1 use super::item::ParamCfg;
2 use super::{Parser, PathStyle, PrevTokenKind, TokenType};
4 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
6 use rustc_error_codes::*;
7 use rustc_errors::{pluralize, struct_span_err, Applicability, PResult};
8 use rustc_span::source_map::Span;
9 use rustc_span::symbol::kw;
11 self, BareFnTy, FunctionRetTy, GenericParam, Ident, Lifetime, MutTy, Ty, TyKind,
14 GenericBound, GenericBounds, PolyTraitRef, TraitBoundModifier, TraitObjectSyntax,
16 use syntax::ast::{Mac, Mutability};
18 use syntax::token::{self, Token};
20 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
21 /// `IDENT<<u8 as Trait>::AssocTy>`.
23 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
24 /// that `IDENT` is not the ident of a fn trait.
25 fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
26 t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl)
31 pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
32 self.parse_ty_common(true, true, false)
35 /// Parse a type suitable for a function or function pointer parameter.
36 /// The difference from `parse_ty` is that this version allows `...`
37 /// (`CVarArgs`) at the top level of the the type.
38 pub(super) fn parse_ty_for_param(&mut self) -> PResult<'a, P<Ty>> {
39 self.parse_ty_common(true, true, true)
42 /// Parses a type in restricted contexts where `+` is not permitted.
44 /// Example 1: `&'a TYPE`
45 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
46 /// Example 2: `value1 as TYPE + value2`
47 /// `+` is prohibited to avoid interactions with expression grammar.
48 pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
49 self.parse_ty_common(false, true, false)
52 /// Parses an optional return type `[ -> TY ]` in a function declaration.
53 pub(super) fn parse_ret_ty(
56 allow_qpath_recovery: bool,
57 ) -> PResult<'a, FunctionRetTy> {
58 Ok(if self.eat(&token::RArrow) {
59 // FIXME(Centril): Can we unconditionally `allow_plus`?
60 FunctionRetTy::Ty(self.parse_ty_common(allow_plus, allow_qpath_recovery, false)?)
62 FunctionRetTy::Default(self.token.span.shrink_to_lo())
69 allow_qpath_recovery: bool,
70 // Is `...` (`CVarArgs`) legal in the immediate top level call?
71 allow_c_variadic: bool,
72 ) -> PResult<'a, P<Ty>> {
73 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
74 maybe_whole!(self, NtTy, |x| x);
76 let lo = self.token.span;
77 let mut impl_dyn_multi = false;
78 let kind = if self.check(&token::OpenDelim(token::Paren)) {
79 self.parse_ty_tuple_or_parens(lo, allow_plus)?
80 } else if self.eat(&token::Not) {
83 } else if self.eat(&token::BinOp(token::Star)) {
85 } else if self.eat(&token::OpenDelim(token::Bracket)) {
86 self.parse_array_or_slice_ty()?
87 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
90 self.parse_borrowed_pointee()?
91 } else if self.eat_keyword_noexpect(kw::Typeof) {
92 self.parse_typeof_ty()?
93 } else if self.eat_keyword(kw::Underscore) {
94 // A type to be inferred `_`
96 } else if self.token_is_bare_fn_keyword() {
97 // Function pointer type
98 self.parse_ty_bare_fn(Vec::new())?
99 } else if self.check_keyword(kw::For) {
100 // Function pointer type or bound list (trait object type) starting with a poly-trait.
101 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
102 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
103 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
104 if self.token_is_bare_fn_keyword() {
105 self.parse_ty_bare_fn(lifetime_defs)?
107 let path = self.parse_path(PathStyle::Type)?;
108 let parse_plus = allow_plus && self.check_plus();
109 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
111 } else if self.eat_keyword(kw::Impl) {
112 self.parse_impl_ty(&mut impl_dyn_multi)?
113 } else if self.is_explicit_dyn_type() {
114 self.parse_dyn_ty(&mut impl_dyn_multi)?
115 } else if self.check(&token::Question)
116 || self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus())
118 // Bound list (trait object type)
119 let bounds = self.parse_generic_bounds_common(allow_plus, None)?;
120 TyKind::TraitObject(bounds, TraitObjectSyntax::None)
121 } else if self.eat_lt() {
123 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
124 TyKind::Path(Some(qself), path)
125 } else if self.token.is_path_start() {
126 self.parse_path_start_ty(lo, allow_plus)?
127 } else if self.eat(&token::DotDotDot) {
128 if allow_c_variadic {
131 // FIXME(Centril): Should we just allow `...` syntactically
132 // anywhere in a type and use semantic restrictions instead?
133 self.error_illegal_c_varadic_ty(lo);
137 let msg = format!("expected type, found {}", super::token_descr(&self.token));
138 let mut err = self.struct_span_err(self.token.span, &msg);
139 err.span_label(self.token.span, "expected type");
140 self.maybe_annotate_with_ascription(&mut err, true);
144 let span = lo.to(self.prev_span);
145 let ty = self.mk_ty(span, kind);
147 // Try to recover from use of `+` with incorrect priority.
148 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
149 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
150 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
154 /// - `(TYPE)`, a parenthesized type.
155 /// - `(TYPE,)`, a tuple with a single field of type TYPE.
156 fn parse_ty_tuple_or_parens(&mut self, lo: Span, allow_plus: bool) -> PResult<'a, TyKind> {
157 let mut trailing_plus = false;
158 let (ts, trailing) = self.parse_paren_comma_seq(|p| {
159 let ty = p.parse_ty()?;
160 trailing_plus = p.prev_token_kind == PrevTokenKind::Plus;
164 if ts.len() == 1 && !trailing {
165 let ty = ts.into_iter().nth(0).unwrap().into_inner();
166 let maybe_bounds = allow_plus && self.token.is_like_plus();
168 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
169 TyKind::Path(None, path) if maybe_bounds => {
170 self.parse_remaining_bounds(Vec::new(), path, lo, true)
172 TyKind::TraitObject(mut bounds, TraitObjectSyntax::None)
173 if maybe_bounds && bounds.len() == 1 && !trailing_plus =>
175 let path = match bounds.remove(0) {
176 GenericBound::Trait(pt, ..) => pt.trait_ref.path,
177 GenericBound::Outlives(..) => {
178 self.span_bug(ty.span, "unexpected lifetime bound")
181 self.parse_remaining_bounds(Vec::new(), path, lo, true)
184 _ => Ok(TyKind::Paren(P(ty))),
191 fn parse_remaining_bounds(
193 generic_params: Vec<GenericParam>,
197 ) -> PResult<'a, TyKind> {
198 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
199 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
201 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
202 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
204 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
207 /// Parses a raw pointer type: `*[const | mut] $type`.
208 fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> {
209 let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {
210 let span = self.prev_span;
211 let msg = "expected mut or const in raw pointer type";
212 self.struct_span_err(span, msg)
213 .span_label(span, msg)
214 .help("use `*mut T` or `*const T` as appropriate")
218 let ty = self.parse_ty_no_plus()?;
219 Ok(TyKind::Ptr(MutTy { ty, mutbl }))
222 /// Parses an array (`[TYPE; EXPR]`) or slice (`[TYPE]`) type.
223 /// The opening `[` bracket is already eaten.
224 fn parse_array_or_slice_ty(&mut self) -> PResult<'a, TyKind> {
225 let elt_ty = self.parse_ty()?;
226 let ty = if self.eat(&token::Semi) {
227 TyKind::Array(elt_ty, self.parse_anon_const_expr()?)
229 TyKind::Slice(elt_ty)
231 self.expect(&token::CloseDelim(token::Bracket))?;
235 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
236 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
237 let mutbl = self.parse_mutability();
238 let ty = self.parse_ty_no_plus()?;
239 Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))
242 // Parses the `typeof(EXPR)`.
243 // To avoid ambiguity, the type is surrounded by parenthesis.
244 fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
245 self.expect(&token::OpenDelim(token::Paren))?;
246 let expr = self.parse_anon_const_expr()?;
247 self.expect(&token::CloseDelim(token::Paren))?;
248 Ok(TyKind::Typeof(expr))
251 /// Is the current token one of the keywords that signals a bare function type?
252 fn token_is_bare_fn_keyword(&mut self) -> bool {
253 self.check_keyword(kw::Fn)
254 || self.check_keyword(kw::Unsafe)
255 || self.check_keyword(kw::Extern)
258 /// Parses a function pointer type (`TyKind::BareFn`).
260 /// [unsafe] [extern "ABI"] fn (S) -> T
261 /// ^~~~~^ ^~~~^ ^~^ ^
263 /// | | | Return type
264 /// Function Style ABI Parameter types
266 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
267 let unsafety = self.parse_unsafety();
268 let ext = self.parse_extern()?;
269 self.expect_keyword(kw::Fn)?;
270 let cfg = ParamCfg { is_self_allowed: false, is_name_required: |_| false };
271 let decl = self.parse_fn_decl(cfg, false)?;
272 Ok(TyKind::BareFn(P(BareFnTy { ext, unsafety, generic_params, decl })))
275 /// Parses an `impl B0 + ... + Bn` type.
276 fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
277 // Always parse bounds greedily for better error recovery.
278 let bounds = self.parse_generic_bounds(None)?;
279 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
280 Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
283 /// Is a `dyn B0 + ... + Bn` type allowed here?
284 fn is_explicit_dyn_type(&mut self) -> bool {
285 self.check_keyword(kw::Dyn)
286 && (self.token.span.rust_2018()
287 || self.look_ahead(1, |t| {
288 t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t)
292 /// Parses a `dyn B0 + ... + Bn` type.
294 /// Note that this does *not* parse bare trait objects.
295 fn parse_dyn_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
296 self.bump(); // `dyn`
297 // Always parse bounds greedily for better error recovery.
298 let bounds = self.parse_generic_bounds(None)?;
299 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
300 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn))
303 /// Parses a type starting with a path.
306 /// 1. a type macro, `mac!(...)`,
307 /// 2. a bare trait object, `B0 + ... + Bn`,
308 /// 3. or a path, `path::to::MyType`.
309 fn parse_path_start_ty(&mut self, lo: Span, allow_plus: bool) -> PResult<'a, TyKind> {
311 let path = self.parse_path(PathStyle::Type)?;
312 if self.eat(&token::Not) {
313 // Macro invocation in type position
316 args: self.parse_mac_args()?,
317 prior_type_ascription: self.last_type_ascription,
319 } else if allow_plus && self.check_plus() {
320 // `Trait1 + Trait2 + 'a`
321 self.parse_remaining_bounds(Vec::new(), path, lo, true)
324 Ok(TyKind::Path(None, path))
328 fn error_illegal_c_varadic_ty(&self, lo: Span) {
330 self.sess.span_diagnostic,
331 lo.to(self.prev_span),
333 "C-variadic type `...` may not be nested inside another type",
338 pub(super) fn parse_generic_bounds(
340 colon_span: Option<Span>,
341 ) -> PResult<'a, GenericBounds> {
342 self.parse_generic_bounds_common(true, colon_span)
345 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
347 /// See `parse_generic_bound` for the `BOUND` grammar.
348 fn parse_generic_bounds_common(
351 colon_span: Option<Span>,
352 ) -> PResult<'a, GenericBounds> {
353 let mut bounds = Vec::new();
354 let mut negative_bounds = Vec::new();
355 while self.can_begin_bound() {
356 match self.parse_generic_bound()? {
357 Ok(bound) => bounds.push(bound),
358 Err(neg_sp) => negative_bounds.push(neg_sp),
360 if !allow_plus || !self.eat_plus() {
365 if !negative_bounds.is_empty() {
366 self.error_negative_bounds(colon_span, &bounds, negative_bounds);
372 /// Can the current token begin a bound?
373 fn can_begin_bound(&mut self) -> bool {
374 // This needs to be synchronized with `TokenKind::can_begin_bound`.
376 || self.check_lifetime()
377 || self.check(&token::Not) // Used for error reporting only.
378 || self.check(&token::Question)
379 || self.check_keyword(kw::For)
380 || self.check(&token::OpenDelim(token::Paren))
383 fn error_negative_bounds(
385 colon_span: Option<Span>,
386 bounds: &[GenericBound],
387 negative_bounds: Vec<Span>,
389 let negative_bounds_len = negative_bounds.len();
390 let last_span = *negative_bounds.last().expect("no negative bounds, but still error?");
391 let mut err = self.struct_span_err(negative_bounds, "negative bounds are not supported");
392 err.span_label(last_span, "negative bounds are not supported");
393 if let Some(bound_list) = colon_span {
394 let bound_list = bound_list.to(self.prev_span);
395 let mut new_bound_list = String::new();
396 if !bounds.is_empty() {
397 let mut snippets = bounds.iter().map(|bound| self.span_to_snippet(bound.span()));
398 while let Some(Ok(snippet)) = snippets.next() {
399 new_bound_list.push_str(" + ");
400 new_bound_list.push_str(&snippet);
402 new_bound_list = new_bound_list.replacen(" +", ":", 1);
404 err.tool_only_span_suggestion(
406 &format!("remove the bound{}", pluralize!(negative_bounds_len)),
408 Applicability::MachineApplicable,
414 /// Parses a bound according to the grammar:
416 /// BOUND = TY_BOUND | LT_BOUND
418 fn parse_generic_bound(&mut self) -> PResult<'a, Result<GenericBound, Span>> {
419 let anchor_lo = self.prev_span;
420 let lo = self.token.span;
421 let has_parens = self.eat(&token::OpenDelim(token::Paren));
422 let inner_lo = self.token.span;
423 let is_negative = self.eat(&token::Not);
424 let question = self.eat(&token::Question).then_some(self.prev_span);
425 let bound = if self.token.is_lifetime() {
426 self.parse_generic_lt_bound(lo, inner_lo, has_parens, question)?
428 self.parse_generic_ty_bound(lo, has_parens, question)?
430 Ok(if is_negative { Err(anchor_lo.to(self.prev_span)) } else { Ok(bound) })
433 /// Parses a lifetime ("outlives") bound, e.g. `'a`, according to:
435 /// LT_BOUND = LIFETIME
437 fn parse_generic_lt_bound(
442 question: Option<Span>,
443 ) -> PResult<'a, GenericBound> {
444 self.error_opt_out_lifetime(question);
445 let bound = GenericBound::Outlives(self.expect_lifetime());
447 // FIXME(Centril): Consider not erroring here and accepting `('lt)` instead,
448 // possibly introducing `GenericBound::Paren(P<GenericBound>)`?
449 self.recover_paren_lifetime(lo, inner_lo)?;
454 fn error_opt_out_lifetime(&self, question: Option<Span>) {
455 if let Some(span) = question {
456 self.struct_span_err(span, "`?` may only modify trait bounds, not lifetime bounds")
461 /// Recover on `('lifetime)` with `(` already eaten.
462 fn recover_paren_lifetime(&mut self, lo: Span, inner_lo: Span) -> PResult<'a, ()> {
463 let inner_span = inner_lo.to(self.prev_span);
464 self.expect(&token::CloseDelim(token::Paren))?;
465 let mut err = self.struct_span_err(
466 lo.to(self.prev_span),
467 "parenthesized lifetime bounds are not supported",
469 if let Ok(snippet) = self.span_to_snippet(inner_span) {
470 err.span_suggestion_short(
471 lo.to(self.prev_span),
472 "remove the parentheses",
474 Applicability::MachineApplicable,
481 /// Parses a type bound according to:
483 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
484 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
486 fn parse_generic_ty_bound(
490 question: Option<Span>,
491 ) -> PResult<'a, GenericBound> {
492 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
493 let path = self.parse_path(PathStyle::Type)?;
495 self.expect(&token::CloseDelim(token::Paren))?;
497 let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
498 let modifier = question.map_or(TraitBoundModifier::None, |_| TraitBoundModifier::Maybe);
499 Ok(GenericBound::Trait(poly_trait, modifier))
502 /// Optionally parses `for<$generic_params>`.
503 pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
504 if self.eat_keyword(kw::For) {
506 let params = self.parse_generic_params()?;
508 // We rely on AST validation to rule out invalid cases: There must not be type
509 // parameters, and the lifetime parameters must not have bounds.
516 pub fn check_lifetime(&mut self) -> bool {
517 self.expected_tokens.push(TokenType::Lifetime);
518 self.token.is_lifetime()
521 /// Parses a single lifetime `'a` or panics.
522 pub fn expect_lifetime(&mut self) -> Lifetime {
523 if let Some(ident) = self.token.lifetime() {
524 let span = self.token.span;
526 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
528 self.span_bug(self.token.span, "not a lifetime")
532 pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
533 P(Ty { kind, span, id: ast::DUMMY_NODE_ID })