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, LATEST_STABLE_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};
22 use std::convert::TryFrom;
27 /// Parses a source module as a crate. This is the main entry point for the parser.
28 pub fn parse_crate_mod(&mut self) -> PResult<'a, ast::Crate> {
29 let (attrs, items, span) = self.parse_mod(&token::Eof)?;
30 Ok(ast::Crate { attrs, items, span, is_placeholder: None })
33 /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
34 fn parse_item_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
35 let unsafety = self.parse_unsafety();
36 self.expect_keyword(kw::Mod)?;
37 let id = self.parse_ident()?;
38 let mod_kind = if self.eat(&token::Semi) {
41 self.expect(&token::OpenDelim(token::Brace))?;
42 let (mut inner_attrs, items, inner_span) =
43 self.parse_mod(&token::CloseDelim(token::Brace))?;
44 attrs.append(&mut inner_attrs);
45 ModKind::Loaded(items, Inline::Yes, inner_span)
47 Ok((id, ItemKind::Mod(unsafety, mod_kind)))
50 /// Parses the contents of a module (inner attributes followed by module items).
54 ) -> PResult<'a, (Vec<Attribute>, Vec<P<Item>>, Span)> {
55 let lo = self.token.span;
56 let attrs = self.parse_inner_attributes()?;
58 let mut items = vec![];
59 while let Some(item) = self.parse_item(ForceCollect::No)? {
61 self.maybe_consume_incorrect_semicolon(&items);
65 let token_str = super::token_descr(&self.token);
66 if !self.maybe_consume_incorrect_semicolon(&items) {
67 let msg = &format!("expected item, found {}", token_str);
68 let mut err = self.struct_span_err(self.token.span, msg);
69 err.span_label(self.token.span, "expected item");
74 Ok((attrs, items, lo.to(self.prev_token.span)))
78 pub(super) type ItemInfo = (Ident, ItemKind);
81 pub fn parse_item(&mut self, force_collect: ForceCollect) -> PResult<'a, Option<P<Item>>> {
82 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
83 self.parse_item_(fn_parse_mode, force_collect).map(|i| i.map(P))
88 fn_parse_mode: FnParseMode,
89 force_collect: ForceCollect,
90 ) -> PResult<'a, Option<Item>> {
91 let attrs = self.parse_outer_attributes()?;
92 self.parse_item_common(attrs, true, false, fn_parse_mode, force_collect)
95 pub(super) fn parse_item_common(
100 fn_parse_mode: FnParseMode,
101 force_collect: ForceCollect,
102 ) -> PResult<'a, Option<Item>> {
103 // Don't use `maybe_whole` so that we have precise control
104 // over when we bump the parser
105 if let token::Interpolated(nt) = &self.token.kind {
106 if let token::NtItem(item) = &**nt {
107 let mut item = item.clone();
110 attrs.prepend_to_nt_inner(&mut item.attrs);
111 return Ok(Some(item.into_inner()));
115 let mut unclosed_delims = vec![];
117 self.collect_tokens_trailing_token(attrs, force_collect, |this: &mut Self, attrs| {
119 this.parse_item_common_(attrs, mac_allowed, attrs_allowed, fn_parse_mode);
120 unclosed_delims.append(&mut this.unclosed_delims);
121 Ok((item?, TrailingToken::None))
124 self.unclosed_delims.append(&mut unclosed_delims);
128 fn parse_item_common_(
130 mut attrs: Vec<Attribute>,
133 fn_parse_mode: FnParseMode,
134 ) -> PResult<'a, Option<Item>> {
135 let lo = self.token.span;
136 let vis = self.parse_visibility(FollowedByType::No)?;
137 let mut def = self.parse_defaultness();
139 self.parse_item_kind(&mut attrs, mac_allowed, lo, &vis, &mut def, fn_parse_mode)?;
140 if let Some((ident, kind)) = kind {
141 self.error_on_unconsumed_default(def, &kind);
142 let span = lo.to(self.prev_token.span);
143 let id = DUMMY_NODE_ID;
144 let item = Item { ident, attrs, id, kind, vis, span, tokens: None };
145 return Ok(Some(item));
148 // At this point, we have failed to parse an item.
149 self.error_on_unmatched_vis(&vis);
150 self.error_on_unmatched_defaultness(def);
152 self.recover_attrs_no_item(&attrs)?;
157 /// Error in-case a non-inherited visibility was parsed but no item followed.
158 fn error_on_unmatched_vis(&self, vis: &Visibility) {
159 if let VisibilityKind::Inherited = vis.kind {
162 let vs = pprust::vis_to_string(&vis);
163 let vs = vs.trim_end();
164 self.struct_span_err(vis.span, &format!("visibility `{}` is not followed by an item", vs))
165 .span_label(vis.span, "the visibility")
166 .help(&format!("you likely meant to define an item, e.g., `{} fn foo() {{}}`", vs))
170 /// Error in-case a `default` was parsed but no item followed.
171 fn error_on_unmatched_defaultness(&self, def: Defaultness) {
172 if let Defaultness::Default(sp) = def {
173 self.struct_span_err(sp, "`default` is not followed by an item")
174 .span_label(sp, "the `default` qualifier")
175 .note("only `fn`, `const`, `type`, or `impl` items may be prefixed by `default`")
180 /// Error in-case `default` was parsed in an in-appropriate context.
181 fn error_on_unconsumed_default(&self, def: Defaultness, kind: &ItemKind) {
182 if let Defaultness::Default(span) = def {
183 let msg = format!("{} {} cannot be `default`", kind.article(), kind.descr());
184 self.struct_span_err(span, &msg)
185 .span_label(span, "`default` because of this")
186 .note("only associated `fn`, `const`, and `type` items can be `default`")
191 /// Parses one of the items allowed by the flags.
194 attrs: &mut Vec<Attribute>,
195 macros_allowed: bool,
198 def: &mut Defaultness,
199 fn_parse_mode: FnParseMode,
200 ) -> PResult<'a, Option<ItemInfo>> {
201 let def_final = def == &Defaultness::Final;
202 let mut def = || mem::replace(def, Defaultness::Final);
204 let info = if self.eat_keyword(kw::Use) {
206 let tree = self.parse_use_tree()?;
208 // If wildcard or glob-like brace syntax doesn't have `;`,
209 // the user may not know `*` or `{}` should be the last.
210 if let Err(mut e) = self.expect_semi() {
212 UseTreeKind::Glob => {
213 e.note("the wildcard token must be last on the path").emit();
215 UseTreeKind::Nested(..) => {
216 e.note("glob-like brace syntax must be last on the path").emit();
223 (Ident::empty(), ItemKind::Use(tree))
224 } else if self.check_fn_front_matter(def_final) {
226 let (ident, sig, generics, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis)?;
227 (ident, ItemKind::Fn(Box::new(Fn { defaultness: def(), sig, generics, body })))
228 } else if self.eat_keyword(kw::Extern) {
229 if self.eat_keyword(kw::Crate) {
231 self.parse_item_extern_crate()?
234 self.parse_item_foreign_mod(attrs, Unsafe::No)?
236 } else if self.is_unsafe_foreign_mod() {
238 let unsafety = self.parse_unsafety();
239 self.expect_keyword(kw::Extern)?;
240 self.parse_item_foreign_mod(attrs, unsafety)?
241 } else if self.is_static_global() {
243 self.bump(); // `static`
244 let m = self.parse_mutability();
245 let (ident, ty, expr) = self.parse_item_global(Some(m))?;
246 (ident, ItemKind::Static(ty, m, expr))
247 } else if let Const::Yes(const_span) = self.parse_constness() {
249 if self.token.is_keyword(kw::Impl) {
250 // recover from `const impl`, suggest `impl const`
251 self.recover_const_impl(const_span, attrs, def())?
253 self.recover_const_mut(const_span);
254 let (ident, ty, expr) = self.parse_item_global(None)?;
255 (ident, ItemKind::Const(def(), ty, expr))
257 } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
259 self.parse_item_trait(attrs, lo)?
260 } else if self.check_keyword(kw::Impl)
261 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
264 self.parse_item_impl(attrs, def())?
265 } else if self.check_keyword(kw::Mod)
266 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Mod])
269 self.parse_item_mod(attrs)?
270 } else if self.eat_keyword(kw::Type) {
272 self.parse_type_alias(def())?
273 } else if self.eat_keyword(kw::Enum) {
275 self.parse_item_enum()?
276 } else if self.eat_keyword(kw::Struct) {
278 self.parse_item_struct()?
279 } else if self.is_kw_followed_by_ident(kw::Union) {
281 self.bump(); // `union`
282 self.parse_item_union()?
283 } else if self.eat_keyword(kw::Macro) {
285 self.parse_item_decl_macro(lo)?
286 } else if let IsMacroRulesItem::Yes { has_bang } = self.is_macro_rules_item() {
288 self.parse_item_macro_rules(vis, has_bang)?
289 } else if vis.kind.is_pub() && self.isnt_macro_invocation() {
290 self.recover_missing_kw_before_item()?;
292 } else if macros_allowed && self.check_path() {
293 // MACRO INVOCATION ITEM
294 (Ident::empty(), ItemKind::MacCall(self.parse_item_macro(vis)?))
301 /// When parsing a statement, would the start of a path be an item?
302 pub(super) fn is_path_start_item(&mut self) -> bool {
303 self.is_crate_vis() // no: `crate::b`, yes: `crate $item`
304 || self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
305 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
306 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
307 || matches!(self.is_macro_rules_item(), IsMacroRulesItem::Yes{..}) // no: `macro_rules::b`, yes: `macro_rules! mac`
310 /// Are we sure this could not possibly be a macro invocation?
311 fn isnt_macro_invocation(&mut self) -> bool {
312 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
315 /// Recover on encountering a struct or method definition where the user
316 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
317 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
318 // Space between `pub` keyword and the identifier
321 // ^^^ `sp` points here
322 let sp = self.prev_token.span.between(self.token.span);
323 let full_sp = self.prev_token.span.to(self.token.span);
324 let ident_sp = self.token.span;
325 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
326 // possible public struct definition where `struct` was forgotten
327 let ident = self.parse_ident().unwrap();
328 let msg = format!("add `struct` here to parse `{}` as a public struct", ident);
329 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
330 err.span_suggestion_short(
334 Applicability::MaybeIncorrect, // speculative
337 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
338 let ident = self.parse_ident().unwrap();
340 let kw_name = self.recover_first_param();
341 self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
342 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
343 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
345 ("fn", kw_name, false)
346 } else if self.check(&token::OpenDelim(token::Brace)) {
348 ("fn", kw_name, false)
349 } else if self.check(&token::Colon) {
353 ("fn` or `struct", "function or struct", true)
356 let msg = format!("missing `{}` for {} definition", kw, kw_name);
357 let mut err = self.struct_span_err(sp, &msg);
359 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
361 format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name);
362 err.span_suggestion_short(
366 Applicability::MachineApplicable,
368 } else if let Ok(snippet) = self.span_to_snippet(ident_sp) {
371 "if you meant to call a macro, try",
372 format!("{}!", snippet),
373 // this is the `ambiguous` conditional branch
374 Applicability::MaybeIncorrect,
378 "if you meant to call a macro, remove the `pub` \
379 and add a trailing `!` after the identifier",
383 } else if self.look_ahead(1, |t| *t == token::Lt) {
384 let ident = self.parse_ident().unwrap();
385 self.eat_to_tokens(&[&token::Gt]);
387 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
388 ("fn", self.recover_first_param(), false)
389 } else if self.check(&token::OpenDelim(token::Brace)) {
390 ("struct", "struct", false)
392 ("fn` or `struct", "function or struct", true)
394 let msg = format!("missing `{}` for {} definition", kw, kw_name);
395 let mut err = self.struct_span_err(sp, &msg);
397 err.span_suggestion_short(
399 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
401 Applicability::MachineApplicable,
410 /// Parses an item macro, e.g., `item!();`.
411 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, MacCall> {
412 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
413 self.expect(&token::Not)?; // `!`
414 match self.parse_mac_args() {
415 // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
417 self.eat_semi_for_macro_if_needed(&args);
418 self.complain_if_pub_macro(vis, false);
419 Ok(MacCall { path, args, prior_type_ascription: self.last_type_ascription })
423 // Maybe the user misspelled `macro_rules` (issue #91227)
424 if self.token.is_ident()
425 && path.segments.len() == 1
426 && lev_distance("macro_rules", &path.segments[0].ident.to_string()) <= 3
430 "perhaps you meant to define a macro",
431 "macro_rules".to_string(),
432 Applicability::MachineApplicable,
440 /// Recover if we parsed attributes and expected an item but there was none.
441 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
442 let (start, end) = match attrs {
444 [x0 @ xn] | [x0, .., xn] => (x0, xn),
446 let msg = if end.is_doc_comment() {
447 "expected item after doc comment"
449 "expected item after attributes"
451 let mut err = self.struct_span_err(end.span, msg);
452 if end.is_doc_comment() {
453 err.span_label(end.span, "this doc comment doesn't document anything");
455 if let [.., penultimate, _] = attrs {
456 err.span_label(start.span.to(penultimate.span), "other attributes here");
461 fn is_async_fn(&self) -> bool {
462 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
465 fn parse_polarity(&mut self) -> ast::ImplPolarity {
466 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
467 if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
469 ast::ImplPolarity::Negative(self.prev_token.span)
471 ast::ImplPolarity::Positive
475 /// Parses an implementation item.
478 /// impl<'a, T> TYPE { /* impl items */ }
479 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
480 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
481 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
484 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
486 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
487 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
491 attrs: &mut Vec<Attribute>,
492 defaultness: Defaultness,
493 ) -> PResult<'a, ItemInfo> {
494 let unsafety = self.parse_unsafety();
495 self.expect_keyword(kw::Impl)?;
497 // First, parse generic parameters if necessary.
498 let mut generics = if self.choose_generics_over_qpath(0) {
499 self.parse_generics()?
501 let mut generics = Generics::default();
503 // /\ this is where `generics.span` should point when there are no type params.
504 generics.span = self.prev_token.span.shrink_to_hi();
508 let constness = self.parse_constness();
509 if let Const::Yes(span) = constness {
510 self.sess.gated_spans.gate(sym::const_trait_impl, span);
513 let polarity = self.parse_polarity();
515 // Parse both types and traits as a type, then reinterpret if necessary.
516 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Empty, span));
517 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
519 let span = self.prev_token.span.between(self.token.span);
520 self.struct_span_err(span, "missing trait in a trait impl")
525 Applicability::HasPlaceholders,
528 span.to(self.token.span),
529 "for an inherent impl, drop this `for`",
531 Applicability::MaybeIncorrect,
535 kind: TyKind::Path(None, err_path(span)),
541 self.parse_ty_with_generics_recovery(&generics)?
544 // If `for` is missing we try to recover.
545 let has_for = self.eat_keyword(kw::For);
546 let missing_for_span = self.prev_token.span.between(self.token.span);
548 let ty_second = if self.token == token::DotDot {
549 // We need to report this error after `cfg` expansion for compatibility reasons
550 self.bump(); // `..`, do not add it to expected tokens
551 Some(self.mk_ty(self.prev_token.span, TyKind::Err))
552 } else if has_for || self.token.can_begin_type() {
553 Some(self.parse_ty()?)
558 generics.where_clause = self.parse_where_clause()?;
560 let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item(ForceCollect::No))?;
562 let item_kind = match ty_second {
564 // impl Trait for Type
566 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
567 .span_suggestion_short(
571 Applicability::MachineApplicable,
576 let ty_first = ty_first.into_inner();
577 let path = match ty_first.kind {
578 // This notably includes paths passed through `ty` macro fragments (#46438).
579 TyKind::Path(None, path) => path,
581 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
582 err_path(ty_first.span)
585 let trait_ref = TraitRef { path, ref_id: ty_first.id };
587 ItemKind::Impl(Box::new(Impl {
593 of_trait: Some(trait_ref),
600 ItemKind::Impl(Box::new(Impl {
613 Ok((Ident::empty(), item_kind))
616 fn parse_item_list<T>(
618 attrs: &mut Vec<Attribute>,
619 mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
620 ) -> PResult<'a, Vec<T>> {
621 let open_brace_span = self.token.span;
622 self.expect(&token::OpenDelim(token::Brace))?;
623 attrs.append(&mut self.parse_inner_attributes()?);
625 let mut items = Vec::new();
626 while !self.eat(&token::CloseDelim(token::Brace)) {
627 if self.recover_doc_comment_before_brace() {
630 match parse_item(self) {
632 // We have to bail or we'll potentially never make progress.
633 let non_item_span = self.token.span;
634 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
635 self.struct_span_err(non_item_span, "non-item in item list")
636 .span_label(open_brace_span, "item list starts here")
637 .span_label(non_item_span, "non-item starts here")
638 .span_label(self.prev_token.span, "item list ends here")
642 Ok(Some(item)) => items.extend(item),
644 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
645 err.span_label(open_brace_span, "while parsing this item list starting here")
646 .span_label(self.prev_token.span, "the item list ends here")
655 /// Recover on a doc comment before `}`.
656 fn recover_doc_comment_before_brace(&mut self) -> bool {
657 if let token::DocComment(..) = self.token.kind {
658 if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
663 "found a documentation comment that doesn't document anything",
665 .span_label(self.token.span, "this doc comment doesn't document anything")
667 "doc comments must come before what they document, maybe a \
668 comment was intended with `//`?",
678 /// Parses defaultness (i.e., `default` or nothing).
679 fn parse_defaultness(&mut self) -> Defaultness {
680 // We are interested in `default` followed by another identifier.
681 // However, we must avoid keywords that occur as binary operators.
682 // Currently, the only applicable keyword is `as` (`default as Ty`).
683 if self.check_keyword(kw::Default)
684 && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
686 self.bump(); // `default`
687 Defaultness::Default(self.prev_token.uninterpolated_span())
693 /// Is this an `(unsafe auto? | auto) trait` item?
694 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
696 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
698 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
701 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
702 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
703 let unsafety = self.parse_unsafety();
704 // Parse optional `auto` prefix.
705 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
707 self.expect_keyword(kw::Trait)?;
708 let ident = self.parse_ident()?;
709 let mut generics = self.parse_generics()?;
711 // Parse optional colon and supertrait bounds.
712 let had_colon = self.eat(&token::Colon);
713 let span_at_colon = self.prev_token.span;
714 let bounds = if had_colon {
715 self.parse_generic_bounds(Some(self.prev_token.span))?
720 let span_before_eq = self.prev_token.span;
721 if self.eat(&token::Eq) {
722 // It's a trait alias.
724 let span = span_at_colon.to(span_before_eq);
725 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
728 let bounds = self.parse_generic_bounds(None)?;
729 generics.where_clause = self.parse_where_clause()?;
732 let whole_span = lo.to(self.prev_token.span);
733 if is_auto == IsAuto::Yes {
734 let msg = "trait aliases cannot be `auto`";
735 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
737 if let Unsafe::Yes(_) = unsafety {
738 let msg = "trait aliases cannot be `unsafe`";
739 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
742 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
744 Ok((ident, ItemKind::TraitAlias(generics, bounds)))
746 // It's a normal trait.
747 generics.where_clause = self.parse_where_clause()?;
748 let items = self.parse_item_list(attrs, |p| p.parse_trait_item(ForceCollect::No))?;
751 ItemKind::Trait(Box::new(Trait { is_auto, unsafety, generics, bounds, items })),
756 pub fn parse_impl_item(
758 force_collect: ForceCollect,
759 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
760 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
761 self.parse_assoc_item(fn_parse_mode, force_collect)
764 pub fn parse_trait_item(
766 force_collect: ForceCollect,
767 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
769 FnParseMode { req_name: |edition| edition >= Edition::Edition2018, req_body: false };
770 self.parse_assoc_item(fn_parse_mode, force_collect)
773 /// Parses associated items.
776 fn_parse_mode: FnParseMode,
777 force_collect: ForceCollect,
778 ) -> PResult<'a, Option<Option<P<AssocItem>>>> {
779 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
780 |Item { attrs, id, span, vis, ident, kind, tokens }| {
781 let kind = match AssocItemKind::try_from(kind) {
783 Err(kind) => match kind {
784 ItemKind::Static(a, _, b) => {
785 self.struct_span_err(span, "associated `static` items are not allowed")
787 AssocItemKind::Const(Defaultness::Final, a, b)
789 _ => return self.error_bad_item_kind(span, &kind, "`trait`s or `impl`s"),
792 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
797 /// Emits an error that the where clause at the end of a type alias is not
798 /// allowed and suggests moving it.
799 fn error_ty_alias_where(
801 before_where_clause_present: bool,
802 before_where_clause_span: Span,
803 after_predicates: &[WherePredicate],
804 after_where_clause_span: Span,
807 self.struct_span_err(after_where_clause_span, "where clause not allowed here");
808 if !after_predicates.is_empty() {
809 let mut state = crate::pprust::State::new();
810 if !before_where_clause_present {
812 state.word_space("where");
814 state.word_space(",");
816 let mut first = true;
817 for p in after_predicates.iter() {
819 state.word_space(",");
822 state.print_where_predicate(p);
824 let suggestion = state.s.eof();
826 before_where_clause_span.shrink_to_hi(),
829 Applicability::MachineApplicable,
835 /// Parses a `type` alias with the following grammar:
837 /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
839 /// The `"type"` has already been eaten.
840 fn parse_type_alias(&mut self, defaultness: Defaultness) -> PResult<'a, ItemInfo> {
841 let ident = self.parse_ident()?;
842 let mut generics = self.parse_generics()?;
844 // Parse optional colon and param bounds.
846 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
848 generics.where_clause = self.parse_where_clause()?;
850 let ty = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
852 if self.token.is_keyword(kw::Where) {
853 let after_where_clause = self.parse_where_clause()?;
855 self.error_ty_alias_where(
856 generics.where_clause.has_where_token,
857 generics.where_clause.span,
858 &after_where_clause.predicates,
859 after_where_clause.span,
862 generics.where_clause.predicates.extend(after_where_clause.predicates.into_iter());
867 Ok((ident, ItemKind::TyAlias(Box::new(TyAlias { defaultness, generics, bounds, ty }))))
870 /// Parses a `UseTree`.
873 /// USE_TREE = [`::`] `*` |
874 /// [`::`] `{` USE_TREE_LIST `}` |
876 /// PATH `::` `{` USE_TREE_LIST `}` |
877 /// PATH [`as` IDENT]
879 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
880 let lo = self.token.span;
882 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo(), tokens: None };
883 let kind = if self.check(&token::OpenDelim(token::Brace))
884 || self.check(&token::BinOp(token::Star))
885 || self.is_import_coupler()
887 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
888 let mod_sep_ctxt = self.token.span.ctxt();
889 if self.eat(&token::ModSep) {
892 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
895 self.parse_use_tree_glob_or_nested()?
897 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
898 prefix = self.parse_path(PathStyle::Mod)?;
900 if self.eat(&token::ModSep) {
901 self.parse_use_tree_glob_or_nested()?
903 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
907 Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.span) })
910 /// Parses `*` or `{...}`.
911 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
912 Ok(if self.eat(&token::BinOp(token::Star)) {
915 UseTreeKind::Nested(self.parse_use_tree_list()?)
919 /// Parses a `UseTreeKind::Nested(list)`.
922 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
924 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
925 self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
929 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
930 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
933 fn parse_ident_or_underscore(&mut self) -> PResult<'a, Ident> {
934 match self.token.ident() {
935 Some((ident @ Ident { name: kw::Underscore, .. }, false)) => {
939 _ => self.parse_ident(),
943 /// Parses `extern crate` links.
948 /// extern crate foo;
949 /// extern crate bar as foo;
951 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
952 // Accept `extern crate name-like-this` for better diagnostics
953 let orig_name = self.parse_crate_name_with_dashes()?;
954 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
955 (rename, Some(orig_name.name))
960 Ok((item_name, ItemKind::ExternCrate(orig_name)))
963 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, Ident> {
964 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
965 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
967 let mut ident = if self.token.is_keyword(kw::SelfLower) {
968 self.parse_path_segment_ident()
972 let mut idents = vec![];
973 let mut replacement = vec![];
974 let mut fixed_crate_name = false;
975 // Accept `extern crate name-like-this` for better diagnostics.
976 let dash = token::BinOp(token::BinOpToken::Minus);
977 if self.token == dash {
978 // Do not include `-` as part of the expected tokens list.
979 while self.eat(&dash) {
980 fixed_crate_name = true;
981 replacement.push((self.prev_token.span, "_".to_string()));
982 idents.push(self.parse_ident()?);
985 if fixed_crate_name {
986 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
987 let mut fixed_name = format!("{}", ident.name);
989 fixed_name.push_str(&format!("_{}", part.name));
991 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
993 self.struct_span_err(fixed_name_sp, error_msg)
994 .span_label(fixed_name_sp, "dash-separated idents are not valid")
995 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
1001 /// Parses `extern` for foreign ABIs modules.
1003 /// `extern` is expected to have been consumed before calling this method.
1007 /// ```ignore (only-for-syntax-highlight)
1011 fn parse_item_foreign_mod(
1013 attrs: &mut Vec<Attribute>,
1015 ) -> PResult<'a, ItemInfo> {
1016 let abi = self.parse_abi(); // ABI?
1017 let items = self.parse_item_list(attrs, |p| p.parse_foreign_item(ForceCollect::No))?;
1018 let module = ast::ForeignMod { unsafety, abi, items };
1019 Ok((Ident::empty(), ItemKind::ForeignMod(module)))
1022 /// Parses a foreign item (one in an `extern { ... }` block).
1023 pub fn parse_foreign_item(
1025 force_collect: ForceCollect,
1026 ) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
1027 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: false };
1028 Ok(self.parse_item_(fn_parse_mode, force_collect)?.map(
1029 |Item { attrs, id, span, vis, ident, kind, tokens }| {
1030 let kind = match ForeignItemKind::try_from(kind) {
1032 Err(kind) => match kind {
1033 ItemKind::Const(_, a, b) => {
1034 self.error_on_foreign_const(span, ident);
1035 ForeignItemKind::Static(a, Mutability::Not, b)
1037 _ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
1040 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
1045 fn error_bad_item_kind<T>(&self, span: Span, kind: &ItemKind, ctx: &str) -> Option<T> {
1046 let span = self.sess.source_map().guess_head_span(span);
1047 let descr = kind.descr();
1048 self.struct_span_err(span, &format!("{} is not supported in {}", descr, ctx))
1049 .help(&format!("consider moving the {} out to a nearby module scope", descr))
1054 fn error_on_foreign_const(&self, span: Span, ident: Ident) {
1055 self.struct_span_err(ident.span, "extern items cannot be `const`")
1057 span.with_hi(ident.span.lo()),
1058 "try using a static value",
1059 "static ".to_string(),
1060 Applicability::MachineApplicable,
1062 .note("for more information, visit https://doc.rust-lang.org/std/keyword.extern.html")
1066 fn is_unsafe_foreign_mod(&self) -> bool {
1067 self.token.is_keyword(kw::Unsafe)
1068 && self.is_keyword_ahead(1, &[kw::Extern])
1070 2 + self.look_ahead(2, |t| t.can_begin_literal_maybe_minus() as usize),
1071 |t| t.kind == token::OpenDelim(token::Brace),
1075 fn is_static_global(&mut self) -> bool {
1076 if self.check_keyword(kw::Static) {
1077 // Check if this could be a closure.
1078 !self.look_ahead(1, |token| {
1079 if token.is_keyword(kw::Move) {
1082 matches!(token.kind, token::BinOp(token::Or) | token::OrOr)
1089 /// Recover on `const mut` with `const` already eaten.
1090 fn recover_const_mut(&mut self, const_span: Span) {
1091 if self.eat_keyword(kw::Mut) {
1092 let span = self.prev_token.span;
1093 self.struct_span_err(span, "const globals cannot be mutable")
1094 .span_label(span, "cannot be mutable")
1097 "you might want to declare a static instead",
1098 "static".to_owned(),
1099 Applicability::MaybeIncorrect,
1105 /// Recover on `const impl` with `const` already eaten.
1106 fn recover_const_impl(
1109 attrs: &mut Vec<Attribute>,
1110 defaultness: Defaultness,
1111 ) -> PResult<'a, ItemInfo> {
1112 let impl_span = self.token.span;
1113 let mut err = self.expected_ident_found();
1115 // Only try to recover if this is implementing a trait for a type
1116 let mut impl_info = match self.parse_item_impl(attrs, defaultness) {
1117 Ok(impl_info) => impl_info,
1118 Err(mut recovery_error) => {
1119 // Recovery failed, raise the "expected identifier" error
1120 recovery_error.cancel();
1126 ItemKind::Impl(box Impl { of_trait: Some(ref trai), ref mut constness, .. }) => {
1127 *constness = Const::Yes(const_span);
1129 let before_trait = trai.path.span.shrink_to_lo();
1130 let const_up_to_impl = const_span.with_hi(impl_span.lo());
1131 err.multipart_suggestion(
1132 "you might have meant to write a const trait impl",
1133 vec![(const_up_to_impl, "".to_owned()), (before_trait, "const ".to_owned())],
1134 Applicability::MaybeIncorrect,
1138 ItemKind::Impl { .. } => return Err(err),
1139 _ => unreachable!(),
1145 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
1146 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
1148 /// When `m` is `"const"`, `$ident` may also be `"_"`.
1149 fn parse_item_global(
1151 m: Option<Mutability>,
1152 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
1153 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
1155 // Parse the type of a `const` or `static mut?` item.
1156 // That is, the `":" $ty` fragment.
1157 let ty = if self.eat(&token::Colon) {
1160 self.recover_missing_const_type(id, m)
1163 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
1164 self.expect_semi()?;
1168 /// We were supposed to parse `:` but the `:` was missing.
1169 /// This means that the type is missing.
1170 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
1171 // Construct the error and stash it away with the hope
1172 // that typeck will later enrich the error with a type.
1173 let kind = match m {
1174 Some(Mutability::Mut) => "static mut",
1175 Some(Mutability::Not) => "static",
1178 let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
1179 err.span_suggestion(
1181 "provide a type for the item",
1182 format!("{}: <type>", id),
1183 Applicability::HasPlaceholders,
1185 err.stash(id.span, StashKey::ItemNoType);
1187 // The user intended that the type be inferred,
1188 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
1189 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID, tokens: None })
1192 /// Parses an enum declaration.
1193 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
1194 let id = self.parse_ident()?;
1195 let mut generics = self.parse_generics()?;
1196 generics.where_clause = self.parse_where_clause()?;
1199 self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
1200 self.recover_stmt();
1204 let enum_definition = EnumDef { variants: variants.into_iter().flatten().collect() };
1205 Ok((id, ItemKind::Enum(enum_definition, generics)))
1208 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
1209 let variant_attrs = self.parse_outer_attributes()?;
1210 self.collect_tokens_trailing_token(
1213 |this, variant_attrs| {
1214 let vlo = this.token.span;
1216 let vis = this.parse_visibility(FollowedByType::No)?;
1217 if !this.recover_nested_adt_item(kw::Enum)? {
1218 return Ok((None, TrailingToken::None));
1220 let ident = this.parse_field_ident("enum", vlo)?;
1222 let struct_def = if this.check(&token::OpenDelim(token::Brace)) {
1223 // Parse a struct variant.
1224 let (fields, recovered) = this.parse_record_struct_body("struct")?;
1225 VariantData::Struct(fields, recovered)
1226 } else if this.check(&token::OpenDelim(token::Paren)) {
1227 VariantData::Tuple(this.parse_tuple_struct_body()?, DUMMY_NODE_ID)
1229 VariantData::Unit(DUMMY_NODE_ID)
1233 if this.eat(&token::Eq) { Some(this.parse_anon_const_expr()?) } else { None };
1235 let vr = ast::Variant {
1239 attrs: variant_attrs.into(),
1242 span: vlo.to(this.prev_token.span),
1243 is_placeholder: false,
1246 Ok((Some(vr), TrailingToken::MaybeComma))
1251 /// Parses `struct Foo { ... }`.
1252 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1253 let class_name = self.parse_ident()?;
1255 let mut generics = self.parse_generics()?;
1257 // There is a special case worth noting here, as reported in issue #17904.
1258 // If we are parsing a tuple struct it is the case that the where clause
1259 // should follow the field list. Like so:
1261 // struct Foo<T>(T) where T: Copy;
1263 // If we are parsing a normal record-style struct it is the case
1264 // that the where clause comes before the body, and after the generics.
1265 // So if we look ahead and see a brace or a where-clause we begin
1266 // parsing a record style struct.
1268 // Otherwise if we look ahead and see a paren we parse a tuple-style
1271 let vdata = if self.token.is_keyword(kw::Where) {
1272 generics.where_clause = self.parse_where_clause()?;
1273 if self.eat(&token::Semi) {
1274 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1275 VariantData::Unit(DUMMY_NODE_ID)
1277 // If we see: `struct Foo<T> where T: Copy { ... }`
1278 let (fields, recovered) = self.parse_record_struct_body("struct")?;
1279 VariantData::Struct(fields, recovered)
1281 // No `where` so: `struct Foo<T>;`
1282 } else if self.eat(&token::Semi) {
1283 VariantData::Unit(DUMMY_NODE_ID)
1284 // Record-style struct definition
1285 } else if self.token == token::OpenDelim(token::Brace) {
1286 let (fields, recovered) = self.parse_record_struct_body("struct")?;
1287 VariantData::Struct(fields, recovered)
1288 // Tuple-style struct definition with optional where-clause.
1289 } else if self.token == token::OpenDelim(token::Paren) {
1290 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1291 generics.where_clause = self.parse_where_clause()?;
1292 self.expect_semi()?;
1295 let token_str = super::token_descr(&self.token);
1297 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
1300 let mut err = self.struct_span_err(self.token.span, msg);
1301 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1305 Ok((class_name, ItemKind::Struct(vdata, generics)))
1308 /// Parses `union Foo { ... }`.
1309 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1310 let class_name = self.parse_ident()?;
1312 let mut generics = self.parse_generics()?;
1314 let vdata = if self.token.is_keyword(kw::Where) {
1315 generics.where_clause = self.parse_where_clause()?;
1316 let (fields, recovered) = self.parse_record_struct_body("union")?;
1317 VariantData::Struct(fields, recovered)
1318 } else if self.token == token::OpenDelim(token::Brace) {
1319 let (fields, recovered) = self.parse_record_struct_body("union")?;
1320 VariantData::Struct(fields, recovered)
1322 let token_str = super::token_descr(&self.token);
1323 let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
1324 let mut err = self.struct_span_err(self.token.span, msg);
1325 err.span_label(self.token.span, "expected `where` or `{` after union name");
1329 Ok((class_name, ItemKind::Union(vdata, generics)))
1332 fn parse_record_struct_body(
1335 ) -> PResult<'a, (Vec<FieldDef>, /* recovered */ bool)> {
1336 let mut fields = Vec::new();
1337 let mut recovered = false;
1338 if self.eat(&token::OpenDelim(token::Brace)) {
1339 while self.token != token::CloseDelim(token::Brace) {
1340 let field = self.parse_field_def(adt_ty).map_err(|e| {
1341 self.consume_block(token::Brace, ConsumeClosingDelim::No);
1346 Ok(field) => fields.push(field),
1353 self.eat(&token::CloseDelim(token::Brace));
1355 let token_str = super::token_descr(&self.token);
1356 let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
1357 let mut err = self.struct_span_err(self.token.span, msg);
1358 err.span_label(self.token.span, "expected `where`, or `{` after struct name");
1362 Ok((fields, recovered))
1365 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<FieldDef>> {
1366 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1367 // Unit like structs are handled in parse_item_struct function
1368 self.parse_paren_comma_seq(|p| {
1369 let attrs = p.parse_outer_attributes()?;
1370 p.collect_tokens_trailing_token(attrs, ForceCollect::No, |p, attrs| {
1371 let lo = p.token.span;
1372 let vis = p.parse_visibility(FollowedByType::Yes)?;
1373 let ty = p.parse_ty()?;
1377 span: lo.to(ty.span),
1382 attrs: attrs.into(),
1383 is_placeholder: false,
1385 TrailingToken::MaybeComma,
1392 /// Parses an element of a struct declaration.
1393 fn parse_field_def(&mut self, adt_ty: &str) -> PResult<'a, FieldDef> {
1394 let attrs = self.parse_outer_attributes()?;
1395 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
1396 let lo = this.token.span;
1397 let vis = this.parse_visibility(FollowedByType::No)?;
1398 Ok((this.parse_single_struct_field(adt_ty, lo, vis, attrs)?, TrailingToken::None))
1402 /// Parses a structure field declaration.
1403 fn parse_single_struct_field(
1408 attrs: Vec<Attribute>,
1409 ) -> PResult<'a, FieldDef> {
1410 let mut seen_comma: bool = false;
1411 let a_var = self.parse_name_and_ty(adt_ty, lo, vis, attrs)?;
1412 if self.token == token::Comma {
1415 match self.token.kind {
1419 token::CloseDelim(token::Brace) => {}
1420 token::DocComment(..) => {
1421 let previous_span = self.prev_token.span;
1422 let mut err = self.span_err(self.token.span, Error::UselessDocComment);
1423 self.bump(); // consume the doc comment
1424 let comma_after_doc_seen = self.eat(&token::Comma);
1425 // `seen_comma` is always false, because we are inside doc block
1426 // condition is here to make code more readable
1427 if !seen_comma && comma_after_doc_seen {
1430 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
1434 let sp = self.sess.source_map().next_point(previous_span);
1435 err.span_suggestion(
1437 "missing comma here",
1439 Applicability::MachineApplicable,
1446 let sp = self.prev_token.span.shrink_to_hi();
1447 let mut err = self.struct_span_err(
1449 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1452 // Try to recover extra trailing angle brackets
1453 let mut recovered = false;
1454 if let TyKind::Path(_, Path { segments, .. }) = &a_var.ty.kind {
1455 if let Some(last_segment) = segments.last() {
1456 recovered = self.check_trailing_angle_brackets(
1458 &[&token::Comma, &token::CloseDelim(token::Brace)],
1461 // Handle a case like `Vec<u8>>,` where we can continue parsing fields
1463 self.eat(&token::Comma);
1464 // `check_trailing_angle_brackets` already emitted a nicer error
1470 if self.token.is_ident() {
1471 // This is likely another field; emit the diagnostic and keep going
1472 err.span_suggestion(
1474 "try adding a comma",
1476 Applicability::MachineApplicable,
1483 // Make sure an error was emitted (either by recovering an angle bracket,
1484 // or by finding an identifier as the next token), since we're
1485 // going to continue parsing
1486 assert!(self.sess.span_diagnostic.has_errors());
1495 fn expect_field_ty_separator(&mut self) -> PResult<'a, ()> {
1496 if let Err(mut err) = self.expect(&token::Colon) {
1497 let sm = self.sess.source_map();
1498 let eq_typo = self.token.kind == token::Eq && self.look_ahead(1, |t| t.is_path_start());
1499 let semi_typo = self.token.kind == token::Semi
1500 && self.look_ahead(1, |t| {
1502 // We check that we are in a situation like `foo; bar` to avoid bad suggestions
1503 // when there's no type and `;` was used instead of a comma.
1504 && match (sm.lookup_line(self.token.span.hi()), sm.lookup_line(t.span.lo())) {
1505 (Ok(l), Ok(r)) => l.line == r.line,
1509 if eq_typo || semi_typo {
1511 // Gracefully handle small typos.
1512 err.span_suggestion_short(
1513 self.prev_token.span,
1514 "field names and their types are separated with `:`",
1516 Applicability::MachineApplicable,
1526 /// Parses a structure field.
1527 fn parse_name_and_ty(
1532 attrs: Vec<Attribute>,
1533 ) -> PResult<'a, FieldDef> {
1534 let name = self.parse_field_ident(adt_ty, lo)?;
1535 self.expect_field_ty_separator()?;
1536 let ty = self.parse_ty()?;
1537 if self.token.kind == token::Eq {
1539 let const_expr = self.parse_anon_const_expr()?;
1540 let sp = ty.span.shrink_to_hi().to(const_expr.value.span);
1541 self.struct_span_err(sp, "default values on `struct` fields aren't supported")
1544 "remove this unsupported default value",
1546 Applicability::MachineApplicable,
1551 span: lo.to(self.prev_token.span),
1556 attrs: attrs.into(),
1557 is_placeholder: false,
1561 /// Parses a field identifier. Specialized version of `parse_ident_common`
1562 /// for better diagnostics and suggestions.
1563 fn parse_field_ident(&mut self, adt_ty: &str, lo: Span) -> PResult<'a, Ident> {
1564 let (ident, is_raw) = self.ident_or_err()?;
1565 if !is_raw && ident.is_reserved() {
1566 let err = if self.check_fn_front_matter(false) {
1567 let inherited_vis = Visibility {
1568 span: rustc_span::DUMMY_SP,
1569 kind: VisibilityKind::Inherited,
1572 // We use `parse_fn` to get a span for the function
1573 let fn_parse_mode = FnParseMode { req_name: |_| true, req_body: true };
1574 if let Err(mut db) =
1575 self.parse_fn(&mut Vec::new(), fn_parse_mode, lo, &inherited_vis)
1579 let mut err = self.struct_span_err(
1580 lo.to(self.prev_token.span),
1581 &format!("functions are not allowed in {} definitions", adt_ty),
1583 err.help("unlike in C++, Java, and C#, functions are declared in `impl` blocks");
1584 err.help("see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information");
1587 self.expected_ident_found()
1595 /// Parses a declarative macro 2.0 definition.
1596 /// The `macro` keyword has already been parsed.
1598 /// MacBody = "{" TOKEN_STREAM "}" ;
1599 /// MacParams = "(" TOKEN_STREAM ")" ;
1600 /// DeclMac = "macro" Ident MacParams? MacBody ;
1602 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1603 let ident = self.parse_ident()?;
1604 let body = if self.check(&token::OpenDelim(token::Brace)) {
1605 self.parse_mac_args()? // `MacBody`
1606 } else if self.check(&token::OpenDelim(token::Paren)) {
1607 let params = self.parse_token_tree(); // `MacParams`
1608 let pspan = params.span();
1609 if !self.check(&token::OpenDelim(token::Brace)) {
1610 return self.unexpected();
1612 let body = self.parse_token_tree(); // `MacBody`
1613 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1614 let bspan = body.span();
1615 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1616 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1617 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1618 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1620 return self.unexpected();
1623 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
1624 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: false })))
1627 /// Is this a possibly malformed start of a `macro_rules! foo` item definition?
1629 fn is_macro_rules_item(&mut self) -> IsMacroRulesItem {
1630 if self.check_keyword(kw::MacroRules) {
1631 let macro_rules_span = self.token.span;
1633 if self.look_ahead(1, |t| *t == token::Not) && self.look_ahead(2, |t| t.is_ident()) {
1634 return IsMacroRulesItem::Yes { has_bang: true };
1635 } else if self.look_ahead(1, |t| (t.is_ident())) {
1637 self.struct_span_err(macro_rules_span, "expected `!` after `macro_rules`")
1641 "macro_rules!".to_owned(),
1642 Applicability::MachineApplicable,
1646 return IsMacroRulesItem::Yes { has_bang: false };
1650 IsMacroRulesItem::No
1653 /// Parses a `macro_rules! foo { ... }` declarative macro.
1654 fn parse_item_macro_rules(
1658 ) -> PResult<'a, ItemInfo> {
1659 self.expect_keyword(kw::MacroRules)?; // `macro_rules`
1662 self.expect(&token::Not)?; // `!`
1664 let ident = self.parse_ident()?;
1666 if self.eat(&token::Not) {
1667 // Handle macro_rules! foo!
1668 let span = self.prev_token.span;
1669 self.struct_span_err(span, "macro names aren't followed by a `!`")
1674 Applicability::MachineApplicable,
1679 let body = self.parse_mac_args()?;
1680 self.eat_semi_for_macro_if_needed(&body);
1681 self.complain_if_pub_macro(vis, true);
1683 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, macro_rules: true })))
1686 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1687 /// If that's not the case, emit an error.
1688 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1689 if let VisibilityKind::Inherited = vis.kind {
1693 let vstr = pprust::vis_to_string(vis);
1694 let vstr = vstr.trim_end();
1696 let msg = format!("can't qualify macro_rules invocation with `{}`", vstr);
1697 self.struct_span_err(vis.span, &msg)
1700 "try exporting the macro",
1701 "#[macro_export]".to_owned(),
1702 Applicability::MaybeIncorrect, // speculative
1706 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1709 "remove the visibility",
1711 Applicability::MachineApplicable,
1713 .help(&format!("try adjusting the macro to put `{}` inside the invocation", vstr))
1718 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1719 if args.need_semicolon() && !self.eat(&token::Semi) {
1720 self.report_invalid_macro_expansion_item(args);
1724 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1725 let span = args.span().expect("undelimited macro call");
1726 let mut err = self.struct_span_err(
1728 "macros that expand to items must be delimited with braces or followed by a semicolon",
1730 if self.unclosed_delims.is_empty() {
1731 let DelimSpan { open, close } = match args {
1732 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1733 MacArgs::Delimited(dspan, ..) => *dspan,
1735 err.multipart_suggestion(
1736 "change the delimiters to curly braces",
1737 vec![(open, "{".to_string()), (close, '}'.to_string())],
1738 Applicability::MaybeIncorrect,
1741 err.span_suggestion(
1743 "change the delimiters to curly braces",
1744 " { /* items */ }".to_string(),
1745 Applicability::HasPlaceholders,
1748 err.span_suggestion(
1749 span.shrink_to_hi(),
1752 Applicability::MaybeIncorrect,
1757 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1758 /// it is, we try to parse the item and report error about nested types.
1759 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1760 if (self.token.is_keyword(kw::Enum)
1761 || self.token.is_keyword(kw::Struct)
1762 || self.token.is_keyword(kw::Union))
1763 && self.look_ahead(1, |t| t.is_ident())
1765 let kw_token = self.token.clone();
1766 let kw_str = pprust::token_to_string(&kw_token);
1767 let item = self.parse_item(ForceCollect::No)?;
1769 self.struct_span_err(
1771 &format!("`{}` definition cannot be nested inside `{}`", kw_str, keyword),
1775 &format!("consider creating a new `{}` definition instead of nesting", kw_str),
1777 Applicability::MaybeIncorrect,
1780 // We successfully parsed the item but we must inform the caller about nested problem.
1787 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1789 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1791 /// This function pointer accepts an edition, because in edition 2015, trait declarations
1792 /// were allowed to omit parameter names. In 2018, they became required.
1793 type ReqName = fn(Edition) -> bool;
1795 /// Parsing configuration for functions.
1797 /// The syntax of function items is slightly different within trait definitions,
1798 /// impl blocks, and modules. It is still parsed using the same code, just with
1799 /// different flags set, so that even when the input is wrong and produces a parse
1800 /// error, it still gets into the AST and the rest of the parser and
1801 /// type checker can run.
1802 #[derive(Clone, Copy)]
1803 pub(crate) struct FnParseMode {
1804 /// A function pointer that decides if, per-parameter `p`, `p` must have a
1805 /// pattern or just a type. This field affects parsing of the parameters list.
1808 /// fn foo(alef: A) -> X { X::new() }
1809 /// -----^^ affects parsing this part of the function signature
1811 /// if req_name returns false, then this name is optional
1816 /// if req_name returns true, this is an error
1819 /// Calling this function pointer should only return false if:
1821 /// * The item is being parsed inside of a trait definition.
1822 /// Within an impl block or a module, it should always evaluate
1824 /// * The span is from Edition 2015. In particular, you can get a
1825 /// 2015 span inside a 2021 crate using macros.
1826 pub req_name: ReqName,
1827 /// If this flag is set to `true`, then plain, semicolon-terminated function
1828 /// prototypes are not allowed here.
1831 /// fn foo(alef: A) -> X { X::new() }
1834 /// this is always allowed
1836 /// fn bar(alef: A, bet: B) -> X;
1839 /// if req_body is set to true, this is an error
1842 /// This field should only be set to false if the item is inside of a trait
1843 /// definition or extern block. Within an impl block or a module, it should
1844 /// always be set to true.
1848 /// Parsing of functions and methods.
1849 impl<'a> Parser<'a> {
1850 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1853 attrs: &mut Vec<Attribute>,
1854 fn_parse_mode: FnParseMode,
1857 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1858 let header = self.parse_fn_front_matter(vis)?; // `const ... fn`
1859 let ident = self.parse_ident()?; // `foo`
1860 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1862 self.parse_fn_decl(fn_parse_mode.req_name, AllowPlus::Yes, RecoverReturnSign::Yes)?; // `(p: u8, ...)`
1863 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1865 let mut sig_hi = self.prev_token.span;
1866 let body = self.parse_fn_body(attrs, &ident, &mut sig_hi, fn_parse_mode.req_body)?; // `;` or `{ ... }`.
1867 let fn_sig_span = sig_lo.to(sig_hi);
1868 Ok((ident, FnSig { header, decl, span: fn_sig_span }, generics, body))
1871 /// Parse the "body" of a function.
1872 /// This can either be `;` when there's no body,
1873 /// or e.g. a block when the function is a provided one.
1876 attrs: &mut Vec<Attribute>,
1880 ) -> PResult<'a, Option<P<Block>>> {
1881 let has_semi = if req_body {
1882 self.token.kind == TokenKind::Semi
1884 // Only include `;` in list of expected tokens if body is not required
1885 self.check(&TokenKind::Semi)
1887 let (inner_attrs, body) = if has_semi {
1888 // Include the trailing semicolon in the span of the signature
1889 self.expect_semi()?;
1890 *sig_hi = self.prev_token.span;
1892 } else if self.check(&token::OpenDelim(token::Brace)) || self.token.is_whole_block() {
1893 self.parse_inner_attrs_and_block().map(|(attrs, body)| (attrs, Some(body)))?
1894 } else if self.token.kind == token::Eq {
1895 // Recover `fn foo() = $expr;`.
1897 let eq_sp = self.prev_token.span;
1898 let _ = self.parse_expr()?;
1899 self.expect_semi()?; // `;`
1900 let span = eq_sp.to(self.prev_token.span);
1901 self.struct_span_err(span, "function body cannot be `= expression;`")
1902 .multipart_suggestion(
1903 "surround the expression with `{` and `}` instead of `=` and `;`",
1904 vec![(eq_sp, "{".to_string()), (self.prev_token.span, " }".to_string())],
1905 Applicability::MachineApplicable,
1908 (Vec::new(), Some(self.mk_block_err(span)))
1910 let expected = if req_body {
1911 &[token::OpenDelim(token::Brace)][..]
1913 &[token::Semi, token::OpenDelim(token::Brace)]
1915 if let Err(mut err) = self.expected_one_of_not_found(&[], &expected) {
1916 if self.token.kind == token::CloseDelim(token::Brace) {
1917 // The enclosing `mod`, `trait` or `impl` is being closed, so keep the `fn` in
1918 // the AST for typechecking.
1919 err.span_label(ident.span, "while parsing this `fn`");
1927 attrs.extend(inner_attrs);
1931 /// Is the current token the start of an `FnHeader` / not a valid parse?
1933 /// `check_pub` adds additional `pub` to the checks in case users place it
1934 /// wrongly, can be used to ensure `pub` never comes after `default`.
1935 pub(super) fn check_fn_front_matter(&mut self, check_pub: bool) -> bool {
1936 // We use an over-approximation here.
1937 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1938 // `pub` is added in case users got confused with the ordering like `async pub fn`,
1939 // only if it wasn't preceeded by `default` as `default pub` is invalid.
1940 let quals: &[Symbol] = if check_pub {
1941 &[kw::Pub, kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1943 &[kw::Const, kw::Async, kw::Unsafe, kw::Extern]
1945 self.check_keyword(kw::Fn) // Definitely an `fn`.
1946 // `$qual fn` or `$qual $qual`:
1947 || quals.iter().any(|&kw| self.check_keyword(kw))
1948 && self.look_ahead(1, |t| {
1949 // `$qual fn`, e.g. `const fn` or `async fn`.
1950 t.is_keyword(kw::Fn)
1951 // Two qualifiers `$qual $qual` is enough, e.g. `async unsafe`.
1952 || t.is_non_raw_ident_where(|i| quals.contains(&i.name)
1953 // Rule out 2015 `const async: T = val`.
1955 // Rule out unsafe extern block.
1956 && !self.is_unsafe_foreign_mod())
1959 || self.check_keyword(kw::Extern)
1960 && self.look_ahead(1, |t| t.can_begin_literal_maybe_minus())
1961 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
1964 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
1965 /// up to and including the `fn` keyword. The formal grammar is:
1968 /// Extern = "extern" StringLit? ;
1969 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
1970 /// FnFrontMatter = FnQual "fn" ;
1973 /// `vis` represents the visibility that was already parsed, if any. Use
1974 /// `Visibility::Inherited` when no visibility is known.
1975 pub(super) fn parse_fn_front_matter(&mut self, orig_vis: &Visibility) -> PResult<'a, FnHeader> {
1976 let sp_start = self.token.span;
1977 let constness = self.parse_constness();
1979 let async_start_sp = self.token.span;
1980 let asyncness = self.parse_asyncness();
1982 let unsafe_start_sp = self.token.span;
1983 let unsafety = self.parse_unsafety();
1985 let ext_start_sp = self.token.span;
1986 let ext = self.parse_extern();
1988 if let Async::Yes { span, .. } = asyncness {
1989 self.ban_async_in_2015(span);
1992 if !self.eat_keyword(kw::Fn) {
1993 // It is possible for `expect_one_of` to recover given the contents of
1994 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
1995 // account for this.
1996 match self.expect_one_of(&[], &[]) {
1998 Ok(false) => unreachable!(),
2000 // Qualifier keywords ordering check
2006 // This will allow the machine fix to directly place the keyword in the correct place or to indicate
2007 // that the keyword is already present and the second instance should be removed.
2008 let wrong_kw = if self.check_keyword(kw::Const) {
2010 Const::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2011 Const::No => Some(WrongKw::Misplaced(async_start_sp)),
2013 } else if self.check_keyword(kw::Async) {
2015 Async::Yes { span, .. } => Some(WrongKw::Duplicated(span)),
2016 Async::No => Some(WrongKw::Misplaced(unsafe_start_sp)),
2018 } else if self.check_keyword(kw::Unsafe) {
2020 Unsafe::Yes(sp) => Some(WrongKw::Duplicated(sp)),
2021 Unsafe::No => Some(WrongKw::Misplaced(ext_start_sp)),
2027 // The keyword is already present, suggest removal of the second instance
2028 if let Some(WrongKw::Duplicated(original_sp)) = wrong_kw {
2029 let original_kw = self
2030 .span_to_snippet(original_sp)
2031 .expect("Span extracted directly from keyword should always work");
2033 err.span_suggestion(
2034 self.token.uninterpolated_span(),
2035 &format!("`{}` already used earlier, remove this one", original_kw),
2037 Applicability::MachineApplicable,
2039 .span_note(original_sp, &format!("`{}` first seen here", original_kw));
2041 // The keyword has not been seen yet, suggest correct placement in the function front matter
2042 else if let Some(WrongKw::Misplaced(correct_pos_sp)) = wrong_kw {
2043 let correct_pos_sp = correct_pos_sp.to(self.prev_token.span);
2044 if let Ok(current_qual) = self.span_to_snippet(correct_pos_sp) {
2045 let misplaced_qual_sp = self.token.uninterpolated_span();
2046 let misplaced_qual = self.span_to_snippet(misplaced_qual_sp).unwrap();
2048 err.span_suggestion(
2049 correct_pos_sp.to(misplaced_qual_sp),
2050 &format!("`{}` must come before `{}`", misplaced_qual, current_qual),
2051 format!("{} {}", misplaced_qual, current_qual),
2052 Applicability::MachineApplicable,
2053 ).note("keyword order for functions declaration is `default`, `pub`, `const`, `async`, `unsafe`, `extern`");
2056 // Recover incorrect visibility order such as `async pub`
2057 else if self.check_keyword(kw::Pub) {
2058 let sp = sp_start.to(self.prev_token.span);
2059 if let Ok(snippet) = self.span_to_snippet(sp) {
2060 let current_vis = match self.parse_visibility(FollowedByType::No) {
2067 let vs = pprust::vis_to_string(¤t_vis);
2068 let vs = vs.trim_end();
2070 // There was no explicit visibility
2071 if matches!(orig_vis.kind, VisibilityKind::Inherited) {
2072 err.span_suggestion(
2073 sp_start.to(self.prev_token.span),
2074 &format!("visibility `{}` must come before `{}`", vs, snippet),
2075 format!("{} {}", vs, snippet),
2076 Applicability::MachineApplicable,
2079 // There was an explicit visibility
2081 err.span_suggestion(
2083 "there is already a visibility modifier, remove one",
2085 Applicability::MachineApplicable,
2087 .span_note(orig_vis.span, "explicit visibility first seen here");
2096 Ok(FnHeader { constness, unsafety, asyncness, ext })
2099 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
2100 fn ban_async_in_2015(&self, span: Span) {
2101 if span.rust_2015() {
2102 let diag = self.diagnostic();
2103 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in Rust 2015")
2104 .span_label(span, "to use `async fn`, switch to Rust 2018 or later")
2105 .help(&format!("set `edition = \"{}\"` in `Cargo.toml`", LATEST_STABLE_EDITION))
2106 .note("for more on editions, read https://doc.rust-lang.org/edition-guide")
2111 /// Parses the parameter list and result type of a function declaration.
2112 pub(super) fn parse_fn_decl(
2115 ret_allow_plus: AllowPlus,
2116 recover_return_sign: RecoverReturnSign,
2117 ) -> PResult<'a, P<FnDecl>> {
2119 inputs: self.parse_fn_params(req_name)?,
2120 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes, recover_return_sign)?,
2124 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
2125 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
2126 let mut first_param = true;
2127 // Parse the arguments, starting out with `self` being allowed...
2128 let (mut params, _) = self.parse_paren_comma_seq(|p| {
2129 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
2131 let lo = p.prev_token.span;
2132 // Skip every token until next possible arg or end.
2133 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
2134 // Create a placeholder argument for proper arg count (issue #34264).
2135 Ok(dummy_arg(Ident::new(kw::Empty, lo.to(p.prev_token.span))))
2137 // ...now that we've parsed the first argument, `self` is no longer allowed.
2138 first_param = false;
2141 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
2142 self.deduplicate_recovered_params_names(&mut params);
2146 /// Parses a single function parameter.
2148 /// - `self` is syntactically allowed when `first_param` holds.
2149 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
2150 let lo = self.token.span;
2151 let attrs = self.parse_outer_attributes()?;
2152 self.collect_tokens_trailing_token(attrs, ForceCollect::No, |this, attrs| {
2153 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
2154 if let Some(mut param) = this.parse_self_param()? {
2155 param.attrs = attrs.into();
2156 let res = if first_param { Ok(param) } else { this.recover_bad_self_param(param) };
2157 return Ok((res?, TrailingToken::None));
2160 let is_name_required = match this.token.kind {
2161 token::DotDotDot => false,
2162 _ => req_name(this.token.span.edition()),
2164 let (pat, ty) = if is_name_required || this.is_named_param() {
2165 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
2167 let (pat, colon) = this.parse_fn_param_pat_colon()?;
2169 let mut err = this.unexpected::<()>().unwrap_err();
2170 return if let Some(ident) =
2171 this.parameter_without_type(&mut err, pat, is_name_required, first_param)
2174 Ok((dummy_arg(ident), TrailingToken::None))
2180 this.eat_incorrect_doc_comment_for_param_type();
2181 (pat, this.parse_ty_for_param()?)
2183 debug!("parse_param_general ident_to_pat");
2184 let parser_snapshot_before_ty = this.clone();
2185 this.eat_incorrect_doc_comment_for_param_type();
2186 let mut ty = this.parse_ty_for_param();
2188 && this.token != token::Comma
2189 && this.token != token::CloseDelim(token::Paren)
2191 // This wasn't actually a type, but a pattern looking like a type,
2192 // so we are going to rollback and re-parse for recovery.
2193 ty = this.unexpected();
2197 let ident = Ident::new(kw::Empty, this.prev_token.span);
2198 let bm = BindingMode::ByValue(Mutability::Not);
2199 let pat = this.mk_pat_ident(ty.span, bm, ident);
2202 // If this is a C-variadic argument and we hit an error, return the error.
2203 Err(err) if this.token == token::DotDotDot => return Err(err),
2204 // Recover from attempting to parse the argument as a type without pattern.
2207 *this = parser_snapshot_before_ty;
2208 this.recover_arg_parse()?
2213 let span = lo.until(this.token.span);
2217 attrs: attrs.into(),
2218 id: ast::DUMMY_NODE_ID,
2219 is_placeholder: false,
2224 TrailingToken::None,
2229 /// Returns the parsed optional self parameter and whether a self shortcut was used.
2230 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
2231 // Extract an identifier *after* having confirmed that the token is one.
2232 let expect_self_ident = |this: &mut Self| match this.token.ident() {
2233 Some((ident, false)) => {
2237 _ => unreachable!(),
2239 // Is `self` `n` tokens ahead?
2240 let is_isolated_self = |this: &Self, n| {
2241 this.is_keyword_ahead(n, &[kw::SelfLower])
2242 && this.look_ahead(n + 1, |t| t != &token::ModSep)
2244 // Is `mut self` `n` tokens ahead?
2245 let is_isolated_mut_self =
2246 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
2247 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
2248 let parse_self_possibly_typed = |this: &mut Self, m| {
2249 let eself_ident = expect_self_ident(this);
2250 let eself_hi = this.prev_token.span;
2251 let eself = if this.eat(&token::Colon) {
2252 SelfKind::Explicit(this.parse_ty()?, m)
2256 Ok((eself, eself_ident, eself_hi))
2258 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
2259 let recover_self_ptr = |this: &mut Self| {
2260 let msg = "cannot pass `self` by raw pointer";
2261 let span = this.token.span;
2262 this.struct_span_err(span, msg).span_label(span, msg).emit();
2264 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_token.span))
2267 // Parse optional `self` parameter of a method.
2268 // Only a limited set of initial token sequences is considered `self` parameters; anything
2269 // else is parsed as a normal function parameter list, so some lookahead is required.
2270 let eself_lo = self.token.span;
2271 let (eself, eself_ident, eself_hi) = match self.token.uninterpolate().kind {
2272 token::BinOp(token::And) => {
2273 let eself = if is_isolated_self(self, 1) {
2276 SelfKind::Region(None, Mutability::Not)
2277 } else if is_isolated_mut_self(self, 1) {
2281 SelfKind::Region(None, Mutability::Mut)
2282 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
2285 let lt = self.expect_lifetime();
2286 SelfKind::Region(Some(lt), Mutability::Not)
2287 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
2290 let lt = self.expect_lifetime();
2292 SelfKind::Region(Some(lt), Mutability::Mut)
2297 (eself, expect_self_ident(self), self.prev_token.span)
2300 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
2302 recover_self_ptr(self)?
2304 // `*mut self` and `*const self`
2305 token::BinOp(token::Star)
2306 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
2310 recover_self_ptr(self)?
2312 // `self` and `self: TYPE`
2313 token::Ident(..) if is_isolated_self(self, 0) => {
2314 parse_self_possibly_typed(self, Mutability::Not)?
2316 // `mut self` and `mut self: TYPE`
2317 token::Ident(..) if is_isolated_mut_self(self, 0) => {
2319 parse_self_possibly_typed(self, Mutability::Mut)?
2321 _ => return Ok(None),
2324 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
2325 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
2328 fn is_named_param(&self) -> bool {
2329 let offset = match self.token.kind {
2330 token::Interpolated(ref nt) => match **nt {
2331 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
2334 token::BinOp(token::And) | token::AndAnd => 1,
2335 _ if self.token.is_keyword(kw::Mut) => 1,
2339 self.look_ahead(offset, |t| t.is_ident())
2340 && self.look_ahead(offset + 1, |t| t == &token::Colon)
2343 fn recover_first_param(&mut self) -> &'static str {
2345 .parse_outer_attributes()
2346 .and_then(|_| self.parse_self_param())
2347 .map_err(|mut e| e.cancel())
2349 Ok(Some(_)) => "method",
2355 enum IsMacroRulesItem {
2356 Yes { has_bang: bool },