1 // ignore-tidy-filelength
3 use crate::ast::{AngleBracketedArgs, AsyncArgument, ParenthesizedArgs, AttrStyle, BareFnTy};
4 use crate::ast::{GenericBound, TraitBoundModifier};
5 use crate::ast::Unsafety;
6 use crate::ast::{Mod, AnonConst, Arg, ArgSource, 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, LocalSource};
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, TypeBinding, 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::{TokenAndSpan, UnmatchedBrace};
40 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
41 use crate::parse::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, hygiene::CompilerDesugaringKind};
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 /* ident is handled by common.rs */
197 pub struct Parser<'a> {
198 pub sess: &'a ParseSess,
199 /// the current token:
200 pub token: token::Token,
201 /// the span of the current token:
203 /// the span of the previous token:
204 meta_var_span: Option<Span>,
206 /// the previous token kind
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 /// Whether 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 /// Whether 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) -> TokenAndSpan {
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 TokenAndSpan { tok: token::Eof, sp: 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(sp, tok) => return TokenAndSpan { tok: tok, sp: sp },
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) -> TokenAndSpan {
331 let (sp, name) = match self.next() {
332 TokenAndSpan { sp, tok: token::DocComment(name) } => (sp, 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::Token::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 {
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::Token) -> 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.tok;
503 parser.span = tok.sp;
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) -> TokenAndSpan {
519 let mut next = if self.desugar_doc_comments {
520 self.token_cursor.next_desugared()
522 self.token_cursor.next()
524 if next.sp.is_dummy() {
525 // Tweak the location for better diagnostics, but keep syntactic context intact.
526 next.sp = self.prev_span.with_ctxt(next.sp.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::Token) -> 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::Token],
581 inedible: &[token::Token],
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::Token) -> 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::Token) -> 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,
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>(
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::Token],
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>(
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.span = next.sp;
1027 self.token = next.tok;
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::Token, 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::Token) -> 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,
1129 arguments: Vec::new(),
1136 /// Parses unsafety: `unsafe` or nothing.
1137 fn parse_unsafety(&mut self) -> Unsafety {
1138 if self.eat_keyword(kw::Unsafe) {
1145 /// Parses the items in a trait declaration.
1146 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1147 maybe_whole!(self, NtTraitItem, |x| x);
1148 let attrs = self.parse_outer_attributes()?;
1149 let mut unclosed_delims = vec![];
1150 let (mut item, tokens) = self.collect_tokens(|this| {
1151 let item = this.parse_trait_item_(at_end, attrs);
1152 unclosed_delims.append(&mut this.unclosed_delims);
1155 self.unclosed_delims.append(&mut unclosed_delims);
1156 // See `parse_item` for why this clause is here.
1157 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1158 item.tokens = Some(tokens);
1163 fn parse_trait_item_(&mut self,
1165 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1168 let (name, node, generics) = if self.eat_keyword(kw::Type) {
1169 self.parse_trait_item_assoc_ty()?
1170 } else if self.is_const_item() {
1171 self.expect_keyword(kw::Const)?;
1172 let ident = self.parse_ident()?;
1173 self.expect(&token::Colon)?;
1174 let ty = self.parse_ty()?;
1175 let default = if self.eat(&token::Eq) {
1176 let expr = self.parse_expr()?;
1177 self.expect(&token::Semi)?;
1180 self.expect(&token::Semi)?;
1183 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1184 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1185 // trait item macro.
1186 (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1188 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
1190 let ident = self.parse_ident()?;
1191 let mut generics = self.parse_generics()?;
1193 let mut decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1194 // This is somewhat dubious; We don't want to allow
1195 // argument names to be left off if there is a
1198 // We don't allow argument names to be left off in edition 2018.
1199 p.parse_arg_general(p.span.rust_2018(), true, false)
1201 generics.where_clause = self.parse_where_clause()?;
1202 self.construct_async_arguments(&mut asyncness, &mut decl);
1204 let sig = ast::MethodSig {
1214 let body = match self.token {
1218 debug!("parse_trait_methods(): parsing required method");
1221 token::OpenDelim(token::Brace) => {
1222 debug!("parse_trait_methods(): parsing provided method");
1224 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1225 attrs.extend(inner_attrs.iter().cloned());
1228 token::Interpolated(ref nt) => {
1230 token::NtBlock(..) => {
1232 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1233 attrs.extend(inner_attrs.iter().cloned());
1237 return self.expected_semi_or_open_brace();
1242 return self.expected_semi_or_open_brace();
1245 (ident, ast::TraitItemKind::Method(sig, body), generics)
1249 id: ast::DUMMY_NODE_ID,
1254 span: lo.to(self.prev_span),
1259 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1260 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1261 if self.eat(&token::RArrow) {
1262 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1264 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1269 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1270 self.parse_ty_common(true, true, false)
1273 /// Parses a type in restricted contexts where `+` is not permitted.
1275 /// Example 1: `&'a TYPE`
1276 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1277 /// Example 2: `value1 as TYPE + value2`
1278 /// `+` is prohibited to avoid interactions with expression grammar.
1279 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1280 self.parse_ty_common(false, true, false)
1283 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1284 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1285 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1286 maybe_whole!(self, NtTy, |x| x);
1289 let mut impl_dyn_multi = false;
1290 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1291 // `(TYPE)` is a parenthesized type.
1292 // `(TYPE,)` is a tuple with a single field of type TYPE.
1293 let mut ts = vec![];
1294 let mut last_comma = false;
1295 while self.token != token::CloseDelim(token::Paren) {
1296 ts.push(self.parse_ty()?);
1297 if self.eat(&token::Comma) {
1304 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1305 self.expect(&token::CloseDelim(token::Paren))?;
1307 if ts.len() == 1 && !last_comma {
1308 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1309 let maybe_bounds = allow_plus && self.token.is_like_plus();
1311 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1312 TyKind::Path(None, ref path) if maybe_bounds => {
1313 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1315 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1316 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1317 let path = match bounds[0] {
1318 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1319 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1321 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1324 _ => TyKind::Paren(P(ty))
1329 } else if self.eat(&token::Not) {
1332 } else if self.eat(&token::BinOp(token::Star)) {
1334 TyKind::Ptr(self.parse_ptr()?)
1335 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1337 let t = self.parse_ty()?;
1338 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1339 let t = match self.maybe_parse_fixed_length_of_vec()? {
1340 None => TyKind::Slice(t),
1341 Some(length) => TyKind::Array(t, AnonConst {
1342 id: ast::DUMMY_NODE_ID,
1346 self.expect(&token::CloseDelim(token::Bracket))?;
1348 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1351 self.parse_borrowed_pointee()?
1352 } else if self.eat_keyword_noexpect(kw::Typeof) {
1354 // In order to not be ambiguous, the type must be surrounded by parens.
1355 self.expect(&token::OpenDelim(token::Paren))?;
1357 id: ast::DUMMY_NODE_ID,
1358 value: self.parse_expr()?,
1360 self.expect(&token::CloseDelim(token::Paren))?;
1362 } else if self.eat_keyword(kw::Underscore) {
1363 // A type to be inferred `_`
1365 } else if self.token_is_bare_fn_keyword() {
1366 // Function pointer type
1367 self.parse_ty_bare_fn(Vec::new())?
1368 } else if self.check_keyword(kw::For) {
1369 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1370 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1371 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1373 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1374 if self.token_is_bare_fn_keyword() {
1375 self.parse_ty_bare_fn(lifetime_defs)?
1377 let path = self.parse_path(PathStyle::Type)?;
1378 let parse_plus = allow_plus && self.check_plus();
1379 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1381 } else if self.eat_keyword(kw::Impl) {
1382 // Always parse bounds greedily for better error recovery.
1383 let bounds = self.parse_generic_bounds(None)?;
1384 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1385 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1386 } else if self.check_keyword(kw::Dyn) &&
1387 (self.span.rust_2018() ||
1388 self.look_ahead(1, |t| t.can_begin_bound() &&
1389 !can_continue_type_after_non_fn_ident(t))) {
1390 self.bump(); // `dyn`
1391 // Always parse bounds greedily for better error recovery.
1392 let bounds = self.parse_generic_bounds(None)?;
1393 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1394 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1395 } else if self.check(&token::Question) ||
1396 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1397 // Bound list (trait object type)
1398 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1399 TraitObjectSyntax::None)
1400 } else if self.eat_lt() {
1402 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1403 TyKind::Path(Some(qself), path)
1404 } else if self.token.is_path_start() {
1406 let path = self.parse_path(PathStyle::Type)?;
1407 if self.eat(&token::Not) {
1408 // Macro invocation in type position
1409 let (delim, tts) = self.expect_delimited_token_tree()?;
1410 let node = Mac_ { path, tts, delim };
1411 TyKind::Mac(respan(lo.to(self.prev_span), node))
1413 // Just a type path or bound list (trait object type) starting with a trait.
1415 // `Trait1 + Trait2 + 'a`
1416 if allow_plus && self.check_plus() {
1417 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1419 TyKind::Path(None, path)
1422 } else if self.check(&token::DotDotDot) {
1423 if allow_c_variadic {
1424 self.eat(&token::DotDotDot);
1427 return Err(self.fatal(
1428 "only foreign functions are allowed to be C-variadic"
1432 let msg = format!("expected type, found {}", self.this_token_descr());
1433 return Err(self.fatal(&msg));
1436 let span = lo.to(self.prev_span);
1437 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1439 // Try to recover from use of `+` with incorrect priority.
1440 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1441 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1442 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1445 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1446 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1447 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1448 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1450 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1451 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1453 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1456 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1457 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1458 let mutbl = self.parse_mutability();
1459 let ty = self.parse_ty_no_plus()?;
1460 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1463 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1464 let mutbl = if self.eat_keyword(kw::Mut) {
1466 } else if self.eat_keyword(kw::Const) {
1467 Mutability::Immutable
1469 let span = self.prev_span;
1470 let msg = "expected mut or const in raw pointer type";
1471 self.struct_span_err(span, msg)
1472 .span_label(span, msg)
1473 .help("use `*mut T` or `*const T` as appropriate")
1475 Mutability::Immutable
1477 let t = self.parse_ty_no_plus()?;
1478 Ok(MutTy { ty: t, mutbl: mutbl })
1481 fn is_named_argument(&self) -> bool {
1482 let offset = match self.token {
1483 token::Interpolated(ref nt) => match **nt {
1484 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1487 token::BinOp(token::And) | token::AndAnd => 1,
1488 _ if self.token.is_keyword(kw::Mut) => 1,
1492 self.look_ahead(offset, |t| t.is_ident()) &&
1493 self.look_ahead(offset + 1, |t| t == &token::Colon)
1496 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1498 /// This version of parse arg doesn't necessarily require identifier names.
1499 fn parse_arg_general(
1502 is_trait_item: bool,
1503 allow_c_variadic: bool,
1504 ) -> PResult<'a, Arg> {
1505 if let Ok(Some(arg)) = self.parse_self_arg() {
1506 return self.recover_bad_self_arg(arg, is_trait_item);
1509 let (pat, ty) = if require_name || self.is_named_argument() {
1510 debug!("parse_arg_general parse_pat (require_name:{})", require_name);
1511 self.eat_incorrect_doc_comment("method arguments");
1512 let pat = self.parse_pat(Some("argument name"))?;
1514 if let Err(mut err) = self.expect(&token::Colon) {
1515 if let Some(ident) = self.argument_without_type(
1522 return Ok(dummy_arg(ident));
1528 self.eat_incorrect_doc_comment("a method argument's type");
1529 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1531 debug!("parse_arg_general ident_to_pat");
1532 let parser_snapshot_before_ty = self.clone();
1533 self.eat_incorrect_doc_comment("a method argument's type");
1534 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1535 if ty.is_ok() && self.token != token::Comma &&
1536 self.token != token::CloseDelim(token::Paren) {
1537 // This wasn't actually a type, but a pattern looking like a type,
1538 // so we are going to rollback and re-parse for recovery.
1539 ty = self.unexpected();
1543 let ident = Ident::new(kw::Invalid, self.prev_span);
1545 id: ast::DUMMY_NODE_ID,
1546 node: PatKind::Ident(
1547 BindingMode::ByValue(Mutability::Immutable), ident, None),
1553 // If this is a C-variadic argument and we hit an error, return the
1555 if self.token == token::DotDotDot {
1558 // Recover from attempting to parse the argument as a type without pattern.
1560 mem::replace(self, parser_snapshot_before_ty);
1561 self.recover_arg_parse()?
1566 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal })
1569 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1570 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1571 let pat = self.parse_pat(Some("argument name"))?;
1572 let t = if self.eat(&token::Colon) {
1576 id: ast::DUMMY_NODE_ID,
1577 node: TyKind::Infer,
1578 span: self.prev_span,
1584 id: ast::DUMMY_NODE_ID,
1585 source: ast::ArgSource::Normal,
1589 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1590 if self.eat(&token::Semi) {
1591 Ok(Some(self.parse_expr()?))
1597 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1598 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1599 maybe_whole_expr!(self);
1601 let minus_lo = self.span;
1602 let minus_present = self.eat(&token::BinOp(token::Minus));
1604 let literal = self.parse_lit()?;
1605 let hi = self.prev_span;
1606 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1609 let minus_hi = self.prev_span;
1610 let unary = self.mk_unary(UnOp::Neg, expr);
1611 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1617 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
1619 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
1620 let span = self.span;
1622 Ok(Ident::new(ident.name, span))
1624 _ => self.parse_ident(),
1628 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
1630 token::Ident(ident, false) if ident.name == kw::Underscore => {
1631 let span = self.span;
1633 Ok(Ident::new(ident.name, span))
1635 _ => self.parse_ident(),
1639 /// Parses a qualified path.
1640 /// Assumes that the leading `<` has been parsed already.
1642 /// `qualified_path = <type [as trait_ref]>::path`
1647 /// `<T as U>::F::a<S>` (without disambiguator)
1648 /// `<T as U>::F::a::<S>` (with disambiguator)
1649 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
1650 let lo = self.prev_span;
1651 let ty = self.parse_ty()?;
1653 // `path` will contain the prefix of the path up to the `>`,
1654 // if any (e.g., `U` in the `<T as U>::*` examples
1655 // above). `path_span` has the span of that path, or an empty
1656 // span in the case of something like `<T>::Bar`.
1657 let (mut path, path_span);
1658 if self.eat_keyword(kw::As) {
1659 let path_lo = self.span;
1660 path = self.parse_path(PathStyle::Type)?;
1661 path_span = path_lo.to(self.prev_span);
1663 path = ast::Path { segments: Vec::new(), span: DUMMY_SP };
1664 path_span = self.span.to(self.span);
1667 // See doc comment for `unmatched_angle_bracket_count`.
1668 self.expect(&token::Gt)?;
1669 if self.unmatched_angle_bracket_count > 0 {
1670 self.unmatched_angle_bracket_count -= 1;
1671 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1674 self.expect(&token::ModSep)?;
1676 let qself = QSelf { ty, path_span, position: path.segments.len() };
1677 self.parse_path_segments(&mut path.segments, style)?;
1679 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
1682 /// Parses simple paths.
1684 /// `path = [::] segment+`
1685 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
1688 /// `a::b::C<D>` (without disambiguator)
1689 /// `a::b::C::<D>` (with disambiguator)
1690 /// `Fn(Args)` (without disambiguator)
1691 /// `Fn::(Args)` (with disambiguator)
1692 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1693 maybe_whole!(self, NtPath, |path| {
1694 if style == PathStyle::Mod &&
1695 path.segments.iter().any(|segment| segment.args.is_some()) {
1696 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
1701 let lo = self.meta_var_span.unwrap_or(self.span);
1702 let mut segments = Vec::new();
1703 let mod_sep_ctxt = self.span.ctxt();
1704 if self.eat(&token::ModSep) {
1705 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
1707 self.parse_path_segments(&mut segments, style)?;
1709 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
1712 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
1713 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
1715 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1716 let meta_ident = match self.token {
1717 token::Interpolated(ref nt) => match **nt {
1718 token::NtMeta(ref meta) => match meta.node {
1719 ast::MetaItemKind::Word => Some(meta.path.clone()),
1726 if let Some(path) = meta_ident {
1730 self.parse_path(style)
1733 crate fn parse_path_segments(&mut self,
1734 segments: &mut Vec<PathSegment>,
1736 -> PResult<'a, ()> {
1738 let segment = self.parse_path_segment(style)?;
1739 if style == PathStyle::Expr {
1740 // In order to check for trailing angle brackets, we must have finished
1741 // recursing (`parse_path_segment` can indirectly call this function),
1742 // that is, the next token must be the highlighted part of the below example:
1744 // `Foo::<Bar as Baz<T>>::Qux`
1747 // As opposed to the below highlight (if we had only finished the first
1750 // `Foo::<Bar as Baz<T>>::Qux`
1753 // `PathStyle::Expr` is only provided at the root invocation and never in
1754 // `parse_path_segment` to recurse and therefore can be checked to maintain
1756 self.check_trailing_angle_brackets(&segment, token::ModSep);
1758 segments.push(segment);
1760 if self.is_import_coupler() || !self.eat(&token::ModSep) {
1766 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
1767 let ident = self.parse_path_segment_ident()?;
1769 let is_args_start = |token: &token::Token| match *token {
1770 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
1771 | token::LArrow => true,
1774 let check_args_start = |this: &mut Self| {
1775 this.expected_tokens.extend_from_slice(
1776 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
1778 is_args_start(&this.token)
1781 Ok(if style == PathStyle::Type && check_args_start(self) ||
1782 style != PathStyle::Mod && self.check(&token::ModSep)
1783 && self.look_ahead(1, |t| is_args_start(t)) {
1784 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
1785 // it isn't, then we reset the unmatched angle bracket count as we're about to start
1786 // parsing a new path.
1787 if style == PathStyle::Expr {
1788 self.unmatched_angle_bracket_count = 0;
1789 self.max_angle_bracket_count = 0;
1792 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
1793 self.eat(&token::ModSep);
1795 let args = if self.eat_lt() {
1797 let (args, bindings) =
1798 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
1800 let span = lo.to(self.prev_span);
1801 AngleBracketedArgs { args, bindings, span }.into()
1805 let (inputs, recovered) = self.parse_seq_to_before_tokens(
1806 &[&token::CloseDelim(token::Paren)],
1807 SeqSep::trailing_allowed(token::Comma),
1808 TokenExpectType::Expect,
1813 let span = lo.to(self.prev_span);
1814 let output = if self.eat(&token::RArrow) {
1815 Some(self.parse_ty_common(false, false, false)?)
1819 ParenthesizedArgs { inputs, output, span }.into()
1822 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
1824 // Generic arguments are not found.
1825 PathSegment::from_ident(ident)
1829 crate fn check_lifetime(&mut self) -> bool {
1830 self.expected_tokens.push(TokenType::Lifetime);
1831 self.token.is_lifetime()
1834 /// Parses a single lifetime `'a` or panics.
1835 crate fn expect_lifetime(&mut self) -> Lifetime {
1836 if let Some(ident) = self.token.lifetime() {
1837 let span = self.span;
1839 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
1841 self.span_bug(self.span, "not a lifetime")
1845 fn eat_label(&mut self) -> Option<Label> {
1846 if let Some(ident) = self.token.lifetime() {
1847 let span = self.span;
1849 Some(Label { ident: Ident::new(ident.name, span) })
1855 /// Parses mutability (`mut` or nothing).
1856 fn parse_mutability(&mut self) -> Mutability {
1857 if self.eat_keyword(kw::Mut) {
1860 Mutability::Immutable
1864 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
1865 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token {
1866 self.expect_no_suffix(self.span, "a tuple index", suffix);
1868 Ok(Ident::new(symbol, self.prev_span))
1870 self.parse_ident_common(false)
1874 /// Parse ident (COLON expr)?
1875 fn parse_field(&mut self) -> PResult<'a, Field> {
1876 let attrs = self.parse_outer_attributes()?;
1879 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1880 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
1881 t == &token::Colon || t == &token::Eq
1883 let fieldname = self.parse_field_name()?;
1885 // Check for an equals token. This means the source incorrectly attempts to
1886 // initialize a field with an eq rather than a colon.
1887 if self.token == token::Eq {
1889 .struct_span_err(self.span, "expected `:`, found `=`")
1891 fieldname.span.shrink_to_hi().to(self.span),
1892 "replace equals symbol with a colon",
1894 Applicability::MachineApplicable,
1899 (fieldname, self.parse_expr()?, false)
1901 let fieldname = self.parse_ident_common(false)?;
1903 // Mimic `x: x` for the `x` field shorthand.
1904 let path = ast::Path::from_ident(fieldname);
1905 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
1906 (fieldname, expr, true)
1910 span: lo.to(expr.span),
1913 attrs: attrs.into(),
1917 crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
1918 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
1921 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
1922 ExprKind::Unary(unop, expr)
1925 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1926 ExprKind::Binary(binop, lhs, rhs)
1929 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
1930 ExprKind::Call(f, args)
1933 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
1934 ExprKind::Index(expr, idx)
1938 start: Option<P<Expr>>,
1939 end: Option<P<Expr>>,
1940 limits: RangeLimits)
1941 -> PResult<'a, ast::ExprKind> {
1942 if end.is_none() && limits == RangeLimits::Closed {
1943 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
1945 Ok(ExprKind::Range(start, end, limits))
1949 fn mk_assign_op(&self, binop: ast::BinOp,
1950 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1951 ExprKind::AssignOp(binop, lhs, rhs)
1954 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
1955 let delim = match self.token {
1956 token::OpenDelim(delim) => delim,
1958 let msg = "expected open delimiter";
1959 let mut err = self.fatal(msg);
1960 err.span_label(self.span, msg);
1964 let tts = match self.parse_token_tree() {
1965 TokenTree::Delimited(_, _, tts) => tts,
1966 _ => unreachable!(),
1968 let delim = match delim {
1969 token::Paren => MacDelimiter::Parenthesis,
1970 token::Bracket => MacDelimiter::Bracket,
1971 token::Brace => MacDelimiter::Brace,
1972 token::NoDelim => self.bug("unexpected no delimiter"),
1974 Ok((delim, tts.into()))
1977 /// At the bottom (top?) of the precedence hierarchy,
1978 /// Parses things like parenthesized exprs, macros, `return`, etc.
1980 /// N.B., this does not parse outer attributes, and is private because it only works
1981 /// correctly if called from `parse_dot_or_call_expr()`.
1982 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1983 maybe_recover_from_interpolated_ty_qpath!(self, true);
1984 maybe_whole_expr!(self);
1986 // Outer attributes are already parsed and will be
1987 // added to the return value after the fact.
1989 // Therefore, prevent sub-parser from parsing
1990 // attributes by giving them a empty "already parsed" list.
1991 let mut attrs = ThinVec::new();
1994 let mut hi = self.span;
1998 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2000 token::OpenDelim(token::Paren) => {
2003 attrs.extend(self.parse_inner_attributes()?);
2005 // (e) is parenthesized e
2006 // (e,) is a tuple with only one field, e
2007 let mut es = vec![];
2008 let mut trailing_comma = false;
2009 let mut recovered = false;
2010 while self.token != token::CloseDelim(token::Paren) {
2011 es.push(match self.parse_expr() {
2014 // recover from parse error in tuple list
2015 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2018 recovered = self.expect_one_of(
2020 &[token::Comma, token::CloseDelim(token::Paren)],
2022 if self.eat(&token::Comma) {
2023 trailing_comma = true;
2025 trailing_comma = false;
2033 hi = self.prev_span;
2034 ex = if es.len() == 1 && !trailing_comma {
2035 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2040 token::OpenDelim(token::Brace) => {
2041 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2043 token::BinOp(token::Or) | token::OrOr => {
2044 return self.parse_lambda_expr(attrs);
2046 token::OpenDelim(token::Bracket) => {
2049 attrs.extend(self.parse_inner_attributes()?);
2051 if self.eat(&token::CloseDelim(token::Bracket)) {
2053 ex = ExprKind::Array(Vec::new());
2056 let first_expr = self.parse_expr()?;
2057 if self.eat(&token::Semi) {
2058 // Repeating array syntax: [ 0; 512 ]
2059 let count = AnonConst {
2060 id: ast::DUMMY_NODE_ID,
2061 value: self.parse_expr()?,
2063 self.expect(&token::CloseDelim(token::Bracket))?;
2064 ex = ExprKind::Repeat(first_expr, count);
2065 } else if self.eat(&token::Comma) {
2066 // Vector with two or more elements.
2067 let remaining_exprs = self.parse_seq_to_end(
2068 &token::CloseDelim(token::Bracket),
2069 SeqSep::trailing_allowed(token::Comma),
2070 |p| Ok(p.parse_expr()?)
2072 let mut exprs = vec![first_expr];
2073 exprs.extend(remaining_exprs);
2074 ex = ExprKind::Array(exprs);
2076 // Vector with one element.
2077 self.expect(&token::CloseDelim(token::Bracket))?;
2078 ex = ExprKind::Array(vec![first_expr]);
2081 hi = self.prev_span;
2085 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2087 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2089 if self.span.rust_2018() && self.check_keyword(kw::Async) {
2090 return if self.is_async_block() { // check for `async {` and `async move {`
2091 self.parse_async_block(attrs)
2093 self.parse_lambda_expr(attrs)
2096 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
2097 return self.parse_lambda_expr(attrs);
2099 if self.eat_keyword(kw::If) {
2100 return self.parse_if_expr(attrs);
2102 if self.eat_keyword(kw::For) {
2103 let lo = self.prev_span;
2104 return self.parse_for_expr(None, lo, attrs);
2106 if self.eat_keyword(kw::While) {
2107 let lo = self.prev_span;
2108 return self.parse_while_expr(None, lo, attrs);
2110 if let Some(label) = self.eat_label() {
2111 let lo = label.ident.span;
2112 self.expect(&token::Colon)?;
2113 if self.eat_keyword(kw::While) {
2114 return self.parse_while_expr(Some(label), lo, attrs)
2116 if self.eat_keyword(kw::For) {
2117 return self.parse_for_expr(Some(label), lo, attrs)
2119 if self.eat_keyword(kw::Loop) {
2120 return self.parse_loop_expr(Some(label), lo, attrs)
2122 if self.token == token::OpenDelim(token::Brace) {
2123 return self.parse_block_expr(Some(label),
2125 BlockCheckMode::Default,
2128 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2129 let mut err = self.fatal(msg);
2130 err.span_label(self.span, msg);
2133 if self.eat_keyword(kw::Loop) {
2134 let lo = self.prev_span;
2135 return self.parse_loop_expr(None, lo, attrs);
2137 if self.eat_keyword(kw::Continue) {
2138 let label = self.eat_label();
2139 let ex = ExprKind::Continue(label);
2140 let hi = self.prev_span;
2141 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2143 if self.eat_keyword(kw::Match) {
2144 let match_sp = self.prev_span;
2145 return self.parse_match_expr(attrs).map_err(|mut err| {
2146 err.span_label(match_sp, "while parsing this match expression");
2150 if self.eat_keyword(kw::Unsafe) {
2151 return self.parse_block_expr(
2154 BlockCheckMode::Unsafe(ast::UserProvided),
2157 if self.is_do_catch_block() {
2158 let mut db = self.fatal("found removed `do catch` syntax");
2159 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2162 if self.is_try_block() {
2164 assert!(self.eat_keyword(kw::Try));
2165 return self.parse_try_block(lo, 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 self.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 // parse a stream of tokens into a list of TokenTree's,
2685 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2686 let mut tts = Vec::new();
2687 while self.token != token::Eof {
2688 tts.push(self.parse_token_tree());
2693 pub fn parse_tokens(&mut self) -> TokenStream {
2694 let mut result = Vec::new();
2697 token::Eof | token::CloseDelim(..) => break,
2698 _ => result.push(self.parse_token_tree().into()),
2701 TokenStream::new(result)
2704 /// Parse a prefix-unary-operator expr
2705 fn parse_prefix_expr(&mut self,
2706 already_parsed_attrs: Option<ThinVec<Attribute>>)
2707 -> PResult<'a, P<Expr>> {
2708 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2710 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
2711 let (hi, ex) = match self.token {
2714 let e = self.parse_prefix_expr(None);
2715 let (span, e) = self.interpolated_or_expr_span(e)?;
2716 (lo.to(span), self.mk_unary(UnOp::Not, e))
2718 // Suggest `!` for bitwise negation when encountering a `~`
2721 let e = self.parse_prefix_expr(None);
2722 let (span, e) = self.interpolated_or_expr_span(e)?;
2723 let span_of_tilde = lo;
2724 let mut err = self.diagnostic()
2725 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
2726 err.span_suggestion_short(
2728 "use `!` to perform bitwise negation",
2730 Applicability::MachineApplicable
2733 (lo.to(span), self.mk_unary(UnOp::Not, e))
2735 token::BinOp(token::Minus) => {
2737 let e = self.parse_prefix_expr(None);
2738 let (span, e) = self.interpolated_or_expr_span(e)?;
2739 (lo.to(span), self.mk_unary(UnOp::Neg, e))
2741 token::BinOp(token::Star) => {
2743 let e = self.parse_prefix_expr(None);
2744 let (span, e) = self.interpolated_or_expr_span(e)?;
2745 (lo.to(span), self.mk_unary(UnOp::Deref, e))
2747 token::BinOp(token::And) | token::AndAnd => {
2749 let m = self.parse_mutability();
2750 let e = self.parse_prefix_expr(None);
2751 let (span, e) = self.interpolated_or_expr_span(e)?;
2752 (lo.to(span), ExprKind::AddrOf(m, e))
2754 token::Ident(..) if self.token.is_keyword(kw::Box) => {
2756 let e = self.parse_prefix_expr(None);
2757 let (span, e) = self.interpolated_or_expr_span(e)?;
2758 (lo.to(span), ExprKind::Box(e))
2760 token::Ident(..) if self.token.is_ident_named(sym::not) => {
2761 // `not` is just an ordinary identifier in Rust-the-language,
2762 // but as `rustc`-the-compiler, we can issue clever diagnostics
2763 // for confused users who really want to say `!`
2764 let token_cannot_continue_expr = |t: &token::Token| match *t {
2765 // These tokens can start an expression after `!`, but
2766 // can't continue an expression after an ident
2767 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
2768 token::Literal(..) | token::Pound => true,
2769 token::Interpolated(ref nt) => match **nt {
2770 token::NtIdent(..) | token::NtExpr(..) |
2771 token::NtBlock(..) | token::NtPath(..) => true,
2776 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
2777 if cannot_continue_expr {
2779 // Emit the error ...
2780 let mut err = self.diagnostic()
2781 .struct_span_err(self.span,
2782 &format!("unexpected {} after identifier",
2783 self.this_token_descr()));
2784 // span the `not` plus trailing whitespace to avoid
2785 // trailing whitespace after the `!` in our suggestion
2786 let to_replace = self.sess.source_map()
2787 .span_until_non_whitespace(lo.to(self.span));
2788 err.span_suggestion_short(
2790 "use `!` to perform logical negation",
2792 Applicability::MachineApplicable
2795 // —and recover! (just as if we were in the block
2796 // for the `token::Not` arm)
2797 let e = self.parse_prefix_expr(None);
2798 let (span, e) = self.interpolated_or_expr_span(e)?;
2799 (lo.to(span), self.mk_unary(UnOp::Not, e))
2801 return self.parse_dot_or_call_expr(Some(attrs));
2804 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
2806 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2809 /// Parses an associative expression.
2811 /// This parses an expression accounting for associativity and precedence of the operators in
2814 fn parse_assoc_expr(&mut self,
2815 already_parsed_attrs: Option<ThinVec<Attribute>>)
2816 -> PResult<'a, P<Expr>> {
2817 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2820 /// Parses an associative expression with operators of at least `min_prec` precedence.
2821 fn parse_assoc_expr_with(&mut self,
2824 -> PResult<'a, P<Expr>> {
2825 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2828 let attrs = match lhs {
2829 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2832 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
2833 return self.parse_prefix_range_expr(attrs);
2835 self.parse_prefix_expr(attrs)?
2839 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
2841 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2844 (false, _) => {} // continue parsing the expression
2845 // An exhaustive check is done in the following block, but these are checked first
2846 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
2847 // want to keep their span info to improve diagnostics in these cases in a later stage.
2848 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
2849 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
2850 (true, Some(AssocOp::Add)) => { // `{ 42 } + 42
2851 // These cases are ambiguous and can't be identified in the parser alone
2852 let sp = self.sess.source_map().start_point(self.span);
2853 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
2856 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
2859 (true, Some(_)) => {
2860 // We've found an expression that would be parsed as a statement, but the next
2861 // token implies this should be parsed as an expression.
2862 // For example: `if let Some(x) = x { x } else { 0 } / 2`
2863 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
2864 "expected expression, found `{}`",
2865 pprust::token_to_string(&self.token),
2867 err.span_label(self.span, "expected expression");
2868 self.sess.expr_parentheses_needed(
2871 Some(pprust::expr_to_string(&lhs),
2876 self.expected_tokens.push(TokenType::Operator);
2877 while let Some(op) = AssocOp::from_token(&self.token) {
2879 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
2880 // it refers to. Interpolated identifiers are unwrapped early and never show up here
2881 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
2882 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
2883 let lhs_span = match (self.prev_token_kind, &lhs.node) {
2884 (PrevTokenKind::Interpolated, _) => self.prev_span,
2885 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
2886 if path.segments.len() == 1 => self.prev_span,
2890 let cur_op_span = self.span;
2891 let restrictions = if op.is_assign_like() {
2892 self.restrictions & Restrictions::NO_STRUCT_LITERAL
2896 let prec = op.precedence();
2897 if prec < min_prec {
2900 // Check for deprecated `...` syntax
2901 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
2902 self.err_dotdotdot_syntax(self.span);
2906 if op.is_comparison() {
2907 self.check_no_chained_comparison(&lhs, &op);
2910 if op == AssocOp::As {
2911 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
2913 } else if op == AssocOp::Colon {
2914 let maybe_path = self.could_ascription_be_path(&lhs.node);
2915 let next_sp = self.span;
2917 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
2920 self.bad_type_ascription(
2931 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
2932 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
2933 // generalise it to the Fixity::None code.
2935 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
2936 // two variants are handled with `parse_prefix_range_expr` call above.
2937 let rhs = if self.is_at_start_of_range_notation_rhs() {
2938 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
2942 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2947 let limits = if op == AssocOp::DotDot {
2948 RangeLimits::HalfOpen
2953 let r = self.mk_range(Some(lhs), rhs, limits)?;
2954 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
2958 let fixity = op.fixity();
2959 let prec_adjustment = match fixity {
2962 // We currently have no non-associative operators that are not handled above by
2963 // the special cases. The code is here only for future convenience.
2966 let rhs = self.with_res(
2967 restrictions - Restrictions::STMT_EXPR,
2968 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
2971 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
2972 // including the attributes.
2976 .filter(|a| a.style == AttrStyle::Outer)
2978 .map_or(lhs_span, |a| a.span);
2979 let span = lhs_span.to(rhs.span);
2981 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
2982 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
2983 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
2984 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
2985 AssocOp::Greater | AssocOp::GreaterEqual => {
2986 let ast_op = op.to_ast_binop().unwrap();
2987 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
2988 self.mk_expr(span, binary, ThinVec::new())
2990 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
2991 AssocOp::AssignOp(k) => {
2993 token::Plus => BinOpKind::Add,
2994 token::Minus => BinOpKind::Sub,
2995 token::Star => BinOpKind::Mul,
2996 token::Slash => BinOpKind::Div,
2997 token::Percent => BinOpKind::Rem,
2998 token::Caret => BinOpKind::BitXor,
2999 token::And => BinOpKind::BitAnd,
3000 token::Or => BinOpKind::BitOr,
3001 token::Shl => BinOpKind::Shl,
3002 token::Shr => BinOpKind::Shr,
3004 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3005 self.mk_expr(span, aopexpr, ThinVec::new())
3007 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3008 self.bug("AssocOp should have been handled by special case")
3012 if let Fixity::None = fixity { break }
3017 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3018 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3019 -> PResult<'a, P<Expr>> {
3020 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3021 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3024 // Save the state of the parser before parsing type normally, in case there is a
3025 // LessThan comparison after this cast.
3026 let parser_snapshot_before_type = self.clone();
3027 match self.parse_ty_no_plus() {
3029 Ok(mk_expr(self, rhs))
3031 Err(mut type_err) => {
3032 // Rewind to before attempting to parse the type with generics, to recover
3033 // from situations like `x as usize < y` in which we first tried to parse
3034 // `usize < y` as a type with generic arguments.
3035 let parser_snapshot_after_type = self.clone();
3036 mem::replace(self, parser_snapshot_before_type);
3038 match self.parse_path(PathStyle::Expr) {
3040 let (op_noun, op_verb) = match self.token {
3041 token::Lt => ("comparison", "comparing"),
3042 token::BinOp(token::Shl) => ("shift", "shifting"),
3044 // We can end up here even without `<` being the next token, for
3045 // example because `parse_ty_no_plus` returns `Err` on keywords,
3046 // but `parse_path` returns `Ok` on them due to error recovery.
3047 // Return original error and parser state.
3048 mem::replace(self, parser_snapshot_after_type);
3049 return Err(type_err);
3053 // Successfully parsed the type path leaving a `<` yet to parse.
3056 // Report non-fatal diagnostics, keep `x as usize` as an expression
3057 // in AST and continue parsing.
3058 let msg = format!("`<` is interpreted as a start of generic \
3059 arguments for `{}`, not a {}", path, op_noun);
3060 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3061 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3062 "interpreted as generic arguments");
3063 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3065 let expr = mk_expr(self, P(Ty {
3067 node: TyKind::Path(None, path),
3068 id: ast::DUMMY_NODE_ID
3071 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3072 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3073 err.span_suggestion(
3075 &format!("try {} the cast value", op_verb),
3076 format!("({})", expr_str),
3077 Applicability::MachineApplicable
3083 Err(mut path_err) => {
3084 // Couldn't parse as a path, return original error and parser state.
3086 mem::replace(self, parser_snapshot_after_type);
3094 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3095 fn parse_prefix_range_expr(&mut self,
3096 already_parsed_attrs: Option<ThinVec<Attribute>>)
3097 -> PResult<'a, P<Expr>> {
3098 // Check for deprecated `...` syntax
3099 if self.token == token::DotDotDot {
3100 self.err_dotdotdot_syntax(self.span);
3103 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3104 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3106 let tok = self.token.clone();
3107 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3109 let mut hi = self.span;
3111 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3112 // RHS must be parsed with more associativity than the dots.
3113 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3114 Some(self.parse_assoc_expr_with(next_prec,
3115 LhsExpr::NotYetParsed)
3123 let limits = if tok == token::DotDot {
3124 RangeLimits::HalfOpen
3129 let r = self.mk_range(None, opt_end, limits)?;
3130 Ok(self.mk_expr(lo.to(hi), r, attrs))
3133 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3134 if self.token.can_begin_expr() {
3135 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3136 if self.token == token::OpenDelim(token::Brace) {
3137 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3145 /// Parses an `if` or `if let` expression (`if` token already eaten).
3146 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3147 if self.check_keyword(kw::Let) {
3148 return self.parse_if_let_expr(attrs);
3150 let lo = self.prev_span;
3151 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3153 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3154 // verify that the last statement is either an implicit return (no `;`) or an explicit
3155 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3156 // the dead code lint.
3157 if self.eat_keyword(kw::Else) || !cond.returns() {
3158 let sp = self.sess.source_map().next_point(lo);
3159 let mut err = self.diagnostic()
3160 .struct_span_err(sp, "missing condition for `if` statemement");
3161 err.span_label(sp, "expected if condition here");
3164 let not_block = self.token != token::OpenDelim(token::Brace);
3165 let thn = self.parse_block().map_err(|mut err| {
3167 err.span_label(lo, "this `if` statement has a condition, but no block");
3171 let mut els: Option<P<Expr>> = None;
3172 let mut hi = thn.span;
3173 if self.eat_keyword(kw::Else) {
3174 let elexpr = self.parse_else_expr()?;
3178 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3181 /// Parses an `if let` expression (`if` token already eaten).
3182 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3183 -> PResult<'a, P<Expr>> {
3184 let lo = self.prev_span;
3185 self.expect_keyword(kw::Let)?;
3186 let pats = self.parse_pats()?;
3187 self.expect(&token::Eq)?;
3188 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3189 let thn = self.parse_block()?;
3190 let (hi, els) = if self.eat_keyword(kw::Else) {
3191 let expr = self.parse_else_expr()?;
3192 (expr.span, Some(expr))
3196 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3199 /// Parses `move |args| expr`.
3200 fn parse_lambda_expr(&mut self,
3201 attrs: ThinVec<Attribute>)
3202 -> PResult<'a, P<Expr>>
3205 let movability = if self.eat_keyword(kw::Static) {
3210 let asyncness = if self.span.rust_2018() {
3211 self.parse_asyncness()
3215 let capture_clause = if self.eat_keyword(kw::Move) {
3220 let decl = self.parse_fn_block_decl()?;
3221 let decl_hi = self.prev_span;
3222 let body = match decl.output {
3223 FunctionRetTy::Default(_) => {
3224 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3225 self.parse_expr_res(restrictions, None)?
3228 // If an explicit return type is given, require a
3229 // block to appear (RFC 968).
3230 let body_lo = self.span;
3231 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3237 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3241 // `else` token already eaten
3242 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3243 if self.eat_keyword(kw::If) {
3244 return self.parse_if_expr(ThinVec::new());
3246 let blk = self.parse_block()?;
3247 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3251 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3252 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3254 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3255 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3257 let pat = self.parse_top_level_pat()?;
3258 if !self.eat_keyword(kw::In) {
3259 let in_span = self.prev_span.between(self.span);
3260 let mut err = self.sess.span_diagnostic
3261 .struct_span_err(in_span, "missing `in` in `for` loop");
3262 err.span_suggestion_short(
3263 in_span, "try adding `in` here", " in ".into(),
3264 // has been misleading, at least in the past (closed Issue #48492)
3265 Applicability::MaybeIncorrect
3269 let in_span = self.prev_span;
3270 self.check_for_for_in_in_typo(in_span);
3271 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3272 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3273 attrs.extend(iattrs);
3275 let hi = self.prev_span;
3276 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3279 /// Parses a `while` or `while let` expression (`while` token already eaten).
3280 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3282 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3283 if self.token.is_keyword(kw::Let) {
3284 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3286 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3287 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3288 attrs.extend(iattrs);
3289 let span = span_lo.to(body.span);
3290 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3293 /// Parses a `while let` expression (`while` token already eaten).
3294 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3296 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3297 self.expect_keyword(kw::Let)?;
3298 let pats = self.parse_pats()?;
3299 self.expect(&token::Eq)?;
3300 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3301 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3302 attrs.extend(iattrs);
3303 let span = span_lo.to(body.span);
3304 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3307 // parse `loop {...}`, `loop` token already eaten
3308 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3310 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3311 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3312 attrs.extend(iattrs);
3313 let span = span_lo.to(body.span);
3314 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3317 /// Parses an `async move {...}` expression.
3318 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3319 -> PResult<'a, P<Expr>>
3321 let span_lo = self.span;
3322 self.expect_keyword(kw::Async)?;
3323 let capture_clause = if self.eat_keyword(kw::Move) {
3328 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3329 attrs.extend(iattrs);
3331 span_lo.to(body.span),
3332 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3335 /// Parses a `try {...}` expression (`try` token already eaten).
3336 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3337 -> PResult<'a, P<Expr>>
3339 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3340 attrs.extend(iattrs);
3341 if self.eat_keyword(kw::Catch) {
3342 let mut error = self.struct_span_err(self.prev_span,
3343 "keyword `catch` cannot follow a `try` block");
3344 error.help("try using `match` on the result of the `try` block instead");
3348 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
3352 // `match` token already eaten
3353 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3354 let match_span = self.prev_span;
3355 let lo = self.prev_span;
3356 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3358 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3359 if self.token == token::Token::Semi {
3360 e.span_suggestion_short(
3362 "try removing this `match`",
3364 Applicability::MaybeIncorrect // speculative
3369 attrs.extend(self.parse_inner_attributes()?);
3371 let mut arms: Vec<Arm> = Vec::new();
3372 while self.token != token::CloseDelim(token::Brace) {
3373 match self.parse_arm() {
3374 Ok(arm) => arms.push(arm),
3376 // Recover by skipping to the end of the block.
3378 self.recover_stmt();
3379 let span = lo.to(self.span);
3380 if self.token == token::CloseDelim(token::Brace) {
3383 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3389 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3392 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3393 let attrs = self.parse_outer_attributes()?;
3395 let pats = self.parse_pats()?;
3396 let guard = if self.eat_keyword(kw::If) {
3397 Some(Guard::If(self.parse_expr()?))
3401 let arrow_span = self.span;
3402 self.expect(&token::FatArrow)?;
3403 let arm_start_span = self.span;
3405 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3406 .map_err(|mut err| {
3407 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3411 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3412 && self.token != token::CloseDelim(token::Brace);
3417 let cm = self.sess.source_map();
3418 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3419 .map_err(|mut err| {
3420 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3421 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3422 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3423 && expr_lines.lines.len() == 2
3424 && self.token == token::FatArrow => {
3425 // We check whether there's any trailing code in the parse span,
3426 // if there isn't, we very likely have the following:
3429 // | -- - missing comma
3435 // | parsed until here as `"y" & X`
3436 err.span_suggestion_short(
3437 cm.next_point(arm_start_span),
3438 "missing a comma here to end this `match` arm",
3440 Applicability::MachineApplicable
3444 err.span_label(arrow_span,
3445 "while parsing the `match` arm starting here");
3451 self.eat(&token::Comma);
3463 /// Parses an expression.
3465 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3466 self.parse_expr_res(Restrictions::empty(), None)
3469 /// Evaluates the closure with restrictions in place.
3471 /// Afters the closure is evaluated, restrictions are reset.
3472 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
3473 where F: FnOnce(&mut Self) -> T
3475 let old = self.restrictions;
3476 self.restrictions = r;
3478 self.restrictions = old;
3483 /// Parses an expression, subject to the given restrictions.
3485 fn parse_expr_res(&mut self, r: Restrictions,
3486 already_parsed_attrs: Option<ThinVec<Attribute>>)
3487 -> PResult<'a, P<Expr>> {
3488 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3491 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
3492 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
3493 if self.eat(&token::Eq) {
3494 Ok(Some(self.parse_expr()?))
3496 Ok(Some(self.parse_expr()?))
3502 /// Parses patterns, separated by '|' s.
3503 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3504 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
3505 self.eat(&token::BinOp(token::Or));
3507 let mut pats = Vec::new();
3509 pats.push(self.parse_top_level_pat()?);
3511 if self.token == token::OrOr {
3512 let mut err = self.struct_span_err(self.span,
3513 "unexpected token `||` after pattern");
3514 err.span_suggestion(
3516 "use a single `|` to specify multiple patterns",
3518 Applicability::MachineApplicable
3522 } else if self.eat(&token::BinOp(token::Or)) {
3523 // This is a No-op. Continue the loop to parse the next
3531 // Parses a parenthesized list of patterns like
3532 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
3533 // - a vector of the patterns that were parsed
3534 // - an option indicating the index of the `..` element
3535 // - a boolean indicating whether a trailing comma was present.
3536 // Trailing commas are significant because (p) and (p,) are different patterns.
3537 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3538 self.expect(&token::OpenDelim(token::Paren))?;
3539 let result = match self.parse_pat_list() {
3540 Ok(result) => result,
3541 Err(mut err) => { // recover from parse error in tuple pattern list
3543 self.consume_block(token::Paren);
3544 return Ok((vec![], Some(0), false));
3547 self.expect(&token::CloseDelim(token::Paren))?;
3551 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3552 let mut fields = Vec::new();
3553 let mut ddpos = None;
3554 let mut prev_dd_sp = None;
3555 let mut trailing_comma = false;
3557 if self.eat(&token::DotDot) {
3558 if ddpos.is_none() {
3559 ddpos = Some(fields.len());
3560 prev_dd_sp = Some(self.prev_span);
3562 // Emit a friendly error, ignore `..` and continue parsing
3563 let mut err = self.struct_span_err(
3565 "`..` can only be used once per tuple or tuple struct pattern",
3567 err.span_label(self.prev_span, "can only be used once per pattern");
3568 if let Some(sp) = prev_dd_sp {
3569 err.span_label(sp, "previously present here");
3573 } else if !self.check(&token::CloseDelim(token::Paren)) {
3574 fields.push(self.parse_pat(None)?);
3579 trailing_comma = self.eat(&token::Comma);
3580 if !trailing_comma {
3585 if ddpos == Some(fields.len()) && trailing_comma {
3586 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
3587 let msg = "trailing comma is not permitted after `..`";
3588 self.struct_span_err(self.prev_span, msg)
3589 .span_label(self.prev_span, msg)
3593 Ok((fields, ddpos, trailing_comma))
3596 fn parse_pat_vec_elements(
3598 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3599 let mut before = Vec::new();
3600 let mut slice = None;
3601 let mut after = Vec::new();
3602 let mut first = true;
3603 let mut before_slice = true;
3605 while self.token != token::CloseDelim(token::Bracket) {
3609 self.expect(&token::Comma)?;
3611 if self.token == token::CloseDelim(token::Bracket)
3612 && (before_slice || !after.is_empty()) {
3618 if self.eat(&token::DotDot) {
3620 if self.check(&token::Comma) ||
3621 self.check(&token::CloseDelim(token::Bracket)) {
3622 slice = Some(P(Pat {
3623 id: ast::DUMMY_NODE_ID,
3624 node: PatKind::Wild,
3625 span: self.prev_span,
3627 before_slice = false;
3633 let subpat = self.parse_pat(None)?;
3634 if before_slice && self.eat(&token::DotDot) {
3635 slice = Some(subpat);
3636 before_slice = false;
3637 } else if before_slice {
3638 before.push(subpat);
3644 Ok((before, slice, after))
3650 attrs: Vec<Attribute>
3651 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
3652 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3654 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3655 // Parsing a pattern of the form "fieldname: pat"
3656 let fieldname = self.parse_field_name()?;
3658 let pat = self.parse_pat(None)?;
3660 (pat, fieldname, false)
3662 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3663 let is_box = self.eat_keyword(kw::Box);
3664 let boxed_span = self.span;
3665 let is_ref = self.eat_keyword(kw::Ref);
3666 let is_mut = self.eat_keyword(kw::Mut);
3667 let fieldname = self.parse_ident()?;
3668 hi = self.prev_span;
3670 let bind_type = match (is_ref, is_mut) {
3671 (true, true) => BindingMode::ByRef(Mutability::Mutable),
3672 (true, false) => BindingMode::ByRef(Mutability::Immutable),
3673 (false, true) => BindingMode::ByValue(Mutability::Mutable),
3674 (false, false) => BindingMode::ByValue(Mutability::Immutable),
3676 let fieldpat = P(Pat {
3677 id: ast::DUMMY_NODE_ID,
3678 node: PatKind::Ident(bind_type, fieldname, None),
3679 span: boxed_span.to(hi),
3682 let subpat = if is_box {
3684 id: ast::DUMMY_NODE_ID,
3685 node: PatKind::Box(fieldpat),
3691 (subpat, fieldname, true)
3694 Ok(source_map::Spanned {
3696 node: ast::FieldPat {
3700 attrs: attrs.into(),
3705 /// Parses the fields of a struct-like pattern.
3706 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
3707 let mut fields = Vec::new();
3708 let mut etc = false;
3709 let mut ate_comma = true;
3710 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
3711 let mut etc_span = None;
3713 while self.token != token::CloseDelim(token::Brace) {
3714 let attrs = self.parse_outer_attributes()?;
3717 // check that a comma comes after every field
3719 let err = self.struct_span_err(self.prev_span, "expected `,`");
3720 if let Some(mut delayed) = delayed_err {
3727 if self.check(&token::DotDot) || self.token == token::DotDotDot {
3729 let mut etc_sp = self.span;
3731 if self.token == token::DotDotDot { // Issue #46718
3732 // Accept `...` as if it were `..` to avoid further errors
3733 let mut err = self.struct_span_err(self.span,
3734 "expected field pattern, found `...`");
3735 err.span_suggestion(
3737 "to omit remaining fields, use one fewer `.`",
3739 Applicability::MachineApplicable
3743 self.bump(); // `..` || `...`
3745 if self.token == token::CloseDelim(token::Brace) {
3746 etc_span = Some(etc_sp);
3749 let token_str = self.this_token_descr();
3750 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
3752 err.span_label(self.span, "expected `}`");
3753 let mut comma_sp = None;
3754 if self.token == token::Comma { // Issue #49257
3755 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
3756 err.span_label(etc_sp,
3757 "`..` must be at the end and cannot have a trailing comma");
3758 comma_sp = Some(self.span);
3763 etc_span = Some(etc_sp.until(self.span));
3764 if self.token == token::CloseDelim(token::Brace) {
3765 // If the struct looks otherwise well formed, recover and continue.
3766 if let Some(sp) = comma_sp {
3767 err.span_suggestion_short(
3769 "remove this comma",
3771 Applicability::MachineApplicable,
3776 } else if self.token.is_ident() && ate_comma {
3777 // Accept fields coming after `..,`.
3778 // This way we avoid "pattern missing fields" errors afterwards.
3779 // We delay this error until the end in order to have a span for a
3781 if let Some(mut delayed_err) = delayed_err {
3785 delayed_err = Some(err);
3788 if let Some(mut err) = delayed_err {
3795 fields.push(match self.parse_pat_field(lo, attrs) {
3798 if let Some(mut delayed_err) = delayed_err {
3804 ate_comma = self.eat(&token::Comma);
3807 if let Some(mut err) = delayed_err {
3808 if let Some(etc_span) = etc_span {
3809 err.multipart_suggestion(
3810 "move the `..` to the end of the field list",
3812 (etc_span, String::new()),
3813 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
3815 Applicability::MachineApplicable,
3820 return Ok((fields, etc));
3823 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3824 if self.token.is_path_start() {
3826 let (qself, path) = if self.eat_lt() {
3827 // Parse a qualified path
3828 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3831 // Parse an unqualified path
3832 (None, self.parse_path(PathStyle::Expr)?)
3834 let hi = self.prev_span;
3835 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
3837 self.parse_literal_maybe_minus()
3841 // helper function to decide whether to parse as ident binding or to try to do
3842 // something more complex like range patterns
3843 fn parse_as_ident(&mut self) -> bool {
3844 self.look_ahead(1, |t| match *t {
3845 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
3846 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
3847 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
3848 // range pattern branch
3849 token::DotDot => None,
3851 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
3852 token::Comma | token::CloseDelim(token::Bracket) => true,
3857 /// A wrapper around `parse_pat` with some special error handling for the
3858 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
3859 /// to subpatterns within such).
3860 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
3861 let pat = self.parse_pat(None)?;
3862 if self.token == token::Comma {
3863 // An unexpected comma after a top-level pattern is a clue that the
3864 // user (perhaps more accustomed to some other language) forgot the
3865 // parentheses in what should have been a tuple pattern; return a
3866 // suggestion-enhanced error here rather than choking on the comma
3868 let comma_span = self.span;
3870 if let Err(mut err) = self.parse_pat_list() {
3871 // We didn't expect this to work anyway; we just wanted
3872 // to advance to the end of the comma-sequence so we know
3873 // the span to suggest parenthesizing
3876 let seq_span = pat.span.to(self.prev_span);
3877 let mut err = self.struct_span_err(comma_span,
3878 "unexpected `,` in pattern");
3879 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
3880 err.span_suggestion(
3882 "try adding parentheses to match on a tuple..",
3883 format!("({})", seq_snippet),
3884 Applicability::MachineApplicable
3887 "..or a vertical bar to match on multiple alternatives",
3888 format!("{}", seq_snippet.replace(",", " |")),
3889 Applicability::MachineApplicable
3897 /// Parses a pattern.
3898 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
3899 self.parse_pat_with_range_pat(true, expected)
3902 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
3904 fn parse_pat_with_range_pat(
3906 allow_range_pat: bool,
3907 expected: Option<&'static str>,
3908 ) -> PResult<'a, P<Pat>> {
3909 maybe_recover_from_interpolated_ty_qpath!(self, true);
3910 maybe_whole!(self, NtPat, |x| x);
3915 token::BinOp(token::And) | token::AndAnd => {
3916 // Parse &pat / &mut pat
3918 let mutbl = self.parse_mutability();
3919 if let token::Lifetime(ident) = self.token {
3920 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
3922 err.span_label(self.span, "unexpected lifetime");
3925 let subpat = self.parse_pat_with_range_pat(false, expected)?;
3926 pat = PatKind::Ref(subpat, mutbl);
3928 token::OpenDelim(token::Paren) => {
3929 // Parse (pat,pat,pat,...) as tuple pattern
3930 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
3931 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
3932 PatKind::Paren(fields.into_iter().nth(0).unwrap())
3934 PatKind::Tuple(fields, ddpos)
3937 token::OpenDelim(token::Bracket) => {
3938 // Parse [pat,pat,...] as slice pattern
3940 let (before, slice, after) = self.parse_pat_vec_elements()?;
3941 self.expect(&token::CloseDelim(token::Bracket))?;
3942 pat = PatKind::Slice(before, slice, after);
3944 // At this point, token != &, &&, (, [
3945 _ => if self.eat_keyword(kw::Underscore) {
3947 pat = PatKind::Wild;
3948 } else if self.eat_keyword(kw::Mut) {
3949 // Parse mut ident @ pat / mut ref ident @ pat
3950 let mutref_span = self.prev_span.to(self.span);
3951 let binding_mode = if self.eat_keyword(kw::Ref) {
3953 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
3956 "try switching the order",
3958 Applicability::MachineApplicable
3960 BindingMode::ByRef(Mutability::Mutable)
3962 BindingMode::ByValue(Mutability::Mutable)
3964 pat = self.parse_pat_ident(binding_mode)?;
3965 } else if self.eat_keyword(kw::Ref) {
3966 // Parse ref ident @ pat / ref mut ident @ pat
3967 let mutbl = self.parse_mutability();
3968 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
3969 } else if self.eat_keyword(kw::Box) {
3971 let subpat = self.parse_pat_with_range_pat(false, None)?;
3972 pat = PatKind::Box(subpat);
3973 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
3974 self.parse_as_ident() {
3975 // Parse ident @ pat
3976 // This can give false positives and parse nullary enums,
3977 // they are dealt with later in resolve
3978 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
3979 pat = self.parse_pat_ident(binding_mode)?;
3980 } else if self.token.is_path_start() {
3981 // Parse pattern starting with a path
3982 let (qself, path) = if self.eat_lt() {
3983 // Parse a qualified path
3984 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3987 // Parse an unqualified path
3988 (None, self.parse_path(PathStyle::Expr)?)
3991 token::Not if qself.is_none() => {
3992 // Parse macro invocation
3994 let (delim, tts) = self.expect_delimited_token_tree()?;
3995 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
3996 pat = PatKind::Mac(mac);
3998 token::DotDotDot | token::DotDotEq | token::DotDot => {
3999 let end_kind = match self.token {
4000 token::DotDot => RangeEnd::Excluded,
4001 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4002 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4003 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4006 let op_span = self.span;
4008 let span = lo.to(self.prev_span);
4009 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4011 let end = self.parse_pat_range_end()?;
4012 let op = Spanned { span: op_span, node: end_kind };
4013 pat = PatKind::Range(begin, end, op);
4015 token::OpenDelim(token::Brace) => {
4016 if qself.is_some() {
4017 let msg = "unexpected `{` after qualified path";
4018 let mut err = self.fatal(msg);
4019 err.span_label(self.span, msg);
4022 // Parse struct pattern
4024 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4026 self.recover_stmt();
4030 pat = PatKind::Struct(path, fields, etc);
4032 token::OpenDelim(token::Paren) => {
4033 if qself.is_some() {
4034 let msg = "unexpected `(` after qualified path";
4035 let mut err = self.fatal(msg);
4036 err.span_label(self.span, msg);
4039 // Parse tuple struct or enum pattern
4040 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4041 pat = PatKind::TupleStruct(path, fields, ddpos)
4043 _ => pat = PatKind::Path(qself, path),
4046 // Try to parse everything else as literal with optional minus
4047 match self.parse_literal_maybe_minus() {
4049 let op_span = self.span;
4050 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4051 self.check(&token::DotDotDot) {
4052 let end_kind = if self.eat(&token::DotDotDot) {
4053 RangeEnd::Included(RangeSyntax::DotDotDot)
4054 } else if self.eat(&token::DotDotEq) {
4055 RangeEnd::Included(RangeSyntax::DotDotEq)
4056 } else if self.eat(&token::DotDot) {
4059 panic!("impossible case: we already matched \
4060 on a range-operator token")
4062 let end = self.parse_pat_range_end()?;
4063 let op = Spanned { span: op_span, node: end_kind };
4064 pat = PatKind::Range(begin, end, op);
4066 pat = PatKind::Lit(begin);
4070 self.cancel(&mut err);
4071 let expected = expected.unwrap_or("pattern");
4073 "expected {}, found {}",
4075 self.this_token_descr(),
4077 let mut err = self.fatal(&msg);
4078 err.span_label(self.span, format!("expected {}", expected));
4079 let sp = self.sess.source_map().start_point(self.span);
4080 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4081 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4089 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4090 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4092 if !allow_range_pat {
4095 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4097 PatKind::Range(..) => {
4098 let mut err = self.struct_span_err(
4100 "the range pattern here has ambiguous interpretation",
4102 err.span_suggestion(
4104 "add parentheses to clarify the precedence",
4105 format!("({})", pprust::pat_to_string(&pat)),
4106 // "ambiguous interpretation" implies that we have to be guessing
4107 Applicability::MaybeIncorrect
4118 /// Parses `ident` or `ident @ pat`.
4119 /// used by the copy foo and ref foo patterns to give a good
4120 /// error message when parsing mistakes like `ref foo(a, b)`.
4121 fn parse_pat_ident(&mut self,
4122 binding_mode: ast::BindingMode)
4123 -> PResult<'a, PatKind> {
4124 let ident = self.parse_ident()?;
4125 let sub = if self.eat(&token::At) {
4126 Some(self.parse_pat(Some("binding pattern"))?)
4131 // just to be friendly, if they write something like
4133 // we end up here with ( as the current token. This shortly
4134 // leads to a parse error. Note that if there is no explicit
4135 // binding mode then we do not end up here, because the lookahead
4136 // will direct us over to parse_enum_variant()
4137 if self.token == token::OpenDelim(token::Paren) {
4138 return Err(self.span_fatal(
4140 "expected identifier, found enum pattern"))
4143 Ok(PatKind::Ident(binding_mode, ident, sub))
4146 /// Parses a local variable declaration.
4147 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4148 let lo = self.prev_span;
4149 let pat = self.parse_top_level_pat()?;
4151 let (err, ty) = if self.eat(&token::Colon) {
4152 // Save the state of the parser before parsing type normally, in case there is a `:`
4153 // instead of an `=` typo.
4154 let parser_snapshot_before_type = self.clone();
4155 let colon_sp = self.prev_span;
4156 match self.parse_ty() {
4157 Ok(ty) => (None, Some(ty)),
4159 // Rewind to before attempting to parse the type and continue parsing
4160 let parser_snapshot_after_type = self.clone();
4161 mem::replace(self, parser_snapshot_before_type);
4163 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4164 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4165 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4171 let init = match (self.parse_initializer(err.is_some()), err) {
4172 (Ok(init), None) => { // init parsed, ty parsed
4175 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4176 // Could parse the type as if it were the initializer, it is likely there was a
4177 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4178 err.span_suggestion_short(
4180 "use `=` if you meant to assign",
4182 Applicability::MachineApplicable
4185 // As this was parsed successfully, continue as if the code has been fixed for the
4186 // rest of the file. It will still fail due to the emitted error, but we avoid
4190 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4192 // Couldn't parse the type nor the initializer, only raise the type error and
4193 // return to the parser state before parsing the type as the initializer.
4194 // let x: <parse_error>;
4195 mem::replace(self, snapshot);
4198 (Err(err), None) => { // init error, ty parsed
4199 // Couldn't parse the initializer and we're not attempting to recover a failed
4200 // parse of the type, return the error.
4204 let hi = if self.token == token::Semi {
4213 id: ast::DUMMY_NODE_ID,
4216 source: LocalSource::Normal,
4220 /// Parses a structure field.
4221 fn parse_name_and_ty(&mut self,
4224 attrs: Vec<Attribute>)
4225 -> PResult<'a, StructField> {
4226 let name = self.parse_ident()?;
4227 self.expect(&token::Colon)?;
4228 let ty = self.parse_ty()?;
4230 span: lo.to(self.prev_span),
4233 id: ast::DUMMY_NODE_ID,
4239 /// Emits an expected-item-after-attributes error.
4240 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4241 let message = match attrs.last() {
4242 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4243 _ => "expected item after attributes",
4246 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4247 if attrs.last().unwrap().is_sugared_doc {
4248 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4253 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4254 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4255 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4256 Ok(self.parse_stmt_(true))
4259 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4260 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4262 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4267 fn is_async_block(&self) -> bool {
4268 self.token.is_keyword(kw::Async) &&
4271 self.is_keyword_ahead(1, &[kw::Move]) &&
4272 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4274 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4279 fn is_async_fn(&self) -> bool {
4280 self.token.is_keyword(kw::Async) &&
4281 self.is_keyword_ahead(1, &[kw::Fn])
4284 fn is_do_catch_block(&self) -> bool {
4285 self.token.is_keyword(kw::Do) &&
4286 self.is_keyword_ahead(1, &[kw::Catch]) &&
4287 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4288 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4291 fn is_try_block(&self) -> bool {
4292 self.token.is_keyword(kw::Try) &&
4293 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
4294 self.span.rust_2018() &&
4295 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
4296 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4299 fn is_union_item(&self) -> bool {
4300 self.token.is_keyword(kw::Union) &&
4301 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4304 fn is_crate_vis(&self) -> bool {
4305 self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4308 fn is_existential_type_decl(&self) -> bool {
4309 self.token.is_keyword(kw::Existential) &&
4310 self.is_keyword_ahead(1, &[kw::Type])
4313 fn is_auto_trait_item(&self) -> bool {
4315 (self.token.is_keyword(kw::Auto) &&
4316 self.is_keyword_ahead(1, &[kw::Trait]))
4317 || // unsafe auto trait
4318 (self.token.is_keyword(kw::Unsafe) &&
4319 self.is_keyword_ahead(1, &[kw::Auto]) &&
4320 self.is_keyword_ahead(2, &[kw::Trait]))
4323 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4324 -> PResult<'a, Option<P<Item>>> {
4325 let token_lo = self.span;
4326 let (ident, def) = match self.token {
4327 token::Ident(ident, false) if ident.name == kw::Macro => {
4329 let ident = self.parse_ident()?;
4330 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4331 match self.parse_token_tree() {
4332 TokenTree::Delimited(_, _, tts) => tts,
4333 _ => unreachable!(),
4335 } else if self.check(&token::OpenDelim(token::Paren)) {
4336 let args = self.parse_token_tree();
4337 let body = if self.check(&token::OpenDelim(token::Brace)) {
4338 self.parse_token_tree()
4343 TokenStream::new(vec![
4345 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
4353 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4355 token::Ident(ident, _) if ident.name == sym::macro_rules &&
4356 self.look_ahead(1, |t| *t == token::Not) => {
4357 let prev_span = self.prev_span;
4358 self.complain_if_pub_macro(&vis.node, prev_span);
4362 let ident = self.parse_ident()?;
4363 let (delim, tokens) = self.expect_delimited_token_tree()?;
4364 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
4365 self.report_invalid_macro_expansion_item();
4368 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4370 _ => return Ok(None),
4373 let span = lo.to(self.prev_span);
4374 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4377 fn parse_stmt_without_recovery(&mut self,
4378 macro_legacy_warnings: bool)
4379 -> PResult<'a, Option<Stmt>> {
4380 maybe_whole!(self, NtStmt, |x| Some(x));
4382 let attrs = self.parse_outer_attributes()?;
4385 Ok(Some(if self.eat_keyword(kw::Let) {
4387 id: ast::DUMMY_NODE_ID,
4388 node: StmtKind::Local(self.parse_local(attrs.into())?),
4389 span: lo.to(self.prev_span),
4391 } else if let Some(macro_def) = self.eat_macro_def(
4393 &source_map::respan(lo, VisibilityKind::Inherited),
4397 id: ast::DUMMY_NODE_ID,
4398 node: StmtKind::Item(macro_def),
4399 span: lo.to(self.prev_span),
4401 // Starts like a simple path, being careful to avoid contextual keywords
4402 // such as a union items, item with `crate` visibility or auto trait items.
4403 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4404 // like a path (1 token), but it fact not a path.
4405 // `union::b::c` - path, `union U { ... }` - not a path.
4406 // `crate::b::c` - path, `crate struct S;` - not a path.
4407 } else if self.token.is_path_start() &&
4408 !self.token.is_qpath_start() &&
4409 !self.is_union_item() &&
4410 !self.is_crate_vis() &&
4411 !self.is_existential_type_decl() &&
4412 !self.is_auto_trait_item() &&
4413 !self.is_async_fn() {
4414 let pth = self.parse_path(PathStyle::Expr)?;
4416 if !self.eat(&token::Not) {
4417 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4418 self.parse_struct_expr(lo, pth, ThinVec::new())?
4420 let hi = self.prev_span;
4421 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4424 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4425 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4426 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4429 return Ok(Some(Stmt {
4430 id: ast::DUMMY_NODE_ID,
4431 node: StmtKind::Expr(expr),
4432 span: lo.to(self.prev_span),
4436 // it's a macro invocation
4437 let id = match self.token {
4438 token::OpenDelim(_) => Ident::invalid(), // no special identifier
4439 _ => self.parse_ident()?,
4442 // check that we're pointing at delimiters (need to check
4443 // again after the `if`, because of `parse_ident`
4444 // consuming more tokens).
4446 token::OpenDelim(_) => {}
4448 // we only expect an ident if we didn't parse one
4450 let ident_str = if id.name == kw::Invalid {
4455 let tok_str = self.this_token_descr();
4456 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
4459 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
4464 let (delim, tts) = self.expect_delimited_token_tree()?;
4465 let hi = self.prev_span;
4467 let style = if delim == MacDelimiter::Brace {
4468 MacStmtStyle::Braces
4470 MacStmtStyle::NoBraces
4473 if id.name == kw::Invalid {
4474 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
4475 let node = if delim == MacDelimiter::Brace ||
4476 self.token == token::Semi || self.token == token::Eof {
4477 StmtKind::Mac(P((mac, style, attrs.into())))
4479 // We used to incorrectly stop parsing macro-expanded statements here.
4480 // If the next token will be an error anyway but could have parsed with the
4481 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
4482 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
4483 // These can continue an expression, so we can't stop parsing and warn.
4484 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
4485 token::BinOp(token::Minus) | token::BinOp(token::Star) |
4486 token::BinOp(token::And) | token::BinOp(token::Or) |
4487 token::AndAnd | token::OrOr |
4488 token::DotDot | token::DotDotDot | token::DotDotEq => false,
4491 self.warn_missing_semicolon();
4492 StmtKind::Mac(P((mac, style, attrs.into())))
4494 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
4495 let e = self.maybe_recover_from_bad_qpath(e, true)?;
4496 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
4497 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
4501 id: ast::DUMMY_NODE_ID,
4506 // if it has a special ident, it's definitely an item
4508 // Require a semicolon or braces.
4509 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
4510 self.report_invalid_macro_expansion_item();
4512 let span = lo.to(hi);
4514 id: ast::DUMMY_NODE_ID,
4516 node: StmtKind::Item({
4518 span, id /*id is good here*/,
4519 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
4520 respan(lo, VisibilityKind::Inherited),
4526 // FIXME: Bad copy of attrs
4527 let old_directory_ownership =
4528 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
4529 let item = self.parse_item_(attrs.clone(), false, true)?;
4530 self.directory.ownership = old_directory_ownership;
4534 id: ast::DUMMY_NODE_ID,
4535 span: lo.to(i.span),
4536 node: StmtKind::Item(i),
4539 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
4540 if !attrs.is_empty() {
4541 if s.prev_token_kind == PrevTokenKind::DocComment {
4542 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
4543 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
4544 s.span_err(s.span, "expected statement after outer attribute");
4549 // Do not attempt to parse an expression if we're done here.
4550 if self.token == token::Semi {
4551 unused_attrs(&attrs, self);
4556 if self.token == token::CloseDelim(token::Brace) {
4557 unused_attrs(&attrs, self);
4561 // Remainder are line-expr stmts.
4562 let e = self.parse_expr_res(
4563 Restrictions::STMT_EXPR, Some(attrs.into()))?;
4565 id: ast::DUMMY_NODE_ID,
4566 span: lo.to(e.span),
4567 node: StmtKind::Expr(e),
4574 /// Checks if this expression is a successfully parsed statement.
4575 fn expr_is_complete(&self, e: &Expr) -> bool {
4576 self.restrictions.contains(Restrictions::STMT_EXPR) &&
4577 !classify::expr_requires_semi_to_be_stmt(e)
4580 /// Parses a block. No inner attributes are allowed.
4581 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
4582 maybe_whole!(self, NtBlock, |x| x);
4586 if !self.eat(&token::OpenDelim(token::Brace)) {
4588 let tok = self.this_token_descr();
4589 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
4590 let do_not_suggest_help =
4591 self.token.is_keyword(kw::In) || self.token == token::Colon;
4593 if self.token.is_ident_named(sym::and) {
4594 e.span_suggestion_short(
4596 "use `&&` instead of `and` for the boolean operator",
4598 Applicability::MaybeIncorrect,
4601 if self.token.is_ident_named(sym::or) {
4602 e.span_suggestion_short(
4604 "use `||` instead of `or` for the boolean operator",
4606 Applicability::MaybeIncorrect,
4610 // Check to see if the user has written something like
4615 // Which is valid in other languages, but not Rust.
4616 match self.parse_stmt_without_recovery(false) {
4618 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
4619 || do_not_suggest_help {
4620 // if the next token is an open brace (e.g., `if a b {`), the place-
4621 // inside-a-block suggestion would be more likely wrong than right
4622 e.span_label(sp, "expected `{`");
4625 let mut stmt_span = stmt.span;
4626 // expand the span to include the semicolon, if it exists
4627 if self.eat(&token::Semi) {
4628 stmt_span = stmt_span.with_hi(self.prev_span.hi());
4630 let sugg = pprust::to_string(|s| {
4631 use crate::print::pprust::{PrintState, INDENT_UNIT};
4632 s.ibox(INDENT_UNIT)?;
4634 s.print_stmt(&stmt)?;
4635 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
4639 "try placing this code inside a block",
4641 // speculative, has been misleading in the past (closed Issue #46836)
4642 Applicability::MaybeIncorrect
4646 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4647 self.cancel(&mut e);
4651 e.span_label(sp, "expected `{`");
4655 self.parse_block_tail(lo, BlockCheckMode::Default)
4658 /// Parses a block. Inner attributes are allowed.
4659 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
4660 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
4663 self.expect(&token::OpenDelim(token::Brace))?;
4664 Ok((self.parse_inner_attributes()?,
4665 self.parse_block_tail(lo, BlockCheckMode::Default)?))
4668 /// Parses the rest of a block expression or function body.
4669 /// Precondition: already parsed the '{'.
4670 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
4671 let mut stmts = vec![];
4672 while !self.eat(&token::CloseDelim(token::Brace)) {
4673 let stmt = match self.parse_full_stmt(false) {
4676 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
4678 id: ast::DUMMY_NODE_ID,
4679 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
4685 if let Some(stmt) = stmt {
4687 } else if self.token == token::Eof {
4690 // Found only `;` or `}`.
4696 id: ast::DUMMY_NODE_ID,
4698 span: lo.to(self.prev_span),
4702 /// Parses a statement, including the trailing semicolon.
4703 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
4704 // skip looking for a trailing semicolon when we have an interpolated statement
4705 maybe_whole!(self, NtStmt, |x| Some(x));
4707 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
4709 None => return Ok(None),
4713 StmtKind::Expr(ref expr) if self.token != token::Eof => {
4714 // expression without semicolon
4715 if classify::expr_requires_semi_to_be_stmt(expr) {
4716 // Just check for errors and recover; do not eat semicolon yet.
4718 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
4721 self.recover_stmt();
4725 StmtKind::Local(..) => {
4726 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
4727 if macro_legacy_warnings && self.token != token::Semi {
4728 self.warn_missing_semicolon();
4730 self.expect_one_of(&[], &[token::Semi])?;
4736 if self.eat(&token::Semi) {
4737 stmt = stmt.add_trailing_semicolon();
4740 stmt.span = stmt.span.with_hi(self.prev_span.hi());
4744 fn warn_missing_semicolon(&self) {
4745 self.diagnostic().struct_span_warn(self.span, {
4746 &format!("expected `;`, found {}", self.this_token_descr())
4748 "This was erroneously allowed and will become a hard error in a future release"
4752 fn err_dotdotdot_syntax(&self, span: Span) {
4753 self.diagnostic().struct_span_err(span, {
4754 "unexpected token: `...`"
4756 span, "use `..` for an exclusive range", "..".to_owned(),
4757 Applicability::MaybeIncorrect
4759 span, "or `..=` for an inclusive range", "..=".to_owned(),
4760 Applicability::MaybeIncorrect
4764 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
4767 /// BOUND = TY_BOUND | LT_BOUND
4768 /// LT_BOUND = LIFETIME (e.g., `'a`)
4769 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
4770 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
4772 fn parse_generic_bounds_common(&mut self,
4774 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4775 let mut bounds = Vec::new();
4776 let mut negative_bounds = Vec::new();
4777 let mut last_plus_span = None;
4778 let mut was_negative = false;
4780 // This needs to be synchronized with `Token::can_begin_bound`.
4781 let is_bound_start = self.check_path() || self.check_lifetime() ||
4782 self.check(&token::Not) || // used for error reporting only
4783 self.check(&token::Question) ||
4784 self.check_keyword(kw::For) ||
4785 self.check(&token::OpenDelim(token::Paren));
4788 let has_parens = self.eat(&token::OpenDelim(token::Paren));
4789 let inner_lo = self.span;
4790 let is_negative = self.eat(&token::Not);
4791 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
4792 if self.token.is_lifetime() {
4793 if let Some(question_span) = question {
4794 self.span_err(question_span,
4795 "`?` may only modify trait bounds, not lifetime bounds");
4797 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
4799 let inner_span = inner_lo.to(self.prev_span);
4800 self.expect(&token::CloseDelim(token::Paren))?;
4801 let mut err = self.struct_span_err(
4802 lo.to(self.prev_span),
4803 "parenthesized lifetime bounds are not supported"
4805 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
4806 err.span_suggestion_short(
4807 lo.to(self.prev_span),
4808 "remove the parentheses",
4810 Applicability::MachineApplicable
4816 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
4817 let path = self.parse_path(PathStyle::Type)?;
4819 self.expect(&token::CloseDelim(token::Paren))?;
4821 let poly_span = lo.to(self.prev_span);
4823 was_negative = true;
4824 if let Some(sp) = last_plus_span.or(colon_span) {
4825 negative_bounds.push(sp.to(poly_span));
4828 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
4829 let modifier = if question.is_some() {
4830 TraitBoundModifier::Maybe
4832 TraitBoundModifier::None
4834 bounds.push(GenericBound::Trait(poly_trait, modifier));
4841 if !allow_plus || !self.eat_plus() {
4844 last_plus_span = Some(self.prev_span);
4848 if !negative_bounds.is_empty() || was_negative {
4849 let plural = negative_bounds.len() > 1;
4850 let last_span = negative_bounds.last().map(|sp| *sp);
4851 let mut err = self.struct_span_err(
4853 "negative trait bounds are not supported",
4855 if let Some(sp) = last_span {
4856 err.span_label(sp, "negative trait bounds are not supported");
4858 if let Some(bound_list) = colon_span {
4859 let bound_list = bound_list.to(self.prev_span);
4860 let mut new_bound_list = String::new();
4861 if !bounds.is_empty() {
4862 let mut snippets = bounds.iter().map(|bound| bound.span())
4863 .map(|span| self.sess.source_map().span_to_snippet(span));
4864 while let Some(Ok(snippet)) = snippets.next() {
4865 new_bound_list.push_str(" + ");
4866 new_bound_list.push_str(&snippet);
4868 new_bound_list = new_bound_list.replacen(" +", ":", 1);
4870 err.span_suggestion_hidden(
4872 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
4874 Applicability::MachineApplicable,
4883 crate fn parse_generic_bounds(&mut self,
4884 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4885 self.parse_generic_bounds_common(true, colon_span)
4888 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4891 /// BOUND = LT_BOUND (e.g., `'a`)
4893 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
4894 let mut lifetimes = Vec::new();
4895 while self.check_lifetime() {
4896 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
4898 if !self.eat_plus() {
4905 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
4906 fn parse_ty_param(&mut self,
4907 preceding_attrs: Vec<Attribute>)
4908 -> PResult<'a, GenericParam> {
4909 let ident = self.parse_ident()?;
4911 // Parse optional colon and param bounds.
4912 let bounds = if self.eat(&token::Colon) {
4913 self.parse_generic_bounds(Some(self.prev_span))?
4918 let default = if self.eat(&token::Eq) {
4919 Some(self.parse_ty()?)
4926 id: ast::DUMMY_NODE_ID,
4927 attrs: preceding_attrs.into(),
4929 kind: GenericParamKind::Type {
4935 /// Parses the following grammar:
4937 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
4938 fn parse_trait_item_assoc_ty(&mut self)
4939 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
4940 let ident = self.parse_ident()?;
4941 let mut generics = self.parse_generics()?;
4943 // Parse optional colon and param bounds.
4944 let bounds = if self.eat(&token::Colon) {
4945 self.parse_generic_bounds(None)?
4949 generics.where_clause = self.parse_where_clause()?;
4951 let default = if self.eat(&token::Eq) {
4952 Some(self.parse_ty()?)
4956 self.expect(&token::Semi)?;
4958 Ok((ident, TraitItemKind::Type(bounds, default), generics))
4961 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
4962 self.expect_keyword(kw::Const)?;
4963 let ident = self.parse_ident()?;
4964 self.expect(&token::Colon)?;
4965 let ty = self.parse_ty()?;
4969 id: ast::DUMMY_NODE_ID,
4970 attrs: preceding_attrs.into(),
4972 kind: GenericParamKind::Const {
4978 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
4979 /// a trailing comma and erroneous trailing attributes.
4980 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
4981 let mut params = Vec::new();
4983 let attrs = self.parse_outer_attributes()?;
4984 if self.check_lifetime() {
4985 let lifetime = self.expect_lifetime();
4986 // Parse lifetime parameter.
4987 let bounds = if self.eat(&token::Colon) {
4988 self.parse_lt_param_bounds()
4992 params.push(ast::GenericParam {
4993 ident: lifetime.ident,
4995 attrs: attrs.into(),
4997 kind: ast::GenericParamKind::Lifetime,
4999 } else if self.check_keyword(kw::Const) {
5000 // Parse const parameter.
5001 params.push(self.parse_const_param(attrs)?);
5002 } else if self.check_ident() {
5003 // Parse type parameter.
5004 params.push(self.parse_ty_param(attrs)?);
5006 // Check for trailing attributes and stop parsing.
5007 if !attrs.is_empty() {
5008 if !params.is_empty() {
5009 self.struct_span_err(
5011 &format!("trailing attribute after generic parameter"),
5013 .span_label(attrs[0].span, "attributes must go before parameters")
5016 self.struct_span_err(
5018 &format!("attribute without generic parameters"),
5022 "attributes are only permitted when preceding parameters",
5030 if !self.eat(&token::Comma) {
5037 /// Parses a set of optional generic type parameter declarations. Where
5038 /// clauses are not parsed here, and must be added later via
5039 /// `parse_where_clause()`.
5041 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5042 /// | ( < lifetimes , typaramseq ( , )? > )
5043 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5044 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5045 let span_lo = self.span;
5046 let (params, span) = if self.eat_lt() {
5047 let params = self.parse_generic_params()?;
5049 (params, span_lo.to(self.prev_span))
5051 (vec![], self.prev_span.between(self.span))
5055 where_clause: WhereClause {
5056 id: ast::DUMMY_NODE_ID,
5057 predicates: Vec::new(),
5064 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5065 /// For the purposes of understanding the parsing logic of generic arguments, this function
5066 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5067 /// had the correct amount of leading angle brackets.
5069 /// ```ignore (diagnostics)
5070 /// bar::<<<<T as Foo>::Output>();
5071 /// ^^ help: remove extra angle brackets
5073 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5077 ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5078 // We need to detect whether there are extra leading left angle brackets and produce an
5079 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5080 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5081 // then there won't be matching `>` tokens to find.
5083 // To explain how this detection works, consider the following example:
5085 // ```ignore (diagnostics)
5086 // bar::<<<<T as Foo>::Output>();
5087 // ^^ help: remove extra angle brackets
5090 // Parsing of the left angle brackets starts in this function. We start by parsing the
5091 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5094 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5095 // *Unmatched count:* 1
5096 // *`parse_path_segment` calls deep:* 0
5098 // This has the effect of recursing as this function is called if a `<` character
5099 // is found within the expected generic arguments:
5101 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5102 // *Unmatched count:* 2
5103 // *`parse_path_segment` calls deep:* 1
5105 // Eventually we will have recursed until having consumed all of the `<` tokens and
5106 // this will be reflected in the count:
5108 // *Upcoming tokens:* `T as Foo>::Output>;`
5109 // *Unmatched count:* 4
5110 // `parse_path_segment` calls deep:* 3
5112 // The parser will continue until reaching the first `>` - this will decrement the
5113 // unmatched angle bracket count and return to the parent invocation of this function
5114 // having succeeded in parsing:
5116 // *Upcoming tokens:* `::Output>;`
5117 // *Unmatched count:* 3
5118 // *`parse_path_segment` calls deep:* 2
5120 // This will continue until the next `>` character which will also return successfully
5121 // to the parent invocation of this function and decrement the count:
5123 // *Upcoming tokens:* `;`
5124 // *Unmatched count:* 2
5125 // *`parse_path_segment` calls deep:* 1
5127 // At this point, this function will expect to find another matching `>` character but
5128 // won't be able to and will return an error. This will continue all the way up the
5129 // call stack until the first invocation:
5131 // *Upcoming tokens:* `;`
5132 // *Unmatched count:* 2
5133 // *`parse_path_segment` calls deep:* 0
5135 // In doing this, we have managed to work out how many unmatched leading left angle
5136 // brackets there are, but we cannot recover as the unmatched angle brackets have
5137 // already been consumed. To remedy this, we keep a snapshot of the parser state
5138 // before we do the above. We can then inspect whether we ended up with a parsing error
5139 // and unmatched left angle brackets and if so, restore the parser state before we
5140 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5141 // recover by attempting to parse again.
5143 // In practice, the recursion of this function is indirect and there will be other
5144 // locations that consume some `<` characters - as long as we update the count when
5145 // this happens, it isn't an issue.
5147 let is_first_invocation = style == PathStyle::Expr;
5148 // Take a snapshot before attempting to parse - we can restore this later.
5149 let snapshot = if is_first_invocation {
5155 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5156 match self.parse_generic_args() {
5157 Ok(value) => Ok(value),
5158 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5159 // Cancel error from being unable to find `>`. We know the error
5160 // must have been this due to a non-zero unmatched angle bracket
5164 // Swap `self` with our backup of the parser state before attempting to parse
5165 // generic arguments.
5166 let snapshot = mem::replace(self, snapshot.unwrap());
5169 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5170 snapshot.count={:?}",
5171 snapshot.unmatched_angle_bracket_count,
5174 // Eat the unmatched angle brackets.
5175 for _ in 0..snapshot.unmatched_angle_bracket_count {
5179 // Make a span over ${unmatched angle bracket count} characters.
5180 let span = lo.with_hi(
5181 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5183 let plural = snapshot.unmatched_angle_bracket_count > 1;
5188 "unmatched angle bracket{}",
5189 if plural { "s" } else { "" }
5195 "remove extra angle bracket{}",
5196 if plural { "s" } else { "" }
5199 Applicability::MachineApplicable,
5203 // Try again without unmatched angle bracket characters.
5204 self.parse_generic_args()
5210 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5211 /// possibly including trailing comma.
5212 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5213 let mut args = Vec::new();
5214 let mut bindings = Vec::new();
5215 let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
5216 let mut assoc_ty_bindings: Vec<Span> = Vec::new();
5218 let args_lo = self.span;
5221 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5222 // Parse lifetime argument.
5223 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5224 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5225 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
5226 // Parse associated type binding.
5228 let ident = self.parse_ident()?;
5230 let ty = self.parse_ty()?;
5231 let span = lo.to(self.prev_span);
5232 bindings.push(TypeBinding {
5233 id: ast::DUMMY_NODE_ID,
5238 assoc_ty_bindings.push(span);
5239 } else if self.check_const_arg() {
5240 // Parse const argument.
5241 let expr = if let token::OpenDelim(token::Brace) = self.token {
5242 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
5243 } else if self.token.is_ident() {
5244 // FIXME(const_generics): to distinguish between idents for types and consts,
5245 // we should introduce a GenericArg::Ident in the AST and distinguish when
5246 // lowering to the HIR. For now, idents for const args are not permitted.
5247 if self.token.is_keyword(kw::True) || self.token.is_keyword(kw::False) {
5248 self.parse_literal_maybe_minus()?
5251 self.fatal("identifiers may currently not be used for const generics")
5255 self.parse_literal_maybe_minus()?
5257 let value = AnonConst {
5258 id: ast::DUMMY_NODE_ID,
5261 args.push(GenericArg::Const(value));
5262 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5263 } else if self.check_type() {
5264 // Parse type argument.
5265 args.push(GenericArg::Type(self.parse_ty()?));
5266 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5271 if !self.eat(&token::Comma) {
5276 // FIXME: we would like to report this in ast_validation instead, but we currently do not
5277 // preserve ordering of generic parameters with respect to associated type binding, so we
5278 // lose that information after parsing.
5279 if misplaced_assoc_ty_bindings.len() > 0 {
5280 let mut err = self.struct_span_err(
5281 args_lo.to(self.prev_span),
5282 "associated type bindings must be declared after generic parameters",
5284 for span in misplaced_assoc_ty_bindings {
5287 "this associated type binding should be moved after the generic parameters",
5293 Ok((args, bindings))
5296 /// Parses an optional where-clause and places it in `generics`.
5298 /// ```ignore (only-for-syntax-highlight)
5299 /// where T : Trait<U, V> + 'b, 'a : 'b
5301 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5302 let mut where_clause = WhereClause {
5303 id: ast::DUMMY_NODE_ID,
5304 predicates: Vec::new(),
5308 if !self.eat_keyword(kw::Where) {
5309 return Ok(where_clause);
5311 let lo = self.prev_span;
5313 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5314 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5315 // change we parse those generics now, but report an error.
5316 if self.choose_generics_over_qpath() {
5317 let generics = self.parse_generics()?;
5318 self.struct_span_err(
5320 "generic parameters on `where` clauses are reserved for future use",
5322 .span_label(generics.span, "currently unsupported")
5328 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5329 let lifetime = self.expect_lifetime();
5330 // Bounds starting with a colon are mandatory, but possibly empty.
5331 self.expect(&token::Colon)?;
5332 let bounds = self.parse_lt_param_bounds();
5333 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5334 ast::WhereRegionPredicate {
5335 span: lo.to(self.prev_span),
5340 } else if self.check_type() {
5341 // Parse optional `for<'a, 'b>`.
5342 // This `for` is parsed greedily and applies to the whole predicate,
5343 // the bounded type can have its own `for` applying only to it.
5344 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
5345 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
5346 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
5347 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5349 // Parse type with mandatory colon and (possibly empty) bounds,
5350 // or with mandatory equality sign and the second type.
5351 let ty = self.parse_ty()?;
5352 if self.eat(&token::Colon) {
5353 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
5354 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5355 ast::WhereBoundPredicate {
5356 span: lo.to(self.prev_span),
5357 bound_generic_params: lifetime_defs,
5362 // FIXME: Decide what should be used here, `=` or `==`.
5363 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5364 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5365 let rhs_ty = self.parse_ty()?;
5366 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5367 ast::WhereEqPredicate {
5368 span: lo.to(self.prev_span),
5371 id: ast::DUMMY_NODE_ID,
5375 return self.unexpected();
5381 if !self.eat(&token::Comma) {
5386 where_clause.span = lo.to(self.prev_span);
5390 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
5391 -> PResult<'a, (Vec<Arg> , bool)> {
5392 self.expect(&token::OpenDelim(token::Paren))?;
5395 let mut c_variadic = false;
5396 let (args, recovered): (Vec<Option<Arg>>, bool) =
5397 self.parse_seq_to_before_end(
5398 &token::CloseDelim(token::Paren),
5399 SeqSep::trailing_allowed(token::Comma),
5401 // If the argument is a C-variadic argument we should not
5402 // enforce named arguments.
5403 let enforce_named_args = if p.token == token::DotDotDot {
5408 match p.parse_arg_general(enforce_named_args, false,
5411 if let TyKind::CVarArgs = arg.ty.node {
5413 if p.token != token::CloseDelim(token::Paren) {
5416 "`...` must be the last argument of a C-variadic function");
5427 let lo = p.prev_span;
5428 // Skip every token until next possible arg or end.
5429 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5430 // Create a placeholder argument for proper arg count (issue #34264).
5431 let span = lo.to(p.prev_span);
5432 Ok(Some(dummy_arg(Ident::new(kw::Invalid, span))))
5439 self.eat(&token::CloseDelim(token::Paren));
5442 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5444 if c_variadic && args.is_empty() {
5446 "C-variadic function must be declared with at least one named argument");
5449 Ok((args, c_variadic))
5452 /// Parses the argument list and result type of a function declaration.
5453 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
5455 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
5456 let ret_ty = self.parse_ret_ty(true)?;
5465 /// Returns the parsed optional self argument and whether a self shortcut was used.
5466 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
5467 let expect_ident = |this: &mut Self| match this.token {
5468 // Preserve hygienic context.
5469 token::Ident(ident, _) =>
5470 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
5473 let isolated_self = |this: &mut Self, n| {
5474 this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
5475 this.look_ahead(n + 1, |t| t != &token::ModSep)
5478 // Parse optional self parameter of a method.
5479 // Only a limited set of initial token sequences is considered self parameters, anything
5480 // else is parsed as a normal function parameter list, so some lookahead is required.
5481 let eself_lo = self.span;
5482 let (eself, eself_ident, eself_hi) = match self.token {
5483 token::BinOp(token::And) => {
5489 (if isolated_self(self, 1) {
5491 SelfKind::Region(None, Mutability::Immutable)
5492 } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
5493 isolated_self(self, 2) {
5496 SelfKind::Region(None, Mutability::Mutable)
5497 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5498 isolated_self(self, 2) {
5500 let lt = self.expect_lifetime();
5501 SelfKind::Region(Some(lt), Mutability::Immutable)
5502 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5503 self.is_keyword_ahead(2, &[kw::Mut]) &&
5504 isolated_self(self, 3) {
5506 let lt = self.expect_lifetime();
5508 SelfKind::Region(Some(lt), Mutability::Mutable)
5511 }, expect_ident(self), self.prev_span)
5513 token::BinOp(token::Star) => {
5518 // Emit special error for `self` cases.
5519 let msg = "cannot pass `self` by raw pointer";
5520 (if isolated_self(self, 1) {
5522 self.struct_span_err(self.span, msg)
5523 .span_label(self.span, msg)
5525 SelfKind::Value(Mutability::Immutable)
5526 } else if self.look_ahead(1, |t| t.is_mutability()) &&
5527 isolated_self(self, 2) {
5530 self.struct_span_err(self.span, msg)
5531 .span_label(self.span, msg)
5533 SelfKind::Value(Mutability::Immutable)
5536 }, expect_ident(self), self.prev_span)
5538 token::Ident(..) => {
5539 if isolated_self(self, 0) {
5542 let eself_ident = expect_ident(self);
5543 let eself_hi = self.prev_span;
5544 (if self.eat(&token::Colon) {
5545 let ty = self.parse_ty()?;
5546 SelfKind::Explicit(ty, Mutability::Immutable)
5548 SelfKind::Value(Mutability::Immutable)
5549 }, eself_ident, eself_hi)
5550 } else if self.token.is_keyword(kw::Mut) &&
5551 isolated_self(self, 1) {
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::Mutable)
5561 SelfKind::Value(Mutability::Mutable)
5562 }, eself_ident, eself_hi)
5567 _ => return Ok(None),
5570 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
5571 Ok(Some(Arg::from_self(eself, eself_ident)))
5574 /// Parses the parameter list and result type of a function that may have a `self` parameter.
5575 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
5576 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
5578 self.expect(&token::OpenDelim(token::Paren))?;
5580 // Parse optional self argument
5581 let self_arg = self.parse_self_arg()?;
5583 // Parse the rest of the function parameter list.
5584 let sep = SeqSep::trailing_allowed(token::Comma);
5585 let (mut fn_inputs, recovered) = if let Some(self_arg) = self_arg {
5586 if self.check(&token::CloseDelim(token::Paren)) {
5587 (vec![self_arg], false)
5588 } else if self.eat(&token::Comma) {
5589 let mut fn_inputs = vec![self_arg];
5590 let (mut input, recovered) = self.parse_seq_to_before_end(
5591 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
5592 fn_inputs.append(&mut input);
5593 (fn_inputs, recovered)
5595 match self.expect_one_of(&[], &[]) {
5596 Err(err) => return Err(err),
5597 Ok(recovered) => (vec![self_arg], recovered),
5601 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5605 // Parse closing paren and return type.
5606 self.expect(&token::CloseDelim(token::Paren))?;
5608 // Replace duplicated recovered arguments with `_` pattern to avoid unecessary errors.
5609 self.deduplicate_recovered_arg_names(&mut fn_inputs);
5613 output: self.parse_ret_ty(true)?,
5618 /// Parses the `|arg, arg|` header of a closure.
5619 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
5620 let inputs_captures = {
5621 if self.eat(&token::OrOr) {
5624 self.expect(&token::BinOp(token::Or))?;
5625 let args = self.parse_seq_to_before_tokens(
5626 &[&token::BinOp(token::Or), &token::OrOr],
5627 SeqSep::trailing_allowed(token::Comma),
5628 TokenExpectType::NoExpect,
5629 |p| p.parse_fn_block_arg()
5635 let output = self.parse_ret_ty(true)?;
5638 inputs: inputs_captures,
5644 /// Parses the name and optional generic types of a function header.
5645 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
5646 let id = self.parse_ident()?;
5647 let generics = self.parse_generics()?;
5651 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
5652 attrs: Vec<Attribute>) -> P<Item> {
5656 id: ast::DUMMY_NODE_ID,
5664 /// Parses an item-position function declaration.
5665 fn parse_item_fn(&mut self,
5667 mut asyncness: Spanned<IsAsync>,
5668 constness: Spanned<Constness>,
5670 -> PResult<'a, ItemInfo> {
5671 let (ident, mut generics) = self.parse_fn_header()?;
5672 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
5673 let mut decl = self.parse_fn_decl(allow_c_variadic)?;
5674 generics.where_clause = self.parse_where_clause()?;
5675 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5676 self.construct_async_arguments(&mut asyncness, &mut decl);
5677 let header = FnHeader { unsafety, asyncness, constness, abi };
5678 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
5681 /// Returns `true` if we are looking at `const ID`
5682 /// (returns `false` for things like `const fn`, etc.).
5683 fn is_const_item(&self) -> bool {
5684 self.token.is_keyword(kw::Const) &&
5685 !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
5688 /// Parses all the "front matter" for a `fn` declaration, up to
5689 /// and including the `fn` keyword:
5693 /// - `const unsafe fn`
5696 fn parse_fn_front_matter(&mut self)
5704 let is_const_fn = self.eat_keyword(kw::Const);
5705 let const_span = self.prev_span;
5706 let unsafety = self.parse_unsafety();
5707 let asyncness = self.parse_asyncness();
5708 let asyncness = respan(self.prev_span, asyncness);
5709 let (constness, unsafety, abi) = if is_const_fn {
5710 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
5712 let abi = if self.eat_keyword(kw::Extern) {
5713 self.parse_opt_abi()?.unwrap_or(Abi::C)
5717 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
5719 if !self.eat_keyword(kw::Fn) {
5720 // It is possible for `expect_one_of` to recover given the contents of
5721 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
5722 // account for this.
5723 if !self.expect_one_of(&[], &[])? { unreachable!() }
5725 Ok((constness, unsafety, asyncness, abi))
5728 /// Parses an impl item.
5729 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
5730 maybe_whole!(self, NtImplItem, |x| x);
5731 let attrs = self.parse_outer_attributes()?;
5732 let mut unclosed_delims = vec![];
5733 let (mut item, tokens) = self.collect_tokens(|this| {
5734 let item = this.parse_impl_item_(at_end, attrs);
5735 unclosed_delims.append(&mut this.unclosed_delims);
5738 self.unclosed_delims.append(&mut unclosed_delims);
5740 // See `parse_item` for why this clause is here.
5741 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
5742 item.tokens = Some(tokens);
5747 fn parse_impl_item_(&mut self,
5749 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
5751 let vis = self.parse_visibility(false)?;
5752 let defaultness = self.parse_defaultness();
5753 let (name, node, generics) = if let Some(type_) = self.eat_type() {
5754 let (name, alias, generics) = type_?;
5755 let kind = match alias {
5756 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
5757 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
5759 (name, kind, generics)
5760 } else if self.is_const_item() {
5761 // This parses the grammar:
5762 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
5763 self.expect_keyword(kw::Const)?;
5764 let name = self.parse_ident()?;
5765 self.expect(&token::Colon)?;
5766 let typ = self.parse_ty()?;
5767 self.expect(&token::Eq)?;
5768 let expr = self.parse_expr()?;
5769 self.expect(&token::Semi)?;
5770 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
5772 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
5773 attrs.extend(inner_attrs);
5774 (name, node, generics)
5778 id: ast::DUMMY_NODE_ID,
5779 span: lo.to(self.prev_span),
5790 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
5792 VisibilityKind::Inherited => {}
5794 let is_macro_rules: bool = match self.token {
5795 token::Ident(sid, _) => sid.name == sym::macro_rules,
5798 let mut err = if is_macro_rules {
5799 let mut err = self.diagnostic()
5800 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
5801 err.span_suggestion(
5803 "try exporting the macro",
5804 "#[macro_export]".to_owned(),
5805 Applicability::MaybeIncorrect // speculative
5809 let mut err = self.diagnostic()
5810 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
5811 err.help("try adjusting the macro to put `pub` inside the invocation");
5819 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
5820 -> DiagnosticBuilder<'a>
5822 let expected_kinds = if item_type == "extern" {
5823 "missing `fn`, `type`, or `static`"
5825 "missing `fn`, `type`, or `const`"
5828 // Given this code `path(`, it seems like this is not
5829 // setting the visibility of a macro invocation, but rather
5830 // a mistyped method declaration.
5831 // Create a diagnostic pointing out that `fn` is missing.
5833 // x | pub path(&self) {
5834 // | ^ missing `fn`, `type`, or `const`
5836 // ^^ `sp` below will point to this
5837 let sp = prev_span.between(self.prev_span);
5838 let mut err = self.diagnostic().struct_span_err(
5840 &format!("{} for {}-item declaration",
5841 expected_kinds, item_type));
5842 err.span_label(sp, expected_kinds);
5846 /// Parse a method or a macro invocation in a trait impl.
5847 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
5848 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
5849 ast::ImplItemKind)> {
5850 // code copied from parse_macro_use_or_failure... abstraction!
5851 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
5853 Ok((Ident::invalid(), vec![], ast::Generics::default(),
5854 ast::ImplItemKind::Macro(mac)))
5856 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
5857 let ident = self.parse_ident()?;
5858 let mut generics = self.parse_generics()?;
5859 let mut decl = self.parse_fn_decl_with_self(|p| {
5860 p.parse_arg_general(true, true, false)
5862 generics.where_clause = self.parse_where_clause()?;
5863 self.construct_async_arguments(&mut asyncness, &mut decl);
5865 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5866 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
5867 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
5868 ast::MethodSig { header, decl },
5874 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
5875 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
5876 let ident = self.parse_ident()?;
5877 let mut tps = self.parse_generics()?;
5879 // Parse optional colon and supertrait bounds.
5880 let bounds = if self.eat(&token::Colon) {
5881 self.parse_generic_bounds(Some(self.prev_span))?
5886 if self.eat(&token::Eq) {
5887 // it's a trait alias
5888 let bounds = self.parse_generic_bounds(None)?;
5889 tps.where_clause = self.parse_where_clause()?;
5890 self.expect(&token::Semi)?;
5891 if is_auto == IsAuto::Yes {
5892 let msg = "trait aliases cannot be `auto`";
5893 self.struct_span_err(self.prev_span, msg)
5894 .span_label(self.prev_span, msg)
5897 if unsafety != Unsafety::Normal {
5898 let msg = "trait aliases cannot be `unsafe`";
5899 self.struct_span_err(self.prev_span, msg)
5900 .span_label(self.prev_span, msg)
5903 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
5905 // it's a normal trait
5906 tps.where_clause = self.parse_where_clause()?;
5907 self.expect(&token::OpenDelim(token::Brace))?;
5908 let mut trait_items = vec![];
5909 while !self.eat(&token::CloseDelim(token::Brace)) {
5910 if let token::DocComment(_) = self.token {
5911 if self.look_ahead(1,
5912 |tok| tok == &token::Token::CloseDelim(token::Brace)) {
5913 let mut err = self.diagnostic().struct_span_err_with_code(
5915 "found a documentation comment that doesn't document anything",
5916 DiagnosticId::Error("E0584".into()),
5918 err.help("doc comments must come before what they document, maybe a \
5919 comment was intended with `//`?",
5926 let mut at_end = false;
5927 match self.parse_trait_item(&mut at_end) {
5928 Ok(item) => trait_items.push(item),
5932 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5937 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
5941 fn choose_generics_over_qpath(&self) -> bool {
5942 // There's an ambiguity between generic parameters and qualified paths in impls.
5943 // If we see `<` it may start both, so we have to inspect some following tokens.
5944 // The following combinations can only start generics,
5945 // but not qualified paths (with one exception):
5946 // `<` `>` - empty generic parameters
5947 // `<` `#` - generic parameters with attributes
5948 // `<` (LIFETIME|IDENT) `>` - single generic parameter
5949 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
5950 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
5951 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
5952 // `<` const - generic const parameter
5953 // The only truly ambiguous case is
5954 // `<` IDENT `>` `::` IDENT ...
5955 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
5956 // because this is what almost always expected in practice, qualified paths in impls
5957 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
5958 self.token == token::Lt &&
5959 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
5960 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
5961 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
5962 t == &token::Colon || t == &token::Eq) ||
5963 self.is_keyword_ahead(1, &[kw::Const]))
5966 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
5967 self.expect(&token::OpenDelim(token::Brace))?;
5968 let attrs = self.parse_inner_attributes()?;
5970 let mut impl_items = Vec::new();
5971 while !self.eat(&token::CloseDelim(token::Brace)) {
5972 let mut at_end = false;
5973 match self.parse_impl_item(&mut at_end) {
5974 Ok(impl_item) => impl_items.push(impl_item),
5978 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5983 Ok((impl_items, attrs))
5986 /// Parses an implementation item, `impl` keyword is already parsed.
5988 /// impl<'a, T> TYPE { /* impl items */ }
5989 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
5990 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
5992 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
5993 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
5994 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
5995 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
5996 -> PResult<'a, ItemInfo> {
5997 // First, parse generic parameters if necessary.
5998 let mut generics = if self.choose_generics_over_qpath() {
5999 self.parse_generics()?
6001 ast::Generics::default()
6004 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6005 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6007 ast::ImplPolarity::Negative
6009 ast::ImplPolarity::Positive
6012 // Parse both types and traits as a type, then reinterpret if necessary.
6013 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
6014 let ty_first = if self.token.is_keyword(kw::For) &&
6015 self.look_ahead(1, |t| t != &token::Lt) {
6016 let span = self.prev_span.between(self.span);
6017 self.struct_span_err(span, "missing trait in a trait impl").emit();
6018 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6023 // If `for` is missing we try to recover.
6024 let has_for = self.eat_keyword(kw::For);
6025 let missing_for_span = self.prev_span.between(self.span);
6027 let ty_second = if self.token == token::DotDot {
6028 // We need to report this error after `cfg` expansion for compatibility reasons
6029 self.bump(); // `..`, do not add it to expected tokens
6030 Some(DummyResult::raw_ty(self.prev_span, true))
6031 } else if has_for || self.token.can_begin_type() {
6032 Some(self.parse_ty()?)
6037 generics.where_clause = self.parse_where_clause()?;
6039 let (impl_items, attrs) = self.parse_impl_body()?;
6041 let item_kind = match ty_second {
6042 Some(ty_second) => {
6043 // impl Trait for Type
6045 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6046 .span_suggestion_short(
6049 " for ".to_string(),
6050 Applicability::MachineApplicable,
6054 let ty_first = ty_first.into_inner();
6055 let path = match ty_first.node {
6056 // This notably includes paths passed through `ty` macro fragments (#46438).
6057 TyKind::Path(None, path) => path,
6059 self.span_err(ty_first.span, "expected a trait, found type");
6060 err_path(ty_first.span)
6063 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6065 ItemKind::Impl(unsafety, polarity, defaultness,
6066 generics, Some(trait_ref), ty_second, impl_items)
6070 ItemKind::Impl(unsafety, polarity, defaultness,
6071 generics, None, ty_first, impl_items)
6075 Ok((Ident::invalid(), item_kind, Some(attrs)))
6078 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6079 if self.eat_keyword(kw::For) {
6081 let params = self.parse_generic_params()?;
6083 // We rely on AST validation to rule out invalid cases: There must not be type
6084 // parameters, and the lifetime parameters must not have bounds.
6091 /// Parses `struct Foo { ... }`.
6092 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6093 let class_name = self.parse_ident()?;
6095 let mut generics = self.parse_generics()?;
6097 // There is a special case worth noting here, as reported in issue #17904.
6098 // If we are parsing a tuple struct it is the case that the where clause
6099 // should follow the field list. Like so:
6101 // struct Foo<T>(T) where T: Copy;
6103 // If we are parsing a normal record-style struct it is the case
6104 // that the where clause comes before the body, and after the generics.
6105 // So if we look ahead and see a brace or a where-clause we begin
6106 // parsing a record style struct.
6108 // Otherwise if we look ahead and see a paren we parse a tuple-style
6111 let vdata = if self.token.is_keyword(kw::Where) {
6112 generics.where_clause = self.parse_where_clause()?;
6113 if self.eat(&token::Semi) {
6114 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6115 VariantData::Unit(ast::DUMMY_NODE_ID)
6117 // If we see: `struct Foo<T> where T: Copy { ... }`
6118 let (fields, recovered) = self.parse_record_struct_body()?;
6119 VariantData::Struct(fields, recovered)
6121 // No `where` so: `struct Foo<T>;`
6122 } else if self.eat(&token::Semi) {
6123 VariantData::Unit(ast::DUMMY_NODE_ID)
6124 // Record-style struct definition
6125 } else if self.token == token::OpenDelim(token::Brace) {
6126 let (fields, recovered) = self.parse_record_struct_body()?;
6127 VariantData::Struct(fields, recovered)
6128 // Tuple-style struct definition with optional where-clause.
6129 } else if self.token == token::OpenDelim(token::Paren) {
6130 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6131 generics.where_clause = self.parse_where_clause()?;
6132 self.expect(&token::Semi)?;
6135 let token_str = self.this_token_descr();
6136 let mut err = self.fatal(&format!(
6137 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6140 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6144 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6147 /// Parses `union Foo { ... }`.
6148 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6149 let class_name = self.parse_ident()?;
6151 let mut generics = self.parse_generics()?;
6153 let vdata = if self.token.is_keyword(kw::Where) {
6154 generics.where_clause = self.parse_where_clause()?;
6155 let (fields, recovered) = self.parse_record_struct_body()?;
6156 VariantData::Struct(fields, recovered)
6157 } else if self.token == token::OpenDelim(token::Brace) {
6158 let (fields, recovered) = self.parse_record_struct_body()?;
6159 VariantData::Struct(fields, recovered)
6161 let token_str = self.this_token_descr();
6162 let mut err = self.fatal(&format!(
6163 "expected `where` or `{{` after union name, found {}", token_str));
6164 err.span_label(self.span, "expected `where` or `{` after union name");
6168 Ok((class_name, ItemKind::Union(vdata, generics), None))
6171 fn parse_record_struct_body(
6173 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6174 let mut fields = Vec::new();
6175 let mut recovered = false;
6176 if self.eat(&token::OpenDelim(token::Brace)) {
6177 while self.token != token::CloseDelim(token::Brace) {
6178 let field = self.parse_struct_decl_field().map_err(|e| {
6179 self.recover_stmt();
6184 Ok(field) => fields.push(field),
6190 self.eat(&token::CloseDelim(token::Brace));
6192 let token_str = self.this_token_descr();
6193 let mut err = self.fatal(&format!(
6194 "expected `where`, or `{{` after struct name, found {}", token_str));
6195 err.span_label(self.span, "expected `where`, or `{` after struct name");
6199 Ok((fields, recovered))
6202 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6203 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6204 // Unit like structs are handled in parse_item_struct function
6205 let fields = self.parse_unspanned_seq(
6206 &token::OpenDelim(token::Paren),
6207 &token::CloseDelim(token::Paren),
6208 SeqSep::trailing_allowed(token::Comma),
6210 let attrs = p.parse_outer_attributes()?;
6212 let vis = p.parse_visibility(true)?;
6213 let ty = p.parse_ty()?;
6215 span: lo.to(ty.span),
6218 id: ast::DUMMY_NODE_ID,
6227 /// Parses a structure field declaration.
6228 fn parse_single_struct_field(&mut self,
6231 attrs: Vec<Attribute> )
6232 -> PResult<'a, StructField> {
6233 let mut seen_comma: bool = false;
6234 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
6235 if self.token == token::Comma {
6242 token::CloseDelim(token::Brace) => {}
6243 token::DocComment(_) => {
6244 let previous_span = self.prev_span;
6245 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
6246 self.bump(); // consume the doc comment
6247 let comma_after_doc_seen = self.eat(&token::Comma);
6248 // `seen_comma` is always false, because we are inside doc block
6249 // condition is here to make code more readable
6250 if seen_comma == false && comma_after_doc_seen == true {
6253 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
6256 if seen_comma == false {
6257 let sp = self.sess.source_map().next_point(previous_span);
6258 err.span_suggestion(
6260 "missing comma here",
6262 Applicability::MachineApplicable
6269 let sp = self.sess.source_map().next_point(self.prev_span);
6270 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
6271 self.this_token_descr()));
6272 if self.token.is_ident() {
6273 // This is likely another field; emit the diagnostic and keep going
6274 err.span_suggestion(
6276 "try adding a comma",
6278 Applicability::MachineApplicable,
6289 /// Parses an element of a struct declaration.
6290 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6291 let attrs = self.parse_outer_attributes()?;
6293 let vis = self.parse_visibility(false)?;
6294 self.parse_single_struct_field(lo, vis, attrs)
6297 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
6298 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
6299 /// If the following element can't be a tuple (i.e., it's a function definition), then
6300 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
6301 /// so emit a proper diagnostic.
6302 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6303 maybe_whole!(self, NtVis, |x| x);
6305 self.expected_tokens.push(TokenType::Keyword(kw::Crate));
6306 if self.is_crate_vis() {
6307 self.bump(); // `crate`
6308 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6311 if !self.eat_keyword(kw::Pub) {
6312 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6313 // keyword to grab a span from for inherited visibility; an empty span at the
6314 // beginning of the current token would seem to be the "Schelling span".
6315 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
6317 let lo = self.prev_span;
6319 if self.check(&token::OpenDelim(token::Paren)) {
6320 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6321 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6322 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6323 // by the following tokens.
6324 if self.is_keyword_ahead(1, &[kw::Crate]) &&
6325 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
6329 self.bump(); // `crate`
6330 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6332 lo.to(self.prev_span),
6333 VisibilityKind::Crate(CrateSugar::PubCrate),
6336 } else if self.is_keyword_ahead(1, &[kw::In]) {
6339 self.bump(); // `in`
6340 let path = self.parse_path(PathStyle::Mod)?; // `path`
6341 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6342 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6344 id: ast::DUMMY_NODE_ID,
6347 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6348 self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
6350 // `pub(self)` or `pub(super)`
6352 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6353 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6354 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6356 id: ast::DUMMY_NODE_ID,
6359 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6360 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6362 let msg = "incorrect visibility restriction";
6363 let suggestion = r##"some possible visibility restrictions are:
6364 `pub(crate)`: visible only on the current crate
6365 `pub(super)`: visible only in the current module's parent
6366 `pub(in path::to::module)`: visible only on the specified path"##;
6367 let path = self.parse_path(PathStyle::Mod)?;
6369 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6370 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6371 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6372 err.help(suggestion);
6373 err.span_suggestion(
6374 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6376 err.emit(); // emit diagnostic, but continue with public visibility
6380 Ok(respan(lo, VisibilityKind::Public))
6383 /// Parses defaultness (i.e., `default` or nothing).
6384 fn parse_defaultness(&mut self) -> Defaultness {
6385 // `pub` is included for better error messages
6386 if self.check_keyword(kw::Default) &&
6387 self.is_keyword_ahead(1, &[
6397 self.bump(); // `default`
6398 Defaultness::Default
6404 /// Given a termination token, parses all of the items in a module.
6405 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
6406 let mut items = vec![];
6407 while let Some(item) = self.parse_item()? {
6409 self.maybe_consume_incorrect_semicolon(&items);
6412 if !self.eat(term) {
6413 let token_str = self.this_token_descr();
6414 if !self.maybe_consume_incorrect_semicolon(&items) {
6415 let mut err = self.fatal(&format!("expected item, found {}", token_str));
6416 err.span_label(self.span, "expected item");
6421 let hi = if self.span.is_dummy() {
6428 inner: inner_lo.to(hi),
6434 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6435 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
6436 self.expect(&token::Colon)?;
6437 let ty = self.parse_ty()?;
6438 self.expect(&token::Eq)?;
6439 let e = self.parse_expr()?;
6440 self.expect(&token::Semi)?;
6441 let item = match m {
6442 Some(m) => ItemKind::Static(ty, m, e),
6443 None => ItemKind::Const(ty, e),
6445 Ok((id, item, None))
6448 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6449 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6450 let (in_cfg, outer_attrs) = {
6451 let mut strip_unconfigured = crate::config::StripUnconfigured {
6453 features: None, // don't perform gated feature checking
6455 let mut outer_attrs = outer_attrs.to_owned();
6456 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
6457 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
6460 let id_span = self.span;
6461 let id = self.parse_ident()?;
6462 if self.eat(&token::Semi) {
6463 if in_cfg && self.recurse_into_file_modules {
6464 // This mod is in an external file. Let's go get it!
6465 let ModulePathSuccess { path, directory_ownership, warn } =
6466 self.submod_path(id, &outer_attrs, id_span)?;
6467 let (module, mut attrs) =
6468 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
6469 // Record that we fetched the mod from an external file
6471 let attr = Attribute {
6472 id: attr::mk_attr_id(),
6473 style: ast::AttrStyle::Outer,
6474 path: ast::Path::from_ident(
6475 Ident::with_empty_ctxt(sym::warn_directory_ownership)),
6476 tokens: TokenStream::empty(),
6477 is_sugared_doc: false,
6480 attr::mark_known(&attr);
6483 Ok((id, ItemKind::Mod(module), Some(attrs)))
6485 let placeholder = ast::Mod {
6490 Ok((id, ItemKind::Mod(placeholder), None))
6493 let old_directory = self.directory.clone();
6494 self.push_directory(id, &outer_attrs);
6496 self.expect(&token::OpenDelim(token::Brace))?;
6497 let mod_inner_lo = self.span;
6498 let attrs = self.parse_inner_attributes()?;
6499 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
6501 self.directory = old_directory;
6502 Ok((id, ItemKind::Mod(module), Some(attrs)))
6506 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
6507 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6508 self.directory.path.to_mut().push(&path.as_str());
6509 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
6511 // We have to push on the current module name in the case of relative
6512 // paths in order to ensure that any additional module paths from inline
6513 // `mod x { ... }` come after the relative extension.
6515 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
6516 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
6517 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
6518 if let Some(ident) = relative.take() { // remove the relative offset
6519 self.directory.path.to_mut().push(ident.as_str());
6522 self.directory.path.to_mut().push(&id.as_str());
6526 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
6527 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6530 // On windows, the base path might have the form
6531 // `\\?\foo\bar` in which case it does not tolerate
6532 // mixed `/` and `\` separators, so canonicalize
6535 let s = s.replace("/", "\\");
6536 Some(dir_path.join(s))
6542 /// Returns a path to a module.
6543 pub fn default_submod_path(
6545 relative: Option<ast::Ident>,
6547 source_map: &SourceMap) -> ModulePath
6549 // If we're in a foo.rs file instead of a mod.rs file,
6550 // we need to look for submodules in
6551 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
6552 // `./<id>.rs` and `./<id>/mod.rs`.
6553 let relative_prefix_string;
6554 let relative_prefix = if let Some(ident) = relative {
6555 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
6556 &relative_prefix_string
6561 let mod_name = id.to_string();
6562 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
6563 let secondary_path_str = format!("{}{}{}mod.rs",
6564 relative_prefix, mod_name, path::MAIN_SEPARATOR);
6565 let default_path = dir_path.join(&default_path_str);
6566 let secondary_path = dir_path.join(&secondary_path_str);
6567 let default_exists = source_map.file_exists(&default_path);
6568 let secondary_exists = source_map.file_exists(&secondary_path);
6570 let result = match (default_exists, secondary_exists) {
6571 (true, false) => Ok(ModulePathSuccess {
6573 directory_ownership: DirectoryOwnership::Owned {
6578 (false, true) => Ok(ModulePathSuccess {
6579 path: secondary_path,
6580 directory_ownership: DirectoryOwnership::Owned {
6585 (false, false) => Err(Error::FileNotFoundForModule {
6586 mod_name: mod_name.clone(),
6587 default_path: default_path_str,
6588 secondary_path: secondary_path_str,
6589 dir_path: dir_path.display().to_string(),
6591 (true, true) => Err(Error::DuplicatePaths {
6592 mod_name: mod_name.clone(),
6593 default_path: default_path_str,
6594 secondary_path: secondary_path_str,
6600 path_exists: default_exists || secondary_exists,
6605 fn submod_path(&mut self,
6607 outer_attrs: &[Attribute],
6609 -> PResult<'a, ModulePathSuccess> {
6610 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
6611 return Ok(ModulePathSuccess {
6612 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
6613 // All `#[path]` files are treated as though they are a `mod.rs` file.
6614 // This means that `mod foo;` declarations inside `#[path]`-included
6615 // files are siblings,
6617 // Note that this will produce weirdness when a file named `foo.rs` is
6618 // `#[path]` included and contains a `mod foo;` declaration.
6619 // If you encounter this, it's your own darn fault :P
6620 Some(_) => DirectoryOwnership::Owned { relative: None },
6621 _ => DirectoryOwnership::UnownedViaMod(true),
6628 let relative = match self.directory.ownership {
6629 DirectoryOwnership::Owned { relative } => relative,
6630 DirectoryOwnership::UnownedViaBlock |
6631 DirectoryOwnership::UnownedViaMod(_) => None,
6633 let paths = Parser::default_submod_path(
6634 id, relative, &self.directory.path, self.sess.source_map());
6636 match self.directory.ownership {
6637 DirectoryOwnership::Owned { .. } => {
6638 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
6640 DirectoryOwnership::UnownedViaBlock => {
6642 "Cannot declare a non-inline module inside a block \
6643 unless it has a path attribute";
6644 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
6645 if paths.path_exists {
6646 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
6648 err.span_note(id_sp, &msg);
6652 DirectoryOwnership::UnownedViaMod(warn) => {
6654 if let Ok(result) = paths.result {
6655 return Ok(ModulePathSuccess { warn: true, ..result });
6658 let mut err = self.diagnostic().struct_span_err(id_sp,
6659 "cannot declare a new module at this location");
6660 if !id_sp.is_dummy() {
6661 let src_path = self.sess.source_map().span_to_filename(id_sp);
6662 if let FileName::Real(src_path) = src_path {
6663 if let Some(stem) = src_path.file_stem() {
6664 let mut dest_path = src_path.clone();
6665 dest_path.set_file_name(stem);
6666 dest_path.push("mod.rs");
6667 err.span_note(id_sp,
6668 &format!("maybe move this module `{}` to its own \
6669 directory via `{}`", src_path.display(),
6670 dest_path.display()));
6674 if paths.path_exists {
6675 err.span_note(id_sp,
6676 &format!("... or maybe `use` the module `{}` instead \
6677 of possibly redeclaring it",
6685 /// Reads a module from a source file.
6686 fn eval_src_mod(&mut self,
6688 directory_ownership: DirectoryOwnership,
6691 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
6692 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
6693 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
6694 let mut err = String::from("circular modules: ");
6695 let len = included_mod_stack.len();
6696 for p in &included_mod_stack[i.. len] {
6697 err.push_str(&p.to_string_lossy());
6698 err.push_str(" -> ");
6700 err.push_str(&path.to_string_lossy());
6701 return Err(self.span_fatal(id_sp, &err[..]));
6703 included_mod_stack.push(path.clone());
6704 drop(included_mod_stack);
6707 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
6708 p0.cfg_mods = self.cfg_mods;
6709 let mod_inner_lo = p0.span;
6710 let mod_attrs = p0.parse_inner_attributes()?;
6711 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
6713 self.sess.included_mod_stack.borrow_mut().pop();
6717 /// Parses a function declaration from a foreign module.
6718 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6719 -> PResult<'a, ForeignItem> {
6720 self.expect_keyword(kw::Fn)?;
6722 let (ident, mut generics) = self.parse_fn_header()?;
6723 let decl = self.parse_fn_decl(true)?;
6724 generics.where_clause = self.parse_where_clause()?;
6726 self.expect(&token::Semi)?;
6727 Ok(ast::ForeignItem {
6730 node: ForeignItemKind::Fn(decl, generics),
6731 id: ast::DUMMY_NODE_ID,
6737 /// Parses a static item from a foreign module.
6738 /// Assumes that the `static` keyword is already parsed.
6739 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6740 -> PResult<'a, ForeignItem> {
6741 let mutbl = self.parse_mutability();
6742 let ident = self.parse_ident()?;
6743 self.expect(&token::Colon)?;
6744 let ty = self.parse_ty()?;
6746 self.expect(&token::Semi)?;
6750 node: ForeignItemKind::Static(ty, mutbl),
6751 id: ast::DUMMY_NODE_ID,
6757 /// Parses a type from a foreign module.
6758 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6759 -> PResult<'a, ForeignItem> {
6760 self.expect_keyword(kw::Type)?;
6762 let ident = self.parse_ident()?;
6764 self.expect(&token::Semi)?;
6765 Ok(ast::ForeignItem {
6768 node: ForeignItemKind::Ty,
6769 id: ast::DUMMY_NODE_ID,
6775 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
6776 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
6777 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
6779 let mut ident = if self.token.is_keyword(kw::SelfLower) {
6780 self.parse_path_segment_ident()
6784 let mut idents = vec![];
6785 let mut replacement = vec![];
6786 let mut fixed_crate_name = false;
6787 // Accept `extern crate name-like-this` for better diagnostics
6788 let dash = token::Token::BinOp(token::BinOpToken::Minus);
6789 if self.token == dash { // Do not include `-` as part of the expected tokens list
6790 while self.eat(&dash) {
6791 fixed_crate_name = true;
6792 replacement.push((self.prev_span, "_".to_string()));
6793 idents.push(self.parse_ident()?);
6796 if fixed_crate_name {
6797 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
6798 let mut fixed_name = format!("{}", ident.name);
6799 for part in idents {
6800 fixed_name.push_str(&format!("_{}", part.name));
6802 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
6804 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
6805 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
6806 err.multipart_suggestion(
6809 Applicability::MachineApplicable,
6816 /// Parses `extern crate` links.
6821 /// extern crate foo;
6822 /// extern crate bar as foo;
6824 fn parse_item_extern_crate(&mut self,
6826 visibility: Visibility,
6827 attrs: Vec<Attribute>)
6828 -> PResult<'a, P<Item>> {
6829 // Accept `extern crate name-like-this` for better diagnostics
6830 let orig_name = self.parse_crate_name_with_dashes()?;
6831 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
6832 (rename, Some(orig_name.name))
6836 self.expect(&token::Semi)?;
6838 let span = lo.to(self.prev_span);
6839 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
6842 /// Parses `extern` for foreign ABIs modules.
6844 /// `extern` is expected to have been
6845 /// consumed before calling this method.
6849 /// ```ignore (only-for-syntax-highlight)
6853 fn parse_item_foreign_mod(&mut self,
6855 opt_abi: Option<Abi>,
6856 visibility: Visibility,
6857 mut attrs: Vec<Attribute>)
6858 -> PResult<'a, P<Item>> {
6859 self.expect(&token::OpenDelim(token::Brace))?;
6861 let abi = opt_abi.unwrap_or(Abi::C);
6863 attrs.extend(self.parse_inner_attributes()?);
6865 let mut foreign_items = vec![];
6866 while !self.eat(&token::CloseDelim(token::Brace)) {
6867 foreign_items.push(self.parse_foreign_item()?);
6870 let prev_span = self.prev_span;
6871 let m = ast::ForeignMod {
6873 items: foreign_items
6875 let invalid = Ident::invalid();
6876 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
6879 /// Parses `type Foo = Bar;`
6881 /// `existential type Foo: Bar;`
6884 /// without modifying the parser state.
6885 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
6886 // This parses the grammar:
6887 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
6888 if self.check_keyword(kw::Type) ||
6889 self.check_keyword(kw::Existential) &&
6890 self.is_keyword_ahead(1, &[kw::Type]) {
6891 let existential = self.eat_keyword(kw::Existential);
6892 assert!(self.eat_keyword(kw::Type));
6893 Some(self.parse_existential_or_alias(existential))
6899 /// Parses a type alias or existential type.
6900 fn parse_existential_or_alias(
6903 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
6904 let ident = self.parse_ident()?;
6905 let mut tps = self.parse_generics()?;
6906 tps.where_clause = self.parse_where_clause()?;
6907 let alias = if existential {
6908 self.expect(&token::Colon)?;
6909 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6910 AliasKind::Existential(bounds)
6912 self.expect(&token::Eq)?;
6913 let ty = self.parse_ty()?;
6916 self.expect(&token::Semi)?;
6917 Ok((ident, alias, tps))
6920 /// Parses the part of an enum declaration following the `{`.
6921 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
6922 let mut variants = Vec::new();
6923 let mut any_disr = vec![];
6924 while self.token != token::CloseDelim(token::Brace) {
6925 let variant_attrs = self.parse_outer_attributes()?;
6926 let vlo = self.span;
6929 let mut disr_expr = None;
6931 let ident = self.parse_ident()?;
6932 if self.check(&token::OpenDelim(token::Brace)) {
6933 // Parse a struct variant.
6934 let (fields, recovered) = self.parse_record_struct_body()?;
6935 struct_def = VariantData::Struct(fields, recovered);
6936 } else if self.check(&token::OpenDelim(token::Paren)) {
6937 struct_def = VariantData::Tuple(
6938 self.parse_tuple_struct_body()?,
6941 } else if self.eat(&token::Eq) {
6942 disr_expr = Some(AnonConst {
6943 id: ast::DUMMY_NODE_ID,
6944 value: self.parse_expr()?,
6946 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
6949 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6951 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6954 let vr = ast::Variant_ {
6956 id: ast::DUMMY_NODE_ID,
6957 attrs: variant_attrs,
6961 variants.push(respan(vlo.to(self.prev_span), vr));
6963 if !self.eat(&token::Comma) {
6964 if self.token.is_ident() && !self.token.is_reserved_ident() {
6965 let sp = self.sess.source_map().next_point(self.prev_span);
6966 let mut err = self.struct_span_err(sp, "missing comma");
6967 err.span_suggestion_short(
6971 Applicability::MaybeIncorrect,
6979 self.expect(&token::CloseDelim(token::Brace))?;
6980 self.maybe_report_invalid_custom_discriminants(any_disr, &variants);
6982 Ok(ast::EnumDef { variants })
6985 /// Parses an enum declaration.
6986 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
6987 let id = self.parse_ident()?;
6988 let mut generics = self.parse_generics()?;
6989 generics.where_clause = self.parse_where_clause()?;
6990 self.expect(&token::OpenDelim(token::Brace))?;
6992 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
6993 self.recover_stmt();
6994 self.eat(&token::CloseDelim(token::Brace));
6997 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7000 /// Parses a string as an ABI spec on an extern type or module. Consumes
7001 /// the `extern` keyword, if one is found.
7002 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7004 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
7005 token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
7007 self.expect_no_suffix(sp, "an ABI spec", suffix);
7009 match abi::lookup(&symbol.as_str()) {
7010 Some(abi) => Ok(Some(abi)),
7012 let prev_span = self.prev_span;
7013 let mut err = struct_span_err!(
7014 self.sess.span_diagnostic,
7017 "invalid ABI: found `{}`",
7019 err.span_label(prev_span, "invalid ABI");
7020 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7031 fn is_static_global(&mut self) -> bool {
7032 if self.check_keyword(kw::Static) {
7033 // Check if this could be a closure
7034 !self.look_ahead(1, |token| {
7035 if token.is_keyword(kw::Move) {
7039 token::BinOp(token::Or) | token::OrOr => true,
7050 attrs: Vec<Attribute>,
7051 macros_allowed: bool,
7052 attributes_allowed: bool,
7053 ) -> PResult<'a, Option<P<Item>>> {
7054 let mut unclosed_delims = vec![];
7055 let (ret, tokens) = self.collect_tokens(|this| {
7056 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7057 unclosed_delims.append(&mut this.unclosed_delims);
7060 self.unclosed_delims.append(&mut unclosed_delims);
7062 // Once we've parsed an item and recorded the tokens we got while
7063 // parsing we may want to store `tokens` into the item we're about to
7064 // return. Note, though, that we specifically didn't capture tokens
7065 // related to outer attributes. The `tokens` field here may later be
7066 // used with procedural macros to convert this item back into a token
7067 // stream, but during expansion we may be removing attributes as we go
7070 // If we've got inner attributes then the `tokens` we've got above holds
7071 // these inner attributes. If an inner attribute is expanded we won't
7072 // actually remove it from the token stream, so we'll just keep yielding
7073 // it (bad!). To work around this case for now we just avoid recording
7074 // `tokens` if we detect any inner attributes. This should help keep
7075 // expansion correct, but we should fix this bug one day!
7078 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7079 i.tokens = Some(tokens);
7086 /// Parses one of the items allowed by the flags.
7087 fn parse_item_implementation(
7089 attrs: Vec<Attribute>,
7090 macros_allowed: bool,
7091 attributes_allowed: bool,
7092 ) -> PResult<'a, Option<P<Item>>> {
7093 maybe_whole!(self, NtItem, |item| {
7094 let mut item = item.into_inner();
7095 let mut attrs = attrs;
7096 mem::swap(&mut item.attrs, &mut attrs);
7097 item.attrs.extend(attrs);
7103 let visibility = self.parse_visibility(false)?;
7105 if self.eat_keyword(kw::Use) {
7107 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7108 self.expect(&token::Semi)?;
7110 let span = lo.to(self.prev_span);
7112 self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
7113 return Ok(Some(item));
7116 if self.eat_keyword(kw::Extern) {
7117 if self.eat_keyword(kw::Crate) {
7118 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7121 let opt_abi = self.parse_opt_abi()?;
7123 if self.eat_keyword(kw::Fn) {
7124 // EXTERN FUNCTION ITEM
7125 let fn_span = self.prev_span;
7126 let abi = opt_abi.unwrap_or(Abi::C);
7127 let (ident, item_, extra_attrs) =
7128 self.parse_item_fn(Unsafety::Normal,
7129 respan(fn_span, IsAsync::NotAsync),
7130 respan(fn_span, Constness::NotConst),
7132 let prev_span = self.prev_span;
7133 let item = self.mk_item(lo.to(prev_span),
7137 maybe_append(attrs, extra_attrs));
7138 return Ok(Some(item));
7139 } else if self.check(&token::OpenDelim(token::Brace)) {
7140 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7146 if self.is_static_global() {
7149 let m = if self.eat_keyword(kw::Mut) {
7152 Mutability::Immutable
7154 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7155 let prev_span = self.prev_span;
7156 let item = self.mk_item(lo.to(prev_span),
7160 maybe_append(attrs, extra_attrs));
7161 return Ok(Some(item));
7163 if self.eat_keyword(kw::Const) {
7164 let const_span = self.prev_span;
7165 if self.check_keyword(kw::Fn)
7166 || (self.check_keyword(kw::Unsafe)
7167 && self.is_keyword_ahead(1, &[kw::Fn])) {
7168 // CONST FUNCTION ITEM
7169 let unsafety = self.parse_unsafety();
7171 let (ident, item_, extra_attrs) =
7172 self.parse_item_fn(unsafety,
7173 respan(const_span, IsAsync::NotAsync),
7174 respan(const_span, Constness::Const),
7176 let prev_span = self.prev_span;
7177 let item = self.mk_item(lo.to(prev_span),
7181 maybe_append(attrs, extra_attrs));
7182 return Ok(Some(item));
7186 if self.eat_keyword(kw::Mut) {
7187 let prev_span = self.prev_span;
7188 let mut err = self.diagnostic()
7189 .struct_span_err(prev_span, "const globals cannot be mutable");
7190 err.span_label(prev_span, "cannot be mutable");
7191 err.span_suggestion(
7193 "you might want to declare a static instead",
7194 "static".to_owned(),
7195 Applicability::MaybeIncorrect,
7199 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
7200 let prev_span = self.prev_span;
7201 let item = self.mk_item(lo.to(prev_span),
7205 maybe_append(attrs, extra_attrs));
7206 return Ok(Some(item));
7209 // Parse `async unsafe? fn`.
7210 if self.check_keyword(kw::Async) {
7211 let async_span = self.span;
7212 if self.is_keyword_ahead(1, &[kw::Fn])
7213 || self.is_keyword_ahead(2, &[kw::Fn])
7215 // ASYNC FUNCTION ITEM
7216 self.bump(); // `async`
7217 let unsafety = self.parse_unsafety(); // `unsafe`?
7218 self.expect_keyword(kw::Fn)?; // `fn`
7219 let fn_span = self.prev_span;
7220 let (ident, item_, extra_attrs) =
7221 self.parse_item_fn(unsafety,
7222 respan(async_span, IsAsync::Async {
7223 closure_id: ast::DUMMY_NODE_ID,
7224 return_impl_trait_id: ast::DUMMY_NODE_ID,
7225 arguments: Vec::new(),
7227 respan(fn_span, Constness::NotConst),
7229 let prev_span = self.prev_span;
7230 let item = self.mk_item(lo.to(prev_span),
7234 maybe_append(attrs, extra_attrs));
7235 if self.span.rust_2015() {
7236 self.diagnostic().struct_span_err_with_code(
7238 "`async fn` is not permitted in the 2015 edition",
7239 DiagnosticId::Error("E0670".into())
7242 return Ok(Some(item));
7245 if self.check_keyword(kw::Unsafe) &&
7246 self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
7248 // UNSAFE TRAIT ITEM
7249 self.bump(); // `unsafe`
7250 let is_auto = if self.eat_keyword(kw::Trait) {
7253 self.expect_keyword(kw::Auto)?;
7254 self.expect_keyword(kw::Trait)?;
7257 let (ident, item_, extra_attrs) =
7258 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
7259 let prev_span = self.prev_span;
7260 let item = self.mk_item(lo.to(prev_span),
7264 maybe_append(attrs, extra_attrs));
7265 return Ok(Some(item));
7267 if self.check_keyword(kw::Impl) ||
7268 self.check_keyword(kw::Unsafe) &&
7269 self.is_keyword_ahead(1, &[kw::Impl]) ||
7270 self.check_keyword(kw::Default) &&
7271 self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
7273 let defaultness = self.parse_defaultness();
7274 let unsafety = self.parse_unsafety();
7275 self.expect_keyword(kw::Impl)?;
7276 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
7277 let span = lo.to(self.prev_span);
7278 return Ok(Some(self.mk_item(span, ident, item, visibility,
7279 maybe_append(attrs, extra_attrs))));
7281 if self.check_keyword(kw::Fn) {
7284 let fn_span = self.prev_span;
7285 let (ident, item_, extra_attrs) =
7286 self.parse_item_fn(Unsafety::Normal,
7287 respan(fn_span, IsAsync::NotAsync),
7288 respan(fn_span, Constness::NotConst),
7290 let prev_span = self.prev_span;
7291 let item = self.mk_item(lo.to(prev_span),
7295 maybe_append(attrs, extra_attrs));
7296 return Ok(Some(item));
7298 if self.check_keyword(kw::Unsafe)
7299 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
7300 // UNSAFE FUNCTION ITEM
7301 self.bump(); // `unsafe`
7302 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
7303 self.check(&token::OpenDelim(token::Brace));
7304 let abi = if self.eat_keyword(kw::Extern) {
7305 self.parse_opt_abi()?.unwrap_or(Abi::C)
7309 self.expect_keyword(kw::Fn)?;
7310 let fn_span = self.prev_span;
7311 let (ident, item_, extra_attrs) =
7312 self.parse_item_fn(Unsafety::Unsafe,
7313 respan(fn_span, IsAsync::NotAsync),
7314 respan(fn_span, Constness::NotConst),
7316 let prev_span = self.prev_span;
7317 let item = self.mk_item(lo.to(prev_span),
7321 maybe_append(attrs, extra_attrs));
7322 return Ok(Some(item));
7324 if self.eat_keyword(kw::Mod) {
7326 let (ident, item_, extra_attrs) =
7327 self.parse_item_mod(&attrs[..])?;
7328 let prev_span = self.prev_span;
7329 let item = self.mk_item(lo.to(prev_span),
7333 maybe_append(attrs, extra_attrs));
7334 return Ok(Some(item));
7336 if let Some(type_) = self.eat_type() {
7337 let (ident, alias, generics) = type_?;
7339 let item_ = match alias {
7340 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7341 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7343 let prev_span = self.prev_span;
7344 let item = self.mk_item(lo.to(prev_span),
7349 return Ok(Some(item));
7351 if self.eat_keyword(kw::Enum) {
7353 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7354 let prev_span = self.prev_span;
7355 let item = self.mk_item(lo.to(prev_span),
7359 maybe_append(attrs, extra_attrs));
7360 return Ok(Some(item));
7362 if self.check_keyword(kw::Trait)
7363 || (self.check_keyword(kw::Auto)
7364 && self.is_keyword_ahead(1, &[kw::Trait]))
7366 let is_auto = if self.eat_keyword(kw::Trait) {
7369 self.expect_keyword(kw::Auto)?;
7370 self.expect_keyword(kw::Trait)?;
7374 let (ident, item_, extra_attrs) =
7375 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7376 let prev_span = self.prev_span;
7377 let item = self.mk_item(lo.to(prev_span),
7381 maybe_append(attrs, extra_attrs));
7382 return Ok(Some(item));
7384 if self.eat_keyword(kw::Struct) {
7386 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7387 let prev_span = self.prev_span;
7388 let item = self.mk_item(lo.to(prev_span),
7392 maybe_append(attrs, extra_attrs));
7393 return Ok(Some(item));
7395 if self.is_union_item() {
7398 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7399 let prev_span = self.prev_span;
7400 let item = self.mk_item(lo.to(prev_span),
7404 maybe_append(attrs, extra_attrs));
7405 return Ok(Some(item));
7407 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7408 return Ok(Some(macro_def));
7411 // Verify whether we have encountered a struct or method definition where the user forgot to
7412 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7413 if visibility.node.is_pub() &&
7414 self.check_ident() &&
7415 self.look_ahead(1, |t| *t != token::Not)
7417 // Space between `pub` keyword and the identifier
7420 // ^^^ `sp` points here
7421 let sp = self.prev_span.between(self.span);
7422 let full_sp = self.prev_span.to(self.span);
7423 let ident_sp = self.span;
7424 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7425 // possible public struct definition where `struct` was forgotten
7426 let ident = self.parse_ident().unwrap();
7427 let msg = format!("add `struct` here to parse `{}` as a public struct",
7429 let mut err = self.diagnostic()
7430 .struct_span_err(sp, "missing `struct` for struct definition");
7431 err.span_suggestion_short(
7432 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7435 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7436 let ident = self.parse_ident().unwrap();
7438 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
7443 self.consume_block(token::Paren);
7444 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
7445 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
7447 ("fn", kw_name, false)
7448 } else if self.check(&token::OpenDelim(token::Brace)) {
7450 ("fn", kw_name, false)
7451 } else if self.check(&token::Colon) {
7455 ("fn` or `struct", "function or struct", true)
7458 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7459 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7461 self.consume_block(token::Brace);
7462 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
7466 err.span_suggestion_short(
7467 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
7470 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
7471 err.span_suggestion(
7473 "if you meant to call a macro, try",
7474 format!("{}!", snippet),
7475 // this is the `ambiguous` conditional branch
7476 Applicability::MaybeIncorrect
7479 err.help("if you meant to call a macro, remove the `pub` \
7480 and add a trailing `!` after the identifier");
7484 } else if self.look_ahead(1, |t| *t == token::Lt) {
7485 let ident = self.parse_ident().unwrap();
7486 self.eat_to_tokens(&[&token::Gt]);
7488 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
7489 if let Ok(Some(_)) = self.parse_self_arg() {
7490 ("fn", "method", false)
7492 ("fn", "function", false)
7494 } else if self.check(&token::OpenDelim(token::Brace)) {
7495 ("struct", "struct", false)
7497 ("fn` or `struct", "function or struct", true)
7499 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7500 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7502 err.span_suggestion_short(
7504 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
7505 format!(" {} ", kw),
7506 Applicability::MachineApplicable,
7512 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
7515 /// Parses a foreign item.
7516 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
7517 maybe_whole!(self, NtForeignItem, |ni| ni);
7519 let attrs = self.parse_outer_attributes()?;
7521 let visibility = self.parse_visibility(false)?;
7523 // FOREIGN STATIC ITEM
7524 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
7525 if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
7526 if self.token.is_keyword(kw::Const) {
7528 .struct_span_err(self.span, "extern items cannot be `const`")
7531 "try using a static value",
7532 "static".to_owned(),
7533 Applicability::MachineApplicable
7536 self.bump(); // `static` or `const`
7537 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
7539 // FOREIGN FUNCTION ITEM
7540 if self.check_keyword(kw::Fn) {
7541 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
7543 // FOREIGN TYPE ITEM
7544 if self.check_keyword(kw::Type) {
7545 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
7548 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
7552 ident: Ident::invalid(),
7553 span: lo.to(self.prev_span),
7554 id: ast::DUMMY_NODE_ID,
7557 node: ForeignItemKind::Macro(mac),
7562 if !attrs.is_empty() {
7563 self.expected_item_err(&attrs)?;
7571 /// This is the fall-through for parsing items.
7572 fn parse_macro_use_or_failure(
7574 attrs: Vec<Attribute> ,
7575 macros_allowed: bool,
7576 attributes_allowed: bool,
7578 visibility: Visibility
7579 ) -> PResult<'a, Option<P<Item>>> {
7580 if macros_allowed && self.token.is_path_start() &&
7581 !(self.is_async_fn() && self.span.rust_2015()) {
7582 // MACRO INVOCATION ITEM
7584 let prev_span = self.prev_span;
7585 self.complain_if_pub_macro(&visibility.node, prev_span);
7587 let mac_lo = self.span;
7590 let pth = self.parse_path(PathStyle::Mod)?;
7591 self.expect(&token::Not)?;
7593 // a 'special' identifier (like what `macro_rules!` uses)
7594 // is optional. We should eventually unify invoc syntax
7596 let id = if self.token.is_ident() {
7599 Ident::invalid() // no special identifier
7601 // eat a matched-delimiter token tree:
7602 let (delim, tts) = self.expect_delimited_token_tree()?;
7603 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
7604 self.report_invalid_macro_expansion_item();
7607 let hi = self.prev_span;
7608 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
7609 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
7610 return Ok(Some(item));
7613 // FAILURE TO PARSE ITEM
7614 match visibility.node {
7615 VisibilityKind::Inherited => {}
7617 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
7621 if !attributes_allowed && !attrs.is_empty() {
7622 self.expected_item_err(&attrs)?;
7627 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
7628 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
7629 at_end: &mut bool) -> PResult<'a, Option<Mac>>
7631 if self.token.is_path_start() &&
7632 !(self.is_async_fn() && self.span.rust_2015()) {
7633 let prev_span = self.prev_span;
7635 let pth = self.parse_path(PathStyle::Mod)?;
7637 if pth.segments.len() == 1 {
7638 if !self.eat(&token::Not) {
7639 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
7642 self.expect(&token::Not)?;
7645 if let Some(vis) = vis {
7646 self.complain_if_pub_macro(&vis.node, prev_span);
7651 // eat a matched-delimiter token tree:
7652 let (delim, tts) = self.expect_delimited_token_tree()?;
7653 if delim != MacDelimiter::Brace {
7654 self.expect(&token::Semi)?;
7657 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
7663 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
7664 where F: FnOnce(&mut Self) -> PResult<'a, R>
7666 // Record all tokens we parse when parsing this item.
7667 let mut tokens = Vec::new();
7668 let prev_collecting = match self.token_cursor.frame.last_token {
7669 LastToken::Collecting(ref mut list) => {
7670 Some(mem::replace(list, Vec::new()))
7672 LastToken::Was(ref mut last) => {
7673 tokens.extend(last.take());
7677 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
7678 let prev = self.token_cursor.stack.len();
7680 let last_token = if self.token_cursor.stack.len() == prev {
7681 &mut self.token_cursor.frame.last_token
7683 &mut self.token_cursor.stack[prev].last_token
7686 // Pull out the tokens that we've collected from the call to `f` above.
7687 let mut collected_tokens = match *last_token {
7688 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
7689 LastToken::Was(_) => panic!("our vector went away?"),
7692 // If we're not at EOF our current token wasn't actually consumed by
7693 // `f`, but it'll still be in our list that we pulled out. In that case
7695 let extra_token = if self.token != token::Eof {
7696 collected_tokens.pop()
7701 // If we were previously collecting tokens, then this was a recursive
7702 // call. In that case we need to record all the tokens we collected in
7703 // our parent list as well. To do that we push a clone of our stream
7704 // onto the previous list.
7705 match prev_collecting {
7707 list.extend(collected_tokens.iter().cloned());
7708 list.extend(extra_token);
7709 *last_token = LastToken::Collecting(list);
7712 *last_token = LastToken::Was(extra_token);
7716 Ok((ret?, TokenStream::new(collected_tokens)))
7719 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
7720 let attrs = self.parse_outer_attributes()?;
7721 self.parse_item_(attrs, true, false)
7725 fn is_import_coupler(&mut self) -> bool {
7726 self.check(&token::ModSep) &&
7727 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
7728 *t == token::BinOp(token::Star))
7731 /// Parses a `UseTree`.
7734 /// USE_TREE = [`::`] `*` |
7735 /// [`::`] `{` USE_TREE_LIST `}` |
7737 /// PATH `::` `{` USE_TREE_LIST `}` |
7738 /// PATH [`as` IDENT]
7740 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
7743 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
7744 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
7745 self.check(&token::BinOp(token::Star)) ||
7746 self.is_import_coupler() {
7747 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
7748 let mod_sep_ctxt = self.span.ctxt();
7749 if self.eat(&token::ModSep) {
7750 prefix.segments.push(
7751 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
7755 if self.eat(&token::BinOp(token::Star)) {
7758 UseTreeKind::Nested(self.parse_use_tree_list()?)
7761 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
7762 prefix = self.parse_path(PathStyle::Mod)?;
7764 if self.eat(&token::ModSep) {
7765 if self.eat(&token::BinOp(token::Star)) {
7768 UseTreeKind::Nested(self.parse_use_tree_list()?)
7771 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
7775 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
7778 /// Parses a `UseTreeKind::Nested(list)`.
7781 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
7783 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
7784 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
7785 &token::CloseDelim(token::Brace),
7786 SeqSep::trailing_allowed(token::Comma), |this| {
7787 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
7791 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
7792 if self.eat_keyword(kw::As) {
7793 self.parse_ident_or_underscore().map(Some)
7799 /// Parses a source module as a crate. This is the main entry point for the parser.
7800 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
7802 let krate = Ok(ast::Crate {
7803 attrs: self.parse_inner_attributes()?,
7804 module: self.parse_mod_items(&token::Eof, lo)?,
7805 span: lo.to(self.span),
7810 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
7811 let ret = match self.token {
7812 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
7813 (symbol, ast::StrStyle::Cooked, suffix),
7814 token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
7815 (symbol, ast::StrStyle::Raw(n), suffix),
7822 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
7823 match self.parse_optional_str() {
7824 Some((s, style, suf)) => {
7825 let sp = self.prev_span;
7826 self.expect_no_suffix(sp, "a string literal", suf);
7830 let msg = "expected string literal";
7831 let mut err = self.fatal(msg);
7832 err.span_label(self.span, msg);
7838 fn report_invalid_macro_expansion_item(&self) {
7839 self.struct_span_err(
7841 "macros that expand to items must be delimited with braces or followed by a semicolon",
7842 ).multipart_suggestion(
7843 "change the delimiters to curly braces",
7845 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
7846 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
7848 Applicability::MaybeIncorrect,
7850 self.sess.source_map.next_point(self.prev_span),
7853 Applicability::MaybeIncorrect,
7857 /// When lowering a `async fn` to the HIR, we need to move all of the arguments of the function
7858 /// into the generated closure so that they are dropped when the future is polled and not when
7861 /// The arguments of the function are replaced in HIR lowering with the arguments created by
7862 /// this function and the statements created here are inserted at the top of the closure body.
7863 fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
7864 // FIXME(davidtwco): This function should really live in the HIR lowering but because
7865 // the types constructed here need to be used in parts of resolve so that the correct
7866 // locals are considered upvars, it is currently easier for it to live here in the parser,
7867 // where it can be constructed once.
7868 if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
7869 for (index, input) in decl.inputs.iter_mut().enumerate() {
7870 let id = ast::DUMMY_NODE_ID;
7871 let span = input.pat.span;
7872 let desugared_span = self.sess.source_map()
7873 .mark_span_with_reason(CompilerDesugaringKind::Async, span, None);
7875 // Construct a name for our temporary argument.
7876 let name = format!("__arg{}", index);
7877 let ident = Ident::from_str(&name).gensym();
7879 // Check if this is a ident pattern, if so, we can optimize and avoid adding a
7880 // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
7882 let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
7883 PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
7884 // Simple patterns like this don't have a generated argument, but they are
7885 // moved into the closure with a statement, so any `mut` bindings on the
7886 // argument will be unused. This binding mode can't be removed, because
7887 // this would affect the input to procedural macros, but they can have
7888 // their span marked as being the result of a compiler desugaring so
7889 // that they aren't linted against.
7890 input.pat.span = desugared_span;
7892 (binding_mode, ident, true)
7894 _ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
7897 // Construct an argument representing `__argN: <ty>` to replace the argument of the
7898 // async function if it isn't a simple pattern.
7899 let arg = if is_simple_pattern {
7903 ty: input.ty.clone(),
7907 node: PatKind::Ident(
7908 BindingMode::ByValue(Mutability::Immutable), ident, None,
7910 span: desugared_span,
7912 source: ArgSource::AsyncFn(input.pat.clone()),
7916 // Construct a `let __argN = __argN;` statement to insert at the top of the
7917 // async closure. This makes sure that the argument is captured by the closure and
7918 // that the drop order is correct.
7919 let move_local = Local {
7922 node: PatKind::Ident(binding_mode, ident, None),
7923 span: desugared_span,
7925 // We explicitly do not specify the type for this statement. When the user's
7926 // argument type is `impl Trait` then this would require the
7927 // `impl_trait_in_bindings` feature to also be present for that same type to
7928 // be valid in this binding. At the time of writing (13 Mar 19),
7929 // `impl_trait_in_bindings` is not stable.
7933 node: ExprKind::Path(None, ast::Path {
7935 segments: vec![PathSegment { ident, id, args: None }],
7938 attrs: ThinVec::new(),
7942 attrs: ThinVec::new(),
7943 source: LocalSource::AsyncFn,
7946 // Construct a `let <pat> = __argN;` statement to insert at the top of the
7947 // async closure if this isn't a simple pattern.
7948 let pat_stmt = if is_simple_pattern {
7953 node: StmtKind::Local(P(Local {
7954 pat: input.pat.clone(),
7955 ..move_local.clone()
7961 let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
7962 arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
7968 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
7969 for unmatched in unclosed_delims.iter() {
7970 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
7971 "incorrect close delimiter: `{}`",
7972 pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
7974 err.span_label(unmatched.found_span, "incorrect close delimiter");
7975 if let Some(sp) = unmatched.candidate_span {
7976 err.span_label(sp, "close delimiter possibly meant for this");
7978 if let Some(sp) = unmatched.unclosed_span {
7979 err.span_label(sp, "un-closed delimiter");
7983 unclosed_delims.clear();