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.struct_span_err(self.token.span, &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(
188 generic_params: Vec<GenericParam>,
192 ) -> PResult<'a, TyKind> {
193 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
194 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
196 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
197 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
199 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
202 /// Parses a raw pointer type: `*[const | mut] $type`.
203 fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> {
204 let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {
205 let span = self.prev_span;
206 let msg = "expected mut or const in raw pointer type";
207 self.struct_span_err(span, msg)
208 .span_label(span, msg)
209 .help("use `*mut T` or `*const T` as appropriate")
211 Mutability::Immutable
213 let ty = self.parse_ty_no_plus()?;
214 Ok(TyKind::Ptr(MutTy { ty, mutbl }))
217 /// Parses an array (`[TYPE; EXPR]`) or slice (`[TYPE]`) type.
218 /// The opening `[` bracket is already eaten.
219 fn parse_array_or_slice_ty(&mut self) -> PResult<'a, TyKind> {
220 let elt_ty = self.parse_ty()?;
221 let ty = if self.eat(&token::Semi) {
222 TyKind::Array(elt_ty, self.parse_anon_const_expr()?)
224 TyKind::Slice(elt_ty)
226 self.expect(&token::CloseDelim(token::Bracket))?;
230 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
231 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
232 let mutbl = self.parse_mutability();
233 let ty = self.parse_ty_no_plus()?;
234 Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }))
237 // Parses the `typeof(EXPR)`.
238 // To avoid ambiguity, the type is surrounded by parenthesis.
239 fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> {
240 self.expect(&token::OpenDelim(token::Paren))?;
241 let expr = self.parse_anon_const_expr()?;
242 self.expect(&token::CloseDelim(token::Paren))?;
243 Ok(TyKind::Typeof(expr))
246 /// Is the current token one of the keywords that signals a bare function type?
247 fn token_is_bare_fn_keyword(&mut self) -> bool {
248 self.check_keyword(kw::Fn) ||
249 self.check_keyword(kw::Unsafe) ||
250 self.check_keyword(kw::Extern)
253 /// Parses a `TyKind::BareFn` type.
254 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
257 [unsafe] [extern "ABI"] fn (S) -> T
267 let unsafety = self.parse_unsafety();
268 let ext = self.parse_extern()?;
269 self.expect_keyword(kw::Fn)?;
271 is_self_allowed: false,
272 is_name_required: |_| false,
274 let decl = self.parse_fn_decl(cfg, false)?;
275 Ok(TyKind::BareFn(P(BareFnTy {
283 /// Parses an `impl B0 + ... + Bn` type.
284 fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
285 // Always parse bounds greedily for better error recovery.
286 let bounds = self.parse_generic_bounds(None)?;
287 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
288 Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds))
291 /// Is a `dyn B0 + ... + Bn` type allowed here?
292 fn is_explicit_dyn_type(&mut self) -> bool {
293 self.check_keyword(kw::Dyn)
294 && (self.token.span.rust_2018()
295 || self.look_ahead(1, |t| {
296 t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t)
300 /// Parses a `dyn B0 + ... + Bn` type.
302 /// Note that this does *not* parse bare trait objects.
303 fn parse_dyn_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> {
304 self.bump(); // `dyn`
305 // Always parse bounds greedily for better error recovery.
306 let bounds = self.parse_generic_bounds(None)?;
307 *impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
308 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn))
311 /// Parses a type starting with a path.
314 /// 1. a type macro, `mac!(...)`,
315 /// 2. a bare trait object, `B0 + ... + Bn`,
316 /// 3. or a path, `path::to::MyType`.
317 fn parse_path_start_ty(&mut self, lo: Span, allow_plus: bool) -> PResult<'a, TyKind> {
319 let path = self.parse_path(PathStyle::Type)?;
320 if self.eat(&token::Not) {
321 // Macro invocation in type position
324 args: self.parse_mac_args()?,
325 prior_type_ascription: self.last_type_ascription,
327 } else if allow_plus && self.check_plus() {
328 // `Trait1 + Trait2 + 'a`
329 self.parse_remaining_bounds(Vec::new(), path, lo, true)
332 Ok(TyKind::Path(None, path))
336 fn error_illegal_c_varadic_ty(&self, lo: Span) {
338 self.sess.span_diagnostic,
339 lo.to(self.prev_span),
341 "C-variadic type `...` may not be nested inside another type",
346 pub(super) fn parse_generic_bounds(
348 colon_span: Option<Span>,
349 ) -> PResult<'a, GenericBounds> {
350 self.parse_generic_bounds_common(true, colon_span)
353 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
356 /// BOUND = TY_BOUND | LT_BOUND
357 /// LT_BOUND = LIFETIME (e.g., `'a`)
358 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
359 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
361 fn parse_generic_bounds_common(
364 colon_span: Option<Span>,
365 ) -> PResult<'a, GenericBounds> {
366 let mut bounds = Vec::new();
367 let mut negative_bounds = Vec::new();
368 let mut last_plus_span = None;
369 let mut was_negative = false;
370 while self.can_begin_bound() {
371 let lo = self.token.span;
372 let has_parens = self.eat(&token::OpenDelim(token::Paren));
373 let inner_lo = self.token.span;
374 let is_negative = self.eat(&token::Not);
375 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
376 if self.token.is_lifetime() {
377 self.error_opt_out_lifetime(question);
378 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
380 self.recover_paren_lifetime(lo, inner_lo)?;
383 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
384 let path = self.parse_path(PathStyle::Type)?;
386 self.expect(&token::CloseDelim(token::Paren))?;
388 let poly_span = lo.to(self.prev_span);
391 if let Some(sp) = last_plus_span.or(colon_span) {
392 negative_bounds.push(sp.to(poly_span));
395 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
396 let modifier = if question.is_some() {
397 TraitBoundModifier::Maybe
399 TraitBoundModifier::None
401 bounds.push(GenericBound::Trait(poly_trait, modifier));
405 if !allow_plus || !self.eat_plus() {
408 last_plus_span = Some(self.prev_span);
412 if !negative_bounds.is_empty() || was_negative {
413 let negative_bounds_len = negative_bounds.len();
414 let last_span = negative_bounds.last().map(|sp| *sp);
415 let mut err = self.struct_span_err(
417 "negative trait bounds are not supported",
419 if let Some(sp) = last_span {
420 err.span_label(sp, "negative trait bounds are not supported");
422 if let Some(bound_list) = colon_span {
423 let bound_list = bound_list.to(self.prev_span);
424 let mut new_bound_list = String::new();
425 if !bounds.is_empty() {
426 let mut snippets = bounds.iter().map(|bound| bound.span())
427 .map(|span| self.span_to_snippet(span));
428 while let Some(Ok(snippet)) = snippets.next() {
429 new_bound_list.push_str(" + ");
430 new_bound_list.push_str(&snippet);
432 new_bound_list = new_bound_list.replacen(" +", ":", 1);
434 err.span_suggestion_hidden(
436 &format!("remove the trait bound{}", pluralize!(negative_bounds_len)),
438 Applicability::MachineApplicable,
447 /// Can the current token begin a bound?
448 fn can_begin_bound(&mut self) -> bool {
449 // This needs to be synchronized with `TokenKind::can_begin_bound`.
451 || self.check_lifetime()
452 || self.check(&token::Not) // Used for error reporting only.
453 || self.check(&token::Question)
454 || self.check_keyword(kw::For)
455 || self.check(&token::OpenDelim(token::Paren))
458 fn error_opt_out_lifetime(&self, question: Option<Span>) {
459 if let Some(span) = question {
460 self.struct_span_err(span, "`?` may only modify trait bounds, not lifetime bounds")
465 /// Recover on `('lifetime)` with `(` already eaten.
466 fn recover_paren_lifetime(&mut self, lo: Span, inner_lo: Span) -> PResult<'a, ()> {
467 let inner_span = inner_lo.to(self.prev_span);
468 self.expect(&token::CloseDelim(token::Paren))?;
469 let mut err = self.struct_span_err(
470 lo.to(self.prev_span),
471 "parenthesized lifetime bounds are not supported"
473 if let Ok(snippet) = self.span_to_snippet(inner_span) {
474 err.span_suggestion_short(
475 lo.to(self.prev_span),
476 "remove the parentheses",
478 Applicability::MachineApplicable
485 pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
486 if self.eat_keyword(kw::For) {
488 let params = self.parse_generic_params()?;
490 // We rely on AST validation to rule out invalid cases: There must not be type
491 // parameters, and the lifetime parameters must not have bounds.
498 pub fn check_lifetime(&mut self) -> bool {
499 self.expected_tokens.push(TokenType::Lifetime);
500 self.token.is_lifetime()
503 /// Parses a single lifetime `'a` or panics.
504 pub fn expect_lifetime(&mut self) -> Lifetime {
505 if let Some(ident) = self.token.lifetime() {
506 let span = self.token.span;
508 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
510 self.span_bug(self.token.span, "not a lifetime")
514 pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
515 P(Ty { kind, span, id: ast::DUMMY_NODE_ID })