diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs index fda59d000ea..1f01ad009dc 100644 --- a/compiler/rustc_hir_analysis/src/astconv/mod.rs +++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs @@ -701,6 +701,16 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o { let mut dup_bindings = FxHashMap::default(); for binding in &assoc_bindings { + // Don't register additional associated type bounds for negative bounds, + // since we should have emitten an error for them earlier, and they will + // not be well-formed! + if polarity == ty::ImplPolarity::Negative { + self.tcx() + .sess + .delay_span_bug(binding.span, "negative trait bounds should not have bindings"); + continue; + } + // Specify type to assert that error was already reported in `Err` case. let _: Result<_, ErrorGuaranteed> = self.add_predicates_for_ast_type_binding( hir_id, diff --git a/compiler/rustc_infer/src/traits/util.rs b/compiler/rustc_infer/src/traits/util.rs index ef01d5d513b..f54e5e5e56f 100644 --- a/compiler/rustc_infer/src/traits/util.rs +++ b/compiler/rustc_infer/src/traits/util.rs @@ -200,6 +200,10 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> { let bound_predicate = elaboratable.predicate().kind(); match bound_predicate.skip_binder() { ty::PredicateKind::Clause(ty::Clause::Trait(data)) => { + // Negative trait bounds do not imply any supertrait bounds + if data.polarity == ty::ImplPolarity::Negative { + return; + } // Get predicates implied by the trait, or only super predicates if we only care about self predicates. let predicates = if self.only_self { tcx.super_predicates_of(data.def_id()) 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 1db9b8ce92e..a8864f47ef0 100644 --- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs +++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs @@ -57,6 +57,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { if obligation.polarity() == ty::ImplPolarity::Negative { self.assemble_candidates_for_trait_alias(obligation, &mut candidates); self.assemble_candidates_from_impls(obligation, &mut candidates); + self.assemble_candidates_from_caller_bounds(stack, &mut candidates)?; } else { self.assemble_candidates_for_trait_alias(obligation, &mut candidates); @@ -187,6 +188,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { // Keep only those bounds which may apply, and propagate overflow if it occurs. for bound in matching_bounds { + if bound.skip_binder().polarity != stack.obligation.predicate.skip_binder().polarity { + continue; + } + // FIXME(oli-obk): it is suspicious that we are dropping the constness and // polarity here. let wc = self.where_clause_may_apply(stack, bound.map_bound(|t| t.trait_ref))?; diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs index 40e19abc0d0..0590e02d84a 100644 --- a/compiler/rustc_trait_selection/src/traits/wf.rs +++ b/compiler/rustc_trait_selection/src/traits/wf.rs @@ -328,6 +328,13 @@ impl<'tcx> WfPredicates<'tcx> { let tcx = self.tcx; let trait_ref = &trait_pred.trait_ref; + // Negative trait predicates don't require supertraits to hold, just + // that their substs are WF. + if trait_pred.polarity == ty::ImplPolarity::Negative { + self.compute_negative_trait_pred(trait_ref); + return; + } + // if the trait predicate is not const, the wf obligations should not be const as well. let obligations = if trait_pred.constness == ty::BoundConstness::NotConst { self.nominal_obligations_without_const(trait_ref.def_id, trait_ref.substs) @@ -393,6 +400,14 @@ impl<'tcx> WfPredicates<'tcx> { ); } + // Compute the obligations that are required for `trait_ref` to be WF, + // given that it is a *negative* trait predicate. + fn compute_negative_trait_pred(&mut self, trait_ref: &ty::TraitRef<'tcx>) { + for arg in trait_ref.substs { + self.compute(arg); + } + } + /// Pushes the obligations required for `trait_ref::Item` to be WF /// into `self.out`. fn compute_projection(&mut self, data: ty::AliasTy<'tcx>) { diff --git a/tests/ui/traits/negative-bounds/simple.stderr b/tests/ui/traits/negative-bounds/simple.stderr index efd82c09d62..a3cab41a2ce 100644 --- a/tests/ui/traits/negative-bounds/simple.stderr +++ b/tests/ui/traits/negative-bounds/simple.stderr @@ -7,19 +7,7 @@ LL | #![feature(negative_bounds, negative_impls)] = note: `#[warn(incomplete_features)]` on by default error[E0277]: the trait bound `T: !Copy` is not satisfied - --> $DIR/simple.rs:6:16 - | -LL | not_copy::(); - | ^ the trait `!Copy` is not implemented for `T` - | -note: required by a bound in `not_copy` - --> $DIR/simple.rs:3:16 - | -LL | fn not_copy() {} - | ^^^^^ required by this bound in `not_copy` - -error[E0277]: the trait bound `T: !Copy` is not satisfied - --> $DIR/simple.rs:10:16 + --> $DIR/simple.rs:11:16 | LL | not_copy::(); | ^ the trait `!Copy` is not implemented for `T` @@ -77,6 +65,6 @@ LL + #[derive(Copy)] LL | struct NotNecessarilyCopyable; | -error: aborting due to 5 previous errors +error: aborting due to 4 previous errors; 1 warning emitted For more information about this error, try `rustc --explain E0277`.