse_outer_attributes()?;
1163 let mut unclosed_delims = vec![];
1164 let (mut item, tokens) = self.collect_tokens(|this| {
1165 let item = this.parse_trait_item_(at_end, attrs);
1166 unclosed_delims.append(&mut this.unclosed_delims);
1169 self.unclosed_delims.append(&mut unclosed_delims);
1170 // See `parse_item` for why this clause is here.
1171 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1172 item.tokens = Some(tokens);
1177 fn parse_trait_item_(&mut self,
1179 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1180 let lo = self.token.span;
1182 let (name, node, generics) = if self.eat_keyword(kw::Type) {
1183 self.parse_trait_item_assoc_ty()?
1184 } else if self.is_const_item() {
1185 self.expect_keyword(kw::Const)?;
1186 let ident = self.parse_ident()?;
1187 self.expect(&token::Colon)?;
1188 let ty = self.parse_ty()?;
1189 let default = if self.eat(&token::Eq) {
1190 let expr = self.parse_expr()?;
1191 self.expect(&token::Semi)?;
1194 self.expect(&token::Semi)?;
1197 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1198 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1199 // trait item macro.
1200 (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1202 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
1204 let ident = self.parse_ident()?;
1205 let mut generics = self.parse_generics()?;
1207 let decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1208 // This is somewhat dubious; We don't want to allow
1209 // argument names to be left off if there is a
1212 // We don't allow argument names to be left off in edition 2018.
1213 p.parse_arg_general(p.token.span.rust_2018(), true, false)
1215 generics.where_clause = self.parse_where_clause()?;
1217 let sig = ast::MethodSig {
1227 let body = match self.token.kind {
1231 debug!("parse_trait_methods(): parsing required method");
1234 token::OpenDelim(token::Brace) => {
1235 debug!("parse_trait_methods(): parsing provided method");
1237 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1238 attrs.extend(inner_attrs.iter().cloned());
1241 token::Interpolated(ref nt) => {
1243 token::NtBlock(..) => {
1245 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1246 attrs.extend(inner_attrs.iter().cloned());
1250 return self.expected_semi_or_open_brace();
1255 return self.expected_semi_or_open_brace();
1258 (ident, ast::TraitItemKind::Method(sig, body), generics)
1262 id: ast::DUMMY_NODE_ID,
1267 span: lo.to(self.prev_span),
1272 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1273 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1274 if self.eat(&token::RArrow) {
1275 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1277 Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
1282 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1283 self.parse_ty_common(true, true, false)
1286 /// Parses a type in restricted contexts where `+` is not permitted.
1288 /// Example 1: `&'a TYPE`
1289 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1290 /// Example 2: `value1 as TYPE + value2`
1291 /// `+` is prohibited to avoid interactions with expression grammar.
1292 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1293 self.parse_ty_common(false, true, false)
1296 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1297 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1298 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1299 maybe_whole!(self, NtTy, |x| x);
1301 let lo = self.token.span;
1302 let mut impl_dyn_multi = false;
1303 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1304 // `(TYPE)` is a parenthesized type.
1305 // `(TYPE,)` is a tuple with a single field of type TYPE.
1306 let mut ts = vec![];
1307 let mut last_comma = false;
1308 while self.token != token::CloseDelim(token::Paren) {
1309 ts.push(self.parse_ty()?);
1310 if self.eat(&token::Comma) {
1317 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1318 self.expect(&token::CloseDelim(token::Paren))?;
1320 if ts.len() == 1 && !last_comma {
1321 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1322 let maybe_bounds = allow_plus && self.token.is_like_plus();
1324 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1325 TyKind::Path(None, ref path) if maybe_bounds => {
1326 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1328 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1329 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1330 let path = match bounds[0] {
1331 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1332 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1334 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1337 _ => TyKind::Paren(P(ty))
1342 } else if self.eat(&token::Not) {
1345 } else if self.eat(&token::BinOp(token::Star)) {
1347 TyKind::Ptr(self.parse_ptr()?)
1348 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1350 let t = self.parse_ty()?;
1351 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1352 let t = match self.maybe_parse_fixed_length_of_vec()? {
1353 None => TyKind::Slice(t),
1354 Some(length) => TyKind::Array(t, AnonConst {
1355 id: ast::DUMMY_NODE_ID,
1359 self.expect(&token::CloseDelim(token::Bracket))?;
1361 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1364 self.parse_borrowed_pointee()?
1365 } else if self.eat_keyword_noexpect(kw::Typeof) {
1367 // In order to not be ambiguous, the type must be surrounded by parens.
1368 self.expect(&token::OpenDelim(token::Paren))?;
1370 id: ast::DUMMY_NODE_ID,
1371 value: self.parse_expr()?,
1373 self.expect(&token::CloseDelim(token::Paren))?;
1375 } else if self.eat_keyword(kw::Underscore) {
1376 // A type to be inferred `_`
1378 } else if self.token_is_bare_fn_keyword() {
1379 // Function pointer type
1380 self.parse_ty_bare_fn(Vec::new())?
1381 } else if self.check_keyword(kw::For) {
1382 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1383 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1384 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1385 let lo = self.token.span;
1386 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1387 if self.token_is_bare_fn_keyword() {
1388 self.parse_ty_bare_fn(lifetime_defs)?
1390 let path = self.parse_path(PathStyle::Type)?;
1391 let parse_plus = allow_plus && self.check_plus();
1392 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1394 } else if self.eat_keyword(kw::Impl) {
1395 // Always parse bounds greedily for better error recovery.
1396 let bounds = self.parse_generic_bounds(None)?;
1397 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1398 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1399 } else if self.check_keyword(kw::Dyn) &&
1400 (self.token.span.rust_2018() ||
1401 self.look_ahead(1, |t| t.can_begin_bound() &&
1402 !can_continue_type_after_non_fn_ident(t))) {
1403 self.bump(); // `dyn`
1404 // Always parse bounds greedily for better error recovery.
1405 let bounds = self.parse_generic_bounds(None)?;
1406 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1407 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1408 } else if self.check(&token::Question) ||
1409 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1410 // Bound list (trait object type)
1411 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1412 TraitObjectSyntax::None)
1413 } else if self.eat_lt() {
1415 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1416 TyKind::Path(Some(qself), path)
1417 } else if self.token.is_path_start() {
1419 let path = self.parse_path(PathStyle::Type)?;
1420 if self.eat(&token::Not) {
1421 // Macro invocation in type position
1422 let (delim, tts) = self.expect_delimited_token_tree()?;
1423 let node = Mac_ { path, tts, delim };
1424 TyKind::Mac(respan(lo.to(self.prev_span), node))
1426 // Just a type path or bound list (trait object type) starting with a trait.
1428 // `Trait1 + Trait2 + 'a`
1429 if allow_plus && self.check_plus() {
1430 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1432 TyKind::Path(None, path)
1435 } else if self.check(&token::DotDotDot) {
1436 if allow_c_variadic {
1437 self.eat(&token::DotDotDot);
1440 return Err(self.fatal(
1441 "only foreign functions are allowed to be C-variadic"
1445 let msg = format!("expected type, found {}", self.this_token_descr());
1446 return Err(self.fatal(&msg));
1449 let span = lo.to(self.prev_span);
1450 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1452 // Try to recover from use of `+` with incorrect priority.
1453 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1454 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1455 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1458 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1459 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1460 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1461 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1463 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1464 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1466 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1469 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1470 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1471 let mutbl = self.parse_mutability();
1472 let ty = self.parse_ty_no_plus()?;
1473 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1476 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1477 let mutbl = if self.eat_keyword(kw::Mut) {
1479 } else if self.eat_keyword(kw::Const) {
1480 Mutability::Immutable
1482 let span = self.prev_span;
1483 let msg = "expected mut or const in raw pointer type";
1484 self.struct_span_err(span, msg)
1485 .span_label(span, msg)
1486 .help("use `*mut T` or `*const T` as appropriate")
1488 Mutability::Immutable
1490 let t = self.parse_ty_no_plus()?;
1491 Ok(MutTy { ty: t, mutbl: mutbl })
1494 fn is_named_argument(&self) -> bool {
1495 let offset = match self.token.kind {
1496 token::Interpolated(ref nt) => match **nt {
1497 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1500 token::BinOp(token::And) | token::AndAnd => 1,
1501 _ if self.token.is_keyword(kw::Mut) => 1,
1505 self.look_ahead(offset, |t| t.is_ident()) &&
1506 self.look_ahead(offset + 1, |t| t == &token::Colon)
1509 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1511 /// This version of parse arg doesn't necessarily require identifier names.
1512 fn parse_arg_general(
1515 is_trait_item: bool,
1516 allow_c_variadic: bool,
1517 ) -> PResult<'a, Arg> {
1518 if let Ok(Some(arg)) = self.parse_self_arg() {
1519 return self.recover_bad_self_arg(arg, is_trait_item);
1522 let (pat, ty) = if require_name || self.is_named_argument() {
1523 debug!("parse_arg_general parse_pat (require_name:{})", require_name);
1524 self.eat_incorrect_doc_comment("method arguments");
1525 let pat = self.parse_pat(Some("argument name"))?;
1527 if let Err(mut err) = self.expect(&token::Colon) {
1528 if let Some(ident) = self.argument_without_type(
1535 return Ok(dummy_arg(ident));
1541 self.eat_incorrect_doc_comment("a method argument's type");
1542 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1544 debug!("parse_arg_general ident_to_pat");
1545 let parser_snapshot_before_ty = self.clone();
1546 self.eat_incorrect_doc_comment("a method argument's type");
1547 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1548 if ty.is_ok() && self.token != token::Comma &&
1549 self.token != token::CloseDelim(token::Paren) {
1550 // This wasn't actually a type, but a pattern looking like a type,
1551 // so we are going to rollback and re-parse for recovery.
1552 ty = self.unexpected();
1556 let ident = Ident::new(kw::Invalid, self.prev_span);
1558 id: ast::DUMMY_NODE_ID,
1559 node: PatKind::Ident(
1560 BindingMode::ByValue(Mutability::Immutable), ident, None),
1566 // If this is a C-variadic argument and we hit an error, return the
1568 if self.token == token::DotDotDot {
1571 // Recover from attempting to parse the argument as a type without pattern.
1573 mem::replace(self, parser_snapshot_before_ty);
1574 self.recover_arg_parse()?
1579 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
1582 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1583 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1584 let pat = self.parse_pat(Some("argument name"))?;
1585 let t = if self.eat(&token::Colon) {
1589 id: ast::DUMMY_NODE_ID,
1590 node: TyKind::Infer,
1591 span: self.prev_span,
1597 id: ast::DUMMY_NODE_ID
1601 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1602 if self.eat(&token::Semi) {
1603 Ok(Some(self.parse_expr()?))
1609 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1610 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1611 maybe_whole_expr!(self);
1613 let minus_lo = self.token.span;
1614 let minus_present = self.eat(&token::BinOp(token::Minus));
1615 let lo = self.token.span;
1616 let literal = self.parse_lit()?;
1617 let hi = self.prev_span;
1618 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1621 let minus_hi = self.prev_span;
1622 let unary = self.mk_unary(UnOp::Neg, expr);
1623 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1629 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
1630 match self.token.kind {
1631 token::Ident(name, _) if name.is_path_segment_keyword() => {
1632 let span = self.token.span;
1634 Ok(Ident::new(name, span))
1636 _ => self.parse_ident(),
1640 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
1641 match self.token.kind {
1642 token::Ident(name, false) if name == kw::Underscore => {
1643 let span = self.token.span;
1645 Ok(Ident::new(name, span))
1647 _ => self.parse_ident(),
1651 /// Parses a qualified path.
1652 /// Assumes that the leading `<` has been parsed already.
1654 /// `qualified_path = <type [as trait_ref]>::path`
1659 /// `<T as U>::F::a<S>` (without disambiguator)
1660 /// `<T as U>::F::a::<S>` (with disambiguator)
1661 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
1662 let lo = self.prev_span;
1663 let ty = self.parse_ty()?;
1665 // `path` will contain the prefix of the path up to the `>`,
1666 // if any (e.g., `U` in the `<T as U>::*` examples
1667 // above). `path_span` has the span of that path, or an empty
1668 // span in the case of something like `<T>::Bar`.
1669 let (mut path, path_span);
1670 if self.eat_keyword(kw::As) {
1671 let path_lo = self.token.span;
1672 path = self.parse_path(PathStyle::Type)?;
1673 path_span = path_lo.to(self.prev_span);
1675 path_span = self.token.span.to(self.token.span);
1676 path = ast::Path { segments: Vec::new(), span: path_span };
1679 // See doc comment for `unmatched_angle_bracket_count`.
1680 self.expect(&token::Gt)?;
1681 if self.unmatched_angle_bracket_count > 0 {
1682 self.unmatched_angle_bracket_count -= 1;
1683 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1686 self.expect(&token::ModSep)?;
1688 let qself = QSelf { ty, path_span, position: path.segments.len() };
1689 self.parse_path_segments(&mut path.segments, style)?;
1691 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
1694 /// Parses simple paths.
1696 /// `path = [::] segment+`
1697 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
1700 /// `a::b::C<D>` (without disambiguator)
1701 /// `a::b::C::<D>` (with disambiguator)
1702 /// `Fn(Args)` (without disambiguator)
1703 /// `Fn::(Args)` (with disambiguator)
1704 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1705 maybe_whole!(self, NtPath, |path| {
1706 if style == PathStyle::Mod &&
1707 path.segments.iter().any(|segment| segment.args.is_some()) {
1708 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
1713 let lo = self.meta_var_span.unwrap_or(self.token.span);
1714 let mut segments = Vec::new();
1715 let mod_sep_ctxt = self.token.span.ctxt();
1716 if self.eat(&token::ModSep) {
1717 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
1719 self.parse_path_segments(&mut segments, style)?;
1721 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
1724 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
1725 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
1727 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1728 let meta_ident = match self.token.kind {
1729 token::Interpolated(ref nt) => match **nt {
1730 token::NtMeta(ref meta) => match meta.node {
1731 ast::MetaItemKind::Word => Some(meta.path.clone()),
1738 if let Some(path) = meta_ident {
1742 self.parse_path(style)
1745 crate fn parse_path_segments(&mut self,
1746 segments: &mut Vec<PathSegment>,
1748 -> PResult<'a, ()> {
1750 let segment = self.parse_path_segment(style)?;
1751 if style == PathStyle::Expr {
1752 // In order to check for trailing angle brackets, we must have finished
1753 // recursing (`parse_path_segment` can indirectly call this function),
1754 // that is, the next token must be the highlighted part of the below example:
1756 // `Foo::<Bar as Baz<T>>::Qux`
1759 // As opposed to the below highlight (if we had only finished the first
1762 // `Foo::<Bar as Baz<T>>::Qux`
1765 // `PathStyle::Expr` is only provided at the root invocation and never in
1766 // `parse_path_segment` to recurse and therefore can be checked to maintain
1768 self.check_trailing_angle_brackets(&segment, token::ModSep);
1770 segments.push(segment);
1772 if self.is_import_coupler() || !self.eat(&token::ModSep) {
1778 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
1779 let ident = self.parse_path_segment_ident()?;
1781 let is_args_start = |token: &TokenKind| match *token {
1782 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
1783 | token::LArrow => true,
1786 let check_args_start = |this: &mut Self| {
1787 this.expected_tokens.extend_from_slice(
1788 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
1790 is_args_start(&this.token)
1793 Ok(if style == PathStyle::Type && check_args_start(self) ||
1794 style != PathStyle::Mod && self.check(&token::ModSep)
1795 && self.look_ahead(1, |t| is_args_start(t)) {
1796 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
1797 // it isn't, then we reset the unmatched angle bracket count as we're about to start
1798 // parsing a new path.
1799 if style == PathStyle::Expr {
1800 self.unmatched_angle_bracket_count = 0;
1801 self.max_angle_bracket_count = 0;
1804 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
1805 self.eat(&token::ModSep);
1806 let lo = self.token.span;
1807 let args = if self.eat_lt() {
1809 let (args, constraints) =
1810 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
1812 let span = lo.to(self.prev_span);
1813 AngleBracketedArgs { args, constraints, span }.into()
1817 let (inputs, recovered) = self.parse_seq_to_before_tokens(
1818 &[&token::CloseDelim(token::Paren)],
1819 SeqSep::trailing_allowed(token::Comma),
1820 TokenExpectType::Expect,
1825 let span = lo.to(self.prev_span);
1826 let output = if self.eat(&token::RArrow) {
1827 Some(self.parse_ty_common(false, false, false)?)
1831 ParenthesizedArgs { inputs, output, span }.into()
1834 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
1836 // Generic arguments are not found.
1837 PathSegment::from_ident(ident)
1841 crate fn check_lifetime(&mut self) -> bool {
1842 self.expected_tokens.push(TokenType::Lifetime);
1843 self.token.is_lifetime()
1846 /// Parses a single lifetime `'a` or panics.
1847 crate fn expect_lifetime(&mut self) -> Lifetime {
1848 if let Some(ident) = self.token.lifetime() {
1849 let span = self.token.span;
1851 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
1853 self.span_bug(self.token.span, "not a lifetime")
1857 fn eat_label(&mut self) -> Option<Label> {
1858 if let Some(ident) = self.token.lifetime() {
1859 let span = self.token.span;
1861 Some(Label { ident: Ident::new(ident.name, span) })
1867 /// Parses mutability (`mut` or nothing).
1868 fn parse_mutability(&mut self) -> Mutability {
1869 if self.eat_keyword(kw::Mut) {
1872 Mutability::Immutable
1876 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
1877 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) =
1879 self.expect_no_suffix(self.token.span, "a tuple index", suffix);
1881 Ok(Ident::new(symbol, self.prev_span))
1883 self.parse_ident_common(false)
1887 /// Parse ident (COLON expr)?
1888 fn parse_field(&mut self) -> PResult<'a, Field> {
1889 let attrs = self.parse_outer_attributes()?;
1890 let lo = self.token.span;
1892 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1893 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
1894 t == &token::Colon || t == &token::Eq
1896 let fieldname = self.parse_field_name()?;
1898 // Check for an equals token. This means the source incorrectly attempts to
1899 // initialize a field with an eq rather than a colon.
1900 if self.token == token::Eq {
1902 .struct_span_err(self.token.span, "expected `:`, found `=`")
1904 fieldname.span.shrink_to_hi().to(self.token.span),
1905 "replace equals symbol with a colon",
1907 Applicability::MachineApplicable,
1912 (fieldname, self.parse_expr()?, false)
1914 let fieldname = self.parse_ident_common(false)?;
1916 // Mimic `x: x` for the `x` field shorthand.
1917 let path = ast::Path::from_ident(fieldname);
1918 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
1919 (fieldname, expr, true)
1923 span: lo.to(expr.span),
1926 attrs: attrs.into(),
1930 crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
1931 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
1934 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
1935 ExprKind::Unary(unop, expr)
1938 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1939 ExprKind::Binary(binop, lhs, rhs)
1942 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
1943 ExprKind::Call(f, args)
1946 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
1947 ExprKind::Index(expr, idx)
1951 start: Option<P<Expr>>,
1952 end: Option<P<Expr>>,
1953 limits: RangeLimits)
1954 -> PResult<'a, ast::ExprKind> {
1955 if end.is_none() && limits == RangeLimits::Closed {
1956 Err(self.span_fatal_err(self.token.span, Error::InclusiveRangeWithNoEnd))
1958 Ok(ExprKind::Range(start, end, limits))
1962 fn mk_assign_op(&self, binop: ast::BinOp,
1963 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1964 ExprKind::AssignOp(binop, lhs, rhs)
1967 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
1968 let delim = match self.token.kind {
1969 token::OpenDelim(delim) => delim,
1971 let msg = "expected open delimiter";
1972 let mut err = self.fatal(msg);
1973 err.span_label(self.token.span, msg);
1977 let tts = match self.parse_token_tree() {
1978 TokenTree::Delimited(_, _, tts) => tts,
1979 _ => unreachable!(),
1981 let delim = match delim {
1982 token::Paren => MacDelimiter::Parenthesis,
1983 token::Bracket => MacDelimiter::Bracket,
1984 token::Brace => MacDelimiter::Brace,
1985 token::NoDelim => self.bug("unexpected no delimiter"),
1987 Ok((delim, tts.into()))
1990 /// At the bottom (top?) of the precedence hierarchy,
1991 /// Parses things like parenthesized exprs, macros, `return`, etc.
1993 /// N.B., this does not parse outer attributes, and is private because it only works
1994 /// correctly if called from `parse_dot_or_call_expr()`.
1995 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1996 maybe_recover_from_interpolated_ty_qpath!(self, true);
1997 maybe_whole_expr!(self);
1999 // Outer attributes are already parsed and will be
2000 // added to the return value after the fact.
2002 // Therefore, prevent sub-parser from parsing
2003 // attributes by giving them a empty "already parsed" list.
2004 let mut attrs = ThinVec::new();
2006 let lo = self.token.span;
2007 let mut hi = self.token.span;
2011 // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
2012 match self.token.kind {
2013 token::OpenDelim(token::Paren) => {
2016 attrs.extend(self.parse_inner_attributes()?);
2018 // (e) is parenthesized e
2019 // (e,) is a tuple with only one field, e
2020 let mut es = vec![];
2021 let mut trailing_comma = false;
2022 let mut recovered = false;
2023 while self.token != token::CloseDelim(token::Paren) {
2024 es.push(match self.parse_expr() {
2027 // recover from parse error in tuple list
2028 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2031 recovered = self.expect_one_of(
2033 &[token::Comma, token::CloseDelim(token::Paren)],
2035 if self.eat(&token::Comma) {
2036 trailing_comma = true;
2038 trailing_comma = false;
2046 hi = self.prev_span;
2047 ex = if es.len() == 1 && !trailing_comma {
2048 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2053 token::OpenDelim(token::Brace) => {
2054 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2056 token::BinOp(token::Or) | token::OrOr => {
2057 return self.parse_lambda_expr(attrs);
2059 token::OpenDelim(token::Bracket) => {
2062 attrs.extend(self.parse_inner_attributes()?);
2064 if self.eat(&token::CloseDelim(token::Bracket)) {
2066 ex = ExprKind::Array(Vec::new());
2069 let first_expr = self.parse_expr()?;
2070 if self.eat(&token::Semi) {
2071 // Repeating array syntax: [ 0; 512 ]
2072 let count = AnonConst {
2073 id: ast::DUMMY_NODE_ID,
2074 value: self.parse_expr()?,
2076 self.expect(&token::CloseDelim(token::Bracket))?;
2077 ex = ExprKind::Repeat(first_expr, count);
2078 } else if self.eat(&token::Comma) {
2079 // Vector with two or more elements.
2080 let remaining_exprs = self.parse_seq_to_end(
2081 &token::CloseDelim(token::Bracket),
2082 SeqSep::trailing_allowed(token::Comma),
2083 |p| Ok(p.parse_expr()?)
2085 let mut exprs = vec![first_expr];
2086 exprs.extend(remaining_exprs);
2087 ex = ExprKind::Array(exprs);
2089 // Vector with one element.
2090 self.expect(&token::CloseDelim(token::Bracket))?;
2091 ex = ExprKind::Array(vec![first_expr]);
2094 hi = self.prev_span;
2098 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2100 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2102 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
2103 return self.parse_lambda_expr(attrs);
2105 if self.eat_keyword(kw::If) {
2106 return self.parse_if_expr(attrs);
2108 if self.eat_keyword(kw::For) {
2109 let lo = self.prev_span;
2110 return self.parse_for_expr(None, lo, attrs);
2112 if self.eat_keyword(kw::While) {
2113 let lo = self.prev_span;
2114 return self.parse_while_expr(None, lo, attrs);
2116 if let Some(label) = self.eat_label() {
2117 let lo = label.ident.span;
2118 self.expect(&token::Colon)?;
2119 if self.eat_keyword(kw::While) {
2120 return self.parse_while_expr(Some(label), lo, attrs)
2122 if self.eat_keyword(kw::For) {
2123 return self.parse_for_expr(Some(label), lo, attrs)
2125 if self.eat_keyword(kw::Loop) {
2126 return self.parse_loop_expr(Some(label), lo, attrs)
2128 if self.token == token::OpenDelim(token::Brace) {
2129 return self.parse_block_expr(Some(label),
2131 BlockCheckMode::Default,
2134 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2135 let mut err = self.fatal(msg);
2136 err.span_label(self.token.span, msg);
2139 if self.eat_keyword(kw::Loop) {
2140 let lo = self.prev_span;
2141 return self.parse_loop_expr(None, lo, attrs);
2143 if self.eat_keyword(kw::Continue) {
2144 let label = self.eat_label();
2145 let ex = ExprKind::Continue(label);
2146 let hi = self.prev_span;
2147 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2149 if self.eat_keyword(kw::Match) {
2150 let match_sp = self.prev_span;
2151 return self.parse_match_expr(attrs).map_err(|mut err| {
2152 err.span_label(match_sp, "while parsing this match expression");
2156 if self.eat_keyword(kw::Unsafe) {
2157 return self.parse_block_expr(
2160 BlockCheckMode::Unsafe(ast::UserProvided),
2163 if self.is_do_catch_block() {
2164 let mut db = self.fatal("found removed `do catch` syntax");
2165 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2168 if self.is_try_block() {
2169 let lo = self.token.span;
2170 assert!(self.eat_keyword(kw::Try));
2171 return self.parse_try_block(lo, attrs);
2174 // Span::rust_2018() is somewhat expensive; don't get it repeatedly.
2175 let is_span_rust_2018 = self.token.span.rust_2018();
2176 if is_span_rust_2018 && self.check_keyword(kw::Async) {
2177 return if self.is_async_block() { // check for `async {` and `async move {`
2178 self.parse_async_block(attrs)
2180 self.parse_lambda_expr(attrs)
2183 if self.eat_keyword(kw::Return) {
2184 if self.token.can_begin_expr() {
2185 let e = self.parse_expr()?;
2187 ex = ExprKind::Ret(Some(e));
2189 ex = ExprKind::Ret(None);
2191 } else if self.eat_keyword(kw::Break) {
2192 let label = self.eat_label();
2193 let e = if self.token.can_begin_expr()
2194 && !(self.token == token::OpenDelim(token::Brace)
2195 && self.restrictions.contains(
2196 Restrictions::NO_STRUCT_LITERAL)) {
2197 Some(self.parse_expr()?)
2201 ex = ExprKind::Break(label, e);
2202 hi = self.prev_span;
2203 } else if self.eat_keyword(kw::Yield) {
2204 if self.token.can_begin_expr() {
2205 let e = self.parse_expr()?;
2207 ex = ExprKind::Yield(Some(e));
2209 ex = ExprKind::Yield(None);
2211 } else if self.token.is_keyword(kw::Let) {
2212 // Catch this syntax error here, instead of in `parse_ident`, so
2213 // that we can explicitly mention that let is not to be used as an expression
2214 let mut db = self.fatal("expected expression, found statement (`let`)");
2215 db.span_label(self.token.span, "expected expression");
2216 db.note("variable declaration using `let` is a statement");
2218 } else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
2219 let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
2222 } else if self.token.is_path_start() {
2223 let path = self.parse_path(PathStyle::Expr)?;
2225 // `!`, as an operator, is prefix, so we know this isn't that
2226 if self.eat(&token::Not) {
2227 // MACRO INVOCATION expression
2228 let (delim, tts) = self.expect_delimited_token_tree()?;
2229 hi = self.prev_span;
2230 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2231 } else if self.check(&token::OpenDelim(token::Brace)) {
2232 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
2236 ex = ExprKind::Path(None, path);
2240 ex = ExprKind::Path(None, path);
2243 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2244 // Don't complain about bare semicolons after unclosed braces
2245 // recovery in order to keep the error count down. Fixing the
2246 // delimiters will possibly also fix the bare semicolon found in
2247 // expression context. For example, silence the following error:
2249 // error: expected expression, found `;`
2253 // | ^ expected expression
2256 return Ok(self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()));
2258 match self.parse_literal_maybe_minus() {
2261 ex = expr.node.clone();
2264 self.cancel(&mut err);
2265 return Err(self.expected_expression_found());
2272 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2273 self.maybe_recover_from_bad_qpath(expr, true)
2276 /// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
2277 /// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
2278 /// `await { <expr> }`.
2279 fn parse_await_macro_or_alt(
2283 ) -> PResult<'a, (Span, ExprKind)> {
2284 if self.token == token::Not {
2285 // Handle correct `await!(<expr>)`.
2286 // FIXME: make this an error when `await!` is no longer supported
2287 // https://github.com/rust-lang/rust/issues/60610
2288 self.expect(&token::Not)?;
2289 self.expect(&token::OpenDelim(token::Paren))?;
2290 let expr = self.parse_expr().map_err(|mut err| {
2291 err.span_label(await_sp, "while parsing this await macro call");
2294 self.expect(&token::CloseDelim(token::Paren))?;
2295 Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
2296 } else { // Handle `await <expr>`.
2297 self.parse_incorrect_await_syntax(lo, await_sp)
2301 fn maybe_parse_struct_expr(
2305 attrs: &ThinVec<Attribute>,
2306 ) -> Option<PResult<'a, P<Expr>>> {
2307 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2308 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
2309 // `{ ident, ` cannot start a block
2310 self.look_ahead(2, |t| t == &token::Comma) ||
2311 self.look_ahead(2, |t| t == &token::Colon) && (
2312 // `{ ident: token, ` cannot start a block
2313 self.look_ahead(4, |t| t == &token::Comma) ||
2314 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
2315 self.look_ahead(3, |t| !t.can_begin_type())
2319 if struct_allowed || certainly_not_a_block() {
2320 // This is a struct literal, but we don't can't accept them here
2321 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
2322 if let (Ok(expr), false) = (&expr, struct_allowed) {
2323 let mut err = self.diagnostic().struct_span_err(
2325 "struct literals are not allowed here",
2327 err.multipart_suggestion(
2328 "surround the struct literal with parentheses",
2330 (lo.shrink_to_lo(), "(".to_string()),
2331 (expr.span.shrink_to_hi(), ")".to_string()),
2333 Applicability::MachineApplicable,
2342 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2343 -> PResult<'a, P<Expr>> {
2344 let struct_sp = lo.to(self.prev_span);
2346 let mut fields = Vec::new();
2347 let mut base = None;
2349 attrs.extend(self.parse_inner_attributes()?);
2351 while self.token != token::CloseDelim(token::Brace) {
2352 if self.eat(&token::DotDot) {
2353 let exp_span = self.prev_span;
2354 match self.parse_expr() {
2360 self.recover_stmt();
2363 if self.token == token::Comma {
2364 let mut err = self.sess.span_diagnostic.mut_span_err(
2365 exp_span.to(self.prev_span),
2366 "cannot use a comma after the base struct",
2368 err.span_suggestion_short(
2370 "remove this comma",
2372 Applicability::MachineApplicable
2374 err.note("the base struct must always be the last field");
2376 self.recover_stmt();
2381 let mut recovery_field = None;
2382 if let token::Ident(name, _) = self.token.kind {
2383 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2384 // Use in case of error after field-looking code: `S { foo: () with a }`
2385 recovery_field = Some(ast::Field {
2386 ident: Ident::new(name, self.token.span),
2387 span: self.token.span,
2388 expr: self.mk_expr(self.token.span, ExprKind::Err, ThinVec::new()),
2389 is_shorthand: false,
2390 attrs: ThinVec::new(),
2394 let mut parsed_field = None;
2395 match self.parse_field() {
2396 Ok(f) => parsed_field = Some(f),
2398 e.span_label(struct_sp, "while parsing this struct");
2401 // If the next token is a comma, then try to parse
2402 // what comes next as additional fields, rather than
2403 // bailing out until next `}`.
2404 if self.token != token::Comma {
2405 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2406 if self.token != token::Comma {
2413 match self.expect_one_of(&[token::Comma],
2414 &[token::CloseDelim(token::Brace)]) {
2415 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2416 // only include the field if there's no parse error for the field name
2420 if let Some(f) = recovery_field {
2423 e.span_label(struct_sp, "while parsing this struct");
2425 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2426 self.eat(&token::Comma);
2431 let span = lo.to(self.token.span);
2432 self.expect(&token::CloseDelim(token::Brace))?;
2433 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2436 fn parse_or_use_outer_attributes(&mut self,
2437 already_parsed_attrs: Option<ThinVec<Attribute>>)
2438 -> PResult<'a, ThinVec<Attribute>> {
2439 if let Some(attrs) = already_parsed_attrs {
2442 self.parse_outer_attributes().map(|a| a.into())
2446 /// Parses a block or unsafe block.
2447 crate fn parse_block_expr(
2449 opt_label: Option<Label>,
2451 blk_mode: BlockCheckMode,
2452 outer_attrs: ThinVec<Attribute>,
2453 ) -> PResult<'a, P<Expr>> {
2454 self.expect(&token::OpenDelim(token::Brace))?;
2456 let mut attrs = outer_attrs;
2457 attrs.extend(self.parse_inner_attributes()?);
2459 let blk = self.parse_block_tail(lo, blk_mode)?;
2460 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2463 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2464 fn parse_dot_or_call_expr(&mut self,
2465 already_parsed_attrs: Option<ThinVec<Attribute>>)
2466 -> PResult<'a, P<Expr>> {
2467 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2469 let b = self.parse_bottom_expr();
2470 let (span, b) = self.interpolated_or_expr_span(b)?;
2471 self.parse_dot_or_call_expr_with(b, span, attrs)
2474 fn parse_dot_or_call_expr_with(&mut self,
2477 mut attrs: ThinVec<Attribute>)
2478 -> PResult<'a, P<Expr>> {
2479 // Stitch the list of outer attributes onto the return value.
2480 // A little bit ugly, but the best way given the current code
2482 self.parse_dot_or_call_expr_with_(e0, lo)
2484 expr.map(|mut expr| {
2485 attrs.extend::<Vec<_>>(expr.attrs.into());
2488 ExprKind::If(..) | ExprKind::IfLet(..) => {
2489 if !expr.attrs.is_empty() {
2490 // Just point to the first attribute in there...
2491 let span = expr.attrs[0].span;
2494 "attributes are not yet allowed on `if` \
2505 // Assuming we have just parsed `.`, continue parsing into an expression.
2506 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2507 if self.token.span.rust_2018() && self.eat_keyword(kw::Await) {
2508 let span = lo.to(self.prev_span);
2509 let await_expr = self.mk_expr(
2511 ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
2514 self.recover_from_await_method_call();
2515 return Ok(await_expr);
2517 let segment = self.parse_path_segment(PathStyle::Expr)?;
2518 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
2520 Ok(match self.token.kind {
2521 token::OpenDelim(token::Paren) => {
2522 // Method call `expr.f()`
2523 let mut args = self.parse_unspanned_seq(
2524 &token::OpenDelim(token::Paren),
2525 &token::CloseDelim(token::Paren),
2526 SeqSep::trailing_allowed(token::Comma),
2527 |p| Ok(p.parse_expr()?)
2529 args.insert(0, self_arg);
2531 let span = lo.to(self.prev_span);
2532 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
2535 // Field access `expr.f`
2536 if let Some(args) = segment.args {
2537 self.span_err(args.span(),
2538 "field expressions may not have generic arguments");
2541 let span = lo.to(self.prev_span);
2542 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
2547 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2552 while self.eat(&token::Question) {
2553 let hi = self.prev_span;
2554 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
2558 if self.eat(&token::Dot) {
2559 match self.token.kind {
2560 token::Ident(..) => {
2561 e = self.parse_dot_suffix(e, lo)?;
2563 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
2564 let span = self.token.span;
2566 let field = ExprKind::Field(e, Ident::new(symbol, span));
2567 e = self.mk_expr(lo.to(span), field, ThinVec::new());
2569 self.expect_no_suffix(span, "a tuple index", suffix);
2571 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
2573 let fstr = symbol.as_str();
2574 let msg = format!("unexpected token: `{}`", symbol);
2575 let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
2576 err.span_label(self.prev_span, "unexpected token");
2577 if fstr.chars().all(|x| "0123456789.".contains(x)) {
2578 let float = match fstr.parse::<f64>().ok() {
2582 let sugg = pprust::to_string(|s| {
2583 use crate::print::pprust::PrintState;
2587 s.print_usize(float.trunc() as usize)?;
2590 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
2592 err.span_suggestion(
2593 lo.to(self.prev_span),
2594 "try parenthesizing the first index",
2596 Applicability::MachineApplicable
2603 // FIXME Could factor this out into non_fatal_unexpected or something.
2604 let actual = self.this_token_to_string();
2605 self.span_err(self.token.span, &format!("unexpected token: `{}`", actual));
2610 if self.expr_is_complete(&e) { break; }
2611 match self.token.kind {
2613 token::OpenDelim(token::Paren) => {
2614 let seq = self.parse_unspanned_seq(
2615 &token::OpenDelim(token::Paren),
2616 &token::CloseDelim(token::Paren),
2617 SeqSep::trailing_allowed(token::Comma),
2618 |p| Ok(p.parse_expr()?)
2620 let nd = self.mk_call(e, es);
2621 let hi = self.prev_span;
2622 self.mk_expr(lo.to(hi), nd, ThinVec::new())
2624 e = self.recover_seq_parse_error(token::Paren, lo, seq);
2628 // Could be either an index expression or a slicing expression.
2629 token::OpenDelim(token::Bracket) => {
2631 let ix = self.parse_expr()?;
2632 hi = self.token.span;
2633 self.expect(&token::CloseDelim(token::Bracket))?;
2634 let index = self.mk_index(e, ix);
2635 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
2643 crate fn process_potential_macro_variable(&mut self) {
2644 self.token = match self.token.kind {
2645 token::Dollar if self.token.span.ctxt() != SyntaxContext::empty() &&
2646 self.look_ahead(1, |t| t.is_ident()) => {
2648 let name = match self.token.kind {
2649 token::Ident(name, _) => name,
2652 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
2653 err.span_label(self.token.span, "unknown macro variable");
2658 token::Interpolated(ref nt) => {
2659 self.meta_var_span = Some(self.token.span);
2660 // Interpolated identifier and lifetime tokens are replaced with usual identifier
2661 // and lifetime tokens, so the former are never encountered during normal parsing.
2663 token::NtIdent(ident, is_raw) =>
2664 Token::new(token::Ident(ident.name, is_raw), ident.span),
2665 token::NtLifetime(ident) =>
2666 Token::new(token::Lifetime(ident.name), ident.span),
2674 /// Parses a single token tree from the input.
2675 crate fn parse_token_tree(&mut self) -> TokenTree {
2676 match self.token.kind {
2677 token::OpenDelim(..) => {
2678 let frame = mem::replace(&mut self.token_cursor.frame,
2679 self.token_cursor.stack.pop().unwrap());
2680 self.token.span = frame.span.entire();
2682 TokenTree::Delimited(
2685 frame.tree_cursor.stream.into(),
2688 token::CloseDelim(_) | token::Eof => unreachable!(),
2690 let token = self.token.take();
2692 TokenTree::Token(token)
2697 /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
2698 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2699 let mut tts = Vec::new();
2700 while self.token != token::Eof {
2701 tts.push(self.parse_token_tree());
2706 pub fn parse_tokens(&mut self) -> TokenStream {
2707 let mut result = Vec::new();
2709 match self.token.kind {
2710 token::Eof | token::CloseDelim(..) => break,
2711 _ => result.push(self.parse_token_tree().into()),
2714 TokenStream::new(result)
2717 /// Parse a prefix-unary-operator expr
2718 fn parse_prefix_expr(&mut self,
2719 already_parsed_attrs: Option<ThinVec<Attribute>>)
2720 -> PResult<'a, P<Expr>> {
2721 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2722 let lo = self.token.span;
2723 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
2724 let (hi, ex) = match self.token.kind {
2727 let e = self.parse_prefix_expr(None);
2728 let (span, e) = self.interpolated_or_expr_span(e)?;
2729 (lo.to(span), self.mk_unary(UnOp::Not, e))
2731 // Suggest `!` for bitwise negation when encountering a `~`
2734 let e = self.parse_prefix_expr(None);
2735 let (span, e) = self.interpolated_or_expr_span(e)?;
2736 let span_of_tilde = lo;
2737 let mut err = self.diagnostic()
2738 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
2739 err.span_suggestion_short(
2741 "use `!` to perform bitwise negation",
2743 Applicability::MachineApplicable
2746 (lo.to(span), self.mk_unary(UnOp::Not, e))
2748 token::BinOp(token::Minus) => {
2750 let e = self.parse_prefix_expr(None);
2751 let (span, e) = self.interpolated_or_expr_span(e)?;
2752 (lo.to(span), self.mk_unary(UnOp::Neg, e))
2754 token::BinOp(token::Star) => {
2756 let e = self.parse_prefix_expr(None);
2757 let (span, e) = self.interpolated_or_expr_span(e)?;
2758 (lo.to(span), self.mk_unary(UnOp::Deref, e))
2760 token::BinOp(token::And) | token::AndAnd => {
2762 let m = self.parse_mutability();
2763 let e = self.parse_prefix_expr(None);
2764 let (span, e) = self.interpolated_or_expr_span(e)?;
2765 (lo.to(span), ExprKind::AddrOf(m, e))
2767 token::Ident(..) if self.token.is_keyword(kw::Box) => {
2769 let e = self.parse_prefix_expr(None);
2770 let (span, e) = self.interpolated_or_expr_span(e)?;
2771 (lo.to(span), ExprKind::Box(e))
2773 token::Ident(..) if self.token.is_ident_named(sym::not) => {
2774 // `not` is just an ordinary identifier in Rust-the-language,
2775 // but as `rustc`-the-compiler, we can issue clever diagnostics
2776 // for confused users who really want to say `!`
2777 let token_cannot_continue_expr = |t: &Token| match t.kind {
2778 // These tokens can start an expression after `!`, but
2779 // can't continue an expression after an ident
2780 token::Ident(name, is_raw) => token::ident_can_begin_expr(name, t.span, is_raw),
2781 token::Literal(..) | token::Pound => true,
2782 token::Interpolated(ref nt) => match **nt {
2783 token::NtIdent(..) | token::NtExpr(..) |
2784 token::NtBlock(..) | token::NtPath(..) => true,
2789 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
2790 if cannot_continue_expr {
2792 // Emit the error ...
2793 let mut err = self.diagnostic()
2794 .struct_span_err(self.token.span,
2795 &format!("unexpected {} after identifier",
2796 self.this_token_descr()));
2797 // span the `not` plus trailing whitespace to avoid
2798 // trailing whitespace after the `!` in our suggestion
2799 let to_replace = self.sess.source_map()
2800 .span_until_non_whitespace(lo.to(self.token.span));
2801 err.span_suggestion_short(
2803 "use `!` to perform logical negation",
2805 Applicability::MachineApplicable
2808 // —and recover! (just as if we were in the block
2809 // for the `token::Not` arm)
2810 let e = self.parse_prefix_expr(None);
2811 let (span, e) = self.interpolated_or_expr_span(e)?;
2812 (lo.to(span), self.mk_unary(UnOp::Not, e))
2814 return self.parse_dot_or_call_expr(Some(attrs));
2817 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
2819 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2822 /// Parses an associative expression.
2824 /// This parses an expression accounting for associativity and precedence of the operators in
2827 fn parse_assoc_expr(&mut self,
2828 already_parsed_attrs: Option<ThinVec<Attribute>>)
2829 -> PResult<'a, P<Expr>> {
2830 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2833 /// Parses an associative expression with operators of at least `min_prec` precedence.
2834 fn parse_assoc_expr_with(&mut self,
2837 -> PResult<'a, P<Expr>> {
2838 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2841 let attrs = match lhs {
2842 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2845 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
2846 return self.parse_prefix_range_expr(attrs);
2848 self.parse_prefix_expr(attrs)?
2852 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
2854 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2857 (false, _) => {} // continue parsing the expression
2858 // An exhaustive check is done in the following block, but these are checked first
2859 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
2860 // want to keep their span info to improve diagnostics in these cases in a later stage.
2861 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
2862 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
2863 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
2864 (true, Some(AssocOp::Add)) // `{ 42 } + 42
2865 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
2866 // `if x { a } else { b } && if y { c } else { d }`
2867 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
2868 // These cases are ambiguous and can't be identified in the parser alone
2869 let sp = self.sess.source_map().start_point(self.token.span);
2870 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
2873 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
2876 (true, Some(_)) => {
2877 // We've found an expression that would be parsed as a statement, but the next
2878 // token implies this should be parsed as an expression.
2879 // For example: `if let Some(x) = x { x } else { 0 } / 2`
2880 let mut err = self.sess.span_diagnostic.struct_span_err(self.token.span, &format!(
2881 "expected expression, found `{}`",
2882 pprust::token_to_string(&self.token),
2884 err.span_label(self.token.span, "expected expression");
2885 self.sess.expr_parentheses_needed(
2888 Some(pprust::expr_to_string(&lhs),
2893 self.expected_tokens.push(TokenType::Operator);
2894 while let Some(op) = AssocOp::from_token(&self.token) {
2896 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
2897 // it refers to. Interpolated identifiers are unwrapped early and never show up here
2898 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
2899 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
2900 let lhs_span = match (self.prev_token_kind, &lhs.node) {
2901 (PrevTokenKind::Interpolated, _) => self.prev_span,
2902 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
2903 if path.segments.len() == 1 => self.prev_span,
2907 let cur_op_span = self.token.span;
2908 let restrictions = if op.is_assign_like() {
2909 self.restrictions & Restrictions::NO_STRUCT_LITERAL
2913 let prec = op.precedence();
2914 if prec < min_prec {
2917 // Check for deprecated `...` syntax
2918 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
2919 self.err_dotdotdot_syntax(self.token.span);
2923 if op.is_comparison() {
2924 self.check_no_chained_comparison(&lhs, &op);
2927 if op == AssocOp::As {
2928 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
2930 } else if op == AssocOp::Colon {
2931 let maybe_path = self.could_ascription_be_path(&lhs.node);
2932 let next_sp = self.token.span;
2934 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
2937 self.bad_type_ascription(
2948 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
2949 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
2950 // generalise it to the Fixity::None code.
2952 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
2953 // two variants are handled with `parse_prefix_range_expr` call above.
2954 let rhs = if self.is_at_start_of_range_notation_rhs() {
2955 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
2959 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2964 let limits = if op == AssocOp::DotDot {
2965 RangeLimits::HalfOpen
2970 let r = self.mk_range(Some(lhs), rhs, limits)?;
2971 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
2975 let fixity = op.fixity();
2976 let prec_adjustment = match fixity {
2979 // We currently have no non-associative operators that are not handled above by
2980 // the special cases. The code is here only for future convenience.
2983 let rhs = self.with_res(
2984 restrictions - Restrictions::STMT_EXPR,
2985 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
2988 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
2989 // including the attributes.
2993 .filter(|a| a.style == AttrStyle::Outer)
2995 .map_or(lhs_span, |a| a.span);
2996 let span = lhs_span.to(rhs.span);
2998 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
2999 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3000 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3001 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3002 AssocOp::Greater | AssocOp::GreaterEqual => {
3003 let ast_op = op.to_ast_binop().unwrap();
3004 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
3005 self.mk_expr(span, binary, ThinVec::new())
3007 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3008 AssocOp::AssignOp(k) => {
3010 token::Plus => BinOpKind::Add,
3011 token::Minus => BinOpKind::Sub,
3012 token::Star => BinOpKind::Mul,
3013 token::Slash => BinOpKind::Div,
3014 token::Percent => BinOpKind::Rem,
3015 token::Caret => BinOpKind::BitXor,
3016 token::And => BinOpKind::BitAnd,
3017 token::Or => BinOpKind::BitOr,
3018 token::Shl => BinOpKind::Shl,
3019 token::Shr => BinOpKind::Shr,
3021 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3022 self.mk_expr(span, aopexpr, ThinVec::new())
3024 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3025 self.bug("AssocOp should have been handled by special case")
3029 if let Fixity::None = fixity { break }
3034 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3035 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3036 -> PResult<'a, P<Expr>> {
3037 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3038 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3041 // Save the state of the parser before parsing type normally, in case there is a
3042 // LessThan comparison after this cast.
3043 let parser_snapshot_before_type = self.clone();
3044 match self.parse_ty_no_plus() {
3046 Ok(mk_expr(self, rhs))
3048 Err(mut type_err) => {
3049 // Rewind to before attempting to parse the type with generics, to recover
3050 // from situations like `x as usize < y` in which we first tried to parse
3051 // `usize < y` as a type with generic arguments.
3052 let parser_snapshot_after_type = self.clone();
3053 mem::replace(self, parser_snapshot_before_type);
3055 match self.parse_path(PathStyle::Expr) {
3057 let (op_noun, op_verb) = match self.token.kind {
3058 token::Lt => ("comparison", "comparing"),
3059 token::BinOp(token::Shl) => ("shift", "shifting"),
3061 // We can end up here even without `<` being the next token, for
3062 // example because `parse_ty_no_plus` returns `Err` on keywords,
3063 // but `parse_path` returns `Ok` on them due to error recovery.
3064 // Return original error and parser state.
3065 mem::replace(self, parser_snapshot_after_type);
3066 return Err(type_err);
3070 // Successfully parsed the type path leaving a `<` yet to parse.
3073 // Report non-fatal diagnostics, keep `x as usize` as an expression
3074 // in AST and continue parsing.
3075 let msg = format!("`<` is interpreted as a start of generic \
3076 arguments for `{}`, not a {}", path, op_noun);
3078 self.sess.span_diagnostic.struct_span_err(self.token.span, &msg);
3079 let span_after_type = parser_snapshot_after_type.token.span;
3080 err.span_label(self.look_ahead_span(1).to(span_after_type),
3081 "interpreted as generic arguments");
3082 err.span_label(self.token.span, format!("not interpreted as {}", op_noun));
3084 let expr = mk_expr(self, P(Ty {
3086 node: TyKind::Path(None, path),
3087 id: ast::DUMMY_NODE_ID
3090 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3091 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3092 err.span_suggestion(
3094 &format!("try {} the cast value", op_verb),
3095 format!("({})", expr_str),
3096 Applicability::MachineApplicable
3102 Err(mut path_err) => {
3103 // Couldn't parse as a path, return original error and parser state.
3105 mem::replace(self, parser_snapshot_after_type);
3113 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3114 fn parse_prefix_range_expr(&mut self,
3115 already_parsed_attrs: Option<ThinVec<Attribute>>)
3116 -> PResult<'a, P<Expr>> {
3117 // Check for deprecated `...` syntax
3118 if self.token == token::DotDotDot {
3119 self.err_dotdotdot_syntax(self.token.span);
3122 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3123 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3125 let tok = self.token.clone();
3126 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3127 let lo = self.token.span;
3128 let mut hi = self.token.span;
3130 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3131 // RHS must be parsed with more associativity than the dots.
3132 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3133 Some(self.parse_assoc_expr_with(next_prec,
3134 LhsExpr::NotYetParsed)
3142 let limits = if tok == token::DotDot {
3143 RangeLimits::HalfOpen
3148 let r = self.mk_range(None, opt_end, limits)?;
3149 Ok(self.mk_expr(lo.to(hi), r, attrs))
3152 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3153 if self.token.can_begin_expr() {
3154 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3155 if self.token == token::OpenDelim(token::Brace) {
3156 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3164 /// Parses an `if` or `if let` expression (`if` token already eaten).
3165 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3166 if self.check_keyword(kw::Let) {
3167 return self.parse_if_let_expr(attrs);
3169 let lo = self.prev_span;
3170 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3172 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3173 // verify that the last statement is either an implicit return (no `;`) or an explicit
3174 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3175 // the dead code lint.
3176 if self.eat_keyword(kw::Else) || !cond.returns() {
3177 let sp = self.sess.source_map().next_point(lo);
3178 let mut err = self.diagnostic()
3179 .struct_span_err(sp, "missing condition for `if` statemement");
3180 err.span_label(sp, "expected if condition here");
3183 let not_block = self.token != token::OpenDelim(token::Brace);
3184 let thn = self.parse_block().map_err(|mut err| {
3186 err.span_label(lo, "this `if` statement has a condition, but no block");
3190 let mut els: Option<P<Expr>> = None;
3191 let mut hi = thn.span;
3192 if self.eat_keyword(kw::Else) {
3193 let elexpr = self.parse_else_expr()?;
3197 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3200 /// Parses an `if let` expression (`if` token already eaten).
3201 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3202 -> PResult<'a, P<Expr>> {
3203 let lo = self.prev_span;
3204 self.expect_keyword(kw::Let)?;
3205 let pats = self.parse_pats()?;
3206 self.expect(&token::Eq)?;
3207 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3208 let thn = self.parse_block()?;
3209 let (hi, els) = if self.eat_keyword(kw::Else) {
3210 let expr = self.parse_else_expr()?;
3211 (expr.span, Some(expr))
3215 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3218 /// Parses `move |args| expr`.
3219 fn parse_lambda_expr(&mut self,
3220 attrs: ThinVec<Attribute>)
3221 -> PResult<'a, P<Expr>>
3223 let lo = self.token.span;
3224 let movability = if self.eat_keyword(kw::Static) {
3229 let asyncness = if self.token.span.rust_2018() {
3230 self.parse_asyncness()
3234 let capture_clause = if self.eat_keyword(kw::Move) {
3239 let decl = self.parse_fn_block_decl()?;
3240 let decl_hi = self.prev_span;
3241 let body = match decl.output {
3242 FunctionRetTy::Default(_) => {
3243 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3244 self.parse_expr_res(restrictions, None)?
3247 // If an explicit return type is given, require a
3248 // block to appear (RFC 968).
3249 let body_lo = self.token.span;
3250 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3256 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3260 // `else` token already eaten
3261 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3262 if self.eat_keyword(kw::If) {
3263 return self.parse_if_expr(ThinVec::new());
3265 let blk = self.parse_block()?;
3266 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3270 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3271 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3273 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3274 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3276 let pat = self.parse_top_level_pat()?;
3277 if !self.eat_keyword(kw::In) {
3278 let in_span = self.prev_span.between(self.token.span);
3279 let mut err = self.sess.span_diagnostic
3280 .struct_span_err(in_span, "missing `in` in `for` loop");
3281 err.span_suggestion_short(
3282 in_span, "try adding `in` here", " in ".into(),
3283 // has been misleading, at least in the past (closed Issue #48492)
3284 Applicability::MaybeIncorrect
3288 let in_span = self.prev_span;
3289 self.check_for_for_in_in_typo(in_span);
3290 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3291 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3292 attrs.extend(iattrs);
3294 let hi = self.prev_span;
3295 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3298 /// Parses a `while` or `while let` expression (`while` token already eaten).
3299 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3301 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3302 if self.token.is_keyword(kw::Let) {
3303 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3305 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3306 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3307 attrs.extend(iattrs);
3308 let span = span_lo.to(body.span);
3309 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3312 /// Parses a `while let` expression (`while` token already eaten).
3313 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3315 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3316 self.expect_keyword(kw::Let)?;
3317 let pats = self.parse_pats()?;
3318 self.expect(&token::Eq)?;
3319 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3320 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3321 attrs.extend(iattrs);
3322 let span = span_lo.to(body.span);
3323 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3326 // parse `loop {...}`, `loop` token already eaten
3327 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3329 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3330 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3331 attrs.extend(iattrs);
3332 let span = span_lo.to(body.span);
3333 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3336 /// Parses an `async move {...}` expression.
3337 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3338 -> PResult<'a, P<Expr>>
3340 let span_lo = self.token.span;
3341 self.expect_keyword(kw::Async)?;
3342 let capture_clause = if self.eat_keyword(kw::Move) {
3347 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3348 attrs.extend(iattrs);
3350 span_lo.to(body.span),
3351 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3354 /// Parses a `try {...}` expression (`try` token already eaten).
3355 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3356 -> PResult<'a, P<Expr>>
3358 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3359 attrs.extend(iattrs);
3360 if self.eat_keyword(kw::Catch) {
3361 let mut error = self.struct_span_err(self.prev_span,
3362 "keyword `catch` cannot follow a `try` block");
3363 error.help("try using `match` on the result of the `try` block instead");
3367 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
3371 // `match` token already eaten
3372 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3373 let match_span = self.prev_span;
3374 let lo = self.prev_span;
3375 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3377 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3378 if self.token == token::Semi {
3379 e.span_suggestion_short(
3381 "try removing this `match`",
3383 Applicability::MaybeIncorrect // speculative
3388 attrs.extend(self.parse_inner_attributes()?);
3390 let mut arms: Vec<Arm> = Vec::new();
3391 while self.token != token::CloseDelim(token::Brace) {
3392 match self.parse_arm() {
3393 Ok(arm) => arms.push(arm),
3395 // Recover by skipping to the end of the block.
3397 self.recover_stmt();
3398 let span = lo.to(self.token.span);
3399 if self.token == token::CloseDelim(token::Brace) {
3402 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3406 let hi = self.token.span;
3408 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3411 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3412 let attrs = self.parse_outer_attributes()?;
3413 let lo = self.token.span;
3414 let pats = self.parse_pats()?;
3415 let guard = if self.eat_keyword(kw::If) {
3416 Some(Guard::If(self.parse_expr()?))
3420 let arrow_span = self.token.span;
3421 self.expect(&token::FatArrow)?;
3422 let arm_start_span = self.token.span;
3424 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3425 .map_err(|mut err| {
3426 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3430 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3431 && self.token != token::CloseDelim(token::Brace);
3433 let hi = self.token.span;
3436 let cm = self.sess.source_map();
3437 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3438 .map_err(|mut err| {
3439 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3440 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3441 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3442 && expr_lines.lines.len() == 2
3443 && self.token == token::FatArrow => {
3444 // We check whether there's any trailing code in the parse span,
3445 // if there isn't, we very likely have the following:
3448 // | -- - missing comma
3452 // | - ^^ self.token.span
3454 // | parsed until here as `"y" & X`
3455 err.span_suggestion_short(
3456 cm.next_point(arm_start_span),
3457 "missing a comma here to end this `match` arm",
3459 Applicability::MachineApplicable
3463 err.span_label(arrow_span,
3464 "while parsing the `match` arm starting here");
3470 self.eat(&token::Comma);
3482 /// Parses an expression.
3484 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3485 self.parse_expr_res(Restrictions::empty(), None)
3488 /// Evaluates the closure with restrictions in place.
3490 /// Afters the closure is evaluated, restrictions are reset.
3491 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
3492 where F: FnOnce(&mut Self) -> T
3494 let old = self.restrictions;
3495 self.restrictions = r;
3497 self.restrictions = old;
3502 /// Parses an expression, subject to the given restrictions.
3504 fn parse_expr_res(&mut self, r: Restrictions,
3505 already_parsed_attrs: Option<ThinVec<Attribute>>)
3506 -> PResult<'a, P<Expr>> {
3507 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3510 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
3511 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
3512 if self.eat(&token::Eq) {
3513 Ok(Some(self.parse_expr()?))
3515 Ok(Some(self.parse_expr()?))
3521 /// Parses patterns, separated by '|' s.
3522 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3523 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
3524 self.eat(&token::BinOp(token::Or));
3526 let mut pats = Vec::new();
3528 pats.push(self.parse_top_level_pat()?);
3530 if self.token == token::OrOr {
3531 let mut err = self.struct_span_err(self.token.span,
3532 "unexpected token `||` after pattern");
3533 err.span_suggestion(
3535 "use a single `|` to specify multiple patterns",
3537 Applicability::MachineApplicable
3541 } else if self.eat(&token::BinOp(token::Or)) {
3542 // This is a No-op. Continue the loop to parse the next
3550 // Parses a parenthesized list of patterns like
3551 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
3552 // - a vector of the patterns that were parsed
3553 // - an option indicating the index of the `..` element
3554 // - a boolean indicating whether a trailing comma was present.
3555 // Trailing commas are significant because (p) and (p,) are different patterns.
3556 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3557 self.expect(&token::OpenDelim(token::Paren))?;
3558 let result = match self.parse_pat_list() {
3559 Ok(result) => result,
3560 Err(mut err) => { // recover from parse error in tuple pattern list
3562 self.consume_block(token::Paren);
3563 return Ok((vec![], Some(0), false));
3566 self.expect(&token::CloseDelim(token::Paren))?;
3570 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3571 let mut fields = Vec::new();
3572 let mut ddpos = None;
3573 let mut prev_dd_sp = None;
3574 let mut trailing_comma = false;
3576 if self.eat(&token::DotDot) {
3577 if ddpos.is_none() {
3578 ddpos = Some(fields.len());
3579 prev_dd_sp = Some(self.prev_span);
3581 // Emit a friendly error, ignore `..` and continue parsing
3582 let mut err = self.struct_span_err(
3584 "`..` can only be used once per tuple or tuple struct pattern",
3586 err.span_label(self.prev_span, "can only be used once per pattern");
3587 if let Some(sp) = prev_dd_sp {
3588 err.span_label(sp, "previously present here");
3592 } else if !self.check(&token::CloseDelim(token::Paren)) {
3593 fields.push(self.parse_pat(None)?);
3598 trailing_comma = self.eat(&token::Comma);
3599 if !trailing_comma {
3604 if ddpos == Some(fields.len()) && trailing_comma {
3605 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
3606 let msg = "trailing comma is not permitted after `..`";
3607 self.struct_span_err(self.prev_span, msg)
3608 .span_label(self.prev_span, msg)
3612 Ok((fields, ddpos, trailing_comma))
3615 fn parse_pat_vec_elements(
3617 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3618 let mut before = Vec::new();
3619 let mut slice = None;
3620 let mut after = Vec::new();
3621 let mut first = true;
3622 let mut before_slice = true;
3624 while self.token != token::CloseDelim(token::Bracket) {
3628 self.expect(&token::Comma)?;
3630 if self.token == token::CloseDelim(token::Bracket)
3631 && (before_slice || !after.is_empty()) {
3637 if self.eat(&token::DotDot) {
3639 if self.check(&token::Comma) ||
3640 self.check(&token::CloseDelim(token::Bracket)) {
3641 slice = Some(P(Pat {
3642 id: ast::DUMMY_NODE_ID,
3643 node: PatKind::Wild,
3644 span: self.prev_span,
3646 before_slice = false;
3652 let subpat = self.parse_pat(None)?;
3653 if before_slice && self.eat(&token::DotDot) {
3654 slice = Some(subpat);
3655 before_slice = false;
3656 } else if before_slice {
3657 before.push(subpat);
3663 Ok((before, slice, after))
3669 attrs: Vec<Attribute>
3670 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
3671 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3673 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3674 // Parsing a pattern of the form "fieldname: pat"
3675 let fieldname = self.parse_field_name()?;
3677 let pat = self.parse_pat(None)?;
3679 (pat, fieldname, false)
3681 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3682 let is_box = self.eat_keyword(kw::Box);
3683 let boxed_span = self.token.span;
3684 let is_ref = self.eat_keyword(kw::Ref);
3685 let is_mut = self.eat_keyword(kw::Mut);
3686 let fieldname = self.parse_ident()?;
3687 hi = self.prev_span;
3689 let bind_type = match (is_ref, is_mut) {
3690 (true, true) => BindingMode::ByRef(Mutability::Mutable),
3691 (true, false) => BindingMode::ByRef(Mutability::Immutable),
3692 (false, true) => BindingMode::ByValue(Mutability::Mutable),
3693 (false, false) => BindingMode::ByValue(Mutability::Immutable),
3695 let fieldpat = P(Pat {
3696 id: ast::DUMMY_NODE_ID,
3697 node: PatKind::Ident(bind_type, fieldname, None),
3698 span: boxed_span.to(hi),
3701 let subpat = if is_box {
3703 id: ast::DUMMY_NODE_ID,
3704 node: PatKind::Box(fieldpat),
3710 (subpat, fieldname, true)
3713 Ok(source_map::Spanned {
3715 node: ast::FieldPat {
3719 attrs: attrs.into(),
3724 /// Parses the fields of a struct-like pattern.
3725 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
3726 let mut fields = Vec::new();
3727 let mut etc = false;
3728 let mut ate_comma = true;
3729 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
3730 let mut etc_span = None;
3732 while self.token != token::CloseDelim(token::Brace) {
3733 let attrs = self.parse_outer_attributes()?;
3734 let lo = self.token.span;
3736 // check that a comma comes after every field
3738 let err = self.struct_span_err(self.prev_span, "expected `,`");
3739 if let Some(mut delayed) = delayed_err {
3746 if self.check(&token::DotDot) || self.token == token::DotDotDot {
3748 let mut etc_sp = self.token.span;
3750 if self.token == token::DotDotDot { // Issue #46718
3751 // Accept `...` as if it were `..` to avoid further errors
3752 let mut err = self.struct_span_err(self.token.span,
3753 "expected field pattern, found `...`");
3754 err.span_suggestion(
3756 "to omit remaining fields, use one fewer `.`",
3758 Applicability::MachineApplicable
3762 self.bump(); // `..` || `...`
3764 if self.token == token::CloseDelim(token::Brace) {
3765 etc_span = Some(etc_sp);
3768 let token_str = self.this_token_descr();
3769 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
3771 err.span_label(self.token.span, "expected `}`");
3772 let mut comma_sp = None;
3773 if self.token == token::Comma { // Issue #49257
3774 let nw_span = self.sess.source_map().span_until_non_whitespace(self.token.span);
3775 etc_sp = etc_sp.to(nw_span);
3776 err.span_label(etc_sp,
3777 "`..` must be at the end and cannot have a trailing comma");
3778 comma_sp = Some(self.token.span);
3783 etc_span = Some(etc_sp.until(self.token.span));
3784 if self.token == token::CloseDelim(token::Brace) {
3785 // If the struct looks otherwise well formed, recover and continue.
3786 if let Some(sp) = comma_sp {
3787 err.span_suggestion_short(
3789 "remove this comma",
3791 Applicability::MachineApplicable,
3796 } else if self.token.is_ident() && ate_comma {
3797 // Accept fields coming after `..,`.
3798 // This way we avoid "pattern missing fields" errors afterwards.
3799 // We delay this error until the end in order to have a span for a
3801 if let Some(mut delayed_err) = delayed_err {
3805 delayed_err = Some(err);
3808 if let Some(mut err) = delayed_err {
3815 fields.push(match self.parse_pat_field(lo, attrs) {
3818 if let Some(mut delayed_err) = delayed_err {
3824 ate_comma = self.eat(&token::Comma);
3827 if let Some(mut err) = delayed_err {
3828 if let Some(etc_span) = etc_span {
3829 err.multipart_suggestion(
3830 "move the `..` to the end of the field list",
3832 (etc_span, String::new()),
3833 (self.token.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
3835 Applicability::MachineApplicable,
3840 return Ok((fields, etc));
3843 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3844 if self.token.is_path_start() {
3845 let lo = self.token.span;
3846 let (qself, path) = if self.eat_lt() {
3847 // Parse a qualified path
3848 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3851 // Parse an unqualified path
3852 (None, self.parse_path(PathStyle::Expr)?)
3854 let hi = self.prev_span;
3855 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
3857 self.parse_literal_maybe_minus()
3861 // helper function to decide whether to parse as ident binding or to try to do
3862 // something more complex like range patterns
3863 fn parse_as_ident(&mut self) -> bool {
3864 self.look_ahead(1, |t| match t.kind {
3865 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
3866 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
3867 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
3868 // range pattern branch
3869 token::DotDot => None,
3871 }).unwrap_or_else(|| self.look_ahead(2, |t| match t.kind {
3872 token::Comma | token::CloseDelim(token::Bracket) => true,
3877 /// A wrapper around `parse_pat` with some special error handling for the
3878 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
3879 /// to subpatterns within such).
3880 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
3881 let pat = self.parse_pat(None)?;
3882 if self.token == token::Comma {
3883 // An unexpected comma after a top-level pattern is a clue that the
3884 // user (perhaps more accustomed to some other language) forgot the
3885 // parentheses in what should have been a tuple pattern; return a
3886 // suggestion-enhanced error here rather than choking on the comma
3888 let comma_span = self.token.span;
3890 if let Err(mut err) = self.parse_pat_list() {
3891 // We didn't expect this to work anyway; we just wanted
3892 // to advance to the end of the comma-sequence so we know
3893 // the span to suggest parenthesizing
3896 let seq_span = pat.span.to(self.prev_span);
3897 let mut err = self.struct_span_err(comma_span,
3898 "unexpected `,` in pattern");
3899 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
3900 err.span_suggestion(
3902 "try adding parentheses to match on a tuple..",
3903 format!("({})", seq_snippet),
3904 Applicability::MachineApplicable
3907 "..or a vertical bar to match on multiple alternatives",
3908 format!("{}", seq_snippet.replace(",", " |")),
3909 Applicability::MachineApplicable
3917 /// Parses a pattern.
3918 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
3919 self.parse_pat_with_range_pat(true, expected)
3922 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
3924 fn parse_pat_with_range_pat(
3926 allow_range_pat: bool,
3927 expected: Option<&'static str>,
3928 ) -> PResult<'a, P<Pat>> {
3929 maybe_recover_from_interpolated_ty_qpath!(self, true);
3930 maybe_whole!(self, NtPat, |x| x);
3932 let lo = self.token.span;
3934 match self.token.kind {
3935 token::BinOp(token::And) | token::AndAnd => {
3936 // Parse &pat / &mut pat
3938 let mutbl = self.parse_mutability();
3939 if let token::Lifetime(name) = self.token.kind {
3940 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern", name));
3941 err.span_label(self.token.span, "unexpected lifetime");
3944 let subpat = self.parse_pat_with_range_pat(false, expected)?;
3945 pat = PatKind::Ref(subpat, mutbl);
3947 token::OpenDelim(token::Paren) => {
3948 // Parse (pat,pat,pat,...) as tuple pattern
3949 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
3950 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
3951 PatKind::Paren(fields.into_iter().nth(0).unwrap())
3953 PatKind::Tuple(fields, ddpos)
3956 token::OpenDelim(token::Bracket) => {
3957 // Parse [pat,pat,...] as slice pattern
3959 let (before, slice, after) = self.parse_pat_vec_elements()?;
3960 self.expect(&token::CloseDelim(token::Bracket))?;
3961 pat = PatKind::Slice(before, slice, after);
3963 // At this point, token != &, &&, (, [
3964 _ => if self.eat_keyword(kw::Underscore) {
3966 pat = PatKind::Wild;
3967 } else if self.eat_keyword(kw::Mut) {
3968 // Parse mut ident @ pat / mut ref ident @ pat
3969 let mutref_span = self.prev_span.to(self.token.span);
3970 let binding_mode = if self.eat_keyword(kw::Ref) {
3972 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
3975 "try switching the order",
3977 Applicability::MachineApplicable
3979 BindingMode::ByRef(Mutability::Mutable)
3981 BindingMode::ByValue(Mutability::Mutable)
3983 pat = self.parse_pat_ident(binding_mode)?;
3984 } else if self.eat_keyword(kw::Ref) {
3985 // Parse ref ident @ pat / ref mut ident @ pat
3986 let mutbl = self.parse_mutability();
3987 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
3988 } else if self.eat_keyword(kw::Box) {
3990 let subpat = self.parse_pat_with_range_pat(false, None)?;
3991 pat = PatKind::Box(subpat);
3992 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
3993 self.parse_as_ident() {
3994 // Parse ident @ pat
3995 // This can give false positives and parse nullary enums,
3996 // they are dealt with later in resolve
3997 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
3998 pat = self.parse_pat_ident(binding_mode)?;
3999 } else if self.token.is_path_start() {
4000 // Parse pattern starting with a path
4001 let (qself, path) = if self.eat_lt() {
4002 // Parse a qualified path
4003 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4006 // Parse an unqualified path
4007 (None, self.parse_path(PathStyle::Expr)?)
4009 match self.token.kind {
4010 token::Not if qself.is_none() => {
4011 // Parse macro invocation
4013 let (delim, tts) = self.expect_delimited_token_tree()?;
4014 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4015 pat = PatKind::Mac(mac);
4017 token::DotDotDot | token::DotDotEq | token::DotDot => {
4018 let end_kind = match self.token.kind {
4019 token::DotDot => RangeEnd::Excluded,
4020 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4021 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4022 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4025 let op_span = self.token.span;
4027 let span = lo.to(self.prev_span);
4028 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4030 let end = self.parse_pat_range_end()?;
4031 let op = Spanned { span: op_span, node: end_kind };
4032 pat = PatKind::Range(begin, end, op);
4034 token::OpenDelim(token::Brace) => {
4035 if qself.is_some() {
4036 let msg = "unexpected `{` after qualified path";
4037 let mut err = self.fatal(msg);
4038 err.span_label(self.token.span, msg);
4041 // Parse struct pattern
4043 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4045 self.recover_stmt();
4049 pat = PatKind::Struct(path, fields, etc);
4051 token::OpenDelim(token::Paren) => {
4052 if qself.is_some() {
4053 let msg = "unexpected `(` after qualified path";
4054 let mut err = self.fatal(msg);
4055 err.span_label(self.token.span, msg);
4058 // Parse tuple struct or enum pattern
4059 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4060 pat = PatKind::TupleStruct(path, fields, ddpos)
4062 _ => pat = PatKind::Path(qself, path),
4065 // Try to parse everything else as literal with optional minus
4066 match self.parse_literal_maybe_minus() {
4068 let op_span = self.token.span;
4069 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4070 self.check(&token::DotDotDot) {
4071 let end_kind = if self.eat(&token::DotDotDot) {
4072 RangeEnd::Included(RangeSyntax::DotDotDot)
4073 } else if self.eat(&token::DotDotEq) {
4074 RangeEnd::Included(RangeSyntax::DotDotEq)
4075 } else if self.eat(&token::DotDot) {
4078 panic!("impossible case: we already matched \
4079 on a range-operator token")
4081 let end = self.parse_pat_range_end()?;
4082 let op = Spanned { span: op_span, node: end_kind };
4083 pat = PatKind::Range(begin, end, op);
4085 pat = PatKind::Lit(begin);
4089 self.cancel(&mut err);
4090 let expected = expected.unwrap_or("pattern");
4092 "expected {}, found {}",
4094 self.this_token_descr(),
4096 let mut err = self.fatal(&msg);
4097 err.span_label(self.token.span, format!("expected {}", expected));
4098 let sp = self.sess.source_map().start_point(self.token.span);
4099 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4100 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4108 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4109 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4111 if !allow_range_pat {
4114 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4116 PatKind::Range(..) => {
4117 let mut err = self.struct_span_err(
4119 "the range pattern here has ambiguous interpretation",
4121 err.span_suggestion(
4123 "add parentheses to clarify the precedence",
4124 format!("({})", pprust::pat_to_string(&pat)),
4125 // "ambiguous interpretation" implies that we have to be guessing
4126 Applicability::MaybeIncorrect
4137 /// Parses `ident` or `ident @ pat`.
4138 /// used by the copy foo and ref foo patterns to give a good
4139 /// error message when parsing mistakes like `ref foo(a, b)`.
4140 fn parse_pat_ident(&mut self,
4141 binding_mode: ast::BindingMode)
4142 -> PResult<'a, PatKind> {
4143 let ident = self.parse_ident()?;
4144 let sub = if self.eat(&token::At) {
4145 Some(self.parse_pat(Some("binding pattern"))?)
4150 // just to be friendly, if they write something like
4152 // we end up here with ( as the current token. This shortly
4153 // leads to a parse error. Note that if there is no explicit
4154 // binding mode then we do not end up here, because the lookahead
4155 // will direct us over to parse_enum_variant()
4156 if self.token == token::OpenDelim(token::Paren) {
4157 return Err(self.span_fatal(
4159 "expected identifier, found enum pattern"))
4162 Ok(PatKind::Ident(binding_mode, ident, sub))
4165 /// Parses a local variable declaration.
4166 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4167 let lo = self.prev_span;
4168 let pat = self.parse_top_level_pat()?;
4170 let (err, ty) = if self.eat(&token::Colon) {
4171 // Save the state of the parser before parsing type normally, in case there is a `:`
4172 // instead of an `=` typo.
4173 let parser_snapshot_before_type = self.clone();
4174 let colon_sp = self.prev_span;
4175 match self.parse_ty() {
4176 Ok(ty) => (None, Some(ty)),
4178 // Rewind to before attempting to parse the type and continue parsing
4179 let parser_snapshot_after_type = self.clone();
4180 mem::replace(self, parser_snapshot_before_type);
4182 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4183 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4184 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4190 let init = match (self.parse_initializer(err.is_some()), err) {
4191 (Ok(init), None) => { // init parsed, ty parsed
4194 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4195 // Could parse the type as if it were the initializer, it is likely there was a
4196 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4197 err.span_suggestion_short(
4199 "use `=` if you meant to assign",
4201 Applicability::MachineApplicable
4204 // As this was parsed successfully, continue as if the code has been fixed for the
4205 // rest of the file. It will still fail due to the emitted error, but we avoid
4209 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4211 // Couldn't parse the type nor the initializer, only raise the type error and
4212 // return to the parser state before parsing the type as the initializer.
4213 // let x: <parse_error>;
4214 mem::replace(self, snapshot);
4217 (Err(err), None) => { // init error, ty parsed
4218 // Couldn't parse the initializer and we're not attempting to recover a failed
4219 // parse of the type, return the error.
4223 let hi = if self.token == token::Semi {
4232 id: ast::DUMMY_NODE_ID,
4238 /// Parses a structure field.
4239 fn parse_name_and_ty(&mut self,
4242 attrs: Vec<Attribute>)
4243 -> PResult<'a, StructField> {
4244 let name = self.parse_ident()?;
4245 self.expect(&token::Colon)?;
4246 let ty = self.parse_ty()?;
4248 span: lo.to(self.prev_span),
4251 id: ast::DUMMY_NODE_ID,
4257 /// Emits an expected-item-after-attributes error.
4258 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4259 let message = match attrs.last() {
4260 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4261 _ => "expected item after attributes",
4264 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4265 if attrs.last().unwrap().is_sugared_doc {
4266 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4271 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4272 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4273 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4274 Ok(self.parse_stmt_(true))
4277 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4278 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4280 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4285 fn is_async_block(&self) -> bool {
4286 self.token.is_keyword(kw::Async) &&
4289 self.is_keyword_ahead(1, &[kw::Move]) &&
4290 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4292 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4297 fn is_async_fn(&self) -> bool {
4298 self.token.is_keyword(kw::Async) &&
4299 self.is_keyword_ahead(1, &[kw::Fn])
4302 fn is_do_catch_block(&self) -> bool {
4303 self.token.is_keyword(kw::Do) &&
4304 self.is_keyword_ahead(1, &[kw::Catch]) &&
4305 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4306 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4309 fn is_try_block(&self) -> bool {
4310 self.token.is_keyword(kw::Try) &&
4311 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
4312 self.token.span.rust_2018() &&
4313 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
4314 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4317 fn is_union_item(&self) -> bool {
4318 self.token.is_keyword(kw::Union) &&
4319 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4322 fn is_crate_vis(&self) -> bool {
4323 self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4326 fn is_existential_type_decl(&self) -> bool {
4327 self.token.is_keyword(kw::Existential) &&
4328 self.is_keyword_ahead(1, &[kw::Type])
4331 fn is_auto_trait_item(&self) -> bool {
4333 (self.token.is_keyword(kw::Auto) &&
4334 self.is_keyword_ahead(1, &[kw::Trait]))
4335 || // unsafe auto trait
4336 (self.token.is_keyword(kw::Unsafe) &&
4337 self.is_keyword_ahead(1, &[kw::Auto]) &&
4338 self.is_keyword_ahead(2, &[kw::Trait]))
4341 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4342 -> PResult<'a, Option<P<Item>>> {
4343 let token_lo = self.token.span;
4344 let (ident, def) = match self.token.kind {
4345 token::Ident(name, false) if name == kw::Macro => {
4347 let ident = self.parse_ident()?;
4348 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4349 match self.parse_token_tree() {
4350 TokenTree::Delimited(_, _, tts) => tts,
4351 _ => unreachable!(),
4353 } else if self.check(&token::OpenDelim(token::Paren)) {
4354 let args = self.parse_token_tree();
4355 let body = if self.check(&token::OpenDelim(token::Brace)) {
4356 self.parse_token_tree()
4361 TokenStream::new(vec![
4363 TokenTree::token(token::FatArrow, token_lo.to(self.prev_span)).into(),
4371 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4373 token::Ident(name, _) if name == sym::macro_rules &&
4374 self.look_ahead(1, |t| *t == token::Not) => {
4375 let prev_span = self.prev_span;
4376 self.complain_if_pub_macro(&vis.node, prev_span);
4380 let ident = self.parse_ident()?;
4381 let (delim, tokens) = self.expect_delimited_token_tree()?;
4382 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
4383 self.report_invalid_macro_expansion_item();
4386 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4388 _ => return Ok(None),
4391 let span = lo.to(self.prev_span);
4392 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4395 fn parse_stmt_without_recovery(&mut self,
4396 macro_legacy_warnings: bool)
4397 -> PResult<'a, Option<Stmt>> {
4398 maybe_whole!(self, NtStmt, |x| Some(x));
4400 let attrs = self.parse_outer_attributes()?;
4401 let lo = self.token.span;
4403 Ok(Some(if self.eat_keyword(kw::Let) {
4405 id: ast::DUMMY_NODE_ID,
4406 node: StmtKind::Local(self.parse_local(attrs.into())?),
4407 span: lo.to(self.prev_span),
4409 } else if let Some(macro_def) = self.eat_macro_def(
4411 &source_map::respan(lo, VisibilityKind::Inherited),
4415 id: ast::DUMMY_NODE_ID,
4416 node: StmtKind::Item(macro_def),
4417 span: lo.to(self.prev_span),
4419 // Starts like a simple path, being careful to avoid contextual keywords
4420 // such as a union items, item with `crate` visibility or auto trait items.
4421 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4422 // like a path (1 token), but it fact not a path.
4423 // `union::b::c` - path, `union U { ... }` - not a path.
4424 // `crate::b::c` - path, `crate struct S;` - not a path.
4425 } else if self.token.is_path_start() &&
4426 !self.token.is_qpath_start() &&
4427 !self.is_union_item() &&
4428 !self.is_crate_vis() &&
4429 !self.is_existential_type_decl() &&
4430 !self.is_auto_trait_item() &&
4431 !self.is_async_fn() {
4432 let pth = self.parse_path(PathStyle::Expr)?;
4434 if !self.eat(&token::Not) {
4435 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4436 self.parse_struct_expr(lo, pth, ThinVec::new())?
4438 let hi = self.prev_span;
4439 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4442 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4443 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4444 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4447 return Ok(Some(Stmt {
4448 id: ast::DUMMY_NODE_ID,
4449 node: StmtKind::Expr(expr),
4450 span: lo.to(self.prev_span),
4454 // it's a macro invocation
4455 let id = match self.token.kind {
4456 token::OpenDelim(_) => Ident::invalid(), // no special identifier
4457 _ => self.parse_ident()?,
4460 // check that we're pointing at delimiters (need to check
4461 // again after the `if`, because of `parse_ident`
4462 // consuming more tokens).
4463 match self.token.kind {
4464 token::OpenDelim(_) => {}
4466 // we only expect an ident if we didn't parse one
4468 let ident_str = if id.name == kw::Invalid {
4473 let tok_str = self.this_token_descr();
4474 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
4477 err.span_label(self.token.span, format!("expected {}`(` or `{{`", ident_str));
4482 let (delim, tts) = self.expect_delimited_token_tree()?;
4483 let hi = self.prev_span;
4485 let style = if delim == MacDelimiter::Brace {
4486 MacStmtStyle::Braces
4488 MacStmtStyle::NoBraces
4491 if id.name == kw::Invalid {
4492 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
4493 let node = if delim == MacDelimiter::Brace ||
4494 self.token == token::Semi || self.token == token::Eof {
4495 StmtKind::Mac(P((mac, style, attrs.into())))
4497 // We used to incorrectly stop parsing macro-expanded statements here.
4498 // If the next token will be an error anyway but could have parsed with the
4499 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
4500 else if macro_legacy_warnings &&
4501 self.token.can_begin_expr() &&
4502 match self.token.kind {
4503 // These can continue an expression, so we can't stop parsing and warn.
4504 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
4505 token::BinOp(token::Minus) | token::BinOp(token::Star) |
4506 token::BinOp(token::And) | token::BinOp(token::Or) |
4507 token::AndAnd | token::OrOr |
4508 token::DotDot | token::DotDotDot | token::DotDotEq => false,
4511 self.warn_missing_semicolon();
4512 StmtKind::Mac(P((mac, style, attrs.into())))
4514 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
4515 let e = self.maybe_recover_from_bad_qpath(e, true)?;
4516 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
4517 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
4521 id: ast::DUMMY_NODE_ID,
4526 // if it has a special ident, it's definitely an item
4528 // Require a semicolon or braces.
4529 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
4530 self.report_invalid_macro_expansion_item();
4532 let span = lo.to(hi);
4534 id: ast::DUMMY_NODE_ID,
4536 node: StmtKind::Item({
4538 span, id /*id is good here*/,
4539 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
4540 respan(lo, VisibilityKind::Inherited),
4546 // FIXME: Bad copy of attrs
4547 let old_directory_ownership =
4548 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
4549 let item = self.parse_item_(attrs.clone(), false, true)?;
4550 self.directory.ownership = old_directory_ownership;
4554 id: ast::DUMMY_NODE_ID,
4555 span: lo.to(i.span),
4556 node: StmtKind::Item(i),
4559 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
4560 if !attrs.is_empty() {
4561 if s.prev_token_kind == PrevTokenKind::DocComment {
4562 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
4563 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
4565 s.token.span, "expected statement after outer attribute"
4571 // Do not attempt to parse an expression if we're done here.
4572 if self.token == token::Semi {
4573 unused_attrs(&attrs, self);
4578 if self.token == token::CloseDelim(token::Brace) {
4579 unused_attrs(&attrs, self);
4583 // Remainder are line-expr stmts.
4584 let e = self.parse_expr_res(
4585 Restrictions::STMT_EXPR, Some(attrs.into()))?;
4587 id: ast::DUMMY_NODE_ID,
4588 span: lo.to(e.span),
4589 node: StmtKind::Expr(e),
4596 /// Checks if this expression is a successfully parsed statement.
4597 fn expr_is_complete(&self, e: &Expr) -> bool {
4598 self.restrictions.contains(Restrictions::STMT_EXPR) &&
4599 !classify::expr_requires_semi_to_be_stmt(e)
4602 /// Parses a block. No inner attributes are allowed.
4603 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
4604 maybe_whole!(self, NtBlock, |x| x);
4606 let lo = self.token.span;
4608 if !self.eat(&token::OpenDelim(token::Brace)) {
4609 let sp = self.token.span;
4610 let tok = self.this_token_descr();
4611 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
4612 let do_not_suggest_help =
4613 self.token.is_keyword(kw::In) || self.token == token::Colon;
4615 if self.token.is_ident_named(sym::and) {
4616 e.span_suggestion_short(
4618 "use `&&` instead of `and` for the boolean operator",
4620 Applicability::MaybeIncorrect,
4623 if self.token.is_ident_named(sym::or) {
4624 e.span_suggestion_short(
4626 "use `||` instead of `or` for the boolean operator",
4628 Applicability::MaybeIncorrect,
4632 // Check to see if the user has written something like
4637 // Which is valid in other languages, but not Rust.
4638 match self.parse_stmt_without_recovery(false) {
4640 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
4641 || do_not_suggest_help {
4642 // if the next token is an open brace (e.g., `if a b {`), the place-
4643 // inside-a-block suggestion would be more likely wrong than right
4644 e.span_label(sp, "expected `{`");
4647 let mut stmt_span = stmt.span;
4648 // expand the span to include the semicolon, if it exists
4649 if self.eat(&token::Semi) {
4650 stmt_span = stmt_span.with_hi(self.prev_span.hi());
4652 let sugg = pprust::to_string(|s| {
4653 use crate::print::pprust::{PrintState, INDENT_UNIT};
4654 s.ibox(INDENT_UNIT)?;
4656 s.print_stmt(&stmt)?;
4657 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
4661 "try placing this code inside a block",
4663 // speculative, has been misleading in the past (closed Issue #46836)
4664 Applicability::MaybeIncorrect
4668 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4669 self.cancel(&mut e);
4673 e.span_label(sp, "expected `{`");
4677 self.parse_block_tail(lo, BlockCheckMode::Default)
4680 /// Parses a block. Inner attributes are allowed.
4681 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
4682 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
4684 let lo = self.token.span;
4685 self.expect(&token::OpenDelim(token::Brace))?;
4686 Ok((self.parse_inner_attributes()?,
4687 self.parse_block_tail(lo, BlockCheckMode::Default)?))
4690 /// Parses the rest of a block expression or function body.
4691 /// Precondition: already parsed the '{'.
4692 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
4693 let mut stmts = vec![];
4694 while !self.eat(&token::CloseDelim(token::Brace)) {
4695 let stmt = match self.parse_full_stmt(false) {
4698 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
4700 id: ast::DUMMY_NODE_ID,
4701 node: StmtKind::Expr(DummyResult::raw_expr(self.token.span, true)),
4702 span: self.token.span,
4707 if let Some(stmt) = stmt {
4709 } else if self.token == token::Eof {
4712 // Found only `;` or `}`.
4718 id: ast::DUMMY_NODE_ID,
4720 span: lo.to(self.prev_span),
4724 /// Parses a statement, including the trailing semicolon.
4725 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
4726 // skip looking for a trailing semicolon when we have an interpolated statement
4727 maybe_whole!(self, NtStmt, |x| Some(x));
4729 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
4731 None => return Ok(None),
4735 StmtKind::Expr(ref expr) if self.token != token::Eof => {
4736 // expression without semicolon
4737 if classify::expr_requires_semi_to_be_stmt(expr) {
4738 // Just check for errors and recover; do not eat semicolon yet.
4740 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
4743 self.recover_stmt();
4747 StmtKind::Local(..) => {
4748 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
4749 if macro_legacy_warnings && self.token != token::Semi {
4750 self.warn_missing_semicolon();
4752 self.expect_one_of(&[], &[token::Semi])?;
4758 if self.eat(&token::Semi) {
4759 stmt = stmt.add_trailing_semicolon();
4762 stmt.span = stmt.span.with_hi(self.prev_span.hi());
4766 fn warn_missing_semicolon(&self) {
4767 self.diagnostic().struct_span_warn(self.token.span, {
4768 &format!("expected `;`, found {}", self.this_token_descr())
4770 "This was erroneously allowed and will become a hard error in a future release"
4774 fn err_dotdotdot_syntax(&self, span: Span) {
4775 self.diagnostic().struct_span_err(span, {
4776 "unexpected token: `...`"
4778 span, "use `..` for an exclusive range", "..".to_owned(),
4779 Applicability::MaybeIncorrect
4781 span, "or `..=` for an inclusive range", "..=".to_owned(),
4782 Applicability::MaybeIncorrect
4786 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
4789 /// BOUND = TY_BOUND | LT_BOUND
4790 /// LT_BOUND = LIFETIME (e.g., `'a`)
4791 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
4792 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
4794 fn parse_generic_bounds_common(&mut self,
4796 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4797 let mut bounds = Vec::new();
4798 let mut negative_bounds = Vec::new();
4799 let mut last_plus_span = None;
4800 let mut was_negative = false;
4802 // This needs to be synchronized with `TokenKind::can_begin_bound`.
4803 let is_bound_start = self.check_path() || self.check_lifetime() ||
4804 self.check(&token::Not) || // used for error reporting only
4805 self.check(&token::Question) ||
4806 self.check_keyword(kw::For) ||
4807 self.check(&token::OpenDelim(token::Paren));
4809 let lo = self.token.span;
4810 let has_parens = self.eat(&token::OpenDelim(token::Paren));
4811 let inner_lo = self.token.span;
4812 let is_negative = self.eat(&token::Not);
4813 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
4814 if self.token.is_lifetime() {
4815 if let Some(question_span) = question {
4816 self.span_err(question_span,
4817 "`?` may only modify trait bounds, not lifetime bounds");
4819 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
4821 let inner_span = inner_lo.to(self.prev_span);
4822 self.expect(&token::CloseDelim(token::Paren))?;
4823 let mut err = self.struct_span_err(
4824 lo.to(self.prev_span),
4825 "parenthesized lifetime bounds are not supported"
4827 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
4828 err.span_suggestion_short(
4829 lo.to(self.prev_span),
4830 "remove the parentheses",
4832 Applicability::MachineApplicable
4838 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
4839 let path = self.parse_path(PathStyle::Type)?;
4841 self.expect(&token::CloseDelim(token::Paren))?;
4843 let poly_span = lo.to(self.prev_span);
4845 was_negative = true;
4846 if let Some(sp) = last_plus_span.or(colon_span) {
4847 negative_bounds.push(sp.to(poly_span));
4850 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
4851 let modifier = if question.is_some() {
4852 TraitBoundModifier::Maybe
4854 TraitBoundModifier::None
4856 bounds.push(GenericBound::Trait(poly_trait, modifier));
4863 if !allow_plus || !self.eat_plus() {
4866 last_plus_span = Some(self.prev_span);
4870 if !negative_bounds.is_empty() || was_negative {
4871 let plural = negative_bounds.len() > 1;
4872 let last_span = negative_bounds.last().map(|sp| *sp);
4873 let mut err = self.struct_span_err(
4875 "negative trait bounds are not supported",
4877 if let Some(sp) = last_span {
4878 err.span_label(sp, "negative trait bounds are not supported");
4880 if let Some(bound_list) = colon_span {
4881 let bound_list = bound_list.to(self.prev_span);
4882 let mut new_bound_list = String::new();
4883 if !bounds.is_empty() {
4884 let mut snippets = bounds.iter().map(|bound| bound.span())
4885 .map(|span| self.sess.source_map().span_to_snippet(span));
4886 while let Some(Ok(snippet)) = snippets.next() {
4887 new_bound_list.push_str(" + ");
4888 new_bound_list.push_str(&snippet);
4890 new_bound_list = new_bound_list.replacen(" +", ":", 1);
4892 err.span_suggestion_hidden(
4894 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
4896 Applicability::MachineApplicable,
4905 crate fn parse_generic_bounds(&mut self,
4906 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4907 self.parse_generic_bounds_common(true, colon_span)
4910 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4913 /// BOUND = LT_BOUND (e.g., `'a`)
4915 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
4916 let mut lifetimes = Vec::new();
4917 while self.check_lifetime() {
4918 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
4920 if !self.eat_plus() {
4927 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
4928 fn parse_ty_param(&mut self,
4929 preceding_attrs: Vec<Attribute>)
4930 -> PResult<'a, GenericParam> {
4931 let ident = self.parse_ident()?;
4933 // Parse optional colon and param bounds.
4934 let bounds = if self.eat(&token::Colon) {
4935 self.parse_generic_bounds(Some(self.prev_span))?
4940 let default = if self.eat(&token::Eq) {
4941 Some(self.parse_ty()?)
4948 id: ast::DUMMY_NODE_ID,
4949 attrs: preceding_attrs.into(),
4951 kind: GenericParamKind::Type {
4957 /// Parses the following grammar:
4959 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
4960 fn parse_trait_item_assoc_ty(&mut self)
4961 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
4962 let ident = self.parse_ident()?;
4963 let mut generics = self.parse_generics()?;
4965 // Parse optional colon and param bounds.
4966 let bounds = if self.eat(&token::Colon) {
4967 self.parse_generic_bounds(None)?
4971 generics.where_clause = self.parse_where_clause()?;
4973 let default = if self.eat(&token::Eq) {
4974 Some(self.parse_ty()?)
4978 self.expect(&token::Semi)?;
4980 Ok((ident, TraitItemKind::Type(bounds, default), generics))
4983 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
4984 self.expect_keyword(kw::Const)?;
4985 let ident = self.parse_ident()?;
4986 self.expect(&token::Colon)?;
4987 let ty = self.parse_ty()?;
4991 id: ast::DUMMY_NODE_ID,
4992 attrs: preceding_attrs.into(),
4994 kind: GenericParamKind::Const {
5000 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
5001 /// a trailing comma and erroneous trailing attributes.
5002 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
5003 let mut params = Vec::new();
5005 let attrs = self.parse_outer_attributes()?;
5006 if self.check_lifetime() {
5007 let lifetime = self.expect_lifetime();
5008 // Parse lifetime parameter.
5009 let bounds = if self.eat(&token::Colon) {
5010 self.parse_lt_param_bounds()
5014 params.push(ast::GenericParam {
5015 ident: lifetime.ident,
5017 attrs: attrs.into(),
5019 kind: ast::GenericParamKind::Lifetime,
5021 } else if self.check_keyword(kw::Const) {
5022 // Parse const parameter.
5023 params.push(self.parse_const_param(attrs)?);
5024 } else if self.check_ident() {
5025 // Parse type parameter.
5026 params.push(self.parse_ty_param(attrs)?);
5028 // Check for trailing attributes and stop parsing.
5029 if !attrs.is_empty() {
5030 if !params.is_empty() {
5031 self.struct_span_err(
5033 &format!("trailing attribute after generic parameter"),
5035 .span_label(attrs[0].span, "attributes must go before parameters")
5038 self.struct_span_err(
5040 &format!("attribute without generic parameters"),
5044 "attributes are only permitted when preceding parameters",
5052 if !self.eat(&token::Comma) {
5059 /// Parses a set of optional generic type parameter declarations. Where
5060 /// clauses are not parsed here, and must be added later via
5061 /// `parse_where_clause()`.
5063 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5064 /// | ( < lifetimes , typaramseq ( , )? > )
5065 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5066 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5067 let span_lo = self.token.span;
5068 let (params, span) = if self.eat_lt() {
5069 let params = self.parse_generic_params()?;
5071 (params, span_lo.to(self.prev_span))
5073 (vec![], self.prev_span.between(self.token.span))
5077 where_clause: WhereClause {
5078 id: ast::DUMMY_NODE_ID,
5079 predicates: Vec::new(),
5086 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5087 /// For the purposes of understanding the parsing logic of generic arguments, this function
5088 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5089 /// had the correct amount of leading angle brackets.
5091 /// ```ignore (diagnostics)
5092 /// bar::<<<<T as Foo>::Output>();
5093 /// ^^ help: remove extra angle brackets
5095 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5099 ) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
5100 // We need to detect whether there are extra leading left angle brackets and produce an
5101 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5102 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5103 // then there won't be matching `>` tokens to find.
5105 // To explain how this detection works, consider the following example:
5107 // ```ignore (diagnostics)
5108 // bar::<<<<T as Foo>::Output>();
5109 // ^^ help: remove extra angle brackets
5112 // Parsing of the left angle brackets starts in this function. We start by parsing the
5113 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5116 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5117 // *Unmatched count:* 1
5118 // *`parse_path_segment` calls deep:* 0
5120 // This has the effect of recursing as this function is called if a `<` character
5121 // is found within the expected generic arguments:
5123 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5124 // *Unmatched count:* 2
5125 // *`parse_path_segment` calls deep:* 1
5127 // Eventually we will have recursed until having consumed all of the `<` tokens and
5128 // this will be reflected in the count:
5130 // *Upcoming tokens:* `T as Foo>::Output>;`
5131 // *Unmatched count:* 4
5132 // `parse_path_segment` calls deep:* 3
5134 // The parser will continue until reaching the first `>` - this will decrement the
5135 // unmatched angle bracket count and return to the parent invocation of this function
5136 // having succeeded in parsing:
5138 // *Upcoming tokens:* `::Output>;`
5139 // *Unmatched count:* 3
5140 // *`parse_path_segment` calls deep:* 2
5142 // This will continue until the next `>` character which will also return successfully
5143 // to the parent invocation of this function and decrement the count:
5145 // *Upcoming tokens:* `;`
5146 // *Unmatched count:* 2
5147 // *`parse_path_segment` calls deep:* 1
5149 // At this point, this function will expect to find another matching `>` character but
5150 // won't be able to and will return an error. This will continue all the way up the
5151 // call stack until the first invocation:
5153 // *Upcoming tokens:* `;`
5154 // *Unmatched count:* 2
5155 // *`parse_path_segment` calls deep:* 0
5157 // In doing this, we have managed to work out how many unmatched leading left angle
5158 // brackets there are, but we cannot recover as the unmatched angle brackets have
5159 // already been consumed. To remedy this, we keep a snapshot of the parser state
5160 // before we do the above. We can then inspect whether we ended up with a parsing error
5161 // and unmatched left angle brackets and if so, restore the parser state before we
5162 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5163 // recover by attempting to parse again.
5165 // In practice, the recursion of this function is indirect and there will be other
5166 // locations that consume some `<` characters - as long as we update the count when
5167 // this happens, it isn't an issue.
5169 let is_first_invocation = style == PathStyle::Expr;
5170 // Take a snapshot before attempting to parse - we can restore this later.
5171 let snapshot = if is_first_invocation {
5177 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5178 match self.parse_generic_args() {
5179 Ok(value) => Ok(value),
5180 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5181 // Cancel error from being unable to find `>`. We know the error
5182 // must have been this due to a non-zero unmatched angle bracket
5186 // Swap `self` with our backup of the parser state before attempting to parse
5187 // generic arguments.
5188 let snapshot = mem::replace(self, snapshot.unwrap());
5191 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5192 snapshot.count={:?}",
5193 snapshot.unmatched_angle_bracket_count,
5196 // Eat the unmatched angle brackets.
5197 for _ in 0..snapshot.unmatched_angle_bracket_count {
5201 // Make a span over ${unmatched angle bracket count} characters.
5202 let span = lo.with_hi(
5203 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5205 let plural = snapshot.unmatched_angle_bracket_count > 1;
5210 "unmatched angle bracket{}",
5211 if plural { "s" } else { "" }
5217 "remove extra angle bracket{}",
5218 if plural { "s" } else { "" }
5221 Applicability::MachineApplicable,
5225 // Try again without unmatched angle bracket characters.
5226 self.parse_generic_args()
5232 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5233 /// possibly including trailing comma.
5234 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
5235 let mut args = Vec::new();
5236 let mut constraints = Vec::new();
5237 let mut misplaced_assoc_ty_constraints: Vec<Span> = Vec::new();
5238 let mut assoc_ty_constraints: Vec<Span> = Vec::new();
5240 let args_lo = self.token.span;
5243 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5244 // Parse lifetime argument.
5245 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5246 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5247 } else if self.check_ident() && self.look_ahead(1,
5248 |t| t == &token::Eq || t == &token::Colon) {
5249 // Parse associated type constraint.
5250 let lo = self.token.span;
5251 let ident = self.parse_ident()?;
5252 let kind = if self.eat(&token::Eq) {
5253 AssocTyConstraintKind::Equality {
5254 ty: self.parse_ty()?,
5256 } else if self.eat(&token::Colon) {
5257 AssocTyConstraintKind::Bound {
5258 bounds: self.parse_generic_bounds(Some(self.prev_span))?,
5263 let span = lo.to(self.prev_span);
5264 constraints.push(AssocTyConstraint {
5265 id: ast::DUMMY_NODE_ID,
5270 assoc_ty_constraints.push(span);
5271 } else if self.check_const_arg() {
5272 // Parse const argument.
5273 let expr = if let token::OpenDelim(token::Brace) = self.token.kind {
5274 self.parse_block_expr(
5275 None, self.token.span, BlockCheckMode::Default, ThinVec::new()
5277 } else if self.token.is_ident() {
5278 // FIXME(const_generics): to distinguish between idents for types and consts,
5279 // we should introduce a GenericArg::Ident in the AST and distinguish when
5280 // lowering to the HIR. For now, idents for const args are not permitted.
5281 if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
5282 self.parse_literal_maybe_minus()?
5285 self.fatal("identifiers may currently not be used for const generics")
5289 self.parse_literal_maybe_minus()?
5291 let value = AnonConst {
5292 id: ast::DUMMY_NODE_ID,
5295 args.push(GenericArg::Const(value));
5296 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5297 } else if self.check_type() {
5298 // Parse type argument.
5299 args.push(GenericArg::Type(self.parse_ty()?));
5300 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5305 if !self.eat(&token::Comma) {
5310 // FIXME: we would like to report this in ast_validation instead, but we currently do not
5311 // preserve ordering of generic parameters with respect to associated type binding, so we
5312 // lose that information after parsing.
5313 if misplaced_assoc_ty_constraints.len() > 0 {
5314 let mut err = self.struct_span_err(
5315 args_lo.to(self.prev_span),
5316 "associated type bindings must be declared after generic parameters",
5318 for span in misplaced_assoc_ty_constraints {
5321 "this associated type binding should be moved after the generic parameters",
5327 Ok((args, constraints))
5330 /// Parses an optional where-clause and places it in `generics`.
5332 /// ```ignore (only-for-syntax-highlight)
5333 /// where T : Trait<U, V> + 'b, 'a : 'b
5335 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5336 let mut where_clause = WhereClause {
5337 id: ast::DUMMY_NODE_ID,
5338 predicates: Vec::new(),
5339 span: self.prev_span.to(self.prev_span),
5342 if !self.eat_keyword(kw::Where) {
5343 return Ok(where_clause);
5345 let lo = self.prev_span;
5347 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5348 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5349 // change we parse those generics now, but report an error.
5350 if self.choose_generics_over_qpath() {
5351 let generics = self.parse_generics()?;
5352 self.struct_span_err(
5354 "generic parameters on `where` clauses are reserved for future use",
5356 .span_label(generics.span, "currently unsupported")
5361 let lo = self.token.span;
5362 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5363 let lifetime = self.expect_lifetime();
5364 // Bounds starting with a colon are mandatory, but possibly empty.
5365 self.expect(&token::Colon)?;
5366 let bounds = self.parse_lt_param_bounds();
5367 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5368 ast::WhereRegionPredicate {
5369 span: lo.to(self.prev_span),
5374 } else if self.check_type() {
5375 // Parse optional `for<'a, 'b>`.
5376 // This `for` is parsed greedily and applies to the whole predicate,
5377 // the bounded type can have its own `for` applying only to it.
5379 // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
5380 // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
5381 // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
5382 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5384 // Parse type with mandatory colon and (possibly empty) bounds,
5385 // or with mandatory equality sign and the second type.
5386 let ty = self.parse_ty()?;
5387 if self.eat(&token::Colon) {
5388 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
5389 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5390 ast::WhereBoundPredicate {
5391 span: lo.to(self.prev_span),
5392 bound_generic_params: lifetime_defs,
5397 // FIXME: Decide what should be used here, `=` or `==`.
5398 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5399 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5400 let rhs_ty = self.parse_ty()?;
5401 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5402 ast::WhereEqPredicate {
5403 span: lo.to(self.prev_span),
5406 id: ast::DUMMY_NODE_ID,
5410 return self.unexpected();
5416 if !self.eat(&token::Comma) {
5421 where_clause.span = lo.to(self.prev_span);
5425 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
5426 -> PResult<'a, (Vec<Arg> , bool)> {
5427 self.expect(&token::OpenDelim(token::Paren))?;
5429 let sp = self.token.span;
5430 let mut c_variadic = false;
5431 let (args, recovered): (Vec<Option<Arg>>, bool) =
5432 self.parse_seq_to_before_end(
5433 &token::CloseDelim(token::Paren),
5434 SeqSep::trailing_allowed(token::Comma),
5436 // If the argument is a C-variadic argument we should not
5437 // enforce named arguments.
5438 let enforce_named_args = if p.token == token::DotDotDot {
5443 match p.parse_arg_general(enforce_named_args, false,
5446 if let TyKind::CVarArgs = arg.ty.node {
5448 if p.token != token::CloseDelim(token::Paren) {
5449 let span = p.token.span;
5451 "`...` must be the last argument of a C-variadic function");
5462 let lo = p.prev_span;
5463 // Skip every token until next possible arg or end.
5464 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5465 // Create a placeholder argument for proper arg count (issue #34264).
5466 let span = lo.to(p.prev_span);
5467 Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
5474 self.eat(&token::CloseDelim(token::Paren));
5477 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5479 if c_variadic && args.is_empty() {
5481 "C-variadic function must be declared with at least one named argument");
5484 Ok((args, c_variadic))
5487 /// Parses the argument list and result type of a function declaration.
5488 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
5490 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
5491 let ret_ty = self.parse_ret_ty(true)?;
5500 /// Returns the parsed optional self argument and whether a self shortcut was used.
5501 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
5502 let expect_ident = |this: &mut Self| match this.token.kind {
5503 // Preserve hygienic context.
5504 token::Ident(name, _) =>
5505 { let span = this.token.span; this.bump(); Ident::new(name, span) }
5508 let isolated_self = |this: &mut Self, n| {
5509 this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
5510 this.look_ahead(n + 1, |t| t != &token::ModSep)
5513 // Parse optional `self` parameter of a method.
5514 // Only a limited set of initial token sequences is considered `self` parameters; anything
5515 // else is parsed as a normal function parameter list, so some lookahead is required.
5516 let eself_lo = self.token.span;
5517 let (eself, eself_ident, eself_hi) = match self.token.kind {
5518 token::BinOp(token::And) => {
5524 (if isolated_self(self, 1) {
5526 SelfKind::Region(None, Mutability::Immutable)
5527 } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
5528 isolated_self(self, 2) {
5531 SelfKind::Region(None, Mutability::Mutable)
5532 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5533 isolated_self(self, 2) {
5535 let lt = self.expect_lifetime();
5536 SelfKind::Region(Some(lt), Mutability::Immutable)
5537 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5538 self.is_keyword_ahead(2, &[kw::Mut]) &&
5539 isolated_self(self, 3) {
5541 let lt = self.expect_lifetime();
5543 SelfKind::Region(Some(lt), Mutability::Mutable)
5546 }, expect_ident(self), self.prev_span)
5548 token::BinOp(token::Star) => {
5553 // Emit special error for `self` cases.
5554 let msg = "cannot pass `self` by raw pointer";
5555 (if isolated_self(self, 1) {
5557 self.struct_span_err(self.token.span, msg)
5558 .span_label(self.token.span, msg)
5560 SelfKind::Value(Mutability::Immutable)
5561 } else if self.look_ahead(1, |t| t.is_mutability()) &&
5562 isolated_self(self, 2) {
5565 self.struct_span_err(self.token.span, msg)
5566 .span_label(self.token.span, msg)
5568 SelfKind::Value(Mutability::Immutable)
5571 }, expect_ident(self), self.prev_span)
5573 token::Ident(..) => {
5574 if isolated_self(self, 0) {
5577 let eself_ident = expect_ident(self);
5578 let eself_hi = self.prev_span;
5579 (if self.eat(&token::Colon) {
5580 let ty = self.parse_ty()?;
5581 SelfKind::Explicit(ty, Mutability::Immutable)
5583 SelfKind::Value(Mutability::Immutable)
5584 }, eself_ident, eself_hi)
5585 } else if self.token.is_keyword(kw::Mut) &&
5586 isolated_self(self, 1) {
5590 let eself_ident = expect_ident(self);
5591 let eself_hi = self.prev_span;
5592 (if self.eat(&token::Colon) {
5593 let ty = self.parse_ty()?;
5594 SelfKind::Explicit(ty, Mutability::Mutable)
5596 SelfKind::Value(Mutability::Mutable)
5597 }, eself_ident, eself_hi)
5602 _ => return Ok(None),
5605 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
5606 Ok(Some(Arg::from_self(eself, eself_ident)))
5609 /// Parses the parameter list and result type of a function that may have a `self` parameter.
5610 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
5611 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
5613 self.expect(&token::OpenDelim(token::Paren))?;
5615 // Parse optional self argument.
5616 let self_arg = self.parse_self_arg()?;
5618 // Parse the rest of the function parameter list.
5619 let sep = SeqSep::trailing_allowed(token::Comma);
5620 let (mut fn_inputs, recovered) = if let Some(self_arg) = self_arg {
5621 if self.check(&token::CloseDelim(token::Paren)) {
5622 (vec![self_arg], false)
5623 } else if self.eat(&token::Comma) {
5624 let mut fn_inputs = vec![self_arg];
5625 let (mut input, recovered) = self.parse_seq_to_before_end(
5626 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
5627 fn_inputs.append(&mut input);
5628 (fn_inputs, recovered)
5630 match self.expect_one_of(&[], &[]) {
5631 Err(err) => return Err(err),
5632 Ok(recovered) => (vec![self_arg], recovered),
5636 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5640 // Parse closing paren and return type.
5641 self.expect(&token::CloseDelim(token::Paren))?;
5643 // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
5644 self.deduplicate_recovered_arg_names(&mut fn_inputs);
5648 output: self.parse_ret_ty(true)?,
5653 /// Parses the `|arg, arg|` header of a closure.
5654 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
5655 let inputs_captures = {
5656 if self.eat(&token::OrOr) {
5659 self.expect(&token::BinOp(token::Or))?;
5660 let args = self.parse_seq_to_before_tokens(
5661 &[&token::BinOp(token::Or), &token::OrOr],
5662 SeqSep::trailing_allowed(token::Comma),
5663 TokenExpectType::NoExpect,
5664 |p| p.parse_fn_block_arg()
5670 let output = self.parse_ret_ty(true)?;
5673 inputs: inputs_captures,
5679 /// Parses the name and optional generic types of a function header.
5680 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
5681 let id = self.parse_ident()?;
5682 let generics = self.parse_generics()?;
5686 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
5687 attrs: Vec<Attribute>) -> P<Item> {
5691 id: ast::DUMMY_NODE_ID,
5699 /// Parses an item-position function declaration.
5700 fn parse_item_fn(&mut self,
5702 asyncness: Spanned<IsAsync>,
5703 constness: Spanned<Constness>,
5705 -> PResult<'a, ItemInfo> {
5706 let (ident, mut generics) = self.parse_fn_header()?;
5707 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
5708 let decl = self.parse_fn_decl(allow_c_variadic)?;
5709 generics.where_clause = self.parse_where_clause()?;
5710 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5711 let header = FnHeader { unsafety, asyncness, constness, abi };
5712 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
5715 /// Returns `true` if we are looking at `const ID`
5716 /// (returns `false` for things like `const fn`, etc.).
5717 fn is_const_item(&self) -> bool {
5718 self.token.is_keyword(kw::Const) &&
5719 !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
5722 /// Parses all the "front matter" for a `fn` declaration, up to
5723 /// and including the `fn` keyword:
5727 /// - `const unsafe fn`
5730 fn parse_fn_front_matter(&mut self)
5738 let is_const_fn = self.eat_keyword(kw::Const);
5739 let const_span = self.prev_span;
5740 let unsafety = self.parse_unsafety();
5741 let asyncness = self.parse_asyncness();
5742 let asyncness = respan(self.prev_span, asyncness);
5743 let (constness, unsafety, abi) = if is_const_fn {
5744 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
5746 let abi = if self.eat_keyword(kw::Extern) {
5747 self.parse_opt_abi()?.unwrap_or(Abi::C)
5751 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
5753 if !self.eat_keyword(kw::Fn) {
5754 // It is possible for `expect_one_of` to recover given the contents of
5755 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
5756 // account for this.
5757 if !self.expect_one_of(&[], &[])? { unreachable!() }
5759 Ok((constness, unsafety, asyncness, abi))
5762 /// Parses an impl item.
5763 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
5764 maybe_whole!(self, NtImplItem, |x| x);
5765 let attrs = self.parse_outer_attributes()?;
5766 let mut unclosed_delims = vec![];
5767 let (mut item, tokens) = self.collect_tokens(|this| {
5768 let item = this.parse_impl_item_(at_end, attrs);
5769 unclosed_delims.append(&mut this.unclosed_delims);
5772 self.unclosed_delims.append(&mut unclosed_delims);
5774 // See `parse_item` for why this clause is here.
5775 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
5776 item.tokens = Some(tokens);
5781 fn parse_impl_item_(&mut self,
5783 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
5784 let lo = self.token.span;
5785 let vis = self.parse_visibility(false)?;
5786 let defaultness = self.parse_defaultness();
5787 let (name, node, generics) = if let Some(type_) = self.eat_type() {
5788 let (name, alias, generics) = type_?;
5789 let kind = match alias {
5790 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
5791 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
5793 (name, kind, generics)
5794 } else if self.is_const_item() {
5795 // This parses the grammar:
5796 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
5797 self.expect_keyword(kw::Const)?;
5798 let name = self.parse_ident()?;
5799 self.expect(&token::Colon)?;
5800 let typ = self.parse_ty()?;
5801 self.expect(&token::Eq)?;
5802 let expr = self.parse_expr()?;
5803 self.expect(&token::Semi)?;
5804 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
5806 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
5807 attrs.extend(inner_attrs);
5808 (name, node, generics)
5812 id: ast::DUMMY_NODE_ID,
5813 span: lo.to(self.prev_span),
5824 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
5826 VisibilityKind::Inherited => {}
5828 let mut err = if self.token.is_keyword(sym::macro_rules) {
5829 let mut err = self.diagnostic()
5830 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
5831 err.span_suggestion(
5833 "try exporting the macro",
5834 "#[macro_export]".to_owned(),
5835 Applicability::MaybeIncorrect // speculative
5839 let mut err = self.diagnostic()
5840 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
5841 err.help("try adjusting the macro to put `pub` inside the invocation");
5849 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
5850 -> DiagnosticBuilder<'a>
5852 let expected_kinds = if item_type == "extern" {
5853 "missing `fn`, `type`, or `static`"
5855 "missing `fn`, `type`, or `const`"
5858 // Given this code `path(`, it seems like this is not
5859 // setting the visibility of a macro invocation, but rather
5860 // a mistyped method declaration.
5861 // Create a diagnostic pointing out that `fn` is missing.
5863 // x | pub path(&self) {
5864 // | ^ missing `fn`, `type`, or `const`
5866 // ^^ `sp` below will point to this
5867 let sp = prev_span.between(self.prev_span);
5868 let mut err = self.diagnostic().struct_span_err(
5870 &format!("{} for {}-item declaration",
5871 expected_kinds, item_type));
5872 err.span_label(sp, expected_kinds);
5876 /// Parse a method or a macro invocation in a trait impl.
5877 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
5878 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
5879 ast::ImplItemKind)> {
5880 // code copied from parse_macro_use_or_failure... abstraction!
5881 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
5883 Ok((Ident::invalid(), vec![], ast::Generics::default(),
5884 ast::ImplItemKind::Macro(mac)))
5886 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
5887 let ident = self.parse_ident()?;
5888 let mut generics = self.parse_generics()?;
5889 let decl = self.parse_fn_decl_with_self(|p| {
5890 p.parse_arg_general(true, true, false)
5892 generics.where_clause = self.parse_where_clause()?;
5894 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5895 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
5896 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
5897 ast::MethodSig { header, decl },
5903 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
5904 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
5905 let ident = self.parse_ident()?;
5906 let mut tps = self.parse_generics()?;
5908 // Parse optional colon and supertrait bounds.
5909 let bounds = if self.eat(&token::Colon) {
5910 self.parse_generic_bounds(Some(self.prev_span))?
5915 if self.eat(&token::Eq) {
5916 // it's a trait alias
5917 let bounds = self.parse_generic_bounds(None)?;
5918 tps.where_clause = self.parse_where_clause()?;
5919 self.expect(&token::Semi)?;
5920 if is_auto == IsAuto::Yes {
5921 let msg = "trait aliases cannot be `auto`";
5922 self.struct_span_err(self.prev_span, msg)
5923 .span_label(self.prev_span, msg)
5926 if unsafety != Unsafety::Normal {
5927 let msg = "trait aliases cannot be `unsafe`";
5928 self.struct_span_err(self.prev_span, msg)
5929 .span_label(self.prev_span, msg)
5932 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
5934 // it's a normal trait
5935 tps.where_clause = self.parse_where_clause()?;
5936 self.expect(&token::OpenDelim(token::Brace))?;
5937 let mut trait_items = vec![];
5938 while !self.eat(&token::CloseDelim(token::Brace)) {
5939 if let token::DocComment(_) = self.token.kind {
5940 if self.look_ahead(1,
5941 |tok| tok == &token::CloseDelim(token::Brace)) {
5942 let mut err = self.diagnostic().struct_span_err_with_code(
5944 "found a documentation comment that doesn't document anything",
5945 DiagnosticId::Error("E0584".into()),
5947 err.help("doc comments must come before what they document, maybe a \
5948 comment was intended with `//`?",
5955 let mut at_end = false;
5956 match self.parse_trait_item(&mut at_end) {
5957 Ok(item) => trait_items.push(item),
5961 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5966 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
5970 fn choose_generics_over_qpath(&self) -> bool {
5971 // There's an ambiguity between generic parameters and qualified paths in impls.
5972 // If we see `<` it may start both, so we have to inspect some following tokens.
5973 // The following combinations can only start generics,
5974 // but not qualified paths (with one exception):
5975 // `<` `>` - empty generic parameters
5976 // `<` `#` - generic parameters with attributes
5977 // `<` (LIFETIME|IDENT) `>` - single generic parameter
5978 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
5979 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
5980 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
5981 // `<` const - generic const parameter
5982 // The only truly ambiguous case is
5983 // `<` IDENT `>` `::` IDENT ...
5984 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
5985 // because this is what almost always expected in practice, qualified paths in impls
5986 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
5987 self.token == token::Lt &&
5988 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
5989 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
5990 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
5991 t == &token::Colon || t == &token::Eq) ||
5992 self.is_keyword_ahead(1, &[kw::Const]))
5995 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
5996 self.expect(&token::OpenDelim(token::Brace))?;
5997 let attrs = self.parse_inner_attributes()?;
5999 let mut impl_items = Vec::new();
6000 while !self.eat(&token::CloseDelim(token::Brace)) {
6001 let mut at_end = false;
6002 match self.parse_impl_item(&mut at_end) {
6003 Ok(impl_item) => impl_items.push(impl_item),
6007 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6012 Ok((impl_items, attrs))
6015 /// Parses an implementation item, `impl` keyword is already parsed.
6017 /// impl<'a, T> TYPE { /* impl items */ }
6018 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
6019 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
6021 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
6022 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
6023 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
6024 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
6025 -> PResult<'a, ItemInfo> {
6026 // First, parse generic parameters if necessary.
6027 let mut generics = if self.choose_generics_over_qpath() {
6028 self.parse_generics()?
6030 ast::Generics::default()
6033 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6034 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6036 ast::ImplPolarity::Negative
6038 ast::ImplPolarity::Positive
6041 // Parse both types and traits as a type, then reinterpret if necessary.
6042 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
6043 let ty_first = if self.token.is_keyword(kw::For) &&
6044 self.look_ahead(1, |t| t != &token::Lt) {
6045 let span = self.prev_span.between(self.token.span);
6046 self.struct_span_err(span, "missing trait in a trait impl").emit();
6047 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6052 // If `for` is missing we try to recover.
6053 let has_for = self.eat_keyword(kw::For);
6054 let missing_for_span = self.prev_span.between(self.token.span);
6056 let ty_second = if self.token == token::DotDot {
6057 // We need to report this error after `cfg` expansion for compatibility reasons
6058 self.bump(); // `..`, do not add it to expected tokens
6059 Some(DummyResult::raw_ty(self.prev_span, true))
6060 } else if has_for || self.token.can_begin_type() {
6061 Some(self.parse_ty()?)
6066 generics.where_clause = self.parse_where_clause()?;
6068 let (impl_items, attrs) = self.parse_impl_body()?;
6070 let item_kind = match ty_second {
6071 Some(ty_second) => {
6072 // impl Trait for Type
6074 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6075 .span_suggestion_short(
6078 " for ".to_string(),
6079 Applicability::MachineApplicable,
6083 let ty_first = ty_first.into_inner();
6084 let path = match ty_first.node {
6085 // This notably includes paths passed through `ty` macro fragments (#46438).
6086 TyKind::Path(None, path) => path,
6088 self.span_err(ty_first.span, "expected a trait, found type");
6089 err_path(ty_first.span)
6092 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6094 ItemKind::Impl(unsafety, polarity, defaultness,
6095 generics, Some(trait_ref), ty_second, impl_items)
6099 ItemKind::Impl(unsafety, polarity, defaultness,
6100 generics, None, ty_first, impl_items)
6104 Ok((Ident::invalid(), item_kind, Some(attrs)))
6107 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6108 if self.eat_keyword(kw::For) {
6110 let params = self.parse_generic_params()?;
6112 // We rely on AST validation to rule out invalid cases: There must not be type
6113 // parameters, and the lifetime parameters must not have bounds.
6120 /// Parses `struct Foo { ... }`.
6121 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6122 let class_name = self.parse_ident()?;
6124 let mut generics = self.parse_generics()?;
6126 // There is a special case worth noting here, as reported in issue #17904.
6127 // If we are parsing a tuple struct it is the case that the where clause
6128 // should follow the field list. Like so:
6130 // struct Foo<T>(T) where T: Copy;
6132 // If we are parsing a normal record-style struct it is the case
6133 // that the where clause comes before the body, and after the generics.
6134 // So if we look ahead and see a brace or a where-clause we begin
6135 // parsing a record style struct.
6137 // Otherwise if we look ahead and see a paren we parse a tuple-style
6140 let vdata = if self.token.is_keyword(kw::Where) {
6141 generics.where_clause = self.parse_where_clause()?;
6142 if self.eat(&token::Semi) {
6143 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6144 VariantData::Unit(ast::DUMMY_NODE_ID)
6146 // If we see: `struct Foo<T> where T: Copy { ... }`
6147 let (fields, recovered) = self.parse_record_struct_body()?;
6148 VariantData::Struct(fields, recovered)
6150 // No `where` so: `struct Foo<T>;`
6151 } else if self.eat(&token::Semi) {
6152 VariantData::Unit(ast::DUMMY_NODE_ID)
6153 // Record-style struct definition
6154 } else if self.token == token::OpenDelim(token::Brace) {
6155 let (fields, recovered) = self.parse_record_struct_body()?;
6156 VariantData::Struct(fields, recovered)
6157 // Tuple-style struct definition with optional where-clause.
6158 } else if self.token == token::OpenDelim(token::Paren) {
6159 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6160 generics.where_clause = self.parse_where_clause()?;
6161 self.expect(&token::Semi)?;
6164 let token_str = self.this_token_descr();
6165 let mut err = self.fatal(&format!(
6166 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6169 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
6173 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6176 /// Parses `union Foo { ... }`.
6177 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6178 let class_name = self.parse_ident()?;
6180 let mut generics = self.parse_generics()?;
6182 let vdata = if self.token.is_keyword(kw::Where) {
6183 generics.where_clause = self.parse_where_clause()?;
6184 let (fields, recovered) = self.parse_record_struct_body()?;
6185 VariantData::Struct(fields, recovered)
6186 } else if self.token == token::OpenDelim(token::Brace) {
6187 let (fields, recovered) = self.parse_record_struct_body()?;
6188 VariantData::Struct(fields, recovered)
6190 let token_str = self.this_token_descr();
6191 let mut err = self.fatal(&format!(
6192 "expected `where` or `{{` after union name, found {}", token_str));
6193 err.span_label(self.token.span, "expected `where` or `{` after union name");
6197 Ok((class_name, ItemKind::Union(vdata, generics), None))
6200 fn parse_record_struct_body(
6202 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6203 let mut fields = Vec::new();
6204 let mut recovered = false;
6205 if self.eat(&token::OpenDelim(token::Brace)) {
6206 while self.token != token::CloseDelim(token::Brace) {
6207 let field = self.parse_struct_decl_field().map_err(|e| {
6208 self.recover_stmt();
6213 Ok(field) => fields.push(field),
6219 self.eat(&token::CloseDelim(token::Brace));
6221 let token_str = self.this_token_descr();
6222 let mut err = self.fatal(&format!(
6223 "expected `where`, or `{{` after struct name, found {}", token_str));
6224 err.span_label(self.token.span, "expected `where`, or `{` after struct name");
6228 Ok((fields, recovered))
6231 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6232 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6233 // Unit like structs are handled in parse_item_struct function
6234 let fields = self.parse_unspanned_seq(
6235 &token::OpenDelim(token::Paren),
6236 &token::CloseDelim(token::Paren),
6237 SeqSep::trailing_allowed(token::Comma),
6239 let attrs = p.parse_outer_attributes()?;
6240 let lo = p.token.span;
6241 let vis = p.parse_visibility(true)?;
6242 let ty = p.parse_ty()?;
6244 span: lo.to(ty.span),
6247 id: ast::DUMMY_NODE_ID,
6256 /// Parses a structure field declaration.
6257 fn parse_single_struct_field(&mut self,
6260 attrs: Vec<Attribute> )
6261 -> PResult<'a, StructField> {
6262 let mut seen_comma: bool = false;
6263 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
6264 if self.token == token::Comma {
6267 match self.token.kind {
6271 token::CloseDelim(token::Brace) => {}
6272 token::DocComment(_) => {
6273 let previous_span = self.prev_span;
6274 let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
6275 self.bump(); // consume the doc comment
6276 let comma_after_doc_seen = self.eat(&token::Comma);
6277 // `seen_comma` is always false, because we are inside doc block
6278 // condition is here to make code more readable
6279 if seen_comma == false && comma_after_doc_seen == true {
6282 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
6285 if seen_comma == false {
6286 let sp = self.sess.source_map().next_point(previous_span);
6287 err.span_suggestion(
6289 "missing comma here",
6291 Applicability::MachineApplicable
6298 let sp = self.sess.source_map().next_point(self.prev_span);
6299 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
6300 self.this_token_descr()));
6301 if self.token.is_ident() {
6302 // This is likely another field; emit the diagnostic and keep going
6303 err.span_suggestion(
6305 "try adding a comma",
6307 Applicability::MachineApplicable,
6318 /// Parses an element of a struct declaration.
6319 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6320 let attrs = self.parse_outer_attributes()?;
6321 let lo = self.token.span;
6322 let vis = self.parse_visibility(false)?;
6323 self.parse_single_struct_field(lo, vis, attrs)
6326 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
6327 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
6328 /// If the following element can't be a tuple (i.e., it's a function definition), then
6329 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
6330 /// so emit a proper diagnostic.
6331 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6332 maybe_whole!(self, NtVis, |x| x);
6334 self.expected_tokens.push(TokenType::Keyword(kw::Crate));
6335 if self.is_crate_vis() {
6336 self.bump(); // `crate`
6337 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6340 if !self.eat_keyword(kw::Pub) {
6341 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6342 // keyword to grab a span from for inherited visibility; an empty span at the
6343 // beginning of the current token would seem to be the "Schelling span".
6344 return Ok(respan(self.token.span.shrink_to_lo(), VisibilityKind::Inherited))
6346 let lo = self.prev_span;
6348 if self.check(&token::OpenDelim(token::Paren)) {
6349 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6350 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6351 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6352 // by the following tokens.
6353 if self.is_keyword_ahead(1, &[kw::Crate]) &&
6354 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
6358 self.bump(); // `crate`
6359 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6361 lo.to(self.prev_span),
6362 VisibilityKind::Crate(CrateSugar::PubCrate),
6365 } else if self.is_keyword_ahead(1, &[kw::In]) {
6368 self.bump(); // `in`
6369 let path = self.parse_path(PathStyle::Mod)?; // `path`
6370 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6371 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6373 id: ast::DUMMY_NODE_ID,
6376 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6377 self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
6379 // `pub(self)` or `pub(super)`
6381 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6382 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6383 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6385 id: ast::DUMMY_NODE_ID,
6388 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6389 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6391 let msg = "incorrect visibility restriction";
6392 let suggestion = r##"some possible visibility restrictions are:
6393 `pub(crate)`: visible only on the current crate
6394 `pub(super)`: visible only in the current module's parent
6395 `pub(in path::to::module)`: visible only on the specified path"##;
6396 let path = self.parse_path(PathStyle::Mod)?;
6398 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6399 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6400 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6401 err.help(suggestion);
6402 err.span_suggestion(
6403 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6405 err.emit(); // emit diagnostic, but continue with public visibility
6409 Ok(respan(lo, VisibilityKind::Public))
6412 /// Parses defaultness (i.e., `default` or nothing).
6413 fn parse_defaultness(&mut self) -> Defaultness {
6414 // `pub` is included for better error messages
6415 if self.check_keyword(kw::Default) &&
6416 self.is_keyword_ahead(1, &[
6426 self.bump(); // `default`
6427 Defaultness::Default
6433 /// Given a termination token, parses all of the items in a module.
6434 fn parse_mod_items(&mut self, term: &TokenKind, inner_lo: Span) -> PResult<'a, Mod> {
6435 let mut items = vec![];
6436 while let Some(item) = self.parse_item()? {
6438 self.maybe_consume_incorrect_semicolon(&items);
6441 if !self.eat(term) {
6442 let token_str = self.this_token_descr();
6443 if !self.maybe_consume_incorrect_semicolon(&items) {
6444 let mut err = self.fatal(&format!("expected item, found {}", token_str));
6445 err.span_label(self.token.span, "expected item");
6450 let hi = if self.token.span.is_dummy() {
6457 inner: inner_lo.to(hi),
6463 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6464 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
6465 self.expect(&token::Colon)?;
6466 let ty = self.parse_ty()?;
6467 self.expect(&token::Eq)?;
6468 let e = self.parse_expr()?;
6469 self.expect(&token::Semi)?;
6470 let item = match m {
6471 Some(m) => ItemKind::Static(ty, m, e),
6472 None => ItemKind::Const(ty, e),
6474 Ok((id, item, None))
6477 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6478 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6479 let (in_cfg, outer_attrs) = {
6480 let mut strip_unconfigured = crate::config::StripUnconfigured {
6482 features: None, // don't perform gated feature checking
6484 let mut outer_attrs = outer_attrs.to_owned();
6485 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
6486 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
6489 let id_span = self.token.span;
6490 let id = self.parse_ident()?;
6491 if self.eat(&token::Semi) {
6492 if in_cfg && self.recurse_into_file_modules {
6493 // This mod is in an external file. Let's go get it!
6494 let ModulePathSuccess { path, directory_ownership, warn } =
6495 self.submod_path(id, &outer_attrs, id_span)?;
6496 let (module, mut attrs) =
6497 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
6498 // Record that we fetched the mod from an external file
6500 let attr = Attribute {
6501 id: attr::mk_attr_id(),
6502 style: ast::AttrStyle::Outer,
6503 path: ast::Path::from_ident(
6504 Ident::with_empty_ctxt(sym::warn_directory_ownership)),
6505 tokens: TokenStream::empty(),
6506 is_sugared_doc: false,
6509 attr::mark_known(&attr);
6512 Ok((id, ItemKind::Mod(module), Some(attrs)))
6514 let placeholder = ast::Mod {
6519 Ok((id, ItemKind::Mod(placeholder), None))
6522 let old_directory = self.directory.clone();
6523 self.push_directory(id, &outer_attrs);
6525 self.expect(&token::OpenDelim(token::Brace))?;
6526 let mod_inner_lo = self.token.span;
6527 let attrs = self.parse_inner_attributes()?;
6528 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
6530 self.directory = old_directory;
6531 Ok((id, ItemKind::Mod(module), Some(attrs)))
6535 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
6536 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6537 self.directory.path.to_mut().push(&path.as_str());
6538 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
6540 // We have to push on the current module name in the case of relative
6541 // paths in order to ensure that any additional module paths from inline
6542 // `mod x { ... }` come after the relative extension.
6544 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
6545 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
6546 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
6547 if let Some(ident) = relative.take() { // remove the relative offset
6548 self.directory.path.to_mut().push(ident.as_str());
6551 self.directory.path.to_mut().push(&id.as_str());
6555 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
6556 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6559 // On windows, the base path might have the form
6560 // `\\?\foo\bar` in which case it does not tolerate
6561 // mixed `/` and `\` separators, so canonicalize
6564 let s = s.replace("/", "\\");
6565 Some(dir_path.join(s))
6571 /// Returns a path to a module.
6572 pub fn default_submod_path(
6574 relative: Option<ast::Ident>,
6576 source_map: &SourceMap) -> ModulePath
6578 // If we're in a foo.rs file instead of a mod.rs file,
6579 // we need to look for submodules in
6580 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
6581 // `./<id>.rs` and `./<id>/mod.rs`.
6582 let relative_prefix_string;
6583 let relative_prefix = if let Some(ident) = relative {
6584 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
6585 &relative_prefix_string
6590 let mod_name = id.to_string();
6591 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
6592 let secondary_path_str = format!("{}{}{}mod.rs",
6593 relative_prefix, mod_name, path::MAIN_SEPARATOR);
6594 let default_path = dir_path.join(&default_path_str);
6595 let secondary_path = dir_path.join(&secondary_path_str);
6596 let default_exists = source_map.file_exists(&default_path);
6597 let secondary_exists = source_map.file_exists(&secondary_path);
6599 let result = match (default_exists, secondary_exists) {
6600 (true, false) => Ok(ModulePathSuccess {
6602 directory_ownership: DirectoryOwnership::Owned {
6607 (false, true) => Ok(ModulePathSuccess {
6608 path: secondary_path,
6609 directory_ownership: DirectoryOwnership::Owned {
6614 (false, false) => Err(Error::FileNotFoundForModule {
6615 mod_name: mod_name.clone(),
6616 default_path: default_path_str,
6617 secondary_path: secondary_path_str,
6618 dir_path: dir_path.display().to_string(),
6620 (true, true) => Err(Error::DuplicatePaths {
6621 mod_name: mod_name.clone(),
6622 default_path: default_path_str,
6623 secondary_path: secondary_path_str,
6629 path_exists: default_exists || secondary_exists,
6634 fn submod_path(&mut self,
6636 outer_attrs: &[Attribute],
6638 -> PResult<'a, ModulePathSuccess> {
6639 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
6640 return Ok(ModulePathSuccess {
6641 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
6642 // All `#[path]` files are treated as though they are a `mod.rs` file.
6643 // This means that `mod foo;` declarations inside `#[path]`-included
6644 // files are siblings,
6646 // Note that this will produce weirdness when a file named `foo.rs` is
6647 // `#[path]` included and contains a `mod foo;` declaration.
6648 // If you encounter this, it's your own darn fault :P
6649 Some(_) => DirectoryOwnership::Owned { relative: None },
6650 _ => DirectoryOwnership::UnownedViaMod(true),
6657 let relative = match self.directory.ownership {
6658 DirectoryOwnership::Owned { relative } => relative,
6659 DirectoryOwnership::UnownedViaBlock |
6660 DirectoryOwnership::UnownedViaMod(_) => None,
6662 let paths = Parser::default_submod_path(
6663 id, relative, &self.directory.path, self.sess.source_map());
6665 match self.directory.ownership {
6666 DirectoryOwnership::Owned { .. } => {
6667 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
6669 DirectoryOwnership::UnownedViaBlock => {
6671 "Cannot declare a non-inline module inside a block \
6672 unless it has a path attribute";
6673 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
6674 if paths.path_exists {
6675 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
6677 err.span_note(id_sp, &msg);
6681 DirectoryOwnership::UnownedViaMod(warn) => {
6683 if let Ok(result) = paths.result {
6684 return Ok(ModulePathSuccess { warn: true, ..result });
6687 let mut err = self.diagnostic().struct_span_err(id_sp,
6688 "cannot declare a new module at this location");
6689 if !id_sp.is_dummy() {
6690 let src_path = self.sess.source_map().span_to_filename(id_sp);
6691 if let FileName::Real(src_path) = src_path {
6692 if let Some(stem) = src_path.file_stem() {
6693 let mut dest_path = src_path.clone();
6694 dest_path.set_file_name(stem);
6695 dest_path.push("mod.rs");
6696 err.span_note(id_sp,
6697 &format!("maybe move this module `{}` to its own \
6698 directory via `{}`", src_path.display(),
6699 dest_path.display()));
6703 if paths.path_exists {
6704 err.span_note(id_sp,
6705 &format!("... or maybe `use` the module `{}` instead \
6706 of possibly redeclaring it",
6714 /// Reads a module from a source file.
6715 fn eval_src_mod(&mut self,
6717 directory_ownership: DirectoryOwnership,
6720 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
6721 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
6722 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
6723 let mut err = String::from("circular modules: ");
6724 let len = included_mod_stack.len();
6725 for p in &included_mod_stack[i.. len] {
6726 err.push_str(&p.to_string_lossy());
6727 err.push_str(" -> ");
6729 err.push_str(&path.to_string_lossy());
6730 return Err(self.span_fatal(id_sp, &err[..]));
6732 included_mod_stack.push(path.clone());
6733 drop(included_mod_stack);
6736 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
6737 p0.cfg_mods = self.cfg_mods;
6738 let mod_inner_lo = p0.token.span;
6739 let mod_attrs = p0.parse_inner_attributes()?;
6740 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
6742 self.sess.included_mod_stack.borrow_mut().pop();
6746 /// Parses a function declaration from a foreign module.
6747 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6748 -> PResult<'a, ForeignItem> {
6749 self.expect_keyword(kw::Fn)?;
6751 let (ident, mut generics) = self.parse_fn_header()?;
6752 let decl = self.parse_fn_decl(true)?;
6753 generics.where_clause = self.parse_where_clause()?;
6754 let hi = self.token.span;
6755 self.expect(&token::Semi)?;
6756 Ok(ast::ForeignItem {
6759 node: ForeignItemKind::Fn(decl, generics),
6760 id: ast::DUMMY_NODE_ID,
6766 /// Parses a static item from a foreign module.
6767 /// Assumes that the `static` keyword is already parsed.
6768 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6769 -> PResult<'a, ForeignItem> {
6770 let mutbl = self.parse_mutability();
6771 let ident = self.parse_ident()?;
6772 self.expect(&token::Colon)?;
6773 let ty = self.parse_ty()?;
6774 let hi = self.token.span;
6775 self.expect(&token::Semi)?;
6779 node: ForeignItemKind::Static(ty, mutbl),
6780 id: ast::DUMMY_NODE_ID,
6786 /// Parses a type from a foreign module.
6787 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6788 -> PResult<'a, ForeignItem> {
6789 self.expect_keyword(kw::Type)?;
6791 let ident = self.parse_ident()?;
6792 let hi = self.token.span;
6793 self.expect(&token::Semi)?;
6794 Ok(ast::ForeignItem {
6797 node: ForeignItemKind::Ty,
6798 id: ast::DUMMY_NODE_ID,
6804 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
6805 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
6806 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
6808 let mut ident = if self.token.is_keyword(kw::SelfLower) {
6809 self.parse_path_segment_ident()
6813 let mut idents = vec![];
6814 let mut replacement = vec![];
6815 let mut fixed_crate_name = false;
6816 // Accept `extern crate name-like-this` for better diagnostics
6817 let dash = token::BinOp(token::BinOpToken::Minus);
6818 if self.token == dash { // Do not include `-` as part of the expected tokens list
6819 while self.eat(&dash) {
6820 fixed_crate_name = true;
6821 replacement.push((self.prev_span, "_".to_string()));
6822 idents.push(self.parse_ident()?);
6825 if fixed_crate_name {
6826 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
6827 let mut fixed_name = format!("{}", ident.name);
6828 for part in idents {
6829 fixed_name.push_str(&format!("_{}", part.name));
6831 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
6833 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
6834 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
6835 err.multipart_suggestion(
6838 Applicability::MachineApplicable,
6845 /// Parses `extern crate` links.
6850 /// extern crate foo;
6851 /// extern crate bar as foo;
6853 fn parse_item_extern_crate(&mut self,
6855 visibility: Visibility,
6856 attrs: Vec<Attribute>)
6857 -> PResult<'a, P<Item>> {
6858 // Accept `extern crate name-like-this` for better diagnostics
6859 let orig_name = self.parse_crate_name_with_dashes()?;
6860 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
6861 (rename, Some(orig_name.name))
6865 self.expect(&token::Semi)?;
6867 let span = lo.to(self.prev_span);
6868 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
6871 /// Parses `extern` for foreign ABIs modules.
6873 /// `extern` is expected to have been
6874 /// consumed before calling this method.
6878 /// ```ignore (only-for-syntax-highlight)
6882 fn parse_item_foreign_mod(&mut self,
6884 opt_abi: Option<Abi>,
6885 visibility: Visibility,
6886 mut attrs: Vec<Attribute>)
6887 -> PResult<'a, P<Item>> {
6888 self.expect(&token::OpenDelim(token::Brace))?;
6890 let abi = opt_abi.unwrap_or(Abi::C);
6892 attrs.extend(self.parse_inner_attributes()?);
6894 let mut foreign_items = vec![];
6895 while !self.eat(&token::CloseDelim(token::Brace)) {
6896 foreign_items.push(self.parse_foreign_item()?);
6899 let prev_span = self.prev_span;
6900 let m = ast::ForeignMod {
6902 items: foreign_items
6904 let invalid = Ident::invalid();
6905 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
6908 /// Parses `type Foo = Bar;`
6910 /// `existential type Foo: Bar;`
6913 /// without modifying the parser state.
6914 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
6915 // This parses the grammar:
6916 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
6917 if self.check_keyword(kw::Type) ||
6918 self.check_keyword(kw::Existential) &&
6919 self.is_keyword_ahead(1, &[kw::Type]) {
6920 let existential = self.eat_keyword(kw::Existential);
6921 assert!(self.eat_keyword(kw::Type));
6922 Some(self.parse_existential_or_alias(existential))
6928 /// Parses a type alias or existential type.
6929 fn parse_existential_or_alias(
6932 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
6933 let ident = self.parse_ident()?;
6934 let mut tps = self.parse_generics()?;
6935 tps.where_clause = self.parse_where_clause()?;
6936 let alias = if existential {
6937 self.expect(&token::Colon)?;
6938 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6939 AliasKind::Existential(bounds)
6941 self.expect(&token::Eq)?;
6942 let ty = self.parse_ty()?;
6945 self.expect(&token::Semi)?;
6946 Ok((ident, alias, tps))
6949 /// Parses the part of an enum declaration following the `{`.
6950 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
6951 let mut variants = Vec::new();
6952 let mut any_disr = vec![];
6953 while self.token != token::CloseDelim(token::Brace) {
6954 let variant_attrs = self.parse_outer_attributes()?;
6955 let vlo = self.token.span;
6958 let mut disr_expr = None;
6960 let ident = self.parse_ident()?;
6961 if self.check(&token::OpenDelim(token::Brace)) {
6962 // Parse a struct variant.
6963 let (fields, recovered) = self.parse_record_struct_body()?;
6964 struct_def = VariantData::Struct(fields, recovered);
6965 } else if self.check(&token::OpenDelim(token::Paren)) {
6966 struct_def = VariantData::Tuple(
6967 self.parse_tuple_struct_body()?,
6970 } else if self.eat(&token::Eq) {
6971 disr_expr = Some(AnonConst {
6972 id: ast::DUMMY_NODE_ID,
6973 value: self.parse_expr()?,
6975 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
6978 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6980 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6983 let vr = ast::Variant_ {
6985 id: ast::DUMMY_NODE_ID,
6986 attrs: variant_attrs,
6990 variants.push(respan(vlo.to(self.prev_span), vr));
6992 if !self.eat(&token::Comma) {
6993 if self.token.is_ident() && !self.token.is_reserved_ident() {
6994 let sp = self.sess.source_map().next_point(self.prev_span);
6995 let mut err = self.struct_span_err(sp, "missing comma");
6996 err.span_suggestion_short(
7000 Applicability::MaybeIncorrect,
7008 self.expect(&token::CloseDelim(token::Brace))?;
7009 self.maybe_report_invalid_custom_discriminants(any_disr, &variants);
7011 Ok(ast::EnumDef { variants })
7014 /// Parses an enum declaration.
7015 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
7016 let id = self.parse_ident()?;
7017 let mut generics = self.parse_generics()?;
7018 generics.where_clause = self.parse_where_clause()?;
7019 self.expect(&token::OpenDelim(token::Brace))?;
7021 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
7022 self.recover_stmt();
7023 self.eat(&token::CloseDelim(token::Brace));
7026 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7029 /// Parses a string as an ABI spec on an extern type or module. Consumes
7030 /// the `extern` keyword, if one is found.
7031 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7032 match self.token.kind {
7033 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
7034 token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
7035 let sp = self.token.span;
7036 self.expect_no_suffix(sp, "an ABI spec", suffix);
7038 match abi::lookup(&symbol.as_str()) {
7039 Some(abi) => Ok(Some(abi)),
7041 let prev_span = self.prev_span;
7042 let mut err = struct_span_err!(
7043 self.sess.span_diagnostic,
7046 "invalid ABI: found `{}`",
7048 err.span_label(prev_span, "invalid ABI");
7049 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7060 fn is_static_global(&mut self) -> bool {
7061 if self.check_keyword(kw::Static) {
7062 // Check if this could be a closure
7063 !self.look_ahead(1, |token| {
7064 if token.is_keyword(kw::Move) {
7068 token::BinOp(token::Or) | token::OrOr => true,
7079 attrs: Vec<Attribute>,
7080 macros_allowed: bool,
7081 attributes_allowed: bool,
7082 ) -> PResult<'a, Option<P<Item>>> {
7083 let mut unclosed_delims = vec![];
7084 let (ret, tokens) = self.collect_tokens(|this| {
7085 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7086 unclosed_delims.append(&mut this.unclosed_delims);
7089 self.unclosed_delims.append(&mut unclosed_delims);
7091 // Once we've parsed an item and recorded the tokens we got while
7092 // parsing we may want to store `tokens` into the item we're about to
7093 // return. Note, though, that we specifically didn't capture tokens
7094 // related to outer attributes. The `tokens` field here may later be
7095 // used with procedural macros to convert this item back into a token
7096 // stream, but during expansion we may be removing attributes as we go
7099 // If we've got inner attributes then the `tokens` we've got above holds
7100 // these inner attributes. If an inner attribute is expanded we won't
7101 // actually remove it from the token stream, so we'll just keep yielding
7102 // it (bad!). To work around this case for now we just avoid recording
7103 // `tokens` if we detect any inner attributes. This should help keep
7104 // expansion correct, but we should fix this bug one day!
7107 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7108 i.tokens = Some(tokens);
7115 /// Parses one of the items allowed by the flags.
7116 fn parse_item_implementation(
7118 attrs: Vec<Attribute>,
7119 macros_allowed: bool,
7120 attributes_allowed: bool,
7121 ) -> PResult<'a, Option<P<Item>>> {
7122 maybe_whole!(self, NtItem, |item| {
7123 let mut item = item.into_inner();
7124 let mut attrs = attrs;
7125 mem::swap(&mut item.attrs, &mut attrs);
7126 item.attrs.extend(attrs);
7130 let lo = self.token.span;
7132 let visibility = self.parse_visibility(false)?;
7134 if self.eat_keyword(kw::Use) {
7136 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7137 self.expect(&token::Semi)?;
7139 let span = lo.to(self.prev_span);
7141 self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
7142 return Ok(Some(item));
7145 if self.eat_keyword(kw::Extern) {
7146 if self.eat_keyword(kw::Crate) {
7147 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7150 let opt_abi = self.parse_opt_abi()?;
7152 if self.eat_keyword(kw::Fn) {
7153 // EXTERN FUNCTION ITEM
7154 let fn_span = self.prev_span;
7155 let abi = opt_abi.unwrap_or(Abi::C);
7156 let (ident, item_, extra_attrs) =
7157 self.parse_item_fn(Unsafety::Normal,
7158 respan(fn_span, IsAsync::NotAsync),
7159 respan(fn_span, Constness::NotConst),
7161 let prev_span = self.prev_span;
7162 let item = self.mk_item(lo.to(prev_span),
7166 maybe_append(attrs, extra_attrs));
7167 return Ok(Some(item));
7168 } else if self.check(&token::OpenDelim(token::Brace)) {
7169 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7175 if self.is_static_global() {
7178 let m = if self.eat_keyword(kw::Mut) {
7181 Mutability::Immutable
7183 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7184 let prev_span = self.prev_span;
7185 let item = self.mk_item(lo.to(prev_span),
7189 maybe_append(attrs, extra_attrs));
7190 return Ok(Some(item));
7192 if self.eat_keyword(kw::Const) {
7193 let const_span = self.prev_span;
7194 if self.check_keyword(kw::Fn)
7195 || (self.check_keyword(kw::Unsafe)
7196 && self.is_keyword_ahead(1, &[kw::Fn])) {
7197 // CONST FUNCTION ITEM
7198 let unsafety = self.parse_unsafety();
7200 let (ident, item_, extra_attrs) =
7201 self.parse_item_fn(unsafety,
7202 respan(const_span, IsAsync::NotAsync),
7203 respan(const_span, Constness::Const),
7205 let prev_span = self.prev_span;
7206 let item = self.mk_item(lo.to(prev_span),
7210 maybe_append(attrs, extra_attrs));
7211 return Ok(Some(item));
7215 if self.eat_keyword(kw::Mut) {
7216 let prev_span = self.prev_span;
7217 let mut err = self.diagnostic()
7218 .struct_span_err(prev_span, "const globals cannot be mutable");
7219 err.span_label(prev_span, "cannot be mutable");
7220 err.span_suggestion(
7222 "you might want to declare a static instead",
7223 "static".to_owned(),
7224 Applicability::MaybeIncorrect,
7228 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
7229 let prev_span = self.prev_span;
7230 let item = self.mk_item(lo.to(prev_span),
7234 maybe_append(attrs, extra_attrs));
7235 return Ok(Some(item));
7238 // Parse `async unsafe? fn`.
7239 if self.check_keyword(kw::Async) {
7240 let async_span = self.token.span;
7241 if self.is_keyword_ahead(1, &[kw::Fn])
7242 || self.is_keyword_ahead(2, &[kw::Fn])
7244 // ASYNC FUNCTION ITEM
7245 self.bump(); // `async`
7246 let unsafety = self.parse_unsafety(); // `unsafe`?
7247 self.expect_keyword(kw::Fn)?; // `fn`
7248 let fn_span = self.prev_span;
7249 let (ident, item_, extra_attrs) =
7250 self.parse_item_fn(unsafety,
7251 respan(async_span, IsAsync::Async {
7252 closure_id: ast::DUMMY_NODE_ID,
7253 return_impl_trait_id: ast::DUMMY_NODE_ID,
7255 respan(fn_span, Constness::NotConst),
7257 let prev_span = self.prev_span;
7258 let item = self.mk_item(lo.to(prev_span),
7262 maybe_append(attrs, extra_attrs));
7263 if self.token.span.rust_2015() {
7264 self.diagnostic().struct_span_err_with_code(
7266 "`async fn` is not permitted in the 2015 edition",
7267 DiagnosticId::Error("E0670".into())
7270 return Ok(Some(item));
7273 if self.check_keyword(kw::Unsafe) &&
7274 self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
7276 // UNSAFE TRAIT ITEM
7277 self.bump(); // `unsafe`
7278 let is_auto = if self.eat_keyword(kw::Trait) {
7281 self.expect_keyword(kw::Auto)?;
7282 self.expect_keyword(kw::Trait)?;
7285 let (ident, item_, extra_attrs) =
7286 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
7287 let prev_span = self.prev_span;
7288 let item = self.mk_item(lo.to(prev_span),
7292 maybe_append(attrs, extra_attrs));
7293 return Ok(Some(item));
7295 if self.check_keyword(kw::Impl) ||
7296 self.check_keyword(kw::Unsafe) &&
7297 self.is_keyword_ahead(1, &[kw::Impl]) ||
7298 self.check_keyword(kw::Default) &&
7299 self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
7301 let defaultness = self.parse_defaultness();
7302 let unsafety = self.parse_unsafety();
7303 self.expect_keyword(kw::Impl)?;
7304 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
7305 let span = lo.to(self.prev_span);
7306 return Ok(Some(self.mk_item(span, ident, item, visibility,
7307 maybe_append(attrs, extra_attrs))));
7309 if self.check_keyword(kw::Fn) {
7312 let fn_span = self.prev_span;
7313 let (ident, item_, extra_attrs) =
7314 self.parse_item_fn(Unsafety::Normal,
7315 respan(fn_span, IsAsync::NotAsync),
7316 respan(fn_span, Constness::NotConst),
7318 let prev_span = self.prev_span;
7319 let item = self.mk_item(lo.to(prev_span),
7323 maybe_append(attrs, extra_attrs));
7324 return Ok(Some(item));
7326 if self.check_keyword(kw::Unsafe)
7327 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
7328 // UNSAFE FUNCTION ITEM
7329 self.bump(); // `unsafe`
7330 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
7331 self.check(&token::OpenDelim(token::Brace));
7332 let abi = if self.eat_keyword(kw::Extern) {
7333 self.parse_opt_abi()?.unwrap_or(Abi::C)
7337 self.expect_keyword(kw::Fn)?;
7338 let fn_span = self.prev_span;
7339 let (ident, item_, extra_attrs) =
7340 self.parse_item_fn(Unsafety::Unsafe,
7341 respan(fn_span, IsAsync::NotAsync),
7342 respan(fn_span, Constness::NotConst),
7344 let prev_span = self.prev_span;
7345 let item = self.mk_item(lo.to(prev_span),
7349 maybe_append(attrs, extra_attrs));
7350 return Ok(Some(item));
7352 if self.eat_keyword(kw::Mod) {
7354 let (ident, item_, extra_attrs) =
7355 self.parse_item_mod(&attrs[..])?;
7356 let prev_span = self.prev_span;
7357 let item = self.mk_item(lo.to(prev_span),
7361 maybe_append(attrs, extra_attrs));
7362 return Ok(Some(item));
7364 if let Some(type_) = self.eat_type() {
7365 let (ident, alias, generics) = type_?;
7367 let item_ = match alias {
7368 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7369 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7371 let prev_span = self.prev_span;
7372 let item = self.mk_item(lo.to(prev_span),
7377 return Ok(Some(item));
7379 if self.eat_keyword(kw::Enum) {
7381 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7382 let prev_span = self.prev_span;
7383 let item = self.mk_item(lo.to(prev_span),
7387 maybe_append(attrs, extra_attrs));
7388 return Ok(Some(item));
7390 if self.check_keyword(kw::Trait)
7391 || (self.check_keyword(kw::Auto)
7392 && self.is_keyword_ahead(1, &[kw::Trait]))
7394 let is_auto = if self.eat_keyword(kw::Trait) {
7397 self.expect_keyword(kw::Auto)?;
7398 self.expect_keyword(kw::Trait)?;
7402 let (ident, item_, extra_attrs) =
7403 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7404 let prev_span = self.prev_span;
7405 let item = self.mk_item(lo.to(prev_span),
7409 maybe_append(attrs, extra_attrs));
7410 return Ok(Some(item));
7412 if self.eat_keyword(kw::Struct) {
7414 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7415 let prev_span = self.prev_span;
7416 let item = self.mk_item(lo.to(prev_span),
7420 maybe_append(attrs, extra_attrs));
7421 return Ok(Some(item));
7423 if self.is_union_item() {
7426 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7427 let prev_span = self.prev_span;
7428 let item = self.mk_item(lo.to(prev_span),
7432 maybe_append(attrs, extra_attrs));
7433 return Ok(Some(item));
7435 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7436 return Ok(Some(macro_def));
7439 // Verify whether we have encountered a struct or method definition where the user forgot to
7440 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7441 if visibility.node.is_pub() &&
7442 self.check_ident() &&
7443 self.look_ahead(1, |t| *t != token::Not)
7445 // Space between `pub` keyword and the identifier
7448 // ^^^ `sp` points here
7449 let sp = self.prev_span.between(self.token.span);
7450 let full_sp = self.prev_span.to(self.token.span);
7451 let ident_sp = self.token.span;
7452 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7453 // possible public struct definition where `struct` was forgotten
7454 let ident = self.parse_ident().unwrap();
7455 let msg = format!("add `struct` here to parse `{}` as a public struct",
7457 let mut err = self.diagnostic()
7458 .struct_span_err(sp, "missing `struct` for struct definition");
7459 err.span_suggestion_short(
7460 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7463 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7464 let ident = self.parse_ident().unwrap();
7466 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
7471 self.consume_block(token::Paren);
7472 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
7473 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
7475 ("fn", kw_name, false)
7476 } else if self.check(&token::OpenDelim(token::Brace)) {
7478 ("fn", kw_name, false)
7479 } else if self.check(&token::Colon) {
7483 ("fn` or `struct", "function or struct", true)
7486 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7487 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7489 self.consume_block(token::Brace);
7490 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
7494 err.span_suggestion_short(
7495 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
7498 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
7499 err.span_suggestion(
7501 "if you meant to call a macro, try",
7502 format!("{}!", snippet),
7503 // this is the `ambiguous` conditional branch
7504 Applicability::MaybeIncorrect
7507 err.help("if you meant to call a macro, remove the `pub` \
7508 and add a trailing `!` after the identifier");
7512 } else if self.look_ahead(1, |t| *t == token::Lt) {
7513 let ident = self.parse_ident().unwrap();
7514 self.eat_to_tokens(&[&token::Gt]);
7516 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
7517 if let Ok(Some(_)) = self.parse_self_arg() {
7518 ("fn", "method", false)
7520 ("fn", "function", false)
7522 } else if self.check(&token::OpenDelim(token::Brace)) {
7523 ("struct", "struct", false)
7525 ("fn` or `struct", "function or struct", true)
7527 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7528 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7530 err.span_suggestion_short(
7532 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
7533 format!(" {} ", kw),
7534 Applicability::MachineApplicable,
7540 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
7543 /// Parses a foreign item.
7544 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
7545 maybe_whole!(self, NtForeignItem, |ni| ni);
7547 let attrs = self.parse_outer_attributes()?;
7548 let lo = self.token.span;
7549 let visibility = self.parse_visibility(false)?;
7551 // FOREIGN STATIC ITEM
7552 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
7553 if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
7554 if self.token.is_keyword(kw::Const) {
7556 .struct_span_err(self.token.span, "extern items cannot be `const`")
7559 "try using a static value",
7560 "static".to_owned(),
7561 Applicability::MachineApplicable
7564 self.bump(); // `static` or `const`
7565 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
7567 // FOREIGN FUNCTION ITEM
7568 if self.check_keyword(kw::Fn) {
7569 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
7571 // FOREIGN TYPE ITEM
7572 if self.check_keyword(kw::Type) {
7573 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
7576 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
7580 ident: Ident::invalid(),
7581 span: lo.to(self.prev_span),
7582 id: ast::DUMMY_NODE_ID,
7585 node: ForeignItemKind::Macro(mac),
7590 if !attrs.is_empty() {
7591 self.expected_item_err(&attrs)?;
7599 /// This is the fall-through for parsing items.
7600 fn parse_macro_use_or_failure(
7602 attrs: Vec<Attribute> ,
7603 macros_allowed: bool,
7604 attributes_allowed: bool,
7606 visibility: Visibility
7607 ) -> PResult<'a, Option<P<Item>>> {
7608 if macros_allowed && self.token.is_path_start() &&
7609 !(self.is_async_fn() && self.token.span.rust_2015()) {
7610 // MACRO INVOCATION ITEM
7612 let prev_span = self.prev_span;
7613 self.complain_if_pub_macro(&visibility.node, prev_span);
7615 let mac_lo = self.token.span;
7618 let pth = self.parse_path(PathStyle::Mod)?;
7619 self.expect(&token::Not)?;
7621 // a 'special' identifier (like what `macro_rules!` uses)
7622 // is optional. We should eventually unify invoc syntax
7624 let id = if self.token.is_ident() {
7627 Ident::invalid() // no special identifier
7629 // eat a matched-delimiter token tree:
7630 let (delim, tts) = self.expect_delimited_token_tree()?;
7631 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
7632 self.report_invalid_macro_expansion_item();
7635 let hi = self.prev_span;
7636 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
7637 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
7638 return Ok(Some(item));
7641 // FAILURE TO PARSE ITEM
7642 match visibility.node {
7643 VisibilityKind::Inherited => {}
7645 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
7649 if !attributes_allowed && !attrs.is_empty() {
7650 self.expected_item_err(&attrs)?;
7655 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
7656 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
7657 at_end: &mut bool) -> PResult<'a, Option<Mac>>
7659 if self.token.is_path_start() &&
7660 !(self.is_async_fn() && self.token.span.rust_2015()) {
7661 let prev_span = self.prev_span;
7662 let lo = self.token.span;
7663 let pth = self.parse_path(PathStyle::Mod)?;
7665 if pth.segments.len() == 1 {
7666 if !self.eat(&token::Not) {
7667 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
7670 self.expect(&token::Not)?;
7673 if let Some(vis) = vis {
7674 self.complain_if_pub_macro(&vis.node, prev_span);
7679 // eat a matched-delimiter token tree:
7680 let (delim, tts) = self.expect_delimited_token_tree()?;
7681 if delim != MacDelimiter::Brace {
7682 self.expect(&token::Semi)?;
7685 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
7691 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
7692 where F: FnOnce(&mut Self) -> PResult<'a, R>
7694 // Record all tokens we parse when parsing this item.
7695 let mut tokens = Vec::new();
7696 let prev_collecting = match self.token_cursor.frame.last_token {
7697 LastToken::Collecting(ref mut list) => {
7698 Some(mem::replace(list, Vec::new()))
7700 LastToken::Was(ref mut last) => {
7701 tokens.extend(last.take());
7705 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
7706 let prev = self.token_cursor.stack.len();
7708 let last_token = if self.token_cursor.stack.len() == prev {
7709 &mut self.token_cursor.frame.last_token
7711 &mut self.token_cursor.stack[prev].last_token
7714 // Pull out the tokens that we've collected from the call to `f` above.
7715 let mut collected_tokens = match *last_token {
7716 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
7717 LastToken::Was(_) => panic!("our vector went away?"),
7720 // If we're not at EOF our current token wasn't actually consumed by
7721 // `f`, but it'll still be in our list that we pulled out. In that case
7723 let extra_token = if self.token != token::Eof {
7724 collected_tokens.pop()
7729 // If we were previously collecting tokens, then this was a recursive
7730 // call. In that case we need to record all the tokens we collected in
7731 // our parent list as well. To do that we push a clone of our stream
7732 // onto the previous list.
7733 match prev_collecting {
7735 list.extend(collected_tokens.iter().cloned());
7736 list.extend(extra_token);
7737 *last_token = LastToken::Collecting(list);
7740 *last_token = LastToken::Was(extra_token);
7744 Ok((ret?, TokenStream::new(collected_tokens)))
7747 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
7748 let attrs = self.parse_outer_attributes()?;
7749 self.parse_item_(attrs, true, false)
7753 fn is_import_coupler(&mut self) -> bool {
7754 self.check(&token::ModSep) &&
7755 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
7756 *t == token::BinOp(token::Star))
7759 /// Parses a `UseTree`.
7762 /// USE_TREE = [`::`] `*` |
7763 /// [`::`] `{` USE_TREE_LIST `}` |
7765 /// PATH `::` `{` USE_TREE_LIST `}` |
7766 /// PATH [`as` IDENT]
7768 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
7769 let lo = self.token.span;
7771 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
7772 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
7773 self.check(&token::BinOp(token::Star)) ||
7774 self.is_import_coupler() {
7775 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
7776 let mod_sep_ctxt = self.token.span.ctxt();
7777 if self.eat(&token::ModSep) {
7778 prefix.segments.push(
7779 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
7783 if self.eat(&token::BinOp(token::Star)) {
7786 UseTreeKind::Nested(self.parse_use_tree_list()?)
7789 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
7790 prefix = self.parse_path(PathStyle::Mod)?;
7792 if self.eat(&token::ModSep) {
7793 if self.eat(&token::BinOp(token::Star)) {
7796 UseTreeKind::Nested(self.parse_use_tree_list()?)
7799 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
7803 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
7806 /// Parses a `UseTreeKind::Nested(list)`.
7809 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
7811 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
7812 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
7813 &token::CloseDelim(token::Brace),
7814 SeqSep::trailing_allowed(token::Comma), |this| {
7815 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
7819 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
7820 if self.eat_keyword(kw::As) {
7821 self.parse_ident_or_underscore().map(Some)
7827 /// Parses a source module as a crate. This is the main entry point for the parser.
7828 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
7829 let lo = self.token.span;
7830 let krate = Ok(ast::Crate {
7831 attrs: self.parse_inner_attributes()?,
7832 module: self.parse_mod_items(&token::Eof, lo)?,
7833 span: lo.to(self.token.span),
7838 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
7839 let ret = match self.token.kind {
7840 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
7841 (symbol, ast::StrStyle::Cooked, suffix),
7842 token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
7843 (symbol, ast::StrStyle::Raw(n), suffix),
7850 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
7851 match self.parse_optional_str() {
7852 Some((s, style, suf)) => {
7853 let sp = self.prev_span;
7854 self.expect_no_suffix(sp, "a string literal", suf);
7858 let msg = "expected string literal";
7859 let mut err = self.fatal(msg);
7860 err.span_label(self.token.span, msg);
7866 fn report_invalid_macro_expansion_item(&self) {
7867 self.struct_span_err(
7869 "macros that expand to items must be delimited with braces or followed by a semicolon",
7870 ).multipart_suggestion(
7871 "change the delimiters to curly braces",
7873 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
7874 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
7876 Applicability::MaybeIncorrect,
7878 self.sess.source_map.next_point(self.prev_span),
7881 Applicability::MaybeIncorrect,
7886 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
7887 for unmatched in unclosed_delims.iter() {
7888 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
7889 "incorrect close delimiter: `{}`",
7890 pprust::token_to_string(&token::CloseDelim(unmatched.found_delim)),
7892 err.span_label(unmatched.found_span, "incorrect close delimiter");
7893 if let Some(sp) = unmatched.candidate_span {
7894 err.span_label(sp, "close delimiter possibly meant for this");
7896 if let Some(sp) = unmatched.unclosed_span {
7897 err.span_label(sp, "un-closed delimiter");
7901 unclosed_delims.clear();