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;
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 /// Creates a placeholder argument.
455 fn dummy_arg(span: Span) -> Arg {
456 let ident = Ident::new(kw::Invalid, span);
458 id: ast::DUMMY_NODE_ID,
459 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
465 id: ast::DUMMY_NODE_ID
467 Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal }
470 #[derive(Copy, Clone, Debug)]
471 crate enum TokenExpectType {
476 impl<'a> Parser<'a> {
480 directory: Option<Directory<'a>>,
481 recurse_into_file_modules: bool,
482 desugar_doc_comments: bool,
483 subparser_name: Option<&'static str>,
485 let mut parser = Parser {
487 token: token::Whitespace,
491 prev_token_kind: PrevTokenKind::Other,
492 restrictions: Restrictions::empty(),
493 recurse_into_file_modules,
494 directory: Directory {
495 path: Cow::from(PathBuf::new()),
496 ownership: DirectoryOwnership::Owned { relative: None }
498 root_module_name: None,
499 expected_tokens: Vec::new(),
500 token_cursor: TokenCursor {
501 frame: TokenCursorFrame::new(
508 desugar_doc_comments,
510 unmatched_angle_bracket_count: 0,
511 max_angle_bracket_count: 0,
512 unclosed_delims: Vec::new(),
513 last_unexpected_token_span: None,
517 let tok = parser.next_tok();
518 parser.token = tok.tok;
519 parser.span = tok.sp;
521 if let Some(directory) = directory {
522 parser.directory = directory;
523 } else if !parser.span.is_dummy() {
524 if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
526 parser.directory.path = Cow::from(path);
530 parser.process_potential_macro_variable();
534 fn next_tok(&mut self) -> TokenAndSpan {
535 let mut next = if self.desugar_doc_comments {
536 self.token_cursor.next_desugared()
538 self.token_cursor.next()
540 if next.sp.is_dummy() {
541 // Tweak the location for better diagnostics, but keep syntactic context intact.
542 next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
547 /// Converts the current token to a string using `self`'s reader.
548 pub fn this_token_to_string(&self) -> String {
549 pprust::token_to_string(&self.token)
552 crate fn token_descr(&self) -> Option<&'static str> {
553 Some(match &self.token {
554 t if t.is_special_ident() => "reserved identifier",
555 t if t.is_used_keyword() => "keyword",
556 t if t.is_unused_keyword() => "reserved keyword",
557 token::DocComment(..) => "doc comment",
562 crate fn this_token_descr(&self) -> String {
563 if let Some(prefix) = self.token_descr() {
564 format!("{} `{}`", prefix, self.this_token_to_string())
566 format!("`{}`", self.this_token_to_string())
570 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
571 match self.expect_one_of(&[], &[]) {
573 Ok(_) => unreachable!(),
577 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
578 pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
579 if self.expected_tokens.is_empty() {
580 if self.token == *t {
584 self.unexpected_try_recover(t)
587 self.expect_one_of(slice::from_ref(t), &[])
591 /// Expect next token to be edible or inedible token. If edible,
592 /// then consume it; if inedible, then return without consuming
593 /// anything. Signal a fatal error if next token is unexpected.
594 pub fn expect_one_of(
596 edible: &[token::Token],
597 inedible: &[token::Token],
598 ) -> PResult<'a, bool /* recovered */> {
599 if edible.contains(&self.token) {
602 } else if inedible.contains(&self.token) {
603 // leave it in the input
605 } else if self.last_unexpected_token_span == Some(self.span) {
608 self.expected_one_of_not_found(edible, inedible)
612 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
613 fn interpolated_or_expr_span(
615 expr: PResult<'a, P<Expr>>,
616 ) -> PResult<'a, (Span, P<Expr>)> {
618 if self.prev_token_kind == PrevTokenKind::Interpolated {
626 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
627 self.parse_ident_common(true)
630 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
632 token::Ident(ident, _) => {
633 if self.token.is_reserved_ident() {
634 let mut err = self.expected_ident_found();
641 let span = self.span;
643 Ok(Ident::new(ident.name, span))
646 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
647 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
649 self.expected_ident_found()
655 /// Checks if the next token is `tok`, and returns `true` if so.
657 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
659 crate fn check(&mut self, tok: &token::Token) -> bool {
660 let is_present = self.token == *tok;
661 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
665 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
666 pub fn eat(&mut self, tok: &token::Token) -> bool {
667 let is_present = self.check(tok);
668 if is_present { self.bump() }
672 fn check_keyword(&mut self, kw: Symbol) -> bool {
673 self.expected_tokens.push(TokenType::Keyword(kw));
674 self.token.is_keyword(kw)
677 /// If the next token is the given keyword, eats it and returns
678 /// `true`. Otherwise, returns `false`.
679 pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
680 if self.check_keyword(kw) {
688 fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
689 if self.token.is_keyword(kw) {
697 /// If the given word is not a keyword, signals an error.
698 /// If the next token is not the given word, signals an error.
699 /// Otherwise, eats it.
700 fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
701 if !self.eat_keyword(kw) {
708 crate fn check_ident(&mut self) -> bool {
709 if self.token.is_ident() {
712 self.expected_tokens.push(TokenType::Ident);
717 fn check_path(&mut self) -> bool {
718 if self.token.is_path_start() {
721 self.expected_tokens.push(TokenType::Path);
726 fn check_type(&mut self) -> bool {
727 if self.token.can_begin_type() {
730 self.expected_tokens.push(TokenType::Type);
735 fn check_const_arg(&mut self) -> bool {
736 if self.token.can_begin_const_arg() {
739 self.expected_tokens.push(TokenType::Const);
744 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
745 /// and continues. If a `+` is not seen, returns `false`.
747 /// This is used when token-splitting `+=` into `+`.
748 /// See issue #47856 for an example of when this may occur.
749 fn eat_plus(&mut self) -> bool {
750 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
752 token::BinOp(token::Plus) => {
756 token::BinOpEq(token::Plus) => {
757 let span = self.span.with_lo(self.span.lo() + BytePos(1));
758 self.bump_with(token::Eq, span);
766 /// Checks to see if the next token is either `+` or `+=`.
767 /// Otherwise returns `false`.
768 fn check_plus(&mut self) -> bool {
769 if self.token.is_like_plus() {
773 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
778 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
779 /// `&` and continues. If an `&` is not seen, signals an error.
780 fn expect_and(&mut self) -> PResult<'a, ()> {
781 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
783 token::BinOp(token::And) => {
788 let span = self.span.with_lo(self.span.lo() + BytePos(1));
789 Ok(self.bump_with(token::BinOp(token::And), span))
791 _ => self.unexpected()
795 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
796 /// `|` and continues. If an `|` is not seen, signals an error.
797 fn expect_or(&mut self) -> PResult<'a, ()> {
798 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
800 token::BinOp(token::Or) => {
805 let span = self.span.with_lo(self.span.lo() + BytePos(1));
806 Ok(self.bump_with(token::BinOp(token::Or), span))
808 _ => self.unexpected()
812 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
813 literal::expect_no_suffix(&self.sess.span_diagnostic, sp, kind, suffix)
816 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
817 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
818 /// and continue. If a `<` is not seen, returns false.
820 /// This is meant to be used when parsing generics on a path to get the
822 fn eat_lt(&mut self) -> bool {
823 self.expected_tokens.push(TokenType::Token(token::Lt));
824 let ate = match self.token {
829 token::BinOp(token::Shl) => {
830 let span = self.span.with_lo(self.span.lo() + BytePos(1));
831 self.bump_with(token::Lt, span);
835 let span = self.span.with_lo(self.span.lo() + BytePos(1));
836 self.bump_with(token::BinOp(token::Minus), span);
843 // See doc comment for `unmatched_angle_bracket_count`.
844 self.unmatched_angle_bracket_count += 1;
845 self.max_angle_bracket_count += 1;
846 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
852 fn expect_lt(&mut self) -> PResult<'a, ()> {
860 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
861 /// with a single `>` and continues. If a `>` is not seen, signals an error.
862 fn expect_gt(&mut self) -> PResult<'a, ()> {
863 self.expected_tokens.push(TokenType::Token(token::Gt));
864 let ate = match self.token {
869 token::BinOp(token::Shr) => {
870 let span = self.span.with_lo(self.span.lo() + BytePos(1));
871 Some(self.bump_with(token::Gt, span))
873 token::BinOpEq(token::Shr) => {
874 let span = self.span.with_lo(self.span.lo() + BytePos(1));
875 Some(self.bump_with(token::Ge, span))
878 let span = self.span.with_lo(self.span.lo() + BytePos(1));
879 Some(self.bump_with(token::Eq, span))
886 // See doc comment for `unmatched_angle_bracket_count`.
887 if self.unmatched_angle_bracket_count > 0 {
888 self.unmatched_angle_bracket_count -= 1;
889 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
894 None => self.unexpected(),
898 /// Parses a sequence, including the closing delimiter. The function
899 /// `f` must consume tokens until reaching the next separator or
901 pub fn parse_seq_to_end<T, F>(&mut self,
905 -> PResult<'a, Vec<T>> where
906 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
908 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
915 /// Parses a sequence, not including the closing delimiter. The function
916 /// `f` must consume tokens until reaching the next separator or
918 pub fn parse_seq_to_before_end<T, F>(
923 ) -> PResult<'a, (Vec<T>, bool)>
924 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
926 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
929 crate fn parse_seq_to_before_tokens<T, F>(
931 kets: &[&token::Token],
933 expect: TokenExpectType,
935 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
936 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
938 let mut first = true;
939 let mut recovered = false;
941 while !kets.iter().any(|k| {
943 TokenExpectType::Expect => self.check(k),
944 TokenExpectType::NoExpect => self.token == **k,
948 token::CloseDelim(..) | token::Eof => break,
951 if let Some(ref t) = sep.sep {
955 match self.expect(t) {
962 // Attempt to keep parsing if it was a similar separator
963 if let Some(ref tokens) = t.similar_tokens() {
964 if tokens.contains(&self.token) {
969 // Attempt to keep parsing if it was an omitted separator
984 if sep.trailing_sep_allowed && kets.iter().any(|k| {
986 TokenExpectType::Expect => self.check(k),
987 TokenExpectType::NoExpect => self.token == **k,
1000 /// Parses a sequence, including the closing delimiter. The function
1001 /// `f` must consume tokens until reaching the next separator or
1002 /// closing bracket.
1003 fn parse_unspanned_seq<T, F>(
1009 ) -> PResult<'a, Vec<T>> where
1010 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1013 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1020 /// Advance the parser by one token
1021 pub fn bump(&mut self) {
1022 if self.prev_token_kind == PrevTokenKind::Eof {
1023 // Bumping after EOF is a bad sign, usually an infinite loop.
1024 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1027 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1029 // Record last token kind for possible error recovery.
1030 self.prev_token_kind = match self.token {
1031 token::DocComment(..) => PrevTokenKind::DocComment,
1032 token::Comma => PrevTokenKind::Comma,
1033 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1034 token::BinOp(token::Or) => PrevTokenKind::BitOr,
1035 token::Interpolated(..) => PrevTokenKind::Interpolated,
1036 token::Eof => PrevTokenKind::Eof,
1037 token::Ident(..) => PrevTokenKind::Ident,
1038 _ => PrevTokenKind::Other,
1041 let next = self.next_tok();
1042 self.span = next.sp;
1043 self.token = next.tok;
1044 self.expected_tokens.clear();
1045 // check after each token
1046 self.process_potential_macro_variable();
1049 /// Advance the parser using provided token as a next one. Use this when
1050 /// consuming a part of a token. For example a single `<` from `<<`.
1051 fn bump_with(&mut self, next: token::Token, span: Span) {
1052 self.prev_span = self.span.with_hi(span.lo());
1053 // It would be incorrect to record the kind of the current token, but
1054 // fortunately for tokens currently using `bump_with`, the
1055 // prev_token_kind will be of no use anyway.
1056 self.prev_token_kind = PrevTokenKind::Other;
1059 self.expected_tokens.clear();
1062 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1063 F: FnOnce(&token::Token) -> R,
1066 return f(&self.token)
1069 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1070 Some(tree) => match tree {
1071 TokenTree::Token(_, tok) => tok,
1072 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1074 None => token::CloseDelim(self.token_cursor.frame.delim),
1078 crate fn look_ahead_span(&self, dist: usize) -> Span {
1083 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1084 Some(TokenTree::Token(span, _)) => span,
1085 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1086 None => self.look_ahead_span(dist - 1),
1090 /// Returns whether any of the given keywords are `dist` tokens ahead of the current one.
1091 fn is_keyword_ahead(&self, dist: usize, kws: &[Symbol]) -> bool {
1092 self.look_ahead(dist, |t| kws.iter().any(|&kw| t.is_keyword(kw)))
1095 /// Is the current token one of the keywords that signals a bare function type?
1096 fn token_is_bare_fn_keyword(&mut self) -> bool {
1097 self.check_keyword(kw::Fn) ||
1098 self.check_keyword(kw::Unsafe) ||
1099 self.check_keyword(kw::Extern)
1102 /// Parses a `TyKind::BareFn` type.
1103 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1106 [unsafe] [extern "ABI"] fn (S) -> T
1116 let unsafety = self.parse_unsafety();
1117 let abi = if self.eat_keyword(kw::Extern) {
1118 self.parse_opt_abi()?.unwrap_or(Abi::C)
1123 self.expect_keyword(kw::Fn)?;
1124 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1125 let ret_ty = self.parse_ret_ty(false)?;
1126 let decl = P(FnDecl {
1131 Ok(TyKind::BareFn(P(BareFnTy {
1139 /// Parses asyncness: `async` or nothing.
1140 fn parse_asyncness(&mut self) -> IsAsync {
1141 if self.eat_keyword(kw::Async) {
1143 closure_id: ast::DUMMY_NODE_ID,
1144 return_impl_trait_id: ast::DUMMY_NODE_ID,
1145 arguments: Vec::new(),
1152 /// Parses unsafety: `unsafe` or nothing.
1153 fn parse_unsafety(&mut self) -> Unsafety {
1154 if self.eat_keyword(kw::Unsafe) {
1161 /// Parses the items in a trait declaration.
1162 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1163 maybe_whole!(self, NtTraitItem, |x| x);
1164 let attrs = self.parse_outer_attributes()?;
1165 let mut unclosed_delims = vec![];
1166 let (mut item, tokens) = self.collect_tokens(|this| {
1167 let item = this.parse_trait_item_(at_end, attrs);
1168 unclosed_delims.append(&mut this.unclosed_delims);
1171 self.unclosed_delims.append(&mut unclosed_delims);
1172 // See `parse_item` for why this clause is here.
1173 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1174 item.tokens = Some(tokens);
1179 fn parse_trait_item_(&mut self,
1181 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1184 let (name, node, generics) = if self.eat_keyword(kw::Type) {
1185 self.parse_trait_item_assoc_ty()?
1186 } else if self.is_const_item() {
1187 self.expect_keyword(kw::Const)?;
1188 let ident = self.parse_ident()?;
1189 self.expect(&token::Colon)?;
1190 let ty = self.parse_ty()?;
1191 let default = if self.eat(&token::Eq) {
1192 let expr = self.parse_expr()?;
1193 self.expect(&token::Semi)?;
1196 self.expect(&token::Semi)?;
1199 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1200 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1201 // trait item macro.
1202 (Ident::invalid(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1204 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
1206 let ident = self.parse_ident()?;
1207 let mut generics = self.parse_generics()?;
1209 let mut decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1210 // This is somewhat dubious; We don't want to allow
1211 // argument names to be left off if there is a
1214 // We don't allow argument names to be left off in edition 2018.
1215 p.parse_arg_general(p.span.rust_2018(), true, false)
1217 generics.where_clause = self.parse_where_clause()?;
1218 self.construct_async_arguments(&mut asyncness, &mut decl);
1220 let sig = ast::MethodSig {
1230 let body = match self.token {
1234 debug!("parse_trait_methods(): parsing required method");
1237 token::OpenDelim(token::Brace) => {
1238 debug!("parse_trait_methods(): parsing provided method");
1240 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1241 attrs.extend(inner_attrs.iter().cloned());
1244 token::Interpolated(ref nt) => {
1246 token::NtBlock(..) => {
1248 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1249 attrs.extend(inner_attrs.iter().cloned());
1253 return self.expected_semi_or_open_brace();
1258 return self.expected_semi_or_open_brace();
1261 (ident, ast::TraitItemKind::Method(sig, body), generics)
1265 id: ast::DUMMY_NODE_ID,
1270 span: lo.to(self.prev_span),
1275 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1276 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1277 if self.eat(&token::RArrow) {
1278 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1280 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1285 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1286 self.parse_ty_common(true, true, false)
1289 /// Parses a type in restricted contexts where `+` is not permitted.
1291 /// Example 1: `&'a TYPE`
1292 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1293 /// Example 2: `value1 as TYPE + value2`
1294 /// `+` is prohibited to avoid interactions with expression grammar.
1295 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1296 self.parse_ty_common(false, true, false)
1299 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1300 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1301 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1302 maybe_whole!(self, NtTy, |x| x);
1305 let mut impl_dyn_multi = false;
1306 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1307 // `(TYPE)` is a parenthesized type.
1308 // `(TYPE,)` is a tuple with a single field of type TYPE.
1309 let mut ts = vec![];
1310 let mut last_comma = false;
1311 while self.token != token::CloseDelim(token::Paren) {
1312 ts.push(self.parse_ty()?);
1313 if self.eat(&token::Comma) {
1320 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1321 self.expect(&token::CloseDelim(token::Paren))?;
1323 if ts.len() == 1 && !last_comma {
1324 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1325 let maybe_bounds = allow_plus && self.token.is_like_plus();
1327 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1328 TyKind::Path(None, ref path) if maybe_bounds => {
1329 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1331 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1332 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1333 let path = match bounds[0] {
1334 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1335 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1337 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1340 _ => TyKind::Paren(P(ty))
1345 } else if self.eat(&token::Not) {
1348 } else if self.eat(&token::BinOp(token::Star)) {
1350 TyKind::Ptr(self.parse_ptr()?)
1351 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1353 let t = self.parse_ty()?;
1354 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1355 let t = match self.maybe_parse_fixed_length_of_vec()? {
1356 None => TyKind::Slice(t),
1357 Some(length) => TyKind::Array(t, AnonConst {
1358 id: ast::DUMMY_NODE_ID,
1362 self.expect(&token::CloseDelim(token::Bracket))?;
1364 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1367 self.parse_borrowed_pointee()?
1368 } else if self.eat_keyword_noexpect(kw::Typeof) {
1370 // In order to not be ambiguous, the type must be surrounded by parens.
1371 self.expect(&token::OpenDelim(token::Paren))?;
1373 id: ast::DUMMY_NODE_ID,
1374 value: self.parse_expr()?,
1376 self.expect(&token::CloseDelim(token::Paren))?;
1378 } else if self.eat_keyword(kw::Underscore) {
1379 // A type to be inferred `_`
1381 } else if self.token_is_bare_fn_keyword() {
1382 // Function pointer type
1383 self.parse_ty_bare_fn(Vec::new())?
1384 } else if self.check_keyword(kw::For) {
1385 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1386 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1387 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1389 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1390 if self.token_is_bare_fn_keyword() {
1391 self.parse_ty_bare_fn(lifetime_defs)?
1393 let path = self.parse_path(PathStyle::Type)?;
1394 let parse_plus = allow_plus && self.check_plus();
1395 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1397 } else if self.eat_keyword(kw::Impl) {
1398 // Always parse bounds greedily for better error recovery.
1399 let bounds = self.parse_generic_bounds(None)?;
1400 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1401 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1402 } else if self.check_keyword(kw::Dyn) &&
1403 (self.span.rust_2018() ||
1404 self.look_ahead(1, |t| t.can_begin_bound() &&
1405 !can_continue_type_after_non_fn_ident(t))) {
1406 self.bump(); // `dyn`
1407 // Always parse bounds greedily for better error recovery.
1408 let bounds = self.parse_generic_bounds(None)?;
1409 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1410 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1411 } else if self.check(&token::Question) ||
1412 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1413 // Bound list (trait object type)
1414 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1415 TraitObjectSyntax::None)
1416 } else if self.eat_lt() {
1418 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1419 TyKind::Path(Some(qself), path)
1420 } else if self.token.is_path_start() {
1422 let path = self.parse_path(PathStyle::Type)?;
1423 if self.eat(&token::Not) {
1424 // Macro invocation in type position
1425 let (delim, tts) = self.expect_delimited_token_tree()?;
1426 let node = Mac_ { path, tts, delim };
1427 TyKind::Mac(respan(lo.to(self.prev_span), node))
1429 // Just a type path or bound list (trait object type) starting with a trait.
1431 // `Trait1 + Trait2 + 'a`
1432 if allow_plus && self.check_plus() {
1433 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1435 TyKind::Path(None, path)
1438 } else if self.check(&token::DotDotDot) {
1439 if allow_c_variadic {
1440 self.eat(&token::DotDotDot);
1443 return Err(self.fatal(
1444 "only foreign functions are allowed to be C-variadic"
1448 let msg = format!("expected type, found {}", self.this_token_descr());
1449 return Err(self.fatal(&msg));
1452 let span = lo.to(self.prev_span);
1453 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1455 // Try to recover from use of `+` with incorrect priority.
1456 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1457 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1458 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1461 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1462 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1463 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1464 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1466 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1467 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1469 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1472 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1473 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1474 let mutbl = self.parse_mutability();
1475 let ty = self.parse_ty_no_plus()?;
1476 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1479 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1480 let mutbl = if self.eat_keyword(kw::Mut) {
1482 } else if self.eat_keyword(kw::Const) {
1483 Mutability::Immutable
1485 let span = self.prev_span;
1486 let msg = "expected mut or const in raw pointer type";
1487 self.struct_span_err(span, msg)
1488 .span_label(span, msg)
1489 .help("use `*mut T` or `*const T` as appropriate")
1491 Mutability::Immutable
1493 let t = self.parse_ty_no_plus()?;
1494 Ok(MutTy { ty: t, mutbl: mutbl })
1497 fn is_named_argument(&self) -> bool {
1498 let offset = match self.token {
1499 token::Interpolated(ref nt) => match **nt {
1500 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1503 token::BinOp(token::And) | token::AndAnd => 1,
1504 _ if self.token.is_keyword(kw::Mut) => 1,
1508 self.look_ahead(offset, |t| t.is_ident()) &&
1509 self.look_ahead(offset + 1, |t| t == &token::Colon)
1512 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1514 /// This version of parse arg doesn't necessarily require identifier names.
1515 fn parse_arg_general(
1518 is_trait_item: bool,
1519 allow_c_variadic: bool,
1520 ) -> PResult<'a, Arg> {
1521 if let Ok(Some(arg)) = self.parse_self_arg() {
1522 return self.recover_bad_self_arg(arg, is_trait_item);
1525 let (pat, ty) = if require_name || self.is_named_argument() {
1526 debug!("parse_arg_general parse_pat (require_name:{})", require_name);
1527 self.eat_incorrect_doc_comment("method arguments");
1528 let pat = self.parse_pat(Some("argument name"))?;
1530 if let Err(mut err) = self.expect(&token::Colon) {
1531 self.argument_without_type(&mut err, pat, require_name, is_trait_item);
1535 self.eat_incorrect_doc_comment("a method argument's type");
1536 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1538 debug!("parse_arg_general ident_to_pat");
1539 let parser_snapshot_before_ty = self.clone();
1540 self.eat_incorrect_doc_comment("a method argument's type");
1541 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1542 if ty.is_ok() && self.token != token::Comma &&
1543 self.token != token::CloseDelim(token::Paren) {
1544 // This wasn't actually a type, but a pattern looking like a type,
1545 // so we are going to rollback and re-parse for recovery.
1546 ty = self.unexpected();
1550 let ident = Ident::new(kw::Invalid, self.prev_span);
1552 id: ast::DUMMY_NODE_ID,
1553 node: PatKind::Ident(
1554 BindingMode::ByValue(Mutability::Immutable), ident, None),
1560 // If this is a C-variadic argument and we hit an error, return the
1562 if self.token == token::DotDotDot {
1565 // Recover from attempting to parse the argument as a type without pattern.
1567 mem::replace(self, parser_snapshot_before_ty);
1568 self.recover_arg_parse()?
1573 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal })
1576 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1577 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1578 let pat = self.parse_pat(Some("argument name"))?;
1579 let t = if self.eat(&token::Colon) {
1583 id: ast::DUMMY_NODE_ID,
1584 node: TyKind::Infer,
1585 span: self.prev_span,
1591 id: ast::DUMMY_NODE_ID,
1592 source: ast::ArgSource::Normal,
1596 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1597 if self.eat(&token::Semi) {
1598 Ok(Some(self.parse_expr()?))
1604 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1605 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1606 maybe_whole_expr!(self);
1608 let minus_lo = self.span;
1609 let minus_present = self.eat(&token::BinOp(token::Minus));
1611 let literal = self.parse_lit()?;
1612 let hi = self.prev_span;
1613 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1616 let minus_hi = self.prev_span;
1617 let unary = self.mk_unary(UnOp::Neg, expr);
1618 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1624 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
1626 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
1627 let span = self.span;
1629 Ok(Ident::new(ident.name, span))
1631 _ => self.parse_ident(),
1635 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
1637 token::Ident(ident, false) if ident.name == kw::Underscore => {
1638 let span = self.span;
1640 Ok(Ident::new(ident.name, span))
1642 _ => self.parse_ident(),
1646 /// Parses a qualified path.
1647 /// Assumes that the leading `<` has been parsed already.
1649 /// `qualified_path = <type [as trait_ref]>::path`
1654 /// `<T as U>::F::a<S>` (without disambiguator)
1655 /// `<T as U>::F::a::<S>` (with disambiguator)
1656 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
1657 let lo = self.prev_span;
1658 let ty = self.parse_ty()?;
1660 // `path` will contain the prefix of the path up to the `>`,
1661 // if any (e.g., `U` in the `<T as U>::*` examples
1662 // above). `path_span` has the span of that path, or an empty
1663 // span in the case of something like `<T>::Bar`.
1664 let (mut path, path_span);
1665 if self.eat_keyword(kw::As) {
1666 let path_lo = self.span;
1667 path = self.parse_path(PathStyle::Type)?;
1668 path_span = path_lo.to(self.prev_span);
1670 path = ast::Path { segments: Vec::new(), span: DUMMY_SP };
1671 path_span = self.span.to(self.span);
1674 // See doc comment for `unmatched_angle_bracket_count`.
1675 self.expect(&token::Gt)?;
1676 if self.unmatched_angle_bracket_count > 0 {
1677 self.unmatched_angle_bracket_count -= 1;
1678 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1681 self.expect(&token::ModSep)?;
1683 let qself = QSelf { ty, path_span, position: path.segments.len() };
1684 self.parse_path_segments(&mut path.segments, style)?;
1686 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
1689 /// Parses simple paths.
1691 /// `path = [::] segment+`
1692 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
1695 /// `a::b::C<D>` (without disambiguator)
1696 /// `a::b::C::<D>` (with disambiguator)
1697 /// `Fn(Args)` (without disambiguator)
1698 /// `Fn::(Args)` (with disambiguator)
1699 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1700 maybe_whole!(self, NtPath, |path| {
1701 if style == PathStyle::Mod &&
1702 path.segments.iter().any(|segment| segment.args.is_some()) {
1703 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
1708 let lo = self.meta_var_span.unwrap_or(self.span);
1709 let mut segments = Vec::new();
1710 let mod_sep_ctxt = self.span.ctxt();
1711 if self.eat(&token::ModSep) {
1712 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
1714 self.parse_path_segments(&mut segments, style)?;
1716 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
1719 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
1720 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
1722 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
1723 let meta_ident = match self.token {
1724 token::Interpolated(ref nt) => match **nt {
1725 token::NtMeta(ref meta) => match meta.node {
1726 ast::MetaItemKind::Word => Some(meta.path.clone()),
1733 if let Some(path) = meta_ident {
1737 self.parse_path(style)
1740 crate fn parse_path_segments(&mut self,
1741 segments: &mut Vec<PathSegment>,
1743 -> PResult<'a, ()> {
1745 let segment = self.parse_path_segment(style)?;
1746 if style == PathStyle::Expr {
1747 // In order to check for trailing angle brackets, we must have finished
1748 // recursing (`parse_path_segment` can indirectly call this function),
1749 // that is, the next token must be the highlighted part of the below example:
1751 // `Foo::<Bar as Baz<T>>::Qux`
1754 // As opposed to the below highlight (if we had only finished the first
1757 // `Foo::<Bar as Baz<T>>::Qux`
1760 // `PathStyle::Expr` is only provided at the root invocation and never in
1761 // `parse_path_segment` to recurse and therefore can be checked to maintain
1763 self.check_trailing_angle_brackets(&segment, token::ModSep);
1765 segments.push(segment);
1767 if self.is_import_coupler() || !self.eat(&token::ModSep) {
1773 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
1774 let ident = self.parse_path_segment_ident()?;
1776 let is_args_start = |token: &token::Token| match *token {
1777 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
1778 | token::LArrow => true,
1781 let check_args_start = |this: &mut Self| {
1782 this.expected_tokens.extend_from_slice(
1783 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
1785 is_args_start(&this.token)
1788 Ok(if style == PathStyle::Type && check_args_start(self) ||
1789 style != PathStyle::Mod && self.check(&token::ModSep)
1790 && self.look_ahead(1, |t| is_args_start(t)) {
1791 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
1792 // it isn't, then we reset the unmatched angle bracket count as we're about to start
1793 // parsing a new path.
1794 if style == PathStyle::Expr {
1795 self.unmatched_angle_bracket_count = 0;
1796 self.max_angle_bracket_count = 0;
1799 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
1800 self.eat(&token::ModSep);
1802 let args = if self.eat_lt() {
1804 let (args, bindings) =
1805 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
1807 let span = lo.to(self.prev_span);
1808 AngleBracketedArgs { args, bindings, span }.into()
1812 let (inputs, recovered) = self.parse_seq_to_before_tokens(
1813 &[&token::CloseDelim(token::Paren)],
1814 SeqSep::trailing_allowed(token::Comma),
1815 TokenExpectType::Expect,
1820 let span = lo.to(self.prev_span);
1821 let output = if self.eat(&token::RArrow) {
1822 Some(self.parse_ty_common(false, false, false)?)
1826 ParenthesizedArgs { inputs, output, span }.into()
1829 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
1831 // Generic arguments are not found.
1832 PathSegment::from_ident(ident)
1836 crate fn check_lifetime(&mut self) -> bool {
1837 self.expected_tokens.push(TokenType::Lifetime);
1838 self.token.is_lifetime()
1841 /// Parses a single lifetime `'a` or panics.
1842 crate fn expect_lifetime(&mut self) -> Lifetime {
1843 if let Some(ident) = self.token.lifetime() {
1844 let span = self.span;
1846 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
1848 self.span_bug(self.span, "not a lifetime")
1852 fn eat_label(&mut self) -> Option<Label> {
1853 if let Some(ident) = self.token.lifetime() {
1854 let span = self.span;
1856 Some(Label { ident: Ident::new(ident.name, span) })
1862 /// Parses mutability (`mut` or nothing).
1863 fn parse_mutability(&mut self) -> Mutability {
1864 if self.eat_keyword(kw::Mut) {
1867 Mutability::Immutable
1871 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
1872 if let token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) = self.token {
1873 self.expect_no_suffix(self.span, "a tuple index", suffix);
1875 Ok(Ident::new(symbol, self.prev_span))
1877 self.parse_ident_common(false)
1881 /// Parse ident (COLON expr)?
1882 fn parse_field(&mut self) -> PResult<'a, Field> {
1883 let attrs = self.parse_outer_attributes()?;
1886 // Check if a colon exists one ahead. This means we're parsing a fieldname.
1887 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
1888 t == &token::Colon || t == &token::Eq
1890 let fieldname = self.parse_field_name()?;
1892 // Check for an equals token. This means the source incorrectly attempts to
1893 // initialize a field with an eq rather than a colon.
1894 if self.token == token::Eq {
1896 .struct_span_err(self.span, "expected `:`, found `=`")
1898 fieldname.span.shrink_to_hi().to(self.span),
1899 "replace equals symbol with a colon",
1901 Applicability::MachineApplicable,
1906 (fieldname, self.parse_expr()?, false)
1908 let fieldname = self.parse_ident_common(false)?;
1910 // Mimic `x: x` for the `x` field shorthand.
1911 let path = ast::Path::from_ident(fieldname);
1912 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
1913 (fieldname, expr, true)
1917 span: lo.to(expr.span),
1920 attrs: attrs.into(),
1924 crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
1925 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
1928 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
1929 ExprKind::Unary(unop, expr)
1932 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1933 ExprKind::Binary(binop, lhs, rhs)
1936 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
1937 ExprKind::Call(f, args)
1940 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
1941 ExprKind::Index(expr, idx)
1945 start: Option<P<Expr>>,
1946 end: Option<P<Expr>>,
1947 limits: RangeLimits)
1948 -> PResult<'a, ast::ExprKind> {
1949 if end.is_none() && limits == RangeLimits::Closed {
1950 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
1952 Ok(ExprKind::Range(start, end, limits))
1956 fn mk_assign_op(&self, binop: ast::BinOp,
1957 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
1958 ExprKind::AssignOp(binop, lhs, rhs)
1961 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
1962 let delim = match self.token {
1963 token::OpenDelim(delim) => delim,
1965 let msg = "expected open delimiter";
1966 let mut err = self.fatal(msg);
1967 err.span_label(self.span, msg);
1971 let tts = match self.parse_token_tree() {
1972 TokenTree::Delimited(_, _, tts) => tts,
1973 _ => unreachable!(),
1975 let delim = match delim {
1976 token::Paren => MacDelimiter::Parenthesis,
1977 token::Bracket => MacDelimiter::Bracket,
1978 token::Brace => MacDelimiter::Brace,
1979 token::NoDelim => self.bug("unexpected no delimiter"),
1981 Ok((delim, tts.into()))
1984 /// At the bottom (top?) of the precedence hierarchy,
1985 /// Parses things like parenthesized exprs, macros, `return`, etc.
1987 /// N.B., this does not parse outer attributes, and is private because it only works
1988 /// correctly if called from `parse_dot_or_call_expr()`.
1989 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
1990 maybe_recover_from_interpolated_ty_qpath!(self, true);
1991 maybe_whole_expr!(self);
1993 // Outer attributes are already parsed and will be
1994 // added to the return value after the fact.
1996 // Therefore, prevent sub-parser from parsing
1997 // attributes by giving them a empty "already parsed" list.
1998 let mut attrs = ThinVec::new();
2001 let mut hi = self.span;
2005 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2007 token::OpenDelim(token::Paren) => {
2010 attrs.extend(self.parse_inner_attributes()?);
2012 // (e) is parenthesized e
2013 // (e,) is a tuple with only one field, e
2014 let mut es = vec![];
2015 let mut trailing_comma = false;
2016 let mut recovered = false;
2017 while self.token != token::CloseDelim(token::Paren) {
2018 es.push(match self.parse_expr() {
2021 // recover from parse error in tuple list
2022 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2025 recovered = self.expect_one_of(
2027 &[token::Comma, token::CloseDelim(token::Paren)],
2029 if self.eat(&token::Comma) {
2030 trailing_comma = true;
2032 trailing_comma = false;
2040 hi = self.prev_span;
2041 ex = if es.len() == 1 && !trailing_comma {
2042 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2047 token::OpenDelim(token::Brace) => {
2048 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2050 token::BinOp(token::Or) | token::OrOr => {
2051 return self.parse_lambda_expr(attrs);
2053 token::OpenDelim(token::Bracket) => {
2056 attrs.extend(self.parse_inner_attributes()?);
2058 if self.eat(&token::CloseDelim(token::Bracket)) {
2060 ex = ExprKind::Array(Vec::new());
2063 let first_expr = self.parse_expr()?;
2064 if self.eat(&token::Semi) {
2065 // Repeating array syntax: [ 0; 512 ]
2066 let count = AnonConst {
2067 id: ast::DUMMY_NODE_ID,
2068 value: self.parse_expr()?,
2070 self.expect(&token::CloseDelim(token::Bracket))?;
2071 ex = ExprKind::Repeat(first_expr, count);
2072 } else if self.eat(&token::Comma) {
2073 // Vector with two or more elements.
2074 let remaining_exprs = self.parse_seq_to_end(
2075 &token::CloseDelim(token::Bracket),
2076 SeqSep::trailing_allowed(token::Comma),
2077 |p| Ok(p.parse_expr()?)
2079 let mut exprs = vec![first_expr];
2080 exprs.extend(remaining_exprs);
2081 ex = ExprKind::Array(exprs);
2083 // Vector with one element.
2084 self.expect(&token::CloseDelim(token::Bracket))?;
2085 ex = ExprKind::Array(vec![first_expr]);
2088 hi = self.prev_span;
2092 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2094 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2096 if self.span.rust_2018() && self.check_keyword(kw::Async) {
2097 return if self.is_async_block() { // check for `async {` and `async move {`
2098 self.parse_async_block(attrs)
2100 self.parse_lambda_expr(attrs)
2103 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
2104 return self.parse_lambda_expr(attrs);
2106 if self.eat_keyword(kw::If) {
2107 return self.parse_if_expr(attrs);
2109 if self.eat_keyword(kw::For) {
2110 let lo = self.prev_span;
2111 return self.parse_for_expr(None, lo, attrs);
2113 if self.eat_keyword(kw::While) {
2114 let lo = self.prev_span;
2115 return self.parse_while_expr(None, lo, attrs);
2117 if let Some(label) = self.eat_label() {
2118 let lo = label.ident.span;
2119 self.expect(&token::Colon)?;
2120 if self.eat_keyword(kw::While) {
2121 return self.parse_while_expr(Some(label), lo, attrs)
2123 if self.eat_keyword(kw::For) {
2124 return self.parse_for_expr(Some(label), lo, attrs)
2126 if self.eat_keyword(kw::Loop) {
2127 return self.parse_loop_expr(Some(label), lo, attrs)
2129 if self.token == token::OpenDelim(token::Brace) {
2130 return self.parse_block_expr(Some(label),
2132 BlockCheckMode::Default,
2135 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2136 let mut err = self.fatal(msg);
2137 err.span_label(self.span, msg);
2140 if self.eat_keyword(kw::Loop) {
2141 let lo = self.prev_span;
2142 return self.parse_loop_expr(None, lo, attrs);
2144 if self.eat_keyword(kw::Continue) {
2145 let label = self.eat_label();
2146 let ex = ExprKind::Continue(label);
2147 let hi = self.prev_span;
2148 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2150 if self.eat_keyword(kw::Match) {
2151 let match_sp = self.prev_span;
2152 return self.parse_match_expr(attrs).map_err(|mut err| {
2153 err.span_label(match_sp, "while parsing this match expression");
2157 if self.eat_keyword(kw::Unsafe) {
2158 return self.parse_block_expr(
2161 BlockCheckMode::Unsafe(ast::UserProvided),
2164 if self.is_do_catch_block() {
2165 let mut db = self.fatal("found removed `do catch` syntax");
2166 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2169 if self.is_try_block() {
2171 assert!(self.eat_keyword(kw::Try));
2172 return self.parse_try_block(lo, attrs);
2174 if self.eat_keyword(kw::Return) {
2175 if self.token.can_begin_expr() {
2176 let e = self.parse_expr()?;
2178 ex = ExprKind::Ret(Some(e));
2180 ex = ExprKind::Ret(None);
2182 } else if self.eat_keyword(kw::Break) {
2183 let label = self.eat_label();
2184 let e = if self.token.can_begin_expr()
2185 && !(self.token == token::OpenDelim(token::Brace)
2186 && self.restrictions.contains(
2187 Restrictions::NO_STRUCT_LITERAL)) {
2188 Some(self.parse_expr()?)
2192 ex = ExprKind::Break(label, e);
2193 hi = self.prev_span;
2194 } else if self.eat_keyword(kw::Yield) {
2195 if self.token.can_begin_expr() {
2196 let e = self.parse_expr()?;
2198 ex = ExprKind::Yield(Some(e));
2200 ex = ExprKind::Yield(None);
2202 } else if self.token.is_keyword(kw::Let) {
2203 // Catch this syntax error here, instead of in `parse_ident`, so
2204 // that we can explicitly mention that let is not to be used as an expression
2205 let mut db = self.fatal("expected expression, found statement (`let`)");
2206 db.span_label(self.span, "expected expression");
2207 db.note("variable declaration using `let` is a statement");
2209 } else if self.span.rust_2018() && self.eat_keyword(kw::Await) {
2210 let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
2213 } else if self.token.is_path_start() {
2214 let path = self.parse_path(PathStyle::Expr)?;
2216 // `!`, as an operator, is prefix, so we know this isn't that
2217 if self.eat(&token::Not) {
2218 // MACRO INVOCATION expression
2219 let (delim, tts) = self.expect_delimited_token_tree()?;
2220 hi = self.prev_span;
2221 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2222 } else if self.check(&token::OpenDelim(token::Brace)) {
2223 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
2227 ex = ExprKind::Path(None, path);
2231 ex = ExprKind::Path(None, path);
2234 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2235 // Don't complain about bare semicolons after unclosed braces
2236 // recovery in order to keep the error count down. Fixing the
2237 // delimiters will possibly also fix the bare semicolon found in
2238 // expression context. For example, silence the following error:
2240 // error: expected expression, found `;`
2244 // | ^ expected expression
2247 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2249 match self.parse_literal_maybe_minus() {
2252 ex = expr.node.clone();
2255 self.cancel(&mut err);
2256 return Err(self.expected_expression_found());
2263 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2264 self.maybe_recover_from_bad_qpath(expr, true)
2267 /// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
2268 /// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
2269 /// `await { <expr> }`.
2270 fn parse_await_macro_or_alt(
2274 ) -> PResult<'a, (Span, ExprKind)> {
2275 if self.token == token::Not {
2276 // Handle correct `await!(<expr>)`.
2277 // FIXME: make this an error when `await!` is no longer supported
2278 // https://github.com/rust-lang/rust/issues/60610
2279 self.expect(&token::Not)?;
2280 self.expect(&token::OpenDelim(token::Paren))?;
2281 let expr = self.parse_expr().map_err(|mut err| {
2282 err.span_label(await_sp, "while parsing this await macro call");
2285 self.expect(&token::CloseDelim(token::Paren))?;
2286 Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
2287 } else { // Handle `await <expr>`.
2288 self.parse_incorrect_await_syntax(lo, await_sp)
2292 fn maybe_parse_struct_expr(
2296 attrs: &ThinVec<Attribute>,
2297 ) -> Option<PResult<'a, P<Expr>>> {
2298 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2299 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
2300 // `{ ident, ` cannot start a block
2301 self.look_ahead(2, |t| t == &token::Comma) ||
2302 self.look_ahead(2, |t| t == &token::Colon) && (
2303 // `{ ident: token, ` cannot start a block
2304 self.look_ahead(4, |t| t == &token::Comma) ||
2305 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
2306 self.look_ahead(3, |t| !t.can_begin_type())
2310 if struct_allowed || certainly_not_a_block() {
2311 // This is a struct literal, but we don't can't accept them here
2312 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
2313 if let (Ok(expr), false) = (&expr, struct_allowed) {
2314 let mut err = self.diagnostic().struct_span_err(
2316 "struct literals are not allowed here",
2318 err.multipart_suggestion(
2319 "surround the struct literal with parentheses",
2321 (lo.shrink_to_lo(), "(".to_string()),
2322 (expr.span.shrink_to_hi(), ")".to_string()),
2324 Applicability::MachineApplicable,
2333 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2334 -> PResult<'a, P<Expr>> {
2335 let struct_sp = lo.to(self.prev_span);
2337 let mut fields = Vec::new();
2338 let mut base = None;
2340 attrs.extend(self.parse_inner_attributes()?);
2342 while self.token != token::CloseDelim(token::Brace) {
2343 if self.eat(&token::DotDot) {
2344 let exp_span = self.prev_span;
2345 match self.parse_expr() {
2351 self.recover_stmt();
2354 if self.token == token::Comma {
2355 let mut err = self.sess.span_diagnostic.mut_span_err(
2356 exp_span.to(self.prev_span),
2357 "cannot use a comma after the base struct",
2359 err.span_suggestion_short(
2361 "remove this comma",
2363 Applicability::MachineApplicable
2365 err.note("the base struct must always be the last field");
2367 self.recover_stmt();
2372 let mut recovery_field = None;
2373 if let token::Ident(ident, _) = self.token {
2374 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2375 // Use in case of error after field-looking code: `S { foo: () with a }`
2376 let mut ident = ident.clone();
2377 ident.span = self.span;
2378 recovery_field = Some(ast::Field {
2381 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2382 is_shorthand: false,
2383 attrs: ThinVec::new(),
2387 let mut parsed_field = None;
2388 match self.parse_field() {
2389 Ok(f) => parsed_field = Some(f),
2391 e.span_label(struct_sp, "while parsing this struct");
2394 // If the next token is a comma, then try to parse
2395 // what comes next as additional fields, rather than
2396 // bailing out until next `}`.
2397 if self.token != token::Comma {
2398 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2399 if self.token != token::Comma {
2406 match self.expect_one_of(&[token::Comma],
2407 &[token::CloseDelim(token::Brace)]) {
2408 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2409 // only include the field if there's no parse error for the field name
2413 if let Some(f) = recovery_field {
2416 e.span_label(struct_sp, "while parsing this struct");
2418 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2419 self.eat(&token::Comma);
2424 let span = lo.to(self.span);
2425 self.expect(&token::CloseDelim(token::Brace))?;
2426 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2429 fn parse_or_use_outer_attributes(&mut self,
2430 already_parsed_attrs: Option<ThinVec<Attribute>>)
2431 -> PResult<'a, ThinVec<Attribute>> {
2432 if let Some(attrs) = already_parsed_attrs {
2435 self.parse_outer_attributes().map(|a| a.into())
2439 /// Parses a block or unsafe block.
2440 crate fn parse_block_expr(
2442 opt_label: Option<Label>,
2444 blk_mode: BlockCheckMode,
2445 outer_attrs: ThinVec<Attribute>,
2446 ) -> PResult<'a, P<Expr>> {
2447 self.expect(&token::OpenDelim(token::Brace))?;
2449 let mut attrs = outer_attrs;
2450 attrs.extend(self.parse_inner_attributes()?);
2452 let blk = self.parse_block_tail(lo, blk_mode)?;
2453 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2456 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2457 fn parse_dot_or_call_expr(&mut self,
2458 already_parsed_attrs: Option<ThinVec<Attribute>>)
2459 -> PResult<'a, P<Expr>> {
2460 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2462 let b = self.parse_bottom_expr();
2463 let (span, b) = self.interpolated_or_expr_span(b)?;
2464 self.parse_dot_or_call_expr_with(b, span, attrs)
2467 fn parse_dot_or_call_expr_with(&mut self,
2470 mut attrs: ThinVec<Attribute>)
2471 -> PResult<'a, P<Expr>> {
2472 // Stitch the list of outer attributes onto the return value.
2473 // A little bit ugly, but the best way given the current code
2475 self.parse_dot_or_call_expr_with_(e0, lo)
2477 expr.map(|mut expr| {
2478 attrs.extend::<Vec<_>>(expr.attrs.into());
2481 ExprKind::If(..) | ExprKind::IfLet(..) => {
2482 if !expr.attrs.is_empty() {
2483 // Just point to the first attribute in there...
2484 let span = expr.attrs[0].span;
2487 "attributes are not yet allowed on `if` \
2498 // Assuming we have just parsed `.`, continue parsing into an expression.
2499 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2500 if self.span.rust_2018() && self.eat_keyword(kw::Await) {
2501 let span = lo.to(self.prev_span);
2502 let await_expr = self.mk_expr(
2504 ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
2507 self.recover_from_await_method_call();
2508 return Ok(await_expr);
2510 let segment = self.parse_path_segment(PathStyle::Expr)?;
2511 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
2513 Ok(match self.token {
2514 token::OpenDelim(token::Paren) => {
2515 // Method call `expr.f()`
2516 let mut args = self.parse_unspanned_seq(
2517 &token::OpenDelim(token::Paren),
2518 &token::CloseDelim(token::Paren),
2519 SeqSep::trailing_allowed(token::Comma),
2520 |p| Ok(p.parse_expr()?)
2522 args.insert(0, self_arg);
2524 let span = lo.to(self.prev_span);
2525 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
2528 // Field access `expr.f`
2529 if let Some(args) = segment.args {
2530 self.span_err(args.span(),
2531 "field expressions may not have generic arguments");
2534 let span = lo.to(self.prev_span);
2535 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
2540 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2545 while self.eat(&token::Question) {
2546 let hi = self.prev_span;
2547 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
2551 if self.eat(&token::Dot) {
2553 token::Ident(..) => {
2554 e = self.parse_dot_suffix(e, lo)?;
2556 token::Literal(token::Lit { kind: token::Integer, symbol, suffix }) => {
2557 let span = self.span;
2559 let field = ExprKind::Field(e, Ident::new(symbol, span));
2560 e = self.mk_expr(lo.to(span), field, ThinVec::new());
2562 self.expect_no_suffix(span, "a tuple index", suffix);
2564 token::Literal(token::Lit { kind: token::Float, symbol, .. }) => {
2566 let fstr = symbol.as_str();
2567 let msg = format!("unexpected token: `{}`", symbol);
2568 let mut err = self.diagnostic().struct_span_err(self.prev_span, &msg);
2569 err.span_label(self.prev_span, "unexpected token");
2570 if fstr.chars().all(|x| "0123456789.".contains(x)) {
2571 let float = match fstr.parse::<f64>().ok() {
2575 let sugg = pprust::to_string(|s| {
2576 use crate::print::pprust::PrintState;
2580 s.print_usize(float.trunc() as usize)?;
2583 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
2585 err.span_suggestion(
2586 lo.to(self.prev_span),
2587 "try parenthesizing the first index",
2589 Applicability::MachineApplicable
2596 // FIXME Could factor this out into non_fatal_unexpected or something.
2597 let actual = self.this_token_to_string();
2598 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
2603 if self.expr_is_complete(&e) { break; }
2606 token::OpenDelim(token::Paren) => {
2607 let seq = self.parse_unspanned_seq(
2608 &token::OpenDelim(token::Paren),
2609 &token::CloseDelim(token::Paren),
2610 SeqSep::trailing_allowed(token::Comma),
2611 |p| Ok(p.parse_expr()?)
2613 let nd = self.mk_call(e, es);
2614 let hi = self.prev_span;
2615 self.mk_expr(lo.to(hi), nd, ThinVec::new())
2617 e = self.recover_seq_parse_error(token::Paren, lo, seq);
2621 // Could be either an index expression or a slicing expression.
2622 token::OpenDelim(token::Bracket) => {
2624 let ix = self.parse_expr()?;
2626 self.expect(&token::CloseDelim(token::Bracket))?;
2627 let index = self.mk_index(e, ix);
2628 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
2636 crate fn process_potential_macro_variable(&mut self) {
2637 let (token, span) = match self.token {
2638 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
2639 self.look_ahead(1, |t| t.is_ident()) => {
2641 let name = match self.token {
2642 token::Ident(ident, _) => ident,
2645 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
2646 err.span_label(self.span, "unknown macro variable");
2651 token::Interpolated(ref nt) => {
2652 self.meta_var_span = Some(self.span);
2653 // Interpolated identifier and lifetime tokens are replaced with usual identifier
2654 // and lifetime tokens, so the former are never encountered during normal parsing.
2656 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
2657 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
2667 /// Parses a single token tree from the input.
2668 crate fn parse_token_tree(&mut self) -> TokenTree {
2670 token::OpenDelim(..) => {
2671 let frame = mem::replace(&mut self.token_cursor.frame,
2672 self.token_cursor.stack.pop().unwrap());
2673 self.span = frame.span.entire();
2675 TokenTree::Delimited(
2678 frame.tree_cursor.stream.into(),
2681 token::CloseDelim(_) | token::Eof => unreachable!(),
2683 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
2685 TokenTree::Token(span, token)
2690 // parse a stream of tokens into a list of TokenTree's,
2692 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
2693 let mut tts = Vec::new();
2694 while self.token != token::Eof {
2695 tts.push(self.parse_token_tree());
2700 pub fn parse_tokens(&mut self) -> TokenStream {
2701 let mut result = Vec::new();
2704 token::Eof | token::CloseDelim(..) => break,
2705 _ => result.push(self.parse_token_tree().into()),
2708 TokenStream::new(result)
2711 /// Parse a prefix-unary-operator expr
2712 fn parse_prefix_expr(&mut self,
2713 already_parsed_attrs: Option<ThinVec<Attribute>>)
2714 -> PResult<'a, P<Expr>> {
2715 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2717 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
2718 let (hi, ex) = match self.token {
2721 let e = self.parse_prefix_expr(None);
2722 let (span, e) = self.interpolated_or_expr_span(e)?;
2723 (lo.to(span), self.mk_unary(UnOp::Not, e))
2725 // Suggest `!` for bitwise negation when encountering a `~`
2728 let e = self.parse_prefix_expr(None);
2729 let (span, e) = self.interpolated_or_expr_span(e)?;
2730 let span_of_tilde = lo;
2731 let mut err = self.diagnostic()
2732 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
2733 err.span_suggestion_short(
2735 "use `!` to perform bitwise negation",
2737 Applicability::MachineApplicable
2740 (lo.to(span), self.mk_unary(UnOp::Not, e))
2742 token::BinOp(token::Minus) => {
2744 let e = self.parse_prefix_expr(None);
2745 let (span, e) = self.interpolated_or_expr_span(e)?;
2746 (lo.to(span), self.mk_unary(UnOp::Neg, e))
2748 token::BinOp(token::Star) => {
2750 let e = self.parse_prefix_expr(None);
2751 let (span, e) = self.interpolated_or_expr_span(e)?;
2752 (lo.to(span), self.mk_unary(UnOp::Deref, e))
2754 token::BinOp(token::And) | token::AndAnd => {
2756 let m = self.parse_mutability();
2757 let e = self.parse_prefix_expr(None);
2758 let (span, e) = self.interpolated_or_expr_span(e)?;
2759 (lo.to(span), ExprKind::AddrOf(m, e))
2761 token::Ident(..) if self.token.is_keyword(kw::Box) => {
2763 let e = self.parse_prefix_expr(None);
2764 let (span, e) = self.interpolated_or_expr_span(e)?;
2765 (lo.to(span), ExprKind::Box(e))
2767 token::Ident(..) if self.token.is_ident_named(sym::not) => {
2768 // `not` is just an ordinary identifier in Rust-the-language,
2769 // but as `rustc`-the-compiler, we can issue clever diagnostics
2770 // for confused users who really want to say `!`
2771 let token_cannot_continue_expr = |t: &token::Token| match *t {
2772 // These tokens can start an expression after `!`, but
2773 // can't continue an expression after an ident
2774 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
2775 token::Literal(..) | token::Pound => true,
2776 token::Interpolated(ref nt) => match **nt {
2777 token::NtIdent(..) | token::NtExpr(..) |
2778 token::NtBlock(..) | token::NtPath(..) => true,
2783 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
2784 if cannot_continue_expr {
2786 // Emit the error ...
2787 let mut err = self.diagnostic()
2788 .struct_span_err(self.span,
2789 &format!("unexpected {} after identifier",
2790 self.this_token_descr()));
2791 // span the `not` plus trailing whitespace to avoid
2792 // trailing whitespace after the `!` in our suggestion
2793 let to_replace = self.sess.source_map()
2794 .span_until_non_whitespace(lo.to(self.span));
2795 err.span_suggestion_short(
2797 "use `!` to perform logical negation",
2799 Applicability::MachineApplicable
2802 // —and recover! (just as if we were in the block
2803 // for the `token::Not` arm)
2804 let e = self.parse_prefix_expr(None);
2805 let (span, e) = self.interpolated_or_expr_span(e)?;
2806 (lo.to(span), self.mk_unary(UnOp::Not, e))
2808 return self.parse_dot_or_call_expr(Some(attrs));
2811 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
2813 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2816 /// Parses an associative expression.
2818 /// This parses an expression accounting for associativity and precedence of the operators in
2821 fn parse_assoc_expr(&mut self,
2822 already_parsed_attrs: Option<ThinVec<Attribute>>)
2823 -> PResult<'a, P<Expr>> {
2824 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
2827 /// Parses an associative expression with operators of at least `min_prec` precedence.
2828 fn parse_assoc_expr_with(&mut self,
2831 -> PResult<'a, P<Expr>> {
2832 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
2835 let attrs = match lhs {
2836 LhsExpr::AttributesParsed(attrs) => Some(attrs),
2839 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
2840 return self.parse_prefix_range_expr(attrs);
2842 self.parse_prefix_expr(attrs)?
2846 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
2848 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
2851 (false, _) => {} // continue parsing the expression
2852 // An exhaustive check is done in the following block, but these are checked first
2853 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
2854 // want to keep their span info to improve diagnostics in these cases in a later stage.
2855 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
2856 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
2857 (true, Some(AssocOp::Add)) => { // `{ 42 } + 42
2858 // These cases are ambiguous and can't be identified in the parser alone
2859 let sp = self.sess.source_map().start_point(self.span);
2860 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
2863 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
2866 (true, Some(_)) => {
2867 // We've found an expression that would be parsed as a statement, but the next
2868 // token implies this should be parsed as an expression.
2869 // For example: `if let Some(x) = x { x } else { 0 } / 2`
2870 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
2871 "expected expression, found `{}`",
2872 pprust::token_to_string(&self.token),
2874 err.span_label(self.span, "expected expression");
2875 self.sess.expr_parentheses_needed(
2878 Some(pprust::expr_to_string(&lhs),
2883 self.expected_tokens.push(TokenType::Operator);
2884 while let Some(op) = AssocOp::from_token(&self.token) {
2886 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
2887 // it refers to. Interpolated identifiers are unwrapped early and never show up here
2888 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
2889 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
2890 let lhs_span = match (self.prev_token_kind, &lhs.node) {
2891 (PrevTokenKind::Interpolated, _) => self.prev_span,
2892 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
2893 if path.segments.len() == 1 => self.prev_span,
2897 let cur_op_span = self.span;
2898 let restrictions = if op.is_assign_like() {
2899 self.restrictions & Restrictions::NO_STRUCT_LITERAL
2903 let prec = op.precedence();
2904 if prec < min_prec {
2907 // Check for deprecated `...` syntax
2908 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
2909 self.err_dotdotdot_syntax(self.span);
2913 if op.is_comparison() {
2914 self.check_no_chained_comparison(&lhs, &op);
2917 if op == AssocOp::As {
2918 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
2920 } else if op == AssocOp::Colon {
2921 let maybe_path = self.could_ascription_be_path(&lhs.node);
2922 let next_sp = self.span;
2924 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
2927 self.bad_type_ascription(
2938 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
2939 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
2940 // generalise it to the Fixity::None code.
2942 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
2943 // two variants are handled with `parse_prefix_range_expr` call above.
2944 let rhs = if self.is_at_start_of_range_notation_rhs() {
2945 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
2949 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
2954 let limits = if op == AssocOp::DotDot {
2955 RangeLimits::HalfOpen
2960 let r = self.mk_range(Some(lhs), rhs, limits)?;
2961 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
2965 let fixity = op.fixity();
2966 let prec_adjustment = match fixity {
2969 // We currently have no non-associative operators that are not handled above by
2970 // the special cases. The code is here only for future convenience.
2973 let rhs = self.with_res(
2974 restrictions - Restrictions::STMT_EXPR,
2975 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
2978 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
2979 // including the attributes.
2983 .filter(|a| a.style == AttrStyle::Outer)
2985 .map_or(lhs_span, |a| a.span);
2986 let span = lhs_span.to(rhs.span);
2988 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
2989 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
2990 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
2991 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
2992 AssocOp::Greater | AssocOp::GreaterEqual => {
2993 let ast_op = op.to_ast_binop().unwrap();
2994 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
2995 self.mk_expr(span, binary, ThinVec::new())
2997 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
2998 AssocOp::AssignOp(k) => {
3000 token::Plus => BinOpKind::Add,
3001 token::Minus => BinOpKind::Sub,
3002 token::Star => BinOpKind::Mul,
3003 token::Slash => BinOpKind::Div,
3004 token::Percent => BinOpKind::Rem,
3005 token::Caret => BinOpKind::BitXor,
3006 token::And => BinOpKind::BitAnd,
3007 token::Or => BinOpKind::BitOr,
3008 token::Shl => BinOpKind::Shl,
3009 token::Shr => BinOpKind::Shr,
3011 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3012 self.mk_expr(span, aopexpr, ThinVec::new())
3014 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3015 self.bug("AssocOp should have been handled by special case")
3019 if let Fixity::None = fixity { break }
3024 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3025 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3026 -> PResult<'a, P<Expr>> {
3027 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3028 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3031 // Save the state of the parser before parsing type normally, in case there is a
3032 // LessThan comparison after this cast.
3033 let parser_snapshot_before_type = self.clone();
3034 match self.parse_ty_no_plus() {
3036 Ok(mk_expr(self, rhs))
3038 Err(mut type_err) => {
3039 // Rewind to before attempting to parse the type with generics, to recover
3040 // from situations like `x as usize < y` in which we first tried to parse
3041 // `usize < y` as a type with generic arguments.
3042 let parser_snapshot_after_type = self.clone();
3043 mem::replace(self, parser_snapshot_before_type);
3045 match self.parse_path(PathStyle::Expr) {
3047 let (op_noun, op_verb) = match self.token {
3048 token::Lt => ("comparison", "comparing"),
3049 token::BinOp(token::Shl) => ("shift", "shifting"),
3051 // We can end up here even without `<` being the next token, for
3052 // example because `parse_ty_no_plus` returns `Err` on keywords,
3053 // but `parse_path` returns `Ok` on them due to error recovery.
3054 // Return original error and parser state.
3055 mem::replace(self, parser_snapshot_after_type);
3056 return Err(type_err);
3060 // Successfully parsed the type path leaving a `<` yet to parse.
3063 // Report non-fatal diagnostics, keep `x as usize` as an expression
3064 // in AST and continue parsing.
3065 let msg = format!("`<` is interpreted as a start of generic \
3066 arguments for `{}`, not a {}", path, op_noun);
3067 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3068 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3069 "interpreted as generic arguments");
3070 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3072 let expr = mk_expr(self, P(Ty {
3074 node: TyKind::Path(None, path),
3075 id: ast::DUMMY_NODE_ID
3078 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3079 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3080 err.span_suggestion(
3082 &format!("try {} the cast value", op_verb),
3083 format!("({})", expr_str),
3084 Applicability::MachineApplicable
3090 Err(mut path_err) => {
3091 // Couldn't parse as a path, return original error and parser state.
3093 mem::replace(self, parser_snapshot_after_type);
3101 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3102 fn parse_prefix_range_expr(&mut self,
3103 already_parsed_attrs: Option<ThinVec<Attribute>>)
3104 -> PResult<'a, P<Expr>> {
3105 // Check for deprecated `...` syntax
3106 if self.token == token::DotDotDot {
3107 self.err_dotdotdot_syntax(self.span);
3110 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3111 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3113 let tok = self.token.clone();
3114 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3116 let mut hi = self.span;
3118 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3119 // RHS must be parsed with more associativity than the dots.
3120 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3121 Some(self.parse_assoc_expr_with(next_prec,
3122 LhsExpr::NotYetParsed)
3130 let limits = if tok == token::DotDot {
3131 RangeLimits::HalfOpen
3136 let r = self.mk_range(None, opt_end, limits)?;
3137 Ok(self.mk_expr(lo.to(hi), r, attrs))
3140 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3141 if self.token.can_begin_expr() {
3142 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3143 if self.token == token::OpenDelim(token::Brace) {
3144 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3152 /// Parses an `if` or `if let` expression (`if` token already eaten).
3153 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3154 if self.check_keyword(kw::Let) {
3155 return self.parse_if_let_expr(attrs);
3157 let lo = self.prev_span;
3158 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3160 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3161 // verify that the last statement is either an implicit return (no `;`) or an explicit
3162 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3163 // the dead code lint.
3164 if self.eat_keyword(kw::Else) || !cond.returns() {
3165 let sp = self.sess.source_map().next_point(lo);
3166 let mut err = self.diagnostic()
3167 .struct_span_err(sp, "missing condition for `if` statemement");
3168 err.span_label(sp, "expected if condition here");
3171 let not_block = self.token != token::OpenDelim(token::Brace);
3172 let thn = self.parse_block().map_err(|mut err| {
3174 err.span_label(lo, "this `if` statement has a condition, but no block");
3178 let mut els: Option<P<Expr>> = None;
3179 let mut hi = thn.span;
3180 if self.eat_keyword(kw::Else) {
3181 let elexpr = self.parse_else_expr()?;
3185 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3188 /// Parses an `if let` expression (`if` token already eaten).
3189 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3190 -> PResult<'a, P<Expr>> {
3191 let lo = self.prev_span;
3192 self.expect_keyword(kw::Let)?;
3193 let pats = self.parse_pats()?;
3194 self.expect(&token::Eq)?;
3195 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3196 let thn = self.parse_block()?;
3197 let (hi, els) = if self.eat_keyword(kw::Else) {
3198 let expr = self.parse_else_expr()?;
3199 (expr.span, Some(expr))
3203 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3206 /// Parses `move |args| expr`.
3207 fn parse_lambda_expr(&mut self,
3208 attrs: ThinVec<Attribute>)
3209 -> PResult<'a, P<Expr>>
3212 let movability = if self.eat_keyword(kw::Static) {
3217 let asyncness = if self.span.rust_2018() {
3218 self.parse_asyncness()
3222 let capture_clause = if self.eat_keyword(kw::Move) {
3227 let decl = self.parse_fn_block_decl()?;
3228 let decl_hi = self.prev_span;
3229 let body = match decl.output {
3230 FunctionRetTy::Default(_) => {
3231 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3232 self.parse_expr_res(restrictions, None)?
3235 // If an explicit return type is given, require a
3236 // block to appear (RFC 968).
3237 let body_lo = self.span;
3238 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3244 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3248 // `else` token already eaten
3249 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3250 if self.eat_keyword(kw::If) {
3251 return self.parse_if_expr(ThinVec::new());
3253 let blk = self.parse_block()?;
3254 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3258 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3259 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3261 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3262 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3264 let pat = self.parse_top_level_pat()?;
3265 if !self.eat_keyword(kw::In) {
3266 let in_span = self.prev_span.between(self.span);
3267 let mut err = self.sess.span_diagnostic
3268 .struct_span_err(in_span, "missing `in` in `for` loop");
3269 err.span_suggestion_short(
3270 in_span, "try adding `in` here", " in ".into(),
3271 // has been misleading, at least in the past (closed Issue #48492)
3272 Applicability::MaybeIncorrect
3276 let in_span = self.prev_span;
3277 self.check_for_for_in_in_typo(in_span);
3278 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3279 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3280 attrs.extend(iattrs);
3282 let hi = self.prev_span;
3283 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3286 /// Parses a `while` or `while let` expression (`while` token already eaten).
3287 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3289 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3290 if self.token.is_keyword(kw::Let) {
3291 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3293 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3294 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3295 attrs.extend(iattrs);
3296 let span = span_lo.to(body.span);
3297 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3300 /// Parses a `while let` expression (`while` token already eaten).
3301 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3303 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3304 self.expect_keyword(kw::Let)?;
3305 let pats = self.parse_pats()?;
3306 self.expect(&token::Eq)?;
3307 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3308 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3309 attrs.extend(iattrs);
3310 let span = span_lo.to(body.span);
3311 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3314 // parse `loop {...}`, `loop` token already eaten
3315 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3317 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3318 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3319 attrs.extend(iattrs);
3320 let span = span_lo.to(body.span);
3321 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3324 /// Parses an `async move {...}` expression.
3325 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3326 -> PResult<'a, P<Expr>>
3328 let span_lo = self.span;
3329 self.expect_keyword(kw::Async)?;
3330 let capture_clause = if self.eat_keyword(kw::Move) {
3335 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3336 attrs.extend(iattrs);
3338 span_lo.to(body.span),
3339 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3342 /// Parses a `try {...}` expression (`try` token already eaten).
3343 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3344 -> PResult<'a, P<Expr>>
3346 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3347 attrs.extend(iattrs);
3348 if self.eat_keyword(kw::Catch) {
3349 let mut error = self.struct_span_err(self.prev_span,
3350 "keyword `catch` cannot follow a `try` block");
3351 error.help("try using `match` on the result of the `try` block instead");
3355 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
3359 // `match` token already eaten
3360 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3361 let match_span = self.prev_span;
3362 let lo = self.prev_span;
3363 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3365 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3366 if self.token == token::Token::Semi {
3367 e.span_suggestion_short(
3369 "try removing this `match`",
3371 Applicability::MaybeIncorrect // speculative
3376 attrs.extend(self.parse_inner_attributes()?);
3378 let mut arms: Vec<Arm> = Vec::new();
3379 while self.token != token::CloseDelim(token::Brace) {
3380 match self.parse_arm() {
3381 Ok(arm) => arms.push(arm),
3383 // Recover by skipping to the end of the block.
3385 self.recover_stmt();
3386 let span = lo.to(self.span);
3387 if self.token == token::CloseDelim(token::Brace) {
3390 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3396 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3399 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3400 let attrs = self.parse_outer_attributes()?;
3402 let pats = self.parse_pats()?;
3403 let guard = if self.eat_keyword(kw::If) {
3404 Some(Guard::If(self.parse_expr()?))
3408 let arrow_span = self.span;
3409 self.expect(&token::FatArrow)?;
3410 let arm_start_span = self.span;
3412 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3413 .map_err(|mut err| {
3414 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3418 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3419 && self.token != token::CloseDelim(token::Brace);
3424 let cm = self.sess.source_map();
3425 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3426 .map_err(|mut err| {
3427 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3428 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3429 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3430 && expr_lines.lines.len() == 2
3431 && self.token == token::FatArrow => {
3432 // We check whether there's any trailing code in the parse span,
3433 // if there isn't, we very likely have the following:
3436 // | -- - missing comma
3442 // | parsed until here as `"y" & X`
3443 err.span_suggestion_short(
3444 cm.next_point(arm_start_span),
3445 "missing a comma here to end this `match` arm",
3447 Applicability::MachineApplicable
3451 err.span_label(arrow_span,
3452 "while parsing the `match` arm starting here");
3458 self.eat(&token::Comma);
3470 /// Parses an expression.
3472 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
3473 self.parse_expr_res(Restrictions::empty(), None)
3476 /// Evaluates the closure with restrictions in place.
3478 /// Afters the closure is evaluated, restrictions are reset.
3479 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
3480 where F: FnOnce(&mut Self) -> T
3482 let old = self.restrictions;
3483 self.restrictions = r;
3485 self.restrictions = old;
3490 /// Parses an expression, subject to the given restrictions.
3492 fn parse_expr_res(&mut self, r: Restrictions,
3493 already_parsed_attrs: Option<ThinVec<Attribute>>)
3494 -> PResult<'a, P<Expr>> {
3495 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
3498 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
3499 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
3500 if self.eat(&token::Eq) {
3501 Ok(Some(self.parse_expr()?))
3503 Ok(Some(self.parse_expr()?))
3509 /// Parses patterns, separated by '|' s.
3510 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
3511 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
3512 self.eat(&token::BinOp(token::Or));
3514 let mut pats = Vec::new();
3516 pats.push(self.parse_top_level_pat()?);
3518 if self.token == token::OrOr {
3519 let mut err = self.struct_span_err(self.span,
3520 "unexpected token `||` after pattern");
3521 err.span_suggestion(
3523 "use a single `|` to specify multiple patterns",
3525 Applicability::MachineApplicable
3529 } else if self.eat(&token::BinOp(token::Or)) {
3530 // This is a No-op. Continue the loop to parse the next
3538 // Parses a parenthesized list of patterns like
3539 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
3540 // - a vector of the patterns that were parsed
3541 // - an option indicating the index of the `..` element
3542 // - a boolean indicating whether a trailing comma was present.
3543 // Trailing commas are significant because (p) and (p,) are different patterns.
3544 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3545 self.expect(&token::OpenDelim(token::Paren))?;
3546 let result = match self.parse_pat_list() {
3547 Ok(result) => result,
3548 Err(mut err) => { // recover from parse error in tuple pattern list
3550 self.consume_block(token::Paren);
3551 return Ok((vec![], Some(0), false));
3554 self.expect(&token::CloseDelim(token::Paren))?;
3558 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
3559 let mut fields = Vec::new();
3560 let mut ddpos = None;
3561 let mut prev_dd_sp = None;
3562 let mut trailing_comma = false;
3564 if self.eat(&token::DotDot) {
3565 if ddpos.is_none() {
3566 ddpos = Some(fields.len());
3567 prev_dd_sp = Some(self.prev_span);
3569 // Emit a friendly error, ignore `..` and continue parsing
3570 let mut err = self.struct_span_err(
3572 "`..` can only be used once per tuple or tuple struct pattern",
3574 err.span_label(self.prev_span, "can only be used once per pattern");
3575 if let Some(sp) = prev_dd_sp {
3576 err.span_label(sp, "previously present here");
3580 } else if !self.check(&token::CloseDelim(token::Paren)) {
3581 fields.push(self.parse_pat(None)?);
3586 trailing_comma = self.eat(&token::Comma);
3587 if !trailing_comma {
3592 if ddpos == Some(fields.len()) && trailing_comma {
3593 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
3594 let msg = "trailing comma is not permitted after `..`";
3595 self.struct_span_err(self.prev_span, msg)
3596 .span_label(self.prev_span, msg)
3600 Ok((fields, ddpos, trailing_comma))
3603 fn parse_pat_vec_elements(
3605 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
3606 let mut before = Vec::new();
3607 let mut slice = None;
3608 let mut after = Vec::new();
3609 let mut first = true;
3610 let mut before_slice = true;
3612 while self.token != token::CloseDelim(token::Bracket) {
3616 self.expect(&token::Comma)?;
3618 if self.token == token::CloseDelim(token::Bracket)
3619 && (before_slice || !after.is_empty()) {
3625 if self.eat(&token::DotDot) {
3627 if self.check(&token::Comma) ||
3628 self.check(&token::CloseDelim(token::Bracket)) {
3629 slice = Some(P(Pat {
3630 id: ast::DUMMY_NODE_ID,
3631 node: PatKind::Wild,
3632 span: self.prev_span,
3634 before_slice = false;
3640 let subpat = self.parse_pat(None)?;
3641 if before_slice && self.eat(&token::DotDot) {
3642 slice = Some(subpat);
3643 before_slice = false;
3644 } else if before_slice {
3645 before.push(subpat);
3651 Ok((before, slice, after))
3657 attrs: Vec<Attribute>
3658 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
3659 // Check if a colon exists one ahead. This means we're parsing a fieldname.
3661 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
3662 // Parsing a pattern of the form "fieldname: pat"
3663 let fieldname = self.parse_field_name()?;
3665 let pat = self.parse_pat(None)?;
3667 (pat, fieldname, false)
3669 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
3670 let is_box = self.eat_keyword(kw::Box);
3671 let boxed_span = self.span;
3672 let is_ref = self.eat_keyword(kw::Ref);
3673 let is_mut = self.eat_keyword(kw::Mut);
3674 let fieldname = self.parse_ident()?;
3675 hi = self.prev_span;
3677 let bind_type = match (is_ref, is_mut) {
3678 (true, true) => BindingMode::ByRef(Mutability::Mutable),
3679 (true, false) => BindingMode::ByRef(Mutability::Immutable),
3680 (false, true) => BindingMode::ByValue(Mutability::Mutable),
3681 (false, false) => BindingMode::ByValue(Mutability::Immutable),
3683 let fieldpat = P(Pat {
3684 id: ast::DUMMY_NODE_ID,
3685 node: PatKind::Ident(bind_type, fieldname, None),
3686 span: boxed_span.to(hi),
3689 let subpat = if is_box {
3691 id: ast::DUMMY_NODE_ID,
3692 node: PatKind::Box(fieldpat),
3698 (subpat, fieldname, true)
3701 Ok(source_map::Spanned {
3703 node: ast::FieldPat {
3707 attrs: attrs.into(),
3712 /// Parses the fields of a struct-like pattern.
3713 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
3714 let mut fields = Vec::new();
3715 let mut etc = false;
3716 let mut ate_comma = true;
3717 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
3718 let mut etc_span = None;
3720 while self.token != token::CloseDelim(token::Brace) {
3721 let attrs = self.parse_outer_attributes()?;
3724 // check that a comma comes after every field
3726 let err = self.struct_span_err(self.prev_span, "expected `,`");
3727 if let Some(mut delayed) = delayed_err {
3734 if self.check(&token::DotDot) || self.token == token::DotDotDot {
3736 let mut etc_sp = self.span;
3738 if self.token == token::DotDotDot { // Issue #46718
3739 // Accept `...` as if it were `..` to avoid further errors
3740 let mut err = self.struct_span_err(self.span,
3741 "expected field pattern, found `...`");
3742 err.span_suggestion(
3744 "to omit remaining fields, use one fewer `.`",
3746 Applicability::MachineApplicable
3750 self.bump(); // `..` || `...`
3752 if self.token == token::CloseDelim(token::Brace) {
3753 etc_span = Some(etc_sp);
3756 let token_str = self.this_token_descr();
3757 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
3759 err.span_label(self.span, "expected `}`");
3760 let mut comma_sp = None;
3761 if self.token == token::Comma { // Issue #49257
3762 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
3763 err.span_label(etc_sp,
3764 "`..` must be at the end and cannot have a trailing comma");
3765 comma_sp = Some(self.span);
3770 etc_span = Some(etc_sp.until(self.span));
3771 if self.token == token::CloseDelim(token::Brace) {
3772 // If the struct looks otherwise well formed, recover and continue.
3773 if let Some(sp) = comma_sp {
3774 err.span_suggestion_short(
3776 "remove this comma",
3778 Applicability::MachineApplicable,
3783 } else if self.token.is_ident() && ate_comma {
3784 // Accept fields coming after `..,`.
3785 // This way we avoid "pattern missing fields" errors afterwards.
3786 // We delay this error until the end in order to have a span for a
3788 if let Some(mut delayed_err) = delayed_err {
3792 delayed_err = Some(err);
3795 if let Some(mut err) = delayed_err {
3802 fields.push(match self.parse_pat_field(lo, attrs) {
3805 if let Some(mut delayed_err) = delayed_err {
3811 ate_comma = self.eat(&token::Comma);
3814 if let Some(mut err) = delayed_err {
3815 if let Some(etc_span) = etc_span {
3816 err.multipart_suggestion(
3817 "move the `..` to the end of the field list",
3819 (etc_span, String::new()),
3820 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
3822 Applicability::MachineApplicable,
3827 return Ok((fields, etc));
3830 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
3831 if self.token.is_path_start() {
3833 let (qself, path) = if self.eat_lt() {
3834 // Parse a qualified path
3835 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3838 // Parse an unqualified path
3839 (None, self.parse_path(PathStyle::Expr)?)
3841 let hi = self.prev_span;
3842 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
3844 self.parse_literal_maybe_minus()
3848 // helper function to decide whether to parse as ident binding or to try to do
3849 // something more complex like range patterns
3850 fn parse_as_ident(&mut self) -> bool {
3851 self.look_ahead(1, |t| match *t {
3852 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
3853 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
3854 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
3855 // range pattern branch
3856 token::DotDot => None,
3858 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
3859 token::Comma | token::CloseDelim(token::Bracket) => true,
3864 /// A wrapper around `parse_pat` with some special error handling for the
3865 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
3866 /// to subpatterns within such).
3867 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
3868 let pat = self.parse_pat(None)?;
3869 if self.token == token::Comma {
3870 // An unexpected comma after a top-level pattern is a clue that the
3871 // user (perhaps more accustomed to some other language) forgot the
3872 // parentheses in what should have been a tuple pattern; return a
3873 // suggestion-enhanced error here rather than choking on the comma
3875 let comma_span = self.span;
3877 if let Err(mut err) = self.parse_pat_list() {
3878 // We didn't expect this to work anyway; we just wanted
3879 // to advance to the end of the comma-sequence so we know
3880 // the span to suggest parenthesizing
3883 let seq_span = pat.span.to(self.prev_span);
3884 let mut err = self.struct_span_err(comma_span,
3885 "unexpected `,` in pattern");
3886 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
3887 err.span_suggestion(
3889 "try adding parentheses to match on a tuple..",
3890 format!("({})", seq_snippet),
3891 Applicability::MachineApplicable
3894 "..or a vertical bar to match on multiple alternatives",
3895 format!("{}", seq_snippet.replace(",", " |")),
3896 Applicability::MachineApplicable
3904 /// Parses a pattern.
3905 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
3906 self.parse_pat_with_range_pat(true, expected)
3909 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
3911 fn parse_pat_with_range_pat(
3913 allow_range_pat: bool,
3914 expected: Option<&'static str>,
3915 ) -> PResult<'a, P<Pat>> {
3916 maybe_recover_from_interpolated_ty_qpath!(self, true);
3917 maybe_whole!(self, NtPat, |x| x);
3922 token::BinOp(token::And) | token::AndAnd => {
3923 // Parse &pat / &mut pat
3925 let mutbl = self.parse_mutability();
3926 if let token::Lifetime(ident) = self.token {
3927 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
3929 err.span_label(self.span, "unexpected lifetime");
3932 let subpat = self.parse_pat_with_range_pat(false, expected)?;
3933 pat = PatKind::Ref(subpat, mutbl);
3935 token::OpenDelim(token::Paren) => {
3936 // Parse (pat,pat,pat,...) as tuple pattern
3937 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
3938 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
3939 PatKind::Paren(fields.into_iter().nth(0).unwrap())
3941 PatKind::Tuple(fields, ddpos)
3944 token::OpenDelim(token::Bracket) => {
3945 // Parse [pat,pat,...] as slice pattern
3947 let (before, slice, after) = self.parse_pat_vec_elements()?;
3948 self.expect(&token::CloseDelim(token::Bracket))?;
3949 pat = PatKind::Slice(before, slice, after);
3951 // At this point, token != &, &&, (, [
3952 _ => if self.eat_keyword(kw::Underscore) {
3954 pat = PatKind::Wild;
3955 } else if self.eat_keyword(kw::Mut) {
3956 // Parse mut ident @ pat / mut ref ident @ pat
3957 let mutref_span = self.prev_span.to(self.span);
3958 let binding_mode = if self.eat_keyword(kw::Ref) {
3960 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
3963 "try switching the order",
3965 Applicability::MachineApplicable
3967 BindingMode::ByRef(Mutability::Mutable)
3969 BindingMode::ByValue(Mutability::Mutable)
3971 pat = self.parse_pat_ident(binding_mode)?;
3972 } else if self.eat_keyword(kw::Ref) {
3973 // Parse ref ident @ pat / ref mut ident @ pat
3974 let mutbl = self.parse_mutability();
3975 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
3976 } else if self.eat_keyword(kw::Box) {
3978 let subpat = self.parse_pat_with_range_pat(false, None)?;
3979 pat = PatKind::Box(subpat);
3980 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
3981 self.parse_as_ident() {
3982 // Parse ident @ pat
3983 // This can give false positives and parse nullary enums,
3984 // they are dealt with later in resolve
3985 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
3986 pat = self.parse_pat_ident(binding_mode)?;
3987 } else if self.token.is_path_start() {
3988 // Parse pattern starting with a path
3989 let (qself, path) = if self.eat_lt() {
3990 // Parse a qualified path
3991 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
3994 // Parse an unqualified path
3995 (None, self.parse_path(PathStyle::Expr)?)
3998 token::Not if qself.is_none() => {
3999 // Parse macro invocation
4001 let (delim, tts) = self.expect_delimited_token_tree()?;
4002 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4003 pat = PatKind::Mac(mac);
4005 token::DotDotDot | token::DotDotEq | token::DotDot => {
4006 let end_kind = match self.token {
4007 token::DotDot => RangeEnd::Excluded,
4008 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4009 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4010 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4013 let op_span = self.span;
4015 let span = lo.to(self.prev_span);
4016 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4018 let end = self.parse_pat_range_end()?;
4019 let op = Spanned { span: op_span, node: end_kind };
4020 pat = PatKind::Range(begin, end, op);
4022 token::OpenDelim(token::Brace) => {
4023 if qself.is_some() {
4024 let msg = "unexpected `{` after qualified path";
4025 let mut err = self.fatal(msg);
4026 err.span_label(self.span, msg);
4029 // Parse struct pattern
4031 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4033 self.recover_stmt();
4037 pat = PatKind::Struct(path, fields, etc);
4039 token::OpenDelim(token::Paren) => {
4040 if qself.is_some() {
4041 let msg = "unexpected `(` after qualified path";
4042 let mut err = self.fatal(msg);
4043 err.span_label(self.span, msg);
4046 // Parse tuple struct or enum pattern
4047 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4048 pat = PatKind::TupleStruct(path, fields, ddpos)
4050 _ => pat = PatKind::Path(qself, path),
4053 // Try to parse everything else as literal with optional minus
4054 match self.parse_literal_maybe_minus() {
4056 let op_span = self.span;
4057 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4058 self.check(&token::DotDotDot) {
4059 let end_kind = if self.eat(&token::DotDotDot) {
4060 RangeEnd::Included(RangeSyntax::DotDotDot)
4061 } else if self.eat(&token::DotDotEq) {
4062 RangeEnd::Included(RangeSyntax::DotDotEq)
4063 } else if self.eat(&token::DotDot) {
4066 panic!("impossible case: we already matched \
4067 on a range-operator token")
4069 let end = self.parse_pat_range_end()?;
4070 let op = Spanned { span: op_span, node: end_kind };
4071 pat = PatKind::Range(begin, end, op);
4073 pat = PatKind::Lit(begin);
4077 self.cancel(&mut err);
4078 let expected = expected.unwrap_or("pattern");
4080 "expected {}, found {}",
4082 self.this_token_descr(),
4084 let mut err = self.fatal(&msg);
4085 err.span_label(self.span, format!("expected {}", expected));
4086 let sp = self.sess.source_map().start_point(self.span);
4087 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4088 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4096 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4097 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4099 if !allow_range_pat {
4102 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4104 PatKind::Range(..) => {
4105 let mut err = self.struct_span_err(
4107 "the range pattern here has ambiguous interpretation",
4109 err.span_suggestion(
4111 "add parentheses to clarify the precedence",
4112 format!("({})", pprust::pat_to_string(&pat)),
4113 // "ambiguous interpretation" implies that we have to be guessing
4114 Applicability::MaybeIncorrect
4125 /// Parses `ident` or `ident @ pat`.
4126 /// used by the copy foo and ref foo patterns to give a good
4127 /// error message when parsing mistakes like `ref foo(a, b)`.
4128 fn parse_pat_ident(&mut self,
4129 binding_mode: ast::BindingMode)
4130 -> PResult<'a, PatKind> {
4131 let ident = self.parse_ident()?;
4132 let sub = if self.eat(&token::At) {
4133 Some(self.parse_pat(Some("binding pattern"))?)
4138 // just to be friendly, if they write something like
4140 // we end up here with ( as the current token. This shortly
4141 // leads to a parse error. Note that if there is no explicit
4142 // binding mode then we do not end up here, because the lookahead
4143 // will direct us over to parse_enum_variant()
4144 if self.token == token::OpenDelim(token::Paren) {
4145 return Err(self.span_fatal(
4147 "expected identifier, found enum pattern"))
4150 Ok(PatKind::Ident(binding_mode, ident, sub))
4153 /// Parses a local variable declaration.
4154 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4155 let lo = self.prev_span;
4156 let pat = self.parse_top_level_pat()?;
4158 let (err, ty) = if self.eat(&token::Colon) {
4159 // Save the state of the parser before parsing type normally, in case there is a `:`
4160 // instead of an `=` typo.
4161 let parser_snapshot_before_type = self.clone();
4162 let colon_sp = self.prev_span;
4163 match self.parse_ty() {
4164 Ok(ty) => (None, Some(ty)),
4166 // Rewind to before attempting to parse the type and continue parsing
4167 let parser_snapshot_after_type = self.clone();
4168 mem::replace(self, parser_snapshot_before_type);
4170 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4171 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4172 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4178 let init = match (self.parse_initializer(err.is_some()), err) {
4179 (Ok(init), None) => { // init parsed, ty parsed
4182 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4183 // Could parse the type as if it were the initializer, it is likely there was a
4184 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4185 err.span_suggestion_short(
4187 "use `=` if you meant to assign",
4189 Applicability::MachineApplicable
4192 // As this was parsed successfully, continue as if the code has been fixed for the
4193 // rest of the file. It will still fail due to the emitted error, but we avoid
4197 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4199 // Couldn't parse the type nor the initializer, only raise the type error and
4200 // return to the parser state before parsing the type as the initializer.
4201 // let x: <parse_error>;
4202 mem::replace(self, snapshot);
4205 (Err(err), None) => { // init error, ty parsed
4206 // Couldn't parse the initializer and we're not attempting to recover a failed
4207 // parse of the type, return the error.
4211 let hi = if self.token == token::Semi {
4220 id: ast::DUMMY_NODE_ID,
4223 source: LocalSource::Normal,
4227 /// Parses a structure field.
4228 fn parse_name_and_ty(&mut self,
4231 attrs: Vec<Attribute>)
4232 -> PResult<'a, StructField> {
4233 let name = self.parse_ident()?;
4234 self.expect(&token::Colon)?;
4235 let ty = self.parse_ty()?;
4237 span: lo.to(self.prev_span),
4240 id: ast::DUMMY_NODE_ID,
4246 /// Emits an expected-item-after-attributes error.
4247 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4248 let message = match attrs.last() {
4249 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4250 _ => "expected item after attributes",
4253 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4254 if attrs.last().unwrap().is_sugared_doc {
4255 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4260 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4261 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4262 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4263 Ok(self.parse_stmt_(true))
4266 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4267 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4269 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4274 fn is_async_block(&self) -> bool {
4275 self.token.is_keyword(kw::Async) &&
4278 self.is_keyword_ahead(1, &[kw::Move]) &&
4279 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4281 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4286 fn is_async_fn(&self) -> bool {
4287 self.token.is_keyword(kw::Async) &&
4288 self.is_keyword_ahead(1, &[kw::Fn])
4291 fn is_do_catch_block(&self) -> bool {
4292 self.token.is_keyword(kw::Do) &&
4293 self.is_keyword_ahead(1, &[kw::Catch]) &&
4294 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4295 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4298 fn is_try_block(&self) -> bool {
4299 self.token.is_keyword(kw::Try) &&
4300 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
4301 self.span.rust_2018() &&
4302 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
4303 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4306 fn is_union_item(&self) -> bool {
4307 self.token.is_keyword(kw::Union) &&
4308 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4311 fn is_crate_vis(&self) -> bool {
4312 self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4315 fn is_existential_type_decl(&self) -> bool {
4316 self.token.is_keyword(kw::Existential) &&
4317 self.is_keyword_ahead(1, &[kw::Type])
4320 fn is_auto_trait_item(&self) -> bool {
4322 (self.token.is_keyword(kw::Auto) &&
4323 self.is_keyword_ahead(1, &[kw::Trait]))
4324 || // unsafe auto trait
4325 (self.token.is_keyword(kw::Unsafe) &&
4326 self.is_keyword_ahead(1, &[kw::Auto]) &&
4327 self.is_keyword_ahead(2, &[kw::Trait]))
4330 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4331 -> PResult<'a, Option<P<Item>>> {
4332 let token_lo = self.span;
4333 let (ident, def) = match self.token {
4334 token::Ident(ident, false) if ident.name == kw::Macro => {
4336 let ident = self.parse_ident()?;
4337 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4338 match self.parse_token_tree() {
4339 TokenTree::Delimited(_, _, tts) => tts,
4340 _ => unreachable!(),
4342 } else if self.check(&token::OpenDelim(token::Paren)) {
4343 let args = self.parse_token_tree();
4344 let body = if self.check(&token::OpenDelim(token::Brace)) {
4345 self.parse_token_tree()
4350 TokenStream::new(vec![
4352 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
4360 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4362 token::Ident(ident, _) if ident.name == sym::macro_rules &&
4363 self.look_ahead(1, |t| *t == token::Not) => {
4364 let prev_span = self.prev_span;
4365 self.complain_if_pub_macro(&vis.node, prev_span);
4369 let ident = self.parse_ident()?;
4370 let (delim, tokens) = self.expect_delimited_token_tree()?;
4371 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
4372 self.report_invalid_macro_expansion_item();
4375 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4377 _ => return Ok(None),
4380 let span = lo.to(self.prev_span);
4381 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4384 fn parse_stmt_without_recovery(&mut self,
4385 macro_legacy_warnings: bool)
4386 -> PResult<'a, Option<Stmt>> {
4387 maybe_whole!(self, NtStmt, |x| Some(x));
4389 let attrs = self.parse_outer_attributes()?;
4392 Ok(Some(if self.eat_keyword(kw::Let) {
4394 id: ast::DUMMY_NODE_ID,
4395 node: StmtKind::Local(self.parse_local(attrs.into())?),
4396 span: lo.to(self.prev_span),
4398 } else if let Some(macro_def) = self.eat_macro_def(
4400 &source_map::respan(lo, VisibilityKind::Inherited),
4404 id: ast::DUMMY_NODE_ID,
4405 node: StmtKind::Item(macro_def),
4406 span: lo.to(self.prev_span),
4408 // Starts like a simple path, being careful to avoid contextual keywords
4409 // such as a union items, item with `crate` visibility or auto trait items.
4410 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4411 // like a path (1 token), but it fact not a path.
4412 // `union::b::c` - path, `union U { ... }` - not a path.
4413 // `crate::b::c` - path, `crate struct S;` - not a path.
4414 } else if self.token.is_path_start() &&
4415 !self.token.is_qpath_start() &&
4416 !self.is_union_item() &&
4417 !self.is_crate_vis() &&
4418 !self.is_existential_type_decl() &&
4419 !self.is_auto_trait_item() &&
4420 !self.is_async_fn() {
4421 let pth = self.parse_path(PathStyle::Expr)?;
4423 if !self.eat(&token::Not) {
4424 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4425 self.parse_struct_expr(lo, pth, ThinVec::new())?
4427 let hi = self.prev_span;
4428 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4431 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4432 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4433 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4436 return Ok(Some(Stmt {
4437 id: ast::DUMMY_NODE_ID,
4438 node: StmtKind::Expr(expr),
4439 span: lo.to(self.prev_span),
4443 // it's a macro invocation
4444 let id = match self.token {
4445 token::OpenDelim(_) => Ident::invalid(), // no special identifier
4446 _ => self.parse_ident()?,
4449 // check that we're pointing at delimiters (need to check
4450 // again after the `if`, because of `parse_ident`
4451 // consuming more tokens).
4453 token::OpenDelim(_) => {}
4455 // we only expect an ident if we didn't parse one
4457 let ident_str = if id.name == kw::Invalid {
4462 let tok_str = self.this_token_descr();
4463 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
4466 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
4471 let (delim, tts) = self.expect_delimited_token_tree()?;
4472 let hi = self.prev_span;
4474 let style = if delim == MacDelimiter::Brace {
4475 MacStmtStyle::Braces
4477 MacStmtStyle::NoBraces
4480 if id.name == kw::Invalid {
4481 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
4482 let node = if delim == MacDelimiter::Brace ||
4483 self.token == token::Semi || self.token == token::Eof {
4484 StmtKind::Mac(P((mac, style, attrs.into())))
4486 // We used to incorrectly stop parsing macro-expanded statements here.
4487 // If the next token will be an error anyway but could have parsed with the
4488 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
4489 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
4490 // These can continue an expression, so we can't stop parsing and warn.
4491 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
4492 token::BinOp(token::Minus) | token::BinOp(token::Star) |
4493 token::BinOp(token::And) | token::BinOp(token::Or) |
4494 token::AndAnd | token::OrOr |
4495 token::DotDot | token::DotDotDot | token::DotDotEq => false,
4498 self.warn_missing_semicolon();
4499 StmtKind::Mac(P((mac, style, attrs.into())))
4501 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
4502 let e = self.maybe_recover_from_bad_qpath(e, true)?;
4503 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
4504 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
4508 id: ast::DUMMY_NODE_ID,
4513 // if it has a special ident, it's definitely an item
4515 // Require a semicolon or braces.
4516 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
4517 self.report_invalid_macro_expansion_item();
4519 let span = lo.to(hi);
4521 id: ast::DUMMY_NODE_ID,
4523 node: StmtKind::Item({
4525 span, id /*id is good here*/,
4526 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
4527 respan(lo, VisibilityKind::Inherited),
4533 // FIXME: Bad copy of attrs
4534 let old_directory_ownership =
4535 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
4536 let item = self.parse_item_(attrs.clone(), false, true)?;
4537 self.directory.ownership = old_directory_ownership;
4541 id: ast::DUMMY_NODE_ID,
4542 span: lo.to(i.span),
4543 node: StmtKind::Item(i),
4546 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
4547 if !attrs.is_empty() {
4548 if s.prev_token_kind == PrevTokenKind::DocComment {
4549 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
4550 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
4551 s.span_err(s.span, "expected statement after outer attribute");
4556 // Do not attempt to parse an expression if we're done here.
4557 if self.token == token::Semi {
4558 unused_attrs(&attrs, self);
4563 if self.token == token::CloseDelim(token::Brace) {
4564 unused_attrs(&attrs, self);
4568 // Remainder are line-expr stmts.
4569 let e = self.parse_expr_res(
4570 Restrictions::STMT_EXPR, Some(attrs.into()))?;
4572 id: ast::DUMMY_NODE_ID,
4573 span: lo.to(e.span),
4574 node: StmtKind::Expr(e),
4581 /// Checks if this expression is a successfully parsed statement.
4582 fn expr_is_complete(&self, e: &Expr) -> bool {
4583 self.restrictions.contains(Restrictions::STMT_EXPR) &&
4584 !classify::expr_requires_semi_to_be_stmt(e)
4587 /// Parses a block. No inner attributes are allowed.
4588 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
4589 maybe_whole!(self, NtBlock, |x| x);
4593 if !self.eat(&token::OpenDelim(token::Brace)) {
4595 let tok = self.this_token_descr();
4596 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
4597 let do_not_suggest_help =
4598 self.token.is_keyword(kw::In) || self.token == token::Colon;
4600 if self.token.is_ident_named(sym::and) {
4601 e.span_suggestion_short(
4603 "use `&&` instead of `and` for the boolean operator",
4605 Applicability::MaybeIncorrect,
4608 if self.token.is_ident_named(sym::or) {
4609 e.span_suggestion_short(
4611 "use `||` instead of `or` for the boolean operator",
4613 Applicability::MaybeIncorrect,
4617 // Check to see if the user has written something like
4622 // Which is valid in other languages, but not Rust.
4623 match self.parse_stmt_without_recovery(false) {
4625 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
4626 || do_not_suggest_help {
4627 // if the next token is an open brace (e.g., `if a b {`), the place-
4628 // inside-a-block suggestion would be more likely wrong than right
4629 e.span_label(sp, "expected `{`");
4632 let mut stmt_span = stmt.span;
4633 // expand the span to include the semicolon, if it exists
4634 if self.eat(&token::Semi) {
4635 stmt_span = stmt_span.with_hi(self.prev_span.hi());
4637 let sugg = pprust::to_string(|s| {
4638 use crate::print::pprust::{PrintState, INDENT_UNIT};
4639 s.ibox(INDENT_UNIT)?;
4641 s.print_stmt(&stmt)?;
4642 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
4646 "try placing this code inside a block",
4648 // speculative, has been misleading in the past (closed Issue #46836)
4649 Applicability::MaybeIncorrect
4653 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4654 self.cancel(&mut e);
4658 e.span_label(sp, "expected `{`");
4662 self.parse_block_tail(lo, BlockCheckMode::Default)
4665 /// Parses a block. Inner attributes are allowed.
4666 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
4667 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
4670 self.expect(&token::OpenDelim(token::Brace))?;
4671 Ok((self.parse_inner_attributes()?,
4672 self.parse_block_tail(lo, BlockCheckMode::Default)?))
4675 /// Parses the rest of a block expression or function body.
4676 /// Precondition: already parsed the '{'.
4677 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
4678 let mut stmts = vec![];
4679 while !self.eat(&token::CloseDelim(token::Brace)) {
4680 let stmt = match self.parse_full_stmt(false) {
4683 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
4685 id: ast::DUMMY_NODE_ID,
4686 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
4692 if let Some(stmt) = stmt {
4694 } else if self.token == token::Eof {
4697 // Found only `;` or `}`.
4703 id: ast::DUMMY_NODE_ID,
4705 span: lo.to(self.prev_span),
4709 /// Parses a statement, including the trailing semicolon.
4710 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
4711 // skip looking for a trailing semicolon when we have an interpolated statement
4712 maybe_whole!(self, NtStmt, |x| Some(x));
4714 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
4716 None => return Ok(None),
4720 StmtKind::Expr(ref expr) if self.token != token::Eof => {
4721 // expression without semicolon
4722 if classify::expr_requires_semi_to_be_stmt(expr) {
4723 // Just check for errors and recover; do not eat semicolon yet.
4725 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
4728 self.recover_stmt();
4732 StmtKind::Local(..) => {
4733 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
4734 if macro_legacy_warnings && self.token != token::Semi {
4735 self.warn_missing_semicolon();
4737 self.expect_one_of(&[], &[token::Semi])?;
4743 if self.eat(&token::Semi) {
4744 stmt = stmt.add_trailing_semicolon();
4747 stmt.span = stmt.span.with_hi(self.prev_span.hi());
4751 fn warn_missing_semicolon(&self) {
4752 self.diagnostic().struct_span_warn(self.span, {
4753 &format!("expected `;`, found {}", self.this_token_descr())
4755 "This was erroneously allowed and will become a hard error in a future release"
4759 fn err_dotdotdot_syntax(&self, span: Span) {
4760 self.diagnostic().struct_span_err(span, {
4761 "unexpected token: `...`"
4763 span, "use `..` for an exclusive range", "..".to_owned(),
4764 Applicability::MaybeIncorrect
4766 span, "or `..=` for an inclusive range", "..=".to_owned(),
4767 Applicability::MaybeIncorrect
4771 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
4774 /// BOUND = TY_BOUND | LT_BOUND
4775 /// LT_BOUND = LIFETIME (e.g., `'a`)
4776 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
4777 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
4779 fn parse_generic_bounds_common(&mut self,
4781 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4782 let mut bounds = Vec::new();
4783 let mut negative_bounds = Vec::new();
4784 let mut last_plus_span = None;
4785 let mut was_negative = false;
4787 // This needs to be synchronized with `Token::can_begin_bound`.
4788 let is_bound_start = self.check_path() || self.check_lifetime() ||
4789 self.check(&token::Not) || // used for error reporting only
4790 self.check(&token::Question) ||
4791 self.check_keyword(kw::For) ||
4792 self.check(&token::OpenDelim(token::Paren));
4795 let has_parens = self.eat(&token::OpenDelim(token::Paren));
4796 let inner_lo = self.span;
4797 let is_negative = self.eat(&token::Not);
4798 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
4799 if self.token.is_lifetime() {
4800 if let Some(question_span) = question {
4801 self.span_err(question_span,
4802 "`?` may only modify trait bounds, not lifetime bounds");
4804 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
4806 let inner_span = inner_lo.to(self.prev_span);
4807 self.expect(&token::CloseDelim(token::Paren))?;
4808 let mut err = self.struct_span_err(
4809 lo.to(self.prev_span),
4810 "parenthesized lifetime bounds are not supported"
4812 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
4813 err.span_suggestion_short(
4814 lo.to(self.prev_span),
4815 "remove the parentheses",
4817 Applicability::MachineApplicable
4823 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
4824 let path = self.parse_path(PathStyle::Type)?;
4826 self.expect(&token::CloseDelim(token::Paren))?;
4828 let poly_span = lo.to(self.prev_span);
4830 was_negative = true;
4831 if let Some(sp) = last_plus_span.or(colon_span) {
4832 negative_bounds.push(sp.to(poly_span));
4835 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
4836 let modifier = if question.is_some() {
4837 TraitBoundModifier::Maybe
4839 TraitBoundModifier::None
4841 bounds.push(GenericBound::Trait(poly_trait, modifier));
4848 if !allow_plus || !self.eat_plus() {
4851 last_plus_span = Some(self.prev_span);
4855 if !negative_bounds.is_empty() || was_negative {
4856 let plural = negative_bounds.len() > 1;
4857 let last_span = negative_bounds.last().map(|sp| *sp);
4858 let mut err = self.struct_span_err(
4860 "negative trait bounds are not supported",
4862 if let Some(sp) = last_span {
4863 err.span_label(sp, "negative trait bounds are not supported");
4865 if let Some(bound_list) = colon_span {
4866 let bound_list = bound_list.to(self.prev_span);
4867 let mut new_bound_list = String::new();
4868 if !bounds.is_empty() {
4869 let mut snippets = bounds.iter().map(|bound| bound.span())
4870 .map(|span| self.sess.source_map().span_to_snippet(span));
4871 while let Some(Ok(snippet)) = snippets.next() {
4872 new_bound_list.push_str(" + ");
4873 new_bound_list.push_str(&snippet);
4875 new_bound_list = new_bound_list.replacen(" +", ":", 1);
4877 err.span_suggestion_hidden(
4879 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
4881 Applicability::MachineApplicable,
4890 crate fn parse_generic_bounds(&mut self,
4891 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
4892 self.parse_generic_bounds_common(true, colon_span)
4895 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
4898 /// BOUND = LT_BOUND (e.g., `'a`)
4900 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
4901 let mut lifetimes = Vec::new();
4902 while self.check_lifetime() {
4903 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
4905 if !self.eat_plus() {
4912 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
4913 fn parse_ty_param(&mut self,
4914 preceding_attrs: Vec<Attribute>)
4915 -> PResult<'a, GenericParam> {
4916 let ident = self.parse_ident()?;
4918 // Parse optional colon and param bounds.
4919 let bounds = if self.eat(&token::Colon) {
4920 self.parse_generic_bounds(Some(self.prev_span))?
4925 let default = if self.eat(&token::Eq) {
4926 Some(self.parse_ty()?)
4933 id: ast::DUMMY_NODE_ID,
4934 attrs: preceding_attrs.into(),
4936 kind: GenericParamKind::Type {
4942 /// Parses the following grammar:
4944 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
4945 fn parse_trait_item_assoc_ty(&mut self)
4946 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
4947 let ident = self.parse_ident()?;
4948 let mut generics = self.parse_generics()?;
4950 // Parse optional colon and param bounds.
4951 let bounds = if self.eat(&token::Colon) {
4952 self.parse_generic_bounds(None)?
4956 generics.where_clause = self.parse_where_clause()?;
4958 let default = if self.eat(&token::Eq) {
4959 Some(self.parse_ty()?)
4963 self.expect(&token::Semi)?;
4965 Ok((ident, TraitItemKind::Type(bounds, default), generics))
4968 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
4969 self.expect_keyword(kw::Const)?;
4970 let ident = self.parse_ident()?;
4971 self.expect(&token::Colon)?;
4972 let ty = self.parse_ty()?;
4976 id: ast::DUMMY_NODE_ID,
4977 attrs: preceding_attrs.into(),
4979 kind: GenericParamKind::Const {
4985 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
4986 /// a trailing comma and erroneous trailing attributes.
4987 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
4988 let mut params = Vec::new();
4990 let attrs = self.parse_outer_attributes()?;
4991 if self.check_lifetime() {
4992 let lifetime = self.expect_lifetime();
4993 // Parse lifetime parameter.
4994 let bounds = if self.eat(&token::Colon) {
4995 self.parse_lt_param_bounds()
4999 params.push(ast::GenericParam {
5000 ident: lifetime.ident,
5002 attrs: attrs.into(),
5004 kind: ast::GenericParamKind::Lifetime,
5006 } else if self.check_keyword(kw::Const) {
5007 // Parse const parameter.
5008 params.push(self.parse_const_param(attrs)?);
5009 } else if self.check_ident() {
5010 // Parse type parameter.
5011 params.push(self.parse_ty_param(attrs)?);
5013 // Check for trailing attributes and stop parsing.
5014 if !attrs.is_empty() {
5015 if !params.is_empty() {
5016 self.struct_span_err(
5018 &format!("trailing attribute after generic parameter"),
5020 .span_label(attrs[0].span, "attributes must go before parameters")
5023 self.struct_span_err(
5025 &format!("attribute without generic parameters"),
5029 "attributes are only permitted when preceding parameters",
5037 if !self.eat(&token::Comma) {
5044 /// Parses a set of optional generic type parameter declarations. Where
5045 /// clauses are not parsed here, and must be added later via
5046 /// `parse_where_clause()`.
5048 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5049 /// | ( < lifetimes , typaramseq ( , )? > )
5050 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5051 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5052 let span_lo = self.span;
5054 let params = self.parse_generic_params()?;
5058 where_clause: WhereClause {
5059 id: ast::DUMMY_NODE_ID,
5060 predicates: Vec::new(),
5063 span: span_lo.to(self.prev_span),
5066 Ok(ast::Generics::default())
5070 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5071 /// For the purposes of understanding the parsing logic of generic arguments, this function
5072 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5073 /// had the correct amount of leading angle brackets.
5075 /// ```ignore (diagnostics)
5076 /// bar::<<<<T as Foo>::Output>();
5077 /// ^^ help: remove extra angle brackets
5079 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5083 ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5084 // We need to detect whether there are extra leading left angle brackets and produce an
5085 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5086 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5087 // then there won't be matching `>` tokens to find.
5089 // To explain how this detection works, consider the following example:
5091 // ```ignore (diagnostics)
5092 // bar::<<<<T as Foo>::Output>();
5093 // ^^ help: remove extra angle brackets
5096 // Parsing of the left angle brackets starts in this function. We start by parsing the
5097 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5100 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5101 // *Unmatched count:* 1
5102 // *`parse_path_segment` calls deep:* 0
5104 // This has the effect of recursing as this function is called if a `<` character
5105 // is found within the expected generic arguments:
5107 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5108 // *Unmatched count:* 2
5109 // *`parse_path_segment` calls deep:* 1
5111 // Eventually we will have recursed until having consumed all of the `<` tokens and
5112 // this will be reflected in the count:
5114 // *Upcoming tokens:* `T as Foo>::Output>;`
5115 // *Unmatched count:* 4
5116 // `parse_path_segment` calls deep:* 3
5118 // The parser will continue until reaching the first `>` - this will decrement the
5119 // unmatched angle bracket count and return to the parent invocation of this function
5120 // having succeeded in parsing:
5122 // *Upcoming tokens:* `::Output>;`
5123 // *Unmatched count:* 3
5124 // *`parse_path_segment` calls deep:* 2
5126 // This will continue until the next `>` character which will also return successfully
5127 // to the parent invocation of this function and decrement the count:
5129 // *Upcoming tokens:* `;`
5130 // *Unmatched count:* 2
5131 // *`parse_path_segment` calls deep:* 1
5133 // At this point, this function will expect to find another matching `>` character but
5134 // won't be able to and will return an error. This will continue all the way up the
5135 // call stack until the first invocation:
5137 // *Upcoming tokens:* `;`
5138 // *Unmatched count:* 2
5139 // *`parse_path_segment` calls deep:* 0
5141 // In doing this, we have managed to work out how many unmatched leading left angle
5142 // brackets there are, but we cannot recover as the unmatched angle brackets have
5143 // already been consumed. To remedy this, we keep a snapshot of the parser state
5144 // before we do the above. We can then inspect whether we ended up with a parsing error
5145 // and unmatched left angle brackets and if so, restore the parser state before we
5146 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5147 // recover by attempting to parse again.
5149 // In practice, the recursion of this function is indirect and there will be other
5150 // locations that consume some `<` characters - as long as we update the count when
5151 // this happens, it isn't an issue.
5153 let is_first_invocation = style == PathStyle::Expr;
5154 // Take a snapshot before attempting to parse - we can restore this later.
5155 let snapshot = if is_first_invocation {
5161 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5162 match self.parse_generic_args() {
5163 Ok(value) => Ok(value),
5164 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5165 // Cancel error from being unable to find `>`. We know the error
5166 // must have been this due to a non-zero unmatched angle bracket
5170 // Swap `self` with our backup of the parser state before attempting to parse
5171 // generic arguments.
5172 let snapshot = mem::replace(self, snapshot.unwrap());
5175 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5176 snapshot.count={:?}",
5177 snapshot.unmatched_angle_bracket_count,
5180 // Eat the unmatched angle brackets.
5181 for _ in 0..snapshot.unmatched_angle_bracket_count {
5185 // Make a span over ${unmatched angle bracket count} characters.
5186 let span = lo.with_hi(
5187 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5189 let plural = snapshot.unmatched_angle_bracket_count > 1;
5194 "unmatched angle bracket{}",
5195 if plural { "s" } else { "" }
5201 "remove extra angle bracket{}",
5202 if plural { "s" } else { "" }
5205 Applicability::MachineApplicable,
5209 // Try again without unmatched angle bracket characters.
5210 self.parse_generic_args()
5216 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5217 /// possibly including trailing comma.
5218 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5219 let mut args = Vec::new();
5220 let mut bindings = Vec::new();
5221 let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
5222 let mut assoc_ty_bindings: Vec<Span> = Vec::new();
5224 let args_lo = self.span;
5227 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5228 // Parse lifetime argument.
5229 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5230 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5231 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
5232 // Parse associated type binding.
5234 let ident = self.parse_ident()?;
5236 let ty = self.parse_ty()?;
5237 let span = lo.to(self.prev_span);
5238 bindings.push(TypeBinding {
5239 id: ast::DUMMY_NODE_ID,
5244 assoc_ty_bindings.push(span);
5245 } else if self.check_const_arg() {
5246 // Parse const argument.
5247 let expr = if let token::OpenDelim(token::Brace) = self.token {
5248 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
5249 } else if self.token.is_ident() {
5250 // FIXME(const_generics): to distinguish between idents for types and consts,
5251 // we should introduce a GenericArg::Ident in the AST and distinguish when
5252 // lowering to the HIR. For now, idents for const args are not permitted.
5254 self.fatal("identifiers may currently not be used for const generics")
5257 self.parse_literal_maybe_minus()?
5259 let value = AnonConst {
5260 id: ast::DUMMY_NODE_ID,
5263 args.push(GenericArg::Const(value));
5264 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5265 } else if self.check_type() {
5266 // Parse type argument.
5267 args.push(GenericArg::Type(self.parse_ty()?));
5268 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5273 if !self.eat(&token::Comma) {
5278 // FIXME: we would like to report this in ast_validation instead, but we currently do not
5279 // preserve ordering of generic parameters with respect to associated type binding, so we
5280 // lose that information after parsing.
5281 if misplaced_assoc_ty_bindings.len() > 0 {
5282 let mut err = self.struct_span_err(
5283 args_lo.to(self.prev_span),
5284 "associated type bindings must be declared after generic parameters",
5286 for span in misplaced_assoc_ty_bindings {
5289 "this associated type binding should be moved after the generic parameters",
5295 Ok((args, bindings))
5298 /// Parses an optional where-clause and places it in `generics`.
5300 /// ```ignore (only-for-syntax-highlight)
5301 /// where T : Trait<U, V> + 'b, 'a : 'b
5303 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5304 let mut where_clause = WhereClause {
5305 id: ast::DUMMY_NODE_ID,
5306 predicates: Vec::new(),
5310 if !self.eat_keyword(kw::Where) {
5311 return Ok(where_clause);
5313 let lo = self.prev_span;
5315 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5316 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5317 // change we parse those generics now, but report an error.
5318 if self.choose_generics_over_qpath() {
5319 let generics = self.parse_generics()?;
5320 self.struct_span_err(
5322 "generic parameters on `where` clauses are reserved for future use",
5324 .span_label(generics.span, "currently unsupported")
5330 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5331 let lifetime = self.expect_lifetime();
5332 // Bounds starting with a colon are mandatory, but possibly empty.
5333 self.expect(&token::Colon)?;
5334 let bounds = self.parse_lt_param_bounds();
5335 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5336 ast::WhereRegionPredicate {
5337 span: lo.to(self.prev_span),
5342 } else if self.check_type() {
5343 // Parse optional `for<'a, 'b>`.
5344 // This `for` is parsed greedily and applies to the whole predicate,
5345 // the bounded type can have its own `for` applying only to it.
5346 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
5347 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
5348 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
5349 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5351 // Parse type with mandatory colon and (possibly empty) bounds,
5352 // or with mandatory equality sign and the second type.
5353 let ty = self.parse_ty()?;
5354 if self.eat(&token::Colon) {
5355 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
5356 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5357 ast::WhereBoundPredicate {
5358 span: lo.to(self.prev_span),
5359 bound_generic_params: lifetime_defs,
5364 // FIXME: Decide what should be used here, `=` or `==`.
5365 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5366 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5367 let rhs_ty = self.parse_ty()?;
5368 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5369 ast::WhereEqPredicate {
5370 span: lo.to(self.prev_span),
5373 id: ast::DUMMY_NODE_ID,
5377 return self.unexpected();
5383 if !self.eat(&token::Comma) {
5388 where_clause.span = lo.to(self.prev_span);
5392 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
5393 -> PResult<'a, (Vec<Arg> , bool)> {
5394 self.expect(&token::OpenDelim(token::Paren))?;
5397 let mut c_variadic = false;
5398 let (args, recovered): (Vec<Option<Arg>>, bool) =
5399 self.parse_seq_to_before_end(
5400 &token::CloseDelim(token::Paren),
5401 SeqSep::trailing_allowed(token::Comma),
5403 // If the argument is a C-variadic argument we should not
5404 // enforce named arguments.
5405 let enforce_named_args = if p.token == token::DotDotDot {
5410 match p.parse_arg_general(enforce_named_args, false,
5413 if let TyKind::CVarArgs = arg.ty.node {
5415 if p.token != token::CloseDelim(token::Paren) {
5418 "`...` must be the last argument of a C-variadic function");
5429 let lo = p.prev_span;
5430 // Skip every token until next possible arg or end.
5431 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5432 // Create a placeholder argument for proper arg count (issue #34264).
5433 let span = lo.to(p.prev_span);
5434 Ok(Some(dummy_arg(span)))
5441 self.eat(&token::CloseDelim(token::Paren));
5444 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5446 if c_variadic && args.is_empty() {
5448 "C-variadic function must be declared with at least one named argument");
5451 Ok((args, c_variadic))
5454 /// Parses the argument list and result type of a function declaration.
5455 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
5457 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
5458 let ret_ty = self.parse_ret_ty(true)?;
5467 /// Returns the parsed optional self argument and whether a self shortcut was used.
5468 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
5469 let expect_ident = |this: &mut Self| match this.token {
5470 // Preserve hygienic context.
5471 token::Ident(ident, _) =>
5472 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
5475 let isolated_self = |this: &mut Self, n| {
5476 this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
5477 this.look_ahead(n + 1, |t| t != &token::ModSep)
5480 // Parse optional self parameter of a method.
5481 // Only a limited set of initial token sequences is considered self parameters, anything
5482 // else is parsed as a normal function parameter list, so some lookahead is required.
5483 let eself_lo = self.span;
5484 let (eself, eself_ident, eself_hi) = match self.token {
5485 token::BinOp(token::And) => {
5491 (if isolated_self(self, 1) {
5493 SelfKind::Region(None, Mutability::Immutable)
5494 } else if self.is_keyword_ahead(1, &[kw::Mut]) &&
5495 isolated_self(self, 2) {
5498 SelfKind::Region(None, Mutability::Mutable)
5499 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5500 isolated_self(self, 2) {
5502 let lt = self.expect_lifetime();
5503 SelfKind::Region(Some(lt), Mutability::Immutable)
5504 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
5505 self.is_keyword_ahead(2, &[kw::Mut]) &&
5506 isolated_self(self, 3) {
5508 let lt = self.expect_lifetime();
5510 SelfKind::Region(Some(lt), Mutability::Mutable)
5513 }, expect_ident(self), self.prev_span)
5515 token::BinOp(token::Star) => {
5520 // Emit special error for `self` cases.
5521 let msg = "cannot pass `self` by raw pointer";
5522 (if isolated_self(self, 1) {
5524 self.struct_span_err(self.span, msg)
5525 .span_label(self.span, msg)
5527 SelfKind::Value(Mutability::Immutable)
5528 } else if self.look_ahead(1, |t| t.is_mutability()) &&
5529 isolated_self(self, 2) {
5532 self.struct_span_err(self.span, msg)
5533 .span_label(self.span, msg)
5535 SelfKind::Value(Mutability::Immutable)
5538 }, expect_ident(self), self.prev_span)
5540 token::Ident(..) => {
5541 if isolated_self(self, 0) {
5544 let eself_ident = expect_ident(self);
5545 let eself_hi = self.prev_span;
5546 (if self.eat(&token::Colon) {
5547 let ty = self.parse_ty()?;
5548 SelfKind::Explicit(ty, Mutability::Immutable)
5550 SelfKind::Value(Mutability::Immutable)
5551 }, eself_ident, eself_hi)
5552 } else if self.token.is_keyword(kw::Mut) &&
5553 isolated_self(self, 1) {
5557 let eself_ident = expect_ident(self);
5558 let eself_hi = self.prev_span;
5559 (if self.eat(&token::Colon) {
5560 let ty = self.parse_ty()?;
5561 SelfKind::Explicit(ty, Mutability::Mutable)
5563 SelfKind::Value(Mutability::Mutable)
5564 }, eself_ident, eself_hi)
5569 _ => return Ok(None),
5572 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
5573 Ok(Some(Arg::from_self(eself, eself_ident)))
5576 /// Parses the parameter list and result type of a function that may have a `self` parameter.
5577 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
5578 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
5580 self.expect(&token::OpenDelim(token::Paren))?;
5582 // Parse optional self argument
5583 let self_arg = self.parse_self_arg()?;
5585 // Parse the rest of the function parameter list.
5586 let sep = SeqSep::trailing_allowed(token::Comma);
5587 let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
5588 if self.check(&token::CloseDelim(token::Paren)) {
5589 (vec![self_arg], false)
5590 } else if self.eat(&token::Comma) {
5591 let mut fn_inputs = vec![self_arg];
5592 let (mut input, recovered) = self.parse_seq_to_before_end(
5593 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
5594 fn_inputs.append(&mut input);
5595 (fn_inputs, recovered)
5597 match self.expect_one_of(&[], &[]) {
5598 Err(err) => return Err(err),
5599 Ok(recovered) => (vec![self_arg], recovered),
5603 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
5607 // Parse closing paren and return type.
5608 self.expect(&token::CloseDelim(token::Paren))?;
5612 output: self.parse_ret_ty(true)?,
5617 /// Parses the `|arg, arg|` header of a closure.
5618 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
5619 let inputs_captures = {
5620 if self.eat(&token::OrOr) {
5623 self.expect(&token::BinOp(token::Or))?;
5624 let args = self.parse_seq_to_before_tokens(
5625 &[&token::BinOp(token::Or), &token::OrOr],
5626 SeqSep::trailing_allowed(token::Comma),
5627 TokenExpectType::NoExpect,
5628 |p| p.parse_fn_block_arg()
5634 let output = self.parse_ret_ty(true)?;
5637 inputs: inputs_captures,
5643 /// Parses the name and optional generic types of a function header.
5644 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
5645 let id = self.parse_ident()?;
5646 let generics = self.parse_generics()?;
5650 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
5651 attrs: Vec<Attribute>) -> P<Item> {
5655 id: ast::DUMMY_NODE_ID,
5663 /// Parses an item-position function declaration.
5664 fn parse_item_fn(&mut self,
5666 mut asyncness: Spanned<IsAsync>,
5667 constness: Spanned<Constness>,
5669 -> PResult<'a, ItemInfo> {
5670 let (ident, mut generics) = self.parse_fn_header()?;
5671 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
5672 let mut decl = self.parse_fn_decl(allow_c_variadic)?;
5673 generics.where_clause = self.parse_where_clause()?;
5674 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5675 self.construct_async_arguments(&mut asyncness, &mut decl);
5676 let header = FnHeader { unsafety, asyncness, constness, abi };
5677 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
5680 /// Returns `true` if we are looking at `const ID`
5681 /// (returns `false` for things like `const fn`, etc.).
5682 fn is_const_item(&self) -> bool {
5683 self.token.is_keyword(kw::Const) &&
5684 !self.is_keyword_ahead(1, &[kw::Fn, kw::Unsafe])
5687 /// Parses all the "front matter" for a `fn` declaration, up to
5688 /// and including the `fn` keyword:
5692 /// - `const unsafe fn`
5695 fn parse_fn_front_matter(&mut self)
5703 let is_const_fn = self.eat_keyword(kw::Const);
5704 let const_span = self.prev_span;
5705 let unsafety = self.parse_unsafety();
5706 let asyncness = self.parse_asyncness();
5707 let asyncness = respan(self.prev_span, asyncness);
5708 let (constness, unsafety, abi) = if is_const_fn {
5709 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
5711 let abi = if self.eat_keyword(kw::Extern) {
5712 self.parse_opt_abi()?.unwrap_or(Abi::C)
5716 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
5718 if !self.eat_keyword(kw::Fn) {
5719 // It is possible for `expect_one_of` to recover given the contents of
5720 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
5721 // account for this.
5722 if !self.expect_one_of(&[], &[])? { unreachable!() }
5724 Ok((constness, unsafety, asyncness, abi))
5727 /// Parses an impl item.
5728 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
5729 maybe_whole!(self, NtImplItem, |x| x);
5730 let attrs = self.parse_outer_attributes()?;
5731 let mut unclosed_delims = vec![];
5732 let (mut item, tokens) = self.collect_tokens(|this| {
5733 let item = this.parse_impl_item_(at_end, attrs);
5734 unclosed_delims.append(&mut this.unclosed_delims);
5737 self.unclosed_delims.append(&mut unclosed_delims);
5739 // See `parse_item` for why this clause is here.
5740 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
5741 item.tokens = Some(tokens);
5746 fn parse_impl_item_(&mut self,
5748 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
5750 let vis = self.parse_visibility(false)?;
5751 let defaultness = self.parse_defaultness();
5752 let (name, node, generics) = if let Some(type_) = self.eat_type() {
5753 let (name, alias, generics) = type_?;
5754 let kind = match alias {
5755 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
5756 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
5758 (name, kind, generics)
5759 } else if self.is_const_item() {
5760 // This parses the grammar:
5761 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
5762 self.expect_keyword(kw::Const)?;
5763 let name = self.parse_ident()?;
5764 self.expect(&token::Colon)?;
5765 let typ = self.parse_ty()?;
5766 self.expect(&token::Eq)?;
5767 let expr = self.parse_expr()?;
5768 self.expect(&token::Semi)?;
5769 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
5771 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
5772 attrs.extend(inner_attrs);
5773 (name, node, generics)
5777 id: ast::DUMMY_NODE_ID,
5778 span: lo.to(self.prev_span),
5789 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
5791 VisibilityKind::Inherited => {}
5793 let is_macro_rules: bool = match self.token {
5794 token::Ident(sid, _) => sid.name == sym::macro_rules,
5797 let mut err = if is_macro_rules {
5798 let mut err = self.diagnostic()
5799 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
5800 err.span_suggestion(
5802 "try exporting the macro",
5803 "#[macro_export]".to_owned(),
5804 Applicability::MaybeIncorrect // speculative
5808 let mut err = self.diagnostic()
5809 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
5810 err.help("try adjusting the macro to put `pub` inside the invocation");
5818 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
5819 -> DiagnosticBuilder<'a>
5821 let expected_kinds = if item_type == "extern" {
5822 "missing `fn`, `type`, or `static`"
5824 "missing `fn`, `type`, or `const`"
5827 // Given this code `path(`, it seems like this is not
5828 // setting the visibility of a macro invocation, but rather
5829 // a mistyped method declaration.
5830 // Create a diagnostic pointing out that `fn` is missing.
5832 // x | pub path(&self) {
5833 // | ^ missing `fn`, `type`, or `const`
5835 // ^^ `sp` below will point to this
5836 let sp = prev_span.between(self.prev_span);
5837 let mut err = self.diagnostic().struct_span_err(
5839 &format!("{} for {}-item declaration",
5840 expected_kinds, item_type));
5841 err.span_label(sp, expected_kinds);
5845 /// Parse a method or a macro invocation in a trait impl.
5846 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
5847 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
5848 ast::ImplItemKind)> {
5849 // code copied from parse_macro_use_or_failure... abstraction!
5850 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
5852 Ok((Ident::invalid(), vec![], ast::Generics::default(),
5853 ast::ImplItemKind::Macro(mac)))
5855 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
5856 let ident = self.parse_ident()?;
5857 let mut generics = self.parse_generics()?;
5858 let mut decl = self.parse_fn_decl_with_self(|p| {
5859 p.parse_arg_general(true, true, false)
5861 generics.where_clause = self.parse_where_clause()?;
5862 self.construct_async_arguments(&mut asyncness, &mut decl);
5864 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
5865 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
5866 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
5867 ast::MethodSig { header, decl },
5873 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
5874 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
5875 let ident = self.parse_ident()?;
5876 let mut tps = self.parse_generics()?;
5878 // Parse optional colon and supertrait bounds.
5879 let bounds = if self.eat(&token::Colon) {
5880 self.parse_generic_bounds(Some(self.prev_span))?
5885 if self.eat(&token::Eq) {
5886 // it's a trait alias
5887 let bounds = self.parse_generic_bounds(None)?;
5888 tps.where_clause = self.parse_where_clause()?;
5889 self.expect(&token::Semi)?;
5890 if is_auto == IsAuto::Yes {
5891 let msg = "trait aliases cannot be `auto`";
5892 self.struct_span_err(self.prev_span, msg)
5893 .span_label(self.prev_span, msg)
5896 if unsafety != Unsafety::Normal {
5897 let msg = "trait aliases cannot be `unsafe`";
5898 self.struct_span_err(self.prev_span, msg)
5899 .span_label(self.prev_span, msg)
5902 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
5904 // it's a normal trait
5905 tps.where_clause = self.parse_where_clause()?;
5906 self.expect(&token::OpenDelim(token::Brace))?;
5907 let mut trait_items = vec![];
5908 while !self.eat(&token::CloseDelim(token::Brace)) {
5909 if let token::DocComment(_) = self.token {
5910 if self.look_ahead(1,
5911 |tok| tok == &token::Token::CloseDelim(token::Brace)) {
5912 let mut err = self.diagnostic().struct_span_err_with_code(
5914 "found a documentation comment that doesn't document anything",
5915 DiagnosticId::Error("E0584".into()),
5917 err.help("doc comments must come before what they document, maybe a \
5918 comment was intended with `//`?",
5925 let mut at_end = false;
5926 match self.parse_trait_item(&mut at_end) {
5927 Ok(item) => trait_items.push(item),
5931 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5936 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
5940 fn choose_generics_over_qpath(&self) -> bool {
5941 // There's an ambiguity between generic parameters and qualified paths in impls.
5942 // If we see `<` it may start both, so we have to inspect some following tokens.
5943 // The following combinations can only start generics,
5944 // but not qualified paths (with one exception):
5945 // `<` `>` - empty generic parameters
5946 // `<` `#` - generic parameters with attributes
5947 // `<` (LIFETIME|IDENT) `>` - single generic parameter
5948 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
5949 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
5950 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
5951 // `<` const - generic const parameter
5952 // The only truly ambiguous case is
5953 // `<` IDENT `>` `::` IDENT ...
5954 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
5955 // because this is what almost always expected in practice, qualified paths in impls
5956 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
5957 self.token == token::Lt &&
5958 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
5959 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
5960 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
5961 t == &token::Colon || t == &token::Eq) ||
5962 self.is_keyword_ahead(1, &[kw::Const]))
5965 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
5966 self.expect(&token::OpenDelim(token::Brace))?;
5967 let attrs = self.parse_inner_attributes()?;
5969 let mut impl_items = Vec::new();
5970 while !self.eat(&token::CloseDelim(token::Brace)) {
5971 let mut at_end = false;
5972 match self.parse_impl_item(&mut at_end) {
5973 Ok(impl_item) => impl_items.push(impl_item),
5977 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
5982 Ok((impl_items, attrs))
5985 /// Parses an implementation item, `impl` keyword is already parsed.
5987 /// impl<'a, T> TYPE { /* impl items */ }
5988 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
5989 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
5991 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
5992 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
5993 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
5994 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
5995 -> PResult<'a, ItemInfo> {
5996 // First, parse generic parameters if necessary.
5997 let mut generics = if self.choose_generics_over_qpath() {
5998 self.parse_generics()?
6000 ast::Generics::default()
6003 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6004 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6006 ast::ImplPolarity::Negative
6008 ast::ImplPolarity::Positive
6011 // Parse both types and traits as a type, then reinterpret if necessary.
6012 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
6013 let ty_first = if self.token.is_keyword(kw::For) &&
6014 self.look_ahead(1, |t| t != &token::Lt) {
6015 let span = self.prev_span.between(self.span);
6016 self.struct_span_err(span, "missing trait in a trait impl").emit();
6017 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6022 // If `for` is missing we try to recover.
6023 let has_for = self.eat_keyword(kw::For);
6024 let missing_for_span = self.prev_span.between(self.span);
6026 let ty_second = if self.token == token::DotDot {
6027 // We need to report this error after `cfg` expansion for compatibility reasons
6028 self.bump(); // `..`, do not add it to expected tokens
6029 Some(DummyResult::raw_ty(self.prev_span, true))
6030 } else if has_for || self.token.can_begin_type() {
6031 Some(self.parse_ty()?)
6036 generics.where_clause = self.parse_where_clause()?;
6038 let (impl_items, attrs) = self.parse_impl_body()?;
6040 let item_kind = match ty_second {
6041 Some(ty_second) => {
6042 // impl Trait for Type
6044 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6045 .span_suggestion_short(
6048 " for ".to_string(),
6049 Applicability::MachineApplicable,
6053 let ty_first = ty_first.into_inner();
6054 let path = match ty_first.node {
6055 // This notably includes paths passed through `ty` macro fragments (#46438).
6056 TyKind::Path(None, path) => path,
6058 self.span_err(ty_first.span, "expected a trait, found type");
6059 err_path(ty_first.span)
6062 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6064 ItemKind::Impl(unsafety, polarity, defaultness,
6065 generics, Some(trait_ref), ty_second, impl_items)
6069 ItemKind::Impl(unsafety, polarity, defaultness,
6070 generics, None, ty_first, impl_items)
6074 Ok((Ident::invalid(), item_kind, Some(attrs)))
6077 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6078 if self.eat_keyword(kw::For) {
6080 let params = self.parse_generic_params()?;
6082 // We rely on AST validation to rule out invalid cases: There must not be type
6083 // parameters, and the lifetime parameters must not have bounds.
6090 /// Parses `struct Foo { ... }`.
6091 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6092 let class_name = self.parse_ident()?;
6094 let mut generics = self.parse_generics()?;
6096 // There is a special case worth noting here, as reported in issue #17904.
6097 // If we are parsing a tuple struct it is the case that the where clause
6098 // should follow the field list. Like so:
6100 // struct Foo<T>(T) where T: Copy;
6102 // If we are parsing a normal record-style struct it is the case
6103 // that the where clause comes before the body, and after the generics.
6104 // So if we look ahead and see a brace or a where-clause we begin
6105 // parsing a record style struct.
6107 // Otherwise if we look ahead and see a paren we parse a tuple-style
6110 let vdata = if self.token.is_keyword(kw::Where) {
6111 generics.where_clause = self.parse_where_clause()?;
6112 if self.eat(&token::Semi) {
6113 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6114 VariantData::Unit(ast::DUMMY_NODE_ID)
6116 // If we see: `struct Foo<T> where T: Copy { ... }`
6117 let (fields, recovered) = self.parse_record_struct_body()?;
6118 VariantData::Struct(fields, recovered)
6120 // No `where` so: `struct Foo<T>;`
6121 } else if self.eat(&token::Semi) {
6122 VariantData::Unit(ast::DUMMY_NODE_ID)
6123 // Record-style struct definition
6124 } else if self.token == token::OpenDelim(token::Brace) {
6125 let (fields, recovered) = self.parse_record_struct_body()?;
6126 VariantData::Struct(fields, recovered)
6127 // Tuple-style struct definition with optional where-clause.
6128 } else if self.token == token::OpenDelim(token::Paren) {
6129 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6130 generics.where_clause = self.parse_where_clause()?;
6131 self.expect(&token::Semi)?;
6134 let token_str = self.this_token_descr();
6135 let mut err = self.fatal(&format!(
6136 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6139 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6143 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6146 /// Parses `union Foo { ... }`.
6147 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6148 let class_name = self.parse_ident()?;
6150 let mut generics = self.parse_generics()?;
6152 let vdata = if self.token.is_keyword(kw::Where) {
6153 generics.where_clause = self.parse_where_clause()?;
6154 let (fields, recovered) = self.parse_record_struct_body()?;
6155 VariantData::Struct(fields, recovered)
6156 } else if self.token == token::OpenDelim(token::Brace) {
6157 let (fields, recovered) = self.parse_record_struct_body()?;
6158 VariantData::Struct(fields, recovered)
6160 let token_str = self.this_token_descr();
6161 let mut err = self.fatal(&format!(
6162 "expected `where` or `{{` after union name, found {}", token_str));
6163 err.span_label(self.span, "expected `where` or `{` after union name");
6167 Ok((class_name, ItemKind::Union(vdata, generics), None))
6170 fn parse_record_struct_body(
6172 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6173 let mut fields = Vec::new();
6174 let mut recovered = false;
6175 if self.eat(&token::OpenDelim(token::Brace)) {
6176 while self.token != token::CloseDelim(token::Brace) {
6177 let field = self.parse_struct_decl_field().map_err(|e| {
6178 self.recover_stmt();
6183 Ok(field) => fields.push(field),
6189 self.eat(&token::CloseDelim(token::Brace));
6191 let token_str = self.this_token_descr();
6192 let mut err = self.fatal(&format!(
6193 "expected `where`, or `{{` after struct name, found {}", token_str));
6194 err.span_label(self.span, "expected `where`, or `{` after struct name");
6198 Ok((fields, recovered))
6201 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6202 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6203 // Unit like structs are handled in parse_item_struct function
6204 let fields = self.parse_unspanned_seq(
6205 &token::OpenDelim(token::Paren),
6206 &token::CloseDelim(token::Paren),
6207 SeqSep::trailing_allowed(token::Comma),
6209 let attrs = p.parse_outer_attributes()?;
6211 let vis = p.parse_visibility(true)?;
6212 let ty = p.parse_ty()?;
6214 span: lo.to(ty.span),
6217 id: ast::DUMMY_NODE_ID,
6226 /// Parses a structure field declaration.
6227 fn parse_single_struct_field(&mut self,
6230 attrs: Vec<Attribute> )
6231 -> PResult<'a, StructField> {
6232 let mut seen_comma: bool = false;
6233 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
6234 if self.token == token::Comma {
6241 token::CloseDelim(token::Brace) => {}
6242 token::DocComment(_) => {
6243 let previous_span = self.prev_span;
6244 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
6245 self.bump(); // consume the doc comment
6246 let comma_after_doc_seen = self.eat(&token::Comma);
6247 // `seen_comma` is always false, because we are inside doc block
6248 // condition is here to make code more readable
6249 if seen_comma == false && comma_after_doc_seen == true {
6252 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
6255 if seen_comma == false {
6256 let sp = self.sess.source_map().next_point(previous_span);
6257 err.span_suggestion(
6259 "missing comma here",
6261 Applicability::MachineApplicable
6268 let sp = self.sess.source_map().next_point(self.prev_span);
6269 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
6270 self.this_token_descr()));
6271 if self.token.is_ident() {
6272 // This is likely another field; emit the diagnostic and keep going
6273 err.span_suggestion(
6275 "try adding a comma",
6277 Applicability::MachineApplicable,
6288 /// Parses an element of a struct declaration.
6289 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6290 let attrs = self.parse_outer_attributes()?;
6292 let vis = self.parse_visibility(false)?;
6293 self.parse_single_struct_field(lo, vis, attrs)
6296 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
6297 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
6298 /// If the following element can't be a tuple (i.e., it's a function definition), then
6299 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
6300 /// so emit a proper diagnostic.
6301 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6302 maybe_whole!(self, NtVis, |x| x);
6304 self.expected_tokens.push(TokenType::Keyword(kw::Crate));
6305 if self.is_crate_vis() {
6306 self.bump(); // `crate`
6307 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6310 if !self.eat_keyword(kw::Pub) {
6311 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6312 // keyword to grab a span from for inherited visibility; an empty span at the
6313 // beginning of the current token would seem to be the "Schelling span".
6314 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
6316 let lo = self.prev_span;
6318 if self.check(&token::OpenDelim(token::Paren)) {
6319 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6320 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6321 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6322 // by the following tokens.
6323 if self.is_keyword_ahead(1, &[kw::Crate]) &&
6324 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
6328 self.bump(); // `crate`
6329 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6331 lo.to(self.prev_span),
6332 VisibilityKind::Crate(CrateSugar::PubCrate),
6335 } else if self.is_keyword_ahead(1, &[kw::In]) {
6338 self.bump(); // `in`
6339 let path = self.parse_path(PathStyle::Mod)?; // `path`
6340 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6341 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6343 id: ast::DUMMY_NODE_ID,
6346 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6347 self.is_keyword_ahead(1, &[kw::Super, kw::SelfLower])
6349 // `pub(self)` or `pub(super)`
6351 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6352 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6353 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6355 id: ast::DUMMY_NODE_ID,
6358 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6359 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6361 let msg = "incorrect visibility restriction";
6362 let suggestion = r##"some possible visibility restrictions are:
6363 `pub(crate)`: visible only on the current crate
6364 `pub(super)`: visible only in the current module's parent
6365 `pub(in path::to::module)`: visible only on the specified path"##;
6366 let path = self.parse_path(PathStyle::Mod)?;
6368 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6369 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6370 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6371 err.help(suggestion);
6372 err.span_suggestion(
6373 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6375 err.emit(); // emit diagnostic, but continue with public visibility
6379 Ok(respan(lo, VisibilityKind::Public))
6382 /// Parses defaultness (i.e., `default` or nothing).
6383 fn parse_defaultness(&mut self) -> Defaultness {
6384 // `pub` is included for better error messages
6385 if self.check_keyword(kw::Default) &&
6386 self.is_keyword_ahead(1, &[
6396 self.bump(); // `default`
6397 Defaultness::Default
6403 /// Given a termination token, parses all of the items in a module.
6404 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
6405 let mut items = vec![];
6406 while let Some(item) = self.parse_item()? {
6408 self.maybe_consume_incorrect_semicolon(&items);
6411 if !self.eat(term) {
6412 let token_str = self.this_token_descr();
6413 if !self.maybe_consume_incorrect_semicolon(&items) {
6414 let mut err = self.fatal(&format!("expected item, found {}", token_str));
6415 err.span_label(self.span, "expected item");
6420 let hi = if self.span.is_dummy() {
6427 inner: inner_lo.to(hi),
6433 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6434 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
6435 self.expect(&token::Colon)?;
6436 let ty = self.parse_ty()?;
6437 self.expect(&token::Eq)?;
6438 let e = self.parse_expr()?;
6439 self.expect(&token::Semi)?;
6440 let item = match m {
6441 Some(m) => ItemKind::Static(ty, m, e),
6442 None => ItemKind::Const(ty, e),
6444 Ok((id, item, None))
6447 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6448 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6449 let (in_cfg, outer_attrs) = {
6450 let mut strip_unconfigured = crate::config::StripUnconfigured {
6452 features: None, // don't perform gated feature checking
6454 let mut outer_attrs = outer_attrs.to_owned();
6455 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
6456 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
6459 let id_span = self.span;
6460 let id = self.parse_ident()?;
6461 if self.eat(&token::Semi) {
6462 if in_cfg && self.recurse_into_file_modules {
6463 // This mod is in an external file. Let's go get it!
6464 let ModulePathSuccess { path, directory_ownership, warn } =
6465 self.submod_path(id, &outer_attrs, id_span)?;
6466 let (module, mut attrs) =
6467 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
6468 // Record that we fetched the mod from an external file
6470 let attr = Attribute {
6471 id: attr::mk_attr_id(),
6472 style: ast::AttrStyle::Outer,
6473 path: ast::Path::from_ident(
6474 Ident::with_empty_ctxt(sym::warn_directory_ownership)),
6475 tokens: TokenStream::empty(),
6476 is_sugared_doc: false,
6479 attr::mark_known(&attr);
6482 Ok((id, ItemKind::Mod(module), Some(attrs)))
6484 let placeholder = ast::Mod {
6489 Ok((id, ItemKind::Mod(placeholder), None))
6492 let old_directory = self.directory.clone();
6493 self.push_directory(id, &outer_attrs);
6495 self.expect(&token::OpenDelim(token::Brace))?;
6496 let mod_inner_lo = self.span;
6497 let attrs = self.parse_inner_attributes()?;
6498 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
6500 self.directory = old_directory;
6501 Ok((id, ItemKind::Mod(module), Some(attrs)))
6505 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
6506 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6507 self.directory.path.to_mut().push(&path.as_str());
6508 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
6510 // We have to push on the current module name in the case of relative
6511 // paths in order to ensure that any additional module paths from inline
6512 // `mod x { ... }` come after the relative extension.
6514 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
6515 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
6516 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
6517 if let Some(ident) = relative.take() { // remove the relative offset
6518 self.directory.path.to_mut().push(ident.as_str());
6521 self.directory.path.to_mut().push(&id.as_str());
6525 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
6526 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
6529 // On windows, the base path might have the form
6530 // `\\?\foo\bar` in which case it does not tolerate
6531 // mixed `/` and `\` separators, so canonicalize
6534 let s = s.replace("/", "\\");
6535 Some(dir_path.join(s))
6541 /// Returns a path to a module.
6542 pub fn default_submod_path(
6544 relative: Option<ast::Ident>,
6546 source_map: &SourceMap) -> ModulePath
6548 // If we're in a foo.rs file instead of a mod.rs file,
6549 // we need to look for submodules in
6550 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
6551 // `./<id>.rs` and `./<id>/mod.rs`.
6552 let relative_prefix_string;
6553 let relative_prefix = if let Some(ident) = relative {
6554 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
6555 &relative_prefix_string
6560 let mod_name = id.to_string();
6561 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
6562 let secondary_path_str = format!("{}{}{}mod.rs",
6563 relative_prefix, mod_name, path::MAIN_SEPARATOR);
6564 let default_path = dir_path.join(&default_path_str);
6565 let secondary_path = dir_path.join(&secondary_path_str);
6566 let default_exists = source_map.file_exists(&default_path);
6567 let secondary_exists = source_map.file_exists(&secondary_path);
6569 let result = match (default_exists, secondary_exists) {
6570 (true, false) => Ok(ModulePathSuccess {
6572 directory_ownership: DirectoryOwnership::Owned {
6577 (false, true) => Ok(ModulePathSuccess {
6578 path: secondary_path,
6579 directory_ownership: DirectoryOwnership::Owned {
6584 (false, false) => Err(Error::FileNotFoundForModule {
6585 mod_name: mod_name.clone(),
6586 default_path: default_path_str,
6587 secondary_path: secondary_path_str,
6588 dir_path: dir_path.display().to_string(),
6590 (true, true) => Err(Error::DuplicatePaths {
6591 mod_name: mod_name.clone(),
6592 default_path: default_path_str,
6593 secondary_path: secondary_path_str,
6599 path_exists: default_exists || secondary_exists,
6604 fn submod_path(&mut self,
6606 outer_attrs: &[Attribute],
6608 -> PResult<'a, ModulePathSuccess> {
6609 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
6610 return Ok(ModulePathSuccess {
6611 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
6612 // All `#[path]` files are treated as though they are a `mod.rs` file.
6613 // This means that `mod foo;` declarations inside `#[path]`-included
6614 // files are siblings,
6616 // Note that this will produce weirdness when a file named `foo.rs` is
6617 // `#[path]` included and contains a `mod foo;` declaration.
6618 // If you encounter this, it's your own darn fault :P
6619 Some(_) => DirectoryOwnership::Owned { relative: None },
6620 _ => DirectoryOwnership::UnownedViaMod(true),
6627 let relative = match self.directory.ownership {
6628 DirectoryOwnership::Owned { relative } => relative,
6629 DirectoryOwnership::UnownedViaBlock |
6630 DirectoryOwnership::UnownedViaMod(_) => None,
6632 let paths = Parser::default_submod_path(
6633 id, relative, &self.directory.path, self.sess.source_map());
6635 match self.directory.ownership {
6636 DirectoryOwnership::Owned { .. } => {
6637 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
6639 DirectoryOwnership::UnownedViaBlock => {
6641 "Cannot declare a non-inline module inside a block \
6642 unless it has a path attribute";
6643 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
6644 if paths.path_exists {
6645 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
6647 err.span_note(id_sp, &msg);
6651 DirectoryOwnership::UnownedViaMod(warn) => {
6653 if let Ok(result) = paths.result {
6654 return Ok(ModulePathSuccess { warn: true, ..result });
6657 let mut err = self.diagnostic().struct_span_err(id_sp,
6658 "cannot declare a new module at this location");
6659 if !id_sp.is_dummy() {
6660 let src_path = self.sess.source_map().span_to_filename(id_sp);
6661 if let FileName::Real(src_path) = src_path {
6662 if let Some(stem) = src_path.file_stem() {
6663 let mut dest_path = src_path.clone();
6664 dest_path.set_file_name(stem);
6665 dest_path.push("mod.rs");
6666 err.span_note(id_sp,
6667 &format!("maybe move this module `{}` to its own \
6668 directory via `{}`", src_path.display(),
6669 dest_path.display()));
6673 if paths.path_exists {
6674 err.span_note(id_sp,
6675 &format!("... or maybe `use` the module `{}` instead \
6676 of possibly redeclaring it",
6684 /// Reads a module from a source file.
6685 fn eval_src_mod(&mut self,
6687 directory_ownership: DirectoryOwnership,
6690 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
6691 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
6692 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
6693 let mut err = String::from("circular modules: ");
6694 let len = included_mod_stack.len();
6695 for p in &included_mod_stack[i.. len] {
6696 err.push_str(&p.to_string_lossy());
6697 err.push_str(" -> ");
6699 err.push_str(&path.to_string_lossy());
6700 return Err(self.span_fatal(id_sp, &err[..]));
6702 included_mod_stack.push(path.clone());
6703 drop(included_mod_stack);
6706 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
6707 p0.cfg_mods = self.cfg_mods;
6708 let mod_inner_lo = p0.span;
6709 let mod_attrs = p0.parse_inner_attributes()?;
6710 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
6712 self.sess.included_mod_stack.borrow_mut().pop();
6716 /// Parses a function declaration from a foreign module.
6717 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6718 -> PResult<'a, ForeignItem> {
6719 self.expect_keyword(kw::Fn)?;
6721 let (ident, mut generics) = self.parse_fn_header()?;
6722 let decl = self.parse_fn_decl(true)?;
6723 generics.where_clause = self.parse_where_clause()?;
6725 self.expect(&token::Semi)?;
6726 Ok(ast::ForeignItem {
6729 node: ForeignItemKind::Fn(decl, generics),
6730 id: ast::DUMMY_NODE_ID,
6736 /// Parses a static item from a foreign module.
6737 /// Assumes that the `static` keyword is already parsed.
6738 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6739 -> PResult<'a, ForeignItem> {
6740 let mutbl = self.parse_mutability();
6741 let ident = self.parse_ident()?;
6742 self.expect(&token::Colon)?;
6743 let ty = self.parse_ty()?;
6745 self.expect(&token::Semi)?;
6749 node: ForeignItemKind::Static(ty, mutbl),
6750 id: ast::DUMMY_NODE_ID,
6756 /// Parses a type from a foreign module.
6757 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
6758 -> PResult<'a, ForeignItem> {
6759 self.expect_keyword(kw::Type)?;
6761 let ident = self.parse_ident()?;
6763 self.expect(&token::Semi)?;
6764 Ok(ast::ForeignItem {
6767 node: ForeignItemKind::Ty,
6768 id: ast::DUMMY_NODE_ID,
6774 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
6775 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
6776 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
6778 let mut ident = if self.token.is_keyword(kw::SelfLower) {
6779 self.parse_path_segment_ident()
6783 let mut idents = vec![];
6784 let mut replacement = vec![];
6785 let mut fixed_crate_name = false;
6786 // Accept `extern crate name-like-this` for better diagnostics
6787 let dash = token::Token::BinOp(token::BinOpToken::Minus);
6788 if self.token == dash { // Do not include `-` as part of the expected tokens list
6789 while self.eat(&dash) {
6790 fixed_crate_name = true;
6791 replacement.push((self.prev_span, "_".to_string()));
6792 idents.push(self.parse_ident()?);
6795 if fixed_crate_name {
6796 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
6797 let mut fixed_name = format!("{}", ident.name);
6798 for part in idents {
6799 fixed_name.push_str(&format!("_{}", part.name));
6801 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
6803 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
6804 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
6805 err.multipart_suggestion(
6808 Applicability::MachineApplicable,
6815 /// Parses `extern crate` links.
6820 /// extern crate foo;
6821 /// extern crate bar as foo;
6823 fn parse_item_extern_crate(&mut self,
6825 visibility: Visibility,
6826 attrs: Vec<Attribute>)
6827 -> PResult<'a, P<Item>> {
6828 // Accept `extern crate name-like-this` for better diagnostics
6829 let orig_name = self.parse_crate_name_with_dashes()?;
6830 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
6831 (rename, Some(orig_name.name))
6835 self.expect(&token::Semi)?;
6837 let span = lo.to(self.prev_span);
6838 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
6841 /// Parses `extern` for foreign ABIs modules.
6843 /// `extern` is expected to have been
6844 /// consumed before calling this method.
6848 /// ```ignore (only-for-syntax-highlight)
6852 fn parse_item_foreign_mod(&mut self,
6854 opt_abi: Option<Abi>,
6855 visibility: Visibility,
6856 mut attrs: Vec<Attribute>)
6857 -> PResult<'a, P<Item>> {
6858 self.expect(&token::OpenDelim(token::Brace))?;
6860 let abi = opt_abi.unwrap_or(Abi::C);
6862 attrs.extend(self.parse_inner_attributes()?);
6864 let mut foreign_items = vec![];
6865 while !self.eat(&token::CloseDelim(token::Brace)) {
6866 foreign_items.push(self.parse_foreign_item()?);
6869 let prev_span = self.prev_span;
6870 let m = ast::ForeignMod {
6872 items: foreign_items
6874 let invalid = Ident::invalid();
6875 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
6878 /// Parses `type Foo = Bar;`
6880 /// `existential type Foo: Bar;`
6883 /// without modifying the parser state.
6884 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
6885 // This parses the grammar:
6886 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
6887 if self.check_keyword(kw::Type) ||
6888 self.check_keyword(kw::Existential) &&
6889 self.is_keyword_ahead(1, &[kw::Type]) {
6890 let existential = self.eat_keyword(kw::Existential);
6891 assert!(self.eat_keyword(kw::Type));
6892 Some(self.parse_existential_or_alias(existential))
6898 /// Parses a type alias or existential type.
6899 fn parse_existential_or_alias(
6902 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
6903 let ident = self.parse_ident()?;
6904 let mut tps = self.parse_generics()?;
6905 tps.where_clause = self.parse_where_clause()?;
6906 let alias = if existential {
6907 self.expect(&token::Colon)?;
6908 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6909 AliasKind::Existential(bounds)
6911 self.expect(&token::Eq)?;
6912 let ty = self.parse_ty()?;
6915 self.expect(&token::Semi)?;
6916 Ok((ident, alias, tps))
6919 /// Parses the part of an enum declaration following the `{`.
6920 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
6921 let mut variants = Vec::new();
6922 let mut any_disr = vec![];
6923 while self.token != token::CloseDelim(token::Brace) {
6924 let variant_attrs = self.parse_outer_attributes()?;
6925 let vlo = self.span;
6928 let mut disr_expr = None;
6930 let ident = self.parse_ident()?;
6931 if self.check(&token::OpenDelim(token::Brace)) {
6932 // Parse a struct variant.
6933 let (fields, recovered) = self.parse_record_struct_body()?;
6934 struct_def = VariantData::Struct(fields, recovered);
6935 } else if self.check(&token::OpenDelim(token::Paren)) {
6936 struct_def = VariantData::Tuple(
6937 self.parse_tuple_struct_body()?,
6940 } else if self.eat(&token::Eq) {
6941 disr_expr = Some(AnonConst {
6942 id: ast::DUMMY_NODE_ID,
6943 value: self.parse_expr()?,
6945 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
6948 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6950 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
6953 let vr = ast::Variant_ {
6955 id: ast::DUMMY_NODE_ID,
6956 attrs: variant_attrs,
6960 variants.push(respan(vlo.to(self.prev_span), vr));
6962 if !self.eat(&token::Comma) {
6963 if self.token.is_ident() && !self.token.is_reserved_ident() {
6964 let sp = self.sess.source_map().next_point(self.prev_span);
6965 let mut err = self.struct_span_err(sp, "missing comma");
6966 err.span_suggestion_short(
6970 Applicability::MaybeIncorrect,
6978 self.expect(&token::CloseDelim(token::Brace))?;
6979 self.maybe_report_invalid_custom_discriminants(any_disr, &variants);
6981 Ok(ast::EnumDef { variants })
6984 /// Parses an enum declaration.
6985 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
6986 let id = self.parse_ident()?;
6987 let mut generics = self.parse_generics()?;
6988 generics.where_clause = self.parse_where_clause()?;
6989 self.expect(&token::OpenDelim(token::Brace))?;
6991 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
6992 self.recover_stmt();
6993 self.eat(&token::CloseDelim(token::Brace));
6996 Ok((id, ItemKind::Enum(enum_definition, generics), None))
6999 /// Parses a string as an ABI spec on an extern type or module. Consumes
7000 /// the `extern` keyword, if one is found.
7001 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7003 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) |
7004 token::Literal(token::Lit { kind: token::StrRaw(..), symbol, suffix }) => {
7006 self.expect_no_suffix(sp, "an ABI spec", suffix);
7008 match abi::lookup(&symbol.as_str()) {
7009 Some(abi) => Ok(Some(abi)),
7011 let prev_span = self.prev_span;
7012 let mut err = struct_span_err!(
7013 self.sess.span_diagnostic,
7016 "invalid ABI: found `{}`",
7018 err.span_label(prev_span, "invalid ABI");
7019 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7030 fn is_static_global(&mut self) -> bool {
7031 if self.check_keyword(kw::Static) {
7032 // Check if this could be a closure
7033 !self.look_ahead(1, |token| {
7034 if token.is_keyword(kw::Move) {
7038 token::BinOp(token::Or) | token::OrOr => true,
7049 attrs: Vec<Attribute>,
7050 macros_allowed: bool,
7051 attributes_allowed: bool,
7052 ) -> PResult<'a, Option<P<Item>>> {
7053 let mut unclosed_delims = vec![];
7054 let (ret, tokens) = self.collect_tokens(|this| {
7055 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7056 unclosed_delims.append(&mut this.unclosed_delims);
7059 self.unclosed_delims.append(&mut unclosed_delims);
7061 // Once we've parsed an item and recorded the tokens we got while
7062 // parsing we may want to store `tokens` into the item we're about to
7063 // return. Note, though, that we specifically didn't capture tokens
7064 // related to outer attributes. The `tokens` field here may later be
7065 // used with procedural macros to convert this item back into a token
7066 // stream, but during expansion we may be removing attributes as we go
7069 // If we've got inner attributes then the `tokens` we've got above holds
7070 // these inner attributes. If an inner attribute is expanded we won't
7071 // actually remove it from the token stream, so we'll just keep yielding
7072 // it (bad!). To work around this case for now we just avoid recording
7073 // `tokens` if we detect any inner attributes. This should help keep
7074 // expansion correct, but we should fix this bug one day!
7077 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7078 i.tokens = Some(tokens);
7085 /// Parses one of the items allowed by the flags.
7086 fn parse_item_implementation(
7088 attrs: Vec<Attribute>,
7089 macros_allowed: bool,
7090 attributes_allowed: bool,
7091 ) -> PResult<'a, Option<P<Item>>> {
7092 maybe_whole!(self, NtItem, |item| {
7093 let mut item = item.into_inner();
7094 let mut attrs = attrs;
7095 mem::swap(&mut item.attrs, &mut attrs);
7096 item.attrs.extend(attrs);
7102 let visibility = self.parse_visibility(false)?;
7104 if self.eat_keyword(kw::Use) {
7106 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7107 self.expect(&token::Semi)?;
7109 let span = lo.to(self.prev_span);
7111 self.mk_item(span, Ident::invalid(), item_, visibility, attrs);
7112 return Ok(Some(item));
7115 if self.eat_keyword(kw::Extern) {
7116 if self.eat_keyword(kw::Crate) {
7117 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7120 let opt_abi = self.parse_opt_abi()?;
7122 if self.eat_keyword(kw::Fn) {
7123 // EXTERN FUNCTION ITEM
7124 let fn_span = self.prev_span;
7125 let abi = opt_abi.unwrap_or(Abi::C);
7126 let (ident, item_, extra_attrs) =
7127 self.parse_item_fn(Unsafety::Normal,
7128 respan(fn_span, IsAsync::NotAsync),
7129 respan(fn_span, Constness::NotConst),
7131 let prev_span = self.prev_span;
7132 let item = self.mk_item(lo.to(prev_span),
7136 maybe_append(attrs, extra_attrs));
7137 return Ok(Some(item));
7138 } else if self.check(&token::OpenDelim(token::Brace)) {
7139 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7145 if self.is_static_global() {
7148 let m = if self.eat_keyword(kw::Mut) {
7151 Mutability::Immutable
7153 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7154 let prev_span = self.prev_span;
7155 let item = self.mk_item(lo.to(prev_span),
7159 maybe_append(attrs, extra_attrs));
7160 return Ok(Some(item));
7162 if self.eat_keyword(kw::Const) {
7163 let const_span = self.prev_span;
7164 if self.check_keyword(kw::Fn)
7165 || (self.check_keyword(kw::Unsafe)
7166 && self.is_keyword_ahead(1, &[kw::Fn])) {
7167 // CONST FUNCTION ITEM
7168 let unsafety = self.parse_unsafety();
7170 let (ident, item_, extra_attrs) =
7171 self.parse_item_fn(unsafety,
7172 respan(const_span, IsAsync::NotAsync),
7173 respan(const_span, Constness::Const),
7175 let prev_span = self.prev_span;
7176 let item = self.mk_item(lo.to(prev_span),
7180 maybe_append(attrs, extra_attrs));
7181 return Ok(Some(item));
7185 if self.eat_keyword(kw::Mut) {
7186 let prev_span = self.prev_span;
7187 let mut err = self.diagnostic()
7188 .struct_span_err(prev_span, "const globals cannot be mutable");
7189 err.span_label(prev_span, "cannot be mutable");
7190 err.span_suggestion(
7192 "you might want to declare a static instead",
7193 "static".to_owned(),
7194 Applicability::MaybeIncorrect,
7198 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
7199 let prev_span = self.prev_span;
7200 let item = self.mk_item(lo.to(prev_span),
7204 maybe_append(attrs, extra_attrs));
7205 return Ok(Some(item));
7208 // `unsafe async fn` or `async fn`
7210 self.check_keyword(kw::Unsafe) &&
7211 self.is_keyword_ahead(1, &[kw::Async])
7213 self.check_keyword(kw::Async) &&
7214 self.is_keyword_ahead(1, &[kw::Fn])
7217 // ASYNC FUNCTION ITEM
7218 let unsafety = self.parse_unsafety();
7219 self.expect_keyword(kw::Async)?;
7220 let async_span = self.prev_span;
7221 self.expect_keyword(kw::Fn)?;
7222 let fn_span = self.prev_span;
7223 let (ident, item_, extra_attrs) =
7224 self.parse_item_fn(unsafety,
7225 respan(async_span, IsAsync::Async {
7226 closure_id: ast::DUMMY_NODE_ID,
7227 return_impl_trait_id: ast::DUMMY_NODE_ID,
7228 arguments: Vec::new(),
7230 respan(fn_span, Constness::NotConst),
7232 let prev_span = self.prev_span;
7233 let item = self.mk_item(lo.to(prev_span),
7237 maybe_append(attrs, extra_attrs));
7238 if self.span.rust_2015() {
7239 self.diagnostic().struct_span_err_with_code(
7241 "`async fn` is not permitted in the 2015 edition",
7242 DiagnosticId::Error("E0670".into())
7245 return Ok(Some(item));
7247 if self.check_keyword(kw::Unsafe) &&
7248 self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
7250 // UNSAFE TRAIT ITEM
7251 self.bump(); // `unsafe`
7252 let is_auto = if self.eat_keyword(kw::Trait) {
7255 self.expect_keyword(kw::Auto)?;
7256 self.expect_keyword(kw::Trait)?;
7259 let (ident, item_, extra_attrs) =
7260 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
7261 let prev_span = self.prev_span;
7262 let item = self.mk_item(lo.to(prev_span),
7266 maybe_append(attrs, extra_attrs));
7267 return Ok(Some(item));
7269 if self.check_keyword(kw::Impl) ||
7270 self.check_keyword(kw::Unsafe) &&
7271 self.is_keyword_ahead(1, &[kw::Impl]) ||
7272 self.check_keyword(kw::Default) &&
7273 self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe]) {
7275 let defaultness = self.parse_defaultness();
7276 let unsafety = self.parse_unsafety();
7277 self.expect_keyword(kw::Impl)?;
7278 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
7279 let span = lo.to(self.prev_span);
7280 return Ok(Some(self.mk_item(span, ident, item, visibility,
7281 maybe_append(attrs, extra_attrs))));
7283 if self.check_keyword(kw::Fn) {
7286 let fn_span = self.prev_span;
7287 let (ident, item_, extra_attrs) =
7288 self.parse_item_fn(Unsafety::Normal,
7289 respan(fn_span, IsAsync::NotAsync),
7290 respan(fn_span, Constness::NotConst),
7292 let prev_span = self.prev_span;
7293 let item = self.mk_item(lo.to(prev_span),
7297 maybe_append(attrs, extra_attrs));
7298 return Ok(Some(item));
7300 if self.check_keyword(kw::Unsafe)
7301 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
7302 // UNSAFE FUNCTION ITEM
7303 self.bump(); // `unsafe`
7304 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
7305 self.check(&token::OpenDelim(token::Brace));
7306 let abi = if self.eat_keyword(kw::Extern) {
7307 self.parse_opt_abi()?.unwrap_or(Abi::C)
7311 self.expect_keyword(kw::Fn)?;
7312 let fn_span = self.prev_span;
7313 let (ident, item_, extra_attrs) =
7314 self.parse_item_fn(Unsafety::Unsafe,
7315 respan(fn_span, IsAsync::NotAsync),
7316 respan(fn_span, Constness::NotConst),
7318 let prev_span = self.prev_span;
7319 let item = self.mk_item(lo.to(prev_span),
7323 maybe_append(attrs, extra_attrs));
7324 return Ok(Some(item));
7326 if self.eat_keyword(kw::Mod) {
7328 let (ident, item_, extra_attrs) =
7329 self.parse_item_mod(&attrs[..])?;
7330 let prev_span = self.prev_span;
7331 let item = self.mk_item(lo.to(prev_span),
7335 maybe_append(attrs, extra_attrs));
7336 return Ok(Some(item));
7338 if let Some(type_) = self.eat_type() {
7339 let (ident, alias, generics) = type_?;
7341 let item_ = match alias {
7342 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7343 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7345 let prev_span = self.prev_span;
7346 let item = self.mk_item(lo.to(prev_span),
7351 return Ok(Some(item));
7353 if self.eat_keyword(kw::Enum) {
7355 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7356 let prev_span = self.prev_span;
7357 let item = self.mk_item(lo.to(prev_span),
7361 maybe_append(attrs, extra_attrs));
7362 return Ok(Some(item));
7364 if self.check_keyword(kw::Trait)
7365 || (self.check_keyword(kw::Auto)
7366 && self.is_keyword_ahead(1, &[kw::Trait]))
7368 let is_auto = if self.eat_keyword(kw::Trait) {
7371 self.expect_keyword(kw::Auto)?;
7372 self.expect_keyword(kw::Trait)?;
7376 let (ident, item_, extra_attrs) =
7377 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7378 let prev_span = self.prev_span;
7379 let item = self.mk_item(lo.to(prev_span),
7383 maybe_append(attrs, extra_attrs));
7384 return Ok(Some(item));
7386 if self.eat_keyword(kw::Struct) {
7388 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7389 let prev_span = self.prev_span;
7390 let item = self.mk_item(lo.to(prev_span),
7394 maybe_append(attrs, extra_attrs));
7395 return Ok(Some(item));
7397 if self.is_union_item() {
7400 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7401 let prev_span = self.prev_span;
7402 let item = self.mk_item(lo.to(prev_span),
7406 maybe_append(attrs, extra_attrs));
7407 return Ok(Some(item));
7409 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7410 return Ok(Some(macro_def));
7413 // Verify whether we have encountered a struct or method definition where the user forgot to
7414 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7415 if visibility.node.is_pub() &&
7416 self.check_ident() &&
7417 self.look_ahead(1, |t| *t != token::Not)
7419 // Space between `pub` keyword and the identifier
7422 // ^^^ `sp` points here
7423 let sp = self.prev_span.between(self.span);
7424 let full_sp = self.prev_span.to(self.span);
7425 let ident_sp = self.span;
7426 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7427 // possible public struct definition where `struct` was forgotten
7428 let ident = self.parse_ident().unwrap();
7429 let msg = format!("add `struct` here to parse `{}` as a public struct",
7431 let mut err = self.diagnostic()
7432 .struct_span_err(sp, "missing `struct` for struct definition");
7433 err.span_suggestion_short(
7434 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7437 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7438 let ident = self.parse_ident().unwrap();
7440 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
7445 self.consume_block(token::Paren);
7446 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
7447 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
7449 ("fn", kw_name, false)
7450 } else if self.check(&token::OpenDelim(token::Brace)) {
7452 ("fn", kw_name, false)
7453 } else if self.check(&token::Colon) {
7457 ("fn` or `struct", "function or struct", true)
7460 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7461 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7463 self.consume_block(token::Brace);
7464 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
7468 err.span_suggestion_short(
7469 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
7472 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
7473 err.span_suggestion(
7475 "if you meant to call a macro, try",
7476 format!("{}!", snippet),
7477 // this is the `ambiguous` conditional branch
7478 Applicability::MaybeIncorrect
7481 err.help("if you meant to call a macro, remove the `pub` \
7482 and add a trailing `!` after the identifier");
7486 } else if self.look_ahead(1, |t| *t == token::Lt) {
7487 let ident = self.parse_ident().unwrap();
7488 self.eat_to_tokens(&[&token::Gt]);
7490 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
7491 if let Ok(Some(_)) = self.parse_self_arg() {
7492 ("fn", "method", false)
7494 ("fn", "function", false)
7496 } else if self.check(&token::OpenDelim(token::Brace)) {
7497 ("struct", "struct", false)
7499 ("fn` or `struct", "function or struct", true)
7501 let msg = format!("missing `{}` for {} definition", kw, kw_name);
7502 let mut err = self.diagnostic().struct_span_err(sp, &msg);
7504 err.span_suggestion_short(
7506 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
7507 format!(" {} ", kw),
7508 Applicability::MachineApplicable,
7514 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
7517 /// Parses a foreign item.
7518 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
7519 maybe_whole!(self, NtForeignItem, |ni| ni);
7521 let attrs = self.parse_outer_attributes()?;
7523 let visibility = self.parse_visibility(false)?;
7525 // FOREIGN STATIC ITEM
7526 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
7527 if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
7528 if self.token.is_keyword(kw::Const) {
7530 .struct_span_err(self.span, "extern items cannot be `const`")
7533 "try using a static value",
7534 "static".to_owned(),
7535 Applicability::MachineApplicable
7538 self.bump(); // `static` or `const`
7539 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
7541 // FOREIGN FUNCTION ITEM
7542 if self.check_keyword(kw::Fn) {
7543 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
7545 // FOREIGN TYPE ITEM
7546 if self.check_keyword(kw::Type) {
7547 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
7550 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
7554 ident: Ident::invalid(),
7555 span: lo.to(self.prev_span),
7556 id: ast::DUMMY_NODE_ID,
7559 node: ForeignItemKind::Macro(mac),
7564 if !attrs.is_empty() {
7565 self.expected_item_err(&attrs)?;
7573 /// This is the fall-through for parsing items.
7574 fn parse_macro_use_or_failure(
7576 attrs: Vec<Attribute> ,
7577 macros_allowed: bool,
7578 attributes_allowed: bool,
7580 visibility: Visibility
7581 ) -> PResult<'a, Option<P<Item>>> {
7582 if macros_allowed && self.token.is_path_start() &&
7583 !(self.is_async_fn() && self.span.rust_2015()) {
7584 // MACRO INVOCATION ITEM
7586 let prev_span = self.prev_span;
7587 self.complain_if_pub_macro(&visibility.node, prev_span);
7589 let mac_lo = self.span;
7592 let pth = self.parse_path(PathStyle::Mod)?;
7593 self.expect(&token::Not)?;
7595 // a 'special' identifier (like what `macro_rules!` uses)
7596 // is optional. We should eventually unify invoc syntax
7598 let id = if self.token.is_ident() {
7601 Ident::invalid() // no special identifier
7603 // eat a matched-delimiter token tree:
7604 let (delim, tts) = self.expect_delimited_token_tree()?;
7605 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
7606 self.report_invalid_macro_expansion_item();
7609 let hi = self.prev_span;
7610 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
7611 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
7612 return Ok(Some(item));
7615 // FAILURE TO PARSE ITEM
7616 match visibility.node {
7617 VisibilityKind::Inherited => {}
7619 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
7623 if !attributes_allowed && !attrs.is_empty() {
7624 self.expected_item_err(&attrs)?;
7629 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
7630 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
7631 at_end: &mut bool) -> PResult<'a, Option<Mac>>
7633 if self.token.is_path_start() &&
7634 !(self.is_async_fn() && self.span.rust_2015()) {
7635 let prev_span = self.prev_span;
7637 let pth = self.parse_path(PathStyle::Mod)?;
7639 if pth.segments.len() == 1 {
7640 if !self.eat(&token::Not) {
7641 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
7644 self.expect(&token::Not)?;
7647 if let Some(vis) = vis {
7648 self.complain_if_pub_macro(&vis.node, prev_span);
7653 // eat a matched-delimiter token tree:
7654 let (delim, tts) = self.expect_delimited_token_tree()?;
7655 if delim != MacDelimiter::Brace {
7656 self.expect(&token::Semi)?;
7659 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
7665 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
7666 where F: FnOnce(&mut Self) -> PResult<'a, R>
7668 // Record all tokens we parse when parsing this item.
7669 let mut tokens = Vec::new();
7670 let prev_collecting = match self.token_cursor.frame.last_token {
7671 LastToken::Collecting(ref mut list) => {
7672 Some(mem::replace(list, Vec::new()))
7674 LastToken::Was(ref mut last) => {
7675 tokens.extend(last.take());
7679 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
7680 let prev = self.token_cursor.stack.len();
7682 let last_token = if self.token_cursor.stack.len() == prev {
7683 &mut self.token_cursor.frame.last_token
7685 &mut self.token_cursor.stack[prev].last_token
7688 // Pull out the tokens that we've collected from the call to `f` above.
7689 let mut collected_tokens = match *last_token {
7690 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
7691 LastToken::Was(_) => panic!("our vector went away?"),
7694 // If we're not at EOF our current token wasn't actually consumed by
7695 // `f`, but it'll still be in our list that we pulled out. In that case
7697 let extra_token = if self.token != token::Eof {
7698 collected_tokens.pop()
7703 // If we were previously collecting tokens, then this was a recursive
7704 // call. In that case we need to record all the tokens we collected in
7705 // our parent list as well. To do that we push a clone of our stream
7706 // onto the previous list.
7707 match prev_collecting {
7709 list.extend(collected_tokens.iter().cloned());
7710 list.extend(extra_token);
7711 *last_token = LastToken::Collecting(list);
7714 *last_token = LastToken::Was(extra_token);
7718 Ok((ret?, TokenStream::new(collected_tokens)))
7721 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
7722 let attrs = self.parse_outer_attributes()?;
7723 self.parse_item_(attrs, true, false)
7727 fn is_import_coupler(&mut self) -> bool {
7728 self.check(&token::ModSep) &&
7729 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
7730 *t == token::BinOp(token::Star))
7733 /// Parses a `UseTree`.
7736 /// USE_TREE = [`::`] `*` |
7737 /// [`::`] `{` USE_TREE_LIST `}` |
7739 /// PATH `::` `{` USE_TREE_LIST `}` |
7740 /// PATH [`as` IDENT]
7742 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
7745 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
7746 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
7747 self.check(&token::BinOp(token::Star)) ||
7748 self.is_import_coupler() {
7749 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
7750 let mod_sep_ctxt = self.span.ctxt();
7751 if self.eat(&token::ModSep) {
7752 prefix.segments.push(
7753 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
7757 if self.eat(&token::BinOp(token::Star)) {
7760 UseTreeKind::Nested(self.parse_use_tree_list()?)
7763 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
7764 prefix = self.parse_path(PathStyle::Mod)?;
7766 if self.eat(&token::ModSep) {
7767 if self.eat(&token::BinOp(token::Star)) {
7770 UseTreeKind::Nested(self.parse_use_tree_list()?)
7773 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
7777 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
7780 /// Parses a `UseTreeKind::Nested(list)`.
7783 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
7785 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
7786 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
7787 &token::CloseDelim(token::Brace),
7788 SeqSep::trailing_allowed(token::Comma), |this| {
7789 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
7793 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
7794 if self.eat_keyword(kw::As) {
7795 self.parse_ident_or_underscore().map(Some)
7801 /// Parses a source module as a crate. This is the main entry point for the parser.
7802 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
7804 let krate = Ok(ast::Crate {
7805 attrs: self.parse_inner_attributes()?,
7806 module: self.parse_mod_items(&token::Eof, lo)?,
7807 span: lo.to(self.span),
7812 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
7813 let ret = match self.token {
7814 token::Literal(token::Lit { kind: token::Str, symbol, suffix }) =>
7815 (symbol, ast::StrStyle::Cooked, suffix),
7816 token::Literal(token::Lit { kind: token::StrRaw(n), symbol, suffix }) =>
7817 (symbol, ast::StrStyle::Raw(n), suffix),
7824 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
7825 match self.parse_optional_str() {
7826 Some((s, style, suf)) => {
7827 let sp = self.prev_span;
7828 self.expect_no_suffix(sp, "a string literal", suf);
7832 let msg = "expected string literal";
7833 let mut err = self.fatal(msg);
7834 err.span_label(self.span, msg);
7840 fn report_invalid_macro_expansion_item(&self) {
7841 self.struct_span_err(
7843 "macros that expand to items must be delimited with braces or followed by a semicolon",
7844 ).multipart_suggestion(
7845 "change the delimiters to curly braces",
7847 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
7848 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
7850 Applicability::MaybeIncorrect,
7852 self.sess.source_map.next_point(self.prev_span),
7855 Applicability::MaybeIncorrect,
7859 /// When lowering a `async fn` to the HIR, we need to move all of the arguments of the function
7860 /// into the generated closure so that they are dropped when the future is polled and not when
7863 /// The arguments of the function are replaced in HIR lowering with the arguments created by
7864 /// this function and the statements created here are inserted at the top of the closure body.
7865 fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
7866 // FIXME(davidtwco): This function should really live in the HIR lowering but because
7867 // the types constructed here need to be used in parts of resolve so that the correct
7868 // locals are considered upvars, it is currently easier for it to live here in the parser,
7869 // where it can be constructed once.
7870 if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
7871 for (index, input) in decl.inputs.iter_mut().enumerate() {
7872 let id = ast::DUMMY_NODE_ID;
7873 let span = input.pat.span;
7874 let desugared_span = self.sess.source_map()
7875 .mark_span_with_reason(CompilerDesugaringKind::Async, span, None);
7877 // Construct a name for our temporary argument.
7878 let name = format!("__arg{}", index);
7879 let ident = Ident::from_str(&name).gensym();
7881 // Check if this is a ident pattern, if so, we can optimize and avoid adding a
7882 // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
7884 let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
7885 PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
7886 // Simple patterns like this don't have a generated argument, but they are
7887 // moved into the closure with a statement, so any `mut` bindings on the
7888 // argument will be unused. This binding mode can't be removed, because
7889 // this would affect the input to procedural macros, but they can have
7890 // their span marked as being the result of a compiler desugaring so
7891 // that they aren't linted against.
7892 input.pat.span = desugared_span;
7894 (binding_mode, ident, true)
7896 _ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
7899 // Construct an argument representing `__argN: <ty>` to replace the argument of the
7900 // async function if it isn't a simple pattern.
7901 let arg = if is_simple_pattern {
7905 ty: input.ty.clone(),
7909 node: PatKind::Ident(
7910 BindingMode::ByValue(Mutability::Immutable), ident, None,
7912 span: desugared_span,
7914 source: ArgSource::AsyncFn(input.pat.clone()),
7918 // Construct a `let __argN = __argN;` statement to insert at the top of the
7919 // async closure. This makes sure that the argument is captured by the closure and
7920 // that the drop order is correct.
7921 let move_local = Local {
7924 node: PatKind::Ident(binding_mode, ident, None),
7925 span: desugared_span,
7927 // We explicitly do not specify the type for this statement. When the user's
7928 // argument type is `impl Trait` then this would require the
7929 // `impl_trait_in_bindings` feature to also be present for that same type to
7930 // be valid in this binding. At the time of writing (13 Mar 19),
7931 // `impl_trait_in_bindings` is not stable.
7935 node: ExprKind::Path(None, ast::Path {
7937 segments: vec![PathSegment { ident, id, args: None }],
7940 attrs: ThinVec::new(),
7944 attrs: ThinVec::new(),
7945 source: LocalSource::AsyncFn,
7948 // Construct a `let <pat> = __argN;` statement to insert at the top of the
7949 // async closure if this isn't a simple pattern.
7950 let pat_stmt = if is_simple_pattern {
7955 node: StmtKind::Local(P(Local {
7956 pat: input.pat.clone(),
7957 ..move_local.clone()
7963 let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
7964 arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
7970 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
7971 for unmatched in unclosed_delims.iter() {
7972 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
7973 "incorrect close delimiter: `{}`",
7974 pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
7976 err.span_label(unmatched.found_span, "incorrect close delimiter");
7977 if let Some(sp) = unmatched.candidate_span {
7978 err.span_label(sp, "close delimiter possibly meant for this");
7980 if let Some(sp) = unmatched.unclosed_span {
7981 err.span_label(sp, "un-closed delimiter");
7985 unclosed_delims.clear();