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::source_map::{self, SourceMap, Spanned, respan};
38 use crate::parse::{SeqSep, classify, literal, token};
39 use crate::parse::lexer::UnmatchedBrace;
40 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
41 use crate::parse::token::{Token, DelimToken};
42 use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
43 use crate::util::parser::{AssocOp, Fixity};
44 use crate::print::pprust;
46 use crate::parse::PResult;
48 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
49 use crate::symbol::{kw, sym, Symbol};
50 use crate::parse::diagnostics::{Error, dummy_arg};
52 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
53 use rustc_target::spec::abi::{self, Abi};
54 use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
60 use std::path::{self, Path, PathBuf};
64 /// Whether the type alias or associated type is a concrete type or an existential type
66 /// Just a new name for the same type
68 /// Only trait impls of the type will be usable, not the actual type itself
69 Existential(GenericBounds),
73 struct Restrictions: u8 {
74 const STMT_EXPR = 1 << 0;
75 const NO_STRUCT_LITERAL = 1 << 1;
79 type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
81 /// Specifies how to parse a path.
82 #[derive(Copy, Clone, PartialEq)]
84 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
85 /// with something else. For example, in expressions `segment < ....` can be interpreted
86 /// as a comparison and `segment ( ....` can be interpreted as a function call.
87 /// In all such contexts the non-path interpretation is preferred by default for practical
88 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
89 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
91 /// In other contexts, notably in types, no ambiguity exists and paths can be written
92 /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
93 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
95 /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
96 /// visibilities or attributes.
97 /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
98 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
99 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
100 /// tokens when something goes wrong.
104 #[derive(Clone, Copy, PartialEq, Debug)]
105 crate enum SemiColonMode {
111 #[derive(Clone, Copy, PartialEq, Debug)]
112 crate enum BlockMode {
117 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
118 /// dropped into the token stream, which happens while parsing the result of
119 /// macro expansion). Placement of these is not as complex as I feared it would
120 /// be. The important thing is to make sure that lookahead doesn't balk at
121 /// `token::Interpolated` tokens.
122 macro_rules! maybe_whole_expr {
124 if let token::Interpolated(nt) = &$p.token {
126 token::NtExpr(e) | token::NtLiteral(e) => {
131 token::NtPath(path) => {
132 let path = path.clone();
134 return Ok($p.mk_expr($p.span, ExprKind::Path(None, path), ThinVec::new()));
136 token::NtBlock(block) => {
137 let block = block.clone();
139 return Ok($p.mk_expr($p.span, ExprKind::Block(block, None), ThinVec::new()));
147 /// As maybe_whole_expr, but for things other than expressions
148 macro_rules! maybe_whole {
149 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
150 if let token::Interpolated(nt) = &$p.token {
151 if let token::$constructor(x) = &**nt {
160 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
161 macro_rules! maybe_recover_from_interpolated_ty_qpath {
162 ($self: expr, $allow_qpath_recovery: expr) => {
163 if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
164 if let token::Interpolated(nt) = &$self.token {
165 if let token::NtTy(ty) = &**nt {
168 return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
175 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
176 if let Some(ref mut rhs) = rhs {
182 #[derive(Debug, Clone, Copy, PartialEq)]
194 // NOTE: `Ident`s are handled by `common.rs`.
197 pub struct Parser<'a> {
198 pub sess: &'a ParseSess,
199 /// the current token:
200 pub token: token::TokenKind,
201 /// the span of the current token:
203 meta_var_span: Option<Span>,
204 /// The span of the previous token.
206 /// The kind of the previous troken.
207 prev_token_kind: PrevTokenKind,
208 restrictions: Restrictions,
209 /// Used to determine the path to externally loaded source files.
210 crate directory: Directory<'a>,
211 /// `true` to parse sub-modules in other files.
212 pub recurse_into_file_modules: bool,
213 /// Name of the root module this parser originated from. If `None`, then the
214 /// name is not known. This does not change while the parser is descending
215 /// into modules, and sub-parsers have new values for this name.
216 pub root_module_name: Option<String>,
217 crate expected_tokens: Vec<TokenType>,
218 crate token_cursor: TokenCursor,
219 desugar_doc_comments: bool,
220 /// `true` we should configure out of line modules as we parse.
222 /// This field is used to keep track of how many left angle brackets we have seen. This is
223 /// required in order to detect extra leading left angle brackets (`<` characters) and error
226 /// See the comments in the `parse_path_segment` function for more details.
227 crate unmatched_angle_bracket_count: u32,
228 crate max_angle_bracket_count: u32,
229 /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
230 /// it gets removed from here. Every entry left at the end gets emitted as an independent
232 crate unclosed_delims: Vec<UnmatchedBrace>,
233 crate last_unexpected_token_span: Option<Span>,
234 /// If present, this `Parser` is not parsing Rust code but rather a macro call.
235 crate subparser_name: Option<&'static str>,
238 impl<'a> Drop for Parser<'a> {
240 let diag = self.diagnostic();
241 emit_unclosed_delims(&mut self.unclosed_delims, diag);
246 crate struct TokenCursor {
247 crate frame: TokenCursorFrame,
248 crate stack: Vec<TokenCursorFrame>,
252 crate struct TokenCursorFrame {
253 crate delim: token::DelimToken,
254 crate span: DelimSpan,
255 crate open_delim: bool,
256 crate tree_cursor: tokenstream::Cursor,
257 crate close_delim: bool,
258 crate last_token: LastToken,
261 /// This is used in `TokenCursorFrame` above to track tokens that are consumed
262 /// by the parser, and then that's transitively used to record the tokens that
263 /// each parse AST item is created with.
265 /// Right now this has two states, either collecting tokens or not collecting
266 /// tokens. If we're collecting tokens we just save everything off into a local
267 /// `Vec`. This should eventually though likely save tokens from the original
268 /// token stream and just use slicing of token streams to avoid creation of a
269 /// whole new vector.
271 /// The second state is where we're passively not recording tokens, but the last
272 /// token is still tracked for when we want to start recording tokens. This
273 /// "last token" means that when we start recording tokens we'll want to ensure
274 /// that this, the first token, is included in the output.
276 /// You can find some more example usage of this in the `collect_tokens` method
279 crate enum LastToken {
280 Collecting(Vec<TreeAndJoint>),
281 Was(Option<TreeAndJoint>),
284 impl TokenCursorFrame {
285 fn new(sp: DelimSpan, delim: DelimToken, tts: &TokenStream) -> Self {
289 open_delim: delim == token::NoDelim,
290 tree_cursor: tts.clone().into_trees(),
291 close_delim: delim == token::NoDelim,
292 last_token: LastToken::Was(None),
298 fn next(&mut self) -> Token {
300 let tree = if !self.frame.open_delim {
301 self.frame.open_delim = true;
302 TokenTree::open_tt(self.frame.span.open, self.frame.delim)
303 } else if let Some(tree) = self.frame.tree_cursor.next() {
305 } else if !self.frame.close_delim {
306 self.frame.close_delim = true;
307 TokenTree::close_tt(self.frame.span.close, self.frame.delim)
308 } else if let Some(frame) = self.stack.pop() {
312 return Token { kind: token::Eof, span: DUMMY_SP }
315 match self.frame.last_token {
316 LastToken::Collecting(ref mut v) => v.push(tree.clone().into()),
317 LastToken::Was(ref mut t) => *t = Some(tree.clone().into()),
321 TokenTree::Token(span, kind) => return Token { kind, span },
322 TokenTree::Delimited(sp, delim, tts) => {
323 let frame = TokenCursorFrame::new(sp, delim, &tts);
324 self.stack.push(mem::replace(&mut self.frame, frame));
330 fn next_desugared(&mut self) -> Token {
331 let (sp, name) = match self.next() {
332 Token { span, kind: token::DocComment(name) } => (span, name),
336 let stripped = strip_doc_comment_decoration(&name.as_str());
338 // Searches for the occurrences of `"#*` and returns the minimum number of `#`s
339 // required to wrap the text.
340 let mut num_of_hashes = 0;
342 for ch in stripped.chars() {
345 '#' if count > 0 => count + 1,
348 num_of_hashes = cmp::max(num_of_hashes, count);
351 let delim_span = DelimSpan::from_single(sp);
352 let body = TokenTree::Delimited(
356 TokenTree::Token(sp, token::Ident(ast::Ident::with_empty_ctxt(sym::doc), false)),
357 TokenTree::Token(sp, token::Eq),
358 TokenTree::Token(sp, token::TokenKind::lit(
359 token::StrRaw(num_of_hashes), Symbol::intern(&stripped), None
362 .iter().cloned().collect::<TokenStream>().into(),
365 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
368 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
369 [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
370 .iter().cloned().collect::<TokenStream>().into()
372 [TokenTree::Token(sp, token::Pound), body]
373 .iter().cloned().collect::<TokenStream>().into()
381 #[derive(Clone, PartialEq)]
382 crate enum TokenType {
383 Token(token::TokenKind),
394 crate fn to_string(&self) -> String {
396 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
397 TokenType::Keyword(kw) => format!("`{}`", kw),
398 TokenType::Operator => "an operator".to_string(),
399 TokenType::Lifetime => "lifetime".to_string(),
400 TokenType::Ident => "identifier".to_string(),
401 TokenType::Path => "path".to_string(),
402 TokenType::Type => "type".to_string(),
403 TokenType::Const => "const".to_string(),
408 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
409 /// `IDENT<<u8 as Trait>::AssocTy>`.
411 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
412 /// that `IDENT` is not the ident of a fn trait.
413 fn can_continue_type_after_non_fn_ident(t: &token::TokenKind) -> bool {
414 t == &token::ModSep || t == &token::Lt ||
415 t == &token::BinOp(token::Shl)
418 /// Information about the path to a module.
419 pub struct ModulePath {
422 pub result: Result<ModulePathSuccess, Error>,
425 pub struct ModulePathSuccess {
427 pub directory_ownership: DirectoryOwnership,
434 AttributesParsed(ThinVec<Attribute>),
435 AlreadyParsed(P<Expr>),
438 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
439 fn from(o: Option<ThinVec<Attribute>>) -> Self {
440 if let Some(attrs) = o {
441 LhsExpr::AttributesParsed(attrs)
443 LhsExpr::NotYetParsed
448 impl From<P<Expr>> for LhsExpr {
449 fn from(expr: P<Expr>) -> Self {
450 LhsExpr::AlreadyParsed(expr)
454 #[derive(Copy, Clone, Debug)]
455 crate enum TokenExpectType {
460 impl<'a> Parser<'a> {
464 directory: Option<Directory<'a>>,
465 recurse_into_file_modules: bool,
466 desugar_doc_comments: bool,
467 subparser_name: Option<&'static str>,
469 let mut parser = Parser {
471 token: token::Whitespace,
475 prev_token_kind: PrevTokenKind::Other,
476 restrictions: Restrictions::empty(),
477 recurse_into_file_modules,
478 directory: Directory {
479 path: Cow::from(PathBuf::new()),
480 ownership: DirectoryOwnership::Owned { relative: None }
482 root_module_name: None,
483 expected_tokens: Vec::new(),
484 token_cursor: TokenCursor {
485 frame: TokenCursorFrame::new(
492 desugar_doc_comments,
494 unmatched_angle_bracket_count: 0,
495 max_angle_bracket_count: 0,
496 unclosed_delims: Vec::new(),
497 last_unexpected_token_span: None,
501 let tok = parser.next_tok();
502 parser.token = tok.kind;
503 parser.span = tok.span;
505 if let Some(directory) = directory {
506 parser.directory = directory;
507 } else if !parser.span.is_dummy() {
508 if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
510 parser.directory.path = Cow::from(path);
514 parser.process_potential_macro_variable();
518 fn next_tok(&mut self) -> Token {
519 let mut next = if self.desugar_doc_comments {
520 self.token_cursor.next_desugared()
522 self.token_cursor.next()
524 if next.span.is_dummy() {
525 // Tweak the location for better diagnostics, but keep syntactic context intact.
526 next.span = self.prev_span.with_ctxt(next.span.ctxt());
531 /// Converts the current token to a string using `self`'s reader.
532 pub fn this_token_to_string(&self) -> String {
533 pprust::token_to_string(&self.token)
536 crate fn token_descr(&self) -> Option<&'static str> {
537 Some(match &self.token {
538 t if t.is_special_ident() => "reserved identifier",
539 t if t.is_used_keyword() => "keyword",
540 t if t.is_unused_keyword() => "reserved keyword",
541 token::DocComment(..) => "doc comment",
546 crate fn this_token_descr(&self) -> String {
547 if let Some(prefix) = self.token_descr() {
548 format!("{} `{}`", prefix, self.this_token_to_string())
550 format!("`{}`", self.this_token_to_string())
554 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
555 match self.expect_one_of(&[], &[]) {
557 Ok(_) => unreachable!(),
561 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
562 pub fn expect(&mut self, t: &token::TokenKind) -> PResult<'a, bool /* recovered */> {
563 if self.expected_tokens.is_empty() {
564 if self.token == *t {
568 self.unexpected_try_recover(t)
571 self.expect_one_of(slice::from_ref(t), &[])
575 /// Expect next token to be edible or inedible token. If edible,
576 /// then consume it; if inedible, then return without consuming
577 /// anything. Signal a fatal error if next token is unexpected.
578 pub fn expect_one_of(
580 edible: &[token::TokenKind],
581 inedible: &[token::TokenKind],
582 ) -> PResult<'a, bool /* recovered */> {
583 if edible.contains(&self.token) {
586 } else if inedible.contains(&self.token) {
587 // leave it in the input
589 } else if self.last_unexpected_token_span == Some(self.span) {
592 self.expected_one_of_not_found(edible, inedible)
596 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
597 fn interpolated_or_expr_span(
599 expr: PResult<'a, P<Expr>>,
600 ) -> PResult<'a, (Span, P<Expr>)> {
602 if self.prev_token_kind == PrevTokenKind::Interpolated {
610 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
611 self.parse_ident_common(true)
614 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
616 token::Ident(ident, _) => {
617 if self.token.is_reserved_ident() {
618 let mut err = self.expected_ident_found();
625 let span = self.span;
627 Ok(Ident::new(ident.name, span))
630 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
631 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
633 self.expected_ident_found()
639 /// Checks if the next token is `tok`, and returns `true` if so.
641 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
643 crate fn check(&mut self, tok: &token::TokenKind) -> bool {
644 let is_present = self.token == *tok;
645 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
649 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
650 pub fn eat(&mut self, tok: &token::TokenKind) -> bool {
651 let is_present = self.check(tok);
652 if is_present { self.bump() }
656 fn check_keyword(&mut self, kw: Symbol) -> bool {
657 self.expected_tokens.push(TokenType::Keyword(kw));
658 self.token.is_keyword(kw)
661 /// If the next token is the given keyword, eats it and returns
662 /// `true`. Otherwise, returns `false`.
663 pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
664 if self.check_keyword(kw) {
672 fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
673 if self.token.is_keyword(kw) {
681 /// If the given word is not a keyword, signals an error.
682 /// If the next token is not the given word, signals an error.
683 /// Otherwise, eats it.
684 fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
685 if !self.eat_keyword(kw) {
692 crate fn check_ident(&mut self) -> bool {
693 if self.token.is_ident() {
696 self.expected_tokens.push(TokenType::Ident);
701 fn check_path(&mut self) -> bool {
702 if self.token.is_path_start() {
705 self.expected_tokens.push(TokenType::Path);
710 fn check_type(&mut self) -> bool {
711 if self.token.can_begin_type() {
714 self.expected_tokens.push(TokenType::Type);
719 fn check_const_arg(&mut self) -> bool {
720 if self.token.can_begin_const_arg() {
723 self.expected_tokens.push(TokenType::Const);
728 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
729 /// and continues. If a `+` is not seen, returns `false`.
731 /// This is used when token-splitting `+=` into `+`.
732 /// See issue #47856 for an example of when this may occur.
733 fn eat_plus(&mut self) -> bool {
734 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
736 token::BinOp(token::Plus) => {
740 token::BinOpEq(token::Plus) => {
741 let span = self.span.with_lo(self.span.lo() + BytePos(1));
742 self.bump_with(token::Eq, span);
750 /// Checks to see if the next token is either `+` or `+=`.
751 /// Otherwise returns `false`.
752 fn check_plus(&mut self) -> bool {
753 if self.token.is_like_plus() {
757 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
762 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
763 /// `&` and continues. If an `&` is not seen, signals an error.
764 fn expect_and(&mut self) -> PResult<'a, ()> {
765 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
767 token::BinOp(token::And) => {
772 let span = self.span.with_lo(self.span.lo() + BytePos(1));
773 Ok(self.bump_with(token::BinOp(token::And), span))
775 _ => self.unexpected()
779 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
780 /// `|` and continues. If an `|` is not seen, signals an error.
781 fn expect_or(&mut self) -> PResult<'a, ()> {
782 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
784 token::BinOp(token::Or) => {
789 let span = self.span.with_lo(self.span.lo() + BytePos(1));
790 Ok(self.bump_with(token::BinOp(token::Or), span))
792 _ => self.unexpected()
796 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
797 literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
800 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
801 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
802 /// and continue. If a `<` is not seen, returns false.
804 /// This is meant to be used when parsing generics on a path to get the
806 fn eat_lt(&mut self) -> bool {
807 self.expected_tokens.push(TokenType::Token(token::Lt));
808 let ate = match self.token {
813 token::BinOp(token::Shl) => {
814 let span = self.span.with_lo(self.span.lo() + BytePos(1));
815 self.bump_with(token::Lt, span);
819 let span = self.span.with_lo(self.span.lo() + BytePos(1));
820 self.bump_with(token::BinOp(token::Minus), span);
827 // See doc comment for `unmatched_angle_bracket_count`.
828 self.unmatched_angle_bracket_count += 1;
829 self.max_angle_bracket_count += 1;
830 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
836 fn expect_lt(&mut self) -> PResult<'a, ()> {
844 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
845 /// with a single `>` and continues. If a `>` is not seen, signals an error.
846 fn expect_gt(&mut self) -> PResult<'a, ()> {
847 self.expected_tokens.push(TokenType::Token(token::Gt));
848 let ate = match self.token {
853 token::BinOp(token::Shr) => {
854 let span = self.span.with_lo(self.span.lo() + BytePos(1));
855 Some(self.bump_with(token::Gt, span))
857 token::BinOpEq(token::Shr) => {
858 let span = self.span.with_lo(self.span.lo() + BytePos(1));
859 Some(self.bump_with(token::Ge, span))
862 let span = self.span.with_lo(self.span.lo() + BytePos(1));
863 Some(self.bump_with(token::Eq, span))
870 // See doc comment for `unmatched_angle_bracket_count`.
871 if self.unmatched_angle_bracket_count > 0 {
872 self.unmatched_angle_bracket_count -= 1;
873 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
878 None => self.unexpected(),
882 /// Parses a sequence, including the closing delimiter. The function
883 /// `f` must consume tokens until reaching the next separator or
885 pub fn parse_seq_to_end<T, F>(&mut self,
886 ket: &token::TokenKind,
889 -> PResult<'a, Vec<T>> where
890 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
892 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
899 /// Parses a sequence, not including the closing delimiter. The function
900 /// `f` must consume tokens until reaching the next separator or
902 pub fn parse_seq_to_before_end<T, F>(
904 ket: &token::TokenKind,
907 ) -> PResult<'a, (Vec<T>, bool)>
908 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
910 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
913 crate fn parse_seq_to_before_tokens<T, F>(
915 kets: &[&token::TokenKind],
917 expect: TokenExpectType,
919 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
920 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
922 let mut first = true;
923 let mut recovered = false;
925 while !kets.iter().any(|k| {
927 TokenExpectType::Expect => self.check(k),
928 TokenExpectType::NoExpect => self.token == **k,
932 token::CloseDelim(..) | token::Eof => break,
935 if let Some(ref t) = sep.sep {
939 match self.expect(t) {
946 // Attempt to keep parsing if it was a similar separator
947 if let Some(ref tokens) = t.similar_tokens() {
948 if tokens.contains(&self.token) {
953 // Attempt to keep parsing if it was an omitted separator
968 if sep.trailing_sep_allowed && kets.iter().any(|k| {
970 TokenExpectType::Expect => self.check(k),
971 TokenExpectType::NoExpect => self.token == **k,
984 /// Parses a sequence, including the closing delimiter. The function
985 /// `f` must consume tokens until reaching the next separator or
987 fn parse_unspanned_seq<T, F>(
989 bra: &token::TokenKind,
990 ket: &token::TokenKind,
993 ) -> PResult<'a, Vec<T>> where
994 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
997 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1004 /// Advance the parser by one token
1005 pub fn bump(&mut self) {
1006 if self.prev_token_kind == PrevTokenKind::Eof {
1007 // Bumping after EOF is a bad sign, usually an infinite loop.
1008 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1011 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1013 // Record last token kind for possible error recovery.
1014 self.prev_token_kind = match self.token {
1015 token::DocComment(..) => PrevTokenKind::DocComment,
1016 token::Comma => PrevTokenKind::Comma,
1017 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1018 token::BinOp(token::Or) => PrevTokenKind::BitOr,
1019 token::Interpolated(..) => PrevTokenKind::Interpolated,
1020 token::Eof => PrevTokenKind::Eof,
1021 token::Ident(..) => PrevTokenKind::Ident,
1022 _ => PrevTokenKind::Other,
1025 let next = self.next_tok();
1026 self.token = next.kind;
1027 self.span = next.span;
1028 self.expected_tokens.clear();
1029 // check after each token
1030 self.process_potential_macro_variable();
1033 /// Advance the parser using provided token as a next one. Use this when
1034 /// consuming a part of a token. For example a single `<` from `<<`.
1035 fn bump_with(&mut self, next: token::TokenKind, span: Span) {
1036 self.prev_span = self.span.with_hi(span.lo());
1037 // It would be incorrect to record the kind of the current token, but
1038 // fortunately for tokens currently using `bump_with`, the
1039 // prev_token_kind will be of no use anyway.
1040 self.prev_token_kind = PrevTokenKind::Other;
1043 self.expected_tokens.clear();
1046 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1047 F: FnOnce(&token::TokenKind) -> R,
1050 return f(&self.token)
1053 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1054 Some(tree) => match tree {
1055 TokenTree::Token(_, tok) => tok,
1056 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1058 None => token::CloseDelim(self.token_cursor.frame.delim),
1062 crate fn look_ahead_span(&self, dist: usize) -> Span {
1067 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1068 Some(TokenTree::Token(span, _)) => span,
1069 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1070 None => self.look_ahead_span(dist - 1),
1074 /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
1075 fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
1076 self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
1079 /// Is the current token one of the keywords that signals a bare function type?
1080 fn token_is_bare_fn_keyword(&mut self) -> bool {
1081 self.check_keyword(kw::Fn) ||
1082 self.check_keyword(kw::Unsafe) ||
1083 self.check_keyword(kw::Extern)
1086 /// Parses a `TyKind::BareFn` type.
1087 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1090 [unsafe] [extern "ABI"] fn (S) -> T
1100 let unsafety = self.parse_unsafety();
1101 let abi = if self.eat_keyword(kw::Extern) {
1102 self.parse_opt_abi()?.unwrap_or(Abi::C)
1107 self.expect_keyword(kw::Fn)?;
1108 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1109 let ret_ty = self.parse_ret_ty(false)?;
1110 let decl = P(FnDecl {
1115 Ok(TyKind::BareFn(P(BareFnTy {
1123 /// Parses asyncness: `async` or nothing.
1124 fn parse_asyncness(&mut self) -> IsAsync {
1125 if self.eat_keyword(kw::Async) {
1127 closure_id: ast::DUMMY_NODE_ID,
1128 return_impl_trait_id: ast::DUMMY_NODE_ID,
1135 /// Parses unsafety: `unsafe` or nothing.
1136 fn parse_unsafety(&mut self) -> Unsafety {
1137 if self.eat_keyword(kw::Unsafe) {
1144 /// Parses the items in a trait declaration.
1145 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1146 maybe_whole!(self, NtTraitItem, |x| x);
1147 let attrs = self.parse_outer_attributes()?;
1148 let mut unclosed_delims = vec![];
1149 let (mut item, tokens) = self.collect_tokens(|this| {
1150 let item = this.parse_trait_item_(at_end, attrs);
1151 unclosed_delims.append(&mut this.unclosed_delims);
1154 self.unclosed_delims.append(&mut unclosed_delims);
1155 // See `parse_item` for why this clause is here.
1156 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1157 item.tokens = Some(tokens);
1162 fn parse_trait_item_(&mut self,
1164 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1167 let (name, node, generics) = if self.eat_keyword(kw::Type) {
1168 self.parse_trait_item_assoc_ty()?
1169 } else if self.is_const_item() {
1170 self.expect_keyword(kw::Const)?;
1171 let ident = self.parse_ident()?;
1172 self.expect(&token::Colon)?;
1173 let ty = self.parse_ty()?;
1174 let default = if self.eat(&token::Eq) {
1175 let expr = self.parse_expr()?;
1176 self.expect(&token::Semi)?;
1179 self.expect(&token::Semi)?;
1182 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1183 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1184 // trait item macro.
1185 (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1187 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
1189 let ident = self.parse_ident()?;
1190 let mut generics = self.parse_generics()?;
1192 let decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1193 // This is somewhat dubious; We don't want to allow
1194 // argument names to be left off if there is a
1197 // We don't allow argument names to be left off in edition 2018.
1198 p.parse_arg_general(p.span.rust_2018(), true, false)
1200 generics.where_clause = self.parse_where_clause()?;
1202 let sig = ast::MethodSig {
1212 let body = match self.token {
1216 debug!("parse_trait_methods(): parsing required method");
1219 token::OpenDelim(token::Brace) => {
1220 debug!("parse_trait_methods(): parsing provided method");
1222 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1223 attrs.extend(inner_attrs.iter().cloned());
1226 token::Interpolated(ref nt) => {
1228 token::NtBlock(..) => {
1230 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1231 attrs.extend(inner_attrs.iter().cloned());
1235 return self.expected_semi_or_open_brace();
1240 return self.expected_semi_or_open_brace();
1243 (ident, ast::TraitItemKind::Method(sig, body), generics)
1247 id: ast::DUMMY_NODE_ID,
1252 span: lo.to(self.prev_span),
1257 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1258 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1259 if self.eat(&token::RArrow) {
1260 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1262 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1267 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1268 self.parse_ty_common(true, true, false)
1271 /// Parses a type in restricted contexts where `+` is not permitted.
1273 /// Example 1: `&'a TYPE`
1274 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1275 /// Example 2: `value1 as TYPE + value2`
1276 /// `+` is prohibited to avoid interactions with expression grammar.
1277 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1278 self.parse_ty_common(false, true, false)
1281 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1282 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1283 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1284 maybe_whole!(self, NtTy, |x| x);
1287 let mut impl_dyn_multi = false;
1288 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1289 // `(TYPE)` is a parenthesized type.
1290 // `(TYPE,)` is a tuple with a single field of type TYPE.
1291 let mut ts = vec![];
1292 let mut last_comma = false;
1293 while self.token != token::CloseDelim(token::Paren) {
1294 ts.push(self.parse_ty()?);
1295 if self.eat(&token::Comma) {
1302 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1303 self.expect(&token::CloseDelim(token::Paren))?;
1305 if ts.len() == 1 && !last_comma {
1306 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1307 let maybe_bounds = allow_plus && self.token.is_like_plus();
1309 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1310 TyKind::Path(None, ref path) if maybe_bounds => {
1311 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1313 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1314 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1315 let path = match bounds[0] {
1316 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1317 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1319 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1322 _ => TyKind::Paren(P(ty))
1327 } else if self.eat(&token::Not) {
1330 } else if self.eat(&token::BinOp(token::Star)) {
1332 TyKind::Ptr(self.parse_ptr()?)
1333 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1335 let t = self.parse_ty()?;
1336 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1337 let t = match self.maybe_parse_fixed_length_of_vec()? {
1338 None => TyKind::Slice(t),
1339 Some(length) => TyKind::Array(t, AnonConst {
1340 id: ast::DUMMY_NODE_ID,
1344 self.expect(&token::CloseDelim(token::Bracket))?;
1346 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1349 self.parse_borrowed_pointee()?
1350 } else if self.eat_keyword_noexpect(kw::Typeof) {
1352 // In order to not be ambiguous, the type must be surrounded by parens.
1353 self.expect(&token::OpenDelim(token::Paren))?;
1355 id: ast::DUMMY_NODE_ID,
1356 value: self.parse_expr()?,
1358 self.expect(&token::CloseDelim(token::Paren))?;
1360 } else if self.eat_keyword(kw::Underscore) {
1361 // A type to be inferred `_`
1363 } else if self.token_is_bare_fn_keyword() {
1364 // Function pointer type
1365 self.parse_ty_bare_fn(Vec::new())?
1366 } else if self.check_keyword(kw::For) {
1367 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1368 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1369 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1371 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1372 if self.token_is_bare_fn_keyword() {
1373 self.parse_ty_bare_fn(lifetime_defs)?
1375 let path = self.parse_path(PathStyle::Type)?;
1376 let parse_plus = allow_plus && self.check_plus();
1377 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1379 } else if self.eat_keyword(kw::Impl) {
1380 // Always parse bounds greedily for better error recovery.
1381 let bounds = self.parse_generic_bounds(None)?;
1382 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1383 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1384 } else if self.check_keyword(kw::Dyn) &&
1385 (self.span.rust_2018() ||
1386 self.look_ahead(1, |t| t.can_begin_bound() &&
1387 !can_continue_type_after_non_fn_ident(t))) {
1388 self.bump(); // `dyn`
1389 // Always parse bounds greedily for better error recovery.
1390 let bounds = self.parse_generic_bounds(None)?;
1391 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1392 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1393 } else if self.check(&token::Question) ||
1394 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1395 // Bound list (trait object type)
1396 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1397 TraitObjectSyntax::None)
1398 } else if self.eat_lt() {
1400 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1401 TyKind::Path(Some(qself), path)
1402 } else if self.token.is_path_start() {
1404 let path = self.parse_path(PathStyle::Type)?;
1405 if self.eat(&token::Not) {
1406 // Macro invocation in type position
1407 let (delim, tts) = self.expect_delimited_token_tree()?;
1408 let node = Mac_ { path, tts, delim };
1409 TyKind::Mac(respan(lo.to(self.prev_span), node))
1411 // Just a type path or bound list (trait object type) starting with a trait.
1413 // `Trait1 + Trait2 + 'a`
1414 if allow_plus && self.check_plus() {
1415 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1417 TyKind::Path(None, path)
1420 } else if self.check(&token::DotDotDot) {
1421 if allow_c_variadic {
1422 self.eat(&token::DotDotDot);
1425 return Err(self.fatal(
1426 "only foreign functions are allowed to be C-variadic"
1430 let msg = format!("expected type, found {}", self.this_token_descr());
1431 return Err(self.fatal(&msg));
1434 let span = lo.to(self.prev_span);
1435 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1437 // Try to recover from use of `+` with incorrect priority.
1438 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1439 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1440 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1443 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1444 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1445 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1446 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1448 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1449 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1451 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1454 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1455 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1456 let mutbl = self.parse_mutability();
1457 let ty = self.parse_ty_no_plus()?;
1458 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1461 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1462 let mutbl = if self.eat_keyword(kw::Mut) {
1464 } else if self.eat_keyword(kw::Const) {
1465 Mutability::Immutable
1467 let span = self.prev_span;
1468 let msg = "expected mut or const in raw pointer type";
1469 self.struct_span_err(span, msg)
1470 .span_label(span, msg)
1471 .help("use `*mut T` or `*const T` as appropriate")
1473 Mutability::Immutable
1475 let t = self.parse_ty_no_plus()?;
1476 Ok(MutTy { ty: t, mutbl: mutbl })
1479 fn is_named_argument(&self) -> bool {
1480 let offset = match self.token {
1481 token::Interpolated(ref nt) => match **nt {
1482 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1485 token::BinOp(token::And) | token::AndAnd => 1,
1486 _ if self.token.is_keyword(kw::Mut) => 1,
1490 self.look_ahead(offset, |t| t.is_ident()) &&
1491 self.look_ahead(offset + 1, |t| t == &token::Colon)
1494 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1496 /// This version of parse arg doesn't necessarily require identifier names.
1497 fn parse_arg_general(
1500 is_trait_item: bool,
1501 allow_c_variadic: bool,
1502 ) -> PResult<'a, Arg> {
1503 if let Ok(Some(arg)) = self.parse_self_arg() {
1504 return self.recover_bad_self_arg(arg, is_trait_item);
1507 let (pat, ty) = if require_name || self.is_named_argument() {
1508 debug!("parse_arg_general parse_pat (require_name:{})", require_name);
1509 self.eat_incorrect_doc_comment("method arguments");
1510 let pat = self.parse_pat(Some("argument name"))?;
1512 if let Err(mut err) = self.expect(&token::Colon) {
1513 if let Some(ident) = self.argument_without_type(
1520 return Ok(dummy_arg(ident));
1526 self.eat_incorrect_doc_comment("a method argument's type");
1527 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1529 debug!("parse_arg_general ident_to_pat");
1530 let parser_snapshot_before_ty = self.clone();
1531 self.eat_incorrect_doc_comment("a method argument's type");
1532 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1533 if ty.is_ok() && self.token != token::Comma &&
1534 self.token != token::CloseDelim(token::Paren) {
1535 // This wasn't actually a type, but a pattern looking like a type,
1536 // so we are going to rollback and re-parse for recovery.
1537 ty = self.unexpected();
1541 let ident = Ident::new(kw::Invalid, self.prev_span);
1543 id: ast::DUMMY_NODE_ID,
1544 node: PatKind::Ident(
1545 BindingMode::ByValue(Mutability::Immutable), ident, None),
1551 // If this is a C-variadic argument and we hit an error, return the
1553 if self.token == token::DotDotDot {
1556 // Recover from attempting to parse the argument as a type without pattern.
1558 mem::replace(self, parser_snapshot_before_ty);
1559 self.recover_arg_parse()?
1564 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID })
1567 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1568 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1569 let pat = self.parse_pat(Some("argument name"))?;
1570 let t = if self.eat(&token::Colon) {
1574 id: ast::DUMMY_NODE_ID,
1575 node: TyKind::Infer,
1576 span: self.prev_span,
1582 id: ast::DUMMY_NODE_ID
1586 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1587 if self.eat(&token::Semi) {
1588 Ok(Some(self.parse_expr()?))
1594 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1595 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1596 maybe_whole_expr!(self);
1598 let minus_lo = self.span;
1599 let minus_present = self.eat(&token::BinOp(token::Minus));
1601 let literal = self.parse_lit()?;
1602 let hi = self.prev_span;
1603 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1606 let minus_hi = self.prev_span;
1607 let unary = self.mk_unary(UnOp::Neg, expr);
1608 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1614 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
1616 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
1617 let span = self.span;
1619 Ok(Ident::new(ident.name, span))
1621 _ => self.parse_ident(),
1625 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
1627 token::Ident(ident, false) if ident.name == kw::Underscore => {
1628 let span = self.span;
1630 Ok(Ident::new(ident.name, span))
1632 _ => self.parse_ident(),
1636 /// Parses a qualified path.
1637 /// Assumes that the leading `<` has been parsed already.
1639 /// `qualified_path = <type [as trait_ref]>::path`
1644 /// `<T as U>::F::a<S>` (without disambiguator)
1645 /// `<T as U>::F::a::<S>` (with disambiguator)
1646 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
1647 let lo = self.prev_span;
1648 let ty = self.parse_ty()?;
1650 // `path` will contain the prefix of the path up to the `>`,
1651 // if any (e.g., `U` in the `<T as U>::*` examples
1652 // above). `path_span` has the span of that path, or an empty
1653 // span in the case of something like `<T>::Bar`.
1654 let (mut path, path_span);
1655 if self.eat_keyword(kw::As) {
1656 let path_lo = self.span;
1657 path = self.parse_path(PathStyle::Type)?;
1658 path_span = path_lo.to(self.prev_span);
1660 path_span = self.span.to(self.span);
1661 path = ast::Path { segments: Vec::new(), span: path_span };
1664 // See doc comment for `unmatched_angle_bracket_count`.
1665 self.expect(&token::Gt)?;
1666 if self.unmatched_angle_bracket_count > 0 {
1667 self.unmatched_angle_bracket_count -= 1;
1668 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1671 self.expect(&token::ModSep)?;
1673 let qself = QSelf { ty, path_span, position: path.segments.len() };
1674 self.parse_path_segments(&mut path.segments, style)?;
1676 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
1679 /// Parses simple paths.
1681 /// `path = [::] segment+`
1682 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
1685 /// `a::b::C<D>` (without disambiguator)
1686 /// `a::b::C::<D>` (with disambiguator)
1687 /// `Fn(Args)` (without disambiguator)
1688 /// `Fn::(Args)` (with disambiguator)
1689 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1690 maybe_whole!(self, NtPath, |path| {
1691 if style == PathStyle::Mod &&
1692 path.segments.iter().any(|segment| segment.args.is_some()) {
1693 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
1698 let lo = self.meta_var_span.unwrap_or(self.span);
1699 let mut segments = Vec::new();
1700 let mod_sep_ctxt = self.span.ctxt();
1701 if self.eat(&token::ModSep) {
1702 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
1704 self.parse_path_segments(&mut segments, style)?;
1706 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
1709 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
1710 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
1712 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1713 let meta_ident = match self.token {
1714 token::Interpolated(ref nt) => match **nt {
1715 token::NtMeta(ref meta) => match meta.node {
1716 ast::MetaItemKind::Word => Some(meta.path.clone()),
1723 if let Some(path) = meta_ident {
1727 self.parse_path(style)
1730 crate fn parse_path_segments(&mut self,
1731 segments: &mut Vec<PathSegment>,
1733 -> PResult<'a, ()> {
1735 let segment = self.parse_path_segment(style)?;
1736 if style == PathStyle::Expr {
1737 // In order to check for trailing angle brackets, we must have finished
1738 // recursing (`parse_path_segment` can indirectly call this function),
1739 // that is, the next token must be the highlighted part of the below example:
1741 // `Foo::<Bar as Baz<T>>::Qux`
1744 // As opposed to the below highlight (if we had only finished the first
1747 // `Foo::<Bar as Baz<T>>::Qux`
1750 // `PathStyle::Expr` is only provided at the root invocation and never in
1751 // `parse_path_segment` to recurse and therefore can be checked to maintain
1753 self.check_trailing_angle_brackets(&segment, token::ModSep);
1755 segments.push(segment);
1757 if self.is_import_coupler() || !self.eat(&token::ModSep) {
1763 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
1764 let ident = self.parse_path_segment_ident()?;
1766 let is_args_start = |token: &token::TokenKind| match *token {
1767 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
1768 | token::LArrow => true,
1771 let check_args_start = |this: &mut Self| {
1772 this.expected_tokens.extend_from_slice(
1773 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
1775 is_args_start(&this.token)
1778 Ok(if style == PathStyle::Type && check_args_start(self) ||
1779 style != PathStyle::Mod && self.check(&token::ModSep)
1780 && self.look_ahead(1, |t| is_args_start(t)) {
1781 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
1782 // it isn't, then we reset the unmatched angle bracket count as we're about to start
1783 // parsing a new path.
1784 if style == PathStyle::Expr {
1785 self.unmatched_angle_bracket_count = 0;
1786 self.max_angle_bracket_count = 0;
1789 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
1790 self.eat(&token::ModSep);
1792 let args = if self.eat_lt() {
1794 let (args, constraints) =
1795 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
1797 let span = lo.to(self.prev_span);
1798 AngleBracketedArgs { args, constraints, span }.into()
1802 let (inputs, recovered) = self.parse_seq_to_before_tokens(
1803 &[&token::CloseDelim(token::Paren)],
1804 SeqSep::trailing_allowed(token::Comma),
1805 TokenExpectType::Expect,
1810 let span = lo.to(self.prev_span);
1811 let output = if self.eat(&token::RArrow) {
1812 Some(self.parse_ty_common(false, false, false)?)
1816 ParenthesizedArgs { inputs, output, span }.into()
1819 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
1821 // Generic arguments are not found.
1822 PathSegment::from_ident(ident)
1826 crate fn check_lifetime(&mut self) -> bool {
1827 self.expected_tokens.push(TokenType::Lifetime);
1828 self.token.is_lifetime()
1831 /// Parses a single lifetime `'a` or panics.
1832 crate fn expect_lifetime(&mut self) -> Lifetime {
1833 if let Some(ident) = self.token.lifetime() {
1834 let span = self.span;
1836 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
1838 self.span_bug(self.span, "not a lifetime")
1842 fn eat_label(&mut self) -> Option<Label> {
1843 if let Some(ident) = self.token.lifetime() {
1844 let span = self.span;
1846 Some(Label { ident: Ident::new(ident.name, span) })
1852 /// Parses mutability (`mut` or nothing).
1853 fn parse_mutability(&mut self) -> Mutability {
1854 if self.eat_keyword(kw::Mut) {
1857 Mutability::Immutable
1861 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
1862 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token {
1863 self.expect_no_suffix(self.span, "a tuple index", suffix);
1865 Ok(Ident::new(symbol, self.prev_span))
1867 self.parse_ident_common(false)
1871 /// Parse ident (COLON expr)?
1872 fn parse_field(&mut self) -> PResult<'a, Field> {
1873 let attrs = self.parse_outer_attributes()?;
1876 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1877 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
1878 t == &token::Colon || t == &token::Eq
1880 let fieldname = self.parse_field_name()?;
1882 // Check for an equals token. This means the source incorrectly attempts to
1883 // initialize a field with an eq rather than a colon.
1884 if self.token == token::Eq {
1886 .struct_span_err(self.span, "expected `:`, found `=`")
1888 fieldname.span.shrink_to_hi().to(self.span),
1889 "replace equals symbol with a colon",
1891 Applicability::MachineApplicable,
1896 (fieldname, self.parse_expr()?, false)
1898 let fieldname = self.parse_ident_common(false)?;
1900 // Mimic `x: x` for the `x` field shorthand.
1901 let path = ast::Path::from_ident(fieldname);
1902 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
1903 (fieldname, expr, true)
1907 span: lo.to(expr.span),
1910 attrs: attrs.into(),
1914 crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
1915 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
1918 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
1919 ExprKind::Unary(unop, expr)
1922 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1923 ExprKind::Binary(binop, lhs, rhs)
1926 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
1927 ExprKind::Call(f, args)
1930 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
1931 ExprKind::Index(expr, idx)
1935 start: Option<P<Expr>>,
1936 end: Option<P<Expr>>,
1937 limits: RangeLimits)
1938 -> PResult<'a, ast::ExprKind> {
1939 if end.is_none() && limits == RangeLimits::Closed {
1940 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
1942 Ok(ExprKind::Range(start, end, limits))
1946 fn mk_assign_op(&self, binop: ast::BinOp,
1947 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1948 ExprKind::AssignOp(binop, lhs, rhs)
1951 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
1952 let delim = match self.token {
1953 token::OpenDelim(delim) => delim,
1955 let msg = "expected open delimiter";
1956 let mut err = self.fatal(msg);
1957 err.span_label(self.span, msg);
1961 let tts = match self.parse_token_tree() {
1962 TokenTree::Delimited(_, _, tts) => tts,
1963 _ => unreachable!(),
1965 let delim = match delim {
1966 token::Paren => MacDelimiter::Parenthesis,
1967 token::Bracket => MacDelimiter::Bracket,
1968 token::Brace => MacDelimiter::Brace,
1969 token::NoDelim => self.bug("unexpected no delimiter"),
1971 Ok((delim, tts.into()))
1974 /// At the bottom (top?) of the precedence hierarchy,
1975 /// Parses things like parenthesized exprs, macros, `return`, etc.
1977 /// N.B., this does not parse outer attributes, and is private because it only works
1978 /// correctly if called from `parse_dot_or_call_expr()`.
1979 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1980 maybe_recover_from_interpolated_ty_qpath!(self, true);
1981 maybe_whole_expr!(self);
1983 // Outer attributes are already parsed and will be
1984 // added to the return value after the fact.
1986 // Therefore, prevent sub-parser from parsing
1987 // attributes by giving them a empty "already parsed" list.
1988 let mut attrs = ThinVec::new();
1991 let mut hi = self.span;
1995 // Note: when adding new syntax here, don't forget to adjust TokenKind::can_begin_expr().
1997 token::OpenDelim(token::Paren) => {
2000 attrs.extend(self.parse_inner_attributes()?);
2002 // (e) is parenthesized e
2003 // (e,) is a tuple with only one field, e
2004 let mut es = vec![];
2005 let mut trailing_comma = false;
2006 let mut recovered = false;
2007 while self.token != token::CloseDelim(token::Paren) {
2008 es.push(match self.parse_expr() {
2011 // recover from parse error in tuple list
2012 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2015 recovered = self.expect_one_of(
2017 &[token::Comma, token::CloseDelim(token::Paren)],
2019 if self.eat(&token::Comma) {
2020 trailing_comma = true;
2022 trailing_comma = false;
2030 hi = self.prev_span;
2031 ex = if es.len() == 1 && !trailing_comma {
2032 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2037 token::OpenDelim(token::Brace) => {
2038 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2040 token::BinOp(token::Or) | token::OrOr => {
2041 return self.parse_lambda_expr(attrs);
2043 token::OpenDelim(token::Bracket) => {
2046 attrs.extend(self.parse_inner_attributes()?);
2048 if self.eat(&token::CloseDelim(token::Bracket)) {
2050 ex = ExprKind::Array(Vec::new());
2053 let first_expr = self.parse_expr()?;
2054 if self.eat(&token::Semi) {
2055 // Repeating array syntax: [ 0; 512 ]
2056 let count = AnonConst {
2057 id: ast::DUMMY_NODE_ID,
2058 value: self.parse_expr()?,
2060 self.expect(&token::CloseDelim(token::Bracket))?;
2061 ex = ExprKind::Repeat(first_expr, count);
2062 } else if self.eat(&token::Comma) {
2063 // Vector with two or more elements.
2064 let remaining_exprs = self.parse_seq_to_end(
2065 &token::CloseDelim(token::Bracket),
2066 SeqSep::trailing_allowed(token::Comma),
2067 |p| Ok(p.parse_expr()?)
2069 let mut exprs = vec![first_expr];
2070 exprs.extend(remaining_exprs);
2071 ex = ExprKind::Array(exprs);
2073 // Vector with one element.
2074 self.expect(&token::CloseDelim(token::Bracket))?;
2075 ex = ExprKind::Array(vec![first_expr]);
2078 hi = self.prev_span;
2082 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2084 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2086 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
2087 return self.parse_lambda_expr(attrs);
2089 if self.eat_keyword(kw::If) {
2090 return self.parse_if_expr(attrs);
2092 if self.eat_keyword(kw::For) {
2093 let lo = self.prev_span;
2094 return self.parse_for_expr(None, lo, attrs);
2096 if self.eat_keyword(kw::While) {
2097 let lo = self.prev_span;
2098 return self.parse_while_expr(None, lo, attrs);
2100 if let Some(label) = self.eat_label() {
2101 let lo = label.ident.span;
2102 self.expect(&token::Colon)?;
2103 if self.eat_keyword(kw::While) {
2104 return self.parse_while_expr(Some(label), lo, attrs)
2106 if self.eat_keyword(kw::For) {
2107 return self.parse_for_expr(Some(label), lo, attrs)
2109 if self.eat_keyword(kw::Loop) {
2110 return self.parse_loop_expr(Some(label), lo, attrs)
2112 if self.token == token::OpenDelim(token::Brace) {
2113 return self.parse_block_expr(Some(label),
2115 BlockCheckMode::Default,
2118 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2119 let mut err = self.fatal(msg);
2120 err.span_label(self.span, msg);
2123 if self.eat_keyword(kw::Loop) {
2124 let lo = self.prev_span;
2125 return self.parse_loop_expr(None, lo, attrs);
2127 if self.eat_keyword(kw::Continue) {
2128 let label = self.eat_label();
2129 let ex = ExprKind::Continue(label);
2130 let hi = self.prev_span;
2131 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2133 if self.eat_keyword(kw::Match) {
2134 let match_sp = self.prev_span;
2135 return self.parse_match_expr(attrs).map_err(|mut err| {
2136 err.span_label(match_sp, "while parsing this match expression");
2140 if self.eat_keyword(kw::Unsafe) {
2141 return self.parse_block_expr(
2144 BlockCheckMode::Unsafe(ast::UserProvided),
2147 if self.is_do_catch_block() {
2148 let mut db = self.fatal("found removed `do catch` syntax");
2149 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2152 if self.is_try_block() {
2154 assert!(self.eat_keyword(kw::Try));
2155 return self.parse_try_block(lo, attrs);
2158 // Span::rust_2018() is somewhat expensive; don't get it repeatedly.
2159 let is_span_rust_2018 = self.span.rust_2018();
2160 if is_span_rust_2018 && self.check_keyword(kw::Async) {
2161 return if self.is_async_block() { // check for `async {` and `async move {`
2162 self.parse_async_block(attrs)
2164 self.parse_lambda_expr(attrs)
2167 if self.eat_keyword(kw::Return) {
2168 if self.token.can_begin_expr() {
2169 let e = self.parse_expr()?;
2171 ex = ExprKind::Ret(Some(e));
2173 ex = ExprKind::Ret(None);
2175 } else if self.eat_keyword(kw::Break) {
2176 let label = self.eat_label();
2177 let e = if self.token.can_begin_expr()
2178 && !(self.token == token::OpenDelim(token::Brace)
2179 && self.restrictions.contains(
2180 Restrictions::NO_STRUCT_LITERAL)) {
2181 Some(self.parse_expr()?)
2185 ex = ExprKind::Break(label, e);
2186 hi = self.prev_span;
2187 } else if self.eat_keyword(kw::Yield) {
2188 if self.token.can_begin_expr() {
2189 let e = self.parse_expr()?;
2191 ex = ExprKind::Yield(Some(e));
2193 ex = ExprKind::Yield(None);
2195 } else if self.token.is_keyword(kw::Let) {
2196 // Catch this syntax error here, instead of in `parse_ident`, so
2197 // that we can explicitly mention that let is not to be used as an expression
2198 let mut db = self.fatal("expected expression, found statement (`let`)");
2199 db.span_label(self.span, "expected expression");
2200 db.note("variable declaration using `let` is a statement");
2202 } else if is_span_rust_2018 && self.eat_keyword(kw::Await) {
2203 let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
2206 } else if self.token.is_path_start() {
2207 let path = self.parse_path(PathStyle::Expr)?;
2209 // `!`, as an operator, is prefix, so we know this isn't that
2210 if self.eat(&token::Not) {
2211 // MACRO INVOCATION expression
2212 let (delim, tts) = self.expect_delimited_token_tree()?;
2213 hi = self.prev_span;
2214 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2215 } else if self.check(&token::OpenDelim(token::Brace)) {
2216 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
2220 ex = ExprKind::Path(None, path);
2224 ex = ExprKind::Path(None, path);
2227 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2228 // Don't complain about bare semicolons after unclosed braces
2229 // recovery in order to keep the error count down. Fixing the
2230 // delimiters will possibly also fix the bare semicolon found in
2231 // expression context. For example, silence the following error:
2233 // error: expected expression, found `;`
2237 // | ^ expected expression
2240 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2242 match self.parse_literal_maybe_minus() {
2245 ex = expr.node.clone();
2248 self.cancel(&mut err);
2249 return Err(self.expected_expression_found());
2256 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2257 self.maybe_recover_from_bad_qpath(expr, true)
2260 /// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
2261 /// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
2262 /// `await { <expr> }`.
2263 fn parse_await_macro_or_alt(
2267 ) -> PResult<'a, (Span, ExprKind)> {
2268 if self.token == token::Not {
2269 // Handle correct `await!(<expr>)`.
2270 // FIXME: make this an error when `await!` is no longer supported
2271 // https://github.com/rust-lang/rust/issues/60610
2272 self.expect(&token::Not)?;
2273 self.expect(&token::OpenDelim(token::Paren))?;
2274 let expr = self.parse_expr().map_err(|mut err| {
2275 err.span_label(await_sp, "while parsing this await macro call");
2278 self.expect(&token::CloseDelim(token::Paren))?;
2279 Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
2280 } else { // Handle `await <expr>`.
2281 self.parse_incorrect_await_syntax(lo, await_sp)
2285 fn maybe_parse_struct_expr(
2289 attrs: &ThinVec<Attribute>,
2290 ) -> Option<PResult<'a, P<Expr>>> {
2291 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2292 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
2293 // `{ ident, ` cannot start a block
2294 self.look_ahead(2, |t| t == &token::Comma) ||
2295 self.look_ahead(2, |t| t == &token::Colon) && (
2296 // `{ ident: token, ` cannot start a block
2297 self.look_ahead(4, |t| t == &token::Comma) ||
2298 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
2299 self.look_ahead(3, |t| !t.can_begin_type())
2303 if struct_allowed || certainly_not_a_block() {
2304 // This is a struct literal, but we don't can't accept them here
2305 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
2306 if let (Ok(expr), false) = (&expr, struct_allowed) {
2307 let mut err = self.diagnostic().struct_span_err(
2309 "struct literals are not allowed here",
2311 err.multipart_suggestion(
2312 "surround the struct literal with parentheses",
2314 (lo.shrink_to_lo(), "(".to_string()),
2315 (expr.span.shrink_to_hi(), ")".to_string()),
2317 Applicability::MachineApplicable,
2326 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2327 -> PResult<'a, P<Expr>> {
2328 let struct_sp = lo.to(self.prev_span);
2330 let mut fields = Vec::new();
2331 let mut base = None;
2333 attrs.extend(self.parse_inner_attributes()?);
2335 while self.token != token::CloseDelim(token::Brace) {
2336 if self.eat(&token::DotDot) {
2337 let exp_span = self.prev_span;
2338 match self.parse_expr() {
2344 self.recover_stmt();
2347 if self.token == token::Comma {
2348 let mut err = self.sess.span_diagnostic.mut_span_err(
2349 exp_span.to(self.prev_span),
2350 "cannot use a comma after the base struct",
2352 err.span_suggestion_short(
2354 "remove this comma",
2356 Applicability::MachineApplicable
2358 err.note("the base struct must always be the last field");
2360 self.recover_stmt();
2365 let mut recovery_field = None;
2366 if let token::Ident(ident, _) = self.token {
2367 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2368 // Use in case of error after field-looking code: `S { foo: () with a }`
2369 let mut ident = ident.clone();
2370 ident.span = self.span;
2371 recovery_field = Some(ast::Field {
2374 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2375 is_shorthand: false,
2376 attrs: ThinVec::new(),
2380 let mut parsed_field = None;
2381 match self.parse_field() {
2382 Ok(f) => parsed_field = Some(f),
2384 e.span_label(struct_sp, "while parsing this struct");
2387 // If the next token is a comma, then try to parse
2388 // what comes next as additional fields, rather than
2389 // bailing out until next `}`.
2390 if self.token != token::Comma {
2391 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2392 if self.token != token::Comma {
2399 match self.expect_one_of(&[token::Comma],
2400 &[token::CloseDelim(token::Brace)]) {
2401 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2402 // only include the field if there's no parse error for the field name
2406 if let Some(f) = recovery_field {
2409 e.span_label(struct_sp, "while parsing this struct");
2411 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2412 self.eat(&token::Comma);
2417 let span = lo.to(self.span);
2418 self.expect(&token::CloseDelim(token::Brace))?;
2419 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2422 fn parse_or_use_outer_attributes(&mut self,
2423 already_parsed_attrs: Option<ThinVec<Attribute>>)
2424 -> PResult<'a, ThinVec<Attribute>> {
2425 if let Some(attrs) = already_parsed_attrs {
2428 self.parse_outer_attributes().map(|a| a.into())
2432 /// Parses a block or unsafe block.
2433 crate fn parse_block_expr(
2435 opt_label: Option<Label>,
2437 blk_mode: BlockCheckMode,
2438 outer_attrs: ThinVec<Attribute>,
2439 ) -> PResult<'a, P<Expr>> {
2440 self.expect(&token::OpenDelim(token::Brace))?;
2442 let mut attrs = outer_attrs;
2443 attrs.extend(self.parse_inner_attributes()?);
2445 let blk = self.parse_block_tail(lo, blk_mode)?;
2446 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2449 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2450 fn parse_dot_or_call_expr(&mut self,
2451 already_parsed_attrs: Option<ThinVec<Attribute>>)
2452 -> PResult<'a, P<Expr>> {
2453 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2455 let b = self.parse_bottom_expr();
2456 let (span, b) = self.interpolated_or_expr_span(b)?;
2457 self.parse_dot_or_call_expr_with(b, span, attrs)
2460 fn parse_dot_or_call_expr_with(&mut self,
2463 mut attrs: ThinVec<Attribute>)
2464 -> PResult<'a, P<Expr>> {
2465 // Stitch the list of outer attributes onto the return value.
2466 // A little bit ugly, but the best way given the current code
2468 self.parse_dot_or_call_expr_with_(e0, lo)
2470 expr.map(|mut expr| {
2471 attrs.extend::<Vec<_>>(expr.attrs.into());
2474 ExprKind::If(..) | ExprKind::IfLet(..) => {
2475 if !expr.attrs.is_empty() {
2476 // Just point to the first attribute in there...
2477 let span = expr.attrs[0].span;
2480 "attributes are not yet allowed on `if` \
2491 // Assuming we have just parsed `.`, continue parsing into an expression.
2492 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2493 if self.span.rust_2018() && self.eat_keyword(kw::Await) {
2494 let span = lo.to(self.prev_span);
2495 let await_expr = self.mk_expr(
2497 ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
2500 self.recover_from_await_method_call();
2501 return Ok(await_expr);
2503 let segment = self.parse_path_segment(PathStyle::Expr)?;
2504 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
2506 Ok(match self.token {
2507 token::OpenDelim(token::Paren) => {
2508 // Method call `expr.f()`
2509 let mut args = self.parse_unspanned_seq(
2510 &token::OpenDelim(token::Paren),
2511 &token::CloseDelim(token::Paren),
2512 SeqSep::trailing_allowed(token::Comma),
2513 |p| Ok(p.parse_expr()?)
2515 args.insert(0, self_arg);
2517 let span = lo.to(self.prev_span);
2518 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
2521 // Field access `expr.f`
2522 if let Some(args) = segment.args {
2523 self.span_err(args.span(),
2524 "field expressions may not have generic arguments");
2527 let span = lo.to(self.prev_span);
2528 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
2533 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2538 while self.eat(&token::Question) {
2539 let hi = self.prev_span;
2540 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
2544 if self.eat(&token::Dot) {
2546 token::Ident(..) => {
2547 e = self.parse_dot_suffix(e, lo)?;
2549 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
2550 let span = self.span;
2552 let field = ExprKind::Field(e, Ident::new(symbol, span));
2553 e = self.mk_expr(lo.to(span), field, ThinVec::new());
2555 self.expect_no_suffix(span, "a tuple index", suffix);
2557 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
2559 let fstr = symbol.as_str();
2560 let msg = format!("unexpected token: `{}`", symbol);
2561 let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
2562 err.span_label(self.prev_span, "unexpected token");
2563 if fstr.chars().all(|x| "0123456789.".contains(x)) {
2564 let float = match fstr.parse::<f64>().ok() {
2568 let sugg = pprust::to_string(|s| {
2569 use crate::print::pprust::PrintState;
2573 s.print_usize(float.trunc() as usize)?;
2576 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
2578 err.span_suggestion(
2579 lo.to(self.prev_span),
2580 "try parenthesizing the first index",
2582 Applicability::MachineApplicable
2589 // FIXME Could factor this out into non_fatal_unexpected or something.
2590 let actual = self.this_token_to_string();
2591 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
2596 if self.expr_is_complete(&e) { break; }
2599 token::OpenDelim(token::Paren) => {
2600 let seq = self.parse_unspanned_seq(
2601 &token::OpenDelim(token::Paren),
2602 &token::CloseDelim(token::Paren),
2603 SeqSep::trailing_allowed(token::Comma),
2604 |p| Ok(p.parse_expr()?)
2606 let nd = self.mk_call(e, es);
2607 let hi = self.prev_span;
2608 self.mk_expr(lo.to(hi), nd, ThinVec::new())
2610 e = self.recover_seq_parse_error(token::Paren, lo, seq);
2614 // Could be either an index expression or a slicing expression.
2615 token::OpenDelim(token::Bracket) => {
2617 let ix = self.parse_expr()?;
2619 self.expect(&token::CloseDelim(token::Bracket))?;
2620 let index = self.mk_index(e, ix);
2621 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
2629 crate fn process_potential_macro_variable(&mut self) {
2630 let (token, span) = match self.token {
2631 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
2632 self.look_ahead(1, |t| t.is_ident()) => {
2634 let name = match self.token {
2635 token::Ident(ident, _) => ident,
2638 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
2639 err.span_label(self.span, "unknown macro variable");
2644 token::Interpolated(ref nt) => {
2645 self.meta_var_span = Some(self.span);
2646 // Interpolated identifier and lifetime tokens are replaced with usual identifier
2647 // and lifetime tokens, so the former are never encountered during normal parsing.
2649 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
2650 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
2660 /// Parses a single token tree from the input.
2661 crate fn parse_token_tree(&mut self) -> TokenTree {
2663 token::OpenDelim(..) => {
2664 let frame = mem::replace(&mut self.token_cursor.frame,
2665 self.token_cursor.stack.pop().unwrap());
2666 self.span = frame.span.entire();
2668 TokenTree::Delimited(
2671 frame.tree_cursor.stream.into(),
2674 token::CloseDelim(_) | token::Eof => unreachable!(),
2676 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
2678 TokenTree::Token(span, token)
2683 /// Parses a stream of tokens into a list of `TokenTree`s, up to EOF.
2684 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2685 let mut tts = Vec::new();
2686 while self.token != token::Eof {
2687 tts.push(self.parse_token_tree());
2692 pub fn parse_tokens(&mut self) -> TokenStream {
2693 let mut result = Vec::new();
2696 token::Eof | token::CloseDelim(..) => break,
2697 _ => result.push(self.parse_token_tree().into()),
2700 TokenStream::new(result)
2703 /// Parse a prefix-unary-operator expr
2704 fn parse_prefix_expr(&mut self,
2705 already_parsed_attrs: Option<ThinVec<Attribute>>)
2706 -> PResult<'a, P<Expr>> {
2707 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2709 // Note: when adding new unary operators, don't forget to adjust TokenKind::can_begin_expr()
2710 let (hi, ex) = match self.token {
2713 let e = self.parse_prefix_expr(None);
2714 let (span, e) = self.interpolated_or_expr_span(e)?;
2715 (lo.to(span), self.mk_unary(UnOp::Not, e))
2717 // Suggest `!` for bitwise negation when encountering a `~`
2720 let e = self.parse_prefix_expr(None);
2721 let (span, e) = self.interpolated_or_expr_span(e)?;
2722 let span_of_tilde = lo;
2723 let mut err = self.diagnostic()
2724 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
2725 err.span_suggestion_short(
2727 "use `!` to perform bitwise negation",
2729 Applicability::MachineApplicable
2732 (lo.to(span), self.mk_unary(UnOp::Not, e))
2734 token::BinOp(token::Minus) => {
2736 let e = self.parse_prefix_expr(None);
2737 let (span, e) = self.interpolated_or_expr_span(e)?;
2738 (lo.to(span), self.mk_unary(UnOp::Neg, e))
2740 token::BinOp(token::Star) => {
2742 let e = self.parse_prefix_expr(None);
2743 let (span, e) = self.interpolated_or_expr_span(e)?;
2744 (lo.to(span), self.mk_unary(UnOp::Deref, e))
2746 token::BinOp(token::And) | token::AndAnd => {
2748 let m = self.parse_mutability();
2749 let e = self.parse_prefix_expr(None);
2750 let (span, e) = self.interpolated_or_expr_span(e)?;
2751 (lo.to(span), ExprKind::AddrOf(m, e))
2753 token::Ident(..) if self.token.is_keyword(kw::Box) => {
2755 let e = self.parse_prefix_expr(None);
2756 let (span, e) = self.interpolated_or_expr_span(e)?;
2757 (lo.to(span), ExprKind::Box(e))
2759 token::Ident(..) if self.token.is_ident_named(sym::not) => {
2760 // `not` is just an ordinary identifier in Rust-the-language,
2761 // but as `rustc`-the-compiler, we can issue clever diagnostics
2762 // for confused users who really want to say `!`
2763 let token_cannot_continue_expr = |t: &token::TokenKind| match *t {
2764 // These tokens can start an expression after `!`, but
2765 // can't continue an expression after an ident
2766 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
2767 token::Literal(..) | token::Pound => true,
2768 token::Interpolated(ref nt) => match **nt {
2769 token::NtIdent(..) | token::NtExpr(..) |
2770 token::NtBlock(..) | token::NtPath(..) => true,
2775 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
2776 if cannot_continue_expr {
2778 // Emit the error ...
2779 let mut err = self.diagnostic()
2780 .struct_span_err(self.span,
2781 &format!("unexpected {} after identifier",
2782 self.this_token_descr()));
2783 // span the `not` plus trailing whitespace to avoid
2784 // trailing whitespace after the `!` in our suggestion
2785 let to_replace = self.sess.source_map()
2786 .span_until_non_whitespace(lo.to(self.span));
2787 err.span_suggestion_short(
2789 "use `!` to perform logical negation",
2791 Applicability::MachineApplicable
2794 // —and recover! (just as if we were in the block
2795 // for the `token::Not` arm)
2796 let e = self.parse_prefix_expr(None);
2797 let (span, e) = self.interpolated_or_expr_span(e)?;
2798 (lo.to(span), self.mk_unary(UnOp::Not, e))
2800 return self.parse_dot_or_call_expr(Some(attrs));
2803 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
2805 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2808 /// Parses an associative expression.
2810 /// This parses an expression accounting for associativity and precedence of the operators in
2813 fn parse_assoc_expr(&mut self,
2814 already_parsed_attrs: Option<ThinVec<Attribute>>)
2815 -> PResult<'a, P<Expr>> {
2816 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2819 /// Parses an associative expression with operators of at least `min_prec` precedence.
2820 fn parse_assoc_expr_with(&mut self,
2823 -> PResult<'a, P<Expr>> {
2824 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2827 let attrs = match lhs {
2828 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2831 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
2832 return self.parse_prefix_range_expr(attrs);
2834 self.parse_prefix_expr(attrs)?
2838 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
2840 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2843 (false, _) => {} // continue parsing the expression
2844 // An exhaustive check is done in the following block, but these are checked first
2845 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
2846 // want to keep their span info to improve diagnostics in these cases in a later stage.
2847 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
2848 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
2849 (true, Some(AssocOp::LAnd)) | // `{ 42 } &&x` (#61475)
2850 (true, Some(AssocOp::Add)) // `{ 42 } + 42
2851 // If the next token is a keyword, then the tokens above *are* unambiguously incorrect:
2852 // `if x { a } else { b } && if y { c } else { d }`
2853 if !self.look_ahead(1, |t| t.is_reserved_ident()) => {
2854 // These cases are ambiguous and can't be identified in the parser alone
2855 let sp = self.sess.source_map().start_point(self.span);
2856 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
2859 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
2862 (true, Some(_)) => {
2863 // We've found an expression that would be parsed as a statement, but the next
2864 // token implies this should be parsed as an expression.
2865 // For example: `if let Some(x) = x { x } else { 0 } / 2`
2866 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
2867 "expected expression, found `{}`",
2868 pprust::token_to_string(&self.token),
2870 err.span_label(self.span, "expected expression");
2871 self.sess.expr_parentheses_needed(
2874 Some(pprust::expr_to_string(&lhs),
2879 self.expected_tokens.push(TokenType::Operator);
2880 while let Some(op) = AssocOp::from_token(&self.token) {
2882 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
2883 // it refers to. Interpolated identifiers are unwrapped early and never show up here
2884 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
2885 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
2886 let lhs_span = match (self.prev_token_kind, &lhs.node) {
2887 (PrevTokenKind::Interpolated, _) => self.prev_span,
2888 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
2889 if path.segments.len() == 1 => self.prev_span,
2893 let cur_op_span = self.span;
2894 let restrictions = if op.is_assign_like() {
2895 self.restrictions & Restrictions::NO_STRUCT_LITERAL
2899 let prec = op.precedence();
2900 if prec < min_prec {
2903 // Check for deprecated `...` syntax
2904 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
2905 self.err_dotdotdot_syntax(self.span);
2909 if op.is_comparison() {
2910 self.check_no_chained_comparison(&lhs, &op);
2913 if op == AssocOp::As {
2914 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
2916 } else if op == AssocOp::Colon {
2917 let maybe_path = self.could_ascription_be_path(&lhs.node);
2918 let next_sp = self.span;
2920 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
2923 self.bad_type_ascription(
2934 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
2935 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
2936 // generalise it to the Fixity::None code.
2938 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
2939 // two variants are handled with `parse_prefix_range_expr` call above.
2940 let rhs = if self.is_at_start_of_range_notation_rhs() {
2941 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
2945 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2950 let limits = if op == AssocOp::DotDot {
2951 RangeLimits::HalfOpen
2956 let r = self.mk_range(Some(lhs), rhs, limits)?;
2957 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
2961 let fixity = op.fixity();
2962 let prec_adjustment = match fixity {
2965 // We currently have no non-associative operators that are not handled above by
2966 // the special cases. The code is here only for future convenience.
2969 let rhs = self.with_res(
2970 restrictions - Restrictions::STMT_EXPR,
2971 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
2974 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
2975 // including the attributes.
2979 .filter(|a| a.style == AttrStyle::Outer)
2981 .map_or(lhs_span, |a| a.span);
2982 let span = lhs_span.to(rhs.span);
2984 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
2985 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
2986 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
2987 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
2988 AssocOp::Greater | AssocOp::GreaterEqual => {
2989 let ast_op = op.to_ast_binop().unwrap();
2990 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
2991 self.mk_expr(span, binary, ThinVec::new())
2993 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
2994 AssocOp::AssignOp(k) => {
2996 token::Plus => BinOpKind::Add,
2997 token::Minus => BinOpKind::Sub,
2998 token::Star => BinOpKind::Mul,
2999 token::Slash => BinOpKind::Div,
3000 token::Percent => BinOpKind::Rem,
3001 token::Caret => BinOpKind::BitXor,
3002 token::And => BinOpKind::BitAnd,
3003 token::Or => BinOpKind::BitOr,
3004 token::Shl => BinOpKind::Shl,
3005 token::Shr => BinOpKind::Shr,
3007 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3008 self.mk_expr(span, aopexpr, ThinVec::new())
3010 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3011 self.bug("AssocOp should have been handled by special case")
3015 if let Fixity::None = fixity { break }
3020 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3021 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3022 -> PResult<'a, P<Expr>> {
3023 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3024 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3027 // Save the state of the parser before parsing type normally, in case there is a
3028 // LessThan comparison after this cast.
3029 let parser_snapshot_before_type = self.clone();
3030 match self.parse_ty_no_plus() {
3032 Ok(mk_expr(self, rhs))
3034 Err(mut type_err) => {
3035 // Rewind to before attempting to parse the type with generics, to recover
3036 // from situations like `x as usize < y` in which we first tried to parse
3037 // `usize < y` as a type with generic arguments.
3038 let parser_snapshot_after_type = self.clone();
3039 mem::replace(self, parser_snapshot_before_type);
3041 match self.parse_path(PathStyle::Expr) {
3043 let (op_noun, op_verb) = match self.token {
3044 token::Lt => ("comparison", "comparing"),
3045 token::BinOp(token::Shl) => ("shift", "shifting"),
3047 // We can end up here even without `<` being the next token, for
3048 // example because `parse_ty_no_plus` returns `Err` on keywords,
3049 // but `parse_path` returns `Ok` on them due to error recovery.
3050 // Return original error and parser state.
3051 mem::replace(self, parser_snapshot_after_type);
3052 return Err(type_err);
3056 // Successfully parsed the type path leaving a `<` yet to parse.
3059 // Report non-fatal diagnostics, keep `x as usize` as an expression
3060 // in AST and continue parsing.
3061 let msg = format!("`<` is interpreted as a start of generic \
3062 arguments for `{}`, not a {}", path, op_noun);
3063 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3064 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3065 "interpreted as generic arguments");
3066 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3068 let expr = mk_expr(self, P(Ty {
3070 node: TyKind::Path(None, path),
3071 id: ast::DUMMY_NODE_ID
3074 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3075 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3076 err.span_suggestion(
3078 &format!("try {} the cast value", op_verb),
3079 format!("({})", expr_str),
3080 Applicability::MachineApplicable
3086 Err(mut path_err) => {
3087 // Couldn't parse as a path, return original error and parser state.
3089 mem::replace(self, parser_snapshot_after_type);
3097 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3098 fn parse_prefix_range_expr(&mut self,
3099 already_parsed_attrs: Option<ThinVec<Attribute>>)
3100 -> PResult<'a, P<Expr>> {
3101 // Check for deprecated `...` syntax
3102 if self.token == token::DotDotDot {
3103 self.err_dotdotdot_syntax(self.span);
3106 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3107 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3109 let tok = self.token.clone();
3110 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3112 let mut hi = self.span;
3114 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3115 // RHS must be parsed with more associativity than the dots.
3116 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3117 Some(self.parse_assoc_expr_with(next_prec,
3118 LhsExpr::NotYetParsed)
3126 let limits = if tok == token::DotDot {
3127 RangeLimits::HalfOpen
3132 let r = self.mk_range(None, opt_end, limits)?;
3133 Ok(self.mk_expr(lo.to(hi), r, attrs))
3136 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3137 if self.token.can_begin_expr() {
3138 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3139 if self.token == token::OpenDelim(token::Brace) {
3140 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3148 /// Parses an `if` or `if let` expression (`if` token already eaten).
3149 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3150 if self.check_keyword(kw::Let) {
3151 return self.parse_if_let_expr(attrs);
3153 let lo = self.prev_span;
3154 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3156 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3157 // verify that the last statement is either an implicit return (no `;`) or an explicit
3158 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3159 // the dead code lint.
3160 if self.eat_keyword(kw::Else) || !cond.returns() {
3161 let sp = self.sess.source_map().next_point(lo);
3162 let mut err = self.diagnostic()
3163 .struct_span_err(sp, "missing condition for `if` statemement");
3164 err.span_label(sp, "expected if condition here");
3167 let not_block = self.token != token::OpenDelim(token::Brace);
3168 let thn = self.parse_block().map_err(|mut err| {
3170 err.span_label(lo, "this `if` statement has a condition, but no block");
3174 let mut els: Option<P<Expr>> = None;
3175 let mut hi = thn.span;
3176 if self.eat_keyword(kw::Else) {
3177 let elexpr = self.parse_else_expr()?;
3181 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3184 /// Parses an `if let` expression (`if` token already eaten).
3185 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3186 -> PResult<'a, P<Expr>> {
3187 let lo = self.prev_span;
3188 self.expect_keyword(kw::Let)?;
3189 let pats = self.parse_pats()?;
3190 self.expect(&token::Eq)?;
3191 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3192 let thn = self.parse_block()?;
3193 let (hi, els) = if self.eat_keyword(kw::Else) {
3194 let expr = self.parse_else_expr()?;
3195 (expr.span, Some(expr))
3199 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3202 /// Parses `move |args| expr`.
3203 fn parse_lambda_expr(&mut self,
3204 attrs: ThinVec<Attribute>)
3205 -> PResult<'a, P<Expr>>
3208 let movability = if self.eat_keyword(kw::Static) {
3213 let asyncness = if self.span.rust_2018() {
3214 self.parse_asyncness()
3218 let capture_clause = if self.eat_keyword(kw::Move) {
3223 let decl = self.parse_fn_block_decl()?;
3224 let decl_hi = self.prev_span;
3225 let body = match decl.output {
3226 FunctionRetTy::Default(_) => {
3227 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3228 self.parse_expr_res(restrictions, None)?
3231 // If an explicit return type is given, require a
3232 // block to appear (RFC 968).
3233 let body_lo = self.span;
3234 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3240 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3244 // `else` token already eaten
3245 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3246 if self.eat_keyword(kw::If) {
3247 return self.parse_if_expr(ThinVec::new());
3249 let blk = self.parse_block()?;
3250 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3254 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3255 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3257 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3258 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3260 let pat = self.parse_top_level_pat()?;
3261 if !self.eat_keyword(kw::In) {
3262 let in_span = self.prev_span.between(self.span);
3263 let mut err = self.sess.span_diagnostic
3264 .struct_span_err(in_span, "missing `in` in `for` loop");
3265 err.span_suggestion_short(
3266 in_span, "try adding `in` here", " in ".into(),
3267 // has been misleading, at least in the past (closed Issue #48492)
3268 Applicability::MaybeIncorrect
3272 let in_span = self.prev_span;
3273 self.check_for_for_in_in_typo(in_span);
3274 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3275 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3276 attrs.extend(iattrs);
3278 let hi = self.prev_span;
3279 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3282 /// Parses a `while` or `while let` expression (`while` token already eaten).
3283 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3285 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3286 if self.token.is_keyword(kw::Let) {
3287 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3289 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3290 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3291 attrs.extend(iattrs);
3292 let span = span_lo.to(body.span);
3293 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3296 /// Parses a `while let` expression (`while` token already eaten).
3297 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3299 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3300 self.expect_keyword(kw::Let)?;
3301 let pats = self.parse_pats()?;
3302 self.expect(&token::Eq)?;
3303 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3304 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3305 attrs.extend(iattrs);
3306 let span = span_lo.to(body.span);
3307 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3310 // parse `loop {...}`, `loop` token already eaten
3311 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3313 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3314 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3315 attrs.extend(iattrs);
3316 let span = span_lo.to(body.span);
3317 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3320 /// Parses an `async move {...}` expression.
3321 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3322 -> PResult<'a, P<Expr>>
3324 let span_lo = self.span;
3325 self.expect_keyword(kw::Async)?;
3326 let capture_clause = if self.eat_keyword(kw::Move) {
3331 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3332 attrs.extend(iattrs);
3334 span_lo.to(body.span),
3335 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3338 /// Parses a `try {...}` expression (`try` token already eaten).
3339 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3340 -> PResult<'a, P<Expr>>
3342 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3343 attrs.extend(iattrs);
3344 if self.eat_keyword(kw::Catch) {
3345 let mut error = self.struct_span_err(self.prev_span,
3346 "keyword `catch` cannot follow a `try` block");
3347 error.help("try using `match` on the result of the `try` block instead");
3351 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
3355 // `match` token already eaten
3356 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3357 let match_span = self.prev_span;
3358 let lo = self.prev_span;
3359 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3361 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3362 if self.token == token::Semi {
3363 e.span_suggestion_short(
3365 "try removing this `match`",
3367 Applicability::MaybeIncorrect // speculative
3372 attrs.extend(self.parse_inner_attributes()?);
3374 let mut arms: Vec<Arm> = Vec::new();
3375 while self.token != token::CloseDelim(token::Brace) {
3376 match self.parse_arm() {
3377 Ok(arm) => arms.push(arm),
3379 // Recover by skipping to the end of the block.
3381 self.recover_stmt();
3382 let span = lo.to(self.span);
3383 if self.token == token::CloseDelim(token::Brace) {
3386 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3392 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3395 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3396 let attrs = self.parse_outer_attributes()?;
3398 let pats = self.parse_pats()?;
3399 let guard = if self.eat_keyword(kw::If) {
3400 Some(Guard::If(self.parse_expr()?))
3404 let arrow_span = self.span;
3405 self.expect(&token::FatArrow)?;
3406 let arm_start_span = self.span;
3408 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3409 .map_err(|mut err| {
3410 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3414 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3415 && self.token != token::CloseDelim(token::Brace);
3420 let cm = self.sess.source_map();
3421 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3422 .map_err(|mut err| {
3423 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3424 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3425 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3426 && expr_lines.lines.len() == 2
3427 && self.token == token::FatArrow => {
3428 // We check whether there's any trailing code in the parse span,
3429 // if there isn't, we very likely have the following:
3432 // | -- - missing comma
3438 // | parsed until here as `"y" & X`
3439 err.span_suggestion_short(
3440 cm.next_point(arm_start_span),
3441 "missing a comma here to end this `match` arm",
3443 Applicability::MachineApplicable
3447 err.span_label(arrow_span,
3448 "while parsing the `match` arm starting here");
3454 self.eat(&token::Comma);
3466 /// Parses an expression.
3468 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3469 self.parse_expr_res(Restrictions::empty(), None)
3472 /// Evaluates the closure with restrictions in place.
3474 /// Afters the closure is evaluated, restrictions are reset.
3475 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
3476 where F: FnOnce(&mut Self) -> T
3478 let old = self.restrictions;
3479 self.restrictions = r;
3481 self.restrictions = old;
3486 /// Parses an expression, subject to the given restrictions.
3488 fn parse_expr_res(&mut self, r: Restrictions,
3489 already_parsed_attrs: Option<ThinVec<Attribute>>)
3490 -> PResult<'a, P<Expr>> {
3491 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3494 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
3495 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
3496 if self.eat(&token::Eq) {
3497 Ok(Some(self.parse_expr()?))
3499 Ok(Some(self.parse_expr()?))
3505 /// Parses patterns, separated by '|' s.
3506 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3507 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
3508 self.eat(&token::BinOp(token::Or));
3510 let mut pats = Vec::new();
3512 pats.push(self.parse_top_level_pat()?);
3514 if self.token == token::OrOr {
3515 let mut err = self.struct_span_err(self.span,
3516 "unexpected token `||` after pattern");
3517 err.span_suggestion(
3519 "use a single `|` to specify multiple patterns",
3521 Applicability::MachineApplicable
3525 } else if self.eat(&token::BinOp(token::Or)) {
3526 // This is a No-op. Continue the loop to parse the next
3534 // Parses a parenthesized list of patterns like
3535 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
3536 // - a vector of the patterns that were parsed
3537 // - an option indicating the index of the `..` element
3538 // - a boolean indicating whether a trailing comma was present.
3539 // Trailing commas are significant because (p) and (p,) are different patterns.
3540 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3541 self.expect(&token::OpenDelim(token::Paren))?;
3542 let result = match self.parse_pat_list() {
3543 Ok(result) => result,
3544 Err(mut err) => { // recover from parse error in tuple pattern list
3546 self.consume_block(token::Paren);
3547 return Ok((vec![], Some(0), false));
3550 self.expect(&token::CloseDelim(token::Paren))?;
3554 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3555 let mut fields = Vec::new();
3556 let mut ddpos = None;
3557 let mut prev_dd_sp = None;
3558 let mut trailing_comma = false;
3560 if self.eat(&token::DotDot) {
3561 if ddpos.is_none() {
3562 ddpos = Some(fields.len());
3563 prev_dd_sp = Some(self.prev_span);
3565 // Emit a friendly error, ignore `..` and continue parsing
3566 let mut err = self.struct_span_err(
3568 "`..` can only be used once per tuple or tuple struct pattern",
3570 err.span_label(self.prev_span, "can only be used once per pattern");
3571 if let Some(sp) = prev_dd_sp {
3572 err.span_label(sp, "previously present here");
3576 } else if !self.check(&token::CloseDelim(token::Paren)) {
3577 fields.push(self.parse_pat(None)?);
3582 trailing_comma = self.eat(&token::Comma);
3583 if !trailing_comma {
3588 if ddpos == Some(fields.len()) && trailing_comma {
3589 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
3590 let msg = "trailing comma is not permitted after `..`";
3591 self.struct_span_err(self.prev_span, msg)
3592 .span_label(self.prev_span, msg)
3596 Ok((fields, ddpos, trailing_comma))
3599 fn parse_pat_vec_elements(
3601 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3602 let mut before = Vec::new();
3603 let mut slice = None;
3604 let mut after = Vec::new();
3605 let mut first = true;
3606 let mut before_slice = true;
3608 while self.token != token::CloseDelim(token::Bracket) {
3612 self.expect(&token::Comma)?;
3614 if self.token == token::CloseDelim(token::Bracket)
3615 && (before_slice || !after.is_empty()) {
3621 if self.eat(&token::DotDot) {
3623 if self.check(&token::Comma) ||
3624 self.check(&token::CloseDelim(token::Bracket)) {
3625 slice = Some(P(Pat {
3626 id: ast::DUMMY_NODE_ID,
3627 node: PatKind::Wild,
3628 span: self.prev_span,
3630 before_slice = false;
3636 let subpat = self.parse_pat(None)?;
3637 if before_slice && self.eat(&token::DotDot) {
3638 slice = Some(subpat);
3639 before_slice = false;
3640 } else if before_slice {
3641 before.push(subpat);
3647 Ok((before, slice, after))
3653 attrs: Vec<Attribute>
3654 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
3655 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3657 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3658 // Parsing a pattern of the form "fieldname: pat"
3659 let fieldname = self.parse_field_name()?;
3661 let pat = self.parse_pat(None)?;
3663 (pat, fieldname, false)
3665 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3666 let is_box = self.eat_keyword(kw::Box);
3667 let boxed_span = self.span;
3668 let is_ref = self.eat_keyword(kw::Ref);
3669 let is_mut = self.eat_keyword(kw::Mut);
3670 let fieldname = self.parse_ident()?;
3671 hi = self.prev_span;
3673 let bind_type = match (is_ref, is_mut) {
3674 (true, true) => BindingMode::ByRef(Mutability::Mutable),
3675 (true, false) => BindingMode::ByRef(Mutability::Immutable),
3676 (false, true) => BindingMode::ByValue(Mutability::Mutable),
3677 (false, false) => BindingMode::ByValue(Mutability::Immutable),
3679 let fieldpat = P(Pat {
3680 id: ast::DUMMY_NODE_ID,
3681 node: PatKind::Ident(bind_type, fieldname, None),
3682 span: boxed_span.to(hi),
3685 let subpat = if is_box {
3687 id: ast::DUMMY_NODE_ID,
3688 node: PatKind::Box(fieldpat),
3694 (subpat, fieldname, true)
3697 Ok(source_map::Spanned {
3699 node: ast::FieldPat {
3703 attrs: attrs.into(),
3708 /// Parses the fields of a struct-like pattern.
3709 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
3710 let mut fields = Vec::new();
3711 let mut etc = false;
3712 let mut ate_comma = true;
3713 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
3714 let mut etc_span = None;
3716 while self.token != token::CloseDelim(token::Brace) {
3717 let attrs = self.parse_outer_attributes()?;
3720 // check that a comma comes after every field
3722 let err = self.struct_span_err(self.prev_span, "expected `,`");
3723 if let Some(mut delayed) = delayed_err {
3730 if self.check(&token::DotDot) || self.token == token::DotDotDot {
3732 let mut etc_sp = self.span;
3734 if self.token == token::DotDotDot { // Issue #46718
3735 // Accept `...` as if it were `..` to avoid further errors
3736 let mut err = self.struct_span_err(self.span,
3737 "expected field pattern, found `...`");
3738 err.span_suggestion(
3740 "to omit remaining fields, use one fewer `.`",
3742 Applicability::MachineApplicable
3746 self.bump(); // `..` || `...`
3748 if self.token == token::CloseDelim(token::Brace) {
3749 etc_span = Some(etc_sp);
3752 let token_str = self.this_token_descr();
3753 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
3755 err.span_label(self.span, "expected `}`");
3756 let mut comma_sp = None;
3757 if self.token == token::Comma { // Issue #49257
3758 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
3759 err.span_label(etc_sp,
3760 "`..` must be at the end and cannot have a trailing comma");
3761 comma_sp = Some(self.span);
3766 etc_span = Some(etc_sp.until(self.span));
3767 if self.token == token::CloseDelim(token::Brace) {
3768 // If the struct looks otherwise well formed, recover and continue.
3769 if let Some(sp) = comma_sp {
3770 err.span_suggestion_short(
3772 "remove this comma",
3774 Applicability::MachineApplicable,
3779 } else if self.token.is_ident() && ate_comma {
3780 // Accept fields coming after `..,`.
3781 // This way we avoid "pattern missing fields" errors afterwards.
3782 // We delay this error until the end in order to have a span for a
3784 if let Some(mut delayed_err) = delayed_err {
3788 delayed_err = Some(err);
3791 if let Some(mut err) = delayed_err {
3798 fields.push(match self.parse_pat_field(lo, attrs) {
3801 if let Some(mut delayed_err) = delayed_err {
3807 ate_comma = self.eat(&token::Comma);
3810 if let Some(mut err) = delayed_err {
3811 if let Some(etc_span) = etc_span {
3812 err.multipart_suggestion(
3813 "move the `..` to the end of the field list",
3815 (etc_span, String::new()),
3816 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
3818 Applicability::MachineApplicable,
3823 return Ok((fields, etc));
3826 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3827 if self.token.is_path_start() {
3829 let (qself, path) = if self.eat_lt() {
3830 // Parse a qualified path
3831 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3834 // Parse an unqualified path
3835 (None, self.parse_path(PathStyle::Expr)?)
3837 let hi = self.prev_span;
3838 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
3840 self.parse_literal_maybe_minus()
3844 // helper function to decide whether to parse as ident binding or to try to do
3845 // something more complex like range patterns
3846 fn parse_as_ident(&mut self) -> bool {
3847 self.look_ahead(1, |t| match *t {
3848 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
3849 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
3850 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
3851 // range pattern branch
3852 token::DotDot => None,
3854 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
3855 token::Comma | token::CloseDelim(token::Bracket) => true,
3860 /// A wrapper around `parse_pat` with some special error handling for the
3861 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
3862 /// to subpatterns within such).
3863 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
3864 let pat = self.parse_pat(None)?;
3865 if self.token == token::Comma {
3866 // An unexpected comma after a top-level pattern is a clue that the
3867 // user (perhaps more accustomed to some other language) forgot the
3868 // parentheses in what should have been a tuple pattern; return a
3869 // suggestion-enhanced error here rather than choking on the comma
3871 let comma_span = self.span;
3873 if let Err(mut err) = self.parse_pat_list() {
3874 // We didn't expect this to work anyway; we just wanted
3875 // to advance to the end of the comma-sequence so we know
3876 // the span to suggest parenthesizing
3879 let seq_span = pat.span.to(self.prev_span);
3880 let mut err = self.struct_span_err(comma_span,
3881 "unexpected `,` in pattern");
3882 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
3883 err.span_suggestion(
3885 "try adding parentheses to match on a tuple..",
3886 format!("({})", seq_snippet),
3887 Applicability::MachineApplicable
3890 "..or a vertical bar to match on multiple alternatives",
3891 format!("{}", seq_snippet.replace(",", " |")),
3892 Applicability::MachineApplicable
3900 /// Parses a pattern.
3901 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
3902 self.parse_pat_with_range_pat(true, expected)
3905 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
3907 fn parse_pat_with_range_pat(
3909 allow_range_pat: bool,
3910 expected: Option<&'static str>,
3911 ) -> PResult<'a, P<Pat>> {
3912 maybe_recover_from_interpolated_ty_qpath!(self, true);
3913 maybe_whole!(self, NtPat, |x| x);
3918 token::BinOp(token::And) | token::AndAnd => {
3919 // Parse &pat / &mut pat
3921 let mutbl = self.parse_mutability();
3922 if let token::Lifetime(ident) = self.token {
3923 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
3925 err.span_label(self.span, "unexpected lifetime");
3928 let subpat = self.parse_pat_with_range_pat(false, expected)?;
3929 pat = PatKind::Ref(subpat, mutbl);
3931 token::OpenDelim(token::Paren) => {
3932 // Parse (pat,pat,pat,...) as tuple pattern
3933 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
3934 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
3935 PatKind::Paren(fields.into_iter().nth(0).unwrap())
3937 PatKind::Tuple(fields, ddpos)
3940 token::OpenDelim(token::Bracket) => {
3941 // Parse [pat,pat,...] as slice pattern
3943 let (before, slice, after) = self.parse_pat_vec_elements()?;
3944 self.expect(&token::CloseDelim(token::Bracket))?;
3945 pat = PatKind::Slice(before, slice, after);
3947 // At this point, token != &, &&, (, [
3948 _ => if self.eat_keyword(kw::Underscore) {
3950 pat = PatKind::Wild;
3951 } else if self.eat_keyword(kw::Mut) {
3952 // Parse mut ident @ pat / mut ref ident @ pat
3953 let mutref_span = self.prev_span.to(self.span);
3954 let binding_mode = if self.eat_keyword(kw::Ref) {
3956 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
3959 "try switching the order",
3961 Applicability::MachineApplicable
3963 BindingMode::ByRef(Mutability::Mutable)
3965 BindingMode::ByValue(Mutability::Mutable)
3967 pat = self.parse_pat_ident(binding_mode)?;
3968 } else if self.eat_keyword(kw::Ref) {
3969 // Parse ref ident @ pat / ref mut ident @ pat
3970 let mutbl = self.parse_mutability();
3971 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
3972 } else if self.eat_keyword(kw::Box) {
3974 let subpat = self.parse_pat_with_range_pat(false, None)?;
3975 pat = PatKind::Box(subpat);
3976 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
3977 self.parse_as_ident() {
3978 // Parse ident @ pat
3979 // This can give false positives and parse nullary enums,
3980 // they are dealt with later in resolve
3981 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
3982 pat = self.parse_pat_ident(binding_mode)?;
3983 } else if self.token.is_path_start() {
3984 // Parse pattern starting with a path
3985 let (qself, path) = if self.eat_lt() {
3986 // Parse a qualified path
3987 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3990 // Parse an unqualified path
3991 (None, self.parse_path(PathStyle::Expr)?)
3994 token::Not if qself.is_none() => {
3995 // Parse macro invocation
3997 let (delim, tts) = self.expect_delimited_token_tree()?;
3998 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
3999 pat = PatKind::Mac(mac);
4001 token::DotDotDot | token::DotDotEq | token::DotDot => {
4002 let end_kind = match self.token {
4003 token::DotDot => RangeEnd::Excluded,
4004 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4005 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4006 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4009 let op_span = self.span;
4011 let span = lo.to(self.prev_span);
4012 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4014 let end = self.parse_pat_range_end()?;
4015 let op = Spanned { span: op_span, node: end_kind };
4016 pat = PatKind::Range(begin, end, op);
4018 token::OpenDelim(token::Brace) => {
4019 if qself.is_some() {
4020 let msg = "unexpected `{` after qualified path";
4021 let mut err = self.fatal(msg);
4022 err.span_label(self.span, msg);
4025 // Parse struct pattern
4027 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4029 self.recover_stmt();
4033 pat = PatKind::Struct(path, fields, etc);
4035 token::OpenDelim(token::Paren) => {
4036 if qself.is_some() {
4037 let msg = "unexpected `(` after qualified path";
4038 let mut err = self.fatal(msg);
4039 err.span_label(self.span, msg);
4042 // Parse tuple struct or enum pattern
4043 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4044 pat = PatKind::TupleStruct(path, fields, ddpos)
4046 _ => pat = PatKind::Path(qself, path),
4049 // Try to parse everything else as literal with optional minus
4050 match self.parse_literal_maybe_minus() {
4052 let op_span = self.span;
4053 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4054 self.check(&token::DotDotDot) {
4055 let end_kind = if self.eat(&token::DotDotDot) {
4056 RangeEnd::Included(RangeSyntax::DotDotDot)
4057 } else if self.eat(&token::DotDotEq) {
4058 RangeEnd::Included(RangeSyntax::DotDotEq)
4059 } else if self.eat(&token::DotDot) {
4062 panic!("impossible case: we already matched \
4063 on a range-operator token")
4065 let end = self.parse_pat_range_end()?;
4066 let op = Spanned { span: op_span, node: end_kind };
4067 pat = PatKind::Range(begin, end, op);
4069 pat = PatKind::Lit(begin);
4073 self.cancel(&mut err);
4074 let expected = expected.unwrap_or("pattern");
4076 "expected {}, found {}",
4078 self.this_token_descr(),
4080 let mut err = self.fatal(&msg);
4081 err.span_label(self.span, format!("expected {}", expected));
4082 let sp = self.sess.source_map().start_point(self.span);
4083 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4084 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4092 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4093 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4095 if !allow_range_pat {
4098 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4100 PatKind::Range(..) => {
4101 let mut err = self.struct_span_err(
4103 "the range pattern here has ambiguous interpretation",
4105 err.span_suggestion(
4107 "add parentheses to clarify the precedence",
4108 format!("({})", pprust::pat_to_string(&pat)),
4109 // "ambiguous interpretation" implies that we have to be guessing
4110 Applicability::MaybeIncorrect
4121 /// Parses `ident` or `ident @ pat`.
4122 /// used by the copy foo and ref foo patterns to give a good
4123 /// error message when parsing mistakes like `ref foo(a, b)`.
4124 fn parse_pat_ident(&mut self,
4125 binding_mode: ast::BindingMode)
4126 -> PResult<'a, PatKind> {
4127 let ident = self.parse_ident()?;
4128 let sub = if self.eat(&token::At) {
4129 Some(self.parse_pat(Some("binding pattern"))?)
4134 // just to be friendly, if they write something like
4136 // we end up here with ( as the current token. This shortly
4137 // leads to a parse error. Note that if there is no explicit
4138 // binding mode then we do not end up here, because the lookahead
4139 // will direct us over to parse_enum_variant()
4140 if self.token == token::OpenDelim(token::Paren) {
4141 return Err(self.span_fatal(
4143 "expected identifier, found enum pattern"))
4146 Ok(PatKind::Ident(binding_mode, ident, sub))
4149 /// Parses a local variable declaration.
4150 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4151 let lo = self.prev_span;
4152 let pat = self.parse_top_level_pat()?;
4154 let (err, ty) = if self.eat(&token::Colon) {
4155 // Save the state of the parser before parsing type normally, in case there is a `:`
4156 // instead of an `=` typo.
4157 let parser_snapshot_before_type = self.clone();
4158 let colon_sp = self.prev_span;
4159 match self.parse_ty() {
4160 Ok(ty) => (None, Some(ty)),
4162 // Rewind to before attempting to parse the type and continue parsing
4163 let parser_snapshot_after_type = self.clone();
4164 mem::replace(self, parser_snapshot_before_type);
4166 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4167 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4168 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4174 let init = match (self.parse_initializer(err.is_some()), err) {
4175 (Ok(init), None) => { // init parsed, ty parsed
4178 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4179 // Could parse the type as if it were the initializer, it is likely there was a
4180 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4181 err.span_suggestion_short(
4183 "use `=` if you meant to assign",
4185 Applicability::MachineApplicable
4188 // As this was parsed successfully, continue as if the code has been fixed for the
4189 // rest of the file. It will still fail due to the emitted error, but we avoid
4193 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4195 // Couldn't parse the type nor the initializer, only raise the type error and
4196 // return to the parser state before parsing the type as the initializer.
4197 // let x: <parse_error>;
4198 mem::replace(self, snapshot);
4201 (Err(err), None) => { // init error, ty parsed
4202 // Couldn't parse the initializer and we're not attempting to recover a failed
4203 // parse of the type, return the error.
4207 let hi = if self.token == token::Semi {
4216 id: ast::DUMMY_NODE_ID,
4222 /// Parses a structure field.
4223 fn parse_name_and_ty(&mut self,
4226 attrs: Vec<Attribute>)
4227 -> PResult<'a, StructField> {
4228 let name = self.parse_ident()?;
4229 self.expect(&token::Colon)?;
4230 let ty = self.parse_ty()?;
4232 span: lo.to(self.prev_span),
4235 id: ast::DUMMY_NODE_ID,
4241 /// Emits an expected-item-after-attributes error.
4242 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4243 let message = match attrs.last() {
4244 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4245 _ => "expected item after attributes",
4248 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4249 if attrs.last().unwrap().is_sugared_doc {
4250 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4255 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4256 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4257 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4258 Ok(self.parse_stmt_(true))
4261 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4262 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4264 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4269 fn is_async_block(&self) -> bool {
4270 self.token.is_keyword(kw::Async) &&
4273 self.is_keyword_ahead(1, &[kw::Move]) &&
4274 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4276 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4281 fn is_async_fn(&self) -> bool {
4282 self.token.is_keyword(kw::Async) &&
4283 self.is_keyword_ahead(1, &[kw::Fn])
4286 fn is_do_catch_block(&self) -> bool {
4287 self.token.is_keyword(kw::Do) &&
4288 self.is_keyword_ahead(1, &[kw::Catch]) &&
4289 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4290 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4293 fn is_try_block(&self) -> bool {
4294 self.token.is_keyword(kw::Try) &&
4295 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
4296 self.span.rust_2018() &&
4297 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
4298 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4301 fn is_union_item(&self) -> bool {
4302 self.token.is_keyword(kw::Union) &&
4303 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4306 fn is_crate_vis(&self) -> bool {
4307 self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4310 fn is_existential_type_decl(&self) -> bool {
4311 self.token.is_keyword(kw::Existential) &&
4312 self.is_keyword_ahead(1, &[kw::Type])
4315 fn is_auto_trait_item(&self) -> bool {
4317 (self.token.is_keyword(kw::Auto) &&
4318 self.is_keyword_ahead(1, &[kw::Trait]))
4319 || // unsafe auto trait
4320 (self.token.is_keyword(kw::Unsafe) &&
4321 self.is_keyword_ahead(1, &[kw::Auto]) &&
4322 self.is_keyword_ahead(2, &[kw::Trait]))
4325 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4326 -> PResult<'a, Option<P<Item>>> {
4327 let token_lo = self.span;
4328 let (ident, def) = match self.token {
4329 token::Ident(ident, false) if ident.name == kw::Macro => {
4331 let ident = self.parse_ident()?;
4332 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4333 match self.parse_token_tree() {
4334 TokenTree::Delimited(_, _, tts) => tts,
4335 _ => unreachable!(),
4337 } else if self.check(&token::OpenDelim(token::Paren)) {
4338 let args = self.parse_token_tree();
4339 let body = if self.check(&token::OpenDelim(token::Brace)) {
4340 self.parse_token_tree()
4345 TokenStream::new(vec![
4347 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
4355 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4357 token::Ident(ident, _) if ident.name == sym::macro_rules &&
4358 self.look_ahead(1, |t| *t == token::Not) => {
4359 let prev_span = self.prev_span;
4360 self.complain_if_pub_macro(&vis.node, prev_span);
4364 let ident = self.parse_ident()?;
4365 let (delim, tokens) = self.expect_delimited_token_tree()?;
4366 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
4367 self.report_invalid_macro_expansion_item();
4370 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4372 _ => return Ok(None),
4375 let span = lo.to(self.prev_span);
4376 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4379 fn parse_stmt_without_recovery(&mut self,
4380 macro_legacy_warnings: bool)
4381 -> PResult<'a, Option<Stmt>> {
4382 maybe_whole!(self, NtStmt, |x| Some(x));
4384 let attrs = self.parse_outer_attributes()?;
4387 Ok(Some(if self.eat_keyword(kw::Let) {
4389 id: ast::DUMMY_NODE_ID,
4390 node: StmtKind::Local(self.parse_local(attrs.into())?),
4391 span: lo.to(self.prev_span),
4393 } else if let Some(macro_def) = self.eat_macro_def(
4395 &source_map::respan(lo, VisibilityKind::Inherited),
4399 id: ast::DUMMY_NODE_ID,
4400 node: StmtKind::Item(macro_def),
4401 span: lo.to(self.prev_span),
4403 // Starts like a simple path, being careful to avoid contextual keywords
4404 // such as a union items, item with `crate` visibility or auto trait items.
4405 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4406 // like a path (1 token), but it fact not a path.
4407 // `union::b::c` - path, `union U { ... }` - not a path.
4408 // `crate::b::c` - path, `crate struct S;` - not a path.
4409 } else if self.token.is_path_start() &&
4410 !self.token.is_qpath_start() &&
4411 !self.is_union_item() &&
4412 !self.is_crate_vis() &&
4413 !self.is_existential_type_decl() &&
4414 !self.is_auto_trait_item() &&
4415 !self.is_async_fn() {
4416 let pth = self.parse_path(PathStyle::Expr)?;
4418 if !self.eat(&token::Not) {
4419 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4420 self.parse_struct_expr(lo, pth, ThinVec::new())?
4422 let hi = self.prev_span;
4423 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4426 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4427 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4428 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4431 return Ok(Some(Stmt {
4432 id: ast::DUMMY_NODE_ID,
4433 node: StmtKind::Expr(expr),
4434 span: lo.to(self.prev_span),
4438 // it's a macro invocation
4439 let id = match self.token {
4440 token::OpenDelim(_) => Ident::invalid(), // no special identifier
4441 _ => self.parse_ident()?,
4444 // check that we're pointing at delimiters (need to check
4445 // again after the `if`, because of `parse_ident`
4446 // consuming more tokens).
4448 token::OpenDelim(_) => {}
4450 // we only expect an ident if we didn't parse one
4452 let ident_str = if id.name == kw::Invalid {
4457 let tok_str = self.this_token_descr();
4458 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
4461 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
4466 let (delim, tts) = self.expect_delimited_token_tree()?;
4467 let hi = self.prev_span;
4469 let style = if delim == MacDelimiter::Brace {
4470 MacStmtStyle::Braces
4472 MacStmtStyle::NoBraces
4475 if id.name == kw::Invalid {
4476 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
4477 let node = if delim == MacDelimiter::Brace ||
4478 self.token == token::Semi || self.token == token::Eof {
4479 StmtKind::Mac(P((mac, style, attrs.into())))
4481 // We used to incorrectly stop parsing macro-expanded statements here.
4482 // If the next token will be an error anyway but could have parsed with the
4483 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
4484 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
4485 // These can continue an expression, so we can't stop parsing and warn.
4486 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
4487 token::BinOp(token::Minus) | token::BinOp(token::Star) |
4488 token::BinOp(token::And) | token::BinOp(token::Or) |
4489 token::AndAnd | token::OrOr |
4490 token::DotDot | token::DotDotDot | token::DotDotEq => false,
4493 self.warn_missing_semicolon();
4494 StmtKind::Mac(P((mac, style, attrs.into())))
4496 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
4497 let e = self.maybe_recover_from_bad_qpath(e, true)?;
4498 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
4499 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
4503 id: ast::DUMMY_NODE_ID,
4508 // if it has a special ident, it's definitely an item
4510 // Require a semicolon or braces.
4511 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
4512 self.report_invalid_macro_expansion_item();
4514 let span = lo.to(hi);
4516 id: ast::DUMMY_NODE_ID,
4518 node: StmtKind::Item({
4520 span, id /*id is good here*/,
4521 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
4522 respan(lo, VisibilityKind::Inherited),
4528 // FIXME: Bad copy of attrs
4529 let old_directory_ownership =
4530 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
4531 let item = self.parse_item_(attrs.clone(), false, true)?;
4532 self.directory.ownership = old_directory_ownership;
4536 id: ast::DUMMY_NODE_ID,
4537 span: lo.to(i.span),
4538 node: StmtKind::Item(i),
4541 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
4542 if !attrs.is_empty() {
4543 if s.prev_token_kind == PrevTokenKind::DocComment {
4544 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
4545 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
4546 s.span_err(s.span, "expected statement after outer attribute");
4551 // Do not attempt to parse an expression if we're done here.
4552 if self.token == token::Semi {
4553 unused_attrs(&attrs, self);
4558 if self.token == token::CloseDelim(token::Brace) {
4559 unused_attrs(&attrs, self);
4563 // Remainder are line-expr stmts.
4564 let e = self.parse_expr_res(
4565 Restrictions::STMT_EXPR, Some(attrs.into()))?;
4567 id: ast::DUMMY_NODE_ID,
4568 span: lo.to(e.span),
4569 node: StmtKind::Expr(e),
4576 /// Checks if this expression is a successfully parsed statement.
4577 fn expr_is_complete(&self, e: &Expr) -> bool {
4578 self.restrictions.contains(Restrictions::STMT_EXPR) &&
4579 !classify::expr_requires_semi_to_be_stmt(e)
4582 /// Parses a block. No inner attributes are allowed.
4583 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
4584 maybe_whole!(self, NtBlock, |x| x);
4588 if !self.eat(&token::OpenDelim(token::Brace)) {
4590 let tok = self.this_token_descr();
4591 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
4592 let do_not_suggest_help =
4593 self.token.is_keyword(kw::In) || self.token == token::Colon;
4595 if self.token.is_ident_named(sym::and) {
4596 e.span_suggestion_short(
4598 "use `&&` instead of `and` for the boolean operator",
4600 Applicability::MaybeIncorrect,
4603 if self.token.is_ident_named(sym::or) {
4604 e.span_suggestion_short(
4606 "use `||` instead of `or` for the boolean operator",
4608 Applicability::MaybeIncorrect,
4612 // Check to see if the user has written something like
4617 // Which is valid in other languages, but not Rust.
4618 match self.parse_stmt_without_recovery(false) {
4620 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
4621 || do_not_suggest_help {
4622 // if the next token is an open brace (e.g., `if a b {`), the place-
4623 // inside-a-block suggestion would be more likely wrong than right
4624 e.span_label(sp, "expected `{`");
4627 let mut stmt_span = stmt.span;
4628 // expand the span to include the semicolon, if it exists
4629 if self.eat(&token::Semi) {
4630 stmt_span = stmt_span.with_hi(self.prev_span.hi());
4632 let sugg = pprust::to_string(|s| {
4633 use crate::print::pprust::{PrintState, INDENT_UNIT};
4634 s.ibox(INDENT_UNIT)?;
4636 s.print_stmt(&stmt)?;
4637 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
4641 "try placing this code inside a block",
4643 // speculative, has been misleading in the past (closed Issue #46836)
4644 Applicability::MaybeIncorrect
4648 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4649 self.cancel(&mut e);
4653 e.span_label(sp, "expected `{`");
4657 self.parse_block_tail(lo, BlockCheckMode::Default)
4660 /// Parses a block. Inner attributes are allowed.
4661 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
4662 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
4665 self.expect(&token::OpenDelim(token::Brace))?;
4666 Ok((self.parse_inner_attributes()?,
4667 self.parse_block_tail(lo, BlockCheckMode::Default)?))
4670 /// Parses the rest of a block expression or function body.
4671 /// Precondition: already parsed the '{'.
4672 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
4673 let mut stmts = vec![];
4674 while !self.eat(&token::CloseDelim(token::Brace)) {
4675 let stmt = match self.parse_full_stmt(false) {
4678 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
4680 id: ast::DUMMY_NODE_ID,
4681 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
4687 if let Some(stmt) = stmt {
4689 } else if self.token == token::Eof {
4692 // Found only `;` or `}`.
4698 id: ast::DUMMY_NODE_ID,
4700 span: lo.to(self.prev_span),
4704 /// Parses a statement, including the trailing semicolon.
4705 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
4706 // skip looking for a trailing semicolon when we have an interpolated statement
4707 maybe_whole!(self, NtStmt, |x| Some(x));
4709 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
4711 None => return Ok(None),
4715 StmtKind::Expr(ref expr) if self.token != token::Eof => {
4716 // expression without semicolon
4717 if classify::expr_requires_semi_to_be_stmt(expr) {
4718 // Just check for errors and recover; do not eat semicolon yet.
4720 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
4723 self.recover_stmt();
4727 StmtKind::Local(..) => {
4728 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
4729 if macro_legacy_warnings && self.token != token::Semi {
4730 self.warn_missing_semicolon();
4732 self.expect_one_of(&[], &[token::Semi])?;
4738 if self.eat(&token::Semi) {
4739 stmt = stmt.add_trailing_semicolon();
4742 stmt.span = stmt.span.with_hi(self.prev_span.hi());
4746 fn warn_missing_semicolon(&self) {
4747 self.diagnostic().struct_span_warn(self.span, {
4748 &format!("expected `;`, found {}", self.this_token_descr())
4750 "This was erroneously allowed and will become a hard error in a future release"
4754 fn err_dotdotdot_syntax(&self, span: Span) {
4755 self.diagnostic().struct_span_err(span, {
4756 "unexpected token: `...`"
4758 span, "use `..` for an exclusive range", "..".to_owned(),
4759 Applicability::MaybeIncorrect
4761 span, "or `..=` for an inclusive range", "..=".to_owned(),
4762 Applicability::MaybeIncorrect
4766 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
4769 /// BOUND = TY_BOUND | LT_BOUND
4770 /// LT_BOUND = LIFETIME (e.g., `'a`)
4771 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
4772 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
4774 fn parse_generic_bounds_common(&mut self,
4776 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4777 let mut bounds = Vec::new();
4778 let mut negative_bounds = Vec::new();
4779 let mut last_plus_span = None;
4780 let mut was_negative = false;
4782 // This needs to be synchronized with `TokenKind::can_begin_bound`.
4783 let is_bound_start = self.check_path() || self.check_lifetime() ||
4784 self.check(&token::Not) || // used for error reporting only
4785 self.check(&token::Question) ||
4786 self.check_keyword(kw::For) ||
4787 self.check(&token::OpenDelim(token::Paren));
4790 let has_parens = self.eat(&token::OpenDelim(token::Paren));
4791 let inner_lo = self.span;
4792 let is_negative = self.eat(&token::Not);
4793 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
4794 if self.token.is_lifetime() {
4795 if let Some(question_span) = question {
4796 self.span_err(question_span,
4797 "`?` may only modify trait bounds, not lifetime bounds");
4799 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
4801 let inner_span = inner_lo.to(self.prev_span);
4802 self.expect(&token::CloseDelim(token::Paren))?;
4803 let mut err = self.struct_span_err(
4804 lo.to(self.prev_span),
4805 "parenthesized lifetime bounds are not supported"
4807 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
4808 err.span_suggestion_short(
4809 lo.to(self.prev_span),
4810 "remove the parentheses",
4812 Applicability::MachineApplicable
4818 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
4819 let path = self.parse_path(PathStyle::Type)?;
4821 self.expect(&token::CloseDelim(token::Paren))?;
4823 let poly_span = lo.to(self.prev_span);
4825 was_negative = true;
4826 if let Some(sp) = last_plus_span.or(colon_span) {
4827 negative_bounds.push(sp.to(poly_span));
4830 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
4831 let modifier = if question.is_some() {
4832 TraitBoundModifier::Maybe
4834 TraitBoundModifier::None
4836 bounds.push(GenericBound::Trait(poly_trait, modifier));
4843 if !allow_plus || !self.eat_plus() {
4846 last_plus_span = Some(self.prev_span);
4850 if !negative_bounds.is_empty() || was_negative {
4851 let plural = negative_bounds.len() > 1;
4852 let last_span = negative_bounds.last().map(|sp| *sp);
4853 let mut err = self.struct_span_err(
4855 "negative trait bounds are not supported",
4857 if let Some(sp) = last_span {
4858 err.span_label(sp, "negative trait bounds are not supported");
4860 if let Some(bound_list) = colon_span {
4861 let bound_list = bound_list.to(self.prev_span);
4862 let mut new_bound_list = String::new();
4863 if !bounds.is_empty() {
4864 let mut snippets = bounds.iter().map(|bound| bound.span())
4865 .map(|span| self.sess.source_map().span_to_snippet(span));
4866 while let Some(Ok(snippet)) = snippets.next() {
4867 new_bound_list.push_str(" + ");
4868 new_bound_list.push_str(&snippet);
4870 new_bound_list = new_bound_list.replacen(" +", ":", 1);
4872 err.span_suggestion_hidden(
4874 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
4876 Applicability::MachineApplicable,
4885 crate fn parse_generic_bounds(&mut self,
4886 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4887 self.parse_generic_bounds_common(true, colon_span)
4890 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4893 /// BOUND = LT_BOUND (e.g., `'a`)
4895 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
4896 let mut lifetimes = Vec::new();
4897 while self.check_lifetime() {
4898 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
4900 if !self.eat_plus() {
4907 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
4908 fn parse_ty_param(&mut self,
4909 preceding_attrs: Vec<Attribute>)
4910 -> PResult<'a, GenericParam> {
4911 let ident = self.parse_ident()?;
4913 // Parse optional colon and param bounds.
4914 let bounds = if self.eat(&token::Colon) {
4915 self.parse_generic_bounds(Some(self.prev_span))?
4920 let default = if self.eat(&token::Eq) {
4921 Some(self.parse_ty()?)
4928 id: ast::DUMMY_NODE_ID,
4929 attrs: preceding_attrs.into(),
4931 kind: GenericParamKind::Type {
4937 /// Parses the following grammar:
4939 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
4940 fn parse_trait_item_assoc_ty(&mut self)
4941 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
4942 let ident = self.parse_ident()?;
4943 let mut generics = self.parse_generics()?;
4945 // Parse optional colon and param bounds.
4946 let bounds = if self.eat(&token::Colon) {
4947 self.parse_generic_bounds(None)?
4951 generics.where_clause = self.parse_where_clause()?;
4953 let default = if self.eat(&token::Eq) {
4954 Some(self.parse_ty()?)
4958 self.expect(&token::Semi)?;
4960 Ok((ident, TraitItemKind::Type(bounds, default), generics))
4963 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
4964 self.expect_keyword(kw::Const)?;
4965 let ident = self.parse_ident()?;
4966 self.expect(&token::Colon)?;
4967 let ty = self.parse_ty()?;
4971 id: ast::DUMMY_NODE_ID,
4972 attrs: preceding_attrs.into(),
4974 kind: GenericParamKind::Const {
4980 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
4981 /// a trailing comma and erroneous trailing attributes.
4982 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
4983 let mut params = Vec::new();
4985 let attrs = self.parse_outer_attributes()?;
4986 if self.check_lifetime() {
4987 let lifetime = self.expect_lifetime();
4988 // Parse lifetime parameter.
4989 let bounds = if self.eat(&token::Colon) {
4990 self.parse_lt_param_bounds()
4994 params.push(ast::GenericParam {
4995 ident: lifetime.ident,
4997 attrs: attrs.into(),
4999 kind: ast::GenericParamKind::Lifetime,
5001 } else if self.check_keyword(kw::Const) {
5002 // Parse const parameter.
5003 params.push(self.parse_const_param(attrs)?);
5004 } else if self.check_ident() {
5005 // Parse type parameter.
5006 params.push(self.parse_ty_param(attrs)?);
5008 // Check for trailing attributes and stop parsing.
5009 if !attrs.is_empty() {
5010 if !params.is_empty() {
5011 self.struct_span_err(
5013 &format!("trailing attribute after generic parameter"),
5015 .span_label(attrs[0].span, "attributes must go before parameters")
5018 self.struct_span_err(
5020 &format!("attribute without generic parameters"),
5024 "attributes are only permitted when preceding parameters",
5032 if !self.eat(&token::Comma) {
5039 /// Parses a set of optional generic type parameter declarations. Where
5040 /// clauses are not parsed here, and must be added later via
5041 /// `parse_where_clause()`.
5043 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5044 /// | ( < lifetimes , typaramseq ( , )? > )
5045 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5046 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5047 let span_lo = self.span;
5048 let (params, span) = if self.eat_lt() {
5049 let params = self.parse_generic_params()?;
5051 (params, span_lo.to(self.prev_span))
5053 (vec![], self.prev_span.between(self.span))
5057 where_clause: WhereClause {
5058 id: ast::DUMMY_NODE_ID,
5059 predicates: Vec::new(),
5066 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5067 /// For the purposes of understanding the parsing logic of generic arguments, this function
5068 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5069 /// had the correct amount of leading angle brackets.
5071 /// ```ignore (diagnostics)
5072 /// bar::<<<<T as Foo>::Output>();
5073 /// ^^ help: remove extra angle brackets
5075 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5079 ) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
5080 // We need to detect whether there are extra leading left angle brackets and produce an
5081 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5082 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5083 // then there won't be matching `>` tokens to find.
5085 // To explain how this detection works, consider the following example:
5087 // ```ignore (diagnostics)
5088 // bar::<<<<T as Foo>::Output>();
5089 // ^^ help: remove extra angle brackets
5092 // Parsing of the left angle brackets starts in this function. We start by parsing the
5093 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5096 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5097 // *Unmatched count:* 1
5098 // *`parse_path_segment` calls deep:* 0
5100 // This has the effect of recursing as this function is called if a `<` character
5101 // is found within the expected generic arguments:
5103 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5104 // *Unmatched count:* 2
5105 // *`parse_path_segment` calls deep:* 1
5107 // Eventually we will have recursed until having consumed all of the `<` tokens and
5108 // this will be reflected in the count:
5110 // *Upcoming tokens:* `T as Foo>::Output>;`
5111 // *Unmatched count:* 4
5112 // `parse_path_segment` calls deep:* 3
5114 // The parser will continue until reaching the first `>` - this will decrement the
5115 // unmatched angle bracket count and return to the parent invocation of this function
5116 // having succeeded in parsing:
5118 // *Upcoming tokens:* `::Output>;`
5119 // *Unmatched count:* 3
5120 // *`parse_path_segment` calls deep:* 2
5122 // This will continue until the next `>` character which will also return successfully
5123 // to the parent invocation of this function and decrement the count:
5125 // *Upcoming tokens:* `;`
5126 // *Unmatched count:* 2
5127 // *`parse_path_segment` calls deep:* 1
5129 // At this point, this function will expect to find another matching `>` character but
5130 // won't be able to and will return an error. This will continue all the way up the
5131 // call stack until the first invocation:
5133 // *Upcoming tokens:* `;`
5134 // *Unmatched count:* 2
5135 // *`parse_path_segment` calls deep:* 0
5137 // In doing this, we have managed to work out how many unmatched leading left angle
5138 // brackets there are, but we cannot recover as the unmatched angle brackets have
5139 // already been consumed. To remedy this, we keep a snapshot of the parser state
5140 // before we do the above. We can then inspect whether we ended up with a parsing error
5141 // and unmatched left angle brackets and if so, restore the parser state before we
5142 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5143 // recover by attempting to parse again.
5145 // In practice, the recursion of this function is indirect and there will be other
5146 // locations that consume some `<` characters - as long as we update the count when
5147 // this happens, it isn't an issue.
5149 let is_first_invocation = style == PathStyle::Expr;
5150 // Take a snapshot before attempting to parse - we can restore this later.
5151 let snapshot = if is_first_invocation {
5157 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5158 match self.parse_generic_args() {
5159 Ok(value) => Ok(value),
5160 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5161 // Cancel error from being unable to find `>`. We know the error
5162 // must have been this due to a non-zero unmatched angle bracket
5166 // Swap `self` with our backup of the parser state before attempting to parse
5167 // generic arguments.
5168 let snapshot = mem::replace(self, snapshot.unwrap());
5171 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5172 snapshot.count={:?}",
5173 snapshot.unmatched_angle_bracket_count,
5176 // Eat the unmatched angle brackets.
5177 for _ in 0..snapshot.unmatched_angle_bracket_count {
5181 // Make a span over ${unmatched angle bracket count} characters.
5182 let span = lo.with_hi(
5183 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5185 let plural = snapshot.unmatched_angle_bracket_count > 1;
5190 "unmatched angle bracket{}",
5191 if plural { "s" } else { "" }
5197 "remove extra angle bracket{}",
5198 if plural { "s" } else { "" }
5201 Applicability::MachineApplicable,
5205 // Try again without unmatched angle bracket characters.
5206 self.parse_generic_args()
5212 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5213 /// possibly including trailing comma.
5214 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<AssocTyConstraint>)> {
5215 let mut args = Vec::new();
5216 let mut constraints = Vec::new();
5217 let mut misplaced_assoc_ty_constraints: Vec<Span> = Vec::new();
5218 let mut assoc_ty_constraints: Vec<Span> = Vec::new();
5220 let args_lo = self.span;
5223 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5224 // Parse lifetime argument.
5225 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5226 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5227 } else if self.check_ident() && self.look_ahead(1,
5228 |t| t == &token::Eq || t == &token::Colon) {
5229 // Parse associated type constraint.
5231 let ident = self.parse_ident()?;
5232 let kind = if self.eat(&token::Eq) {
5233 AssocTyConstraintKind::Equality {
5234 ty: self.parse_ty()?,
5236 } else if self.eat(&token::Colon) {
5237 AssocTyConstraintKind::Bound {
5238 bounds: self.parse_generic_bounds(Some(self.prev_span))?,
5243 let span = lo.to(self.prev_span);
5244 constraints.push(AssocTyConstraint {
5245 id: ast::DUMMY_NODE_ID,
5250 assoc_ty_constraints.push(span);
5251 } else if self.check_const_arg() {
5252 // Parse const argument.
5253 let expr = if let token::OpenDelim(token::Brace) = self.token {
5254 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
5255 } else if self.token.is_ident() {
5256 // FIXME(const_generics): to distinguish between idents for types and consts,
5257 // we should introduce a GenericArg::Ident in the AST and distinguish when
5258 // lowering to the HIR. For now, idents for const args are not permitted.
5259 if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
5260 self.parse_literal_maybe_minus()?
5263 self.fatal("identifiers may currently not be used for const generics")
5267 self.parse_literal_maybe_minus()?
5269 let value = AnonConst {
5270 id: ast::DUMMY_NODE_ID,
5273 args.push(GenericArg::Const(value));
5274 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5275 } else if self.check_type() {
5276 // Parse type argument.
5277 args.push(GenericArg::Type(self.parse_ty()?));
5278 misplaced_assoc_ty_constraints.append(&mut assoc_ty_constraints);
5283 if !self.eat(&token::Comma) {
5288 // FIXME: we would like to report this in ast_validation instead, but we currently do not
5289 // preserve ordering of generic parameters with respect to associated type binding, so we
5290 // lose that information after parsing.
5291 if misplaced_assoc_ty_constraints.len() > 0 {
5292 let mut err = self.struct_span_err(
5293 args_lo.to(self.prev_span),
5294 "associated type bindings must be declared after generic parameters",
5296 for span in misplaced_assoc_ty_constraints {
5299 "this associated type binding should be moved after the generic parameters",
5305 Ok((args, constraints))
5308 /// Parses an optional where-clause and places it in `generics`.
5310 /// ```ignore (only-for-syntax-highlight)
5311 /// where T : Trait<U, V> + 'b, 'a : 'b
5313 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5314 let mut where_clause = WhereClause {
5315 id: ast::DUMMY_NODE_ID,
5316 predicates: Vec::new(),
5317 span: self.prev_span.to(self.prev_span),
5320 if !self.eat_keyword(kw::Where) {
5321 return Ok(where_clause);
5323 let lo = self.prev_span;
5325 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5326 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5327 // change we parse those generics now, but report an error.
5328 if self.choose_generics_over_qpath() {
5329 let generics = self.parse_generics()?;
5330 self.struct_span_err(
5332 "generic parameters on `where` clauses are reserved for future use",
5334 .span_label(generics.span, "currently unsupported")
5340 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5341 let lifetime = self.expect_lifetime();
5342 // Bounds starting with a colon are mandatory, but possibly empty.
5343 self.expect(&token::Colon)?;
5344 let bounds = self.parse_lt_param_bounds();
5345 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5346 ast::WhereRegionPredicate {
5347 span: lo.to(self.prev_span),
5352 } else if self.check_type() {
5353 // Parse optional `for<'a, 'b>`.
5354 // This `for` is parsed greedily and applies to the whole predicate,
5355 // the bounded type can have its own `for` applying only to it.
5357 // * `for<'a> Trait1<'a>: Trait2<'a /* ok */>`
5358 // * `(for<'a> Trait1<'a>): Trait2<'a /* not ok */>`
5359 // * `for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /* ok */, 'b /* not ok */>`
5360 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5362 // Parse type with mandatory colon and (possibly empty) bounds,
5363 // or with mandatory equality sign and the second type.
5364 let ty = self.parse_ty()?;
5365 if self.eat(&token::Colon) {
5366 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
5367 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5368 ast::WhereBoundPredicate {
5369 span: lo.to(self.prev_span),
5370 bound_generic_params: lifetime_defs,
5375 // FIXME: Decide what should be used here, `=` or `==`.
5376 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5377 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5378 let rhs_ty = self.parse_ty()?;
5379 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5380 ast::WhereEqPredicate {
5381 span: lo.to(self.prev_span),
5384 id: ast::DUMMY_NODE_ID,
5388 return self.unexpected();
5394 if !self.eat(&token::Comma) {
5399 where_clause.span = lo.to(self.prev_span);
5403 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
5404 -> PResult<'a, (Vec<Arg> , bool)> {
5405 self.expect(&token::OpenDelim(token::Paren))?;
5408 let mut c_variadic = false;
5409 let (args, recovered): (Vec<Option<Arg>>, bool) =
5410 self.parse_seq_to_before_end(
5411 &token::CloseDelim(token::Paren),
5412 SeqSep::trailing_allowed(token::Comma),
5414 // If the argument is a C-variadic argument we should not
5415 // enforce named arguments.
5416 let enforce_named_args = if p.token == token::DotDotDot {
5421 match p.parse_arg_general(enforce_named_args, false,
5424 if let TyKind::CVarArgs = arg.ty.node {
5426 if p.token != token::CloseDelim(token::Paren) {
5429 "`...` must be the last argument of a C-variadic function");
5440 let lo = p.prev_span;
5441 // Skip every token until next possible arg or end.
5442 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5443 // Create a placeholder argument for proper arg count (issue #34264).
5444 let span = lo.to(p.prev_span);
5445 Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
5452 self.eat(&token::CloseDelim(token::Paren));
5455 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5457 if c_variadic && args.is_empty() {
5459 "C-variadic function must be declared with at least one named argument");
5462 Ok((args, c_variadic))
5465 /// Parses the argument list and result type of a function declaration.
5466 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
5468 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
5469 let ret_ty = self.parse_ret_ty(true)?;
5478 /// Returns the parsed optional self argument and whether a self shortcut was used.
5479 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
5480 let expect_ident = |this: &mut Self| match this.token {
5481 // Preserve hygienic context.
5482 token::Ident(ident, _) =>
5483 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
5486 let isolated_self = |this: &mut Self, n| {
5487 this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
5488 this.look_ahead(n + 1, |t| t != &token::ModSep)
5491 // Parse optional `self` parameter of a method.
5492 // Only a limited set of initial token sequences is considered `self` parameters; anything
5493 // else is parsed as a normal function parameter list, so some lookahead is required.
5494 let eself_lo = self.span;
5495 let (eself, eself_ident, eself_hi) = match self.token {
5496 token::BinOp(token::And) => {
5502 (if isolated_self(self, 1) {
5504 SelfKind::Region(None, Mutability::Immutable)
5505 } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
5506 isolated_self(self, 2) {
5509 SelfKind::Region(None, Mutability::Mutable)
5510 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5511 isolated_self(self, 2) {
5513 let lt = self.expect_lifetime();
5514 SelfKind::Region(Some(lt), Mutability::Immutable)
5515 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5516 self.is_keyword_ahead(2, &[kw::Mut]) &&
5517 isolated_self(self, 3) {
5519 let lt = self.expect_lifetime();
5521 SelfKind::Region(Some(lt), Mutability::Mutable)
5524 }, expect_ident(self), self.prev_span)
5526 token::BinOp(token::Star) => {
5531 // Emit special error for `self` cases.
5532 let msg = "cannot pass `self` by raw pointer";
5533 (if isolated_self(self, 1) {
5535 self.struct_span_err(self.span, msg)
5536 .span_label(self.span, msg)
5538 SelfKind::Value(Mutability::Immutable)
5539 } else if self.look_ahead(1, |t| t.is_mutability()) &&
5540 isolated_self(self, 2) {
5543 self.struct_span_err(self.span, msg)
5544 .span_label(self.span, msg)
5546 SelfKind::Value(Mutability::Immutable)
5549 }, expect_ident(self), self.prev_span)
5551 token::Ident(..) => {
5552 if isolated_self(self, 0) {
5555 let eself_ident = expect_ident(self);
5556 let eself_hi = self.prev_span;
5557 (if self.eat(&token::Colon) {
5558 let ty = self.parse_ty()?;
5559 SelfKind::Explicit(ty, Mutability::Immutable)
5561 SelfKind::Value(Mutability::Immutable)
5562 }, eself_ident, eself_hi)
5563 } else if self.token.is_keyword(kw::Mut) &&
5564 isolated_self(self, 1) {
5568 let eself_ident = expect_ident(self);
5569 let eself_hi = self.prev_span;
5570 (if self.eat(&token::Colon) {
5571 let ty = self.parse_ty()?;
5572 SelfKind::Explicit(ty, Mutability::Mutable)
5574 SelfKind::Value(Mutability::Mutable)
5575 }, eself_ident, eself_hi)
5580 _ => return Ok(None),
5583 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
5584 Ok(Some(Arg::from_self(eself, eself_ident)))
5587 /// Parses the parameter list and result type of a function that may have a `self` parameter.
5588 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
5589 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
5591 self.expect(&token::OpenDelim(token::Paren))?;
5593 // Parse optional self argument.
5594 let self_arg = self.parse_self_arg()?;
5596 // Parse the rest of the function parameter list.
5597 let sep = SeqSep::trailing_allowed(token::Comma);
5598 let (mut fn_inputs, recovered) = if let Some(self_arg) = self_arg {
5599 if self.check(&token::CloseDelim(token::Paren)) {
5600 (vec![self_arg], false)
5601 } else if self.eat(&token::Comma) {
5602 let mut fn_inputs = vec![self_arg];
5603 let (mut input, recovered) = self.parse_seq_to_before_end(
5604 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
5605 fn_inputs.append(&mut input);
5606 (fn_inputs, recovered)
5608 match self.expect_one_of(&[], &[]) {
5609 Err(err) => return Err(err),
5610 Ok(recovered) => (vec![self_arg], recovered),
5614 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5618 // Parse closing paren and return type.
5619 self.expect(&token::CloseDelim(token::Paren))?;
5621 // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
5622 self.deduplicate_recovered_arg_names(&mut fn_inputs);
5626 output: self.parse_ret_ty(true)?,
5631 /// Parses the `|arg, arg|` header of a closure.
5632 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
5633 let inputs_captures = {
5634 if self.eat(&token::OrOr) {
5637 self.expect(&token::BinOp(token::Or))?;
5638 let args = self.parse_seq_to_before_tokens(
5639 &[&token::BinOp(token::Or), &token::OrOr],
5640 SeqSep::trailing_allowed(token::Comma),
5641 TokenExpectType::NoExpect,
5642 |p| p.parse_fn_block_arg()
5648 let output = self.parse_ret_ty(true)?;
5651 inputs: inputs_captures,
5657 /// Parses the name and optional generic types of a function header.
5658 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
5659 let id = self.parse_ident()?;
5660 let generics = self.parse_generics()?;
5664 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
5665 attrs: Vec<Attribute>) -> P<Item> {
5669 id: ast::DUMMY_NODE_ID,
5677 /// Parses an item-position function declaration.
5678 fn parse_item_fn(&mut self,
5680 asyncness: Spanned<IsAsync>,
5681 constness: Spanned<Constness>,
5683 -> PResult<'a, ItemInfo> {
5684 let (ident, mut generics) = self.parse_fn_header()?;
5685 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
5686 let decl = self.parse_fn_decl(allow_c_variadic)?;
5687 generics.where_clause = self.parse_where_clause()?;
5688 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5689 let header = FnHeader { unsafety, asyncness, constness, abi };
5690 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
5693 /// Returns `true` if we are looking at `const ID`
5694 /// (returns `false` for things like `const fn`, etc.).
5695 fn is_const_item(&self) -> bool {
5696 self.token.is_keyword(kw::Const) &&
5697 !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
5700 /// Parses all the "front matter" for a `fn` declaration, up to
5701 /// and including the `fn` keyword:
5705 /// - `const unsafe fn`
5708 fn parse_fn_front_matter(&mut self)
5716 let is_const_fn = self.eat_keyword(kw::Const);
5717 let const_span = self.prev_span;
5718 let unsafety = self.parse_unsafety();
5719 let asyncness = self.parse_asyncness();
5720 let asyncness = respan(self.prev_span, asyncness);
5721 let (constness, unsafety, abi) = if is_const_fn {
5722 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
5724 let abi = if self.eat_keyword(kw::Extern) {
5725 self.parse_opt_abi()?.unwrap_or(Abi::C)
5729 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
5731 if !self.eat_keyword(kw::Fn) {
5732 // It is possible for `expect_one_of` to recover given the contents of
5733 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
5734 // account for this.
5735 if !self.expect_one_of(&[], &[])? { unreachable!() }
5737 Ok((constness, unsafety, asyncness, abi))
5740 /// Parses an impl item.
5741 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
5742 maybe_whole!(self, NtImplItem, |x| x);
5743 let attrs = self.parse_outer_attributes()?;
5744 let mut unclosed_delims = vec![];
5745 let (mut item, tokens) = self.collect_tokens(|this| {
5746 let item = this.parse_impl_item_(at_end, attrs);
5747 unclosed_delims.append(&mut this.unclosed_delims);
5750 self.unclosed_delims.append(&mut unclosed_delims);
5752 // See `parse_item` for why this clause is here.
5753 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
5754 item.tokens = Some(tokens);
5759 fn parse_impl_item_(&mut self,
5761 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
5763 let vis = self.parse_visibility(false)?;
5764 let defaultness = self.parse_defaultness();
5765 let (name, node, generics) = if let Some(type_) = self.eat_type() {
5766 let (name, alias, generics) = type_?;
5767 let kind = match alias {
5768 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
5769 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
5771 (name, kind, generics)
5772 } else if self.is_const_item() {
5773 // This parses the grammar:
5774 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
5775 self.expect_keyword(kw::Const)?;
5776 let name = self.parse_ident()?;
5777 self.expect(&token::Colon)?;
5778 let typ = self.parse_ty()?;
5779 self.expect(&token::Eq)?;
5780 let expr = self.parse_expr()?;
5781 self.expect(&token::Semi)?;
5782 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
5784 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
5785 attrs.extend(inner_attrs);
5786 (name, node, generics)
5790 id: ast::DUMMY_NODE_ID,
5791 span: lo.to(self.prev_span),
5802 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
5804 VisibilityKind::Inherited => {}
5806 let is_macro_rules: bool = match self.token {
5807 token::Ident(sid, _) => sid.name == sym::macro_rules,
5810 let mut err = if is_macro_rules {
5811 let mut err = self.diagnostic()
5812 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
5813 err.span_suggestion(
5815 "try exporting the macro",
5816 "#[macro_export]".to_owned(),
5817 Applicability::MaybeIncorrect // speculative
5821 let mut err = self.diagnostic()
5822 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
5823 err.help("try adjusting the macro to put `pub` inside the invocation");
5831 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
5832 -> DiagnosticBuilder<'a>
5834 let expected_kinds = if item_type == "extern" {
5835 "missing `fn`, `type`, or `static`"
5837 "missing `fn`, `type`, or `const`"
5840 // Given this code `path(`, it seems like this is not
5841 // setting the visibility of a macro invocation, but rather
5842 // a mistyped method declaration.
5843 // Create a diagnostic pointing out that `fn` is missing.
5845 // x | pub path(&self) {
5846 // | ^ missing `fn`, `type`, or `const`
5848 // ^^ `sp` below will point to this
5849 let sp = prev_span.between(self.prev_span);
5850 let mut err = self.diagnostic().struct_span_err(
5852 &format!("{} for {}-item declaration",
5853 expected_kinds, item_type));
5854 err.span_label(sp, expected_kinds);
5858 /// Parse a method or a macro invocation in a trait impl.
5859 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
5860 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
5861 ast::ImplItemKind)> {
5862 // code copied from parse_macro_use_or_failure... abstraction!
5863 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
5865 Ok((Ident::invalid(), vec![], ast::Generics::default(),
5866 ast::ImplItemKind::Macro(mac)))
5868 let (constness, unsafety, asyncness, abi) = self.parse_fn_front_matter()?;
5869 let ident = self.parse_ident()?;
5870 let mut generics = self.parse_generics()?;
5871 let decl = self.parse_fn_decl_with_self(|p| {
5872 p.parse_arg_general(true, true, false)
5874 generics.where_clause = self.parse_where_clause()?;
5876 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5877 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
5878 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
5879 ast::MethodSig { header, decl },
5885 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
5886 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
5887 let ident = self.parse_ident()?;
5888 let mut tps = self.parse_generics()?;
5890 // Parse optional colon and supertrait bounds.
5891 let bounds = if self.eat(&token::Colon) {
5892 self.parse_generic_bounds(Some(self.prev_span))?
5897 if self.eat(&token::Eq) {
5898 // it's a trait alias
5899 let bounds = self.parse_generic_bounds(None)?;
5900 tps.where_clause = self.parse_where_clause()?;
5901 self.expect(&token::Semi)?;
5902 if is_auto == IsAuto::Yes {
5903 let msg = "trait aliases cannot be `auto`";
5904 self.struct_span_err(self.prev_span, msg)
5905 .span_label(self.prev_span, msg)
5908 if unsafety != Unsafety::Normal {
5909 let msg = "trait aliases cannot be `unsafe`";
5910 self.struct_span_err(self.prev_span, msg)
5911 .span_label(self.prev_span, msg)
5914 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
5916 // it's a normal trait
5917 tps.where_clause = self.parse_where_clause()?;
5918 self.expect(&token::OpenDelim(token::Brace))?;
5919 let mut trait_items = vec![];
5920 while !self.eat(&token::CloseDelim(token::Brace)) {
5921 if let token::DocComment(_) = self.token {
5922 if self.look_ahead(1,
5923 |tok| tok == &token::CloseDelim(token::Brace)) {
5924 let mut err = self.diagnostic().struct_span_err_with_code(
5926 "found a documentation comment that doesn't document anything",
5927 DiagnosticId::Error("E0584".into()),
5929 err.help("doc comments must come before what they document, maybe a \
5930 comment was intended with `//`?",
5937 let mut at_end = false;
5938 match self.parse_trait_item(&mut at_end) {
5939 Ok(item) => trait_items.push(item),
5943 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5948 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
5952 fn choose_generics_over_qpath(&self) -> bool {
5953 // There's an ambiguity between generic parameters and qualified paths in impls.
5954 // If we see `<` it may start both, so we have to inspect some following tokens.
5955 // The following combinations can only start generics,
5956 // but not qualified paths (with one exception):
5957 // `<` `>` - empty generic parameters
5958 // `<` `#` - generic parameters with attributes
5959 // `<` (LIFETIME|IDENT) `>` - single generic parameter
5960 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
5961 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
5962 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
5963 // `<` const - generic const parameter
5964 // The only truly ambiguous case is
5965 // `<` IDENT `>` `::` IDENT ...
5966 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
5967 // because this is what almost always expected in practice, qualified paths in impls
5968 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
5969 self.token == token::Lt &&
5970 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
5971 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
5972 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
5973 t == &token::Colon || t == &token::Eq) ||
5974 self.is_keyword_ahead(1, &[kw::Const]))
5977 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
5978 self.expect(&token::OpenDelim(token::Brace))?;
5979 let attrs = self.parse_inner_attributes()?;
5981 let mut impl_items = Vec::new();
5982 while !self.eat(&token::CloseDelim(token::Brace)) {
5983 let mut at_end = false;
5984 match self.parse_impl_item(&mut at_end) {
5985 Ok(impl_item) => impl_items.push(impl_item),
5989 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5994 Ok((impl_items, attrs))
5997 /// Parses an implementation item, `impl` keyword is already parsed.
5999 /// impl<'a, T> TYPE { /* impl items */ }
6000 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
6001 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
6003 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
6004 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
6005 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
6006 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
6007 -> PResult<'a, ItemInfo> {
6008 // First, parse generic parameters if necessary.
6009 let mut generics = if self.choose_generics_over_qpath() {
6010 self.parse_generics()?
6012 ast::Generics::default()
6015 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6016 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6018 ast::ImplPolarity::Negative
6020 ast::ImplPolarity::Positive
6023 // Parse both types and traits as a type, then reinterpret if necessary.
6024 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
6025 let ty_first = if self.token.is_keyword(kw::For) &&
6026 self.look_ahead(1, |t| t != &token::Lt) {
6027 let span = self.prev_span.between(self.span);
6028 self.struct_span_err(span, "missing trait in a trait impl").emit();
6029 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6034 // If `for` is missing we try to recover.
6035 let has_for = self.eat_keyword(kw::For);
6036 let missing_for_span = self.prev_span.between(self.span);
6038 let ty_second = if self.token == token::DotDot {
6039 // We need to report this error after `cfg` expansion for compatibility reasons
6040 self.bump(); // `..`, do not add it to expected tokens
6041 Some(DummyResult::raw_ty(self.prev_span, true))
6042 } else if has_for || self.token.can_begin_type() {
6043 Some(self.parse_ty()?)
6048 generics.where_clause = self.parse_where_clause()?;
6050 let (impl_items, attrs) = self.parse_impl_body()?;
6052 let item_kind = match ty_second {
6053 Some(ty_second) => {
6054 // impl Trait for Type
6056 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6057 .span_suggestion_short(
6060 " for ".to_string(),
6061 Applicability::MachineApplicable,
6065 let ty_first = ty_first.into_inner();
6066 let path = match ty_first.node {
6067 // This notably includes paths passed through `ty` macro fragments (#46438).
6068 TyKind::Path(None, path) => path,
6070 self.span_err(ty_first.span, "expected a trait, found type");
6071 err_path(ty_first.span)
6074 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6076 ItemKind::Impl(unsafety, polarity, defaultness,
6077 generics, Some(trait_ref), ty_second, impl_items)
6081 ItemKind::Impl(unsafety, polarity, defaultness,
6082 generics, None, ty_first, impl_items)
6086 Ok((Ident::invalid(), item_kind, Some(attrs)))
6089 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6090 if self.eat_keyword(kw::For) {
6092 let params = self.parse_generic_params()?;
6094 // We rely on AST validation to rule out invalid cases: There must not be type
6095 // parameters, and the lifetime parameters must not have bounds.
6102 /// Parses `struct Foo { ... }`.
6103 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6104 let class_name = self.parse_ident()?;
6106 let mut generics = self.parse_generics()?;
6108 // There is a special case worth noting here, as reported in issue #17904.
6109 // If we are parsing a tuple struct it is the case that the where clause
6110 // should follow the field list. Like so:
6112 // struct Foo<T>(T) where T: Copy;
6114 // If we are parsing a normal record-style struct it is the case
6115 // that the where clause comes before the body, and after the generics.
6116 // So if we look ahead and see a brace or a where-clause we begin
6117 // parsing a record style struct.
6119 // Otherwise if we look ahead and see a paren we parse a tuple-style
6122 let vdata = if self.token.is_keyword(kw::Where) {
6123 generics.where_clause = self.parse_where_clause()?;
6124 if self.eat(&token::Semi) {
6125 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6126 VariantData::Unit(ast::DUMMY_NODE_ID)
6128 // If we see: `struct Foo<T> where T: Copy { ... }`
6129 let (fields, recovered) = self.parse_record_struct_body()?;
6130 VariantData::Struct(fields, recovered)
6132 // No `where` so: `struct Foo<T>;`
6133 } else if self.eat(&token::Semi) {
6134 VariantData::Unit(ast::DUMMY_NODE_ID)
6135 // Record-style struct definition
6136 } else if self.token == token::OpenDelim(token::Brace) {
6137 let (fields, recovered) = self.parse_record_struct_body()?;
6138 VariantData::Struct(fields, recovered)
6139 // Tuple-style struct definition with optional where-clause.
6140 } else if self.token == token::OpenDelim(token::Paren) {
6141 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6142 generics.where_clause = self.parse_where_clause()?;
6143 self.expect(&token::Semi)?;
6146 let token_str = self.this_token_descr();
6147 let mut err = self.fatal(&format!(
6148 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6151 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6155 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6158 /// Parses `union Foo { ... }`.
6159 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6160 let class_name = self.parse_ident()?;
6162 let mut generics = self.parse_generics()?;
6164 let vdata = if self.token.is_keyword(kw::Where) {
6165 generics.where_clause = self.parse_where_clause()?;
6166 let (fields, recovered) = self.parse_record_struct_body()?;
6167 VariantData::Struct(fields, recovered)
6168 } else if self.token == token::OpenDelim(token::Brace) {
6169 let (fields, recovered) = self.parse_record_struct_body()?;
6170 VariantData::Struct(fields, recovered)
6172 let token_str = self.this_token_descr();
6173 let mut err = self.fatal(&format!(
6174 "expected `where` or `{{` after union name, found {}", token_str));
6175 err.span_label(self.span, "expected `where` or `{` after union name");
6179 Ok((class_name, ItemKind::Union(vdata, generics), None))
6182 fn parse_record_struct_body(
6184 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6185 let mut fields = Vec::new();
6186 let mut recovered = false;
6187 if self.eat(&token::OpenDelim(token::Brace)) {
6188 while self.token != token::CloseDelim(token::Brace) {
6189 let field = self.parse_struct_decl_field().map_err(|e| {
6190 self.recover_stmt();
6195 Ok(field) => fields.push(field),
6201 self.eat(&token::CloseDelim(token::Brace));
6203 let token_str = self.this_token_descr();
6204 let mut err = self.fatal(&format!(
6205 "expected `where`, or `{{` after struct name, found {}", token_str));
6206 err.span_label(self.span, "expected `where`, or `{` after struct name");
6210 Ok((fields, recovered))
6213 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6214 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6215 // Unit like structs are handled in parse_item_struct function
6216 let fields = self.parse_unspanned_seq(
6217 &token::OpenDelim(token::Paren),
6218 &token::CloseDelim(token::Paren),
6219 SeqSep::trailing_allowed(token::Comma),
6221 let attrs = p.parse_outer_attributes()?;
6223 let vis = p.parse_visibility(true)?;
6224 let ty = p.parse_ty()?;
6226 span: lo.to(ty.span),
6229 id: ast::DUMMY_NODE_ID,
6238 /// Parses a structure field declaration.
6239 fn parse_single_struct_field(&mut self,
6242 attrs: Vec<Attribute> )
6243 -> PResult<'a, StructField> {
6244 let mut seen_comma: bool = false;
6245 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
6246 if self.token == token::Comma {
6253 token::CloseDelim(token::Brace) => {}
6254 token::DocComment(_) => {
6255 let previous_span = self.prev_span;
6256 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
6257 self.bump(); // consume the doc comment
6258 let comma_after_doc_seen = self.eat(&token::Comma);
6259 // `seen_comma` is always false, because we are inside doc block
6260 // condition is here to make code more readable
6261 if seen_comma == false && comma_after_doc_seen == true {
6264 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
6267 if seen_comma == false {
6268 let sp = self.sess.source_map().next_point(previous_span);
6269 err.span_suggestion(
6271 "missing comma here",
6273 Applicability::MachineApplicable
6280 let sp = self.sess.source_map().next_point(self.prev_span);
6281 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
6282 self.this_token_descr()));
6283 if self.token.is_ident() {
6284 // This is likely another field; emit the diagnostic and keep going
6285 err.span_suggestion(
6287 "try adding a comma",
6289 Applicability::MachineApplicable,
6300 /// Parses an element of a struct declaration.
6301 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6302 let attrs = self.parse_outer_attributes()?;
6304 let vis = self.parse_visibility(false)?;
6305 self.parse_single_struct_field(lo, vis, attrs)
6308 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
6309 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
6310 /// If the following element can't be a tuple (i.e., it's a function definition), then
6311 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
6312 /// so emit a proper diagnostic.
6313 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6314 maybe_whole!(self, NtVis, |x| x);
6316 self.expected_tokens.push(TokenType::Keyword(kw::Crate));
6317 if self.is_crate_vis() {
6318 self.bump(); // `crate`
6319 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6322 if !self.eat_keyword(kw::Pub) {
6323 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6324 // keyword to grab a span from for inherited visibility; an empty span at the
6325 // beginning of the current token would seem to be the "Schelling span".
6326 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
6328 let lo = self.prev_span;
6330 if self.check(&token::OpenDelim(token::Paren)) {
6331 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6332 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6333 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6334 // by the following tokens.
6335 if self.is_keyword_ahead(1, &[kw::Crate]) &&
6336 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
6340 self.bump(); // `crate`
6341 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6343 lo.to(self.prev_span),
6344 VisibilityKind::Crate(CrateSugar::PubCrate),
6347 } else if self.is_keyword_ahead(1, &[kw::In]) {
6350 self.bump(); // `in`
6351 let path = self.parse_path(PathStyle::Mod)?; // `path`
6352 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6353 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6355 id: ast::DUMMY_NODE_ID,
6358 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6359 self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
6361 // `pub(self)` or `pub(super)`
6363 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6364 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6365 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6367 id: ast::DUMMY_NODE_ID,
6370 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6371 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6373 let msg = "incorrect visibility restriction";
6374 let suggestion = r##"some possible visibility restrictions are:
6375 `pub(crate)`: visible only on the current crate
6376 `pub(super)`: visible only in the current module's parent
6377 `pub(in path::to::module)`: visible only on the specified path"##;
6378 let path = self.parse_path(PathStyle::Mod)?;
6380 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6381 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6382 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6383 err.help(suggestion);
6384 err.span_suggestion(
6385 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6387 err.emit(); // emit diagnostic, but continue with public visibility
6391 Ok(respan(lo, VisibilityKind::Public))
6394 /// Parses defaultness (i.e., `default` or nothing).
6395 fn parse_defaultness(&mut self) -> Defaultness {
6396 // `pub` is included for better error messages
6397 if self.check_keyword(kw::Default) &&
6398 self.is_keyword_ahead(1, &[
6408 self.bump(); // `default`
6409 Defaultness::Default
6415 /// Given a termination token, parses all of the items in a module.
6416 fn parse_mod_items(&mut self, term: &token::TokenKind, inner_lo: Span) -> PResult<'a, Mod> {
6417 let mut items = vec![];
6418 while let Some(item) = self.parse_item()? {
6420 self.maybe_consume_incorrect_semicolon(&items);
6423 if !self.eat(term) {
6424 let token_str = self.this_token_descr();
6425 if !self.maybe_consume_incorrect_semicolon(&items) {
6426 let mut err = self.fatal(&format!("expected item, found {}", token_str));
6427 err.span_label(self.span, "expected item");
6432 let hi = if self.span.is_dummy() {
6439 inner: inner_lo.to(hi),
6445 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6446 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
6447 self.expect(&token::Colon)?;
6448 let ty = self.parse_ty()?;
6449 self.expect(&token::Eq)?;
6450 let e = self.parse_expr()?;
6451 self.expect(&token::Semi)?;
6452 let item = match m {
6453 Some(m) => ItemKind::Static(ty, m, e),
6454 None => ItemKind::Const(ty, e),
6456 Ok((id, item, None))
6459 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6460 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6461 let (in_cfg, outer_attrs) = {
6462 let mut strip_unconfigured = crate::config::StripUnconfigured {
6464 features: None, // don't perform gated feature checking
6466 let mut outer_attrs = outer_attrs.to_owned();
6467 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
6468 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
6471 let id_span = self.span;
6472 let id = self.parse_ident()?;
6473 if self.eat(&token::Semi) {
6474 if in_cfg && self.recurse_into_file_modules {
6475 // This mod is in an external file. Let's go get it!
6476 let ModulePathSuccess { path, directory_ownership, warn } =
6477 self.submod_path(id, &outer_attrs, id_span)?;
6478 let (module, mut attrs) =
6479 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
6480 // Record that we fetched the mod from an external file
6482 let attr = Attribute {
6483 id: attr::mk_attr_id(),
6484 style: ast::AttrStyle::Outer,
6485 path: ast::Path::from_ident(
6486 Ident::with_empty_ctxt(sym::warn_directory_ownership)),
6487 tokens: TokenStream::empty(),
6488 is_sugared_doc: false,
6491 attr::mark_known(&attr);
6494 Ok((id, ItemKind::Mod(module), Some(attrs)))
6496 let placeholder = ast::Mod {
6501 Ok((id, ItemKind::Mod(placeholder), None))
6504 let old_directory = self.directory.clone();
6505 self.push_directory(id, &outer_attrs);
6507 self.expect(&token::OpenDelim(token::Brace))?;
6508 let mod_inner_lo = self.span;
6509 let attrs = self.parse_inner_attributes()?;
6510 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
6512 self.directory = old_directory;
6513 Ok((id, ItemKind::Mod(module), Some(attrs)))
6517 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
6518 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6519 self.directory.path.to_mut().push(&path.as_str());
6520 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
6522 // We have to push on the current module name in the case of relative
6523 // paths in order to ensure that any additional module paths from inline
6524 // `mod x { ... }` come after the relative extension.
6526 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
6527 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
6528 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
6529 if let Some(ident) = relative.take() { // remove the relative offset
6530 self.directory.path.to_mut().push(ident.as_str());
6533 self.directory.path.to_mut().push(&id.as_str());
6537 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
6538 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6541 // On windows, the base path might have the form
6542 // `\\?\foo\bar` in which case it does not tolerate
6543 // mixed `/` and `\` separators, so canonicalize
6546 let s = s.replace("/", "\\");
6547 Some(dir_path.join(s))
6553 /// Returns a path to a module.
6554 pub fn default_submod_path(
6556 relative: Option<ast::Ident>,
6558 source_map: &SourceMap) -> ModulePath
6560 // If we're in a foo.rs file instead of a mod.rs file,
6561 // we need to look for submodules in
6562 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
6563 // `./<id>.rs` and `./<id>/mod.rs`.
6564 let relative_prefix_string;
6565 let relative_prefix = if let Some(ident) = relative {
6566 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
6567 &relative_prefix_string
6572 let mod_name = id.to_string();
6573 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
6574 let secondary_path_str = format!("{}{}{}mod.rs",
6575 relative_prefix, mod_name, path::MAIN_SEPARATOR);
6576 let default_path = dir_path.join(&default_path_str);
6577 let secondary_path = dir_path.join(&secondary_path_str);
6578 let default_exists = source_map.file_exists(&default_path);
6579 let secondary_exists = source_map.file_exists(&secondary_path);
6581 let result = match (default_exists, secondary_exists) {
6582 (true, false) => Ok(ModulePathSuccess {
6584 directory_ownership: DirectoryOwnership::Owned {
6589 (false, true) => Ok(ModulePathSuccess {
6590 path: secondary_path,
6591 directory_ownership: DirectoryOwnership::Owned {
6596 (false, false) => Err(Error::FileNotFoundForModule {
6597 mod_name: mod_name.clone(),
6598 default_path: default_path_str,
6599 secondary_path: secondary_path_str,
6600 dir_path: dir_path.display().to_string(),
6602 (true, true) => Err(Error::DuplicatePaths {
6603 mod_name: mod_name.clone(),
6604 default_path: default_path_str,
6605 secondary_path: secondary_path_str,
6611 path_exists: default_exists || secondary_exists,
6616 fn submod_path(&mut self,
6618 outer_attrs: &[Attribute],
6620 -> PResult<'a, ModulePathSuccess> {
6621 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
6622 return Ok(ModulePathSuccess {
6623 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
6624 // All `#[path]` files are treated as though they are a `mod.rs` file.
6625 // This means that `mod foo;` declarations inside `#[path]`-included
6626 // files are siblings,
6628 // Note that this will produce weirdness when a file named `foo.rs` is
6629 // `#[path]` included and contains a `mod foo;` declaration.
6630 // If you encounter this, it's your own darn fault :P
6631 Some(_) => DirectoryOwnership::Owned { relative: None },
6632 _ => DirectoryOwnership::UnownedViaMod(true),
6639 let relative = match self.directory.ownership {
6640 DirectoryOwnership::Owned { relative } => relative,
6641 DirectoryOwnership::UnownedViaBlock |
6642 DirectoryOwnership::UnownedViaMod(_) => None,
6644 let paths = Parser::default_submod_path(
6645 id, relative, &self.directory.path, self.sess.source_map());
6647 match self.directory.ownership {
6648 DirectoryOwnership::Owned { .. } => {
6649 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
6651 DirectoryOwnership::UnownedViaBlock => {
6653 "Cannot declare a non-inline module inside a block \
6654 unless it has a path attribute";
6655 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
6656 if paths.path_exists {
6657 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
6659 err.span_note(id_sp, &msg);
6663 DirectoryOwnership::UnownedViaMod(warn) => {
6665 if let Ok(result) = paths.result {
6666 return Ok(ModulePathSuccess { warn: true, ..result });
6669 let mut err = self.diagnostic().struct_span_err(id_sp,
6670 "cannot declare a new module at this location");
6671 if !id_sp.is_dummy() {
6672 let src_path = self.sess.source_map().span_to_filename(id_sp);
6673 if let FileName::Real(src_path) = src_path {
6674 if let Some(stem) = src_path.file_stem() {
6675 let mut dest_path = src_path.clone();
6676 dest_path.set_file_name(stem);
6677 dest_path.push("mod.rs");
6678 err.span_note(id_sp,
6679 &format!("maybe move this module `{}` to its own \
6680 directory via `{}`", src_path.display(),
6681 dest_path.display()));
6685 if paths.path_exists {
6686 err.span_note(id_sp,
6687 &format!("... or maybe `use` the module `{}` instead \
6688 of possibly redeclaring it",
6696 /// Reads a module from a source file.
6697 fn eval_src_mod(&mut self,
6699 directory_ownership: DirectoryOwnership,
6702 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
6703 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
6704 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
6705 let mut err = String::from("circular modules: ");
6706 let len = included_mod_stack.len();
6707 for p in &included_mod_stack[i.. len] {
6708 err.push_str(&p.to_string_lossy());
6709 err.push_str(" -> ");
6711 err.push_str(&path.to_string_lossy());
6712 return Err(self.span_fatal(id_sp, &err[..]));
6714 included_mod_stack.push(path.clone());
6715 drop(included_mod_stack);
6718 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
6719 p0.cfg_mods = self.cfg_mods;
6720 let mod_inner_lo = p0.span;
6721 let mod_attrs = p0.parse_inner_attributes()?;
6722 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
6724 self.sess.included_mod_stack.borrow_mut().pop();
6728 /// Parses a function declaration from a foreign module.
6729 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6730 -> PResult<'a, ForeignItem> {
6731 self.expect_keyword(kw::Fn)?;
6733 let (ident, mut generics) = self.parse_fn_header()?;
6734 let decl = self.parse_fn_decl(true)?;
6735 generics.where_clause = self.parse_where_clause()?;
6737 self.expect(&token::Semi)?;
6738 Ok(ast::ForeignItem {
6741 node: ForeignItemKind::Fn(decl, generics),
6742 id: ast::DUMMY_NODE_ID,
6748 /// Parses a static item from a foreign module.
6749 /// Assumes that the `static` keyword is already parsed.
6750 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6751 -> PResult<'a, ForeignItem> {
6752 let mutbl = self.parse_mutability();
6753 let ident = self.parse_ident()?;
6754 self.expect(&token::Colon)?;
6755 let ty = self.parse_ty()?;
6757 self.expect(&token::Semi)?;
6761 node: ForeignItemKind::Static(ty, mutbl),
6762 id: ast::DUMMY_NODE_ID,
6768 /// Parses a type from a foreign module.
6769 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6770 -> PResult<'a, ForeignItem> {
6771 self.expect_keyword(kw::Type)?;
6773 let ident = self.parse_ident()?;
6775 self.expect(&token::Semi)?;
6776 Ok(ast::ForeignItem {
6779 node: ForeignItemKind::Ty,
6780 id: ast::DUMMY_NODE_ID,
6786 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
6787 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
6788 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
6790 let mut ident = if self.token.is_keyword(kw::SelfLower) {
6791 self.parse_path_segment_ident()
6795 let mut idents = vec![];
6796 let mut replacement = vec![];
6797 let mut fixed_crate_name = false;
6798 // Accept `extern crate name-like-this` for better diagnostics
6799 let dash = token::BinOp(token::BinOpToken::Minus);
6800 if self.token == dash { // Do not include `-` as part of the expected tokens list
6801 while self.eat(&dash) {
6802 fixed_crate_name = true;
6803 replacement.push((self.prev_span, "_".to_string()));
6804 idents.push(self.parse_ident()?);
6807 if fixed_crate_name {
6808 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
6809 let mut fixed_name = format!("{}", ident.name);
6810 for part in idents {
6811 fixed_name.push_str(&format!("_{}", part.name));
6813 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
6815 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
6816 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
6817 err.multipart_suggestion(
6820 Applicability::MachineApplicable,
6827 /// Parses `extern crate` links.
6832 /// extern crate foo;
6833 /// extern crate bar as foo;
6835 fn parse_item_extern_crate(&mut self,
6837 visibility: Visibility,
6838 attrs: Vec<Attribute>)
6839 -> PResult<'a, P<Item>> {
6840 // Accept `extern crate name-like-this` for better diagnostics
6841 let orig_name = self.parse_crate_name_with_dashes()?;
6842 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
6843 (rename, Some(orig_name.name))
6847 self.expect(&token::Semi)?;
6849 let span = lo.to(self.prev_span);
6850 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
6853 /// Parses `extern` for foreign ABIs modules.
6855 /// `extern` is expected to have been
6856 /// consumed before calling this method.
6860 /// ```ignore (only-for-syntax-highlight)
6864 fn parse_item_foreign_mod(&mut self,
6866 opt_abi: Option<Abi>,
6867 visibility: Visibility,
6868 mut attrs: Vec<Attribute>)
6869 -> PResult<'a, P<Item>> {
6870 self.expect(&token::OpenDelim(token::Brace))?;
6872 let abi = opt_abi.unwrap_or(Abi::C);
6874 attrs.extend(self.parse_inner_attributes()?);
6876 let mut foreign_items = vec![];
6877 while !self.eat(&token::CloseDelim(token::Brace)) {
6878 foreign_items.push(self.parse_foreign_item()?);
6881 let prev_span = self.prev_span;
6882 let m = ast::ForeignMod {
6884 items: foreign_items
6886 let invalid = Ident::invalid();
6887 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
6890 /// Parses `type Foo = Bar;`
6892 /// `existential type Foo: Bar;`
6895 /// without modifying the parser state.
6896 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
6897 // This parses the grammar:
6898 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
6899 if self.check_keyword(kw::Type) ||
6900 self.check_keyword(kw::Existential) &&
6901 self.is_keyword_ahead(1, &[kw::Type]) {
6902 let existential = self.eat_keyword(kw::Existential);
6903 assert!(self.eat_keyword(kw::Type));
6904 Some(self.parse_existential_or_alias(existential))
6910 /// Parses a type alias or existential type.
6911 fn parse_existential_or_alias(
6914 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
6915 let ident = self.parse_ident()?;
6916 let mut tps = self.parse_generics()?;
6917 tps.where_clause = self.parse_where_clause()?;
6918 let alias = if existential {
6919 self.expect(&token::Colon)?;
6920 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6921 AliasKind::Existential(bounds)
6923 self.expect(&token::Eq)?;
6924 let ty = self.parse_ty()?;
6927 self.expect(&token::Semi)?;
6928 Ok((ident, alias, tps))
6931 /// Parses the part of an enum declaration following the `{`.
6932 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
6933 let mut variants = Vec::new();
6934 let mut any_disr = vec![];
6935 while self.token != token::CloseDelim(token::Brace) {
6936 let variant_attrs = self.parse_outer_attributes()?;
6937 let vlo = self.span;
6940 let mut disr_expr = None;
6942 let ident = self.parse_ident()?;
6943 if self.check(&token::OpenDelim(token::Brace)) {
6944 // Parse a struct variant.
6945 let (fields, recovered) = self.parse_record_struct_body()?;
6946 struct_def = VariantData::Struct(fields, recovered);
6947 } else if self.check(&token::OpenDelim(token::Paren)) {
6948 struct_def = VariantData::Tuple(
6949 self.parse_tuple_struct_body()?,
6952 } else if self.eat(&token::Eq) {
6953 disr_expr = Some(AnonConst {
6954 id: ast::DUMMY_NODE_ID,
6955 value: self.parse_expr()?,
6957 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
6960 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6962 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6965 let vr = ast::Variant_ {
6967 id: ast::DUMMY_NODE_ID,
6968 attrs: variant_attrs,
6972 variants.push(respan(vlo.to(self.prev_span), vr));
6974 if !self.eat(&token::Comma) {
6975 if self.token.is_ident() && !self.token.is_reserved_ident() {
6976 let sp = self.sess.source_map().next_point(self.prev_span);
6977 let mut err = self.struct_span_err(sp, "missing comma");
6978 err.span_suggestion_short(
6982 Applicability::MaybeIncorrect,
6990 self.expect(&token::CloseDelim(token::Brace))?;
6991 self.maybe_report_invalid_custom_discriminants(any_disr, &variants);
6993 Ok(ast::EnumDef { variants })
6996 /// Parses an enum declaration.
6997 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
6998 let id = self.parse_ident()?;
6999 let mut generics = self.parse_generics()?;
7000 generics.where_clause = self.parse_where_clause()?;
7001 self.expect(&token::OpenDelim(token::Brace))?;
7003 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
7004 self.recover_stmt();
7005 self.eat(&token::CloseDelim(token::Brace));
7008 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7011 /// Parses a string as an ABI spec on an extern type or module. Consumes
7012 /// the `extern` keyword, if one is found.
7013 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7015 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
7016 token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
7018 self.expect_no_suffix(sp, "an ABI spec", suffix);
7020 match abi::lookup(&symbol.as_str()) {
7021 Some(abi) => Ok(Some(abi)),
7023 let prev_span = self.prev_span;
7024 let mut err = struct_span_err!(
7025 self.sess.span_diagnostic,
7028 "invalid ABI: found `{}`",
7030 err.span_label(prev_span, "invalid ABI");
7031 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7042 fn is_static_global(&mut self) -> bool {
7043 if self.check_keyword(kw::Static) {
7044 // Check if this could be a closure
7045 !self.look_ahead(1, |token| {
7046 if token.is_keyword(kw::Move) {
7050 token::BinOp(token::Or) | token::OrOr => true,
7061 attrs: Vec<Attribute>,
7062 macros_allowed: bool,
7063 attributes_allowed: bool,
7064 ) -> PResult<'a, Option<P<Item>>> {
7065 let mut unclosed_delims = vec![];
7066 let (ret, tokens) = self.collect_tokens(|this| {
7067 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7068 unclosed_delims.append(&mut this.unclosed_delims);
7071 self.unclosed_delims.append(&mut unclosed_delims);
7073 // Once we've parsed an item and recorded the tokens we got while
7074 // parsing we may want to store `tokens` into the item we're about to
7075 // return. Note, though, that we specifically didn't capture tokens
7076 // related to outer attributes. The `tokens` field here may later be
7077 // used with procedural macros to convert this item back into a token
7078 // stream, but during expansion we may be removing attributes as we go
7081 // If we've got inner attributes then the `tokens` we've got above holds
7082 // these inner attributes. If an inner attribute is expanded we won't
7083 // actually remove it from the token stream, so we'll just keep yielding
7084 // it (bad!). To work around this case for now we just avoid recording
7085 // `tokens` if we detect any inner attributes. This should help keep
7086 // expansion correct, but we should fix this bug one day!
7089 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7090 i.tokens = Some(tokens);
7097 /// Parses one of the items allowed by the flags.
7098 fn parse_item_implementation(
7100 attrs: Vec<Attribute>,
7101 macros_allowed: bool,
7102 attributes_allowed: bool,
7103 ) -> PResult<'a, Option<P<Item>>> {
7104 maybe_whole!(self, NtItem, |item| {
7105 let mut item = item.into_inner();
7106 let mut attrs = attrs;
7107 mem::swap(&mut item.attrs, &mut attrs);
7108 item.attrs.extend(attrs);
7114 let visibility = self.parse_visibility(false)?;
7116 if self.eat_keyword(kw::Use) {
7118 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7119 self.expect(&token::Semi)?;
7121 let span = lo.to(self.prev_span);
7123 self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
7124 return Ok(Some(item));
7127 if self.eat_keyword(kw::Extern) {
7128 if self.eat_keyword(kw::Crate) {
7129 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7132 let opt_abi = self.parse_opt_abi()?;
7134 if self.eat_keyword(kw::Fn) {
7135 // EXTERN FUNCTION ITEM
7136 let fn_span = self.prev_span;
7137 let abi = opt_abi.unwrap_or(Abi::C);
7138 let (ident, item_, extra_attrs) =
7139 self.parse_item_fn(Unsafety::Normal,
7140 respan(fn_span, IsAsync::NotAsync),
7141 respan(fn_span, Constness::NotConst),
7143 let prev_span = self.prev_span;
7144 let item = self.mk_item(lo.to(prev_span),
7148 maybe_append(attrs, extra_attrs));
7149 return Ok(Some(item));
7150 } else if self.check(&token::OpenDelim(token::Brace)) {
7151 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7157 if self.is_static_global() {
7160 let m = if self.eat_keyword(kw::Mut) {
7163 Mutability::Immutable
7165 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7166 let prev_span = self.prev_span;
7167 let item = self.mk_item(lo.to(prev_span),
7171 maybe_append(attrs, extra_attrs));
7172 return Ok(Some(item));
7174 if self.eat_keyword(kw::Const) {
7175 let const_span = self.prev_span;
7176 if self.check_keyword(kw::Fn)
7177 || (self.check_keyword(kw::Unsafe)
7178 && self.is_keyword_ahead(1, &[kw::Fn])) {
7179 // CONST FUNCTION ITEM
7180 let unsafety = self.parse_unsafety();
7182 let (ident, item_, extra_attrs) =
7183 self.parse_item_fn(unsafety,
7184 respan(const_span, IsAsync::NotAsync),
7185 respan(const_span, Constness::Const),
7187 let prev_span = self.prev_span;
7188 let item = self.mk_item(lo.to(prev_span),
7192 maybe_append(attrs, extra_attrs));
7193 return Ok(Some(item));
7197 if self.eat_keyword(kw::Mut) {
7198 let prev_span = self.prev_span;
7199 let mut err = self.diagnostic()
7200 .struct_span_err(prev_span, "const globals cannot be mutable");
7201 err.span_label(prev_span, "cannot be mutable");
7202 err.span_suggestion(
7204 "you might want to declare a static instead",
7205 "static".to_owned(),
7206 Applicability::MaybeIncorrect,
7210 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
7211 let prev_span = self.prev_span;
7212 let item = self.mk_item(lo.to(prev_span),
7216 maybe_append(attrs, extra_attrs));
7217 return Ok(Some(item));
7220 // Parse `async unsafe? fn`.
7221 if self.check_keyword(kw::Async) {
7222 let async_span = self.span;
7223 if self.is_keyword_ahead(1, &[kw::Fn])
7224 || self.is_keyword_ahead(2, &[kw::Fn])
7226 // ASYNC FUNCTION ITEM
7227 self.bump(); // `async`
7228 let unsafety = self.parse_unsafety(); // `unsafe`?
7229 self.expect_keyword(kw::Fn)?; // `fn`
7230 let fn_span = self.prev_span;
7231 let (ident, item_, extra_attrs) =
7232 self.parse_item_fn(unsafety,
7233 respan(async_span, IsAsync::Async {
7234 closure_id: ast::DUMMY_NODE_ID,
7235 return_impl_trait_id: ast::DUMMY_NODE_ID,
7237 respan(fn_span, Constness::NotConst),
7239 let prev_span = self.prev_span;
7240 let item = self.mk_item(lo.to(prev_span),
7244 maybe_append(attrs, extra_attrs));
7245 if self.span.rust_2015() {
7246 self.diagnostic().struct_span_err_with_code(
7248 "`async fn` is not permitted in the 2015 edition",
7249 DiagnosticId::Error("E0670".into())
7252 return Ok(Some(item));
7255 if self.check_keyword(kw::Unsafe) &&
7256 self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
7258 // UNSAFE TRAIT ITEM
7259 self.bump(); // `unsafe`
7260 let is_auto = if self.eat_keyword(kw::Trait) {
7263 self.expect_keyword(kw::Auto)?;
7264 self.expect_keyword(kw::Trait)?;
7267 let (ident, item_, extra_attrs) =
7268 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
7269 let prev_span = self.prev_span;
7270 let item = self.mk_item(lo.to(prev_span),
7274 maybe_append(attrs, extra_attrs));
7275 return Ok(Some(item));
7277 if self.check_keyword(kw::Impl) ||
7278 self.check_keyword(kw::Unsafe) &&
7279 self.is_keyword_ahead(1, &[kw::Impl]) ||
7280 self.check_keyword(kw::Default) &&
7281 self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
7283 let defaultness = self.parse_defaultness();
7284 let unsafety = self.parse_unsafety();
7285 self.expect_keyword(kw::Impl)?;
7286 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
7287 let span = lo.to(self.prev_span);
7288 return Ok(Some(self.mk_item(span, ident, item, visibility,
7289 maybe_append(attrs, extra_attrs))));
7291 if self.check_keyword(kw::Fn) {
7294 let fn_span = self.prev_span;
7295 let (ident, item_, extra_attrs) =
7296 self.parse_item_fn(Unsafety::Normal,
7297 respan(fn_span, IsAsync::NotAsync),
7298 respan(fn_span, Constness::NotConst),
7300 let prev_span = self.prev_span;
7301 let item = self.mk_item(lo.to(prev_span),
7305 maybe_append(attrs, extra_attrs));
7306 return Ok(Some(item));
7308 if self.check_keyword(kw::Unsafe)
7309 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
7310 // UNSAFE FUNCTION ITEM
7311 self.bump(); // `unsafe`
7312 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
7313 self.check(&token::OpenDelim(token::Brace));
7314 let abi = if self.eat_keyword(kw::Extern) {
7315 self.parse_opt_abi()?.unwrap_or(Abi::C)
7319 self.expect_keyword(kw::Fn)?;
7320 let fn_span = self.prev_span;
7321 let (ident, item_, extra_attrs) =
7322 self.parse_item_fn(Unsafety::Unsafe,
7323 respan(fn_span, IsAsync::NotAsync),
7324 respan(fn_span, Constness::NotConst),
7326 let prev_span = self.prev_span;
7327 let item = self.mk_item(lo.to(prev_span),
7331 maybe_append(attrs, extra_attrs));
7332 return Ok(Some(item));
7334 if self.eat_keyword(kw::Mod) {
7336 let (ident, item_, extra_attrs) =
7337 self.parse_item_mod(&attrs[..])?;
7338 let prev_span = self.prev_span;
7339 let item = self.mk_item(lo.to(prev_span),
7343 maybe_append(attrs, extra_attrs));
7344 return Ok(Some(item));
7346 if let Some(type_) = self.eat_type() {
7347 let (ident, alias, generics) = type_?;
7349 let item_ = match alias {
7350 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7351 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7353 let prev_span = self.prev_span;
7354 let item = self.mk_item(lo.to(prev_span),
7359 return Ok(Some(item));
7361 if self.eat_keyword(kw::Enum) {
7363 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7364 let prev_span = self.prev_span;
7365 let item = self.mk_item(lo.to(prev_span),
7369 maybe_append(attrs, extra_attrs));
7370 return Ok(Some(item));
7372 if self.check_keyword(kw::Trait)
7373 || (self.check_keyword(kw::Auto)
7374 && self.is_keyword_ahead(1, &[kw::Trait]))
7376 let is_auto = if self.eat_keyword(kw::Trait) {
7379 self.expect_keyword(kw::Auto)?;
7380 self.expect_keyword(kw::Trait)?;
7384 let (ident, item_, extra_attrs) =
7385 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7386 let prev_span = self.prev_span;
7387 let item = self.mk_item(lo.to(prev_span),
7391 maybe_append(attrs, extra_attrs));
7392 return Ok(Some(item));
7394 if self.eat_keyword(kw::Struct) {
7396 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7397 let prev_span = self.prev_span;
7398 let item = self.mk_item(lo.to(prev_span),
7402 maybe_append(attrs, extra_attrs));
7403 return Ok(Some(item));
7405 if self.is_union_item() {
7408 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7409 let prev_span = self.prev_span;
7410 let item = self.mk_item(lo.to(prev_span),
7414 maybe_append(attrs, extra_attrs));
7415 return Ok(Some(item));
7417 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7418 return Ok(Some(macro_def));
7421 // Verify whether we have encountered a struct or method definition where the user forgot to
7422 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7423 if visibility.node.is_pub() &&
7424 self.check_ident() &&
7425 self.look_ahead(1, |t| *t != token::Not)
7427 // Space between `pub` keyword and the identifier
7430 // ^^^ `sp` points here
7431 let sp = self.prev_span.between(self.span);
7432 let full_sp = self.prev_span.to(self.span);
7433 let ident_sp = self.span;
7434 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7435 // possible public struct definition where `struct` was forgotten
7436 let ident = self.parse_ident().unwrap();
7437 let msg = format!("add `struct` here to parse `{}` as a public struct",
7439 let mut err = self.diagnostic()
7440 .struct_span_err(sp, "missing `struct` for struct definition");
7441 err.span_suggestion_short(
7442 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7445 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7446 let ident = self.parse_ident().unwrap();
7448 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
7453 self.consume_block(token::Paren);
7454 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
7455 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
7457 ("fn", kw_name, false)
7458 } else if self.check(&token::OpenDelim(token::Brace)) {
7460 ("fn", kw_name, false)
7461 } else if self.check(&token::Colon) {
7465 ("fn` or `struct", "function or struct", true)
7468 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7469 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7471 self.consume_block(token::Brace);
7472 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
7476 err.span_suggestion_short(
7477 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
7480 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
7481 err.span_suggestion(
7483 "if you meant to call a macro, try",
7484 format!("{}!", snippet),
7485 // this is the `ambiguous` conditional branch
7486 Applicability::MaybeIncorrect
7489 err.help("if you meant to call a macro, remove the `pub` \
7490 and add a trailing `!` after the identifier");
7494 } else if self.look_ahead(1, |t| *t == token::Lt) {
7495 let ident = self.parse_ident().unwrap();
7496 self.eat_to_tokens(&[&token::Gt]);
7498 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
7499 if let Ok(Some(_)) = self.parse_self_arg() {
7500 ("fn", "method", false)
7502 ("fn", "function", false)
7504 } else if self.check(&token::OpenDelim(token::Brace)) {
7505 ("struct", "struct", false)
7507 ("fn` or `struct", "function or struct", true)
7509 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7510 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7512 err.span_suggestion_short(
7514 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
7515 format!(" {} ", kw),
7516 Applicability::MachineApplicable,
7522 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
7525 /// Parses a foreign item.
7526 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
7527 maybe_whole!(self, NtForeignItem, |ni| ni);
7529 let attrs = self.parse_outer_attributes()?;
7531 let visibility = self.parse_visibility(false)?;
7533 // FOREIGN STATIC ITEM
7534 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
7535 if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
7536 if self.token.is_keyword(kw::Const) {
7538 .struct_span_err(self.span, "extern items cannot be `const`")
7541 "try using a static value",
7542 "static".to_owned(),
7543 Applicability::MachineApplicable
7546 self.bump(); // `static` or `const`
7547 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
7549 // FOREIGN FUNCTION ITEM
7550 if self.check_keyword(kw::Fn) {
7551 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
7553 // FOREIGN TYPE ITEM
7554 if self.check_keyword(kw::Type) {
7555 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
7558 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
7562 ident: Ident::invalid(),
7563 span: lo.to(self.prev_span),
7564 id: ast::DUMMY_NODE_ID,
7567 node: ForeignItemKind::Macro(mac),
7572 if !attrs.is_empty() {
7573 self.expected_item_err(&attrs)?;
7581 /// This is the fall-through for parsing items.
7582 fn parse_macro_use_or_failure(
7584 attrs: Vec<Attribute> ,
7585 macros_allowed: bool,
7586 attributes_allowed: bool,
7588 visibility: Visibility
7589 ) -> PResult<'a, Option<P<Item>>> {
7590 if macros_allowed && self.token.is_path_start() &&
7591 !(self.is_async_fn() && self.span.rust_2015()) {
7592 // MACRO INVOCATION ITEM
7594 let prev_span = self.prev_span;
7595 self.complain_if_pub_macro(&visibility.node, prev_span);
7597 let mac_lo = self.span;
7600 let pth = self.parse_path(PathStyle::Mod)?;
7601 self.expect(&token::Not)?;
7603 // a 'special' identifier (like what `macro_rules!` uses)
7604 // is optional. We should eventually unify invoc syntax
7606 let id = if self.token.is_ident() {
7609 Ident::invalid() // no special identifier
7611 // eat a matched-delimiter token tree:
7612 let (delim, tts) = self.expect_delimited_token_tree()?;
7613 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
7614 self.report_invalid_macro_expansion_item();
7617 let hi = self.prev_span;
7618 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
7619 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
7620 return Ok(Some(item));
7623 // FAILURE TO PARSE ITEM
7624 match visibility.node {
7625 VisibilityKind::Inherited => {}
7627 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
7631 if !attributes_allowed && !attrs.is_empty() {
7632 self.expected_item_err(&attrs)?;
7637 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
7638 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
7639 at_end: &mut bool) -> PResult<'a, Option<Mac>>
7641 if self.token.is_path_start() &&
7642 !(self.is_async_fn() && self.span.rust_2015()) {
7643 let prev_span = self.prev_span;
7645 let pth = self.parse_path(PathStyle::Mod)?;
7647 if pth.segments.len() == 1 {
7648 if !self.eat(&token::Not) {
7649 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
7652 self.expect(&token::Not)?;
7655 if let Some(vis) = vis {
7656 self.complain_if_pub_macro(&vis.node, prev_span);
7661 // eat a matched-delimiter token tree:
7662 let (delim, tts) = self.expect_delimited_token_tree()?;
7663 if delim != MacDelimiter::Brace {
7664 self.expect(&token::Semi)?;
7667 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
7673 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
7674 where F: FnOnce(&mut Self) -> PResult<'a, R>
7676 // Record all tokens we parse when parsing this item.
7677 let mut tokens = Vec::new();
7678 let prev_collecting = match self.token_cursor.frame.last_token {
7679 LastToken::Collecting(ref mut list) => {
7680 Some(mem::replace(list, Vec::new()))
7682 LastToken::Was(ref mut last) => {
7683 tokens.extend(last.take());
7687 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
7688 let prev = self.token_cursor.stack.len();
7690 let last_token = if self.token_cursor.stack.len() == prev {
7691 &mut self.token_cursor.frame.last_token
7693 &mut self.token_cursor.stack[prev].last_token
7696 // Pull out the tokens that we've collected from the call to `f` above.
7697 let mut collected_tokens = match *last_token {
7698 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
7699 LastToken::Was(_) => panic!("our vector went away?"),
7702 // If we're not at EOF our current token wasn't actually consumed by
7703 // `f`, but it'll still be in our list that we pulled out. In that case
7705 let extra_token = if self.token != token::Eof {
7706 collected_tokens.pop()
7711 // If we were previously collecting tokens, then this was a recursive
7712 // call. In that case we need to record all the tokens we collected in
7713 // our parent list as well. To do that we push a clone of our stream
7714 // onto the previous list.
7715 match prev_collecting {
7717 list.extend(collected_tokens.iter().cloned());
7718 list.extend(extra_token);
7719 *last_token = LastToken::Collecting(list);
7722 *last_token = LastToken::Was(extra_token);
7726 Ok((ret?, TokenStream::new(collected_tokens)))
7729 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
7730 let attrs = self.parse_outer_attributes()?;
7731 self.parse_item_(attrs, true, false)
7735 fn is_import_coupler(&mut self) -> bool {
7736 self.check(&token::ModSep) &&
7737 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
7738 *t == token::BinOp(token::Star))
7741 /// Parses a `UseTree`.
7744 /// USE_TREE = [`::`] `*` |
7745 /// [`::`] `{` USE_TREE_LIST `}` |
7747 /// PATH `::` `{` USE_TREE_LIST `}` |
7748 /// PATH [`as` IDENT]
7750 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
7753 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
7754 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
7755 self.check(&token::BinOp(token::Star)) ||
7756 self.is_import_coupler() {
7757 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
7758 let mod_sep_ctxt = self.span.ctxt();
7759 if self.eat(&token::ModSep) {
7760 prefix.segments.push(
7761 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
7765 if self.eat(&token::BinOp(token::Star)) {
7768 UseTreeKind::Nested(self.parse_use_tree_list()?)
7771 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
7772 prefix = self.parse_path(PathStyle::Mod)?;
7774 if self.eat(&token::ModSep) {
7775 if self.eat(&token::BinOp(token::Star)) {
7778 UseTreeKind::Nested(self.parse_use_tree_list()?)
7781 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
7785 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
7788 /// Parses a `UseTreeKind::Nested(list)`.
7791 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
7793 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
7794 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
7795 &token::CloseDelim(token::Brace),
7796 SeqSep::trailing_allowed(token::Comma), |this| {
7797 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
7801 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
7802 if self.eat_keyword(kw::As) {
7803 self.parse_ident_or_underscore().map(Some)
7809 /// Parses a source module as a crate. This is the main entry point for the parser.
7810 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
7812 let krate = Ok(ast::Crate {
7813 attrs: self.parse_inner_attributes()?,
7814 module: self.parse_mod_items(&token::Eof, lo)?,
7815 span: lo.to(self.span),
7820 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
7821 let ret = match self.token {
7822 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
7823 (symbol, ast::StrStyle::Cooked, suffix),
7824 token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
7825 (symbol, ast::StrStyle::Raw(n), suffix),
7832 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
7833 match self.parse_optional_str() {
7834 Some((s, style, suf)) => {
7835 let sp = self.prev_span;
7836 self.expect_no_suffix(sp, "a string literal", suf);
7840 let msg = "expected string literal";
7841 let mut err = self.fatal(msg);
7842 err.span_label(self.span, msg);
7848 fn report_invalid_macro_expansion_item(&self) {
7849 self.struct_span_err(
7851 "macros that expand to items must be delimited with braces or followed by a semicolon",
7852 ).multipart_suggestion(
7853 "change the delimiters to curly braces",
7855 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
7856 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
7858 Applicability::MaybeIncorrect,
7860 self.sess.source_map.next_point(self.prev_span),
7863 Applicability::MaybeIncorrect,
7868 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
7869 for unmatched in unclosed_delims.iter() {
7870 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
7871 "incorrect close delimiter: `{}`",
7872 pprust::token_to_string(&token::CloseDelim(unmatched.found_delim)),
7874 err.span_label(unmatched.found_span, "incorrect close delimiter");
7875 if let Some(sp) = unmatched.candidate_span {
7876 err.span_label(sp, "close delimiter possibly meant for this");
7878 if let Some(sp) = unmatched.unclosed_span {
7879 err.span_label(sp, "un-closed delimiter");
7883 unclosed_delims.clear();