diff options
Diffstat (limited to 'compiler/rustc_infer/src')
| -rw-r--r-- | compiler/rustc_infer/src/traits/util.rs | 209 |
1 files changed, 112 insertions, 97 deletions
diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs index f3797499866..c7f7ed14940 100644 --- a/compiler/rustc_infer/src/traits/util.rs +++ b/compiler/rustc_infer/src/traits/util.rs @@ -1,7 +1,7 @@ use smallvec::smallvec; use crate::infer::outlives::components::{push_outlives_components, Component}; -use crate::traits::{self, Obligation, ObligationCause, PredicateObligation}; +use crate::traits::{self, Obligation, PredicateObligation}; use rustc_data_structures::fx::{FxHashSet, FxIndexSet}; use rustc_middle::ty::{self, ToPredicate, TyCtxt}; use rustc_span::symbol::Ident; @@ -66,99 +66,129 @@ impl<'tcx> Extend<ty::Predicate<'tcx>> for PredicateSet<'tcx> { /// 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<'tcx> { - stack: Vec<PredicateObligation<'tcx>>, +pub struct Elaborator<'tcx, O> { + stack: Vec<O>, visited: PredicateSet<'tcx>, } -pub fn elaborate_trait_ref<'tcx>( - tcx: TyCtxt<'tcx>, - trait_ref: ty::PolyTraitRef<'tcx>, -) -> impl Iterator<Item = ty::Predicate<'tcx>> { - elaborate_predicates(tcx, std::iter::once(trait_ref.without_const().to_predicate(tcx))) +/// Describes how to elaborate an obligation into a sub-obligation. +/// +/// For [`Obligation`], a sub-obligation is combined with the current obligation's +/// param-env and cause code. For [`ty::Predicate`], none of this is needed, since +/// there is no param-env or cause code to copy over. +pub trait Elaboratable<'tcx> { + fn predicate(&self) -> ty::Predicate<'tcx>; + + // Makes a new `Self` but with a different predicate. + fn child(&self, predicate: ty::Predicate<'tcx>) -> Self; + + // Makes a new `Self` but with a different predicate and a different cause + // code (if `Self` has one). + fn child_with_derived_cause( + &self, + predicate: ty::Predicate<'tcx>, + span: Span, + parent_trait_pred: ty::PolyTraitPredicate<'tcx>, + index: usize, + ) -> Self; } -pub fn elaborate_trait_refs<'tcx>( - tcx: TyCtxt<'tcx>, - trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>, -) -> impl Iterator<Item = ty::Predicate<'tcx>> { - let predicates = trait_refs.map(move |trait_ref| trait_ref.without_const().to_predicate(tcx)); - elaborate_predicates(tcx, predicates) +impl<'tcx> Elaboratable<'tcx> for PredicateObligation<'tcx> { + fn predicate(&self) -> ty::Predicate<'tcx> { + self.predicate + } + + fn child(&self, predicate: ty::Predicate<'tcx>) -> Self { + Obligation { + cause: self.cause.clone(), + param_env: self.param_env, + recursion_depth: 0, + predicate, + } + } + + fn child_with_derived_cause( + &self, + predicate: ty::Predicate<'tcx>, + span: Span, + parent_trait_pred: ty::PolyTraitPredicate<'tcx>, + index: usize, + ) -> Self { + let cause = self.cause.clone().derived_cause(parent_trait_pred, |derived| { + traits::ImplDerivedObligation(Box::new(traits::ImplDerivedObligationCause { + derived, + impl_or_alias_def_id: parent_trait_pred.def_id(), + impl_def_predicate_index: Some(index), + span, + })) + }); + Obligation { cause, param_env: self.param_env, recursion_depth: 0, predicate } + } } -pub fn elaborate_predicates<'tcx>( - tcx: TyCtxt<'tcx>, - predicates: impl Iterator<Item = ty::Predicate<'tcx>>, -) -> impl Iterator<Item = ty::Predicate<'tcx>> { - elaborate_obligations( - tcx, - predicates - .map(|predicate| { - Obligation::new( - tcx, - // We'll dump the cause/param-env later - ObligationCause::dummy(), - ty::ParamEnv::empty(), - predicate, - ) - }) - .collect(), - ) - .map(|obl| obl.predicate) +impl<'tcx> Elaboratable<'tcx> for ty::Predicate<'tcx> { + fn predicate(&self) -> ty::Predicate<'tcx> { + *self + } + + fn child(&self, predicate: ty::Predicate<'tcx>) -> Self { + predicate + } + + fn child_with_derived_cause( + &self, + predicate: ty::Predicate<'tcx>, + _span: Span, + _parent_trait_pred: ty::PolyTraitPredicate<'tcx>, + _index: usize, + ) -> Self { + predicate + } } -pub fn elaborate_predicates_with_span<'tcx>( - tcx: TyCtxt<'tcx>, - predicates: impl Iterator<Item = (ty::Predicate<'tcx>, Span)>, -) -> impl Iterator<Item = (ty::Predicate<'tcx>, Span)> { - elaborate_obligations( - tcx, - predicates - .map(|(predicate, span)| { - Obligation::new( - tcx, - // We'll dump the cause/param-env later - ObligationCause::dummy_with_span(span), - ty::ParamEnv::empty(), - predicate, - ) - }) - .collect(), - ) - .map(|obl| (obl.predicate, obl.cause.span)) +impl<'tcx> Elaboratable<'tcx> for (ty::Predicate<'tcx>, Span) { + fn predicate(&self) -> ty::Predicate<'tcx> { + self.0 + } + + fn child(&self, predicate: ty::Predicate<'tcx>) -> Self { + (predicate, self.1) + } + + fn child_with_derived_cause( + &self, + predicate: ty::Predicate<'tcx>, + _span: Span, + _parent_trait_pred: ty::PolyTraitPredicate<'tcx>, + _index: usize, + ) -> Self { + (predicate, self.1) + } } -pub fn elaborate_obligations<'tcx>( +pub fn elaborate<'tcx, O: Elaboratable<'tcx>>( tcx: TyCtxt<'tcx>, - obligations: Vec<PredicateObligation<'tcx>>, -) -> Elaborator<'tcx> { + obligations: impl IntoIterator<Item = O>, +) -> Elaborator<'tcx, O> { let mut elaborator = Elaborator { stack: Vec::new(), visited: PredicateSet::new(tcx) }; elaborator.extend_deduped(obligations); elaborator } -fn predicate_obligation<'tcx>( - predicate: ty::Predicate<'tcx>, - param_env: ty::ParamEnv<'tcx>, - cause: ObligationCause<'tcx>, -) -> PredicateObligation<'tcx> { - Obligation { cause, param_env, recursion_depth: 0, predicate } -} - -impl<'tcx> Elaborator<'tcx> { - fn extend_deduped(&mut self, obligations: impl IntoIterator<Item = PredicateObligation<'tcx>>) { +impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> { + fn extend_deduped(&mut self, obligations: impl IntoIterator<Item = O>) { // 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 { }`. // let visited = &mut self.visited; - self.stack.extend(obligations.into_iter().filter(|o| self.visited.insert(o.predicate))); + self.stack.extend(obligations.into_iter().filter(|o| self.visited.insert(o.predicate()))); } - fn elaborate(&mut self, obligation: &PredicateObligation<'tcx>) { + fn elaborate(&mut self, elaboratable: &O) { let tcx = self.visited.tcx; - let bound_predicate = obligation.predicate.kind(); + let bound_predicate = elaboratable.predicate().kind(); match bound_predicate.skip_binder() { ty::PredicateKind::Clause(ty::Clause::Trait(data)) => { // Get predicates declared on the trait. @@ -170,24 +200,11 @@ impl<'tcx> Elaborator<'tcx> { if data.constness == ty::BoundConstness::NotConst { pred = pred.without_const(tcx); } - - let cause = obligation.cause.clone().derived_cause( - bound_predicate.rebind(data), - |derived| { - traits::ImplDerivedObligation(Box::new( - traits::ImplDerivedObligationCause { - derived, - impl_or_alias_def_id: data.def_id(), - impl_def_predicate_index: Some(index), - span, - }, - )) - }, - ); - predicate_obligation( + elaboratable.child_with_derived_cause( pred.subst_supertrait(tcx, &bound_predicate.rebind(data.trait_ref)), - obligation.param_env, - cause, + span, + bound_predicate.rebind(data), + index, ) }); debug!(?data, ?obligations, "super_predicates"); @@ -290,13 +307,7 @@ impl<'tcx> Elaborator<'tcx> { .map(|predicate_kind| { bound_predicate.rebind(predicate_kind).to_predicate(tcx) }) - .map(|predicate| { - predicate_obligation( - predicate, - obligation.param_env, - obligation.cause.clone(), - ) - }), + .map(|predicate| elaboratable.child(predicate)), ); } ty::PredicateKind::TypeWellFormedFromEnv(..) => { @@ -313,8 +324,8 @@ impl<'tcx> Elaborator<'tcx> { } } -impl<'tcx> Iterator for Elaborator<'tcx> { - type Item = PredicateObligation<'tcx>; +impl<'tcx, O: Elaboratable<'tcx>> Iterator for Elaborator<'tcx, O> { + type Item = O; fn size_hint(&self) -> (usize, Option<usize>) { (self.stack.len(), None) @@ -339,17 +350,21 @@ pub fn supertraits<'tcx>( tcx: TyCtxt<'tcx>, trait_ref: ty::PolyTraitRef<'tcx>, ) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> { - FilterToTraits::new(elaborate_trait_ref(tcx, trait_ref)) + let pred: ty::Predicate<'tcx> = trait_ref.to_predicate(tcx); + FilterToTraits::new(elaborate(tcx, [pred])) } pub fn transitive_bounds<'tcx>( tcx: TyCtxt<'tcx>, trait_refs: impl Iterator<Item = ty::PolyTraitRef<'tcx>>, ) -> impl Iterator<Item = ty::PolyTraitRef<'tcx>> { - FilterToTraits::new(elaborate_trait_refs(tcx, trait_refs)) + FilterToTraits::new(elaborate( + tcx, + trait_refs.map(|trait_ref| -> ty::Predicate<'tcx> { trait_ref.to_predicate(tcx) }), + )) } -/// A specialized variant of `elaborate_trait_refs` that only elaborates trait references that may +/// A specialized variant of `elaborate` that only elaborates trait references that may /// define the given associated type `assoc_name`. It uses the /// `super_predicates_that_define_assoc_type` query to avoid enumerating super-predicates that /// aren't related to `assoc_item`. This is used when resolving types like `Self::Item` or |