1 // ignore-tidy-filelength
3 use crate::ast::{AngleBracketedArgs, AsyncArgument, ParenthesizedArgs, AttrStyle, BareFnTy};
4 use crate::ast::{GenericBound, TraitBoundModifier};
5 use crate::ast::Unsafety;
6 use crate::ast::{Mod, AnonConst, Arg, ArgSource, Arm, Guard, Attribute, BindingMode, TraitItemKind};
8 use crate::ast::{BlockCheckMode, CaptureBy, Movability};
9 use crate::ast::{Constness, Crate};
10 use crate::ast::Defaultness;
11 use crate::ast::EnumDef;
12 use crate::ast::{Expr, ExprKind, RangeLimits};
13 use crate::ast::{Field, FnDecl, FnHeader};
14 use crate::ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
15 use crate::ast::{GenericParam, GenericParamKind};
16 use crate::ast::GenericArg;
17 use crate::ast::{Ident, ImplItem, IsAsync, IsAuto, Item, ItemKind};
18 use crate::ast::{Label, Lifetime};
19 use crate::ast::{Local, LocalSource};
20 use crate::ast::MacStmtStyle;
21 use crate::ast::{Mac, Mac_, MacDelimiter};
22 use crate::ast::{MutTy, Mutability};
23 use crate::ast::{Pat, PatKind, PathSegment};
24 use crate::ast::{PolyTraitRef, QSelf};
25 use crate::ast::{Stmt, StmtKind};
26 use crate::ast::{VariantData, StructField};
27 use crate::ast::StrStyle;
28 use crate::ast::SelfKind;
29 use crate::ast::{TraitItem, TraitRef, TraitObjectSyntax};
30 use crate::ast::{Ty, TyKind, TypeBinding, GenericBounds};
31 use crate::ast::{Visibility, VisibilityKind, WhereClause, CrateSugar};
32 use crate::ast::{UseTree, UseTreeKind};
33 use crate::ast::{BinOpKind, UnOp};
34 use crate::ast::{RangeEnd, RangeSyntax};
35 use crate::{ast, attr};
36 use crate::ext::base::DummyResult;
37 use crate::source_map::{self, SourceMap, Spanned, respan};
38 use crate::parse::{SeqSep, classify, literal, token};
39 use crate::parse::lexer::{TokenAndSpan, UnmatchedBrace};
40 use crate::parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
41 use crate::parse::token::DelimToken;
42 use crate::parse::{new_sub_parser_from_file, ParseSess, Directory, DirectoryOwnership};
43 use crate::util::parser::{AssocOp, Fixity};
44 use crate::print::pprust;
46 use crate::parse::PResult;
48 use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
49 use crate::symbol::{kw, sym, Symbol};
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)]
107 crate enum SemiColonMode {
113 #[derive(Clone, Copy, PartialEq, Debug)]
114 crate enum BlockMode {
119 /// Possibly accepts an `token::Interpolated` expression (a pre-parsed expression
120 /// dropped into the token stream, which happens while parsing the result of
121 /// macro expansion). Placement of these is not as complex as I feared it would
122 /// be. The important thing is to make sure that lookahead doesn't balk at
123 /// `token::Interpolated` tokens.
124 macro_rules! maybe_whole_expr {
126 if let token::Interpolated(nt) = &$p.token {
128 token::NtExpr(e) | token::NtLiteral(e) => {
133 token::NtPath(path) => {
134 let path = path.clone();
136 return Ok($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::with_empty_ctxt(sym::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 {
392 crate fn to_string(&self) -> String {
394 TokenType::Token(ref t) => format!("`{}`", pprust::token_to_string(t)),
395 TokenType::Keyword(kw) => format!("`{}`", kw),
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(kw::Invalid, 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 /// Expect next token to be edible or inedible token. If edible,
677 /// then consume it; if inedible, then return without consuming
678 /// anything. Signal a fatal error if next token is unexpected.
679 pub fn expect_one_of(
681 edible: &[token::Token],
682 inedible: &[token::Token],
683 ) -> PResult<'a, bool /* recovered */> {
684 fn tokens_to_string(tokens: &[TokenType]) -> String {
685 let mut i = tokens.iter();
686 // This might be a sign we need a connect method on Iterator.
688 .map_or(String::new(), |t| t.to_string());
689 i.enumerate().fold(b, |mut b, (i, a)| {
690 if tokens.len() > 2 && i == tokens.len() - 2 {
692 } else if tokens.len() == 2 && i == tokens.len() - 2 {
697 b.push_str(&a.to_string());
701 if edible.contains(&self.token) {
704 } else if inedible.contains(&self.token) {
705 // leave it in the input
707 } else if self.last_unexpected_token_span == Some(self.span) {
710 let mut expected = edible.iter()
711 .map(|x| TokenType::Token(x.clone()))
712 .chain(inedible.iter().map(|x| TokenType::Token(x.clone())))
713 .chain(self.expected_tokens.iter().cloned())
714 .collect::<Vec<_>>();
715 expected.sort_by_cached_key(|x| x.to_string());
717 let expect = tokens_to_string(&expected[..]);
718 let actual = self.this_token_to_string();
719 let (msg_exp, (label_sp, label_exp)) = if expected.len() > 1 {
720 let short_expect = if expected.len() > 6 {
721 format!("{} possible tokens", expected.len())
725 (format!("expected one of {}, found `{}`", expect, actual),
726 (self.sess.source_map().next_point(self.prev_span),
727 format!("expected one of {} here", short_expect)))
728 } else if expected.is_empty() {
729 (format!("unexpected token: `{}`", actual),
730 (self.prev_span, "unexpected token after this".to_string()))
732 (format!("expected {}, found `{}`", expect, actual),
733 (self.sess.source_map().next_point(self.prev_span),
734 format!("expected {} here", expect)))
736 self.last_unexpected_token_span = Some(self.span);
737 let mut err = self.fatal(&msg_exp);
738 if self.token.is_ident_named("and") {
739 err.span_suggestion_short(
741 "use `&&` instead of `and` for the boolean operator",
743 Applicability::MaybeIncorrect,
746 if self.token.is_ident_named("or") {
747 err.span_suggestion_short(
749 "use `||` instead of `or` for the boolean operator",
751 Applicability::MaybeIncorrect,
754 let sp = if self.token == token::Token::Eof {
755 // This is EOF, don't want to point at the following char, but rather the last token
760 match self.recover_closing_delimiter(&expected.iter().filter_map(|tt| match tt {
761 TokenType::Token(t) => Some(t.clone()),
763 }).collect::<Vec<_>>(), err) {
766 return Ok(recovered);
770 let is_semi_suggestable = expected.iter().any(|t| match t {
771 TokenType::Token(token::Semi) => true, // we expect a `;` here
773 }) && ( // a `;` would be expected before the current keyword
774 self.token.is_keyword(kw::Break) ||
775 self.token.is_keyword(kw::Continue) ||
776 self.token.is_keyword(kw::For) ||
777 self.token.is_keyword(kw::If) ||
778 self.token.is_keyword(kw::Let) ||
779 self.token.is_keyword(kw::Loop) ||
780 self.token.is_keyword(kw::Match) ||
781 self.token.is_keyword(kw::Return) ||
782 self.token.is_keyword(kw::While)
784 let cm = self.sess.source_map();
785 match (cm.lookup_line(self.span.lo()), cm.lookup_line(sp.lo())) {
786 (Ok(ref a), Ok(ref b)) if a.line != b.line && is_semi_suggestable => {
787 // The spans are in different lines, expected `;` and found `let` or `return`.
788 // High likelihood that it is only a missing `;`.
789 err.span_suggestion_short(
791 "a semicolon may be missing here",
793 Applicability::MaybeIncorrect,
798 (Ok(ref a), Ok(ref b)) if a.line == b.line => {
799 // When the spans are in the same line, it means that the only content between
800 // them is whitespace, point at the found token in that case:
802 // X | () => { syntax error };
803 // | ^^^^^ expected one of 8 possible tokens here
805 // instead of having:
807 // X | () => { syntax error };
808 // | -^^^^^ unexpected token
810 // | expected one of 8 possible tokens here
811 err.span_label(self.span, label_exp);
813 _ if self.prev_span == syntax_pos::DUMMY_SP => {
814 // Account for macro context where the previous span might not be
815 // available to avoid incorrect output (#54841).
816 err.span_label(self.span, "unexpected token");
819 err.span_label(sp, label_exp);
820 err.span_label(self.span, "unexpected token");
827 /// Returns the span of expr, if it was not interpolated or the span of the interpolated token.
828 fn interpolated_or_expr_span(&self,
829 expr: PResult<'a, P<Expr>>)
830 -> PResult<'a, (Span, P<Expr>)> {
832 if self.prev_token_kind == PrevTokenKind::Interpolated {
840 fn expected_ident_found(&self) -> DiagnosticBuilder<'a> {
841 let mut err = self.struct_span_err(self.span,
842 &format!("expected identifier, found {}",
843 self.this_token_descr()));
844 if let token::Ident(ident, false) = &self.token {
845 if ident.is_raw_guess() {
848 "you can escape reserved keywords to use them as identifiers",
849 format!("r#{}", ident),
850 Applicability::MaybeIncorrect,
854 if let Some(token_descr) = self.token_descr() {
855 err.span_label(self.span, format!("expected identifier, found {}", token_descr));
857 err.span_label(self.span, "expected identifier");
858 if self.token == token::Comma && self.look_ahead(1, |t| t.is_ident()) {
863 Applicability::MachineApplicable,
870 pub fn parse_ident(&mut self) -> PResult<'a, ast::Ident> {
871 self.parse_ident_common(true)
874 fn parse_ident_common(&mut self, recover: bool) -> PResult<'a, ast::Ident> {
876 token::Ident(ident, _) => {
877 if self.token.is_reserved_ident() {
878 let mut err = self.expected_ident_found();
885 let span = self.span;
887 Ok(Ident::new(ident.name, span))
890 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
891 self.span_fatal_err(self.prev_span, Error::UselessDocComment)
893 self.expected_ident_found()
899 /// Checks if the next token is `tok`, and returns `true` if so.
901 /// This method will automatically add `tok` to `expected_tokens` if `tok` is not
903 crate fn check(&mut self, tok: &token::Token) -> bool {
904 let is_present = self.token == *tok;
905 if !is_present { self.expected_tokens.push(TokenType::Token(tok.clone())); }
909 /// Consumes a token 'tok' if it exists. Returns whether the given token was present.
910 pub fn eat(&mut self, tok: &token::Token) -> bool {
911 let is_present = self.check(tok);
912 if is_present { self.bump() }
916 fn check_keyword(&mut self, kw: Symbol) -> bool {
917 self.expected_tokens.push(TokenType::Keyword(kw));
918 self.token.is_keyword(kw)
921 /// If the next token is the given keyword, eats it and returns
922 /// `true`. Otherwise, returns `false`.
923 pub fn eat_keyword(&mut self, kw: Symbol) -> bool {
924 if self.check_keyword(kw) {
932 fn eat_keyword_noexpect(&mut self, kw: Symbol) -> bool {
933 if self.token.is_keyword(kw) {
941 /// If the given word is not a keyword, signals an error.
942 /// If the next token is not the given word, signals an error.
943 /// Otherwise, eats it.
944 fn expect_keyword(&mut self, kw: Symbol) -> PResult<'a, ()> {
945 if !self.eat_keyword(kw) {
952 fn check_ident(&mut self) -> bool {
953 if self.token.is_ident() {
956 self.expected_tokens.push(TokenType::Ident);
961 fn check_path(&mut self) -> bool {
962 if self.token.is_path_start() {
965 self.expected_tokens.push(TokenType::Path);
970 fn check_type(&mut self) -> bool {
971 if self.token.can_begin_type() {
974 self.expected_tokens.push(TokenType::Type);
979 fn check_const_arg(&mut self) -> bool {
980 if self.token.can_begin_const_arg() {
983 self.expected_tokens.push(TokenType::Const);
988 /// Expects and consumes a `+`. if `+=` is seen, replaces it with a `=`
989 /// and continues. If a `+` is not seen, returns `false`.
991 /// This is used when token-splitting `+=` into `+`.
992 /// See issue #47856 for an example of when this may occur.
993 fn eat_plus(&mut self) -> bool {
994 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
996 token::BinOp(token::Plus) => {
1000 token::BinOpEq(token::Plus) => {
1001 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1002 self.bump_with(token::Eq, span);
1010 /// Checks to see if the next token is either `+` or `+=`.
1011 /// Otherwise returns `false`.
1012 fn check_plus(&mut self) -> bool {
1013 if self.token.is_like_plus() {
1017 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Plus)));
1022 /// Expects and consumes an `&`. If `&&` is seen, replaces it with a single
1023 /// `&` and continues. If an `&` is not seen, signals an error.
1024 fn expect_and(&mut self) -> PResult<'a, ()> {
1025 self.expected_tokens.push(TokenType::Token(token::BinOp(token::And)));
1027 token::BinOp(token::And) => {
1032 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1033 Ok(self.bump_with(token::BinOp(token::And), span))
1035 _ => self.unexpected()
1039 /// Expects and consumes an `|`. If `||` is seen, replaces it with a single
1040 /// `|` and continues. If an `|` is not seen, signals an error.
1041 fn expect_or(&mut self) -> PResult<'a, ()> {
1042 self.expected_tokens.push(TokenType::Token(token::BinOp(token::Or)));
1044 token::BinOp(token::Or) => {
1049 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1050 Ok(self.bump_with(token::BinOp(token::Or), span))
1052 _ => self.unexpected()
1056 fn expect_no_suffix(&self, sp: Span, kind: &str, suffix: Option<ast::Name>) {
1057 literal::expect_no_suffix(sp, &self.sess.span_diagnostic, kind, suffix)
1060 /// Attempts to consume a `<`. If `<<` is seen, replaces it with a single
1061 /// `<` and continue. If `<-` is seen, replaces it with a single `<`
1062 /// and continue. If a `<` is not seen, returns false.
1064 /// This is meant to be used when parsing generics on a path to get the
1066 fn eat_lt(&mut self) -> bool {
1067 self.expected_tokens.push(TokenType::Token(token::Lt));
1068 let ate = match self.token {
1073 token::BinOp(token::Shl) => {
1074 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1075 self.bump_with(token::Lt, span);
1079 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1080 self.bump_with(token::BinOp(token::Minus), span);
1087 // See doc comment for `unmatched_angle_bracket_count`.
1088 self.unmatched_angle_bracket_count += 1;
1089 self.max_angle_bracket_count += 1;
1090 debug!("eat_lt: (increment) count={:?}", self.unmatched_angle_bracket_count);
1096 fn expect_lt(&mut self) -> PResult<'a, ()> {
1104 /// Expects and consumes a single `>` token. if a `>>` is seen, replaces it
1105 /// with a single `>` and continues. If a `>` is not seen, signals an error.
1106 fn expect_gt(&mut self) -> PResult<'a, ()> {
1107 self.expected_tokens.push(TokenType::Token(token::Gt));
1108 let ate = match self.token {
1113 token::BinOp(token::Shr) => {
1114 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1115 Some(self.bump_with(token::Gt, span))
1117 token::BinOpEq(token::Shr) => {
1118 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1119 Some(self.bump_with(token::Ge, span))
1122 let span = self.span.with_lo(self.span.lo() + BytePos(1));
1123 Some(self.bump_with(token::Eq, span))
1130 // See doc comment for `unmatched_angle_bracket_count`.
1131 if self.unmatched_angle_bracket_count > 0 {
1132 self.unmatched_angle_bracket_count -= 1;
1133 debug!("expect_gt: (decrement) count={:?}", self.unmatched_angle_bracket_count);
1138 None => self.unexpected(),
1142 /// Eats and discards tokens until one of `kets` is encountered. Respects token trees,
1143 /// passes through any errors encountered. Used for error recovery.
1144 fn eat_to_tokens(&mut self, kets: &[&token::Token]) {
1145 let handler = self.diagnostic();
1147 if let Err(ref mut err) = self.parse_seq_to_before_tokens(kets,
1149 TokenExpectType::Expect,
1150 |p| Ok(p.parse_token_tree())) {
1151 handler.cancel(err);
1155 /// Parses a sequence, including the closing delimiter. The function
1156 /// `f` must consume tokens until reaching the next separator or
1157 /// closing bracket.
1158 pub fn parse_seq_to_end<T, F>(&mut self,
1162 -> PResult<'a, Vec<T>> where
1163 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1165 let (val, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1172 /// Parses a sequence, not including the closing delimiter. The function
1173 /// `f` must consume tokens until reaching the next separator or
1174 /// closing bracket.
1175 pub fn parse_seq_to_before_end<T, F>(
1180 ) -> PResult<'a, (Vec<T>, bool)>
1181 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1183 self.parse_seq_to_before_tokens(&[ket], sep, TokenExpectType::Expect, f)
1186 fn parse_seq_to_before_tokens<T, F>(
1188 kets: &[&token::Token],
1190 expect: TokenExpectType,
1192 ) -> PResult<'a, (Vec<T>, bool /* recovered */)>
1193 where F: FnMut(&mut Parser<'a>) -> PResult<'a, T>
1195 let mut first = true;
1196 let mut recovered = false;
1198 while !kets.iter().any(|k| {
1200 TokenExpectType::Expect => self.check(k),
1201 TokenExpectType::NoExpect => self.token == **k,
1205 token::CloseDelim(..) | token::Eof => break,
1208 if let Some(ref t) = sep.sep {
1212 match self.expect(t) {
1219 // Attempt to keep parsing if it was a similar separator
1220 if let Some(ref tokens) = t.similar_tokens() {
1221 if tokens.contains(&self.token) {
1226 // Attempt to keep parsing if it was an omitted separator
1241 if sep.trailing_sep_allowed && kets.iter().any(|k| {
1243 TokenExpectType::Expect => self.check(k),
1244 TokenExpectType::NoExpect => self.token == **k,
1257 /// Parses a sequence, including the closing delimiter. The function
1258 /// `f` must consume tokens until reaching the next separator or
1259 /// closing bracket.
1260 fn parse_unspanned_seq<T, F>(
1266 ) -> PResult<'a, Vec<T>> where
1267 F: FnMut(&mut Parser<'a>) -> PResult<'a, T>,
1270 let (result, recovered) = self.parse_seq_to_before_end(ket, sep, f)?;
1277 /// Advance the parser by one token
1278 pub fn bump(&mut self) {
1279 if self.prev_token_kind == PrevTokenKind::Eof {
1280 // Bumping after EOF is a bad sign, usually an infinite loop.
1281 self.bug("attempted to bump the parser past EOF (may be stuck in a loop)");
1284 self.prev_span = self.meta_var_span.take().unwrap_or(self.span);
1286 // Record last token kind for possible error recovery.
1287 self.prev_token_kind = match self.token {
1288 token::DocComment(..) => PrevTokenKind::DocComment,
1289 token::Comma => PrevTokenKind::Comma,
1290 token::BinOp(token::Plus) => PrevTokenKind::Plus,
1291 token::BinOp(token::Or) => PrevTokenKind::BitOr,
1292 token::Interpolated(..) => PrevTokenKind::Interpolated,
1293 token::Eof => PrevTokenKind::Eof,
1294 token::Ident(..) => PrevTokenKind::Ident,
1295 _ => PrevTokenKind::Other,
1298 let next = self.next_tok();
1299 self.span = next.sp;
1300 self.token = next.tok;
1301 self.expected_tokens.clear();
1302 // check after each token
1303 self.process_potential_macro_variable();
1306 /// Advance the parser using provided token as a next one. Use this when
1307 /// consuming a part of a token. For example a single `<` from `<<`.
1308 fn bump_with(&mut self, next: token::Token, span: Span) {
1309 self.prev_span = self.span.with_hi(span.lo());
1310 // It would be incorrect to record the kind of the current token, but
1311 // fortunately for tokens currently using `bump_with`, the
1312 // prev_token_kind will be of no use anyway.
1313 self.prev_token_kind = PrevTokenKind::Other;
1316 self.expected_tokens.clear();
1319 pub fn look_ahead<R, F>(&self, dist: usize, f: F) -> R where
1320 F: FnOnce(&token::Token) -> R,
1323 return f(&self.token)
1326 f(&match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1327 Some(tree) => match tree {
1328 TokenTree::Token(_, tok) => tok,
1329 TokenTree::Delimited(_, delim, _) => token::OpenDelim(delim),
1331 None => token::CloseDelim(self.token_cursor.frame.delim),
1335 crate fn look_ahead_span(&self, dist: usize) -> Span {
1340 match self.token_cursor.frame.tree_cursor.look_ahead(dist - 1) {
1341 Some(TokenTree::Token(span, _)) => span,
1342 Some(TokenTree::Delimited(span, ..)) => span.entire(),
1343 None => self.look_ahead_span(dist - 1),
1346 pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
1347 self.sess.span_diagnostic.struct_span_fatal(self.span, m)
1349 pub fn span_fatal<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1350 self.sess.span_diagnostic.struct_span_fatal(sp, m)
1352 fn span_fatal_err<S: Into<MultiSpan>>(&self, sp: S, err: Error) -> DiagnosticBuilder<'a> {
1353 err.span_err(sp, self.diagnostic())
1355 fn bug(&self, m: &str) -> ! {
1356 self.sess.span_diagnostic.span_bug(self.span, m)
1358 fn span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) {
1359 self.sess.span_diagnostic.span_err(sp, m)
1361 crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
1362 self.sess.span_diagnostic.struct_span_err(sp, m)
1364 crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
1365 self.sess.span_diagnostic.span_bug(sp, m)
1368 fn cancel(&self, err: &mut DiagnosticBuilder<'_>) {
1369 self.sess.span_diagnostic.cancel(err)
1372 crate fn diagnostic(&self) -> &'a errors::Handler {
1373 &self.sess.span_diagnostic
1376 /// Is the current token one of the keywords that signals a bare function type?
1377 fn token_is_bare_fn_keyword(&mut self) -> bool {
1378 self.check_keyword(kw::Fn) ||
1379 self.check_keyword(kw::Unsafe) ||
1380 self.check_keyword(kw::Extern)
1383 /// Parses a `TyKind::BareFn` type.
1384 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
1387 [unsafe] [extern "ABI"] fn (S) -> T
1397 let unsafety = self.parse_unsafety();
1398 let abi = if self.eat_keyword(kw::Extern) {
1399 self.parse_opt_abi()?.unwrap_or(Abi::C)
1404 self.expect_keyword(kw::Fn)?;
1405 let (inputs, c_variadic) = self.parse_fn_args(false, true)?;
1406 let ret_ty = self.parse_ret_ty(false)?;
1407 let decl = P(FnDecl {
1412 Ok(TyKind::BareFn(P(BareFnTy {
1420 /// Parses asyncness: `async` or nothing.
1421 fn parse_asyncness(&mut self) -> IsAsync {
1422 if self.eat_keyword(kw::Async) {
1424 closure_id: ast::DUMMY_NODE_ID,
1425 return_impl_trait_id: ast::DUMMY_NODE_ID,
1426 arguments: Vec::new(),
1433 /// Parses unsafety: `unsafe` or nothing.
1434 fn parse_unsafety(&mut self) -> Unsafety {
1435 if self.eat_keyword(kw::Unsafe) {
1442 /// Parses the items in a trait declaration.
1443 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
1444 maybe_whole!(self, NtTraitItem, |x| x);
1445 let attrs = self.parse_outer_attributes()?;
1446 let mut unclosed_delims = vec![];
1447 let (mut item, tokens) = self.collect_tokens(|this| {
1448 let item = this.parse_trait_item_(at_end, attrs);
1449 unclosed_delims.append(&mut this.unclosed_delims);
1452 self.unclosed_delims.append(&mut unclosed_delims);
1453 // See `parse_item` for why this clause is here.
1454 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
1455 item.tokens = Some(tokens);
1460 fn parse_trait_item_(&mut self,
1462 mut attrs: Vec<Attribute>) -> PResult<'a, TraitItem> {
1465 let (name, node, generics) = if self.eat_keyword(kw::Type) {
1466 self.parse_trait_item_assoc_ty()?
1467 } else if self.is_const_item() {
1468 self.expect_keyword(kw::Const)?;
1469 let ident = self.parse_ident()?;
1470 self.expect(&token::Colon)?;
1471 let ty = self.parse_ty()?;
1472 let default = if self.eat(&token::Eq) {
1473 let expr = self.parse_expr()?;
1474 self.expect(&token::Semi)?;
1477 self.expect(&token::Semi)?;
1480 (ident, TraitItemKind::Const(ty, default), ast::Generics::default())
1481 } else if let Some(mac) = self.parse_assoc_macro_invoc("trait", None, &mut false)? {
1482 // trait item macro.
1483 (Ident::with_empty_ctxt(kw::Invalid),
1484 ast::TraitItemKind::Macro(mac),
1485 ast::Generics::default())
1487 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
1489 let ident = self.parse_ident()?;
1490 let mut generics = self.parse_generics()?;
1492 let mut decl = self.parse_fn_decl_with_self(|p: &mut Parser<'a>| {
1493 // This is somewhat dubious; We don't want to allow
1494 // argument names to be left off if there is a
1497 // We don't allow argument names to be left off in edition 2018.
1498 p.parse_arg_general(p.span.rust_2018(), true, false)
1500 generics.where_clause = self.parse_where_clause()?;
1501 self.construct_async_arguments(&mut asyncness, &mut decl);
1503 let sig = ast::MethodSig {
1513 let body = match self.token {
1517 debug!("parse_trait_methods(): parsing required method");
1520 token::OpenDelim(token::Brace) => {
1521 debug!("parse_trait_methods(): parsing provided method");
1523 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1524 attrs.extend(inner_attrs.iter().cloned());
1527 token::Interpolated(ref nt) => {
1529 token::NtBlock(..) => {
1531 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
1532 attrs.extend(inner_attrs.iter().cloned());
1536 let token_str = self.this_token_descr();
1537 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1539 err.span_label(self.span, "expected `;` or `{`");
1545 let token_str = self.this_token_descr();
1546 let mut err = self.fatal(&format!("expected `;` or `{{`, found {}",
1548 err.span_label(self.span, "expected `;` or `{`");
1552 (ident, ast::TraitItemKind::Method(sig, body), generics)
1556 id: ast::DUMMY_NODE_ID,
1561 span: lo.to(self.prev_span),
1566 /// Parses an optional return type `[ -> TY ]` in a function declaration.
1567 fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
1568 if self.eat(&token::RArrow) {
1569 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
1571 Ok(FunctionRetTy::Default(self.span.shrink_to_lo()))
1576 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
1577 self.parse_ty_common(true, true, false)
1580 /// Parses a type in restricted contexts where `+` is not permitted.
1582 /// Example 1: `&'a TYPE`
1583 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
1584 /// Example 2: `value1 as TYPE + value2`
1585 /// `+` is prohibited to avoid interactions with expression grammar.
1586 fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
1587 self.parse_ty_common(false, true, false)
1590 fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
1591 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
1592 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
1593 maybe_whole!(self, NtTy, |x| x);
1596 let mut impl_dyn_multi = false;
1597 let node = if self.eat(&token::OpenDelim(token::Paren)) {
1598 // `(TYPE)` is a parenthesized type.
1599 // `(TYPE,)` is a tuple with a single field of type TYPE.
1600 let mut ts = vec![];
1601 let mut last_comma = false;
1602 while self.token != token::CloseDelim(token::Paren) {
1603 ts.push(self.parse_ty()?);
1604 if self.eat(&token::Comma) {
1611 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
1612 self.expect(&token::CloseDelim(token::Paren))?;
1614 if ts.len() == 1 && !last_comma {
1615 let ty = ts.into_iter().nth(0).unwrap().into_inner();
1616 let maybe_bounds = allow_plus && self.token.is_like_plus();
1618 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
1619 TyKind::Path(None, ref path) if maybe_bounds => {
1620 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
1622 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
1623 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
1624 let path = match bounds[0] {
1625 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
1626 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
1628 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1631 _ => TyKind::Paren(P(ty))
1636 } else if self.eat(&token::Not) {
1639 } else if self.eat(&token::BinOp(token::Star)) {
1641 TyKind::Ptr(self.parse_ptr()?)
1642 } else if self.eat(&token::OpenDelim(token::Bracket)) {
1644 let t = self.parse_ty()?;
1645 // Parse optional `; EXPR` in `[TYPE; EXPR]`
1646 let t = match self.maybe_parse_fixed_length_of_vec()? {
1647 None => TyKind::Slice(t),
1648 Some(length) => TyKind::Array(t, AnonConst {
1649 id: ast::DUMMY_NODE_ID,
1653 self.expect(&token::CloseDelim(token::Bracket))?;
1655 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
1658 self.parse_borrowed_pointee()?
1659 } else if self.eat_keyword_noexpect(kw::Typeof) {
1661 // In order to not be ambiguous, the type must be surrounded by parens.
1662 self.expect(&token::OpenDelim(token::Paren))?;
1664 id: ast::DUMMY_NODE_ID,
1665 value: self.parse_expr()?,
1667 self.expect(&token::CloseDelim(token::Paren))?;
1669 } else if self.eat_keyword(kw::Underscore) {
1670 // A type to be inferred `_`
1672 } else if self.token_is_bare_fn_keyword() {
1673 // Function pointer type
1674 self.parse_ty_bare_fn(Vec::new())?
1675 } else if self.check_keyword(kw::For) {
1676 // Function pointer type or bound list (trait object type) starting with a poly-trait.
1677 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
1678 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
1680 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
1681 if self.token_is_bare_fn_keyword() {
1682 self.parse_ty_bare_fn(lifetime_defs)?
1684 let path = self.parse_path(PathStyle::Type)?;
1685 let parse_plus = allow_plus && self.check_plus();
1686 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
1688 } else if self.eat_keyword(kw::Impl) {
1689 // Always parse bounds greedily for better error recovery.
1690 let bounds = self.parse_generic_bounds(None)?;
1691 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1692 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
1693 } else if self.check_keyword(kw::Dyn) &&
1694 (self.span.rust_2018() ||
1695 self.look_ahead(1, |t| t.can_begin_bound() &&
1696 !can_continue_type_after_non_fn_ident(t))) {
1697 self.bump(); // `dyn`
1698 // Always parse bounds greedily for better error recovery.
1699 let bounds = self.parse_generic_bounds(None)?;
1700 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
1701 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
1702 } else if self.check(&token::Question) ||
1703 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
1704 // Bound list (trait object type)
1705 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
1706 TraitObjectSyntax::None)
1707 } else if self.eat_lt() {
1709 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
1710 TyKind::Path(Some(qself), path)
1711 } else if self.token.is_path_start() {
1713 let path = self.parse_path(PathStyle::Type)?;
1714 if self.eat(&token::Not) {
1715 // Macro invocation in type position
1716 let (delim, tts) = self.expect_delimited_token_tree()?;
1717 let node = Mac_ { path, tts, delim };
1718 TyKind::Mac(respan(lo.to(self.prev_span), node))
1720 // Just a type path or bound list (trait object type) starting with a trait.
1722 // `Trait1 + Trait2 + 'a`
1723 if allow_plus && self.check_plus() {
1724 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
1726 TyKind::Path(None, path)
1729 } else if self.check(&token::DotDotDot) {
1730 if allow_c_variadic {
1731 self.eat(&token::DotDotDot);
1734 return Err(self.fatal(
1735 "only foreign functions are allowed to be C-variadic"
1739 let msg = format!("expected type, found {}", self.this_token_descr());
1740 return Err(self.fatal(&msg));
1743 let span = lo.to(self.prev_span);
1744 let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID });
1746 // Try to recover from use of `+` with incorrect priority.
1747 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
1748 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
1749 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
1752 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
1753 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
1754 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
1755 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
1757 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
1758 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
1760 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
1763 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
1764 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
1765 let mutbl = self.parse_mutability();
1766 let ty = self.parse_ty_no_plus()?;
1767 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
1770 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
1771 let mutbl = if self.eat_keyword(kw::Mut) {
1773 } else if self.eat_keyword(kw::Const) {
1774 Mutability::Immutable
1776 let span = self.prev_span;
1777 let msg = "expected mut or const in raw pointer type";
1778 self.struct_span_err(span, msg)
1779 .span_label(span, msg)
1780 .help("use `*mut T` or `*const T` as appropriate")
1782 Mutability::Immutable
1784 let t = self.parse_ty_no_plus()?;
1785 Ok(MutTy { ty: t, mutbl: mutbl })
1788 fn is_named_argument(&self) -> bool {
1789 let offset = match self.token {
1790 token::Interpolated(ref nt) => match **nt {
1791 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1794 token::BinOp(token::And) | token::AndAnd => 1,
1795 _ if self.token.is_keyword(kw::Mut) => 1,
1799 self.look_ahead(offset, |t| t.is_ident()) &&
1800 self.look_ahead(offset + 1, |t| t == &token::Colon)
1803 /// Skips unexpected attributes and doc comments in this position and emits an appropriate
1805 fn eat_incorrect_doc_comment(&mut self, applied_to: &str) {
1806 if let token::DocComment(_) = self.token {
1807 let mut err = self.diagnostic().struct_span_err(
1809 &format!("documentation comments cannot be applied to {}", applied_to),
1811 err.span_label(self.span, "doc comments are not allowed here");
1814 } else if self.token == token::Pound && self.look_ahead(1, |t| {
1815 *t == token::OpenDelim(token::Bracket)
1818 // Skip every token until next possible arg.
1819 while self.token != token::CloseDelim(token::Bracket) {
1822 let sp = lo.to(self.span);
1824 let mut err = self.diagnostic().struct_span_err(
1826 &format!("attributes cannot be applied to {}", applied_to),
1828 err.span_label(sp, "attributes are not allowed here");
1833 /// This version of parse arg doesn't necessarily require identifier names.
1834 fn parse_arg_general(&mut self, require_name: bool, is_trait_item: bool,
1835 allow_c_variadic: bool) -> PResult<'a, Arg> {
1836 if let Ok(Some(_)) = self.parse_self_arg() {
1837 let mut err = self.struct_span_err(self.prev_span,
1838 "unexpected `self` argument in function");
1839 err.span_label(self.prev_span,
1840 "`self` is only valid as the first argument of an associated function");
1844 let (pat, ty) = if require_name || self.is_named_argument() {
1845 debug!("parse_arg_general parse_pat (require_name:{})",
1847 self.eat_incorrect_doc_comment("method arguments");
1848 let pat = self.parse_pat(Some("argument name"))?;
1850 if let Err(mut err) = self.expect(&token::Colon) {
1851 // If we find a pattern followed by an identifier, it could be an (incorrect)
1852 // C-style parameter declaration.
1853 if self.check_ident() && self.look_ahead(1, |t| {
1854 *t == token::Comma || *t == token::CloseDelim(token::Paren)
1856 let ident = self.parse_ident().unwrap();
1857 let span = pat.span.with_hi(ident.span.hi());
1859 err.span_suggestion(
1861 "declare the type after the parameter binding",
1862 String::from("<identifier>: <type>"),
1863 Applicability::HasPlaceholders,
1865 } else if require_name && is_trait_item {
1866 if let PatKind::Ident(_, ident, _) = pat.node {
1867 err.span_suggestion(
1869 "explicitly ignore parameter",
1870 format!("_: {}", ident),
1871 Applicability::MachineApplicable,
1875 err.note("anonymous parameters are removed in the 2018 edition (see RFC 1685)");
1881 self.eat_incorrect_doc_comment("a method argument's type");
1882 (pat, self.parse_ty_common(true, true, allow_c_variadic)?)
1884 debug!("parse_arg_general ident_to_pat");
1885 let parser_snapshot_before_ty = self.clone();
1886 self.eat_incorrect_doc_comment("a method argument's type");
1887 let mut ty = self.parse_ty_common(true, true, allow_c_variadic);
1888 if ty.is_ok() && self.token != token::Comma &&
1889 self.token != token::CloseDelim(token::Paren) {
1890 // This wasn't actually a type, but a pattern looking like a type,
1891 // so we are going to rollback and re-parse for recovery.
1892 ty = self.unexpected();
1896 let ident = Ident::new(kw::Invalid, self.prev_span);
1898 id: ast::DUMMY_NODE_ID,
1899 node: PatKind::Ident(
1900 BindingMode::ByValue(Mutability::Immutable), ident, None),
1906 // If this is a C-variadic argument and we hit an error, return the
1908 if self.token == token::DotDotDot {
1911 // Recover from attempting to parse the argument as a type without pattern.
1913 mem::replace(self, parser_snapshot_before_ty);
1914 let pat = self.parse_pat(Some("argument name"))?;
1915 self.expect(&token::Colon)?;
1916 let ty = self.parse_ty()?;
1918 let mut err = self.diagnostic().struct_span_err_with_code(
1920 "patterns aren't allowed in methods without bodies",
1921 DiagnosticId::Error("E0642".into()),
1923 err.span_suggestion_short(
1925 "give this argument a name or use an underscore to ignore it",
1927 Applicability::MachineApplicable,
1931 // Pretend the pattern is `_`, to avoid duplicate errors from AST validation.
1933 node: PatKind::Wild,
1935 id: ast::DUMMY_NODE_ID
1942 Ok(Arg { ty, pat, id: ast::DUMMY_NODE_ID, source: ast::ArgSource::Normal })
1945 /// Parses a single function argument.
1946 crate fn parse_arg(&mut self) -> PResult<'a, Arg> {
1947 self.parse_arg_general(true, false, false)
1950 /// Parses an argument in a lambda header (e.g., `|arg, arg|`).
1951 fn parse_fn_block_arg(&mut self) -> PResult<'a, Arg> {
1952 let pat = self.parse_pat(Some("argument name"))?;
1953 let t = if self.eat(&token::Colon) {
1957 id: ast::DUMMY_NODE_ID,
1958 node: TyKind::Infer,
1959 span: self.prev_span,
1965 id: ast::DUMMY_NODE_ID,
1966 source: ast::ArgSource::Normal,
1970 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
1971 if self.eat(&token::Semi) {
1972 Ok(Some(self.parse_expr()?))
1978 /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
1979 crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
1980 maybe_whole_expr!(self);
1982 let minus_lo = self.span;
1983 let minus_present = self.eat(&token::BinOp(token::Minus));
1985 let literal = self.parse_lit()?;
1986 let hi = self.prev_span;
1987 let expr = self.mk_expr(lo.to(hi), ExprKind::Lit(literal), ThinVec::new());
1990 let minus_hi = self.prev_span;
1991 let unary = self.mk_unary(UnOp::Neg, expr);
1992 Ok(self.mk_expr(minus_lo.to(minus_hi), unary, ThinVec::new()))
1998 fn parse_path_segment_ident(&mut self) -> PResult<'a, ast::Ident> {
2000 token::Ident(ident, _) if self.token.is_path_segment_keyword() => {
2001 let span = self.span;
2003 Ok(Ident::new(ident.name, span))
2005 _ => self.parse_ident(),
2009 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
2011 token::Ident(ident, false) if ident.name == kw::Underscore => {
2012 let span = self.span;
2014 Ok(Ident::new(ident.name, span))
2016 _ => self.parse_ident(),
2020 /// Parses a qualified path.
2021 /// Assumes that the leading `<` has been parsed already.
2023 /// `qualified_path = <type [as trait_ref]>::path`
2028 /// `<T as U>::F::a<S>` (without disambiguator)
2029 /// `<T as U>::F::a::<S>` (with disambiguator)
2030 fn parse_qpath(&mut self, style: PathStyle) -> PResult<'a, (QSelf, ast::Path)> {
2031 let lo = self.prev_span;
2032 let ty = self.parse_ty()?;
2034 // `path` will contain the prefix of the path up to the `>`,
2035 // if any (e.g., `U` in the `<T as U>::*` examples
2036 // above). `path_span` has the span of that path, or an empty
2037 // span in the case of something like `<T>::Bar`.
2038 let (mut path, path_span);
2039 if self.eat_keyword(kw::As) {
2040 let path_lo = self.span;
2041 path = self.parse_path(PathStyle::Type)?;
2042 path_span = path_lo.to(self.prev_span);
2044 path = ast::Path { segments: Vec::new(), span: syntax_pos::DUMMY_SP };
2045 path_span = self.span.to(self.span);
2048 // See doc comment for `unmatched_angle_bracket_count`.
2049 self.expect(&token::Gt)?;
2050 if self.unmatched_angle_bracket_count > 0 {
2051 self.unmatched_angle_bracket_count -= 1;
2052 debug!("parse_qpath: (decrement) count={:?}", self.unmatched_angle_bracket_count);
2055 self.expect(&token::ModSep)?;
2057 let qself = QSelf { ty, path_span, position: path.segments.len() };
2058 self.parse_path_segments(&mut path.segments, style)?;
2060 Ok((qself, ast::Path { segments: path.segments, span: lo.to(self.prev_span) }))
2063 /// Parses simple paths.
2065 /// `path = [::] segment+`
2066 /// `segment = ident | ident[::]<args> | ident[::](args) [-> type]`
2069 /// `a::b::C<D>` (without disambiguator)
2070 /// `a::b::C::<D>` (with disambiguator)
2071 /// `Fn(Args)` (without disambiguator)
2072 /// `Fn::(Args)` (with disambiguator)
2073 pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2074 maybe_whole!(self, NtPath, |path| {
2075 if style == PathStyle::Mod &&
2076 path.segments.iter().any(|segment| segment.args.is_some()) {
2077 self.diagnostic().span_err(path.span, "unexpected generic arguments in path");
2082 let lo = self.meta_var_span.unwrap_or(self.span);
2083 let mut segments = Vec::new();
2084 let mod_sep_ctxt = self.span.ctxt();
2085 if self.eat(&token::ModSep) {
2086 segments.push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
2088 self.parse_path_segments(&mut segments, style)?;
2090 Ok(ast::Path { segments, span: lo.to(self.prev_span) })
2093 /// Like `parse_path`, but also supports parsing `Word` meta items into paths for
2094 /// backwards-compatibility. This is used when parsing derive macro paths in `#[derive]`
2096 pub fn parse_path_allowing_meta(&mut self, style: PathStyle) -> PResult<'a, ast::Path> {
2097 let meta_ident = match self.token {
2098 token::Interpolated(ref nt) => match **nt {
2099 token::NtMeta(ref meta) => match meta.node {
2100 ast::MetaItemKind::Word => Some(meta.path.clone()),
2107 if let Some(path) = meta_ident {
2111 self.parse_path(style)
2114 crate fn parse_path_segments(&mut self,
2115 segments: &mut Vec<PathSegment>,
2117 -> PResult<'a, ()> {
2119 let segment = self.parse_path_segment(style)?;
2120 if style == PathStyle::Expr {
2121 // In order to check for trailing angle brackets, we must have finished
2122 // recursing (`parse_path_segment` can indirectly call this function),
2123 // that is, the next token must be the highlighted part of the below example:
2125 // `Foo::<Bar as Baz<T>>::Qux`
2128 // As opposed to the below highlight (if we had only finished the first
2131 // `Foo::<Bar as Baz<T>>::Qux`
2134 // `PathStyle::Expr` is only provided at the root invocation and never in
2135 // `parse_path_segment` to recurse and therefore can be checked to maintain
2137 self.check_trailing_angle_brackets(&segment, token::ModSep);
2139 segments.push(segment);
2141 if self.is_import_coupler() || !self.eat(&token::ModSep) {
2147 fn parse_path_segment(&mut self, style: PathStyle) -> PResult<'a, PathSegment> {
2148 let ident = self.parse_path_segment_ident()?;
2150 let is_args_start = |token: &token::Token| match *token {
2151 token::Lt | token::BinOp(token::Shl) | token::OpenDelim(token::Paren)
2152 | token::LArrow => true,
2155 let check_args_start = |this: &mut Self| {
2156 this.expected_tokens.extend_from_slice(
2157 &[TokenType::Token(token::Lt), TokenType::Token(token::OpenDelim(token::Paren))]
2159 is_args_start(&this.token)
2162 Ok(if style == PathStyle::Type && check_args_start(self) ||
2163 style != PathStyle::Mod && self.check(&token::ModSep)
2164 && self.look_ahead(1, |t| is_args_start(t)) {
2165 // We use `style == PathStyle::Expr` to check if this is in a recursion or not. If
2166 // it isn't, then we reset the unmatched angle bracket count as we're about to start
2167 // parsing a new path.
2168 if style == PathStyle::Expr {
2169 self.unmatched_angle_bracket_count = 0;
2170 self.max_angle_bracket_count = 0;
2173 // Generic arguments are found - `<`, `(`, `::<` or `::(`.
2174 self.eat(&token::ModSep);
2176 let args = if self.eat_lt() {
2178 let (args, bindings) =
2179 self.parse_generic_args_with_leaning_angle_bracket_recovery(style, lo)?;
2181 let span = lo.to(self.prev_span);
2182 AngleBracketedArgs { args, bindings, span }.into()
2186 let (inputs, recovered) = self.parse_seq_to_before_tokens(
2187 &[&token::CloseDelim(token::Paren)],
2188 SeqSep::trailing_allowed(token::Comma),
2189 TokenExpectType::Expect,
2194 let span = lo.to(self.prev_span);
2195 let output = if self.eat(&token::RArrow) {
2196 Some(self.parse_ty_common(false, false, false)?)
2200 ParenthesizedArgs { inputs, output, span }.into()
2203 PathSegment { ident, args, id: ast::DUMMY_NODE_ID }
2205 // Generic arguments are not found.
2206 PathSegment::from_ident(ident)
2210 crate fn check_lifetime(&mut self) -> bool {
2211 self.expected_tokens.push(TokenType::Lifetime);
2212 self.token.is_lifetime()
2215 /// Parses a single lifetime `'a` or panics.
2216 crate fn expect_lifetime(&mut self) -> Lifetime {
2217 if let Some(ident) = self.token.lifetime() {
2218 let span = self.span;
2220 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
2222 self.span_bug(self.span, "not a lifetime")
2226 fn eat_label(&mut self) -> Option<Label> {
2227 if let Some(ident) = self.token.lifetime() {
2228 let span = self.span;
2230 Some(Label { ident: Ident::new(ident.name, span) })
2236 /// Parses mutability (`mut` or nothing).
2237 fn parse_mutability(&mut self) -> Mutability {
2238 if self.eat_keyword(kw::Mut) {
2241 Mutability::Immutable
2245 fn parse_field_name(&mut self) -> PResult<'a, Ident> {
2246 if let token::Literal(token::Integer(name), suffix) = self.token {
2247 self.expect_no_suffix(self.span, "a tuple index", suffix);
2249 Ok(Ident::new(name, self.prev_span))
2251 self.parse_ident_common(false)
2255 /// Parse ident (COLON expr)?
2256 fn parse_field(&mut self) -> PResult<'a, Field> {
2257 let attrs = self.parse_outer_attributes()?;
2260 // Check if a colon exists one ahead. This means we're parsing a fieldname.
2261 let (fieldname, expr, is_shorthand) = if self.look_ahead(1, |t| {
2262 t == &token::Colon || t == &token::Eq
2264 let fieldname = self.parse_field_name()?;
2266 // Check for an equals token. This means the source incorrectly attempts to
2267 // initialize a field with an eq rather than a colon.
2268 if self.token == token::Eq {
2270 .struct_span_err(self.span, "expected `:`, found `=`")
2272 fieldname.span.shrink_to_hi().to(self.span),
2273 "replace equals symbol with a colon",
2275 Applicability::MachineApplicable,
2280 (fieldname, self.parse_expr()?, false)
2282 let fieldname = self.parse_ident_common(false)?;
2284 // Mimic `x: x` for the `x` field shorthand.
2285 let path = ast::Path::from_ident(fieldname);
2286 let expr = self.mk_expr(fieldname.span, ExprKind::Path(None, path), ThinVec::new());
2287 (fieldname, expr, true)
2291 span: lo.to(expr.span),
2294 attrs: attrs.into(),
2298 crate fn mk_expr(&self, span: Span, node: ExprKind, attrs: ThinVec<Attribute>) -> P<Expr> {
2299 P(Expr { node, span, attrs, id: ast::DUMMY_NODE_ID })
2302 fn mk_unary(&self, unop: ast::UnOp, expr: P<Expr>) -> ast::ExprKind {
2303 ExprKind::Unary(unop, expr)
2306 fn mk_binary(&self, binop: ast::BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2307 ExprKind::Binary(binop, lhs, rhs)
2310 fn mk_call(&self, f: P<Expr>, args: Vec<P<Expr>>) -> ast::ExprKind {
2311 ExprKind::Call(f, args)
2314 fn mk_index(&self, expr: P<Expr>, idx: P<Expr>) -> ast::ExprKind {
2315 ExprKind::Index(expr, idx)
2319 start: Option<P<Expr>>,
2320 end: Option<P<Expr>>,
2321 limits: RangeLimits)
2322 -> PResult<'a, ast::ExprKind> {
2323 if end.is_none() && limits == RangeLimits::Closed {
2324 Err(self.span_fatal_err(self.span, Error::InclusiveRangeWithNoEnd))
2326 Ok(ExprKind::Range(start, end, limits))
2330 fn mk_assign_op(&self, binop: ast::BinOp,
2331 lhs: P<Expr>, rhs: P<Expr>) -> ast::ExprKind {
2332 ExprKind::AssignOp(binop, lhs, rhs)
2335 fn expect_delimited_token_tree(&mut self) -> PResult<'a, (MacDelimiter, TokenStream)> {
2336 let delim = match self.token {
2337 token::OpenDelim(delim) => delim,
2339 let msg = "expected open delimiter";
2340 let mut err = self.fatal(msg);
2341 err.span_label(self.span, msg);
2345 let tts = match self.parse_token_tree() {
2346 TokenTree::Delimited(_, _, tts) => tts,
2347 _ => unreachable!(),
2349 let delim = match delim {
2350 token::Paren => MacDelimiter::Parenthesis,
2351 token::Bracket => MacDelimiter::Bracket,
2352 token::Brace => MacDelimiter::Brace,
2353 token::NoDelim => self.bug("unexpected no delimiter"),
2355 Ok((delim, tts.into()))
2358 /// At the bottom (top?) of the precedence hierarchy,
2359 /// Parses things like parenthesized exprs, macros, `return`, etc.
2361 /// N.B., this does not parse outer attributes, and is private because it only works
2362 /// correctly if called from `parse_dot_or_call_expr()`.
2363 fn parse_bottom_expr(&mut self) -> PResult<'a, P<Expr>> {
2364 maybe_recover_from_interpolated_ty_qpath!(self, true);
2365 maybe_whole_expr!(self);
2367 // Outer attributes are already parsed and will be
2368 // added to the return value after the fact.
2370 // Therefore, prevent sub-parser from parsing
2371 // attributes by giving them a empty "already parsed" list.
2372 let mut attrs = ThinVec::new();
2375 let mut hi = self.span;
2379 // Note: when adding new syntax here, don't forget to adjust Token::can_begin_expr().
2381 token::OpenDelim(token::Paren) => {
2384 attrs.extend(self.parse_inner_attributes()?);
2386 // (e) is parenthesized e
2387 // (e,) is a tuple with only one field, e
2388 let mut es = vec![];
2389 let mut trailing_comma = false;
2390 let mut recovered = false;
2391 while self.token != token::CloseDelim(token::Paren) {
2392 es.push(match self.parse_expr() {
2395 // recover from parse error in tuple list
2396 return Ok(self.recover_seq_parse_error(token::Paren, lo, Err(err)));
2399 recovered = self.expect_one_of(
2401 &[token::Comma, token::CloseDelim(token::Paren)],
2403 if self.eat(&token::Comma) {
2404 trailing_comma = true;
2406 trailing_comma = false;
2414 hi = self.prev_span;
2415 ex = if es.len() == 1 && !trailing_comma {
2416 ExprKind::Paren(es.into_iter().nth(0).unwrap())
2421 token::OpenDelim(token::Brace) => {
2422 return self.parse_block_expr(None, lo, BlockCheckMode::Default, attrs);
2424 token::BinOp(token::Or) | token::OrOr => {
2425 return self.parse_lambda_expr(attrs);
2427 token::OpenDelim(token::Bracket) => {
2430 attrs.extend(self.parse_inner_attributes()?);
2432 if self.eat(&token::CloseDelim(token::Bracket)) {
2434 ex = ExprKind::Array(Vec::new());
2437 let first_expr = self.parse_expr()?;
2438 if self.eat(&token::Semi) {
2439 // Repeating array syntax: [ 0; 512 ]
2440 let count = AnonConst {
2441 id: ast::DUMMY_NODE_ID,
2442 value: self.parse_expr()?,
2444 self.expect(&token::CloseDelim(token::Bracket))?;
2445 ex = ExprKind::Repeat(first_expr, count);
2446 } else if self.eat(&token::Comma) {
2447 // Vector with two or more elements.
2448 let remaining_exprs = self.parse_seq_to_end(
2449 &token::CloseDelim(token::Bracket),
2450 SeqSep::trailing_allowed(token::Comma),
2451 |p| Ok(p.parse_expr()?)
2453 let mut exprs = vec![first_expr];
2454 exprs.extend(remaining_exprs);
2455 ex = ExprKind::Array(exprs);
2457 // Vector with one element.
2458 self.expect(&token::CloseDelim(token::Bracket))?;
2459 ex = ExprKind::Array(vec![first_expr]);
2462 hi = self.prev_span;
2466 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
2468 return Ok(self.mk_expr(lo.to(hi), ExprKind::Path(Some(qself), path), attrs));
2470 if self.span.rust_2018() && self.check_keyword(kw::Async) {
2471 return if self.is_async_block() { // check for `async {` and `async move {`
2472 self.parse_async_block(attrs)
2474 self.parse_lambda_expr(attrs)
2477 if self.check_keyword(kw::Move) || self.check_keyword(kw::Static) {
2478 return self.parse_lambda_expr(attrs);
2480 if self.eat_keyword(kw::If) {
2481 return self.parse_if_expr(attrs);
2483 if self.eat_keyword(kw::For) {
2484 let lo = self.prev_span;
2485 return self.parse_for_expr(None, lo, attrs);
2487 if self.eat_keyword(kw::While) {
2488 let lo = self.prev_span;
2489 return self.parse_while_expr(None, lo, attrs);
2491 if let Some(label) = self.eat_label() {
2492 let lo = label.ident.span;
2493 self.expect(&token::Colon)?;
2494 if self.eat_keyword(kw::While) {
2495 return self.parse_while_expr(Some(label), lo, attrs)
2497 if self.eat_keyword(kw::For) {
2498 return self.parse_for_expr(Some(label), lo, attrs)
2500 if self.eat_keyword(kw::Loop) {
2501 return self.parse_loop_expr(Some(label), lo, attrs)
2503 if self.token == token::OpenDelim(token::Brace) {
2504 return self.parse_block_expr(Some(label),
2506 BlockCheckMode::Default,
2509 let msg = "expected `while`, `for`, `loop` or `{` after a label";
2510 let mut err = self.fatal(msg);
2511 err.span_label(self.span, msg);
2514 if self.eat_keyword(kw::Loop) {
2515 let lo = self.prev_span;
2516 return self.parse_loop_expr(None, lo, attrs);
2518 if self.eat_keyword(kw::Continue) {
2519 let label = self.eat_label();
2520 let ex = ExprKind::Continue(label);
2521 let hi = self.prev_span;
2522 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
2524 if self.eat_keyword(kw::Match) {
2525 let match_sp = self.prev_span;
2526 return self.parse_match_expr(attrs).map_err(|mut err| {
2527 err.span_label(match_sp, "while parsing this match expression");
2531 if self.eat_keyword(kw::Unsafe) {
2532 return self.parse_block_expr(
2535 BlockCheckMode::Unsafe(ast::UserProvided),
2538 if self.is_do_catch_block() {
2539 let mut db = self.fatal("found removed `do catch` syntax");
2540 db.help("Following RFC #2388, the new non-placeholder syntax is `try`");
2543 if self.is_try_block() {
2545 assert!(self.eat_keyword(kw::Try));
2546 return self.parse_try_block(lo, attrs);
2548 if self.eat_keyword(kw::Return) {
2549 if self.token.can_begin_expr() {
2550 let e = self.parse_expr()?;
2552 ex = ExprKind::Ret(Some(e));
2554 ex = ExprKind::Ret(None);
2556 } else if self.eat_keyword(kw::Break) {
2557 let label = self.eat_label();
2558 let e = if self.token.can_begin_expr()
2559 && !(self.token == token::OpenDelim(token::Brace)
2560 && self.restrictions.contains(
2561 Restrictions::NO_STRUCT_LITERAL)) {
2562 Some(self.parse_expr()?)
2566 ex = ExprKind::Break(label, e);
2567 hi = self.prev_span;
2568 } else if self.eat_keyword(kw::Yield) {
2569 if self.token.can_begin_expr() {
2570 let e = self.parse_expr()?;
2572 ex = ExprKind::Yield(Some(e));
2574 ex = ExprKind::Yield(None);
2576 } else if self.token.is_keyword(kw::Let) {
2577 // Catch this syntax error here, instead of in `parse_ident`, so
2578 // that we can explicitly mention that let is not to be used as an expression
2579 let mut db = self.fatal("expected expression, found statement (`let`)");
2580 db.span_label(self.span, "expected expression");
2581 db.note("variable declaration using `let` is a statement");
2583 } else if self.span.rust_2018() && self.eat_keyword(kw::Await) {
2584 let (await_hi, e_kind) = self.parse_await_macro_or_alt(lo, self.prev_span)?;
2587 } else if self.token.is_path_start() {
2588 let path = self.parse_path(PathStyle::Expr)?;
2590 // `!`, as an operator, is prefix, so we know this isn't that
2591 if self.eat(&token::Not) {
2592 // MACRO INVOCATION expression
2593 let (delim, tts) = self.expect_delimited_token_tree()?;
2594 hi = self.prev_span;
2595 ex = ExprKind::Mac(respan(lo.to(hi), Mac_ { path, tts, delim }));
2596 } else if self.check(&token::OpenDelim(token::Brace)) {
2597 if let Some(expr) = self.maybe_parse_struct_expr(lo, &path, &attrs) {
2601 ex = ExprKind::Path(None, path);
2605 ex = ExprKind::Path(None, path);
2608 if !self.unclosed_delims.is_empty() && self.check(&token::Semi) {
2609 // Don't complain about bare semicolons after unclosed braces
2610 // recovery in order to keep the error count down. Fixing the
2611 // delimiters will possibly also fix the bare semicolon found in
2612 // expression context. For example, silence the following error:
2614 // error: expected expression, found `;`
2618 // | ^ expected expression
2621 return Ok(self.mk_expr(self.span, ExprKind::Err, ThinVec::new()));
2623 match self.parse_literal_maybe_minus() {
2626 ex = expr.node.clone();
2629 self.cancel(&mut err);
2630 let msg = format!("expected expression, found {}",
2631 self.this_token_descr());
2632 let mut err = self.fatal(&msg);
2633 let sp = self.sess.source_map().start_point(self.span);
2634 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow()
2637 self.sess.expr_parentheses_needed(&mut err, *sp, None);
2639 err.span_label(self.span, "expected expression");
2647 let expr = self.mk_expr(lo.to(hi), ex, attrs);
2648 self.maybe_recover_from_bad_qpath(expr, true)
2651 /// Parse `await!(<expr>)` calls, or alternatively recover from incorrect but reasonable
2652 /// alternative syntaxes `await <expr>`, `await? <expr>`, `await(<expr>)` and
2653 /// `await { <expr> }`.
2654 fn parse_await_macro_or_alt(
2658 ) -> PResult<'a, (Span, ExprKind)> {
2659 if self.token == token::Not {
2660 // Handle correct `await!(<expr>)`.
2661 // FIXME: make this an error when `await!` is no longer supported
2662 // https://github.com/rust-lang/rust/issues/60610
2663 self.expect(&token::Not)?;
2664 self.expect(&token::OpenDelim(token::Paren))?;
2665 let expr = self.parse_expr().map_err(|mut err| {
2666 err.span_label(await_sp, "while parsing this await macro call");
2669 self.expect(&token::CloseDelim(token::Paren))?;
2670 Ok((self.prev_span, ExprKind::Await(ast::AwaitOrigin::MacroLike, expr)))
2671 } else { // Handle `await <expr>`.
2672 self.parse_incorrect_await_syntax(lo, await_sp)
2676 fn maybe_parse_struct_expr(
2680 attrs: &ThinVec<Attribute>,
2681 ) -> Option<PResult<'a, P<Expr>>> {
2682 let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
2683 let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
2684 // `{ ident, ` cannot start a block
2685 self.look_ahead(2, |t| t == &token::Comma) ||
2686 self.look_ahead(2, |t| t == &token::Colon) && (
2687 // `{ ident: token, ` cannot start a block
2688 self.look_ahead(4, |t| t == &token::Comma) ||
2689 // `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
2690 self.look_ahead(3, |t| !t.can_begin_type())
2694 if struct_allowed || certainly_not_a_block() {
2695 // This is a struct literal, but we don't can't accept them here
2696 let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
2697 if let (Ok(expr), false) = (&expr, struct_allowed) {
2698 let mut err = self.diagnostic().struct_span_err(
2700 "struct literals are not allowed here",
2702 err.multipart_suggestion(
2703 "surround the struct literal with parentheses",
2705 (lo.shrink_to_lo(), "(".to_string()),
2706 (expr.span.shrink_to_hi(), ")".to_string()),
2708 Applicability::MachineApplicable,
2717 fn parse_struct_expr(&mut self, lo: Span, pth: ast::Path, mut attrs: ThinVec<Attribute>)
2718 -> PResult<'a, P<Expr>> {
2719 let struct_sp = lo.to(self.prev_span);
2721 let mut fields = Vec::new();
2722 let mut base = None;
2724 attrs.extend(self.parse_inner_attributes()?);
2726 while self.token != token::CloseDelim(token::Brace) {
2727 if self.eat(&token::DotDot) {
2728 let exp_span = self.prev_span;
2729 match self.parse_expr() {
2735 self.recover_stmt();
2738 if self.token == token::Comma {
2739 let mut err = self.sess.span_diagnostic.mut_span_err(
2740 exp_span.to(self.prev_span),
2741 "cannot use a comma after the base struct",
2743 err.span_suggestion_short(
2745 "remove this comma",
2747 Applicability::MachineApplicable
2749 err.note("the base struct must always be the last field");
2751 self.recover_stmt();
2756 let mut recovery_field = None;
2757 if let token::Ident(ident, _) = self.token {
2758 if !self.token.is_reserved_ident() && self.look_ahead(1, |t| *t == token::Colon) {
2759 // Use in case of error after field-looking code: `S { foo: () with a }`
2760 let mut ident = ident.clone();
2761 ident.span = self.span;
2762 recovery_field = Some(ast::Field {
2765 expr: self.mk_expr(self.span, ExprKind::Err, ThinVec::new()),
2766 is_shorthand: false,
2767 attrs: ThinVec::new(),
2771 let mut parsed_field = None;
2772 match self.parse_field() {
2773 Ok(f) => parsed_field = Some(f),
2775 e.span_label(struct_sp, "while parsing this struct");
2778 // If the next token is a comma, then try to parse
2779 // what comes next as additional fields, rather than
2780 // bailing out until next `}`.
2781 if self.token != token::Comma {
2782 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2783 if self.token != token::Comma {
2790 match self.expect_one_of(&[token::Comma],
2791 &[token::CloseDelim(token::Brace)]) {
2792 Ok(_) => if let Some(f) = parsed_field.or(recovery_field) {
2793 // only include the field if there's no parse error for the field name
2797 if let Some(f) = recovery_field {
2800 e.span_label(struct_sp, "while parsing this struct");
2802 self.recover_stmt_(SemiColonMode::Comma, BlockMode::Ignore);
2803 self.eat(&token::Comma);
2808 let span = lo.to(self.span);
2809 self.expect(&token::CloseDelim(token::Brace))?;
2810 return Ok(self.mk_expr(span, ExprKind::Struct(pth, fields, base), attrs));
2813 fn parse_or_use_outer_attributes(&mut self,
2814 already_parsed_attrs: Option<ThinVec<Attribute>>)
2815 -> PResult<'a, ThinVec<Attribute>> {
2816 if let Some(attrs) = already_parsed_attrs {
2819 self.parse_outer_attributes().map(|a| a.into())
2823 /// Parses a block or unsafe block.
2824 crate fn parse_block_expr(
2826 opt_label: Option<Label>,
2828 blk_mode: BlockCheckMode,
2829 outer_attrs: ThinVec<Attribute>,
2830 ) -> PResult<'a, P<Expr>> {
2831 self.expect(&token::OpenDelim(token::Brace))?;
2833 let mut attrs = outer_attrs;
2834 attrs.extend(self.parse_inner_attributes()?);
2836 let blk = self.parse_block_tail(lo, blk_mode)?;
2837 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, opt_label), attrs));
2840 /// Parses `a.b` or `a(13)` or `a[4]` or just `a`.
2841 fn parse_dot_or_call_expr(&mut self,
2842 already_parsed_attrs: Option<ThinVec<Attribute>>)
2843 -> PResult<'a, P<Expr>> {
2844 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
2846 let b = self.parse_bottom_expr();
2847 let (span, b) = self.interpolated_or_expr_span(b)?;
2848 self.parse_dot_or_call_expr_with(b, span, attrs)
2851 fn parse_dot_or_call_expr_with(&mut self,
2854 mut attrs: ThinVec<Attribute>)
2855 -> PResult<'a, P<Expr>> {
2856 // Stitch the list of outer attributes onto the return value.
2857 // A little bit ugly, but the best way given the current code
2859 self.parse_dot_or_call_expr_with_(e0, lo)
2861 expr.map(|mut expr| {
2862 attrs.extend::<Vec<_>>(expr.attrs.into());
2865 ExprKind::If(..) | ExprKind::IfLet(..) => {
2866 if !expr.attrs.is_empty() {
2867 // Just point to the first attribute in there...
2868 let span = expr.attrs[0].span;
2871 "attributes are not yet allowed on `if` \
2882 // Assuming we have just parsed `.`, continue parsing into an expression.
2883 fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
2884 if self.span.rust_2018() && self.eat_keyword(kw::Await) {
2885 let span = lo.to(self.prev_span);
2886 let await_expr = self.mk_expr(
2888 ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
2891 self.recover_from_await_method_call();
2892 return Ok(await_expr);
2894 let segment = self.parse_path_segment(PathStyle::Expr)?;
2895 self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));
2897 Ok(match self.token {
2898 token::OpenDelim(token::Paren) => {
2899 // Method call `expr.f()`
2900 let mut args = self.parse_unspanned_seq(
2901 &token::OpenDelim(token::Paren),
2902 &token::CloseDelim(token::Paren),
2903 SeqSep::trailing_allowed(token::Comma),
2904 |p| Ok(p.parse_expr()?)
2906 args.insert(0, self_arg);
2908 let span = lo.to(self.prev_span);
2909 self.mk_expr(span, ExprKind::MethodCall(segment, args), ThinVec::new())
2912 // Field access `expr.f`
2913 if let Some(args) = segment.args {
2914 self.span_err(args.span(),
2915 "field expressions may not have generic arguments");
2918 let span = lo.to(self.prev_span);
2919 self.mk_expr(span, ExprKind::Field(self_arg, segment.ident), ThinVec::new())
2924 /// This function checks if there are trailing angle brackets and produces
2925 /// a diagnostic to suggest removing them.
2927 /// ```ignore (diagnostic)
2928 /// let _ = vec![1, 2, 3].into_iter().collect::<Vec<usize>>>>();
2929 /// ^^ help: remove extra angle brackets
2931 fn check_trailing_angle_brackets(&mut self, segment: &PathSegment, end: token::Token) {
2932 // This function is intended to be invoked after parsing a path segment where there are two
2935 // 1. A specific token is expected after the path segment.
2936 // eg. `x.foo(`, `x.foo::<u32>(` (parenthesis - method call),
2937 // `Foo::`, or `Foo::<Bar>::` (mod sep - continued path).
2938 // 2. No specific token is expected after the path segment.
2939 // eg. `x.foo` (field access)
2941 // This function is called after parsing `.foo` and before parsing the token `end` (if
2942 // present). This includes any angle bracket arguments, such as `.foo::<u32>` or
2945 // We only care about trailing angle brackets if we previously parsed angle bracket
2946 // arguments. This helps stop us incorrectly suggesting that extra angle brackets be
2947 // removed in this case:
2949 // `x.foo >> (3)` (where `x.foo` is a `u32` for example)
2951 // This case is particularly tricky as we won't notice it just looking at the tokens -
2952 // it will appear the same (in terms of upcoming tokens) as below (since the `::<u32>` will
2953 // have already been parsed):
2955 // `x.foo::<u32>>>(3)`
2956 let parsed_angle_bracket_args = segment.args
2958 .map(|args| args.is_angle_bracketed())
2962 "check_trailing_angle_brackets: parsed_angle_bracket_args={:?}",
2963 parsed_angle_bracket_args,
2965 if !parsed_angle_bracket_args {
2969 // Keep the span at the start so we can highlight the sequence of `>` characters to be
2973 // We need to look-ahead to see if we have `>` characters without moving the cursor forward
2974 // (since we might have the field access case and the characters we're eating are
2975 // actual operators and not trailing characters - ie `x.foo >> 3`).
2976 let mut position = 0;
2978 // We can encounter `>` or `>>` tokens in any order, so we need to keep track of how
2979 // many of each (so we can correctly pluralize our error messages) and continue to
2981 let mut number_of_shr = 0;
2982 let mut number_of_gt = 0;
2983 while self.look_ahead(position, |t| {
2984 trace!("check_trailing_angle_brackets: t={:?}", t);
2985 if *t == token::BinOp(token::BinOpToken::Shr) {
2988 } else if *t == token::Gt {
2998 // If we didn't find any trailing `>` characters, then we have nothing to error about.
3000 "check_trailing_angle_brackets: number_of_gt={:?} number_of_shr={:?}",
3001 number_of_gt, number_of_shr,
3003 if number_of_gt < 1 && number_of_shr < 1 {
3007 // Finally, double check that we have our end token as otherwise this is the
3009 if self.look_ahead(position, |t| {
3010 trace!("check_trailing_angle_brackets: t={:?}", t);
3013 // Eat from where we started until the end token so that parsing can continue
3014 // as if we didn't have those extra angle brackets.
3015 self.eat_to_tokens(&[&end]);
3016 let span = lo.until(self.span);
3018 let plural = number_of_gt > 1 || number_of_shr >= 1;
3022 &format!("unmatched angle bracket{}", if plural { "s" } else { "" }),
3026 &format!("remove extra angle bracket{}", if plural { "s" } else { "" }),
3028 Applicability::MachineApplicable,
3034 fn parse_dot_or_call_expr_with_(&mut self, e0: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
3039 while self.eat(&token::Question) {
3040 let hi = self.prev_span;
3041 e = self.mk_expr(lo.to(hi), ExprKind::Try(e), ThinVec::new());
3045 if self.eat(&token::Dot) {
3047 token::Ident(..) => {
3048 e = self.parse_dot_suffix(e, lo)?;
3050 token::Literal(token::Integer(name), suffix) => {
3051 let span = self.span;
3053 let field = ExprKind::Field(e, Ident::new(name, span));
3054 e = self.mk_expr(lo.to(span), field, ThinVec::new());
3056 self.expect_no_suffix(span, "a tuple index", suffix);
3058 token::Literal(token::Float(n), _suf) => {
3060 let fstr = n.as_str();
3061 let mut err = self.diagnostic()
3062 .struct_span_err(self.prev_span, &format!("unexpected token: `{}`", n));
3063 err.span_label(self.prev_span, "unexpected token");
3064 if fstr.chars().all(|x| "0123456789.".contains(x)) {
3065 let float = match fstr.parse::<f64>().ok() {
3069 let sugg = pprust::to_string(|s| {
3070 use crate::print::pprust::PrintState;
3074 s.print_usize(float.trunc() as usize)?;
3077 s.s.word(fstr.splitn(2, ".").last().unwrap().to_string())
3079 err.span_suggestion(
3080 lo.to(self.prev_span),
3081 "try parenthesizing the first index",
3083 Applicability::MachineApplicable
3090 // FIXME Could factor this out into non_fatal_unexpected or something.
3091 let actual = self.this_token_to_string();
3092 self.span_err(self.span, &format!("unexpected token: `{}`", actual));
3097 if self.expr_is_complete(&e) { break; }
3100 token::OpenDelim(token::Paren) => {
3101 let seq = self.parse_unspanned_seq(
3102 &token::OpenDelim(token::Paren),
3103 &token::CloseDelim(token::Paren),
3104 SeqSep::trailing_allowed(token::Comma),
3105 |p| Ok(p.parse_expr()?)
3107 let nd = self.mk_call(e, es);
3108 let hi = self.prev_span;
3109 self.mk_expr(lo.to(hi), nd, ThinVec::new())
3111 e = self.recover_seq_parse_error(token::Paren, lo, seq);
3115 // Could be either an index expression or a slicing expression.
3116 token::OpenDelim(token::Bracket) => {
3118 let ix = self.parse_expr()?;
3120 self.expect(&token::CloseDelim(token::Bracket))?;
3121 let index = self.mk_index(e, ix);
3122 e = self.mk_expr(lo.to(hi), index, ThinVec::new())
3130 crate fn process_potential_macro_variable(&mut self) {
3131 let (token, span) = match self.token {
3132 token::Dollar if self.span.ctxt() != syntax_pos::hygiene::SyntaxContext::empty() &&
3133 self.look_ahead(1, |t| t.is_ident()) => {
3135 let name = match self.token {
3136 token::Ident(ident, _) => ident,
3139 let mut err = self.fatal(&format!("unknown macro variable `{}`", name));
3140 err.span_label(self.span, "unknown macro variable");
3145 token::Interpolated(ref nt) => {
3146 self.meta_var_span = Some(self.span);
3147 // Interpolated identifier and lifetime tokens are replaced with usual identifier
3148 // and lifetime tokens, so the former are never encountered during normal parsing.
3150 token::NtIdent(ident, is_raw) => (token::Ident(ident, is_raw), ident.span),
3151 token::NtLifetime(ident) => (token::Lifetime(ident), ident.span),
3161 /// Parses a single token tree from the input.
3162 crate fn parse_token_tree(&mut self) -> TokenTree {
3164 token::OpenDelim(..) => {
3165 let frame = mem::replace(&mut self.token_cursor.frame,
3166 self.token_cursor.stack.pop().unwrap());
3167 self.span = frame.span.entire();
3169 TokenTree::Delimited(
3172 frame.tree_cursor.stream.into(),
3175 token::CloseDelim(_) | token::Eof => unreachable!(),
3177 let (token, span) = (mem::replace(&mut self.token, token::Whitespace), self.span);
3179 TokenTree::Token(span, token)
3184 // parse a stream of tokens into a list of TokenTree's,
3186 pub fn parse_all_token_trees(&mut self) -> PResult<'a, Vec<TokenTree>> {
3187 let mut tts = Vec::new();
3188 while self.token != token::Eof {
3189 tts.push(self.parse_token_tree());
3194 pub fn parse_tokens(&mut self) -> TokenStream {
3195 let mut result = Vec::new();
3198 token::Eof | token::CloseDelim(..) => break,
3199 _ => result.push(self.parse_token_tree().into()),
3202 TokenStream::new(result)
3205 /// Parse a prefix-unary-operator expr
3206 fn parse_prefix_expr(&mut self,
3207 already_parsed_attrs: Option<ThinVec<Attribute>>)
3208 -> PResult<'a, P<Expr>> {
3209 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3211 // Note: when adding new unary operators, don't forget to adjust Token::can_begin_expr()
3212 let (hi, ex) = match self.token {
3215 let e = self.parse_prefix_expr(None);
3216 let (span, e) = self.interpolated_or_expr_span(e)?;
3217 (lo.to(span), self.mk_unary(UnOp::Not, e))
3219 // Suggest `!` for bitwise negation when encountering a `~`
3222 let e = self.parse_prefix_expr(None);
3223 let (span, e) = self.interpolated_or_expr_span(e)?;
3224 let span_of_tilde = lo;
3225 let mut err = self.diagnostic()
3226 .struct_span_err(span_of_tilde, "`~` cannot be used as a unary operator");
3227 err.span_suggestion_short(
3229 "use `!` to perform bitwise negation",
3231 Applicability::MachineApplicable
3234 (lo.to(span), self.mk_unary(UnOp::Not, e))
3236 token::BinOp(token::Minus) => {
3238 let e = self.parse_prefix_expr(None);
3239 let (span, e) = self.interpolated_or_expr_span(e)?;
3240 (lo.to(span), self.mk_unary(UnOp::Neg, e))
3242 token::BinOp(token::Star) => {
3244 let e = self.parse_prefix_expr(None);
3245 let (span, e) = self.interpolated_or_expr_span(e)?;
3246 (lo.to(span), self.mk_unary(UnOp::Deref, e))
3248 token::BinOp(token::And) | token::AndAnd => {
3250 let m = self.parse_mutability();
3251 let e = self.parse_prefix_expr(None);
3252 let (span, e) = self.interpolated_or_expr_span(e)?;
3253 (lo.to(span), ExprKind::AddrOf(m, e))
3255 token::Ident(..) if self.token.is_keyword(kw::In) => {
3257 let place = self.parse_expr_res(
3258 Restrictions::NO_STRUCT_LITERAL,
3261 let blk = self.parse_block()?;
3262 let span = blk.span;
3263 let blk_expr = self.mk_expr(span, ExprKind::Block(blk, None), ThinVec::new());
3264 (lo.to(span), ExprKind::ObsoleteInPlace(place, blk_expr))
3266 token::Ident(..) if self.token.is_keyword(kw::Box) => {
3268 let e = self.parse_prefix_expr(None);
3269 let (span, e) = self.interpolated_or_expr_span(e)?;
3270 (lo.to(span), ExprKind::Box(e))
3272 token::Ident(..) if self.token.is_ident_named("not") => {
3273 // `not` is just an ordinary identifier in Rust-the-language,
3274 // but as `rustc`-the-compiler, we can issue clever diagnostics
3275 // for confused users who really want to say `!`
3276 let token_cannot_continue_expr = |t: &token::Token| match *t {
3277 // These tokens can start an expression after `!`, but
3278 // can't continue an expression after an ident
3279 token::Ident(ident, is_raw) => token::ident_can_begin_expr(ident, is_raw),
3280 token::Literal(..) | token::Pound => true,
3281 token::Interpolated(ref nt) => match **nt {
3282 token::NtIdent(..) | token::NtExpr(..) |
3283 token::NtBlock(..) | token::NtPath(..) => true,
3288 let cannot_continue_expr = self.look_ahead(1, token_cannot_continue_expr);
3289 if cannot_continue_expr {
3291 // Emit the error ...
3292 let mut err = self.diagnostic()
3293 .struct_span_err(self.span,
3294 &format!("unexpected {} after identifier",
3295 self.this_token_descr()));
3296 // span the `not` plus trailing whitespace to avoid
3297 // trailing whitespace after the `!` in our suggestion
3298 let to_replace = self.sess.source_map()
3299 .span_until_non_whitespace(lo.to(self.span));
3300 err.span_suggestion_short(
3302 "use `!` to perform logical negation",
3304 Applicability::MachineApplicable
3307 // —and recover! (just as if we were in the block
3308 // for the `token::Not` arm)
3309 let e = self.parse_prefix_expr(None);
3310 let (span, e) = self.interpolated_or_expr_span(e)?;
3311 (lo.to(span), self.mk_unary(UnOp::Not, e))
3313 return self.parse_dot_or_call_expr(Some(attrs));
3316 _ => { return self.parse_dot_or_call_expr(Some(attrs)); }
3318 return Ok(self.mk_expr(lo.to(hi), ex, attrs));
3321 /// Parses an associative expression.
3323 /// This parses an expression accounting for associativity and precedence of the operators in
3326 fn parse_assoc_expr(&mut self,
3327 already_parsed_attrs: Option<ThinVec<Attribute>>)
3328 -> PResult<'a, P<Expr>> {
3329 self.parse_assoc_expr_with(0, already_parsed_attrs.into())
3332 /// Parses an associative expression with operators of at least `min_prec` precedence.
3333 fn parse_assoc_expr_with(&mut self,
3336 -> PResult<'a, P<Expr>> {
3337 let mut lhs = if let LhsExpr::AlreadyParsed(expr) = lhs {
3340 let attrs = match lhs {
3341 LhsExpr::AttributesParsed(attrs) => Some(attrs),
3344 if [token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token) {
3345 return self.parse_prefix_range_expr(attrs);
3347 self.parse_prefix_expr(attrs)?
3351 match (self.expr_is_complete(&lhs), AssocOp::from_token(&self.token)) {
3353 // Semi-statement forms are odd. See https://github.com/rust-lang/rust/issues/29071
3356 (false, _) => {} // continue parsing the expression
3357 // An exhaustive check is done in the following block, but these are checked first
3358 // because they *are* ambiguous but also reasonable looking incorrect syntax, so we
3359 // want to keep their span info to improve diagnostics in these cases in a later stage.
3360 (true, Some(AssocOp::Multiply)) | // `{ 42 } *foo = bar;` or `{ 42 } * 3`
3361 (true, Some(AssocOp::Subtract)) | // `{ 42 } -5`
3362 (true, Some(AssocOp::Add)) => { // `{ 42 } + 42
3363 // These cases are ambiguous and can't be identified in the parser alone
3364 let sp = self.sess.source_map().start_point(self.span);
3365 self.sess.ambiguous_block_expr_parse.borrow_mut().insert(sp, lhs.span);
3368 (true, Some(ref op)) if !op.can_continue_expr_unambiguously() => {
3371 (true, Some(_)) => {
3372 // We've found an expression that would be parsed as a statement, but the next
3373 // token implies this should be parsed as an expression.
3374 // For example: `if let Some(x) = x { x } else { 0 } / 2`
3375 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &format!(
3376 "expected expression, found `{}`",
3377 pprust::token_to_string(&self.token),
3379 err.span_label(self.span, "expected expression");
3380 self.sess.expr_parentheses_needed(
3383 Some(pprust::expr_to_string(&lhs),
3388 self.expected_tokens.push(TokenType::Operator);
3389 while let Some(op) = AssocOp::from_token(&self.token) {
3391 // Adjust the span for interpolated LHS to point to the `$lhs` token and not to what
3392 // it refers to. Interpolated identifiers are unwrapped early and never show up here
3393 // as `PrevTokenKind::Interpolated` so if LHS is a single identifier we always process
3394 // it as "interpolated", it doesn't change the answer for non-interpolated idents.
3395 let lhs_span = match (self.prev_token_kind, &lhs.node) {
3396 (PrevTokenKind::Interpolated, _) => self.prev_span,
3397 (PrevTokenKind::Ident, &ExprKind::Path(None, ref path))
3398 if path.segments.len() == 1 => self.prev_span,
3402 let cur_op_span = self.span;
3403 let restrictions = if op.is_assign_like() {
3404 self.restrictions & Restrictions::NO_STRUCT_LITERAL
3408 let prec = op.precedence();
3409 if prec < min_prec {
3412 // Check for deprecated `...` syntax
3413 if self.token == token::DotDotDot && op == AssocOp::DotDotEq {
3414 self.err_dotdotdot_syntax(self.span);
3418 if op.is_comparison() {
3419 self.check_no_chained_comparison(&lhs, &op);
3422 if op == AssocOp::As {
3423 lhs = self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Cast)?;
3425 } else if op == AssocOp::Colon {
3426 let maybe_path = self.could_ascription_be_path(&lhs.node);
3427 let next_sp = self.span;
3429 lhs = match self.parse_assoc_op_cast(lhs, lhs_span, ExprKind::Type) {
3432 self.bad_type_ascription(
3443 } else if op == AssocOp::DotDot || op == AssocOp::DotDotEq {
3444 // If we didn’t have to handle `x..`/`x..=`, it would be pretty easy to
3445 // generalise it to the Fixity::None code.
3447 // We have 2 alternatives here: `x..y`/`x..=y` and `x..`/`x..=` The other
3448 // two variants are handled with `parse_prefix_range_expr` call above.
3449 let rhs = if self.is_at_start_of_range_notation_rhs() {
3450 Some(self.parse_assoc_expr_with(prec + 1, LhsExpr::NotYetParsed)?)
3454 let (lhs_span, rhs_span) = (lhs.span, if let Some(ref x) = rhs {
3459 let limits = if op == AssocOp::DotDot {
3460 RangeLimits::HalfOpen
3465 let r = self.mk_range(Some(lhs), rhs, limits)?;
3466 lhs = self.mk_expr(lhs_span.to(rhs_span), r, ThinVec::new());
3470 let fixity = op.fixity();
3471 let prec_adjustment = match fixity {
3474 // We currently have no non-associative operators that are not handled above by
3475 // the special cases. The code is here only for future convenience.
3478 let rhs = self.with_res(
3479 restrictions - Restrictions::STMT_EXPR,
3480 |this| this.parse_assoc_expr_with(prec + prec_adjustment, LhsExpr::NotYetParsed)
3483 // Make sure that the span of the parent node is larger than the span of lhs and rhs,
3484 // including the attributes.
3488 .filter(|a| a.style == AttrStyle::Outer)
3490 .map_or(lhs_span, |a| a.span);
3491 let span = lhs_span.to(rhs.span);
3493 AssocOp::Add | AssocOp::Subtract | AssocOp::Multiply | AssocOp::Divide |
3494 AssocOp::Modulus | AssocOp::LAnd | AssocOp::LOr | AssocOp::BitXor |
3495 AssocOp::BitAnd | AssocOp::BitOr | AssocOp::ShiftLeft | AssocOp::ShiftRight |
3496 AssocOp::Equal | AssocOp::Less | AssocOp::LessEqual | AssocOp::NotEqual |
3497 AssocOp::Greater | AssocOp::GreaterEqual => {
3498 let ast_op = op.to_ast_binop().unwrap();
3499 let binary = self.mk_binary(source_map::respan(cur_op_span, ast_op), lhs, rhs);
3500 self.mk_expr(span, binary, ThinVec::new())
3502 AssocOp::Assign => self.mk_expr(span, ExprKind::Assign(lhs, rhs), ThinVec::new()),
3503 AssocOp::ObsoleteInPlace =>
3504 self.mk_expr(span, ExprKind::ObsoleteInPlace(lhs, rhs), ThinVec::new()),
3505 AssocOp::AssignOp(k) => {
3507 token::Plus => BinOpKind::Add,
3508 token::Minus => BinOpKind::Sub,
3509 token::Star => BinOpKind::Mul,
3510 token::Slash => BinOpKind::Div,
3511 token::Percent => BinOpKind::Rem,
3512 token::Caret => BinOpKind::BitXor,
3513 token::And => BinOpKind::BitAnd,
3514 token::Or => BinOpKind::BitOr,
3515 token::Shl => BinOpKind::Shl,
3516 token::Shr => BinOpKind::Shr,
3518 let aopexpr = self.mk_assign_op(source_map::respan(cur_op_span, aop), lhs, rhs);
3519 self.mk_expr(span, aopexpr, ThinVec::new())
3521 AssocOp::As | AssocOp::Colon | AssocOp::DotDot | AssocOp::DotDotEq => {
3522 self.bug("AssocOp should have been handled by special case")
3526 if let Fixity::None = fixity { break }
3531 fn parse_assoc_op_cast(&mut self, lhs: P<Expr>, lhs_span: Span,
3532 expr_kind: fn(P<Expr>, P<Ty>) -> ExprKind)
3533 -> PResult<'a, P<Expr>> {
3534 let mk_expr = |this: &mut Self, rhs: P<Ty>| {
3535 this.mk_expr(lhs_span.to(rhs.span), expr_kind(lhs, rhs), ThinVec::new())
3538 // Save the state of the parser before parsing type normally, in case there is a
3539 // LessThan comparison after this cast.
3540 let parser_snapshot_before_type = self.clone();
3541 match self.parse_ty_no_plus() {
3543 Ok(mk_expr(self, rhs))
3545 Err(mut type_err) => {
3546 // Rewind to before attempting to parse the type with generics, to recover
3547 // from situations like `x as usize < y` in which we first tried to parse
3548 // `usize < y` as a type with generic arguments.
3549 let parser_snapshot_after_type = self.clone();
3550 mem::replace(self, parser_snapshot_before_type);
3552 match self.parse_path(PathStyle::Expr) {
3554 let (op_noun, op_verb) = match self.token {
3555 token::Lt => ("comparison", "comparing"),
3556 token::BinOp(token::Shl) => ("shift", "shifting"),
3558 // We can end up here even without `<` being the next token, for
3559 // example because `parse_ty_no_plus` returns `Err` on keywords,
3560 // but `parse_path` returns `Ok` on them due to error recovery.
3561 // Return original error and parser state.
3562 mem::replace(self, parser_snapshot_after_type);
3563 return Err(type_err);
3567 // Successfully parsed the type path leaving a `<` yet to parse.
3570 // Report non-fatal diagnostics, keep `x as usize` as an expression
3571 // in AST and continue parsing.
3572 let msg = format!("`<` is interpreted as a start of generic \
3573 arguments for `{}`, not a {}", path, op_noun);
3574 let mut err = self.sess.span_diagnostic.struct_span_err(self.span, &msg);
3575 err.span_label(self.look_ahead_span(1).to(parser_snapshot_after_type.span),
3576 "interpreted as generic arguments");
3577 err.span_label(self.span, format!("not interpreted as {}", op_noun));
3579 let expr = mk_expr(self, P(Ty {
3581 node: TyKind::Path(None, path),
3582 id: ast::DUMMY_NODE_ID
3585 let expr_str = self.sess.source_map().span_to_snippet(expr.span)
3586 .unwrap_or_else(|_| pprust::expr_to_string(&expr));
3587 err.span_suggestion(
3589 &format!("try {} the cast value", op_verb),
3590 format!("({})", expr_str),
3591 Applicability::MachineApplicable
3597 Err(mut path_err) => {
3598 // Couldn't parse as a path, return original error and parser state.
3600 mem::replace(self, parser_snapshot_after_type);
3608 /// Produce an error if comparison operators are chained (RFC #558).
3609 /// We only need to check lhs, not rhs, because all comparison ops
3610 /// have same precedence and are left-associative
3611 fn check_no_chained_comparison(&self, lhs: &Expr, outer_op: &AssocOp) {
3612 debug_assert!(outer_op.is_comparison(),
3613 "check_no_chained_comparison: {:?} is not comparison",
3616 ExprKind::Binary(op, _, _) if op.node.is_comparison() => {
3617 // respan to include both operators
3618 let op_span = op.span.to(self.span);
3619 let mut err = self.diagnostic().struct_span_err(op_span,
3620 "chained comparison operators require parentheses");
3621 if op.node == BinOpKind::Lt &&
3622 *outer_op == AssocOp::Less || // Include `<` to provide this recommendation
3623 *outer_op == AssocOp::Greater // even in a case like the following:
3624 { // Foo<Bar<Baz<Qux, ()>>>
3626 "use `::<...>` instead of `<...>` if you meant to specify type arguments");
3627 err.help("or use `(...)` if you meant to specify fn arguments");
3635 /// Parse prefix-forms of range notation: `..expr`, `..`, `..=expr`
3636 fn parse_prefix_range_expr(&mut self,
3637 already_parsed_attrs: Option<ThinVec<Attribute>>)
3638 -> PResult<'a, P<Expr>> {
3639 // Check for deprecated `...` syntax
3640 if self.token == token::DotDotDot {
3641 self.err_dotdotdot_syntax(self.span);
3644 debug_assert!([token::DotDot, token::DotDotDot, token::DotDotEq].contains(&self.token),
3645 "parse_prefix_range_expr: token {:?} is not DotDot/DotDotEq",
3647 let tok = self.token.clone();
3648 let attrs = self.parse_or_use_outer_attributes(already_parsed_attrs)?;
3650 let mut hi = self.span;
3652 let opt_end = if self.is_at_start_of_range_notation_rhs() {
3653 // RHS must be parsed with more associativity than the dots.
3654 let next_prec = AssocOp::from_token(&tok).unwrap().precedence() + 1;
3655 Some(self.parse_assoc_expr_with(next_prec,
3656 LhsExpr::NotYetParsed)
3664 let limits = if tok == token::DotDot {
3665 RangeLimits::HalfOpen
3670 let r = self.mk_range(None, opt_end, limits)?;
3671 Ok(self.mk_expr(lo.to(hi), r, attrs))
3674 fn is_at_start_of_range_notation_rhs(&self) -> bool {
3675 if self.token.can_begin_expr() {
3676 // parse `for i in 1.. { }` as infinite loop, not as `for i in (1..{})`.
3677 if self.token == token::OpenDelim(token::Brace) {
3678 return !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
3686 /// Parses an `if` or `if let` expression (`if` token already eaten).
3687 fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3688 if self.check_keyword(kw::Let) {
3689 return self.parse_if_let_expr(attrs);
3691 let lo = self.prev_span;
3692 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3694 // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
3695 // verify that the last statement is either an implicit return (no `;`) or an explicit
3696 // return. This won't catch blocks with an explicit `return`, but that would be caught by
3697 // the dead code lint.
3698 if self.eat_keyword(kw::Else) || !cond.returns() {
3699 let sp = self.sess.source_map().next_point(lo);
3700 let mut err = self.diagnostic()
3701 .struct_span_err(sp, "missing condition for `if` statemement");
3702 err.span_label(sp, "expected if condition here");
3705 let not_block = self.token != token::OpenDelim(token::Brace);
3706 let thn = self.parse_block().map_err(|mut err| {
3708 err.span_label(lo, "this `if` statement has a condition, but no block");
3712 let mut els: Option<P<Expr>> = None;
3713 let mut hi = thn.span;
3714 if self.eat_keyword(kw::Else) {
3715 let elexpr = self.parse_else_expr()?;
3719 Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
3722 /// Parses an `if let` expression (`if` token already eaten).
3723 fn parse_if_let_expr(&mut self, attrs: ThinVec<Attribute>)
3724 -> PResult<'a, P<Expr>> {
3725 let lo = self.prev_span;
3726 self.expect_keyword(kw::Let)?;
3727 let pats = self.parse_pats()?;
3728 self.expect(&token::Eq)?;
3729 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3730 let thn = self.parse_block()?;
3731 let (hi, els) = if self.eat_keyword(kw::Else) {
3732 let expr = self.parse_else_expr()?;
3733 (expr.span, Some(expr))
3737 Ok(self.mk_expr(lo.to(hi), ExprKind::IfLet(pats, expr, thn, els), attrs))
3740 /// Parses `move |args| expr`.
3741 fn parse_lambda_expr(&mut self,
3742 attrs: ThinVec<Attribute>)
3743 -> PResult<'a, P<Expr>>
3746 let movability = if self.eat_keyword(kw::Static) {
3751 let asyncness = if self.span.rust_2018() {
3752 self.parse_asyncness()
3756 let capture_clause = if self.eat_keyword(kw::Move) {
3761 let decl = self.parse_fn_block_decl()?;
3762 let decl_hi = self.prev_span;
3763 let body = match decl.output {
3764 FunctionRetTy::Default(_) => {
3765 let restrictions = self.restrictions - Restrictions::STMT_EXPR;
3766 self.parse_expr_res(restrictions, None)?
3769 // If an explicit return type is given, require a
3770 // block to appear (RFC 968).
3771 let body_lo = self.span;
3772 self.parse_block_expr(None, body_lo, BlockCheckMode::Default, ThinVec::new())?
3778 ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
3782 // `else` token already eaten
3783 fn parse_else_expr(&mut self) -> PResult<'a, P<Expr>> {
3784 if self.eat_keyword(kw::If) {
3785 return self.parse_if_expr(ThinVec::new());
3787 let blk = self.parse_block()?;
3788 return Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), ThinVec::new()));
3792 /// Parse a 'for' .. 'in' expression ('for' token already eaten)
3793 fn parse_for_expr(&mut self, opt_label: Option<Label>,
3795 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3796 // Parse: `for <src_pat> in <src_expr> <src_loop_block>`
3798 let pat = self.parse_top_level_pat()?;
3799 if !self.eat_keyword(kw::In) {
3800 let in_span = self.prev_span.between(self.span);
3801 let mut err = self.sess.span_diagnostic
3802 .struct_span_err(in_span, "missing `in` in `for` loop");
3803 err.span_suggestion_short(
3804 in_span, "try adding `in` here", " in ".into(),
3805 // has been misleading, at least in the past (closed Issue #48492)
3806 Applicability::MaybeIncorrect
3810 let in_span = self.prev_span;
3811 if self.eat_keyword(kw::In) {
3812 // a common typo: `for _ in in bar {}`
3813 let mut err = self.sess.span_diagnostic.struct_span_err(
3815 "expected iterable, found keyword `in`",
3817 err.span_suggestion_short(
3818 in_span.until(self.prev_span),
3819 "remove the duplicated `in`",
3821 Applicability::MachineApplicable,
3823 err.note("if you meant to use emplacement syntax, it is obsolete (for now, anyway)");
3824 err.note("for more information on the status of emplacement syntax, see <\
3825 https://github.com/rust-lang/rust/issues/27779#issuecomment-378416911>");
3828 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3829 let (iattrs, loop_block) = self.parse_inner_attrs_and_block()?;
3830 attrs.extend(iattrs);
3832 let hi = self.prev_span;
3833 Ok(self.mk_expr(span_lo.to(hi), ExprKind::ForLoop(pat, expr, loop_block, opt_label), attrs))
3836 /// Parses a `while` or `while let` expression (`while` token already eaten).
3837 fn parse_while_expr(&mut self, opt_label: Option<Label>,
3839 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3840 if self.token.is_keyword(kw::Let) {
3841 return self.parse_while_let_expr(opt_label, span_lo, attrs);
3843 let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3844 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3845 attrs.extend(iattrs);
3846 let span = span_lo.to(body.span);
3847 return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs));
3850 /// Parses a `while let` expression (`while` token already eaten).
3851 fn parse_while_let_expr(&mut self, opt_label: Option<Label>,
3853 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3854 self.expect_keyword(kw::Let)?;
3855 let pats = self.parse_pats()?;
3856 self.expect(&token::Eq)?;
3857 let expr = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
3858 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3859 attrs.extend(iattrs);
3860 let span = span_lo.to(body.span);
3861 return Ok(self.mk_expr(span, ExprKind::WhileLet(pats, expr, body, opt_label), attrs));
3864 // parse `loop {...}`, `loop` token already eaten
3865 fn parse_loop_expr(&mut self, opt_label: Option<Label>,
3867 mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3868 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3869 attrs.extend(iattrs);
3870 let span = span_lo.to(body.span);
3871 Ok(self.mk_expr(span, ExprKind::Loop(body, opt_label), attrs))
3874 /// Parses an `async move {...}` expression.
3875 pub fn parse_async_block(&mut self, mut attrs: ThinVec<Attribute>)
3876 -> PResult<'a, P<Expr>>
3878 let span_lo = self.span;
3879 self.expect_keyword(kw::Async)?;
3880 let capture_clause = if self.eat_keyword(kw::Move) {
3885 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3886 attrs.extend(iattrs);
3888 span_lo.to(body.span),
3889 ExprKind::Async(capture_clause, ast::DUMMY_NODE_ID, body), attrs))
3892 /// Parses a `try {...}` expression (`try` token already eaten).
3893 fn parse_try_block(&mut self, span_lo: Span, mut attrs: ThinVec<Attribute>)
3894 -> PResult<'a, P<Expr>>
3896 let (iattrs, body) = self.parse_inner_attrs_and_block()?;
3897 attrs.extend(iattrs);
3898 if self.eat_keyword(kw::Catch) {
3899 let mut error = self.struct_span_err(self.prev_span,
3900 "keyword `catch` cannot follow a `try` block");
3901 error.help("try using `match` on the result of the `try` block instead");
3905 Ok(self.mk_expr(span_lo.to(body.span), ExprKind::TryBlock(body), attrs))
3909 // `match` token already eaten
3910 fn parse_match_expr(&mut self, mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
3911 let match_span = self.prev_span;
3912 let lo = self.prev_span;
3913 let discriminant = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL,
3915 if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
3916 if self.token == token::Token::Semi {
3917 e.span_suggestion_short(
3919 "try removing this `match`",
3921 Applicability::MaybeIncorrect // speculative
3926 attrs.extend(self.parse_inner_attributes()?);
3928 let mut arms: Vec<Arm> = Vec::new();
3929 while self.token != token::CloseDelim(token::Brace) {
3930 match self.parse_arm() {
3931 Ok(arm) => arms.push(arm),
3933 // Recover by skipping to the end of the block.
3935 self.recover_stmt();
3936 let span = lo.to(self.span);
3937 if self.token == token::CloseDelim(token::Brace) {
3940 return Ok(self.mk_expr(span, ExprKind::Match(discriminant, arms), attrs));
3946 return Ok(self.mk_expr(lo.to(hi), ExprKind::Match(discriminant, arms), attrs));
3949 crate fn parse_arm(&mut self) -> PResult<'a, Arm> {
3950 let attrs = self.parse_outer_attributes()?;
3951 let pats = self.parse_pats()?;
3952 let guard = if self.eat_keyword(kw::If) {
3953 Some(Guard::If(self.parse_expr()?))
3957 let arrow_span = self.span;
3958 self.expect(&token::FatArrow)?;
3959 let arm_start_span = self.span;
3961 let expr = self.parse_expr_res(Restrictions::STMT_EXPR, None)
3962 .map_err(|mut err| {
3963 err.span_label(arrow_span, "while parsing the `match` arm starting here");
3967 let require_comma = classify::expr_requires_semi_to_be_stmt(&expr)
3968 && self.token != token::CloseDelim(token::Brace);
3971 let cm = self.sess.source_map();
3972 self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])
3973 .map_err(|mut err| {
3974 match (cm.span_to_lines(expr.span), cm.span_to_lines(arm_start_span)) {
3975 (Ok(ref expr_lines), Ok(ref arm_start_lines))
3976 if arm_start_lines.lines[0].end_col == expr_lines.lines[0].end_col
3977 && expr_lines.lines.len() == 2
3978 && self.token == token::FatArrow => {
3979 // We check whether there's any trailing code in the parse span,
3980 // if there isn't, we very likely have the following:
3983 // | -- - missing comma
3989 // | parsed until here as `"y" & X`
3990 err.span_suggestion_short(
3991 cm.next_point(arm_start_span),
3992 "missing a comma here to end this `match` arm",
3994 Applicability::MachineApplicable
3998 err.span_label(arrow_span,
3999 "while parsing the `match` arm starting here");
4005 self.eat(&token::Comma);
4016 /// Parses an expression.
4018 pub fn parse_expr(&mut self) -> PResult<'a, P<Expr>> {
4019 self.parse_expr_res(Restrictions::empty(), None)
4022 /// Evaluates the closure with restrictions in place.
4024 /// Afters the closure is evaluated, restrictions are reset.
4025 fn with_res<F, T>(&mut self, r: Restrictions, f: F) -> T
4026 where F: FnOnce(&mut Self) -> T
4028 let old = self.restrictions;
4029 self.restrictions = r;
4031 self.restrictions = old;
4036 /// Parses an expression, subject to the given restrictions.
4038 fn parse_expr_res(&mut self, r: Restrictions,
4039 already_parsed_attrs: Option<ThinVec<Attribute>>)
4040 -> PResult<'a, P<Expr>> {
4041 self.with_res(r, |this| this.parse_assoc_expr(already_parsed_attrs))
4044 /// Parses the RHS of a local variable declaration (e.g., '= 14;').
4045 fn parse_initializer(&mut self, skip_eq: bool) -> PResult<'a, Option<P<Expr>>> {
4046 if self.eat(&token::Eq) {
4047 Ok(Some(self.parse_expr()?))
4049 Ok(Some(self.parse_expr()?))
4055 /// Parses patterns, separated by '|' s.
4056 fn parse_pats(&mut self) -> PResult<'a, Vec<P<Pat>>> {
4057 // Allow a '|' before the pats (RFC 1925 + RFC 2530)
4058 self.eat(&token::BinOp(token::Or));
4060 let mut pats = Vec::new();
4062 pats.push(self.parse_top_level_pat()?);
4064 if self.token == token::OrOr {
4065 let mut err = self.struct_span_err(self.span,
4066 "unexpected token `||` after pattern");
4067 err.span_suggestion(
4069 "use a single `|` to specify multiple patterns",
4071 Applicability::MachineApplicable
4075 } else if self.eat(&token::BinOp(token::Or)) {
4076 // This is a No-op. Continue the loop to parse the next
4084 // Parses a parenthesized list of patterns like
4085 // `()`, `(p)`, `(p,)`, `(p, q)`, or `(p, .., q)`. Returns:
4086 // - a vector of the patterns that were parsed
4087 // - an option indicating the index of the `..` element
4088 // - a boolean indicating whether a trailing comma was present.
4089 // Trailing commas are significant because (p) and (p,) are different patterns.
4090 fn parse_parenthesized_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4091 self.expect(&token::OpenDelim(token::Paren))?;
4092 let result = match self.parse_pat_list() {
4093 Ok(result) => result,
4094 Err(mut err) => { // recover from parse error in tuple pattern list
4096 self.consume_block(token::Paren);
4097 return Ok((vec![], Some(0), false));
4100 self.expect(&token::CloseDelim(token::Paren))?;
4104 fn parse_pat_list(&mut self) -> PResult<'a, (Vec<P<Pat>>, Option<usize>, bool)> {
4105 let mut fields = Vec::new();
4106 let mut ddpos = None;
4107 let mut prev_dd_sp = None;
4108 let mut trailing_comma = false;
4110 if self.eat(&token::DotDot) {
4111 if ddpos.is_none() {
4112 ddpos = Some(fields.len());
4113 prev_dd_sp = Some(self.prev_span);
4115 // Emit a friendly error, ignore `..` and continue parsing
4116 let mut err = self.struct_span_err(
4118 "`..` can only be used once per tuple or tuple struct pattern",
4120 err.span_label(self.prev_span, "can only be used once per pattern");
4121 if let Some(sp) = prev_dd_sp {
4122 err.span_label(sp, "previously present here");
4126 } else if !self.check(&token::CloseDelim(token::Paren)) {
4127 fields.push(self.parse_pat(None)?);
4132 trailing_comma = self.eat(&token::Comma);
4133 if !trailing_comma {
4138 if ddpos == Some(fields.len()) && trailing_comma {
4139 // `..` needs to be followed by `)` or `, pat`, `..,)` is disallowed.
4140 let msg = "trailing comma is not permitted after `..`";
4141 self.struct_span_err(self.prev_span, msg)
4142 .span_label(self.prev_span, msg)
4146 Ok((fields, ddpos, trailing_comma))
4149 fn parse_pat_vec_elements(
4151 ) -> PResult<'a, (Vec<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>)> {
4152 let mut before = Vec::new();
4153 let mut slice = None;
4154 let mut after = Vec::new();
4155 let mut first = true;
4156 let mut before_slice = true;
4158 while self.token != token::CloseDelim(token::Bracket) {
4162 self.expect(&token::Comma)?;
4164 if self.token == token::CloseDelim(token::Bracket)
4165 && (before_slice || !after.is_empty()) {
4171 if self.eat(&token::DotDot) {
4173 if self.check(&token::Comma) ||
4174 self.check(&token::CloseDelim(token::Bracket)) {
4175 slice = Some(P(Pat {
4176 id: ast::DUMMY_NODE_ID,
4177 node: PatKind::Wild,
4178 span: self.prev_span,
4180 before_slice = false;
4186 let subpat = self.parse_pat(None)?;
4187 if before_slice && self.eat(&token::DotDot) {
4188 slice = Some(subpat);
4189 before_slice = false;
4190 } else if before_slice {
4191 before.push(subpat);
4197 Ok((before, slice, after))
4203 attrs: Vec<Attribute>
4204 ) -> PResult<'a, source_map::Spanned<ast::FieldPat>> {
4205 // Check if a colon exists one ahead. This means we're parsing a fieldname.
4207 let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
4208 // Parsing a pattern of the form "fieldname: pat"
4209 let fieldname = self.parse_field_name()?;
4211 let pat = self.parse_pat(None)?;
4213 (pat, fieldname, false)
4215 // Parsing a pattern of the form "(box) (ref) (mut) fieldname"
4216 let is_box = self.eat_keyword(kw::Box);
4217 let boxed_span = self.span;
4218 let is_ref = self.eat_keyword(kw::Ref);
4219 let is_mut = self.eat_keyword(kw::Mut);
4220 let fieldname = self.parse_ident()?;
4221 hi = self.prev_span;
4223 let bind_type = match (is_ref, is_mut) {
4224 (true, true) => BindingMode::ByRef(Mutability::Mutable),
4225 (true, false) => BindingMode::ByRef(Mutability::Immutable),
4226 (false, true) => BindingMode::ByValue(Mutability::Mutable),
4227 (false, false) => BindingMode::ByValue(Mutability::Immutable),
4229 let fieldpat = P(Pat {
4230 id: ast::DUMMY_NODE_ID,
4231 node: PatKind::Ident(bind_type, fieldname, None),
4232 span: boxed_span.to(hi),
4235 let subpat = if is_box {
4237 id: ast::DUMMY_NODE_ID,
4238 node: PatKind::Box(fieldpat),
4244 (subpat, fieldname, true)
4247 Ok(source_map::Spanned {
4249 node: ast::FieldPat {
4253 attrs: attrs.into(),
4258 /// Parses the fields of a struct-like pattern.
4259 fn parse_pat_fields(&mut self) -> PResult<'a, (Vec<source_map::Spanned<ast::FieldPat>>, bool)> {
4260 let mut fields = Vec::new();
4261 let mut etc = false;
4262 let mut ate_comma = true;
4263 let mut delayed_err: Option<DiagnosticBuilder<'a>> = None;
4264 let mut etc_span = None;
4266 while self.token != token::CloseDelim(token::Brace) {
4267 let attrs = self.parse_outer_attributes()?;
4270 // check that a comma comes after every field
4272 let err = self.struct_span_err(self.prev_span, "expected `,`");
4273 if let Some(mut delayed) = delayed_err {
4280 if self.check(&token::DotDot) || self.token == token::DotDotDot {
4282 let mut etc_sp = self.span;
4284 if self.token == token::DotDotDot { // Issue #46718
4285 // Accept `...` as if it were `..` to avoid further errors
4286 let mut err = self.struct_span_err(self.span,
4287 "expected field pattern, found `...`");
4288 err.span_suggestion(
4290 "to omit remaining fields, use one fewer `.`",
4292 Applicability::MachineApplicable
4296 self.bump(); // `..` || `...`
4298 if self.token == token::CloseDelim(token::Brace) {
4299 etc_span = Some(etc_sp);
4302 let token_str = self.this_token_descr();
4303 let mut err = self.fatal(&format!("expected `}}`, found {}", token_str));
4305 err.span_label(self.span, "expected `}`");
4306 let mut comma_sp = None;
4307 if self.token == token::Comma { // Issue #49257
4308 etc_sp = etc_sp.to(self.sess.source_map().span_until_non_whitespace(self.span));
4309 err.span_label(etc_sp,
4310 "`..` must be at the end and cannot have a trailing comma");
4311 comma_sp = Some(self.span);
4316 etc_span = Some(etc_sp.until(self.span));
4317 if self.token == token::CloseDelim(token::Brace) {
4318 // If the struct looks otherwise well formed, recover and continue.
4319 if let Some(sp) = comma_sp {
4320 err.span_suggestion_short(
4322 "remove this comma",
4324 Applicability::MachineApplicable,
4329 } else if self.token.is_ident() && ate_comma {
4330 // Accept fields coming after `..,`.
4331 // This way we avoid "pattern missing fields" errors afterwards.
4332 // We delay this error until the end in order to have a span for a
4334 if let Some(mut delayed_err) = delayed_err {
4338 delayed_err = Some(err);
4341 if let Some(mut err) = delayed_err {
4348 fields.push(match self.parse_pat_field(lo, attrs) {
4351 if let Some(mut delayed_err) = delayed_err {
4357 ate_comma = self.eat(&token::Comma);
4360 if let Some(mut err) = delayed_err {
4361 if let Some(etc_span) = etc_span {
4362 err.multipart_suggestion(
4363 "move the `..` to the end of the field list",
4365 (etc_span, String::new()),
4366 (self.span, format!("{}.. }}", if ate_comma { "" } else { ", " })),
4368 Applicability::MachineApplicable,
4373 return Ok((fields, etc));
4376 fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
4377 if self.token.is_path_start() {
4379 let (qself, path) = if self.eat_lt() {
4380 // Parse a qualified path
4381 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4384 // Parse an unqualified path
4385 (None, self.parse_path(PathStyle::Expr)?)
4387 let hi = self.prev_span;
4388 Ok(self.mk_expr(lo.to(hi), ExprKind::Path(qself, path), ThinVec::new()))
4390 self.parse_literal_maybe_minus()
4394 // helper function to decide whether to parse as ident binding or to try to do
4395 // something more complex like range patterns
4396 fn parse_as_ident(&mut self) -> bool {
4397 self.look_ahead(1, |t| match *t {
4398 token::OpenDelim(token::Paren) | token::OpenDelim(token::Brace) |
4399 token::DotDotDot | token::DotDotEq | token::ModSep | token::Not => Some(false),
4400 // ensure slice patterns [a, b.., c] and [a, b, c..] don't go into the
4401 // range pattern branch
4402 token::DotDot => None,
4404 }).unwrap_or_else(|| self.look_ahead(2, |t| match *t {
4405 token::Comma | token::CloseDelim(token::Bracket) => true,
4410 /// A wrapper around `parse_pat` with some special error handling for the
4411 /// "top-level" patterns in a match arm, `for` loop, `let`, &c. (in contrast
4412 /// to subpatterns within such).
4413 fn parse_top_level_pat(&mut self) -> PResult<'a, P<Pat>> {
4414 let pat = self.parse_pat(None)?;
4415 if self.token == token::Comma {
4416 // An unexpected comma after a top-level pattern is a clue that the
4417 // user (perhaps more accustomed to some other language) forgot the
4418 // parentheses in what should have been a tuple pattern; return a
4419 // suggestion-enhanced error here rather than choking on the comma
4421 let comma_span = self.span;
4423 if let Err(mut err) = self.parse_pat_list() {
4424 // We didn't expect this to work anyway; we just wanted
4425 // to advance to the end of the comma-sequence so we know
4426 // the span to suggest parenthesizing
4429 let seq_span = pat.span.to(self.prev_span);
4430 let mut err = self.struct_span_err(comma_span,
4431 "unexpected `,` in pattern");
4432 if let Ok(seq_snippet) = self.sess.source_map().span_to_snippet(seq_span) {
4433 err.span_suggestion(
4435 "try adding parentheses to match on a tuple..",
4436 format!("({})", seq_snippet),
4437 Applicability::MachineApplicable
4440 "..or a vertical bar to match on multiple alternatives",
4441 format!("{}", seq_snippet.replace(",", " |")),
4442 Applicability::MachineApplicable
4450 /// Parses a pattern.
4451 pub fn parse_pat(&mut self, expected: Option<&'static str>) -> PResult<'a, P<Pat>> {
4452 self.parse_pat_with_range_pat(true, expected)
4455 /// Parses a pattern, with a setting whether modern range patterns (e.g., `a..=b`, `a..b` are
4457 fn parse_pat_with_range_pat(
4459 allow_range_pat: bool,
4460 expected: Option<&'static str>,
4461 ) -> PResult<'a, P<Pat>> {
4462 maybe_recover_from_interpolated_ty_qpath!(self, true);
4463 maybe_whole!(self, NtPat, |x| x);
4468 token::BinOp(token::And) | token::AndAnd => {
4469 // Parse &pat / &mut pat
4471 let mutbl = self.parse_mutability();
4472 if let token::Lifetime(ident) = self.token {
4473 let mut err = self.fatal(&format!("unexpected lifetime `{}` in pattern",
4475 err.span_label(self.span, "unexpected lifetime");
4478 let subpat = self.parse_pat_with_range_pat(false, expected)?;
4479 pat = PatKind::Ref(subpat, mutbl);
4481 token::OpenDelim(token::Paren) => {
4482 // Parse (pat,pat,pat,...) as tuple pattern
4483 let (fields, ddpos, trailing_comma) = self.parse_parenthesized_pat_list()?;
4484 pat = if fields.len() == 1 && ddpos.is_none() && !trailing_comma {
4485 PatKind::Paren(fields.into_iter().nth(0).unwrap())
4487 PatKind::Tuple(fields, ddpos)
4490 token::OpenDelim(token::Bracket) => {
4491 // Parse [pat,pat,...] as slice pattern
4493 let (before, slice, after) = self.parse_pat_vec_elements()?;
4494 self.expect(&token::CloseDelim(token::Bracket))?;
4495 pat = PatKind::Slice(before, slice, after);
4497 // At this point, token != &, &&, (, [
4498 _ => if self.eat_keyword(kw::Underscore) {
4500 pat = PatKind::Wild;
4501 } else if self.eat_keyword(kw::Mut) {
4502 // Parse mut ident @ pat / mut ref ident @ pat
4503 let mutref_span = self.prev_span.to(self.span);
4504 let binding_mode = if self.eat_keyword(kw::Ref) {
4506 .struct_span_err(mutref_span, "the order of `mut` and `ref` is incorrect")
4509 "try switching the order",
4511 Applicability::MachineApplicable
4513 BindingMode::ByRef(Mutability::Mutable)
4515 BindingMode::ByValue(Mutability::Mutable)
4517 pat = self.parse_pat_ident(binding_mode)?;
4518 } else if self.eat_keyword(kw::Ref) {
4519 // Parse ref ident @ pat / ref mut ident @ pat
4520 let mutbl = self.parse_mutability();
4521 pat = self.parse_pat_ident(BindingMode::ByRef(mutbl))?;
4522 } else if self.eat_keyword(kw::Box) {
4524 let subpat = self.parse_pat_with_range_pat(false, None)?;
4525 pat = PatKind::Box(subpat);
4526 } else if self.token.is_ident() && !self.token.is_reserved_ident() &&
4527 self.parse_as_ident() {
4528 // Parse ident @ pat
4529 // This can give false positives and parse nullary enums,
4530 // they are dealt with later in resolve
4531 let binding_mode = BindingMode::ByValue(Mutability::Immutable);
4532 pat = self.parse_pat_ident(binding_mode)?;
4533 } else if self.token.is_path_start() {
4534 // Parse pattern starting with a path
4535 let (qself, path) = if self.eat_lt() {
4536 // Parse a qualified path
4537 let (qself, path) = self.parse_qpath(PathStyle::Expr)?;
4540 // Parse an unqualified path
4541 (None, self.parse_path(PathStyle::Expr)?)
4544 token::Not if qself.is_none() => {
4545 // Parse macro invocation
4547 let (delim, tts) = self.expect_delimited_token_tree()?;
4548 let mac = respan(lo.to(self.prev_span), Mac_ { path, tts, delim });
4549 pat = PatKind::Mac(mac);
4551 token::DotDotDot | token::DotDotEq | token::DotDot => {
4552 let end_kind = match self.token {
4553 token::DotDot => RangeEnd::Excluded,
4554 token::DotDotDot => RangeEnd::Included(RangeSyntax::DotDotDot),
4555 token::DotDotEq => RangeEnd::Included(RangeSyntax::DotDotEq),
4556 _ => panic!("can only parse `..`/`...`/`..=` for ranges \
4559 let op_span = self.span;
4561 let span = lo.to(self.prev_span);
4562 let begin = self.mk_expr(span, ExprKind::Path(qself, path), ThinVec::new());
4564 let end = self.parse_pat_range_end()?;
4565 let op = Spanned { span: op_span, node: end_kind };
4566 pat = PatKind::Range(begin, end, op);
4568 token::OpenDelim(token::Brace) => {
4569 if qself.is_some() {
4570 let msg = "unexpected `{` after qualified path";
4571 let mut err = self.fatal(msg);
4572 err.span_label(self.span, msg);
4575 // Parse struct pattern
4577 let (fields, etc) = self.parse_pat_fields().unwrap_or_else(|mut e| {
4579 self.recover_stmt();
4583 pat = PatKind::Struct(path, fields, etc);
4585 token::OpenDelim(token::Paren) => {
4586 if qself.is_some() {
4587 let msg = "unexpected `(` after qualified path";
4588 let mut err = self.fatal(msg);
4589 err.span_label(self.span, msg);
4592 // Parse tuple struct or enum pattern
4593 let (fields, ddpos, _) = self.parse_parenthesized_pat_list()?;
4594 pat = PatKind::TupleStruct(path, fields, ddpos)
4596 _ => pat = PatKind::Path(qself, path),
4599 // Try to parse everything else as literal with optional minus
4600 match self.parse_literal_maybe_minus() {
4602 let op_span = self.span;
4603 if self.check(&token::DotDot) || self.check(&token::DotDotEq) ||
4604 self.check(&token::DotDotDot) {
4605 let end_kind = if self.eat(&token::DotDotDot) {
4606 RangeEnd::Included(RangeSyntax::DotDotDot)
4607 } else if self.eat(&token::DotDotEq) {
4608 RangeEnd::Included(RangeSyntax::DotDotEq)
4609 } else if self.eat(&token::DotDot) {
4612 panic!("impossible case: we already matched \
4613 on a range-operator token")
4615 let end = self.parse_pat_range_end()?;
4616 let op = Spanned { span: op_span, node: end_kind };
4617 pat = PatKind::Range(begin, end, op);
4619 pat = PatKind::Lit(begin);
4623 self.cancel(&mut err);
4624 let expected = expected.unwrap_or("pattern");
4626 "expected {}, found {}",
4628 self.this_token_descr(),
4630 let mut err = self.fatal(&msg);
4631 err.span_label(self.span, format!("expected {}", expected));
4632 let sp = self.sess.source_map().start_point(self.span);
4633 if let Some(sp) = self.sess.ambiguous_block_expr_parse.borrow().get(&sp) {
4634 self.sess.expr_parentheses_needed(&mut err, *sp, None);
4642 let pat = P(Pat { node: pat, span: lo.to(self.prev_span), id: ast::DUMMY_NODE_ID });
4643 let pat = self.maybe_recover_from_bad_qpath(pat, true)?;
4645 if !allow_range_pat {
4648 _, _, Spanned { node: RangeEnd::Included(RangeSyntax::DotDotDot), .. }
4650 PatKind::Range(..) => {
4651 let mut err = self.struct_span_err(
4653 "the range pattern here has ambiguous interpretation",
4655 err.span_suggestion(
4657 "add parentheses to clarify the precedence",
4658 format!("({})", pprust::pat_to_string(&pat)),
4659 // "ambiguous interpretation" implies that we have to be guessing
4660 Applicability::MaybeIncorrect
4671 /// Parses `ident` or `ident @ pat`.
4672 /// used by the copy foo and ref foo patterns to give a good
4673 /// error message when parsing mistakes like `ref foo(a, b)`.
4674 fn parse_pat_ident(&mut self,
4675 binding_mode: ast::BindingMode)
4676 -> PResult<'a, PatKind> {
4677 let ident = self.parse_ident()?;
4678 let sub = if self.eat(&token::At) {
4679 Some(self.parse_pat(Some("binding pattern"))?)
4684 // just to be friendly, if they write something like
4686 // we end up here with ( as the current token. This shortly
4687 // leads to a parse error. Note that if there is no explicit
4688 // binding mode then we do not end up here, because the lookahead
4689 // will direct us over to parse_enum_variant()
4690 if self.token == token::OpenDelim(token::Paren) {
4691 return Err(self.span_fatal(
4693 "expected identifier, found enum pattern"))
4696 Ok(PatKind::Ident(binding_mode, ident, sub))
4699 /// Parses a local variable declaration.
4700 fn parse_local(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Local>> {
4701 let lo = self.prev_span;
4702 let pat = self.parse_top_level_pat()?;
4704 let (err, ty) = if self.eat(&token::Colon) {
4705 // Save the state of the parser before parsing type normally, in case there is a `:`
4706 // instead of an `=` typo.
4707 let parser_snapshot_before_type = self.clone();
4708 let colon_sp = self.prev_span;
4709 match self.parse_ty() {
4710 Ok(ty) => (None, Some(ty)),
4712 // Rewind to before attempting to parse the type and continue parsing
4713 let parser_snapshot_after_type = self.clone();
4714 mem::replace(self, parser_snapshot_before_type);
4716 let snippet = self.sess.source_map().span_to_snippet(pat.span).unwrap();
4717 err.span_label(pat.span, format!("while parsing the type for `{}`", snippet));
4718 (Some((parser_snapshot_after_type, colon_sp, err)), None)
4724 let init = match (self.parse_initializer(err.is_some()), err) {
4725 (Ok(init), None) => { // init parsed, ty parsed
4728 (Ok(init), Some((_, colon_sp, mut err))) => { // init parsed, ty error
4729 // Could parse the type as if it were the initializer, it is likely there was a
4730 // typo in the code: `:` instead of `=`. Add suggestion and emit the error.
4731 err.span_suggestion_short(
4733 "use `=` if you meant to assign",
4735 Applicability::MachineApplicable
4738 // As this was parsed successfully, continue as if the code has been fixed for the
4739 // rest of the file. It will still fail due to the emitted error, but we avoid
4743 (Err(mut init_err), Some((snapshot, _, ty_err))) => { // init error, ty error
4745 // Couldn't parse the type nor the initializer, only raise the type error and
4746 // return to the parser state before parsing the type as the initializer.
4747 // let x: <parse_error>;
4748 mem::replace(self, snapshot);
4751 (Err(err), None) => { // init error, ty parsed
4752 // Couldn't parse the initializer and we're not attempting to recover a failed
4753 // parse of the type, return the error.
4757 let hi = if self.token == token::Semi {
4766 id: ast::DUMMY_NODE_ID,
4769 source: LocalSource::Normal,
4773 /// Parses a structure field.
4774 fn parse_name_and_ty(&mut self,
4777 attrs: Vec<Attribute>)
4778 -> PResult<'a, StructField> {
4779 let name = self.parse_ident()?;
4780 self.expect(&token::Colon)?;
4781 let ty = self.parse_ty()?;
4783 span: lo.to(self.prev_span),
4786 id: ast::DUMMY_NODE_ID,
4792 /// Emits an expected-item-after-attributes error.
4793 fn expected_item_err(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
4794 let message = match attrs.last() {
4795 Some(&Attribute { is_sugared_doc: true, .. }) => "expected item after doc comment",
4796 _ => "expected item after attributes",
4799 let mut err = self.diagnostic().struct_span_err(self.prev_span, message);
4800 if attrs.last().unwrap().is_sugared_doc {
4801 err.span_label(self.prev_span, "this doc comment doesn't document anything");
4806 /// Parse a statement. This stops just before trailing semicolons on everything but items.
4807 /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
4808 pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
4809 Ok(self.parse_stmt_(true))
4812 fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
4813 self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
4815 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
4820 fn is_async_block(&self) -> bool {
4821 self.token.is_keyword(kw::Async) &&
4824 self.look_ahead(1, |t| t.is_keyword(kw::Move)) &&
4825 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace))
4827 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace))
4832 fn is_async_fn(&self) -> bool {
4833 self.token.is_keyword(kw::Async) &&
4834 self.look_ahead(1, |t| t.is_keyword(kw::Fn))
4837 fn is_do_catch_block(&self) -> bool {
4838 self.token.is_keyword(kw::Do) &&
4839 self.look_ahead(1, |t| t.is_keyword(kw::Catch)) &&
4840 self.look_ahead(2, |t| *t == token::OpenDelim(token::Brace)) &&
4841 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4844 fn is_try_block(&self) -> bool {
4845 self.token.is_keyword(kw::Try) &&
4846 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) &&
4847 self.span.rust_2018() &&
4848 // prevent `while try {} {}`, `if try {} {} else {}`, etc.
4849 !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL)
4852 fn is_union_item(&self) -> bool {
4853 self.token.is_keyword(kw::Union) &&
4854 self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
4857 fn is_crate_vis(&self) -> bool {
4858 self.token.is_keyword(kw::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
4861 fn is_existential_type_decl(&self) -> bool {
4862 self.token.is_keyword(kw::Existential) &&
4863 self.look_ahead(1, |t| t.is_keyword(kw::Type))
4866 fn is_auto_trait_item(&self) -> bool {
4868 (self.token.is_keyword(kw::Auto)
4869 && self.look_ahead(1, |t| t.is_keyword(kw::Trait)))
4870 || // unsafe auto trait
4871 (self.token.is_keyword(kw::Unsafe) &&
4872 self.look_ahead(1, |t| t.is_keyword(kw::Auto)) &&
4873 self.look_ahead(2, |t| t.is_keyword(kw::Trait)))
4876 fn eat_macro_def(&mut self, attrs: &[Attribute], vis: &Visibility, lo: Span)
4877 -> PResult<'a, Option<P<Item>>> {
4878 let token_lo = self.span;
4879 let (ident, def) = match self.token {
4880 token::Ident(ident, false) if ident.name == kw::Macro => {
4882 let ident = self.parse_ident()?;
4883 let tokens = if self.check(&token::OpenDelim(token::Brace)) {
4884 match self.parse_token_tree() {
4885 TokenTree::Delimited(_, _, tts) => tts,
4886 _ => unreachable!(),
4888 } else if self.check(&token::OpenDelim(token::Paren)) {
4889 let args = self.parse_token_tree();
4890 let body = if self.check(&token::OpenDelim(token::Brace)) {
4891 self.parse_token_tree()
4896 TokenStream::new(vec![
4898 TokenTree::Token(token_lo.to(self.prev_span), token::FatArrow).into(),
4906 (ident, ast::MacroDef { tokens: tokens.into(), legacy: false })
4908 token::Ident(ident, _) if ident.name == sym::macro_rules &&
4909 self.look_ahead(1, |t| *t == token::Not) => {
4910 let prev_span = self.prev_span;
4911 self.complain_if_pub_macro(&vis.node, prev_span);
4915 let ident = self.parse_ident()?;
4916 let (delim, tokens) = self.expect_delimited_token_tree()?;
4917 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
4918 self.report_invalid_macro_expansion_item();
4921 (ident, ast::MacroDef { tokens: tokens, legacy: true })
4923 _ => return Ok(None),
4926 let span = lo.to(self.prev_span);
4927 Ok(Some(self.mk_item(span, ident, ItemKind::MacroDef(def), vis.clone(), attrs.to_vec())))
4930 fn parse_stmt_without_recovery(&mut self,
4931 macro_legacy_warnings: bool)
4932 -> PResult<'a, Option<Stmt>> {
4933 maybe_whole!(self, NtStmt, |x| Some(x));
4935 let attrs = self.parse_outer_attributes()?;
4938 Ok(Some(if self.eat_keyword(kw::Let) {
4940 id: ast::DUMMY_NODE_ID,
4941 node: StmtKind::Local(self.parse_local(attrs.into())?),
4942 span: lo.to(self.prev_span),
4944 } else if let Some(macro_def) = self.eat_macro_def(
4946 &source_map::respan(lo, VisibilityKind::Inherited),
4950 id: ast::DUMMY_NODE_ID,
4951 node: StmtKind::Item(macro_def),
4952 span: lo.to(self.prev_span),
4954 // Starts like a simple path, being careful to avoid contextual keywords
4955 // such as a union items, item with `crate` visibility or auto trait items.
4956 // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
4957 // like a path (1 token), but it fact not a path.
4958 // `union::b::c` - path, `union U { ... }` - not a path.
4959 // `crate::b::c` - path, `crate struct S;` - not a path.
4960 } else if self.token.is_path_start() &&
4961 !self.token.is_qpath_start() &&
4962 !self.is_union_item() &&
4963 !self.is_crate_vis() &&
4964 !self.is_existential_type_decl() &&
4965 !self.is_auto_trait_item() &&
4966 !self.is_async_fn() {
4967 let pth = self.parse_path(PathStyle::Expr)?;
4969 if !self.eat(&token::Not) {
4970 let expr = if self.check(&token::OpenDelim(token::Brace)) {
4971 self.parse_struct_expr(lo, pth, ThinVec::new())?
4973 let hi = self.prev_span;
4974 self.mk_expr(lo.to(hi), ExprKind::Path(None, pth), ThinVec::new())
4977 let expr = self.with_res(Restrictions::STMT_EXPR, |this| {
4978 let expr = this.parse_dot_or_call_expr_with(expr, lo, attrs.into())?;
4979 this.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(expr))
4982 return Ok(Some(Stmt {
4983 id: ast::DUMMY_NODE_ID,
4984 node: StmtKind::Expr(expr),
4985 span: lo.to(self.prev_span),
4989 // it's a macro invocation
4990 let id = match self.token {
4991 token::OpenDelim(_) => Ident::with_empty_ctxt(kw::Invalid), // no special identifier
4992 _ => self.parse_ident()?,
4995 // check that we're pointing at delimiters (need to check
4996 // again after the `if`, because of `parse_ident`
4997 // consuming more tokens).
4999 token::OpenDelim(_) => {}
5001 // we only expect an ident if we didn't parse one
5003 let ident_str = if id.name == kw::Invalid {
5008 let tok_str = self.this_token_descr();
5009 let mut err = self.fatal(&format!("expected {}`(` or `{{`, found {}",
5012 err.span_label(self.span, format!("expected {}`(` or `{{`", ident_str));
5017 let (delim, tts) = self.expect_delimited_token_tree()?;
5018 let hi = self.prev_span;
5020 let style = if delim == MacDelimiter::Brace {
5021 MacStmtStyle::Braces
5023 MacStmtStyle::NoBraces
5026 if id.name == kw::Invalid {
5027 let mac = respan(lo.to(hi), Mac_ { path: pth, tts, delim });
5028 let node = if delim == MacDelimiter::Brace ||
5029 self.token == token::Semi || self.token == token::Eof {
5030 StmtKind::Mac(P((mac, style, attrs.into())))
5032 // We used to incorrectly stop parsing macro-expanded statements here.
5033 // If the next token will be an error anyway but could have parsed with the
5034 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
5035 else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
5036 // These can continue an expression, so we can't stop parsing and warn.
5037 token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
5038 token::BinOp(token::Minus) | token::BinOp(token::Star) |
5039 token::BinOp(token::And) | token::BinOp(token::Or) |
5040 token::AndAnd | token::OrOr |
5041 token::DotDot | token::DotDotDot | token::DotDotEq => false,
5044 self.warn_missing_semicolon();
5045 StmtKind::Mac(P((mac, style, attrs.into())))
5047 let e = self.mk_expr(mac.span, ExprKind::Mac(mac), ThinVec::new());
5048 let e = self.maybe_recover_from_bad_qpath(e, true)?;
5049 let e = self.parse_dot_or_call_expr_with(e, lo, attrs.into())?;
5050 let e = self.parse_assoc_expr_with(0, LhsExpr::AlreadyParsed(e))?;
5054 id: ast::DUMMY_NODE_ID,
5059 // if it has a special ident, it's definitely an item
5061 // Require a semicolon or braces.
5062 if style != MacStmtStyle::Braces && !self.eat(&token::Semi) {
5063 self.report_invalid_macro_expansion_item();
5065 let span = lo.to(hi);
5067 id: ast::DUMMY_NODE_ID,
5069 node: StmtKind::Item({
5071 span, id /*id is good here*/,
5072 ItemKind::Mac(respan(span, Mac_ { path: pth, tts, delim })),
5073 respan(lo, VisibilityKind::Inherited),
5079 // FIXME: Bad copy of attrs
5080 let old_directory_ownership =
5081 mem::replace(&mut self.directory.ownership, DirectoryOwnership::UnownedViaBlock);
5082 let item = self.parse_item_(attrs.clone(), false, true)?;
5083 self.directory.ownership = old_directory_ownership;
5087 id: ast::DUMMY_NODE_ID,
5088 span: lo.to(i.span),
5089 node: StmtKind::Item(i),
5092 let unused_attrs = |attrs: &[Attribute], s: &mut Self| {
5093 if !attrs.is_empty() {
5094 if s.prev_token_kind == PrevTokenKind::DocComment {
5095 s.span_fatal_err(s.prev_span, Error::UselessDocComment).emit();
5096 } else if attrs.iter().any(|a| a.style == AttrStyle::Outer) {
5097 s.span_err(s.span, "expected statement after outer attribute");
5102 // Do not attempt to parse an expression if we're done here.
5103 if self.token == token::Semi {
5104 unused_attrs(&attrs, self);
5109 if self.token == token::CloseDelim(token::Brace) {
5110 unused_attrs(&attrs, self);
5114 // Remainder are line-expr stmts.
5115 let e = self.parse_expr_res(
5116 Restrictions::STMT_EXPR, Some(attrs.into()))?;
5118 id: ast::DUMMY_NODE_ID,
5119 span: lo.to(e.span),
5120 node: StmtKind::Expr(e),
5127 /// Checks if this expression is a successfully parsed statement.
5128 fn expr_is_complete(&self, e: &Expr) -> bool {
5129 self.restrictions.contains(Restrictions::STMT_EXPR) &&
5130 !classify::expr_requires_semi_to_be_stmt(e)
5133 /// Parses a block. No inner attributes are allowed.
5134 pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
5135 maybe_whole!(self, NtBlock, |x| x);
5139 if !self.eat(&token::OpenDelim(token::Brace)) {
5141 let tok = self.this_token_descr();
5142 let mut e = self.span_fatal(sp, &format!("expected `{{`, found {}", tok));
5143 let do_not_suggest_help =
5144 self.token.is_keyword(kw::In) || self.token == token::Colon;
5146 if self.token.is_ident_named("and") {
5147 e.span_suggestion_short(
5149 "use `&&` instead of `and` for the boolean operator",
5151 Applicability::MaybeIncorrect,
5154 if self.token.is_ident_named("or") {
5155 e.span_suggestion_short(
5157 "use `||` instead of `or` for the boolean operator",
5159 Applicability::MaybeIncorrect,
5163 // Check to see if the user has written something like
5168 // Which is valid in other languages, but not Rust.
5169 match self.parse_stmt_without_recovery(false) {
5171 if self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace))
5172 || do_not_suggest_help {
5173 // if the next token is an open brace (e.g., `if a b {`), the place-
5174 // inside-a-block suggestion would be more likely wrong than right
5175 e.span_label(sp, "expected `{`");
5178 let mut stmt_span = stmt.span;
5179 // expand the span to include the semicolon, if it exists
5180 if self.eat(&token::Semi) {
5181 stmt_span = stmt_span.with_hi(self.prev_span.hi());
5183 let sugg = pprust::to_string(|s| {
5184 use crate::print::pprust::{PrintState, INDENT_UNIT};
5185 s.ibox(INDENT_UNIT)?;
5187 s.print_stmt(&stmt)?;
5188 s.bclose_maybe_open(stmt.span, INDENT_UNIT, false)
5192 "try placing this code inside a block",
5194 // speculative, has been misleading in the past (closed Issue #46836)
5195 Applicability::MaybeIncorrect
5199 self.recover_stmt_(SemiColonMode::Break, BlockMode::Ignore);
5200 self.cancel(&mut e);
5204 e.span_label(sp, "expected `{`");
5208 self.parse_block_tail(lo, BlockCheckMode::Default)
5211 /// Parses a block. Inner attributes are allowed.
5212 fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
5213 maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
5216 self.expect(&token::OpenDelim(token::Brace))?;
5217 Ok((self.parse_inner_attributes()?,
5218 self.parse_block_tail(lo, BlockCheckMode::Default)?))
5221 /// Parses the rest of a block expression or function body.
5222 /// Precondition: already parsed the '{'.
5223 fn parse_block_tail(&mut self, lo: Span, s: BlockCheckMode) -> PResult<'a, P<Block>> {
5224 let mut stmts = vec![];
5225 while !self.eat(&token::CloseDelim(token::Brace)) {
5226 let stmt = match self.parse_full_stmt(false) {
5229 self.recover_stmt_(SemiColonMode::Ignore, BlockMode::Ignore);
5231 id: ast::DUMMY_NODE_ID,
5232 node: StmtKind::Expr(DummyResult::raw_expr(self.span, true)),
5238 if let Some(stmt) = stmt {
5240 } else if self.token == token::Eof {
5243 // Found only `;` or `}`.
5249 id: ast::DUMMY_NODE_ID,
5251 span: lo.to(self.prev_span),
5255 /// Parses a statement, including the trailing semicolon.
5256 crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
5257 // skip looking for a trailing semicolon when we have an interpolated statement
5258 maybe_whole!(self, NtStmt, |x| Some(x));
5260 let mut stmt = match self.parse_stmt_without_recovery(macro_legacy_warnings)? {
5262 None => return Ok(None),
5266 StmtKind::Expr(ref expr) if self.token != token::Eof => {
5267 // expression without semicolon
5268 if classify::expr_requires_semi_to_be_stmt(expr) {
5269 // Just check for errors and recover; do not eat semicolon yet.
5271 self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
5274 self.recover_stmt();
5278 StmtKind::Local(..) => {
5279 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
5280 if macro_legacy_warnings && self.token != token::Semi {
5281 self.warn_missing_semicolon();
5283 self.expect_one_of(&[], &[token::Semi])?;
5289 if self.eat(&token::Semi) {
5290 stmt = stmt.add_trailing_semicolon();
5293 stmt.span = stmt.span.with_hi(self.prev_span.hi());
5297 fn warn_missing_semicolon(&self) {
5298 self.diagnostic().struct_span_warn(self.span, {
5299 &format!("expected `;`, found {}", self.this_token_descr())
5301 "This was erroneously allowed and will become a hard error in a future release"
5305 fn err_dotdotdot_syntax(&self, span: Span) {
5306 self.diagnostic().struct_span_err(span, {
5307 "unexpected token: `...`"
5309 span, "use `..` for an exclusive range", "..".to_owned(),
5310 Applicability::MaybeIncorrect
5312 span, "or `..=` for an inclusive range", "..=".to_owned(),
5313 Applicability::MaybeIncorrect
5317 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
5320 /// BOUND = TY_BOUND | LT_BOUND
5321 /// LT_BOUND = LIFETIME (e.g., `'a`)
5322 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
5323 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
5325 fn parse_generic_bounds_common(&mut self,
5327 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5328 let mut bounds = Vec::new();
5329 let mut negative_bounds = Vec::new();
5330 let mut last_plus_span = None;
5331 let mut was_negative = false;
5333 // This needs to be synchronized with `Token::can_begin_bound`.
5334 let is_bound_start = self.check_path() || self.check_lifetime() ||
5335 self.check(&token::Not) || // used for error reporting only
5336 self.check(&token::Question) ||
5337 self.check_keyword(kw::For) ||
5338 self.check(&token::OpenDelim(token::Paren));
5341 let has_parens = self.eat(&token::OpenDelim(token::Paren));
5342 let inner_lo = self.span;
5343 let is_negative = self.eat(&token::Not);
5344 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
5345 if self.token.is_lifetime() {
5346 if let Some(question_span) = question {
5347 self.span_err(question_span,
5348 "`?` may only modify trait bounds, not lifetime bounds");
5350 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
5352 let inner_span = inner_lo.to(self.prev_span);
5353 self.expect(&token::CloseDelim(token::Paren))?;
5354 let mut err = self.struct_span_err(
5355 lo.to(self.prev_span),
5356 "parenthesized lifetime bounds are not supported"
5358 if let Ok(snippet) = self.sess.source_map().span_to_snippet(inner_span) {
5359 err.span_suggestion_short(
5360 lo.to(self.prev_span),
5361 "remove the parentheses",
5363 Applicability::MachineApplicable
5369 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5370 let path = self.parse_path(PathStyle::Type)?;
5372 self.expect(&token::CloseDelim(token::Paren))?;
5374 let poly_span = lo.to(self.prev_span);
5376 was_negative = true;
5377 if let Some(sp) = last_plus_span.or(colon_span) {
5378 negative_bounds.push(sp.to(poly_span));
5381 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
5382 let modifier = if question.is_some() {
5383 TraitBoundModifier::Maybe
5385 TraitBoundModifier::None
5387 bounds.push(GenericBound::Trait(poly_trait, modifier));
5394 if !allow_plus || !self.eat_plus() {
5397 last_plus_span = Some(self.prev_span);
5401 if !negative_bounds.is_empty() || was_negative {
5402 let plural = negative_bounds.len() > 1;
5403 let last_span = negative_bounds.last().map(|sp| *sp);
5404 let mut err = self.struct_span_err(
5406 "negative trait bounds are not supported",
5408 if let Some(sp) = last_span {
5409 err.span_label(sp, "negative trait bounds are not supported");
5411 if let Some(bound_list) = colon_span {
5412 let bound_list = bound_list.to(self.prev_span);
5413 let mut new_bound_list = String::new();
5414 if !bounds.is_empty() {
5415 let mut snippets = bounds.iter().map(|bound| bound.span())
5416 .map(|span| self.sess.source_map().span_to_snippet(span));
5417 while let Some(Ok(snippet)) = snippets.next() {
5418 new_bound_list.push_str(" + ");
5419 new_bound_list.push_str(&snippet);
5421 new_bound_list = new_bound_list.replacen(" +", ":", 1);
5423 err.span_suggestion_hidden(
5425 &format!("remove the trait bound{}", if plural { "s" } else { "" }),
5427 Applicability::MachineApplicable,
5436 crate fn parse_generic_bounds(&mut self,
5437 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
5438 self.parse_generic_bounds_common(true, colon_span)
5441 /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
5444 /// BOUND = LT_BOUND (e.g., `'a`)
5446 fn parse_lt_param_bounds(&mut self) -> GenericBounds {
5447 let mut lifetimes = Vec::new();
5448 while self.check_lifetime() {
5449 lifetimes.push(ast::GenericBound::Outlives(self.expect_lifetime()));
5451 if !self.eat_plus() {
5458 /// Matches `typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?`.
5459 fn parse_ty_param(&mut self,
5460 preceding_attrs: Vec<Attribute>)
5461 -> PResult<'a, GenericParam> {
5462 let ident = self.parse_ident()?;
5464 // Parse optional colon and param bounds.
5465 let bounds = if self.eat(&token::Colon) {
5466 self.parse_generic_bounds(Some(self.prev_span))?
5471 let default = if self.eat(&token::Eq) {
5472 Some(self.parse_ty()?)
5479 id: ast::DUMMY_NODE_ID,
5480 attrs: preceding_attrs.into(),
5482 kind: GenericParamKind::Type {
5488 /// Parses the following grammar:
5490 /// TraitItemAssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
5491 fn parse_trait_item_assoc_ty(&mut self)
5492 -> PResult<'a, (Ident, TraitItemKind, ast::Generics)> {
5493 let ident = self.parse_ident()?;
5494 let mut generics = self.parse_generics()?;
5496 // Parse optional colon and param bounds.
5497 let bounds = if self.eat(&token::Colon) {
5498 self.parse_generic_bounds(None)?
5502 generics.where_clause = self.parse_where_clause()?;
5504 let default = if self.eat(&token::Eq) {
5505 Some(self.parse_ty()?)
5509 self.expect(&token::Semi)?;
5511 Ok((ident, TraitItemKind::Type(bounds, default), generics))
5514 fn parse_const_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, GenericParam> {
5515 self.expect_keyword(kw::Const)?;
5516 let ident = self.parse_ident()?;
5517 self.expect(&token::Colon)?;
5518 let ty = self.parse_ty()?;
5522 id: ast::DUMMY_NODE_ID,
5523 attrs: preceding_attrs.into(),
5525 kind: GenericParamKind::Const {
5531 /// Parses a (possibly empty) list of lifetime and type parameters, possibly including
5532 /// a trailing comma and erroneous trailing attributes.
5533 crate fn parse_generic_params(&mut self) -> PResult<'a, Vec<ast::GenericParam>> {
5534 let mut params = Vec::new();
5536 let attrs = self.parse_outer_attributes()?;
5537 if self.check_lifetime() {
5538 let lifetime = self.expect_lifetime();
5539 // Parse lifetime parameter.
5540 let bounds = if self.eat(&token::Colon) {
5541 self.parse_lt_param_bounds()
5545 params.push(ast::GenericParam {
5546 ident: lifetime.ident,
5548 attrs: attrs.into(),
5550 kind: ast::GenericParamKind::Lifetime,
5552 } else if self.check_keyword(kw::Const) {
5553 // Parse const parameter.
5554 params.push(self.parse_const_param(attrs)?);
5555 } else if self.check_ident() {
5556 // Parse type parameter.
5557 params.push(self.parse_ty_param(attrs)?);
5559 // Check for trailing attributes and stop parsing.
5560 if !attrs.is_empty() {
5561 if !params.is_empty() {
5562 self.struct_span_err(
5564 &format!("trailing attribute after generic parameter"),
5566 .span_label(attrs[0].span, "attributes must go before parameters")
5569 self.struct_span_err(
5571 &format!("attribute without generic parameters"),
5575 "attributes are only permitted when preceding parameters",
5583 if !self.eat(&token::Comma) {
5590 /// Parses a set of optional generic type parameter declarations. Where
5591 /// clauses are not parsed here, and must be added later via
5592 /// `parse_where_clause()`.
5594 /// matches generics = ( ) | ( < > ) | ( < typaramseq ( , )? > ) | ( < lifetimes ( , )? > )
5595 /// | ( < lifetimes , typaramseq ( , )? > )
5596 /// where typaramseq = ( typaram ) | ( typaram , typaramseq )
5597 fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
5598 let span_lo = self.span;
5600 let params = self.parse_generic_params()?;
5604 where_clause: WhereClause {
5605 id: ast::DUMMY_NODE_ID,
5606 predicates: Vec::new(),
5607 span: syntax_pos::DUMMY_SP,
5609 span: span_lo.to(self.prev_span),
5612 Ok(ast::Generics::default())
5616 /// Parses generic args (within a path segment) with recovery for extra leading angle brackets.
5617 /// For the purposes of understanding the parsing logic of generic arguments, this function
5618 /// can be thought of being the same as just calling `self.parse_generic_args()` if the source
5619 /// had the correct amount of leading angle brackets.
5621 /// ```ignore (diagnostics)
5622 /// bar::<<<<T as Foo>::Output>();
5623 /// ^^ help: remove extra angle brackets
5625 fn parse_generic_args_with_leaning_angle_bracket_recovery(
5629 ) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5630 // We need to detect whether there are extra leading left angle brackets and produce an
5631 // appropriate error and suggestion. This cannot be implemented by looking ahead at
5632 // upcoming tokens for a matching `>` character - if there are unmatched `<` tokens
5633 // then there won't be matching `>` tokens to find.
5635 // To explain how this detection works, consider the following example:
5637 // ```ignore (diagnostics)
5638 // bar::<<<<T as Foo>::Output>();
5639 // ^^ help: remove extra angle brackets
5642 // Parsing of the left angle brackets starts in this function. We start by parsing the
5643 // `<` token (incrementing the counter of unmatched angle brackets on `Parser` via
5646 // *Upcoming tokens:* `<<<<T as Foo>::Output>;`
5647 // *Unmatched count:* 1
5648 // *`parse_path_segment` calls deep:* 0
5650 // This has the effect of recursing as this function is called if a `<` character
5651 // is found within the expected generic arguments:
5653 // *Upcoming tokens:* `<<<T as Foo>::Output>;`
5654 // *Unmatched count:* 2
5655 // *`parse_path_segment` calls deep:* 1
5657 // Eventually we will have recursed until having consumed all of the `<` tokens and
5658 // this will be reflected in the count:
5660 // *Upcoming tokens:* `T as Foo>::Output>;`
5661 // *Unmatched count:* 4
5662 // `parse_path_segment` calls deep:* 3
5664 // The parser will continue until reaching the first `>` - this will decrement the
5665 // unmatched angle bracket count and return to the parent invocation of this function
5666 // having succeeded in parsing:
5668 // *Upcoming tokens:* `::Output>;`
5669 // *Unmatched count:* 3
5670 // *`parse_path_segment` calls deep:* 2
5672 // This will continue until the next `>` character which will also return successfully
5673 // to the parent invocation of this function and decrement the count:
5675 // *Upcoming tokens:* `;`
5676 // *Unmatched count:* 2
5677 // *`parse_path_segment` calls deep:* 1
5679 // At this point, this function will expect to find another matching `>` character but
5680 // won't be able to and will return an error. This will continue all the way up the
5681 // call stack until the first invocation:
5683 // *Upcoming tokens:* `;`
5684 // *Unmatched count:* 2
5685 // *`parse_path_segment` calls deep:* 0
5687 // In doing this, we have managed to work out how many unmatched leading left angle
5688 // brackets there are, but we cannot recover as the unmatched angle brackets have
5689 // already been consumed. To remedy this, we keep a snapshot of the parser state
5690 // before we do the above. We can then inspect whether we ended up with a parsing error
5691 // and unmatched left angle brackets and if so, restore the parser state before we
5692 // consumed any `<` characters to emit an error and consume the erroneous tokens to
5693 // recover by attempting to parse again.
5695 // In practice, the recursion of this function is indirect and there will be other
5696 // locations that consume some `<` characters - as long as we update the count when
5697 // this happens, it isn't an issue.
5699 let is_first_invocation = style == PathStyle::Expr;
5700 // Take a snapshot before attempting to parse - we can restore this later.
5701 let snapshot = if is_first_invocation {
5707 debug!("parse_generic_args_with_leading_angle_bracket_recovery: (snapshotting)");
5708 match self.parse_generic_args() {
5709 Ok(value) => Ok(value),
5710 Err(ref mut e) if is_first_invocation && self.unmatched_angle_bracket_count > 0 => {
5711 // Cancel error from being unable to find `>`. We know the error
5712 // must have been this due to a non-zero unmatched angle bracket
5716 // Swap `self` with our backup of the parser state before attempting to parse
5717 // generic arguments.
5718 let snapshot = mem::replace(self, snapshot.unwrap());
5721 "parse_generic_args_with_leading_angle_bracket_recovery: (snapshot failure) \
5722 snapshot.count={:?}",
5723 snapshot.unmatched_angle_bracket_count,
5726 // Eat the unmatched angle brackets.
5727 for _ in 0..snapshot.unmatched_angle_bracket_count {
5731 // Make a span over ${unmatched angle bracket count} characters.
5732 let span = lo.with_hi(
5733 lo.lo() + BytePos(snapshot.unmatched_angle_bracket_count)
5735 let plural = snapshot.unmatched_angle_bracket_count > 1;
5740 "unmatched angle bracket{}",
5741 if plural { "s" } else { "" }
5747 "remove extra angle bracket{}",
5748 if plural { "s" } else { "" }
5751 Applicability::MachineApplicable,
5755 // Try again without unmatched angle bracket characters.
5756 self.parse_generic_args()
5762 /// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
5763 /// possibly including trailing comma.
5764 fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
5765 let mut args = Vec::new();
5766 let mut bindings = Vec::new();
5767 let mut misplaced_assoc_ty_bindings: Vec<Span> = Vec::new();
5768 let mut assoc_ty_bindings: Vec<Span> = Vec::new();
5770 let args_lo = self.span;
5773 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5774 // Parse lifetime argument.
5775 args.push(GenericArg::Lifetime(self.expect_lifetime()));
5776 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5777 } else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
5778 // Parse associated type binding.
5780 let ident = self.parse_ident()?;
5782 let ty = self.parse_ty()?;
5783 let span = lo.to(self.prev_span);
5784 bindings.push(TypeBinding {
5785 id: ast::DUMMY_NODE_ID,
5790 assoc_ty_bindings.push(span);
5791 } else if self.check_const_arg() {
5792 // Parse const argument.
5793 let expr = if let token::OpenDelim(token::Brace) = self.token {
5794 self.parse_block_expr(None, self.span, BlockCheckMode::Default, ThinVec::new())?
5795 } else if self.token.is_ident() {
5796 // FIXME(const_generics): to distinguish between idents for types and consts,
5797 // we should introduce a GenericArg::Ident in the AST and distinguish when
5798 // lowering to the HIR. For now, idents for const args are not permitted.
5800 self.fatal("identifiers may currently not be used for const generics")
5803 self.parse_literal_maybe_minus()?
5805 let value = AnonConst {
5806 id: ast::DUMMY_NODE_ID,
5809 args.push(GenericArg::Const(value));
5810 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5811 } else if self.check_type() {
5812 // Parse type argument.
5813 args.push(GenericArg::Type(self.parse_ty()?));
5814 misplaced_assoc_ty_bindings.append(&mut assoc_ty_bindings);
5819 if !self.eat(&token::Comma) {
5824 // FIXME: we would like to report this in ast_validation instead, but we currently do not
5825 // preserve ordering of generic parameters with respect to associated type binding, so we
5826 // lose that information after parsing.
5827 if misplaced_assoc_ty_bindings.len() > 0 {
5828 let mut err = self.struct_span_err(
5829 args_lo.to(self.prev_span),
5830 "associated type bindings must be declared after generic parameters",
5832 for span in misplaced_assoc_ty_bindings {
5835 "this associated type binding should be moved after the generic parameters",
5841 Ok((args, bindings))
5844 /// Parses an optional where-clause and places it in `generics`.
5846 /// ```ignore (only-for-syntax-highlight)
5847 /// where T : Trait<U, V> + 'b, 'a : 'b
5849 fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
5850 let mut where_clause = WhereClause {
5851 id: ast::DUMMY_NODE_ID,
5852 predicates: Vec::new(),
5853 span: syntax_pos::DUMMY_SP,
5856 if !self.eat_keyword(kw::Where) {
5857 return Ok(where_clause);
5859 let lo = self.prev_span;
5861 // We are considering adding generics to the `where` keyword as an alternative higher-rank
5862 // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking
5863 // change we parse those generics now, but report an error.
5864 if self.choose_generics_over_qpath() {
5865 let generics = self.parse_generics()?;
5866 self.struct_span_err(
5868 "generic parameters on `where` clauses are reserved for future use",
5870 .span_label(generics.span, "currently unsupported")
5876 if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
5877 let lifetime = self.expect_lifetime();
5878 // Bounds starting with a colon are mandatory, but possibly empty.
5879 self.expect(&token::Colon)?;
5880 let bounds = self.parse_lt_param_bounds();
5881 where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
5882 ast::WhereRegionPredicate {
5883 span: lo.to(self.prev_span),
5888 } else if self.check_type() {
5889 // Parse optional `for<'a, 'b>`.
5890 // This `for` is parsed greedily and applies to the whole predicate,
5891 // the bounded type can have its own `for` applying only to it.
5892 // Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
5893 // Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
5894 // Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
5895 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
5897 // Parse type with mandatory colon and (possibly empty) bounds,
5898 // or with mandatory equality sign and the second type.
5899 let ty = self.parse_ty()?;
5900 if self.eat(&token::Colon) {
5901 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
5902 where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
5903 ast::WhereBoundPredicate {
5904 span: lo.to(self.prev_span),
5905 bound_generic_params: lifetime_defs,
5910 // FIXME: Decide what should be used here, `=` or `==`.
5911 // FIXME: We are just dropping the binders in lifetime_defs on the floor here.
5912 } else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
5913 let rhs_ty = self.parse_ty()?;
5914 where_clause.predicates.push(ast::WherePredicate::EqPredicate(
5915 ast::WhereEqPredicate {
5916 span: lo.to(self.prev_span),
5919 id: ast::DUMMY_NODE_ID,
5923 return self.unexpected();
5929 if !self.eat(&token::Comma) {
5934 where_clause.span = lo.to(self.prev_span);
5938 fn parse_fn_args(&mut self, named_args: bool, allow_c_variadic: bool)
5939 -> PResult<'a, (Vec<Arg> , bool)> {
5940 self.expect(&token::OpenDelim(token::Paren))?;
5943 let mut c_variadic = false;
5944 let (args, recovered): (Vec<Option<Arg>>, bool) =
5945 self.parse_seq_to_before_end(
5946 &token::CloseDelim(token::Paren),
5947 SeqSep::trailing_allowed(token::Comma),
5949 // If the argument is a C-variadic argument we should not
5950 // enforce named arguments.
5951 let enforce_named_args = if p.token == token::DotDotDot {
5956 match p.parse_arg_general(enforce_named_args, false,
5959 if let TyKind::CVarArgs = arg.ty.node {
5961 if p.token != token::CloseDelim(token::Paren) {
5964 "`...` must be the last argument of a C-variadic function");
5975 let lo = p.prev_span;
5976 // Skip every token until next possible arg or end.
5977 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
5978 // Create a placeholder argument for proper arg count (issue #34264).
5979 let span = lo.to(p.prev_span);
5980 Ok(Some(dummy_arg(span)))
5987 self.eat(&token::CloseDelim(token::Paren));
5990 let args: Vec<_> = args.into_iter().filter_map(|x| x).collect();
5992 if c_variadic && args.is_empty() {
5994 "C-variadic function must be declared with at least one named argument");
5997 Ok((args, c_variadic))
6000 /// Parses the argument list and result type of a function declaration.
6001 fn parse_fn_decl(&mut self, allow_c_variadic: bool) -> PResult<'a, P<FnDecl>> {
6003 let (args, c_variadic) = self.parse_fn_args(true, allow_c_variadic)?;
6004 let ret_ty = self.parse_ret_ty(true)?;
6013 /// Returns the parsed optional self argument and whether a self shortcut was used.
6014 fn parse_self_arg(&mut self) -> PResult<'a, Option<Arg>> {
6015 let expect_ident = |this: &mut Self| match this.token {
6016 // Preserve hygienic context.
6017 token::Ident(ident, _) =>
6018 { let span = this.span; this.bump(); Ident::new(ident.name, span) }
6021 let isolated_self = |this: &mut Self, n| {
6022 this.look_ahead(n, |t| t.is_keyword(kw::SelfLower)) &&
6023 this.look_ahead(n + 1, |t| t != &token::ModSep)
6026 // Parse optional self parameter of a method.
6027 // Only a limited set of initial token sequences is considered self parameters, anything
6028 // else is parsed as a normal function parameter list, so some lookahead is required.
6029 let eself_lo = self.span;
6030 let (eself, eself_ident, eself_hi) = match self.token {
6031 token::BinOp(token::And) => {
6037 (if isolated_self(self, 1) {
6039 SelfKind::Region(None, Mutability::Immutable)
6040 } else if self.look_ahead(1, |t| t.is_keyword(kw::Mut)) &&
6041 isolated_self(self, 2) {
6044 SelfKind::Region(None, Mutability::Mutable)
6045 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6046 isolated_self(self, 2) {
6048 let lt = self.expect_lifetime();
6049 SelfKind::Region(Some(lt), Mutability::Immutable)
6050 } else if self.look_ahead(1, |t| t.is_lifetime()) &&
6051 self.look_ahead(2, |t| t.is_keyword(kw::Mut)) &&
6052 isolated_self(self, 3) {
6054 let lt = self.expect_lifetime();
6056 SelfKind::Region(Some(lt), Mutability::Mutable)
6059 }, expect_ident(self), self.prev_span)
6061 token::BinOp(token::Star) => {
6066 // Emit special error for `self` cases.
6067 let msg = "cannot pass `self` by raw pointer";
6068 (if isolated_self(self, 1) {
6070 self.struct_span_err(self.span, msg)
6071 .span_label(self.span, msg)
6073 SelfKind::Value(Mutability::Immutable)
6074 } else if self.look_ahead(1, |t| t.is_mutability()) &&
6075 isolated_self(self, 2) {
6078 self.struct_span_err(self.span, msg)
6079 .span_label(self.span, msg)
6081 SelfKind::Value(Mutability::Immutable)
6084 }, expect_ident(self), self.prev_span)
6086 token::Ident(..) => {
6087 if isolated_self(self, 0) {
6090 let eself_ident = expect_ident(self);
6091 let eself_hi = self.prev_span;
6092 (if self.eat(&token::Colon) {
6093 let ty = self.parse_ty()?;
6094 SelfKind::Explicit(ty, Mutability::Immutable)
6096 SelfKind::Value(Mutability::Immutable)
6097 }, eself_ident, eself_hi)
6098 } else if self.token.is_keyword(kw::Mut) &&
6099 isolated_self(self, 1) {
6103 let eself_ident = expect_ident(self);
6104 let eself_hi = self.prev_span;
6105 (if self.eat(&token::Colon) {
6106 let ty = self.parse_ty()?;
6107 SelfKind::Explicit(ty, Mutability::Mutable)
6109 SelfKind::Value(Mutability::Mutable)
6110 }, eself_ident, eself_hi)
6115 _ => return Ok(None),
6118 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
6119 Ok(Some(Arg::from_self(eself, eself_ident)))
6122 /// Parses the parameter list and result type of a function that may have a `self` parameter.
6123 fn parse_fn_decl_with_self<F>(&mut self, parse_arg_fn: F) -> PResult<'a, P<FnDecl>>
6124 where F: FnMut(&mut Parser<'a>) -> PResult<'a, Arg>,
6126 self.expect(&token::OpenDelim(token::Paren))?;
6128 // Parse optional self argument
6129 let self_arg = self.parse_self_arg()?;
6131 // Parse the rest of the function parameter list.
6132 let sep = SeqSep::trailing_allowed(token::Comma);
6133 let (fn_inputs, recovered) = if let Some(self_arg) = self_arg {
6134 if self.check(&token::CloseDelim(token::Paren)) {
6135 (vec![self_arg], false)
6136 } else if self.eat(&token::Comma) {
6137 let mut fn_inputs = vec![self_arg];
6138 let (mut input, recovered) = self.parse_seq_to_before_end(
6139 &token::CloseDelim(token::Paren), sep, parse_arg_fn)?;
6140 fn_inputs.append(&mut input);
6141 (fn_inputs, recovered)
6143 match self.expect_one_of(&[], &[]) {
6144 Err(err) => return Err(err),
6145 Ok(recovered) => (vec![self_arg], recovered),
6149 self.parse_seq_to_before_end(&token::CloseDelim(token::Paren), sep, parse_arg_fn)?
6153 // Parse closing paren and return type.
6154 self.expect(&token::CloseDelim(token::Paren))?;
6158 output: self.parse_ret_ty(true)?,
6163 /// Parses the `|arg, arg|` header of a closure.
6164 fn parse_fn_block_decl(&mut self) -> PResult<'a, P<FnDecl>> {
6165 let inputs_captures = {
6166 if self.eat(&token::OrOr) {
6169 self.expect(&token::BinOp(token::Or))?;
6170 let args = self.parse_seq_to_before_tokens(
6171 &[&token::BinOp(token::Or), &token::OrOr],
6172 SeqSep::trailing_allowed(token::Comma),
6173 TokenExpectType::NoExpect,
6174 |p| p.parse_fn_block_arg()
6180 let output = self.parse_ret_ty(true)?;
6183 inputs: inputs_captures,
6189 /// Parses the name and optional generic types of a function header.
6190 fn parse_fn_header(&mut self) -> PResult<'a, (Ident, ast::Generics)> {
6191 let id = self.parse_ident()?;
6192 let generics = self.parse_generics()?;
6196 fn mk_item(&self, span: Span, ident: Ident, node: ItemKind, vis: Visibility,
6197 attrs: Vec<Attribute>) -> P<Item> {
6201 id: ast::DUMMY_NODE_ID,
6209 /// Parses an item-position function declaration.
6210 fn parse_item_fn(&mut self,
6212 mut asyncness: Spanned<IsAsync>,
6213 constness: Spanned<Constness>,
6215 -> PResult<'a, ItemInfo> {
6216 let (ident, mut generics) = self.parse_fn_header()?;
6217 let allow_c_variadic = abi == Abi::C && unsafety == Unsafety::Unsafe;
6218 let mut decl = self.parse_fn_decl(allow_c_variadic)?;
6219 generics.where_clause = self.parse_where_clause()?;
6220 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6221 self.construct_async_arguments(&mut asyncness, &mut decl);
6222 let header = FnHeader { unsafety, asyncness, constness, abi };
6223 Ok((ident, ItemKind::Fn(decl, header, generics, body), Some(inner_attrs)))
6226 /// Returns `true` if we are looking at `const ID`
6227 /// (returns `false` for things like `const fn`, etc.).
6228 fn is_const_item(&self) -> bool {
6229 self.token.is_keyword(kw::Const) &&
6230 !self.look_ahead(1, |t| t.is_keyword(kw::Fn)) &&
6231 !self.look_ahead(1, |t| t.is_keyword(kw::Unsafe))
6234 /// Parses all the "front matter" for a `fn` declaration, up to
6235 /// and including the `fn` keyword:
6239 /// - `const unsafe fn`
6242 fn parse_fn_front_matter(&mut self)
6250 let is_const_fn = self.eat_keyword(kw::Const);
6251 let const_span = self.prev_span;
6252 let unsafety = self.parse_unsafety();
6253 let asyncness = self.parse_asyncness();
6254 let asyncness = respan(self.prev_span, asyncness);
6255 let (constness, unsafety, abi) = if is_const_fn {
6256 (respan(const_span, Constness::Const), unsafety, Abi::Rust)
6258 let abi = if self.eat_keyword(kw::Extern) {
6259 self.parse_opt_abi()?.unwrap_or(Abi::C)
6263 (respan(self.prev_span, Constness::NotConst), unsafety, abi)
6265 if !self.eat_keyword(kw::Fn) {
6266 // It is possible for `expect_one_of` to recover given the contents of
6267 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
6268 // account for this.
6269 if !self.expect_one_of(&[], &[])? { unreachable!() }
6271 Ok((constness, unsafety, asyncness, abi))
6274 /// Parses an impl item.
6275 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
6276 maybe_whole!(self, NtImplItem, |x| x);
6277 let attrs = self.parse_outer_attributes()?;
6278 let mut unclosed_delims = vec![];
6279 let (mut item, tokens) = self.collect_tokens(|this| {
6280 let item = this.parse_impl_item_(at_end, attrs);
6281 unclosed_delims.append(&mut this.unclosed_delims);
6284 self.unclosed_delims.append(&mut unclosed_delims);
6286 // See `parse_item` for why this clause is here.
6287 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
6288 item.tokens = Some(tokens);
6293 fn parse_impl_item_(&mut self,
6295 mut attrs: Vec<Attribute>) -> PResult<'a, ImplItem> {
6297 let vis = self.parse_visibility(false)?;
6298 let defaultness = self.parse_defaultness();
6299 let (name, node, generics) = if let Some(type_) = self.eat_type() {
6300 let (name, alias, generics) = type_?;
6301 let kind = match alias {
6302 AliasKind::Weak(typ) => ast::ImplItemKind::Type(typ),
6303 AliasKind::Existential(bounds) => ast::ImplItemKind::Existential(bounds),
6305 (name, kind, generics)
6306 } else if self.is_const_item() {
6307 // This parses the grammar:
6308 // ImplItemConst = "const" Ident ":" Ty "=" Expr ";"
6309 self.expect_keyword(kw::Const)?;
6310 let name = self.parse_ident()?;
6311 self.expect(&token::Colon)?;
6312 let typ = self.parse_ty()?;
6313 self.expect(&token::Eq)?;
6314 let expr = self.parse_expr()?;
6315 self.expect(&token::Semi)?;
6316 (name, ast::ImplItemKind::Const(typ, expr), ast::Generics::default())
6318 let (name, inner_attrs, generics, node) = self.parse_impl_method(&vis, at_end)?;
6319 attrs.extend(inner_attrs);
6320 (name, node, generics)
6324 id: ast::DUMMY_NODE_ID,
6325 span: lo.to(self.prev_span),
6336 fn complain_if_pub_macro(&self, vis: &VisibilityKind, sp: Span) {
6338 VisibilityKind::Inherited => {}
6340 let is_macro_rules: bool = match self.token {
6341 token::Ident(sid, _) => sid.name == Symbol::intern("macro_rules"),
6344 let mut err = if is_macro_rules {
6345 let mut err = self.diagnostic()
6346 .struct_span_err(sp, "can't qualify macro_rules invocation with `pub`");
6347 err.span_suggestion(
6349 "try exporting the macro",
6350 "#[macro_export]".to_owned(),
6351 Applicability::MaybeIncorrect // speculative
6355 let mut err = self.diagnostic()
6356 .struct_span_err(sp, "can't qualify macro invocation with `pub`");
6357 err.help("try adjusting the macro to put `pub` inside the invocation");
6365 fn missing_assoc_item_kind_err(&self, item_type: &str, prev_span: Span)
6366 -> DiagnosticBuilder<'a>
6368 let expected_kinds = if item_type == "extern" {
6369 "missing `fn`, `type`, or `static`"
6371 "missing `fn`, `type`, or `const`"
6374 // Given this code `path(`, it seems like this is not
6375 // setting the visibility of a macro invocation, but rather
6376 // a mistyped method declaration.
6377 // Create a diagnostic pointing out that `fn` is missing.
6379 // x | pub path(&self) {
6380 // | ^ missing `fn`, `type`, or `const`
6382 // ^^ `sp` below will point to this
6383 let sp = prev_span.between(self.prev_span);
6384 let mut err = self.diagnostic().struct_span_err(
6386 &format!("{} for {}-item declaration",
6387 expected_kinds, item_type));
6388 err.span_label(sp, expected_kinds);
6392 /// Parse a method or a macro invocation in a trait impl.
6393 fn parse_impl_method(&mut self, vis: &Visibility, at_end: &mut bool)
6394 -> PResult<'a, (Ident, Vec<Attribute>, ast::Generics,
6395 ast::ImplItemKind)> {
6396 // code copied from parse_macro_use_or_failure... abstraction!
6397 if let Some(mac) = self.parse_assoc_macro_invoc("impl", Some(vis), at_end)? {
6399 Ok((Ident::with_empty_ctxt(kw::Invalid), vec![], ast::Generics::default(),
6400 ast::ImplItemKind::Macro(mac)))
6402 let (constness, unsafety, mut asyncness, abi) = self.parse_fn_front_matter()?;
6403 let ident = self.parse_ident()?;
6404 let mut generics = self.parse_generics()?;
6405 let mut decl = self.parse_fn_decl_with_self(|p| p.parse_arg())?;
6406 generics.where_clause = self.parse_where_clause()?;
6407 self.construct_async_arguments(&mut asyncness, &mut decl);
6409 let (inner_attrs, body) = self.parse_inner_attrs_and_block()?;
6410 let header = ast::FnHeader { abi, unsafety, constness, asyncness };
6411 Ok((ident, inner_attrs, generics, ast::ImplItemKind::Method(
6412 ast::MethodSig { header, decl },
6418 /// Parses `trait Foo { ... }` or `trait Foo = Bar;`.
6419 fn parse_item_trait(&mut self, is_auto: IsAuto, unsafety: Unsafety) -> PResult<'a, ItemInfo> {
6420 let ident = self.parse_ident()?;
6421 let mut tps = self.parse_generics()?;
6423 // Parse optional colon and supertrait bounds.
6424 let bounds = if self.eat(&token::Colon) {
6425 self.parse_generic_bounds(Some(self.prev_span))?
6430 if self.eat(&token::Eq) {
6431 // it's a trait alias
6432 let bounds = self.parse_generic_bounds(None)?;
6433 tps.where_clause = self.parse_where_clause()?;
6434 self.expect(&token::Semi)?;
6435 if is_auto == IsAuto::Yes {
6436 let msg = "trait aliases cannot be `auto`";
6437 self.struct_span_err(self.prev_span, msg)
6438 .span_label(self.prev_span, msg)
6441 if unsafety != Unsafety::Normal {
6442 let msg = "trait aliases cannot be `unsafe`";
6443 self.struct_span_err(self.prev_span, msg)
6444 .span_label(self.prev_span, msg)
6447 Ok((ident, ItemKind::TraitAlias(tps, bounds), None))
6449 // it's a normal trait
6450 tps.where_clause = self.parse_where_clause()?;
6451 self.expect(&token::OpenDelim(token::Brace))?;
6452 let mut trait_items = vec![];
6453 while !self.eat(&token::CloseDelim(token::Brace)) {
6454 if let token::DocComment(_) = self.token {
6455 if self.look_ahead(1,
6456 |tok| tok == &token::Token::CloseDelim(token::Brace)) {
6457 let mut err = self.diagnostic().struct_span_err_with_code(
6459 "found a documentation comment that doesn't document anything",
6460 DiagnosticId::Error("E0584".into()),
6462 err.help("doc comments must come before what they document, maybe a \
6463 comment was intended with `//`?",
6470 let mut at_end = false;
6471 match self.parse_trait_item(&mut at_end) {
6472 Ok(item) => trait_items.push(item),
6476 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6481 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, trait_items), None))
6485 fn choose_generics_over_qpath(&self) -> bool {
6486 // There's an ambiguity between generic parameters and qualified paths in impls.
6487 // If we see `<` it may start both, so we have to inspect some following tokens.
6488 // The following combinations can only start generics,
6489 // but not qualified paths (with one exception):
6490 // `<` `>` - empty generic parameters
6491 // `<` `#` - generic parameters with attributes
6492 // `<` (LIFETIME|IDENT) `>` - single generic parameter
6493 // `<` (LIFETIME|IDENT) `,` - first generic parameter in a list
6494 // `<` (LIFETIME|IDENT) `:` - generic parameter with bounds
6495 // `<` (LIFETIME|IDENT) `=` - generic parameter with a default
6496 // `<` const - generic const parameter
6497 // The only truly ambiguous case is
6498 // `<` IDENT `>` `::` IDENT ...
6499 // we disambiguate it in favor of generics (`impl<T> ::absolute::Path<T> { ... }`)
6500 // because this is what almost always expected in practice, qualified paths in impls
6501 // (`impl <Type>::AssocTy { ... }`) aren't even allowed by type checker at the moment.
6502 self.token == token::Lt &&
6503 (self.look_ahead(1, |t| t == &token::Pound || t == &token::Gt) ||
6504 self.look_ahead(1, |t| t.is_lifetime() || t.is_ident()) &&
6505 self.look_ahead(2, |t| t == &token::Gt || t == &token::Comma ||
6506 t == &token::Colon || t == &token::Eq) ||
6507 self.look_ahead(1, |t| t.is_keyword(kw::Const)))
6510 fn parse_impl_body(&mut self) -> PResult<'a, (Vec<ImplItem>, Vec<Attribute>)> {
6511 self.expect(&token::OpenDelim(token::Brace))?;
6512 let attrs = self.parse_inner_attributes()?;
6514 let mut impl_items = Vec::new();
6515 while !self.eat(&token::CloseDelim(token::Brace)) {
6516 let mut at_end = false;
6517 match self.parse_impl_item(&mut at_end) {
6518 Ok(impl_item) => impl_items.push(impl_item),
6522 self.recover_stmt_(SemiColonMode::Break, BlockMode::Break);
6527 Ok((impl_items, attrs))
6530 /// Parses an implementation item, `impl` keyword is already parsed.
6532 /// impl<'a, T> TYPE { /* impl items */ }
6533 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
6534 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
6536 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
6537 /// `impl` GENERICS `!`? TYPE `for`? (TYPE | `..`) (`where` PREDICATES)? `{` BODY `}`
6538 /// `impl` GENERICS `!`? TYPE (`where` PREDICATES)? `{` BODY `}`
6539 fn parse_item_impl(&mut self, unsafety: Unsafety, defaultness: Defaultness)
6540 -> PResult<'a, ItemInfo> {
6541 // First, parse generic parameters if necessary.
6542 let mut generics = if self.choose_generics_over_qpath() {
6543 self.parse_generics()?
6545 ast::Generics::default()
6548 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
6549 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
6551 ast::ImplPolarity::Negative
6553 ast::ImplPolarity::Positive
6556 // Parse both types and traits as a type, then reinterpret if necessary.
6557 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
6558 let ty_first = if self.token.is_keyword(kw::For) &&
6559 self.look_ahead(1, |t| t != &token::Lt) {
6560 let span = self.prev_span.between(self.span);
6561 self.struct_span_err(span, "missing trait in a trait impl").emit();
6562 P(Ty { node: TyKind::Path(None, err_path(span)), span, id: ast::DUMMY_NODE_ID })
6567 // If `for` is missing we try to recover.
6568 let has_for = self.eat_keyword(kw::For);
6569 let missing_for_span = self.prev_span.between(self.span);
6571 let ty_second = if self.token == token::DotDot {
6572 // We need to report this error after `cfg` expansion for compatibility reasons
6573 self.bump(); // `..`, do not add it to expected tokens
6574 Some(DummyResult::raw_ty(self.prev_span, true))
6575 } else if has_for || self.token.can_begin_type() {
6576 Some(self.parse_ty()?)
6581 generics.where_clause = self.parse_where_clause()?;
6583 let (impl_items, attrs) = self.parse_impl_body()?;
6585 let item_kind = match ty_second {
6586 Some(ty_second) => {
6587 // impl Trait for Type
6589 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
6590 .span_suggestion_short(
6593 " for ".to_string(),
6594 Applicability::MachineApplicable,
6598 let ty_first = ty_first.into_inner();
6599 let path = match ty_first.node {
6600 // This notably includes paths passed through `ty` macro fragments (#46438).
6601 TyKind::Path(None, path) => path,
6603 self.span_err(ty_first.span, "expected a trait, found type");
6604 err_path(ty_first.span)
6607 let trait_ref = TraitRef { path, ref_id: ty_first.id };
6609 ItemKind::Impl(unsafety, polarity, defaultness,
6610 generics, Some(trait_ref), ty_second, impl_items)
6614 ItemKind::Impl(unsafety, polarity, defaultness,
6615 generics, None, ty_first, impl_items)
6619 Ok((Ident::with_empty_ctxt(kw::Invalid), item_kind, Some(attrs)))
6622 fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
6623 if self.eat_keyword(kw::For) {
6625 let params = self.parse_generic_params()?;
6627 // We rely on AST validation to rule out invalid cases: There must not be type
6628 // parameters, and the lifetime parameters must not have bounds.
6635 /// Parses `struct Foo { ... }`.
6636 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
6637 let class_name = self.parse_ident()?;
6639 let mut generics = self.parse_generics()?;
6641 // There is a special case worth noting here, as reported in issue #17904.
6642 // If we are parsing a tuple struct it is the case that the where clause
6643 // should follow the field list. Like so:
6645 // struct Foo<T>(T) where T: Copy;
6647 // If we are parsing a normal record-style struct it is the case
6648 // that the where clause comes before the body, and after the generics.
6649 // So if we look ahead and see a brace or a where-clause we begin
6650 // parsing a record style struct.
6652 // Otherwise if we look ahead and see a paren we parse a tuple-style
6655 let vdata = if self.token.is_keyword(kw::Where) {
6656 generics.where_clause = self.parse_where_clause()?;
6657 if self.eat(&token::Semi) {
6658 // If we see a: `struct Foo<T> where T: Copy;` style decl.
6659 VariantData::Unit(ast::DUMMY_NODE_ID)
6661 // If we see: `struct Foo<T> where T: Copy { ... }`
6662 let (fields, recovered) = self.parse_record_struct_body()?;
6663 VariantData::Struct(fields, recovered)
6665 // No `where` so: `struct Foo<T>;`
6666 } else if self.eat(&token::Semi) {
6667 VariantData::Unit(ast::DUMMY_NODE_ID)
6668 // Record-style struct definition
6669 } else if self.token == token::OpenDelim(token::Brace) {
6670 let (fields, recovered) = self.parse_record_struct_body()?;
6671 VariantData::Struct(fields, recovered)
6672 // Tuple-style struct definition with optional where-clause.
6673 } else if self.token == token::OpenDelim(token::Paren) {
6674 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, ast::DUMMY_NODE_ID);
6675 generics.where_clause = self.parse_where_clause()?;
6676 self.expect(&token::Semi)?;
6679 let token_str = self.this_token_descr();
6680 let mut err = self.fatal(&format!(
6681 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
6684 err.span_label(self.span, "expected `where`, `{`, `(`, or `;` after struct name");
6688 Ok((class_name, ItemKind::Struct(vdata, generics), None))
6691 /// Parses `union Foo { ... }`.
6692 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
6693 let class_name = self.parse_ident()?;
6695 let mut generics = self.parse_generics()?;
6697 let vdata = if self.token.is_keyword(kw::Where) {
6698 generics.where_clause = self.parse_where_clause()?;
6699 let (fields, recovered) = self.parse_record_struct_body()?;
6700 VariantData::Struct(fields, recovered)
6701 } else if self.token == token::OpenDelim(token::Brace) {
6702 let (fields, recovered) = self.parse_record_struct_body()?;
6703 VariantData::Struct(fields, recovered)
6705 let token_str = self.this_token_descr();
6706 let mut err = self.fatal(&format!(
6707 "expected `where` or `{{` after union name, found {}", token_str));
6708 err.span_label(self.span, "expected `where` or `{` after union name");
6712 Ok((class_name, ItemKind::Union(vdata, generics), None))
6715 fn parse_record_struct_body(
6717 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
6718 let mut fields = Vec::new();
6719 let mut recovered = false;
6720 if self.eat(&token::OpenDelim(token::Brace)) {
6721 while self.token != token::CloseDelim(token::Brace) {
6722 let field = self.parse_struct_decl_field().map_err(|e| {
6723 self.recover_stmt();
6728 Ok(field) => fields.push(field),
6734 self.eat(&token::CloseDelim(token::Brace));
6736 let token_str = self.this_token_descr();
6737 let mut err = self.fatal(&format!(
6738 "expected `where`, or `{{` after struct name, found {}", token_str));
6739 err.span_label(self.span, "expected `where`, or `{` after struct name");
6743 Ok((fields, recovered))
6746 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
6747 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
6748 // Unit like structs are handled in parse_item_struct function
6749 let fields = self.parse_unspanned_seq(
6750 &token::OpenDelim(token::Paren),
6751 &token::CloseDelim(token::Paren),
6752 SeqSep::trailing_allowed(token::Comma),
6754 let attrs = p.parse_outer_attributes()?;
6756 let vis = p.parse_visibility(true)?;
6757 let ty = p.parse_ty()?;
6759 span: lo.to(ty.span),
6762 id: ast::DUMMY_NODE_ID,
6771 /// Parses a structure field declaration.
6772 fn parse_single_struct_field(&mut self,
6775 attrs: Vec<Attribute> )
6776 -> PResult<'a, StructField> {
6777 let mut seen_comma: bool = false;
6778 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
6779 if self.token == token::Comma {
6786 token::CloseDelim(token::Brace) => {}
6787 token::DocComment(_) => {
6788 let previous_span = self.prev_span;
6789 let mut err = self.span_fatal_err(self.span, Error::UselessDocComment);
6790 self.bump(); // consume the doc comment
6791 let comma_after_doc_seen = self.eat(&token::Comma);
6792 // `seen_comma` is always false, because we are inside doc block
6793 // condition is here to make code more readable
6794 if seen_comma == false && comma_after_doc_seen == true {
6797 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
6800 if seen_comma == false {
6801 let sp = self.sess.source_map().next_point(previous_span);
6802 err.span_suggestion(
6804 "missing comma here",
6806 Applicability::MachineApplicable
6813 let sp = self.sess.source_map().next_point(self.prev_span);
6814 let mut err = self.struct_span_err(sp, &format!("expected `,`, or `}}`, found {}",
6815 self.this_token_descr()));
6816 if self.token.is_ident() {
6817 // This is likely another field; emit the diagnostic and keep going
6818 err.span_suggestion(
6820 "try adding a comma",
6822 Applicability::MachineApplicable,
6833 /// Parses an element of a struct declaration.
6834 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
6835 let attrs = self.parse_outer_attributes()?;
6837 let vis = self.parse_visibility(false)?;
6838 self.parse_single_struct_field(lo, vis, attrs)
6841 /// Parses `pub`, `pub(crate)` and `pub(in path)` plus shortcuts `crate` for `pub(crate)`,
6842 /// `pub(self)` for `pub(in self)` and `pub(super)` for `pub(in super)`.
6843 /// If the following element can't be a tuple (i.e., it's a function definition), then
6844 /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
6845 /// so emit a proper diagnostic.
6846 pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
6847 maybe_whole!(self, NtVis, |x| x);
6849 self.expected_tokens.push(TokenType::Keyword(kw::Crate));
6850 if self.is_crate_vis() {
6851 self.bump(); // `crate`
6852 return Ok(respan(self.prev_span, VisibilityKind::Crate(CrateSugar::JustCrate)));
6855 if !self.eat_keyword(kw::Pub) {
6856 // We need a span for our `Spanned<VisibilityKind>`, but there's inherently no
6857 // keyword to grab a span from for inherited visibility; an empty span at the
6858 // beginning of the current token would seem to be the "Schelling span".
6859 return Ok(respan(self.span.shrink_to_lo(), VisibilityKind::Inherited))
6861 let lo = self.prev_span;
6863 if self.check(&token::OpenDelim(token::Paren)) {
6864 // We don't `self.bump()` the `(` yet because this might be a struct definition where
6865 // `()` or a tuple might be allowed. For example, `struct Struct(pub (), pub (usize));`.
6866 // Because of this, we only `bump` the `(` if we're assured it is appropriate to do so
6867 // by the following tokens.
6868 if self.look_ahead(1, |t| t.is_keyword(kw::Crate)) &&
6869 self.look_ahead(2, |t| t != &token::ModSep) // account for `pub(crate::foo)`
6873 self.bump(); // `crate`
6874 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6876 lo.to(self.prev_span),
6877 VisibilityKind::Crate(CrateSugar::PubCrate),
6880 } else if self.look_ahead(1, |t| t.is_keyword(kw::In)) {
6883 self.bump(); // `in`
6884 let path = self.parse_path(PathStyle::Mod)?; // `path`
6885 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6886 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6888 id: ast::DUMMY_NODE_ID,
6891 } else if self.look_ahead(2, |t| t == &token::CloseDelim(token::Paren)) &&
6892 self.look_ahead(1, |t| t.is_keyword(kw::Super) ||
6893 t.is_keyword(kw::SelfLower))
6895 // `pub(self)` or `pub(super)`
6897 let path = self.parse_path(PathStyle::Mod)?; // `super`/`self`
6898 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6899 let vis = respan(lo.to(self.prev_span), VisibilityKind::Restricted {
6901 id: ast::DUMMY_NODE_ID,
6904 } else if !can_take_tuple { // Provide this diagnostic if this is not a tuple struct
6905 // `pub(something) fn ...` or `struct X { pub(something) y: Z }`
6907 let msg = "incorrect visibility restriction";
6908 let suggestion = r##"some possible visibility restrictions are:
6909 `pub(crate)`: visible only on the current crate
6910 `pub(super)`: visible only in the current module's parent
6911 `pub(in path::to::module)`: visible only on the specified path"##;
6912 let path = self.parse_path(PathStyle::Mod)?;
6914 let help_msg = format!("make this visible only to module `{}` with `in`", path);
6915 self.expect(&token::CloseDelim(token::Paren))?; // `)`
6916 let mut err = struct_span_err!(self.sess.span_diagnostic, sp, E0704, "{}", msg);
6917 err.help(suggestion);
6918 err.span_suggestion(
6919 sp, &help_msg, format!("in {}", path), Applicability::MachineApplicable
6921 err.emit(); // emit diagnostic, but continue with public visibility
6925 Ok(respan(lo, VisibilityKind::Public))
6928 /// Parses defaultness (i.e., `default` or nothing).
6929 fn parse_defaultness(&mut self) -> Defaultness {
6930 // `pub` is included for better error messages
6931 if self.check_keyword(kw::Default) &&
6932 self.look_ahead(1, |t| t.is_keyword(kw::Impl) ||
6933 t.is_keyword(kw::Const) ||
6934 t.is_keyword(kw::Fn) ||
6935 t.is_keyword(kw::Unsafe) ||
6936 t.is_keyword(kw::Extern) ||
6937 t.is_keyword(kw::Type) ||
6938 t.is_keyword(kw::Pub)) {
6939 self.bump(); // `default`
6940 Defaultness::Default
6946 /// Given a termination token, parses all of the items in a module.
6947 fn parse_mod_items(&mut self, term: &token::Token, inner_lo: Span) -> PResult<'a, Mod> {
6948 let mut items = vec![];
6949 while let Some(item) = self.parse_item()? {
6951 self.maybe_consume_incorrect_semicolon(&items);
6954 if !self.eat(term) {
6955 let token_str = self.this_token_descr();
6956 if !self.maybe_consume_incorrect_semicolon(&items) {
6957 let mut err = self.fatal(&format!("expected item, found {}", token_str));
6958 err.span_label(self.span, "expected item");
6963 let hi = if self.span.is_dummy() {
6970 inner: inner_lo.to(hi),
6976 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
6977 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
6978 self.expect(&token::Colon)?;
6979 let ty = self.parse_ty()?;
6980 self.expect(&token::Eq)?;
6981 let e = self.parse_expr()?;
6982 self.expect(&token::Semi)?;
6983 let item = match m {
6984 Some(m) => ItemKind::Static(ty, m, e),
6985 None => ItemKind::Const(ty, e),
6987 Ok((id, item, None))
6990 /// Parse a `mod <foo> { ... }` or `mod <foo>;` item
6991 fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
6992 let (in_cfg, outer_attrs) = {
6993 let mut strip_unconfigured = crate::config::StripUnconfigured {
6995 features: None, // don't perform gated feature checking
6997 let mut outer_attrs = outer_attrs.to_owned();
6998 strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
6999 (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
7002 let id_span = self.span;
7003 let id = self.parse_ident()?;
7004 if self.eat(&token::Semi) {
7005 if in_cfg && self.recurse_into_file_modules {
7006 // This mod is in an external file. Let's go get it!
7007 let ModulePathSuccess { path, directory_ownership, warn } =
7008 self.submod_path(id, &outer_attrs, id_span)?;
7009 let (module, mut attrs) =
7010 self.eval_src_mod(path, directory_ownership, id.to_string(), id_span)?;
7011 // Record that we fetched the mod from an external file
7013 let attr = Attribute {
7014 id: attr::mk_attr_id(),
7015 style: ast::AttrStyle::Outer,
7016 path: ast::Path::from_ident(
7017 Ident::with_empty_ctxt(sym::warn_directory_ownership)),
7018 tokens: TokenStream::empty(),
7019 is_sugared_doc: false,
7020 span: syntax_pos::DUMMY_SP,
7022 attr::mark_known(&attr);
7025 Ok((id, ItemKind::Mod(module), Some(attrs)))
7027 let placeholder = ast::Mod {
7028 inner: syntax_pos::DUMMY_SP,
7032 Ok((id, ItemKind::Mod(placeholder), None))
7035 let old_directory = self.directory.clone();
7036 self.push_directory(id, &outer_attrs);
7038 self.expect(&token::OpenDelim(token::Brace))?;
7039 let mod_inner_lo = self.span;
7040 let attrs = self.parse_inner_attributes()?;
7041 let module = self.parse_mod_items(&token::CloseDelim(token::Brace), mod_inner_lo)?;
7043 self.directory = old_directory;
7044 Ok((id, ItemKind::Mod(module), Some(attrs)))
7048 fn push_directory(&mut self, id: Ident, attrs: &[Attribute]) {
7049 if let Some(path) = attr::first_attr_value_str_by_name(attrs, sym::path) {
7050 self.directory.path.to_mut().push(&path.as_str());
7051 self.directory.ownership = DirectoryOwnership::Owned { relative: None };
7053 // We have to push on the current module name in the case of relative
7054 // paths in order to ensure that any additional module paths from inline
7055 // `mod x { ... }` come after the relative extension.
7057 // For example, a `mod z { ... }` inside `x/y.rs` should set the current
7058 // directory path to `/x/y/z`, not `/x/z` with a relative offset of `y`.
7059 if let DirectoryOwnership::Owned { relative } = &mut self.directory.ownership {
7060 if let Some(ident) = relative.take() { // remove the relative offset
7061 self.directory.path.to_mut().push(ident.as_str());
7064 self.directory.path.to_mut().push(&id.as_str());
7068 pub fn submod_path_from_attr(attrs: &[Attribute], dir_path: &Path) -> Option<PathBuf> {
7069 if let Some(s) = attr::first_attr_value_str_by_name(attrs, sym::path) {
7072 // On windows, the base path might have the form
7073 // `\\?\foo\bar` in which case it does not tolerate
7074 // mixed `/` and `\` separators, so canonicalize
7077 let s = s.replace("/", "\\");
7078 Some(dir_path.join(s))
7084 /// Returns a path to a module.
7085 pub fn default_submod_path(
7087 relative: Option<ast::Ident>,
7089 source_map: &SourceMap) -> ModulePath
7091 // If we're in a foo.rs file instead of a mod.rs file,
7092 // we need to look for submodules in
7093 // `./foo/<id>.rs` and `./foo/<id>/mod.rs` rather than
7094 // `./<id>.rs` and `./<id>/mod.rs`.
7095 let relative_prefix_string;
7096 let relative_prefix = if let Some(ident) = relative {
7097 relative_prefix_string = format!("{}{}", ident.as_str(), path::MAIN_SEPARATOR);
7098 &relative_prefix_string
7103 let mod_name = id.to_string();
7104 let default_path_str = format!("{}{}.rs", relative_prefix, mod_name);
7105 let secondary_path_str = format!("{}{}{}mod.rs",
7106 relative_prefix, mod_name, path::MAIN_SEPARATOR);
7107 let default_path = dir_path.join(&default_path_str);
7108 let secondary_path = dir_path.join(&secondary_path_str);
7109 let default_exists = source_map.file_exists(&default_path);
7110 let secondary_exists = source_map.file_exists(&secondary_path);
7112 let result = match (default_exists, secondary_exists) {
7113 (true, false) => Ok(ModulePathSuccess {
7115 directory_ownership: DirectoryOwnership::Owned {
7120 (false, true) => Ok(ModulePathSuccess {
7121 path: secondary_path,
7122 directory_ownership: DirectoryOwnership::Owned {
7127 (false, false) => Err(Error::FileNotFoundForModule {
7128 mod_name: mod_name.clone(),
7129 default_path: default_path_str,
7130 secondary_path: secondary_path_str,
7131 dir_path: dir_path.display().to_string(),
7133 (true, true) => Err(Error::DuplicatePaths {
7134 mod_name: mod_name.clone(),
7135 default_path: default_path_str,
7136 secondary_path: secondary_path_str,
7142 path_exists: default_exists || secondary_exists,
7147 fn submod_path(&mut self,
7149 outer_attrs: &[Attribute],
7151 -> PResult<'a, ModulePathSuccess> {
7152 if let Some(path) = Parser::submod_path_from_attr(outer_attrs, &self.directory.path) {
7153 return Ok(ModulePathSuccess {
7154 directory_ownership: match path.file_name().and_then(|s| s.to_str()) {
7155 // All `#[path]` files are treated as though they are a `mod.rs` file.
7156 // This means that `mod foo;` declarations inside `#[path]`-included
7157 // files are siblings,
7159 // Note that this will produce weirdness when a file named `foo.rs` is
7160 // `#[path]` included and contains a `mod foo;` declaration.
7161 // If you encounter this, it's your own darn fault :P
7162 Some(_) => DirectoryOwnership::Owned { relative: None },
7163 _ => DirectoryOwnership::UnownedViaMod(true),
7170 let relative = match self.directory.ownership {
7171 DirectoryOwnership::Owned { relative } => relative,
7172 DirectoryOwnership::UnownedViaBlock |
7173 DirectoryOwnership::UnownedViaMod(_) => None,
7175 let paths = Parser::default_submod_path(
7176 id, relative, &self.directory.path, self.sess.source_map());
7178 match self.directory.ownership {
7179 DirectoryOwnership::Owned { .. } => {
7180 paths.result.map_err(|err| self.span_fatal_err(id_sp, err))
7182 DirectoryOwnership::UnownedViaBlock => {
7184 "Cannot declare a non-inline module inside a block \
7185 unless it has a path attribute";
7186 let mut err = self.diagnostic().struct_span_err(id_sp, msg);
7187 if paths.path_exists {
7188 let msg = format!("Maybe `use` the module `{}` instead of redeclaring it",
7190 err.span_note(id_sp, &msg);
7194 DirectoryOwnership::UnownedViaMod(warn) => {
7196 if let Ok(result) = paths.result {
7197 return Ok(ModulePathSuccess { warn: true, ..result });
7200 let mut err = self.diagnostic().struct_span_err(id_sp,
7201 "cannot declare a new module at this location");
7202 if !id_sp.is_dummy() {
7203 let src_path = self.sess.source_map().span_to_filename(id_sp);
7204 if let FileName::Real(src_path) = src_path {
7205 if let Some(stem) = src_path.file_stem() {
7206 let mut dest_path = src_path.clone();
7207 dest_path.set_file_name(stem);
7208 dest_path.push("mod.rs");
7209 err.span_note(id_sp,
7210 &format!("maybe move this module `{}` to its own \
7211 directory via `{}`", src_path.display(),
7212 dest_path.display()));
7216 if paths.path_exists {
7217 err.span_note(id_sp,
7218 &format!("... or maybe `use` the module `{}` instead \
7219 of possibly redeclaring it",
7227 /// Reads a module from a source file.
7228 fn eval_src_mod(&mut self,
7230 directory_ownership: DirectoryOwnership,
7233 -> PResult<'a, (ast::Mod, Vec<Attribute> )> {
7234 let mut included_mod_stack = self.sess.included_mod_stack.borrow_mut();
7235 if let Some(i) = included_mod_stack.iter().position(|p| *p == path) {
7236 let mut err = String::from("circular modules: ");
7237 let len = included_mod_stack.len();
7238 for p in &included_mod_stack[i.. len] {
7239 err.push_str(&p.to_string_lossy());
7240 err.push_str(" -> ");
7242 err.push_str(&path.to_string_lossy());
7243 return Err(self.span_fatal(id_sp, &err[..]));
7245 included_mod_stack.push(path.clone());
7246 drop(included_mod_stack);
7249 new_sub_parser_from_file(self.sess, &path, directory_ownership, Some(name), id_sp);
7250 p0.cfg_mods = self.cfg_mods;
7251 let mod_inner_lo = p0.span;
7252 let mod_attrs = p0.parse_inner_attributes()?;
7253 let mut m0 = p0.parse_mod_items(&token::Eof, mod_inner_lo)?;
7255 self.sess.included_mod_stack.borrow_mut().pop();
7259 /// Parses a function declaration from a foreign module.
7260 fn parse_item_foreign_fn(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7261 -> PResult<'a, ForeignItem> {
7262 self.expect_keyword(kw::Fn)?;
7264 let (ident, mut generics) = self.parse_fn_header()?;
7265 let decl = self.parse_fn_decl(true)?;
7266 generics.where_clause = self.parse_where_clause()?;
7268 self.expect(&token::Semi)?;
7269 Ok(ast::ForeignItem {
7272 node: ForeignItemKind::Fn(decl, generics),
7273 id: ast::DUMMY_NODE_ID,
7279 /// Parses a static item from a foreign module.
7280 /// Assumes that the `static` keyword is already parsed.
7281 fn parse_item_foreign_static(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7282 -> PResult<'a, ForeignItem> {
7283 let mutbl = self.parse_mutability();
7284 let ident = self.parse_ident()?;
7285 self.expect(&token::Colon)?;
7286 let ty = self.parse_ty()?;
7288 self.expect(&token::Semi)?;
7292 node: ForeignItemKind::Static(ty, mutbl),
7293 id: ast::DUMMY_NODE_ID,
7299 /// Parses a type from a foreign module.
7300 fn parse_item_foreign_type(&mut self, vis: ast::Visibility, lo: Span, attrs: Vec<Attribute>)
7301 -> PResult<'a, ForeignItem> {
7302 self.expect_keyword(kw::Type)?;
7304 let ident = self.parse_ident()?;
7306 self.expect(&token::Semi)?;
7307 Ok(ast::ForeignItem {
7310 node: ForeignItemKind::Ty,
7311 id: ast::DUMMY_NODE_ID,
7317 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
7318 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
7319 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
7321 let mut ident = if self.token.is_keyword(kw::SelfLower) {
7322 self.parse_path_segment_ident()
7326 let mut idents = vec![];
7327 let mut replacement = vec![];
7328 let mut fixed_crate_name = false;
7329 // Accept `extern crate name-like-this` for better diagnostics
7330 let dash = token::Token::BinOp(token::BinOpToken::Minus);
7331 if self.token == dash { // Do not include `-` as part of the expected tokens list
7332 while self.eat(&dash) {
7333 fixed_crate_name = true;
7334 replacement.push((self.prev_span, "_".to_string()));
7335 idents.push(self.parse_ident()?);
7338 if fixed_crate_name {
7339 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
7340 let mut fixed_name = format!("{}", ident.name);
7341 for part in idents {
7342 fixed_name.push_str(&format!("_{}", part.name));
7344 ident = Ident::from_str(&fixed_name).with_span_pos(fixed_name_sp);
7346 let mut err = self.struct_span_err(fixed_name_sp, error_msg);
7347 err.span_label(fixed_name_sp, "dash-separated idents are not valid");
7348 err.multipart_suggestion(
7351 Applicability::MachineApplicable,
7358 /// Parses `extern crate` links.
7363 /// extern crate foo;
7364 /// extern crate bar as foo;
7366 fn parse_item_extern_crate(&mut self,
7368 visibility: Visibility,
7369 attrs: Vec<Attribute>)
7370 -> PResult<'a, P<Item>> {
7371 // Accept `extern crate name-like-this` for better diagnostics
7372 let orig_name = self.parse_crate_name_with_dashes()?;
7373 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
7374 (rename, Some(orig_name.name))
7378 self.expect(&token::Semi)?;
7380 let span = lo.to(self.prev_span);
7381 Ok(self.mk_item(span, item_name, ItemKind::ExternCrate(orig_name), visibility, attrs))
7384 /// Parses `extern` for foreign ABIs modules.
7386 /// `extern` is expected to have been
7387 /// consumed before calling this method.
7391 /// ```ignore (only-for-syntax-highlight)
7395 fn parse_item_foreign_mod(&mut self,
7397 opt_abi: Option<Abi>,
7398 visibility: Visibility,
7399 mut attrs: Vec<Attribute>)
7400 -> PResult<'a, P<Item>> {
7401 self.expect(&token::OpenDelim(token::Brace))?;
7403 let abi = opt_abi.unwrap_or(Abi::C);
7405 attrs.extend(self.parse_inner_attributes()?);
7407 let mut foreign_items = vec![];
7408 while !self.eat(&token::CloseDelim(token::Brace)) {
7409 foreign_items.push(self.parse_foreign_item()?);
7412 let prev_span = self.prev_span;
7413 let m = ast::ForeignMod {
7415 items: foreign_items
7417 let invalid = Ident::with_empty_ctxt(kw::Invalid);
7418 Ok(self.mk_item(lo.to(prev_span), invalid, ItemKind::ForeignMod(m), visibility, attrs))
7421 /// Parses `type Foo = Bar;`
7423 /// `existential type Foo: Bar;`
7426 /// without modifying the parser state.
7427 fn eat_type(&mut self) -> Option<PResult<'a, (Ident, AliasKind, ast::Generics)>> {
7428 // This parses the grammar:
7429 // Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
7430 if self.check_keyword(kw::Type) ||
7431 self.check_keyword(kw::Existential) &&
7432 self.look_ahead(1, |t| t.is_keyword(kw::Type)) {
7433 let existential = self.eat_keyword(kw::Existential);
7434 assert!(self.eat_keyword(kw::Type));
7435 Some(self.parse_existential_or_alias(existential))
7441 /// Parses a type alias or existential type.
7442 fn parse_existential_or_alias(
7445 ) -> PResult<'a, (Ident, AliasKind, ast::Generics)> {
7446 let ident = self.parse_ident()?;
7447 let mut tps = self.parse_generics()?;
7448 tps.where_clause = self.parse_where_clause()?;
7449 let alias = if existential {
7450 self.expect(&token::Colon)?;
7451 let bounds = self.parse_generic_bounds(Some(self.prev_span))?;
7452 AliasKind::Existential(bounds)
7454 self.expect(&token::Eq)?;
7455 let ty = self.parse_ty()?;
7458 self.expect(&token::Semi)?;
7459 Ok((ident, alias, tps))
7462 /// Parses the part of an enum declaration following the `{`.
7463 fn parse_enum_def(&mut self, _generics: &ast::Generics) -> PResult<'a, EnumDef> {
7464 let mut variants = Vec::new();
7465 let mut all_nullary = true;
7466 let mut any_disr = vec![];
7467 while self.token != token::CloseDelim(token::Brace) {
7468 let variant_attrs = self.parse_outer_attributes()?;
7469 let vlo = self.span;
7472 let mut disr_expr = None;
7474 let ident = self.parse_ident()?;
7475 if self.check(&token::OpenDelim(token::Brace)) {
7476 // Parse a struct variant.
7477 all_nullary = false;
7478 let (fields, recovered) = self.parse_record_struct_body()?;
7479 struct_def = VariantData::Struct(fields, recovered);
7480 } else if self.check(&token::OpenDelim(token::Paren)) {
7481 all_nullary = false;
7482 struct_def = VariantData::Tuple(
7483 self.parse_tuple_struct_body()?,
7486 } else if self.eat(&token::Eq) {
7487 disr_expr = Some(AnonConst {
7488 id: ast::DUMMY_NODE_ID,
7489 value: self.parse_expr()?,
7491 if let Some(sp) = disr_expr.as_ref().map(|c| c.value.span) {
7494 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7496 struct_def = VariantData::Unit(ast::DUMMY_NODE_ID);
7499 let vr = ast::Variant_ {
7501 id: ast::DUMMY_NODE_ID,
7502 attrs: variant_attrs,
7506 variants.push(respan(vlo.to(self.prev_span), vr));
7508 if !self.eat(&token::Comma) {
7509 if self.token.is_ident() && !self.token.is_reserved_ident() {
7510 let sp = self.sess.source_map().next_point(self.prev_span);
7511 let mut err = self.struct_span_err(sp, "missing comma");
7512 err.span_suggestion_short(
7516 Applicability::MaybeIncorrect,
7524 self.expect(&token::CloseDelim(token::Brace))?;
7525 if !any_disr.is_empty() && !all_nullary {
7526 let mut err = self.struct_span_err(
7528 "discriminator values can only be used with a field-less enum",
7530 for sp in any_disr {
7531 err.span_label(sp, "only valid in field-less enums");
7536 Ok(ast::EnumDef { variants })
7539 /// Parses an enum declaration.
7540 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
7541 let id = self.parse_ident()?;
7542 let mut generics = self.parse_generics()?;
7543 generics.where_clause = self.parse_where_clause()?;
7544 self.expect(&token::OpenDelim(token::Brace))?;
7546 let enum_definition = self.parse_enum_def(&generics).map_err(|e| {
7547 self.recover_stmt();
7548 self.eat(&token::CloseDelim(token::Brace));
7551 Ok((id, ItemKind::Enum(enum_definition, generics), None))
7554 /// Parses a string as an ABI spec on an extern type or module. Consumes
7555 /// the `extern` keyword, if one is found.
7556 fn parse_opt_abi(&mut self) -> PResult<'a, Option<Abi>> {
7558 token::Literal(token::Str_(s), suf) | token::Literal(token::StrRaw(s, _), suf) => {
7560 self.expect_no_suffix(sp, "an ABI spec", suf);
7562 match abi::lookup(&s.as_str()) {
7563 Some(abi) => Ok(Some(abi)),
7565 let prev_span = self.prev_span;
7566 let mut err = struct_span_err!(
7567 self.sess.span_diagnostic,
7570 "invalid ABI: found `{}`",
7572 err.span_label(prev_span, "invalid ABI");
7573 err.help(&format!("valid ABIs: {}", abi::all_names().join(", ")));
7584 fn is_static_global(&mut self) -> bool {
7585 if self.check_keyword(kw::Static) {
7586 // Check if this could be a closure
7587 !self.look_ahead(1, |token| {
7588 if token.is_keyword(kw::Move) {
7592 token::BinOp(token::Or) | token::OrOr => true,
7603 attrs: Vec<Attribute>,
7604 macros_allowed: bool,
7605 attributes_allowed: bool,
7606 ) -> PResult<'a, Option<P<Item>>> {
7607 let mut unclosed_delims = vec![];
7608 let (ret, tokens) = self.collect_tokens(|this| {
7609 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
7610 unclosed_delims.append(&mut this.unclosed_delims);
7613 self.unclosed_delims.append(&mut unclosed_delims);
7615 // Once we've parsed an item and recorded the tokens we got while
7616 // parsing we may want to store `tokens` into the item we're about to
7617 // return. Note, though, that we specifically didn't capture tokens
7618 // related to outer attributes. The `tokens` field here may later be
7619 // used with procedural macros to convert this item back into a token
7620 // stream, but during expansion we may be removing attributes as we go
7623 // If we've got inner attributes then the `tokens` we've got above holds
7624 // these inner attributes. If an inner attribute is expanded we won't
7625 // actually remove it from the token stream, so we'll just keep yielding
7626 // it (bad!). To work around this case for now we just avoid recording
7627 // `tokens` if we detect any inner attributes. This should help keep
7628 // expansion correct, but we should fix this bug one day!
7631 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
7632 i.tokens = Some(tokens);
7639 /// Parses one of the items allowed by the flags.
7640 fn parse_item_implementation(
7642 attrs: Vec<Attribute>,
7643 macros_allowed: bool,
7644 attributes_allowed: bool,
7645 ) -> PResult<'a, Option<P<Item>>> {
7646 maybe_whole!(self, NtItem, |item| {
7647 let mut item = item.into_inner();
7648 let mut attrs = attrs;
7649 mem::swap(&mut item.attrs, &mut attrs);
7650 item.attrs.extend(attrs);
7656 let visibility = self.parse_visibility(false)?;
7658 if self.eat_keyword(kw::Use) {
7660 let item_ = ItemKind::Use(P(self.parse_use_tree()?));
7661 self.expect(&token::Semi)?;
7663 let span = lo.to(self.prev_span);
7665 self.mk_item(span, Ident::with_empty_ctxt(kw::Invalid), item_, visibility, attrs);
7666 return Ok(Some(item));
7669 if self.eat_keyword(kw::Extern) {
7670 if self.eat_keyword(kw::Crate) {
7671 return Ok(Some(self.parse_item_extern_crate(lo, visibility, attrs)?));
7674 let opt_abi = self.parse_opt_abi()?;
7676 if self.eat_keyword(kw::Fn) {
7677 // EXTERN FUNCTION ITEM
7678 let fn_span = self.prev_span;
7679 let abi = opt_abi.unwrap_or(Abi::C);
7680 let (ident, item_, extra_attrs) =
7681 self.parse_item_fn(Unsafety::Normal,
7682 respan(fn_span, IsAsync::NotAsync),
7683 respan(fn_span, Constness::NotConst),
7685 let prev_span = self.prev_span;
7686 let item = self.mk_item(lo.to(prev_span),
7690 maybe_append(attrs, extra_attrs));
7691 return Ok(Some(item));
7692 } else if self.check(&token::OpenDelim(token::Brace)) {
7693 return Ok(Some(self.parse_item_foreign_mod(lo, opt_abi, visibility, attrs)?));
7699 if self.is_static_global() {
7702 let m = if self.eat_keyword(kw::Mut) {
7705 Mutability::Immutable
7707 let (ident, item_, extra_attrs) = self.parse_item_const(Some(m))?;
7708 let prev_span = self.prev_span;
7709 let item = self.mk_item(lo.to(prev_span),
7713 maybe_append(attrs, extra_attrs));
7714 return Ok(Some(item));
7716 if self.eat_keyword(kw::Const) {
7717 let const_span = self.prev_span;
7718 if self.check_keyword(kw::Fn)
7719 || (self.check_keyword(kw::Unsafe)
7720 && self.look_ahead(1, |t| t.is_keyword(kw::Fn))) {
7721 // CONST FUNCTION ITEM
7722 let unsafety = self.parse_unsafety();
7724 let (ident, item_, extra_attrs) =
7725 self.parse_item_fn(unsafety,
7726 respan(const_span, IsAsync::NotAsync),
7727 respan(const_span, Constness::Const),
7729 let prev_span = self.prev_span;
7730 let item = self.mk_item(lo.to(prev_span),
7734 maybe_append(attrs, extra_attrs));
7735 return Ok(Some(item));
7739 if self.eat_keyword(kw::Mut) {
7740 let prev_span = self.prev_span;
7741 let mut err = self.diagnostic()
7742 .struct_span_err(prev_span, "const globals cannot be mutable");
7743 err.span_label(prev_span, "cannot be mutable");
7744 err.span_suggestion(
7746 "you might want to declare a static instead",
7747 "static".to_owned(),
7748 Applicability::MaybeIncorrect,
7752 let (ident, item_, extra_attrs) = self.parse_item_const(None)?;
7753 let prev_span = self.prev_span;
7754 let item = self.mk_item(lo.to(prev_span),
7758 maybe_append(attrs, extra_attrs));
7759 return Ok(Some(item));
7762 // `unsafe async fn` or `async fn`
7764 self.check_keyword(kw::Unsafe) &&
7765 self.look_ahead(1, |t| t.is_keyword(kw::Async))
7767 self.check_keyword(kw::Async) &&
7768 self.look_ahead(1, |t| t.is_keyword(kw::Fn))
7771 // ASYNC FUNCTION ITEM
7772 let unsafety = self.parse_unsafety();
7773 self.expect_keyword(kw::Async)?;
7774 let async_span = self.prev_span;
7775 self.expect_keyword(kw::Fn)?;
7776 let fn_span = self.prev_span;
7777 let (ident, item_, extra_attrs) =
7778 self.parse_item_fn(unsafety,
7779 respan(async_span, IsAsync::Async {
7780 closure_id: ast::DUMMY_NODE_ID,
7781 return_impl_trait_id: ast::DUMMY_NODE_ID,
7782 arguments: Vec::new(),
7784 respan(fn_span, Constness::NotConst),
7786 let prev_span = self.prev_span;
7787 let item = self.mk_item(lo.to(prev_span),
7791 maybe_append(attrs, extra_attrs));
7792 if self.span.rust_2015() {
7793 self.diagnostic().struct_span_err_with_code(
7795 "`async fn` is not permitted in the 2015 edition",
7796 DiagnosticId::Error("E0670".into())
7799 return Ok(Some(item));
7801 if self.check_keyword(kw::Unsafe) &&
7802 (self.look_ahead(1, |t| t.is_keyword(kw::Trait)) ||
7803 self.look_ahead(1, |t| t.is_keyword(kw::Auto)))
7805 // UNSAFE TRAIT ITEM
7806 self.bump(); // `unsafe`
7807 let is_auto = if self.eat_keyword(kw::Trait) {
7810 self.expect_keyword(kw::Auto)?;
7811 self.expect_keyword(kw::Trait)?;
7814 let (ident, item_, extra_attrs) =
7815 self.parse_item_trait(is_auto, Unsafety::Unsafe)?;
7816 let prev_span = self.prev_span;
7817 let item = self.mk_item(lo.to(prev_span),
7821 maybe_append(attrs, extra_attrs));
7822 return Ok(Some(item));
7824 if self.check_keyword(kw::Impl) ||
7825 self.check_keyword(kw::Unsafe) &&
7826 self.look_ahead(1, |t| t.is_keyword(kw::Impl)) ||
7827 self.check_keyword(kw::Default) &&
7828 self.look_ahead(1, |t| t.is_keyword(kw::Impl)) ||
7829 self.check_keyword(kw::Default) &&
7830 self.look_ahead(1, |t| t.is_keyword(kw::Unsafe)) {
7832 let defaultness = self.parse_defaultness();
7833 let unsafety = self.parse_unsafety();
7834 self.expect_keyword(kw::Impl)?;
7835 let (ident, item, extra_attrs) = self.parse_item_impl(unsafety, defaultness)?;
7836 let span = lo.to(self.prev_span);
7837 return Ok(Some(self.mk_item(span, ident, item, visibility,
7838 maybe_append(attrs, extra_attrs))));
7840 if self.check_keyword(kw::Fn) {
7843 let fn_span = self.prev_span;
7844 let (ident, item_, extra_attrs) =
7845 self.parse_item_fn(Unsafety::Normal,
7846 respan(fn_span, IsAsync::NotAsync),
7847 respan(fn_span, Constness::NotConst),
7849 let prev_span = self.prev_span;
7850 let item = self.mk_item(lo.to(prev_span),
7854 maybe_append(attrs, extra_attrs));
7855 return Ok(Some(item));
7857 if self.check_keyword(kw::Unsafe)
7858 && self.look_ahead(1, |t| *t != token::OpenDelim(token::Brace)) {
7859 // UNSAFE FUNCTION ITEM
7860 self.bump(); // `unsafe`
7861 // `{` is also expected after `unsafe`, in case of error, include it in the diagnostic
7862 self.check(&token::OpenDelim(token::Brace));
7863 let abi = if self.eat_keyword(kw::Extern) {
7864 self.parse_opt_abi()?.unwrap_or(Abi::C)
7868 self.expect_keyword(kw::Fn)?;
7869 let fn_span = self.prev_span;
7870 let (ident, item_, extra_attrs) =
7871 self.parse_item_fn(Unsafety::Unsafe,
7872 respan(fn_span, IsAsync::NotAsync),
7873 respan(fn_span, Constness::NotConst),
7875 let prev_span = self.prev_span;
7876 let item = self.mk_item(lo.to(prev_span),
7880 maybe_append(attrs, extra_attrs));
7881 return Ok(Some(item));
7883 if self.eat_keyword(kw::Mod) {
7885 let (ident, item_, extra_attrs) =
7886 self.parse_item_mod(&attrs[..])?;
7887 let prev_span = self.prev_span;
7888 let item = self.mk_item(lo.to(prev_span),
7892 maybe_append(attrs, extra_attrs));
7893 return Ok(Some(item));
7895 if let Some(type_) = self.eat_type() {
7896 let (ident, alias, generics) = type_?;
7898 let item_ = match alias {
7899 AliasKind::Weak(ty) => ItemKind::Ty(ty, generics),
7900 AliasKind::Existential(bounds) => ItemKind::Existential(bounds, generics),
7902 let prev_span = self.prev_span;
7903 let item = self.mk_item(lo.to(prev_span),
7908 return Ok(Some(item));
7910 if self.eat_keyword(kw::Enum) {
7912 let (ident, item_, extra_attrs) = self.parse_item_enum()?;
7913 let prev_span = self.prev_span;
7914 let item = self.mk_item(lo.to(prev_span),
7918 maybe_append(attrs, extra_attrs));
7919 return Ok(Some(item));
7921 if self.check_keyword(kw::Trait)
7922 || (self.check_keyword(kw::Auto)
7923 && self.look_ahead(1, |t| t.is_keyword(kw::Trait)))
7925 let is_auto = if self.eat_keyword(kw::Trait) {
7928 self.expect_keyword(kw::Auto)?;
7929 self.expect_keyword(kw::Trait)?;
7933 let (ident, item_, extra_attrs) =
7934 self.parse_item_trait(is_auto, Unsafety::Normal)?;
7935 let prev_span = self.prev_span;
7936 let item = self.mk_item(lo.to(prev_span),
7940 maybe_append(attrs, extra_attrs));
7941 return Ok(Some(item));
7943 if self.eat_keyword(kw::Struct) {
7945 let (ident, item_, extra_attrs) = self.parse_item_struct()?;
7946 let prev_span = self.prev_span;
7947 let item = self.mk_item(lo.to(prev_span),
7951 maybe_append(attrs, extra_attrs));
7952 return Ok(Some(item));
7954 if self.is_union_item() {
7957 let (ident, item_, extra_attrs) = self.parse_item_union()?;
7958 let prev_span = self.prev_span;
7959 let item = self.mk_item(lo.to(prev_span),
7963 maybe_append(attrs, extra_attrs));
7964 return Ok(Some(item));
7966 if let Some(macro_def) = self.eat_macro_def(&attrs, &visibility, lo)? {
7967 return Ok(Some(macro_def));
7970 // Verify whether we have encountered a struct or method definition where the user forgot to
7971 // add the `struct` or `fn` keyword after writing `pub`: `pub S {}`
7972 if visibility.node.is_pub() &&
7973 self.check_ident() &&
7974 self.look_ahead(1, |t| *t != token::Not)
7976 // Space between `pub` keyword and the identifier
7979 // ^^^ `sp` points here
7980 let sp = self.prev_span.between(self.span);
7981 let full_sp = self.prev_span.to(self.span);
7982 let ident_sp = self.span;
7983 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
7984 // possible public struct definition where `struct` was forgotten
7985 let ident = self.parse_ident().unwrap();
7986 let msg = format!("add `struct` here to parse `{}` as a public struct",
7988 let mut err = self.diagnostic()
7989 .struct_span_err(sp, "missing `struct` for struct definition");
7990 err.span_suggestion_short(
7991 sp, &msg, " struct ".into(), Applicability::MaybeIncorrect // speculative
7994 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
7995 let ident = self.parse_ident().unwrap();
7997 let kw_name = if let Ok(Some(_)) = self.parse_self_arg() {
8002 self.consume_block(token::Paren);
8003 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
8004 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
8006 ("fn", kw_name, false)
8007 } else if self.check(&token::OpenDelim(token::Brace)) {
8009 ("fn", kw_name, false)
8010 } else if self.check(&token::Colon) {
8014 ("fn` or `struct", "function or struct", true)
8017 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8018 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8020 self.consume_block(token::Brace);
8021 let suggestion = format!("add `{}` here to parse `{}` as a public {}",
8025 err.span_suggestion_short(
8026 sp, &suggestion, format!(" {} ", kw), Applicability::MachineApplicable
8029 if let Ok(snippet) = self.sess.source_map().span_to_snippet(ident_sp) {
8030 err.span_suggestion(
8032 "if you meant to call a macro, try",
8033 format!("{}!", snippet),
8034 // this is the `ambiguous` conditional branch
8035 Applicability::MaybeIncorrect
8038 err.help("if you meant to call a macro, remove the `pub` \
8039 and add a trailing `!` after the identifier");
8043 } else if self.look_ahead(1, |t| *t == token::Lt) {
8044 let ident = self.parse_ident().unwrap();
8045 self.eat_to_tokens(&[&token::Gt]);
8047 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
8048 if let Ok(Some(_)) = self.parse_self_arg() {
8049 ("fn", "method", false)
8051 ("fn", "function", false)
8053 } else if self.check(&token::OpenDelim(token::Brace)) {
8054 ("struct", "struct", false)
8056 ("fn` or `struct", "function or struct", true)
8058 let msg = format!("missing `{}` for {} definition", kw, kw_name);
8059 let mut err = self.diagnostic().struct_span_err(sp, &msg);
8061 err.span_suggestion_short(
8063 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
8064 format!(" {} ", kw),
8065 Applicability::MachineApplicable,
8071 self.parse_macro_use_or_failure(attrs, macros_allowed, attributes_allowed, lo, visibility)
8074 /// Parses a foreign item.
8075 crate fn parse_foreign_item(&mut self) -> PResult<'a, ForeignItem> {
8076 maybe_whole!(self, NtForeignItem, |ni| ni);
8078 let attrs = self.parse_outer_attributes()?;
8080 let visibility = self.parse_visibility(false)?;
8082 // FOREIGN STATIC ITEM
8083 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
8084 if self.check_keyword(kw::Static) || self.token.is_keyword(kw::Const) {
8085 if self.token.is_keyword(kw::Const) {
8087 .struct_span_err(self.span, "extern items cannot be `const`")
8090 "try using a static value",
8091 "static".to_owned(),
8092 Applicability::MachineApplicable
8095 self.bump(); // `static` or `const`
8096 return Ok(self.parse_item_foreign_static(visibility, lo, attrs)?);
8098 // FOREIGN FUNCTION ITEM
8099 if self.check_keyword(kw::Fn) {
8100 return Ok(self.parse_item_foreign_fn(visibility, lo, attrs)?);
8102 // FOREIGN TYPE ITEM
8103 if self.check_keyword(kw::Type) {
8104 return Ok(self.parse_item_foreign_type(visibility, lo, attrs)?);
8107 match self.parse_assoc_macro_invoc("extern", Some(&visibility), &mut false)? {
8111 ident: Ident::with_empty_ctxt(kw::Invalid),
8112 span: lo.to(self.prev_span),
8113 id: ast::DUMMY_NODE_ID,
8116 node: ForeignItemKind::Macro(mac),
8121 if !attrs.is_empty() {
8122 self.expected_item_err(&attrs)?;
8130 /// This is the fall-through for parsing items.
8131 fn parse_macro_use_or_failure(
8133 attrs: Vec<Attribute> ,
8134 macros_allowed: bool,
8135 attributes_allowed: bool,
8137 visibility: Visibility
8138 ) -> PResult<'a, Option<P<Item>>> {
8139 if macros_allowed && self.token.is_path_start() &&
8140 !(self.is_async_fn() && self.span.rust_2015()) {
8141 // MACRO INVOCATION ITEM
8143 let prev_span = self.prev_span;
8144 self.complain_if_pub_macro(&visibility.node, prev_span);
8146 let mac_lo = self.span;
8149 let pth = self.parse_path(PathStyle::Mod)?;
8150 self.expect(&token::Not)?;
8152 // a 'special' identifier (like what `macro_rules!` uses)
8153 // is optional. We should eventually unify invoc syntax
8155 let id = if self.token.is_ident() {
8158 Ident::with_empty_ctxt(kw::Invalid) // no special identifier
8160 // eat a matched-delimiter token tree:
8161 let (delim, tts) = self.expect_delimited_token_tree()?;
8162 if delim != MacDelimiter::Brace && !self.eat(&token::Semi) {
8163 self.report_invalid_macro_expansion_item();
8166 let hi = self.prev_span;
8167 let mac = respan(mac_lo.to(hi), Mac_ { path: pth, tts, delim });
8168 let item = self.mk_item(lo.to(hi), id, ItemKind::Mac(mac), visibility, attrs);
8169 return Ok(Some(item));
8172 // FAILURE TO PARSE ITEM
8173 match visibility.node {
8174 VisibilityKind::Inherited => {}
8176 return Err(self.span_fatal(self.prev_span, "unmatched visibility `pub`"));
8180 if !attributes_allowed && !attrs.is_empty() {
8181 self.expected_item_err(&attrs)?;
8186 /// Parses a macro invocation inside a `trait`, `impl` or `extern` block.
8187 fn parse_assoc_macro_invoc(&mut self, item_kind: &str, vis: Option<&Visibility>,
8188 at_end: &mut bool) -> PResult<'a, Option<Mac>>
8190 if self.token.is_path_start() &&
8191 !(self.is_async_fn() && self.span.rust_2015()) {
8192 let prev_span = self.prev_span;
8194 let pth = self.parse_path(PathStyle::Mod)?;
8196 if pth.segments.len() == 1 {
8197 if !self.eat(&token::Not) {
8198 return Err(self.missing_assoc_item_kind_err(item_kind, prev_span));
8201 self.expect(&token::Not)?;
8204 if let Some(vis) = vis {
8205 self.complain_if_pub_macro(&vis.node, prev_span);
8210 // eat a matched-delimiter token tree:
8211 let (delim, tts) = self.expect_delimited_token_tree()?;
8212 if delim != MacDelimiter::Brace {
8213 self.expect(&token::Semi)?;
8216 Ok(Some(respan(lo.to(self.prev_span), Mac_ { path: pth, tts, delim })))
8222 fn collect_tokens<F, R>(&mut self, f: F) -> PResult<'a, (R, TokenStream)>
8223 where F: FnOnce(&mut Self) -> PResult<'a, R>
8225 // Record all tokens we parse when parsing this item.
8226 let mut tokens = Vec::new();
8227 let prev_collecting = match self.token_cursor.frame.last_token {
8228 LastToken::Collecting(ref mut list) => {
8229 Some(mem::replace(list, Vec::new()))
8231 LastToken::Was(ref mut last) => {
8232 tokens.extend(last.take());
8236 self.token_cursor.frame.last_token = LastToken::Collecting(tokens);
8237 let prev = self.token_cursor.stack.len();
8239 let last_token = if self.token_cursor.stack.len() == prev {
8240 &mut self.token_cursor.frame.last_token
8242 &mut self.token_cursor.stack[prev].last_token
8245 // Pull out the tokens that we've collected from the call to `f` above.
8246 let mut collected_tokens = match *last_token {
8247 LastToken::Collecting(ref mut v) => mem::replace(v, Vec::new()),
8248 LastToken::Was(_) => panic!("our vector went away?"),
8251 // If we're not at EOF our current token wasn't actually consumed by
8252 // `f`, but it'll still be in our list that we pulled out. In that case
8254 let extra_token = if self.token != token::Eof {
8255 collected_tokens.pop()
8260 // If we were previously collecting tokens, then this was a recursive
8261 // call. In that case we need to record all the tokens we collected in
8262 // our parent list as well. To do that we push a clone of our stream
8263 // onto the previous list.
8264 match prev_collecting {
8266 list.extend(collected_tokens.iter().cloned());
8267 list.extend(extra_token);
8268 *last_token = LastToken::Collecting(list);
8271 *last_token = LastToken::Was(extra_token);
8275 Ok((ret?, TokenStream::new(collected_tokens)))
8278 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
8279 let attrs = self.parse_outer_attributes()?;
8280 self.parse_item_(attrs, true, false)
8284 fn is_import_coupler(&mut self) -> bool {
8285 self.check(&token::ModSep) &&
8286 self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace) ||
8287 *t == token::BinOp(token::Star))
8290 /// Parses a `UseTree`.
8293 /// USE_TREE = [`::`] `*` |
8294 /// [`::`] `{` USE_TREE_LIST `}` |
8296 /// PATH `::` `{` USE_TREE_LIST `}` |
8297 /// PATH [`as` IDENT]
8299 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
8302 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
8303 let kind = if self.check(&token::OpenDelim(token::Brace)) ||
8304 self.check(&token::BinOp(token::Star)) ||
8305 self.is_import_coupler() {
8306 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
8307 let mod_sep_ctxt = self.span.ctxt();
8308 if self.eat(&token::ModSep) {
8309 prefix.segments.push(
8310 PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt))
8314 if self.eat(&token::BinOp(token::Star)) {
8317 UseTreeKind::Nested(self.parse_use_tree_list()?)
8320 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
8321 prefix = self.parse_path(PathStyle::Mod)?;
8323 if self.eat(&token::ModSep) {
8324 if self.eat(&token::BinOp(token::Star)) {
8327 UseTreeKind::Nested(self.parse_use_tree_list()?)
8330 UseTreeKind::Simple(self.parse_rename()?, ast::DUMMY_NODE_ID, ast::DUMMY_NODE_ID)
8334 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
8337 /// Parses a `UseTreeKind::Nested(list)`.
8340 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
8342 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
8343 self.parse_unspanned_seq(&token::OpenDelim(token::Brace),
8344 &token::CloseDelim(token::Brace),
8345 SeqSep::trailing_allowed(token::Comma), |this| {
8346 Ok((this.parse_use_tree()?, ast::DUMMY_NODE_ID))
8350 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
8351 if self.eat_keyword(kw::As) {
8352 self.parse_ident_or_underscore().map(Some)
8358 /// Parses a source module as a crate. This is the main entry point for the parser.
8359 pub fn parse_crate_mod(&mut self) -> PResult<'a, Crate> {
8361 let krate = Ok(ast::Crate {
8362 attrs: self.parse_inner_attributes()?,
8363 module: self.parse_mod_items(&token::Eof, lo)?,
8364 span: lo.to(self.span),
8369 pub fn parse_optional_str(&mut self) -> Option<(Symbol, ast::StrStyle, Option<ast::Name>)> {
8370 let ret = match self.token {
8371 token::Literal(token::Str_(s), suf) => (s, ast::StrStyle::Cooked, suf),
8372 token::Literal(token::StrRaw(s, n), suf) => (s, ast::StrStyle::Raw(n), suf),
8379 pub fn parse_str(&mut self) -> PResult<'a, (Symbol, StrStyle)> {
8380 match self.parse_optional_str() {
8381 Some((s, style, suf)) => {
8382 let sp = self.prev_span;
8383 self.expect_no_suffix(sp, "a string literal", suf);
8387 let msg = "expected string literal";
8388 let mut err = self.fatal(msg);
8389 err.span_label(self.span, msg);
8395 fn report_invalid_macro_expansion_item(&self) {
8396 self.struct_span_err(
8398 "macros that expand to items must be delimited with braces or followed by a semicolon",
8399 ).multipart_suggestion(
8400 "change the delimiters to curly braces",
8402 (self.prev_span.with_hi(self.prev_span.lo() + BytePos(1)), String::from(" {")),
8403 (self.prev_span.with_lo(self.prev_span.hi() - BytePos(1)), '}'.to_string()),
8405 Applicability::MaybeIncorrect,
8407 self.sess.source_map.next_point(self.prev_span),
8410 Applicability::MaybeIncorrect,
8414 /// When lowering a `async fn` to the HIR, we need to move all of the arguments of the function
8415 /// into the generated closure so that they are dropped when the future is polled and not when
8418 /// The arguments of the function are replaced in HIR lowering with the arguments created by
8419 /// this function and the statements created here are inserted at the top of the closure body.
8420 fn construct_async_arguments(&mut self, asyncness: &mut Spanned<IsAsync>, decl: &mut FnDecl) {
8421 // FIXME(davidtwco): This function should really live in the HIR lowering but because
8422 // the types constructed here need to be used in parts of resolve so that the correct
8423 // locals are considered upvars, it is currently easier for it to live here in the parser,
8424 // where it can be constructed once.
8425 if let IsAsync::Async { ref mut arguments, .. } = asyncness.node {
8426 for (index, input) in decl.inputs.iter_mut().enumerate() {
8427 let id = ast::DUMMY_NODE_ID;
8428 let span = input.pat.span;
8430 // Construct a name for our temporary argument.
8431 let name = format!("__arg{}", index);
8432 let ident = Ident::from_str(&name).gensym();
8434 // Check if this is a ident pattern, if so, we can optimize and avoid adding a
8435 // `let <pat> = __argN;` statement, instead just adding a `let <pat> = <pat>;`
8437 let (binding_mode, ident, is_simple_pattern) = match input.pat.node {
8438 PatKind::Ident(binding_mode @ BindingMode::ByValue(_), ident, _) => {
8439 // Simple patterns like this don't have a generated argument, but they are
8440 // moved into the closure with a statement, so any `mut` bindings on the
8441 // argument will be unused. This binding mode can't be removed, because
8442 // this would affect the input to procedural macros, but they can have
8443 // their span marked as being the result of a compiler desugaring so
8444 // that they aren't linted against.
8445 input.pat.span = self.sess.source_map().mark_span_with_reason(
8446 CompilerDesugaringKind::Async, span, None);
8448 (binding_mode, ident, true)
8450 _ => (BindingMode::ByValue(Mutability::Mutable), ident, false),
8453 // Construct an argument representing `__argN: <ty>` to replace the argument of the
8454 // async function if it isn't a simple pattern.
8455 let arg = if is_simple_pattern {
8459 ty: input.ty.clone(),
8463 node: PatKind::Ident(
8464 BindingMode::ByValue(Mutability::Immutable), ident, None,
8468 source: ArgSource::AsyncFn(input.pat.clone()),
8472 // Construct a `let __argN = __argN;` statement to insert at the top of the
8473 // async closure. This makes sure that the argument is captured by the closure and
8474 // that the drop order is correct.
8475 let move_local = Local {
8478 node: PatKind::Ident(binding_mode, ident, None),
8481 // We explicitly do not specify the type for this statement. When the user's
8482 // argument type is `impl Trait` then this would require the
8483 // `impl_trait_in_bindings` feature to also be present for that same type to
8484 // be valid in this binding. At the time of writing (13 Mar 19),
8485 // `impl_trait_in_bindings` is not stable.
8489 node: ExprKind::Path(None, ast::Path {
8491 segments: vec![PathSegment { ident, id, args: None }],
8494 attrs: ThinVec::new(),
8498 attrs: ThinVec::new(),
8499 source: LocalSource::AsyncFn,
8502 // Construct a `let <pat> = __argN;` statement to insert at the top of the
8503 // async closure if this isn't a simple pattern.
8504 let pat_stmt = if is_simple_pattern {
8509 node: StmtKind::Local(P(Local {
8510 pat: input.pat.clone(),
8511 ..move_local.clone()
8517 let move_stmt = Stmt { id, node: StmtKind::Local(P(move_local)), span };
8518 arguments.push(AsyncArgument { ident, arg, pat_stmt, move_stmt });
8524 pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, handler: &errors::Handler) {
8525 for unmatched in unclosed_delims.iter() {
8526 let mut err = handler.struct_span_err(unmatched.found_span, &format!(
8527 "incorrect close delimiter: `{}`",
8528 pprust::token_to_string(&token::Token::CloseDelim(unmatched.found_delim)),
8530 err.span_label(unmatched.found_span, "incorrect close delimiter");
8531 if let Some(sp) = unmatched.candidate_span {
8532 err.span_label(sp, "close delimiter possibly meant for this");
8534 if let Some(sp) = unmatched.unclosed_span {
8535 err.span_label(sp, "un-closed delimiter");
8539 unclosed_delims.clear();