diff options
4 files changed, 22 insertions, 17 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs index fa91a125b6a..c3040f60156 100644 --- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs +++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs @@ -238,14 +238,25 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> { ecx: &mut EvalCtxt<'_, 'tcx>, goal: Goal<'tcx, Self>, ) -> QueryResult<'tcx> { - if goal.predicate.polarity != ty::ImplPolarity::Positive { - return Err(NoSolution); - } - - if let ty::FnPtr(..) = goal.predicate.self_ty().kind() { - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) - } else { - Err(NoSolution) + let self_ty = goal.predicate.self_ty(); + match goal.predicate.polarity { + ty::ImplPolarity::Positive => { + if self_ty.is_fn_ptr() { + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + } else { + Err(NoSolution) + } + } + ty::ImplPolarity::Negative => { + // If a type is rigid and not a fn ptr, then we know for certain + // that it does *not* implement `FnPtr`. + if !self_ty.is_fn_ptr() && self_ty.is_known_rigid() { + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes) + } else { + Err(NoSolution) + } + } + ty::ImplPolarity::Reservation => bug!(), } } diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index 135d872f9de..69f8f194ce3 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -514,13 +514,6 @@ pub fn trait_ref_is_knowable<'tcx, E: Debug>( trait_ref: ty::TraitRef<'tcx>, mut lazily_normalize_ty: impl FnMut(Ty<'tcx>) -> Result<Ty<'tcx>, E>, ) -> Result<Result<(), Conflict>, E> { - if Some(trait_ref.def_id) == tcx.lang_items().fn_ptr_trait() { - // The only types implementing `FnPtr` are function pointers, - // so if there's no impl of `FnPtr` in the current crate, - // then such an impl will never be added in the future. - return Ok(Ok(())); - } - if orphan_check_trait_ref(trait_ref, InCrate::Remote, &mut lazily_normalize_ty)?.is_ok() { // A downstream or cousin crate is allowed to implement some // substitution of this trait-ref. diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs index ee50a36be55..123881d9bc6 100644 --- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs +++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs @@ -52,8 +52,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let mut candidates = SelectionCandidateSet { vec: Vec::new(), ambiguous: false }; - // The only way to prove a NotImplemented(T: Foo) predicate is via a negative impl. - // There are no compiler built-in rules for this. + // Negative trait predicates have different rules than positive trait predicates. if obligation.polarity() == ty::ImplPolarity::Negative { self.assemble_candidates_for_trait_alias(obligation, &mut candidates); self.assemble_candidates_from_impls(obligation, &mut candidates); @@ -1064,6 +1063,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { candidates: &mut SelectionCandidateSet<'tcx>, ) { let self_ty = self.infcx.shallow_resolve(obligation.self_ty()); + match self_ty.skip_binder().kind() { ty::FnPtr(_) => candidates.vec.push(BuiltinCandidate { has_nested: false }), ty::Bool diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index 03243e31348..a1220d45a5c 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -253,6 +253,7 @@ #![feature(try_blocks)] #![feature(unboxed_closures)] #![feature(unsized_fn_params)] +#![feature(with_negative_coherence)] // tidy-alphabetical-end // // Target features: |