| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| use hir::def_id::DefId; |
| use ty::subst::{Kind, Subst, Substs}; |
| use ty::{self, Ty, TyCtxt, ToPredicate, ToPolyTraitRef}; |
| use ty::outlives::Component; |
| use util::nodemap::FxHashSet; |
| use hir::{self}; |
| use traits::specialize::specialization_graph::NodeItem; |
| |
| use super::{Obligation, ObligationCause, PredicateObligation, SelectionContext, Normalized}; |
| |
| fn anonymize_predicate<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>, |
| pred: &ty::Predicate<'tcx>) |
| -> ty::Predicate<'tcx> { |
| match *pred { |
| ty::Predicate::Trait(ref data) => |
| ty::Predicate::Trait(tcx.anonymize_late_bound_regions(data)), |
| |
| ty::Predicate::RegionOutlives(ref data) => |
| ty::Predicate::RegionOutlives(tcx.anonymize_late_bound_regions(data)), |
| |
| ty::Predicate::TypeOutlives(ref data) => |
| ty::Predicate::TypeOutlives(tcx.anonymize_late_bound_regions(data)), |
| |
| ty::Predicate::Projection(ref data) => |
| ty::Predicate::Projection(tcx.anonymize_late_bound_regions(data)), |
| |
| ty::Predicate::WellFormed(data) => |
| ty::Predicate::WellFormed(data), |
| |
| ty::Predicate::ObjectSafe(data) => |
| ty::Predicate::ObjectSafe(data), |
| |
| ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind) => |
| ty::Predicate::ClosureKind(closure_def_id, closure_substs, kind), |
| |
| ty::Predicate::Subtype(ref data) => |
| ty::Predicate::Subtype(tcx.anonymize_late_bound_regions(data)), |
| |
| ty::Predicate::ConstEvaluatable(def_id, substs) => |
| ty::Predicate::ConstEvaluatable(def_id, substs), |
| } |
| } |
| |
| |
| struct PredicateSet<'a, 'gcx: 'a+'tcx, 'tcx: 'a> { |
| tcx: TyCtxt<'a, 'gcx, 'tcx>, |
| set: FxHashSet<ty::Predicate<'tcx>>, |
| } |
| |
| impl<'a, 'gcx, 'tcx> PredicateSet<'a, 'gcx, 'tcx> { |
| fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> PredicateSet<'a, 'gcx, 'tcx> { |
| PredicateSet { tcx: tcx, set: Default::default() } |
| } |
| |
| fn insert(&mut self, pred: &ty::Predicate<'tcx>) -> bool { |
| // We have to be careful here because we want |
| // |
| // for<'a> Foo<&'a int> |
| // |
| // and |
| // |
| // for<'b> Foo<&'b int> |
| // |
| // to be considered equivalent. So normalize all late-bound |
| // regions before we throw things into the underlying set. |
| self.set.insert(anonymize_predicate(self.tcx, pred)) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // `Elaboration` iterator |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /// "Elaboration" is the process of identifying all the predicates that |
| /// are implied by a source predicate. Currently this basically means |
| /// walking the "supertraits" and other similar assumptions. For |
| /// example, if we know that `T : Ord`, the elaborator would deduce |
| /// that `T : PartialOrd` holds as well. Similarly, if we have `trait |
| /// Foo : 'static`, and we know that `T : Foo`, then we know that `T : |
| /// 'static`. |
| pub struct Elaborator<'a, 'gcx: 'a+'tcx, 'tcx: 'a> { |
| stack: Vec<ty::Predicate<'tcx>>, |
| visited: PredicateSet<'a, 'gcx, 'tcx>, |
| } |
| |
| pub fn elaborate_trait_ref<'cx, 'gcx, 'tcx>( |
| tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| trait_ref: ty::PolyTraitRef<'tcx>) |
| -> Elaborator<'cx, 'gcx, 'tcx> |
| { |
| elaborate_predicates(tcx, vec![trait_ref.to_predicate()]) |
| } |
| |
| pub fn elaborate_trait_refs<'cx, 'gcx, 'tcx>( |
| tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| trait_refs: &[ty::PolyTraitRef<'tcx>]) |
| -> Elaborator<'cx, 'gcx, 'tcx> |
| { |
| let predicates = trait_refs.iter() |
| .map(|trait_ref| trait_ref.to_predicate()) |
| .collect(); |
| elaborate_predicates(tcx, predicates) |
| } |
| |
| pub fn elaborate_predicates<'cx, 'gcx, 'tcx>( |
| tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| mut predicates: Vec<ty::Predicate<'tcx>>) |
| -> Elaborator<'cx, 'gcx, 'tcx> |
| { |
| let mut visited = PredicateSet::new(tcx); |
| predicates.retain(|pred| visited.insert(pred)); |
| Elaborator { stack: predicates, visited: visited } |
| } |
| |
| impl<'cx, 'gcx, 'tcx> Elaborator<'cx, 'gcx, 'tcx> { |
| pub fn filter_to_traits(self) -> FilterToTraits<Self> { |
| FilterToTraits::new(self) |
| } |
| |
| fn push(&mut self, predicate: &ty::Predicate<'tcx>) { |
| let tcx = self.visited.tcx; |
| match *predicate { |
| ty::Predicate::Trait(ref data) => { |
| // Predicates declared on the trait. |
| let predicates = tcx.super_predicates_of(data.def_id()); |
| |
| let mut predicates: Vec<_> = |
| predicates.predicates |
| .iter() |
| .map(|(p, _)| p.subst_supertrait(tcx, &data.to_poly_trait_ref())) |
| .collect(); |
| |
| debug!("super_predicates: data={:?} predicates={:?}", |
| data, predicates); |
| |
| // Only keep those bounds that we haven't already |
| // seen. This is necessary to prevent infinite |
| // recursion in some cases. One common case is when |
| // people define `trait Sized: Sized { }` rather than `trait |
| // Sized { }`. |
| predicates.retain(|r| self.visited.insert(r)); |
| |
| self.stack.extend(predicates); |
| } |
| ty::Predicate::WellFormed(..) => { |
| // Currently, we do not elaborate WF predicates, |
| // although we easily could. |
| } |
| ty::Predicate::ObjectSafe(..) => { |
| // Currently, we do not elaborate object-safe |
| // predicates. |
| } |
| ty::Predicate::Subtype(..) => { |
| // Currently, we do not "elaborate" predicates like `X |
| // <: Y`, though conceivably we might. |
| } |
| ty::Predicate::Projection(..) => { |
| // Nothing to elaborate in a projection predicate. |
| } |
| ty::Predicate::ClosureKind(..) => { |
| // Nothing to elaborate when waiting for a closure's kind to be inferred. |
| } |
| ty::Predicate::ConstEvaluatable(..) => { |
| // Currently, we do not elaborate const-evaluatable |
| // predicates. |
| } |
| |
| ty::Predicate::RegionOutlives(..) => { |
| // Nothing to elaborate from `'a: 'b`. |
| } |
| |
| ty::Predicate::TypeOutlives(ref data) => { |
| // We know that `T: 'a` for some type `T`. We can |
| // often elaborate this. For example, if we know that |
| // `[U]: 'a`, that implies that `U: 'a`. Similarly, if |
| // we know `&'a U: 'b`, then we know that `'a: 'b` and |
| // `U: 'b`. |
| // |
| // We can basically ignore bound regions here. So for |
| // example `for<'c> Foo<'a,'c>: 'b` can be elaborated to |
| // `'a: 'b`. |
| |
| // Ignore `for<'a> T: 'a` -- we might in the future |
| // consider this as evidence that `T: 'static`, but |
| // I'm a bit wary of such constructions and so for now |
| // I want to be conservative. --nmatsakis |
| let ty_max = data.skip_binder().0; |
| let r_min = data.skip_binder().1; |
| if r_min.is_late_bound() { |
| return; |
| } |
| |
| let visited = &mut self.visited; |
| self.stack.extend( |
| tcx.outlives_components(ty_max) |
| .into_iter() |
| .filter_map(|component| match component { |
| Component::Region(r) => if r.is_late_bound() { |
| None |
| } else { |
| Some(ty::Predicate::RegionOutlives( |
| ty::Binder::dummy(ty::OutlivesPredicate(r, r_min)))) |
| }, |
| |
| Component::Param(p) => { |
| let ty = tcx.mk_ty_param(p.idx, p.name); |
| Some(ty::Predicate::TypeOutlives( |
| ty::Binder::dummy(ty::OutlivesPredicate(ty, r_min)))) |
| }, |
| |
| Component::UnresolvedInferenceVariable(_) => { |
| None |
| }, |
| |
| Component::Projection(_) | |
| Component::EscapingProjection(_) => { |
| // We can probably do more here. This |
| // corresponds to a case like `<T as |
| // Foo<'a>>::U: 'b`. |
| None |
| }, |
| }) |
| .filter(|p| visited.insert(p))); |
| } |
| } |
| } |
| } |
| |
| impl<'cx, 'gcx, 'tcx> Iterator for Elaborator<'cx, 'gcx, 'tcx> { |
| type Item = ty::Predicate<'tcx>; |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| (self.stack.len(), None) |
| } |
| |
| fn next(&mut self) -> Option<ty::Predicate<'tcx>> { |
| // Extract next item from top-most stack frame, if any. |
| let next_predicate = match self.stack.pop() { |
| Some(predicate) => predicate, |
| None => { |
| // No more stack frames. Done. |
| return None; |
| } |
| }; |
| self.push(&next_predicate); |
| return Some(next_predicate); |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Supertrait iterator |
| /////////////////////////////////////////////////////////////////////////// |
| |
| pub type Supertraits<'cx, 'gcx, 'tcx> = FilterToTraits<Elaborator<'cx, 'gcx, 'tcx>>; |
| |
| pub fn supertraits<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| trait_ref: ty::PolyTraitRef<'tcx>) |
| -> Supertraits<'cx, 'gcx, 'tcx> |
| { |
| elaborate_trait_ref(tcx, trait_ref).filter_to_traits() |
| } |
| |
| pub fn transitive_bounds<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| bounds: &[ty::PolyTraitRef<'tcx>]) |
| -> Supertraits<'cx, 'gcx, 'tcx> |
| { |
| elaborate_trait_refs(tcx, bounds).filter_to_traits() |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Iterator over def-ids of supertraits |
| |
| pub struct SupertraitDefIds<'a, 'gcx: 'a+'tcx, 'tcx: 'a> { |
| tcx: TyCtxt<'a, 'gcx, 'tcx>, |
| stack: Vec<DefId>, |
| visited: FxHashSet<DefId>, |
| } |
| |
| pub fn supertrait_def_ids<'cx, 'gcx, 'tcx>(tcx: TyCtxt<'cx, 'gcx, 'tcx>, |
| trait_def_id: DefId) |
| -> SupertraitDefIds<'cx, 'gcx, 'tcx> |
| { |
| SupertraitDefIds { |
| tcx, |
| stack: vec![trait_def_id], |
| visited: Some(trait_def_id).into_iter().collect(), |
| } |
| } |
| |
| impl<'cx, 'gcx, 'tcx> Iterator for SupertraitDefIds<'cx, 'gcx, 'tcx> { |
| type Item = DefId; |
| |
| fn next(&mut self) -> Option<DefId> { |
| let def_id = match self.stack.pop() { |
| Some(def_id) => def_id, |
| None => { return None; } |
| }; |
| |
| let predicates = self.tcx.super_predicates_of(def_id); |
| let visited = &mut self.visited; |
| self.stack.extend( |
| predicates.predicates |
| .iter() |
| .filter_map(|(p, _)| p.to_opt_poly_trait_ref()) |
| .map(|t| t.def_id()) |
| .filter(|&super_def_id| visited.insert(super_def_id))); |
| Some(def_id) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Other |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /// A filter around an iterator of predicates that makes it yield up |
| /// just trait references. |
| pub struct FilterToTraits<I> { |
| base_iterator: I |
| } |
| |
| impl<I> FilterToTraits<I> { |
| fn new(base: I) -> FilterToTraits<I> { |
| FilterToTraits { base_iterator: base } |
| } |
| } |
| |
| impl<'tcx,I:Iterator<Item=ty::Predicate<'tcx>>> Iterator for FilterToTraits<I> { |
| type Item = ty::PolyTraitRef<'tcx>; |
| |
| fn next(&mut self) -> Option<ty::PolyTraitRef<'tcx>> { |
| loop { |
| match self.base_iterator.next() { |
| None => { |
| return None; |
| } |
| Some(ty::Predicate::Trait(data)) => { |
| return Some(data.to_poly_trait_ref()); |
| } |
| Some(_) => {} |
| } |
| } |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| let (_, upper) = self.base_iterator.size_hint(); |
| (0, upper) |
| } |
| } |
| |
| /////////////////////////////////////////////////////////////////////////// |
| // Other |
| /////////////////////////////////////////////////////////////////////////// |
| |
| /// Instantiate all bound parameters of the impl with the given substs, |
| /// returning the resulting trait ref and all obligations that arise. |
| /// The obligations are closed under normalization. |
| pub fn impl_trait_ref_and_oblig<'a, 'gcx, 'tcx>(selcx: &mut SelectionContext<'a, 'gcx, 'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| impl_def_id: DefId, |
| impl_substs: &Substs<'tcx>) |
| -> (ty::TraitRef<'tcx>, |
| Vec<PredicateObligation<'tcx>>) |
| { |
| let impl_trait_ref = |
| selcx.tcx().impl_trait_ref(impl_def_id).unwrap(); |
| let impl_trait_ref = |
| impl_trait_ref.subst(selcx.tcx(), impl_substs); |
| let Normalized { value: impl_trait_ref, obligations: normalization_obligations1 } = |
| super::normalize(selcx, param_env, ObligationCause::dummy(), &impl_trait_ref); |
| |
| let predicates = selcx.tcx().predicates_of(impl_def_id); |
| let predicates = predicates.instantiate(selcx.tcx(), impl_substs); |
| let Normalized { value: predicates, obligations: normalization_obligations2 } = |
| super::normalize(selcx, param_env, ObligationCause::dummy(), &predicates); |
| let impl_obligations = |
| predicates_for_generics(ObligationCause::dummy(), 0, param_env, &predicates); |
| |
| let impl_obligations: Vec<_> = |
| impl_obligations.into_iter() |
| .chain(normalization_obligations1) |
| .chain(normalization_obligations2) |
| .collect(); |
| |
| (impl_trait_ref, impl_obligations) |
| } |
| |
| /// See `super::obligations_for_generics` |
| pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>, |
| recursion_depth: usize, |
| param_env: ty::ParamEnv<'tcx>, |
| generic_bounds: &ty::InstantiatedPredicates<'tcx>) |
| -> Vec<PredicateObligation<'tcx>> |
| { |
| debug!("predicates_for_generics(generic_bounds={:?})", |
| generic_bounds); |
| |
| generic_bounds.predicates.iter().map(|predicate| { |
| Obligation { cause: cause.clone(), |
| recursion_depth, |
| param_env, |
| predicate: predicate.clone() } |
| }).collect() |
| } |
| |
| pub fn predicate_for_trait_ref<'tcx>( |
| cause: ObligationCause<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| trait_ref: ty::TraitRef<'tcx>, |
| recursion_depth: usize) |
| -> PredicateObligation<'tcx> |
| { |
| Obligation { |
| cause, |
| param_env, |
| recursion_depth, |
| predicate: trait_ref.to_predicate(), |
| } |
| } |
| |
| impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> { |
| pub fn predicate_for_trait_def(self, |
| param_env: ty::ParamEnv<'tcx>, |
| cause: ObligationCause<'tcx>, |
| trait_def_id: DefId, |
| recursion_depth: usize, |
| self_ty: Ty<'tcx>, |
| params: &[Kind<'tcx>]) |
| -> PredicateObligation<'tcx> |
| { |
| let trait_ref = ty::TraitRef { |
| def_id: trait_def_id, |
| substs: self.mk_substs_trait(self_ty, params) |
| }; |
| predicate_for_trait_ref(cause, param_env, trait_ref, recursion_depth) |
| } |
| |
| /// Cast a trait reference into a reference to one of its super |
| /// traits; returns `None` if `target_trait_def_id` is not a |
| /// supertrait. |
| pub fn upcast_choices(self, |
| source_trait_ref: ty::PolyTraitRef<'tcx>, |
| target_trait_def_id: DefId) |
| -> Vec<ty::PolyTraitRef<'tcx>> |
| { |
| if source_trait_ref.def_id() == target_trait_def_id { |
| return vec![source_trait_ref]; // shorcut the most common case |
| } |
| |
| supertraits(self, source_trait_ref) |
| .filter(|r| r.def_id() == target_trait_def_id) |
| .collect() |
| } |
| |
| /// Given a trait `trait_ref`, returns the number of vtable entries |
| /// that come from `trait_ref`, excluding its supertraits. Used in |
| /// computing the vtable base for an upcast trait of a trait object. |
| pub fn count_own_vtable_entries(self, trait_ref: ty::PolyTraitRef<'tcx>) -> usize { |
| let mut entries = 0; |
| // Count number of methods and add them to the total offset. |
| // Skip over associated types and constants. |
| for trait_item in self.associated_items(trait_ref.def_id()) { |
| if trait_item.kind == ty::AssociatedKind::Method { |
| entries += 1; |
| } |
| } |
| entries |
| } |
| |
| /// Given an upcast trait object described by `object`, returns the |
| /// index of the method `method_def_id` (which should be part of |
| /// `object.upcast_trait_ref`) within the vtable for `object`. |
| pub fn get_vtable_index_of_object_method<N>(self, |
| object: &super::VtableObjectData<'tcx, N>, |
| method_def_id: DefId) -> usize { |
| // Count number of methods preceding the one we are selecting and |
| // add them to the total offset. |
| // Skip over associated types and constants. |
| let mut entries = object.vtable_base; |
| for trait_item in self.associated_items(object.upcast_trait_ref.def_id()) { |
| if trait_item.def_id == method_def_id { |
| // The item with the ID we were given really ought to be a method. |
| assert_eq!(trait_item.kind, ty::AssociatedKind::Method); |
| return entries; |
| } |
| if trait_item.kind == ty::AssociatedKind::Method { |
| entries += 1; |
| } |
| } |
| |
| bug!("get_vtable_index_of_object_method: {:?} was not found", |
| method_def_id); |
| } |
| |
| pub fn closure_trait_ref_and_return_type(self, |
| fn_trait_def_id: DefId, |
| self_ty: Ty<'tcx>, |
| sig: ty::PolyFnSig<'tcx>, |
| tuple_arguments: TupleArgumentsFlag) |
| -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>)> |
| { |
| let arguments_tuple = match tuple_arguments { |
| TupleArgumentsFlag::No => sig.skip_binder().inputs()[0], |
| TupleArgumentsFlag::Yes => |
| self.intern_tup(sig.skip_binder().inputs()), |
| }; |
| let trait_ref = ty::TraitRef { |
| def_id: fn_trait_def_id, |
| substs: self.mk_substs_trait(self_ty, &[arguments_tuple.into()]), |
| }; |
| ty::Binder::bind((trait_ref, sig.skip_binder().output())) |
| } |
| |
| pub fn generator_trait_ref_and_outputs(self, |
| fn_trait_def_id: DefId, |
| self_ty: Ty<'tcx>, |
| sig: ty::PolyGenSig<'tcx>) |
| -> ty::Binder<(ty::TraitRef<'tcx>, Ty<'tcx>, Ty<'tcx>)> |
| { |
| let trait_ref = ty::TraitRef { |
| def_id: fn_trait_def_id, |
| substs: self.mk_substs_trait(self_ty, &[]), |
| }; |
| ty::Binder::bind((trait_ref, sig.skip_binder().yield_ty, sig.skip_binder().return_ty)) |
| } |
| |
| pub fn impl_is_default(self, node_item_def_id: DefId) -> bool { |
| match self.hir.as_local_node_id(node_item_def_id) { |
| Some(node_id) => { |
| let item = self.hir.expect_item(node_id); |
| if let hir::ItemKind::Impl(_, _, defaultness, ..) = item.node { |
| defaultness.is_default() |
| } else { |
| false |
| } |
| } |
| None => { |
| self.global_tcx() |
| .impl_defaultness(node_item_def_id) |
| .is_default() |
| } |
| } |
| } |
| |
| pub fn impl_item_is_final(self, node_item: &NodeItem<hir::Defaultness>) -> bool { |
| node_item.item.is_final() && !self.impl_is_default(node_item.node.def_id()) |
| } |
| } |
| |
| pub enum TupleArgumentsFlag { Yes, No } |