1 use super::diagnostics::{dummy_arg, ConsumeClosingDelim, Error};
2 use super::ty::{AllowPlus, RecoverQPath, RecoverReturnSign};
3 use super::{AttrWrapper, FollowedByType, ForceCollect, Parser, PathStyle, TrailingToken};
7 use rustc_ast::token::{self, TokenKind};
8 use rustc_ast::tokenstream::{DelimSpan, TokenStream, TokenTree};
9 use rustc_ast::{self as ast, AttrVec, Attribute, DUMMY_NODE_ID};
10 use rustc_ast::{Async, Const, Defaultness, IsAuto, Mutability, Unsafe, UseTree, UseTreeKind};
11 use rustc_ast::{BindingMode, Block, FnDecl, FnSig, Param, SelfKind};
12 use rustc_ast::{EnumDef, FieldDef, Generics, TraitRef, Ty, TyKind, Variant, VariantData};
13 use rustc_ast::{FnHeader, ForeignItem, Path, PathSegment, Visibility, VisibilityKind};
14 use rustc_ast::{MacArgs, MacCall, MacDelimiter};
15 use rustc_ast_pretty::pprust;
16 use rustc_errors::{struct_span_err, Applicability, PResult, StashKey};
17 use rustc_span::edition::Edition;
18 use rustc_span::lev_distance::lev_distance;
19 use rustc_span::source_map::{self, Span};
20 use rustc_span::symbol::{kw, sym, Ident, Symbol};
21 use rustc_span::DUMMY_SP;
23 use std::convert::TryFrom;
28 /// Parses a source module as a crate. This is the main entry point for the parser.
29 pub fn parse_crate_mod(&mut self) -> PResult<'a, ast::Crate> {
30 let (attrs, items, spans) = self.parse_mod(&token::Eof)?;
31 Ok(ast::Crate { attrs, items, spans, id: DUMMY_NODE_ID, is_placeholder: false })
34 /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
35 fn parse_item_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
36 let unsafety = self.parse_unsafety();
37 self.expect_keyword(kw::Mod)?;
38 let id = self.parse_ident()?;
39 let mod_kind = if self.eat(&token::Semi) {
42 self.expect(&token::OpenDelim(token::Brace))?;
43 let (mut inner_attrs, items, inner_span) =
44 self.parse_mod(&token::CloseDelim(token::Brace))?;
45 attrs.append(&mut inner_attrs);
46 ModKind::Loaded(items, Inline::Yes, inner_span)
48 Ok((id, ItemKind::Mod(unsafety, mod_kind)))
51 /// Parses the contents of a module (inner attributes followed by module items).
55 ) -> PResult<'a, (Vec<Attribute>, Vec<P<Item>>, ModSpans)> {
56 let lo = self.token.span;
57 let attrs = self.parse_inner_attributes()?;
59 let post_attr_lo = self.token.span;
60 let mut items = vec![];
61 while let Some(item) = self.parse_item(ForceCollect::No)? {
63 self.maybe_consume_incorrect_semicolon(&items);
67 let token_str = super::token_descr(&self.token);
68 if !self.maybe_consume_incorrect_semicolon(&items) {
69 let msg = &format!("expected item, found {token_str}");
70 let mut err = self.struct_span_err(self.token.span, msg);
71 err.span_label(self.token.span, "expected item");
76 let inject_use_span = post_attr_lo.data().with_hi(post_attr_lo.lo());
77 let mod_spans = ModSpans { inner_span: lo.to(self.prev_token.span), inject_use_span };
78 Ok((attrs, items, mod_spans))
82 pub(super) type ItemInfo = (Ident, ItemKind);
85 pub fn parse_item(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<P<Item>>> {
86 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
87 self.parse_item_(fn_parse_mode, force_collect).map(|i| i.map(P))
92 fn_parse_mode: FnParseMode,
93 force_collect: ForceCollect,
94 ) -> PResult<'a, Option<Item>> {
95 let attrs = self.parse_outer_attributes()?;
96 self.parse_item_common(attrs, true, false, fn_parse_mode, force_collect)
99 pub(super) fn parse_item_common(
104 fn_parse_mode: FnParseMode,
105 force_collect: ForceCollect,
106 ) -> PResult<'a, Option<Item>> {
107 // Don't use `maybe_whole` so that we have precise control
108 // over when we bump the parser
109 if let token::Interpolated(nt) = &self.token.kind && let token::NtItem(item) = &**nt {
110 let mut item = item.clone();
113 attrs.prepend_to_nt_inner(&mut item.attrs);
114 return Ok(Some(item.into_inner()));
117 let mut unclosed_delims = vec![];
119 self.collect_tokens_trailing_token(attrs, force_collect, |this: &mut Self, attrs| {
121 this.parse_item_common_(attrs, mac_allowed, attrs_allowed, fn_parse_mode);
122 unclosed_delims.append(&mut this.unclosed_delims);
123 Ok((item?, TrailingToken::None))
126 self.unclosed_delims.append(&mut unclosed_delims);
130 fn parse_item_common_(
132 mut attrs: Vec<Attribute>,
135 fn_parse_mode: FnParseMode,
136 ) -> PResult<'a, Option<Item>> {
137 let lo = self.token.span;
138 let vis = self.parse_visibility(FollowedByType::No)?;
139 let mut def = self.parse_defaultness();
141 self.parse_item_kind(&mut attrs, mac_allowed, lo, &vis, &mut def, fn_parse_mode)?;
142 if let Some((ident, kind)) = kind {
143 self.error_on_unconsumed_default(def, &kind);
144 let span = lo.to(self.prev_token.span);
145 let id = DUMMY_NODE_ID;
146 let item = Item { ident, attrs, id, kind, vis, span, tokens: None };
147 return Ok(Some(item));
150 // At this point, we have failed to parse an item.
151 self.error_on_unmatched_vis(&vis);
152 self.error_on_unmatched_defaultness(def);
154 self.recover_attrs_no_item(&attrs)?;
159 /// Error in-case a non-inherited visibility was parsed but no item followed.
160 fn error_on_unmatched_vis(&self, vis: &Visibility) {
161 if let VisibilityKind::Inherited = vis.kind {
164 let vs = pprust::vis_to_string(&vis);
165 let vs = vs.trim_end();
166 self.struct_span_err(vis.span, &format!("visibility `{vs}` is not followed by an item"))
167 .span_label(vis.span, "the visibility")
168 .help(&format!("you likely meant to define an item, e.g., `{vs} fn foo() {{}}`"))
172 /// Error in-case a `default` was parsed but no item followed.
173 fn error_on_unmatched_defaultness(&self, def: Defaultness) {
174 if let Defaultness::Default(sp) = def {
175 self.struct_span_err(sp, "`default` is not followed by an item")
176 .span_label(sp, "the `default` qualifier")
177 .note("only `fn`, `const`, `type`, or `impl` items may be prefixed by `default`")
182 /// Error in-case `default` was parsed in an in-appropriate context.
183 fn error_on_unconsumed_default(&self, def: Defaultness, kind: &ItemKind) {
184 if let Defaultness::Default(span) = def {
185 let msg = format!("{} {} cannot be `default`", kind.article(), kind.descr());
186 self.struct_span_err(span, &msg)
187 .span_label(span, "`default` because of this")
188 .note("only associated `fn`, `const`, and `type` items can be `default`")
193 /// Parses one of the items allowed by the flags.
196 attrs: &mut Vec<Attribute>,
197 macros_allowed: bool,
200 def: &mut Defaultness,
201 fn_parse_mode: FnParseMode,
202 ) -> PResult<'a, Option<ItemInfo>> {
203 let def_final = def == &Defaultness::Final;
204 let mut def = || mem::replace(def, Defaultness::Final);
206 let info = if self.eat_keyword(kw::Use) {
208 let tree = self.parse_use_tree()?;
210 // If wildcard or glob-like brace syntax doesn't have `;`,
211 // the user may not know `*` or `{}` should be the last.
212 if let Err(mut e) = self.expect_semi() {
214 UseTreeKind::Glob => {
215 e.note("the wildcard token must be last on the path");
217 UseTreeKind::Nested(..) => {
218 e.note("glob-like brace syntax must be last on the path");
225 (Ident::empty(), ItemKind::Use(tree))
226 } else if self.check_fn_front_matter(def_final) {
228 let (ident, sig, generics, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis)?;
229 (ident, ItemKind::Fn(Box::new(Fn { defaultness: def(), sig, generics, body })))
230 } else if self.eat_keyword(kw::Extern) {
231 if self.eat_keyword(kw::Crate) {
233 self.parse_item_extern_crate()?
236 self.parse_item_foreign_mod(attrs, Unsafe::No)?
238 } else if self.is_unsafe_foreign_mod() {
240 let unsafety = self.parse_unsafety();
241 self.expect_keyword(kw::Extern)?;
242 self.parse_item_foreign_mod(attrs, unsafety)?
243 } else if self.is_static_global() {
245 self.bump(); // `static`
246 let m = self.parse_mutability();
247 let (ident, ty, expr) = self.parse_item_global(Some(m))?;
248 (ident, ItemKind::Static(ty, m, expr))
249 } else if let Const::Yes(const_span) = self.parse_constness() {
251 if self.token.is_keyword(kw::Impl) {
252 // recover from `const impl`, suggest `impl const`
253 self.recover_const_impl(const_span, attrs, def())?
255 self.recover_const_mut(const_span);
256 let (ident, ty, expr) = self.parse_item_global(None)?;
257 (ident, ItemKind::Const(def(), ty, expr))
259 } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
261 self.parse_item_trait(attrs, lo)?
262 } else if self.check_keyword(kw::Impl)
263 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
266 self.parse_item_impl(attrs, def())?
267 } else if self.check_keyword(kw::Mod)
268 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
271 self.parse_item_mod(attrs)?
272 } else if self.eat_keyword(kw::Type) {
274 self.parse_type_alias(def())?
275 } else if self.eat_keyword(kw::Enum) {
277 self.parse_item_enum()?
278 } else if self.eat_keyword(kw::Struct) {
280 self.parse_item_struct()?
281 } else if self.is_kw_followed_by_ident(kw::Union) {
283 self.bump(); // `union`
284 self.parse_item_union()?
285 } else if self.eat_keyword(kw::Macro) {
287 self.parse_item_decl_macro(lo)?
288 } else if let IsMacroRulesItem::Yes { has_bang } = self.is_macro_rules_item() {
290 self.parse_item_macro_rules(vis, has_bang)?
291 } else if vis.kind.is_pub() && self.isnt_macro_invocation() {
292 self.recover_missing_kw_before_item()?;
294 } else if macros_allowed && self.check_path() {
295 // MACRO INVOCATION ITEM
296 (Ident::empty(), ItemKind::MacCall(self.parse_item_macro(vis)?))
303 /// When parsing a statement, would the start of a path be an item?
304 pub(super) fn is_path_start_item(&mut self) -> bool {
305 self.is_crate_vis() // no: `crate::b`, yes: `crate $item`
306 || self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
307 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
308 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
309 || matches!(self.is_macro_rules_item(), IsMacroRulesItem::Yes{..}) // no: `macro_rules::b`, yes: `macro_rules! mac`
312 /// Are we sure this could not possibly be a macro invocation?
313 fn isnt_macro_invocation(&mut self) -> bool {
314 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
317 /// Recover on encountering a struct or method definition where the user
318 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
319 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
320 // Space between `pub` keyword and the identifier
323 // ^^^ `sp` points here
324 let sp = self.prev_token.span.between(self.token.span);
325 let full_sp = self.prev_token.span.to(self.token.span);
326 let ident_sp = self.token.span;
327 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
328 // possible public struct definition where `struct` was forgotten
329 let ident = self.parse_ident().unwrap();
330 let msg = format!("add `struct` here to parse `{ident}` as a public struct");
331 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
332 err.span_suggestion_short(
336 Applicability::MaybeIncorrect, // speculative
339 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
340 let ident = self.parse_ident().unwrap();
342 let kw_name = self.recover_first_param();
343 self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
344 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
345 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
347 ("fn", kw_name, false)
348 } else if self.check(&token::OpenDelim(token::Brace)) {
350 ("fn", kw_name, false)
351 } else if self.check(&token::Colon) {
355 ("fn` or `struct", "function or struct", true)
358 let msg = format!("missing `{kw}` for {kw_name} definition");
359 let mut err = self.struct_span_err(sp, &msg);
361 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
363 format!("add `{kw}` here to parse `{ident}` as a public {kw_name}");
364 err.span_suggestion_short(
368 Applicability::MachineApplicable,
370 } else if let Ok(snippet) = self.span_to_snippet(ident_sp) {
373 "if you meant to call a macro, try",
374 format!("{}!", snippet),
375 // this is the `ambiguous` conditional branch
376 Applicability::MaybeIncorrect,
380 "if you meant to call a macro, remove the `pub` \
381 and add a trailing `!` after the identifier",
385 } else if self.look_ahead(1, |t| *t == token::Lt) {
386 let ident = self.parse_ident().unwrap();
387 self.eat_to_tokens(&[&token::Gt]);
389 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
390 ("fn", self.recover_first_param(), false)
391 } else if self.check(&token::OpenDelim(token::Brace)) {
392 ("struct", "struct", false)
394 ("fn` or `struct", "function or struct", true)
396 let msg = format!("missing `{kw}` for {kw_name} definition");
397 let mut err = self.struct_span_err(sp, &msg);
399 err.span_suggestion_short(
401 &format!("add `{kw}` here to parse `{ident}` as a public {kw_name}"),
403 Applicability::MachineApplicable,
412 /// Parses an item macro, e.g., `item!();`.
413 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, MacCall> {
414 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
415 self.expect(&token::Not)?; // `!`
416 match self.parse_mac_args() {
417 // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
419 self.eat_semi_for_macro_if_needed(&args);
420 self.complain_if_pub_macro(vis, false);
421 Ok(MacCall { path, args, prior_type_ascription: self.last_type_ascription })
425 // Maybe the user misspelled `macro_rules` (issue #91227)
426 if self.token.is_ident()
427 && path.segments.len() == 1
428 && lev_distance("macro_rules", &path.segments[0].ident.to_string(), 3).is_some()
432 "perhaps you meant to define a macro",
433 "macro_rules".to_string(),
434 Applicability::MachineApplicable,
442 /// Recover if we parsed attributes and expected an item but there was none.
443 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
444 let ([start @ end] | [start, .., end]) = attrs else {
447 let msg = if end.is_doc_comment() {
448 "expected item after doc comment"
450 "expected item after attributes"
452 let mut err = self.struct_span_err(end.span, msg);
453 if end.is_doc_comment() {
454 err.span_label(end.span, "this doc comment doesn't document anything");
456 if end.meta_kind().is_some() {
457 if self.token.kind == TokenKind::Semi {
458 err.span_suggestion_verbose(
460 "consider removing this semicolon",
462 Applicability::MaybeIncorrect,
466 if let [.., penultimate, _] = attrs {
467 err.span_label(start.span.to(penultimate.span), "other attributes here");
472 fn is_async_fn(&self) -> bool {
473 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
476 fn parse_polarity(&mut self) -> ast::ImplPolarity {
477 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
478 if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
480 ast::ImplPolarity::Negative(self.prev_token.span)
482 ast::ImplPolarity::Positive
486 /// Parses an implementation item.
489 /// impl<'a, T> TYPE { /* impl items */ }
490 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
491 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
492 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
495 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
497 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
498 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
502 attrs: &mut Vec<Attribute>,
503 defaultness: Defaultness,
504 ) -> PResult<'a, ItemInfo> {
505 let unsafety = self.parse_unsafety();
506 self.expect_keyword(kw::Impl)?;
508 // First, parse generic parameters if necessary.
509 let mut generics = if self.choose_generics_over_qpath(0) {
510 self.parse_generics()?
512 let mut generics = Generics::default();
514 // /\ this is where `generics.span` should point when there are no type params.
515 generics.span = self.prev_token.span.shrink_to_hi();
519 let constness = self.parse_constness();
520 if let Const::Yes(span) = constness {
521 self.sess.gated_spans.gate(sym::const_trait_impl, span);
524 let polarity = self.parse_polarity();
526 // Parse both types and traits as a type, then reinterpret if necessary.
527 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Empty, span));
528 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
530 let span = self.prev_token.span.between(self.token.span);
531 self.struct_span_err(span, "missing trait in a trait impl")
536 Applicability::HasPlaceholders,
539 span.to(self.token.span),
540 "for an inherent impl, drop this `for`",
542 Applicability::MaybeIncorrect,
546 kind: TyKind::Path(None, err_path(span)),
552 self.parse_ty_with_generics_recovery(&generics)?
555 // If `for` is missing we try to recover.
556 let has_for = self.eat_keyword(kw::For);
557 let missing_for_span = self.prev_token.span.between(self.token.span);
559 let ty_second = if self.token == token::DotDot {
560 // We need to report this error after `cfg` expansion for compatibility reasons
561 self.bump(); // `..`, do not add it to expected tokens
562 Some(self.mk_ty(self.prev_token.span, TyKind::Err))
563 } else if has_for || self.token.can_begin_type() {
564 Some(self.parse_ty()?)
569 generics.where_clause = self.parse_where_clause()?;
571 let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
573 let item_kind = match ty_second {
575 // impl Trait for Type
577 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
578 .span_suggestion_short(
582 Applicability::MachineApplicable,
587 let ty_first = ty_first.into_inner();
588 let path = match ty_first.kind {
589 // This notably includes paths passed through `ty` macro fragments (#46438).
590 TyKind::Path(None, path) => path,
592 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
593 err_path(ty_first.span)
596 let trait_ref = TraitRef { path, ref_id: ty_first.id };
598 ItemKind::Impl(Box::new(Impl {
604 of_trait: Some(trait_ref),
611 ItemKind::Impl(Box::new(Impl {
624 Ok((Ident::empty(), item_kind))
627 fn parse_item_list<T>(
629 attrs: &mut Vec<Attribute>,
630 mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
631 ) -> PResult<'a, Vec<T>> {
632 let open_brace_span = self.token.span;
633 self.expect(&token::OpenDelim(token::Brace))?;
634 attrs.append(&mut self.parse_inner_attributes()?);
636 let mut items = Vec::new();
637 while !self.eat(&token::CloseDelim(token::Brace)) {
638 if self.recover_doc_comment_before_brace() {
641 match parse_item(self) {
643 // We have to bail or we'll potentially never make progress.
644 let non_item_span = self.token.span;
645 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
646 self.struct_span_err(non_item_span, "non-item in item list")
647 .span_label(open_brace_span, "item list starts here")
648 .span_label(non_item_span, "non-item starts here")
649 .span_label(self.prev_token.span, "item list ends here")
653 Ok(Some(item)) => items.extend(item),
655 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
656 err.span_label(open_brace_span, "while parsing this item list starting here")
657 .span_label(self.prev_token.span, "the item list ends here")
666 /// Recover on a doc comment before `}`.
667 fn recover_doc_comment_before_brace(&mut self) -> bool {
668 if let token::DocComment(..) = self.token.kind {
669 if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
674 "found a documentation comment that doesn't document anything",
676 .span_label(self.token.span, "this doc comment doesn't document anything")
678 "doc comments must come before what they document, maybe a \
679 comment was intended with `//`?",
689 /// Parses defaultness (i.e., `default` or nothing).
690 fn parse_defaultness(&mut self) -> Defaultness {
691 // We are interested in `default` followed by another identifier.
692 // However, we must avoid keywords that occur as binary operators.
693 // Currently, the only applicable keyword is `as` (`default as Ty`).
694 if self.check_keyword(kw::Default)
695 && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
697 self.bump(); // `default`
698 Defaultness::Default(self.prev_token.uninterpolated_span())
704 /// Is this an `(unsafe auto? | auto) trait` item?
705 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
707 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
709 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
712 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
713 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
714 let unsafety = self.parse_unsafety();
715 // Parse optional `auto` prefix.
716 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
718 self.expect_keyword(kw::Trait)?;
719 let ident = self.parse_ident()?;
720 let mut generics = self.parse_generics()?;
722 // Parse optional colon and supertrait bounds.
723 let had_colon = self.eat(&token::Colon);
724 let span_at_colon = self.prev_token.span;
725 let bounds = if had_colon {
726 self.parse_generic_bounds(Some(self.prev_token.span))?
731 let span_before_eq = self.prev_token.span;
732 if self.eat(&token::Eq) {
733 // It's a trait alias.
735 let span = span_at_colon.to(span_before_eq);
736 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
739 let bounds = self.parse_generic_bounds(None)?;
740 generics.where_clause = self.parse_where_clause()?;
743 let whole_span = lo.to(self.prev_token.span);
744 if is_auto == IsAuto::Yes {
745 let msg = "trait aliases cannot be `auto`";
746 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
748 if let Unsafe::Yes(_) = unsafety {
749 let msg = "trait aliases cannot be `unsafe`";
750 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
753 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
755 Ok((ident, ItemKind::TraitAlias(generics, bounds)))
757 // It's a normal trait.
758 generics.where_clause = self.parse_where_clause()?;
759 let items = self.parse_item_list(attrs, |p| p.parse_trait_item(ForceCollect::No))?;
762 ItemKind::Trait(Box::new(Trait { is_auto, unsafety, generics, bounds, items })),
767 pub fn parse_impl_item(
769 force_collect: ForceCollect,
770 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
771 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
772 self.parse_assoc_item(fn_parse_mode, force_collect)
775 pub fn parse_trait_item(
777 force_collect: ForceCollect,
778 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
780 FnParseMode { req_name: |edition| edition >= Edition::Edition2018, req_body: false };
781 self.parse_assoc_item(fn_parse_mode, force_collect)
784 /// Parses associated items.
787 fn_parse_mode: FnParseMode,
788 force_collect: ForceCollect,
789 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
790 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
791 |Item { attrs, id, span, vis, ident, kind, tokens }| {
792 let kind = match AssocItemKind::try_from(kind) {
794 Err(kind) => match kind {
795 ItemKind::Static(a, _, b) => {
796 self.struct_span_err(span, "associated `static` items are not allowed")
798 AssocItemKind::Const(Defaultness::Final, a, b)
800 _ => return self.error_bad_item_kind(span, &kind, "`trait`s or `impl`s"),
803 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
808 /// Parses a `type` alias with the following grammar:
810 /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
812 /// The `"type"` has already been eaten.
813 fn parse_type_alias(&mut self, defaultness: Defaultness) -> PResult<'a, ItemInfo> {
814 let ident = self.parse_ident()?;
815 let mut generics = self.parse_generics()?;
817 // Parse optional colon and param bounds.
819 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
820 let before_where_clause = self.parse_where_clause()?;
822 let ty = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
824 let after_where_clause = self.parse_where_clause()?;
826 let where_clauses = (
827 TyAliasWhereClause(before_where_clause.has_where_token, before_where_clause.span),
828 TyAliasWhereClause(after_where_clause.has_where_token, after_where_clause.span),
830 let where_predicates_split = before_where_clause.predicates.len();
831 let mut predicates = before_where_clause.predicates;
832 predicates.extend(after_where_clause.predicates.into_iter());
833 let where_clause = WhereClause {
834 has_where_token: before_where_clause.has_where_token
835 || after_where_clause.has_where_token,
839 generics.where_clause = where_clause;
845 ItemKind::TyAlias(Box::new(TyAlias {
849 where_predicates_split,
856 /// Parses a `UseTree`.
859 /// USE_TREE = [`::`] `*` |
860 /// [`::`] `{` USE_TREE_LIST `}` |
862 /// PATH `::` `{` USE_TREE_LIST `}` |
863 /// PATH [`as` IDENT]
865 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
866 let lo = self.token.span;
868 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo(), tokens: None };
869 let kind = if self.check(&token::OpenDelim(token::Brace))
870 || self.check(&token::BinOp(token::Star))
871 || self.is_import_coupler()
873 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
874 let mod_sep_ctxt = self.token.span.ctxt();
875 if self.eat(&token::ModSep) {
878 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
881 self.parse_use_tree_glob_or_nested()?
883 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
884 prefix = self.parse_path(PathStyle::Mod)?;
886 if self.eat(&token::ModSep) {
887 self.parse_use_tree_glob_or_nested()?
889 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
893 Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.span) })
896 /// Parses `*` or `{...}`.
897 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
898 Ok(if self.eat(&token::BinOp(token::Star)) {
901 UseTreeKind::Nested(self.parse_use_tree_list()?)
905 /// Parses a `UseTreeKind::Nested(list)`.
908 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
910 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
911 self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
915 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
916 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
919 fn parse_ident_or_underscore(&mut self) -> PResult<'a, Ident> {
920 match self.token.ident() {
921 Some((ident @ Ident { name: kw::Underscore, .. }, false)) => {
925 _ => self.parse_ident(),
929 /// Parses `extern crate` links.
934 /// extern crate foo;
935 /// extern crate bar as foo;
937 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
938 // Accept `extern crate name-like-this` for better diagnostics
939 let orig_name = self.parse_crate_name_with_dashes()?;
940 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
941 (rename, Some(orig_name.name))
946 Ok((item_name, ItemKind::ExternCrate(orig_name)))
949 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, Ident> {
950 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
951 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
953 let mut ident = if self.token.is_keyword(kw::SelfLower) {
954 self.parse_path_segment_ident()
958 let mut idents = vec![];
959 let mut replacement = vec![];
960 let mut fixed_crate_name = false;
961 // Accept `extern crate name-like-this` for better diagnostics.
962 let dash = token::BinOp(token::BinOpToken::Minus);
963 if self.token == dash {
964 // Do not include `-` as part of the expected tokens list.
965 while self.eat(&dash) {
966 fixed_crate_name = true;
967 replacement.push((self.prev_token.span, "_".to_string()));
968 idents.push(self.parse_ident()?);
971 if fixed_crate_name {
972 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
973 let mut fixed_name = format!("{}", ident.name);
975 fixed_name.push_str(&format!("_{}", part.name));
977 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
979 self.struct_span_err(fixed_name_sp, error_msg)
980 .span_label(fixed_name_sp, "dash-separated idents are not valid")
981 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
987 /// Parses `extern` for foreign ABIs modules.
989 /// `extern` is expected to have been consumed before calling this method.
993 /// ```ignore (only-for-syntax-highlight)
997 fn parse_item_foreign_mod(
999 attrs: &mut Vec<Attribute>,
1001 ) -> PResult<'a, ItemInfo> {
1002 let sp_start = self.prev_token.span;
1003 let abi = self.parse_abi(); // ABI?
1004 match self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No)) {
1006 let module = ast::ForeignMod { unsafety, abi, items };
1007 Ok((Ident::empty(), ItemKind::ForeignMod(module)))
1010 let current_qual_sp = self.prev_token.span;
1011 let current_qual_sp = current_qual_sp.to(sp_start);
1012 if let Ok(current_qual) = self.span_to_snippet(current_qual_sp) {
1013 if err.message() == "expected `{`, found keyword `unsafe`" {
1014 let invalid_qual_sp = self.token.uninterpolated_span();
1015 let invalid_qual = self.span_to_snippet(invalid_qual_sp).unwrap();
1017 err.span_suggestion(
1018 current_qual_sp.to(invalid_qual_sp),
1019 &format!("`{}` must come before `{}`", invalid_qual, current_qual),
1020 format!("{} {}", invalid_qual, current_qual),
1021 Applicability::MachineApplicable,
1022 ).note("keyword order for functions declaration is `default`, `pub`, `const`, `async`, `unsafe`, `extern`");
1030 /// Parses a foreign item (one in an `extern { ... }` block).
1031 pub fn parse_foreign_item(
1033 force_collect: ForceCollect,
1034 ) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
1035 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: false };
1036 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
1037 |Item { attrs, id, span, vis, ident, kind, tokens }| {
1038 let kind = match ForeignItemKind::try_from(kind) {
1040 Err(kind) => match kind {
1041 ItemKind::Const(_, a, b) => {
1042 self.error_on_foreign_const(span, ident);
1043 ForeignItemKind::Static(a, Mutability::Not, b)
1045 _ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
1048 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
1053 fn error_bad_item_kind<T>(&self, span: Span, kind: &ItemKind, ctx: &str) -> Option<T> {
1054 let span = self.sess.source_map().guess_head_span(span);
1055 let descr = kind.descr();
1056 self.struct_span_err(span, &format!("{descr} is not supported in {ctx}"))
1057 .help(&format!("consider moving the {descr} out to a nearby module scope"))
1062 fn error_on_foreign_const(&self, span: Span, ident: Ident) {
1063 self.struct_span_err(ident.span, "extern items cannot be `const`")
1065 span.with_hi(ident.span.lo()),
1066 "try using a static value",
1067 "static ".to_string(),
1068 Applicability::MachineApplicable,
1070 .note("for more information, visit https://doc.rust-lang.org/std/keyword.extern.html")
1074 fn is_unsafe_foreign_mod(&self) -> bool {
1075 self.token.is_keyword(kw::Unsafe)
1076 && self.is_keyword_ahead(1, &[kw::Extern])
1078 2 + self.look_ahead(2, |t| t.can_begin_literal_maybe_minus() as usize),
1079 |t| t.kind == token::OpenDelim(token::Brace),
1083 fn is_static_global(&mut self) -> bool {
1084 if self.check_keyword(kw::Static) {
1085 // Check if this could be a closure.
1086 !self.look_ahead(1, |token| {
1087 if token.is_keyword(kw::Move) {
1090 matches!(token.kind, token::BinOp(token::Or) | token::OrOr)
1097 /// Recover on `const mut` with `const` already eaten.
1098 fn recover_const_mut(&mut self, const_span: Span) {
1099 if self.eat_keyword(kw::Mut) {
1100 let span = self.prev_token.span;
1101 self.struct_span_err(span, "const globals cannot be mutable")
1102 .span_label(span, "cannot be mutable")
1105 "you might want to declare a static instead",
1106 "static".to_owned(),
1107 Applicability::MaybeIncorrect,
1113 /// Recover on `const impl` with `const` already eaten.
1114 fn recover_const_impl(
1117 attrs: &mut Vec<Attribute>,
1118 defaultness: Defaultness,
1119 ) -> PResult<'a, ItemInfo> {
1120 let impl_span = self.token.span;
1121 let mut err = self.expected_ident_found();
1123 // Only try to recover if this is implementing a trait for a type
1124 let mut impl_info = match self.parse_item_impl(attrs, defaultness) {
1125 Ok(impl_info) => impl_info,
1126 Err(recovery_error) => {
1127 // Recovery failed, raise the "expected identifier" error
1128 recovery_error.cancel();
1134 ItemKind::Impl(box Impl { of_trait: Some(ref trai), ref mut constness, .. }) => {
1135 *constness = Const::Yes(const_span);
1137 let before_trait = trai.path.span.shrink_to_lo();
1138 let const_up_to_impl = const_span.with_hi(impl_span.lo());
1139 err.multipart_suggestion(
1140 "you might have meant to write a const trait impl",
1141 vec![(const_up_to_impl, "".to_owned()), (before_trait, "const ".to_owned())],
1142 Applicability::MaybeIncorrect,
1146 ItemKind::Impl { .. } => return Err(err),
1147 _ => unreachable!(),
1153 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
1154 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
1156 /// When `m` is `"const"`, `$ident` may also be `"_"`.
1157 fn parse_item_global(
1159 m: Option<Mutability>,
1160 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
1161 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
1163 // Parse the type of a `const` or `static mut?` item.
1164 // That is, the `":" $ty` fragment.
1165 let ty = if self.eat(&token::Colon) {
1168 self.recover_missing_const_type(id, m)
1171 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
1172 self.expect_semi()?;
1176 /// We were supposed to parse `:` but the `:` was missing.
1177 /// This means that the type is missing.
1178 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
1179 // Construct the error and stash it away with the hope
1180 // that typeck will later enrich the error with a type.
1181 let kind = match m {
1182 Some(Mutability::Mut) => "static mut",
1183 Some(Mutability::Not) => "static",
1186 let mut err = self.struct_span_err(id.span, &format!("missing type for `{kind}` item"));
1187 err.span_suggestion(
1189 "provide a type for the item",
1190 format!("{id}: <type>"),
1191 Applicability::HasPlaceholders,
1193 err.stash(id.span, StashKey::ItemNoType);
1195 // The user intended that the type be inferred,
1196 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
1197 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID, tokens: None })
1200 /// Parses an enum declaration.
1201 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
1202 let id = self.parse_ident()?;
1203 let mut generics = self.parse_generics()?;
1204 generics.where_clause = self.parse_where_clause()?;
1207 self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
1208 self.recover_stmt();
1212 let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
1213 Ok((id, ItemKind::Enum(enum_definition, generics)))
1216 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
1217 let variant_attrs = self.parse_outer_attributes()?;
1218 self.collect_tokens_trailing_token(
1221 |this, variant_attrs| {
1222 let vlo = this.token.span;
1224 let vis = this.parse_visibility(FollowedByType::No)?;
1225 if !this.recover_nested_adt_item(kw::Enum)? {
1226 return Ok((None, TrailingToken::None));
1228 let ident = this.parse_field_ident("enum", vlo)?;
1230 let struct_def = if this.check(&token::OpenDelim(token::Brace)) {
1231 // Parse a struct variant.
1232 let (fields, recovered) = this.parse_record_struct_body("struct", false)?;
1233 VariantData::Struct(fields, recovered)
1234 } else if this.check(&token::OpenDelim(token::Paren)) {
1235 VariantData::Tuple(this.parse_tuple_struct_body()?, DUMMY_NODE_ID)
1237 VariantData::Unit(DUMMY_NODE_ID)
1241 if this.eat(&token::Eq) { Some(this.parse_anon_const_expr()?) } else { None };
1243 let vr = ast::Variant {
1247 attrs: variant_attrs.into(),
1250 span: vlo.to(this.prev_token.span),
1251 is_placeholder: false,
1254 Ok((Some(vr), TrailingToken::MaybeComma))
1259 /// Parses `struct Foo { ... }`.
1260 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1261 let class_name = self.parse_ident()?;
1263 let mut generics = self.parse_generics()?;
1265 // There is a special case worth noting here, as reported in issue #17904.
1266 // If we are parsing a tuple struct it is the case that the where clause
1267 // should follow the field list. Like so:
1269 // struct Foo<T>(T) where T: Copy;
1271 // If we are parsing a normal record-style struct it is the case
1272 // that the where clause comes before the body, and after the generics.
1273 // So if we look ahead and see a brace or a where-clause we begin
1274 // parsing a record style struct.
1276 // Otherwise if we look ahead and see a paren we parse a tuple-style
1279 let vdata = if self.token.is_keyword(kw::Where) {
1280 generics.where_clause = self.parse_where_clause()?;
1281 if self.eat(&token::Semi) {
1282 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1283 VariantData::Unit(DUMMY_NODE_ID)
1285 // If we see: `struct Foo<T> where T: Copy { ... }`
1286 let (fields, recovered) =
1287 self.parse_record_struct_body("struct", generics.where_clause.has_where_token)?;
1288 VariantData::Struct(fields, recovered)
1290 // No `where` so: `struct Foo<T>;`
1291 } else if self.eat(&token::Semi) {
1292 VariantData::Unit(DUMMY_NODE_ID)
1293 // Record-style struct definition
1294 } else if self.token == token::OpenDelim(token::Brace) {
1295 let (fields, recovered) =
1296 self.parse_record_struct_body("struct", generics.where_clause.has_where_token)?;
1297 VariantData::Struct(fields, recovered)
1298 // Tuple-style struct definition with optional where-clause.
1299 } else if self.token == token::OpenDelim(token::Paren) {
1300 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1301 generics.where_clause = self.parse_where_clause()?;
1302 self.expect_semi()?;
1305 let token_str = super::token_descr(&self.token);
1307 "expected `where`, `{{`, `(`, or `;` after struct name, found {token_str}"
1309 let mut err = self.struct_span_err(self.token.span, msg);
1310 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1314 Ok((class_name, ItemKind::Struct(vdata, generics)))
1317 /// Parses `union Foo { ... }`.
1318 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1319 let class_name = self.parse_ident()?;
1321 let mut generics = self.parse_generics()?;
1323 let vdata = if self.token.is_keyword(kw::Where) {
1324 generics.where_clause = self.parse_where_clause()?;
1325 let (fields, recovered) =
1326 self.parse_record_struct_body("union", generics.where_clause.has_where_token)?;
1327 VariantData::Struct(fields, recovered)
1328 } else if self.token == token::OpenDelim(token::Brace) {
1329 let (fields, recovered) =
1330 self.parse_record_struct_body("union", generics.where_clause.has_where_token)?;
1331 VariantData::Struct(fields, recovered)
1333 let token_str = super::token_descr(&self.token);
1334 let msg = &format!("expected `where` or `{{` after union name, found {token_str}");
1335 let mut err = self.struct_span_err(self.token.span, msg);
1336 err.span_label(self.token.span, "expected `where` or `{` after union name");
1340 Ok((class_name, ItemKind::Union(vdata, generics)))
1343 fn parse_record_struct_body(
1347 ) -> PResult<'a, (Vec<FieldDef>, /* recovered */ bool)> {
1348 let mut fields = Vec::new();
1349 let mut recovered = false;
1350 if self.eat(&token::OpenDelim(token::Brace)) {
1351 while self.token != token::CloseDelim(token::Brace) {
1352 let field = self.parse_field_def(adt_ty).map_err(|e| {
1353 self.consume_block(token::Brace, ConsumeClosingDelim::No);
1358 Ok(field) => fields.push(field),
1365 self.eat(&token::CloseDelim(token::Brace));
1367 let token_str = super::token_descr(&self.token);
1369 "expected {}`{{` after struct name, found {}",
1370 if parsed_where { "" } else { "`where`, or " },
1373 let mut err = self.struct_span_err(self.token.span, msg);
1377 "expected {}`{{` after struct name",
1378 if parsed_where { "" } else { "`where`, or " }
1384 Ok((fields, recovered))
1387 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<FieldDef>> {
1388 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1389 // Unit like structs are handled in parse_item_struct function
1390 self.parse_paren_comma_seq(|p| {
1391 let attrs = p.parse_outer_attributes()?;
1392 p.collect_tokens_trailing_token(attrs, ForceCollect::No, |p, attrs| {
1393 let lo = p.token.span;
1394 let vis = p.parse_visibility(FollowedByType::Yes)?;
1395 let ty = p.parse_ty()?;
1399 span: lo.to(ty.span),
1404 attrs: attrs.into(),
1405 is_placeholder: false,
1407 TrailingToken::MaybeComma,
1414 /// Parses an element of a struct declaration.
1415 fn parse_field_def(&mut self, adt_ty: &str) -> PResult<'a, FieldDef> {
1416 let attrs = self.parse_outer_attributes()?;
1417 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
1418 let lo = this.token.span;
1419 let vis = this.parse_visibility(FollowedByType::No)?;
1420 Ok((this.parse_single_struct_field(adt_ty, lo, vis, attrs)?, TrailingToken::None))
1424 /// Parses a structure field declaration.
1425 fn parse_single_struct_field(
1430 attrs: Vec<Attribute>,
1431 ) -> PResult<'a, FieldDef> {
1432 let mut seen_comma: bool = false;
1433 let a_var = self.parse_name_and_ty(adt_ty, lo, vis, attrs)?;
1434 if self.token == token::Comma {
1437 match self.token.kind {
1441 token::CloseDelim(token::Brace) => {}
1442 token::DocComment(..) => {
1443 let previous_span = self.prev_token.span;
1444 let mut err = self.span_err(self.token.span, Error::UselessDocComment);
1445 self.bump(); // consume the doc comment
1446 let comma_after_doc_seen = self.eat(&token::Comma);
1447 // `seen_comma` is always false, because we are inside doc block
1448 // condition is here to make code more readable
1449 if !seen_comma && comma_after_doc_seen {
1452 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
1456 let sp = self.sess.source_map().next_point(previous_span);
1457 err.span_suggestion(
1459 "missing comma here",
1461 Applicability::MachineApplicable,
1468 let sp = self.prev_token.span.shrink_to_hi();
1469 let mut err = self.struct_span_err(
1471 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1474 // Try to recover extra trailing angle brackets
1475 let mut recovered = false;
1476 if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
1477 if let Some(last_segment) = segments.last() {
1478 recovered = self.check_trailing_angle_brackets(
1480 &[&token::Comma, &token::CloseDelim(token::Brace)],
1483 // Handle a case like `Vec<u8>>,` where we can continue parsing fields
1485 self.eat(&token::Comma);
1486 // `check_trailing_angle_brackets` already emitted a nicer error
1487 // NOTE(eddyb) this was `.cancel()`, but `err`
1488 // gets returned, so we can't fully defuse it.
1494 if self.token.is_ident() {
1495 // This is likely another field; emit the diagnostic and keep going
1496 err.span_suggestion(
1498 "try adding a comma",
1500 Applicability::MachineApplicable,
1507 // Make sure an error was emitted (either by recovering an angle bracket,
1508 // or by finding an identifier as the next token), since we're
1509 // going to continue parsing
1510 assert!(self.sess.span_diagnostic.has_errors().is_some());
1519 fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
1520 if let Err(mut err) = self.expect(&token::Colon) {
1521 let sm = self.sess.source_map();
1522 let eq_typo = self.token.kind == token::Eq && self.look_ahead(1, |t| t.is_path_start());
1523 let semi_typo = self.token.kind == token::Semi
1524 && self.look_ahead(1, |t| {
1526 // We check that we are in a situation like `foo; bar` to avoid bad suggestions
1527 // when there's no type and `;` was used instead of a comma.
1528 && match (sm.lookup_line(self.token.span.hi()), sm.lookup_line(t.span.lo())) {
1529 (Ok(l), Ok(r)) => l.line == r.line,
1533 if eq_typo || semi_typo {
1535 // Gracefully handle small typos.
1536 err.span_suggestion_short(
1537 self.prev_token.span,
1538 "field names and their types are separated with `:`",
1540 Applicability::MachineApplicable,
1550 /// Parses a structure field.
1551 fn parse_name_and_ty(
1556 attrs: Vec<Attribute>,
1557 ) -> PResult<'a, FieldDef> {
1558 let name = self.parse_field_ident(adt_ty, lo)?;
1559 self.expect_field_ty_separator()?;
1560 let ty = self.parse_ty()?;
1561 if self.token.kind == token::Colon && self.look_ahead(1, |tok| tok.kind != token::Colon) {
1562 self.struct_span_err(self.token.span, "found single colon in a struct field type path")
1563 .span_suggestion_verbose(
1565 "write a path separator here",
1567 Applicability::MaybeIncorrect,
1571 if self.token.kind == token::Eq {
1573 let const_expr = self.parse_anon_const_expr()?;
1574 let sp = ty.span.shrink_to_hi().to(const_expr.value.span);
1575 self.struct_span_err(sp, "default values on `struct` fields aren't supported")
1578 "remove this unsupported default value",
1580 Applicability::MachineApplicable,
1585 span: lo.to(self.prev_token.span),
1590 attrs: attrs.into(),
1591 is_placeholder: false,
1595 /// Parses a field identifier. Specialized version of `parse_ident_common`
1596 /// for better diagnostics and suggestions.
1597 fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
1598 let (ident, is_raw) = self.ident_or_err()?;
1599 if !is_raw && ident.is_reserved() {
1600 let err = if self.check_fn_front_matter(false) {
1601 let inherited_vis = Visibility {
1602 span: rustc_span::DUMMY_SP,
1603 kind: VisibilityKind::Inherited,
1606 // We use `parse_fn` to get a span for the function
1607 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
1608 if let Err(mut db) =
1609 self.parse_fn(&mut Vec::new(), fn_parse_mode, lo, &inherited_vis)
1613 let mut err = self.struct_span_err(
1614 lo.to(self.prev_token.span),
1615 &format!("functions are not allowed in {adt_ty} definitions"),
1617 err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
1618 err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
1621 self.expected_ident_found()
1629 /// Parses a declarative macro 2.0 definition.
1630 /// The `macro` keyword has already been parsed.
1632 /// MacBody = "{" TOKEN_STREAM "}" ;
1633 /// MacParams = "(" TOKEN_STREAM ")" ;
1634 /// DeclMac = "macro" Ident MacParams? MacBody ;
1636 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1637 let ident = self.parse_ident()?;
1638 let body = if self.check(&token::OpenDelim(token::Brace)) {
1639 self.parse_mac_args()? // `MacBody`
1640 } else if self.check(&token::OpenDelim(token::Paren)) {
1641 let params = self.parse_token_tree(); // `MacParams`
1642 let pspan = params.span();
1643 if !self.check(&token::OpenDelim(token::Brace)) {
1644 return self.unexpected();
1646 let body = self.parse_token_tree(); // `MacBody`
1647 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1648 let bspan = body.span();
1649 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1650 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1651 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1652 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1654 return self.unexpected();
1657 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
1658 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: false })))
1661 /// Is this a possibly malformed start of a `macro_rules! foo` item definition?
1663 fn is_macro_rules_item(&mut self) -> IsMacroRulesItem {
1664 if self.check_keyword(kw::MacroRules) {
1665 let macro_rules_span = self.token.span;
1667 if self.look_ahead(1, |t| *t == token::Not) && self.look_ahead(2, |t| t.is_ident()) {
1668 return IsMacroRulesItem::Yes { has_bang: true };
1669 } else if self.look_ahead(1, |t| (t.is_ident())) {
1671 self.struct_span_err(macro_rules_span, "expected `!` after `macro_rules`")
1675 "macro_rules!".to_owned(),
1676 Applicability::MachineApplicable,
1680 return IsMacroRulesItem::Yes { has_bang: false };
1684 IsMacroRulesItem::No
1687 /// Parses a `macro_rules! foo { ... }` declarative macro.
1688 fn parse_item_macro_rules(
1692 ) -> PResult<'a, ItemInfo> {
1693 self.expect_keyword(kw::MacroRules)?; // `macro_rules`
1696 self.expect(&token::Not)?; // `!`
1698 let ident = self.parse_ident()?;
1700 if self.eat(&token::Not) {
1701 // Handle macro_rules! foo!
1702 let span = self.prev_token.span;
1703 self.struct_span_err(span, "macro names aren't followed by a `!`")
1708 Applicability::MachineApplicable,
1713 let body = self.parse_mac_args()?;
1714 self.eat_semi_for_macro_if_needed(&body);
1715 self.complain_if_pub_macro(vis, true);
1717 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: true })))
1720 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1721 /// If that's not the case, emit an error.
1722 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1723 if let VisibilityKind::Inherited = vis.kind {
1727 let vstr = pprust::vis_to_string(vis);
1728 let vstr = vstr.trim_end();
1730 let msg = format!("can't qualify macro_rules invocation with `{vstr}`");
1731 self.struct_span_err(vis.span, &msg)
1734 "try exporting the macro",
1735 "#[macro_export]".to_owned(),
1736 Applicability::MaybeIncorrect, // speculative
1740 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1743 "remove the visibility",
1745 Applicability::MachineApplicable,
1747 .help(&format!("try adjusting the macro to put `{vstr}` inside the invocation"))
1752 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1753 if args.need_semicolon() && !self.eat(&token::Semi) {
1754 self.report_invalid_macro_expansion_item(args);
1758 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1759 let span = args.span().expect("undelimited macro call");
1760 let mut err = self.struct_span_err(
1762 "macros that expand to items must be delimited with braces or followed by a semicolon",
1764 if self.unclosed_delims.is_empty() {
1765 let DelimSpan { open, close } = match args {
1766 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1767 MacArgs::Delimited(dspan, ..) => *dspan,
1769 err.multipart_suggestion(
1770 "change the delimiters to curly braces",
1771 vec![(open, "{".to_string()), (close, '}'.to_string())],
1772 Applicability::MaybeIncorrect,
1775 err.span_suggestion(
1777 "change the delimiters to curly braces",
1778 " { /* items */ }".to_string(),
1779 Applicability::HasPlaceholders,
1782 err.span_suggestion(
1783 span.shrink_to_hi(),
1786 Applicability::MaybeIncorrect,
1791 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1792 /// it is, we try to parse the item and report error about nested types.
1793 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1794 if (self.token.is_keyword(kw::Enum)
1795 || self.token.is_keyword(kw::Struct)
1796 || self.token.is_keyword(kw::Union))
1797 && self.look_ahead(1, |t| t.is_ident())
1799 let kw_token = self.token.clone();
1800 let kw_str = pprust::token_to_string(&kw_token);
1801 let item = self.parse_item(ForceCollect::No)?;
1803 self.struct_span_err(
1805 &format!("`{kw_str}` definition cannot be nested inside `{keyword}`"),
1809 &format!("consider creating a new `{kw_str}` definition instead of nesting"),
1811 Applicability::MaybeIncorrect,
1814 // We successfully parsed the item but we must inform the caller about nested problem.
1821 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1823 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1825 /// This function pointer accepts an edition, because in edition 2015, trait declarations
1826 /// were allowed to omit parameter names. In 2018, they became required.
1827 type ReqName = fn(Edition) -> bool;
1829 /// Parsing configuration for functions.
1831 /// The syntax of function items is slightly different within trait definitions,
1832 /// impl blocks, and modules. It is still parsed using the same code, just with
1833 /// different flags set, so that even when the input is wrong and produces a parse
1834 /// error, it still gets into the AST and the rest of the parser and
1835 /// type checker can run.
1836 #[derive(Clone, Copy)]
1837 pub(crate) struct FnParseMode {
1838 /// A function pointer that decides if, per-parameter `p`, `p` must have a
1839 /// pattern or just a type. This field affects parsing of the parameters list.
1842 /// fn foo(alef: A) -> X { X::new() }
1843 /// -----^^ affects parsing this part of the function signature
1845 /// if req_name returns false, then this name is optional
1850 /// if req_name returns true, this is an error
1853 /// Calling this function pointer should only return false if:
1855 /// * The item is being parsed inside of a trait definition.
1856 /// Within an impl block or a module, it should always evaluate
1858 /// * The span is from Edition 2015. In particular, you can get a
1859 /// 2015 span inside a 2021 crate using macros.
1860 pub req_name: ReqName,
1861 /// If this flag is set to `true`, then plain, semicolon-terminated function
1862 /// prototypes are not allowed here.
1865 /// fn foo(alef: A) -> X { X::new() }
1868 /// this is always allowed
1870 /// fn bar(alef: A, bet: B) -> X;
1873 /// if req_body is set to true, this is an error
1876 /// This field should only be set to false if the item is inside of a trait
1877 /// definition or extern block. Within an impl block or a module, it should
1878 /// always be set to true.
1882 /// Parsing of functions and methods.
1883 impl<'a> Parser<'a> {
1884 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1887 attrs: &mut Vec<Attribute>,
1888 fn_parse_mode: FnParseMode,
1891 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1892 let header = self.parse_fn_front_matter(vis)?; // `const ... fn`
1893 let ident = self.parse_ident()?; // `foo`
1894 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1896 self.parse_fn_decl(fn_parse_mode.req_name, AllowPlus::Yes, RecoverReturnSign::Yes)?; // `(p: u8, ...)`
1897 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1899 let mut sig_hi = self.prev_token.span;
1900 let body = self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body)?; // `;` or `{ ... }`.
1901 let fn_sig_span = sig_lo.to(sig_hi);
1902 Ok((ident, FnSig { header, decl, span: fn_sig_span }, generics, body))
1905 /// Parse the "body" of a function.
1906 /// This can either be `;` when there's no body,
1907 /// or e.g. a block when the function is a provided one.
1910 attrs: &mut Vec<Attribute>,
1914 ) -> PResult<'a, Option<P<Block>>> {
1915 let has_semi = if req_body {
1916 self.token.kind == TokenKind::Semi
1918 // Only include `;` in list of expected tokens if body is not required
1919 self.check(&TokenKind::Semi)
1921 let (inner_attrs, body) = if has_semi {
1922 // Include the trailing semicolon in the span of the signature
1923 self.expect_semi()?;
1924 *sig_hi = self.prev_token.span;
1926 } else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
1927 self.parse_inner_attrs_and_block().map(|(attrs, body)| (attrs, Some(body)))?
1928 } else if self.token.kind == token::Eq {
1929 // Recover `fn foo() = $expr;`.
1931 let eq_sp = self.prev_token.span;
1932 let _ = self.parse_expr()?;
1933 self.expect_semi()?; // `;`
1934 let span = eq_sp.to(self.prev_token.span);
1935 self.struct_span_err(span, "function body cannot be `= expression;`")
1936 .multipart_suggestion(
1937 "surround the expression with `{` and `}` instead of `=` and `;`",
1938 vec![(eq_sp, "{".to_string()), (self.prev_token.span, " }".to_string())],
1939 Applicability::MachineApplicable,
1942 (Vec::new(), Some(self.mk_block_err(span)))
1944 let expected = if req_body {
1945 &[token::OpenDelim(token::Brace)][..]
1947 &[token::Semi, token::OpenDelim(token::Brace)]
1949 if let Err(mut err) = self.expected_one_of_not_found(&[], &expected) {
1950 if self.token.kind == token::CloseDelim(token::Brace) {
1951 // The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
1952 // the AST for typechecking.
1953 err.span_label(ident.span, "while parsing this `fn`");
1961 attrs.extend(inner_attrs);
1965 /// Is the current token the start of an `FnHeader` / not a valid parse?
1967 /// `check_pub` adds additional `pub` to the checks in case users place it
1968 /// wrongly, can be used to ensure `pub` never comes after `default`.
1969 pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
1970 // We use an over-approximation here.
1971 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1972 // `pub` is added in case users got confused with the ordering like `async pub fn`,
1973 // only if it wasn't preceded by `default` as `default pub` is invalid.
1974 let quals: &[Symbol] = if check_pub {
1975 &[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1977 &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1979 self.check_keyword(kw::Fn) // Definitely an `fn`.
1980 // `$qual fn` or `$qual $qual`:
1981 || quals.iter().any(|&kw| self.check_keyword(kw))
1982 && self.look_ahead(1, |t| {
1983 // `$qual fn`, e.g. `const fn` or `async fn`.
1984 t.is_keyword(kw::Fn)
1985 // Two qualifiers `$qual $qual` is enough, e.g. `async unsafe`.
1986 || t.is_non_raw_ident_where(|i| quals.contains(&i.name)
1987 // Rule out 2015 `const async: T = val`.
1989 // Rule out unsafe extern block.
1990 && !self.is_unsafe_foreign_mod())
1993 || self.check_keyword(kw::Extern)
1994 && self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
1995 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
1998 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
1999 /// up to and including the `fn` keyword. The formal grammar is:
2002 /// Extern = "extern" StringLit? ;
2003 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
2004 /// FnFrontMatter = FnQual "fn" ;
2007 /// `vis` represents the visibility that was already parsed, if any. Use
2008 /// `Visibility::Inherited` when no visibility is known.
2009 pub(super) fn parse_fn_front_matter(&mut self, orig_vis: &Visibility) -> PResult<'a, FnHeader> {
2010 let sp_start = self.token.span;
2011 let constness = self.parse_constness();
2013 let async_start_sp = self.token.span;
2014 let asyncness = self.parse_asyncness();
2016 let unsafe_start_sp = self.token.span;
2017 let unsafety = self.parse_unsafety();
2019 let ext_start_sp = self.token.span;
2020 let ext = self.parse_extern();
2022 if let Async::Yes { span, .. } = asyncness {
2023 self.ban_async_in_2015(span);
2026 if !self.eat_keyword(kw::Fn) {
2027 // It is possible for `expect_one_of` to recover given the contents of
2028 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
2029 // account for this.
2030 match self.expect_one_of(&[], &[]) {
2032 Ok(false) => unreachable!(),
2034 // Qualifier keywords ordering check
2040 // This will allow the machine fix to directly place the keyword in the correct place or to indicate
2041 // that the keyword is already present and the second instance should be removed.
2042 let wrong_kw = if self.check_keyword(kw::Const) {
2044 Const::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2045 Const::No => Some(WrongKw::Misplaced(async_start_sp)),
2047 } else if self.check_keyword(kw::Async) {
2049 Async::Yes { span, .. } => Some(WrongKw::Duplicated(span)),
2050 Async::No => Some(WrongKw::Misplaced(unsafe_start_sp)),
2052 } else if self.check_keyword(kw::Unsafe) {
2054 Unsafe::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2055 Unsafe::No => Some(WrongKw::Misplaced(ext_start_sp)),
2061 // The keyword is already present, suggest removal of the second instance
2062 if let Some(WrongKw::Duplicated(original_sp)) = wrong_kw {
2063 let original_kw = self
2064 .span_to_snippet(original_sp)
2065 .expect("Span extracted directly from keyword should always work");
2067 err.span_suggestion(
2068 self.token.uninterpolated_span(),
2069 &format!("`{original_kw}` already used earlier, remove this one"),
2071 Applicability::MachineApplicable,
2073 .span_note(original_sp, &format!("`{original_kw}` first seen here"));
2075 // The keyword has not been seen yet, suggest correct placement in the function front matter
2076 else if let Some(WrongKw::Misplaced(correct_pos_sp)) = wrong_kw {
2077 let correct_pos_sp = correct_pos_sp.to(self.prev_token.span);
2078 if let Ok(current_qual) = self.span_to_snippet(correct_pos_sp) {
2079 let misplaced_qual_sp = self.token.uninterpolated_span();
2080 let misplaced_qual = self.span_to_snippet(misplaced_qual_sp).unwrap();
2082 err.span_suggestion(
2083 correct_pos_sp.to(misplaced_qual_sp),
2084 &format!("`{misplaced_qual}` must come before `{current_qual}`"),
2085 format!("{misplaced_qual} {current_qual}"),
2086 Applicability::MachineApplicable,
2087 ).note("keyword order for functions declaration is `default`, `pub`, `const`, `async`, `unsafe`, `extern`");
2090 // Recover incorrect visibility order such as `async pub`
2091 else if self.check_keyword(kw::Pub) {
2092 let sp = sp_start.to(self.prev_token.span);
2093 if let Ok(snippet) = self.span_to_snippet(sp) {
2094 let current_vis = match self.parse_visibility(FollowedByType::No) {
2101 let vs = pprust::vis_to_string(¤t_vis);
2102 let vs = vs.trim_end();
2104 // There was no explicit visibility
2105 if matches!(orig_vis.kind, VisibilityKind::Inherited) {
2106 err.span_suggestion(
2107 sp_start.to(self.prev_token.span),
2108 &format!("visibility `{vs}` must come before `{snippet}`"),
2109 format!("{vs} {snippet}"),
2110 Applicability::MachineApplicable,
2113 // There was an explicit visibility
2115 err.span_suggestion(
2117 "there is already a visibility modifier, remove one",
2119 Applicability::MachineApplicable,
2121 .span_note(orig_vis.span, "explicit visibility first seen here");
2130 Ok(FnHeader { constness, unsafety, asyncness, ext })
2133 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
2134 fn ban_async_in_2015(&self, span: Span) {
2135 if span.rust_2015() {
2136 let diag = self.diagnostic();
2137 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in Rust 2015")
2138 .span_label(span, "to use `async fn`, switch to Rust 2018 or later")
2139 .help_use_latest_edition()
2144 /// Parses the parameter list and result type of a function declaration.
2145 pub(super) fn parse_fn_decl(
2148 ret_allow_plus: AllowPlus,
2149 recover_return_sign: RecoverReturnSign,
2150 ) -> PResult<'a, P<FnDecl>> {
2152 inputs: self.parse_fn_params(req_name)?,
2153 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes, recover_return_sign)?,
2157 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
2158 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
2159 let mut first_param = true;
2160 // Parse the arguments, starting out with `self` being allowed...
2161 let (mut params, _) = self.parse_paren_comma_seq(|p| {
2162 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
2164 let lo = p.prev_token.span;
2165 // Skip every token until next possible arg or end.
2166 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
2167 // Create a placeholder argument for proper arg count (issue #34264).
2168 Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span))))
2170 // ...now that we've parsed the first argument, `self` is no longer allowed.
2171 first_param = false;
2174 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
2175 self.deduplicate_recovered_params_names(&mut params);
2179 /// Parses a single function parameter.
2181 /// - `self` is syntactically allowed when `first_param` holds.
2182 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
2183 let lo = self.token.span;
2184 let attrs = self.parse_outer_attributes()?;
2185 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2186 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
2187 if let Some(mut param) = this.parse_self_param()? {
2188 param.attrs = attrs.into();
2189 let res = if first_param { Ok(param) } else { this.recover_bad_self_param(param) };
2190 return Ok((res?, TrailingToken::None));
2193 let is_name_required = match this.token.kind {
2194 token::DotDotDot => false,
2195 _ => req_name(this.token.span.edition()),
2197 let (pat, ty) = if is_name_required || this.is_named_param() {
2198 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
2200 let (pat, colon) = this.parse_fn_param_pat_colon()?;
2202 let mut err = this.unexpected::<()>().unwrap_err();
2203 return if let Some(ident) =
2204 this.parameter_without_type(&mut err, pat, is_name_required, first_param)
2207 Ok((dummy_arg(ident), TrailingToken::None))
2213 this.eat_incorrect_doc_comment_for_param_type();
2214 (pat, this.parse_ty_for_param()?)
2216 debug!("parse_param_general ident_to_pat");
2217 let parser_snapshot_before_ty = this.clone();
2218 this.eat_incorrect_doc_comment_for_param_type();
2219 let mut ty = this.parse_ty_for_param();
2221 && this.token != token::Comma
2222 && this.token != token::CloseDelim(token::Paren)
2224 // This wasn't actually a type, but a pattern looking like a type,
2225 // so we are going to rollback and re-parse for recovery.
2226 ty = this.unexpected();
2230 let ident = Ident::new(kw::Empty, this.prev_token.span);
2231 let bm = BindingMode::ByValue(Mutability::Not);
2232 let pat = this.mk_pat_ident(ty.span, bm, ident);
2235 // If this is a C-variadic argument and we hit an error, return the error.
2236 Err(err) if this.token == token::DotDotDot => return Err(err),
2237 // Recover from attempting to parse the argument as a type without pattern.
2240 *this = parser_snapshot_before_ty;
2241 this.recover_arg_parse()?
2246 let span = lo.until(this.token.span);
2250 attrs: attrs.into(),
2251 id: ast::DUMMY_NODE_ID,
2252 is_placeholder: false,
2257 TrailingToken::None,
2262 /// Returns the parsed optional self parameter and whether a self shortcut was used.
2263 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
2264 // Extract an identifier *after* having confirmed that the token is one.
2265 let expect_self_ident = |this: &mut Self| match this.token.ident() {
2266 Some((ident, false)) => {
2270 _ => unreachable!(),
2272 // Is `self` `n` tokens ahead?
2273 let is_isolated_self = |this: &Self, n| {
2274 this.is_keyword_ahead(n, &[kw::SelfLower])
2275 && this.look_ahead(n + 1, |t| t != &token::ModSep)
2277 // Is `mut self` `n` tokens ahead?
2278 let is_isolated_mut_self =
2279 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
2280 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
2281 let parse_self_possibly_typed = |this: &mut Self, m| {
2282 let eself_ident = expect_self_ident(this);
2283 let eself_hi = this.prev_token.span;
2284 let eself = if this.eat(&token::Colon) {
2285 SelfKind::Explicit(this.parse_ty()?, m)
2289 Ok((eself, eself_ident, eself_hi))
2291 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
2292 let recover_self_ptr = |this: &mut Self| {
2293 let msg = "cannot pass `self` by raw pointer";
2294 let span = this.token.span;
2295 this.struct_span_err(span, msg).span_label(span, msg).emit();
2297 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_token.span))
2300 // Parse optional `self` parameter of a method.
2301 // Only a limited set of initial token sequences is considered `self` parameters; anything
2302 // else is parsed as a normal function parameter list, so some lookahead is required.
2303 let eself_lo = self.token.span;
2304 let (eself, eself_ident, eself_hi) = match self.token.uninterpolate().kind {
2305 token::BinOp(token::And) => {
2306 let eself = if is_isolated_self(self, 1) {
2309 SelfKind::Region(None, Mutability::Not)
2310 } else if is_isolated_mut_self(self, 1) {
2314 SelfKind::Region(None, Mutability::Mut)
2315 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
2318 let lt = self.expect_lifetime();
2319 SelfKind::Region(Some(lt), Mutability::Not)
2320 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
2323 let lt = self.expect_lifetime();
2325 SelfKind::Region(Some(lt), Mutability::Mut)
2330 (eself, expect_self_ident(self), self.prev_token.span)
2333 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
2335 recover_self_ptr(self)?
2337 // `*mut self` and `*const self`
2338 token::BinOp(token::Star)
2339 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
2343 recover_self_ptr(self)?
2345 // `self` and `self: TYPE`
2346 token::Ident(..) if is_isolated_self(self, 0) => {
2347 parse_self_possibly_typed(self, Mutability::Not)?
2349 // `mut self` and `mut self: TYPE`
2350 token::Ident(..) if is_isolated_mut_self(self, 0) => {
2352 parse_self_possibly_typed(self, Mutability::Mut)?
2354 _ => return Ok(None),
2357 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
2358 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
2361 fn is_named_param(&self) -> bool {
2362 let offset = match self.token.kind {
2363 token::Interpolated(ref nt) => match **nt {
2364 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
2367 token::BinOp(token::And) | token::AndAnd => 1,
2368 _ if self.token.is_keyword(kw::Mut) => 1,
2372 self.look_ahead(offset, |t| t.is_ident())
2373 && self.look_ahead(offset + 1, |t| t == &token::Colon)
2376 fn recover_first_param(&mut self) -> &'static str {
2378 .parse_outer_attributes()
2379 .and_then(|_| self.parse_self_param())
2380 .map_err(|e| e.cancel())
2382 Ok(Some(_)) => "method",
2388 enum IsMacroRulesItem {
2389 Yes { has_bang: bool },