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`.
15 use rustc::middle::const_val::ConstVal;
16 use rustc_data_structures::accumulate_vec::AccumulateVec;
19 use hir::def_id::DefId;
20 use middle::resolve_lifetime as rl;
21 use namespace::Namespace;
22 use rustc::ty::subst::{Kind, Subst, Substs};
24 use rustc::ty::{self, Ty, TyCtxt, ToPredicate, TypeFoldable};
25 use rustc::ty::wf::object_region_bounds;
26 use rustc_back::slice;
27 use require_c_abi_if_variadic;
28 use util::common::ErrorReported;
29 use util::nodemap::FxHashSet;
32 use syntax::{abi, ast};
33 use syntax::symbol::Symbol;
34 use syntax::feature_gate::{GateIssue, emit_feature_err};
37 pub trait AstConv<'gcx, 'tcx> {
38 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
40 /// Returns the set of bounds in scope for the type parameter with
42 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
43 -> ty::GenericPredicates<'tcx>;
45 /// What lifetime should we use when a lifetime is omitted (and not elided)?
46 fn re_infer(&self, span: Span, _def: Option<&ty::RegionParameterDef>)
47 -> Option<ty::Region<'tcx>>;
49 /// What type should we use when a type is omitted?
50 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
52 /// Same as ty_infer, but with a known type parameter definition.
53 fn ty_infer_for_def(&self,
54 _def: &ty::TypeParameterDef,
55 _substs: &[Kind<'tcx>],
56 span: Span) -> Ty<'tcx> {
60 /// Projecting an associated type from a (potentially)
61 /// higher-ranked trait reference is more complicated, because of
62 /// the possibility of late-bound regions appearing in the
63 /// associated type binding. This is not legal in function
64 /// signatures for that reason. In a function body, we can always
65 /// handle it because we can use inference variables to remove the
66 /// late-bound regions.
67 fn projected_ty_from_poly_trait_ref(&self,
70 poly_trait_ref: ty::PolyTraitRef<'tcx>)
73 /// Normalize an associated type coming from the user.
74 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
76 /// Invoked when we encounter an error from some prior pass
77 /// (e.g. resolve) that is translated into a ty-error. This is
78 /// used to help suppress derived errors typeck might otherwise
80 fn set_tainted_by_errors(&self);
82 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
85 struct ConvertedBinding<'tcx> {
91 /// Dummy type used for the `Self` of a `TraitRef` created for converting
92 /// a trait object, and which gets removed in `ExistentialTraitRef`.
93 /// This type must not appear anywhere in other converted types.
94 const TRAIT_OBJECT_DUMMY_SELF: ty::TypeVariants<'static> = ty::TyInfer(ty::FreshTy(0));
96 impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
97 pub fn ast_region_to_region(&self,
98 lifetime: &hir::Lifetime,
99 def: Option<&ty::RegionParameterDef>)
102 let tcx = self.tcx();
103 let lifetime_name = |def_id| {
104 tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap())
107 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
108 let r = match tcx.named_region(hir_id) {
109 Some(rl::Region::Static) => {
113 Some(rl::Region::LateBound(debruijn, id)) => {
114 let name = lifetime_name(id);
115 tcx.mk_region(ty::ReLateBound(debruijn,
116 ty::BrNamed(id, name)))
119 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
120 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
123 Some(rl::Region::EarlyBound(index, id)) => {
124 let name = lifetime_name(id);
125 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
132 Some(rl::Region::Free(scope, id)) => {
133 let name = lifetime_name(id);
134 tcx.mk_region(ty::ReFree(ty::FreeRegion {
136 bound_region: ty::BrNamed(id, name)
139 // (*) -- not late-bound, won't change
143 self.re_infer(lifetime.span, def).expect("unelided lifetime in signature")
147 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
154 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
155 /// returns an appropriate set of substitutions for this particular reference to `I`.
156 pub fn ast_path_substs_for_ty(&self,
159 item_segment: &hir::PathSegment)
160 -> &'tcx Substs<'tcx>
163 let (substs, assoc_bindings) =
164 item_segment.with_parameters(|parameters| {
165 self.create_substs_for_ast_path(
169 item_segment.infer_types,
173 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
178 /// Given the type/region arguments provided to some path (along with
179 /// an implicit Self, if this is a trait reference) returns the complete
180 /// set of substitutions. This may involve applying defaulted type parameters.
182 /// Note that the type listing given here is *exactly* what the user provided.
183 fn create_substs_for_ast_path(&self,
186 parameters: &hir::PathParameters,
188 self_ty: Option<Ty<'tcx>>)
189 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
191 let tcx = self.tcx();
193 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
195 def_id, self_ty, parameters);
197 // If the type is parameterized by this region, then replace this
198 // region with the current anon region binding (in other words,
199 // whatever & would get replaced with).
200 let decl_generics = tcx.generics_of(def_id);
201 let num_types_provided = parameters.types.len();
202 let expected_num_region_params = decl_generics.regions.len();
203 let supplied_num_region_params = parameters.lifetimes.len();
204 if expected_num_region_params != supplied_num_region_params {
205 report_lifetime_number_error(tcx, span,
206 supplied_num_region_params,
207 expected_num_region_params);
210 // If a self-type was declared, one should be provided.
211 assert_eq!(decl_generics.has_self, self_ty.is_some());
213 // Check the number of type parameters supplied by the user.
214 let ty_param_defs = &decl_generics.types[self_ty.is_some() as usize..];
215 if !infer_types || num_types_provided > ty_param_defs.len() {
216 check_type_argument_count(tcx, span, num_types_provided, ty_param_defs);
219 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
220 let default_needs_object_self = |p: &ty::TypeParameterDef| {
221 if is_object && p.has_default {
222 if tcx.at(span).type_of(p.def_id).has_self_ty() {
223 // There is no suitable inference default for a type parameter
224 // that references self, in an object type.
232 let substs = Substs::for_item(tcx, def_id, |def, _| {
233 let i = def.index as usize - self_ty.is_some() as usize;
234 if let Some(lifetime) = parameters.lifetimes.get(i) {
235 self.ast_region_to_region(lifetime, Some(def))
240 let i = def.index as usize;
242 // Handle Self first, so we can adjust the index to match the AST.
243 if let (0, Some(ty)) = (i, self_ty) {
247 let i = i - self_ty.is_some() as usize - decl_generics.regions.len();
248 if i < num_types_provided {
249 // A provided type parameter.
250 self.ast_ty_to_ty(¶meters.types[i])
251 } else if infer_types {
252 // No type parameters were provided, we can infer all.
253 let ty_var = if !default_needs_object_self(def) {
254 self.ty_infer_for_def(def, substs, span)
259 } else if def.has_default {
260 // No type parameter provided, but a default exists.
262 // If we are converting an object type, then the
263 // `Self` parameter is unknown. However, some of the
264 // other type parameters may reference `Self` in their
265 // defaults. This will lead to an ICE if we are not
267 if default_needs_object_self(def) {
268 struct_span_err!(tcx.sess, span, E0393,
269 "the type parameter `{}` must be explicitly specified",
271 .span_label(span, format!("missing reference to `{}`", def.name))
272 .note(&format!("because of the default `Self` reference, \
273 type parameters must be specified on object types"))
277 // This is a default type parameter.
280 tcx.at(span).type_of(def.def_id)
281 .subst_spanned(tcx, substs, Some(span))
285 // We've already errored above about the mismatch.
290 let assoc_bindings = parameters.bindings.iter().map(|binding| {
292 item_name: binding.name,
293 ty: self.ast_ty_to_ty(&binding.ty),
298 debug!("create_substs_for_ast_path(decl_generics={:?}, self_ty={:?}) -> {:?}",
299 decl_generics, self_ty, substs);
301 (substs, assoc_bindings)
304 /// Instantiates the path for the given trait reference, assuming that it's
305 /// bound to a valid trait type. Returns the def_id for the defining trait.
306 /// Fails if the type is a type other than a trait type.
308 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
309 /// are disallowed. Otherwise, they are pushed onto the vector given.
310 pub fn instantiate_mono_trait_ref(&self,
311 trait_ref: &hir::TraitRef,
313 -> ty::TraitRef<'tcx>
315 self.prohibit_type_params(trait_ref.path.segments.split_last().unwrap().1);
317 let trait_def_id = self.trait_def_id(trait_ref);
318 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
321 trait_ref.path.segments.last().unwrap())
324 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
325 let path = &trait_ref.path;
327 Def::Trait(trait_def_id) => trait_def_id,
329 self.tcx().sess.fatal("cannot continue compilation due to previous error");
332 span_fatal!(self.tcx().sess, path.span, E0245, "`{}` is not a trait",
333 self.tcx().hir.node_to_pretty_string(trait_ref.ref_id));
338 pub fn instantiate_poly_trait_ref(&self,
339 ast_trait_ref: &hir::PolyTraitRef,
341 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
342 -> ty::PolyTraitRef<'tcx>
344 let trait_ref = &ast_trait_ref.trait_ref;
345 let trait_def_id = self.trait_def_id(trait_ref);
347 debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
349 self.prohibit_type_params(trait_ref.path.segments.split_last().unwrap().1);
351 let (substs, assoc_bindings) =
352 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
355 trait_ref.path.segments.last().unwrap());
356 let poly_trait_ref = ty::Binder(ty::TraitRef::new(trait_def_id, substs));
358 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
359 // specify type to assert that error was already reported in Err case:
360 let predicate: Result<_, ErrorReported> =
361 self.ast_type_binding_to_poly_projection_predicate(poly_trait_ref, binding);
362 predicate.ok() // ok to ignore Err() because ErrorReported (see above)
365 debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
366 trait_ref, poly_projections, poly_trait_ref);
370 fn ast_path_to_mono_trait_ref(&self,
374 trait_segment: &hir::PathSegment)
375 -> ty::TraitRef<'tcx>
377 let (substs, assoc_bindings) =
378 self.create_substs_for_ast_trait_ref(span,
382 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
383 ty::TraitRef::new(trait_def_id, substs)
386 fn create_substs_for_ast_trait_ref(&self,
390 trait_segment: &hir::PathSegment)
391 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
393 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
396 let trait_def = self.tcx().trait_def(trait_def_id);
398 if !self.tcx().sess.features.borrow().unboxed_closures &&
399 trait_segment.with_parameters(|p| p.parenthesized) != trait_def.paren_sugar {
400 // For now, require that parenthetical notation be used only with `Fn()` etc.
401 let msg = if trait_def.paren_sugar {
402 "the precise format of `Fn`-family traits' type parameters is subject to change. \
403 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
405 "parenthetical notation is only stable when used with `Fn`-family traits"
407 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
408 span, GateIssue::Language, msg);
411 trait_segment.with_parameters(|parameters| {
412 self.create_substs_for_ast_path(span,
415 trait_segment.infer_types,
420 fn trait_defines_associated_type_named(&self,
422 assoc_name: ast::Name)
425 self.tcx().associated_items(trait_def_id).any(|item| {
426 item.kind == ty::AssociatedKind::Type &&
427 self.tcx().hygienic_eq(assoc_name, item.name, trait_def_id)
431 fn ast_type_binding_to_poly_projection_predicate(
433 trait_ref: ty::PolyTraitRef<'tcx>,
434 binding: &ConvertedBinding<'tcx>)
435 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
437 let tcx = self.tcx();
439 // Given something like `U : SomeTrait<T=X>`, we want to produce a
440 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
441 // subtle in the event that `T` is defined in a supertrait of
442 // `SomeTrait`, because in that case we need to upcast.
444 // That is, consider this case:
447 // trait SubTrait : SuperTrait<int> { }
448 // trait SuperTrait<A> { type T; }
450 // ... B : SubTrait<T=foo> ...
453 // We want to produce `<B as SuperTrait<int>>::T == foo`.
455 // Find any late-bound regions declared in `ty` that are not
456 // declared in the trait-ref. These are not wellformed.
460 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
461 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
462 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
463 let late_bound_in_ty = tcx.collect_referenced_late_bound_regions(&ty::Binder(binding.ty));
464 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
465 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
466 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
467 let br_name = match *br {
468 ty::BrNamed(_, name) => name,
472 "anonymous bound region {:?} in binding but not trait ref",
476 struct_span_err!(tcx.sess,
479 "binding for associated type `{}` references lifetime `{}`, \
480 which does not appear in the trait input types",
481 binding.item_name, br_name)
485 // Simple case: X is defined in the current trait.
486 if self.trait_defines_associated_type_named(trait_ref.def_id(), binding.item_name) {
487 return Ok(trait_ref.map_bound(|trait_ref| {
488 ty::ProjectionPredicate {
489 projection_ty: ty::ProjectionTy::from_ref_and_name(
499 // Otherwise, we have to walk through the supertraits to find
502 traits::supertraits(tcx, trait_ref.clone())
503 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), binding.item_name));
505 let candidate = self.one_bound_for_assoc_type(candidates,
506 &trait_ref.to_string(),
510 Ok(candidate.map_bound(|trait_ref| {
511 ty::ProjectionPredicate {
512 projection_ty: ty::ProjectionTy::from_ref_and_name(
522 fn ast_path_to_ty(&self,
525 item_segment: &hir::PathSegment)
528 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
531 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
535 /// Transform a PolyTraitRef into a PolyExistentialTraitRef by
536 /// removing the dummy Self type (TRAIT_OBJECT_DUMMY_SELF).
537 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
538 -> ty::ExistentialTraitRef<'tcx> {
539 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
540 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
543 fn conv_object_ty_poly_trait_ref(&self,
545 trait_bounds: &[hir::PolyTraitRef],
546 lifetime: &hir::Lifetime)
549 let tcx = self.tcx();
551 if trait_bounds.is_empty() {
552 span_err!(tcx.sess, span, E0224,
553 "at least one non-builtin trait is required for an object type");
554 return tcx.types.err;
557 let mut projection_bounds = vec![];
558 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
559 let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
561 &mut projection_bounds);
563 for trait_bound in trait_bounds[1..].iter() {
564 // Sanity check for non-principal trait bounds
565 self.instantiate_poly_trait_ref(trait_bound,
570 let (auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
572 if !trait_bounds.is_empty() {
573 let b = &trait_bounds[0];
574 let span = b.trait_ref.path.span;
575 struct_span_err!(self.tcx().sess, span, E0225,
576 "only auto traits can be used as additional traits in a trait object")
577 .span_label(span, "non-auto additional trait")
581 // Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
582 let existential_principal = principal.map_bound(|trait_ref| {
583 self.trait_ref_to_existential(trait_ref)
585 let existential_projections = projection_bounds.iter().map(|bound| {
586 bound.map_bound(|b| {
587 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
588 ty::ExistentialProjection {
590 item_def_id: b.projection_ty.item_def_id,
591 substs: trait_ref.substs,
596 // check that there are no gross object safety violations,
597 // most importantly, that the supertraits don't contain Self,
599 let object_safety_violations =
600 tcx.astconv_object_safety_violations(principal.def_id());
601 if !object_safety_violations.is_empty() {
602 tcx.report_object_safety_error(
603 span, principal.def_id(), object_safety_violations)
605 return tcx.types.err;
608 let mut associated_types = FxHashSet::default();
609 for tr in traits::supertraits(tcx, principal) {
610 associated_types.extend(tcx.associated_items(tr.def_id())
611 .filter(|item| item.kind == ty::AssociatedKind::Type)
612 .map(|item| item.def_id));
615 for projection_bound in &projection_bounds {
616 associated_types.remove(&projection_bound.0.projection_ty.item_def_id);
619 for item_def_id in associated_types {
620 let assoc_item = tcx.associated_item(item_def_id);
621 let trait_def_id = assoc_item.container.id();
622 struct_span_err!(tcx.sess, span, E0191,
623 "the value of the associated type `{}` (from the trait `{}`) must be specified",
625 tcx.item_path_str(trait_def_id))
626 .span_label(span, format!(
627 "missing associated type `{}` value", assoc_item.name))
632 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
633 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
634 .chain(existential_projections
635 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
636 .collect::<AccumulateVec<[_; 8]>>();
637 v.sort_by(|a, b| a.cmp(tcx, b));
638 let existential_predicates = ty::Binder(tcx.mk_existential_predicates(v.into_iter()));
641 // Explicitly specified region bound. Use that.
642 let region_bound = if !lifetime.is_elided() {
643 self.ast_region_to_region(lifetime, None)
645 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
646 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
647 if tcx.named_region(hir_id).is_some() {
648 self.ast_region_to_region(lifetime, None)
650 self.re_infer(span, None).unwrap_or_else(|| {
651 span_err!(tcx.sess, span, E0228,
652 "the lifetime bound for this object type cannot be deduced \
653 from context; please supply an explicit bound");
660 debug!("region_bound: {:?}", region_bound);
662 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
663 debug!("trait_object_type: {:?}", ty);
667 fn report_ambiguous_associated_type(&self,
672 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
673 .span_label(span, "ambiguous associated type")
674 .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
675 type_str, trait_str, name))
680 // Search for a bound on a type parameter which includes the associated item
681 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
682 // This function will fail if there are no suitable bounds or there is
684 fn find_bound_for_assoc_item(&self,
685 ty_param_def_id: DefId,
686 assoc_name: ast::Name,
688 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
690 let tcx = self.tcx();
692 let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
693 .predicates.into_iter().filter_map(|p| p.to_opt_poly_trait_ref()).collect();
695 // Check that there is exactly one way to find an associated type with the
697 let suitable_bounds =
698 traits::transitive_bounds(tcx, &bounds)
699 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
701 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
702 let param_name = tcx.hir.ty_param_name(param_node_id);
703 self.one_bound_for_assoc_type(suitable_bounds,
704 ¶m_name.as_str(),
710 // Checks that bounds contains exactly one element and reports appropriate
712 fn one_bound_for_assoc_type<I>(&self,
715 assoc_name: ast::Name,
717 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
718 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
720 let bound = match bounds.next() {
721 Some(bound) => bound,
723 struct_span_err!(self.tcx().sess, span, E0220,
724 "associated type `{}` not found for `{}`",
727 .span_label(span, format!("associated type `{}` not found", assoc_name))
729 return Err(ErrorReported);
733 if let Some(bound2) = bounds.next() {
734 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
735 let mut err = struct_span_err!(
736 self.tcx().sess, span, E0221,
737 "ambiguous associated type `{}` in bounds of `{}`",
740 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
742 for bound in bounds {
743 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
744 item.kind == ty::AssociatedKind::Type &&
745 self.tcx().hygienic_eq(assoc_name, item.name, bound.def_id())
747 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
749 if let Some(span) = bound_span {
750 err.span_label(span, format!("ambiguous `{}` from `{}`",
754 span_note!(&mut err, span,
755 "associated type `{}` could derive from `{}`",
766 // Create a type from a path to an associated type.
767 // For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
768 // and item_segment is the path segment for D. We return a type and a def for
770 // Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
771 // parameter or Self.
772 pub fn associated_path_def_to_ty(&self,
777 item_segment: &hir::PathSegment)
780 let tcx = self.tcx();
781 let assoc_name = item_segment.name;
783 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
785 self.prohibit_type_params(slice::ref_slice(item_segment));
787 // Find the type of the associated item, and the trait where the associated
789 let bound = match (&ty.sty, ty_path_def) {
790 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
791 // `Self` in an impl of a trait - we have a concrete self type and a
793 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
794 Some(trait_ref) => trait_ref,
796 // A cycle error occurred, most likely.
797 return (tcx.types.err, Def::Err);
802 traits::supertraits(tcx, ty::Binder(trait_ref))
803 .filter(|r| self.trait_defines_associated_type_named(r.def_id(),
806 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
808 Err(ErrorReported) => return (tcx.types.err, Def::Err),
811 (&ty::TyParam(_), Def::SelfTy(Some(param_did), None)) |
812 (&ty::TyParam(_), Def::TyParam(param_did)) => {
813 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
815 Err(ErrorReported) => return (tcx.types.err, Def::Err),
819 // Don't print TyErr to the user.
820 if !ty.references_error() {
821 self.report_ambiguous_associated_type(span,
824 &assoc_name.as_str());
826 return (tcx.types.err, Def::Err);
830 let trait_did = bound.0.def_id;
831 let (assoc_ident, def_scope) = tcx.adjust(assoc_name, trait_did, ref_id);
832 let item = tcx.associated_items(trait_did).find(|i| {
833 Namespace::from(i.kind) == Namespace::Type &&
834 i.name.to_ident() == assoc_ident
836 .expect("missing associated type");
838 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
839 let ty = self.normalize_ty(span, ty);
841 let def = Def::AssociatedTy(item.def_id);
842 if !item.vis.is_accessible_from(def_scope, tcx) {
843 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
844 tcx.sess.span_err(span, &msg);
846 tcx.check_stability(item.def_id, ref_id, span);
851 fn qpath_to_ty(&self,
853 opt_self_ty: Option<Ty<'tcx>>,
855 trait_segment: &hir::PathSegment,
856 item_segment: &hir::PathSegment)
859 let tcx = self.tcx();
860 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
862 self.prohibit_type_params(slice::ref_slice(item_segment));
864 let self_ty = if let Some(ty) = opt_self_ty {
867 let path_str = tcx.item_path_str(trait_def_id);
868 self.report_ambiguous_associated_type(span,
871 &item_segment.name.as_str());
872 return tcx.types.err;
875 debug!("qpath_to_ty: self_type={:?}", self_ty);
877 let trait_ref = self.ast_path_to_mono_trait_ref(span,
882 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
884 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
887 pub fn prohibit_type_params(&self, segments: &[hir::PathSegment]) {
888 for segment in segments {
889 segment.with_parameters(|parameters| {
890 for typ in ¶meters.types {
891 struct_span_err!(self.tcx().sess, typ.span, E0109,
892 "type parameters are not allowed on this type")
893 .span_label(typ.span, "type parameter not allowed")
897 for lifetime in ¶meters.lifetimes {
898 struct_span_err!(self.tcx().sess, lifetime.span, E0110,
899 "lifetime parameters are not allowed on this type")
900 .span_label(lifetime.span,
901 "lifetime parameter not allowed on this type")
905 for binding in ¶meters.bindings {
906 self.prohibit_projection(binding.span);
913 pub fn prohibit_projection(&self, span: Span) {
914 let mut err = struct_span_err!(self.tcx().sess, span, E0229,
915 "associated type bindings are not allowed here");
916 err.span_label(span, "associated type not allowed here").emit();
919 // Check a type Path and convert it to a Ty.
920 pub fn def_to_ty(&self,
921 opt_self_ty: Option<Ty<'tcx>>,
923 permit_variants: bool)
925 let tcx = self.tcx();
927 debug!("base_def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
928 path.def, opt_self_ty, path.segments);
930 let span = path.span;
932 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
933 Def::Union(did) | Def::TyForeign(did) => {
934 assert_eq!(opt_self_ty, None);
935 self.prohibit_type_params(path.segments.split_last().unwrap().1);
936 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
938 Def::Variant(did) if permit_variants => {
939 // Convert "variant type" as if it were a real type.
940 // The resulting `Ty` is type of the variant's enum for now.
941 assert_eq!(opt_self_ty, None);
942 self.prohibit_type_params(path.segments.split_last().unwrap().1);
943 self.ast_path_to_ty(span,
944 tcx.parent_def_id(did).unwrap(),
945 path.segments.last().unwrap())
947 Def::TyParam(did) => {
948 assert_eq!(opt_self_ty, None);
949 self.prohibit_type_params(&path.segments);
951 let node_id = tcx.hir.as_local_node_id(did).unwrap();
952 let item_id = tcx.hir.get_parent_node(node_id);
953 let item_def_id = tcx.hir.local_def_id(item_id);
954 let generics = tcx.generics_of(item_def_id);
955 let index = generics.type_param_to_index[&tcx.hir.local_def_id(node_id).index];
956 tcx.mk_param(index, tcx.hir.name(node_id))
958 Def::SelfTy(_, Some(def_id)) => {
959 // Self in impl (we know the concrete type).
961 assert_eq!(opt_self_ty, None);
962 self.prohibit_type_params(&path.segments);
964 tcx.at(span).type_of(def_id)
966 Def::SelfTy(Some(_), None) => {
968 assert_eq!(opt_self_ty, None);
969 self.prohibit_type_params(&path.segments);
972 Def::AssociatedTy(def_id) => {
973 self.prohibit_type_params(&path.segments[..path.segments.len()-2]);
974 self.qpath_to_ty(span,
977 &path.segments[path.segments.len()-2],
978 path.segments.last().unwrap())
980 Def::PrimTy(prim_ty) => {
981 assert_eq!(opt_self_ty, None);
982 self.prohibit_type_params(&path.segments);
984 hir::TyBool => tcx.types.bool,
985 hir::TyChar => tcx.types.char,
986 hir::TyInt(it) => tcx.mk_mach_int(it),
987 hir::TyUint(uit) => tcx.mk_mach_uint(uit),
988 hir::TyFloat(ft) => tcx.mk_mach_float(ft),
989 hir::TyStr => tcx.mk_str()
993 self.set_tainted_by_errors();
994 return self.tcx().types.err;
996 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
1000 /// Parses the programmer's textual representation of a type into our
1001 /// internal notion of a type.
1002 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1003 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
1006 let tcx = self.tcx();
1008 let result_ty = match ast_ty.node {
1009 hir::TySlice(ref ty) => {
1010 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1012 hir::TyPtr(ref mt) => {
1013 tcx.mk_ptr(ty::TypeAndMut {
1014 ty: self.ast_ty_to_ty(&mt.ty),
1018 hir::TyRptr(ref region, ref mt) => {
1019 let r = self.ast_region_to_region(region, None);
1020 debug!("TyRef r={:?}", r);
1021 let t = self.ast_ty_to_ty(&mt.ty);
1022 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1027 hir::TyTup(ref fields) => {
1028 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)), false)
1030 hir::TyBareFn(ref bf) => {
1031 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1032 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1034 hir::TyTraitObject(ref bounds, ref lifetime) => {
1035 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1037 hir::TyImplTraitExistential(_) => {
1038 let def_id = tcx.hir.local_def_id(ast_ty.id);
1039 tcx.mk_anon(def_id, Substs::identity_for_item(tcx, def_id))
1041 hir::TyImplTraitUniversal(fn_def_id, _) => {
1042 let impl_trait_def_id = tcx.hir.local_def_id(ast_ty.id);
1043 let generics = tcx.generics_of(fn_def_id);
1044 let index = generics.type_param_to_index[&impl_trait_def_id.index];
1046 Symbol::intern(&tcx.hir.node_to_pretty_string(ast_ty.id)))
1048 hir::TyPath(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1049 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1050 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1051 self.ast_ty_to_ty(qself)
1053 self.def_to_ty(opt_self_ty, path, false)
1055 hir::TyPath(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1056 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1057 let ty = self.ast_ty_to_ty(qself);
1059 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
1064 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1066 hir::TyArray(ref ty, length) => {
1067 let length_def_id = tcx.hir.body_owner_def_id(length);
1068 let substs = Substs::identity_for_item(tcx, length_def_id);
1069 let length = tcx.mk_const(ty::Const {
1070 val: ConstVal::Unevaluated(length_def_id, substs),
1073 let array_ty = tcx.mk_ty(ty::TyArray(self.ast_ty_to_ty(&ty), length));
1074 self.normalize_ty(ast_ty.span, array_ty)
1076 hir::TyTypeof(ref _e) => {
1077 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1078 "`typeof` is a reserved keyword but unimplemented")
1079 .span_label(ast_ty.span, "reserved keyword")
1085 // TyInfer also appears as the type of arguments or return
1086 // values in a ExprClosure, or as
1087 // the type of local variables. Both of these cases are
1088 // handled specially and will not descend into this routine.
1089 self.ty_infer(ast_ty.span)
1096 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1100 pub fn ty_of_arg(&self,
1102 expected_ty: Option<Ty<'tcx>>)
1106 hir::TyInfer if expected_ty.is_some() => {
1107 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1108 expected_ty.unwrap()
1110 _ => self.ast_ty_to_ty(ty),
1114 pub fn ty_of_fn(&self,
1115 unsafety: hir::Unsafety,
1118 -> ty::PolyFnSig<'tcx> {
1121 let tcx = self.tcx();
1122 let input_tys: Vec<Ty> =
1123 decl.inputs.iter().map(|a| self.ty_of_arg(a, None)).collect();
1125 let output_ty = match decl.output {
1126 hir::Return(ref output) => self.ast_ty_to_ty(output),
1127 hir::DefaultReturn(..) => tcx.mk_nil(),
1130 debug!("ty_of_fn: output_ty={:?}", output_ty);
1132 let bare_fn_ty = ty::Binder(tcx.mk_fn_sig(
1133 input_tys.into_iter(),
1140 // Find any late-bound regions declared in return type that do
1141 // not appear in the arguments. These are not wellformed.
1144 // for<'a> fn() -> &'a str <-- 'a is bad
1145 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1146 let inputs = bare_fn_ty.inputs();
1147 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1148 &inputs.map_bound(|i| i.to_owned()));
1149 let output = bare_fn_ty.output();
1150 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1151 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1152 let br_name = match *br {
1153 ty::BrNamed(_, name) => name,
1157 "anonymous bound region {:?} in return but not args",
1161 struct_span_err!(tcx.sess,
1164 "return type references lifetime `{}`, \
1165 which does not appear in the fn input types",
1173 /// Given the bounds on an object, determines what single region bound (if any) we can
1174 /// use to summarize this type. The basic idea is that we will use the bound the user
1175 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1176 /// for region bounds. It may be that we can derive no bound at all, in which case
1177 /// we return `None`.
1178 fn compute_object_lifetime_bound(&self,
1180 existential_predicates: ty::Binder<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>)
1181 -> Option<ty::Region<'tcx>> // if None, use the default
1183 let tcx = self.tcx();
1185 debug!("compute_opt_region_bound(existential_predicates={:?})",
1186 existential_predicates);
1188 // No explicit region bound specified. Therefore, examine trait
1189 // bounds and see if we can derive region bounds from those.
1190 let derived_region_bounds =
1191 object_region_bounds(tcx, existential_predicates);
1193 // If there are no derived region bounds, then report back that we
1194 // can find no region bound. The caller will use the default.
1195 if derived_region_bounds.is_empty() {
1199 // If any of the derived region bounds are 'static, that is always
1201 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1202 return Some(tcx.types.re_static);
1205 // Determine whether there is exactly one unique region in the set
1206 // of derived region bounds. If so, use that. Otherwise, report an
1208 let r = derived_region_bounds[0];
1209 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1210 span_err!(tcx.sess, span, E0227,
1211 "ambiguous lifetime bound, explicit lifetime bound required");
1217 /// Divides a list of general trait bounds into two groups: builtin bounds (Sync/Send) and the
1218 /// remaining general trait bounds.
1219 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1220 trait_bounds: &'b [hir::PolyTraitRef])
1221 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1223 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1224 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1225 match bound.trait_ref.path.def {
1226 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1233 let auto_traits = auto_traits.into_iter().map(|tr| {
1234 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1239 }).collect::<Vec<_>>();
1241 (auto_traits, trait_bounds)
1244 fn check_type_argument_count(tcx: TyCtxt, span: Span, supplied: usize,
1245 ty_param_defs: &[ty::TypeParameterDef]) {
1246 let accepted = ty_param_defs.len();
1247 let required = ty_param_defs.iter().take_while(|x| !x.has_default).count();
1248 if supplied < required {
1249 let expected = if required < accepted {
1254 let arguments_plural = if required == 1 { "" } else { "s" };
1256 struct_span_err!(tcx.sess, span, E0243,
1257 "wrong number of type arguments: {} {}, found {}",
1258 expected, required, supplied)
1260 format!("{} {} type argument{}",
1265 } else if supplied > accepted {
1266 let expected = if required < accepted {
1267 format!("expected at most {}", accepted)
1269 format!("expected {}", accepted)
1271 let arguments_plural = if accepted == 1 { "" } else { "s" };
1273 struct_span_err!(tcx.sess, span, E0244,
1274 "wrong number of type arguments: {}, found {}",
1278 format!("{} type argument{}",
1279 if accepted == 0 { "expected no" } else { &expected },
1286 fn report_lifetime_number_error(tcx: TyCtxt, span: Span, number: usize, expected: usize) {
1287 let label = if number < expected {
1289 format!("expected {} lifetime parameter", expected)
1291 format!("expected {} lifetime parameters", expected)
1294 let additional = number - expected;
1295 if additional == 1 {
1296 "unexpected lifetime parameter".to_string()
1298 format!("{} unexpected lifetime parameters", additional)
1301 struct_span_err!(tcx.sess, span, E0107,
1302 "wrong number of lifetime parameters: expected {}, found {}",
1304 .span_label(span, label)
1308 // A helper struct for conveniently grouping a set of bounds which we pass to
1309 // and return from functions in multiple places.
1310 #[derive(PartialEq, Eq, Clone, Debug)]
1311 pub struct Bounds<'tcx> {
1312 pub region_bounds: Vec<ty::Region<'tcx>>,
1313 pub implicitly_sized: bool,
1314 pub trait_bounds: Vec<ty::PolyTraitRef<'tcx>>,
1315 pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
1318 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1319 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1320 -> Vec<ty::Predicate<'tcx>>
1322 let mut vec = Vec::new();
1324 // If it could be sized, and is, add the sized predicate
1325 if self.implicitly_sized {
1326 if let Some(sized) = tcx.lang_items().sized_trait() {
1327 let trait_ref = ty::TraitRef {
1329 substs: tcx.mk_substs_trait(param_ty, &[])
1331 vec.push(trait_ref.to_predicate());
1335 for ®ion_bound in &self.region_bounds {
1336 // account for the binder being introduced below; no need to shift `param_ty`
1337 // because, at present at least, it can only refer to early-bound regions
1338 let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
1339 vec.push(ty::Binder(ty::OutlivesPredicate(param_ty, region_bound)).to_predicate());
1342 for bound_trait_ref in &self.trait_bounds {
1343 vec.push(bound_trait_ref.to_predicate());
1346 for projection in &self.projection_bounds {
1347 vec.push(projection.to_predicate());