1 use super::{Parser, PathStyle, PrevTokenKind, TokenType};
2 use super::item::ParamCfg;
4 use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
6 use rustc_errors::{PResult, Applicability, pluralize};
7 use rustc_error_codes::*;
9 use syntax::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
10 use syntax::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
11 use syntax::ast::{Mutability, Mac};
12 use syntax::token::{self, Token};
13 use syntax::struct_span_err;
14 use syntax_pos::source_map::Span;
15 use syntax_pos::symbol::kw;
17 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
18 /// `IDENT<<u8 as Trait>::AssocTy>`.
20 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
21 /// that `IDENT` is not the ident of a fn trait.
22 fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
23 t == &token::ModSep || t == &token::Lt ||
24 t == &token::BinOp(token::Shl)
29 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
30 self.parse_ty_common(true, true, false)
33 /// Parse a type suitable for a function or function pointer parameter.
34 /// The difference from `parse_ty` is that this version allows `...`
35 /// (`CVarArgs`) at the top level of the the type.
36 pub(super) fn parse_ty_for_param(&mut self) -> PResult<'a, P<Ty>> {
37 self.parse_ty_common(true, true, true)
40 /// Parses a type in restricted contexts where `+` is not permitted.
42 /// Example 1: `&'a TYPE`
43 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
44 /// Example 2: `value1 as TYPE + value2`
45 /// `+` is prohibited to avoid interactions with expression grammar.
46 pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
47 self.parse_ty_common(false, true, false)
50 /// Parses an optional return type `[ -> TY ]` in a function declaration.
51 pub(super) fn parse_ret_ty(
54 allow_qpath_recovery: bool,
55 ) -> PResult<'a, FunctionRetTy> {
56 Ok(if self.eat(&token::RArrow) {
57 // FIXME(Centril): Can we unconditionally `allow_plus`?
58 FunctionRetTy::Ty(self.parse_ty_common(allow_plus, allow_qpath_recovery, false)?)
60 FunctionRetTy::Default(self.token.span.shrink_to_lo())
67 allow_qpath_recovery: bool,
68 // Is `...` (`CVarArgs`) legal in the immediate top level call?
69 allow_c_variadic: bool,
70 ) -> PResult<'a, P<Ty>> {
71 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
72 maybe_whole!(self, NtTy, |x| x);
74 let lo = self.token.span;
75 let mut impl_dyn_multi = false;
76 let kind = if self.check(&token::OpenDelim(token::Paren)) {
77 self.parse_ty_tuple_or_parens(lo, allow_plus)?
78 } else if self.eat(&token::Not) {
81 } else if self.eat(&token::BinOp(token::Star)) {
83 } else if self.eat(&token::OpenDelim(token::Bracket)) {
84 self.parse_array_or_slice_ty()?
85 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
88 self.parse_borrowed_pointee()?
89 } else if self.eat_keyword_noexpect(kw::Typeof) {
90 self.parse_typeof_ty()?
91 } else if self.eat_keyword(kw::Underscore) {
92 // A type to be inferred `_`
94 } else if self.token_is_bare_fn_keyword() {
95 // Function pointer type
96 self.parse_ty_bare_fn(Vec::new())?
97 } else if self.check_keyword(kw::For) {
98 // Function pointer type or bound list (trait object type) starting with a poly-trait.
99 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
100 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
101 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
102 if self.token_is_bare_fn_keyword() {
103 self.parse_ty_bare_fn(lifetime_defs)?
105 let path = self.parse_path(PathStyle::Type)?;
106 let parse_plus = allow_plus && self.check_plus();
107 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
109 } else if self.eat_keyword(kw::Impl) {
110 self.parse_impl_ty(&mut impl_dyn_multi)?
111 } else if self.is_explicit_dyn_type() {
112 self.parse_dyn_ty(&mut impl_dyn_multi)?
113 } else if self.check(&token::Question)
114 || self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus())
116 // Bound list (trait object type)
117 let bounds = self.parse_generic_bounds_common(allow_plus, None)?;
118 TyKind::TraitObject(bounds, TraitObjectSyntax::None)
119 } else if self.eat_lt() {
121 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
122 TyKind::Path(Some(qself), path)
123 } else if self.token.is_path_start() {
124 self.parse_path_start_ty(lo, allow_plus)?
125 } else if self.eat(&token::DotDotDot) {
126 if allow_c_variadic {
129 // FIXME(Centril): Should we just allow `...` syntactically
130 // anywhere in a type and use semantic restrictions instead?
131 self.error_illegal_c_varadic_ty(lo);
135 let msg = format!("expected type, found {}", self.this_token_descr());
136 let mut err = self.fatal(&msg);
137 err.span_label(self.token.span, "expected type");
138 self.maybe_annotate_with_ascription(&mut err, true);
142 let span = lo.to(self.prev_span);
143 let ty = self.mk_ty(span, kind);
145 // Try to recover from use of `+` with incorrect priority.
146 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
147 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
148 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
152 /// - `(TYPE)`, a parenthesized type.
153 /// - `(TYPE,)`, a tuple with a single field of type TYPE.
154 fn parse_ty_tuple_or_parens(&mut self, lo: Span, allow_plus: bool) -> PResult<'a, TyKind> {
155 let mut trailing_plus = false;
156 let (ts, trailing) = self.parse_paren_comma_seq(|p| {
157 let ty = p.parse_ty()?;
158 trailing_plus = p.prev_token_kind == PrevTokenKind::Plus;
162 if ts.len() == 1 && !trailing {
163 let ty = ts.into_iter().nth(0).unwrap().into_inner();
164 let maybe_bounds = allow_plus && self.token.is_like_plus();
166 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
167 TyKind::Path(None, path) if maybe_bounds => {
168 self.parse_remaining_bounds(Vec::new(), path, lo, true)
170 TyKind::TraitObject(mut bounds, TraitObjectSyntax::None)
171 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
172 let path = match bounds.remove(0) {
173 GenericBound::Trait(pt, ..) => pt.trait_ref.path,
174 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
176 self.parse_remaining_bounds(Vec::new(), path, lo, true)
179 _ => Ok(TyKind::Paren(P(ty)))
186 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
187 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
188 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
189 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
191 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
192 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
194 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
197 /// Parses a raw pointer type: `*[const | mut] $type`.
198 fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> {
199 let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {
200 let span = self.prev_span;
201 let msg = "expected mut or const in raw pointer type";
202 self.struct_span_err(span, msg)
203 .span_label(span, msg)
204 .help("use `*mut T` or `*const T` as appropriate")
206 Mutability::Immutable
208 let ty = self.parse_ty_no_plus()?;
209 Ok(TyKind::Ptr(MutTy { ty, mutbl }))
212 /// Parses an array (`[TYPE; EXPR]`) or slice (`[TYPE]`) type.
213 /// The opening `[` bracket is already eaten.
214 fn parse_array_or_slice_ty(&mut self) -> PResult<'a, TyKind> {
215 let elt_ty = self.parse_ty()?;
216 let ty = if self.eat(&token::Semi) {
217 TyKind::Array(elt_ty, self.parse_anon_const_expr()?)
219 TyKind::Slice(elt_ty)
221 self.expect(&token::CloseDelim(token::Bracket))?;
225 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
226 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
227 let mutbl = self.parse_mutability();
228 let ty = self.parse_ty_no_plus()?;
229 Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))
232 // Parses the `typeof(EXPR)`.
233 // To avoid ambiguity, the type is surrounded by parenthesis.
234 fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
235 self.expect(&token::OpenDelim(token::Paren))?;
236 let expr = self.parse_anon_const_expr()?;
237 self.expect(&token::CloseDelim(token::Paren))?;
238 Ok(TyKind::Typeof(expr))
241 /// Is the current token one of the keywords that signals a bare function type?
242 fn token_is_bare_fn_keyword(&mut self) -> bool {
243 self.check_keyword(kw::Fn) ||
244 self.check_keyword(kw::Unsafe) ||
245 self.check_keyword(kw::Extern)
248 /// Parses a `TyKind::BareFn` type.
249 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
252 [unsafe] [extern "ABI"] fn (S) -> T
262 let unsafety = self.parse_unsafety();
263 let ext = self.parse_extern()?;
264 self.expect_keyword(kw::Fn)?;
266 is_self_allowed: false,
267 is_name_required: |_| false,
269 let decl = self.parse_fn_decl(cfg, false)?;
270 Ok(TyKind::BareFn(P(BareFnTy {
278 /// Parses an `impl B0 + ... + Bn` type.
279 fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
280 // Always parse bounds greedily for better error recovery.
281 let bounds = self.parse_generic_bounds(None)?;
282 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
283 Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
286 /// Is a `dyn B0 + ... + Bn` type allowed here?
287 fn is_explicit_dyn_type(&mut self) -> bool {
288 self.check_keyword(kw::Dyn)
289 && (self.token.span.rust_2018()
290 || self.look_ahead(1, |t| {
291 t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t)
295 /// Parses a `dyn B0 + ... + Bn` type.
297 /// Note that this does *not* parse bare trait objects.
298 fn parse_dyn_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
299 self.bump(); // `dyn`
300 // Always parse bounds greedily for better error recovery.
301 let bounds = self.parse_generic_bounds(None)?;
302 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
303 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn))
306 /// Parses a type starting with a path.
309 /// 1. a type macro, `mac!(...)`,
310 /// 2. a bare trait object, `B0 + ... + Bn`,
311 /// 3. or a path, `path::to::MyType`.
312 fn parse_path_start_ty(&mut self, lo: Span, allow_plus: bool) -> PResult<'a, TyKind> {
314 let path = self.parse_path(PathStyle::Type)?;
315 if self.eat(&token::Not) {
316 // Macro invocation in type position
319 args: self.parse_mac_args()?,
320 prior_type_ascription: self.last_type_ascription,
322 } else if allow_plus && self.check_plus() {
323 // `Trait1 + Trait2 + 'a`
324 self.parse_remaining_bounds(Vec::new(), path, lo, true)
327 Ok(TyKind::Path(None, path))
331 fn error_illegal_c_varadic_ty(&self, lo: Span) {
333 self.sess.span_diagnostic,
334 lo.to(self.prev_span),
336 "C-variadic type `...` may not be nested inside another type",
341 pub(super) fn parse_generic_bounds(&mut self,
342 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
343 self.parse_generic_bounds_common(true, colon_span)
346 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
349 /// BOUND = TY_BOUND | LT_BOUND
350 /// LT_BOUND = LIFETIME (e.g., `'a`)
351 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
352 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
354 fn parse_generic_bounds_common(&mut self,
356 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
357 let mut bounds = Vec::new();
358 let mut negative_bounds = Vec::new();
359 let mut last_plus_span = None;
360 let mut was_negative = false;
362 // This needs to be synchronized with `TokenKind::can_begin_bound`.
363 let is_bound_start = self.check_path() || self.check_lifetime() ||
364 self.check(&token::Not) || // used for error reporting only
365 self.check(&token::Question) ||
366 self.check_keyword(kw::For) ||
367 self.check(&token::OpenDelim(token::Paren));
369 let lo = self.token.span;
370 let has_parens = self.eat(&token::OpenDelim(token::Paren));
371 let inner_lo = self.token.span;
372 let is_negative = self.eat(&token::Not);
373 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
374 if self.token.is_lifetime() {
375 if let Some(question_span) = question {
376 self.span_err(question_span,
377 "`?` may only modify trait bounds, not lifetime bounds");
379 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
381 let inner_span = inner_lo.to(self.prev_span);
382 self.expect(&token::CloseDelim(token::Paren))?;
383 let mut err = self.struct_span_err(
384 lo.to(self.prev_span),
385 "parenthesized lifetime bounds are not supported"
387 if let Ok(snippet) = self.span_to_snippet(inner_span) {
388 err.span_suggestion_short(
389 lo.to(self.prev_span),
390 "remove the parentheses",
392 Applicability::MachineApplicable
398 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
399 let path = self.parse_path(PathStyle::Type)?;
401 self.expect(&token::CloseDelim(token::Paren))?;
403 let poly_span = lo.to(self.prev_span);
406 if let Some(sp) = last_plus_span.or(colon_span) {
407 negative_bounds.push(sp.to(poly_span));
410 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
411 let modifier = if question.is_some() {
412 TraitBoundModifier::Maybe
414 TraitBoundModifier::None
416 bounds.push(GenericBound::Trait(poly_trait, modifier));
423 if !allow_plus || !self.eat_plus() {
426 last_plus_span = Some(self.prev_span);
430 if !negative_bounds.is_empty() || was_negative {
431 let negative_bounds_len = negative_bounds.len();
432 let last_span = negative_bounds.last().map(|sp| *sp);
433 let mut err = self.struct_span_err(
435 "negative trait bounds are not supported",
437 if let Some(sp) = last_span {
438 err.span_label(sp, "negative trait bounds are not supported");
440 if let Some(bound_list) = colon_span {
441 let bound_list = bound_list.to(self.prev_span);
442 let mut new_bound_list = String::new();
443 if !bounds.is_empty() {
444 let mut snippets = bounds.iter().map(|bound| bound.span())
445 .map(|span| self.span_to_snippet(span));
446 while let Some(Ok(snippet)) = snippets.next() {
447 new_bound_list.push_str(" + ");
448 new_bound_list.push_str(&snippet);
450 new_bound_list = new_bound_list.replacen(" +", ":", 1);
452 err.span_suggestion_hidden(
454 &format!("remove the trait bound{}", pluralize!(negative_bounds_len)),
456 Applicability::MachineApplicable,
465 pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
466 if self.eat_keyword(kw::For) {
468 let params = self.parse_generic_params()?;
470 // We rely on AST validation to rule out invalid cases: There must not be type
471 // parameters, and the lifetime parameters must not have bounds.
478 pub fn check_lifetime(&mut self) -> bool {
479 self.expected_tokens.push(TokenType::Lifetime);
480 self.token.is_lifetime()
483 /// Parses a single lifetime `'a` or panics.
484 pub fn expect_lifetime(&mut self) -> Lifetime {
485 if let Some(ident) = self.token.lifetime() {
486 let span = self.token.span;
488 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
490 self.span_bug(self.token.span, "not a lifetime")
494 pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
495 P(Ty { kind, span, id: ast::DUMMY_NODE_ID })