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::{keywords, sym, Symbol};
51 use errors::{Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
52 use rustc_target::spec::abi::{self, Abi};
54 Span, MultiSpan, BytePos, FileName,
55 hygiene::CompilerDesugaringKind,
57 use log::{debug, trace};
62 use std::path::{self, Path, PathBuf};
66 /// Whether the type alias or associated type is a concrete type or an existential type
68 /// Just a new name for the same type
70 /// Only trait impls of the type will be usable, not the actual type itself
71 Existential(GenericBounds),
75 struct Restrictions: u8 {
76 const STMT_EXPR = 1 << 0;
77 const NO_STRUCT_LITERAL = 1 << 1;
81 type ItemInfo = (Ident, ItemKind, Option<Vec<Attribute>>);
83 /// Specifies how to parse a path.
84 #[derive(Copy, Clone, PartialEq)]
86 /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
87 /// with something else. For example, in expressions `segment < ....` can be interpreted
88 /// as a comparison and `segment ( ....` can be interpreted as a function call.
89 /// In all such contexts the non-path interpretation is preferred by default for practical
90 /// reasons, but the path interpretation can be forced by the disambiguator `::`, e.g.
91 /// `x<y>` - comparisons, `x::<y>` - unambiguously a path.
93 /// In other contexts, notably in types, no ambiguity exists and paths can be written
94 /// without the disambiguator, e.g., `x<y>` - unambiguously a path.
95 /// Paths with disambiguators are still accepted, `x::<Y>` - unambiguously a path too.
97 /// A path with generic arguments disallowed, e.g., `foo::bar::Baz`, used in imports,
98 /// visibilities or attributes.
99 /// Technically, this variant is unnecessary and e.g., `Expr` can be used instead
100 /// (paths in "mod" contexts have to be checked later for absence of generic arguments
101 /// anyway, due to macros), but it is used to avoid weird suggestions about expected
102 /// tokens when something goes wrong.
106 #[derive(Clone, Copy, PartialEq, Debug)]
113 #[derive(Clone, Copy, PartialEq, Debug)]
119 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
120 /// dropped into the token stream, which happens while parsing the result of
121 /// macro expansion). Placement of these is not as complex as I feared it would
122 /// be. The important thing is to make sure that lookahead doesn't balk at
123 /// `token::Interpolated` tokens.
124 macro_rules! maybe_whole_expr {
126 if let token::Interpolated(nt) = &$p.token {
128 token::NtExpr(e) | token::NtLiteral(e) => {
133 token::NtPath(path) => {
134 let path = path.clone();
136 return Ok($p.mk_expr($p.span, ExprKind::Path(None, path), ThinVec::new()));
138 token::NtBlock(block) => {
139 let block = block.clone();
141 return Ok($p.mk_expr($p.span, ExprKind::Block(block, None), ThinVec::new()));
149 /// As maybe_whole_expr, but for things other than expressions
150 macro_rules! maybe_whole {
151 ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
152 if let token::Interpolated(nt) = &$p.token {
153 if let token::$constructor(x) = &**nt {
162 /// If the next tokens are ill-formed `$ty::` recover them as `<$ty>::`.
163 macro_rules! maybe_recover_from_interpolated_ty_qpath {
164 ($self: expr, $allow_qpath_recovery: expr) => {
165 if $allow_qpath_recovery && $self.look_ahead(1, |t| t == &token::ModSep) {
166 if let token::Interpolated(nt) = &$self.token {
167 if let token::NtTy(ty) = &**nt {
170 return $self.maybe_recover_from_bad_qpath_stage_2($self.prev_span, ty);
177 fn maybe_append(mut lhs: Vec<Attribute>, mut rhs: Option<Vec<Attribute>>) -> Vec<Attribute> {
178 if let Some(ref mut rhs) = rhs {
184 #[derive(Debug, Clone, Copy, PartialEq)]
196 /* ident is handled by common.rs */
199 pub struct Parser<'a> {
200 pub sess: &'a ParseSess,
201 /// the current token:
202 pub token: token::Token,
203 /// the span of the current token:
205 /// the span of the previous token:
206 meta_var_span: Option<Span>,
208 /// the previous token kind
209 prev_token_kind: PrevTokenKind,
210 restrictions: Restrictions,
211 /// Used to determine the path to externally loaded source files
212 crate directory: Directory<'a>,
213 /// Whether to parse sub-modules in other files.
214 pub recurse_into_file_modules: bool,
215 /// Name of the root module this parser originated from. If `None`, then the
216 /// name is not known. This does not change while the parser is descending
217 /// into modules, and sub-parsers have new values for this name.
218 pub root_module_name: Option<String>,
219 crate expected_tokens: Vec<TokenType>,
220 token_cursor: TokenCursor,
221 desugar_doc_comments: bool,
222 /// Whether we should configure out of line modules as we parse.
224 /// This field is used to keep track of how many left angle brackets we have seen. This is
225 /// required in order to detect extra leading left angle brackets (`<` characters) and error
228 /// See the comments in the `parse_path_segment` function for more details.
229 crate unmatched_angle_bracket_count: u32,
230 crate max_angle_bracket_count: u32,
231 /// List of all unclosed delimiters found by the lexer. If an entry is used for error recovery
232 /// it gets removed from here. Every entry left at the end gets emitted as an independent
234 crate unclosed_delims: Vec<UnmatchedBrace>,
235 last_unexpected_token_span: Option<Span>,
238 impl<'a> Drop for Parser<'a> {
240 let diag = self.diagnostic();
241 emit_unclosed_delims(&mut self.unclosed_delims, diag);
247 frame: TokenCursorFrame,
248 stack: Vec<TokenCursorFrame>,
252 struct TokenCursorFrame {
253 delim: token::DelimToken,
256 tree_cursor: tokenstream::Cursor,
258 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
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: syntax_pos::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(
355 [TokenTree::Token(sp, token::Ident(ast::Ident::from_str("doc"), false)),
356 TokenTree::Token(sp, token::Eq),
357 TokenTree::Token(sp, token::Literal(
358 token::StrRaw(Symbol::intern(&stripped), num_of_hashes), None))
360 .iter().cloned().collect::<TokenStream>().into(),
363 self.stack.push(mem::replace(&mut self.frame, TokenCursorFrame::new(
366 &if doc_comment_style(&name.as_str()) == AttrStyle::Inner {
367 [TokenTree::Token(sp, token::Pound), TokenTree::Token(sp, token::Not), body]
368 .iter().cloned().collect::<TokenStream>().into()
370 [TokenTree::Token(sp, token::Pound), body]
371 .iter().cloned().collect::<TokenStream>().into()
379 #[derive(Clone, PartialEq)]
380 crate enum TokenType {
382 Keyword(keywords::Keyword),
392 fn to_string(&self) -> String {
394 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
395 TokenType::Keyword(kw) => format!("`{}`", kw.name()),
396 TokenType::Operator => "an operator".to_string(),
397 TokenType::Lifetime => "lifetime".to_string(),
398 TokenType::Ident => "identifier".to_string(),
399 TokenType::Path => "path".to_string(),
400 TokenType::Type => "type".to_string(),
401 TokenType::Const => "const".to_string(),
406 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
407 /// `IDENT<<u8 as Trait>::AssocTy>`.
409 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
410 /// that `IDENT` is not the ident of a fn trait.
411 fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
412 t == &token::ModSep || t == &token::Lt ||
413 t == &token::BinOp(token::Shl)
416 /// Information about the path to a module.
417 pub struct ModulePath {
420 pub result: Result<ModulePathSuccess, Error>,
423 pub struct ModulePathSuccess {
425 pub directory_ownership: DirectoryOwnership,
430 FileNotFoundForModule {
432 default_path: String,
433 secondary_path: String,
438 default_path: String,
439 secondary_path: String,
442 InclusiveRangeWithNoEnd,
446 fn span_err<S: Into<MultiSpan>>(self,
448 handler: &errors::Handler) -> DiagnosticBuilder<'_> {
450 Error::FileNotFoundForModule { ref mod_name,
454 let mut err = struct_span_err!(handler, sp, E0583,
455 "file not found for module `{}`", mod_name);
456 err.help(&format!("name the file either {} or {} inside the directory \"{}\"",
462 Error::DuplicatePaths { ref mod_name, ref default_path, ref secondary_path } => {
463 let mut err = struct_span_err!(handler, sp, E0584,
464 "file for module `{}` found at both {} and {}",
468 err.help("delete or rename one of them to remove the ambiguity");
471 Error::UselessDocComment => {
472 let mut err = struct_span_err!(handler, sp, E0585,
473 "found a documentation comment that doesn't document anything");
474 err.help("doc comments must come before what they document, maybe a comment was \
475 intended with `//`?");
478 Error::InclusiveRangeWithNoEnd => {
479 let mut err = struct_span_err!(handler, sp, E0586,
480 "inclusive range with no end");
481 err.help("inclusive ranges must be bounded at the end (`..=b` or `a..=b`)");
491 AttributesParsed(ThinVec<Attribute>),
492 AlreadyParsed(P<Expr>),
495 impl From<Option<ThinVec<Attribute>>> for LhsExpr {
496 fn from(o: Option<ThinVec<Attribute>>) -> Self {
497 if let Some(attrs) = o {
498 LhsExpr::AttributesParsed(attrs)
500 LhsExpr::NotYetParsed
505 impl From<P<Expr>> for LhsExpr {
506 fn from(expr: P<Expr>) -> Self {
507 LhsExpr::AlreadyParsed(expr)
511 /// Creates a placeholder argument.
512 fn dummy_arg(span: Span) -> Arg {
513 let ident = Ident::new(keywords::Invalid.name(), span);
515 id: ast::DUMMY_NODE_ID,
516 node: PatKind::Ident(BindingMode::ByValue(Mutability::Immutable), ident, None),
522 id: ast::DUMMY_NODE_ID
524 Arg { ty: P(ty), pat: pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal }
527 #[derive(Copy, Clone, Debug)]
528 enum TokenExpectType {
533 impl<'a> Parser<'a> {
534 pub fn new(sess: &'a ParseSess,
536 directory: Option<Directory<'a>>,
537 recurse_into_file_modules: bool,
538 desugar_doc_comments: bool)
540 let mut parser = Parser {
542 token: token::Whitespace,
543 span: syntax_pos::DUMMY_SP,
544 prev_span: syntax_pos::DUMMY_SP,
546 prev_token_kind: PrevTokenKind::Other,
547 restrictions: Restrictions::empty(),
548 recurse_into_file_modules,
549 directory: Directory {
550 path: Cow::from(PathBuf::new()),
551 ownership: DirectoryOwnership::Owned { relative: None }
553 root_module_name: None,
554 expected_tokens: Vec::new(),
555 token_cursor: TokenCursor {
556 frame: TokenCursorFrame::new(
563 desugar_doc_comments,
565 unmatched_angle_bracket_count: 0,
566 max_angle_bracket_count: 0,
567 unclosed_delims: Vec::new(),
568 last_unexpected_token_span: None,
571 let tok = parser.next_tok();
572 parser.token = tok.tok;
573 parser.span = tok.sp;
575 if let Some(directory) = directory {
576 parser.directory = directory;
577 } else if !parser.span.is_dummy() {
578 if let FileName::Real(mut path) = sess.source_map().span_to_unmapped_path(parser.span) {
580 parser.directory.path = Cow::from(path);
584 parser.process_potential_macro_variable();
588 fn next_tok(&mut self) -> TokenAndSpan {
589 let mut next = if self.desugar_doc_comments {
590 self.token_cursor.next_desugared()
592 self.token_cursor.next()
594 if next.sp.is_dummy() {
595 // Tweak the location for better diagnostics, but keep syntactic context intact.
596 next.sp = self.prev_span.with_ctxt(next.sp.ctxt());
601 /// Converts the current token to a string using `self`'s reader.
602 pub fn this_token_to_string(&self) -> String {
603 pprust::token_to_string(&self.token)
606 fn token_descr(&self) -> Option<&'static str> {
607 Some(match &self.token {
608 t if t.is_special_ident() => "reserved identifier",
609 t if t.is_used_keyword() => "keyword",
610 t if t.is_unused_keyword() => "reserved keyword",
611 token::DocComment(..) => "doc comment",
616 crate fn this_token_descr(&self) -> String {
617 if let Some(prefix) = self.token_descr() {
618 format!("{} `{}`", prefix, self.this_token_to_string())
620 format!("`{}`", self.this_token_to_string())
624 crate fn unexpected<T>(&mut self) -> PResult<'a, T> {
625 match self.expect_one_of(&[], &[]) {
627 Ok(_) => unreachable!(),
631 /// Expects and consumes the token `t`. Signals an error if the next token is not `t`.
632 pub fn expect(&mut self, t: &token::Token) -> PResult<'a, bool /* recovered */> {
633 if self.expected_tokens.is_empty() {
634 if self.token == *t {
638 let token_str = pprust::token_to_string(t);
639 let this_token_str = self.this_token_descr();
640 let mut err = self.fatal(&format!("expected `{}`, found {}",
644 let sp = if self.token == token::Token::Eof {
645 // EOF, don't want to point at the following char, but rather the last token
648 self.sess.source_map().next_point(self.prev_span)
650 let label_exp = format!("expected `{}`", token_str);
651 match self.recover_closing_delimiter(&[t.clone()], err) {
654 return Ok(recovered);
657 let cm = self.sess.source_map();
658 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
659 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
660 // When the spans are in the same line, it means that the only content
661 // between them is whitespace, point only at the found token.
662 err.span_label(self.span, label_exp);
665 err.span_label(sp, label_exp);
666 err.span_label(self.span, "unexpected token");
672 self.expect_one_of(slice::from_ref(t), &[])
676 fn recover_closing_delimiter(
678 tokens: &[token::Token],
679 mut err: DiagnosticBuilder<'a>,
680 ) -> PResult<'a, bool> {
682 // we want to use the last closing delim that would apply
683 for (i, unmatched) in self.unclosed_delims.iter().enumerate().rev() {
684 if tokens.contains(&token::CloseDelim(unmatched.expected_delim))
685 && Some(self.span) > unmatched.unclosed_span
692 // Recover and assume that the detected unclosed delimiter was meant for
693 // this location. Emit the diagnostic and act as if the delimiter was
694 // present for the parser's sake.
696 // Don't attempt to recover from this unclosed delimiter more than once.
697 let unmatched = self.unclosed_delims.remove(pos);
698 let delim = TokenType::Token(token::CloseDelim(unmatched.expected_delim));
700 // We want to suggest the inclusion of the closing delimiter where it makes
701 // the most sense, which is immediately after the last token:
706 // | help: `)` may belong here (FIXME: #58270)
708 // unclosed delimiter
709 if let Some(sp) = unmatched.unclosed_span {
710 err.span_label(sp, "unclosed delimiter");
712 err.span_suggestion_short(
713 self.sess.source_map().next_point(self.prev_span),
714 &format!("{} may belong here", delim.to_string()),
716 Applicability::MaybeIncorrect,
719 self.expected_tokens.clear(); // reduce errors
726 /// Expect next token to be edible or inedible token. If edible,
727 /// then consume it; if inedible, then return without consuming
728 /// anything. Signal a fatal error if next token is unexpected.
729 pub fn expect_one_of(
731 edible: &[token::Token],
732 inedible: &[token::Token],
733 ) -> PResult<'a, bool /* recovered */> {
734 fn tokens_to_string(tokens: &[TokenType]) -> String {
735 let mut i = tokens.iter();
736 // This might be a sign we need a connect method on Iterator.
738 .map_or(String::new(), |t| t.to_string());
739 i.enumerate().fold(b, |mut b, (i, a)| {
740 if tokens.len() > 2 && i == tokens.len() - 2 {
742 } else if tokens.len() == 2 && i == tokens.len() - 2 {
747 b.push_str(&a.to_string());
751 if edible.contains(&self.token) {
754 } else if inedible.contains(&self.token) {
755 // leave it in the input
757 } else if self.last_unexpected_token_span == Some(self.span) {
760 let mut expected = edible.iter()
761 .map(|x| TokenType::Token(x.clone()))
762 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
763 .chain(self.expected_tokens.iter().cloned())
764 .collect::<Vec<_>>();
765 expected.sort_by_cached_key(|x| x.to_string());
767 let expect = tokens_to_string(&expected[..]);
768 let actual = self.this_token_to_string();
769 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
770 let short_expect = if expected.len() > 6 {
771 format!("{} possible tokens", expected.len())
775 (format!("expected one of {}, found `{}`", expect, actual),
776 (self.sess.source_map().next_point(self.prev_span),
777 format!("expected one of {} here", short_expect)))
778 } else if expected.is_empty() {
779 (format!("unexpected token: `{}`", actual),
780 (self.prev_span, "unexpected token after this".to_string()))
782 (format!("expected {}, found `{}`", expect, actual),
783 (self.sess.source_map().next_point(self.prev_span),
784 format!("expected {} here", expect)))
786 self.last_unexpected_token_span = Some(self.span);
787 let mut err = self.fatal(&msg_exp);
788 if self.token.is_ident_named("and") {
789 err.span_suggestion_short(
791 "use `&&` instead of `and` for the boolean operator",
793 Applicability::MaybeIncorrect,
796 if self.token.is_ident_named("or") {
797 err.span_suggestion_short(
799 "use `||` instead of `or` for the boolean operator",
801 Applicability::MaybeIncorrect,
804 let sp = if self.token == token::Token::Eof {
805 // This is EOF, don't want to point at the following char, but rather the last token
810 match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
811 TokenType::Token(t) => Some(t.clone()),
813 }).collect::<Vec<_>>(), err) {
816 return Ok(recovered);
820 let is_semi_suggestable = expected.iter().any(|t| match t {
821 TokenType::Token(token::Semi) => true, // we expect a `;` here
823 }) && ( // a `;` would be expected before the current keyword
824 self.token.is_keyword(keywords::Break) ||
825 self.token.is_keyword(keywords::Continue) ||
826 self.token.is_keyword(keywords::For) ||
827 self.token.is_keyword(keywords::If) ||
828 self.token.is_keyword(keywords::Let) ||
829 self.token.is_keyword(keywords::Loop) ||
830 self.token.is_keyword(keywords::Match) ||
831 self.token.is_keyword(keywords::Return) ||
832 self.token.is_keyword(keywords::While)
834 let cm = self.sess.source_map();
835 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
836 (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
837 // The spans are in different lines, expected `;` and found `let` or `return`.
838 // High likelihood that it is only a missing `;`.
839 err.span_suggestion_short(
841 "a semicolon may be missing here",
843 Applicability::MaybeIncorrect,
848 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
849 // When the spans are in the same line, it means that the only content between
850 // them is whitespace, point at the found token in that case:
852 // X | () => { syntax error };
853 // | ^^^^^ expected one of 8 possible tokens here
855 // instead of having:
857 // X | () => { syntax error };
858 // | -^^^^^ unexpected token
860 // | expected one of 8 possible tokens here
861 err.span_label(self.span, label_exp);
863 _ if self.prev_span == syntax_pos::DUMMY_SP => {
864 // Account for macro context where the previous span might not be
865 // available to avoid incorrect output (#54841).
866 err.span_label(self.span, "unexpected token");
869 err.span_label(sp, label_exp);
870 err.span_label(self.span, "unexpected token");
877 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
878 fn interpolated_or_expr_span(&self,
879 expr: PResult<'a, P<Expr>>)
880 -> PResult<'a, (Span, P<Expr>)> {
882 if self.prev_token_kind == PrevTokenKind::Interpolated {
890 fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
891 let mut err = self.struct_span_err(self.span,
892 &format!("expected identifier, found {}",
893 self.this_token_descr()));
894 if let token::Ident(ident, false) = &self.token {
895 if ident.is_raw_guess() {
898 "you can escape reserved keywords to use them as identifiers",
899 format!("r#{}", ident),
900 Applicability::MaybeIncorrect,
904 if let Some(token_descr) = self.token_descr() {
905 err.span_label(self.span, format!("expected identifier, found {}", token_descr));
907 err.span_label(self.span, "expected identifier");
908 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
913 Applicability::MachineApplicable,
920 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
921 self.parse_ident_common(true)
924 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
926 token::Ident(ident, _) => {
927 if self.token.is_reserved_ident() {
928 let mut err = self.expected_ident_found();
935 let span = self.span;
937 Ok(Ident::new(ident.name, span))
940 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
941 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
943 self.expected_ident_found()
949 /// Checks if the next token is `tok`, and returns `true` if so.
951 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
953 crate fn check(&mut self, tok: &token::Token) -> bool {
954 let is_present = self.token == *tok;
955 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
959 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
960 pub fn eat(&mut self, tok: &token::Token) -> bool {
961 let is_present = self.check(tok);
962 if is_present { self.bump() }
966 fn check_keyword(&mut self, kw: keywords::Keyword) -> bool {
967 self.expected_tokens.push(TokenType::Keyword(kw));
968 self.token.is_keyword(kw)
971 /// If the next token is the given keyword, eats it and returns
972 /// `true`. Otherwise, returns `false`.
973 pub fn eat_keyword(&mut self, kw: keywords::Keyword) -> bool {
974 if self.check_keyword(kw) {
982 fn eat_keyword_noexpect(&mut self, kw: keywords::Keyword) -> bool {
983 if self.token.is_keyword(kw) {
991 /// If the given word is not a keyword, signals an error.
992 /// If the next token is not the given word, signals an error.
993 /// Otherwise, eats it.
994 fn expect_keyword(&mut self, kw: keywords::Keyword) -> PResult<'a, ()> {
995 if !self.eat_keyword(kw) {
1002 fn check_ident(&mut self) -> bool {
1003 if self.token.is_ident() {
1006 self.expected_tokens.push(TokenType::Ident);
1011 fn check_path(&mut self) -> bool {
1012 if self.token.is_path_start() {
1015 self.expected_tokens.push(TokenType::Path);
1020 fn check_type(&mut self) -> bool {
1021 if self.token.can_begin_type() {
1024 self.expected_tokens.push(TokenType::Type);
1029 fn check_const_arg(&mut self) -> bool {
1030 if self.token.can_begin_const_arg() {
1033 self.expected_tokens.push(TokenType::Const);
1038 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
1039 /// and continues. If a `+` is not seen, returns `false`.
1041 /// This is used when token-splitting `+=` into `+`.
1042 /// See issue #47856 for an example of when this may occur.
1043 fn eat_plus(&mut self) -> bool {
1044 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1046 token::BinOp(token::Plus) => {
1050 token::BinOpEq(token::Plus) => {
1051 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1052 self.bump_with(token::Eq, span);
1060 /// Checks to see if the next token is either `+` or `+=`.
1061 /// Otherwise returns `false`.
1062 fn check_plus(&mut self) -> bool {
1063 if self.token.is_like_plus() {
1067 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1072 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
1073 /// `&` and continues. If an `&` is not seen, signals an error.
1074 fn expect_and(&mut self) -> PResult<'a, ()> {
1075 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
1077 token::BinOp(token::And) => {
1082 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1083 Ok(self.bump_with(token::BinOp(token::And), span))
1085 _ => self.unexpected()
1089 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
1090 /// `|` and continues. If an `|` is not seen, signals an error.
1091 fn expect_or(&mut self) -> PResult<'a, ()> {
1092 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
1094 token::BinOp(token::Or) => {
1099 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1100 Ok(self.bump_with(token::BinOp(token::Or), span))
1102 _ => self.unexpected()
1106 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
1107 literal::expect_no_suffix(sp, &self.sess.span_diagnostic, kind, suffix)
1110 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
1111 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
1112 /// and continue. If a `<` is not seen, returns false.
1114 /// This is meant to be used when parsing generics on a path to get the
1116 fn eat_lt(&mut self) -> bool {
1117 self.expected_tokens.push(TokenType::Token(token::Lt));
1118 let ate = match self.token {
1123 token::BinOp(token::Shl) => {
1124 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1125 self.bump_with(token::Lt, span);
1129 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1130 self.bump_with(token::BinOp(token::Minus), span);
1137 // See doc comment for `unmatched_angle_bracket_count`.
1138 self.unmatched_angle_bracket_count += 1;
1139 self.max_angle_bracket_count += 1;
1140 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
1146 fn expect_lt(&mut self) -> PResult<'a, ()> {
1154 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
1155 /// with a single `>` and continues. If a `>` is not seen, signals an error.
1156 fn expect_gt(&mut self) -> PResult<'a, ()> {
1157 self.expected_tokens.push(TokenType::Token(token::Gt));
1158 let ate = match self.token {
1163 token::BinOp(token::Shr) => {
1164 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1165 Some(self.bump_with(token::Gt, span))
1167 token::BinOpEq(token::Shr) => {
1168 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1169 Some(self.bump_with(token::Ge, span))
1172 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1173 Some(self.bump_with(token::Eq, span))
1180 // See doc comment for `unmatched_angle_bracket_count`.
1181 if self.unmatched_angle_bracket_count > 0 {
1182 self.unmatched_angle_bracket_count -= 1;
1183 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1188 None => self.unexpected(),
1192 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
1193 /// passes through any errors encountered. Used for error recovery.
1194 fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
1195 let handler = self.diagnostic();
1197 if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
1199 TokenExpectType::Expect,
1200 |p| Ok(p.parse_token_tree())) {
1201 handler.cancel(err);
1205 /// Parses a sequence, including the closing delimiter. The function
1206 /// `f` must consume tokens until reaching the next separator or
1207 /// closing bracket.
1208 pub fn parse_seq_to_end<T, F>(&mut self,
1212 -> PResult<'a, Vec<T>> where
1213 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1215 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1222 /// Parses a sequence, not including the closing delimiter. The function
1223 /// `f` must consume tokens until reaching the next separator or
1224 /// closing bracket.
1225 pub fn parse_seq_to_before_end<T, F>(
1230 ) -> PResult<'a, (Vec<T>, bool)>
1231 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1233 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
1236 fn parse_seq_to_before_tokens<T, F>(
1238 kets: &[&token::Token],
1240 expect: TokenExpectType,
1242 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
1243 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1245 let mut first = true;
1246 let mut recovered = false;
1248 while !kets.iter().any(|k| {
1250 TokenExpectType::Expect => self.check(k),
1251 TokenExpectType::NoExpect => self.token == **k,
1255 token::CloseDelim(..) | token::Eof => break,
1258 if let Some(ref t) = sep.sep {
1262 match self.expect(t) {
1269 // Attempt to keep parsing if it was a similar separator
1270 if let Some(ref tokens) = t.similar_tokens() {
1271 if tokens.contains(&self.token) {
1276 // Attempt to keep parsing if it was an omitted separator
1291 if sep.trailing_sep_allowed && kets.iter().any(|k| {
1293 TokenExpectType::Expect => self.check(k),
1294 TokenExpectType::NoExpect => self.token == **k,
1307 /// Parses a sequence, including the closing delimiter. The function
1308 /// `f` must consume tokens until reaching the next separator or
1309 /// closing bracket.
1310 fn parse_unspanned_seq<T, F>(
1316 ) -> PResult<'a, Vec<T>> where
1317 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1320 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1327 /// Advance the parser by one token
1328 pub fn bump(&mut self) {
1329 if self.prev_token_kind == PrevTokenKind::Eof {
1330 // Bumping after EOF is a bad sign, usually an infinite loop.
1331 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1334 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1336 // Record last token kind for possible error recovery.
1337 self.prev_token_kind = match self.token {
1338 token::DocComment(..) => PrevTokenKind::DocComment,
1339 token::Comma => PrevTokenKind::Comma,
1340 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1341 token::BinOp(token::Or) => PrevTokenKind::BitOr,
1342 token::Interpolated(..) => PrevTokenKind::Interpolated,
1343 token::Eof => PrevTokenKind::Eof,
1344 token::Ident(..) => PrevTokenKind::Ident,
1345 _ => PrevTokenKind::Other,
1348 let next = self.next_tok();
1349 self.span = next.sp;
1350 self.token = next.tok;
1351 self.expected_tokens.clear();
1352 // check after each token
1353 self.process_potential_macro_variable();
1356 /// Advance the parser using provided token as a next one. Use this when
1357 /// consuming a part of a token. For example a single `<` from `<<`.
1358 fn bump_with(&mut self, next: token::Token, span: Span) {
1359 self.prev_span = self.span.with_hi(span.lo());
1360 // It would be incorrect to record the kind of the current token, but
1361 // fortunately for tokens currently using `bump_with`, the
1362 // prev_token_kind will be of no use anyway.
1363 self.prev_token_kind = PrevTokenKind::Other;
1366 self.expected_tokens.clear();
1369 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1370 F: FnOnce(&token::Token) -> R,
1373 return f(&self.token)
1376 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1377 Some(tree) => match tree {
1378 TokenTree::Token(_, tok) => tok,
1379 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1381 None => token::CloseDelim(self.token_cursor.frame.delim),
1385 crate fn look_ahead_span(&self, dist: usize) -> Span {
1390 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1391 Some(TokenTree::Token(span, _)) => span,
1392 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1393 None => self.look_ahead_span(dist - 1),
1396 pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
1397 self.sess.span_diagnostic.struct_span_fatal(self.span, m)
1399 pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1400 self.sess.span_diagnostic.struct_span_fatal(sp, m)
1402 fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
1403 err.span_err(sp, self.diagnostic())
1405 fn bug(&self, m: &str) -> ! {
1406 self.sess.span_diagnostic.span_bug(self.span, m)
1408 fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
1409 self.sess.span_diagnostic.span_err(sp, m)
1411 crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1412 self.sess.span_diagnostic.struct_span_err(sp, m)
1414 crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
1415 self.sess.span_diagnostic.span_bug(sp, m)
1418 fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
1419 self.sess.span_diagnostic.cancel(err)
1422 crate fn diagnostic(&self) -> &'a errors::Handler {
1423 &self.sess.span_diagnostic
1426 /// Is the current token one of the keywords that signals a bare function type?
1427 fn token_is_bare_fn_keyword(&mut self) -> bool {
1428 self.check_keyword(keywords::Fn) ||
1429 self.check_keyword(keywords::Unsafe) ||
1430 self.check_keyword(keywords::Extern)
1433 /// Parses a `TyKind::BareFn` type.
1434 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1437 [unsafe] [extern "ABI"] fn (S) -> T
1447 let unsafety = self.parse_unsafety();
1448 let abi = if self.eat_keyword(keywords::Extern) {
1449 self.parse_opt_abi()?.unwrap_or(Abi::C)
1454 self.expect_keyword(keywords::Fn)?;
1455 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1456 let ret_ty = self.parse_ret_ty(false)?;
1457 let decl = P(FnDecl {
1462 Ok(TyKind::BareFn(P(BareFnTy {
1470 /// Parses asyncness: `async` or nothing.
1471 fn parse_asyncness(&mut self) -> IsAsync {
1472 if self.eat_keyword(keywords::Async) {
1474 closure_id: ast::DUMMY_NODE_ID,
1475 return_impl_trait_id: ast::DUMMY_NODE_ID,
1476 arguments: Vec::new(),
1483 /// Parses unsafety: `unsafe` or nothing.
1484 fn parse_unsafety(&mut self) -> Unsafety {
1485 if self.eat_keyword(keywords::Unsafe) {
1492 /// Parses the items in a trait declaration.
1493 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1494 maybe_whole!(self, NtTraitItem, |x| x);
1495 let attrs = self.parse_outer_attributes()?;
1496 let mut unclosed_delims = vec![];
1497 let (mut item, tokens) = self.collect_tokens(|this| {
1498 let item = this.parse_trait_item_(at_end, attrs);
1499 unclosed_delims.append(&mut this.unclosed_delims);
1502 self.unclosed_delims.append(&mut unclosed_delims);
1503 // See `parse_item` for why this clause is here.
1504 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1505 item.tokens = Some(tokens);
1510 fn parse_trait_item_(&mut self,
1512 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1515 let (name, node, generics) = if self.eat_keyword(keywords::Type) {
1516 self.parse_trait_item_assoc_ty()?
1517 } else if self.is_const_item() {
1518 self.expect_keyword(keywords::Const)?;
1519 let ident = self.parse_ident()?;
1520 self.expect(&token::Colon)?;
1521 let ty = self.parse_ty()?;
1522 let default = if self.eat(&token::Eq) {
1523 let expr = self.parse_expr()?;
1524 self.expect(&token::Semi)?;
1527 self.expect(&token::Semi)?;
1530 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1531 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1532 // trait item macro.
1533 (keywords::Invalid.ident(), ast::TraitItemKind::Macro(mac), ast::Generics::default())
1535 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
1537 let ident = self.parse_ident()?;
1538 let mut generics = self.parse_generics()?;
1540 let mut decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1541 // This is somewhat dubious; We don't want to allow
1542 // argument names to be left off if there is a
1545 // We don't allow argument names to be left off in edition 2018.
1546 p.parse_arg_general(p.span.rust_2018(), true, false)
1548 generics.where_clause = self.parse_where_clause()?;
1549 self.construct_async_arguments(&mut asyncness, &mut decl);
1551 let sig = ast::MethodSig {
1561 let body = match self.token {
1565 debug!("parse_trait_methods(): parsing required method");
1568 token::OpenDelim(token::Brace) => {
1569 debug!("parse_trait_methods(): parsing provided method");
1571 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1572 attrs.extend(inner_attrs.iter().cloned());
1575 token::Interpolated(ref nt) => {
1577 token::NtBlock(..) => {
1579 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1580 attrs.extend(inner_attrs.iter().cloned());
1584 let token_str = self.this_token_descr();
1585 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1587 err.span_label(self.span, "expected `;` or `{`");
1593 let token_str = self.this_token_descr();
1594 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1596 err.span_label(self.span, "expected `;` or `{`");
1600 (ident, ast::TraitItemKind::Method(sig, body), generics)
1604 id: ast::DUMMY_NODE_ID,
1609 span: lo.to(self.prev_span),
1614 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1615 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1616 if self.eat(&token::RArrow) {
1617 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1619 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1624 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1625 self.parse_ty_common(true, true, false)
1628 /// Parses a type in restricted contexts where `+` is not permitted.
1630 /// Example 1: `&'a TYPE`
1631 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1632 /// Example 2: `value1 as TYPE + value2`
1633 /// `+` is prohibited to avoid interactions with expression grammar.
1634 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1635 self.parse_ty_common(false, true, false)
1638 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1639 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1640 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1641 maybe_whole!(self, NtTy, |x| x);
1644 let mut impl_dyn_multi = false;
1645 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1646 // `(TYPE)` is a parenthesized type.
1647 // `(TYPE,)` is a tuple with a single field of type TYPE.
1648 let mut ts = vec![];
1649 let mut last_comma = false;
1650 while self.token != token::CloseDelim(token::Paren) {
1651 ts.push(self.parse_ty()?);
1652 if self.eat(&token::Comma) {
1659 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1660 self.expect(&token::CloseDelim(token::Paren))?;
1662 if ts.len() == 1 && !last_comma {
1663 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1664 let maybe_bounds = allow_plus && self.token.is_like_plus();
1666 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1667 TyKind::Path(None, ref path) if maybe_bounds => {
1668 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1670 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1671 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1672 let path = match bounds[0] {
1673 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1674 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1676 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1679 _ => TyKind::Paren(P(ty))
1684 } else if self.eat(&token::Not) {
1687 } else if self.eat(&token::BinOp(token::Star)) {
1689 TyKind::Ptr(self.parse_ptr()?)
1690 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1692 let t = self.parse_ty()?;
1693 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1694 let t = match self.maybe_parse_fixed_length_of_vec()? {
1695 None => TyKind::Slice(t),
1696 Some(length) => TyKind::Array(t, AnonConst {
1697 id: ast::DUMMY_NODE_ID,
1701 self.expect(&token::CloseDelim(token::Bracket))?;
1703 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1706 self.parse_borrowed_pointee()?
1707 } else if self.eat_keyword_noexpect(keywords::Typeof) {
1709 // In order to not be ambiguous, the type must be surrounded by parens.
1710 self.expect(&token::OpenDelim(token::Paren))?;
1712 id: ast::DUMMY_NODE_ID,
1713 value: self.parse_expr()?,
1715 self.expect(&token::CloseDelim(token::Paren))?;
1717 } else if self.eat_keyword(keywords::Underscore) {
1718 // A type to be inferred `_`
1720 } else if self.token_is_bare_fn_keyword() {
1721 // Function pointer type
1722 self.parse_ty_bare_fn(Vec::new())?
1723 } else if self.check_keyword(keywords::For) {
1724 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1725 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1726 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1728 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1729 if self.token_is_bare_fn_keyword() {
1730 self.parse_ty_bare_fn(lifetime_defs)?
1732 let path = self.parse_path(PathStyle::Type)?;
1733 let parse_plus = allow_plus && self.check_plus();
1734 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1736 } else if self.eat_keyword(keywords::Impl) {
1737 // Always parse bounds greedily for better error recovery.
1738 let bounds = self.parse_generic_bounds(None)?;
1739 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1740 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1741 } else if self.check_keyword(keywords::Dyn) &&
1742 (self.span.rust_2018() ||
1743 self.look_ahead(1, |t| t.can_begin_bound() &&
1744 !can_continue_type_after_non_fn_ident(t))) {
1745 self.bump(); // `dyn`
1746 // Always parse bounds greedily for better error recovery.
1747 let bounds = self.parse_generic_bounds(None)?;
1748 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1749 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1750 } else if self.check(&token::Question) ||
1751 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1752 // Bound list (trait object type)
1753 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1754 TraitObjectSyntax::None)
1755 } else if self.eat_lt() {
1757 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1758 TyKind::Path(Some(qself), path)
1759 } else if self.token.is_path_start() {
1761 let path = self.parse_path(PathStyle::Type)?;
1762 if self.eat(&token::Not) {
1763 // Macro invocation in type position
1764 let (delim, tts) = self.expect_delimited_token_tree()?;
1765 let node = Mac_ { path, tts, delim };
1766 TyKind::Mac(respan(lo.to(self.prev_span), node))
1768 // Just a type path or bound list (trait object type) starting with a trait.
1770 // `Trait1 + Trait2 + 'a`
1771 if allow_plus && self.check_plus() {
1772 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1774 TyKind::Path(None, path)
1777 } else if self.check(&token::DotDotDot) {
1778 if allow_c_variadic {
1779 self.eat(&token::DotDotDot);
1782 return Err(self.fatal(
1783 "only foreign functions are allowed to be C-variadic"
1787 let msg = format!("expected type, found {}", self.this_token_descr());
1788 return Err(self.fatal(&msg));
1791 let span = lo.to(self.prev_span);
1792 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1794 // Try to recover from use of `+` with incorrect priority.
1795 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1796 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1797 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1800 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1801 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1802 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1803 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1805 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1806 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1808 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1811 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1812 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1813 let mutbl = self.parse_mutability();
1814 let ty = self.parse_ty_no_plus()?;
1815 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1818 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1819 let mutbl = if self.eat_keyword(keywords::Mut) {
1821 } else if self.eat_keyword(keywords::Const) {
1822 Mutability::Immutable
1824 let span = self.prev_span;
1825 let msg = "expected mut or const in raw pointer type";
1826 self.struct_span_err(span, msg)
1827 .span_label(span, msg)
1828 .help("use `*mut T` or `*const T` as appropriate")
1830 Mutability::Immutable
1832 let t = self.parse_ty_no_plus()?;
1833 Ok(MutTy { ty: t, mutbl: mutbl })
1836 fn is_named_argument(&self) -> bool {
1837 let offset = match self.token {
1838 token::Interpolated(ref nt) => match **nt {
1839 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1842 token::BinOp(token::And) | token::AndAnd => 1,
1843 _ if self.token.is_keyword(keywords::Mut) => 1,
1847 self.look_ahead(offset, |t| t.is_ident()) &&
1848 self.look_ahead(offset + 1, |t| t == &token::Colon)
1851 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1853 fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
1854 if let token::DocComment(_) = self.token {
1855 let mut err = self.diagnostic().struct_span_err(
1857 &format!("documentation comments cannot be applied to {}", applied_to),
1859 err.span_label(self.span, "doc comments are not allowed here");
1862 } else if self.token == token::Pound && self.look_ahead(1, |t| {
1863 *t == token::OpenDelim(token::Bracket)
1866 // Skip every token until next possible arg.
1867 while self.token != token::CloseDelim(token::Bracket) {
1870 let sp = lo.to(self.span);
1872 let mut err = self.diagnostic().struct_span_err(
1874 &format!("attributes cannot be applied to {}", applied_to),
1876 err.span_label(sp, "attributes are not allowed here");
1881 /// This version of parse arg doesn't necessarily require identifier names.
1882 fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool,
1883 allow_c_variadic: bool) -> PResult<'a, Arg> {
1884 if let Ok(Some(_)) = self.parse_self_arg() {
1885 let mut err = self.struct_span_err(self.prev_span,
1886 "unexpected `self` argument in function");
1887 err.span_label(self.prev_span,
1888 "`self` is only valid as the first argument of an associated function");
1892 let (pat, ty) = if require_name || self.is_named_argument() {
1893 debug!("parse_arg_general parse_pat (require_name:{})",
1895 self.eat_incorrect_doc_comment("method arguments");
1896 let pat = self.parse_pat(Some("argument name"))?;
1898 if let Err(mut err) = self.expect(&token::Colon) {
1899 // If we find a pattern followed by an identifier, it could be an (incorrect)
1900 // C-style parameter declaration.
1901 if self.check_ident() && self.look_ahead(1, |t| {
1902 *t == token::Comma || *t == token::CloseDelim(token::Paren)
1904 let ident = self.parse_ident().unwrap();
1905 let span = pat.span.with_hi(ident.span.hi());
1907 err.span_suggestion(
1909 "declare the type after the parameter binding",
1910 String::from("<identifier>: <type>"),
1911 Applicability::HasPlaceholders,
1913 } else if require_name && is_trait_item {
1914 if let PatKind::Ident(_, ident, _) = pat.node {
1915 err.span_suggestion(
1917 "explicitly ignore parameter",
1918 format!("_: {}", ident),
1919 Applicability::MachineApplicable,
1923 err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
1929 self.eat_incorrect_doc_comment("a method argument's type");
1930 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1932 debug!("parse_arg_general ident_to_pat");
1933 let parser_snapshot_before_ty = self.clone();
1934 self.eat_incorrect_doc_comment("a method argument's type");
1935 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1936 if ty.is_ok() && self.token != token::Comma &&
1937 self.token != token::CloseDelim(token::Paren) {
1938 // This wasn't actually a type, but a pattern looking like a type,
1939 // so we are going to rollback and re-parse for recovery.
1940 ty = self.unexpected();
1944 let ident = Ident::new(keywords::Invalid.name(), self.prev_span);
1946 id: ast::DUMMY_NODE_ID,
1947 node: PatKind::Ident(
1948 BindingMode::ByValue(Mutability::Immutable), ident, None),
1954 // If this is a C-variadic argument and we hit an error, return the
1956 if self.token == token::DotDotDot {
1959 // Recover from attempting to parse the argument as a type without pattern.
1961 mem::replace(self, parser_snapshot_before_ty);
1962 let pat = self.parse_pat(Some("argument name"))?;
1963 self.expect(&token::Colon)?;
1964 let ty = self.parse_ty()?;
1966 let mut err = self.diagnostic().struct_span_err_with_code(
1968 "patterns aren't allowed in methods without bodies",
1969 DiagnosticId::Error("E0642".into()),
1971 err.span_suggestion_short(
1973 "give this argument a name or use an underscore to ignore it",
1975 Applicability::MachineApplicable,
1979 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
1981 node: PatKind::Wild,
1983 id: ast::DUMMY_NODE_ID
1990 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal })
1993 /// Parses a single function argument.
1994 crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
1995 self.parse_arg_general(true, false, false)
1998 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1999 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
2000 let pat = self.parse_pat(Some("argument name"))?;
2001 let t = if self.eat(&token::Colon) {
2005 id: ast::DUMMY_NODE_ID,
2006 node: TyKind::Infer,
2007 span: self.prev_span,
2013 id: ast::DUMMY_NODE_ID,
2014 source: ast::ArgSource::Normal,
2018 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
2019 if self.eat(&token::Semi) {
2020 Ok(Some(self.parse_expr()?))
2026 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
2027 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
2028 maybe_whole_expr!(self);
2030 let minus_lo = self.span;
2031 let minus_present = self.eat(&token::BinOp(token::Minus));
2033 let literal = self.parse_lit()?;
2034 let hi = self.prev_span;
2035 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
2038 let minus_hi = self.prev_span;
2039 let unary = self.mk_unary(UnOp::Neg, expr);
2040 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
2046 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
2048 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
2049 let span = self.span;
2051 Ok(Ident::new(ident.name, span))
2053 _ => self.parse_ident(),
2057 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
2059 token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
2060 let span = self.span;
2062 Ok(Ident::new(ident.name, span))
2064 _ => self.parse_ident(),
2068 /// Parses a qualified path.
2069 /// Assumes that the leading `<` has been parsed already.
2071 /// `qualified_path = <type [as trait_ref]>::path`
2076 /// `<T as U>::F::a<S>` (without disambiguator)
2077 /// `<T as U>::F::a::<S>` (with disambiguator)
2078 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
2079 let lo = self.prev_span;
2080 let ty = self.parse_ty()?;
2082 // `path` will contain the prefix of the path up to the `>`,
2083 // if any (e.g., `U` in the `<T as U>::*` examples
2084 // above). `path_span` has the span of that path, or an empty
2085 // span in the case of something like `<T>::Bar`.
2086 let (mut path, path_span);
2087 if self.eat_keyword(keywords::As) {
2088 let path_lo = self.span;
2089 path = self.parse_path(PathStyle::Type)?;
2090 path_span = path_lo.to(self.prev_span);
2092 path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
2093 path_span = self.span.to(self.span);
2096 // See doc comment for `unmatched_angle_bracket_count`.
2097 self.expect(&token::Gt)?;
2098 if self.unmatched_angle_bracket_count > 0 {
2099 self.unmatched_angle_bracket_count -= 1;
2100 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
2103 self.expect(&token::ModSep)?;
2105 let qself = QSelf { ty, path_span, position: path.segments.len() };
2106 self.parse_path_segments(&mut path.segments, style)?;
2108 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
2111 /// Parses simple paths.
2113 /// `path = [::] segment+`
2114 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
2117 /// `a::b::C<D>` (without disambiguator)
2118 /// `a::b::C::<D>` (with disambiguator)
2119 /// `Fn(Args)` (without disambiguator)
2120 /// `Fn::(Args)` (with disambiguator)
2121 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2122 maybe_whole!(self, NtPath, |path| {
2123 if style == PathStyle::Mod &&
2124 path.segments.iter().any(|segment| segment.args.is_some()) {
2125 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
2130 let lo = self.meta_var_span.unwrap_or(self.span);
2131 let mut segments = Vec::new();
2132 let mod_sep_ctxt = self.span.ctxt();
2133 if self.eat(&token::ModSep) {
2134 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
2136 self.parse_path_segments(&mut segments, style)?;
2138 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
2141 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
2142 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
2144 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2145 let meta_ident = match self.token {
2146 token::Interpolated(ref nt) => match **nt {
2147 token::NtMeta(ref meta) => match meta.node {
2148 ast::MetaItemKind::Word => Some(meta.path.clone()),
2155 if let Some(path) = meta_ident {
2159 self.parse_path(style)
2162 crate fn parse_path_segments(&mut self,
2163 segments: &mut Vec<PathSegment>,
2165 -> PResult<'a, ()> {
2167 let segment = self.parse_path_segment(style)?;
2168 if style == PathStyle::Expr {
2169 // In order to check for trailing angle brackets, we must have finished
2170 // recursing (`parse_path_segment` can indirectly call this function),
2171 // that is, the next token must be the highlighted part of the below example:
2173 // `Foo::<Bar as Baz<T>>::Qux`
2176 // As opposed to the below highlight (if we had only finished the first
2179 // `Foo::<Bar as Baz<T>>::Qux`
2182 // `PathStyle::Expr` is only provided at the root invocation and never in
2183 // `parse_path_segment` to recurse and therefore can be checked to maintain
2185 self.check_trailing_angle_brackets(&segment, token::ModSep);
2187 segments.push(segment);
2189 if self.is_import_coupler() || !self.eat(&token::ModSep) {
2195 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
2196 let ident = self.parse_path_segment_ident()?;
2198 let is_args_start = |token: &token::Token| match *token {
2199 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
2200 | token::LArrow => true,
2203 let check_args_start = |this: &mut Self| {
2204 this.expected_tokens.extend_from_slice(
2205 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
2207 is_args_start(&this.token)
2210 Ok(if style == PathStyle::Type && check_args_start(self) ||
2211 style != PathStyle::Mod && self.check(&token::ModSep)
2212 && self.look_ahead(1, |t| is_args_start(t)) {
2213 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
2214 // it isn't, then we reset the unmatched angle bracket count as we're about to start
2215 // parsing a new path.
2216 if style == PathStyle::Expr {
2217 self.unmatched_angle_bracket_count = 0;
2218 self.max_angle_bracket_count = 0;
2221 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
2222 self.eat(&token::ModSep);
2224 let args = if self.eat_lt() {
2226 let (args, bindings) =
2227 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
2229 let span = lo.to(self.prev_span);
2230 AngleBracketedArgs { args, bindings, span }.into()
2234 let (inputs, recovered) = self.parse_seq_to_before_tokens(
2235 &[&token::CloseDelim(token::Paren)],
2236 SeqSep::trailing_allowed(token::Comma),
2237 TokenExpectType::Expect,
2242 let span = lo.to(self.prev_span);
2243 let output = if self.eat(&token::RArrow) {
2244 Some(self.parse_ty_common(false, false, false)?)
2248 ParenthesizedArgs { inputs, output, span }.into()
2251 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
2253 // Generic arguments are not found.
2254 PathSegment::from_ident(ident)
2258 crate fn check_lifetime(&mut self) -> bool {
2259 self.expected_tokens.push(TokenType::Lifetime);
2260 self.token.is_lifetime()
2263 /// Parses a single lifetime `'a` or panics.
2264 crate fn expect_lifetime(&mut self) -> Lifetime {
2265 if let Some(ident) = self.token.lifetime() {
2266 let span = self.span;
2268 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
2270 self.span_bug(self.span, "not a lifetime")
2274 fn eat_label(&mut self) -> Option<Label> {
2275 if let Some(ident) = self.token.lifetime() {
2276 let span = self.span;
2278 Some(Label { ident: Ident::new(ident.name, span) })
2284 /// Parses mutability (`mut` or nothing).
2285 fn parse_mutability(&mut self) -> Mutability {
2286 if self.eat_keyword(keywords::Mut) {
2289 Mutability::Immutable
2293 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
2294 if let token::Literal(token::Integer(name), suffix) = self.token {
2295 self.expect_no_suffix(self.span, "a tuple index", suffix);
2297 Ok(Ident::new(name, self.prev_span))
2299 self.parse_ident_common(false)
2303 /// Parse ident (COLON expr)?
2304 fn parse_field(&mut self) -> PResult<'a, Field> {
2305 let attrs = self.parse_outer_attributes()?;
2308 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2309 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
2310 t == &token::Colon || t == &token::Eq
2312 let fieldname = self.parse_field_name()?;
2314 // Check for an equals token. This means the source incorrectly attempts to
2315 // initialize a field with an eq rather than a colon.
2316 if self.token == token::Eq {
2318 .struct_span_err(self.span, "expected `:`, found `=`")
2320 fieldname.span.shrink_to_hi().to(self.span),
2321 "replace equals symbol with a colon",
2323 Applicability::MachineApplicable,
2328 (fieldname, self.parse_expr()?, false)
2330 let fieldname = self.parse_ident_common(false)?;
2332 // Mimic `x: x` for the `x` field shorthand.
2333 let path = ast::Path::from_ident(fieldname);
2334 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
2335 (fieldname, expr, true)
2339 span: lo.to(expr.span),
2342 attrs: attrs.into(),
2346 fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
2347 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
2350 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
2351 ExprKind::Unary(unop, expr)
2354 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2355 ExprKind::Binary(binop, lhs, rhs)
2358 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
2359 ExprKind::Call(f, args)
2362 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
2363 ExprKind::Index(expr, idx)
2367 start: Option<P<Expr>>,
2368 end: Option<P<Expr>>,
2369 limits: RangeLimits)
2370 -> PResult<'a, ast::ExprKind> {
2371 if end.is_none() && limits == RangeLimits::Closed {
2372 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
2374 Ok(ExprKind::Range(start, end, limits))
2378 fn mk_assign_op(&self, binop: ast::BinOp,
2379 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2380 ExprKind::AssignOp(binop, lhs, rhs)
2383 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
2384 let delim = match self.token {
2385 token::OpenDelim(delim) => delim,
2387 let msg = "expected open delimiter";
2388 let mut err = self.fatal(msg);
2389 err.span_label(self.span, msg);
2393 let tts = match self.parse_token_tree() {
2394 TokenTree::Delimited(_, _, tts) => tts,
2395 _ => unreachable!(),
2397 let delim = match delim {
2398 token::Paren => MacDelimiter::Parenthesis,
2399 token::Bracket => MacDelimiter::Bracket,
2400 token::Brace => MacDelimiter::Brace,
2401 token::NoDelim => self.bug("unexpected no delimiter"),
2403 Ok((delim, tts.into()))
2406 /// At the bottom (top?) of the precedence hierarchy,
2407 /// Parses things like parenthesized exprs, macros, `return`, etc.
2409 /// N.B., this does not parse outer attributes, and is private because it only works
2410 /// correctly if called from `parse_dot_or_call_expr()`.
2411 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2412 maybe_recover_from_interpolated_ty_qpath!(self, true);
2413 maybe_whole_expr!(self);
2415 // Outer attributes are already parsed and will be
2416 // added to the return value after the fact.
2418 // Therefore, prevent sub-parser from parsing
2419 // attributes by giving them a empty "already parsed" list.
2420 let mut attrs = ThinVec::new();
2423 let mut hi = self.span;
2427 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2429 token::OpenDelim(token::Paren) => {
2432 attrs.extend(self.parse_inner_attributes()?);
2434 // (e) is parenthesized e
2435 // (e,) is a tuple with only one field, e
2436 let mut es = vec![];
2437 let mut trailing_comma = false;
2438 let mut recovered = false;
2439 while self.token != token::CloseDelim(token::Paren) {
2440 es.push(match self.parse_expr() {
2443 // recover from parse error in tuple list
2444 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2447 recovered = self.expect_one_of(
2449 &[token::Comma, token::CloseDelim(token::Paren)],
2451 if self.eat(&token::Comma) {
2452 trailing_comma = true;
2454 trailing_comma = false;
2462 hi = self.prev_span;
2463 ex = if es.len() == 1 && !trailing_comma {
2464 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2469 token::OpenDelim(token::Brace) => {
2470 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2472 token::BinOp(token::Or) | token::OrOr => {
2473 return self.parse_lambda_expr(attrs);
2475 token::OpenDelim(token::Bracket) => {
2478 attrs.extend(self.parse_inner_attributes()?);
2480 if self.eat(&token::CloseDelim(token::Bracket)) {
2482 ex = ExprKind::Array(Vec::new());
2485 let first_expr = self.parse_expr()?;
2486 if self.eat(&token::Semi) {
2487 // Repeating array syntax: [ 0; 512 ]
2488 let count = AnonConst {
2489 id: ast::DUMMY_NODE_ID,
2490 value: self.parse_expr()?,
2492 self.expect(&token::CloseDelim(token::Bracket))?;
2493 ex = ExprKind::Repeat(first_expr, count);
2494 } else if self.eat(&token::Comma) {
2495 // Vector with two or more elements.
2496 let remaining_exprs = self.parse_seq_to_end(
2497 &token::CloseDelim(token::Bracket),
2498 SeqSep::trailing_allowed(token::Comma),
2499 |p| Ok(p.parse_expr()?)
2501 let mut exprs = vec![first_expr];
2502 exprs.extend(remaining_exprs);
2503 ex = ExprKind::Array(exprs);
2505 // Vector with one element.
2506 self.expect(&token::CloseDelim(token::Bracket))?;
2507 ex = ExprKind::Array(vec![first_expr]);
2510 hi = self.prev_span;
2514 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2516 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2518 if self.span.rust_2018() && self.check_keyword(keywords::Async) {
2519 return if self.is_async_block() { // check for `async {` and `async move {`
2520 self.parse_async_block(attrs)
2522 self.parse_lambda_expr(attrs)
2525 if self.check_keyword(keywords::Move) || self.check_keyword(keywords::Static) {
2526 return self.parse_lambda_expr(attrs);
2528 if self.eat_keyword(keywords::If) {
2529 return self.parse_if_expr(attrs);
2531 if self.eat_keyword(keywords::For) {
2532 let lo = self.prev_span;
2533 return self.parse_for_expr(None, lo, attrs);
2535 if self.eat_keyword(keywords::While) {
2536 let lo = self.prev_span;
2537 return self.parse_while_expr(None, lo, attrs);
2539 if let Some(label) = self.eat_label() {
2540 let lo = label.ident.span;
2541 self.expect(&token::Colon)?;
2542 if self.eat_keyword(keywords::While) {
2543 return self.parse_while_expr(Some(label), lo, attrs)
2545 if self.eat_keyword(keywords::For) {
2546 return self.parse_for_expr(Some(label), lo, attrs)
2548 if self.eat_keyword(keywords::Loop) {
2549 return self.parse_loop_expr(Some(label), lo, attrs)
2551 if self.token == token::OpenDelim(token::Brace) {
2552 return self.parse_block_expr(Some(label),
2554 BlockCheckMode::Default,
2557 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2558 let mut err = self.fatal(msg);
2559 err.span_label(self.span, msg);
2562 if self.eat_keyword(keywords::Loop) {
2563 let lo = self.prev_span;
2564 return self.parse_loop_expr(None, lo, attrs);
2566 if self.eat_keyword(keywords::Continue) {
2567 let label = self.eat_label();
2568 let ex = ExprKind::Continue(label);
2569 let hi = self.prev_span;
2570 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2572 if self.eat_keyword(keywords::Match) {
2573 let match_sp = self.prev_span;
2574 return self.parse_match_expr(attrs).map_err(|mut err| {
2575 err.span_label(match_sp, "while parsing this match expression");
2579 if self.eat_keyword(keywords::Unsafe) {
2580 return self.parse_block_expr(
2583 BlockCheckMode::Unsafe(ast::UserProvided),
2586 if self.is_do_catch_block() {
2587 let mut db = self.fatal("found removed `do catch` syntax");
2588 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2591 if self.is_try_block() {
2593 assert!(self.eat_keyword(keywords::Try));
2594 return self.parse_try_block(lo, attrs);
2596 if self.eat_keyword(keywords::Return) {
2597 if self.token.can_begin_expr() {
2598 let e = self.parse_expr()?;
2600 ex = ExprKind::Ret(Some(e));
2602 ex = ExprKind::Ret(None);
2604 } else if self.eat_keyword(keywords::Break) {
2605 let label = self.eat_label();
2606 let e = if self.token.can_begin_expr()
2607 && !(self.token == token::OpenDelim(token::Brace)
2608 && self.restrictions.contains(
2609 Restrictions::NO_STRUCT_LITERAL)) {
2610 Some(self.parse_expr()?)
2614 ex = ExprKind::Break(label, e);
2615 hi = self.prev_span;
2616 } else if self.eat_keyword(keywords::Yield) {
2617 if self.token.can_begin_expr() {
2618 let e = self.parse_expr()?;
2620 ex = ExprKind::Yield(Some(e));
2622 ex = ExprKind::Yield(None);
2624 } else if self.token.is_keyword(keywords::Let) {
2625 // Catch this syntax error here, instead of in `parse_ident`, so
2626 // that we can explicitly mention that let is not to be used as an expression
2627 let mut db = self.fatal("expected expression, found statement (`let`)");
2628 db.span_label(self.span, "expected expression");
2629 db.note("variable declaration using `let` is a statement");
2631 } else if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
2632 let await_sp = self.prev_span;
2633 let e = self.parse_async_macro_or_stmt(lo, await_sp)?;
2636 } else if self.token.is_path_start() {
2637 let path = self.parse_path(PathStyle::Expr)?;
2639 // `!`, as an operator, is prefix, so we know this isn't that
2640 if self.eat(&token::Not) {
2641 // MACRO INVOCATION expression
2642 let (delim, tts) = self.expect_delimited_token_tree()?;
2643 hi = self.prev_span;
2644 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2645 } else if self.check(&token::OpenDelim(token::Brace)) {
2646 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
2650 ex = ExprKind::Path(None, path);
2654 ex = ExprKind::Path(None, path);
2657 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2658 // Don't complain about bare semicolons after unclosed braces
2659 // recovery in order to keep the error count down. Fixing the
2660 // delimiters will possibly also fix the bare semicolon found in
2661 // expression context. For example, silence the following error:
2663 // error: expected expression, found `;`
2667 // | ^ expected expression
2670 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2672 match self.parse_literal_maybe_minus() {
2675 ex = expr.node.clone();
2678 self.cancel(&mut err);
2679 let msg = format!("expected expression, found {}",
2680 self.this_token_descr());
2681 let mut err = self.fatal(&msg);
2682 let sp = self.sess.source_map().start_point(self.span);
2683 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow()
2686 self.sess.expr_parentheses_needed(&mut err, *sp, None);
2688 err.span_label(self.span, "expected expression");
2696 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2697 self.maybe_recover_from_bad_qpath(expr, true)
2700 fn parse_async_macro_or_stmt(
2704 ) -> PResult<'a, (Span, ExprKind)> {
2705 Ok(match self.token {
2707 // Handle correct `await!(<expr>)`
2708 // FIXME: make this an error when `await!` is no longer supported
2709 // https://github.com/rust-lang/rust/issues/60610
2710 self.expect(&token::Not)?;
2711 self.expect(&token::OpenDelim(token::Paren))?;
2712 let expr = self.parse_expr().map_err(|mut err| {
2715 "while parsing this await macro call",
2719 self.expect(&token::CloseDelim(token::Paren))?;
2720 (expr.span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr))
2722 token::Question => {
2723 // Handle `await? <expr>`
2725 let expr = self.parse_expr().map_err(|mut err| {
2728 "while parsing this incorrect await statement",
2732 let sp = lo.to(expr.span);
2733 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
2734 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
2735 let expr = self.mk_expr(
2737 ExprKind::Await(ast::AwaitOrigin::FieldLike, expr),
2740 let mut err = self.struct_span_err(
2742 "incorrect use of `await`",
2744 err.span_suggestion(
2746 "`await` is not a statement",
2747 format!("{}.await?", expr_str),
2748 Applicability::MachineApplicable,
2751 (sp, ExprKind::Try(expr))
2754 // Handle `await <expr>`
2755 let expr = if t == &token::OpenDelim(token::Brace) {
2756 // Handle `await { <expr> }`
2757 // this needs to be handled separatedly from the next arm to avoid
2758 // interpreting `await { <expr> }?` as `<expr>?.await`
2759 self.parse_block_expr(
2762 BlockCheckMode::Default,
2767 }.map_err(|mut err| {
2770 "while parsing this incorrect await statement",
2774 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
2775 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
2776 let sp = lo.to(expr.span);
2777 let mut err = self.struct_span_err(
2779 "incorrect use of `await`",
2781 err.span_suggestion(
2783 "`await` is not a statement",
2784 format!("{}.await", expr_str),
2785 Applicability::MachineApplicable,
2788 (sp, ExprKind::Await(ast::AwaitOrigin::FieldLike, expr))
2793 fn maybe_parse_struct_expr(
2797 attrs: &ThinVec<Attribute>,
2798 ) -> Option<PResult<'a, P<Expr>>> {
2799 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2800 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
2801 // `{ ident, ` cannot start a block
2802 self.look_ahead(2, |t| t == &token::Comma) ||
2803 self.look_ahead(2, |t| t == &token::Colon) && (
2804 // `{ ident: token, ` cannot start a block
2805 self.look_ahead(4, |t| t == &token::Comma) ||
2806 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
2807 self.look_ahead(3, |t| !t.can_begin_type())
2811 if struct_allowed || certainly_not_a_block() {
2812 // This is a struct literal, but we don't can't accept them here
2813 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
2814 if let (Ok(expr), false) = (&expr, struct_allowed) {
2815 let mut err = self.diagnostic().struct_span_err(
2817 "struct literals are not allowed here",
2819 err.multipart_suggestion(
2820 "surround the struct literal with parentheses",
2822 (lo.shrink_to_lo(), "(".to_string()),
2823 (expr.span.shrink_to_hi(), ")".to_string()),
2825 Applicability::MachineApplicable,
2834 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2835 -> PResult<'a, P<Expr>> {
2836 let struct_sp = lo.to(self.prev_span);
2838 let mut fields = Vec::new();
2839 let mut base = None;
2841 attrs.extend(self.parse_inner_attributes()?);
2843 while self.token != token::CloseDelim(token::Brace) {
2844 if self.eat(&token::DotDot) {
2845 let exp_span = self.prev_span;
2846 match self.parse_expr() {
2852 self.recover_stmt();
2855 if self.token == token::Comma {
2856 let mut err = self.sess.span_diagnostic.mut_span_err(
2857 exp_span.to(self.prev_span),
2858 "cannot use a comma after the base struct",
2860 err.span_suggestion_short(
2862 "remove this comma",
2864 Applicability::MachineApplicable
2866 err.note("the base struct must always be the last field");
2868 self.recover_stmt();
2873 let mut recovery_field = None;
2874 if let token::Ident(ident, _) = self.token {
2875 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2876 // Use in case of error after field-looking code: `S { foo: () with a }`
2877 let mut ident = ident.clone();
2878 ident.span = self.span;
2879 recovery_field = Some(ast::Field {
2882 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2883 is_shorthand: false,
2884 attrs: ThinVec::new(),
2888 let mut parsed_field = None;
2889 match self.parse_field() {
2890 Ok(f) => parsed_field = Some(f),
2892 e.span_label(struct_sp, "while parsing this struct");
2895 // If the next token is a comma, then try to parse
2896 // what comes next as additional fields, rather than
2897 // bailing out until next `}`.
2898 if self.token != token::Comma {
2899 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2900 if self.token != token::Comma {
2907 match self.expect_one_of(&[token::Comma],
2908 &[token::CloseDelim(token::Brace)]) {
2909 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2910 // only include the field if there's no parse error for the field name
2914 if let Some(f) = recovery_field {
2917 e.span_label(struct_sp, "while parsing this struct");
2919 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2920 self.eat(&token::Comma);
2925 let span = lo.to(self.span);
2926 self.expect(&token::CloseDelim(token::Brace))?;
2927 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2930 fn parse_or_use_outer_attributes(&mut self,
2931 already_parsed_attrs: Option<ThinVec<Attribute>>)
2932 -> PResult<'a, ThinVec<Attribute>> {
2933 if let Some(attrs) = already_parsed_attrs {
2936 self.parse_outer_attributes().map(|a| a.into())
2940 /// Parses a block or unsafe block.
2941 fn parse_block_expr(&mut self, opt_label: Option<Label>,
2942 lo: Span, blk_mode: BlockCheckMode,
2943 outer_attrs: ThinVec<Attribute>)
2944 -> PResult<'a, P<Expr>> {
2945 self.expect(&token::OpenDelim(token::Brace))?;
2947 let mut attrs = outer_attrs;
2948 attrs.extend(self.parse_inner_attributes()?);
2950 let blk = self.parse_block_tail(lo, blk_mode)?;
2951 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2954 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2955 fn parse_dot_or_call_expr(&mut self,
2956 already_parsed_attrs: Option<ThinVec<Attribute>>)
2957 -> PResult<'a, P<Expr>> {
2958 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2960 let b = self.parse_bottom_expr();
2961 let (span, b) = self.interpolated_or_expr_span(b)?;
2962 self.parse_dot_or_call_expr_with(b, span, attrs)
2965 fn parse_dot_or_call_expr_with(&mut self,
2968 mut attrs: ThinVec<Attribute>)
2969 -> PResult<'a, P<Expr>> {
2970 // Stitch the list of outer attributes onto the return value.
2971 // A little bit ugly, but the best way given the current code
2973 self.parse_dot_or_call_expr_with_(e0, lo)
2975 expr.map(|mut expr| {
2976 attrs.extend::<Vec<_>>(expr.attrs.into());
2979 ExprKind::If(..) | ExprKind::IfLet(..) => {
2980 if !expr.attrs.is_empty() {
2981 // Just point to the first attribute in there...
2982 let span = expr.attrs[0].span;
2985 "attributes are not yet allowed on `if` \
2996 // Assuming we have just parsed `.`, continue parsing into an expression.
2997 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2998 if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
2999 let span = lo.to(self.prev_span);
3000 let await_expr = self.mk_expr(
3002 ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
3005 if self.token == token::OpenDelim(token::Paren) &&
3006 self.look_ahead(1, |t| t == &token::CloseDelim(token::Paren))
3011 let sp = lo.to(self.span);
3013 let mut err = self.struct_span_err(span, "incorrect use of `await`");
3014 err.span_suggestion(
3016 "`await` is not a method call, remove the parentheses",
3018 Applicability::MachineApplicable,
3022 return Ok(await_expr);
3024 let segment = self.parse_path_segment(PathStyle::Expr)?;
3025 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
3027 Ok(match self.token {
3028 token::OpenDelim(token::Paren) => {
3029 // Method call `expr.f()`
3030 let mut args = self.parse_unspanned_seq(
3031 &token::OpenDelim(token::Paren),
3032 &token::CloseDelim(token::Paren),
3033 SeqSep::trailing_allowed(token::Comma),
3034 |p| Ok(p.parse_expr()?)
3036 args.insert(0, self_arg);
3038 let span = lo.to(self.prev_span);
3039 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
3042 // Field access `expr.f`
3043 if let Some(args) = segment.args {
3044 self.span_err(args.span(),
3045 "field expressions may not have generic arguments");
3048 let span = lo.to(self.prev_span);
3049 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
3054 /// This function checks if there are trailing angle brackets and produces
3055 /// a diagnostic to suggest removing them.
3057 /// ```ignore (diagnostic)
3058 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
3059 /// ^^ help: remove extra angle brackets
3061 fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
3062 // This function is intended to be invoked after parsing a path segment where there are two
3065 // 1. A specific token is expected after the path segment.
3066 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
3067 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
3068 // 2. No specific token is expected after the path segment.
3069 // eg. `x.foo` (field access)
3071 // This function is called after parsing `.foo` and before parsing the token `end` (if
3072 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
3075 // We only care about trailing angle brackets if we previously parsed angle bracket
3076 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
3077 // removed in this case:
3079 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
3081 // This case is particularly tricky as we won't notice it just looking at the tokens -
3082 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
3083 // have already been parsed):
3085 // `x.foo::<u32>>>(3)`
3086 let parsed_angle_bracket_args = segment.args
3088 .map(|args| args.is_angle_bracketed())
3092 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
3093 parsed_angle_bracket_args,
3095 if !parsed_angle_bracket_args {
3099 // Keep the span at the start so we can highlight the sequence of `>` characters to be
3103 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
3104 // (since we might have the field access case and the characters we're eating are
3105 // actual operators and not trailing characters - ie `x.foo >> 3`).
3106 let mut position = 0;
3108 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
3109 // many of each (so we can correctly pluralize our error messages) and continue to
3111 let mut number_of_shr = 0;
3112 let mut number_of_gt = 0;
3113 while self.look_ahead(position, |t| {
3114 trace!("check_trailing_angle_brackets: t={:?}", t);
3115 if *t == token::BinOp(token::BinOpToken::Shr) {
3118 } else if *t == token::Gt {
3128 // If we didn't find any trailing `>` characters, then we have nothing to error about.
3130 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
3131 number_of_gt, number_of_shr,
3133 if number_of_gt < 1 && number_of_shr < 1 {
3137 // Finally, double check that we have our end token as otherwise this is the
3139 if self.look_ahead(position, |t| {
3140 trace!("check_trailing_angle_brackets: t={:?}", t);
3143 // Eat from where we started until the end token so that parsing can continue
3144 // as if we didn't have those extra angle brackets.
3145 self.eat_to_tokens(&[&end]);
3146 let span = lo.until(self.span);
3148 let plural = number_of_gt > 1 || number_of_shr >= 1;
3152 &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
3156 &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
3158 Applicability::MachineApplicable,
3164 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3169 while self.eat(&token::Question) {
3170 let hi = self.prev_span;
3171 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
3175 if self.eat(&token::Dot) {
3177 token::Ident(..) => {
3178 e = self.parse_dot_suffix(e, lo)?;
3180 token::Literal(token::Integer(name), suffix) => {
3181 let span = self.span;
3183 let field = ExprKind::Field(e, Ident::new(name, span));
3184 e = self.mk_expr(lo.to(span), field, ThinVec::new());
3186 self.expect_no_suffix(span, "a tuple index", suffix);
3188 token::Literal(token::Float(n), _suf) => {
3190 let fstr = n.as_str();
3191 let mut err = self.diagnostic()
3192 .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
3193 err.span_label(self.prev_span, "unexpected token");
3194 if fstr.chars().all(|x| "0123456789.".contains(x)) {
3195 let float = match fstr.parse::<f64>().ok() {
3199 let sugg = pprust::to_string(|s| {
3200 use crate::print::pprust::PrintState;
3204 s.print_usize(float.trunc() as usize)?;
3207 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
3209 err.span_suggestion(
3210 lo.to(self.prev_span),
3211 "try parenthesizing the first index",
3213 Applicability::MachineApplicable
3220 // FIXME Could factor this out into non_fatal_unexpected or something.
3221 let actual = self.this_token_to_string();
3222 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
3227 if self.expr_is_complete(&e) { break; }
3230 token::OpenDelim(token::Paren) => {
3231 let seq = self.parse_unspanned_seq(
3232 &token::OpenDelim(token::Paren),
3233 &token::CloseDelim(token::Paren),
3234 SeqSep::trailing_allowed(token::Comma),
3235 |p| Ok(p.parse_expr()?)
3237 let nd = self.mk_call(e, es);
3238 let hi = self.prev_span;
3239 self.mk_expr(lo.to(hi), nd, ThinVec::new())
3241 e = self.recover_seq_parse_error(token::Paren, lo, seq);
3245 // Could be either an index expression or a slicing expression.
3246 token::OpenDelim(token::Bracket) => {
3248 let ix = self.parse_expr()?;
3250 self.expect(&token::CloseDelim(token::Bracket))?;
3251 let index = self.mk_index(e, ix);
3252 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
3260 fn recover_seq_parse_error(
3262 delim: token::DelimToken,
3264 result: PResult<'a, P<Expr>>,
3270 // recover from parse error
3271 self.consume_block(delim);
3272 self.mk_expr(lo.to(self.prev_span), ExprKind::Err, ThinVec::new())
3277 crate fn process_potential_macro_variable(&mut self) {
3278 let (token, span) = match self.token {
3279 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
3280 self.look_ahead(1, |t| t.is_ident()) => {
3282 let name = match self.token {
3283 token::Ident(ident, _) => ident,
3286 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
3287 err.span_label(self.span, "unknown macro variable");
3292 token::Interpolated(ref nt) => {
3293 self.meta_var_span = Some(self.span);
3294 // Interpolated identifier and lifetime tokens are replaced with usual identifier
3295 // and lifetime tokens, so the former are never encountered during normal parsing.
3297 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
3298 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
3308 /// Parses a single token tree from the input.
3309 crate fn parse_token_tree(&mut self) -> TokenTree {
3311 token::OpenDelim(..) => {
3312 let frame = mem::replace(&mut self.token_cursor.frame,
3313 self.token_cursor.stack.pop().unwrap());
3314 self.span = frame.span.entire();
3316 TokenTree::Delimited(
3319 frame.tree_cursor.stream.into(),
3322 token::CloseDelim(_) | token::Eof => unreachable!(),
3324 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
3326 TokenTree::Token(span, token)
3331 // parse a stream of tokens into a list of TokenTree's,
3333 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
3334 let mut tts = Vec::new();
3335 while self.token != token::Eof {
3336 tts.push(self.parse_token_tree());
3341 pub fn parse_tokens(&mut self) -> TokenStream {
3342 let mut result = Vec::new();
3345 token::Eof | token::CloseDelim(..) => break,
3346 _ => result.push(self.parse_token_tree().into()),
3349 TokenStream::new(result)
3352 /// Parse a prefix-unary-operator expr
3353 fn parse_prefix_expr(&mut self,
3354 already_parsed_attrs: Option<ThinVec<Attribute>>)
3355 -> PResult<'a, P<Expr>> {
3356 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3358 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
3359 let (hi, ex) = match self.token {
3362 let e = self.parse_prefix_expr(None);
3363 let (span, e) = self.interpolated_or_expr_span(e)?;
3364 (lo.to(span), self.mk_unary(UnOp::Not, e))
3366 // Suggest `!` for bitwise negation when encountering a `~`
3369 let e = self.parse_prefix_expr(None);
3370 let (span, e) = self.interpolated_or_expr_span(e)?;
3371 let span_of_tilde = lo;
3372 let mut err = self.diagnostic()
3373 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
3374 err.span_suggestion_short(
3376 "use `!` to perform bitwise negation",
3378 Applicability::MachineApplicable
3381 (lo.to(span), self.mk_unary(UnOp::Not, e))
3383 token::BinOp(token::Minus) => {
3385 let e = self.parse_prefix_expr(None);
3386 let (span, e) = self.interpolated_or_expr_span(e)?;
3387 (lo.to(span), self.mk_unary(UnOp::Neg, e))
3389 token::BinOp(token::Star) => {
3391 let e = self.parse_prefix_expr(None);
3392 let (span, e) = self.interpolated_or_expr_span(e)?;
3393 (lo.to(span), self.mk_unary(UnOp::Deref, e))
3395 token::BinOp(token::And) | token::AndAnd => {
3397 let m = self.parse_mutability();
3398 let e = self.parse_prefix_expr(None);
3399 let (span, e) = self.interpolated_or_expr_span(e)?;
3400 (lo.to(span), ExprKind::AddrOf(m, e))
3402 token::Ident(..) if self.token.is_keyword(keywords::In) => {
3404 let place = self.parse_expr_res(
3405 Restrictions::NO_STRUCT_LITERAL,
3408 let blk = self.parse_block()?;
3409 let span = blk.span;
3410 let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
3411 (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
3413 token::Ident(..) if self.token.is_keyword(keywords::Box) => {
3415 let e = self.parse_prefix_expr(None);
3416 let (span, e) = self.interpolated_or_expr_span(e)?;
3417 (lo.to(span), ExprKind::Box(e))
3419 token::Ident(..) if self.token.is_ident_named("not") => {
3420 // `not` is just an ordinary identifier in Rust-the-language,
3421 // but as `rustc`-the-compiler, we can issue clever diagnostics
3422 // for confused users who really want to say `!`
3423 let token_cannot_continue_expr = |t: &token::Token| match *t {
3424 // These tokens can start an expression after `!`, but
3425 // can't continue an expression after an ident
3426 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
3427 token::Literal(..) | token::Pound => true,
3428 token::Interpolated(ref nt) => match **nt {
3429 token::NtIdent(..) | token::NtExpr(..) |
3430 token::NtBlock(..) | token::NtPath(..) => true,
3435 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
3436 if cannot_continue_expr {
3438 // Emit the error ...
3439 let mut err = self.diagnostic()
3440 .struct_span_err(self.span,
3441 &format!("unexpected {} after identifier",
3442 self.this_token_descr()));
3443 // span the `not` plus trailing whitespace to avoid
3444 // trailing whitespace after the `!` in our suggestion
3445 let to_replace = self.sess.source_map()
3446 .span_until_non_whitespace(lo.to(self.span));
3447 err.span_suggestion_short(
3449 "use `!` to perform logical negation",
3451 Applicability::MachineApplicable
3454 // —and recover! (just as if we were in the block
3455 // for the `token::Not` arm)
3456 let e = self.parse_prefix_expr(None);
3457 let (span, e) = self.interpolated_or_expr_span(e)?;
3458 (lo.to(span), self.mk_unary(UnOp::Not, e))
3460 return self.parse_dot_or_call_expr(Some(attrs));
3463 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
3465 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
3468 /// Parses an associative expression.
3470 /// This parses an expression accounting for associativity and precedence of the operators in
3473 fn parse_assoc_expr(&mut self,
3474 already_parsed_attrs: Option<ThinVec<Attribute>>)
3475 -> PResult<'a, P<Expr>> {
3476 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
3479 /// Parses an associative expression with operators of at least `min_prec` precedence.
3480 fn parse_assoc_expr_with(&mut self,
3483 -> PResult<'a, P<Expr>> {
3484 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
3487 let attrs = match lhs {
3488 LhsExpr::AttributesParsed(attrs) => Some(attrs),
3491 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
3492 return self.parse_prefix_range_expr(attrs);
3494 self.parse_prefix_expr(attrs)?
3498 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
3500 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
3503 (false, _) => {} // continue parsing the expression
3504 // An exhaustive check is done in the following block, but these are checked first
3505 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
3506 // want to keep their span info to improve diagnostics in these cases in a later stage.
3507 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
3508 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
3509 (true, Some(AssocOp::Add)) => { // `{ 42 } + 42
3510 // These cases are ambiguous and can't be identified in the parser alone
3511 let sp = self.sess.source_map().start_point(self.span);
3512 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
3515 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
3518 (true, Some(_)) => {
3519 // We've found an expression that would be parsed as a statement, but the next
3520 // token implies this should be parsed as an expression.
3521 // For example: `if let Some(x) = x { x } else { 0 } / 2`
3522 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
3523 "expected expression, found `{}`",
3524 pprust::token_to_string(&self.token),
3526 err.span_label(self.span, "expected expression");
3527 self.sess.expr_parentheses_needed(
3530 Some(pprust::expr_to_string(&lhs),
3535 self.expected_tokens.push(TokenType::Operator);
3536 while let Some(op) = AssocOp::from_token(&self.token) {
3538 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
3539 // it refers to. Interpolated identifiers are unwrapped early and never show up here
3540 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
3541 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
3542 let lhs_span = match (self.prev_token_kind, &lhs.node) {
3543 (PrevTokenKind::Interpolated, _) => self.prev_span,
3544 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
3545 if path.segments.len() == 1 => self.prev_span,
3549 let cur_op_span = self.span;
3550 let restrictions = if op.is_assign_like() {
3551 self.restrictions & Restrictions::NO_STRUCT_LITERAL
3555 let prec = op.precedence();
3556 if prec < min_prec {
3559 // Check for deprecated `...` syntax
3560 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
3561 self.err_dotdotdot_syntax(self.span);
3565 if op.is_comparison() {
3566 self.check_no_chained_comparison(&lhs, &op);
3569 if op == AssocOp::As {
3570 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
3572 } else if op == AssocOp::Colon {
3573 let maybe_path = self.could_ascription_be_path(&lhs.node);
3574 let next_sp = self.span;
3576 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
3579 self.bad_type_ascription(
3590 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
3591 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
3592 // generalise it to the Fixity::None code.
3594 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
3595 // two variants are handled with `parse_prefix_range_expr` call above.
3596 let rhs = if self.is_at_start_of_range_notation_rhs() {
3597 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
3601 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
3606 let limits = if op == AssocOp::DotDot {
3607 RangeLimits::HalfOpen
3612 let r = self.mk_range(Some(lhs), rhs, limits)?;
3613 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
3617 let fixity = op.fixity();
3618 let prec_adjustment = match fixity {
3621 // We currently have no non-associative operators that are not handled above by
3622 // the special cases. The code is here only for future convenience.
3625 let rhs = self.with_res(
3626 restrictions - Restrictions::STMT_EXPR,
3627 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
3630 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
3631 // including the attributes.
3635 .filter(|a| a.style == AttrStyle::Outer)
3637 .map_or(lhs_span, |a| a.span);
3638 let span = lhs_span.to(rhs.span);
3640 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
3641 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3642 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3643 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3644 AssocOp::Greater | AssocOp::GreaterEqual => {
3645 let ast_op = op.to_ast_binop().unwrap();
3646 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
3647 self.mk_expr(span, binary, ThinVec::new())
3650 self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3651 AssocOp::ObsoleteInPlace =>
3652 self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
3653 AssocOp::AssignOp(k) => {
3655 token::Plus => BinOpKind::Add,
3656 token::Minus => BinOpKind::Sub,
3657 token::Star => BinOpKind::Mul,
3658 token::Slash => BinOpKind::Div,
3659 token::Percent => BinOpKind::Rem,
3660 token::Caret => BinOpKind::BitXor,
3661 token::And => BinOpKind::BitAnd,
3662 token::Or => BinOpKind::BitOr,
3663 token::Shl => BinOpKind::Shl,
3664 token::Shr => BinOpKind::Shr,
3666 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3667 self.mk_expr(span, aopexpr, ThinVec::new())
3669 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3670 self.bug("AssocOp should have been handled by special case")
3674 if let Fixity::None = fixity { break }
3679 fn could_ascription_be_path(&self, node: &ast::ExprKind) -> bool {
3680 self.token.is_ident() &&
3681 if let ast::ExprKind::Path(..) = node { true } else { false } &&
3682 !self.token.is_reserved_ident() && // v `foo:bar(baz)`
3683 self.look_ahead(1, |t| t == &token::OpenDelim(token::Paren)) ||
3684 self.look_ahead(1, |t| t == &token::Lt) && // `foo:bar<baz`
3685 self.look_ahead(2, |t| t.is_ident()) ||
3686 self.look_ahead(1, |t| t == &token::Colon) && // `foo:bar:baz`
3687 self.look_ahead(2, |t| t.is_ident()) ||
3688 self.look_ahead(1, |t| t == &token::ModSep) && // `foo:bar::baz`
3689 self.look_ahead(2, |t| t.is_ident())
3692 fn bad_type_ascription(
3694 err: &mut DiagnosticBuilder<'a>,
3700 err.span_label(self.span, "expecting a type here because of type ascription");
3701 let cm = self.sess.source_map();
3702 let next_pos = cm.lookup_char_pos(next_sp.lo());
3703 let op_pos = cm.lookup_char_pos(cur_op_span.hi());
3704 if op_pos.line != next_pos.line {
3705 err.span_suggestion(
3707 "try using a semicolon",
3709 Applicability::MaybeIncorrect,
3713 err.span_suggestion(
3715 "maybe you meant to write a path separator here",
3717 Applicability::MaybeIncorrect,
3720 err.note("type ascription is a nightly-only feature that lets \
3721 you annotate an expression with a type: `<expr>: <type>`");
3724 "this expression expects an ascribed type after the colon",
3726 err.help("this might be indicative of a syntax error elsewhere");
3731 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3732 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3733 -> PResult<'a, P<Expr>> {
3734 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3735 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3738 // Save the state of the parser before parsing type normally, in case there is a
3739 // LessThan comparison after this cast.
3740 let parser_snapshot_before_type = self.clone();
3741 match self.parse_ty_no_plus() {
3743 Ok(mk_expr(self, rhs))
3745 Err(mut type_err) => {
3746 // Rewind to before attempting to parse the type with generics, to recover
3747 // from situations like `x as usize < y` in which we first tried to parse
3748 // `usize < y` as a type with generic arguments.
3749 let parser_snapshot_after_type = self.clone();
3750 mem::replace(self, parser_snapshot_before_type);
3752 match self.parse_path(PathStyle::Expr) {
3754 let (op_noun, op_verb) = match self.token {
3755 token::Lt => ("comparison", "comparing"),
3756 token::BinOp(token::Shl) => ("shift", "shifting"),
3758 // We can end up here even without `<` being the next token, for
3759 // example because `parse_ty_no_plus` returns `Err` on keywords,
3760 // but `parse_path` returns `Ok` on them due to error recovery.
3761 // Return original error and parser state.
3762 mem::replace(self, parser_snapshot_after_type);
3763 return Err(type_err);
3767 // Successfully parsed the type path leaving a `<` yet to parse.
3770 // Report non-fatal diagnostics, keep `x as usize` as an expression
3771 // in AST and continue parsing.
3772 let msg = format!("`<` is interpreted as a start of generic \
3773 arguments for `{}`, not a {}", path, op_noun);
3774 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3775 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3776 "interpreted as generic arguments");
3777 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3779 let expr = mk_expr(self, P(Ty {
3781 node: TyKind::Path(None, path),
3782 id: ast::DUMMY_NODE_ID
3785 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3786 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3787 err.span_suggestion(
3789 &format!("try {} the cast value", op_verb),
3790 format!("({})", expr_str),
3791 Applicability::MachineApplicable
3797 Err(mut path_err) => {
3798 // Couldn't parse as a path, return original error and parser state.
3800 mem::replace(self, parser_snapshot_after_type);
3808 /// Produce an error if comparison operators are chained (RFC #558).
3809 /// We only need to check lhs, not rhs, because all comparison ops
3810 /// have same precedence and are left-associative
3811 fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) {
3812 debug_assert!(outer_op.is_comparison(),
3813 "check_no_chained_comparison: {:?} is not comparison",
3816 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
3817 // respan to include both operators
3818 let op_span = op.span.to(self.span);
3819 let mut err = self.diagnostic().struct_span_err(op_span,
3820 "chained comparison operators require parentheses");
3821 if op.node == BinOpKind::Lt &&
3822 *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
3823 *outer_op == AssocOp::Greater // even in a case like the following:
3824 { // Foo<Bar<Baz<Qux, ()>>>
3826 "use `::<...>` instead of `<...>` if you meant to specify type arguments");
3827 err.help("or use `(...)` if you meant to specify fn arguments");
3835 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3836 fn parse_prefix_range_expr(&mut self,
3837 already_parsed_attrs: Option<ThinVec<Attribute>>)
3838 -> PResult<'a, P<Expr>> {
3839 // Check for deprecated `...` syntax
3840 if self.token == token::DotDotDot {
3841 self.err_dotdotdot_syntax(self.span);
3844 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3845 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3847 let tok = self.token.clone();
3848 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3850 let mut hi = self.span;
3852 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3853 // RHS must be parsed with more associativity than the dots.
3854 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3855 Some(self.parse_assoc_expr_with(next_prec,
3856 LhsExpr::NotYetParsed)
3864 let limits = if tok == token::DotDot {
3865 RangeLimits::HalfOpen
3870 let r = self.mk_range(None, opt_end, limits)?;
3871 Ok(self.mk_expr(lo.to(hi), r, attrs))
3874 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3875 if self.token.can_begin_expr() {
3876 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3877 if self.token == token::OpenDelim(token::Brace) {
3878 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3886 /// Parses an `if` or `if let` expression (`if` token already eaten).
3887 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3888 if self.check_keyword(keywords::Let) {
3889 return self.parse_if_let_expr(attrs);
3891 let lo = self.prev_span;
3892 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3894 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3895 // verify that the last statement is either an implicit return (no `;`) or an explicit
3896 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3897 // the dead code lint.
3898 if self.eat_keyword(keywords::Else) || !cond.returns() {
3899 let sp = self.sess.source_map().next_point(lo);
3900 let mut err = self.diagnostic()
3901 .struct_span_err(sp, "missing condition for `if` statemement");
3902 err.span_label(sp, "expected if condition here");
3905 let not_block = self.token != token::OpenDelim(token::Brace);
3906 let thn = self.parse_block().map_err(|mut err| {
3908 err.span_label(lo, "this `if` statement has a condition, but no block");
3912 let mut els: Option<P<Expr>> = None;
3913 let mut hi = thn.span;
3914 if self.eat_keyword(keywords::Else) {
3915 let elexpr = self.parse_else_expr()?;
3919 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3922 /// Parses an `if let` expression (`if` token already eaten).
3923 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3924 -> PResult<'a, P<Expr>> {
3925 let lo = self.prev_span;
3926 self.expect_keyword(keywords::Let)?;
3927 let pats = self.parse_pats()?;
3928 self.expect(&token::Eq)?;
3929 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3930 let thn = self.parse_block()?;
3931 let (hi, els) = if self.eat_keyword(keywords::Else) {
3932 let expr = self.parse_else_expr()?;
3933 (expr.span, Some(expr))
3937 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3940 /// Parses `move |args| expr`.
3941 fn parse_lambda_expr(&mut self,
3942 attrs: ThinVec<Attribute>)
3943 -> PResult<'a, P<Expr>>
3946 let movability = if self.eat_keyword(keywords::Static) {
3951 let asyncness = if self.span.rust_2018() {
3952 self.parse_asyncness()
3956 let capture_clause = if self.eat_keyword(keywords::Move) {
3961 let decl = self.parse_fn_block_decl()?;
3962 let decl_hi = self.prev_span;
3963 let body = match decl.output {
3964 FunctionRetTy::Default(_) => {
3965 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3966 self.parse_expr_res(restrictions, None)?
3969 // If an explicit return type is given, require a
3970 // block to appear (RFC 968).
3971 let body_lo = self.span;
3972 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3978 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3982 // `else` token already eaten
3983 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3984 if self.eat_keyword(keywords::If) {
3985 return self.parse_if_expr(ThinVec::new());
3987 let blk = self.parse_block()?;
3988 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3992 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3993 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3995 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3996 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3998 let pat = self.parse_top_level_pat()?;
3999 if !self.eat_keyword(keywords::In) {
4000 let in_span = self.prev_span.between(self.span);
4001 let mut err = self.sess.span_diagnostic
4002 .struct_span_err(in_span, "missing `in` in `for` loop");
4003 err.span_suggestion_short(
4004 in_span, "try adding `in` here", " in ".into(),
4005 // has been misleading, at least in the past (closed Issue #48492)
4006 Applicability::MaybeIncorrect
4010 let in_span = self.prev_span;
4011 if self.eat_keyword(keywords::In) {
4012 // a common typo: `for _ in in bar {}`
4013 let mut err = self.sess.span_diagnostic.struct_span_err(
4015 "expected iterable, found keyword `in`",
4017 err.span_suggestion_short(
4018 in_span.until(self.prev_span),
4019 "remove the duplicated `in`",
4021 Applicability::MachineApplicable,
4023 err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
4024 err.note("for more information on the status of emplacement syntax, see <\
4025 https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
4028 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
4029 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
4030 attrs.extend(iattrs);
4032 let hi = self.prev_span;
4033 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
4036 /// Parses a `while` or `while let` expression (`while` token already eaten).
4037 fn parse_while_expr(&mut self, opt_label: Option<Label>,
4039 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4040 if self.token.is_keyword(keywords::Let) {
4041 return self.parse_while_let_expr(opt_label, span_lo, attrs);
4043 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
4044 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4045 attrs.extend(iattrs);
4046 let span = span_lo.to(body.span);
4047 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
4050 /// Parses a `while let` expression (`while` token already eaten).
4051 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
4053 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4054 self.expect_keyword(keywords::Let)?;
4055 let pats = self.parse_pats()?;
4056 self.expect(&token::Eq)?;
4057 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
4058 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4059 attrs.extend(iattrs);
4060 let span = span_lo.to(body.span);
4061 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
4064 // parse `loop {...}`, `loop` token already eaten
4065 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
4067 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4068 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4069 attrs.extend(iattrs);
4070 let span = span_lo.to(body.span);
4071 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
4074 /// Parses an `async move {...}` expression.
4075 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
4076 -> PResult<'a, P<Expr>>
4078 let span_lo = self.span;
4079 self.expect_keyword(keywords::Async)?;
4080 let capture_clause = if self.eat_keyword(keywords::Move) {
4085 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4086 attrs.extend(iattrs);
4088 span_lo.to(body.span),
4089 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
4092 /// Parses a `try {...}` expression (`try` token already eaten).
4093 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
4094 -> PResult<'a, P<Expr>>
4096 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
4097 attrs.extend(iattrs);
4098 if self.eat_keyword(keywords::Catch) {
4099 let mut error = self.struct_span_err(self.prev_span,
4100 "keyword `catch` cannot follow a `try` block");
4101 error.help("try using `match` on the result of the `try` block instead");
4105 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
4109 // `match` token already eaten
4110 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
4111 let match_span = self.prev_span;
4112 let lo = self.prev_span;
4113 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
4115 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
4116 if self.token == token::Token::Semi {
4117 e.span_suggestion_short(
4119 "try removing this `match`",
4121 Applicability::MaybeIncorrect // speculative
4126 attrs.extend(self.parse_inner_attributes()?);
4128 let mut arms: Vec<Arm> = Vec::new();
4129 while self.token != token::CloseDelim(token::Brace) {
4130 match self.parse_arm() {
4131 Ok(arm) => arms.push(arm),
4133 // Recover by skipping to the end of the block.
4135 self.recover_stmt();
4136 let span = lo.to(self.span);
4137 if self.token == token::CloseDelim(token::Brace) {
4140 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
4146 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
4149 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
4150 let attrs = self.parse_outer_attributes()?;
4151 let pats = self.parse_pats()?;
4152 let guard = if self.eat_keyword(keywords::If) {
4153 Some(Guard::If(self.parse_expr()?))
4157 let arrow_span = self.span;
4158 self.expect(&token::FatArrow)?;
4159 let arm_start_span = self.span;
4161 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
4162 .map_err(|mut err| {
4163 err.span_label(arrow_span, "while parsing the `match` arm starting here");
4167 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
4168 && self.token != token::CloseDelim(token::Brace);
4171 let cm = self.sess.source_map();
4172 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
4173 .map_err(|mut err| {
4174 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
4175 (Ok(ref expr_lines), Ok(ref arm_start_lines))
4176 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
4177 && expr_lines.lines.len() == 2
4178 && self.token == token::FatArrow => {
4179 // We check whether there's any trailing code in the parse span,
4180 // if there isn't, we very likely have the following:
4183 // | -- - missing comma
4189 // | parsed until here as `"y" & X`
4190 err.span_suggestion_short(
4191 cm.next_point(arm_start_span),
4192 "missing a comma here to end this `match` arm",
4194 Applicability::MachineApplicable
4198 err.span_label(arrow_span,
4199 "while parsing the `match` arm starting here");
4205 self.eat(&token::Comma);
4216 /// Parses an expression.
4218 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
4219 self.parse_expr_res(Restrictions::empty(), None)
4222 /// Evaluates the closure with restrictions in place.
4224 /// Afters the closure is evaluated, restrictions are reset.
4225 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
4226 where F: FnOnce(&mut Self) -> T
4228 let old = self.restrictions;
4229 self.restrictions = r;
4231 self.restrictions = old;
4236 /// Parses an expression, subject to the given restrictions.
4238 fn parse_expr_res(&mut self, r: Restrictions,
4239 already_parsed_attrs: Option<ThinVec<Attribute>>)
4240 -> PResult<'a, P<Expr>> {
4241 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
4244 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
4245 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
4246 if self.eat(&token::Eq) {
4247 Ok(Some(self.parse_expr()?))
4249 Ok(Some(self.parse_expr()?))
4255 /// Parses patterns, separated by '|' s.
4256 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
4257 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
4258 self.eat(&token::BinOp(token::Or));
4260 let mut pats = Vec::new();
4262 pats.push(self.parse_top_level_pat()?);
4264 if self.token == token::OrOr {
4265 let mut err = self.struct_span_err(self.span,
4266 "unexpected token `||` after pattern");
4267 err.span_suggestion(
4269 "use a single `|` to specify multiple patterns",
4271 Applicability::MachineApplicable
4275 } else if self.eat(&token::BinOp(token::Or)) {
4276 // This is a No-op. Continue the loop to parse the next
4284 // Parses a parenthesized list of patterns like
4285 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
4286 // - a vector of the patterns that were parsed
4287 // - an option indicating the index of the `..` element
4288 // - a boolean indicating whether a trailing comma was present.
4289 // Trailing commas are significant because (p) and (p,) are different patterns.
4290 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4291 self.expect(&token::OpenDelim(token::Paren))?;
4292 let result = match self.parse_pat_list() {
4293 Ok(result) => result,
4294 Err(mut err) => { // recover from parse error in tuple pattern list
4296 self.consume_block(token::Paren);
4297 return Ok((vec![], Some(0), false));
4300 self.expect(&token::CloseDelim(token::Paren))?;
4304 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4305 let mut fields = Vec::new();
4306 let mut ddpos = None;
4307 let mut prev_dd_sp = None;
4308 let mut trailing_comma = false;
4310 if self.eat(&token::DotDot) {
4311 if ddpos.is_none() {
4312 ddpos = Some(fields.len());
4313 prev_dd_sp = Some(self.prev_span);
4315 // Emit a friendly error, ignore `..` and continue parsing
4316 let mut err = self.struct_span_err(
4318 "`..` can only be used once per tuple or tuple struct pattern",
4320 err.span_label(self.prev_span, "can only be used once per pattern");
4321 if let Some(sp) = prev_dd_sp {
4322 err.span_label(sp, "previously present here");
4326 } else if !self.check(&token::CloseDelim(token::Paren)) {
4327 fields.push(self.parse_pat(None)?);
4332 trailing_comma = self.eat(&token::Comma);
4333 if !trailing_comma {
4338 if ddpos == Some(fields.len()) && trailing_comma {
4339 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
4340 let msg = "trailing comma is not permitted after `..`";
4341 self.struct_span_err(self.prev_span, msg)
4342 .span_label(self.prev_span, msg)
4346 Ok((fields, ddpos, trailing_comma))
4349 fn parse_pat_vec_elements(
4351 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
4352 let mut before = Vec::new();
4353 let mut slice = None;
4354 let mut after = Vec::new();
4355 let mut first = true;
4356 let mut before_slice = true;
4358 while self.token != token::CloseDelim(token::Bracket) {
4362 self.expect(&token::Comma)?;
4364 if self.token == token::CloseDelim(token::Bracket)
4365 && (before_slice || !after.is_empty()) {
4371 if self.eat(&token::DotDot) {
4373 if self.check(&token::Comma) ||
4374 self.check(&token::CloseDelim(token::Bracket)) {
4375 slice = Some(P(Pat {
4376 id: ast::DUMMY_NODE_ID,
4377 node: PatKind::Wild,
4378 span: self.prev_span,
4380 before_slice = false;
4386 let subpat = self.parse_pat(None)?;
4387 if before_slice && self.eat(&token::DotDot) {
4388 slice = Some(subpat);
4389 before_slice = false;
4390 } else if before_slice {
4391 before.push(subpat);
4397 Ok((before, slice, after))
4403 attrs: Vec<Attribute>
4404 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
4405 // Check if a colon exists one ahead. This means we're parsing a fieldname.
4407 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
4408 // Parsing a pattern of the form "fieldname: pat"
4409 let fieldname = self.parse_field_name()?;
4411 let pat = self.parse_pat(None)?;
4413 (pat, fieldname, false)
4415 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
4416 let is_box = self.eat_keyword(keywords::Box);
4417 let boxed_span = self.span;
4418 let is_ref = self.eat_keyword(keywords::Ref);
4419 let is_mut = self.eat_keyword(keywords::Mut);
4420 let fieldname = self.parse_ident()?;
4421 hi = self.prev_span;
4423 let bind_type = match (is_ref, is_mut) {
4424 (true, true) => BindingMode::ByRef(Mutability::Mutable),
4425 (true, false) => BindingMode::ByRef(Mutability::Immutable),
4426 (false, true) => BindingMode::ByValue(Mutability::Mutable),
4427 (false, false) => BindingMode::ByValue(Mutability::Immutable),
4429 let fieldpat = P(Pat {
4430 id: ast::DUMMY_NODE_ID,
4431 node: PatKind::Ident(bind_type, fieldname, None),
4432 span: boxed_span.to(hi),
4435 let subpat = if is_box {
4437 id: ast::DUMMY_NODE_ID,
4438 node: PatKind::Box(fieldpat),
4444 (subpat, fieldname, true)
4447 Ok(source_map::Spanned {
4449 node: ast::FieldPat {
4453 attrs: attrs.into(),
4458 /// Parses the fields of a struct-like pattern.
4459 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
4460 let mut fields = Vec::new();
4461 let mut etc = false;
4462 let mut ate_comma = true;
4463 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
4464 let mut etc_span = None;
4466 while self.token != token::CloseDelim(token::Brace) {
4467 let attrs = self.parse_outer_attributes()?;
4470 // check that a comma comes after every field
4472 let err = self.struct_span_err(self.prev_span, "expected `,`");
4473 if let Some(mut delayed) = delayed_err {
4480 if self.check(&token::DotDot) || self.token == token::DotDotDot {
4482 let mut etc_sp = self.span;
4484 if self.token == token::DotDotDot { // Issue #46718
4485 // Accept `...` as if it were `..` to avoid further errors
4486 let mut err = self.struct_span_err(self.span,
4487 "expected field pattern, found `...`");
4488 err.span_suggestion(
4490 "to omit remaining fields, use one fewer `.`",
4492 Applicability::MachineApplicable
4496 self.bump(); // `..` || `...`
4498 if self.token == token::CloseDelim(token::Brace) {
4499 etc_span = Some(etc_sp);
4502 let token_str = self.this_token_descr();
4503 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
4505 err.span_label(self.span, "expected `}`");
4506 let mut comma_sp = None;
4507 if self.token == token::Comma { // Issue #49257
4508 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
4509 err.span_label(etc_sp,
4510 "`..` must be at the end and cannot have a trailing comma");
4511 comma_sp = Some(self.span);
4516 etc_span = Some(etc_sp.until(self.span));
4517 if self.token == token::CloseDelim(token::Brace) {
4518 // If the struct looks otherwise well formed, recover and continue.
4519 if let Some(sp) = comma_sp {
4520 err.span_suggestion_short(
4522 "remove this comma",
4524 Applicability::MachineApplicable,
4529 } else if self.token.is_ident() && ate_comma {
4530 // Accept fields coming after `..,`.
4531 // This way we avoid "pattern missing fields" errors afterwards.
4532 // We delay this error until the end in order to have a span for a
4534 if let Some(mut delayed_err) = delayed_err {
4538 delayed_err = Some(err);
4541 if let Some(mut err) = delayed_err {
4548 fields.push(match self.parse_pat_field(lo, attrs) {
4551 if let Some(mut delayed_err) = delayed_err {
4557 ate_comma = self.eat(&token::Comma);
4560 if let Some(mut err) = delayed_err {
4561 if let Some(etc_span) = etc_span {
4562 err.multipart_suggestion(
4563 "move the `..` to the end of the field list",
4565 (etc_span, String::new()),
4566 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
4568 Applicability::MachineApplicable,
4573 return Ok((fields, etc));
4576 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
4577 if self.token.is_path_start() {
4579 let (qself, path) = if self.eat_lt() {
4580 // Parse a qualified path
4581 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4584 // Parse an unqualified path
4585 (None, self.parse_path(PathStyle::Expr)?)
4587 let hi = self.prev_span;
4588 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
4590 self.parse_literal_maybe_minus()
4594 // helper function to decide whether to parse as ident binding or to try to do
4595 // something more complex like range patterns
4596 fn parse_as_ident(&mut self) -> bool {
4597 self.look_ahead(1, |t| match *t {
4598 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
4599 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
4600 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
4601 // range pattern branch
4602 token::DotDot => None,
4604 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
4605 token::Comma | token::CloseDelim(token::Bracket) => true,
4610 /// A wrapper around `parse_pat` with some special error handling for the
4611 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
4612 /// to subpatterns within such).
4613 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
4614 let pat = self.parse_pat(None)?;
4615 if self.token == token::Comma {
4616 // An unexpected comma after a top-level pattern is a clue that the
4617 // user (perhaps more accustomed to some other language) forgot the
4618 // parentheses in what should have been a tuple pattern; return a
4619 // suggestion-enhanced error here rather than choking on the comma
4621 let comma_span = self.span;
4623 if let Err(mut err) = self.parse_pat_list() {
4624 // We didn't expect this to work anyway; we just wanted
4625 // to advance to the end of the comma-sequence so we know
4626 // the span to suggest parenthesizing
4629 let seq_span = pat.span.to(self.prev_span);
4630 let mut err = self.struct_span_err(comma_span,
4631 "unexpected `,` in pattern");
4632 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
4633 err.span_suggestion(
4635 "try adding parentheses to match on a tuple..",
4636 format!("({})", seq_snippet),
4637 Applicability::MachineApplicable
4640 "..or a vertical bar to match on multiple alternatives",
4641 format!("{}", seq_snippet.replace(",", " |")),
4642 Applicability::MachineApplicable
4650 /// Parses a pattern.
4651 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
4652 self.parse_pat_with_range_pat(true, expected)
4655 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
4657 fn parse_pat_with_range_pat(
4659 allow_range_pat: bool,
4660 expected: Option<&'static str>,
4661 ) -> PResult<'a, P<Pat>> {
4662 maybe_recover_from_interpolated_ty_qpath!(self, true);
4663 maybe_whole!(self, NtPat, |x| x);
4668 token::BinOp(token::And) | token::AndAnd => {
4669 // Parse &pat / &mut pat
4671 let mutbl = self.parse_mutability();
4672 if let token::Lifetime(ident) = self.token {
4673 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
4675 err.span_label(self.span, "unexpected lifetime");
4678 let subpat = self.parse_pat_with_range_pat(false, expected)?;
4679 pat = PatKind::Ref(subpat, mutbl);
4681 token::OpenDelim(token::Paren) => {
4682 // Parse (pat,pat,pat,...) as tuple pattern
4683 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
4684 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
4685 PatKind::Paren(fields.into_iter().nth(0).unwrap())
4687 PatKind::Tuple(fields, ddpos)
4690 token::OpenDelim(token::Bracket) => {
4691 // Parse [pat,pat,...] as slice pattern
4693 let (before, slice, after) = self.parse_pat_vec_elements()?;
4694 self.expect(&token::CloseDelim(token::Bracket))?;
4695 pat = PatKind::Slice(before, slice, after);
4697 // At this point, token != &, &&, (, [
4698 _ => if self.eat_keyword(keywords::Underscore) {
4700 pat = PatKind::Wild;
4701 } else if self.eat_keyword(keywords::Mut) {
4702 // Parse mut ident @ pat / mut ref ident @ pat
4703 let mutref_span = self.prev_span.to(self.span);
4704 let binding_mode = if self.eat_keyword(keywords::Ref) {
4706 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
4709 "try switching the order",
4711 Applicability::MachineApplicable
4713 BindingMode::ByRef(Mutability::Mutable)
4715 BindingMode::ByValue(Mutability::Mutable)
4717 pat = self.parse_pat_ident(binding_mode)?;
4718 } else if self.eat_keyword(keywords::Ref) {
4719 // Parse ref ident @ pat / ref mut ident @ pat
4720 let mutbl = self.parse_mutability();
4721 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
4722 } else if self.eat_keyword(keywords::Box) {
4724 let subpat = self.parse_pat_with_range_pat(false, None)?;
4725 pat = PatKind::Box(subpat);
4726 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
4727 self.parse_as_ident() {
4728 // Parse ident @ pat
4729 // This can give false positives and parse nullary enums,
4730 // they are dealt with later in resolve
4731 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
4732 pat = self.parse_pat_ident(binding_mode)?;
4733 } else if self.token.is_path_start() {
4734 // Parse pattern starting with a path
4735 let (qself, path) = if self.eat_lt() {
4736 // Parse a qualified path
4737 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4740 // Parse an unqualified path
4741 (None, self.parse_path(PathStyle::Expr)?)
4744 token::Not if qself.is_none() => {
4745 // Parse macro invocation
4747 let (delim, tts) = self.expect_delimited_token_tree()?;
4748 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4749 pat = PatKind::Mac(mac);
4751 token::DotDotDot | token::DotDotEq | token::DotDot => {
4752 let end_kind = match self.token {
4753 token::DotDot => RangeEnd::Excluded,
4754 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4755 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4756 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4759 let op_span = self.span;
4761 let span = lo.to(self.prev_span);
4762 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4764 let end = self.parse_pat_range_end()?;
4765 let op = Spanned { span: op_span, node: end_kind };
4766 pat = PatKind::Range(begin, end, op);
4768 token::OpenDelim(token::Brace) => {
4769 if qself.is_some() {
4770 let msg = "unexpected `{` after qualified path";
4771 let mut err = self.fatal(msg);
4772 err.span_label(self.span, msg);
4775 // Parse struct pattern
4777 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4779 self.recover_stmt();
4783 pat = PatKind::Struct(path, fields, etc);
4785 token::OpenDelim(token::Paren) => {
4786 if qself.is_some() {
4787 let msg = "unexpected `(` after qualified path";
4788 let mut err = self.fatal(msg);
4789 err.span_label(self.span, msg);
4792 // Parse tuple struct or enum pattern
4793 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4794 pat = PatKind::TupleStruct(path, fields, ddpos)
4796 _ => pat = PatKind::Path(qself, path),
4799 // Try to parse everything else as literal with optional minus
4800 match self.parse_literal_maybe_minus() {
4802 let op_span = self.span;
4803 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4804 self.check(&token::DotDotDot) {
4805 let end_kind = if self.eat(&token::DotDotDot) {
4806 RangeEnd::Included(RangeSyntax::DotDotDot)
4807 } else if self.eat(&token::DotDotEq) {
4808 RangeEnd::Included(RangeSyntax::DotDotEq)
4809 } else if self.eat(&token::DotDot) {
4812 panic!("impossible case: we already matched \
4813 on a range-operator token")
4815 let end = self.parse_pat_range_end()?;
4816 let op = Spanned { span: op_span, node: end_kind };
4817 pat = PatKind::Range(begin, end, op);
4819 pat = PatKind::Lit(begin);
4823 self.cancel(&mut err);
4824 let expected = expected.unwrap_or("pattern");
4826 "expected {}, found {}",
4828 self.this_token_descr(),
4830 let mut err = self.fatal(&msg);
4831 err.span_label(self.span, format!("expected {}", expected));
4832 let sp = self.sess.source_map().start_point(self.span);
4833 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4834 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4842 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4843 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4845 if !allow_range_pat {
4848 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4850 PatKind::Range(..) => {
4851 let mut err = self.struct_span_err(
4853 "the range pattern here has ambiguous interpretation",
4855 err.span_suggestion(
4857 "add parentheses to clarify the precedence",
4858 format!("({})", pprust::pat_to_string(&pat)),
4859 // "ambiguous interpretation" implies that we have to be guessing
4860 Applicability::MaybeIncorrect
4871 /// Parses `ident` or `ident @ pat`.
4872 /// used by the copy foo and ref foo patterns to give a good
4873 /// error message when parsing mistakes like `ref foo(a, b)`.
4874 fn parse_pat_ident(&mut self,
4875 binding_mode: ast::BindingMode)
4876 -> PResult<'a, PatKind> {
4877 let ident = self.parse_ident()?;
4878 let sub = if self.eat(&token::At) {
4879 Some(self.parse_pat(Some("binding pattern"))?)
4884 // just to be friendly, if they write something like
4886 // we end up here with ( as the current token. This shortly
4887 // leads to a parse error. Note that if there is no explicit
4888 // binding mode then we do not end up here, because the lookahead
4889 // will direct us over to parse_enum_variant()
4890 if self.token == token::OpenDelim(token::Paren) {
4891 return Err(self.span_fatal(
4893 "expected identifier, found enum pattern"))
4896 Ok(PatKind::Ident(binding_mode, ident, sub))
4899 /// Parses a local variable declaration.
4900 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4901 let lo = self.prev_span;
4902 let pat = self.parse_top_level_pat()?;
4904 let (err, ty) = if self.eat(&token::Colon) {
4905 // Save the state of the parser before parsing type normally, in case there is a `:`
4906 // instead of an `=` typo.
4907 let parser_snapshot_before_type = self.clone();
4908 let colon_sp = self.prev_span;
4909 match self.parse_ty() {
4910 Ok(ty) => (None, Some(ty)),
4912 // Rewind to before attempting to parse the type and continue parsing
4913 let parser_snapshot_after_type = self.clone();
4914 mem::replace(self, parser_snapshot_before_type);
4916 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4917 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4918 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4924 let init = match (self.parse_initializer(err.is_some()), err) {
4925 (Ok(init), None) => { // init parsed, ty parsed
4928 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4929 // Could parse the type as if it were the initializer, it is likely there was a
4930 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4931 err.span_suggestion_short(
4933 "use `=` if you meant to assign",
4935 Applicability::MachineApplicable
4938 // As this was parsed successfully, continue as if the code has been fixed for the
4939 // rest of the file. It will still fail due to the emitted error, but we avoid
4943 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4945 // Couldn't parse the type nor the initializer, only raise the type error and
4946 // return to the parser state before parsing the type as the initializer.
4947 // let x: <parse_error>;
4948 mem::replace(self, snapshot);
4951 (Err(err), None) => { // init error, ty parsed
4952 // Couldn't parse the initializer and we're not attempting to recover a failed
4953 // parse of the type, return the error.
4957 let hi = if self.token == token::Semi {
4966 id: ast::DUMMY_NODE_ID,
4969 source: LocalSource::Normal,
4973 /// Parses a structure field.
4974 fn parse_name_and_ty(&mut self,
4977 attrs: Vec<Attribute>)
4978 -> PResult<'a, StructField> {
4979 let name = self.parse_ident()?;
4980 self.expect(&token::Colon)?;
4981 let ty = self.parse_ty()?;
4983 span: lo.to(self.prev_span),
4986 id: ast::DUMMY_NODE_ID,
4992 /// Emits an expected-item-after-attributes error.
4993 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4994 let message = match attrs.last() {
4995 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4996 _ => "expected item after attributes",
4999 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
5000 if attrs.last().unwrap().is_sugared_doc {
5001 err.span_label(self.prev_span, "this doc comment doesn't document anything");
5006 /// Parse a statement. This stops just before trailing semicolons on everything but items.
5007 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
5008 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
5009 Ok(self.parse_stmt_(true))
5012 // Eat tokens until we can be relatively sure we reached the end of the
5013 // statement. This is something of a best-effort heuristic.
5015 // We terminate when we find an unmatched `}` (without consuming it).
5016 fn recover_stmt(&mut self) {
5017 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore)
5020 // If `break_on_semi` is `Break`, then we will stop consuming tokens after
5021 // finding (and consuming) a `;` outside of `{}` or `[]` (note that this is
5022 // approximate - it can mean we break too early due to macros, but that
5023 // should only lead to sub-optimal recovery, not inaccurate parsing).
5025 // If `break_on_block` is `Break`, then we will stop consuming tokens
5026 // after finding (and consuming) a brace-delimited block.
5027 fn recover_stmt_(&mut self, break_on_semi: SemiColonMode, break_on_block: BlockMode) {
5028 let mut brace_depth = 0;
5029 let mut bracket_depth = 0;
5030 let mut in_block = false;
5031 debug!("recover_stmt_ enter loop (semi={:?}, block={:?})",
5032 break_on_semi, break_on_block);
5034 debug!("recover_stmt_ loop {:?}", self.token);
5036 token::OpenDelim(token::DelimToken::Brace) => {
5039 if break_on_block == BlockMode::Break &&
5041 bracket_depth == 0 {
5045 token::OpenDelim(token::DelimToken::Bracket) => {
5049 token::CloseDelim(token::DelimToken::Brace) => {
5050 if brace_depth == 0 {
5051 debug!("recover_stmt_ return - close delim {:?}", self.token);
5056 if in_block && bracket_depth == 0 && brace_depth == 0 {
5057 debug!("recover_stmt_ return - block end {:?}", self.token);
5061 token::CloseDelim(token::DelimToken::Bracket) => {
5063 if bracket_depth < 0 {
5069 debug!("recover_stmt_ return - Eof");
5074 if break_on_semi == SemiColonMode::Break &&
5076 bracket_depth == 0 {
5077 debug!("recover_stmt_ return - Semi");
5082 if break_on_semi == SemiColonMode::Comma &&
5084 bracket_depth == 0 {
5085 debug!("recover_stmt_ return - Semi");
5098 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
5099 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
5101 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
5106 fn is_async_block(&self) -> bool {
5107 self.token.is_keyword(keywords::Async) &&
5110 self.look_ahead(1, |t| t.is_keyword(keywords::Move)) &&
5111 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
5113 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
5118 fn is_async_fn(&self) -> bool {
5119 self.token.is_keyword(keywords::Async) &&
5120 self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
5123 fn is_do_catch_block(&self) -> bool {
5124 self.token.is_keyword(keywords::Do) &&
5125 self.look_ahead(1, |t| t.is_keyword(keywords::Catch)) &&
5126 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
5127 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
5130 fn is_try_block(&self) -> bool {
5131 self.token.is_keyword(keywords::Try) &&
5132 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
5133 self.span.rust_2018() &&
5134 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
5135 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
5138 fn is_union_item(&self) -> bool {
5139 self.token.is_keyword(keywords::Union) &&
5140 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
5143 fn is_crate_vis(&self) -> bool {
5144 self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
5147 fn is_existential_type_decl(&self) -> bool {
5148 self.token.is_keyword(keywords::Existential) &&
5149 self.look_ahead(1, |t| t.is_keyword(keywords::Type))
5152 fn is_auto_trait_item(&self) -> bool {
5154 (self.token.is_keyword(keywords::Auto)
5155 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
5156 || // unsafe auto trait
5157 (self.token.is_keyword(keywords::Unsafe) &&
5158 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)) &&
5159 self.look_ahead(2, |t| t.is_keyword(keywords::Trait)))
5162 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
5163 -> PResult<'a, Option<P<Item>>> {
5164 let token_lo = self.span;
5165 let (ident, def) = match self.token {
5166 token::Ident(ident, false) if ident.name == keywords::Macro.name() => {
5168 let ident = self.parse_ident()?;
5169 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
5170 match self.parse_token_tree() {
5171 TokenTree::Delimited(_, _, tts) => tts,
5172 _ => unreachable!(),
5174 } else if self.check(&token::OpenDelim(token::Paren)) {
5175 let args = self.parse_token_tree();
5176 let body = if self.check(&token::OpenDelim(token::Brace)) {
5177 self.parse_token_tree()
5182 TokenStream::new(vec![
5184 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
5192 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
5194 token::Ident(ident, _) if ident.name == sym::macro_rules &&
5195 self.look_ahead(1, |t| *t == token::Not) => {
5196 let prev_span = self.prev_span;
5197 self.complain_if_pub_macro(&vis.node, prev_span);
5201 let ident = self.parse_ident()?;
5202 let (delim, tokens) = self.expect_delimited_token_tree()?;
5203 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
5204 self.report_invalid_macro_expansion_item();
5207 (ident, ast::MacroDef { tokens: tokens, legacy: true })
5209 _ => return Ok(None),
5212 let span = lo.to(self.prev_span);
5213 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
5216 fn parse_stmt_without_recovery(&mut self,
5217 macro_legacy_warnings: bool)
5218 -> PResult<'a, Option<Stmt>> {
5219 maybe_whole!(self, NtStmt, |x| Some(x));
5221 let attrs = self.parse_outer_attributes()?;
5224 Ok(Some(if self.eat_keyword(keywords::Let) {
5226 id: ast::DUMMY_NODE_ID,
5227 node: StmtKind::Local(self.parse_local(attrs.into())?),
5228 span: lo.to(self.prev_span),
5230 } else if let Some(macro_def) = self.eat_macro_def(
5232 &source_map::respan(lo, VisibilityKind::Inherited),
5236 id: ast::DUMMY_NODE_ID,
5237 node: StmtKind::Item(macro_def),
5238 span: lo.to(self.prev_span),
5240 // Starts like a simple path, being careful to avoid contextual keywords
5241 // such as a union items, item with `crate` visibility or auto trait items.
5242 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
5243 // like a path (1 token), but it fact not a path.
5244 // `union::b::c` - path, `union U { ... }` - not a path.
5245 // `crate::b::c` - path, `crate struct S;` - not a path.
5246 } else if self.token.is_path_start() &&
5247 !self.token.is_qpath_start() &&
5248 !self.is_union_item() &&
5249 !self.is_crate_vis() &&
5250 !self.is_existential_type_decl() &&
5251 !self.is_auto_trait_item() &&
5252 !self.is_async_fn() {
5253 let pth = self.parse_path(PathStyle::Expr)?;
5255 if !self.eat(&token::Not) {
5256 let expr = if self.check(&token::OpenDelim(token::Brace)) {
5257 self.parse_struct_expr(lo, pth, ThinVec::new())?
5259 let hi = self.prev_span;
5260 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
5263 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
5264 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
5265 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
5268 return Ok(Some(Stmt {
5269 id: ast::DUMMY_NODE_ID,
5270 node: StmtKind::Expr(expr),
5271 span: lo.to(self.prev_span),
5275 // it's a macro invocation
5276 let id = match self.token {
5277 token::OpenDelim(_) => keywords::Invalid.ident(), // no special identifier
5278 _ => self.parse_ident()?,
5281 // check that we're pointing at delimiters (need to check
5282 // again after the `if`, because of `parse_ident`
5283 // consuming more tokens).
5285 token::OpenDelim(_) => {}
5287 // we only expect an ident if we didn't parse one
5289 let ident_str = if id.name == keywords::Invalid.name() {
5294 let tok_str = self.this_token_descr();
5295 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
5298 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
5303 let (delim, tts) = self.expect_delimited_token_tree()?;
5304 let hi = self.prev_span;
5306 let style = if delim == MacDelimiter::Brace {
5307 MacStmtStyle::Braces
5309 MacStmtStyle::NoBraces
5312 if id.name == keywords::Invalid.name() {
5313 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
5314 let node = if delim == MacDelimiter::Brace ||
5315 self.token == token::Semi || self.token == token::Eof {
5316 StmtKind::Mac(P((mac, style, attrs.into())))
5318 // We used to incorrectly stop parsing macro-expanded statements here.
5319 // If the next token will be an error anyway but could have parsed with the
5320 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
5321 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
5322 // These can continue an expression, so we can't stop parsing and warn.
5323 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
5324 token::BinOp(token::Minus) | token::BinOp(token::Star) |
5325 token::BinOp(token::And) | token::BinOp(token::Or) |
5326 token::AndAnd | token::OrOr |
5327 token::DotDot | token::DotDotDot | token::DotDotEq => false,
5330 self.warn_missing_semicolon();
5331 StmtKind::Mac(P((mac, style, attrs.into())))
5333 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
5334 let e = self.maybe_recover_from_bad_qpath(e, true)?;
5335 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
5336 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
5340 id: ast::DUMMY_NODE_ID,
5345 // if it has a special ident, it's definitely an item
5347 // Require a semicolon or braces.
5348 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
5349 self.report_invalid_macro_expansion_item();
5351 let span = lo.to(hi);
5353 id: ast::DUMMY_NODE_ID,
5355 node: StmtKind::Item({
5357 span, id /*id is good here*/,
5358 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
5359 respan(lo, VisibilityKind::Inherited),
5365 // FIXME: Bad copy of attrs
5366 let old_directory_ownership =
5367 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
5368 let item = self.parse_item_(attrs.clone(), false, true)?;
5369 self.directory.ownership = old_directory_ownership;
5373 id: ast::DUMMY_NODE_ID,
5374 span: lo.to(i.span),
5375 node: StmtKind::Item(i),
5378 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
5379 if !attrs.is_empty() {
5380 if s.prev_token_kind == PrevTokenKind::DocComment {
5381 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
5382 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
5383 s.span_err(s.span, "expected statement after outer attribute");
5388 // Do not attempt to parse an expression if we're done here.
5389 if self.token == token::Semi {
5390 unused_attrs(&attrs, self);
5395 if self.token == token::CloseDelim(token::Brace) {
5396 unused_attrs(&attrs, self);
5400 // Remainder are line-expr stmts.
5401 let e = self.parse_expr_res(
5402 Restrictions::STMT_EXPR, Some(attrs.into()))?;
5404 id: ast::DUMMY_NODE_ID,
5405 span: lo.to(e.span),
5406 node: StmtKind::Expr(e),
5413 /// Checks if this expression is a successfully parsed statement.
5414 fn expr_is_complete(&self, e: &Expr) -> bool {
5415 self.restrictions.contains(Restrictions::STMT_EXPR) &&
5416 !classify::expr_requires_semi_to_be_stmt(e)
5419 /// Parses a block. No inner attributes are allowed.
5420 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
5421 maybe_whole!(self, NtBlock, |x| x);
5425 if !self.eat(&token::OpenDelim(token::Brace)) {
5427 let tok = self.this_token_descr();
5428 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
5429 let do_not_suggest_help =
5430 self.token.is_keyword(keywords::In) || self.token == token::Colon;
5432 if self.token.is_ident_named("and") {
5433 e.span_suggestion_short(
5435 "use `&&` instead of `and` for the boolean operator",
5437 Applicability::MaybeIncorrect,
5440 if self.token.is_ident_named("or") {
5441 e.span_suggestion_short(
5443 "use `||` instead of `or` for the boolean operator",
5445 Applicability::MaybeIncorrect,
5449 // Check to see if the user has written something like
5454 // Which is valid in other languages, but not Rust.
5455 match self.parse_stmt_without_recovery(false) {
5457 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
5458 || do_not_suggest_help {
5459 // if the next token is an open brace (e.g., `if a b {`), the place-
5460 // inside-a-block suggestion would be more likely wrong than right
5461 e.span_label(sp, "expected `{`");
5464 let mut stmt_span = stmt.span;
5465 // expand the span to include the semicolon, if it exists
5466 if self.eat(&token::Semi) {
5467 stmt_span = stmt_span.with_hi(self.prev_span.hi());
5469 let sugg = pprust::to_string(|s| {
5470 use crate::print::pprust::{PrintState, INDENT_UNIT};
5471 s.ibox(INDENT_UNIT)?;
5473 s.print_stmt(&stmt)?;
5474 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
5478 "try placing this code inside a block",
5480 // speculative, has been misleading in the past (closed Issue #46836)
5481 Applicability::MaybeIncorrect
5485 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
5486 self.cancel(&mut e);
5490 e.span_label(sp, "expected `{`");
5494 self.parse_block_tail(lo, BlockCheckMode::Default)
5497 /// Parses a block. Inner attributes are allowed.
5498 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
5499 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
5502 self.expect(&token::OpenDelim(token::Brace))?;
5503 Ok((self.parse_inner_attributes()?,
5504 self.parse_block_tail(lo, BlockCheckMode::Default)?))
5507 /// Parses the rest of a block expression or function body.
5508 /// Precondition: already parsed the '{'.
5509 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
5510 let mut stmts = vec![];
5511 while !self.eat(&token::CloseDelim(token::Brace)) {
5512 let stmt = match self.parse_full_stmt(false) {
5515 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
5517 id: ast::DUMMY_NODE_ID,
5518 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
5524 if let Some(stmt) = stmt {
5526 } else if self.token == token::Eof {
5529 // Found only `;` or `}`.
5535 id: ast::DUMMY_NODE_ID,
5537 span: lo.to(self.prev_span),
5541 /// Parses a statement, including the trailing semicolon.
5542 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
5543 // skip looking for a trailing semicolon when we have an interpolated statement
5544 maybe_whole!(self, NtStmt, |x| Some(x));
5546 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
5548 None => return Ok(None),
5552 StmtKind::Expr(ref expr) if self.token != token::Eof => {
5553 // expression without semicolon
5554 if classify::expr_requires_semi_to_be_stmt(expr) {
5555 // Just check for errors and recover; do not eat semicolon yet.
5557 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
5560 self.recover_stmt();
5564 StmtKind::Local(..) => {
5565 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
5566 if macro_legacy_warnings && self.token != token::Semi {
5567 self.warn_missing_semicolon();
5569 self.expect_one_of(&[], &[token::Semi])?;
5575 if self.eat(&token::Semi) {
5576 stmt = stmt.add_trailing_semicolon();
5579 stmt.span = stmt.span.with_hi(self.prev_span.hi());
5583 fn warn_missing_semicolon(&self) {
5584 self.diagnostic().struct_span_warn(self.span, {
5585 &format!("expected `;`, found {}", self.this_token_descr())
5587 "This was erroneously allowed and will become a hard error in a future release"
5591 fn err_dotdotdot_syntax(&self, span: Span) {
5592 self.diagnostic().struct_span_err(span, {
5593 "unexpected token: `...`"
5595 span, "use `..` for an exclusive range", "..".to_owned(),
5596 Applicability::MaybeIncorrect
5598 span, "or `..=` for an inclusive range", "..=".to_owned(),
5599 Applicability::MaybeIncorrect
5603 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
5606 /// BOUND = TY_BOUND | LT_BOUND
5607 /// LT_BOUND = LIFETIME (e.g., `'a`)
5608 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
5609 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
5611 fn parse_generic_bounds_common(&mut self,
5613 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5614 let mut bounds = Vec::new();
5615 let mut negative_bounds = Vec::new();
5616 let mut last_plus_span = None;
5617 let mut was_negative = false;
5619 // This needs to be synchronized with `Token::can_begin_bound`.
5620 let is_bound_start = self.check_path() || self.check_lifetime() ||
5621 self.check(&token::Not) || // used for error reporting only
5622 self.check(&token::Question) ||
5623 self.check_keyword(keywords::For) ||
5624 self.check(&token::OpenDelim(token::Paren));
5627 let has_parens = self.eat(&token::OpenDelim(token::Paren));
5628 let inner_lo = self.span;
5629 let is_negative = self.eat(&token::Not);
5630 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
5631 if self.token.is_lifetime() {
5632 if let Some(question_span) = question {
5633 self.span_err(question_span,
5634 "`?` may only modify trait bounds, not lifetime bounds");
5636 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
5638 let inner_span = inner_lo.to(self.prev_span);
5639 self.expect(&token::CloseDelim(token::Paren))?;
5640 let mut err = self.struct_span_err(
5641 lo.to(self.prev_span),
5642 "parenthesized lifetime bounds are not supported"
5644 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
5645 err.span_suggestion_short(
5646 lo.to(self.prev_span),
5647 "remove the parentheses",
5649 Applicability::MachineApplicable
5655 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5656 let path = self.parse_path(PathStyle::Type)?;
5658 self.expect(&token::CloseDelim(token::Paren))?;
5660 let poly_span = lo.to(self.prev_span);
5662 was_negative = true;
5663 if let Some(sp) = last_plus_span.or(colon_span) {
5664 negative_bounds.push(sp.to(poly_span));
5667 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
5668 let modifier = if question.is_some() {
5669 TraitBoundModifier::Maybe
5671 TraitBoundModifier::None
5673 bounds.push(GenericBound::Trait(poly_trait, modifier));
5680 if !allow_plus || !self.eat_plus() {
5683 last_plus_span = Some(self.prev_span);
5687 if !negative_bounds.is_empty() || was_negative {
5688 let plural = negative_bounds.len() > 1;
5689 let last_span = negative_bounds.last().map(|sp| *sp);
5690 let mut err = self.struct_span_err(
5692 "negative trait bounds are not supported",
5694 if let Some(sp) = last_span {
5695 err.span_label(sp, "negative trait bounds are not supported");
5697 if let Some(bound_list) = colon_span {
5698 let bound_list = bound_list.to(self.prev_span);
5699 let mut new_bound_list = String::new();
5700 if !bounds.is_empty() {
5701 let mut snippets = bounds.iter().map(|bound| bound.span())
5702 .map(|span| self.sess.source_map().span_to_snippet(span));
5703 while let Some(Ok(snippet)) = snippets.next() {
5704 new_bound_list.push_str(" + ");
5705 new_bound_list.push_str(&snippet);
5707 new_bound_list = new_bound_list.replacen(" +", ":", 1);
5709 err.span_suggestion_hidden(
5711 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
5713 Applicability::MachineApplicable,
5722 crate fn parse_generic_bounds(&mut self,
5723 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5724 self.parse_generic_bounds_common(true, colon_span)
5727 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
5730 /// BOUND = LT_BOUND (e.g., `'a`)
5732 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
5733 let mut lifetimes = Vec::new();
5734 while self.check_lifetime() {
5735 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
5737 if !self.eat_plus() {
5744 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
5745 fn parse_ty_param(&mut self,
5746 preceding_attrs: Vec<Attribute>)
5747 -> PResult<'a, GenericParam> {
5748 let ident = self.parse_ident()?;
5750 // Parse optional colon and param bounds.
5751 let bounds = if self.eat(&token::Colon) {
5752 self.parse_generic_bounds(Some(self.prev_span))?
5757 let default = if self.eat(&token::Eq) {
5758 Some(self.parse_ty()?)
5765 id: ast::DUMMY_NODE_ID,
5766 attrs: preceding_attrs.into(),
5768 kind: GenericParamKind::Type {
5774 /// Parses the following grammar:
5776 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
5777 fn parse_trait_item_assoc_ty(&mut self)
5778 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
5779 let ident = self.parse_ident()?;
5780 let mut generics = self.parse_generics()?;
5782 // Parse optional colon and param bounds.
5783 let bounds = if self.eat(&token::Colon) {
5784 self.parse_generic_bounds(None)?
5788 generics.where_clause = self.parse_where_clause()?;
5790 let default = if self.eat(&token::Eq) {
5791 Some(self.parse_ty()?)
5795 self.expect(&token::Semi)?;
5797 Ok((ident, TraitItemKind::Type(bounds, default), generics))
5800 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
5801 self.expect_keyword(keywords::Const)?;
5802 let ident = self.parse_ident()?;
5803 self.expect(&token::Colon)?;
5804 let ty = self.parse_ty()?;
5808 id: ast::DUMMY_NODE_ID,
5809 attrs: preceding_attrs.into(),
5811 kind: GenericParamKind::Const {
5817 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
5818 /// a trailing comma and erroneous trailing attributes.
5819 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
5820 let mut params = Vec::new();
5822 let attrs = self.parse_outer_attributes()?;
5823 if self.check_lifetime() {
5824 let lifetime = self.expect_lifetime();
5825 // Parse lifetime parameter.
5826 let bounds = if self.eat(&token::Colon) {
5827 self.parse_lt_param_bounds()
5831 params.push(ast::GenericParam {
5832 ident: lifetime.ident,
5834 attrs: attrs.into(),
5836 kind: ast::GenericParamKind::Lifetime,
5838 } else if self.check_keyword(keywords::Const) {
5839 // Parse const parameter.
5840 params.push(self.parse_const_param(attrs)?);
5841 } else if self.check_ident() {
5842 // Parse type parameter.
5843 params.push(self.parse_ty_param(attrs)?);
5845 // Check for trailing attributes and stop parsing.
5846 if !attrs.is_empty() {
5847 if !params.is_empty() {
5848 self.struct_span_err(
5850 &format!("trailing attribute after generic parameter"),
5852 .span_label(attrs[0].span, "attributes must go before parameters")
5855 self.struct_span_err(
5857 &format!("attribute without generic parameters"),
5861 "attributes are only permitted when preceding parameters",
5869 if !self.eat(&token::Comma) {
5876 /// Parses a set of optional generic type parameter declarations. Where
5877 /// clauses are not parsed here, and must be added later via
5878 /// `parse_where_clause()`.
5880 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5881 /// | ( < lifetimes , typaramseq ( , )? > )
5882 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5883 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5884 let span_lo = self.span;
5886 let params = self.parse_generic_params()?;
5890 where_clause: WhereClause {
5891 id: ast::DUMMY_NODE_ID,
5892 predicates: Vec::new(),
5893 span: syntax_pos::DUMMY_SP,
5895 span: span_lo.to(self.prev_span),
5898 Ok(ast::Generics::default())
5902 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5903 /// For the purposes of understanding the parsing logic of generic arguments, this function
5904 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5905 /// had the correct amount of leading angle brackets.
5907 /// ```ignore (diagnostics)
5908 /// bar::<<<<T as Foo>::Output>();
5909 /// ^^ help: remove extra angle brackets
5911 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5915 ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5916 // We need to detect whether there are extra leading left angle brackets and produce an
5917 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5918 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5919 // then there won't be matching `>` tokens to find.
5921 // To explain how this detection works, consider the following example:
5923 // ```ignore (diagnostics)
5924 // bar::<<<<T as Foo>::Output>();
5925 // ^^ help: remove extra angle brackets
5928 // Parsing of the left angle brackets starts in this function. We start by parsing the
5929 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5932 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5933 // *Unmatched count:* 1
5934 // *`parse_path_segment` calls deep:* 0
5936 // This has the effect of recursing as this function is called if a `<` character
5937 // is found within the expected generic arguments:
5939 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5940 // *Unmatched count:* 2
5941 // *`parse_path_segment` calls deep:* 1
5943 // Eventually we will have recursed until having consumed all of the `<` tokens and
5944 // this will be reflected in the count:
5946 // *Upcoming tokens:* `T as Foo>::Output>;`
5947 // *Unmatched count:* 4
5948 // `parse_path_segment` calls deep:* 3
5950 // The parser will continue until reaching the first `>` - this will decrement the
5951 // unmatched angle bracket count and return to the parent invocation of this function
5952 // having succeeded in parsing:
5954 // *Upcoming tokens:* `::Output>;`
5955 // *Unmatched count:* 3
5956 // *`parse_path_segment` calls deep:* 2
5958 // This will continue until the next `>` character which will also return successfully
5959 // to the parent invocation of this function and decrement the count:
5961 // *Upcoming tokens:* `;`
5962 // *Unmatched count:* 2
5963 // *`parse_path_segment` calls deep:* 1
5965 // At this point, this function will expect to find another matching `>` character but
5966 // won't be able to and will return an error. This will continue all the way up the
5967 // call stack until the first invocation:
5969 // *Upcoming tokens:* `;`
5970 // *Unmatched count:* 2
5971 // *`parse_path_segment` calls deep:* 0
5973 // In doing this, we have managed to work out how many unmatched leading left angle
5974 // brackets there are, but we cannot recover as the unmatched angle brackets have
5975 // already been consumed. To remedy this, we keep a snapshot of the parser state
5976 // before we do the above. We can then inspect whether we ended up with a parsing error
5977 // and unmatched left angle brackets and if so, restore the parser state before we
5978 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5979 // recover by attempting to parse again.
5981 // In practice, the recursion of this function is indirect and there will be other
5982 // locations that consume some `<` characters - as long as we update the count when
5983 // this happens, it isn't an issue.
5985 let is_first_invocation = style == PathStyle::Expr;
5986 // Take a snapshot before attempting to parse - we can restore this later.
5987 let snapshot = if is_first_invocation {
5993 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5994 match self.parse_generic_args() {
5995 Ok(value) => Ok(value),
5996 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5997 // Cancel error from being unable to find `>`. We know the error
5998 // must have been this due to a non-zero unmatched angle bracket
6002 // Swap `self` with our backup of the parser state before attempting to parse
6003 // generic arguments.
6004 let snapshot = mem::replace(self, snapshot.unwrap());
6007 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
6008 snapshot.count={:?}",
6009 snapshot.unmatched_angle_bracket_count,
6012 // Eat the unmatched angle brackets.
6013 for _ in 0..snapshot.unmatched_angle_bracket_count {
6017 // Make a span over ${unmatched angle bracket count} characters.
6018 let span = lo.with_hi(
6019 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
6021 let plural = snapshot.unmatched_angle_bracket_count > 1;
6026 "unmatched angle bracket{}",
6027 if plural { "s" } else { "" }
6033 "remove extra angle bracket{}",
6034 if plural { "s" } else { "" }
6037 Applicability::MachineApplicable,
6041 // Try again without unmatched angle bracket characters.
6042 self.parse_generic_args()
6048 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
6049 /// possibly including trailing comma.
6050 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
6051 let mut args = Vec::new();
6052 let mut bindings = Vec::new();
6053 let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
6054 let mut assoc_ty_bindings: Vec<Span> = Vec::new();
6056 let args_lo = self.span;
6059 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
6060 // Parse lifetime argument.
6061 args.push(GenericArg::Lifetime(self.expect_lifetime()));
6062 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6063 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
6064 // Parse associated type binding.
6066 let ident = self.parse_ident()?;
6068 let ty = self.parse_ty()?;
6069 let span = lo.to(self.prev_span);
6070 bindings.push(TypeBinding {
6071 id: ast::DUMMY_NODE_ID,
6076 assoc_ty_bindings.push(span);
6077 } else if self.check_const_arg() {
6078 // Parse const argument.
6079 let expr = if let token::OpenDelim(token::Brace) = self.token {
6080 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
6081 } else if self.token.is_ident() {
6082 // FIXME(const_generics): to distinguish between idents for types and consts,
6083 // we should introduce a GenericArg::Ident in the AST and distinguish when
6084 // lowering to the HIR. For now, idents for const args are not permitted.
6086 self.fatal("identifiers may currently not be used for const generics")
6089 self.parse_literal_maybe_minus()?
6091 let value = AnonConst {
6092 id: ast::DUMMY_NODE_ID,
6095 args.push(GenericArg::Const(value));
6096 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6097 } else if self.check_type() {
6098 // Parse type argument.
6099 args.push(GenericArg::Type(self.parse_ty()?));
6100 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
6105 if !self.eat(&token::Comma) {
6110 // FIXME: we would like to report this in ast_validation instead, but we currently do not
6111 // preserve ordering of generic parameters with respect to associated type binding, so we
6112 // lose that information after parsing.
6113 if misplaced_assoc_ty_bindings.len() > 0 {
6114 let mut err = self.struct_span_err(
6115 args_lo.to(self.prev_span),
6116 "associated type bindings must be declared after generic parameters",
6118 for span in misplaced_assoc_ty_bindings {
6121 "this associated type binding should be moved after the generic parameters",
6127 Ok((args, bindings))
6130 /// Parses an optional where-clause and places it in `generics`.
6132 /// ```ignore (only-for-syntax-highlight)
6133 /// where T : Trait<U, V> + 'b, 'a : 'b
6135 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
6136 let mut where_clause = WhereClause {
6137 id: ast::DUMMY_NODE_ID,
6138 predicates: Vec::new(),
6139 span: syntax_pos::DUMMY_SP,
6142 if !self.eat_keyword(keywords::Where) {
6143 return Ok(where_clause);
6145 let lo = self.prev_span;
6147 // We are considering adding generics to the `where` keyword as an alternative higher-rank
6148 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
6149 // change we parse those generics now, but report an error.
6150 if self.choose_generics_over_qpath() {
6151 let generics = self.parse_generics()?;
6152 self.struct_span_err(
6154 "generic parameters on `where` clauses are reserved for future use",
6156 .span_label(generics.span, "currently unsupported")
6162 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
6163 let lifetime = self.expect_lifetime();
6164 // Bounds starting with a colon are mandatory, but possibly empty.
6165 self.expect(&token::Colon)?;
6166 let bounds = self.parse_lt_param_bounds();
6167 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
6168 ast::WhereRegionPredicate {
6169 span: lo.to(self.prev_span),
6174 } else if self.check_type() {
6175 // Parse optional `for<'a, 'b>`.
6176 // This `for` is parsed greedily and applies to the whole predicate,
6177 // the bounded type can have its own `for` applying only to it.
6178 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
6179 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
6180 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
6181 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
6183 // Parse type with mandatory colon and (possibly empty) bounds,
6184 // or with mandatory equality sign and the second type.
6185 let ty = self.parse_ty()?;
6186 if self.eat(&token::Colon) {
6187 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
6188 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
6189 ast::WhereBoundPredicate {
6190 span: lo.to(self.prev_span),
6191 bound_generic_params: lifetime_defs,
6196 // FIXME: Decide what should be used here, `=` or `==`.
6197 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
6198 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
6199 let rhs_ty = self.parse_ty()?;
6200 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
6201 ast::WhereEqPredicate {
6202 span: lo.to(self.prev_span),
6205 id: ast::DUMMY_NODE_ID,
6209 return self.unexpected();
6215 if !self.eat(&token::Comma) {
6220 where_clause.span = lo.to(self.prev_span);
6224 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
6225 -> PResult<'a, (Vec<Arg> , bool)> {
6226 self.expect(&token::OpenDelim(token::Paren))?;
6229 let mut c_variadic = false;
6230 let (args, recovered): (Vec<Option<Arg>>, bool) =
6231 self.parse_seq_to_before_end(
6232 &token::CloseDelim(token::Paren),
6233 SeqSep::trailing_allowed(token::Comma),
6235 // If the argument is a C-variadic argument we should not
6236 // enforce named arguments.
6237 let enforce_named_args = if p.token == token::DotDotDot {
6242 match p.parse_arg_general(enforce_named_args, false,
6245 if let TyKind::CVarArgs = arg.ty.node {
6247 if p.token != token::CloseDelim(token::Paren) {
6250 "`...` must be the last argument of a C-variadic function");
6261 let lo = p.prev_span;
6262 // Skip every token until next possible arg or end.
6263 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
6264 // Create a placeholder argument for proper arg count (issue #34264).
6265 let span = lo.to(p.prev_span);
6266 Ok(Some(dummy_arg(span)))
6273 self.eat(&token::CloseDelim(token::Paren));
6276 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
6278 if c_variadic && args.is_empty() {
6280 "C-variadic function must be declared with at least one named argument");
6283 Ok((args, c_variadic))
6286 /// Parses the argument list and result type of a function declaration.
6287 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
6289 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
6290 let ret_ty = self.parse_ret_ty(true)?;
6299 /// Returns the parsed optional self argument and whether a self shortcut was used.
6300 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
6301 let expect_ident = |this: &mut Self| match this.token {
6302 // Preserve hygienic context.
6303 token::Ident(ident, _) =>
6304 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
6307 let isolated_self = |this: &mut Self, n| {
6308 this.look_ahead(n, |t| t.is_keyword(keywords::SelfLower)) &&
6309 this.look_ahead(n + 1, |t| t != &token::ModSep)
6312 // Parse optional self parameter of a method.
6313 // Only a limited set of initial token sequences is considered self parameters, anything
6314 // else is parsed as a normal function parameter list, so some lookahead is required.
6315 let eself_lo = self.span;
6316 let (eself, eself_ident, eself_hi) = match self.token {
6317 token::BinOp(token::And) => {
6323 (if isolated_self(self, 1) {
6325 SelfKind::Region(None, Mutability::Immutable)
6326 } else if self.look_ahead(1, |t| t.is_keyword(keywords::Mut)) &&
6327 isolated_self(self, 2) {
6330 SelfKind::Region(None, Mutability::Mutable)
6331 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6332 isolated_self(self, 2) {
6334 let lt = self.expect_lifetime();
6335 SelfKind::Region(Some(lt), Mutability::Immutable)
6336 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6337 self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
6338 isolated_self(self, 3) {
6340 let lt = self.expect_lifetime();
6342 SelfKind::Region(Some(lt), Mutability::Mutable)
6345 }, expect_ident(self), self.prev_span)
6347 token::BinOp(token::Star) => {
6352 // Emit special error for `self` cases.
6353 let msg = "cannot pass `self` by raw pointer";
6354 (if isolated_self(self, 1) {
6356 self.struct_span_err(self.span, msg)
6357 .span_label(self.span, msg)
6359 SelfKind::Value(Mutability::Immutable)
6360 } else if self.look_ahead(1, |t| t.is_mutability()) &&
6361 isolated_self(self, 2) {
6364 self.struct_span_err(self.span, msg)
6365 .span_label(self.span, msg)
6367 SelfKind::Value(Mutability::Immutable)
6370 }, expect_ident(self), self.prev_span)
6372 token::Ident(..) => {
6373 if isolated_self(self, 0) {
6376 let eself_ident = expect_ident(self);
6377 let eself_hi = self.prev_span;
6378 (if self.eat(&token::Colon) {
6379 let ty = self.parse_ty()?;
6380 SelfKind::Explicit(ty, Mutability::Immutable)
6382 SelfKind::Value(Mutability::Immutable)
6383 }, eself_ident, eself_hi)
6384 } else if self.token.is_keyword(keywords::Mut) &&
6385 isolated_self(self, 1) {
6389 let eself_ident = expect_ident(self);
6390 let eself_hi = self.prev_span;
6391 (if self.eat(&token::Colon) {
6392 let ty = self.parse_ty()?;
6393 SelfKind::Explicit(ty, Mutability::Mutable)
6395 SelfKind::Value(Mutability::Mutable)
6396 }, eself_ident, eself_hi)
6401 _ => return Ok(None),
6404 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
6405 Ok(Some(Arg::from_self(eself, eself_ident)))
6408 /// Parses the parameter list and result type of a function that may have a `self` parameter.
6409 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
6410 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
6412 self.expect(&token::OpenDelim(token::Paren))?;
6414 // Parse optional self argument
6415 let self_arg = self.parse_self_arg()?;
6417 // Parse the rest of the function parameter list.
6418 let sep = SeqSep::trailing_allowed(token::Comma);
6419 let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
6420 if self.check(&token::CloseDelim(token::Paren)) {
6421 (vec![self_arg], false)
6422 } else if self.eat(&token::Comma) {
6423 let mut fn_inputs = vec![self_arg];
6424 let (mut input, recovered) = self.parse_seq_to_before_end(
6425 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
6426 fn_inputs.append(&mut input);
6427 (fn_inputs, recovered)
6429 match self.expect_one_of(&[], &[]) {
6430 Err(err) => return Err(err),
6431 Ok(recovered) => (vec![self_arg], recovered),
6435 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
6439 // Parse closing paren and return type.
6440 self.expect(&token::CloseDelim(token::Paren))?;
6444 output: self.parse_ret_ty(true)?,
6449 /// Parses the `|arg, arg|` header of a closure.
6450 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
6451 let inputs_captures = {
6452 if self.eat(&token::OrOr) {
6455 self.expect(&token::BinOp(token::Or))?;
6456 let args = self.parse_seq_to_before_tokens(
6457 &[&token::BinOp(token::Or), &token::OrOr],
6458 SeqSep::trailing_allowed(token::Comma),
6459 TokenExpectType::NoExpect,
6460 |p| p.parse_fn_block_arg()
6466 let output = self.parse_ret_ty(true)?;
6469 inputs: inputs_captures,
6475 /// Parses the name and optional generic types of a function header.
6476 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
6477 let id = self.parse_ident()?;
6478 let generics = self.parse_generics()?;
6482 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
6483 attrs: Vec<Attribute>) -> P<Item> {
6487 id: ast::DUMMY_NODE_ID,
6495 /// Parses an item-position function declaration.
6496 fn parse_item_fn(&mut self,
6498 mut asyncness: Spanned<IsAsync>,
6499 constness: Spanned<Constness>,
6501 -> PResult<'a, ItemInfo> {
6502 let (ident, mut generics) = self.parse_fn_header()?;
6503 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
6504 let mut decl = self.parse_fn_decl(allow_c_variadic)?;
6505 generics.where_clause = self.parse_where_clause()?;
6506 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6507 self.construct_async_arguments(&mut asyncness, &mut decl);
6508 let header = FnHeader { unsafety, asyncness, constness, abi };
6509 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
6512 /// Returns `true` if we are looking at `const ID`
6513 /// (returns `false` for things like `const fn`, etc.).
6514 fn is_const_item(&self) -> bool {
6515 self.token.is_keyword(keywords::Const) &&
6516 !self.look_ahead(1, |t| t.is_keyword(keywords::Fn)) &&
6517 !self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe))
6520 /// Parses all the "front matter" for a `fn` declaration, up to
6521 /// and including the `fn` keyword:
6525 /// - `const unsafe fn`
6528 fn parse_fn_front_matter(&mut self)
6536 let is_const_fn = self.eat_keyword(keywords::Const);
6537 let const_span = self.prev_span;
6538 let unsafety = self.parse_unsafety();
6539 let asyncness = self.parse_asyncness();
6540 let asyncness = respan(self.prev_span, asyncness);
6541 let (constness, unsafety, abi) = if is_const_fn {
6542 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
6544 let abi = if self.eat_keyword(keywords::Extern) {
6545 self.parse_opt_abi()?.unwrap_or(Abi::C)
6549 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
6551 if !self.eat_keyword(keywords::Fn) {
6552 // It is possible for `expect_one_of` to recover given the contents of
6553 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
6554 // account for this.
6555 if !self.expect_one_of(&[], &[])? { unreachable!() }
6557 Ok((constness, unsafety, asyncness, abi))
6560 /// Parses an impl item.
6561 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
6562 maybe_whole!(self, NtImplItem, |x| x);
6563 let attrs = self.parse_outer_attributes()?;
6564 let mut unclosed_delims = vec![];
6565 let (mut item, tokens) = self.collect_tokens(|this| {
6566 let item = this.parse_impl_item_(at_end, attrs);
6567 unclosed_delims.append(&mut this.unclosed_delims);
6570 self.unclosed_delims.append(&mut unclosed_delims);
6572 // See `parse_item` for why this clause is here.
6573 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
6574 item.tokens = Some(tokens);
6579 fn parse_impl_item_(&mut self,
6581 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
6583 let vis = self.parse_visibility(false)?;
6584 let defaultness = self.parse_defaultness();
6585 let (name, node, generics) = if let Some(type_) = self.eat_type() {
6586 let (name, alias, generics) = type_?;
6587 let kind = match alias {
6588 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
6589 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
6591 (name, kind, generics)
6592 } else if self.is_const_item() {
6593 // This parses the grammar:
6594 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
6595 self.expect_keyword(keywords::Const)?;
6596 let name = self.parse_ident()?;
6597 self.expect(&token::Colon)?;
6598 let typ = self.parse_ty()?;
6599 self.expect(&token::Eq)?;
6600 let expr = self.parse_expr()?;
6601 self.expect(&token::Semi)?;
6602 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
6604 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
6605 attrs.extend(inner_attrs);
6606 (name, node, generics)
6610 id: ast::DUMMY_NODE_ID,
6611 span: lo.to(self.prev_span),
6622 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
6624 VisibilityKind::Inherited => {}
6626 let is_macro_rules: bool = match self.token {
6627 token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
6630 let mut err = if is_macro_rules {
6631 let mut err = self.diagnostic()
6632 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
6633 err.span_suggestion(
6635 "try exporting the macro",
6636 "#[macro_export]".to_owned(),
6637 Applicability::MaybeIncorrect // speculative
6641 let mut err = self.diagnostic()
6642 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
6643 err.help("try adjusting the macro to put `pub` inside the invocation");
6651 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
6652 -> DiagnosticBuilder<'a>
6654 let expected_kinds = if item_type == "extern" {
6655 "missing `fn`, `type`, or `static`"
6657 "missing `fn`, `type`, or `const`"
6660 // Given this code `path(`, it seems like this is not
6661 // setting the visibility of a macro invocation, but rather
6662 // a mistyped method declaration.
6663 // Create a diagnostic pointing out that `fn` is missing.
6665 // x | pub path(&self) {
6666 // | ^ missing `fn`, `type`, or `const`
6668 // ^^ `sp` below will point to this
6669 let sp = prev_span.between(self.prev_span);
6670 let mut err = self.diagnostic().struct_span_err(
6672 &format!("{} for {}-item declaration",
6673 expected_kinds, item_type));
6674 err.span_label(sp, expected_kinds);
6678 /// Parse a method or a macro invocation in a trait impl.
6679 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
6680 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
6681 ast::ImplItemKind)> {
6682 // code copied from parse_macro_use_or_failure... abstraction!
6683 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
6685 Ok((keywords::Invalid.ident(), vec![], ast::Generics::default(),
6686 ast::ImplItemKind::Macro(mac)))
6688 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
6689 let ident = self.parse_ident()?;
6690 let mut generics = self.parse_generics()?;
6691 let mut decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
6692 generics.where_clause = self.parse_where_clause()?;
6693 self.construct_async_arguments(&mut asyncness, &mut decl);
6695 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6696 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
6697 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
6698 ast::MethodSig { header, decl },
6704 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
6705 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
6706 let ident = self.parse_ident()?;
6707 let mut tps = self.parse_generics()?;
6709 // Parse optional colon and supertrait bounds.
6710 let bounds = if self.eat(&token::Colon) {
6711 self.parse_generic_bounds(Some(self.prev_span))?
6716 if self.eat(&token::Eq) {
6717 // it's a trait alias
6718 let bounds = self.parse_generic_bounds(None)?;
6719 tps.where_clause = self.parse_where_clause()?;
6720 self.expect(&token::Semi)?;
6721 if is_auto == IsAuto::Yes {
6722 let msg = "trait aliases cannot be `auto`";
6723 self.struct_span_err(self.prev_span, msg)
6724 .span_label(self.prev_span, msg)
6727 if unsafety != Unsafety::Normal {
6728 let msg = "trait aliases cannot be `unsafe`";
6729 self.struct_span_err(self.prev_span, msg)
6730 .span_label(self.prev_span, msg)
6733 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
6735 // it's a normal trait
6736 tps.where_clause = self.parse_where_clause()?;
6737 self.expect(&token::OpenDelim(token::Brace))?;
6738 let mut trait_items = vec![];
6739 while !self.eat(&token::CloseDelim(token::Brace)) {
6740 if let token::DocComment(_) = self.token {
6741 if self.look_ahead(1,
6742 |tok| tok == &token::Token::CloseDelim(token::Brace)) {
6743 let mut err = self.diagnostic().struct_span_err_with_code(
6745 "found a documentation comment that doesn't document anything",
6746 DiagnosticId::Error("E0584".into()),
6748 err.help("doc comments must come before what they document, maybe a \
6749 comment was intended with `//`?",
6756 let mut at_end = false;
6757 match self.parse_trait_item(&mut at_end) {
6758 Ok(item) => trait_items.push(item),
6762 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6767 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
6771 fn choose_generics_over_qpath(&self) -> bool {
6772 // There's an ambiguity between generic parameters and qualified paths in impls.
6773 // If we see `<` it may start both, so we have to inspect some following tokens.
6774 // The following combinations can only start generics,
6775 // but not qualified paths (with one exception):
6776 // `<` `>` - empty generic parameters
6777 // `<` `#` - generic parameters with attributes
6778 // `<` (LIFETIME|IDENT) `>` - single generic parameter
6779 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
6780 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
6781 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
6782 // `<` const - generic const parameter
6783 // The only truly ambiguous case is
6784 // `<` IDENT `>` `::` IDENT ...
6785 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
6786 // because this is what almost always expected in practice, qualified paths in impls
6787 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
6788 self.token == token::Lt &&
6789 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
6790 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
6791 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
6792 t == &token::Colon || t == &token::Eq) ||
6793 self.look_ahead(1, |t| t.is_keyword(keywords::Const)))
6796 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
6797 self.expect(&token::OpenDelim(token::Brace))?;
6798 let attrs = self.parse_inner_attributes()?;
6800 let mut impl_items = Vec::new();
6801 while !self.eat(&token::CloseDelim(token::Brace)) {
6802 let mut at_end = false;
6803 match self.parse_impl_item(&mut at_end) {
6804 Ok(impl_item) => impl_items.push(impl_item),
6808 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6813 Ok((impl_items, attrs))
6816 /// Parses an implementation item, `impl` keyword is already parsed.
6818 /// impl<'a, T> TYPE { /* impl items */ }
6819 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
6820 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
6822 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
6823 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
6824 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
6825 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
6826 -> PResult<'a, ItemInfo> {
6827 // First, parse generic parameters if necessary.
6828 let mut generics = if self.choose_generics_over_qpath() {
6829 self.parse_generics()?
6831 ast::Generics::default()
6834 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6835 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6837 ast::ImplPolarity::Negative
6839 ast::ImplPolarity::Positive
6842 // Parse both types and traits as a type, then reinterpret if necessary.
6843 let err_path = |span| ast::Path::from_ident(Ident::new(keywords::Invalid.name(), span));
6844 let ty_first = if self.token.is_keyword(keywords::For) &&
6845 self.look_ahead(1, |t| t != &token::Lt) {
6846 let span = self.prev_span.between(self.span);
6847 self.struct_span_err(span, "missing trait in a trait impl").emit();
6848 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6853 // If `for` is missing we try to recover.
6854 let has_for = self.eat_keyword(keywords::For);
6855 let missing_for_span = self.prev_span.between(self.span);
6857 let ty_second = if self.token == token::DotDot {
6858 // We need to report this error after `cfg` expansion for compatibility reasons
6859 self.bump(); // `..`, do not add it to expected tokens
6860 Some(DummyResult::raw_ty(self.prev_span, true))
6861 } else if has_for || self.token.can_begin_type() {
6862 Some(self.parse_ty()?)
6867 generics.where_clause = self.parse_where_clause()?;
6869 let (impl_items, attrs) = self.parse_impl_body()?;
6871 let item_kind = match ty_second {
6872 Some(ty_second) => {
6873 // impl Trait for Type
6875 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6876 .span_suggestion_short(
6879 " for ".to_string(),
6880 Applicability::MachineApplicable,
6884 let ty_first = ty_first.into_inner();
6885 let path = match ty_first.node {
6886 // This notably includes paths passed through `ty` macro fragments (#46438).
6887 TyKind::Path(None, path) => path,
6889 self.span_err(ty_first.span, "expected a trait, found type");
6890 err_path(ty_first.span)
6893 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6895 ItemKind::Impl(unsafety, polarity, defaultness,
6896 generics, Some(trait_ref), ty_second, impl_items)
6900 ItemKind::Impl(unsafety, polarity, defaultness,
6901 generics, None, ty_first, impl_items)
6905 Ok((keywords::Invalid.ident(), item_kind, Some(attrs)))
6908 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6909 if self.eat_keyword(keywords::For) {
6911 let params = self.parse_generic_params()?;
6913 // We rely on AST validation to rule out invalid cases: There must not be type
6914 // parameters, and the lifetime parameters must not have bounds.
6921 /// Parses `struct Foo { ... }`.
6922 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6923 let class_name = self.parse_ident()?;
6925 let mut generics = self.parse_generics()?;
6927 // There is a special case worth noting here, as reported in issue #17904.
6928 // If we are parsing a tuple struct it is the case that the where clause
6929 // should follow the field list. Like so:
6931 // struct Foo<T>(T) where T: Copy;
6933 // If we are parsing a normal record-style struct it is the case
6934 // that the where clause comes before the body, and after the generics.
6935 // So if we look ahead and see a brace or a where-clause we begin
6936 // parsing a record style struct.
6938 // Otherwise if we look ahead and see a paren we parse a tuple-style
6941 let vdata = if self.token.is_keyword(keywords::Where) {
6942 generics.where_clause = self.parse_where_clause()?;
6943 if self.eat(&token::Semi) {
6944 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6945 VariantData::Unit(ast::DUMMY_NODE_ID)
6947 // If we see: `struct Foo<T> where T: Copy { ... }`
6948 let (fields, recovered) = self.parse_record_struct_body()?;
6949 VariantData::Struct(fields, recovered)
6951 // No `where` so: `struct Foo<T>;`
6952 } else if self.eat(&token::Semi) {
6953 VariantData::Unit(ast::DUMMY_NODE_ID)
6954 // Record-style struct definition
6955 } else if self.token == token::OpenDelim(token::Brace) {
6956 let (fields, recovered) = self.parse_record_struct_body()?;
6957 VariantData::Struct(fields, recovered)
6958 // Tuple-style struct definition with optional where-clause.
6959 } else if self.token == token::OpenDelim(token::Paren) {
6960 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6961 generics.where_clause = self.parse_where_clause()?;
6962 self.expect(&token::Semi)?;
6965 let token_str = self.this_token_descr();
6966 let mut err = self.fatal(&format!(
6967 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6970 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6974 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6977 /// Parses `union Foo { ... }`.
6978 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6979 let class_name = self.parse_ident()?;
6981 let mut generics = self.parse_generics()?;
6983 let vdata = if self.token.is_keyword(keywords::Where) {
6984 generics.where_clause = self.parse_where_clause()?;
6985 let (fields, recovered) = self.parse_record_struct_body()?;
6986 VariantData::Struct(fields, recovered)
6987 } else if self.token == token::OpenDelim(token::Brace) {
6988 let (fields, recovered) = self.parse_record_struct_body()?;
6989 VariantData::Struct(fields, recovered)
6991 let token_str = self.this_token_descr();
6992 let mut err = self.fatal(&format!(
6993 "expected `where` or `{{` after union name, found {}", token_str));
6994 err.span_label(self.span, "expected `where` or `{` after union name");
6998 Ok((class_name, ItemKind::Union(vdata, generics), None))
7001 fn consume_block(&mut self, delim: token::DelimToken) {
7002 let mut brace_depth = 0;
7004 if self.eat(&token::OpenDelim(delim)) {
7006 } else if self.eat(&token::CloseDelim(delim)) {
7007 if brace_depth == 0 {
7013 } else if self.token == token::Eof || self.eat(&token::CloseDelim(token::NoDelim)) {
7021 fn parse_record_struct_body(
7023 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
7024 let mut fields = Vec::new();
7025 let mut recovered = false;
7026 if self.eat(&token::OpenDelim(token::Brace)) {
7027 while self.token != token::CloseDelim(token::Brace) {
7028 let field = self.parse_struct_decl_field().map_err(|e| {
7029 self.recover_stmt();
7034 Ok(field) => fields.push(field),
7040 self.eat(&token::CloseDelim(token::Brace));
7042 let token_str = self.this_token_descr();
7043 let mut err = self.fatal(&format!(
7044 "expected `where`, or `{{` after struct name, found {}", token_str));
7045 err.span_label(self.span, "expected `where`, or `{` after struct name");
7049 Ok((fields, recovered))
7052 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
7053 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
7054 // Unit like structs are handled in parse_item_struct function
7055 let fields = self.parse_unspanned_seq(
7056 &token::OpenDelim(token::Paren),
7057 &token::CloseDelim(token::Paren),
7058 SeqSep::trailing_allowed(token::Comma),
7060 let attrs = p.parse_outer_attributes()?;
7062 let vis = p.parse_visibility(true)?;
7063 let ty = p.parse_ty()?;
7065 span: lo.to(ty.span),
7068 id: ast::DUMMY_NODE_ID,
7077 /// Parses a structure field declaration.
7078 fn parse_single_struct_field(&mut self,
7081 attrs: Vec<Attribute> )
7082 -> PResult<'a, StructField> {
7083 let mut seen_comma: bool = false;
7084 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
7085 if self.token == token::Comma {
7092 token::CloseDelim(token::Brace) => {}
7093 token::DocComment(_) => {
7094 let previous_span = self.prev_span;
7095 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
7096 self.bump(); // consume the doc comment
7097 let comma_after_doc_seen = self.eat(&token::Comma);
7098 // `seen_comma` is always false, because we are inside doc block
7099 // condition is here to make code more readable
7100 if seen_comma == false && comma_after_doc_seen == true {
7103 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
7106 if seen_comma == false {
7107 let sp = self.sess.source_map().next_point(previous_span);
7108 err.span_suggestion(
7110 "missing comma here",
7112 Applicability::MachineApplicable
7119 let sp = self.sess.source_map().next_point(self.prev_span);
7120 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
7121 self.this_token_descr()));
7122 if self.token.is_ident() {
7123 // This is likely another field; emit the diagnostic and keep going
7124 err.span_suggestion(
7126 "try adding a comma",
7128 Applicability::MachineApplicable,
7139 /// Parses an element of a struct declaration.
7140 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
7141 let attrs = self.parse_outer_attributes()?;
7143 let vis = self.parse_visibility(false)?;
7144 self.parse_single_struct_field(lo, vis, attrs)
7147 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
7148 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
7149 /// If the following element can't be a tuple (i.e., it's a function definition), then
7150 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
7151 /// so emit a proper diagnostic.
7152 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
7153 maybe_whole!(self, NtVis, |x| x);
7155 self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
7156 if self.is_crate_vis() {
7157 self.bump(); // `crate`
7158 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
7161 if !self.eat_keyword(keywords::Pub) {
7162 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
7163 // keyword to grab a span from for inherited visibility; an empty span at the
7164 // beginning of the current token would seem to be the "Schelling span".
7165 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
7167 let lo = self.prev_span;
7169 if self.check(&token::OpenDelim(token::Paren)) {
7170 // We don't `self.bump()` the `(` yet because this might be a struct definition where
7171 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
7172 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
7173 // by the following tokens.
7174 if self.look_ahead(1, |t| t.is_keyword(keywords::Crate)) &&
7175 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
7179 self.bump(); // `crate`
7180 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7182 lo.to(self.prev_span),
7183 VisibilityKind::Crate(CrateSugar::PubCrate),
7186 } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
7189 self.bump(); // `in`
7190 let path = self.parse_path(PathStyle::Mod)?; // `path`
7191 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7192 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
7194 id: ast::DUMMY_NODE_ID,
7197 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
7198 self.look_ahead(1, |t| t.is_keyword(keywords::Super) ||
7199 t.is_keyword(keywords::SelfLower))
7201 // `pub(self)` or `pub(super)`
7203 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
7204 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7205 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
7207 id: ast::DUMMY_NODE_ID,
7210 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
7211 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
7213 let msg = "incorrect visibility restriction";
7214 let suggestion = r##"some possible visibility restrictions are:
7215 `pub(crate)`: visible only on the current crate
7216 `pub(super)`: visible only in the current module's parent
7217 `pub(in path::to::module)`: visible only on the specified path"##;
7218 let path = self.parse_path(PathStyle::Mod)?;
7220 let help_msg = format!("make this visible only to module `{}` with `in`", path);
7221 self.expect(&token::CloseDelim(token::Paren))?; // `)`
7222 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
7223 err.help(suggestion);
7224 err.span_suggestion(
7225 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
7227 err.emit(); // emit diagnostic, but continue with public visibility
7231 Ok(respan(lo, VisibilityKind::Public))
7234 /// Parses defaultness (i.e., `default` or nothing).
7235 fn parse_defaultness(&mut self) -> Defaultness {
7236 // `pub` is included for better error messages
7237 if self.check_keyword(keywords::Default) &&
7238 self.look_ahead(1, |t| t.is_keyword(keywords::Impl) ||
7239 t.is_keyword(keywords::Const) ||
7240 t.is_keyword(keywords::Fn) ||
7241 t.is_keyword(keywords::Unsafe) ||
7242 t.is_keyword(keywords::Extern) ||
7243 t.is_keyword(keywords::Type) ||
7244 t.is_keyword(keywords::Pub)) {
7245 self.bump(); // `default`
7246 Defaultness::Default
7252 /// Given a termination token, parses all of the items in a module.
7253 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
7254 let mut items = vec![];
7255 while let Some(item) = self.parse_item()? {
7257 self.maybe_consume_incorrect_semicolon(&items);
7260 if !self.eat(term) {
7261 let token_str = self.this_token_descr();
7262 if !self.maybe_consume_incorrect_semicolon(&items) {
7263 let mut err = self.fatal(&format!("expected item, found {}", token_str));
7264 err.span_label(self.span, "expected item");
7269 let hi = if self.span.is_dummy() {
7276 inner: inner_lo.to(hi),
7282 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
7283 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
7284 self.expect(&token::Colon)?;
7285 let ty = self.parse_ty()?;
7286 self.expect(&token::Eq)?;
7287 let e = self.parse_expr()?;
7288 self.expect(&token::Semi)?;
7289 let item = match m {
7290 Some(m) => ItemKind::Static(ty, m, e),
7291 None => ItemKind::Const(ty, e),
7293 Ok((id, item, None))
7296 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
7297 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
7298 let (in_cfg, outer_attrs) = {
7299 let mut strip_unconfigured = crate::config::StripUnconfigured {
7301 features: None, // don't perform gated feature checking
7303 let mut outer_attrs = outer_attrs.to_owned();
7304 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
7305 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
7308 let id_span = self.span;
7309 let id = self.parse_ident()?;
7310 if self.eat(&token::Semi) {
7311 if in_cfg && self.recurse_into_file_modules {
7312 // This mod is in an external file. Let's go get it!
7313 let ModulePathSuccess { path, directory_ownership, warn } =
7314 self.submod_path(id, &outer_attrs, id_span)?;
7315 let (module, mut attrs) =
7316 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
7317 // Record that we fetched the mod from an external file
7319 let attr = Attribute {
7320 id: attr::mk_attr_id(),
7321 style: ast::AttrStyle::Outer,
7322 path: ast::Path::from_ident(Ident::from_str("warn_directory_ownership")),
7323 tokens: TokenStream::empty(),
7324 is_sugared_doc: false,
7325 span: syntax_pos::DUMMY_SP,
7327 attr::mark_known(&attr);
7330 Ok((id, ItemKind::Mod(module), Some(attrs)))
7332 let placeholder = ast::Mod {
7333 inner: syntax_pos::DUMMY_SP,
7337 Ok((id, ItemKind::Mod(placeholder), None))
7340 let old_directory = self.directory.clone();
7341 self.push_directory(id, &outer_attrs);
7343 self.expect(&token::OpenDelim(token::Brace))?;
7344 let mod_inner_lo = self.span;
7345 let attrs = self.parse_inner_attributes()?;
7346 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
7348 self.directory = old_directory;
7349 Ok((id, ItemKind::Mod(module), Some(attrs)))
7353 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
7354 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
7355 self.directory.path.to_mut().push(&path.as_str());
7356 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
7358 // We have to push on the current module name in the case of relative
7359 // paths in order to ensure that any additional module paths from inline
7360 // `mod x { ... }` come after the relative extension.
7362 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
7363 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
7364 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
7365 if let Some(ident) = relative.take() { // remove the relative offset
7366 self.directory.path.to_mut().push(ident.as_str());
7369 self.directory.path.to_mut().push(&id.as_str());
7373 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
7374 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
7377 // On windows, the base path might have the form
7378 // `\\?\foo\bar` in which case it does not tolerate
7379 // mixed `/` and `\` separators, so canonicalize
7382 let s = s.replace("/", "\\");
7383 Some(dir_path.join(s))
7389 /// Returns a path to a module.
7390 pub fn default_submod_path(
7392 relative: Option<ast::Ident>,
7394 source_map: &SourceMap) -> ModulePath
7396 // If we're in a foo.rs file instead of a mod.rs file,
7397 // we need to look for submodules in
7398 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
7399 // `./<id>.rs` and `./<id>/mod.rs`.
7400 let relative_prefix_string;
7401 let relative_prefix = if let Some(ident) = relative {
7402 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
7403 &relative_prefix_string
7408 let mod_name = id.to_string();
7409 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
7410 let secondary_path_str = format!("{}{}{}mod.rs",
7411 relative_prefix, mod_name, path::MAIN_SEPARATOR);
7412 let default_path = dir_path.join(&default_path_str);
7413 let secondary_path = dir_path.join(&secondary_path_str);
7414 let default_exists = source_map.file_exists(&default_path);
7415 let secondary_exists = source_map.file_exists(&secondary_path);
7417 let result = match (default_exists, secondary_exists) {
7418 (true, false) => Ok(ModulePathSuccess {
7420 directory_ownership: DirectoryOwnership::Owned {
7425 (false, true) => Ok(ModulePathSuccess {
7426 path: secondary_path,
7427 directory_ownership: DirectoryOwnership::Owned {
7432 (false, false) => Err(Error::FileNotFoundForModule {
7433 mod_name: mod_name.clone(),
7434 default_path: default_path_str,
7435 secondary_path: secondary_path_str,
7436 dir_path: dir_path.display().to_string(),
7438 (true, true) => Err(Error::DuplicatePaths {
7439 mod_name: mod_name.clone(),
7440 default_path: default_path_str,
7441 secondary_path: secondary_path_str,
7447 path_exists: default_exists || secondary_exists,
7452 fn submod_path(&mut self,
7454 outer_attrs: &[Attribute],
7456 -> PResult<'a, ModulePathSuccess> {
7457 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
7458 return Ok(ModulePathSuccess {
7459 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
7460 // All `#[path]` files are treated as though they are a `mod.rs` file.
7461 // This means that `mod foo;` declarations inside `#[path]`-included
7462 // files are siblings,
7464 // Note that this will produce weirdness when a file named `foo.rs` is
7465 // `#[path]` included and contains a `mod foo;` declaration.
7466 // If you encounter this, it's your own darn fault :P
7467 Some(_) => DirectoryOwnership::Owned { relative: None },
7468 _ => DirectoryOwnership::UnownedViaMod(true),
7475 let relative = match self.directory.ownership {
7476 DirectoryOwnership::Owned { relative } => relative,
7477 DirectoryOwnership::UnownedViaBlock |
7478 DirectoryOwnership::UnownedViaMod(_) => None,
7480 let paths = Parser::default_submod_path(
7481 id, relative, &self.directory.path, self.sess.source_map());
7483 match self.directory.ownership {
7484 DirectoryOwnership::Owned { .. } => {
7485 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
7487 DirectoryOwnership::UnownedViaBlock => {
7489 "Cannot declare a non-inline module inside a block \
7490 unless it has a path attribute";
7491 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
7492 if paths.path_exists {
7493 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
7495 err.span_note(id_sp, &msg);
7499 DirectoryOwnership::UnownedViaMod(warn) => {
7501 if let Ok(result) = paths.result {
7502 return Ok(ModulePathSuccess { warn: true, ..result });
7505 let mut err = self.diagnostic().struct_span_err(id_sp,
7506 "cannot declare a new module at this location");
7507 if !id_sp.is_dummy() {
7508 let src_path = self.sess.source_map().span_to_filename(id_sp);
7509 if let FileName::Real(src_path) = src_path {
7510 if let Some(stem) = src_path.file_stem() {
7511 let mut dest_path = src_path.clone();
7512 dest_path.set_file_name(stem);
7513 dest_path.push("mod.rs");
7514 err.span_note(id_sp,
7515 &format!("maybe move this module `{}` to its own \
7516 directory via `{}`", src_path.display(),
7517 dest_path.display()));
7521 if paths.path_exists {
7522 err.span_note(id_sp,
7523 &format!("... or maybe `use` the module `{}` instead \
7524 of possibly redeclaring it",
7532 /// Reads a module from a source file.
7533 fn eval_src_mod(&mut self,
7535 directory_ownership: DirectoryOwnership,
7538 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
7539 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
7540 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
7541 let mut err = String::from("circular modules: ");
7542 let len = included_mod_stack.len();
7543 for p in &included_mod_stack[i.. len] {
7544 err.push_str(&p.to_string_lossy());
7545 err.push_str(" -> ");
7547 err.push_str(&path.to_string_lossy());
7548 return Err(self.span_fatal(id_sp, &err[..]));
7550 included_mod_stack.push(path.clone());
7551 drop(included_mod_stack);
7554 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
7555 p0.cfg_mods = self.cfg_mods;
7556 let mod_inner_lo = p0.span;
7557 let mod_attrs = p0.parse_inner_attributes()?;
7558 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
7560 self.sess.included_mod_stack.borrow_mut().pop();
7564 /// Parses a function declaration from a foreign module.
7565 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7566 -> PResult<'a, ForeignItem> {
7567 self.expect_keyword(keywords::Fn)?;
7569 let (ident, mut generics) = self.parse_fn_header()?;
7570 let decl = self.parse_fn_decl(true)?;
7571 generics.where_clause = self.parse_where_clause()?;
7573 self.expect(&token::Semi)?;
7574 Ok(ast::ForeignItem {
7577 node: ForeignItemKind::Fn(decl, generics),
7578 id: ast::DUMMY_NODE_ID,
7584 /// Parses a static item from a foreign module.
7585 /// Assumes that the `static` keyword is already parsed.
7586 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7587 -> PResult<'a, ForeignItem> {
7588 let mutbl = self.parse_mutability();
7589 let ident = self.parse_ident()?;
7590 self.expect(&token::Colon)?;
7591 let ty = self.parse_ty()?;
7593 self.expect(&token::Semi)?;
7597 node: ForeignItemKind::Static(ty, mutbl),
7598 id: ast::DUMMY_NODE_ID,
7604 /// Parses a type from a foreign module.
7605 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7606 -> PResult<'a, ForeignItem> {
7607 self.expect_keyword(keywords::Type)?;
7609 let ident = self.parse_ident()?;
7611 self.expect(&token::Semi)?;
7612 Ok(ast::ForeignItem {
7615 node: ForeignItemKind::Ty,
7616 id: ast::DUMMY_NODE_ID,
7622 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
7623 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
7624 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
7626 let mut ident = if self.token.is_keyword(keywords::SelfLower) {
7627 self.parse_path_segment_ident()
7631 let mut idents = vec![];
7632 let mut replacement = vec![];
7633 let mut fixed_crate_name = false;
7634 // Accept `extern crate name-like-this` for better diagnostics
7635 let dash = token::Token::BinOp(token::BinOpToken::Minus);
7636 if self.token == dash { // Do not include `-` as part of the expected tokens list
7637 while self.eat(&dash) {
7638 fixed_crate_name = true;
7639 replacement.push((self.prev_span, "_".to_string()));
7640 idents.push(self.parse_ident()?);
7643 if fixed_crate_name {
7644 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
7645 let mut fixed_name = format!("{}", ident.name);
7646 for part in idents {
7647 fixed_name.push_str(&format!("_{}", part.name));
7649 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
7651 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
7652 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
7653 err.multipart_suggestion(
7656 Applicability::MachineApplicable,
7663 /// Parses `extern crate` links.
7668 /// extern crate foo;
7669 /// extern crate bar as foo;
7671 fn parse_item_extern_crate(&mut self,
7673 visibility: Visibility,
7674 attrs: Vec<Attribute>)
7675 -> PResult<'a, P<Item>> {
7676 // Accept `extern crate name-like-this` for better diagnostics
7677 let orig_name = self.parse_crate_name_with_dashes()?;
7678 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
7679 (rename, Some(orig_name.name))
7683 self.expect(&token::Semi)?;
7685 let span = lo.to(self.prev_span);
7686 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
7689 /// Parses `extern` for foreign ABIs modules.
7691 /// `extern` is expected to have been
7692 /// consumed before calling this method.
7696 /// ```ignore (only-for-syntax-highlight)
7700 fn parse_item_foreign_mod(&mut self,
7702 opt_abi: Option<Abi>,
7703 visibility: Visibility,
7704 mut attrs: Vec<Attribute>)
7705 -> PResult<'a, P<Item>> {
7706 self.expect(&token::OpenDelim(token::Brace))?;
7708 let abi = opt_abi.unwrap_or(Abi::C);
7710 attrs.extend(self.parse_inner_attributes()?);
7712 let mut foreign_items = vec![];
7713 while !self.eat(&token::CloseDelim(token::Brace)) {
7714 foreign_items.push(self.parse_foreign_item()?);
7717 let prev_span = self.prev_span;
7718 let m = ast::ForeignMod {
7720 items: foreign_items
7722 let invalid = keywords::Invalid.ident();
7723 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
7726 /// Parses `type Foo = Bar;`
7728 /// `existential type Foo: Bar;`
7731 /// without modifying the parser state.
7732 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
7733 // This parses the grammar:
7734 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
7735 if self.check_keyword(keywords::Type) ||
7736 self.check_keyword(keywords::Existential) &&
7737 self.look_ahead(1, |t| t.is_keyword(keywords::Type)) {
7738 let existential = self.eat_keyword(keywords::Existential);
7739 assert!(self.eat_keyword(keywords::Type));
7740 Some(self.parse_existential_or_alias(existential))
7746 /// Parses a type alias or existential type.
7747 fn parse_existential_or_alias(
7750 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
7751 let ident = self.parse_ident()?;
7752 let mut tps = self.parse_generics()?;
7753 tps.where_clause = self.parse_where_clause()?;
7754 let alias = if existential {
7755 self.expect(&token::Colon)?;
7756 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
7757 AliasKind::Existential(bounds)
7759 self.expect(&token::Eq)?;
7760 let ty = self.parse_ty()?;
7763 self.expect(&token::Semi)?;
7764 Ok((ident, alias, tps))
7767 /// Parses the part of an enum declaration following the `{`.
7768 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
7769 let mut variants = Vec::new();
7770 let mut all_nullary = true;
7771 let mut any_disr = vec![];
7772 while self.token != token::CloseDelim(token::Brace) {
7773 let variant_attrs = self.parse_outer_attributes()?;
7774 let vlo = self.span;
7777 let mut disr_expr = None;
7779 let ident = self.parse_ident()?;
7780 if self.check(&token::OpenDelim(token::Brace)) {
7781 // Parse a struct variant.
7782 all_nullary = false;
7783 let (fields, recovered) = self.parse_record_struct_body()?;
7784 struct_def = VariantData::Struct(fields, recovered);
7785 } else if self.check(&token::OpenDelim(token::Paren)) {
7786 all_nullary = false;
7787 struct_def = VariantData::Tuple(
7788 self.parse_tuple_struct_body()?,
7791 } else if self.eat(&token::Eq) {
7792 disr_expr = Some(AnonConst {
7793 id: ast::DUMMY_NODE_ID,
7794 value: self.parse_expr()?,
7796 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
7799 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7801 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7804 let vr = ast::Variant_ {
7806 id: ast::DUMMY_NODE_ID,
7807 attrs: variant_attrs,
7811 variants.push(respan(vlo.to(self.prev_span), vr));
7813 if !self.eat(&token::Comma) {
7814 if self.token.is_ident() && !self.token.is_reserved_ident() {
7815 let sp = self.sess.source_map().next_point(self.prev_span);
7816 let mut err = self.struct_span_err(sp, "missing comma");
7817 err.span_suggestion_short(
7821 Applicability::MaybeIncorrect,
7829 self.expect(&token::CloseDelim(token::Brace))?;
7830 if !any_disr.is_empty() && !all_nullary {
7831 let mut err = self.struct_span_err(
7833 "discriminator values can only be used with a field-less enum",
7835 for sp in any_disr {
7836 err.span_label(sp, "only valid in field-less enums");
7841 Ok(ast::EnumDef { variants })
7844 /// Parses an enum declaration.
7845 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
7846 let id = self.parse_ident()?;
7847 let mut generics = self.parse_generics()?;
7848 generics.where_clause = self.parse_where_clause()?;
7849 self.expect(&token::OpenDelim(token::Brace))?;
7851 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
7852 self.recover_stmt();
7853 self.eat(&token::CloseDelim(token::Brace));
7856 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7859 /// Parses a string as an ABI spec on an extern type or module. Consumes
7860 /// the `extern` keyword, if one is found.
7861 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7863 token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
7865 self.expect_no_suffix(sp, "an ABI spec", suf);
7867 match abi::lookup(&s.as_str()) {
7868 Some(abi) => Ok(Some(abi)),
7870 let prev_span = self.prev_span;
7871 let mut err = struct_span_err!(
7872 self.sess.span_diagnostic,
7875 "invalid ABI: found `{}`",
7877 err.span_label(prev_span, "invalid ABI");
7878 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7889 fn is_static_global(&mut self) -> bool {
7890 if self.check_keyword(keywords::Static) {
7891 // Check if this could be a closure
7892 !self.look_ahead(1, |token| {
7893 if token.is_keyword(keywords::Move) {
7897 token::BinOp(token::Or) | token::OrOr => true,
7908 attrs: Vec<Attribute>,
7909 macros_allowed: bool,
7910 attributes_allowed: bool,
7911 ) -> PResult<'a, Option<P<Item>>> {
7912 let mut unclosed_delims = vec![];
7913 let (ret, tokens) = self.collect_tokens(|this| {
7914 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7915 unclosed_delims.append(&mut this.unclosed_delims);
7918 self.unclosed_delims.append(&mut unclosed_delims);
7920 // Once we've parsed an item and recorded the tokens we got while
7921 // parsing we may want to store `tokens` into the item we're about to
7922 // return. Note, though, that we specifically didn't capture tokens
7923 // related to outer attributes. The `tokens` field here may later be
7924 // used with procedural macros to convert this item back into a token
7925 // stream, but during expansion we may be removing attributes as we go
7928 // If we've got inner attributes then the `tokens` we've got above holds
7929 // these inner attributes. If an inner attribute is expanded we won't
7930 // actually remove it from the token stream, so we'll just keep yielding
7931 // it (bad!). To work around this case for now we just avoid recording
7932 // `tokens` if we detect any inner attributes. This should help keep
7933 // expansion correct, but we should fix this bug one day!
7936 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7937 i.tokens = Some(tokens);
7944 /// Parses one of the items allowed by the flags.
7945 fn parse_item_implementation(
7947 attrs: Vec<Attribute>,
7948 macros_allowed: bool,
7949 attributes_allowed: bool,
7950 ) -> PResult<'a, Option<P<Item>>> {
7951 maybe_whole!(self, NtItem, |item| {
7952 let mut item = item.into_inner();
7953 let mut attrs = attrs;
7954 mem::swap(&mut item.attrs, &mut attrs);
7955 item.attrs.extend(attrs);
7961 let visibility = self.parse_visibility(false)?;
7963 if self.eat_keyword(keywords::Use) {
7965 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7966 self.expect(&token::Semi)?;
7968 let span = lo.to(self.prev_span);
7969 let item = self.mk_item(span, keywords::Invalid.ident(), item_, visibility, attrs);
7970 return Ok(Some(item));
7973 if self.eat_keyword(keywords::Extern) {
7974 if self.eat_keyword(keywords::Crate) {
7975 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7978 let opt_abi = self.parse_opt_abi()?;
7980 if self.eat_keyword(keywords::Fn) {
7981 // EXTERN FUNCTION ITEM
7982 let fn_span = self.prev_span;
7983 let abi = opt_abi.unwrap_or(Abi::C);
7984 let (ident, item_, extra_attrs) =
7985 self.parse_item_fn(Unsafety::Normal,
7986 respan(fn_span, IsAsync::NotAsync),
7987 respan(fn_span, Constness::NotConst),
7989 let prev_span = self.prev_span;
7990 let item = self.mk_item(lo.to(prev_span),
7994 maybe_append(attrs, extra_attrs));
7995 return Ok(Some(item));
7996 } else if self.check(&token::OpenDelim(token::Brace)) {
7997 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
8003 if self.is_static_global() {
8006 let m = if self.eat_keyword(keywords::Mut) {
8009 Mutability::Immutable
8011 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
8012 let prev_span = self.prev_span;
8013 let item = self.mk_item(lo.to(prev_span),
8017 maybe_append(attrs, extra_attrs));
8018 return Ok(Some(item));
8020 if self.eat_keyword(keywords::Const) {
8021 let const_span = self.prev_span;
8022 if self.check_keyword(keywords::Fn)
8023 || (self.check_keyword(keywords::Unsafe)
8024 && self.look_ahead(1, |t| t.is_keyword(keywords::Fn))) {
8025 // CONST FUNCTION ITEM
8026 let unsafety = self.parse_unsafety();
8028 let (ident, item_, extra_attrs) =
8029 self.parse_item_fn(unsafety,
8030 respan(const_span, IsAsync::NotAsync),
8031 respan(const_span, Constness::Const),
8033 let prev_span = self.prev_span;
8034 let item = self.mk_item(lo.to(prev_span),
8038 maybe_append(attrs, extra_attrs));
8039 return Ok(Some(item));
8043 if self.eat_keyword(keywords::Mut) {
8044 let prev_span = self.prev_span;
8045 let mut err = self.diagnostic()
8046 .struct_span_err(prev_span, "const globals cannot be mutable");
8047 err.span_label(prev_span, "cannot be mutable");
8048 err.span_suggestion(
8050 "you might want to declare a static instead",
8051 "static".to_owned(),
8052 Applicability::MaybeIncorrect,
8056 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
8057 let prev_span = self.prev_span;
8058 let item = self.mk_item(lo.to(prev_span),
8062 maybe_append(attrs, extra_attrs));
8063 return Ok(Some(item));
8066 // `unsafe async fn` or `async fn`
8068 self.check_keyword(keywords::Unsafe) &&
8069 self.look_ahead(1, |t| t.is_keyword(keywords::Async))
8071 self.check_keyword(keywords::Async) &&
8072 self.look_ahead(1, |t| t.is_keyword(keywords::Fn))
8075 // ASYNC FUNCTION ITEM
8076 let unsafety = self.parse_unsafety();
8077 self.expect_keyword(keywords::Async)?;
8078 let async_span = self.prev_span;
8079 self.expect_keyword(keywords::Fn)?;
8080 let fn_span = self.prev_span;
8081 let (ident, item_, extra_attrs) =
8082 self.parse_item_fn(unsafety,
8083 respan(async_span, IsAsync::Async {
8084 closure_id: ast::DUMMY_NODE_ID,
8085 return_impl_trait_id: ast::DUMMY_NODE_ID,
8086 arguments: Vec::new(),
8088 respan(fn_span, Constness::NotConst),
8090 let prev_span = self.prev_span;
8091 let item = self.mk_item(lo.to(prev_span),
8095 maybe_append(attrs, extra_attrs));
8096 if self.span.rust_2015() {
8097 self.diagnostic().struct_span_err_with_code(
8099 "`async fn` is not permitted in the 2015 edition",
8100 DiagnosticId::Error("E0670".into())
8103 return Ok(Some(item));
8105 if self.check_keyword(keywords::Unsafe) &&
8106 (self.look_ahead(1, |t| t.is_keyword(keywords::Trait)) ||
8107 self.look_ahead(1, |t| t.is_keyword(keywords::Auto)))
8109 // UNSAFE TRAIT ITEM
8110 self.bump(); // `unsafe`
8111 let is_auto = if self.eat_keyword(keywords::Trait) {
8114 self.expect_keyword(keywords::Auto)?;
8115 self.expect_keyword(keywords::Trait)?;
8118 let (ident, item_, extra_attrs) =
8119 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
8120 let prev_span = self.prev_span;
8121 let item = self.mk_item(lo.to(prev_span),
8125 maybe_append(attrs, extra_attrs));
8126 return Ok(Some(item));
8128 if self.check_keyword(keywords::Impl) ||
8129 self.check_keyword(keywords::Unsafe) &&
8130 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
8131 self.check_keyword(keywords::Default) &&
8132 self.look_ahead(1, |t| t.is_keyword(keywords::Impl)) ||
8133 self.check_keyword(keywords::Default) &&
8134 self.look_ahead(1, |t| t.is_keyword(keywords::Unsafe)) {
8136 let defaultness = self.parse_defaultness();
8137 let unsafety = self.parse_unsafety();
8138 self.expect_keyword(keywords::Impl)?;
8139 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
8140 let span = lo.to(self.prev_span);
8141 return Ok(Some(self.mk_item(span, ident, item, visibility,
8142 maybe_append(attrs, extra_attrs))));
8144 if self.check_keyword(keywords::Fn) {
8147 let fn_span = self.prev_span;
8148 let (ident, item_, extra_attrs) =
8149 self.parse_item_fn(Unsafety::Normal,
8150 respan(fn_span, IsAsync::NotAsync),
8151 respan(fn_span, Constness::NotConst),
8153 let prev_span = self.prev_span;
8154 let item = self.mk_item(lo.to(prev_span),
8158 maybe_append(attrs, extra_attrs));
8159 return Ok(Some(item));
8161 if self.check_keyword(keywords::Unsafe)
8162 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
8163 // UNSAFE FUNCTION ITEM
8164 self.bump(); // `unsafe`
8165 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
8166 self.check(&token::OpenDelim(token::Brace));
8167 let abi = if self.eat_keyword(keywords::Extern) {
8168 self.parse_opt_abi()?.unwrap_or(Abi::C)
8172 self.expect_keyword(keywords::Fn)?;
8173 let fn_span = self.prev_span;
8174 let (ident, item_, extra_attrs) =
8175 self.parse_item_fn(Unsafety::Unsafe,
8176 respan(fn_span, IsAsync::NotAsync),
8177 respan(fn_span, Constness::NotConst),
8179 let prev_span = self.prev_span;
8180 let item = self.mk_item(lo.to(prev_span),
8184 maybe_append(attrs, extra_attrs));
8185 return Ok(Some(item));
8187 if self.eat_keyword(keywords::Mod) {
8189 let (ident, item_, extra_attrs) =
8190 self.parse_item_mod(&attrs[..])?;
8191 let prev_span = self.prev_span;
8192 let item = self.mk_item(lo.to(prev_span),
8196 maybe_append(attrs, extra_attrs));
8197 return Ok(Some(item));
8199 if let Some(type_) = self.eat_type() {
8200 let (ident, alias, generics) = type_?;
8202 let item_ = match alias {
8203 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
8204 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
8206 let prev_span = self.prev_span;
8207 let item = self.mk_item(lo.to(prev_span),
8212 return Ok(Some(item));
8214 if self.eat_keyword(keywords::Enum) {
8216 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
8217 let prev_span = self.prev_span;
8218 let item = self.mk_item(lo.to(prev_span),
8222 maybe_append(attrs, extra_attrs));
8223 return Ok(Some(item));
8225 if self.check_keyword(keywords::Trait)
8226 || (self.check_keyword(keywords::Auto)
8227 && self.look_ahead(1, |t| t.is_keyword(keywords::Trait)))
8229 let is_auto = if self.eat_keyword(keywords::Trait) {
8232 self.expect_keyword(keywords::Auto)?;
8233 self.expect_keyword(keywords::Trait)?;
8237 let (ident, item_, extra_attrs) =
8238 self.parse_item_trait(is_auto, Unsafety::Normal)?;
8239 let prev_span = self.prev_span;
8240 let item = self.mk_item(lo.to(prev_span),
8244 maybe_append(attrs, extra_attrs));
8245 return Ok(Some(item));
8247 if self.eat_keyword(keywords::Struct) {
8249 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
8250 let prev_span = self.prev_span;
8251 let item = self.mk_item(lo.to(prev_span),
8255 maybe_append(attrs, extra_attrs));
8256 return Ok(Some(item));
8258 if self.is_union_item() {
8261 let (ident, item_, extra_attrs) = self.parse_item_union()?;
8262 let prev_span = self.prev_span;
8263 let item = self.mk_item(lo.to(prev_span),
8267 maybe_append(attrs, extra_attrs));
8268 return Ok(Some(item));
8270 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
8271 return Ok(Some(macro_def));
8274 // Verify whether we have encountered a struct or method definition where the user forgot to
8275 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
8276 if visibility.node.is_pub() &&
8277 self.check_ident() &&
8278 self.look_ahead(1, |t| *t != token::Not)
8280 // Space between `pub` keyword and the identifier
8283 // ^^^ `sp` points here
8284 let sp = self.prev_span.between(self.span);
8285 let full_sp = self.prev_span.to(self.span);
8286 let ident_sp = self.span;
8287 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
8288 // possible public struct definition where `struct` was forgotten
8289 let ident = self.parse_ident().unwrap();
8290 let msg = format!("add `struct` here to parse `{}` as a public struct",
8292 let mut err = self.diagnostic()
8293 .struct_span_err(sp, "missing `struct` for struct definition");
8294 err.span_suggestion_short(
8295 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
8298 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
8299 let ident = self.parse_ident().unwrap();
8301 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
8306 self.consume_block(token::Paren);
8307 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
8308 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
8310 ("fn", kw_name, false)
8311 } else if self.check(&token::OpenDelim(token::Brace)) {
8313 ("fn", kw_name, false)
8314 } else if self.check(&token::Colon) {
8318 ("fn` or `struct", "function or struct", true)
8321 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8322 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8324 self.consume_block(token::Brace);
8325 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
8329 err.span_suggestion_short(
8330 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
8333 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
8334 err.span_suggestion(
8336 "if you meant to call a macro, try",
8337 format!("{}!", snippet),
8338 // this is the `ambiguous` conditional branch
8339 Applicability::MaybeIncorrect
8342 err.help("if you meant to call a macro, remove the `pub` \
8343 and add a trailing `!` after the identifier");
8347 } else if self.look_ahead(1, |t| *t == token::Lt) {
8348 let ident = self.parse_ident().unwrap();
8349 self.eat_to_tokens(&[&token::Gt]);
8351 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
8352 if let Ok(Some(_)) = self.parse_self_arg() {
8353 ("fn", "method", false)
8355 ("fn", "function", false)
8357 } else if self.check(&token::OpenDelim(token::Brace)) {
8358 ("struct", "struct", false)
8360 ("fn` or `struct", "function or struct", true)
8362 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8363 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8365 err.span_suggestion_short(
8367 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
8368 format!(" {} ", kw),
8369 Applicability::MachineApplicable,
8375 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
8378 /// Parses a foreign item.
8379 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
8380 maybe_whole!(self, NtForeignItem, |ni| ni);
8382 let attrs = self.parse_outer_attributes()?;
8384 let visibility = self.parse_visibility(false)?;
8386 // FOREIGN STATIC ITEM
8387 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
8388 if self.check_keyword(keywords::Static) || self.token.is_keyword(keywords::Const) {
8389 if self.token.is_keyword(keywords::Const) {
8391 .struct_span_err(self.span, "extern items cannot be `const`")
8394 "try using a static value",
8395 "static".to_owned(),
8396 Applicability::MachineApplicable
8399 self.bump(); // `static` or `const`
8400 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
8402 // FOREIGN FUNCTION ITEM
8403 if self.check_keyword(keywords::Fn) {
8404 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
8406 // FOREIGN TYPE ITEM
8407 if self.check_keyword(keywords::Type) {
8408 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
8411 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
8415 ident: keywords::Invalid.ident(),
8416 span: lo.to(self.prev_span),
8417 id: ast::DUMMY_NODE_ID,
8420 node: ForeignItemKind::Macro(mac),
8425 if !attrs.is_empty() {
8426 self.expected_item_err(&attrs)?;
8434 /// This is the fall-through for parsing items.
8435 fn parse_macro_use_or_failure(
8437 attrs: Vec<Attribute> ,
8438 macros_allowed: bool,
8439 attributes_allowed: bool,
8441 visibility: Visibility
8442 ) -> PResult<'a, Option<P<Item>>> {
8443 if macros_allowed && self.token.is_path_start() &&
8444 !(self.is_async_fn() && self.span.rust_2015()) {
8445 // MACRO INVOCATION ITEM
8447 let prev_span = self.prev_span;
8448 self.complain_if_pub_macro(&visibility.node, prev_span);
8450 let mac_lo = self.span;
8453 let pth = self.parse_path(PathStyle::Mod)?;
8454 self.expect(&token::Not)?;
8456 // a 'special' identifier (like what `macro_rules!` uses)
8457 // is optional. We should eventually unify invoc syntax
8459 let id = if self.token.is_ident() {
8462 keywords::Invalid.ident() // no special identifier
8464 // eat a matched-delimiter token tree:
8465 let (delim, tts) = self.expect_delimited_token_tree()?;
8466 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
8467 self.report_invalid_macro_expansion_item();
8470 let hi = self.prev_span;
8471 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
8472 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
8473 return Ok(Some(item));
8476 // FAILURE TO PARSE ITEM
8477 match visibility.node {
8478 VisibilityKind::Inherited => {}
8480 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
8484 if !attributes_allowed && !attrs.is_empty() {
8485 self.expected_item_err(&attrs)?;
8490 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
8491 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
8492 at_end: &mut bool) -> PResult<'a, Option<Mac>>
8494 if self.token.is_path_start() &&
8495 !(self.is_async_fn() && self.span.rust_2015()) {
8496 let prev_span = self.prev_span;
8498 let pth = self.parse_path(PathStyle::Mod)?;
8500 if pth.segments.len() == 1 {
8501 if !self.eat(&token::Not) {
8502 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
8505 self.expect(&token::Not)?;
8508 if let Some(vis) = vis {
8509 self.complain_if_pub_macro(&vis.node, prev_span);
8514 // eat a matched-delimiter token tree:
8515 let (delim, tts) = self.expect_delimited_token_tree()?;
8516 if delim != MacDelimiter::Brace {
8517 self.expect(&token::Semi)?;
8520 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
8526 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
8527 where F: FnOnce(&mut Self) -> PResult<'a, R>
8529 // Record all tokens we parse when parsing this item.
8530 let mut tokens = Vec::new();
8531 let prev_collecting = match self.token_cursor.frame.last_token {
8532 LastToken::Collecting(ref mut list) => {
8533 Some(mem::replace(list, Vec::new()))
8535 LastToken::Was(ref mut last) => {
8536 tokens.extend(last.take());
8540 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
8541 let prev = self.token_cursor.stack.len();
8543 let last_token = if self.token_cursor.stack.len() == prev {
8544 &mut self.token_cursor.frame.last_token
8546 &mut self.token_cursor.stack[prev].last_token
8549 // Pull out the tokens that we've collected from the call to `f` above.
8550 let mut collected_tokens = match *last_token {
8551 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
8552 LastToken::Was(_) => panic!("our vector went away?"),
8555 // If we're not at EOF our current token wasn't actually consumed by
8556 // `f`, but it'll still be in our list that we pulled out. In that case
8558 let extra_token = if self.token != token::Eof {
8559 collected_tokens.pop()
8564 // If we were previously collecting tokens, then this was a recursive
8565 // call. In that case we need to record all the tokens we collected in
8566 // our parent list as well. To do that we push a clone of our stream
8567 // onto the previous list.
8568 match prev_collecting {
8570 list.extend(collected_tokens.iter().cloned());
8571 list.extend(extra_token);
8572 *last_token = LastToken::Collecting(list);
8575 *last_token = LastToken::Was(extra_token);
8579 Ok((ret?, TokenStream::new(collected_tokens)))
8582 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
8583 let attrs = self.parse_outer_attributes()?;
8584 self.parse_item_(attrs, true, false)
8588 fn is_import_coupler(&mut self) -> bool {
8589 self.check(&token::ModSep) &&
8590 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
8591 *t == token::BinOp(token::Star))
8594 /// Parses a `UseTree`.
8597 /// USE_TREE = [`::`] `*` |
8598 /// [`::`] `{` USE_TREE_LIST `}` |
8600 /// PATH `::` `{` USE_TREE_LIST `}` |
8601 /// PATH [`as` IDENT]
8603 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
8606 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
8607 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
8608 self.check(&token::BinOp(token::Star)) ||
8609 self.is_import_coupler() {
8610 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
8611 let mod_sep_ctxt = self.span.ctxt();
8612 if self.eat(&token::ModSep) {
8613 prefix.segments.push(
8614 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
8618 if self.eat(&token::BinOp(token::Star)) {
8621 UseTreeKind::Nested(self.parse_use_tree_list()?)
8624 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
8625 prefix = self.parse_path(PathStyle::Mod)?;
8627 if self.eat(&token::ModSep) {
8628 if self.eat(&token::BinOp(token::Star)) {
8631 UseTreeKind::Nested(self.parse_use_tree_list()?)
8634 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
8638 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
8641 /// Parses a `UseTreeKind::Nested(list)`.
8644 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
8646 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
8647 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
8648 &token::CloseDelim(token::Brace),
8649 SeqSep::trailing_allowed(token::Comma), |this| {
8650 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
8654 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
8655 if self.eat_keyword(keywords::As) {
8656 self.parse_ident_or_underscore().map(Some)
8662 /// Parses a source module as a crate. This is the main entry point for the parser.
8663 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
8665 let krate = Ok(ast::Crate {
8666 attrs: self.parse_inner_attributes()?,
8667 module: self.parse_mod_items(&token::Eof, lo)?,
8668 span: lo.to(self.span),
8673 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
8674 let ret = match self.token {
8675 token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
8676 token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
8683 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
8684 match self.parse_optional_str() {
8685 Some((s, style, suf)) => {
8686 let sp = self.prev_span;
8687 self.expect_no_suffix(sp, "a string literal", suf);
8691 let msg = "expected string literal";
8692 let mut err = self.fatal(msg);
8693 err.span_label(self.span, msg);
8699 fn report_invalid_macro_expansion_item(&self) {
8700 self.struct_span_err(
8702 "macros that expand to items must be delimited with braces or followed by a semicolon",
8703 ).multipart_suggestion(
8704 "change the delimiters to curly braces",
8706 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
8707 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
8709 Applicability::MaybeIncorrect,
8711 self.sess.source_map.next_point(self.prev_span),
8714 Applicability::MaybeIncorrect,
8718 /// Recover from `pub` keyword in places where it seems _reasonable_ but isn't valid.
8719 fn eat_bad_pub(&mut self) {
8720 if self.token.is_keyword(keywords::Pub) {
8721 match self.parse_visibility(false) {
8723 let mut err = self.diagnostic()
8724 .struct_span_err(vis.span, "unnecessary visibility qualifier");
8725 err.span_label(vis.span, "`pub` not permitted here");
8728 Err(mut err) => err.emit(),
8733 /// When lowering a `async fn` to the HIR, we need to move all of the arguments of the function
8734 /// into the generated closure so that they are dropped when the future is polled and not when
8737 /// The arguments of the function are replaced in HIR lowering with the arguments created by
8738 /// this function and the statements created here are inserted at the top of the closure body.
8739 fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
8740 // FIXME(davidtwco): This function should really live in the HIR lowering but because
8741 // the types constructed here need to be used in parts of resolve so that the correct
8742 // locals are considered upvars, it is currently easier for it to live here in the parser,
8743 // where it can be constructed once.
8744 if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
8745 for (index, input) in decl.inputs.iter_mut().enumerate() {
8746 let id = ast::DUMMY_NODE_ID;
8747 let span = input.pat.span;
8749 // Construct a name for our temporary argument.
8750 let name = format!("__arg{}", index);
8751 let ident = Ident::from_str(&name).gensym();
8753 // Check if this is a ident pattern, if so, we can optimize and avoid adding a
8754 // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
8756 let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
8757 PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
8758 // Simple patterns like this don't have a generated argument, but they are
8759 // moved into the closure with a statement, so any `mut` bindings on the
8760 // argument will be unused. This binding mode can't be removed, because
8761 // this would affect the input to procedural macros, but they can have
8762 // their span marked as being the result of a compiler desugaring so
8763 // that they aren't linted against.
8764 input.pat.span = self.sess.source_map().mark_span_with_reason(
8765 CompilerDesugaringKind::Async, span, None);
8767 (binding_mode, ident, true)
8769 _ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
8772 // Construct an argument representing `__argN: <ty>` to replace the argument of the
8773 // async function if it isn't a simple pattern.
8774 let arg = if is_simple_pattern {
8778 ty: input.ty.clone(),
8782 node: PatKind::Ident(
8783 BindingMode::ByValue(Mutability::Immutable), ident, None,
8787 source: ArgSource::AsyncFn(input.pat.clone()),
8791 // Construct a `let __argN = __argN;` statement to insert at the top of the
8792 // async closure. This makes sure that the argument is captured by the closure and
8793 // that the drop order is correct.
8794 let move_local = Local {
8797 node: PatKind::Ident(binding_mode, ident, None),
8800 // We explicitly do not specify the type for this statement. When the user's
8801 // argument type is `impl Trait` then this would require the
8802 // `impl_trait_in_bindings` feature to also be present for that same type to
8803 // be valid in this binding. At the time of writing (13 Mar 19),
8804 // `impl_trait_in_bindings` is not stable.
8808 node: ExprKind::Path(None, ast::Path {
8810 segments: vec![PathSegment { ident, id, args: None }],
8813 attrs: ThinVec::new(),
8817 attrs: ThinVec::new(),
8818 source: LocalSource::AsyncFn,
8821 // Construct a `let <pat> = __argN;` statement to insert at the top of the
8822 // async closure if this isn't a simple pattern.
8823 let pat_stmt = if is_simple_pattern {
8828 node: StmtKind::Local(P(Local {
8829 pat: input.pat.clone(),
8830 ..move_local.clone()
8836 let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
8837 arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
8843 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
8844 for unmatched in unclosed_delims.iter() {
8845 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
8846 "incorrect close delimiter: `{}`",
8847 pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
8849 err.span_label(unmatched.found_span, "incorrect close delimiter");
8850 if let Some(sp) = unmatched.candidate_span {
8851 err.span_label(sp, "close delimiter possibly meant for this");
8853 if let Some(sp) = unmatched.unclosed_span {
8854 err.span_label(sp, "un-closed delimiter");
8858 unclosed_delims.clear();