1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Conversion from AST representation of types to the ty.rs
12 //! representation. The main routine here is `ast_ty_to_ty()`: each use
13 //! is parameterized by an instance of `AstConv` and a `RegionScope`.
15 //! The parameterization of `ast_ty_to_ty()` is because it behaves
16 //! somewhat differently during the collect and check phases,
17 //! particularly with respect to looking up the types of top-level
18 //! items. In the collect phase, the crate context is used as the
19 //! `AstConv` instance; in this phase, the `get_item_type_scheme()` function
20 //! triggers a recursive call to `ty_of_item()` (note that
21 //! `ast_ty_to_ty()` will detect recursive types and report an error).
22 //! In the check phase, when the FnCtxt is used as the `AstConv`,
23 //! `get_item_type_scheme()` just looks up the item type in `tcx.tcache`.
25 //! The `RegionScope` trait controls what happens when the user does
26 //! not specify a region in some location where a region is required
27 //! (e.g., if the user writes `&Foo` as a type rather than `&'a Foo`).
28 //! See the `rscope` module for more details.
30 //! Unlike the `AstConv` trait, the region scope can change as we descend
31 //! the type. This is to accommodate the fact that (a) fn types are binding
32 //! scopes and (b) the default region may change. To understand case (a),
33 //! consider something like:
35 //! type foo = { x: &a.int, y: |&a.int| }
37 //! The type of `x` is an error because there is no region `a` in scope.
38 //! In the type of `y`, however, region `a` is considered a bound region
39 //! as it does not already appear in scope.
41 //! Case (b) says that if you have a type:
42 //! type foo<'a> = ...;
43 //! type bar = fn(&foo, &a.foo)
44 //! The fully expanded version of type bar is:
45 //! type bar = fn(&'foo &, &a.foo<'a>)
46 //! Note that the self region for the `foo` defaulted to `&` in the first
47 //! case but `&a` in the second. Basically, defaults that appear inside
48 //! an rptr (`&r.T`) use the region `r` that appears in the rptr.
50 use middle::astconv_util::{ast_ty_to_prim_ty, check_path_args, NO_TPS, NO_REGIONS};
51 use middle::const_eval;
53 use middle::resolve_lifetime as rl;
54 use middle::subst::{FnSpace, TypeSpace, SelfSpace, Subst, Substs};
55 use middle::subst::{VecPerParamSpace};
56 use middle::ty::{self, RegionEscape, Ty};
57 use rscope::{self, UnelidableRscope, RegionScope, SpecificRscope,
58 ShiftedRscope, BindingRscope};
60 use util::common::ErrorReported;
61 use util::nodemap::DefIdMap;
62 use util::ppaux::{self, Repr, UserString};
65 use std::iter::{repeat, AdditiveIterator};
66 use syntax::{abi, ast, ast_util};
67 use syntax::codemap::Span;
68 use syntax::parse::token;
69 use syntax::print::pprust;
71 pub trait AstConv<'tcx> {
72 fn tcx<'a>(&'a self) -> &'a ty::ctxt<'tcx>;
73 fn get_item_type_scheme(&self, id: ast::DefId) -> ty::TypeScheme<'tcx>;
74 fn get_trait_def(&self, id: ast::DefId) -> Rc<ty::TraitDef<'tcx>>;
76 /// Return an (optional) substitution to convert bound type parameters that
77 /// are in scope into free ones. This function should only return Some
79 /// See ParameterEnvironment::free_substs for more information.
80 fn get_free_substs(&self) -> Option<&Substs<'tcx>> {
84 /// What type should we use when a type is omitted?
85 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
87 /// Projecting an associated type from a (potentially)
88 /// higher-ranked trait reference is more complicated, because of
89 /// the possibility of late-bound regions appearing in the
90 /// associated type binding. This is not legal in function
91 /// signatures for that reason. In a function body, we can always
92 /// handle it because we can use inference variables to remove the
93 /// late-bound regions.
94 fn projected_ty_from_poly_trait_ref(&self,
96 poly_trait_ref: ty::PolyTraitRef<'tcx>,
100 if ty::binds_late_bound_regions(self.tcx(), &poly_trait_ref) {
101 self.tcx().sess.span_err(
103 "cannot extract an associated type from a higher-ranked trait bound \
107 // no late-bound regions, we can just ignore the binder
108 self.projected_ty(span, poly_trait_ref.0.clone(), item_name)
112 /// Project an associated type from a non-higher-ranked trait reference.
113 /// This is fairly straightforward and can be accommodated in any context.
114 fn projected_ty(&self,
116 _trait_ref: Rc<ty::TraitRef<'tcx>>,
117 _item_name: ast::Name)
120 self.tcx().sess.span_err(
122 "associated types are not accepted in this context");
128 pub fn ast_region_to_region(tcx: &ty::ctxt, lifetime: &ast::Lifetime)
130 let r = match tcx.named_region_map.get(&lifetime.id) {
132 // should have been recorded by the `resolve_lifetime` pass
133 tcx.sess.span_bug(lifetime.span, "unresolved lifetime");
136 Some(&rl::DefStaticRegion) => {
140 Some(&rl::DefLateBoundRegion(debruijn, id)) => {
141 ty::ReLateBound(debruijn, ty::BrNamed(ast_util::local_def(id), lifetime.name))
144 Some(&rl::DefEarlyBoundRegion(space, index, id)) => {
145 ty::ReEarlyBound(id, space, index, lifetime.name)
148 Some(&rl::DefFreeRegion(scope, id)) => {
149 ty::ReFree(ty::FreeRegion {
151 bound_region: ty::BrNamed(ast_util::local_def(id),
157 debug!("ast_region_to_region(lifetime={} id={}) yields {}",
165 pub fn opt_ast_region_to_region<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
169 opt_lifetime: &Option<ast::Lifetime>) -> ty::Region
171 let r = match *opt_lifetime {
172 Some(ref lifetime) => {
173 ast_region_to_region(this.tcx(), lifetime)
177 match rscope.anon_regions(default_span, 1) {
179 debug!("optional region in illegal location");
180 span_err!(this.tcx().sess, default_span, E0106,
181 "missing lifetime specifier");
184 let mut m = String::new();
186 for (i, (name, n)) in v.into_iter().enumerate() {
187 let help_name = if name.is_empty() {
188 format!("argument {}", i + 1)
190 format!("`{}`", name)
193 m.push_str(if n == 1 {
196 format!("one of {}'s {} elided lifetimes", help_name, n)
199 if len == 2 && i == 0 {
201 } else if i == len - 2 {
203 } else if i != len - 1 {
208 span_help!(this.tcx().sess, default_span,
209 "this function's return type contains a borrowed value, but \
210 the signature does not say which {} it is borrowed from",
213 span_help!(this.tcx().sess, default_span,
214 "this function's return type contains a borrowed value, but \
215 there is no value for it to be borrowed from");
216 span_help!(this.tcx().sess, default_span,
217 "consider giving it a 'static lifetime");
219 span_help!(this.tcx().sess, default_span,
220 "this function's return type contains a borrowed value, but \
221 the signature does not say whether it is borrowed from {}",
235 debug!("opt_ast_region_to_region(opt_lifetime={}) yields {}",
236 opt_lifetime.repr(this.tcx()),
242 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
243 /// returns an appropriate set of substitutions for this particular reference to `I`.
244 fn ast_path_substs_for_ty<'tcx,AC,RS>(
247 decl_generics: &ty::Generics<'tcx>,
250 where AC: AstConv<'tcx>, RS: RegionScope
252 let tcx = this.tcx();
254 // ast_path_substs() is only called to convert paths that are
255 // known to refer to traits, types, or structs. In these cases,
256 // all type parameters defined for the item being referenced will
257 // be in the TypeSpace or SelfSpace.
259 // Note: in the case of traits, the self parameter is also
260 // defined, but we don't currently create a `type_param_def` for
261 // `Self` because it is implicit.
262 assert!(decl_generics.regions.all(|d| d.space == TypeSpace));
263 assert!(decl_generics.types.all(|d| d.space != FnSpace));
265 let (regions, types, assoc_bindings) = match path.segments.last().unwrap().parameters {
266 ast::AngleBracketedParameters(ref data) => {
267 convert_angle_bracketed_parameters(this, rscope, data)
269 ast::ParenthesizedParameters(ref data) => {
272 "parenthesized parameters may only be used with a trait");
273 (Vec::new(), convert_parenthesized_parameters(this, data), Vec::new())
277 prohibit_projections(this.tcx(), assoc_bindings.as_slice());
279 create_substs_for_ast_path(this,
288 fn create_substs_for_ast_path<'tcx,AC,RS>(
292 decl_generics: &ty::Generics<'tcx>,
293 self_ty: Option<Ty<'tcx>>,
294 types: Vec<Ty<'tcx>>,
295 regions: Vec<ty::Region>)
297 where AC: AstConv<'tcx>, RS: RegionScope
299 let tcx = this.tcx();
301 // If the type is parameterized by the this region, then replace this
302 // region with the current anon region binding (in other words,
303 // whatever & would get replaced with).
304 let expected_num_region_params = decl_generics.regions.len(TypeSpace);
305 let supplied_num_region_params = regions.len();
306 let regions = if expected_num_region_params == supplied_num_region_params {
310 rscope.anon_regions(span, expected_num_region_params);
312 if supplied_num_region_params != 0 || anon_regions.is_err() {
313 span_err!(tcx.sess, span, E0107,
314 "wrong number of lifetime parameters: expected {}, found {}",
315 expected_num_region_params, supplied_num_region_params);
319 Ok(v) => v.into_iter().collect(),
320 Err(_) => range(0, expected_num_region_params)
321 .map(|_| ty::ReStatic).collect() // hokey
325 // Convert the type parameters supplied by the user.
326 let ty_param_defs = decl_generics.types.get_slice(TypeSpace);
327 let supplied_ty_param_count = types.len();
328 let formal_ty_param_count =
330 .take_while(|x| !ty::is_associated_type(tcx, x.def_id))
332 let required_ty_param_count =
335 x.default.is_none() &&
336 !ty::is_associated_type(tcx, x.def_id)
339 if supplied_ty_param_count < required_ty_param_count {
340 let expected = if required_ty_param_count < formal_ty_param_count {
345 this.tcx().sess.span_fatal(span,
346 format!("wrong number of type arguments: {} {}, found {}",
348 required_ty_param_count,
349 supplied_ty_param_count)[]);
350 } else if supplied_ty_param_count > formal_ty_param_count {
351 let expected = if required_ty_param_count < formal_ty_param_count {
356 this.tcx().sess.span_fatal(span,
357 format!("wrong number of type arguments: {} {}, found {}",
359 formal_ty_param_count,
360 supplied_ty_param_count)[]);
363 if supplied_ty_param_count > required_ty_param_count
364 && !this.tcx().sess.features.borrow().default_type_params {
365 span_err!(this.tcx().sess, span, E0108,
366 "default type parameters are experimental and possibly buggy");
367 span_help!(this.tcx().sess, span,
368 "add #![feature(default_type_params)] to the crate attributes to enable");
371 let mut substs = Substs::new_type(types, regions);
375 // If no self-type is provided, it's still possible that
376 // one was declared, because this could be an object type.
379 // If a self-type is provided, one should have been
380 // "declared" (in other words, this should be a
382 assert!(decl_generics.types.get_self().is_some());
383 substs.types.push(SelfSpace, ty);
387 for param in ty_param_defs[supplied_ty_param_count..].iter() {
388 match param.default {
390 // This is a default type parameter.
391 let default = default.subst_spanned(tcx,
394 substs.types.push(TypeSpace, default);
397 tcx.sess.span_bug(span, "extra parameter without default");
405 struct ConvertedBinding<'tcx> {
406 item_name: ast::Name,
411 fn convert_angle_bracketed_parameters<'tcx, AC, RS>(this: &AC,
413 data: &ast::AngleBracketedParameterData)
416 Vec<ConvertedBinding<'tcx>>)
417 where AC: AstConv<'tcx>, RS: RegionScope
419 let regions: Vec<_> =
420 data.lifetimes.iter()
421 .map(|l| ast_region_to_region(this.tcx(), l))
426 .map(|t| ast_ty_to_ty(this, rscope, &**t))
429 let assoc_bindings: Vec<_> =
431 .map(|b| ConvertedBinding { item_name: b.ident.name,
432 ty: ast_ty_to_ty(this, rscope, &*b.ty),
436 (regions, types, assoc_bindings)
439 /// Returns the appropriate lifetime to use for any output lifetimes
440 /// (if one exists) and a vector of the (pattern, number of lifetimes)
441 /// corresponding to each input type/pattern.
442 fn find_implied_output_region(input_tys: &[Ty], input_pats: Vec<String>)
443 -> (Option<ty::Region>, Vec<(String, uint)>)
445 let mut lifetimes_for_params: Vec<(String, uint)> = Vec::new();
446 let mut possible_implied_output_region = None;
448 for (input_type, input_pat) in input_tys.iter().zip(input_pats.into_iter()) {
449 let mut accumulator = Vec::new();
450 ty::accumulate_lifetimes_in_type(&mut accumulator, *input_type);
452 if accumulator.len() == 1 {
453 // there's a chance that the unique lifetime of this
454 // iteration will be the appropriate lifetime for output
455 // parameters, so lets store it.
456 possible_implied_output_region = Some(accumulator[0])
459 lifetimes_for_params.push((input_pat, accumulator.len()));
462 let implied_output_region = if lifetimes_for_params.iter().map(|&(_, n)| n).sum() == 1 {
463 assert!(possible_implied_output_region.is_some());
464 possible_implied_output_region
468 (implied_output_region, lifetimes_for_params)
471 fn convert_ty_with_lifetime_elision<'tcx,AC>(this: &AC,
472 implied_output_region: Option<ty::Region>,
473 param_lifetimes: Vec<(String, uint)>,
476 where AC: AstConv<'tcx>
478 match implied_output_region {
479 Some(implied_output_region) => {
480 let rb = SpecificRscope::new(implied_output_region);
481 ast_ty_to_ty(this, &rb, ty)
484 // All regions must be explicitly specified in the output
485 // if the lifetime elision rules do not apply. This saves
486 // the user from potentially-confusing errors.
487 let rb = UnelidableRscope::new(param_lifetimes);
488 ast_ty_to_ty(this, &rb, ty)
493 fn convert_parenthesized_parameters<'tcx,AC>(this: &AC,
494 data: &ast::ParenthesizedParameterData)
496 where AC: AstConv<'tcx>
498 let binding_rscope = BindingRscope::new();
499 let inputs = data.inputs.iter()
500 .map(|a_t| ast_ty_to_ty(this, &binding_rscope, &**a_t))
501 .collect::<Vec<Ty<'tcx>>>();
503 let input_params: Vec<_> = repeat(String::new()).take(inputs.len()).collect();
504 let (implied_output_region,
505 params_lifetimes) = find_implied_output_region(&*inputs, input_params);
507 let input_ty = ty::mk_tup(this.tcx(), inputs);
509 let output = match data.output {
510 Some(ref output_ty) => convert_ty_with_lifetime_elision(this,
511 implied_output_region,
514 None => ty::mk_nil(this.tcx()),
517 vec![input_ty, output]
520 pub fn instantiate_poly_trait_ref<'tcx,AC,RS>(
523 ast_trait_ref: &ast::PolyTraitRef,
524 self_ty: Option<Ty<'tcx>>,
525 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
526 -> ty::PolyTraitRef<'tcx>
527 where AC: AstConv<'tcx>, RS: RegionScope
529 let mut projections = Vec::new();
532 instantiate_trait_ref(this, rscope, &ast_trait_ref.trait_ref,
533 self_ty, Some(&mut projections));
535 for projection in projections.into_iter() {
536 poly_projections.push(ty::Binder(projection));
539 ty::Binder(trait_ref)
542 /// Instantiates the path for the given trait reference, assuming that it's
543 /// bound to a valid trait type. Returns the def_id for the defining trait.
544 /// Fails if the type is a type other than a trait type.
546 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
547 /// are disallowed. Otherwise, they are pushed onto the vector given.
548 pub fn instantiate_trait_ref<'tcx,AC,RS>(
551 ast_trait_ref: &ast::TraitRef,
552 self_ty: Option<Ty<'tcx>>,
553 projections: Option<&mut Vec<ty::ProjectionPredicate<'tcx>>>)
554 -> Rc<ty::TraitRef<'tcx>>
555 where AC: AstConv<'tcx>, RS: RegionScope
557 match ::lookup_def_tcx(this.tcx(), ast_trait_ref.path.span, ast_trait_ref.ref_id) {
558 def::DefTrait(trait_def_id) => {
559 let trait_ref = ast_path_to_trait_ref(this,
565 this.tcx().trait_refs.borrow_mut().insert(ast_trait_ref.ref_id, trait_ref.clone());
569 this.tcx().sess.span_fatal(
570 ast_trait_ref.path.span,
571 format!("`{}` is not a trait", ast_trait_ref.path.user_string(this.tcx()))[]);
576 fn ast_path_to_trait_ref<'a,'tcx,AC,RS>(
579 trait_def_id: ast::DefId,
580 self_ty: Option<Ty<'tcx>>,
582 mut projections: Option<&mut Vec<ty::ProjectionPredicate<'tcx>>>)
583 -> Rc<ty::TraitRef<'tcx>>
584 where AC: AstConv<'tcx>, RS: RegionScope
586 debug!("ast_path_to_trait_ref {}", path);
587 let trait_def = this.get_trait_def(trait_def_id);
589 // the trait reference introduces a binding level here, so
590 // we need to shift the `rscope`. It'd be nice if we could
591 // do away with this rscope stuff and work this knowledge
592 // into resolve_lifetimes, as we do with non-omitted
593 // lifetimes. Oh well, not there yet.
594 let shifted_rscope = ShiftedRscope::new(rscope);
596 let (regions, types, assoc_bindings) = match path.segments.last().unwrap().parameters {
597 ast::AngleBracketedParameters(ref data) => {
598 convert_angle_bracketed_parameters(this, &shifted_rscope, data)
600 ast::ParenthesizedParameters(ref data) => {
601 // For now, require that parenthetical notation be used
602 // only with `Fn()` etc.
603 if !this.tcx().sess.features.borrow().unboxed_closures &&
604 this.tcx().lang_items.fn_trait_kind(trait_def_id).is_none()
606 this.tcx().sess.span_err(path.span,
607 "parenthetical notation is only stable when \
608 used with the `Fn` family of traits");
609 span_help!(this.tcx().sess, path.span,
610 "add `#![feature(unboxed_closures)]` to \
611 the crate attributes to enable");
614 (Vec::new(), convert_parenthesized_parameters(this, data), Vec::new())
618 let substs = create_substs_for_ast_path(this,
625 let substs = this.tcx().mk_substs(substs);
627 let trait_ref = Rc::new(ty::TraitRef::new(trait_def_id, substs));
631 prohibit_projections(this.tcx(), assoc_bindings.as_slice());
634 for binding in assoc_bindings.iter() {
635 match ast_type_binding_to_projection_predicate(this, trait_ref.clone(), binding) {
636 Ok(pp) => { v.push(pp); }
637 Err(ErrorReported) => { }
646 pub fn ast_type_binding_to_projection_predicate<'tcx,AC>(
648 trait_ref: Rc<ty::TraitRef<'tcx>>,
649 binding: &ConvertedBinding<'tcx>)
650 -> Result<ty::ProjectionPredicate<'tcx>, ErrorReported>
651 where AC : AstConv<'tcx>
653 // Given something like `U : SomeTrait<T=X>`, we want to produce a
654 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
655 // subtle in the event that `T` is defined in a supertrait of
656 // `SomeTrait`, because in that case we need to upcast.
658 // That is, consider this case:
661 // trait SubTrait : SuperTrait<int> { }
662 // trait SuperTrait<A> { type T; }
664 // ... B : SubTrait<T=foo> ...
667 // We want to produce `<B as SuperTrait<int>>::T == foo`.
669 // FIXME(#19541): supertrait upcasting not actually impl'd :)
671 if !trait_defines_associated_type_named(this, trait_ref.def_id, binding.item_name) {
672 this.tcx().sess.span_err(
674 format!("no associated type `{}` defined in `{}`",
675 token::get_name(binding.item_name),
676 trait_ref.user_string(this.tcx())).as_slice());
677 return Err(ErrorReported);
680 Ok(ty::ProjectionPredicate {
681 projection_ty: ty::ProjectionTy {
682 trait_ref: trait_ref,
683 item_name: binding.item_name,
689 pub fn ast_path_to_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
694 -> TypeAndSubsts<'tcx>
696 let tcx = this.tcx();
700 } = this.get_item_type_scheme(did);
702 let substs = ast_path_substs_for_ty(this,
706 let ty = decl_ty.subst(tcx, &substs);
707 TypeAndSubsts { substs: substs, ty: ty }
710 /// Returns the type that this AST path refers to. If the path has no type
711 /// parameters and the corresponding type has type parameters, fresh type
712 /// and/or region variables are substituted.
714 /// This is used when checking the constructor in struct literals.
715 pub fn ast_path_to_ty_relaxed<'tcx,AC,RS>(
720 -> TypeAndSubsts<'tcx>
721 where AC : AstConv<'tcx>, RS : RegionScope
723 let tcx = this.tcx();
727 } = this.get_item_type_scheme(did);
730 generics.has_type_params(TypeSpace) || generics.has_region_params(TypeSpace);
734 path.segments.iter().all(|s| s.parameters.is_empty());
736 let substs = if needs_defaults {
737 let type_params: Vec<_> = range(0, generics.types.len(TypeSpace))
738 .map(|_| this.ty_infer(path.span)).collect();
740 rscope.anon_regions(path.span, generics.regions.len(TypeSpace))
742 Substs::new(VecPerParamSpace::params_from_type(type_params),
743 VecPerParamSpace::params_from_type(region_params))
745 ast_path_substs_for_ty(this, rscope, &generics, path)
748 let ty = decl_ty.subst(tcx, &substs);
755 /// Converts the given AST type to a built-in type. A "built-in type" is, at
756 /// present, either a core numeric type, a string, or `Box`.
757 pub fn ast_ty_to_builtin_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
761 -> Option<Ty<'tcx>> {
762 match ast_ty_to_prim_ty(this.tcx(), ast_ty) {
763 Some(typ) => return Some(typ),
768 ast::TyPath(ref path, id) => {
769 let a_def = match this.tcx().def_map.borrow().get(&id) {
773 .span_bug(ast_ty.span,
774 format!("unbound path {}",
775 path.repr(this.tcx()))[])
780 // FIXME(#12938): This is a hack until we have full support for
784 def::DefStruct(did) if Some(did) == this.tcx().lang_items.owned_box() => {
785 let ty = ast_path_to_ty(this, rscope, did, path).ty;
787 ty::ty_struct(struct_def_id, ref substs) => {
788 assert_eq!(struct_def_id, did);
789 assert_eq!(substs.types.len(TypeSpace), 1);
790 let referent_ty = *substs.types.get(TypeSpace, 0);
791 Some(ty::mk_uniq(this.tcx(), referent_ty))
794 this.tcx().sess.span_bug(
796 format!("converting `Box` to `{}`",
797 ty.repr(this.tcx()))[]);
808 type TraitAndProjections<'tcx> = (ty::PolyTraitRef<'tcx>, Vec<ty::PolyProjectionPredicate<'tcx>>);
810 fn ast_ty_to_trait_ref<'tcx,AC,RS>(this: &AC,
813 bounds: &[ast::TyParamBound])
814 -> Result<TraitAndProjections<'tcx>, ErrorReported>
815 where AC : AstConv<'tcx>, RS : RegionScope
818 * In a type like `Foo + Send`, we want to wait to collect the
819 * full set of bounds before we make the object type, because we
820 * need them to infer a region bound. (For example, if we tried
821 * made a type from just `Foo`, then it wouldn't be enough to
822 * infer a 'static bound, and hence the user would get an error.)
823 * So this function is used when we're dealing with a sum type to
824 * convert the LHS. It only accepts a type that refers to a trait
825 * name, and reports an error otherwise.
829 ast::TyPath(ref path, id) => {
830 match this.tcx().def_map.borrow().get(&id) {
831 Some(&def::DefTrait(trait_def_id)) => {
832 let mut projection_bounds = Vec::new();
833 let trait_ref = ty::Binder(ast_path_to_trait_ref(this,
838 Some(&mut projection_bounds)));
839 let projection_bounds = projection_bounds.into_iter()
842 Ok((trait_ref, projection_bounds))
845 span_err!(this.tcx().sess, ty.span, E0172, "expected a reference to a trait");
851 span_err!(this.tcx().sess, ty.span, E0178,
852 "expected a path on the left-hand side of `+`, not `{}`",
853 pprust::ty_to_string(ty));
855 ast::TyRptr(None, ref mut_ty) => {
856 span_note!(this.tcx().sess, ty.span,
857 "perhaps you meant `&{}({} +{})`? (per RFC 438)",
858 ppaux::mutability_to_string(mut_ty.mutbl),
859 pprust::ty_to_string(&*mut_ty.ty),
860 pprust::bounds_to_string(bounds));
862 ast::TyRptr(Some(ref lt), ref mut_ty) => {
863 span_note!(this.tcx().sess, ty.span,
864 "perhaps you meant `&{} {}({} +{})`? (per RFC 438)",
865 pprust::lifetime_to_string(lt),
866 ppaux::mutability_to_string(mut_ty.mutbl),
867 pprust::ty_to_string(&*mut_ty.ty),
868 pprust::bounds_to_string(bounds));
872 span_note!(this.tcx().sess, ty.span,
873 "perhaps you forgot parentheses? (per RFC 438)");
881 fn trait_ref_to_object_type<'tcx,AC,RS>(this: &AC,
884 trait_ref: ty::PolyTraitRef<'tcx>,
885 projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
886 bounds: &[ast::TyParamBound])
888 where AC : AstConv<'tcx>, RS : RegionScope
890 let existential_bounds = conv_existential_bounds(this,
893 Some(trait_ref.clone()),
897 let result = ty::mk_trait(this.tcx(), trait_ref, existential_bounds);
898 debug!("trait_ref_to_object_type: result={}",
899 result.repr(this.tcx()));
904 fn associated_path_def_to_ty<'tcx>(this: &AstConv<'tcx>,
906 provenance: def::TyParamProvenance,
907 assoc_name: ast::Name)
910 let tcx = this.tcx();
911 let ty_param_def_id = provenance.def_id();
912 let mut suitable_bounds: Vec<_>;
913 let ty_param_name: ast::Name;
914 { // contain scope of refcell:
915 let ty_param_defs = tcx.ty_param_defs.borrow();
916 let ty_param_def = &ty_param_defs[ty_param_def_id.node];
917 ty_param_name = ty_param_def.name;
919 // FIXME(#19541): we should consider associated types in
920 // super-traits. Probably by elaborating the bounds.
923 ty_param_def.bounds.trait_bounds // FIXME(#20300) -- search where clauses, not bounds
926 .filter(|b| trait_defines_associated_type_named(this, b.def_id(), assoc_name))
930 if suitable_bounds.len() == 0 {
931 tcx.sess.span_err(ast_ty.span,
932 format!("associated type `{}` not found for type parameter `{}`",
933 token::get_name(assoc_name),
934 token::get_name(ty_param_name)).as_slice());
935 return this.tcx().types.err;
938 if suitable_bounds.len() > 1 {
939 tcx.sess.span_err(ast_ty.span,
940 format!("ambiguous associated type `{}` in bounds of `{}`",
941 token::get_name(assoc_name),
942 token::get_name(ty_param_name)).as_slice());
944 for suitable_bound in suitable_bounds.iter() {
945 span_note!(this.tcx().sess, ast_ty.span,
946 "associated type `{}` could derive from `{}`",
947 token::get_name(ty_param_name),
948 suitable_bound.user_string(this.tcx()));
952 let suitable_bound = suitable_bounds.pop().unwrap().clone();
953 return this.projected_ty_from_poly_trait_ref(ast_ty.span, suitable_bound, assoc_name);
956 fn trait_defines_associated_type_named(this: &AstConv,
957 trait_def_id: ast::DefId,
958 assoc_name: ast::Name)
961 let tcx = this.tcx();
962 let trait_def = ty::lookup_trait_def(tcx, trait_def_id);
963 trait_def.associated_type_names.contains(&assoc_name)
966 fn qpath_to_ty<'tcx,AC,RS>(this: &AC,
968 ast_ty: &ast::Ty, // the TyQPath
971 where AC: AstConv<'tcx>, RS: RegionScope
973 debug!("qpath_to_ty(ast_ty={})",
974 ast_ty.repr(this.tcx()));
976 let self_type = ast_ty_to_ty(this, rscope, &*qpath.self_type);
978 debug!("qpath_to_ty: self_type={}", self_type.repr(this.tcx()));
980 let trait_ref = instantiate_trait_ref(this,
986 debug!("qpath_to_ty: trait_ref={}", trait_ref.repr(this.tcx()));
988 return this.projected_ty(ast_ty.span,
990 qpath.item_name.name);
993 // Parses the programmer's textual representation of a type into our
994 // internal notion of a type.
995 pub fn ast_ty_to_ty<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(
996 this: &AC, rscope: &RS, ast_ty: &ast::Ty) -> Ty<'tcx>
998 debug!("ast_ty_to_ty(ast_ty={})",
999 ast_ty.repr(this.tcx()));
1001 let tcx = this.tcx();
1003 let mut ast_ty_to_ty_cache = tcx.ast_ty_to_ty_cache.borrow_mut();
1004 match ast_ty_to_ty_cache.get(&ast_ty.id) {
1005 Some(&ty::atttce_resolved(ty)) => return ty,
1006 Some(&ty::atttce_unresolved) => {
1007 tcx.sess.span_fatal(ast_ty.span,
1008 "illegal recursive type; insert an enum \
1009 or struct in the cycle, if this is \
1012 None => { /* go on */ }
1014 ast_ty_to_ty_cache.insert(ast_ty.id, ty::atttce_unresolved);
1015 drop(ast_ty_to_ty_cache);
1017 let typ = ast_ty_to_builtin_ty(this, rscope, ast_ty).unwrap_or_else(|| {
1019 ast::TyVec(ref ty) => {
1020 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty), None)
1022 ast::TyObjectSum(ref ty, ref bounds) => {
1023 match ast_ty_to_trait_ref(this, rscope, &**ty, bounds[]) {
1024 Ok((trait_ref, projection_bounds)) => {
1025 trait_ref_to_object_type(this, rscope, ast_ty.span,
1026 trait_ref, projection_bounds, bounds[])
1028 Err(ErrorReported) => {
1029 this.tcx().types.err
1033 ast::TyPtr(ref mt) => {
1034 ty::mk_ptr(tcx, ty::mt {
1035 ty: ast_ty_to_ty(this, rscope, &*mt.ty),
1039 ast::TyRptr(ref region, ref mt) => {
1040 let r = opt_ast_region_to_region(this, rscope, ast_ty.span, region);
1041 debug!("ty_rptr r={}", r.repr(this.tcx()));
1042 let t = ast_ty_to_ty(this, rscope, &*mt.ty);
1043 ty::mk_rptr(tcx, tcx.mk_region(r), ty::mt {ty: t, mutbl: mt.mutbl})
1045 ast::TyTup(ref fields) => {
1046 let flds = fields.iter()
1047 .map(|t| ast_ty_to_ty(this, rscope, &**t))
1049 ty::mk_tup(tcx, flds)
1051 ast::TyParen(ref typ) => ast_ty_to_ty(this, rscope, &**typ),
1052 ast::TyBareFn(ref bf) => {
1053 if bf.decl.variadic && bf.abi != abi::C {
1054 tcx.sess.span_err(ast_ty.span,
1055 "variadic function must have C calling convention");
1057 let bare_fn = ty_of_bare_fn(this, bf.unsafety, bf.abi, &*bf.decl);
1058 ty::mk_bare_fn(tcx, None, tcx.mk_bare_fn(bare_fn))
1060 ast::TyClosure(ref f) => {
1061 // Use corresponding trait store to figure out default bounds
1062 // if none were specified.
1063 let bounds = conv_existential_bounds(this,
1068 f.bounds.as_slice());
1069 let region_bound = bounds.region_bound;
1070 let fn_decl = ty_of_closure(this,
1074 ty::RegionTraitStore(
1080 ty::mk_closure(tcx, fn_decl)
1082 ast::TyPolyTraitRef(ref bounds) => {
1083 conv_ty_poly_trait_ref(this, rscope, ast_ty.span, bounds[])
1085 ast::TyPath(ref path, id) => {
1086 let a_def = match tcx.def_map.borrow().get(&id) {
1089 .span_bug(ast_ty.span,
1090 format!("unbound path {}",
1096 def::DefTrait(trait_def_id) => {
1097 // N.B. this case overlaps somewhat with
1098 // TyObjectSum, see that fn for details
1099 let mut projection_bounds = Vec::new();
1100 let trait_ref = ast_path_to_trait_ref(this,
1105 Some(&mut projection_bounds));
1106 let trait_ref = ty::Binder(trait_ref);
1107 let projection_bounds = projection_bounds.into_iter()
1110 trait_ref_to_object_type(this, rscope, path.span,
1111 trait_ref, projection_bounds, &[])
1113 def::DefTy(did, _) | def::DefStruct(did) => {
1114 ast_path_to_ty(this, rscope, did, path).ty
1116 def::DefTyParam(space, index, _, name) => {
1117 check_path_args(tcx, path, NO_TPS | NO_REGIONS);
1118 ty::mk_param(tcx, space, index, name)
1120 def::DefSelfTy(_) => {
1121 // n.b.: resolve guarantees that the this type only appears in a
1122 // trait, which we rely upon in various places when creating
1124 check_path_args(tcx, path, NO_TPS | NO_REGIONS);
1125 ty::mk_self_type(tcx)
1127 def::DefMod(id) => {
1128 tcx.sess.span_fatal(ast_ty.span,
1129 format!("found module name used as a type: {}",
1130 tcx.map.node_to_string(id.node))[]);
1132 def::DefPrimTy(_) => {
1133 panic!("DefPrimTy arm missed in previous ast_ty_to_prim_ty call");
1135 def::DefAssociatedTy(trait_type_id) => {
1136 let path_str = tcx.map.path_to_string(
1137 tcx.map.get_parent(trait_type_id.node));
1138 tcx.sess.span_err(ast_ty.span,
1139 format!("ambiguous associated \
1140 type; specify the type \
1141 using the syntax `<Type \
1150 this.tcx().types.err
1152 def::DefAssociatedPath(provenance, assoc_ident) => {
1153 associated_path_def_to_ty(this, ast_ty, provenance, assoc_ident.name)
1156 tcx.sess.span_fatal(ast_ty.span,
1157 format!("found value name used \
1163 ast::TyQPath(ref qpath) => {
1164 qpath_to_ty(this, rscope, ast_ty, &**qpath)
1166 ast::TyFixedLengthVec(ref ty, ref e) => {
1167 match const_eval::eval_const_expr_partial(tcx, &**e) {
1170 const_eval::const_int(i) =>
1171 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty),
1173 const_eval::const_uint(i) =>
1174 ty::mk_vec(tcx, ast_ty_to_ty(this, rscope, &**ty),
1177 tcx.sess.span_fatal(
1178 ast_ty.span, "expected constant expr for array length");
1183 tcx.sess.span_fatal(
1185 format!("expected constant expr for array \
1191 ast::TyTypeof(ref _e) => {
1192 tcx.sess.span_bug(ast_ty.span, "typeof is reserved but unimplemented");
1195 // TyInfer also appears as the type of arguments or return
1196 // values in a ExprClosure, or as
1197 // the type of local variables. Both of these cases are
1198 // handled specially and will not descend into this routine.
1199 this.ty_infer(ast_ty.span)
1204 tcx.ast_ty_to_ty_cache.borrow_mut().insert(ast_ty.id, ty::atttce_resolved(typ));
1208 pub fn ty_of_arg<'tcx, AC: AstConv<'tcx>, RS: RegionScope>(this: &AC, rscope: &RS,
1210 expected_ty: Option<Ty<'tcx>>)
1213 ast::TyInfer if expected_ty.is_some() => expected_ty.unwrap(),
1214 ast::TyInfer => this.ty_infer(a.ty.span),
1215 _ => ast_ty_to_ty(this, rscope, &*a.ty),
1219 struct SelfInfo<'a, 'tcx> {
1220 untransformed_self_ty: Ty<'tcx>,
1221 explicit_self: &'a ast::ExplicitSelf,
1224 pub fn ty_of_method<'tcx, AC: AstConv<'tcx>>(
1226 unsafety: ast::Unsafety,
1227 untransformed_self_ty: Ty<'tcx>,
1228 explicit_self: &ast::ExplicitSelf,
1231 -> (ty::BareFnTy<'tcx>, ty::ExplicitSelfCategory) {
1232 let self_info = Some(SelfInfo {
1233 untransformed_self_ty: untransformed_self_ty,
1234 explicit_self: explicit_self,
1236 let (bare_fn_ty, optional_explicit_self_category) =
1237 ty_of_method_or_bare_fn(this,
1242 (bare_fn_ty, optional_explicit_self_category.unwrap())
1245 pub fn ty_of_bare_fn<'tcx, AC: AstConv<'tcx>>(this: &AC, unsafety: ast::Unsafety, abi: abi::Abi,
1246 decl: &ast::FnDecl) -> ty::BareFnTy<'tcx> {
1247 let (bare_fn_ty, _) = ty_of_method_or_bare_fn(this, unsafety, abi, None, decl);
1251 fn ty_of_method_or_bare_fn<'a, 'tcx, AC: AstConv<'tcx>>(
1253 unsafety: ast::Unsafety,
1255 opt_self_info: Option<SelfInfo<'a, 'tcx>>,
1257 -> (ty::BareFnTy<'tcx>,
1258 Option<ty::ExplicitSelfCategory>)
1260 debug!("ty_of_method_or_bare_fn");
1262 // New region names that appear inside of the arguments of the function
1263 // declaration are bound to that function type.
1264 let rb = rscope::BindingRscope::new();
1266 // `implied_output_region` is the region that will be assumed for any
1267 // region parameters in the return type. In accordance with the rules for
1268 // lifetime elision, we can determine it in two ways. First (determined
1269 // here), if self is by-reference, then the implied output region is the
1270 // region of the self parameter.
1271 let mut explicit_self_category_result = None;
1272 let (self_ty, mut implied_output_region) = match opt_self_info {
1273 None => (None, None),
1274 Some(self_info) => {
1275 // This type comes from an impl or trait; no late-bound
1276 // regions should be present.
1277 assert!(!self_info.untransformed_self_ty.has_escaping_regions());
1279 // Figure out and record the explicit self category.
1280 let explicit_self_category =
1281 determine_explicit_self_category(this, &rb, &self_info);
1282 explicit_self_category_result = Some(explicit_self_category);
1283 match explicit_self_category {
1284 ty::StaticExplicitSelfCategory => {
1287 ty::ByValueExplicitSelfCategory => {
1288 (Some(self_info.untransformed_self_ty), None)
1290 ty::ByReferenceExplicitSelfCategory(region, mutability) => {
1291 (Some(ty::mk_rptr(this.tcx(),
1292 this.tcx().mk_region(region),
1294 ty: self_info.untransformed_self_ty,
1299 ty::ByBoxExplicitSelfCategory => {
1300 (Some(ty::mk_uniq(this.tcx(), self_info.untransformed_self_ty)), None)
1306 // HACK(eddyb) replace the fake self type in the AST with the actual type.
1307 let input_params = if self_ty.is_some() {
1308 decl.inputs.slice_from(1)
1312 let input_tys = input_params.iter().map(|a| ty_of_arg(this, &rb, a, None));
1313 let input_pats: Vec<String> = input_params.iter()
1314 .map(|a| pprust::pat_to_string(&*a.pat))
1316 let self_and_input_tys: Vec<Ty> =
1317 self_ty.into_iter().chain(input_tys).collect();
1320 // Second, if there was exactly one lifetime (either a substitution or a
1321 // reference) in the arguments, then any anonymous regions in the output
1322 // have that lifetime.
1323 let lifetimes_for_params = if implied_output_region.is_none() {
1324 let input_tys = if self_ty.is_some() {
1325 // Skip the first argument if `self` is present.
1326 self_and_input_tys.slice_from(1)
1328 self_and_input_tys.slice_from(0)
1331 let (ior, lfp) = find_implied_output_region(input_tys, input_pats);
1332 implied_output_region = ior;
1338 let output_ty = match decl.output {
1339 ast::Return(ref output) if output.node == ast::TyInfer =>
1340 ty::FnConverging(this.ty_infer(output.span)),
1341 ast::Return(ref output) =>
1342 ty::FnConverging(convert_ty_with_lifetime_elision(this,
1343 implied_output_region,
1344 lifetimes_for_params,
1346 ast::NoReturn(_) => ty::FnDiverging
1352 sig: ty::Binder(ty::FnSig {
1353 inputs: self_and_input_tys,
1355 variadic: decl.variadic
1357 }, explicit_self_category_result)
1360 fn determine_explicit_self_category<'a, 'tcx, AC: AstConv<'tcx>,
1364 self_info: &SelfInfo<'a, 'tcx>)
1365 -> ty::ExplicitSelfCategory
1367 return match self_info.explicit_self.node {
1368 ast::SelfStatic => ty::StaticExplicitSelfCategory,
1369 ast::SelfValue(_) => ty::ByValueExplicitSelfCategory,
1370 ast::SelfRegion(ref lifetime, mutability, _) => {
1372 opt_ast_region_to_region(this,
1374 self_info.explicit_self.span,
1376 ty::ByReferenceExplicitSelfCategory(region, mutability)
1378 ast::SelfExplicit(ref ast_type, _) => {
1379 let explicit_type = ast_ty_to_ty(this, rscope, &**ast_type);
1381 // We wish to (for now) categorize an explicit self
1382 // declaration like `self: SomeType` into either `self`,
1383 // `&self`, `&mut self`, or `Box<self>`. We do this here
1384 // by some simple pattern matching. A more precise check
1385 // is done later in `check_method_self_type()`.
1390 // impl Foo for &T {
1391 // // Legal declarations:
1392 // fn method1(self: &&T); // ByReferenceExplicitSelfCategory
1393 // fn method2(self: &T); // ByValueExplicitSelfCategory
1394 // fn method3(self: Box<&T>); // ByBoxExplicitSelfCategory
1396 // // Invalid cases will be caught later by `check_method_self_type`:
1397 // fn method_err1(self: &mut T); // ByReferenceExplicitSelfCategory
1401 // To do the check we just count the number of "modifiers"
1402 // on each type and compare them. If they are the same or
1403 // the impl has more, we call it "by value". Otherwise, we
1404 // look at the outermost modifier on the method decl and
1405 // call it by-ref, by-box as appropriate. For method1, for
1406 // example, the impl type has one modifier, but the method
1407 // type has two, so we end up with
1408 // ByReferenceExplicitSelfCategory.
1410 let impl_modifiers = count_modifiers(self_info.untransformed_self_ty);
1411 let method_modifiers = count_modifiers(explicit_type);
1413 debug!("determine_explicit_self_category(self_info.untransformed_self_ty={} \
1416 self_info.untransformed_self_ty.repr(this.tcx()),
1417 explicit_type.repr(this.tcx()),
1421 if impl_modifiers >= method_modifiers {
1422 ty::ByValueExplicitSelfCategory
1424 match explicit_type.sty {
1425 ty::ty_rptr(r, mt) => ty::ByReferenceExplicitSelfCategory(*r, mt.mutbl),
1426 ty::ty_uniq(_) => ty::ByBoxExplicitSelfCategory,
1427 _ => ty::ByValueExplicitSelfCategory,
1433 fn count_modifiers(ty: Ty) -> uint {
1435 ty::ty_rptr(_, mt) => count_modifiers(mt.ty) + 1,
1436 ty::ty_uniq(t) => count_modifiers(t) + 1,
1442 pub fn ty_of_closure<'tcx, AC: AstConv<'tcx>>(
1444 unsafety: ast::Unsafety,
1445 onceness: ast::Onceness,
1446 bounds: ty::ExistentialBounds<'tcx>,
1447 store: ty::TraitStore,
1450 expected_sig: Option<ty::FnSig<'tcx>>)
1451 -> ty::ClosureTy<'tcx>
1453 debug!("ty_of_closure(expected_sig={})",
1454 expected_sig.repr(this.tcx()));
1456 // new region names that appear inside of the fn decl are bound to
1457 // that function type
1458 let rb = rscope::BindingRscope::new();
1460 let input_tys: Vec<_> = decl.inputs.iter().enumerate().map(|(i, a)| {
1461 let expected_arg_ty = expected_sig.as_ref().and_then(|e| {
1462 // no guarantee that the correct number of expected args
1464 if i < e.inputs.len() {
1470 ty_of_arg(this, &rb, a, expected_arg_ty)
1473 let expected_ret_ty = expected_sig.map(|e| e.output);
1475 let output_ty = match decl.output {
1476 ast::Return(ref output) if output.node == ast::TyInfer && expected_ret_ty.is_some() =>
1477 expected_ret_ty.unwrap(),
1478 ast::Return(ref output) if output.node == ast::TyInfer =>
1479 ty::FnConverging(this.ty_infer(output.span)),
1480 ast::Return(ref output) =>
1481 ty::FnConverging(ast_ty_to_ty(this, &rb, &**output)),
1482 ast::NoReturn(_) => ty::FnDiverging
1485 debug!("ty_of_closure: input_tys={}", input_tys.repr(this.tcx()));
1486 debug!("ty_of_closure: output_ty={}", output_ty.repr(this.tcx()));
1494 sig: ty::Binder(ty::FnSig {inputs: input_tys,
1496 variadic: decl.variadic}),
1500 /// Given an existential type like `Foo+'a+Bar`, this routine converts the `'a` and `Bar` intos an
1501 /// `ExistentialBounds` struct. The `main_trait_refs` argument specifies the `Foo` -- it is absent
1502 /// for closures. Eventually this should all be normalized, I think, so that there is no "main
1503 /// trait ref" and instead we just have a flat list of bounds as the existential type.
1504 pub fn conv_existential_bounds<'tcx, AC: AstConv<'tcx>, RS:RegionScope>(
1508 principal_trait_ref: Option<ty::PolyTraitRef<'tcx>>, // None for boxed closures
1509 projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
1510 ast_bounds: &[ast::TyParamBound])
1511 -> ty::ExistentialBounds<'tcx>
1513 let partitioned_bounds =
1514 partition_bounds(this.tcx(), span, ast_bounds);
1516 conv_existential_bounds_from_partitioned_bounds(
1517 this, rscope, span, principal_trait_ref, projection_bounds, partitioned_bounds)
1520 fn conv_ty_poly_trait_ref<'tcx, AC, RS>(
1524 ast_bounds: &[ast::TyParamBound])
1526 where AC: AstConv<'tcx>, RS:RegionScope
1528 let mut partitioned_bounds = partition_bounds(this.tcx(), span, ast_bounds[]);
1530 let mut projection_bounds = Vec::new();
1531 let main_trait_bound = if !partitioned_bounds.trait_bounds.is_empty() {
1532 let trait_bound = partitioned_bounds.trait_bounds.remove(0);
1533 Some(instantiate_poly_trait_ref(this,
1537 &mut projection_bounds))
1539 this.tcx().sess.span_err(
1541 "at least one non-builtin trait is required for an object type");
1546 conv_existential_bounds_from_partitioned_bounds(this,
1549 main_trait_bound.clone(),
1551 partitioned_bounds);
1553 match main_trait_bound {
1554 None => this.tcx().types.err,
1555 Some(principal) => ty::mk_trait(this.tcx(), principal, bounds)
1559 pub fn conv_existential_bounds_from_partitioned_bounds<'tcx, AC, RS>(
1563 principal_trait_ref: Option<ty::PolyTraitRef<'tcx>>, // None for boxed closures
1564 mut projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>, // Empty for boxed closures
1565 partitioned_bounds: PartitionedBounds)
1566 -> ty::ExistentialBounds<'tcx>
1567 where AC: AstConv<'tcx>, RS:RegionScope
1569 let PartitionedBounds { builtin_bounds,
1574 if !trait_bounds.is_empty() {
1575 let b = &trait_bounds[0];
1576 this.tcx().sess.span_err(
1577 b.trait_ref.path.span,
1578 format!("only the builtin traits can be used \
1579 as closure or object bounds")[]);
1582 let region_bound = compute_region_bound(this,
1585 region_bounds.as_slice(),
1586 principal_trait_ref,
1589 ty::sort_bounds_list(projection_bounds.as_mut_slice());
1591 ty::ExistentialBounds {
1592 region_bound: region_bound,
1593 builtin_bounds: builtin_bounds,
1594 projection_bounds: projection_bounds,
1598 /// Given the bounds on a type parameter / existential type, determines what single region bound
1599 /// (if any) we can use to summarize this type. The basic idea is that we will use the bound the
1600 /// user provided, if they provided one, and otherwise search the supertypes of trait bounds for
1601 /// region bounds. It may be that we can derive no bound at all, in which case we return `None`.
1602 fn compute_opt_region_bound<'tcx>(tcx: &ty::ctxt<'tcx>,
1604 explicit_region_bounds: &[&ast::Lifetime],
1605 principal_trait_ref: Option<ty::PolyTraitRef<'tcx>>,
1606 builtin_bounds: ty::BuiltinBounds)
1607 -> Option<ty::Region>
1609 debug!("compute_opt_region_bound(explicit_region_bounds={}, \
1610 principal_trait_ref={}, builtin_bounds={})",
1611 explicit_region_bounds,
1612 principal_trait_ref.repr(tcx),
1613 builtin_bounds.repr(tcx));
1615 if explicit_region_bounds.len() > 1 {
1617 explicit_region_bounds[1].span,
1618 format!("only a single explicit lifetime bound is permitted").as_slice());
1621 if explicit_region_bounds.len() != 0 {
1622 // Explicitly specified region bound. Use that.
1623 let r = explicit_region_bounds[0];
1624 return Some(ast_region_to_region(tcx, r));
1627 // No explicit region bound specified. Therefore, examine trait
1628 // bounds and see if we can derive region bounds from those.
1629 let derived_region_bounds =
1630 ty::object_region_bounds(tcx, principal_trait_ref.as_ref(), builtin_bounds);
1632 // If there are no derived region bounds, then report back that we
1633 // can find no region bound.
1634 if derived_region_bounds.len() == 0 {
1638 // If any of the derived region bounds are 'static, that is always
1640 if derived_region_bounds.iter().any(|r| ty::ReStatic == *r) {
1641 return Some(ty::ReStatic);
1644 // Determine whether there is exactly one unique region in the set
1645 // of derived region bounds. If so, use that. Otherwise, report an
1647 let r = derived_region_bounds[0];
1648 if derived_region_bounds.slice_from(1).iter().any(|r1| r != *r1) {
1651 format!("ambiguous lifetime bound, \
1652 explicit lifetime bound required")[]);
1657 /// A version of `compute_opt_region_bound` for use where some region bound is required
1658 /// (existential types, basically). Reports an error if no region bound can be derived and we are
1659 /// in an `rscope` that does not provide a default.
1660 fn compute_region_bound<'tcx, AC: AstConv<'tcx>, RS:RegionScope>(
1664 region_bounds: &[&ast::Lifetime],
1665 principal_trait_ref: Option<ty::PolyTraitRef<'tcx>>, // None for closures
1666 builtin_bounds: ty::BuiltinBounds)
1669 match compute_opt_region_bound(this.tcx(), span, region_bounds,
1670 principal_trait_ref, builtin_bounds) {
1673 match rscope.default_region_bound(span) {
1676 this.tcx().sess.span_err(
1678 format!("explicit lifetime bound required")[]);
1686 pub struct PartitionedBounds<'a> {
1687 pub builtin_bounds: ty::BuiltinBounds,
1688 pub trait_bounds: Vec<&'a ast::PolyTraitRef>,
1689 pub region_bounds: Vec<&'a ast::Lifetime>,
1692 /// Divides a list of bounds from the AST into three groups: builtin bounds (Copy, Sized etc),
1693 /// general trait bounds, and region bounds.
1694 pub fn partition_bounds<'a>(tcx: &ty::ctxt,
1696 ast_bounds: &'a [ast::TyParamBound])
1697 -> PartitionedBounds<'a>
1699 let mut builtin_bounds = ty::empty_builtin_bounds();
1700 let mut region_bounds = Vec::new();
1701 let mut trait_bounds = Vec::new();
1702 let mut trait_def_ids = DefIdMap::new();
1703 for ast_bound in ast_bounds.iter() {
1705 ast::TraitTyParamBound(ref b, ast::TraitBoundModifier::None) => {
1706 match ::lookup_def_tcx(tcx, b.trait_ref.path.span, b.trait_ref.ref_id) {
1707 def::DefTrait(trait_did) => {
1708 match trait_def_ids.get(&trait_did) {
1709 // Already seen this trait. We forbid
1710 // duplicates in the list (for some
1714 tcx.sess, b.trait_ref.path.span, E0127,
1715 "trait `{}` already appears in the \
1717 b.trait_ref.path.user_string(tcx));
1720 "previous appearance is here");
1728 trait_def_ids.insert(trait_did, b.trait_ref.path.span);
1730 if ty::try_add_builtin_trait(tcx,
1732 &mut builtin_bounds) {
1733 // FIXME(#20302) -- we should check for things like Copy<T>
1734 continue; // success
1738 // Not a trait? that's an error, but it'll get
1742 trait_bounds.push(b);
1744 ast::TraitTyParamBound(_, ast::TraitBoundModifier::Maybe) => {}
1745 ast::RegionTyParamBound(ref l) => {
1746 region_bounds.push(l);
1752 builtin_bounds: builtin_bounds,
1753 trait_bounds: trait_bounds,
1754 region_bounds: region_bounds,
1758 fn prohibit_projections<'tcx>(tcx: &ty::ctxt<'tcx>,
1759 bindings: &[ConvertedBinding<'tcx>])
1761 for binding in bindings.iter().take(1) {
1764 "associated type bindings are not allowed here");