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::{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::Equate(ref data) =>
29 ty::Predicate::Equate(tcx.anonymize_late_bound_regions(data)),
31 ty::Predicate::RegionOutlives(ref data) =>
32 ty::Predicate::RegionOutlives(tcx.anonymize_late_bound_regions(data)),
34 ty::Predicate::TypeOutlives(ref data) =>
35 ty::Predicate::TypeOutlives(tcx.anonymize_late_bound_regions(data)),
37 ty::Predicate::Projection(ref data) =>
38 ty::Predicate::Projection(tcx.anonymize_late_bound_regions(data)),
40 ty::Predicate::WellFormed(data) =>
41 ty::Predicate::WellFormed(data),
43 ty::Predicate::ObjectSafe(data) =>
44 ty::Predicate::ObjectSafe(data),
46 ty::Predicate::ClosureKind(closure_def_id, kind) =>
47 ty::Predicate::ClosureKind(closure_def_id, kind),
49 ty::Predicate::Subtype(ref data) =>
50 ty::Predicate::Subtype(tcx.anonymize_late_bound_regions(data)),
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: FxHashSet() }
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: &[ty::PolyTraitRef<'tcx>])
107 -> Elaborator<'cx, 'gcx, 'tcx>
109 let predicates = trait_refs.iter()
110 .map(|trait_ref| trait_ref.to_predicate())
112 elaborate_predicates(tcx, predicates)
115 pub fn elaborate_predicates<'cx, 'gcx, 'tcx>(
116 tcx: TyCtxt<'cx, 'gcx, 'tcx>,
117 mut predicates: Vec<ty::Predicate<'tcx>>)
118 -> Elaborator<'cx, 'gcx, 'tcx>
120 let mut visited = PredicateSet::new(tcx);
121 predicates.retain(|pred| visited.insert(pred));
122 Elaborator { stack: predicates, visited: visited }
125 impl<'cx, 'gcx, 'tcx> Elaborator<'cx, 'gcx, 'tcx> {
126 pub fn filter_to_traits(self) -> FilterToTraits<Self> {
127 FilterToTraits::new(self)
130 fn push(&mut self, predicate: &ty::Predicate<'tcx>) {
131 let tcx = self.visited.tcx;
133 ty::Predicate::Trait(ref data) => {
134 // Predicates declared on the trait.
135 let predicates = tcx.super_predicates_of(data.def_id());
137 let mut predicates: Vec<_> =
138 predicates.predicates
140 .map(|p| p.subst_supertrait(tcx, &data.to_poly_trait_ref()))
143 debug!("super_predicates: data={:?} predicates={:?}",
146 // Only keep those bounds that we haven't already
147 // seen. This is necessary to prevent infinite
148 // recursion in some cases. One common case is when
149 // people define `trait Sized: Sized { }` rather than `trait
151 predicates.retain(|r| self.visited.insert(r));
153 self.stack.extend(predicates);
155 ty::Predicate::WellFormed(..) => {
156 // Currently, we do not elaborate WF predicates,
157 // although we easily could.
159 ty::Predicate::ObjectSafe(..) => {
160 // Currently, we do not elaborate object-safe
163 ty::Predicate::Equate(..) => {
164 // Currently, we do not "elaborate" predicates like
165 // `X == Y`, though conceivably we might. For example,
166 // `&X == &Y` implies that `X == Y`.
168 ty::Predicate::Subtype(..) => {
169 // Currently, we do not "elaborate" predicates like `X
170 // <: Y`, though conceivably we might.
172 ty::Predicate::Projection(..) => {
173 // Nothing to elaborate in a projection predicate.
175 ty::Predicate::ClosureKind(..) => {
176 // Nothing to elaborate when waiting for a closure's kind to be inferred.
179 ty::Predicate::RegionOutlives(..) => {
180 // Nothing to elaborate from `'a: 'b`.
183 ty::Predicate::TypeOutlives(ref data) => {
184 // We know that `T: 'a` for some type `T`. We can
185 // often elaborate this. For example, if we know that
186 // `[U]: 'a`, that implies that `U: 'a`. Similarly, if
187 // we know `&'a U: 'b`, then we know that `'a: 'b` and
190 // We can basically ignore bound regions here. So for
191 // example `for<'c> Foo<'a,'c>: 'b` can be elaborated to
194 // Ignore `for<'a> T: 'a` -- we might in the future
195 // consider this as evidence that `T: 'static`, but
196 // I'm a bit wary of such constructions and so for now
197 // I want to be conservative. --nmatsakis
198 let ty_max = data.skip_binder().0;
199 let r_min = data.skip_binder().1;
200 if r_min.is_bound() {
204 let visited = &mut self.visited;
206 tcx.outlives_components(ty_max)
208 .filter_map(|component| match component {
209 Component::Region(r) => if r.is_bound() {
212 Some(ty::Predicate::RegionOutlives(
213 ty::Binder(ty::OutlivesPredicate(r, r_min))))
216 Component::Param(p) => {
217 let ty = tcx.mk_param(p.idx, p.name);
218 Some(ty::Predicate::TypeOutlives(
219 ty::Binder(ty::OutlivesPredicate(ty, r_min))))
222 Component::UnresolvedInferenceVariable(_) => {
226 Component::Projection(_) |
227 Component::EscapingProjection(_) => {
228 // We can probably do more here. This
229 // corresponds to a case like `<T as
234 .filter(|p| visited.insert(p)));
240 impl<'cx, 'gcx, 'tcx> Iterator for Elaborator<'cx, 'gcx, 'tcx> {
241 type Item = ty::Predicate<'tcx>;
243 fn next(&mut self) -> Option<ty::Predicate<'tcx>> {
244 // Extract next item from top-most stack frame, if any.
245 let next_predicate = match self.stack.pop() {
246 Some(predicate) => predicate,
248 // No more stack frames. Done.
252 self.push(&next_predicate);
253 return Some(next_predicate);
257 ///////////////////////////////////////////////////////////////////////////
258 // Supertrait iterator
259 ///////////////////////////////////////////////////////////////////////////
261 pub type Supertraits<'cx, 'gcx, 'tcx> = FilterToTraits<Elaborator<'cx, 'gcx, 'tcx>>;
263 pub fn supertraits<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
264 trait_ref: ty::PolyTraitRef<'tcx>)
265 -> Supertraits<'cx, 'gcx, 'tcx>
267 elaborate_trait_ref(tcx, trait_ref).filter_to_traits()
270 pub fn transitive_bounds<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
271 bounds: &[ty::PolyTraitRef<'tcx>])
272 -> Supertraits<'cx, 'gcx, 'tcx>
274 elaborate_trait_refs(tcx, bounds).filter_to_traits()
277 ///////////////////////////////////////////////////////////////////////////
278 // Iterator over def-ids of supertraits
280 pub struct SupertraitDefIds<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
281 tcx: TyCtxt<'a, 'gcx, 'tcx>,
283 visited: FxHashSet<DefId>,
286 pub fn supertrait_def_ids<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>,
288 -> SupertraitDefIds<'cx, 'gcx, 'tcx>
292 stack: vec![trait_def_id],
293 visited: Some(trait_def_id).into_iter().collect(),
297 impl<'cx, 'gcx, 'tcx> Iterator for SupertraitDefIds<'cx, 'gcx, 'tcx> {
300 fn next(&mut self) -> Option<DefId> {
301 let def_id = match self.stack.pop() {
302 Some(def_id) => def_id,
303 None => { return None; }
306 let predicates = self.tcx.super_predicates_of(def_id);
307 let visited = &mut self.visited;
309 predicates.predicates
311 .filter_map(|p| p.to_opt_poly_trait_ref())
313 .filter(|&super_def_id| visited.insert(super_def_id)));
318 ///////////////////////////////////////////////////////////////////////////
320 ///////////////////////////////////////////////////////////////////////////
322 /// A filter around an iterator of predicates that makes it yield up
323 /// just trait references.
324 pub struct FilterToTraits<I> {
328 impl<I> FilterToTraits<I> {
329 fn new(base: I) -> FilterToTraits<I> {
330 FilterToTraits { base_iterator: base }
334 impl<'tcx,I:Iterator<Item=ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> {
335 type Item = ty::PolyTraitRef<'tcx>;
337 fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> {
339 match self.base_iterator.next() {
343 Some(ty::Predicate::Trait(data)) => {
344 return Some(data.to_poly_trait_ref());
353 ///////////////////////////////////////////////////////////////////////////
355 ///////////////////////////////////////////////////////////////////////////
357 /// Instantiate all bound parameters of the impl with the given substs,
358 /// returning the resulting trait ref and all obligations that arise.
359 /// The obligations are closed under normalization.
360 pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tcx>,
362 impl_substs: &Substs<'tcx>)
363 -> (ty::TraitRef<'tcx>,
364 Vec<PredicateObligation<'tcx>>)
367 selcx.tcx().impl_trait_ref(impl_def_id).unwrap();
369 impl_trait_ref.subst(selcx.tcx(), impl_substs);
370 let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 } =
371 super::normalize(selcx, ObligationCause::dummy(), &impl_trait_ref);
373 let predicates = selcx.tcx().predicates_of(impl_def_id);
374 let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
375 let Normalized { value: predicates, obligations: normalization_obligations2 } =
376 super::normalize(selcx, ObligationCause::dummy(), &predicates);
377 let impl_obligations =
378 predicates_for_generics(ObligationCause::dummy(), 0, &predicates);
380 let impl_obligations: Vec<_> =
381 impl_obligations.into_iter()
382 .chain(normalization_obligations1)
383 .chain(normalization_obligations2)
386 (impl_trait_ref, impl_obligations)
389 /// See `super::obligations_for_generics`
390 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
391 recursion_depth: usize,
392 generic_bounds: &ty::InstantiatedPredicates<'tcx>)
393 -> Vec<PredicateObligation<'tcx>>
395 debug!("predicates_for_generics(generic_bounds={:?})",
398 generic_bounds.predicates.iter().map(|predicate| {
399 Obligation { cause: cause.clone(),
400 recursion_depth: recursion_depth,
401 predicate: predicate.clone() }
405 pub fn predicate_for_trait_ref<'tcx>(
406 cause: ObligationCause<'tcx>,
407 trait_ref: ty::TraitRef<'tcx>,
408 recursion_depth: usize)
409 -> PredicateObligation<'tcx>
413 recursion_depth: recursion_depth,
414 predicate: trait_ref.to_predicate(),
418 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
419 pub fn predicate_for_trait_def(self,
420 cause: ObligationCause<'tcx>,
422 recursion_depth: usize,
424 ty_params: &[Ty<'tcx>])
425 -> PredicateObligation<'tcx>
427 let trait_ref = ty::TraitRef {
428 def_id: trait_def_id,
429 substs: self.mk_substs_trait(param_ty, ty_params)
431 predicate_for_trait_ref(cause, trait_ref, recursion_depth)
434 /// Cast a trait reference into a reference to one of its super
435 /// traits; returns `None` if `target_trait_def_id` is not a
437 pub fn upcast_choices(self,
438 source_trait_ref: ty::PolyTraitRef<'tcx>,
439 target_trait_def_id: DefId)
440 -> Vec<ty::PolyTraitRef<'tcx>>
442 if source_trait_ref.def_id() == target_trait_def_id {
443 return vec![source_trait_ref]; // shorcut the most common case
446 supertraits(self, source_trait_ref)
447 .filter(|r| r.def_id() == target_trait_def_id)
451 /// Given a trait `trait_ref`, returns the number of vtable entries
452 /// that come from `trait_ref`, excluding its supertraits. Used in
453 /// computing the vtable base for an upcast trait of a trait object.
454 pub fn count_own_vtable_entries(self, trait_ref: ty::PolyTraitRef<'tcx>) -> usize {
456 // Count number of methods and add them to the total offset.
457 // Skip over associated types and constants.
458 for trait_item in self.associated_items(trait_ref.def_id()) {
459 if trait_item.kind == ty::AssociatedKind::Method {
466 /// Given an upcast trait object described by `object`, returns the
467 /// index of the method `method_def_id` (which should be part of
468 /// `object.upcast_trait_ref`) within the vtable for `object`.
469 pub fn get_vtable_index_of_object_method<N>(self,
470 object: &super::VtableObjectData<'tcx, N>,
471 method_def_id: DefId) -> usize {
472 // Count number of methods preceding the one we are selecting and
473 // add them to the total offset.
474 // Skip over associated types and constants.
475 let mut entries = object.vtable_base;
476 for trait_item in self.associated_items(object.upcast_trait_ref.def_id()) {
477 if trait_item.def_id == method_def_id {
478 // The item with the ID we were given really ought to be a method.
479 assert_eq!(trait_item.kind, ty::AssociatedKind::Method);
482 if trait_item.kind == ty::AssociatedKind::Method {
487 bug!("get_vtable_index_of_object_method: {:?} was not found",
491 pub fn closure_trait_ref_and_return_type(self,
492 fn_trait_def_id: DefId,
494 sig: ty::PolyFnSig<'tcx>,
495 tuple_arguments: TupleArgumentsFlag)
496 -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>)>
498 let arguments_tuple = match tuple_arguments {
499 TupleArgumentsFlag::No => sig.skip_binder().inputs()[0],
500 TupleArgumentsFlag::Yes =>
501 self.intern_tup(sig.skip_binder().inputs(), false),
503 let trait_ref = ty::TraitRef {
504 def_id: fn_trait_def_id,
505 substs: self.mk_substs_trait(self_ty, &[arguments_tuple]),
507 ty::Binder((trait_ref, sig.skip_binder().output()))
510 pub fn impl_is_default(self, node_item_def_id: DefId) -> bool {
511 match self.hir.as_local_node_id(node_item_def_id) {
513 let item = self.hir.expect_item(node_id);
514 if let hir::ItemImpl(_, _, defaultness, ..) = item.node {
515 defaultness.is_default()
524 .impl_defaultness(node_item_def_id)
530 pub fn impl_item_is_final(self, node_item: &NodeItem<hir::Defaultness>) -> bool {
531 node_item.item.is_final() && !self.impl_is_default(node_item.node.def_id())
535 pub enum TupleArgumentsFlag { Yes, No }