1 use super::{Parser, PathStyle, PrevTokenKind, TokenType};
2 use super::item::ParamCfg;
4 use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
7 use syntax::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
8 use syntax::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
9 use syntax::ast::{Mutability, AnonConst, Mac};
10 use syntax::token::{self, Token};
11 use syntax::source_map::Span;
12 use syntax::struct_span_fatal;
13 use syntax_pos::symbol::kw;
15 use errors::{PResult, Applicability, pluralize};
17 use rustc_error_codes::*;
19 /// Returns `true` if `IDENT t` can start a type -- `IDENT::a::b`, `IDENT<u8, u8>`,
20 /// `IDENT<<u8 as Trait>::AssocTy>`.
22 /// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
23 /// that `IDENT` is not the ident of a fn trait.
24 fn can_continue_type_after_non_fn_ident(t: &Token) -> bool {
25 t == &token::ModSep || t == &token::Lt ||
26 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 /// Parses a type in restricted contexts where `+` is not permitted.
37 /// Example 1: `&'a TYPE`
38 /// `+` is prohibited to maintain operator priority (P(+) < P(&)).
39 /// Example 2: `value1 as TYPE + value2`
40 /// `+` is prohibited to avoid interactions with expression grammar.
41 pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> {
42 self.parse_ty_common(false, true, false)
45 /// Parses an optional return type `[ -> TY ]` in a function declaration.
46 pub(super) fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> {
47 if self.eat(&token::RArrow) {
48 Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?))
50 Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo()))
54 pub(super) fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool,
55 allow_c_variadic: bool) -> PResult<'a, P<Ty>> {
56 maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery);
57 maybe_whole!(self, NtTy, |x| x);
59 let lo = self.token.span;
60 let mut impl_dyn_multi = false;
61 let kind = if self.eat(&token::OpenDelim(token::Paren)) {
62 // `(TYPE)` is a parenthesized type.
63 // `(TYPE,)` is a tuple with a single field of type TYPE.
65 let mut last_comma = false;
66 while self.token != token::CloseDelim(token::Paren) {
67 ts.push(self.parse_ty()?);
68 if self.eat(&token::Comma) {
75 let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
76 self.expect(&token::CloseDelim(token::Paren))?;
78 if ts.len() == 1 && !last_comma {
79 let ty = ts.into_iter().nth(0).unwrap().into_inner();
80 let maybe_bounds = allow_plus && self.token.is_like_plus();
82 // `(TY_BOUND_NOPAREN) + BOUND + ...`.
83 TyKind::Path(None, ref path) if maybe_bounds => {
84 self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
86 TyKind::TraitObject(ref bounds, TraitObjectSyntax::None)
87 if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
88 let path = match bounds[0] {
89 GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(),
90 GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"),
92 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
95 _ => TyKind::Paren(P(ty))
100 } else if self.eat(&token::Not) {
103 } else if self.eat(&token::BinOp(token::Star)) {
105 TyKind::Ptr(self.parse_ptr()?)
106 } else if self.eat(&token::OpenDelim(token::Bracket)) {
108 let t = self.parse_ty()?;
109 // Parse optional `; EXPR` in `[TYPE; EXPR]`
110 let t = match self.maybe_parse_fixed_length_of_vec()? {
111 None => TyKind::Slice(t),
112 Some(length) => TyKind::Array(t, AnonConst {
113 id: ast::DUMMY_NODE_ID,
117 self.expect(&token::CloseDelim(token::Bracket))?;
119 } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) {
122 self.parse_borrowed_pointee()?
123 } else if self.eat_keyword_noexpect(kw::Typeof) {
125 // In order to not be ambiguous, the type must be surrounded by parens.
126 self.expect(&token::OpenDelim(token::Paren))?;
128 id: ast::DUMMY_NODE_ID,
129 value: self.parse_expr()?,
131 self.expect(&token::CloseDelim(token::Paren))?;
133 } else if self.eat_keyword(kw::Underscore) {
134 // A type to be inferred `_`
136 } else if self.token_is_bare_fn_keyword() {
137 // Function pointer type
138 self.parse_ty_bare_fn(Vec::new())?
139 } else if self.check_keyword(kw::For) {
140 // Function pointer type or bound list (trait object type) starting with a poly-trait.
141 // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T`
142 // `for<'lt> Trait1<'lt> + Trait2 + 'a`
143 let lo = self.token.span;
144 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
145 if self.token_is_bare_fn_keyword() {
146 self.parse_ty_bare_fn(lifetime_defs)?
148 let path = self.parse_path(PathStyle::Type)?;
149 let parse_plus = allow_plus && self.check_plus();
150 self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
152 } else if self.eat_keyword(kw::Impl) {
153 // Always parse bounds greedily for better error recovery.
154 let bounds = self.parse_generic_bounds(None)?;
155 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
156 TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)
157 } else if self.check_keyword(kw::Dyn) &&
158 (self.token.span.rust_2018() ||
159 self.look_ahead(1, |t| t.can_begin_bound() &&
160 !can_continue_type_after_non_fn_ident(t))) {
161 self.bump(); // `dyn`
162 // Always parse bounds greedily for better error recovery.
163 let bounds = self.parse_generic_bounds(None)?;
164 impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
165 TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)
166 } else if self.check(&token::Question) ||
167 self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) {
168 // Bound list (trait object type)
169 TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?,
170 TraitObjectSyntax::None)
171 } else if self.eat_lt() {
173 let (qself, path) = self.parse_qpath(PathStyle::Type)?;
174 TyKind::Path(Some(qself), path)
175 } else if self.token.is_path_start() {
177 let path = self.parse_path(PathStyle::Type)?;
178 if self.eat(&token::Not) {
179 // Macro invocation in type position
180 let args = self.parse_mac_args()?;
184 prior_type_ascription: self.last_type_ascription,
188 // Just a type path or bound list (trait object type) starting with a trait.
190 // `Trait1 + Trait2 + 'a`
191 if allow_plus && self.check_plus() {
192 self.parse_remaining_bounds(Vec::new(), path, lo, true)?
194 TyKind::Path(None, path)
197 } else if self.check(&token::DotDotDot) {
198 if allow_c_variadic {
199 self.eat(&token::DotDotDot);
202 return Err(struct_span_fatal!(
203 self.sess.span_diagnostic,
206 "only foreign functions are allowed to be C-variadic",
210 let msg = format!("expected type, found {}", self.this_token_descr());
211 let mut err = self.fatal(&msg);
212 err.span_label(self.token.span, "expected type");
213 self.maybe_annotate_with_ascription(&mut err, true);
217 let span = lo.to(self.prev_span);
218 let ty = self.mk_ty(span, kind);
220 // Try to recover from use of `+` with incorrect priority.
221 self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty);
222 self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?;
223 self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery)
226 fn parse_remaining_bounds(&mut self, generic_params: Vec<GenericParam>, path: ast::Path,
227 lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
228 let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_span));
229 let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)];
231 self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded
232 bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?);
234 Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None))
237 fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
238 let mutbl = self.parse_const_or_mut().unwrap_or_else(|| {
239 let span = self.prev_span;
240 let msg = "expected mut or const in raw pointer type";
241 self.struct_span_err(span, msg)
242 .span_label(span, msg)
243 .help("use `*mut T` or `*const T` as appropriate")
245 Mutability::Immutable
247 let t = self.parse_ty_no_plus()?;
248 Ok(MutTy { ty: t, mutbl })
251 fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
252 if self.eat(&token::Semi) {
253 Ok(Some(self.parse_expr()?))
259 fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
260 let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None };
261 let mutbl = self.parse_mutability();
262 let ty = self.parse_ty_no_plus()?;
263 return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl }));
266 /// Is the current token one of the keywords that signals a bare function type?
267 fn token_is_bare_fn_keyword(&mut self) -> bool {
268 self.check_keyword(kw::Fn) ||
269 self.check_keyword(kw::Unsafe) ||
270 self.check_keyword(kw::Extern)
273 /// Parses a `TyKind::BareFn` type.
274 fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> {
277 [unsafe] [extern "ABI"] fn (S) -> T
287 let unsafety = self.parse_unsafety();
288 let ext = self.parse_extern()?;
289 self.expect_keyword(kw::Fn)?;
291 is_self_allowed: false,
292 allow_c_variadic: true,
293 is_name_required: |_| false,
295 let decl = self.parse_fn_decl(cfg, false)?;
296 Ok(TyKind::BareFn(P(BareFnTy {
304 pub(super) fn parse_generic_bounds(&mut self,
305 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
306 self.parse_generic_bounds_common(true, colon_span)
309 /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`.
312 /// BOUND = TY_BOUND | LT_BOUND
313 /// LT_BOUND = LIFETIME (e.g., `'a`)
314 /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
315 /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`)
317 fn parse_generic_bounds_common(&mut self,
319 colon_span: Option<Span>) -> PResult<'a, GenericBounds> {
320 let mut bounds = Vec::new();
321 let mut negative_bounds = Vec::new();
322 let mut last_plus_span = None;
323 let mut was_negative = false;
325 // This needs to be synchronized with `TokenKind::can_begin_bound`.
326 let is_bound_start = self.check_path() || self.check_lifetime() ||
327 self.check(&token::Not) || // used for error reporting only
328 self.check(&token::Question) ||
329 self.check_keyword(kw::For) ||
330 self.check(&token::OpenDelim(token::Paren));
332 let lo = self.token.span;
333 let has_parens = self.eat(&token::OpenDelim(token::Paren));
334 let inner_lo = self.token.span;
335 let is_negative = self.eat(&token::Not);
336 let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
337 if self.token.is_lifetime() {
338 if let Some(question_span) = question {
339 self.span_err(question_span,
340 "`?` may only modify trait bounds, not lifetime bounds");
342 bounds.push(GenericBound::Outlives(self.expect_lifetime()));
344 let inner_span = inner_lo.to(self.prev_span);
345 self.expect(&token::CloseDelim(token::Paren))?;
346 let mut err = self.struct_span_err(
347 lo.to(self.prev_span),
348 "parenthesized lifetime bounds are not supported"
350 if let Ok(snippet) = self.span_to_snippet(inner_span) {
351 err.span_suggestion_short(
352 lo.to(self.prev_span),
353 "remove the parentheses",
355 Applicability::MachineApplicable
361 let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
362 let path = self.parse_path(PathStyle::Type)?;
364 self.expect(&token::CloseDelim(token::Paren))?;
366 let poly_span = lo.to(self.prev_span);
369 if let Some(sp) = last_plus_span.or(colon_span) {
370 negative_bounds.push(sp.to(poly_span));
373 let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span);
374 let modifier = if question.is_some() {
375 TraitBoundModifier::Maybe
377 TraitBoundModifier::None
379 bounds.push(GenericBound::Trait(poly_trait, modifier));
386 if !allow_plus || !self.eat_plus() {
389 last_plus_span = Some(self.prev_span);
393 if !negative_bounds.is_empty() || was_negative {
394 let negative_bounds_len = negative_bounds.len();
395 let last_span = negative_bounds.last().map(|sp| *sp);
396 let mut err = self.struct_span_err(
398 "negative trait bounds are not supported",
400 if let Some(sp) = last_span {
401 err.span_label(sp, "negative trait bounds are not supported");
403 if let Some(bound_list) = colon_span {
404 let bound_list = bound_list.to(self.prev_span);
405 let mut new_bound_list = String::new();
406 if !bounds.is_empty() {
407 let mut snippets = bounds.iter().map(|bound| bound.span())
408 .map(|span| self.span_to_snippet(span));
409 while let Some(Ok(snippet)) = snippets.next() {
410 new_bound_list.push_str(" + ");
411 new_bound_list.push_str(&snippet);
413 new_bound_list = new_bound_list.replacen(" +", ":", 1);
415 err.span_suggestion_hidden(
417 &format!("remove the trait bound{}", pluralize!(negative_bounds_len)),
419 Applicability::MachineApplicable,
428 pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> {
429 if self.eat_keyword(kw::For) {
431 let params = self.parse_generic_params()?;
433 // We rely on AST validation to rule out invalid cases: There must not be type
434 // parameters, and the lifetime parameters must not have bounds.
441 pub fn check_lifetime(&mut self) -> bool {
442 self.expected_tokens.push(TokenType::Lifetime);
443 self.token.is_lifetime()
446 /// Parses a single lifetime `'a` or panics.
447 pub fn expect_lifetime(&mut self) -> Lifetime {
448 if let Some(ident) = self.token.lifetime() {
449 let span = self.token.span;
451 Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID }
453 self.span_bug(self.token.span, "not a lifetime")
457 pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> {
458 P(Ty { kind, span, id: ast::DUMMY_NODE_ID })