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, ForeignItemKind, 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 let (ident, ty, generics) = self.parse_type_alias()?;
160 (ident, ItemKind::TyAlias(ty, generics))
161 } else if self.eat_keyword(kw::Enum) {
163 self.parse_item_enum()?
164 } else if self.eat_keyword(kw::Struct) {
166 self.parse_item_struct()?
167 } else if self.is_kw_followed_by_ident(kw::Union) {
169 self.bump(); // `union`
170 self.parse_item_union()?
171 } else if self.eat_keyword(kw::Macro) {
173 self.parse_item_decl_macro(lo)?
174 } else if self.is_macro_rules_item() {
176 self.parse_item_macro_rules(vis)?
177 } else if vis.node.is_pub() && self.isnt_macro_invocation() {
178 self.recover_missing_kw_before_item()?;
180 } else if macros_allowed && self.token.is_path_start() {
181 // MACRO INVOCATION ITEM
182 (Ident::invalid(), ItemKind::Mac(self.parse_item_macro(vis)?))
189 /// When parsing a statement, would the start of a path be an item?
190 pub(super) fn is_path_start_item(&mut self) -> bool {
191 self.is_crate_vis() // no: `crate::b`, yes: `crate $item`
192 || self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
193 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
194 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
195 || self.is_macro_rules_item() // no: `macro_rules::b`, yes: `macro_rules! mac`
198 /// Are we sure this could not possibly be a macro invocation?
199 fn isnt_macro_invocation(&mut self) -> bool {
200 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
203 /// Recover on encountering a struct or method definition where the user
204 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
205 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
206 // Space between `pub` keyword and the identifier
209 // ^^^ `sp` points here
210 let sp = self.prev_span.between(self.token.span);
211 let full_sp = self.prev_span.to(self.token.span);
212 let ident_sp = self.token.span;
213 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
214 // possible public struct definition where `struct` was forgotten
215 let ident = self.parse_ident().unwrap();
216 let msg = format!("add `struct` here to parse `{}` as a public struct", ident);
217 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
218 err.span_suggestion_short(
222 Applicability::MaybeIncorrect, // speculative
225 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
226 let ident = self.parse_ident().unwrap();
228 let kw_name = self.recover_first_param();
229 self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
230 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
231 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
233 ("fn", kw_name, false)
234 } else if self.check(&token::OpenDelim(token::Brace)) {
236 ("fn", kw_name, false)
237 } else if self.check(&token::Colon) {
241 ("fn` or `struct", "function or struct", true)
244 let msg = format!("missing `{}` for {} definition", kw, kw_name);
245 let mut err = self.struct_span_err(sp, &msg);
247 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
249 format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name);
250 err.span_suggestion_short(
254 Applicability::MachineApplicable,
257 if let Ok(snippet) = self.span_to_snippet(ident_sp) {
260 "if you meant to call a macro, try",
261 format!("{}!", snippet),
262 // this is the `ambiguous` conditional branch
263 Applicability::MaybeIncorrect,
267 "if you meant to call a macro, remove the `pub` \
268 and add a trailing `!` after the identifier",
273 } else if self.look_ahead(1, |t| *t == token::Lt) {
274 let ident = self.parse_ident().unwrap();
275 self.eat_to_tokens(&[&token::Gt]);
277 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
278 ("fn", self.recover_first_param(), false)
279 } else if self.check(&token::OpenDelim(token::Brace)) {
280 ("struct", "struct", false)
282 ("fn` or `struct", "function or struct", true)
284 let msg = format!("missing `{}` for {} definition", kw, kw_name);
285 let mut err = self.struct_span_err(sp, &msg);
287 err.span_suggestion_short(
289 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
291 Applicability::MachineApplicable,
300 /// Parses an item macro, e.g., `item!();`.
301 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, Mac> {
302 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
303 self.expect(&token::Not)?; // `!`
304 let args = self.parse_mac_args()?; // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
305 self.eat_semi_for_macro_if_needed(&args);
306 self.complain_if_pub_macro(vis, false);
307 Ok(Mac { path, args, prior_type_ascription: self.last_type_ascription })
310 /// Recover if we parsed attributes and expected an item but there was none.
311 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
312 let (start, end) = match attrs {
315 [x0, .., xn] => (x0, xn),
317 let msg = if end.is_doc_comment() {
318 "expected item after doc comment"
320 "expected item after attributes"
322 let mut err = self.struct_span_err(end.span, msg);
323 if end.is_doc_comment() {
324 err.span_label(end.span, "this doc comment doesn't document anything");
326 if let [.., penultimate, _] = attrs {
327 err.span_label(start.span.to(penultimate.span), "other attributes here");
332 fn is_async_fn(&self) -> bool {
333 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
336 fn missing_assoc_item_kind_err(
340 ) -> DiagnosticBuilder<'a> {
341 let expected_kinds = if item_type == "extern" {
342 "missing `fn`, `type`, or `static`"
344 "missing `fn`, `type`, or `const`"
347 // Given this code `path(`, it seems like this is not
348 // setting the visibility of a macro invocation, but rather
349 // a mistyped method declaration.
350 // Create a diagnostic pointing out that `fn` is missing.
352 // x | pub path(&self) {
353 // | ^ missing `fn`, `type`, or `const`
355 // ^^ `sp` below will point to this
356 let sp = prev_span.between(self.token.span);
358 .struct_span_err(sp, &format!("{} for {}-item declaration", expected_kinds, item_type));
359 err.span_label(sp, expected_kinds);
363 /// Parses an implementation item, `impl` keyword is already parsed.
366 /// impl<'a, T> TYPE { /* impl items */ }
367 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
368 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
369 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
372 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
374 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
375 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
379 attrs: &mut Vec<Attribute>,
381 defaultness: Defaultness,
382 ) -> PResult<'a, ItemInfo> {
383 // First, parse generic parameters if necessary.
384 let mut generics = if self.choose_generics_over_qpath() {
385 self.parse_generics()?
387 let mut generics = Generics::default();
389 // /\ this is where `generics.span` should point when there are no type params.
390 generics.span = self.prev_span.shrink_to_hi();
394 let constness = self.parse_constness();
395 if let Const::Yes(span) = constness {
396 self.sess.gated_spans.gate(sym::const_trait_impl, span);
399 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
400 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
402 ast::ImplPolarity::Negative
404 ast::ImplPolarity::Positive
407 // Parse both types and traits as a type, then reinterpret if necessary.
408 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
409 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
411 let span = self.prev_span.between(self.token.span);
412 self.struct_span_err(span, "missing trait in a trait impl").emit();
413 P(Ty { kind: TyKind::Path(None, err_path(span)), span, id: DUMMY_NODE_ID })
418 // If `for` is missing we try to recover.
419 let has_for = self.eat_keyword(kw::For);
420 let missing_for_span = self.prev_span.between(self.token.span);
422 let ty_second = if self.token == token::DotDot {
423 // We need to report this error after `cfg` expansion for compatibility reasons
424 self.bump(); // `..`, do not add it to expected tokens
425 Some(self.mk_ty(self.prev_span, TyKind::Err))
426 } else if has_for || self.token.can_begin_type() {
427 Some(self.parse_ty()?)
432 generics.where_clause = self.parse_where_clause()?;
434 let impl_items = self.parse_item_list(attrs, |p, at_end| p.parse_impl_item(at_end))?;
436 let item_kind = match ty_second {
438 // impl Trait for Type
440 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
441 .span_suggestion_short(
445 Applicability::MachineApplicable,
450 let ty_first = ty_first.into_inner();
451 let path = match ty_first.kind {
452 // This notably includes paths passed through `ty` macro fragments (#46438).
453 TyKind::Path(None, path) => path,
455 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
456 err_path(ty_first.span)
459 let trait_ref = TraitRef { path, ref_id: ty_first.id };
467 of_trait: Some(trait_ref),
487 Ok((Ident::invalid(), item_kind))
490 fn parse_item_list<T>(
492 attrs: &mut Vec<Attribute>,
493 mut parse_item: impl FnMut(&mut Parser<'a>, &mut bool) -> PResult<'a, T>,
494 ) -> PResult<'a, Vec<T>> {
495 self.expect(&token::OpenDelim(token::Brace))?;
496 attrs.append(&mut self.parse_inner_attributes()?);
498 let mut items = Vec::new();
499 while !self.eat(&token::CloseDelim(token::Brace)) {
500 if self.recover_doc_comment_before_brace() {
503 let mut at_end = false;
504 match parse_item(self, &mut at_end) {
505 Ok(item) => items.push(item),
509 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
518 /// Recover on a doc comment before `}`.
519 fn recover_doc_comment_before_brace(&mut self) -> bool {
520 if let token::DocComment(_) = self.token.kind {
521 if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
526 "found a documentation comment that doesn't document anything",
528 .span_label(self.token.span, "this doc comment doesn't document anything")
530 "doc comments must come before what they document, maybe a \
531 comment was intended with `//`?",
541 /// Parses defaultness (i.e., `default` or nothing).
542 fn parse_defaultness(&mut self) -> Defaultness {
543 // `pub` is included for better error messages
544 if self.check_keyword(kw::Default)
545 && self.is_keyword_ahead(
559 self.bump(); // `default`
566 /// Is this an `(unsafe auto? | auto) trait` item?
567 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
569 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
571 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
574 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
575 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
576 let unsafety = self.parse_unsafety();
577 // Parse optional `auto` prefix.
578 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
580 self.expect_keyword(kw::Trait)?;
581 let ident = self.parse_ident()?;
582 let mut tps = self.parse_generics()?;
584 // Parse optional colon and supertrait bounds.
585 let had_colon = self.eat(&token::Colon);
586 let span_at_colon = self.prev_span;
588 if had_colon { self.parse_generic_bounds(Some(self.prev_span))? } else { Vec::new() };
590 let span_before_eq = self.prev_span;
591 if self.eat(&token::Eq) {
592 // It's a trait alias.
594 let span = span_at_colon.to(span_before_eq);
595 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
598 let bounds = self.parse_generic_bounds(None)?;
599 tps.where_clause = self.parse_where_clause()?;
602 let whole_span = lo.to(self.prev_span);
603 if is_auto == IsAuto::Yes {
604 let msg = "trait aliases cannot be `auto`";
605 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
607 if let Unsafe::Yes(_) = unsafety {
608 let msg = "trait aliases cannot be `unsafe`";
609 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
612 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
614 Ok((ident, ItemKind::TraitAlias(tps, bounds)))
616 // It's a normal trait.
617 tps.where_clause = self.parse_where_clause()?;
618 let items = self.parse_item_list(attrs, |p, at_end| p.parse_trait_item(at_end))?;
619 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, items)))
623 pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, P<AssocItem>> {
624 maybe_whole!(self, NtImplItem, |x| x);
625 self.parse_assoc_item(at_end, |_| true)
628 pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, P<AssocItem>> {
629 maybe_whole!(self, NtTraitItem, |x| x);
630 // This is somewhat dubious; We don't want to allow
631 // param names to be left off if there is a definition...
633 // We don't allow param names to be left off in edition 2018.
634 self.parse_assoc_item(at_end, |t| t.span.rust_2018())
637 /// Parses associated items.
641 req_name: fn(&token::Token) -> bool,
642 ) -> PResult<'a, P<AssocItem>> {
643 let attrs = self.parse_outer_attributes()?;
644 let mut unclosed_delims = vec![];
645 let (mut item, tokens) = self.collect_tokens(|this| {
646 let item = this.parse_assoc_item_(at_end, attrs, req_name);
647 unclosed_delims.append(&mut this.unclosed_delims);
650 self.unclosed_delims.append(&mut unclosed_delims);
651 // See `parse_item` for why this clause is here.
652 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
653 item.tokens = Some(tokens);
658 fn parse_assoc_item_(
661 mut attrs: Vec<Attribute>,
662 req_name: fn(&token::Token) -> bool,
663 ) -> PResult<'a, AssocItem> {
664 let lo = self.token.span;
665 let vis = self.parse_visibility(FollowedByType::No)?;
666 let defaultness = self.parse_defaultness();
668 let (ident, kind) = if self.eat_keyword(kw::Type) {
669 self.parse_assoc_ty()?
670 } else if self.check_fn_front_matter() {
671 let (ident, sig, generics, body) = self.parse_fn(at_end, &mut attrs, req_name)?;
672 (ident, AssocItemKind::Fn(sig, generics, body))
673 } else if self.eat_keyword(kw::Const) {
674 self.parse_assoc_const()?
675 } else if self.isnt_macro_invocation() {
676 return Err(self.missing_assoc_item_kind_err("associated", self.prev_span));
677 } else if self.token.is_path_start() {
678 let mac = self.parse_item_macro(&vis)?;
680 (Ident::invalid(), AssocItemKind::Macro(mac))
682 self.recover_attrs_no_item(&attrs)?;
686 let span = lo.to(self.prev_span);
687 let id = DUMMY_NODE_ID;
688 Ok(AssocItem { id, span, ident, attrs, vis, defaultness, kind, tokens: None })
691 /// This parses the grammar:
693 /// AssocConst = "const" Ident ":" Ty "=" Expr ";"
694 fn parse_assoc_const(&mut self) -> PResult<'a, (Ident, AssocItemKind)> {
695 self.expect_keyword(kw::Const)?;
696 let (ident, ty, expr) = self.parse_item_const_common(None)?;
697 Ok((ident, AssocItemKind::Const(ty, expr)))
700 /// Parses the following grammar:
702 /// AssocTy = Ident ["<"...">"] [":" [GenericBounds]] ["where" ...] ["=" Ty]
703 fn parse_assoc_ty(&mut self) -> PResult<'a, (Ident, AssocItemKind)> {
704 let ident = self.parse_ident()?;
705 let mut generics = self.parse_generics()?;
707 // Parse optional colon and param bounds.
709 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
710 generics.where_clause = self.parse_where_clause()?;
712 let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
715 Ok((ident, AssocItemKind::TyAlias(generics, bounds, default)))
718 /// Parses a `UseTree`.
721 /// USE_TREE = [`::`] `*` |
722 /// [`::`] `{` USE_TREE_LIST `}` |
724 /// PATH `::` `{` USE_TREE_LIST `}` |
725 /// PATH [`as` IDENT]
727 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
728 let lo = self.token.span;
730 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
731 let kind = if self.check(&token::OpenDelim(token::Brace))
732 || self.check(&token::BinOp(token::Star))
733 || self.is_import_coupler()
735 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
736 let mod_sep_ctxt = self.token.span.ctxt();
737 if self.eat(&token::ModSep) {
740 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
743 self.parse_use_tree_glob_or_nested()?
745 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
746 prefix = self.parse_path(PathStyle::Mod)?;
748 if self.eat(&token::ModSep) {
749 self.parse_use_tree_glob_or_nested()?
751 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
755 Ok(UseTree { prefix, kind, span: lo.to(self.prev_span) })
758 /// Parses `*` or `{...}`.
759 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
760 Ok(if self.eat(&token::BinOp(token::Star)) {
763 UseTreeKind::Nested(self.parse_use_tree_list()?)
767 /// Parses a `UseTreeKind::Nested(list)`.
770 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
772 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
773 self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
777 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
778 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
781 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
782 match self.token.kind {
783 token::Ident(name @ kw::Underscore, false) => {
784 let span = self.token.span;
786 Ok(Ident::new(name, span))
788 _ => self.parse_ident(),
792 /// Parses `extern crate` links.
797 /// extern crate foo;
798 /// extern crate bar as foo;
800 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
801 // Accept `extern crate name-like-this` for better diagnostics
802 let orig_name = self.parse_crate_name_with_dashes()?;
803 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
804 (rename, Some(orig_name.name))
809 Ok((item_name, ItemKind::ExternCrate(orig_name)))
812 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
813 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
814 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
816 let mut ident = if self.token.is_keyword(kw::SelfLower) {
817 self.parse_path_segment_ident()
821 let mut idents = vec![];
822 let mut replacement = vec![];
823 let mut fixed_crate_name = false;
824 // Accept `extern crate name-like-this` for better diagnostics.
825 let dash = token::BinOp(token::BinOpToken::Minus);
826 if self.token == dash {
827 // Do not include `-` as part of the expected tokens list.
828 while self.eat(&dash) {
829 fixed_crate_name = true;
830 replacement.push((self.prev_span, "_".to_string()));
831 idents.push(self.parse_ident()?);
834 if fixed_crate_name {
835 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
836 let mut fixed_name = format!("{}", ident.name);
838 fixed_name.push_str(&format!("_{}", part.name));
840 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
842 self.struct_span_err(fixed_name_sp, error_msg)
843 .span_label(fixed_name_sp, "dash-separated idents are not valid")
844 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
850 /// Parses `extern` for foreign ABIs modules.
852 /// `extern` is expected to have been consumed before calling this method.
856 /// ```ignore (only-for-syntax-highlight)
860 fn parse_item_foreign_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
861 let abi = self.parse_abi(); // ABI?
862 let items = self.parse_item_list(attrs, |p, at_end| p.parse_foreign_item(at_end))?;
863 let module = ast::ForeignMod { abi, items };
864 Ok((Ident::invalid(), ItemKind::ForeignMod(module)))
867 /// Parses a foreign item (one in an `extern { ... }` block).
868 pub fn parse_foreign_item(&mut self, at_end: &mut bool) -> PResult<'a, P<ForeignItem>> {
869 maybe_whole!(self, NtForeignItem, |ni| ni);
871 let mut attrs = self.parse_outer_attributes()?;
872 let lo = self.token.span;
873 let vis = self.parse_visibility(FollowedByType::No)?;
875 let (ident, kind) = if self.eat_keyword(kw::Type) {
877 self.parse_item_foreign_type()?
878 } else if self.check_fn_front_matter() {
879 // FOREIGN FUNCTION ITEM
880 let (ident, sig, generics, body) = self.parse_fn(at_end, &mut attrs, |_| true)?;
881 (ident, ForeignItemKind::Fn(sig, generics, body))
882 } else if self.is_static_global() {
883 // FOREIGN STATIC ITEM
884 self.bump(); // `static`
885 self.parse_item_foreign_static()?
886 } else if self.token.is_keyword(kw::Const) {
887 // Treat `const` as `static` for error recovery, but don't add it to expected tokens.
888 self.bump(); // `const`
889 self.struct_span_err(self.prev_span, "extern items cannot be `const`")
892 "try using a static value",
894 Applicability::MachineApplicable,
897 self.parse_item_foreign_static()?
898 } else if self.isnt_macro_invocation() {
899 return Err(self.missing_assoc_item_kind_err("extern", self.prev_span));
900 } else if self.token.is_path_start() {
901 let mac = self.parse_item_macro(&vis)?;
903 (Ident::invalid(), ForeignItemKind::Macro(mac))
905 self.recover_attrs_no_item(&attrs)?;
908 Ok(P(self.mk_item(lo, ident, kind, vis, attrs)))
911 /// Parses a static item from a foreign module.
912 /// Assumes that the `static` keyword is already parsed.
913 fn parse_item_foreign_static(&mut self) -> PResult<'a, (Ident, ForeignItemKind)> {
914 let mutbl = self.parse_mutability();
915 let (ident, ty, expr) = self.parse_item_const_common(Some(mutbl))?;
916 Ok((ident, ForeignItemKind::Static(ty, mutbl, expr)))
919 /// Parses a type from a foreign module.
920 fn parse_item_foreign_type(&mut self) -> PResult<'a, (Ident, ForeignItemKind)> {
921 let (ident, kind) = self.parse_assoc_ty()?;
922 let kind = match kind {
923 AssocItemKind::TyAlias(g, b, d) => ForeignItemKind::TyAlias(g, b, d),
929 fn is_static_global(&mut self) -> bool {
930 if self.check_keyword(kw::Static) {
931 // Check if this could be a closure.
932 !self.look_ahead(1, |token| {
933 if token.is_keyword(kw::Move) {
937 token::BinOp(token::Or) | token::OrOr => true,
946 /// Recover on `const mut` with `const` already eaten.
947 fn recover_const_mut(&mut self, const_span: Span) {
948 if self.eat_keyword(kw::Mut) {
949 let span = self.prev_span;
950 self.struct_span_err(span, "const globals cannot be mutable")
951 .span_label(span, "cannot be mutable")
954 "you might want to declare a static instead",
956 Applicability::MaybeIncorrect,
962 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
963 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
965 /// When `m` is `"const"`, `$ident` may also be `"_"`.
966 fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
967 let (id, ty, expr) = self.parse_item_const_common(m)?;
969 Some(m) => ItemKind::Static(ty, m, expr),
970 None => ItemKind::Const(ty, expr),
975 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
976 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
978 /// When `m` is `"const"`, `$ident` may also be `"_"`.
979 fn parse_item_const_common(
981 m: Option<Mutability>,
982 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
983 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
985 // Parse the type of a `const` or `static mut?` item.
986 // That is, the `":" $ty` fragment.
987 let ty = if self.eat(&token::Colon) {
990 self.recover_missing_const_type(id, m)
993 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
998 /// We were supposed to parse `:` but the `:` was missing.
999 /// This means that the type is missing.
1000 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
1001 // Construct the error and stash it away with the hope
1002 // that typeck will later enrich the error with a type.
1003 let kind = match m {
1004 Some(Mutability::Mut) => "static mut",
1005 Some(Mutability::Not) => "static",
1008 let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
1009 err.span_suggestion(
1011 "provide a type for the item",
1012 format!("{}: <type>", id),
1013 Applicability::HasPlaceholders,
1015 err.stash(id.span, StashKey::ItemNoType);
1017 // The user intended that the type be inferred,
1018 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
1019 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID })
1022 /// Parses the grammar:
1023 /// Ident ["<"...">"] ["where" ...] ("=" | ":") Ty ";"
1024 fn parse_type_alias(&mut self) -> PResult<'a, (Ident, P<Ty>, Generics)> {
1025 let ident = self.parse_ident()?;
1026 let mut tps = self.parse_generics()?;
1027 tps.where_clause = self.parse_where_clause()?;
1028 self.expect(&token::Eq)?;
1029 let ty = self.parse_ty()?;
1030 self.expect_semi()?;
1031 Ok((ident, ty, tps))
1034 /// Parses an enum declaration.
1035 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
1036 let id = self.parse_ident()?;
1037 let mut generics = self.parse_generics()?;
1038 generics.where_clause = self.parse_where_clause()?;
1041 self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
1042 self.recover_stmt();
1046 let enum_definition =
1047 EnumDef { variants: variants.into_iter().filter_map(|v| v).collect() };
1048 Ok((id, ItemKind::Enum(enum_definition, generics)))
1051 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
1052 let variant_attrs = self.parse_outer_attributes()?;
1053 let vlo = self.token.span;
1055 let vis = self.parse_visibility(FollowedByType::No)?;
1056 if !self.recover_nested_adt_item(kw::Enum)? {
1059 let ident = self.parse_ident()?;
1061 let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
1062 // Parse a struct variant.
1063 let (fields, recovered) = self.parse_record_struct_body()?;
1064 VariantData::Struct(fields, recovered)
1065 } else if self.check(&token::OpenDelim(token::Paren)) {
1066 VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID)
1068 VariantData::Unit(DUMMY_NODE_ID)
1072 if self.eat(&token::Eq) { Some(self.parse_anon_const_expr()?) } else { None };
1074 let vr = ast::Variant {
1078 attrs: variant_attrs,
1081 span: vlo.to(self.prev_span),
1082 is_placeholder: false,
1088 /// Parses `struct Foo { ... }`.
1089 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1090 let class_name = self.parse_ident()?;
1092 let mut generics = self.parse_generics()?;
1094 // There is a special case worth noting here, as reported in issue #17904.
1095 // If we are parsing a tuple struct it is the case that the where clause
1096 // should follow the field list. Like so:
1098 // struct Foo<T>(T) where T: Copy;
1100 // If we are parsing a normal record-style struct it is the case
1101 // that the where clause comes before the body, and after the generics.
1102 // So if we look ahead and see a brace or a where-clause we begin
1103 // parsing a record style struct.
1105 // Otherwise if we look ahead and see a paren we parse a tuple-style
1108 let vdata = if self.token.is_keyword(kw::Where) {
1109 generics.where_clause = self.parse_where_clause()?;
1110 if self.eat(&token::Semi) {
1111 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1112 VariantData::Unit(DUMMY_NODE_ID)
1114 // If we see: `struct Foo<T> where T: Copy { ... }`
1115 let (fields, recovered) = self.parse_record_struct_body()?;
1116 VariantData::Struct(fields, recovered)
1118 // No `where` so: `struct Foo<T>;`
1119 } else if self.eat(&token::Semi) {
1120 VariantData::Unit(DUMMY_NODE_ID)
1121 // Record-style struct definition
1122 } else if self.token == token::OpenDelim(token::Brace) {
1123 let (fields, recovered) = self.parse_record_struct_body()?;
1124 VariantData::Struct(fields, recovered)
1125 // Tuple-style struct definition with optional where-clause.
1126 } else if self.token == token::OpenDelim(token::Paren) {
1127 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1128 generics.where_clause = self.parse_where_clause()?;
1129 self.expect_semi()?;
1132 let token_str = super::token_descr(&self.token);
1134 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
1137 let mut err = self.struct_span_err(self.token.span, msg);
1138 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1142 Ok((class_name, ItemKind::Struct(vdata, generics)))
1145 /// Parses `union Foo { ... }`.
1146 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1147 let class_name = self.parse_ident()?;
1149 let mut generics = self.parse_generics()?;
1151 let vdata = if self.token.is_keyword(kw::Where) {
1152 generics.where_clause = self.parse_where_clause()?;
1153 let (fields, recovered) = self.parse_record_struct_body()?;
1154 VariantData::Struct(fields, recovered)
1155 } else if self.token == token::OpenDelim(token::Brace) {
1156 let (fields, recovered) = self.parse_record_struct_body()?;
1157 VariantData::Struct(fields, recovered)
1159 let token_str = super::token_descr(&self.token);
1160 let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
1161 let mut err = self.struct_span_err(self.token.span, msg);
1162 err.span_label(self.token.span, "expected `where` or `{` after union name");
1166 Ok((class_name, ItemKind::Union(vdata, generics)))
1169 fn parse_record_struct_body(
1171 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
1172 let mut fields = Vec::new();
1173 let mut recovered = false;
1174 if self.eat(&token::OpenDelim(token::Brace)) {
1175 while self.token != token::CloseDelim(token::Brace) {
1176 let field = self.parse_struct_decl_field().map_err(|e| {
1177 self.consume_block(token::Brace, ConsumeClosingDelim::No);
1182 Ok(field) => fields.push(field),
1189 self.eat(&token::CloseDelim(token::Brace));
1191 let token_str = super::token_descr(&self.token);
1192 let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
1193 let mut err = self.struct_span_err(self.token.span, msg);
1194 err.span_label(self.token.span, "expected `where`, or `{` after struct name");
1198 Ok((fields, recovered))
1201 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
1202 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1203 // Unit like structs are handled in parse_item_struct function
1204 self.parse_paren_comma_seq(|p| {
1205 let attrs = p.parse_outer_attributes()?;
1206 let lo = p.token.span;
1207 let vis = p.parse_visibility(FollowedByType::Yes)?;
1208 let ty = p.parse_ty()?;
1210 span: lo.to(ty.span),
1216 is_placeholder: false,
1222 /// Parses an element of a struct declaration.
1223 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
1224 let attrs = self.parse_outer_attributes()?;
1225 let lo = self.token.span;
1226 let vis = self.parse_visibility(FollowedByType::No)?;
1227 self.parse_single_struct_field(lo, vis, attrs)
1230 /// Parses a structure field declaration.
1231 fn parse_single_struct_field(
1235 attrs: Vec<Attribute>,
1236 ) -> PResult<'a, StructField> {
1237 let mut seen_comma: bool = false;
1238 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
1239 if self.token == token::Comma {
1242 match self.token.kind {
1246 token::CloseDelim(token::Brace) => {}
1247 token::DocComment(_) => {
1248 let previous_span = self.prev_span;
1249 let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
1250 self.bump(); // consume the doc comment
1251 let comma_after_doc_seen = self.eat(&token::Comma);
1252 // `seen_comma` is always false, because we are inside doc block
1253 // condition is here to make code more readable
1254 if seen_comma == false && comma_after_doc_seen == true {
1257 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
1260 if seen_comma == false {
1261 let sp = self.sess.source_map().next_point(previous_span);
1262 err.span_suggestion(
1264 "missing comma here",
1266 Applicability::MachineApplicable,
1273 let sp = self.prev_span.shrink_to_hi();
1274 let mut err = self.struct_span_err(
1276 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1278 if self.token.is_ident() {
1279 // This is likely another field; emit the diagnostic and keep going
1280 err.span_suggestion(
1282 "try adding a comma",
1284 Applicability::MachineApplicable,
1295 /// Parses a structure field.
1296 fn parse_name_and_ty(
1300 attrs: Vec<Attribute>,
1301 ) -> PResult<'a, StructField> {
1302 let name = self.parse_ident()?;
1303 self.expect(&token::Colon)?;
1304 let ty = self.parse_ty()?;
1306 span: lo.to(self.prev_span),
1312 is_placeholder: false,
1316 /// Parses a declarative macro 2.0 definition.
1317 /// The `macro` keyword has already been parsed.
1319 /// MacBody = "{" TOKEN_STREAM "}" ;
1320 /// MacParams = "(" TOKEN_STREAM ")" ;
1321 /// DeclMac = "macro" Ident MacParams? MacBody ;
1323 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1324 let ident = self.parse_ident()?;
1325 let body = if self.check(&token::OpenDelim(token::Brace)) {
1326 self.parse_mac_args()? // `MacBody`
1327 } else if self.check(&token::OpenDelim(token::Paren)) {
1328 let params = self.parse_token_tree(); // `MacParams`
1329 let pspan = params.span();
1330 if !self.check(&token::OpenDelim(token::Brace)) {
1331 return self.unexpected();
1333 let body = self.parse_token_tree(); // `MacBody`
1334 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1335 let bspan = body.span();
1336 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1337 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1338 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1339 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1341 return self.unexpected();
1344 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_span));
1345 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: false })))
1348 /// Is this unambiguously the start of a `macro_rules! foo` item defnition?
1349 fn is_macro_rules_item(&mut self) -> bool {
1350 self.check_keyword(sym::macro_rules)
1351 && self.look_ahead(1, |t| *t == token::Not)
1352 && self.look_ahead(2, |t| t.is_ident())
1355 /// Parses a legacy `macro_rules! foo { ... }` declarative macro.
1356 fn parse_item_macro_rules(&mut self, vis: &Visibility) -> PResult<'a, ItemInfo> {
1357 self.expect_keyword(sym::macro_rules)?; // `macro_rules`
1358 self.expect(&token::Not)?; // `!`
1360 let ident = self.parse_ident()?;
1361 let body = self.parse_mac_args()?;
1362 self.eat_semi_for_macro_if_needed(&body);
1363 self.complain_if_pub_macro(vis, true);
1365 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: true })))
1368 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1369 /// If that's not the case, emit an error.
1370 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1371 if let VisibilityKind::Inherited = vis.node {
1375 let vstr = pprust::vis_to_string(vis);
1376 let vstr = vstr.trim_end();
1378 let msg = format!("can't qualify macro_rules invocation with `{}`", vstr);
1379 self.struct_span_err(vis.span, &msg)
1382 "try exporting the macro",
1383 "#[macro_export]".to_owned(),
1384 Applicability::MaybeIncorrect, // speculative
1388 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1391 "remove the visibility",
1393 Applicability::MachineApplicable,
1395 .help(&format!("try adjusting the macro to put `{}` inside the invocation", vstr))
1400 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1401 if args.need_semicolon() && !self.eat(&token::Semi) {
1402 self.report_invalid_macro_expansion_item(args);
1406 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1407 let mut err = self.struct_span_err(
1409 "macros that expand to items must be delimited with braces or followed by a semicolon",
1411 if self.unclosed_delims.is_empty() {
1412 let DelimSpan { open, close } = match args {
1413 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1414 MacArgs::Delimited(dspan, ..) => *dspan,
1416 err.multipart_suggestion(
1417 "change the delimiters to curly braces",
1418 vec![(open, "{".to_string()), (close, '}'.to_string())],
1419 Applicability::MaybeIncorrect,
1422 err.span_suggestion(
1424 "change the delimiters to curly braces",
1425 " { /* items */ }".to_string(),
1426 Applicability::HasPlaceholders,
1429 err.span_suggestion(
1430 self.prev_span.shrink_to_hi(),
1433 Applicability::MaybeIncorrect,
1438 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1439 /// it is, we try to parse the item and report error about nested types.
1440 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1441 if (self.token.is_keyword(kw::Enum)
1442 || self.token.is_keyword(kw::Struct)
1443 || self.token.is_keyword(kw::Union))
1444 && self.look_ahead(1, |t| t.is_ident())
1446 let kw_token = self.token.clone();
1447 let kw_str = pprust::token_to_string(&kw_token);
1448 let item = self.parse_item()?;
1450 self.struct_span_err(
1452 &format!("`{}` definition cannot be nested inside `{}`", kw_str, keyword),
1456 &format!("consider creating a new `{}` definition instead of nesting", kw_str),
1458 Applicability::MaybeIncorrect,
1461 // We successfully parsed the item but we must inform the caller about nested problem.
1473 attrs: Vec<Attribute>,
1475 let span = lo.to(self.prev_span);
1476 Item { ident, attrs, id: DUMMY_NODE_ID, kind, vis, span, tokens: None }
1480 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1482 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1483 type ReqName = fn(&token::Token) -> bool;
1485 /// Parsing of functions and methods.
1486 impl<'a> Parser<'a> {
1487 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1491 attrs: &mut Vec<Attribute>,
1493 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1494 let header = self.parse_fn_front_matter()?; // `const ... fn`
1495 let ident = self.parse_ident()?; // `foo`
1496 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1497 let decl = self.parse_fn_decl(req_name, AllowPlus::Yes)?; // `(p: u8, ...)`
1498 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1499 let body = self.parse_fn_body(at_end, attrs)?; // `;` or `{ ... }`.
1500 Ok((ident, FnSig { header, decl }, generics, body))
1503 /// Parse the "body" of a function.
1504 /// This can either be `;` when there's no body,
1505 /// or e.g. a block when the function is a provided one.
1509 attrs: &mut Vec<Attribute>,
1510 ) -> PResult<'a, Option<P<Block>>> {
1511 let (inner_attrs, body) = match self.token.kind {
1516 token::OpenDelim(token::Brace) => {
1517 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1520 token::Interpolated(ref nt) => match **nt {
1521 token::NtBlock(..) => {
1522 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1525 _ => return self.expected_semi_or_open_brace(),
1527 _ => return self.expected_semi_or_open_brace(),
1529 attrs.extend(inner_attrs);
1534 /// Is the current token the start of an `FnHeader` / not a valid parse?
1535 fn check_fn_front_matter(&mut self) -> bool {
1536 // We use an over-approximation here.
1537 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1538 const QUALS: [Symbol; 4] = [kw::Const, kw::Async, kw::Unsafe, kw::Extern];
1539 self.check_keyword(kw::Fn) // Definitely an `fn`.
1540 // `$qual fn` or `$qual $qual`:
1541 || QUALS.iter().any(|&kw| self.check_keyword(kw))
1542 && self.look_ahead(1, |t| {
1543 // ...qualified and then `fn`, e.g. `const fn`.
1544 t.is_keyword(kw::Fn)
1545 // Two qualifiers. This is enough. Due `async` we need to check that it's reserved.
1546 || t.is_non_raw_ident_where(|i| QUALS.contains(&i.name) && i.is_reserved())
1549 || self.check_keyword(kw::Extern)
1550 && self.look_ahead(1, |t| t.can_begin_literal_or_bool())
1551 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
1554 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
1555 /// up to and including the `fn` keyword. The formal grammar is:
1558 /// Extern = "extern" StringLit ;
1559 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
1560 /// FnFrontMatter = FnQual? "fn" ;
1562 fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
1563 let constness = self.parse_constness();
1564 let asyncness = self.parse_asyncness();
1565 let unsafety = self.parse_unsafety();
1566 let ext = self.parse_extern()?;
1568 if let Async::Yes { span, .. } = asyncness {
1569 self.ban_async_in_2015(span);
1572 if !self.eat_keyword(kw::Fn) {
1573 // It is possible for `expect_one_of` to recover given the contents of
1574 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
1575 // account for this.
1576 if !self.expect_one_of(&[], &[])? {
1581 Ok(FnHeader { constness, unsafety, asyncness, ext })
1584 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
1585 fn ban_async_in_2015(&self, span: Span) {
1586 if span.rust_2015() {
1587 let diag = self.diagnostic();
1588 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in the 2015 edition")
1589 .note("to use `async fn`, switch to Rust 2018")
1590 .help("set `edition = \"2018\"` in `Cargo.toml`")
1591 .note("for more on editions, read https://doc.rust-lang.org/edition-guide")
1596 /// Parses the parameter list and result type of a function declaration.
1597 pub(super) fn parse_fn_decl(
1600 ret_allow_plus: AllowPlus,
1601 ) -> PResult<'a, P<FnDecl>> {
1603 inputs: self.parse_fn_params(req_name)?,
1604 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes)?,
1608 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
1609 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
1610 let mut first_param = true;
1611 // Parse the arguments, starting out with `self` being allowed...
1612 let (mut params, _) = self.parse_paren_comma_seq(|p| {
1613 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
1615 let lo = p.prev_span;
1616 // Skip every token until next possible arg or end.
1617 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
1618 // Create a placeholder argument for proper arg count (issue #34264).
1619 Ok(dummy_arg(Ident::new(kw::Invalid, lo.to(p.prev_span))))
1621 // ...now that we've parsed the first argument, `self` is no longer allowed.
1622 first_param = false;
1625 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
1626 self.deduplicate_recovered_params_names(&mut params);
1630 /// Parses a single function parameter.
1632 /// - `self` is syntactically allowed when `first_param` holds.
1633 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
1634 let lo = self.token.span;
1635 let attrs = self.parse_outer_attributes()?;
1637 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
1638 if let Some(mut param) = self.parse_self_param()? {
1639 param.attrs = attrs.into();
1640 return if first_param { Ok(param) } else { self.recover_bad_self_param(param) };
1643 let is_name_required = match self.token.kind {
1644 token::DotDotDot => false,
1645 _ => req_name(&self.token),
1647 let (pat, ty) = if is_name_required || self.is_named_param() {
1648 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
1650 let pat = self.parse_fn_param_pat()?;
1651 if let Err(mut err) = self.expect(&token::Colon) {
1652 return if let Some(ident) =
1653 self.parameter_without_type(&mut err, pat, is_name_required, first_param)
1656 Ok(dummy_arg(ident))
1662 self.eat_incorrect_doc_comment_for_param_type();
1663 (pat, self.parse_ty_for_param()?)
1665 debug!("parse_param_general ident_to_pat");
1666 let parser_snapshot_before_ty = self.clone();
1667 self.eat_incorrect_doc_comment_for_param_type();
1668 let mut ty = self.parse_ty_for_param();
1670 && self.token != token::Comma
1671 && self.token != token::CloseDelim(token::Paren)
1673 // This wasn't actually a type, but a pattern looking like a type,
1674 // so we are going to rollback and re-parse for recovery.
1675 ty = self.unexpected();
1679 let ident = Ident::new(kw::Invalid, self.prev_span);
1680 let bm = BindingMode::ByValue(Mutability::Not);
1681 let pat = self.mk_pat_ident(ty.span, bm, ident);
1684 // If this is a C-variadic argument and we hit an error, return the error.
1685 Err(err) if self.token == token::DotDotDot => return Err(err),
1686 // Recover from attempting to parse the argument as a type without pattern.
1689 mem::replace(self, parser_snapshot_before_ty);
1690 self.recover_arg_parse()?
1695 let span = lo.to(self.token.span);
1698 attrs: attrs.into(),
1699 id: ast::DUMMY_NODE_ID,
1700 is_placeholder: false,
1707 /// Returns the parsed optional self parameter and whether a self shortcut was used.
1708 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
1709 // Extract an identifier *after* having confirmed that the token is one.
1710 let expect_self_ident = |this: &mut Self| {
1711 match this.token.kind {
1712 // Preserve hygienic context.
1713 token::Ident(name, _) => {
1714 let span = this.token.span;
1716 Ident::new(name, span)
1718 _ => unreachable!(),
1721 // Is `self` `n` tokens ahead?
1722 let is_isolated_self = |this: &Self, n| {
1723 this.is_keyword_ahead(n, &[kw::SelfLower])
1724 && this.look_ahead(n + 1, |t| t != &token::ModSep)
1726 // Is `mut self` `n` tokens ahead?
1727 let is_isolated_mut_self =
1728 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
1729 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
1730 let parse_self_possibly_typed = |this: &mut Self, m| {
1731 let eself_ident = expect_self_ident(this);
1732 let eself_hi = this.prev_span;
1733 let eself = if this.eat(&token::Colon) {
1734 SelfKind::Explicit(this.parse_ty()?, m)
1738 Ok((eself, eself_ident, eself_hi))
1740 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
1741 let recover_self_ptr = |this: &mut Self| {
1742 let msg = "cannot pass `self` by raw pointer";
1743 let span = this.token.span;
1744 this.struct_span_err(span, msg).span_label(span, msg).emit();
1746 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_span))
1749 // Parse optional `self` parameter of a method.
1750 // Only a limited set of initial token sequences is considered `self` parameters; anything
1751 // else is parsed as a normal function parameter list, so some lookahead is required.
1752 let eself_lo = self.token.span;
1753 let (eself, eself_ident, eself_hi) = match self.token.kind {
1754 token::BinOp(token::And) => {
1755 let eself = if is_isolated_self(self, 1) {
1758 SelfKind::Region(None, Mutability::Not)
1759 } else if is_isolated_mut_self(self, 1) {
1763 SelfKind::Region(None, Mutability::Mut)
1764 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
1767 let lt = self.expect_lifetime();
1768 SelfKind::Region(Some(lt), Mutability::Not)
1769 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
1772 let lt = self.expect_lifetime();
1774 SelfKind::Region(Some(lt), Mutability::Mut)
1779 (eself, expect_self_ident(self), self.prev_span)
1782 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
1784 recover_self_ptr(self)?
1786 // `*mut self` and `*const self`
1787 token::BinOp(token::Star)
1788 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
1792 recover_self_ptr(self)?
1794 // `self` and `self: TYPE`
1795 token::Ident(..) if is_isolated_self(self, 0) => {
1796 parse_self_possibly_typed(self, Mutability::Not)?
1798 // `mut self` and `mut self: TYPE`
1799 token::Ident(..) if is_isolated_mut_self(self, 0) => {
1801 parse_self_possibly_typed(self, Mutability::Mut)?
1803 _ => return Ok(None),
1806 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
1807 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
1810 fn is_named_param(&self) -> bool {
1811 let offset = match self.token.kind {
1812 token::Interpolated(ref nt) => match **nt {
1813 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1816 token::BinOp(token::And) | token::AndAnd => 1,
1817 _ if self.token.is_keyword(kw::Mut) => 1,
1821 self.look_ahead(offset, |t| t.is_ident())
1822 && self.look_ahead(offset + 1, |t| t == &token::Colon)
1825 fn recover_first_param(&mut self) -> &'static str {
1827 .parse_outer_attributes()
1828 .and_then(|_| self.parse_self_param())
1829 .map_err(|mut e| e.cancel())
1831 Ok(Some(_)) => "method",