1 // Copyright 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 use hir::def_id::DefId;
12 use ty::subst::{Kind, Subst, Substs};
13 use ty::{self, Ty, TyCtxt, ToPredicate, ToPolyTraitRef};
14 use ty::outlives::Component;
15 use util::nodemap::FxHashSet;
17 use traits::specialize::specialization_graph::NodeItem;
19 use super::{Obligation, ObligationCause, PredicateObligation, SelectionContext, Normalized};
21 fn anonymize_predicate<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
22 pred: &ty::Predicate<'tcx>)
23 -> ty::Predicate<'tcx> {
25 ty::Predicate::Trait(ref data) =>
26 ty::Predicate::Trait(tcx.anonymize_late_bound_regions(data)),
28 ty::Predicate::RegionOutlives(ref data) =>
29 ty::Predicate::RegionOutlives(tcx.anonymize_late_bound_regions(data)),
31 ty::Predicate::TypeOutlives(ref data) =>
32 ty::Predicate::TypeOutlives(tcx.anonymize_late_bound_regions(data)),
34 ty::Predicate::Projection(ref data) =>
35 ty::Predicate::Projection(tcx.anonymize_late_bound_regions(data)),
37 ty::Predicate::WellFormed(data) =>
38 ty::Predicate::WellFormed(data),
40 ty::Predicate::ObjectSafe(data) =>
41 ty::Predicate::ObjectSafe(data),
43 ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) =>
44 ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind),
46 ty::Predicate::Subtype(ref data) =>
47 ty::Predicate::Subtype(tcx.anonymize_late_bound_regions(data)),
49 ty::Predicate::ConstEvaluatable(def_id, substs) =>
50 ty::Predicate::ConstEvaluatable(def_id, substs),
55 struct PredicateSet<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
56 tcx: TyCtxt<'a, 'gcx, 'tcx>,
57 set: FxHashSet<ty::Predicate<'tcx>>,
60 impl<'a, 'gcx, 'tcx> PredicateSet<'a, 'gcx, 'tcx> {
61 fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> PredicateSet<'a, 'gcx, 'tcx> {
62 PredicateSet { tcx: tcx, set: Default::default() }
65 fn insert(&mut self, pred: &ty::Predicate<'tcx>) -> bool {
66 // We have to be careful here because we want
68 // for<'a> Foo<&'a int>
72 // for<'b> Foo<&'b int>
74 // to be considered equivalent. So normalize all late-bound
75 // regions before we throw things into the underlying set.
76 self.set.insert(anonymize_predicate(self.tcx, pred))
80 ///////////////////////////////////////////////////////////////////////////
81 // `Elaboration` iterator
82 ///////////////////////////////////////////////////////////////////////////
84 /// "Elaboration" is the process of identifying all the predicates that
85 /// are implied by a source predicate. Currently this basically means
86 /// walking the "supertraits" and other similar assumptions. For
87 /// example, if we know that `T : Ord`, the elaborator would deduce
88 /// that `T : PartialOrd` holds as well. Similarly, if we have `trait
89 /// Foo : 'static`, and we know that `T : Foo`, then we know that `T :
91 pub struct Elaborator<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
92 stack: Vec<ty::Predicate<'tcx>>,
93 visited: PredicateSet<'a, 'gcx, 'tcx>,
96 pub fn elaborate_trait_ref<'cx, 'gcx, 'tcx>(
97 tcx: TyCtxt<'cx, 'gcx, 'tcx>,
98 trait_ref: ty::PolyTraitRef<'tcx>)
99 -> Elaborator<'cx, 'gcx, 'tcx>
101 elaborate_predicates(tcx, vec![trait_ref.to_predicate()])
104 pub fn elaborate_trait_refs<'cx, 'gcx, 'tcx>(
105 tcx: TyCtxt<'cx, 'gcx, 'tcx>,
106 trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>)
107 -> Elaborator<'cx, 'gcx, 'tcx>
109 let predicates = trait_refs.map(|trait_ref| trait_ref.to_predicate())
111 elaborate_predicates(tcx, predicates)
114 pub fn elaborate_predicates<'cx, 'gcx, 'tcx>(
115 tcx: TyCtxt<'cx, 'gcx, 'tcx>,
116 mut predicates: Vec<ty::Predicate<'tcx>>)
117 -> Elaborator<'cx, 'gcx, 'tcx>
119 let mut visited = PredicateSet::new(tcx);
120 predicates.retain(|pred| visited.insert(pred));
121 Elaborator { stack: predicates, visited: visited }
124 impl<'cx, 'gcx, 'tcx> Elaborator<'cx, 'gcx, 'tcx> {
125 pub fn filter_to_traits(self) -> FilterToTraits<Self> {
126 FilterToTraits::new(self)
129 fn push(&mut self, predicate: &ty::Predicate<'tcx>) {
130 let tcx = self.visited.tcx;
132 ty::Predicate::Trait(ref data) => {
133 // Predicates declared on the trait.
134 let predicates = tcx.super_predicates_of(data.def_id());
136 let mut predicates: Vec<_> =
137 predicates.predicates
139 .map(|(p, _)| p.subst_supertrait(tcx, &data.to_poly_trait_ref()))
142 debug!("super_predicates: data={:?} predicates={:?}",
145 // Only keep those bounds that we haven't already
146 // seen. This is necessary to prevent infinite
147 // recursion in some cases. One common case is when
148 // people define `trait Sized: Sized { }` rather than `trait
150 predicates.retain(|r| self.visited.insert(r));
152 self.stack.extend(predicates);
154 ty::Predicate::WellFormed(..) => {
155 // Currently, we do not elaborate WF predicates,
156 // although we easily could.
158 ty::Predicate::ObjectSafe(..) => {
159 // Currently, we do not elaborate object-safe
162 ty::Predicate::Subtype(..) => {
163 // Currently, we do not "elaborate" predicates like `X
164 // <: Y`, though conceivably we might.
166 ty::Predicate::Projection(..) => {
167 // Nothing to elaborate in a projection predicate.
169 ty::Predicate::ClosureKind(..) => {
170 // Nothing to elaborate when waiting for a closure's kind to be inferred.
172 ty::Predicate::ConstEvaluatable(..) => {
173 // Currently, we do not elaborate const-evaluatable
177 ty::Predicate::RegionOutlives(..) => {
178 // Nothing to elaborate from `'a: 'b`.
181 ty::Predicate::TypeOutlives(ref data) => {
182 // We know that `T: 'a` for some type `T`. We can
183 // often elaborate this. For example, if we know that
184 // `[U]: 'a`, that implies that `U: 'a`. Similarly, if
185 // we know `&'a U: 'b`, then we know that `'a: 'b` and
188 // We can basically ignore bound regions here. So for
189 // example `for<'c> Foo<'a,'c>: 'b` can be elaborated to
192 // Ignore `for<'a> T: 'a` -- we might in the future
193 // consider this as evidence that `T: 'static`, but
194 // I'm a bit wary of such constructions and so for now
195 // I want to be conservative. --nmatsakis
196 let ty_max = data.skip_binder().0;
197 let r_min = data.skip_binder().1;
198 if r_min.is_late_bound() {
202 let visited = &mut self.visited;
204 tcx.outlives_components(ty_max)
206 .filter_map(|component| match component {
207 Component::Region(r) => if r.is_late_bound() {
210 Some(ty::Predicate::RegionOutlives(
211 ty::Binder::dummy(ty::OutlivesPredicate(r, r_min))))
214 Component::Param(p) => {
215 let ty = tcx.mk_ty_param(p.idx, p.name);
216 Some(ty::Predicate::TypeOutlives(
217 ty::Binder::dummy(ty::OutlivesPredicate(ty, r_min))))
220 Component::UnresolvedInferenceVariable(_) => {
224 Component::Projection(_) |
225 Component::EscapingProjection(_) => {
226 // We can probably do more here. This
227 // corresponds to a case like `<T as
232 .filter(|p| visited.insert(p)));
238 impl<'cx, 'gcx, 'tcx> Iterator for Elaborator<'cx, 'gcx, 'tcx> {
239 type Item = ty::Predicate<'tcx>;
241 fn size_hint(&self) -> (usize, Option<usize>) {
242 (self.stack.len(), None)
245 fn next(&mut self) -> Option<ty::Predicate<'tcx>> {
246 // Extract next item from top-most stack frame, if any.
247 let next_predicate = match self.stack.pop() {
248 Some(predicate) => predicate,
250 // No more stack frames. Done.
254 self.push(&next_predicate);
255 return Some(next_predicate);
259 ///////////////////////////////////////////////////////////////////////////
260 // Supertrait iterator
261 ///////////////////////////////////////////////////////////////////////////
263 pub type Supertraits<'cx, 'gcx, 'tcx> = FilterToTraits<Elaborator<'cx, 'gcx, 'tcx>>;
265 pub fn supertraits<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
266 trait_ref: ty::PolyTraitRef<'tcx>)
267 -> Supertraits<'cx, 'gcx, 'tcx>
269 elaborate_trait_ref(tcx, trait_ref).filter_to_traits()
272 pub fn transitive_bounds<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
273 bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>)
274 -> Supertraits<'cx, 'gcx, 'tcx>
276 elaborate_trait_refs(tcx, bounds).filter_to_traits()
279 ///////////////////////////////////////////////////////////////////////////
280 // Iterator over def-ids of supertraits
282 pub struct SupertraitDefIds<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
283 tcx: TyCtxt<'a, 'gcx, 'tcx>,
285 visited: FxHashSet<DefId>,
288 pub fn supertrait_def_ids<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
290 -> SupertraitDefIds<'cx, 'gcx, 'tcx>
294 stack: vec![trait_def_id],
295 visited: Some(trait_def_id).into_iter().collect(),
299 impl<'cx, 'gcx, 'tcx> Iterator for SupertraitDefIds<'cx, 'gcx, 'tcx> {
302 fn next(&mut self) -> Option<DefId> {
303 let def_id = match self.stack.pop() {
304 Some(def_id) => def_id,
305 None => { return None; }
308 let predicates = self.tcx.super_predicates_of(def_id);
309 let visited = &mut self.visited;
311 predicates.predicates
313 .filter_map(|(p, _)| p.to_opt_poly_trait_ref())
315 .filter(|&super_def_id| visited.insert(super_def_id)));
320 ///////////////////////////////////////////////////////////////////////////
322 ///////////////////////////////////////////////////////////////////////////
324 /// A filter around an iterator of predicates that makes it yield up
325 /// just trait references.
326 pub struct FilterToTraits<I> {
330 impl<I> FilterToTraits<I> {
331 fn new(base: I) -> FilterToTraits<I> {
332 FilterToTraits { base_iterator: base }
336 impl<'tcx,I:Iterator<Item = ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
337 type Item = ty::PolyTraitRef<'tcx>;
339 fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> {
341 match self.base_iterator.next() {
345 Some(ty::Predicate::Trait(data)) => {
346 return Some(data.to_poly_trait_ref());
353 fn size_hint(&self) -> (usize, Option<usize>) {
354 let (_, upper) = self.base_iterator.size_hint();
359 ///////////////////////////////////////////////////////////////////////////
361 ///////////////////////////////////////////////////////////////////////////
363 /// Instantiate all bound parameters of the impl with the given substs,
364 /// returning the resulting trait ref and all obligations that arise.
365 /// The obligations are closed under normalization.
366 pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tcx>,
367 param_env: ty::ParamEnv<'tcx>,
369 impl_substs: &Substs<'tcx>)
370 -> (ty::TraitRef<'tcx>,
371 Vec<PredicateObligation<'tcx>>)
374 selcx.tcx().impl_trait_ref(impl_def_id).unwrap();
376 impl_trait_ref.subst(selcx.tcx(), impl_substs);
377 let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 } =
378 super::normalize(selcx, param_env, ObligationCause::dummy(), &impl_trait_ref);
380 let predicates = selcx.tcx().predicates_of(impl_def_id);
381 let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
382 let Normalized { value: predicates, obligations: normalization_obligations2 } =
383 super::normalize(selcx, param_env, ObligationCause::dummy(), &predicates);
384 let impl_obligations =
385 predicates_for_generics(ObligationCause::dummy(), 0, param_env, &predicates);
387 let impl_obligations: Vec<_> =
388 impl_obligations.into_iter()
389 .chain(normalization_obligations1)
390 .chain(normalization_obligations2)
393 (impl_trait_ref, impl_obligations)
396 /// See `super::obligations_for_generics`
397 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
398 recursion_depth: usize,
399 param_env: ty::ParamEnv<'tcx>,
400 generic_bounds: &ty::InstantiatedPredicates<'tcx>)
401 -> Vec<PredicateObligation<'tcx>>
403 debug!("predicates_for_generics(generic_bounds={:?})",
406 generic_bounds.predicates.iter().map(|predicate| {
407 Obligation { cause: cause.clone(),
410 predicate: predicate.clone() }
414 pub fn predicate_for_trait_ref<'tcx>(
415 cause: ObligationCause<'tcx>,
416 param_env: ty::ParamEnv<'tcx>,
417 trait_ref: ty::TraitRef<'tcx>,
418 recursion_depth: usize)
419 -> PredicateObligation<'tcx>
425 predicate: trait_ref.to_predicate(),
429 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
430 pub fn predicate_for_trait_def(self,
431 param_env: ty::ParamEnv<'tcx>,
432 cause: ObligationCause<'tcx>,
434 recursion_depth: usize,
436 params: &[Kind<'tcx>])
437 -> PredicateObligation<'tcx>
439 let trait_ref = ty::TraitRef {
440 def_id: trait_def_id,
441 substs: self.mk_substs_trait(self_ty, params)
443 predicate_for_trait_ref(cause, param_env, trait_ref, recursion_depth)
446 /// Cast a trait reference into a reference to one of its super
447 /// traits; returns `None` if `target_trait_def_id` is not a
449 pub fn upcast_choices(self,
450 source_trait_ref: ty::PolyTraitRef<'tcx>,
451 target_trait_def_id: DefId)
452 -> Vec<ty::PolyTraitRef<'tcx>>
454 if source_trait_ref.def_id() == target_trait_def_id {
455 return vec![source_trait_ref]; // shorcut the most common case
458 supertraits(self, source_trait_ref)
459 .filter(|r| r.def_id() == target_trait_def_id)
463 /// Given a trait `trait_ref`, returns the number of vtable entries
464 /// that come from `trait_ref`, excluding its supertraits. Used in
465 /// computing the vtable base for an upcast trait of a trait object.
466 pub fn count_own_vtable_entries(self, trait_ref: ty::PolyTraitRef<'tcx>) -> usize {
468 // Count number of methods and add them to the total offset.
469 // Skip over associated types and constants.
470 for trait_item in self.associated_items(trait_ref.def_id()) {
471 if trait_item.kind == ty::AssociatedKind::Method {
478 /// Given an upcast trait object described by `object`, returns the
479 /// index of the method `method_def_id` (which should be part of
480 /// `object.upcast_trait_ref`) within the vtable for `object`.
481 pub fn get_vtable_index_of_object_method<N>(self,
482 object: &super::VtableObjectData<'tcx, N>,
483 method_def_id: DefId) -> usize {
484 // Count number of methods preceding the one we are selecting and
485 // add them to the total offset.
486 // Skip over associated types and constants.
487 let mut entries = object.vtable_base;
488 for trait_item in self.associated_items(object.upcast_trait_ref.def_id()) {
489 if trait_item.def_id == method_def_id {
490 // The item with the ID we were given really ought to be a method.
491 assert_eq!(trait_item.kind, ty::AssociatedKind::Method);
494 if trait_item.kind == ty::AssociatedKind::Method {
499 bug!("get_vtable_index_of_object_method: {:?} was not found",
503 pub fn closure_trait_ref_and_return_type(self,
504 fn_trait_def_id: DefId,
506 sig: ty::PolyFnSig<'tcx>,
507 tuple_arguments: TupleArgumentsFlag)
508 -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>)>
510 let arguments_tuple = match tuple_arguments {
511 TupleArgumentsFlag::No => sig.skip_binder().inputs()[0],
512 TupleArgumentsFlag::Yes =>
513 self.intern_tup(sig.skip_binder().inputs()),
515 let trait_ref = ty::TraitRef {
516 def_id: fn_trait_def_id,
517 substs: self.mk_substs_trait(self_ty, &[arguments_tuple.into()]),
519 ty::Binder::bind((trait_ref, sig.skip_binder().output()))
522 pub fn generator_trait_ref_and_outputs(self,
523 fn_trait_def_id: DefId,
525 sig: ty::PolyGenSig<'tcx>)
526 -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>)>
528 let trait_ref = ty::TraitRef {
529 def_id: fn_trait_def_id,
530 substs: self.mk_substs_trait(self_ty, &[]),
532 ty::Binder::bind((trait_ref, sig.skip_binder().yield_ty, sig.skip_binder().return_ty))
535 pub fn impl_is_default(self, node_item_def_id: DefId) -> bool {
536 match self.hir.as_local_node_id(node_item_def_id) {
538 let item = self.hir.expect_item(node_id);
539 if let hir::ItemKind::Impl(_, _, defaultness, ..) = item.node {
540 defaultness.is_default()
547 .impl_defaultness(node_item_def_id)
553 pub fn impl_item_is_final(self, node_item: &NodeItem<hir::Defaultness>) -> bool {
554 node_item.item.is_final() && !self.impl_is_default(node_item.node.def_id())
558 pub enum TupleArgumentsFlag { Yes, No }