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, Delimiter, 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(Delimiter::Brace))?;
43 let (mut inner_attrs, items, inner_span) =
44 self.parse_mod(&token::CloseDelim(Delimiter::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) {
207 self.parse_use_item()?
208 } else if self.check_fn_front_matter(def_final) {
210 let (ident, sig, generics, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis)?;
211 (ident, ItemKind::Fn(Box::new(Fn { defaultness: def(), sig, generics, body })))
212 } else if self.eat_keyword(kw::Extern) {
213 if self.eat_keyword(kw::Crate) {
215 self.parse_item_extern_crate()?
218 self.parse_item_foreign_mod(attrs, Unsafe::No)?
220 } else if self.is_unsafe_foreign_mod() {
222 let unsafety = self.parse_unsafety();
223 self.expect_keyword(kw::Extern)?;
224 self.parse_item_foreign_mod(attrs, unsafety)?
225 } else if self.is_static_global() {
227 self.bump(); // `static`
228 let m = self.parse_mutability();
229 let (ident, ty, expr) = self.parse_item_global(Some(m))?;
230 (ident, ItemKind::Static(ty, m, expr))
231 } else if let Const::Yes(const_span) = self.parse_constness() {
233 if self.token.is_keyword(kw::Impl) {
234 // recover from `const impl`, suggest `impl const`
235 self.recover_const_impl(const_span, attrs, def())?
237 self.recover_const_mut(const_span);
238 let (ident, ty, expr) = self.parse_item_global(None)?;
239 (ident, ItemKind::Const(def(), ty, expr))
241 } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
243 self.parse_item_trait(attrs, lo)?
244 } else if self.check_keyword(kw::Impl)
245 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
248 self.parse_item_impl(attrs, def())?
249 } else if self.check_keyword(kw::Mod)
250 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
253 self.parse_item_mod(attrs)?
254 } else if self.eat_keyword(kw::Type) {
256 self.parse_type_alias(def())?
257 } else if self.eat_keyword(kw::Enum) {
259 self.parse_item_enum()?
260 } else if self.eat_keyword(kw::Struct) {
262 self.parse_item_struct()?
263 } else if self.is_kw_followed_by_ident(kw::Union) {
265 self.bump(); // `union`
266 self.parse_item_union()?
267 } else if self.eat_keyword(kw::Macro) {
269 self.parse_item_decl_macro(lo)?
270 } else if let IsMacroRulesItem::Yes { has_bang } = self.is_macro_rules_item() {
272 self.parse_item_macro_rules(vis, has_bang)?
273 } else if self.isnt_macro_invocation()
274 && (self.token.is_ident_named(Symbol::intern("import"))
275 || self.token.is_ident_named(Symbol::intern("using")))
277 return self.recover_import_as_use();
278 } else if self.isnt_macro_invocation() && vis.kind.is_pub() {
279 self.recover_missing_kw_before_item()?;
281 } else if macros_allowed && self.check_path() {
282 // MACRO INVOCATION ITEM
283 (Ident::empty(), ItemKind::MacCall(self.parse_item_macro(vis)?))
290 fn recover_import_as_use(&mut self) -> PResult<'a, Option<(Ident, ItemKind)>> {
291 let span = self.token.span;
292 let token_name = super::token_descr(&self.token);
293 let snapshot = self.create_snapshot_for_diagnostic();
295 match self.parse_use_item() {
297 self.struct_span_err(span, format!("expected item, found {token_name}"))
298 .span_suggestion_short(
300 "items are imported using the `use` keyword",
302 Applicability::MachineApplicable,
309 self.restore_snapshot(snapshot);
315 fn parse_use_item(&mut self) -> PResult<'a, (Ident, ItemKind)> {
316 let tree = self.parse_use_tree()?;
317 if let Err(mut e) = self.expect_semi() {
319 UseTreeKind::Glob => {
320 e.note("the wildcard token must be last on the path");
322 UseTreeKind::Nested(..) => {
323 e.note("glob-like brace syntax must be last on the path");
329 Ok((Ident::empty(), ItemKind::Use(tree)))
332 /// When parsing a statement, would the start of a path be an item?
333 pub(super) fn is_path_start_item(&mut self) -> bool {
334 self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
335 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
336 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
337 || matches!(self.is_macro_rules_item(), IsMacroRulesItem::Yes{..}) // no: `macro_rules::b`, yes: `macro_rules! mac`
340 /// Are we sure this could not possibly be a macro invocation?
341 fn isnt_macro_invocation(&mut self) -> bool {
342 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
345 /// Recover on encountering a struct or method definition where the user
346 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
347 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
348 // Space between `pub` keyword and the identifier
351 // ^^^ `sp` points here
352 let sp = self.prev_token.span.between(self.token.span);
353 let full_sp = self.prev_token.span.to(self.token.span);
354 let ident_sp = self.token.span;
355 if self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Brace)) {
356 // possible public struct definition where `struct` was forgotten
357 let ident = self.parse_ident().unwrap();
358 let msg = format!("add `struct` here to parse `{ident}` as a public struct");
359 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
360 err.span_suggestion_short(
364 Applicability::MaybeIncorrect, // speculative
367 } else if self.look_ahead(1, |t| *t == token::OpenDelim(Delimiter::Parenthesis)) {
368 let ident = self.parse_ident().unwrap();
370 let kw_name = self.recover_first_param();
371 self.consume_block(Delimiter::Parenthesis, ConsumeClosingDelim::Yes);
372 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
373 self.eat_to_tokens(&[&token::OpenDelim(Delimiter::Brace)]);
375 ("fn", kw_name, false)
376 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
378 ("fn", kw_name, false)
379 } else if self.check(&token::Colon) {
383 ("fn` or `struct", "function or struct", true)
386 let msg = format!("missing `{kw}` for {kw_name} definition");
387 let mut err = self.struct_span_err(sp, &msg);
389 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
391 format!("add `{kw}` here to parse `{ident}` as a public {kw_name}");
392 err.span_suggestion_short(
396 Applicability::MachineApplicable,
398 } else if let Ok(snippet) = self.span_to_snippet(ident_sp) {
401 "if you meant to call a macro, try",
402 format!("{}!", snippet),
403 // this is the `ambiguous` conditional branch
404 Applicability::MaybeIncorrect,
408 "if you meant to call a macro, remove the `pub` \
409 and add a trailing `!` after the identifier",
413 } else if self.look_ahead(1, |t| *t == token::Lt) {
414 let ident = self.parse_ident().unwrap();
415 self.eat_to_tokens(&[&token::Gt]);
417 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(Delimiter::Parenthesis)) {
418 ("fn", self.recover_first_param(), false)
419 } else if self.check(&token::OpenDelim(Delimiter::Brace)) {
420 ("struct", "struct", false)
422 ("fn` or `struct", "function or struct", true)
424 let msg = format!("missing `{kw}` for {kw_name} definition");
425 let mut err = self.struct_span_err(sp, &msg);
427 err.span_suggestion_short(
429 &format!("add `{kw}` here to parse `{ident}` as a public {kw_name}"),
431 Applicability::MachineApplicable,
440 /// Parses an item macro, e.g., `item!();`.
441 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, MacCall> {
442 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
443 self.expect(&token::Not)?; // `!`
444 match self.parse_mac_args() {
445 // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
447 self.eat_semi_for_macro_if_needed(&args);
448 self.complain_if_pub_macro(vis, false);
449 Ok(MacCall { path, args, prior_type_ascription: self.last_type_ascription })
453 // Maybe the user misspelled `macro_rules` (issue #91227)
454 if self.token.is_ident()
455 && path.segments.len() == 1
456 && lev_distance("macro_rules", &path.segments[0].ident.to_string(), 3).is_some()
460 "perhaps you meant to define a macro",
462 Applicability::MachineApplicable,
470 /// Recover if we parsed attributes and expected an item but there was none.
471 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
472 let ([start @ end] | [start, .., end]) = attrs else {
475 let msg = if end.is_doc_comment() {
476 "expected item after doc comment"
478 "expected item after attributes"
480 let mut err = self.struct_span_err(end.span, msg);
481 if end.is_doc_comment() {
482 err.span_label(end.span, "this doc comment doesn't document anything");
484 if end.meta_kind().is_some() {
485 if self.token.kind == TokenKind::Semi {
486 err.span_suggestion_verbose(
488 "consider removing this semicolon",
490 Applicability::MaybeIncorrect,
494 if let [.., penultimate, _] = attrs {
495 err.span_label(start.span.to(penultimate.span), "other attributes here");
500 fn is_async_fn(&self) -> bool {
501 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
504 fn parse_polarity(&mut self) -> ast::ImplPolarity {
505 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
506 if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
508 ast::ImplPolarity::Negative(self.prev_token.span)
510 ast::ImplPolarity::Positive
514 /// Parses an implementation item.
516 /// ```ignore (illustrative)
517 /// impl<'a, T> TYPE { /* impl items */ }
518 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
519 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
520 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
523 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
525 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
526 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
530 attrs: &mut Vec<Attribute>,
531 defaultness: Defaultness,
532 ) -> PResult<'a, ItemInfo> {
533 let unsafety = self.parse_unsafety();
534 self.expect_keyword(kw::Impl)?;
536 // First, parse generic parameters if necessary.
537 let mut generics = if self.choose_generics_over_qpath(0) {
538 self.parse_generics()?
540 let mut generics = Generics::default();
542 // /\ this is where `generics.span` should point when there are no type params.
543 generics.span = self.prev_token.span.shrink_to_hi();
547 let constness = self.parse_constness();
548 if let Const::Yes(span) = constness {
549 self.sess.gated_spans.gate(sym::const_trait_impl, span);
552 let polarity = self.parse_polarity();
554 // Parse both types and traits as a type, then reinterpret if necessary.
555 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Empty, span));
556 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
558 let span = self.prev_token.span.between(self.token.span);
559 self.struct_span_err(span, "missing trait in a trait impl")
564 Applicability::HasPlaceholders,
567 span.to(self.token.span),
568 "for an inherent impl, drop this `for`",
570 Applicability::MaybeIncorrect,
574 kind: TyKind::Path(None, err_path(span)),
580 self.parse_ty_with_generics_recovery(&generics)?
583 // If `for` is missing we try to recover.
584 let has_for = self.eat_keyword(kw::For);
585 let missing_for_span = self.prev_token.span.between(self.token.span);
587 let ty_second = if self.token == token::DotDot {
588 // We need to report this error after `cfg` expansion for compatibility reasons
589 self.bump(); // `..`, do not add it to expected tokens
590 Some(self.mk_ty(self.prev_token.span, TyKind::Err))
591 } else if has_for || self.token.can_begin_type() {
592 Some(self.parse_ty()?)
597 generics.where_clause = self.parse_where_clause()?;
599 let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
601 let item_kind = match ty_second {
603 // impl Trait for Type
605 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
606 .span_suggestion_short(
610 Applicability::MachineApplicable,
615 let ty_first = ty_first.into_inner();
616 let path = match ty_first.kind {
617 // This notably includes paths passed through `ty` macro fragments (#46438).
618 TyKind::Path(None, path) => path,
620 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
621 err_path(ty_first.span)
624 let trait_ref = TraitRef { path, ref_id: ty_first.id };
626 ItemKind::Impl(Box::new(Impl {
632 of_trait: Some(trait_ref),
639 ItemKind::Impl(Box::new(Impl {
652 Ok((Ident::empty(), item_kind))
655 fn parse_item_list<T>(
657 attrs: &mut Vec<Attribute>,
658 mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
659 ) -> PResult<'a, Vec<T>> {
660 let open_brace_span = self.token.span;
661 self.expect(&token::OpenDelim(Delimiter::Brace))?;
662 attrs.append(&mut self.parse_inner_attributes()?);
664 let mut items = Vec::new();
665 while !self.eat(&token::CloseDelim(Delimiter::Brace)) {
666 if self.recover_doc_comment_before_brace() {
669 match parse_item(self) {
671 // We have to bail or we'll potentially never make progress.
672 let non_item_span = self.token.span;
673 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
674 self.struct_span_err(non_item_span, "non-item in item list")
675 .span_label(open_brace_span, "item list starts here")
676 .span_label(non_item_span, "non-item starts here")
677 .span_label(self.prev_token.span, "item list ends here")
681 Ok(Some(item)) => items.extend(item),
683 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::Yes);
684 err.span_label(open_brace_span, "while parsing this item list starting here")
685 .span_label(self.prev_token.span, "the item list ends here")
694 /// Recover on a doc comment before `}`.
695 fn recover_doc_comment_before_brace(&mut self) -> bool {
696 if let token::DocComment(..) = self.token.kind {
697 if self.look_ahead(1, |tok| tok == &token::CloseDelim(Delimiter::Brace)) {
702 "found a documentation comment that doesn't document anything",
704 .span_label(self.token.span, "this doc comment doesn't document anything")
706 "doc comments must come before what they document, maybe a \
707 comment was intended with `//`?",
717 /// Parses defaultness (i.e., `default` or nothing).
718 fn parse_defaultness(&mut self) -> Defaultness {
719 // We are interested in `default` followed by another identifier.
720 // However, we must avoid keywords that occur as binary operators.
721 // Currently, the only applicable keyword is `as` (`default as Ty`).
722 if self.check_keyword(kw::Default)
723 && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
725 self.bump(); // `default`
726 Defaultness::Default(self.prev_token.uninterpolated_span())
732 /// Is this an `(unsafe auto? | auto) trait` item?
733 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
735 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
737 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
740 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
741 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
742 let unsafety = self.parse_unsafety();
743 // Parse optional `auto` prefix.
744 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
746 self.expect_keyword(kw::Trait)?;
747 let ident = self.parse_ident()?;
748 let mut generics = self.parse_generics()?;
750 // Parse optional colon and supertrait bounds.
751 let had_colon = self.eat(&token::Colon);
752 let span_at_colon = self.prev_token.span;
753 let bounds = if had_colon {
754 self.parse_generic_bounds(Some(self.prev_token.span))?
759 let span_before_eq = self.prev_token.span;
760 if self.eat(&token::Eq) {
761 // It's a trait alias.
763 let span = span_at_colon.to(span_before_eq);
764 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
767 let bounds = self.parse_generic_bounds(None)?;
768 generics.where_clause = self.parse_where_clause()?;
771 let whole_span = lo.to(self.prev_token.span);
772 if is_auto == IsAuto::Yes {
773 let msg = "trait aliases cannot be `auto`";
774 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
776 if let Unsafe::Yes(_) = unsafety {
777 let msg = "trait aliases cannot be `unsafe`";
778 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
781 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
783 Ok((ident, ItemKind::TraitAlias(generics, bounds)))
785 // It's a normal trait.
786 generics.where_clause = self.parse_where_clause()?;
787 let items = self.parse_item_list(attrs, |p| p.parse_trait_item(ForceCollect::No))?;
790 ItemKind::Trait(Box::new(Trait { is_auto, unsafety, generics, bounds, items })),
795 pub fn parse_impl_item(
797 force_collect: ForceCollect,
798 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
799 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
800 self.parse_assoc_item(fn_parse_mode, force_collect)
803 pub fn parse_trait_item(
805 force_collect: ForceCollect,
806 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
808 FnParseMode { req_name: |edition| edition >= Edition::Edition2018, req_body: false };
809 self.parse_assoc_item(fn_parse_mode, force_collect)
812 /// Parses associated items.
815 fn_parse_mode: FnParseMode,
816 force_collect: ForceCollect,
817 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
818 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
819 |Item { attrs, id, span, vis, ident, kind, tokens }| {
820 let kind = match AssocItemKind::try_from(kind) {
822 Err(kind) => match kind {
823 ItemKind::Static(a, _, b) => {
824 self.struct_span_err(span, "associated `static` items are not allowed")
826 AssocItemKind::Const(Defaultness::Final, a, b)
828 _ => return self.error_bad_item_kind(span, &kind, "`trait`s or `impl`s"),
831 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
836 /// Parses a `type` alias with the following grammar:
838 /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
840 /// The `"type"` has already been eaten.
841 fn parse_type_alias(&mut self, defaultness: Defaultness) -> PResult<'a, ItemInfo> {
842 let ident = self.parse_ident()?;
843 let mut generics = self.parse_generics()?;
845 // Parse optional colon and param bounds.
847 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
848 let before_where_clause = self.parse_where_clause()?;
850 let ty = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
852 let after_where_clause = self.parse_where_clause()?;
854 let where_clauses = (
855 TyAliasWhereClause(before_where_clause.has_where_token, before_where_clause.span),
856 TyAliasWhereClause(after_where_clause.has_where_token, after_where_clause.span),
858 let where_predicates_split = before_where_clause.predicates.len();
859 let mut predicates = before_where_clause.predicates;
860 predicates.extend(after_where_clause.predicates.into_iter());
861 let where_clause = WhereClause {
862 has_where_token: before_where_clause.has_where_token
863 || after_where_clause.has_where_token,
867 generics.where_clause = where_clause;
873 ItemKind::TyAlias(Box::new(TyAlias {
877 where_predicates_split,
884 /// Parses a `UseTree`.
887 /// USE_TREE = [`::`] `*` |
888 /// [`::`] `{` USE_TREE_LIST `}` |
890 /// PATH `::` `{` USE_TREE_LIST `}` |
891 /// PATH [`as` IDENT]
893 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
894 let lo = self.token.span;
896 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo(), tokens: None };
897 let kind = if self.check(&token::OpenDelim(Delimiter::Brace))
898 || self.check(&token::BinOp(token::Star))
899 || self.is_import_coupler()
901 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
902 let mod_sep_ctxt = self.token.span.ctxt();
903 if self.eat(&token::ModSep) {
906 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
909 self.parse_use_tree_glob_or_nested()?
911 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
912 prefix = self.parse_path(PathStyle::Mod)?;
914 if self.eat(&token::ModSep) {
915 self.parse_use_tree_glob_or_nested()?
917 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
921 Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.span) })
924 /// Parses `*` or `{...}`.
925 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
926 Ok(if self.eat(&token::BinOp(token::Star)) {
929 UseTreeKind::Nested(self.parse_use_tree_list()?)
933 /// Parses a `UseTreeKind::Nested(list)`.
936 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
938 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
939 self.parse_delim_comma_seq(Delimiter::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
943 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
944 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
947 fn parse_ident_or_underscore(&mut self) -> PResult<'a, Ident> {
948 match self.token.ident() {
949 Some((ident @ Ident { name: kw::Underscore, .. }, false)) => {
953 _ => self.parse_ident(),
957 /// Parses `extern crate` links.
961 /// ```ignore (illustrative)
962 /// extern crate foo;
963 /// extern crate bar as foo;
965 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
966 // Accept `extern crate name-like-this` for better diagnostics
967 let orig_name = self.parse_crate_name_with_dashes()?;
968 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
969 (rename, Some(orig_name.name))
974 Ok((item_name, ItemKind::ExternCrate(orig_name)))
977 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, Ident> {
978 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
979 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
981 let mut ident = if self.token.is_keyword(kw::SelfLower) {
982 self.parse_path_segment_ident()
986 let mut idents = vec![];
987 let mut replacement = vec![];
988 let mut fixed_crate_name = false;
989 // Accept `extern crate name-like-this` for better diagnostics.
990 let dash = token::BinOp(token::BinOpToken::Minus);
991 if self.token == dash {
992 // Do not include `-` as part of the expected tokens list.
993 while self.eat(&dash) {
994 fixed_crate_name = true;
995 replacement.push((self.prev_token.span, "_".to_string()));
996 idents.push(self.parse_ident()?);
999 if fixed_crate_name {
1000 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
1001 let mut fixed_name = ident.name.to_string();
1002 for part in idents {
1003 fixed_name.push_str(&format!("_{}", part.name));
1005 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
1007 self.struct_span_err(fixed_name_sp, error_msg)
1008 .span_label(fixed_name_sp, "dash-separated idents are not valid")
1009 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
1015 /// Parses `extern` for foreign ABIs modules.
1017 /// `extern` is expected to have been consumed before calling this method.
1021 /// ```ignore (only-for-syntax-highlight)
1025 fn parse_item_foreign_mod(
1027 attrs: &mut Vec<Attribute>,
1028 mut unsafety: Unsafe,
1029 ) -> PResult<'a, ItemInfo> {
1030 let abi = self.parse_abi(); // ABI?
1031 if unsafety == Unsafe::No
1032 && self.token.is_keyword(kw::Unsafe)
1033 && self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Brace))
1035 let mut err = self.expect(&token::OpenDelim(Delimiter::Brace)).unwrap_err();
1037 unsafety = Unsafe::Yes(self.token.span);
1038 self.eat_keyword(kw::Unsafe);
1040 let module = ast::ForeignMod {
1043 items: self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No))?,
1045 Ok((Ident::empty(), ItemKind::ForeignMod(module)))
1048 /// Parses a foreign item (one in an `extern { ... }` block).
1049 pub fn parse_foreign_item(
1051 force_collect: ForceCollect,
1052 ) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
1053 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: false };
1054 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
1055 |Item { attrs, id, span, vis, ident, kind, tokens }| {
1056 let kind = match ForeignItemKind::try_from(kind) {
1058 Err(kind) => match kind {
1059 ItemKind::Const(_, a, b) => {
1060 self.error_on_foreign_const(span, ident);
1061 ForeignItemKind::Static(a, Mutability::Not, b)
1063 _ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
1066 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
1071 fn error_bad_item_kind<T>(&self, span: Span, kind: &ItemKind, ctx: &str) -> Option<T> {
1072 let span = self.sess.source_map().guess_head_span(span);
1073 let descr = kind.descr();
1074 self.struct_span_err(span, &format!("{descr} is not supported in {ctx}"))
1075 .help(&format!("consider moving the {descr} out to a nearby module scope"))
1080 fn error_on_foreign_const(&self, span: Span, ident: Ident) {
1081 self.struct_span_err(ident.span, "extern items cannot be `const`")
1083 span.with_hi(ident.span.lo()),
1084 "try using a static value",
1086 Applicability::MachineApplicable,
1088 .note("for more information, visit https://doc.rust-lang.org/std/keyword.extern.html")
1092 fn is_unsafe_foreign_mod(&self) -> bool {
1093 self.token.is_keyword(kw::Unsafe)
1094 && self.is_keyword_ahead(1, &[kw::Extern])
1096 2 + self.look_ahead(2, |t| t.can_begin_literal_maybe_minus() as usize),
1097 |t| t.kind == token::OpenDelim(Delimiter::Brace),
1101 fn is_static_global(&mut self) -> bool {
1102 if self.check_keyword(kw::Static) {
1103 // Check if this could be a closure.
1104 !self.look_ahead(1, |token| {
1105 if token.is_keyword(kw::Move) {
1108 matches!(token.kind, token::BinOp(token::Or) | token::OrOr)
1115 /// Recover on `const mut` with `const` already eaten.
1116 fn recover_const_mut(&mut self, const_span: Span) {
1117 if self.eat_keyword(kw::Mut) {
1118 let span = self.prev_token.span;
1119 self.struct_span_err(span, "const globals cannot be mutable")
1120 .span_label(span, "cannot be mutable")
1123 "you might want to declare a static instead",
1125 Applicability::MaybeIncorrect,
1131 /// Recover on `const impl` with `const` already eaten.
1132 fn recover_const_impl(
1135 attrs: &mut Vec<Attribute>,
1136 defaultness: Defaultness,
1137 ) -> PResult<'a, ItemInfo> {
1138 let impl_span = self.token.span;
1139 let mut err = self.expected_ident_found();
1141 // Only try to recover if this is implementing a trait for a type
1142 let mut impl_info = match self.parse_item_impl(attrs, defaultness) {
1143 Ok(impl_info) => impl_info,
1144 Err(recovery_error) => {
1145 // Recovery failed, raise the "expected identifier" error
1146 recovery_error.cancel();
1152 ItemKind::Impl(box Impl { of_trait: Some(ref trai), ref mut constness, .. }) => {
1153 *constness = Const::Yes(const_span);
1155 let before_trait = trai.path.span.shrink_to_lo();
1156 let const_up_to_impl = const_span.with_hi(impl_span.lo());
1157 err.multipart_suggestion(
1158 "you might have meant to write a const trait impl",
1159 vec![(const_up_to_impl, "".to_owned()), (before_trait, "const ".to_owned())],
1160 Applicability::MaybeIncorrect,
1164 ItemKind::Impl { .. } => return Err(err),
1165 _ => unreachable!(),
1171 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
1172 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
1174 /// When `m` is `"const"`, `$ident` may also be `"_"`.
1175 fn parse_item_global(
1177 m: Option<Mutability>,
1178 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
1179 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
1181 // Parse the type of a `const` or `static mut?` item.
1182 // That is, the `":" $ty` fragment.
1183 let ty = if self.eat(&token::Colon) {
1186 self.recover_missing_const_type(id, m)
1189 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
1190 self.expect_semi()?;
1194 /// We were supposed to parse `:` but the `:` was missing.
1195 /// This means that the type is missing.
1196 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
1197 // Construct the error and stash it away with the hope
1198 // that typeck will later enrich the error with a type.
1199 let kind = match m {
1200 Some(Mutability::Mut) => "static mut",
1201 Some(Mutability::Not) => "static",
1204 let mut err = self.struct_span_err(id.span, &format!("missing type for `{kind}` item"));
1205 err.span_suggestion(
1207 "provide a type for the item",
1208 format!("{id}: <type>"),
1209 Applicability::HasPlaceholders,
1211 err.stash(id.span, StashKey::ItemNoType);
1213 // The user intended that the type be inferred,
1214 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
1215 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID, tokens: None })
1218 /// Parses an enum declaration.
1219 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
1220 let id = self.parse_ident()?;
1221 let mut generics = self.parse_generics()?;
1222 generics.where_clause = self.parse_where_clause()?;
1224 let (variants, _) = self
1225 .parse_delim_comma_seq(Delimiter::Brace, |p| p.parse_enum_variant())
1227 self.recover_stmt();
1231 let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
1232 Ok((id, ItemKind::Enum(enum_definition, generics)))
1235 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
1236 let variant_attrs = self.parse_outer_attributes()?;
1237 self.collect_tokens_trailing_token(
1240 |this, variant_attrs| {
1241 let vlo = this.token.span;
1243 let vis = this.parse_visibility(FollowedByType::No)?;
1244 if !this.recover_nested_adt_item(kw::Enum)? {
1245 return Ok((None, TrailingToken::None));
1247 let ident = this.parse_field_ident("enum", vlo)?;
1249 let struct_def = if this.check(&token::OpenDelim(Delimiter::Brace)) {
1250 // Parse a struct variant.
1251 let (fields, recovered) = this.parse_record_struct_body("struct", false)?;
1252 VariantData::Struct(fields, recovered)
1253 } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1254 VariantData::Tuple(this.parse_tuple_struct_body()?, DUMMY_NODE_ID)
1256 VariantData::Unit(DUMMY_NODE_ID)
1260 if this.eat(&token::Eq) { Some(this.parse_anon_const_expr()?) } else { None };
1262 let vr = ast::Variant {
1266 attrs: variant_attrs.into(),
1269 span: vlo.to(this.prev_token.span),
1270 is_placeholder: false,
1273 Ok((Some(vr), TrailingToken::MaybeComma))
1278 /// Parses `struct Foo { ... }`.
1279 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1280 let class_name = self.parse_ident()?;
1282 let mut generics = self.parse_generics()?;
1284 // There is a special case worth noting here, as reported in issue #17904.
1285 // If we are parsing a tuple struct it is the case that the where clause
1286 // should follow the field list. Like so:
1288 // struct Foo<T>(T) where T: Copy;
1290 // If we are parsing a normal record-style struct it is the case
1291 // that the where clause comes before the body, and after the generics.
1292 // So if we look ahead and see a brace or a where-clause we begin
1293 // parsing a record style struct.
1295 // Otherwise if we look ahead and see a paren we parse a tuple-style
1298 let vdata = if self.token.is_keyword(kw::Where) {
1299 generics.where_clause = self.parse_where_clause()?;
1300 if self.eat(&token::Semi) {
1301 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1302 VariantData::Unit(DUMMY_NODE_ID)
1304 // If we see: `struct Foo<T> where T: Copy { ... }`
1305 let (fields, recovered) =
1306 self.parse_record_struct_body("struct", generics.where_clause.has_where_token)?;
1307 VariantData::Struct(fields, recovered)
1309 // No `where` so: `struct Foo<T>;`
1310 } else if self.eat(&token::Semi) {
1311 VariantData::Unit(DUMMY_NODE_ID)
1312 // Record-style struct definition
1313 } else if self.token == token::OpenDelim(Delimiter::Brace) {
1314 let (fields, recovered) =
1315 self.parse_record_struct_body("struct", generics.where_clause.has_where_token)?;
1316 VariantData::Struct(fields, recovered)
1317 // Tuple-style struct definition with optional where-clause.
1318 } else if self.token == token::OpenDelim(Delimiter::Parenthesis) {
1319 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1320 generics.where_clause = self.parse_where_clause()?;
1321 self.expect_semi()?;
1324 let token_str = super::token_descr(&self.token);
1326 "expected `where`, `{{`, `(`, or `;` after struct name, found {token_str}"
1328 let mut err = self.struct_span_err(self.token.span, msg);
1329 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1333 Ok((class_name, ItemKind::Struct(vdata, generics)))
1336 /// Parses `union Foo { ... }`.
1337 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1338 let class_name = self.parse_ident()?;
1340 let mut generics = self.parse_generics()?;
1342 let vdata = if self.token.is_keyword(kw::Where) {
1343 generics.where_clause = self.parse_where_clause()?;
1344 let (fields, recovered) =
1345 self.parse_record_struct_body("union", generics.where_clause.has_where_token)?;
1346 VariantData::Struct(fields, recovered)
1347 } else if self.token == token::OpenDelim(Delimiter::Brace) {
1348 let (fields, recovered) =
1349 self.parse_record_struct_body("union", generics.where_clause.has_where_token)?;
1350 VariantData::Struct(fields, recovered)
1352 let token_str = super::token_descr(&self.token);
1353 let msg = &format!("expected `where` or `{{` after union name, found {token_str}");
1354 let mut err = self.struct_span_err(self.token.span, msg);
1355 err.span_label(self.token.span, "expected `where` or `{` after union name");
1359 Ok((class_name, ItemKind::Union(vdata, generics)))
1362 fn parse_record_struct_body(
1366 ) -> PResult<'a, (Vec<FieldDef>, /* recovered */ bool)> {
1367 let mut fields = Vec::new();
1368 let mut recovered = false;
1369 if self.eat(&token::OpenDelim(Delimiter::Brace)) {
1370 while self.token != token::CloseDelim(Delimiter::Brace) {
1371 let field = self.parse_field_def(adt_ty).map_err(|e| {
1372 self.consume_block(Delimiter::Brace, ConsumeClosingDelim::No);
1377 Ok(field) => fields.push(field),
1384 self.eat(&token::CloseDelim(Delimiter::Brace));
1386 let token_str = super::token_descr(&self.token);
1388 "expected {}`{{` after struct name, found {}",
1389 if parsed_where { "" } else { "`where`, or " },
1392 let mut err = self.struct_span_err(self.token.span, msg);
1396 "expected {}`{{` after struct name",
1397 if parsed_where { "" } else { "`where`, or " }
1403 Ok((fields, recovered))
1406 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<FieldDef>> {
1407 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1408 // Unit like structs are handled in parse_item_struct function
1409 self.parse_paren_comma_seq(|p| {
1410 let attrs = p.parse_outer_attributes()?;
1411 p.collect_tokens_trailing_token(attrs, ForceCollect::No, |p, attrs| {
1412 let lo = p.token.span;
1413 let vis = p.parse_visibility(FollowedByType::Yes)?;
1414 let ty = p.parse_ty()?;
1418 span: lo.to(ty.span),
1423 attrs: attrs.into(),
1424 is_placeholder: false,
1426 TrailingToken::MaybeComma,
1433 /// Parses an element of a struct declaration.
1434 fn parse_field_def(&mut self, adt_ty: &str) -> PResult<'a, FieldDef> {
1435 let attrs = self.parse_outer_attributes()?;
1436 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
1437 let lo = this.token.span;
1438 let vis = this.parse_visibility(FollowedByType::No)?;
1439 Ok((this.parse_single_struct_field(adt_ty, lo, vis, attrs)?, TrailingToken::None))
1443 /// Parses a structure field declaration.
1444 fn parse_single_struct_field(
1449 attrs: Vec<Attribute>,
1450 ) -> PResult<'a, FieldDef> {
1451 let mut seen_comma: bool = false;
1452 let a_var = self.parse_name_and_ty(adt_ty, lo, vis, attrs)?;
1453 if self.token == token::Comma {
1456 match self.token.kind {
1460 token::CloseDelim(Delimiter::Brace) => {}
1461 token::DocComment(..) => {
1462 let previous_span = self.prev_token.span;
1463 let mut err = self.span_err(self.token.span, Error::UselessDocComment);
1464 self.bump(); // consume the doc comment
1465 let comma_after_doc_seen = self.eat(&token::Comma);
1466 // `seen_comma` is always false, because we are inside doc block
1467 // condition is here to make code more readable
1468 if !seen_comma && comma_after_doc_seen {
1471 if comma_after_doc_seen || self.token == token::CloseDelim(Delimiter::Brace) {
1475 let sp = self.sess.source_map().next_point(previous_span);
1476 err.span_suggestion(
1478 "missing comma here",
1480 Applicability::MachineApplicable,
1487 let sp = self.prev_token.span.shrink_to_hi();
1488 let mut err = self.struct_span_err(
1490 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1493 // Try to recover extra trailing angle brackets
1494 let mut recovered = false;
1495 if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
1496 if let Some(last_segment) = segments.last() {
1497 recovered = self.check_trailing_angle_brackets(
1499 &[&token::Comma, &token::CloseDelim(Delimiter::Brace)],
1502 // Handle a case like `Vec<u8>>,` where we can continue parsing fields
1504 self.eat(&token::Comma);
1505 // `check_trailing_angle_brackets` already emitted a nicer error
1506 // NOTE(eddyb) this was `.cancel()`, but `err`
1507 // gets returned, so we can't fully defuse it.
1513 if self.token.is_ident() {
1514 // This is likely another field; emit the diagnostic and keep going
1515 err.span_suggestion(
1517 "try adding a comma",
1519 Applicability::MachineApplicable,
1526 // Make sure an error was emitted (either by recovering an angle bracket,
1527 // or by finding an identifier as the next token), since we're
1528 // going to continue parsing
1529 assert!(self.sess.span_diagnostic.has_errors().is_some());
1538 fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
1539 if let Err(mut err) = self.expect(&token::Colon) {
1540 let sm = self.sess.source_map();
1541 let eq_typo = self.token.kind == token::Eq && self.look_ahead(1, |t| t.is_path_start());
1542 let semi_typo = self.token.kind == token::Semi
1543 && self.look_ahead(1, |t| {
1545 // We check that we are in a situation like `foo; bar` to avoid bad suggestions
1546 // when there's no type and `;` was used instead of a comma.
1547 && match (sm.lookup_line(self.token.span.hi()), sm.lookup_line(t.span.lo())) {
1548 (Ok(l), Ok(r)) => l.line == r.line,
1552 if eq_typo || semi_typo {
1554 // Gracefully handle small typos.
1555 err.span_suggestion_short(
1556 self.prev_token.span,
1557 "field names and their types are separated with `:`",
1559 Applicability::MachineApplicable,
1569 /// Parses a structure field.
1570 fn parse_name_and_ty(
1575 attrs: Vec<Attribute>,
1576 ) -> PResult<'a, FieldDef> {
1577 let name = self.parse_field_ident(adt_ty, lo)?;
1578 self.expect_field_ty_separator()?;
1579 let ty = self.parse_ty()?;
1580 if self.token.kind == token::Colon && self.look_ahead(1, |tok| tok.kind != token::Colon) {
1581 self.struct_span_err(self.token.span, "found single colon in a struct field type path")
1582 .span_suggestion_verbose(
1584 "write a path separator here",
1586 Applicability::MaybeIncorrect,
1590 if self.token.kind == token::Eq {
1592 let const_expr = self.parse_anon_const_expr()?;
1593 let sp = ty.span.shrink_to_hi().to(const_expr.value.span);
1594 self.struct_span_err(sp, "default values on `struct` fields aren't supported")
1597 "remove this unsupported default value",
1599 Applicability::MachineApplicable,
1604 span: lo.to(self.prev_token.span),
1609 attrs: attrs.into(),
1610 is_placeholder: false,
1614 /// Parses a field identifier. Specialized version of `parse_ident_common`
1615 /// for better diagnostics and suggestions.
1616 fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
1617 let (ident, is_raw) = self.ident_or_err()?;
1618 if !is_raw && ident.is_reserved() {
1619 let err = if self.check_fn_front_matter(false) {
1620 let inherited_vis = Visibility {
1621 span: rustc_span::DUMMY_SP,
1622 kind: VisibilityKind::Inherited,
1625 // We use `parse_fn` to get a span for the function
1626 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
1627 if let Err(mut db) =
1628 self.parse_fn(&mut Vec::new(), fn_parse_mode, lo, &inherited_vis)
1632 let mut err = self.struct_span_err(
1633 lo.to(self.prev_token.span),
1634 &format!("functions are not allowed in {adt_ty} definitions"),
1636 err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
1637 err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
1640 self.expected_ident_found()
1648 /// Parses a declarative macro 2.0 definition.
1649 /// The `macro` keyword has already been parsed.
1651 /// MacBody = "{" TOKEN_STREAM "}" ;
1652 /// MacParams = "(" TOKEN_STREAM ")" ;
1653 /// DeclMac = "macro" Ident MacParams? MacBody ;
1655 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1656 let ident = self.parse_ident()?;
1657 let body = if self.check(&token::OpenDelim(Delimiter::Brace)) {
1658 self.parse_mac_args()? // `MacBody`
1659 } else if self.check(&token::OpenDelim(Delimiter::Parenthesis)) {
1660 let params = self.parse_token_tree(); // `MacParams`
1661 let pspan = params.span();
1662 if !self.check(&token::OpenDelim(Delimiter::Brace)) {
1663 return self.unexpected();
1665 let body = self.parse_token_tree(); // `MacBody`
1666 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1667 let bspan = body.span();
1668 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1669 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1670 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1671 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1673 return self.unexpected();
1676 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
1677 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: false })))
1680 /// Is this a possibly malformed start of a `macro_rules! foo` item definition?
1682 fn is_macro_rules_item(&mut self) -> IsMacroRulesItem {
1683 if self.check_keyword(kw::MacroRules) {
1684 let macro_rules_span = self.token.span;
1686 if self.look_ahead(1, |t| *t == token::Not) && self.look_ahead(2, |t| t.is_ident()) {
1687 return IsMacroRulesItem::Yes { has_bang: true };
1688 } else if self.look_ahead(1, |t| (t.is_ident())) {
1690 self.struct_span_err(macro_rules_span, "expected `!` after `macro_rules`")
1695 Applicability::MachineApplicable,
1699 return IsMacroRulesItem::Yes { has_bang: false };
1703 IsMacroRulesItem::No
1706 /// Parses a `macro_rules! foo { ... }` declarative macro.
1707 fn parse_item_macro_rules(
1711 ) -> PResult<'a, ItemInfo> {
1712 self.expect_keyword(kw::MacroRules)?; // `macro_rules`
1715 self.expect(&token::Not)?; // `!`
1717 let ident = self.parse_ident()?;
1719 if self.eat(&token::Not) {
1720 // Handle macro_rules! foo!
1721 let span = self.prev_token.span;
1722 self.struct_span_err(span, "macro names aren't followed by a `!`")
1723 .span_suggestion(span, "remove the `!`", "", Applicability::MachineApplicable)
1727 let body = self.parse_mac_args()?;
1728 self.eat_semi_for_macro_if_needed(&body);
1729 self.complain_if_pub_macro(vis, true);
1731 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: true })))
1734 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1735 /// If that's not the case, emit an error.
1736 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1737 if let VisibilityKind::Inherited = vis.kind {
1741 let vstr = pprust::vis_to_string(vis);
1742 let vstr = vstr.trim_end();
1744 let msg = format!("can't qualify macro_rules invocation with `{vstr}`");
1745 self.struct_span_err(vis.span, &msg)
1748 "try exporting the macro",
1750 Applicability::MaybeIncorrect, // speculative
1754 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1757 "remove the visibility",
1759 Applicability::MachineApplicable,
1761 .help(&format!("try adjusting the macro to put `{vstr}` inside the invocation"))
1766 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1767 if args.need_semicolon() && !self.eat(&token::Semi) {
1768 self.report_invalid_macro_expansion_item(args);
1772 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1773 let span = args.span().expect("undelimited macro call");
1774 let mut err = self.struct_span_err(
1776 "macros that expand to items must be delimited with braces or followed by a semicolon",
1778 if self.unclosed_delims.is_empty() {
1779 let DelimSpan { open, close } = match args {
1780 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1781 MacArgs::Delimited(dspan, ..) => *dspan,
1783 err.multipart_suggestion(
1784 "change the delimiters to curly braces",
1785 vec![(open, "{".to_string()), (close, '}'.to_string())],
1786 Applicability::MaybeIncorrect,
1789 err.span_suggestion(
1791 "change the delimiters to curly braces",
1793 Applicability::HasPlaceholders,
1796 err.span_suggestion(
1797 span.shrink_to_hi(),
1800 Applicability::MaybeIncorrect,
1805 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1806 /// it is, we try to parse the item and report error about nested types.
1807 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1808 if (self.token.is_keyword(kw::Enum)
1809 || self.token.is_keyword(kw::Struct)
1810 || self.token.is_keyword(kw::Union))
1811 && self.look_ahead(1, |t| t.is_ident())
1813 let kw_token = self.token.clone();
1814 let kw_str = pprust::token_to_string(&kw_token);
1815 let item = self.parse_item(ForceCollect::No)?;
1817 self.struct_span_err(
1819 &format!("`{kw_str}` definition cannot be nested inside `{keyword}`"),
1823 &format!("consider creating a new `{kw_str}` definition instead of nesting"),
1825 Applicability::MaybeIncorrect,
1828 // We successfully parsed the item but we must inform the caller about nested problem.
1835 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1837 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1839 /// This function pointer accepts an edition, because in edition 2015, trait declarations
1840 /// were allowed to omit parameter names. In 2018, they became required.
1841 type ReqName = fn(Edition) -> bool;
1843 /// Parsing configuration for functions.
1845 /// The syntax of function items is slightly different within trait definitions,
1846 /// impl blocks, and modules. It is still parsed using the same code, just with
1847 /// different flags set, so that even when the input is wrong and produces a parse
1848 /// error, it still gets into the AST and the rest of the parser and
1849 /// type checker can run.
1850 #[derive(Clone, Copy)]
1851 pub(crate) struct FnParseMode {
1852 /// A function pointer that decides if, per-parameter `p`, `p` must have a
1853 /// pattern or just a type. This field affects parsing of the parameters list.
1856 /// fn foo(alef: A) -> X { X::new() }
1857 /// -----^^ affects parsing this part of the function signature
1859 /// if req_name returns false, then this name is optional
1864 /// if req_name returns true, this is an error
1867 /// Calling this function pointer should only return false if:
1869 /// * The item is being parsed inside of a trait definition.
1870 /// Within an impl block or a module, it should always evaluate
1872 /// * The span is from Edition 2015. In particular, you can get a
1873 /// 2015 span inside a 2021 crate using macros.
1874 pub req_name: ReqName,
1875 /// If this flag is set to `true`, then plain, semicolon-terminated function
1876 /// prototypes are not allowed here.
1879 /// fn foo(alef: A) -> X { X::new() }
1882 /// this is always allowed
1884 /// fn bar(alef: A, bet: B) -> X;
1887 /// if req_body is set to true, this is an error
1890 /// This field should only be set to false if the item is inside of a trait
1891 /// definition or extern block. Within an impl block or a module, it should
1892 /// always be set to true.
1896 /// Parsing of functions and methods.
1897 impl<'a> Parser<'a> {
1898 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1901 attrs: &mut Vec<Attribute>,
1902 fn_parse_mode: FnParseMode,
1905 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1906 let header = self.parse_fn_front_matter(vis)?; // `const ... fn`
1907 let ident = self.parse_ident()?; // `foo`
1908 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1910 self.parse_fn_decl(fn_parse_mode.req_name, AllowPlus::Yes, RecoverReturnSign::Yes)?; // `(p: u8, ...)`
1911 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1913 let mut sig_hi = self.prev_token.span;
1914 let body = self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body)?; // `;` or `{ ... }`.
1915 let fn_sig_span = sig_lo.to(sig_hi);
1916 Ok((ident, FnSig { header, decl, span: fn_sig_span }, generics, body))
1919 /// Parse the "body" of a function.
1920 /// This can either be `;` when there's no body,
1921 /// or e.g. a block when the function is a provided one.
1924 attrs: &mut Vec<Attribute>,
1928 ) -> PResult<'a, Option<P<Block>>> {
1929 let has_semi = if req_body {
1930 self.token.kind == TokenKind::Semi
1932 // Only include `;` in list of expected tokens if body is not required
1933 self.check(&TokenKind::Semi)
1935 let (inner_attrs, body) = if has_semi {
1936 // Include the trailing semicolon in the span of the signature
1937 self.expect_semi()?;
1938 *sig_hi = self.prev_token.span;
1940 } else if self.check(&token::OpenDelim(Delimiter::Brace)) || self.token.is_whole_block() {
1941 self.parse_inner_attrs_and_block().map(|(attrs, body)| (attrs, Some(body)))?
1942 } else if self.token.kind == token::Eq {
1943 // Recover `fn foo() = $expr;`.
1945 let eq_sp = self.prev_token.span;
1946 let _ = self.parse_expr()?;
1947 self.expect_semi()?; // `;`
1948 let span = eq_sp.to(self.prev_token.span);
1949 self.struct_span_err(span, "function body cannot be `= expression;`")
1950 .multipart_suggestion(
1951 "surround the expression with `{` and `}` instead of `=` and `;`",
1952 vec![(eq_sp, "{".to_string()), (self.prev_token.span, " }".to_string())],
1953 Applicability::MachineApplicable,
1956 (Vec::new(), Some(self.mk_block_err(span)))
1958 let expected = if req_body {
1959 &[token::OpenDelim(Delimiter::Brace)][..]
1961 &[token::Semi, token::OpenDelim(Delimiter::Brace)]
1963 if let Err(mut err) = self.expected_one_of_not_found(&[], &expected) {
1964 if self.token.kind == token::CloseDelim(Delimiter::Brace) {
1965 // The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
1966 // the AST for typechecking.
1967 err.span_label(ident.span, "while parsing this `fn`");
1975 attrs.extend(inner_attrs);
1979 /// Is the current token the start of an `FnHeader` / not a valid parse?
1981 /// `check_pub` adds additional `pub` to the checks in case users place it
1982 /// wrongly, can be used to ensure `pub` never comes after `default`.
1983 pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
1984 // We use an over-approximation here.
1985 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1986 // `pub` is added in case users got confused with the ordering like `async pub fn`,
1987 // only if it wasn't preceded by `default` as `default pub` is invalid.
1988 let quals: &[Symbol] = if check_pub {
1989 &[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1991 &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1993 self.check_keyword(kw::Fn) // Definitely an `fn`.
1994 // `$qual fn` or `$qual $qual`:
1995 || quals.iter().any(|&kw| self.check_keyword(kw))
1996 && self.look_ahead(1, |t| {
1997 // `$qual fn`, e.g. `const fn` or `async fn`.
1998 t.is_keyword(kw::Fn)
1999 // Two qualifiers `$qual $qual` is enough, e.g. `async unsafe`.
2000 || t.is_non_raw_ident_where(|i| quals.contains(&i.name)
2001 // Rule out 2015 `const async: T = val`.
2003 // Rule out unsafe extern block.
2004 && !self.is_unsafe_foreign_mod())
2007 || self.check_keyword(kw::Extern)
2008 && self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
2009 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
2012 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
2013 /// up to and including the `fn` keyword. The formal grammar is:
2016 /// Extern = "extern" StringLit? ;
2017 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
2018 /// FnFrontMatter = FnQual "fn" ;
2021 /// `vis` represents the visibility that was already parsed, if any. Use
2022 /// `Visibility::Inherited` when no visibility is known.
2023 pub(super) fn parse_fn_front_matter(&mut self, orig_vis: &Visibility) -> PResult<'a, FnHeader> {
2024 let sp_start = self.token.span;
2025 let constness = self.parse_constness();
2027 let async_start_sp = self.token.span;
2028 let asyncness = self.parse_asyncness();
2030 let unsafe_start_sp = self.token.span;
2031 let unsafety = self.parse_unsafety();
2033 let ext_start_sp = self.token.span;
2034 let ext = self.parse_extern();
2036 if let Async::Yes { span, .. } = asyncness {
2037 self.ban_async_in_2015(span);
2040 if !self.eat_keyword(kw::Fn) {
2041 // It is possible for `expect_one_of` to recover given the contents of
2042 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
2043 // account for this.
2044 match self.expect_one_of(&[], &[]) {
2046 Ok(false) => unreachable!(),
2048 // Qualifier keywords ordering check
2054 // This will allow the machine fix to directly place the keyword in the correct place or to indicate
2055 // that the keyword is already present and the second instance should be removed.
2056 let wrong_kw = if self.check_keyword(kw::Const) {
2058 Const::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2059 Const::No => Some(WrongKw::Misplaced(async_start_sp)),
2061 } else if self.check_keyword(kw::Async) {
2063 Async::Yes { span, .. } => Some(WrongKw::Duplicated(span)),
2064 Async::No => Some(WrongKw::Misplaced(unsafe_start_sp)),
2066 } else if self.check_keyword(kw::Unsafe) {
2068 Unsafe::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2069 Unsafe::No => Some(WrongKw::Misplaced(ext_start_sp)),
2075 // The keyword is already present, suggest removal of the second instance
2076 if let Some(WrongKw::Duplicated(original_sp)) = wrong_kw {
2077 let original_kw = self
2078 .span_to_snippet(original_sp)
2079 .expect("Span extracted directly from keyword should always work");
2081 err.span_suggestion(
2082 self.token.uninterpolated_span(),
2083 &format!("`{original_kw}` already used earlier, remove this one"),
2085 Applicability::MachineApplicable,
2087 .span_note(original_sp, &format!("`{original_kw}` first seen here"));
2089 // The keyword has not been seen yet, suggest correct placement in the function front matter
2090 else if let Some(WrongKw::Misplaced(correct_pos_sp)) = wrong_kw {
2091 let correct_pos_sp = correct_pos_sp.to(self.prev_token.span);
2092 if let Ok(current_qual) = self.span_to_snippet(correct_pos_sp) {
2093 let misplaced_qual_sp = self.token.uninterpolated_span();
2094 let misplaced_qual = self.span_to_snippet(misplaced_qual_sp).unwrap();
2096 err.span_suggestion(
2097 correct_pos_sp.to(misplaced_qual_sp),
2098 &format!("`{misplaced_qual}` must come before `{current_qual}`"),
2099 format!("{misplaced_qual} {current_qual}"),
2100 Applicability::MachineApplicable,
2101 ).note("keyword order for functions declaration is `pub`, `default`, `const`, `async`, `unsafe`, `extern`");
2104 // Recover incorrect visibility order such as `async pub`
2105 else if self.check_keyword(kw::Pub) {
2106 let sp = sp_start.to(self.prev_token.span);
2107 if let Ok(snippet) = self.span_to_snippet(sp) {
2108 let current_vis = match self.parse_visibility(FollowedByType::No) {
2115 let vs = pprust::vis_to_string(¤t_vis);
2116 let vs = vs.trim_end();
2118 // There was no explicit visibility
2119 if matches!(orig_vis.kind, VisibilityKind::Inherited) {
2120 err.span_suggestion(
2121 sp_start.to(self.prev_token.span),
2122 &format!("visibility `{vs}` must come before `{snippet}`"),
2123 format!("{vs} {snippet}"),
2124 Applicability::MachineApplicable,
2127 // There was an explicit visibility
2129 err.span_suggestion(
2131 "there is already a visibility modifier, remove one",
2133 Applicability::MachineApplicable,
2135 .span_note(orig_vis.span, "explicit visibility first seen here");
2144 Ok(FnHeader { constness, unsafety, asyncness, ext })
2147 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
2148 fn ban_async_in_2015(&self, span: Span) {
2149 if span.rust_2015() {
2150 let diag = self.diagnostic();
2151 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in Rust 2015")
2152 .span_label(span, "to use `async fn`, switch to Rust 2018 or later")
2153 .help_use_latest_edition()
2158 /// Parses the parameter list and result type of a function declaration.
2159 pub(super) fn parse_fn_decl(
2162 ret_allow_plus: AllowPlus,
2163 recover_return_sign: RecoverReturnSign,
2164 ) -> PResult<'a, P<FnDecl>> {
2166 inputs: self.parse_fn_params(req_name)?,
2167 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes, recover_return_sign)?,
2171 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
2172 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
2173 let mut first_param = true;
2174 // Parse the arguments, starting out with `self` being allowed...
2175 let (mut params, _) = self.parse_paren_comma_seq(|p| {
2176 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
2178 let lo = p.prev_token.span;
2179 // Skip every token until next possible arg or end.
2180 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(Delimiter::Parenthesis)]);
2181 // Create a placeholder argument for proper arg count (issue #34264).
2182 Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span))))
2184 // ...now that we've parsed the first argument, `self` is no longer allowed.
2185 first_param = false;
2188 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
2189 self.deduplicate_recovered_params_names(&mut params);
2193 /// Parses a single function parameter.
2195 /// - `self` is syntactically allowed when `first_param` holds.
2196 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
2197 let lo = self.token.span;
2198 let attrs = self.parse_outer_attributes()?;
2199 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2200 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
2201 if let Some(mut param) = this.parse_self_param()? {
2202 param.attrs = attrs.into();
2203 let res = if first_param { Ok(param) } else { this.recover_bad_self_param(param) };
2204 return Ok((res?, TrailingToken::None));
2207 let is_name_required = match this.token.kind {
2208 token::DotDotDot => false,
2209 _ => req_name(this.token.span.edition()),
2211 let (pat, ty) = if is_name_required || this.is_named_param() {
2212 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
2214 let (pat, colon) = this.parse_fn_param_pat_colon()?;
2216 let mut err = this.unexpected::<()>().unwrap_err();
2217 return if let Some(ident) =
2218 this.parameter_without_type(&mut err, pat, is_name_required, first_param)
2221 Ok((dummy_arg(ident), TrailingToken::None))
2227 this.eat_incorrect_doc_comment_for_param_type();
2228 (pat, this.parse_ty_for_param()?)
2230 debug!("parse_param_general ident_to_pat");
2231 let parser_snapshot_before_ty = this.clone();
2232 this.eat_incorrect_doc_comment_for_param_type();
2233 let mut ty = this.parse_ty_for_param();
2235 && this.token != token::Comma
2236 && this.token != token::CloseDelim(Delimiter::Parenthesis)
2238 // This wasn't actually a type, but a pattern looking like a type,
2239 // so we are going to rollback and re-parse for recovery.
2240 ty = this.unexpected();
2244 let ident = Ident::new(kw::Empty, this.prev_token.span);
2245 let bm = BindingMode::ByValue(Mutability::Not);
2246 let pat = this.mk_pat_ident(ty.span, bm, ident);
2249 // If this is a C-variadic argument and we hit an error, return the error.
2250 Err(err) if this.token == token::DotDotDot => return Err(err),
2251 // Recover from attempting to parse the argument as a type without pattern.
2254 *this = parser_snapshot_before_ty;
2255 this.recover_arg_parse()?
2260 let span = lo.until(this.token.span);
2264 attrs: attrs.into(),
2265 id: ast::DUMMY_NODE_ID,
2266 is_placeholder: false,
2271 TrailingToken::None,
2276 /// Returns the parsed optional self parameter and whether a self shortcut was used.
2277 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
2278 // Extract an identifier *after* having confirmed that the token is one.
2279 let expect_self_ident = |this: &mut Self| match this.token.ident() {
2280 Some((ident, false)) => {
2284 _ => unreachable!(),
2286 // Is `self` `n` tokens ahead?
2287 let is_isolated_self = |this: &Self, n| {
2288 this.is_keyword_ahead(n, &[kw::SelfLower])
2289 && this.look_ahead(n + 1, |t| t != &token::ModSep)
2291 // Is `mut self` `n` tokens ahead?
2292 let is_isolated_mut_self =
2293 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
2294 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
2295 let parse_self_possibly_typed = |this: &mut Self, m| {
2296 let eself_ident = expect_self_ident(this);
2297 let eself_hi = this.prev_token.span;
2298 let eself = if this.eat(&token::Colon) {
2299 SelfKind::Explicit(this.parse_ty()?, m)
2303 Ok((eself, eself_ident, eself_hi))
2305 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
2306 let recover_self_ptr = |this: &mut Self| {
2307 let msg = "cannot pass `self` by raw pointer";
2308 let span = this.token.span;
2309 this.struct_span_err(span, msg).span_label(span, msg).emit();
2311 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_token.span))
2314 // Parse optional `self` parameter of a method.
2315 // Only a limited set of initial token sequences is considered `self` parameters; anything
2316 // else is parsed as a normal function parameter list, so some lookahead is required.
2317 let eself_lo = self.token.span;
2318 let (eself, eself_ident, eself_hi) = match self.token.uninterpolate().kind {
2319 token::BinOp(token::And) => {
2320 let eself = if is_isolated_self(self, 1) {
2323 SelfKind::Region(None, Mutability::Not)
2324 } else if is_isolated_mut_self(self, 1) {
2328 SelfKind::Region(None, Mutability::Mut)
2329 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
2332 let lt = self.expect_lifetime();
2333 SelfKind::Region(Some(lt), Mutability::Not)
2334 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
2337 let lt = self.expect_lifetime();
2339 SelfKind::Region(Some(lt), Mutability::Mut)
2344 (eself, expect_self_ident(self), self.prev_token.span)
2347 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
2349 recover_self_ptr(self)?
2351 // `*mut self` and `*const self`
2352 token::BinOp(token::Star)
2353 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
2357 recover_self_ptr(self)?
2359 // `self` and `self: TYPE`
2360 token::Ident(..) if is_isolated_self(self, 0) => {
2361 parse_self_possibly_typed(self, Mutability::Not)?
2363 // `mut self` and `mut self: TYPE`
2364 token::Ident(..) if is_isolated_mut_self(self, 0) => {
2366 parse_self_possibly_typed(self, Mutability::Mut)?
2368 _ => return Ok(None),
2371 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
2372 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
2375 fn is_named_param(&self) -> bool {
2376 let offset = match self.token.kind {
2377 token::Interpolated(ref nt) => match **nt {
2378 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
2381 token::BinOp(token::And) | token::AndAnd => 1,
2382 _ if self.token.is_keyword(kw::Mut) => 1,
2386 self.look_ahead(offset, |t| t.is_ident())
2387 && self.look_ahead(offset + 1, |t| t == &token::Colon)
2390 fn recover_first_param(&mut self) -> &'static str {
2392 .parse_outer_attributes()
2393 .and_then(|_| self.parse_self_param())
2394 .map_err(|e| e.cancel())
2396 Ok(Some(_)) => "method",
2402 enum IsMacroRulesItem {
2403 Yes { has_bang: bool },