diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/infer.rs')
-rw-r--r-- | compiler/rustc_trait_selection/src/infer.rs | 73 |
1 files changed, 72 insertions, 1 deletions
diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs index 38153cccf..251f0628a 100644 --- a/compiler/rustc_trait_selection/src/infer.rs +++ b/compiler/rustc_trait_selection/src/infer.rs @@ -1,8 +1,10 @@ +use crate::solve::FulfillmentCtxt; use crate::traits::query::evaluate_obligation::InferCtxtExt as _; use crate::traits::{self, DefiningAnchor, ObligationCtxt}; use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; +use rustc_infer::traits::{TraitEngine, TraitEngineExt}; use rustc_middle::arena::ArenaAllocatable; use rustc_middle::infer::canonical::{Canonical, CanonicalQueryResponse, QueryResponse}; use rustc_middle::traits::query::NoSolution; @@ -27,7 +29,7 @@ pub trait InferCtxtExt<'tcx> { /// - the parameter environment /// /// Invokes `evaluate_obligation`, so in the event that evaluating - /// `Ty: Trait` causes overflow, EvaluatedToRecur (or EvaluatedToUnknown) + /// `Ty: Trait` causes overflow, EvaluatedToErrStackDependent (or EvaluatedToAmbigStackDependent) /// will be returned. fn type_implements_trait( &self, @@ -35,6 +37,13 @@ pub trait InferCtxtExt<'tcx> { params: impl IntoIterator<Item: Into<GenericArg<'tcx>>>, param_env: ty::ParamEnv<'tcx>, ) -> traits::EvaluationResult; + + fn could_impl_trait( + &self, + trait_def_id: DefId, + ty: Ty<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> Option<Vec<traits::FulfillmentError<'tcx>>>; } impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> { @@ -76,6 +85,68 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> { }; self.evaluate_obligation(&obligation).unwrap_or(traits::EvaluationResult::EvaluatedToErr) } + + fn could_impl_trait( + &self, + trait_def_id: DefId, + ty: Ty<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> Option<Vec<traits::FulfillmentError<'tcx>>> { + self.probe(|_snapshot| { + if let ty::Adt(def, args) = ty.kind() + && let Some((impl_def_id, _)) = self + .tcx + .all_impls(trait_def_id) + .filter_map(|impl_def_id| { + self.tcx.impl_trait_ref(impl_def_id).map(|r| (impl_def_id, r)) + }) + .map(|(impl_def_id, imp)| (impl_def_id, imp.skip_binder())) + .find(|(_, imp)| match imp.self_ty().peel_refs().kind() { + ty::Adt(i_def, _) if i_def.did() == def.did() => true, + _ => false, + }) + { + let mut fulfill_cx = FulfillmentCtxt::new(self); + // We get all obligations from the impl to talk about specific + // trait bounds. + let obligations = self + .tcx + .predicates_of(impl_def_id) + .instantiate(self.tcx, args) + .into_iter() + .map(|(clause, span)| { + traits::Obligation::new( + self.tcx, + traits::ObligationCause::dummy_with_span(span), + param_env, + clause, + ) + }) + .collect::<Vec<_>>(); + fulfill_cx.register_predicate_obligations(self, obligations); + let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, [ty]); + let obligation = traits::Obligation::new( + self.tcx, + traits::ObligationCause::dummy(), + param_env, + trait_ref, + ); + fulfill_cx.register_predicate_obligation(self, obligation); + let mut errors = fulfill_cx.select_all_or_error(self); + // We remove the last predicate failure, which corresponds to + // the top-level obligation, because most of the type we only + // care about the other ones, *except* when it is the only one. + // This seems to only be relevant for arbitrary self-types. + // Look at `tests/ui/moves/move-fn-self-receiver.rs`. + if errors.len() > 1 { + errors.truncate(errors.len() - 1); + } + Some(errors) + } else { + None + } + }) + } } pub trait InferCtxtBuilderExt<'tcx> { |