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::feature_gate::{GateIssue, emit_feature_err};
36 pub trait AstConv<'gcx, 'tcx> {
37 fn tcx<'a>(&'a self) -> TyCtxt<'a, 'gcx, 'tcx>;
39 /// Returns the set of bounds in scope for the type parameter with
41 fn get_type_parameter_bounds(&self, span: Span, def_id: DefId)
42 -> ty::GenericPredicates<'tcx>;
44 /// What lifetime should we use when a lifetime is omitted (and not elided)?
45 fn re_infer(&self, span: Span, _def: Option<&ty::RegionParameterDef>)
46 -> Option<ty::Region<'tcx>>;
48 /// What type should we use when a type is omitted?
49 fn ty_infer(&self, span: Span) -> Ty<'tcx>;
51 /// Same as ty_infer, but with a known type parameter definition.
52 fn ty_infer_for_def(&self,
53 _def: &ty::TypeParameterDef,
54 _substs: &[Kind<'tcx>],
55 span: Span) -> Ty<'tcx> {
59 /// Projecting an associated type from a (potentially)
60 /// higher-ranked trait reference is more complicated, because of
61 /// the possibility of late-bound regions appearing in the
62 /// associated type binding. This is not legal in function
63 /// signatures for that reason. In a function body, we can always
64 /// handle it because we can use inference variables to remove the
65 /// late-bound regions.
66 fn projected_ty_from_poly_trait_ref(&self,
69 poly_trait_ref: ty::PolyTraitRef<'tcx>)
72 /// Normalize an associated type coming from the user.
73 fn normalize_ty(&self, span: Span, ty: Ty<'tcx>) -> Ty<'tcx>;
75 /// Invoked when we encounter an error from some prior pass
76 /// (e.g. resolve) that is translated into a ty-error. This is
77 /// used to help suppress derived errors typeck might otherwise
79 fn set_tainted_by_errors(&self);
81 fn record_ty(&self, hir_id: hir::HirId, ty: Ty<'tcx>, span: Span);
84 struct ConvertedBinding<'tcx> {
90 /// Dummy type used for the `Self` of a `TraitRef` created for converting
91 /// a trait object, and which gets removed in `ExistentialTraitRef`.
92 /// This type must not appear anywhere in other converted types.
93 const TRAIT_OBJECT_DUMMY_SELF: ty::TypeVariants<'static> = ty::TyInfer(ty::FreshTy(0));
95 impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
96 pub fn ast_region_to_region(&self,
97 lifetime: &hir::Lifetime,
98 def: Option<&ty::RegionParameterDef>)
101 let tcx = self.tcx();
102 let lifetime_name = |def_id| {
103 tcx.hir.name(tcx.hir.as_local_node_id(def_id).unwrap())
106 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
107 let r = match tcx.named_region(hir_id) {
108 Some(rl::Region::Static) => {
112 Some(rl::Region::LateBound(debruijn, id)) => {
113 let name = lifetime_name(id);
114 tcx.mk_region(ty::ReLateBound(debruijn,
115 ty::BrNamed(id, name)))
118 Some(rl::Region::LateBoundAnon(debruijn, index)) => {
119 tcx.mk_region(ty::ReLateBound(debruijn, ty::BrAnon(index)))
122 Some(rl::Region::EarlyBound(index, id)) => {
123 let name = lifetime_name(id);
124 tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
131 Some(rl::Region::Free(scope, id)) => {
132 let name = lifetime_name(id);
133 tcx.mk_region(ty::ReFree(ty::FreeRegion {
135 bound_region: ty::BrNamed(id, name)
138 // (*) -- not late-bound, won't change
142 self.re_infer(lifetime.span, def).expect("unelided lifetime in signature")
146 debug!("ast_region_to_region(lifetime={:?}) yields {:?}",
153 /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
154 /// returns an appropriate set of substitutions for this particular reference to `I`.
155 pub fn ast_path_substs_for_ty(&self,
158 item_segment: &hir::PathSegment)
159 -> &'tcx Substs<'tcx>
162 let (substs, assoc_bindings) =
163 item_segment.with_parameters(|parameters| {
164 self.create_substs_for_ast_path(
168 item_segment.infer_types,
172 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
177 /// Given the type/region arguments provided to some path (along with
178 /// an implicit Self, if this is a trait reference) returns the complete
179 /// set of substitutions. This may involve applying defaulted type parameters.
181 /// Note that the type listing given here is *exactly* what the user provided.
182 fn create_substs_for_ast_path(&self,
185 parameters: &hir::PathParameters,
187 self_ty: Option<Ty<'tcx>>)
188 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
190 let tcx = self.tcx();
192 debug!("create_substs_for_ast_path(def_id={:?}, self_ty={:?}, \
194 def_id, self_ty, parameters);
196 // If the type is parameterized by this region, then replace this
197 // region with the current anon region binding (in other words,
198 // whatever & would get replaced with).
199 let decl_generics = tcx.generics_of(def_id);
200 let num_types_provided = parameters.types.len();
201 let expected_num_region_params = decl_generics.regions.len();
202 let supplied_num_region_params = parameters.lifetimes.len();
203 if expected_num_region_params != supplied_num_region_params {
204 report_lifetime_number_error(tcx, span,
205 supplied_num_region_params,
206 expected_num_region_params);
209 // If a self-type was declared, one should be provided.
210 assert_eq!(decl_generics.has_self, self_ty.is_some());
212 // Check the number of type parameters supplied by the user.
213 let ty_param_defs = &decl_generics.types[self_ty.is_some() as usize..];
214 if !infer_types || num_types_provided > ty_param_defs.len() {
215 check_type_argument_count(tcx, span, num_types_provided, ty_param_defs);
218 let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
219 let default_needs_object_self = |p: &ty::TypeParameterDef| {
220 if is_object && p.has_default {
221 if tcx.at(span).type_of(p.def_id).has_self_ty() {
222 // There is no suitable inference default for a type parameter
223 // that references self, in an object type.
231 let substs = Substs::for_item(tcx, def_id, |def, _| {
232 let i = def.index as usize - self_ty.is_some() as usize;
233 if let Some(lifetime) = parameters.lifetimes.get(i) {
234 self.ast_region_to_region(lifetime, Some(def))
239 let i = def.index as usize;
241 // Handle Self first, so we can adjust the index to match the AST.
242 if let (0, Some(ty)) = (i, self_ty) {
246 let i = i - self_ty.is_some() as usize - decl_generics.regions.len();
247 if i < num_types_provided {
248 // A provided type parameter.
249 self.ast_ty_to_ty(¶meters.types[i])
250 } else if infer_types {
251 // No type parameters were provided, we can infer all.
252 let ty_var = if !default_needs_object_self(def) {
253 self.ty_infer_for_def(def, substs, span)
258 } else if def.has_default {
259 // No type parameter provided, but a default exists.
261 // If we are converting an object type, then the
262 // `Self` parameter is unknown. However, some of the
263 // other type parameters may reference `Self` in their
264 // defaults. This will lead to an ICE if we are not
266 if default_needs_object_self(def) {
267 struct_span_err!(tcx.sess, span, E0393,
268 "the type parameter `{}` must be explicitly specified",
270 .span_label(span, format!("missing reference to `{}`", def.name))
271 .note(&format!("because of the default `Self` reference, \
272 type parameters must be specified on object types"))
276 // This is a default type parameter.
279 tcx.at(span).type_of(def.def_id)
280 .subst_spanned(tcx, substs, Some(span))
284 // We've already errored above about the mismatch.
289 let assoc_bindings = parameters.bindings.iter().map(|binding| {
291 item_name: binding.name,
292 ty: self.ast_ty_to_ty(&binding.ty),
297 debug!("create_substs_for_ast_path(decl_generics={:?}, self_ty={:?}) -> {:?}",
298 decl_generics, self_ty, substs);
300 (substs, assoc_bindings)
303 /// Instantiates the path for the given trait reference, assuming that it's
304 /// bound to a valid trait type. Returns the def_id for the defining trait.
305 /// Fails if the type is a type other than a trait type.
307 /// If the `projections` argument is `None`, then assoc type bindings like `Foo<T=X>`
308 /// are disallowed. Otherwise, they are pushed onto the vector given.
309 pub fn instantiate_mono_trait_ref(&self,
310 trait_ref: &hir::TraitRef,
312 -> ty::TraitRef<'tcx>
314 self.prohibit_type_params(trait_ref.path.segments.split_last().unwrap().1);
316 let trait_def_id = self.trait_def_id(trait_ref);
317 self.ast_path_to_mono_trait_ref(trait_ref.path.span,
320 trait_ref.path.segments.last().unwrap())
323 fn trait_def_id(&self, trait_ref: &hir::TraitRef) -> DefId {
324 let path = &trait_ref.path;
326 Def::Trait(trait_def_id) => trait_def_id,
328 self.tcx().sess.fatal("cannot continue compilation due to previous error");
331 span_fatal!(self.tcx().sess, path.span, E0245, "`{}` is not a trait",
332 self.tcx().hir.node_to_pretty_string(trait_ref.ref_id));
337 pub fn instantiate_poly_trait_ref(&self,
338 ast_trait_ref: &hir::PolyTraitRef,
340 poly_projections: &mut Vec<ty::PolyProjectionPredicate<'tcx>>)
341 -> ty::PolyTraitRef<'tcx>
343 let trait_ref = &ast_trait_ref.trait_ref;
344 let trait_def_id = self.trait_def_id(trait_ref);
346 debug!("ast_path_to_poly_trait_ref({:?}, def_id={:?})", trait_ref, trait_def_id);
348 self.prohibit_type_params(trait_ref.path.segments.split_last().unwrap().1);
350 let (substs, assoc_bindings) =
351 self.create_substs_for_ast_trait_ref(trait_ref.path.span,
354 trait_ref.path.segments.last().unwrap());
355 let poly_trait_ref = ty::Binder(ty::TraitRef::new(trait_def_id, substs));
357 poly_projections.extend(assoc_bindings.iter().filter_map(|binding| {
358 // specify type to assert that error was already reported in Err case:
359 let predicate: Result<_, ErrorReported> =
360 self.ast_type_binding_to_poly_projection_predicate(poly_trait_ref, binding);
361 predicate.ok() // ok to ignore Err() because ErrorReported (see above)
364 debug!("ast_path_to_poly_trait_ref({:?}, projections={:?}) -> {:?}",
365 trait_ref, poly_projections, poly_trait_ref);
369 fn ast_path_to_mono_trait_ref(&self,
373 trait_segment: &hir::PathSegment)
374 -> ty::TraitRef<'tcx>
376 let (substs, assoc_bindings) =
377 self.create_substs_for_ast_trait_ref(span,
381 assoc_bindings.first().map(|b| self.prohibit_projection(b.span));
382 ty::TraitRef::new(trait_def_id, substs)
385 fn create_substs_for_ast_trait_ref(&self,
389 trait_segment: &hir::PathSegment)
390 -> (&'tcx Substs<'tcx>, Vec<ConvertedBinding<'tcx>>)
392 debug!("create_substs_for_ast_trait_ref(trait_segment={:?})",
395 let trait_def = self.tcx().trait_def(trait_def_id);
397 if !self.tcx().sess.features.borrow().unboxed_closures &&
398 trait_segment.with_parameters(|p| p.parenthesized) != trait_def.paren_sugar {
399 // For now, require that parenthetical notation be used only with `Fn()` etc.
400 let msg = if trait_def.paren_sugar {
401 "the precise format of `Fn`-family traits' type parameters is subject to change. \
402 Use parenthetical notation (Fn(Foo, Bar) -> Baz) instead"
404 "parenthetical notation is only stable when used with `Fn`-family traits"
406 emit_feature_err(&self.tcx().sess.parse_sess, "unboxed_closures",
407 span, GateIssue::Language, msg);
410 trait_segment.with_parameters(|parameters| {
411 self.create_substs_for_ast_path(span,
414 trait_segment.infer_types,
419 fn trait_defines_associated_type_named(&self,
421 assoc_name: ast::Name)
424 self.tcx().associated_items(trait_def_id).any(|item| {
425 item.kind == ty::AssociatedKind::Type &&
426 self.tcx().hygienic_eq(assoc_name, item.name, trait_def_id)
430 fn ast_type_binding_to_poly_projection_predicate(
432 trait_ref: ty::PolyTraitRef<'tcx>,
433 binding: &ConvertedBinding<'tcx>)
434 -> Result<ty::PolyProjectionPredicate<'tcx>, ErrorReported>
436 let tcx = self.tcx();
438 // Given something like `U : SomeTrait<T=X>`, we want to produce a
439 // predicate like `<U as SomeTrait>::T = X`. This is somewhat
440 // subtle in the event that `T` is defined in a supertrait of
441 // `SomeTrait`, because in that case we need to upcast.
443 // That is, consider this case:
446 // trait SubTrait : SuperTrait<int> { }
447 // trait SuperTrait<A> { type T; }
449 // ... B : SubTrait<T=foo> ...
452 // We want to produce `<B as SuperTrait<int>>::T == foo`.
454 // Find any late-bound regions declared in `ty` that are not
455 // declared in the trait-ref. These are not wellformed.
459 // for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
460 // for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
461 let late_bound_in_trait_ref = tcx.collect_constrained_late_bound_regions(&trait_ref);
462 let late_bound_in_ty = tcx.collect_referenced_late_bound_regions(&ty::Binder(binding.ty));
463 debug!("late_bound_in_trait_ref = {:?}", late_bound_in_trait_ref);
464 debug!("late_bound_in_ty = {:?}", late_bound_in_ty);
465 for br in late_bound_in_ty.difference(&late_bound_in_trait_ref) {
466 let br_name = match *br {
467 ty::BrNamed(_, name) => name,
471 "anonymous bound region {:?} in binding but not trait ref",
475 struct_span_err!(tcx.sess,
478 "binding for associated type `{}` references lifetime `{}`, \
479 which does not appear in the trait input types",
480 binding.item_name, br_name)
484 // Simple case: X is defined in the current trait.
485 if self.trait_defines_associated_type_named(trait_ref.def_id(), binding.item_name) {
486 return Ok(trait_ref.map_bound(|trait_ref| {
487 ty::ProjectionPredicate {
488 projection_ty: ty::ProjectionTy::from_ref_and_name(
498 // Otherwise, we have to walk through the supertraits to find
501 traits::supertraits(tcx, trait_ref.clone())
502 .filter(|r| self.trait_defines_associated_type_named(r.def_id(), binding.item_name));
504 let candidate = self.one_bound_for_assoc_type(candidates,
505 &trait_ref.to_string(),
509 Ok(candidate.map_bound(|trait_ref| {
510 ty::ProjectionPredicate {
511 projection_ty: ty::ProjectionTy::from_ref_and_name(
521 fn ast_path_to_ty(&self,
524 item_segment: &hir::PathSegment)
527 let substs = self.ast_path_substs_for_ty(span, did, item_segment);
530 self.tcx().at(span).type_of(did).subst(self.tcx(), substs)
534 /// Transform a PolyTraitRef into a PolyExistentialTraitRef by
535 /// removing the dummy Self type (TRAIT_OBJECT_DUMMY_SELF).
536 fn trait_ref_to_existential(&self, trait_ref: ty::TraitRef<'tcx>)
537 -> ty::ExistentialTraitRef<'tcx> {
538 assert_eq!(trait_ref.self_ty().sty, TRAIT_OBJECT_DUMMY_SELF);
539 ty::ExistentialTraitRef::erase_self_ty(self.tcx(), trait_ref)
542 fn conv_object_ty_poly_trait_ref(&self,
544 trait_bounds: &[hir::PolyTraitRef],
545 lifetime: &hir::Lifetime)
548 let tcx = self.tcx();
550 if trait_bounds.is_empty() {
551 span_err!(tcx.sess, span, E0224,
552 "at least one non-builtin trait is required for an object type");
553 return tcx.types.err;
556 let mut projection_bounds = vec![];
557 let dummy_self = tcx.mk_ty(TRAIT_OBJECT_DUMMY_SELF);
558 let principal = self.instantiate_poly_trait_ref(&trait_bounds[0],
560 &mut projection_bounds);
562 for trait_bound in trait_bounds[1..].iter() {
563 // Sanity check for non-principal trait bounds
564 self.instantiate_poly_trait_ref(trait_bound,
569 let (auto_traits, trait_bounds) = split_auto_traits(tcx, &trait_bounds[1..]);
571 if !trait_bounds.is_empty() {
572 let b = &trait_bounds[0];
573 let span = b.trait_ref.path.span;
574 struct_span_err!(self.tcx().sess, span, E0225,
575 "only auto traits can be used as additional traits in a trait object")
576 .span_label(span, "non-auto additional trait")
580 // Erase the dummy_self (TRAIT_OBJECT_DUMMY_SELF) used above.
581 let existential_principal = principal.map_bound(|trait_ref| {
582 self.trait_ref_to_existential(trait_ref)
584 let existential_projections = projection_bounds.iter().map(|bound| {
585 bound.map_bound(|b| {
586 let trait_ref = self.trait_ref_to_existential(b.projection_ty.trait_ref(tcx));
587 ty::ExistentialProjection {
589 item_def_id: b.projection_ty.item_def_id,
590 substs: trait_ref.substs,
595 // check that there are no gross object safety violations,
596 // most importantly, that the supertraits don't contain Self,
598 let object_safety_violations =
599 tcx.astconv_object_safety_violations(principal.def_id());
600 if !object_safety_violations.is_empty() {
601 tcx.report_object_safety_error(
602 span, principal.def_id(), object_safety_violations)
604 return tcx.types.err;
607 let mut associated_types = FxHashSet::default();
608 for tr in traits::supertraits(tcx, principal) {
609 associated_types.extend(tcx.associated_items(tr.def_id())
610 .filter(|item| item.kind == ty::AssociatedKind::Type)
611 .map(|item| item.def_id));
614 for projection_bound in &projection_bounds {
615 associated_types.remove(&projection_bound.0.projection_ty.item_def_id);
618 for item_def_id in associated_types {
619 let assoc_item = tcx.associated_item(item_def_id);
620 let trait_def_id = assoc_item.container.id();
621 struct_span_err!(tcx.sess, span, E0191,
622 "the value of the associated type `{}` (from the trait `{}`) must be specified",
624 tcx.item_path_str(trait_def_id))
625 .span_label(span, format!(
626 "missing associated type `{}` value", assoc_item.name))
631 iter::once(ty::ExistentialPredicate::Trait(*existential_principal.skip_binder()))
632 .chain(auto_traits.into_iter().map(ty::ExistentialPredicate::AutoTrait))
633 .chain(existential_projections
634 .map(|x| ty::ExistentialPredicate::Projection(*x.skip_binder())))
635 .collect::<AccumulateVec<[_; 8]>>();
636 v.sort_by(|a, b| a.cmp(tcx, b));
637 let existential_predicates = ty::Binder(tcx.mk_existential_predicates(v.into_iter()));
640 // Explicitly specified region bound. Use that.
641 let region_bound = if !lifetime.is_elided() {
642 self.ast_region_to_region(lifetime, None)
644 self.compute_object_lifetime_bound(span, existential_predicates).unwrap_or_else(|| {
645 let hir_id = tcx.hir.node_to_hir_id(lifetime.id);
646 if tcx.named_region(hir_id).is_some() {
647 self.ast_region_to_region(lifetime, None)
649 self.re_infer(span, None).unwrap_or_else(|| {
650 span_err!(tcx.sess, span, E0228,
651 "the lifetime bound for this object type cannot be deduced \
652 from context; please supply an explicit bound");
659 debug!("region_bound: {:?}", region_bound);
661 let ty = tcx.mk_dynamic(existential_predicates, region_bound);
662 debug!("trait_object_type: {:?}", ty);
666 fn report_ambiguous_associated_type(&self,
671 struct_span_err!(self.tcx().sess, span, E0223, "ambiguous associated type")
672 .span_label(span, "ambiguous associated type")
673 .note(&format!("specify the type using the syntax `<{} as {}>::{}`",
674 type_str, trait_str, name))
679 // Search for a bound on a type parameter which includes the associated item
680 // given by `assoc_name`. `ty_param_def_id` is the `DefId` for the type parameter
681 // This function will fail if there are no suitable bounds or there is
683 fn find_bound_for_assoc_item(&self,
684 ty_param_def_id: DefId,
685 assoc_name: ast::Name,
687 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
689 let tcx = self.tcx();
691 let bounds: Vec<_> = self.get_type_parameter_bounds(span, ty_param_def_id)
692 .predicates.into_iter().filter_map(|p| p.to_opt_poly_trait_ref()).collect();
694 // Check that there is exactly one way to find an associated type with the
696 let suitable_bounds =
697 traits::transitive_bounds(tcx, &bounds)
698 .filter(|b| self.trait_defines_associated_type_named(b.def_id(), assoc_name));
700 let param_node_id = tcx.hir.as_local_node_id(ty_param_def_id).unwrap();
701 let param_name = tcx.hir.ty_param_name(param_node_id);
702 self.one_bound_for_assoc_type(suitable_bounds,
703 ¶m_name.as_str(),
709 // Checks that bounds contains exactly one element and reports appropriate
711 fn one_bound_for_assoc_type<I>(&self,
714 assoc_name: ast::Name,
716 -> Result<ty::PolyTraitRef<'tcx>, ErrorReported>
717 where I: Iterator<Item=ty::PolyTraitRef<'tcx>>
719 let bound = match bounds.next() {
720 Some(bound) => bound,
722 struct_span_err!(self.tcx().sess, span, E0220,
723 "associated type `{}` not found for `{}`",
726 .span_label(span, format!("associated type `{}` not found", assoc_name))
728 return Err(ErrorReported);
732 if let Some(bound2) = bounds.next() {
733 let bounds = iter::once(bound).chain(iter::once(bound2)).chain(bounds);
734 let mut err = struct_span_err!(
735 self.tcx().sess, span, E0221,
736 "ambiguous associated type `{}` in bounds of `{}`",
739 err.span_label(span, format!("ambiguous associated type `{}`", assoc_name));
741 for bound in bounds {
742 let bound_span = self.tcx().associated_items(bound.def_id()).find(|item| {
743 item.kind == ty::AssociatedKind::Type &&
744 self.tcx().hygienic_eq(assoc_name, item.name, bound.def_id())
746 .and_then(|item| self.tcx().hir.span_if_local(item.def_id));
748 if let Some(span) = bound_span {
749 err.span_label(span, format!("ambiguous `{}` from `{}`",
753 span_note!(&mut err, span,
754 "associated type `{}` could derive from `{}`",
765 // Create a type from a path to an associated type.
766 // For a path A::B::C::D, ty and ty_path_def are the type and def for A::B::C
767 // and item_segment is the path segment for D. We return a type and a def for
769 // Will fail except for T::A and Self::A; i.e., if ty/ty_path_def are not a type
770 // parameter or Self.
771 pub fn associated_path_def_to_ty(&self,
776 item_segment: &hir::PathSegment)
779 let tcx = self.tcx();
780 let assoc_name = item_segment.name;
782 debug!("associated_path_def_to_ty: {:?}::{}", ty, assoc_name);
784 self.prohibit_type_params(slice::ref_slice(item_segment));
786 // Find the type of the associated item, and the trait where the associated
788 let bound = match (&ty.sty, ty_path_def) {
789 (_, Def::SelfTy(Some(_), Some(impl_def_id))) => {
790 // `Self` in an impl of a trait - we have a concrete self type and a
792 let trait_ref = match tcx.impl_trait_ref(impl_def_id) {
793 Some(trait_ref) => trait_ref,
795 // A cycle error occurred, most likely.
796 return (tcx.types.err, Def::Err);
801 traits::supertraits(tcx, ty::Binder(trait_ref))
802 .filter(|r| self.trait_defines_associated_type_named(r.def_id(),
805 match self.one_bound_for_assoc_type(candidates, "Self", assoc_name, span) {
807 Err(ErrorReported) => return (tcx.types.err, Def::Err),
810 (&ty::TyParam(_), Def::SelfTy(Some(param_did), None)) |
811 (&ty::TyParam(_), Def::TyParam(param_did)) => {
812 match self.find_bound_for_assoc_item(param_did, assoc_name, span) {
814 Err(ErrorReported) => return (tcx.types.err, Def::Err),
818 // Don't print TyErr to the user.
819 if !ty.references_error() {
820 self.report_ambiguous_associated_type(span,
823 &assoc_name.as_str());
825 return (tcx.types.err, Def::Err);
829 let trait_did = bound.0.def_id;
830 let (assoc_ident, def_scope) = tcx.adjust(assoc_name, trait_did, ref_id);
831 let item = tcx.associated_items(trait_did).find(|i| {
832 Namespace::from(i.kind) == Namespace::Type &&
833 i.name.to_ident() == assoc_ident
835 .expect("missing associated type");
837 let ty = self.projected_ty_from_poly_trait_ref(span, item.def_id, bound);
838 let ty = self.normalize_ty(span, ty);
840 let def = Def::AssociatedTy(item.def_id);
841 if !item.vis.is_accessible_from(def_scope, tcx) {
842 let msg = format!("{} `{}` is private", def.kind_name(), assoc_name);
843 tcx.sess.span_err(span, &msg);
845 tcx.check_stability(item.def_id, ref_id, span);
850 fn qpath_to_ty(&self,
852 opt_self_ty: Option<Ty<'tcx>>,
854 trait_segment: &hir::PathSegment,
855 item_segment: &hir::PathSegment)
858 let tcx = self.tcx();
859 let trait_def_id = tcx.parent_def_id(item_def_id).unwrap();
861 self.prohibit_type_params(slice::ref_slice(item_segment));
863 let self_ty = if let Some(ty) = opt_self_ty {
866 let path_str = tcx.item_path_str(trait_def_id);
867 self.report_ambiguous_associated_type(span,
870 &item_segment.name.as_str());
871 return tcx.types.err;
874 debug!("qpath_to_ty: self_type={:?}", self_ty);
876 let trait_ref = self.ast_path_to_mono_trait_ref(span,
881 debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
883 self.normalize_ty(span, tcx.mk_projection(item_def_id, trait_ref.substs))
886 pub fn prohibit_type_params(&self, segments: &[hir::PathSegment]) {
887 for segment in segments {
888 segment.with_parameters(|parameters| {
889 for typ in ¶meters.types {
890 struct_span_err!(self.tcx().sess, typ.span, E0109,
891 "type parameters are not allowed on this type")
892 .span_label(typ.span, "type parameter not allowed")
896 for lifetime in ¶meters.lifetimes {
897 struct_span_err!(self.tcx().sess, lifetime.span, E0110,
898 "lifetime parameters are not allowed on this type")
899 .span_label(lifetime.span,
900 "lifetime parameter not allowed on this type")
904 for binding in ¶meters.bindings {
905 self.prohibit_projection(binding.span);
912 pub fn prohibit_projection(&self, span: Span) {
913 let mut err = struct_span_err!(self.tcx().sess, span, E0229,
914 "associated type bindings are not allowed here");
915 err.span_label(span, "associated type not allowed here").emit();
918 // Check a type Path and convert it to a Ty.
919 pub fn def_to_ty(&self,
920 opt_self_ty: Option<Ty<'tcx>>,
922 permit_variants: bool)
924 let tcx = self.tcx();
926 debug!("base_def_to_ty(def={:?}, opt_self_ty={:?}, path_segments={:?})",
927 path.def, opt_self_ty, path.segments);
929 let span = path.span;
931 Def::Enum(did) | Def::TyAlias(did) | Def::Struct(did) |
932 Def::Union(did) | Def::TyForeign(did) => {
933 assert_eq!(opt_self_ty, None);
934 self.prohibit_type_params(path.segments.split_last().unwrap().1);
935 self.ast_path_to_ty(span, did, path.segments.last().unwrap())
937 Def::Variant(did) if permit_variants => {
938 // Convert "variant type" as if it were a real type.
939 // The resulting `Ty` is type of the variant's enum for now.
940 assert_eq!(opt_self_ty, None);
941 self.prohibit_type_params(path.segments.split_last().unwrap().1);
942 self.ast_path_to_ty(span,
943 tcx.parent_def_id(did).unwrap(),
944 path.segments.last().unwrap())
946 Def::TyParam(did) => {
947 assert_eq!(opt_self_ty, None);
948 self.prohibit_type_params(&path.segments);
950 let node_id = tcx.hir.as_local_node_id(did).unwrap();
951 let item_id = tcx.hir.get_parent_node(node_id);
952 let item_def_id = tcx.hir.local_def_id(item_id);
953 let generics = tcx.generics_of(item_def_id);
954 let index = generics.type_param_to_index[&tcx.hir.local_def_id(node_id).index];
955 tcx.mk_param(index, tcx.hir.name(node_id))
957 Def::SelfTy(_, Some(def_id)) => {
958 // Self in impl (we know the concrete type).
960 assert_eq!(opt_self_ty, None);
961 self.prohibit_type_params(&path.segments);
963 tcx.at(span).type_of(def_id)
965 Def::SelfTy(Some(_), None) => {
967 assert_eq!(opt_self_ty, None);
968 self.prohibit_type_params(&path.segments);
971 Def::AssociatedTy(def_id) => {
972 self.prohibit_type_params(&path.segments[..path.segments.len()-2]);
973 self.qpath_to_ty(span,
976 &path.segments[path.segments.len()-2],
977 path.segments.last().unwrap())
979 Def::PrimTy(prim_ty) => {
980 assert_eq!(opt_self_ty, None);
981 self.prohibit_type_params(&path.segments);
983 hir::TyBool => tcx.types.bool,
984 hir::TyChar => tcx.types.char,
985 hir::TyInt(it) => tcx.mk_mach_int(it),
986 hir::TyUint(uit) => tcx.mk_mach_uint(uit),
987 hir::TyFloat(ft) => tcx.mk_mach_float(ft),
988 hir::TyStr => tcx.mk_str()
992 self.set_tainted_by_errors();
993 return self.tcx().types.err;
995 _ => span_bug!(span, "unexpected definition: {:?}", path.def)
999 /// Parses the programmer's textual representation of a type into our
1000 /// internal notion of a type.
1001 pub fn ast_ty_to_ty(&self, ast_ty: &hir::Ty) -> Ty<'tcx> {
1002 debug!("ast_ty_to_ty(id={:?}, ast_ty={:?})",
1005 let tcx = self.tcx();
1007 let result_ty = match ast_ty.node {
1008 hir::TySlice(ref ty) => {
1009 tcx.mk_slice(self.ast_ty_to_ty(&ty))
1011 hir::TyPtr(ref mt) => {
1012 tcx.mk_ptr(ty::TypeAndMut {
1013 ty: self.ast_ty_to_ty(&mt.ty),
1017 hir::TyRptr(ref region, ref mt) => {
1018 let r = self.ast_region_to_region(region, None);
1019 debug!("TyRef r={:?}", r);
1020 let t = self.ast_ty_to_ty(&mt.ty);
1021 tcx.mk_ref(r, ty::TypeAndMut {ty: t, mutbl: mt.mutbl})
1026 hir::TyTup(ref fields) => {
1027 tcx.mk_tup(fields.iter().map(|t| self.ast_ty_to_ty(&t)), false)
1029 hir::TyBareFn(ref bf) => {
1030 require_c_abi_if_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
1031 tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
1033 hir::TyTraitObject(ref bounds, ref lifetime) => {
1034 self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
1036 hir::TyImplTrait(_) => {
1037 // Figure out if we can allow an `impl Trait` here, by walking up
1038 // to a `fn` or inherent `impl` method, going only through `Ty`
1039 // or `TraitRef` nodes (as nothing else should be in types) and
1040 // ensuring that we reach the `fn`/method signature's return type.
1041 let mut node_id = ast_ty.id;
1042 let fn_decl = loop {
1043 let parent = tcx.hir.get_parent_node(node_id);
1044 match tcx.hir.get(parent) {
1045 hir::map::NodeItem(&hir::Item {
1046 node: hir::ItemFn(ref fn_decl, ..), ..
1047 }) => break Some(fn_decl),
1049 hir::map::NodeImplItem(&hir::ImplItem {
1050 node: hir::ImplItemKind::Method(ref sig, _), ..
1052 match tcx.hir.expect_item(tcx.hir.get_parent(parent)).node {
1053 hir::ItemImpl(.., None, _, _) => {
1054 break Some(&sig.decl)
1060 hir::map::NodeTy(_) | hir::map::NodeTraitRef(_) => {}
1066 let allow = fn_decl.map_or(false, |fd| {
1068 hir::DefaultReturn(_) => false,
1069 hir::Return(ref ty) => ty.id == node_id
1073 // Create the anonymized type.
1075 let def_id = tcx.hir.local_def_id(ast_ty.id);
1076 tcx.mk_anon(def_id, Substs::identity_for_item(tcx, def_id))
1078 span_err!(tcx.sess, ast_ty.span, E0562,
1079 "`impl Trait` not allowed outside of function \
1080 and inherent method return types");
1084 hir::TyPath(hir::QPath::Resolved(ref maybe_qself, ref path)) => {
1085 debug!("ast_ty_to_ty: maybe_qself={:?} path={:?}", maybe_qself, path);
1086 let opt_self_ty = maybe_qself.as_ref().map(|qself| {
1087 self.ast_ty_to_ty(qself)
1089 self.def_to_ty(opt_self_ty, path, false)
1091 hir::TyPath(hir::QPath::TypeRelative(ref qself, ref segment)) => {
1092 debug!("ast_ty_to_ty: qself={:?} segment={:?}", qself, segment);
1093 let ty = self.ast_ty_to_ty(qself);
1095 let def = if let hir::TyPath(hir::QPath::Resolved(_, ref path)) = qself.node {
1100 self.associated_path_def_to_ty(ast_ty.id, ast_ty.span, ty, def, segment).0
1102 hir::TyArray(ref ty, length) => {
1103 let length_def_id = tcx.hir.body_owner_def_id(length);
1104 let substs = Substs::identity_for_item(tcx, length_def_id);
1105 let length = tcx.mk_const(ty::Const {
1106 val: ConstVal::Unevaluated(length_def_id, substs),
1109 let array_ty = tcx.mk_ty(ty::TyArray(self.ast_ty_to_ty(&ty), length));
1110 self.normalize_ty(ast_ty.span, array_ty)
1112 hir::TyTypeof(ref _e) => {
1113 struct_span_err!(tcx.sess, ast_ty.span, E0516,
1114 "`typeof` is a reserved keyword but unimplemented")
1115 .span_label(ast_ty.span, "reserved keyword")
1121 // TyInfer also appears as the type of arguments or return
1122 // values in a ExprClosure, or as
1123 // the type of local variables. Both of these cases are
1124 // handled specially and will not descend into this routine.
1125 self.ty_infer(ast_ty.span)
1132 self.record_ty(ast_ty.hir_id, result_ty, ast_ty.span);
1136 pub fn ty_of_arg(&self,
1138 expected_ty: Option<Ty<'tcx>>)
1142 hir::TyInfer if expected_ty.is_some() => {
1143 self.record_ty(ty.hir_id, expected_ty.unwrap(), ty.span);
1144 expected_ty.unwrap()
1146 _ => self.ast_ty_to_ty(ty),
1150 pub fn ty_of_fn(&self,
1151 unsafety: hir::Unsafety,
1154 -> ty::PolyFnSig<'tcx> {
1157 let tcx = self.tcx();
1158 let input_tys: Vec<Ty> =
1159 decl.inputs.iter().map(|a| self.ty_of_arg(a, None)).collect();
1161 let output_ty = match decl.output {
1162 hir::Return(ref output) => self.ast_ty_to_ty(output),
1163 hir::DefaultReturn(..) => tcx.mk_nil(),
1166 debug!("ty_of_fn: output_ty={:?}", output_ty);
1168 let bare_fn_ty = ty::Binder(tcx.mk_fn_sig(
1169 input_tys.into_iter(),
1176 // Find any late-bound regions declared in return type that do
1177 // not appear in the arguments. These are not wellformed.
1180 // for<'a> fn() -> &'a str <-- 'a is bad
1181 // for<'a> fn(&'a String) -> &'a str <-- 'a is ok
1182 let inputs = bare_fn_ty.inputs();
1183 let late_bound_in_args = tcx.collect_constrained_late_bound_regions(
1184 &inputs.map_bound(|i| i.to_owned()));
1185 let output = bare_fn_ty.output();
1186 let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
1187 for br in late_bound_in_ret.difference(&late_bound_in_args) {
1188 let br_name = match *br {
1189 ty::BrNamed(_, name) => name,
1193 "anonymous bound region {:?} in return but not args",
1197 struct_span_err!(tcx.sess,
1200 "return type references lifetime `{}`, \
1201 which does not appear in the fn input types",
1209 /// Given the bounds on an object, determines what single region bound (if any) we can
1210 /// use to summarize this type. The basic idea is that we will use the bound the user
1211 /// provided, if they provided one, and otherwise search the supertypes of trait bounds
1212 /// for region bounds. It may be that we can derive no bound at all, in which case
1213 /// we return `None`.
1214 fn compute_object_lifetime_bound(&self,
1216 existential_predicates: ty::Binder<&'tcx ty::Slice<ty::ExistentialPredicate<'tcx>>>)
1217 -> Option<ty::Region<'tcx>> // if None, use the default
1219 let tcx = self.tcx();
1221 debug!("compute_opt_region_bound(existential_predicates={:?})",
1222 existential_predicates);
1224 // No explicit region bound specified. Therefore, examine trait
1225 // bounds and see if we can derive region bounds from those.
1226 let derived_region_bounds =
1227 object_region_bounds(tcx, existential_predicates);
1229 // If there are no derived region bounds, then report back that we
1230 // can find no region bound. The caller will use the default.
1231 if derived_region_bounds.is_empty() {
1235 // If any of the derived region bounds are 'static, that is always
1237 if derived_region_bounds.iter().any(|&r| ty::ReStatic == *r) {
1238 return Some(tcx.types.re_static);
1241 // Determine whether there is exactly one unique region in the set
1242 // of derived region bounds. If so, use that. Otherwise, report an
1244 let r = derived_region_bounds[0];
1245 if derived_region_bounds[1..].iter().any(|r1| r != *r1) {
1246 span_err!(tcx.sess, span, E0227,
1247 "ambiguous lifetime bound, explicit lifetime bound required");
1253 /// Divides a list of general trait bounds into two groups: builtin bounds (Sync/Send) and the
1254 /// remaining general trait bounds.
1255 fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
1256 trait_bounds: &'b [hir::PolyTraitRef])
1257 -> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
1259 let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
1260 // Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
1261 match bound.trait_ref.path.def {
1262 Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
1269 let auto_traits = auto_traits.into_iter().map(|tr| {
1270 if let Def::Trait(trait_did) = tr.trait_ref.path.def {
1275 }).collect::<Vec<_>>();
1277 (auto_traits, trait_bounds)
1280 fn check_type_argument_count(tcx: TyCtxt, span: Span, supplied: usize,
1281 ty_param_defs: &[ty::TypeParameterDef]) {
1282 let accepted = ty_param_defs.len();
1283 let required = ty_param_defs.iter().take_while(|x| !x.has_default).count();
1284 if supplied < required {
1285 let expected = if required < accepted {
1290 let arguments_plural = if required == 1 { "" } else { "s" };
1292 struct_span_err!(tcx.sess, span, E0243,
1293 "wrong number of type arguments: {} {}, found {}",
1294 expected, required, supplied)
1296 format!("{} {} type argument{}",
1301 } else if supplied > accepted {
1302 let expected = if required < accepted {
1303 format!("expected at most {}", accepted)
1305 format!("expected {}", accepted)
1307 let arguments_plural = if accepted == 1 { "" } else { "s" };
1309 struct_span_err!(tcx.sess, span, E0244,
1310 "wrong number of type arguments: {}, found {}",
1314 format!("{} type argument{}",
1315 if accepted == 0 { "expected no" } else { &expected },
1322 fn report_lifetime_number_error(tcx: TyCtxt, span: Span, number: usize, expected: usize) {
1323 let label = if number < expected {
1325 format!("expected {} lifetime parameter", expected)
1327 format!("expected {} lifetime parameters", expected)
1330 let additional = number - expected;
1331 if additional == 1 {
1332 "unexpected lifetime parameter".to_string()
1334 format!("{} unexpected lifetime parameters", additional)
1337 struct_span_err!(tcx.sess, span, E0107,
1338 "wrong number of lifetime parameters: expected {}, found {}",
1340 .span_label(span, label)
1344 // A helper struct for conveniently grouping a set of bounds which we pass to
1345 // and return from functions in multiple places.
1346 #[derive(PartialEq, Eq, Clone, Debug)]
1347 pub struct Bounds<'tcx> {
1348 pub region_bounds: Vec<ty::Region<'tcx>>,
1349 pub implicitly_sized: bool,
1350 pub trait_bounds: Vec<ty::PolyTraitRef<'tcx>>,
1351 pub projection_bounds: Vec<ty::PolyProjectionPredicate<'tcx>>,
1354 impl<'a, 'gcx, 'tcx> Bounds<'tcx> {
1355 pub fn predicates(&self, tcx: TyCtxt<'a, 'gcx, 'tcx>, param_ty: Ty<'tcx>)
1356 -> Vec<ty::Predicate<'tcx>>
1358 let mut vec = Vec::new();
1360 // If it could be sized, and is, add the sized predicate
1361 if self.implicitly_sized {
1362 if let Some(sized) = tcx.lang_items().sized_trait() {
1363 let trait_ref = ty::TraitRef {
1365 substs: tcx.mk_substs_trait(param_ty, &[])
1367 vec.push(trait_ref.to_predicate());
1371 for ®ion_bound in &self.region_bounds {
1372 // account for the binder being introduced below; no need to shift `param_ty`
1373 // because, at present at least, it can only refer to early-bound regions
1374 let region_bound = tcx.mk_region(ty::fold::shift_region(*region_bound, 1));
1375 vec.push(ty::Binder(ty::OutlivesPredicate(param_ty, region_bound)).to_predicate());
1378 for bound_trait_ref in &self.trait_bounds {
1379 vec.push(bound_trait_ref.to_predicate());
1382 for projection in &self.projection_bounds {
1383 vec.push(projection.to_predicate());