1 use super::diagnostics::{dummy_arg, ConsumeClosingDelim, Error};
2 use super::ty::{AllowPlus, RecoverQPath};
3 use super::{FollowedByType, Parser, PathStyle};
5 use crate::maybe_whole;
7 use rustc_ast_pretty::pprust;
8 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, PResult, StashKey};
9 use rustc_span::source_map::{self, Span};
10 use rustc_span::symbol::{kw, sym, Symbol};
11 use syntax::ast::{self, AttrStyle, AttrVec, Attribute, Ident, DUMMY_NODE_ID};
12 use syntax::ast::{AssocItem, AssocItemKind, Item, ItemKind, UseTree, UseTreeKind};
13 use syntax::ast::{Async, Const, Defaultness, IsAuto, PathSegment, Unsafe};
14 use syntax::ast::{BindingMode, Block, FnDecl, FnSig, Mac, MacArgs, MacDelimiter, Param, SelfKind};
15 use syntax::ast::{EnumDef, Generics, StructField, TraitRef, Ty, TyKind, Variant, VariantData};
16 use syntax::ast::{FnHeader, ForeignItem, Mutability, Visibility, VisibilityKind};
19 use syntax::tokenstream::{DelimSpan, TokenStream, TokenTree};
24 pub(super) type ItemInfo = (Ident, ItemKind);
27 pub fn parse_item(&mut self) -> PResult<'a, Option<P<Item>>> {
28 let attrs = self.parse_outer_attributes()?;
29 self.parse_item_(attrs, true, false)
32 pub(super) fn parse_item_(
34 attrs: Vec<Attribute>,
36 attributes_allowed: bool,
37 ) -> PResult<'a, Option<P<Item>>> {
38 let mut unclosed_delims = vec![];
39 let (ret, tokens) = self.collect_tokens(|this| {
40 let item = this.parse_item_implementation(attrs, macros_allowed, attributes_allowed);
41 unclosed_delims.append(&mut this.unclosed_delims);
44 self.unclosed_delims.append(&mut unclosed_delims);
46 // Once we've parsed an item and recorded the tokens we got while
47 // parsing we may want to store `tokens` into the item we're about to
48 // return. Note, though, that we specifically didn't capture tokens
49 // related to outer attributes. The `tokens` field here may later be
50 // used with procedural macros to convert this item back into a token
51 // stream, but during expansion we may be removing attributes as we go
54 // If we've got inner attributes then the `tokens` we've got above holds
55 // these inner attributes. If an inner attribute is expanded we won't
56 // actually remove it from the token stream, so we'll just keep yielding
57 // it (bad!). To work around this case for now we just avoid recording
58 // `tokens` if we detect any inner attributes. This should help keep
59 // expansion correct, but we should fix this bug one day!
62 if !i.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
63 i.tokens = Some(tokens);
70 /// Parses one of the items allowed by the flags.
71 fn parse_item_implementation(
73 mut attrs: Vec<Attribute>,
75 attributes_allowed: bool,
76 ) -> PResult<'a, Option<P<Item>>> {
77 maybe_whole!(self, NtItem, |item| {
79 mem::swap(&mut item.attrs, &mut attrs);
80 item.attrs.extend(attrs);
84 let lo = self.token.span;
85 let vis = self.parse_visibility(FollowedByType::No)?;
87 if let Some((ident, kind)) = self.parse_item_kind(&mut attrs, macros_allowed, lo, &vis)? {
88 return Ok(Some(P(self.mk_item(lo, ident, kind, vis, attrs))));
91 // FAILURE TO PARSE ITEM
92 if let VisibilityKind::Inherited = vis.node {
94 let vs = pprust::vis_to_string(&vis);
95 let vs = vs.trim_end();
96 self.struct_span_err(vis.span, &format!("unmatched visibility `{}`", vs))
97 .span_label(vis.span, "the unmatched visibility")
98 .help(&format!("you likely meant to define an item, e.g., `{} fn foo() {{}}`", vs))
102 if !attributes_allowed {
103 self.recover_attrs_no_item(&attrs)?;
108 /// Parses one of the items allowed by the flags.
111 attrs: &mut Vec<Attribute>,
112 macros_allowed: bool,
115 ) -> PResult<'a, Option<ItemInfo>> {
116 let info = if self.eat_keyword(kw::Use) {
118 let tree = self.parse_use_tree()?;
120 (Ident::invalid(), ItemKind::Use(P(tree)))
121 } else if self.check_fn_front_matter() {
123 let (ident, sig, generics, body) = self.parse_fn(&mut false, attrs, |_| true)?;
124 (ident, ItemKind::Fn(sig, generics, body))
125 } else if self.eat_keyword(kw::Extern) {
126 if self.eat_keyword(kw::Crate) {
128 self.parse_item_extern_crate()?
131 self.parse_item_foreign_mod(attrs)?
133 } else if self.is_static_global() {
135 self.bump(); // `static`
136 let m = self.parse_mutability();
137 self.parse_item_const(Some(m))?
138 } else if let Const::Yes(const_span) = self.parse_constness() {
140 self.recover_const_mut(const_span);
141 self.parse_item_const(None)?
142 } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
144 self.parse_item_trait(attrs, lo)?
145 } else if self.check_keyword(kw::Impl)
146 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
147 || self.check_keyword(kw::Default) && self.is_keyword_ahead(1, &[kw::Impl, kw::Unsafe])
150 let defaultness = self.parse_defaultness();
151 let unsafety = self.parse_unsafety();
152 self.expect_keyword(kw::Impl)?;
153 self.parse_item_impl(attrs, unsafety, defaultness)?
154 } else if self.eat_keyword(kw::Mod) {
156 self.parse_item_mod(attrs)?
157 } else if self.eat_keyword(kw::Type) {
159 self.parse_type_alias()?
160 } else if self.eat_keyword(kw::Enum) {
162 self.parse_item_enum()?
163 } else if self.eat_keyword(kw::Struct) {
165 self.parse_item_struct()?
166 } else if self.is_kw_followed_by_ident(kw::Union) {
168 self.bump(); // `union`
169 self.parse_item_union()?
170 } else if self.eat_keyword(kw::Macro) {
172 self.parse_item_decl_macro(lo)?
173 } else if self.is_macro_rules_item() {
175 self.parse_item_macro_rules(vis)?
176 } else if vis.node.is_pub() && self.isnt_macro_invocation() {
177 self.recover_missing_kw_before_item()?;
179 } else if macros_allowed && self.token.is_path_start() {
180 // MACRO INVOCATION ITEM
181 (Ident::invalid(), ItemKind::Mac(self.parse_item_macro(vis)?))
188 /// When parsing a statement, would the start of a path be an item?
189 pub(super) fn is_path_start_item(&mut self) -> bool {
190 self.is_crate_vis() // no: `crate::b`, yes: `crate $item`
191 || self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
192 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
193 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
194 || self.is_macro_rules_item() // no: `macro_rules::b`, yes: `macro_rules! mac`
197 /// Are we sure this could not possibly be a macro invocation?
198 fn isnt_macro_invocation(&mut self) -> bool {
199 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
202 /// Recover on encountering a struct or method definition where the user
203 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
204 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
205 // Space between `pub` keyword and the identifier
208 // ^^^ `sp` points here
209 let sp = self.prev_span.between(self.token.span);
210 let full_sp = self.prev_span.to(self.token.span);
211 let ident_sp = self.token.span;
212 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
213 // possible public struct definition where `struct` was forgotten
214 let ident = self.parse_ident().unwrap();
215 let msg = format!("add `struct` here to parse `{}` as a public struct", ident);
216 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
217 err.span_suggestion_short(
221 Applicability::MaybeIncorrect, // speculative
224 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
225 let ident = self.parse_ident().unwrap();
227 let kw_name = self.recover_first_param();
228 self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
229 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
230 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
232 ("fn", kw_name, false)
233 } else if self.check(&token::OpenDelim(token::Brace)) {
235 ("fn", kw_name, false)
236 } else if self.check(&token::Colon) {
240 ("fn` or `struct", "function or struct", true)
243 let msg = format!("missing `{}` for {} definition", kw, kw_name);
244 let mut err = self.struct_span_err(sp, &msg);
246 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
248 format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name);
249 err.span_suggestion_short(
253 Applicability::MachineApplicable,
256 if let Ok(snippet) = self.span_to_snippet(ident_sp) {
259 "if you meant to call a macro, try",
260 format!("{}!", snippet),
261 // this is the `ambiguous` conditional branch
262 Applicability::MaybeIncorrect,
266 "if you meant to call a macro, remove the `pub` \
267 and add a trailing `!` after the identifier",
272 } else if self.look_ahead(1, |t| *t == token::Lt) {
273 let ident = self.parse_ident().unwrap();
274 self.eat_to_tokens(&[&token::Gt]);
276 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
277 ("fn", self.recover_first_param(), false)
278 } else if self.check(&token::OpenDelim(token::Brace)) {
279 ("struct", "struct", false)
281 ("fn` or `struct", "function or struct", true)
283 let msg = format!("missing `{}` for {} definition", kw, kw_name);
284 let mut err = self.struct_span_err(sp, &msg);
286 err.span_suggestion_short(
288 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
290 Applicability::MachineApplicable,
299 /// Parses an item macro, e.g., `item!();`.
300 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, Mac> {
301 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
302 self.expect(&token::Not)?; // `!`
303 let args = self.parse_mac_args()?; // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
304 self.eat_semi_for_macro_if_needed(&args);
305 self.complain_if_pub_macro(vis, false);
306 Ok(Mac { path, args, prior_type_ascription: self.last_type_ascription })
309 /// Recover if we parsed attributes and expected an item but there was none.
310 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
311 let (start, end) = match attrs {
314 [x0, .., xn] => (x0, xn),
316 let msg = if end.is_doc_comment() {
317 "expected item after doc comment"
319 "expected item after attributes"
321 let mut err = self.struct_span_err(end.span, msg);
322 if end.is_doc_comment() {
323 err.span_label(end.span, "this doc comment doesn't document anything");
325 if let [.., penultimate, _] = attrs {
326 err.span_label(start.span.to(penultimate.span), "other attributes here");
331 fn is_async_fn(&self) -> bool {
332 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
335 /// Given this code `path(`, it seems like this is not
336 /// setting the visibility of a macro invocation,
337 /// but rather a mistyped method declaration.
338 /// Create a diagnostic pointing out that `fn` is missing.
341 /// x | pub path(&self) {
342 /// | ^ missing `fn`, `type`, `const`, or `static`
344 fn missing_nested_item_kind_err(&self, prev_span: Span) -> DiagnosticBuilder<'a> {
345 let sp = prev_span.between(self.token.span);
346 let expected_kinds = "missing `fn`, `type`, `const`, or `static`";
347 let mut err = self.struct_span_err(sp, &format!("{} for item declaration", expected_kinds));
348 err.span_label(sp, expected_kinds);
352 /// Parses an implementation item, `impl` keyword is already parsed.
355 /// impl<'a, T> TYPE { /* impl items */ }
356 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
357 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
358 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
361 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
363 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
364 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
368 attrs: &mut Vec<Attribute>,
370 defaultness: Defaultness,
371 ) -> PResult<'a, ItemInfo> {
372 // First, parse generic parameters if necessary.
373 let mut generics = if self.choose_generics_over_qpath() {
374 self.parse_generics()?
376 let mut generics = Generics::default();
378 // /\ this is where `generics.span` should point when there are no type params.
379 generics.span = self.prev_span.shrink_to_hi();
383 let constness = self.parse_constness();
384 if let Const::Yes(span) = constness {
385 self.sess.gated_spans.gate(sym::const_trait_impl, span);
388 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
389 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
391 ast::ImplPolarity::Negative
393 ast::ImplPolarity::Positive
396 // Parse both types and traits as a type, then reinterpret if necessary.
397 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
398 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
400 let span = self.prev_span.between(self.token.span);
401 self.struct_span_err(span, "missing trait in a trait impl").emit();
402 P(Ty { kind: TyKind::Path(None, err_path(span)), span, id: DUMMY_NODE_ID })
407 // If `for` is missing we try to recover.
408 let has_for = self.eat_keyword(kw::For);
409 let missing_for_span = self.prev_span.between(self.token.span);
411 let ty_second = if self.token == token::DotDot {
412 // We need to report this error after `cfg` expansion for compatibility reasons
413 self.bump(); // `..`, do not add it to expected tokens
414 Some(self.mk_ty(self.prev_span, TyKind::Err))
415 } else if has_for || self.token.can_begin_type() {
416 Some(self.parse_ty()?)
421 generics.where_clause = self.parse_where_clause()?;
423 let impl_items = self.parse_item_list(attrs, |p, at_end| p.parse_impl_item(at_end))?;
425 let item_kind = match ty_second {
427 // impl Trait for Type
429 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
430 .span_suggestion_short(
434 Applicability::MachineApplicable,
439 let ty_first = ty_first.into_inner();
440 let path = match ty_first.kind {
441 // This notably includes paths passed through `ty` macro fragments (#46438).
442 TyKind::Path(None, path) => path,
444 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
445 err_path(ty_first.span)
448 let trait_ref = TraitRef { path, ref_id: ty_first.id };
456 of_trait: Some(trait_ref),
476 Ok((Ident::invalid(), item_kind))
479 fn parse_item_list<T>(
481 attrs: &mut Vec<Attribute>,
482 mut parse_item: impl FnMut(&mut Parser<'a>, &mut bool) -> PResult<'a, T>,
483 ) -> PResult<'a, Vec<T>> {
484 self.expect(&token::OpenDelim(token::Brace))?;
485 attrs.append(&mut self.parse_inner_attributes()?);
487 let mut items = Vec::new();
488 while !self.eat(&token::CloseDelim(token::Brace)) {
489 if self.recover_doc_comment_before_brace() {
492 let mut at_end = false;
493 match parse_item(self, &mut at_end) {
494 Ok(item) => items.push(item),
498 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
507 /// Recover on a doc comment before `}`.
508 fn recover_doc_comment_before_brace(&mut self) -> bool {
509 if let token::DocComment(_) = self.token.kind {
510 if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
515 "found a documentation comment that doesn't document anything",
517 .span_label(self.token.span, "this doc comment doesn't document anything")
519 "doc comments must come before what they document, maybe a \
520 comment was intended with `//`?",
530 /// Parses defaultness (i.e., `default` or nothing).
531 fn parse_defaultness(&mut self) -> Defaultness {
532 // `pub` is included for better error messages
533 if self.check_keyword(kw::Default)
534 && self.is_keyword_ahead(
549 self.bump(); // `default`
556 /// Is this an `(unsafe auto? | auto) trait` item?
557 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
559 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
561 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
564 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
565 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
566 let unsafety = self.parse_unsafety();
567 // Parse optional `auto` prefix.
568 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
570 self.expect_keyword(kw::Trait)?;
571 let ident = self.parse_ident()?;
572 let mut tps = self.parse_generics()?;
574 // Parse optional colon and supertrait bounds.
575 let had_colon = self.eat(&token::Colon);
576 let span_at_colon = self.prev_span;
578 if had_colon { self.parse_generic_bounds(Some(self.prev_span))? } else { Vec::new() };
580 let span_before_eq = self.prev_span;
581 if self.eat(&token::Eq) {
582 // It's a trait alias.
584 let span = span_at_colon.to(span_before_eq);
585 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
588 let bounds = self.parse_generic_bounds(None)?;
589 tps.where_clause = self.parse_where_clause()?;
592 let whole_span = lo.to(self.prev_span);
593 if is_auto == IsAuto::Yes {
594 let msg = "trait aliases cannot be `auto`";
595 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
597 if let Unsafe::Yes(_) = unsafety {
598 let msg = "trait aliases cannot be `unsafe`";
599 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
602 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
604 Ok((ident, ItemKind::TraitAlias(tps, bounds)))
606 // It's a normal trait.
607 tps.where_clause = self.parse_where_clause()?;
608 let items = self.parse_item_list(attrs, |p, at_end| p.parse_trait_item(at_end))?;
609 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, items)))
613 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, P<AssocItem>> {
614 maybe_whole!(self, NtImplItem, |x| x);
615 self.parse_assoc_item(at_end, |_| true)
618 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, P<AssocItem>> {
619 maybe_whole!(self, NtTraitItem, |x| x);
620 // This is somewhat dubious; We don't want to allow
621 // param names to be left off if there is a definition...
623 // We don't allow param names to be left off in edition 2018.
624 self.parse_assoc_item(at_end, |t| t.span.rust_2018())
627 /// Parses associated items.
632 ) -> PResult<'a, P<AssocItem>> {
633 let attrs = self.parse_outer_attributes()?;
634 let mut unclosed_delims = vec![];
635 let (mut item, tokens) = self.collect_tokens(|this| {
636 let item = this.parse_assoc_item_(at_end, attrs, req_name);
637 unclosed_delims.append(&mut this.unclosed_delims);
640 self.unclosed_delims.append(&mut unclosed_delims);
641 // See `parse_item` for why this clause is here.
642 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
643 item.tokens = Some(tokens);
645 self.error_on_assoc_static(&item);
649 fn error_on_assoc_static(&self, item: &AssocItem) {
650 if let AssocItemKind::Static(..) = item.kind {
651 self.struct_span_err(item.span, "associated `static` items are not allowed").emit();
655 fn parse_assoc_item_(
658 mut attrs: Vec<Attribute>,
660 ) -> PResult<'a, AssocItem> {
661 let lo = self.token.span;
662 let vis = self.parse_visibility(FollowedByType::No)?;
663 let defaultness = self.parse_defaultness();
664 let (ident, kind) = self.parse_assoc_item_kind(at_end, &mut attrs, req_name, &vis)?;
665 let span = lo.to(self.prev_span);
666 let id = DUMMY_NODE_ID;
667 Ok(AssocItem { id, span, ident, attrs, vis, defaultness, kind, tokens: None })
670 fn parse_assoc_item_kind(
673 attrs: &mut Vec<Attribute>,
676 ) -> PResult<'a, (Ident, AssocItemKind)> {
677 if self.eat_keyword(kw::Type) {
678 match self.parse_type_alias()? {
679 (ident, ItemKind::TyAlias(a, b, c)) => Ok((ident, AssocItemKind::TyAlias(a, b, c))),
682 } else if self.check_fn_front_matter() {
683 let (ident, sig, generics, body) = self.parse_fn(at_end, attrs, req_name)?;
684 Ok((ident, AssocItemKind::Fn(sig, generics, body)))
685 } else if self.is_static_global() {
686 self.bump(); // `static`
687 let mutbl = self.parse_mutability();
688 let (ident, ty, expr) = self.parse_item_const_common(Some(mutbl))?;
689 Ok((ident, AssocItemKind::Static(ty, mutbl, expr)))
690 } else if self.eat_keyword(kw::Const) {
691 let (ident, ty, expr) = self.parse_item_const_common(None)?;
692 Ok((ident, AssocItemKind::Const(ty, expr)))
693 } else if self.isnt_macro_invocation() {
694 Err(self.missing_nested_item_kind_err(self.prev_span))
695 } else if self.token.is_path_start() {
696 let mac = self.parse_item_macro(&vis)?;
698 Ok((Ident::invalid(), AssocItemKind::Macro(mac)))
700 self.recover_attrs_no_item(attrs)?;
705 /// Parses a `type` alias with the following grammar:
707 /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
709 /// The `"type"` has already been eaten.
710 fn parse_type_alias(&mut self) -> PResult<'a, (Ident, ItemKind)> {
711 let ident = self.parse_ident()?;
712 let mut generics = self.parse_generics()?;
714 // Parse optional colon and param bounds.
716 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
717 generics.where_clause = self.parse_where_clause()?;
719 let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
722 Ok((ident, ItemKind::TyAlias(generics, bounds, default)))
725 /// Parses a `UseTree`.
728 /// USE_TREE = [`::`] `*` |
729 /// [`::`] `{` USE_TREE_LIST `}` |
731 /// PATH `::` `{` USE_TREE_LIST `}` |
732 /// PATH [`as` IDENT]
734 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
735 let lo = self.token.span;
737 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
738 let kind = if self.check(&token::OpenDelim(token::Brace))
739 || self.check(&token::BinOp(token::Star))
740 || self.is_import_coupler()
742 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
743 let mod_sep_ctxt = self.token.span.ctxt();
744 if self.eat(&token::ModSep) {
747 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
750 self.parse_use_tree_glob_or_nested()?
752 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
753 prefix = self.parse_path(PathStyle::Mod)?;
755 if self.eat(&token::ModSep) {
756 self.parse_use_tree_glob_or_nested()?
758 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
762 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
765 /// Parses `*` or `{...}`.
766 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
767 Ok(if self.eat(&token::BinOp(token::Star)) {
770 UseTreeKind::Nested(self.parse_use_tree_list()?)
774 /// Parses a `UseTreeKind::Nested(list)`.
777 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
779 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
780 self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
784 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
785 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
788 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
789 match self.token.kind {
790 token::Ident(name @ kw::Underscore, false) => {
791 let span = self.token.span;
793 Ok(Ident::new(name, span))
795 _ => self.parse_ident(),
799 /// Parses `extern crate` links.
804 /// extern crate foo;
805 /// extern crate bar as foo;
807 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
808 // Accept `extern crate name-like-this` for better diagnostics
809 let orig_name = self.parse_crate_name_with_dashes()?;
810 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
811 (rename, Some(orig_name.name))
816 Ok((item_name, ItemKind::ExternCrate(orig_name)))
819 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
820 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
821 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
823 let mut ident = if self.token.is_keyword(kw::SelfLower) {
824 self.parse_path_segment_ident()
828 let mut idents = vec![];
829 let mut replacement = vec![];
830 let mut fixed_crate_name = false;
831 // Accept `extern crate name-like-this` for better diagnostics.
832 let dash = token::BinOp(token::BinOpToken::Minus);
833 if self.token == dash {
834 // Do not include `-` as part of the expected tokens list.
835 while self.eat(&dash) {
836 fixed_crate_name = true;
837 replacement.push((self.prev_span, "_".to_string()));
838 idents.push(self.parse_ident()?);
841 if fixed_crate_name {
842 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
843 let mut fixed_name = format!("{}", ident.name);
845 fixed_name.push_str(&format!("_{}", part.name));
847 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
849 self.struct_span_err(fixed_name_sp, error_msg)
850 .span_label(fixed_name_sp, "dash-separated idents are not valid")
851 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
857 /// Parses `extern` for foreign ABIs modules.
859 /// `extern` is expected to have been consumed before calling this method.
863 /// ```ignore (only-for-syntax-highlight)
867 fn parse_item_foreign_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
868 let abi = self.parse_abi(); // ABI?
869 let items = self.parse_item_list(attrs, |p, at_end| p.parse_foreign_item(at_end))?;
870 let module = ast::ForeignMod { abi, items };
871 Ok((Ident::invalid(), ItemKind::ForeignMod(module)))
874 /// Parses a foreign item (one in an `extern { ... }` block).
875 pub fn parse_foreign_item(&mut self, at_end: &mut bool) -> PResult<'a, P<ForeignItem>> {
876 maybe_whole!(self, NtForeignItem, |ni| ni);
878 let mut attrs = self.parse_outer_attributes()?;
879 let lo = self.token.span;
880 let vis = self.parse_visibility(FollowedByType::No)?;
881 let (ident, kind) = self.parse_assoc_item_kind(at_end, &mut attrs, |_| true, &vis)?;
882 let item = self.mk_item(lo, ident, kind, vis, attrs);
883 self.error_on_foreign_const(&item);
887 fn error_on_foreign_const(&self, item: &ForeignItem) {
888 if let AssocItemKind::Const(..) = item.kind {
889 self.struct_span_err(item.ident.span, "extern items cannot be `const`")
891 item.span.with_hi(item.ident.span.lo()),
892 "try using a static value",
893 "static ".to_string(),
894 Applicability::MachineApplicable,
897 "for more information, visit https://doc.rust-lang.org/std/keyword.extern.html",
903 fn is_static_global(&mut self) -> bool {
904 if self.check_keyword(kw::Static) {
905 // Check if this could be a closure.
906 !self.look_ahead(1, |token| {
907 if token.is_keyword(kw::Move) {
911 token::BinOp(token::Or) | token::OrOr => true,
920 /// Recover on `const mut` with `const` already eaten.
921 fn recover_const_mut(&mut self, const_span: Span) {
922 if self.eat_keyword(kw::Mut) {
923 let span = self.prev_span;
924 self.struct_span_err(span, "const globals cannot be mutable")
925 .span_label(span, "cannot be mutable")
928 "you might want to declare a static instead",
930 Applicability::MaybeIncorrect,
936 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
937 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
939 /// When `m` is `"const"`, `$ident` may also be `"_"`.
940 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
941 let (id, ty, expr) = self.parse_item_const_common(m)?;
943 Some(m) => ItemKind::Static(ty, m, expr),
944 None => ItemKind::Const(ty, expr),
949 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
950 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
952 /// When `m` is `"const"`, `$ident` may also be `"_"`.
953 fn parse_item_const_common(
955 m: Option<Mutability>,
956 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
957 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
959 // Parse the type of a `const` or `static mut?` item.
960 // That is, the `":" $ty` fragment.
961 let ty = if self.eat(&token::Colon) {
964 self.recover_missing_const_type(id, m)
967 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
972 /// We were supposed to parse `:` but the `:` was missing.
973 /// This means that the type is missing.
974 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
975 // Construct the error and stash it away with the hope
976 // that typeck will later enrich the error with a type.
978 Some(Mutability::Mut) => "static mut",
979 Some(Mutability::Not) => "static",
982 let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
985 "provide a type for the item",
986 format!("{}: <type>", id),
987 Applicability::HasPlaceholders,
989 err.stash(id.span, StashKey::ItemNoType);
991 // The user intended that the type be inferred,
992 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
993 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID })
996 /// Parses an enum declaration.
997 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
998 let id = self.parse_ident()?;
999 let mut generics = self.parse_generics()?;
1000 generics.where_clause = self.parse_where_clause()?;
1003 self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
1004 self.recover_stmt();
1008 let enum_definition =
1009 EnumDef { variants: variants.into_iter().filter_map(|v| v).collect() };
1010 Ok((id, ItemKind::Enum(enum_definition, generics)))
1013 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
1014 let variant_attrs = self.parse_outer_attributes()?;
1015 let vlo = self.token.span;
1017 let vis = self.parse_visibility(FollowedByType::No)?;
1018 if !self.recover_nested_adt_item(kw::Enum)? {
1021 let ident = self.parse_ident()?;
1023 let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
1024 // Parse a struct variant.
1025 let (fields, recovered) = self.parse_record_struct_body()?;
1026 VariantData::Struct(fields, recovered)
1027 } else if self.check(&token::OpenDelim(token::Paren)) {
1028 VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID)
1030 VariantData::Unit(DUMMY_NODE_ID)
1034 if self.eat(&token::Eq) { Some(self.parse_anon_const_expr()?) } else { None };
1036 let vr = ast::Variant {
1040 attrs: variant_attrs,
1043 span: vlo.to(self.prev_span),
1044 is_placeholder: false,
1050 /// Parses `struct Foo { ... }`.
1051 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1052 let class_name = self.parse_ident()?;
1054 let mut generics = self.parse_generics()?;
1056 // There is a special case worth noting here, as reported in issue #17904.
1057 // If we are parsing a tuple struct it is the case that the where clause
1058 // should follow the field list. Like so:
1060 // struct Foo<T>(T) where T: Copy;
1062 // If we are parsing a normal record-style struct it is the case
1063 // that the where clause comes before the body, and after the generics.
1064 // So if we look ahead and see a brace or a where-clause we begin
1065 // parsing a record style struct.
1067 // Otherwise if we look ahead and see a paren we parse a tuple-style
1070 let vdata = if self.token.is_keyword(kw::Where) {
1071 generics.where_clause = self.parse_where_clause()?;
1072 if self.eat(&token::Semi) {
1073 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1074 VariantData::Unit(DUMMY_NODE_ID)
1076 // If we see: `struct Foo<T> where T: Copy { ... }`
1077 let (fields, recovered) = self.parse_record_struct_body()?;
1078 VariantData::Struct(fields, recovered)
1080 // No `where` so: `struct Foo<T>;`
1081 } else if self.eat(&token::Semi) {
1082 VariantData::Unit(DUMMY_NODE_ID)
1083 // Record-style struct definition
1084 } else if self.token == token::OpenDelim(token::Brace) {
1085 let (fields, recovered) = self.parse_record_struct_body()?;
1086 VariantData::Struct(fields, recovered)
1087 // Tuple-style struct definition with optional where-clause.
1088 } else if self.token == token::OpenDelim(token::Paren) {
1089 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1090 generics.where_clause = self.parse_where_clause()?;
1091 self.expect_semi()?;
1094 let token_str = super::token_descr(&self.token);
1096 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
1099 let mut err = self.struct_span_err(self.token.span, msg);
1100 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1104 Ok((class_name, ItemKind::Struct(vdata, generics)))
1107 /// Parses `union Foo { ... }`.
1108 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1109 let class_name = self.parse_ident()?;
1111 let mut generics = self.parse_generics()?;
1113 let vdata = if self.token.is_keyword(kw::Where) {
1114 generics.where_clause = self.parse_where_clause()?;
1115 let (fields, recovered) = self.parse_record_struct_body()?;
1116 VariantData::Struct(fields, recovered)
1117 } else if self.token == token::OpenDelim(token::Brace) {
1118 let (fields, recovered) = self.parse_record_struct_body()?;
1119 VariantData::Struct(fields, recovered)
1121 let token_str = super::token_descr(&self.token);
1122 let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
1123 let mut err = self.struct_span_err(self.token.span, msg);
1124 err.span_label(self.token.span, "expected `where` or `{` after union name");
1128 Ok((class_name, ItemKind::Union(vdata, generics)))
1131 fn parse_record_struct_body(
1133 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
1134 let mut fields = Vec::new();
1135 let mut recovered = false;
1136 if self.eat(&token::OpenDelim(token::Brace)) {
1137 while self.token != token::CloseDelim(token::Brace) {
1138 let field = self.parse_struct_decl_field().map_err(|e| {
1139 self.consume_block(token::Brace, ConsumeClosingDelim::No);
1144 Ok(field) => fields.push(field),
1151 self.eat(&token::CloseDelim(token::Brace));
1153 let token_str = super::token_descr(&self.token);
1154 let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
1155 let mut err = self.struct_span_err(self.token.span, msg);
1156 err.span_label(self.token.span, "expected `where`, or `{` after struct name");
1160 Ok((fields, recovered))
1163 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
1164 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1165 // Unit like structs are handled in parse_item_struct function
1166 self.parse_paren_comma_seq(|p| {
1167 let attrs = p.parse_outer_attributes()?;
1168 let lo = p.token.span;
1169 let vis = p.parse_visibility(FollowedByType::Yes)?;
1170 let ty = p.parse_ty()?;
1172 span: lo.to(ty.span),
1178 is_placeholder: false,
1184 /// Parses an element of a struct declaration.
1185 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
1186 let attrs = self.parse_outer_attributes()?;
1187 let lo = self.token.span;
1188 let vis = self.parse_visibility(FollowedByType::No)?;
1189 self.parse_single_struct_field(lo, vis, attrs)
1192 /// Parses a structure field declaration.
1193 fn parse_single_struct_field(
1197 attrs: Vec<Attribute>,
1198 ) -> PResult<'a, StructField> {
1199 let mut seen_comma: bool = false;
1200 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
1201 if self.token == token::Comma {
1204 match self.token.kind {
1208 token::CloseDelim(token::Brace) => {}
1209 token::DocComment(_) => {
1210 let previous_span = self.prev_span;
1211 let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
1212 self.bump(); // consume the doc comment
1213 let comma_after_doc_seen = self.eat(&token::Comma);
1214 // `seen_comma` is always false, because we are inside doc block
1215 // condition is here to make code more readable
1216 if seen_comma == false && comma_after_doc_seen == true {
1219 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
1222 if seen_comma == false {
1223 let sp = self.sess.source_map().next_point(previous_span);
1224 err.span_suggestion(
1226 "missing comma here",
1228 Applicability::MachineApplicable,
1235 let sp = self.prev_span.shrink_to_hi();
1236 let mut err = self.struct_span_err(
1238 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1240 if self.token.is_ident() {
1241 // This is likely another field; emit the diagnostic and keep going
1242 err.span_suggestion(
1244 "try adding a comma",
1246 Applicability::MachineApplicable,
1257 /// Parses a structure field.
1258 fn parse_name_and_ty(
1262 attrs: Vec<Attribute>,
1263 ) -> PResult<'a, StructField> {
1264 let name = self.parse_ident()?;
1265 self.expect(&token::Colon)?;
1266 let ty = self.parse_ty()?;
1268 span: lo.to(self.prev_span),
1274 is_placeholder: false,
1278 /// Parses a declarative macro 2.0 definition.
1279 /// The `macro` keyword has already been parsed.
1281 /// MacBody = "{" TOKEN_STREAM "}" ;
1282 /// MacParams = "(" TOKEN_STREAM ")" ;
1283 /// DeclMac = "macro" Ident MacParams? MacBody ;
1285 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1286 let ident = self.parse_ident()?;
1287 let body = if self.check(&token::OpenDelim(token::Brace)) {
1288 self.parse_mac_args()? // `MacBody`
1289 } else if self.check(&token::OpenDelim(token::Paren)) {
1290 let params = self.parse_token_tree(); // `MacParams`
1291 let pspan = params.span();
1292 if !self.check(&token::OpenDelim(token::Brace)) {
1293 return self.unexpected();
1295 let body = self.parse_token_tree(); // `MacBody`
1296 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1297 let bspan = body.span();
1298 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1299 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1300 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1301 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1303 return self.unexpected();
1306 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_span));
1307 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: false })))
1310 /// Is this unambiguously the start of a `macro_rules! foo` item defnition?
1311 fn is_macro_rules_item(&mut self) -> bool {
1312 self.check_keyword(kw::MacroRules)
1313 && self.look_ahead(1, |t| *t == token::Not)
1314 && self.look_ahead(2, |t| t.is_ident())
1317 /// Parses a legacy `macro_rules! foo { ... }` declarative macro.
1318 fn parse_item_macro_rules(&mut self, vis: &Visibility) -> PResult<'a, ItemInfo> {
1319 self.expect_keyword(kw::MacroRules)?; // `macro_rules`
1320 self.expect(&token::Not)?; // `!`
1322 let ident = self.parse_ident()?;
1323 let body = self.parse_mac_args()?;
1324 self.eat_semi_for_macro_if_needed(&body);
1325 self.complain_if_pub_macro(vis, true);
1327 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: true })))
1330 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1331 /// If that's not the case, emit an error.
1332 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1333 if let VisibilityKind::Inherited = vis.node {
1337 let vstr = pprust::vis_to_string(vis);
1338 let vstr = vstr.trim_end();
1340 let msg = format!("can't qualify macro_rules invocation with `{}`", vstr);
1341 self.struct_span_err(vis.span, &msg)
1344 "try exporting the macro",
1345 "#[macro_export]".to_owned(),
1346 Applicability::MaybeIncorrect, // speculative
1350 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1353 "remove the visibility",
1355 Applicability::MachineApplicable,
1357 .help(&format!("try adjusting the macro to put `{}` inside the invocation", vstr))
1362 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1363 if args.need_semicolon() && !self.eat(&token::Semi) {
1364 self.report_invalid_macro_expansion_item(args);
1368 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1369 let span = args.span().expect("undelimited macro call");
1370 let mut err = self.struct_span_err(
1372 "macros that expand to items must be delimited with braces or followed by a semicolon",
1374 if self.unclosed_delims.is_empty() {
1375 let DelimSpan { open, close } = match args {
1376 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1377 MacArgs::Delimited(dspan, ..) => *dspan,
1379 err.multipart_suggestion(
1380 "change the delimiters to curly braces",
1381 vec![(open, "{".to_string()), (close, '}'.to_string())],
1382 Applicability::MaybeIncorrect,
1385 err.span_suggestion(
1387 "change the delimiters to curly braces",
1388 " { /* items */ }".to_string(),
1389 Applicability::HasPlaceholders,
1392 err.span_suggestion(
1393 span.shrink_to_hi(),
1396 Applicability::MaybeIncorrect,
1401 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1402 /// it is, we try to parse the item and report error about nested types.
1403 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1404 if (self.token.is_keyword(kw::Enum)
1405 || self.token.is_keyword(kw::Struct)
1406 || self.token.is_keyword(kw::Union))
1407 && self.look_ahead(1, |t| t.is_ident())
1409 let kw_token = self.token.clone();
1410 let kw_str = pprust::token_to_string(&kw_token);
1411 let item = self.parse_item()?;
1413 self.struct_span_err(
1415 &format!("`{}` definition cannot be nested inside `{}`", kw_str, keyword),
1419 &format!("consider creating a new `{}` definition instead of nesting", kw_str),
1421 Applicability::MaybeIncorrect,
1424 // We successfully parsed the item but we must inform the caller about nested problem.
1436 attrs: Vec<Attribute>,
1438 let span = lo.to(self.prev_span);
1439 Item { ident, attrs, id: DUMMY_NODE_ID, kind, vis, span, tokens: None }
1443 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1445 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1446 type ReqName = fn(&token::Token) -> bool;
1448 /// Parsing of functions and methods.
1449 impl<'a> Parser<'a> {
1450 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1454 attrs: &mut Vec<Attribute>,
1456 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1457 let header = self.parse_fn_front_matter()?; // `const ... fn`
1458 let ident = self.parse_ident()?; // `foo`
1459 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1460 let decl = self.parse_fn_decl(req_name, AllowPlus::Yes)?; // `(p: u8, ...)`
1461 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1462 let body = self.parse_fn_body(at_end, attrs)?; // `;` or `{ ... }`.
1463 Ok((ident, FnSig { header, decl }, generics, body))
1466 /// Parse the "body" of a function.
1467 /// This can either be `;` when there's no body,
1468 /// or e.g. a block when the function is a provided one.
1472 attrs: &mut Vec<Attribute>,
1473 ) -> PResult<'a, Option<P<Block>>> {
1474 let (inner_attrs, body) = match self.token.kind {
1479 token::OpenDelim(token::Brace) => {
1480 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1483 token::Interpolated(ref nt) => match **nt {
1484 token::NtBlock(..) => {
1485 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1488 _ => return self.expected_semi_or_open_brace(),
1490 _ => return self.expected_semi_or_open_brace(),
1492 attrs.extend(inner_attrs);
1497 /// Is the current token the start of an `FnHeader` / not a valid parse?
1498 fn check_fn_front_matter(&mut self) -> bool {
1499 // We use an over-approximation here.
1500 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1501 const QUALS: [Symbol; 4] = [kw::Const, kw::Async, kw::Unsafe, kw::Extern];
1502 self.check_keyword(kw::Fn) // Definitely an `fn`.
1503 // `$qual fn` or `$qual $qual`:
1504 || QUALS.iter().any(|&kw| self.check_keyword(kw))
1505 && self.look_ahead(1, |t| {
1506 // ...qualified and then `fn`, e.g. `const fn`.
1507 t.is_keyword(kw::Fn)
1508 // Two qualifiers. This is enough. Due `async` we need to check that it's reserved.
1509 || t.is_non_raw_ident_where(|i| QUALS.contains(&i.name) && i.is_reserved())
1512 || self.check_keyword(kw::Extern)
1513 && self.look_ahead(1, |t| t.can_begin_literal_or_bool())
1514 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
1517 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
1518 /// up to and including the `fn` keyword. The formal grammar is:
1521 /// Extern = "extern" StringLit ;
1522 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
1523 /// FnFrontMatter = FnQual? "fn" ;
1525 fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
1526 let constness = self.parse_constness();
1527 let asyncness = self.parse_asyncness();
1528 let unsafety = self.parse_unsafety();
1529 let ext = self.parse_extern()?;
1531 if let Async::Yes { span, .. } = asyncness {
1532 self.ban_async_in_2015(span);
1535 if !self.eat_keyword(kw::Fn) {
1536 // It is possible for `expect_one_of` to recover given the contents of
1537 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
1538 // account for this.
1539 if !self.expect_one_of(&[], &[])? {
1544 Ok(FnHeader { constness, unsafety, asyncness, ext })
1547 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
1548 fn ban_async_in_2015(&self, span: Span) {
1549 if span.rust_2015() {
1550 let diag = self.diagnostic();
1551 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in the 2015 edition")
1552 .note("to use `async fn`, switch to Rust 2018")
1553 .help("set `edition = \"2018\"` in `Cargo.toml`")
1554 .note("for more on editions, read https://doc.rust-lang.org/edition-guide")
1559 /// Parses the parameter list and result type of a function declaration.
1560 pub(super) fn parse_fn_decl(
1563 ret_allow_plus: AllowPlus,
1564 ) -> PResult<'a, P<FnDecl>> {
1566 inputs: self.parse_fn_params(req_name)?,
1567 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes)?,
1571 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
1572 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
1573 let mut first_param = true;
1574 // Parse the arguments, starting out with `self` being allowed...
1575 let (mut params, _) = self.parse_paren_comma_seq(|p| {
1576 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
1578 let lo = p.prev_span;
1579 // Skip every token until next possible arg or end.
1580 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
1581 // Create a placeholder argument for proper arg count (issue #34264).
1582 Ok(dummy_arg(Ident::new(kw::Invalid, lo.to(p.prev_span))))
1584 // ...now that we've parsed the first argument, `self` is no longer allowed.
1585 first_param = false;
1588 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
1589 self.deduplicate_recovered_params_names(&mut params);
1593 /// Parses a single function parameter.
1595 /// - `self` is syntactically allowed when `first_param` holds.
1596 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
1597 let lo = self.token.span;
1598 let attrs = self.parse_outer_attributes()?;
1600 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
1601 if let Some(mut param) = self.parse_self_param()? {
1602 param.attrs = attrs.into();
1603 return if first_param { Ok(param) } else { self.recover_bad_self_param(param) };
1606 let is_name_required = match self.token.kind {
1607 token::DotDotDot => false,
1608 _ => req_name(&self.token),
1610 let (pat, ty) = if is_name_required || self.is_named_param() {
1611 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
1613 let pat = self.parse_fn_param_pat()?;
1614 if let Err(mut err) = self.expect(&token::Colon) {
1615 return if let Some(ident) =
1616 self.parameter_without_type(&mut err, pat, is_name_required, first_param)
1619 Ok(dummy_arg(ident))
1625 self.eat_incorrect_doc_comment_for_param_type();
1626 (pat, self.parse_ty_for_param()?)
1628 debug!("parse_param_general ident_to_pat");
1629 let parser_snapshot_before_ty = self.clone();
1630 self.eat_incorrect_doc_comment_for_param_type();
1631 let mut ty = self.parse_ty_for_param();
1633 && self.token != token::Comma
1634 && self.token != token::CloseDelim(token::Paren)
1636 // This wasn't actually a type, but a pattern looking like a type,
1637 // so we are going to rollback and re-parse for recovery.
1638 ty = self.unexpected();
1642 let ident = Ident::new(kw::Invalid, self.prev_span);
1643 let bm = BindingMode::ByValue(Mutability::Not);
1644 let pat = self.mk_pat_ident(ty.span, bm, ident);
1647 // If this is a C-variadic argument and we hit an error, return the error.
1648 Err(err) if self.token == token::DotDotDot => return Err(err),
1649 // Recover from attempting to parse the argument as a type without pattern.
1652 mem::replace(self, parser_snapshot_before_ty);
1653 self.recover_arg_parse()?
1658 let span = lo.to(self.token.span);
1661 attrs: attrs.into(),
1662 id: ast::DUMMY_NODE_ID,
1663 is_placeholder: false,
1670 /// Returns the parsed optional self parameter and whether a self shortcut was used.
1671 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
1672 // Extract an identifier *after* having confirmed that the token is one.
1673 let expect_self_ident = |this: &mut Self| {
1674 match this.token.kind {
1675 // Preserve hygienic context.
1676 token::Ident(name, _) => {
1677 let span = this.token.span;
1679 Ident::new(name, span)
1681 _ => unreachable!(),
1684 // Is `self` `n` tokens ahead?
1685 let is_isolated_self = |this: &Self, n| {
1686 this.is_keyword_ahead(n, &[kw::SelfLower])
1687 && this.look_ahead(n + 1, |t| t != &token::ModSep)
1689 // Is `mut self` `n` tokens ahead?
1690 let is_isolated_mut_self =
1691 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
1692 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
1693 let parse_self_possibly_typed = |this: &mut Self, m| {
1694 let eself_ident = expect_self_ident(this);
1695 let eself_hi = this.prev_span;
1696 let eself = if this.eat(&token::Colon) {
1697 SelfKind::Explicit(this.parse_ty()?, m)
1701 Ok((eself, eself_ident, eself_hi))
1703 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
1704 let recover_self_ptr = |this: &mut Self| {
1705 let msg = "cannot pass `self` by raw pointer";
1706 let span = this.token.span;
1707 this.struct_span_err(span, msg).span_label(span, msg).emit();
1709 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_span))
1712 // Parse optional `self` parameter of a method.
1713 // Only a limited set of initial token sequences is considered `self` parameters; anything
1714 // else is parsed as a normal function parameter list, so some lookahead is required.
1715 let eself_lo = self.token.span;
1716 let (eself, eself_ident, eself_hi) = match self.token.kind {
1717 token::BinOp(token::And) => {
1718 let eself = if is_isolated_self(self, 1) {
1721 SelfKind::Region(None, Mutability::Not)
1722 } else if is_isolated_mut_self(self, 1) {
1726 SelfKind::Region(None, Mutability::Mut)
1727 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
1730 let lt = self.expect_lifetime();
1731 SelfKind::Region(Some(lt), Mutability::Not)
1732 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
1735 let lt = self.expect_lifetime();
1737 SelfKind::Region(Some(lt), Mutability::Mut)
1742 (eself, expect_self_ident(self), self.prev_span)
1745 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
1747 recover_self_ptr(self)?
1749 // `*mut self` and `*const self`
1750 token::BinOp(token::Star)
1751 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
1755 recover_self_ptr(self)?
1757 // `self` and `self: TYPE`
1758 token::Ident(..) if is_isolated_self(self, 0) => {
1759 parse_self_possibly_typed(self, Mutability::Not)?
1761 // `mut self` and `mut self: TYPE`
1762 token::Ident(..) if is_isolated_mut_self(self, 0) => {
1764 parse_self_possibly_typed(self, Mutability::Mut)?
1766 _ => return Ok(None),
1769 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
1770 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
1773 fn is_named_param(&self) -> bool {
1774 let offset = match self.token.kind {
1775 token::Interpolated(ref nt) => match **nt {
1776 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1779 token::BinOp(token::And) | token::AndAnd => 1,
1780 _ if self.token.is_keyword(kw::Mut) => 1,
1784 self.look_ahead(offset, |t| t.is_ident())
1785 && self.look_ahead(offset + 1, |t| t == &token::Colon)
1788 fn recover_first_param(&mut self) -> &'static str {
1790 .parse_outer_attributes()
1791 .and_then(|_| self.parse_self_param())
1792 .map_err(|mut e| e.cancel())
1794 Ok(Some(_)) => "method",