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, 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, ForeignItemKind, Item, ItemKind};
13 use syntax::ast::{Async, Const, Defaultness, IsAuto, PathSegment, Unsafe, UseTree, UseTreeKind};
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 self.parse_item_(|_| true).map(|i| i.map(P))
31 fn parse_item_(&mut self, req_name: ReqName) -> PResult<'a, Option<Item>> {
32 let attrs = self.parse_outer_attributes()?;
33 self.parse_item_common(attrs, true, false, req_name)
36 pub(super) fn parse_item_common(
38 mut attrs: Vec<Attribute>,
42 ) -> PResult<'a, Option<Item>> {
43 maybe_whole!(self, NtItem, |item| {
45 mem::swap(&mut item.attrs, &mut attrs);
46 item.attrs.extend(attrs);
47 Some(item.into_inner())
50 let mut unclosed_delims = vec![];
51 let (mut item, tokens) = self.collect_tokens(|this| {
52 let item = this.parse_item_common_(attrs, mac_allowed, attrs_allowed, req_name);
53 unclosed_delims.append(&mut this.unclosed_delims);
56 self.unclosed_delims.append(&mut unclosed_delims);
58 // Once we've parsed an item and recorded the tokens we got while
59 // parsing we may want to store `tokens` into the item we're about to
60 // return. Note, though, that we specifically didn't capture tokens
61 // related to outer attributes. The `tokens` field here may later be
62 // used with procedural macros to convert this item back into a token
63 // stream, but during expansion we may be removing attributes as we go
66 // If we've got inner attributes then the `tokens` we've got above holds
67 // these inner attributes. If an inner attribute is expanded we won't
68 // actually remove it from the token stream, so we'll just keep yielding
69 // it (bad!). To work around this case for now we just avoid recording
70 // `tokens` if we detect any inner attributes. This should help keep
71 // expansion correct, but we should fix this bug one day!
72 if let Some(item) = &mut item {
73 if !item.attrs.iter().any(|attr| attr.style == AttrStyle::Inner) {
74 item.tokens = Some(tokens);
80 fn parse_item_common_(
82 mut attrs: Vec<Attribute>,
86 ) -> PResult<'a, Option<Item>> {
87 let lo = self.token.span;
88 let vis = self.parse_visibility(FollowedByType::No)?;
89 let mut def = self.parse_defaultness();
90 let kind = self.parse_item_kind(&mut attrs, mac_allowed, lo, &vis, &mut def, req_name)?;
91 if let Some((ident, kind)) = kind {
92 self.error_on_unconsumed_default(def, &kind);
93 let span = lo.to(self.prev_token.span);
94 let id = DUMMY_NODE_ID;
95 let item = Item { ident, attrs, id, kind, vis, span, tokens: None };
96 return Ok(Some(item));
99 // At this point, we have failed to parse an item.
100 self.error_on_unmatched_vis(&vis);
101 self.error_on_unmatched_defaultness(def);
103 self.recover_attrs_no_item(&attrs)?;
108 /// Error in-case a non-inherited visibility was parsed but no item followed.
109 fn error_on_unmatched_vis(&self, vis: &Visibility) {
110 if let VisibilityKind::Inherited = vis.node {
113 let vs = pprust::vis_to_string(&vis);
114 let vs = vs.trim_end();
115 self.struct_span_err(vis.span, &format!("visibility `{}` is not followed by an item", vs))
116 .span_label(vis.span, "the visibility")
117 .help(&format!("you likely meant to define an item, e.g., `{} fn foo() {{}}`", vs))
121 /// Error in-case a `default` was parsed but no item followed.
122 fn error_on_unmatched_defaultness(&self, def: Defaultness) {
123 if let Defaultness::Default(sp) = def {
124 self.struct_span_err(sp, "`default` is not followed by an item")
125 .span_label(sp, "the `default` qualifier")
126 .note("only `fn`, `const`, `type`, or `impl` items may be prefixed by `default`")
131 /// Error in-case `default` was parsed in an in-appropriate context.
132 fn error_on_unconsumed_default(&self, def: Defaultness, kind: &ItemKind) {
133 if let Defaultness::Default(span) = def {
134 let msg = format!("{} {} cannot be `default`", kind.article(), kind.descr());
135 self.struct_span_err(span, &msg)
136 .span_label(span, "`default` because of this")
137 .note("only associated `fn`, `const`, and `type` items can be `default`")
142 /// Parses one of the items allowed by the flags.
145 attrs: &mut Vec<Attribute>,
146 macros_allowed: bool,
149 def: &mut Defaultness,
151 ) -> PResult<'a, Option<ItemInfo>> {
152 let mut def = || mem::replace(def, Defaultness::Final);
154 let info = if self.eat_keyword(kw::Use) {
156 let tree = self.parse_use_tree()?;
158 (Ident::invalid(), ItemKind::Use(P(tree)))
159 } else if self.check_fn_front_matter() {
161 let (ident, sig, generics, body) = self.parse_fn(attrs, req_name)?;
162 (ident, ItemKind::Fn(def(), sig, generics, body))
163 } else if self.eat_keyword(kw::Extern) {
164 if self.eat_keyword(kw::Crate) {
166 self.parse_item_extern_crate()?
169 self.parse_item_foreign_mod(attrs)?
171 } else if self.is_static_global() {
173 self.bump(); // `static`
174 let m = self.parse_mutability();
175 let (ident, ty, expr) = self.parse_item_global(Some(m))?;
176 (ident, ItemKind::Static(ty, m, expr))
177 } else if let Const::Yes(const_span) = self.parse_constness() {
179 self.recover_const_mut(const_span);
180 let (ident, ty, expr) = self.parse_item_global(None)?;
181 (ident, ItemKind::Const(def(), ty, expr))
182 } else if self.check_keyword(kw::Trait) || self.check_auto_or_unsafe_trait_item() {
184 self.parse_item_trait(attrs, lo)?
185 } else if self.check_keyword(kw::Impl)
186 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Impl])
189 self.parse_item_impl(attrs, def())?
190 } else if self.eat_keyword(kw::Mod) {
192 self.parse_item_mod(attrs)?
193 } else if self.eat_keyword(kw::Type) {
195 self.parse_type_alias(def())?
196 } else if self.eat_keyword(kw::Enum) {
198 self.parse_item_enum()?
199 } else if self.eat_keyword(kw::Struct) {
201 self.parse_item_struct()?
202 } else if self.is_kw_followed_by_ident(kw::Union) {
204 self.bump(); // `union`
205 self.parse_item_union()?
206 } else if self.eat_keyword(kw::Macro) {
208 self.parse_item_decl_macro(lo)?
209 } else if self.is_macro_rules_item() {
211 self.parse_item_macro_rules(vis)?
212 } else if vis.node.is_pub() && self.isnt_macro_invocation() {
213 self.recover_missing_kw_before_item()?;
215 } else if macros_allowed && self.token.is_path_start() {
216 // MACRO INVOCATION ITEM
217 (Ident::invalid(), ItemKind::Mac(self.parse_item_macro(vis)?))
224 /// When parsing a statement, would the start of a path be an item?
225 pub(super) fn is_path_start_item(&mut self) -> bool {
226 self.is_crate_vis() // no: `crate::b`, yes: `crate $item`
227 || self.is_kw_followed_by_ident(kw::Union) // no: `union::b`, yes: `union U { .. }`
228 || self.check_auto_or_unsafe_trait_item() // no: `auto::b`, yes: `auto trait X { .. }`
229 || self.is_async_fn() // no(2015): `async::b`, yes: `async fn`
230 || self.is_macro_rules_item() // no: `macro_rules::b`, yes: `macro_rules! mac`
233 /// Are we sure this could not possibly be a macro invocation?
234 fn isnt_macro_invocation(&mut self) -> bool {
235 self.check_ident() && self.look_ahead(1, |t| *t != token::Not && *t != token::ModSep)
238 /// Recover on encountering a struct or method definition where the user
239 /// forgot to add the `struct` or `fn` keyword after writing `pub`: `pub S {}`.
240 fn recover_missing_kw_before_item(&mut self) -> PResult<'a, ()> {
241 // Space between `pub` keyword and the identifier
244 // ^^^ `sp` points here
245 let sp = self.prev_token.span.between(self.token.span);
246 let full_sp = self.prev_token.span.to(self.token.span);
247 let ident_sp = self.token.span;
248 if self.look_ahead(1, |t| *t == token::OpenDelim(token::Brace)) {
249 // possible public struct definition where `struct` was forgotten
250 let ident = self.parse_ident().unwrap();
251 let msg = format!("add `struct` here to parse `{}` as a public struct", ident);
252 let mut err = self.struct_span_err(sp, "missing `struct` for struct definition");
253 err.span_suggestion_short(
257 Applicability::MaybeIncorrect, // speculative
260 } else if self.look_ahead(1, |t| *t == token::OpenDelim(token::Paren)) {
261 let ident = self.parse_ident().unwrap();
263 let kw_name = self.recover_first_param();
264 self.consume_block(token::Paren, ConsumeClosingDelim::Yes);
265 let (kw, kw_name, ambiguous) = if self.check(&token::RArrow) {
266 self.eat_to_tokens(&[&token::OpenDelim(token::Brace)]);
268 ("fn", kw_name, false)
269 } else if self.check(&token::OpenDelim(token::Brace)) {
271 ("fn", kw_name, false)
272 } else if self.check(&token::Colon) {
276 ("fn` or `struct", "function or struct", true)
279 let msg = format!("missing `{}` for {} definition", kw, kw_name);
280 let mut err = self.struct_span_err(sp, &msg);
282 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
284 format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name);
285 err.span_suggestion_short(
289 Applicability::MachineApplicable,
292 if let Ok(snippet) = self.span_to_snippet(ident_sp) {
295 "if you meant to call a macro, try",
296 format!("{}!", snippet),
297 // this is the `ambiguous` conditional branch
298 Applicability::MaybeIncorrect,
302 "if you meant to call a macro, remove the `pub` \
303 and add a trailing `!` after the identifier",
308 } else if self.look_ahead(1, |t| *t == token::Lt) {
309 let ident = self.parse_ident().unwrap();
310 self.eat_to_tokens(&[&token::Gt]);
312 let (kw, kw_name, ambiguous) = if self.eat(&token::OpenDelim(token::Paren)) {
313 ("fn", self.recover_first_param(), false)
314 } else if self.check(&token::OpenDelim(token::Brace)) {
315 ("struct", "struct", false)
317 ("fn` or `struct", "function or struct", true)
319 let msg = format!("missing `{}` for {} definition", kw, kw_name);
320 let mut err = self.struct_span_err(sp, &msg);
322 err.span_suggestion_short(
324 &format!("add `{}` here to parse `{}` as a public {}", kw, ident, kw_name),
326 Applicability::MachineApplicable,
335 /// Parses an item macro, e.g., `item!();`.
336 fn parse_item_macro(&mut self, vis: &Visibility) -> PResult<'a, Mac> {
337 let path = self.parse_path(PathStyle::Mod)?; // `foo::bar`
338 self.expect(&token::Not)?; // `!`
339 let args = self.parse_mac_args()?; // `( .. )` or `[ .. ]` (followed by `;`), or `{ .. }`.
340 self.eat_semi_for_macro_if_needed(&args);
341 self.complain_if_pub_macro(vis, false);
342 Ok(Mac { path, args, prior_type_ascription: self.last_type_ascription })
345 /// Recover if we parsed attributes and expected an item but there was none.
346 fn recover_attrs_no_item(&mut self, attrs: &[Attribute]) -> PResult<'a, ()> {
347 let (start, end) = match attrs {
350 [x0, .., xn] => (x0, xn),
352 let msg = if end.is_doc_comment() {
353 "expected item after doc comment"
355 "expected item after attributes"
357 let mut err = self.struct_span_err(end.span, msg);
358 if end.is_doc_comment() {
359 err.span_label(end.span, "this doc comment doesn't document anything");
361 if let [.., penultimate, _] = attrs {
362 err.span_label(start.span.to(penultimate.span), "other attributes here");
367 fn is_async_fn(&self) -> bool {
368 self.token.is_keyword(kw::Async) && self.is_keyword_ahead(1, &[kw::Fn])
371 /// Parses an implementation item.
374 /// impl<'a, T> TYPE { /* impl items */ }
375 /// impl<'a, T> TRAIT for TYPE { /* impl items */ }
376 /// impl<'a, T> !TRAIT for TYPE { /* impl items */ }
377 /// impl<'a, T> const TRAIT for TYPE { /* impl items */ }
380 /// We actually parse slightly more relaxed grammar for better error reporting and recovery.
382 /// "impl" GENERICS "const"? "!"? TYPE "for"? (TYPE | "..") ("where" PREDICATES)? "{" BODY "}"
383 /// "impl" GENERICS "const"? "!"? TYPE ("where" PREDICATES)? "{" BODY "}"
387 attrs: &mut Vec<Attribute>,
388 defaultness: Defaultness,
389 ) -> PResult<'a, ItemInfo> {
390 let unsafety = self.parse_unsafety();
391 self.expect_keyword(kw::Impl)?;
393 // First, parse generic parameters if necessary.
394 let mut generics = if self.choose_generics_over_qpath() {
395 self.parse_generics()?
397 let mut generics = Generics::default();
399 // /\ this is where `generics.span` should point when there are no type params.
400 generics.span = self.prev_token.span.shrink_to_hi();
404 let constness = self.parse_constness();
405 if let Const::Yes(span) = constness {
406 self.sess.gated_spans.gate(sym::const_trait_impl, span);
409 // Disambiguate `impl !Trait for Type { ... }` and `impl ! { ... }` for the never type.
410 let polarity = if self.check(&token::Not) && self.look_ahead(1, |t| t.can_begin_type()) {
412 ast::ImplPolarity::Negative
414 ast::ImplPolarity::Positive
417 // Parse both types and traits as a type, then reinterpret if necessary.
418 let err_path = |span| ast::Path::from_ident(Ident::new(kw::Invalid, span));
419 let ty_first = if self.token.is_keyword(kw::For) && self.look_ahead(1, |t| t != &token::Lt)
421 let span = self.prev_token.span.between(self.token.span);
422 self.struct_span_err(span, "missing trait in a trait impl").emit();
423 P(Ty { kind: TyKind::Path(None, err_path(span)), span, id: DUMMY_NODE_ID })
428 // If `for` is missing we try to recover.
429 let has_for = self.eat_keyword(kw::For);
430 let missing_for_span = self.prev_token.span.between(self.token.span);
432 let ty_second = if self.token == token::DotDot {
433 // We need to report this error after `cfg` expansion for compatibility reasons
434 self.bump(); // `..`, do not add it to expected tokens
435 Some(self.mk_ty(self.prev_token.span, TyKind::Err))
436 } else if has_for || self.token.can_begin_type() {
437 Some(self.parse_ty()?)
442 generics.where_clause = self.parse_where_clause()?;
444 let impl_items = self.parse_item_list(attrs, |p| p.parse_impl_item())?;
446 let item_kind = match ty_second {
448 // impl Trait for Type
450 self.struct_span_err(missing_for_span, "missing `for` in a trait impl")
451 .span_suggestion_short(
455 Applicability::MachineApplicable,
460 let ty_first = ty_first.into_inner();
461 let path = match ty_first.kind {
462 // This notably includes paths passed through `ty` macro fragments (#46438).
463 TyKind::Path(None, path) => path,
465 self.struct_span_err(ty_first.span, "expected a trait, found type").emit();
466 err_path(ty_first.span)
469 let trait_ref = TraitRef { path, ref_id: ty_first.id };
477 of_trait: Some(trait_ref),
497 Ok((Ident::invalid(), item_kind))
500 fn parse_item_list<T>(
502 attrs: &mut Vec<Attribute>,
503 mut parse_item: impl FnMut(&mut Parser<'a>) -> PResult<'a, Option<Option<T>>>,
504 ) -> PResult<'a, Vec<T>> {
505 let open_brace_span = self.token.span;
506 self.expect(&token::OpenDelim(token::Brace))?;
507 attrs.append(&mut self.parse_inner_attributes()?);
509 let mut items = Vec::new();
510 while !self.eat(&token::CloseDelim(token::Brace)) {
511 if self.recover_doc_comment_before_brace() {
514 match parse_item(self) {
516 // We have to bail or we'll potentially never make progress.
517 let non_item_span = self.token.span;
518 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
519 self.struct_span_err(non_item_span, "non-item in item list")
520 .span_label(open_brace_span, "item list starts here")
521 .span_label(non_item_span, "non-item starts here")
522 .span_label(self.prev_token.span, "item list ends here")
526 Ok(Some(item)) => items.extend(item),
528 self.consume_block(token::Brace, ConsumeClosingDelim::Yes);
529 err.span_label(open_brace_span, "while parsing this item list starting here")
530 .span_label(self.prev_token.span, "the item list ends here")
539 /// Recover on a doc comment before `}`.
540 fn recover_doc_comment_before_brace(&mut self) -> bool {
541 if let token::DocComment(_) = self.token.kind {
542 if self.look_ahead(1, |tok| tok == &token::CloseDelim(token::Brace)) {
547 "found a documentation comment that doesn't document anything",
549 .span_label(self.token.span, "this doc comment doesn't document anything")
551 "doc comments must come before what they document, maybe a \
552 comment was intended with `//`?",
562 /// Parses defaultness (i.e., `default` or nothing).
563 fn parse_defaultness(&mut self) -> Defaultness {
564 // We are interested in `default` followed by another identifier.
565 // However, we must avoid keywords that occur as binary operators.
566 // Currently, the only applicable keyword is `as` (`default as Ty`).
567 if self.check_keyword(kw::Default)
568 && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As))
570 self.bump(); // `default`
571 Defaultness::Default(self.normalized_prev_token.span)
577 /// Is this an `(unsafe auto? | auto) trait` item?
578 fn check_auto_or_unsafe_trait_item(&mut self) -> bool {
580 self.check_keyword(kw::Auto) && self.is_keyword_ahead(1, &[kw::Trait])
582 || self.check_keyword(kw::Unsafe) && self.is_keyword_ahead(1, &[kw::Trait, kw::Auto])
585 /// Parses `unsafe? auto? trait Foo { ... }` or `trait Foo = Bar;`.
586 fn parse_item_trait(&mut self, attrs: &mut Vec<Attribute>, lo: Span) -> PResult<'a, ItemInfo> {
587 let unsafety = self.parse_unsafety();
588 // Parse optional `auto` prefix.
589 let is_auto = if self.eat_keyword(kw::Auto) { IsAuto::Yes } else { IsAuto::No };
591 self.expect_keyword(kw::Trait)?;
592 let ident = self.parse_ident()?;
593 let mut tps = self.parse_generics()?;
595 // Parse optional colon and supertrait bounds.
596 let had_colon = self.eat(&token::Colon);
597 let span_at_colon = self.prev_token.span;
598 let bounds = if had_colon {
599 self.parse_generic_bounds(Some(self.prev_token.span))?
604 let span_before_eq = self.prev_token.span;
605 if self.eat(&token::Eq) {
606 // It's a trait alias.
608 let span = span_at_colon.to(span_before_eq);
609 self.struct_span_err(span, "bounds are not allowed on trait aliases").emit();
612 let bounds = self.parse_generic_bounds(None)?;
613 tps.where_clause = self.parse_where_clause()?;
616 let whole_span = lo.to(self.prev_token.span);
617 if is_auto == IsAuto::Yes {
618 let msg = "trait aliases cannot be `auto`";
619 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
621 if let Unsafe::Yes(_) = unsafety {
622 let msg = "trait aliases cannot be `unsafe`";
623 self.struct_span_err(whole_span, msg).span_label(whole_span, msg).emit();
626 self.sess.gated_spans.gate(sym::trait_alias, whole_span);
628 Ok((ident, ItemKind::TraitAlias(tps, bounds)))
630 // It's a normal trait.
631 tps.where_clause = self.parse_where_clause()?;
632 let items = self.parse_item_list(attrs, |p| p.parse_trait_item())?;
633 Ok((ident, ItemKind::Trait(is_auto, unsafety, tps, bounds, items)))
637 pub fn parse_impl_item(&mut self) -> PResult<'a, Option<Option<P<AssocItem>>>> {
638 self.parse_assoc_item(|_| true)
641 pub fn parse_trait_item(&mut self) -> PResult<'a, Option<Option<P<AssocItem>>>> {
642 self.parse_assoc_item(|t| t.span.rust_2018())
645 /// Parses associated items.
646 fn parse_assoc_item(&mut self, req_name: ReqName) -> PResult<'a, Option<Option<P<AssocItem>>>> {
647 Ok(self.parse_item_(req_name)?.map(|Item { attrs, id, span, vis, ident, kind, tokens }| {
648 let kind = match kind {
649 ItemKind::Mac(a) => AssocItemKind::Macro(a),
650 ItemKind::Fn(a, b, c, d) => AssocItemKind::Fn(a, b, c, d),
651 ItemKind::TyAlias(a, b, c, d) => AssocItemKind::TyAlias(a, b, c, d),
652 ItemKind::Const(a, b, c) => AssocItemKind::Const(a, b, c),
653 ItemKind::Static(a, _, b) => {
654 self.struct_span_err(span, "associated `static` items are not allowed").emit();
655 AssocItemKind::Const(Defaultness::Final, a, b)
657 _ => return self.error_bad_item_kind(span, &kind, "`trait`s or `impl`s"),
659 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
663 /// Parses a `type` alias with the following grammar:
665 /// TypeAlias = "type" Ident Generics {":" GenericBounds}? {"=" Ty}? ";" ;
667 /// The `"type"` has already been eaten.
668 fn parse_type_alias(&mut self, def: Defaultness) -> PResult<'a, ItemInfo> {
669 let ident = self.parse_ident()?;
670 let mut generics = self.parse_generics()?;
672 // Parse optional colon and param bounds.
674 if self.eat(&token::Colon) { self.parse_generic_bounds(None)? } else { Vec::new() };
675 generics.where_clause = self.parse_where_clause()?;
677 let default = if self.eat(&token::Eq) { Some(self.parse_ty()?) } else { None };
680 Ok((ident, ItemKind::TyAlias(def, generics, bounds, default)))
683 /// Parses a `UseTree`.
686 /// USE_TREE = [`::`] `*` |
687 /// [`::`] `{` USE_TREE_LIST `}` |
689 /// PATH `::` `{` USE_TREE_LIST `}` |
690 /// PATH [`as` IDENT]
692 fn parse_use_tree(&mut self) -> PResult<'a, UseTree> {
693 let lo = self.token.span;
695 let mut prefix = ast::Path { segments: Vec::new(), span: lo.shrink_to_lo() };
696 let kind = if self.check(&token::OpenDelim(token::Brace))
697 || self.check(&token::BinOp(token::Star))
698 || self.is_import_coupler()
700 // `use *;` or `use ::*;` or `use {...};` or `use ::{...};`
701 let mod_sep_ctxt = self.token.span.ctxt();
702 if self.eat(&token::ModSep) {
705 .push(PathSegment::path_root(lo.shrink_to_lo().with_ctxt(mod_sep_ctxt)));
708 self.parse_use_tree_glob_or_nested()?
710 // `use path::*;` or `use path::{...};` or `use path;` or `use path as bar;`
711 prefix = self.parse_path(PathStyle::Mod)?;
713 if self.eat(&token::ModSep) {
714 self.parse_use_tree_glob_or_nested()?
716 UseTreeKind::Simple(self.parse_rename()?, DUMMY_NODE_ID, DUMMY_NODE_ID)
720 Ok(UseTree { prefix, kind, span: lo.to(self.prev_token.span) })
723 /// Parses `*` or `{...}`.
724 fn parse_use_tree_glob_or_nested(&mut self) -> PResult<'a, UseTreeKind> {
725 Ok(if self.eat(&token::BinOp(token::Star)) {
728 UseTreeKind::Nested(self.parse_use_tree_list()?)
732 /// Parses a `UseTreeKind::Nested(list)`.
735 /// USE_TREE_LIST = Ø | (USE_TREE `,`)* USE_TREE [`,`]
737 fn parse_use_tree_list(&mut self) -> PResult<'a, Vec<(UseTree, ast::NodeId)>> {
738 self.parse_delim_comma_seq(token::Brace, |p| Ok((p.parse_use_tree()?, DUMMY_NODE_ID)))
742 fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
743 if self.eat_keyword(kw::As) { self.parse_ident_or_underscore().map(Some) } else { Ok(None) }
746 fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
747 match self.normalized_token.kind {
748 token::Ident(name @ kw::Underscore, false) => {
750 Ok(Ident::new(name, self.normalized_prev_token.span))
752 _ => self.parse_ident(),
756 /// Parses `extern crate` links.
761 /// extern crate foo;
762 /// extern crate bar as foo;
764 fn parse_item_extern_crate(&mut self) -> PResult<'a, ItemInfo> {
765 // Accept `extern crate name-like-this` for better diagnostics
766 let orig_name = self.parse_crate_name_with_dashes()?;
767 let (item_name, orig_name) = if let Some(rename) = self.parse_rename()? {
768 (rename, Some(orig_name.name))
773 Ok((item_name, ItemKind::ExternCrate(orig_name)))
776 fn parse_crate_name_with_dashes(&mut self) -> PResult<'a, ast::Ident> {
777 let error_msg = "crate name using dashes are not valid in `extern crate` statements";
778 let suggestion_msg = "if the original crate name uses dashes you need to use underscores \
780 let mut ident = if self.token.is_keyword(kw::SelfLower) {
781 self.parse_path_segment_ident()
785 let mut idents = vec![];
786 let mut replacement = vec![];
787 let mut fixed_crate_name = false;
788 // Accept `extern crate name-like-this` for better diagnostics.
789 let dash = token::BinOp(token::BinOpToken::Minus);
790 if self.token == dash {
791 // Do not include `-` as part of the expected tokens list.
792 while self.eat(&dash) {
793 fixed_crate_name = true;
794 replacement.push((self.prev_token.span, "_".to_string()));
795 idents.push(self.parse_ident()?);
798 if fixed_crate_name {
799 let fixed_name_sp = ident.span.to(idents.last().unwrap().span);
800 let mut fixed_name = format!("{}", ident.name);
802 fixed_name.push_str(&format!("_{}", part.name));
804 ident = Ident::from_str_and_span(&fixed_name, fixed_name_sp);
806 self.struct_span_err(fixed_name_sp, error_msg)
807 .span_label(fixed_name_sp, "dash-separated idents are not valid")
808 .multipart_suggestion(suggestion_msg, replacement, Applicability::MachineApplicable)
814 /// Parses `extern` for foreign ABIs modules.
816 /// `extern` is expected to have been consumed before calling this method.
820 /// ```ignore (only-for-syntax-highlight)
824 fn parse_item_foreign_mod(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, ItemInfo> {
825 let abi = self.parse_abi(); // ABI?
826 let items = self.parse_item_list(attrs, |p| p.parse_foreign_item())?;
827 let module = ast::ForeignMod { abi, items };
828 Ok((Ident::invalid(), ItemKind::ForeignMod(module)))
831 /// Parses a foreign item (one in an `extern { ... }` block).
832 pub fn parse_foreign_item(&mut self) -> PResult<'a, Option<Option<P<ForeignItem>>>> {
833 Ok(self.parse_item_(|_| true)?.map(|Item { attrs, id, span, vis, ident, kind, tokens }| {
834 let kind = match kind {
835 ItemKind::Mac(a) => ForeignItemKind::Macro(a),
836 ItemKind::Fn(a, b, c, d) => ForeignItemKind::Fn(a, b, c, d),
837 ItemKind::TyAlias(a, b, c, d) => ForeignItemKind::TyAlias(a, b, c, d),
838 ItemKind::Static(a, b, c) => ForeignItemKind::Static(a, b, c),
839 ItemKind::Const(_, a, b) => {
840 self.error_on_foreign_const(span, ident);
841 ForeignItemKind::Static(a, Mutability::Not, b)
843 _ => return self.error_bad_item_kind(span, &kind, "`extern` blocks"),
845 Some(P(Item { attrs, id, span, vis, ident, kind, tokens }))
849 fn error_bad_item_kind<T>(&self, span: Span, kind: &ItemKind, ctx: &str) -> Option<T> {
850 let span = self.sess.source_map().def_span(span);
851 let msg = format!("{} is not supported in {}", kind.descr(), ctx);
852 self.struct_span_err(span, &msg).emit();
856 fn error_on_foreign_const(&self, span: Span, ident: Ident) {
857 self.struct_span_err(ident.span, "extern items cannot be `const`")
859 span.with_hi(ident.span.lo()),
860 "try using a static value",
861 "static ".to_string(),
862 Applicability::MachineApplicable,
864 .note("for more information, visit https://doc.rust-lang.org/std/keyword.extern.html")
868 fn is_static_global(&mut self) -> bool {
869 if self.check_keyword(kw::Static) {
870 // Check if this could be a closure.
871 !self.look_ahead(1, |token| {
872 if token.is_keyword(kw::Move) {
876 token::BinOp(token::Or) | token::OrOr => true,
885 /// Recover on `const mut` with `const` already eaten.
886 fn recover_const_mut(&mut self, const_span: Span) {
887 if self.eat_keyword(kw::Mut) {
888 let span = self.prev_token.span;
889 self.struct_span_err(span, "const globals cannot be mutable")
890 .span_label(span, "cannot be mutable")
893 "you might want to declare a static instead",
895 Applicability::MaybeIncorrect,
901 /// Parse `["const" | ("static" "mut"?)] $ident ":" $ty (= $expr)?` with
902 /// `["const" | ("static" "mut"?)]` already parsed and stored in `m`.
904 /// When `m` is `"const"`, `$ident` may also be `"_"`.
905 fn parse_item_global(
907 m: Option<Mutability>,
908 ) -> PResult<'a, (Ident, P<Ty>, Option<P<ast::Expr>>)> {
909 let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
911 // Parse the type of a `const` or `static mut?` item.
912 // That is, the `":" $ty` fragment.
913 let ty = if self.eat(&token::Colon) {
916 self.recover_missing_const_type(id, m)
919 let expr = if self.eat(&token::Eq) { Some(self.parse_expr()?) } else { None };
924 /// We were supposed to parse `:` but the `:` was missing.
925 /// This means that the type is missing.
926 fn recover_missing_const_type(&mut self, id: Ident, m: Option<Mutability>) -> P<Ty> {
927 // Construct the error and stash it away with the hope
928 // that typeck will later enrich the error with a type.
930 Some(Mutability::Mut) => "static mut",
931 Some(Mutability::Not) => "static",
934 let mut err = self.struct_span_err(id.span, &format!("missing type for `{}` item", kind));
937 "provide a type for the item",
938 format!("{}: <type>", id),
939 Applicability::HasPlaceholders,
941 err.stash(id.span, StashKey::ItemNoType);
943 // The user intended that the type be inferred,
944 // so treat this as if the user wrote e.g. `const A: _ = expr;`.
945 P(Ty { kind: TyKind::Infer, span: id.span, id: ast::DUMMY_NODE_ID })
948 /// Parses an enum declaration.
949 fn parse_item_enum(&mut self) -> PResult<'a, ItemInfo> {
950 let id = self.parse_ident()?;
951 let mut generics = self.parse_generics()?;
952 generics.where_clause = self.parse_where_clause()?;
955 self.parse_delim_comma_seq(token::Brace, |p| p.parse_enum_variant()).map_err(|e| {
960 let enum_definition =
961 EnumDef { variants: variants.into_iter().filter_map(|v| v).collect() };
962 Ok((id, ItemKind::Enum(enum_definition, generics)))
965 fn parse_enum_variant(&mut self) -> PResult<'a, Option<Variant>> {
966 let variant_attrs = self.parse_outer_attributes()?;
967 let vlo = self.token.span;
969 let vis = self.parse_visibility(FollowedByType::No)?;
970 if !self.recover_nested_adt_item(kw::Enum)? {
973 let ident = self.parse_ident()?;
975 let struct_def = if self.check(&token::OpenDelim(token::Brace)) {
976 // Parse a struct variant.
977 let (fields, recovered) = self.parse_record_struct_body()?;
978 VariantData::Struct(fields, recovered)
979 } else if self.check(&token::OpenDelim(token::Paren)) {
980 VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID)
982 VariantData::Unit(DUMMY_NODE_ID)
986 if self.eat(&token::Eq) { Some(self.parse_anon_const_expr()?) } else { None };
988 let vr = ast::Variant {
992 attrs: variant_attrs,
995 span: vlo.to(self.prev_token.span),
996 is_placeholder: false,
1002 /// Parses `struct Foo { ... }`.
1003 fn parse_item_struct(&mut self) -> PResult<'a, ItemInfo> {
1004 let class_name = self.parse_ident()?;
1006 let mut generics = self.parse_generics()?;
1008 // There is a special case worth noting here, as reported in issue #17904.
1009 // If we are parsing a tuple struct it is the case that the where clause
1010 // should follow the field list. Like so:
1012 // struct Foo<T>(T) where T: Copy;
1014 // If we are parsing a normal record-style struct it is the case
1015 // that the where clause comes before the body, and after the generics.
1016 // So if we look ahead and see a brace or a where-clause we begin
1017 // parsing a record style struct.
1019 // Otherwise if we look ahead and see a paren we parse a tuple-style
1022 let vdata = if self.token.is_keyword(kw::Where) {
1023 generics.where_clause = self.parse_where_clause()?;
1024 if self.eat(&token::Semi) {
1025 // If we see a: `struct Foo<T> where T: Copy;` style decl.
1026 VariantData::Unit(DUMMY_NODE_ID)
1028 // If we see: `struct Foo<T> where T: Copy { ... }`
1029 let (fields, recovered) = self.parse_record_struct_body()?;
1030 VariantData::Struct(fields, recovered)
1032 // No `where` so: `struct Foo<T>;`
1033 } else if self.eat(&token::Semi) {
1034 VariantData::Unit(DUMMY_NODE_ID)
1035 // Record-style struct definition
1036 } else if self.token == token::OpenDelim(token::Brace) {
1037 let (fields, recovered) = self.parse_record_struct_body()?;
1038 VariantData::Struct(fields, recovered)
1039 // Tuple-style struct definition with optional where-clause.
1040 } else if self.token == token::OpenDelim(token::Paren) {
1041 let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
1042 generics.where_clause = self.parse_where_clause()?;
1043 self.expect_semi()?;
1046 let token_str = super::token_descr(&self.token);
1048 "expected `where`, `{{`, `(`, or `;` after struct name, found {}",
1051 let mut err = self.struct_span_err(self.token.span, msg);
1052 err.span_label(self.token.span, "expected `where`, `{`, `(`, or `;` after struct name");
1056 Ok((class_name, ItemKind::Struct(vdata, generics)))
1059 /// Parses `union Foo { ... }`.
1060 fn parse_item_union(&mut self) -> PResult<'a, ItemInfo> {
1061 let class_name = self.parse_ident()?;
1063 let mut generics = self.parse_generics()?;
1065 let vdata = if self.token.is_keyword(kw::Where) {
1066 generics.where_clause = self.parse_where_clause()?;
1067 let (fields, recovered) = self.parse_record_struct_body()?;
1068 VariantData::Struct(fields, recovered)
1069 } else if self.token == token::OpenDelim(token::Brace) {
1070 let (fields, recovered) = self.parse_record_struct_body()?;
1071 VariantData::Struct(fields, recovered)
1073 let token_str = super::token_descr(&self.token);
1074 let msg = &format!("expected `where` or `{{` after union name, found {}", token_str);
1075 let mut err = self.struct_span_err(self.token.span, msg);
1076 err.span_label(self.token.span, "expected `where` or `{` after union name");
1080 Ok((class_name, ItemKind::Union(vdata, generics)))
1083 fn parse_record_struct_body(
1085 ) -> PResult<'a, (Vec<StructField>, /* recovered */ bool)> {
1086 let mut fields = Vec::new();
1087 let mut recovered = false;
1088 if self.eat(&token::OpenDelim(token::Brace)) {
1089 while self.token != token::CloseDelim(token::Brace) {
1090 let field = self.parse_struct_decl_field().map_err(|e| {
1091 self.consume_block(token::Brace, ConsumeClosingDelim::No);
1096 Ok(field) => fields.push(field),
1103 self.eat(&token::CloseDelim(token::Brace));
1105 let token_str = super::token_descr(&self.token);
1106 let msg = &format!("expected `where`, or `{{` after struct name, found {}", token_str);
1107 let mut err = self.struct_span_err(self.token.span, msg);
1108 err.span_label(self.token.span, "expected `where`, or `{` after struct name");
1112 Ok((fields, recovered))
1115 fn parse_tuple_struct_body(&mut self) -> PResult<'a, Vec<StructField>> {
1116 // This is the case where we find `struct Foo<T>(T) where T: Copy;`
1117 // Unit like structs are handled in parse_item_struct function
1118 self.parse_paren_comma_seq(|p| {
1119 let attrs = p.parse_outer_attributes()?;
1120 let lo = p.token.span;
1121 let vis = p.parse_visibility(FollowedByType::Yes)?;
1122 let ty = p.parse_ty()?;
1124 span: lo.to(ty.span),
1130 is_placeholder: false,
1136 /// Parses an element of a struct declaration.
1137 fn parse_struct_decl_field(&mut self) -> PResult<'a, StructField> {
1138 let attrs = self.parse_outer_attributes()?;
1139 let lo = self.token.span;
1140 let vis = self.parse_visibility(FollowedByType::No)?;
1141 self.parse_single_struct_field(lo, vis, attrs)
1144 /// Parses a structure field declaration.
1145 fn parse_single_struct_field(
1149 attrs: Vec<Attribute>,
1150 ) -> PResult<'a, StructField> {
1151 let mut seen_comma: bool = false;
1152 let a_var = self.parse_name_and_ty(lo, vis, attrs)?;
1153 if self.token == token::Comma {
1156 match self.token.kind {
1160 token::CloseDelim(token::Brace) => {}
1161 token::DocComment(_) => {
1162 let previous_span = self.prev_token.span;
1163 let mut err = self.span_fatal_err(self.token.span, Error::UselessDocComment);
1164 self.bump(); // consume the doc comment
1165 let comma_after_doc_seen = self.eat(&token::Comma);
1166 // `seen_comma` is always false, because we are inside doc block
1167 // condition is here to make code more readable
1168 if !seen_comma && comma_after_doc_seen {
1171 if comma_after_doc_seen || self.token == token::CloseDelim(token::Brace) {
1175 let sp = self.sess.source_map().next_point(previous_span);
1176 err.span_suggestion(
1178 "missing comma here",
1180 Applicability::MachineApplicable,
1187 let sp = self.prev_token.span.shrink_to_hi();
1188 let mut err = self.struct_span_err(
1190 &format!("expected `,`, or `}}`, found {}", super::token_descr(&self.token)),
1192 if self.token.is_ident() {
1193 // This is likely another field; emit the diagnostic and keep going
1194 err.span_suggestion(
1196 "try adding a comma",
1198 Applicability::MachineApplicable,
1209 /// Parses a structure field.
1210 fn parse_name_and_ty(
1214 attrs: Vec<Attribute>,
1215 ) -> PResult<'a, StructField> {
1216 let name = self.parse_ident()?;
1217 self.expect(&token::Colon)?;
1218 let ty = self.parse_ty()?;
1220 span: lo.to(self.prev_token.span),
1226 is_placeholder: false,
1230 /// Parses a declarative macro 2.0 definition.
1231 /// The `macro` keyword has already been parsed.
1233 /// MacBody = "{" TOKEN_STREAM "}" ;
1234 /// MacParams = "(" TOKEN_STREAM ")" ;
1235 /// DeclMac = "macro" Ident MacParams? MacBody ;
1237 fn parse_item_decl_macro(&mut self, lo: Span) -> PResult<'a, ItemInfo> {
1238 let ident = self.parse_ident()?;
1239 let body = if self.check(&token::OpenDelim(token::Brace)) {
1240 self.parse_mac_args()? // `MacBody`
1241 } else if self.check(&token::OpenDelim(token::Paren)) {
1242 let params = self.parse_token_tree(); // `MacParams`
1243 let pspan = params.span();
1244 if !self.check(&token::OpenDelim(token::Brace)) {
1245 return self.unexpected();
1247 let body = self.parse_token_tree(); // `MacBody`
1248 // Convert `MacParams MacBody` into `{ MacParams => MacBody }`.
1249 let bspan = body.span();
1250 let arrow = TokenTree::token(token::FatArrow, pspan.between(bspan)); // `=>`
1251 let tokens = TokenStream::new(vec![params.into(), arrow.into(), body.into()]);
1252 let dspan = DelimSpan::from_pair(pspan.shrink_to_lo(), bspan.shrink_to_hi());
1253 P(MacArgs::Delimited(dspan, MacDelimiter::Brace, tokens))
1255 return self.unexpected();
1258 self.sess.gated_spans.gate(sym::decl_macro, lo.to(self.prev_token.span));
1259 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: false })))
1262 /// Is this unambiguously the start of a `macro_rules! foo` item defnition?
1263 fn is_macro_rules_item(&mut self) -> bool {
1264 self.check_keyword(kw::MacroRules)
1265 && self.look_ahead(1, |t| *t == token::Not)
1266 && self.look_ahead(2, |t| t.is_ident())
1269 /// Parses a legacy `macro_rules! foo { ... }` declarative macro.
1270 fn parse_item_macro_rules(&mut self, vis: &Visibility) -> PResult<'a, ItemInfo> {
1271 self.expect_keyword(kw::MacroRules)?; // `macro_rules`
1272 self.expect(&token::Not)?; // `!`
1274 let ident = self.parse_ident()?;
1275 let body = self.parse_mac_args()?;
1276 self.eat_semi_for_macro_if_needed(&body);
1277 self.complain_if_pub_macro(vis, true);
1279 Ok((ident, ItemKind::MacroDef(ast::MacroDef { body, legacy: true })))
1282 /// Item macro invocations or `macro_rules!` definitions need inherited visibility.
1283 /// If that's not the case, emit an error.
1284 fn complain_if_pub_macro(&self, vis: &Visibility, macro_rules: bool) {
1285 if let VisibilityKind::Inherited = vis.node {
1289 let vstr = pprust::vis_to_string(vis);
1290 let vstr = vstr.trim_end();
1292 let msg = format!("can't qualify macro_rules invocation with `{}`", vstr);
1293 self.struct_span_err(vis.span, &msg)
1296 "try exporting the macro",
1297 "#[macro_export]".to_owned(),
1298 Applicability::MaybeIncorrect, // speculative
1302 self.struct_span_err(vis.span, "can't qualify macro invocation with `pub`")
1305 "remove the visibility",
1307 Applicability::MachineApplicable,
1309 .help(&format!("try adjusting the macro to put `{}` inside the invocation", vstr))
1314 fn eat_semi_for_macro_if_needed(&mut self, args: &MacArgs) {
1315 if args.need_semicolon() && !self.eat(&token::Semi) {
1316 self.report_invalid_macro_expansion_item(args);
1320 fn report_invalid_macro_expansion_item(&self, args: &MacArgs) {
1321 let span = args.span().expect("undelimited macro call");
1322 let mut err = self.struct_span_err(
1324 "macros that expand to items must be delimited with braces or followed by a semicolon",
1326 if self.unclosed_delims.is_empty() {
1327 let DelimSpan { open, close } = match args {
1328 MacArgs::Empty | MacArgs::Eq(..) => unreachable!(),
1329 MacArgs::Delimited(dspan, ..) => *dspan,
1331 err.multipart_suggestion(
1332 "change the delimiters to curly braces",
1333 vec![(open, "{".to_string()), (close, '}'.to_string())],
1334 Applicability::MaybeIncorrect,
1337 err.span_suggestion(
1339 "change the delimiters to curly braces",
1340 " { /* items */ }".to_string(),
1341 Applicability::HasPlaceholders,
1344 err.span_suggestion(
1345 span.shrink_to_hi(),
1348 Applicability::MaybeIncorrect,
1353 /// Checks if current token is one of tokens which cannot be nested like `kw::Enum`. In case
1354 /// it is, we try to parse the item and report error about nested types.
1355 fn recover_nested_adt_item(&mut self, keyword: Symbol) -> PResult<'a, bool> {
1356 if (self.token.is_keyword(kw::Enum)
1357 || self.token.is_keyword(kw::Struct)
1358 || self.token.is_keyword(kw::Union))
1359 && self.look_ahead(1, |t| t.is_ident())
1361 let kw_token = self.token.clone();
1362 let kw_str = pprust::token_to_string(&kw_token);
1363 let item = self.parse_item()?;
1365 self.struct_span_err(
1367 &format!("`{}` definition cannot be nested inside `{}`", kw_str, keyword),
1371 &format!("consider creating a new `{}` definition instead of nesting", kw_str),
1373 Applicability::MaybeIncorrect,
1376 // We successfully parsed the item but we must inform the caller about nested problem.
1383 /// The parsing configuration used to parse a parameter list (see `parse_fn_params`).
1385 /// The function decides if, per-parameter `p`, `p` must have a pattern or just a type.
1386 type ReqName = fn(&token::Token) -> bool;
1388 /// Parsing of functions and methods.
1389 impl<'a> Parser<'a> {
1390 /// Parse a function starting from the front matter (`const ...`) to the body `{ ... }` or `;`.
1393 attrs: &mut Vec<Attribute>,
1395 ) -> PResult<'a, (Ident, FnSig, Generics, Option<P<Block>>)> {
1396 let header = self.parse_fn_front_matter()?; // `const ... fn`
1397 let ident = self.parse_ident()?; // `foo`
1398 let mut generics = self.parse_generics()?; // `<'a, T, ...>`
1399 let decl = self.parse_fn_decl(req_name, AllowPlus::Yes)?; // `(p: u8, ...)`
1400 generics.where_clause = self.parse_where_clause()?; // `where T: Ord`
1401 let body = self.parse_fn_body(attrs)?; // `;` or `{ ... }`.
1402 Ok((ident, FnSig { header, decl }, generics, body))
1405 /// Parse the "body" of a function.
1406 /// This can either be `;` when there's no body,
1407 /// or e.g. a block when the function is a provided one.
1408 fn parse_fn_body(&mut self, attrs: &mut Vec<Attribute>) -> PResult<'a, Option<P<Block>>> {
1409 let (inner_attrs, body) = match self.token.kind {
1414 token::OpenDelim(token::Brace) => {
1415 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1418 token::Interpolated(ref nt) => match **nt {
1419 token::NtBlock(..) => {
1420 let (attrs, body) = self.parse_inner_attrs_and_block()?;
1423 _ => return self.expected_semi_or_open_brace(),
1425 _ => return self.expected_semi_or_open_brace(),
1427 attrs.extend(inner_attrs);
1431 /// Is the current token the start of an `FnHeader` / not a valid parse?
1432 fn check_fn_front_matter(&mut self) -> bool {
1433 // We use an over-approximation here.
1434 // `const const`, `fn const` won't parse, but we're not stepping over other syntax either.
1435 const QUALS: [Symbol; 4] = [kw::Const, kw::Async, kw::Unsafe, kw::Extern];
1436 self.check_keyword(kw::Fn) // Definitely an `fn`.
1437 // `$qual fn` or `$qual $qual`:
1438 || QUALS.iter().any(|&kw| self.check_keyword(kw))
1439 && self.look_ahead(1, |t| {
1440 // ...qualified and then `fn`, e.g. `const fn`.
1441 t.is_keyword(kw::Fn)
1442 // Two qualifiers. This is enough. Due `async` we need to check that it's reserved.
1443 || t.is_non_raw_ident_where(|i| QUALS.contains(&i.name) && i.is_reserved())
1446 || self.check_keyword(kw::Extern)
1447 && self.look_ahead(1, |t| t.can_begin_literal_or_bool())
1448 && self.look_ahead(2, |t| t.is_keyword(kw::Fn))
1451 /// Parses all the "front matter" (or "qualifiers") for a `fn` declaration,
1452 /// up to and including the `fn` keyword. The formal grammar is:
1455 /// Extern = "extern" StringLit ;
1456 /// FnQual = "const"? "async"? "unsafe"? Extern? ;
1457 /// FnFrontMatter = FnQual? "fn" ;
1459 fn parse_fn_front_matter(&mut self) -> PResult<'a, FnHeader> {
1460 let constness = self.parse_constness();
1461 let asyncness = self.parse_asyncness();
1462 let unsafety = self.parse_unsafety();
1463 let ext = self.parse_extern()?;
1465 if let Async::Yes { span, .. } = asyncness {
1466 self.ban_async_in_2015(span);
1469 if !self.eat_keyword(kw::Fn) {
1470 // It is possible for `expect_one_of` to recover given the contents of
1471 // `self.expected_tokens`, therefore, do not use `self.unexpected()` which doesn't
1472 // account for this.
1473 if !self.expect_one_of(&[], &[])? {
1478 Ok(FnHeader { constness, unsafety, asyncness, ext })
1481 /// We are parsing `async fn`. If we are on Rust 2015, emit an error.
1482 fn ban_async_in_2015(&self, span: Span) {
1483 if span.rust_2015() {
1484 let diag = self.diagnostic();
1485 struct_span_err!(diag, span, E0670, "`async fn` is not permitted in the 2015 edition")
1486 .note("to use `async fn`, switch to Rust 2018")
1487 .help("set `edition = \"2018\"` in `Cargo.toml`")
1488 .note("for more on editions, read https://doc.rust-lang.org/edition-guide")
1493 /// Parses the parameter list and result type of a function declaration.
1494 pub(super) fn parse_fn_decl(
1497 ret_allow_plus: AllowPlus,
1498 ) -> PResult<'a, P<FnDecl>> {
1500 inputs: self.parse_fn_params(req_name)?,
1501 output: self.parse_ret_ty(ret_allow_plus, RecoverQPath::Yes)?,
1505 /// Parses the parameter list of a function, including the `(` and `)` delimiters.
1506 fn parse_fn_params(&mut self, req_name: ReqName) -> PResult<'a, Vec<Param>> {
1507 let mut first_param = true;
1508 // Parse the arguments, starting out with `self` being allowed...
1509 let (mut params, _) = self.parse_paren_comma_seq(|p| {
1510 let param = p.parse_param_general(req_name, first_param).or_else(|mut e| {
1512 let lo = p.prev_token.span;
1513 // Skip every token until next possible arg or end.
1514 p.eat_to_tokens(&[&token::Comma, &token::CloseDelim(token::Paren)]);
1515 // Create a placeholder argument for proper arg count (issue #34264).
1516 Ok(dummy_arg(Ident::new(kw::Invalid, lo.to(p.prev_token.span))))
1518 // ...now that we've parsed the first argument, `self` is no longer allowed.
1519 first_param = false;
1522 // Replace duplicated recovered params with `_` pattern to avoid unnecessary errors.
1523 self.deduplicate_recovered_params_names(&mut params);
1527 /// Parses a single function parameter.
1529 /// - `self` is syntactically allowed when `first_param` holds.
1530 fn parse_param_general(&mut self, req_name: ReqName, first_param: bool) -> PResult<'a, Param> {
1531 let lo = self.token.span;
1532 let attrs = self.parse_outer_attributes()?;
1534 // Possibly parse `self`. Recover if we parsed it and it wasn't allowed here.
1535 if let Some(mut param) = self.parse_self_param()? {
1536 param.attrs = attrs.into();
1537 return if first_param { Ok(param) } else { self.recover_bad_self_param(param) };
1540 let is_name_required = match self.token.kind {
1541 token::DotDotDot => false,
1542 _ => req_name(&self.normalized_token),
1544 let (pat, ty) = if is_name_required || self.is_named_param() {
1545 debug!("parse_param_general parse_pat (is_name_required:{})", is_name_required);
1547 let pat = self.parse_fn_param_pat()?;
1548 if let Err(mut err) = self.expect(&token::Colon) {
1549 return if let Some(ident) =
1550 self.parameter_without_type(&mut err, pat, is_name_required, first_param)
1553 Ok(dummy_arg(ident))
1559 self.eat_incorrect_doc_comment_for_param_type();
1560 (pat, self.parse_ty_for_param()?)
1562 debug!("parse_param_general ident_to_pat");
1563 let parser_snapshot_before_ty = self.clone();
1564 self.eat_incorrect_doc_comment_for_param_type();
1565 let mut ty = self.parse_ty_for_param();
1567 && self.token != token::Comma
1568 && self.token != token::CloseDelim(token::Paren)
1570 // This wasn't actually a type, but a pattern looking like a type,
1571 // so we are going to rollback and re-parse for recovery.
1572 ty = self.unexpected();
1576 let ident = Ident::new(kw::Invalid, self.prev_token.span);
1577 let bm = BindingMode::ByValue(Mutability::Not);
1578 let pat = self.mk_pat_ident(ty.span, bm, ident);
1581 // If this is a C-variadic argument and we hit an error, return the error.
1582 Err(err) if self.token == token::DotDotDot => return Err(err),
1583 // Recover from attempting to parse the argument as a type without pattern.
1586 mem::replace(self, parser_snapshot_before_ty);
1587 self.recover_arg_parse()?
1592 let span = lo.to(self.token.span);
1595 attrs: attrs.into(),
1596 id: ast::DUMMY_NODE_ID,
1597 is_placeholder: false,
1604 /// Returns the parsed optional self parameter and whether a self shortcut was used.
1605 fn parse_self_param(&mut self) -> PResult<'a, Option<Param>> {
1606 // Extract an identifier *after* having confirmed that the token is one.
1607 let expect_self_ident = |this: &mut Self| {
1608 match this.normalized_token.kind {
1609 // Preserve hygienic context.
1610 token::Ident(name, _) => {
1612 Ident::new(name, this.normalized_prev_token.span)
1614 _ => unreachable!(),
1617 // Is `self` `n` tokens ahead?
1618 let is_isolated_self = |this: &Self, n| {
1619 this.is_keyword_ahead(n, &[kw::SelfLower])
1620 && this.look_ahead(n + 1, |t| t != &token::ModSep)
1622 // Is `mut self` `n` tokens ahead?
1623 let is_isolated_mut_self =
1624 |this: &Self, n| this.is_keyword_ahead(n, &[kw::Mut]) && is_isolated_self(this, n + 1);
1625 // Parse `self` or `self: TYPE`. We already know the current token is `self`.
1626 let parse_self_possibly_typed = |this: &mut Self, m| {
1627 let eself_ident = expect_self_ident(this);
1628 let eself_hi = this.prev_token.span;
1629 let eself = if this.eat(&token::Colon) {
1630 SelfKind::Explicit(this.parse_ty()?, m)
1634 Ok((eself, eself_ident, eself_hi))
1636 // Recover for the grammar `*self`, `*const self`, and `*mut self`.
1637 let recover_self_ptr = |this: &mut Self| {
1638 let msg = "cannot pass `self` by raw pointer";
1639 let span = this.token.span;
1640 this.struct_span_err(span, msg).span_label(span, msg).emit();
1642 Ok((SelfKind::Value(Mutability::Not), expect_self_ident(this), this.prev_token.span))
1645 // Parse optional `self` parameter of a method.
1646 // Only a limited set of initial token sequences is considered `self` parameters; anything
1647 // else is parsed as a normal function parameter list, so some lookahead is required.
1648 let eself_lo = self.token.span;
1649 let (eself, eself_ident, eself_hi) = match self.normalized_token.kind {
1650 token::BinOp(token::And) => {
1651 let eself = if is_isolated_self(self, 1) {
1654 SelfKind::Region(None, Mutability::Not)
1655 } else if is_isolated_mut_self(self, 1) {
1659 SelfKind::Region(None, Mutability::Mut)
1660 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_self(self, 2) {
1663 let lt = self.expect_lifetime();
1664 SelfKind::Region(Some(lt), Mutability::Not)
1665 } else if self.look_ahead(1, |t| t.is_lifetime()) && is_isolated_mut_self(self, 2) {
1668 let lt = self.expect_lifetime();
1670 SelfKind::Region(Some(lt), Mutability::Mut)
1675 (eself, expect_self_ident(self), self.prev_token.span)
1678 token::BinOp(token::Star) if is_isolated_self(self, 1) => {
1680 recover_self_ptr(self)?
1682 // `*mut self` and `*const self`
1683 token::BinOp(token::Star)
1684 if self.look_ahead(1, |t| t.is_mutability()) && is_isolated_self(self, 2) =>
1688 recover_self_ptr(self)?
1690 // `self` and `self: TYPE`
1691 token::Ident(..) if is_isolated_self(self, 0) => {
1692 parse_self_possibly_typed(self, Mutability::Not)?
1694 // `mut self` and `mut self: TYPE`
1695 token::Ident(..) if is_isolated_mut_self(self, 0) => {
1697 parse_self_possibly_typed(self, Mutability::Mut)?
1699 _ => return Ok(None),
1702 let eself = source_map::respan(eself_lo.to(eself_hi), eself);
1703 Ok(Some(Param::from_self(AttrVec::default(), eself, eself_ident)))
1706 fn is_named_param(&self) -> bool {
1707 let offset = match self.token.kind {
1708 token::Interpolated(ref nt) => match **nt {
1709 token::NtPat(..) => return self.look_ahead(1, |t| t == &token::Colon),
1712 token::BinOp(token::And) | token::AndAnd => 1,
1713 _ if self.token.is_keyword(kw::Mut) => 1,
1717 self.look_ahead(offset, |t| t.is_ident())
1718 && self.look_ahead(offset + 1, |t| t == &token::Colon)
1721 fn recover_first_param(&mut self) -> &'static str {
1723 .parse_outer_attributes()
1724 .and_then(|_| self.parse_self_param())
1725 .map_err(|mut e| e.cancel())
1727 Ok(Some(_)) => "method",