diff options
| -rw-r--r-- | compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs | 66 | ||||
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/coherence.rs | 138 | ||||
| -rw-r--r-- | compiler/rustc_type_ir/src/solve/mod.rs | 2 | ||||
| -rw-r--r-- | tests/ui/coherence/normalize-for-errors.next.stderr | 2 | ||||
| -rw-r--r-- | tests/ui/coherence/normalize-for-errors.rs | 2 |
5 files changed, 101 insertions, 109 deletions
diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs index bb05eb4c256..6c9a6011144 100644 --- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs @@ -304,6 +304,11 @@ where let mut candidates = vec![]; + if self.solver_mode() == SolverMode::Coherence { + if let Ok(candidate) = self.consider_coherence_unknowable_candidate(goal) { + return vec![candidate]; + } + } self.assemble_impl_candidates(goal, &mut candidates); self.assemble_builtin_impl_candidates(goal, &mut candidates); @@ -314,11 +319,8 @@ where self.assemble_param_env_candidates(goal, &mut candidates); - match self.solver_mode() { - SolverMode::Normal => self.discard_impls_shadowed_by_env(goal, &mut candidates), - SolverMode::Coherence => { - self.assemble_coherence_unknowable_candidates(goal, &mut candidates) - } + if self.solver_mode() == SolverMode::Normal { + self.discard_impls_shadowed_by_env(goal, &mut candidates); } candidates @@ -682,38 +684,34 @@ where /// also consider impls which may get added in a downstream or sibling crate /// or which an upstream impl may add in a minor release. /// - /// To do so we add an ambiguous candidate in case such an unknown impl could - /// apply to the current goal. + /// To do so we return a single ambiguous candidate in case such an unknown + /// impl could apply to the current goal. #[instrument(level = "trace", skip_all)] - fn assemble_coherence_unknowable_candidates<G: GoalKind<D>>( + fn consider_coherence_unknowable_candidate<G: GoalKind<D>>( &mut self, goal: Goal<I, G>, - candidates: &mut Vec<Candidate<I>>, - ) { - let cx = self.cx(); - - candidates.extend(self.probe_trait_candidate(CandidateSource::CoherenceUnknowable).enter( - |ecx| { - let trait_ref = goal.predicate.trait_ref(cx); - if ecx.trait_ref_is_knowable(goal.param_env, trait_ref)? { - Err(NoSolution) - } else { - // While the trait bound itself may be unknowable, we may be able to - // prove that a super trait is not implemented. For this, we recursively - // prove the super trait bounds of the current goal. - // - // We skip the goal itself as that one would cycle. - let predicate: I::Predicate = trait_ref.upcast(cx); - ecx.add_goals( - GoalSource::Misc, - elaborate::elaborate(cx, [predicate]) - .skip(1) - .map(|predicate| goal.with(cx, predicate)), - ); - ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) - } - }, - )) + ) -> Result<Candidate<I>, NoSolution> { + self.probe_trait_candidate(CandidateSource::CoherenceUnknowable).enter(|ecx| { + let cx = ecx.cx(); + let trait_ref = goal.predicate.trait_ref(cx); + if ecx.trait_ref_is_knowable(goal.param_env, trait_ref)? { + Err(NoSolution) + } else { + // While the trait bound itself may be unknowable, we may be able to + // prove that a super trait is not implemented. For this, we recursively + // prove the super trait bounds of the current goal. + // + // We skip the goal itself as that one would cycle. + let predicate: I::Predicate = trait_ref.upcast(cx); + ecx.add_goals( + GoalSource::Misc, + elaborate::elaborate(cx, [predicate]) + .skip(1) + .map(|predicate| goal.with(cx, predicate)), + ); + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) + } + }) } /// If there's a where-bound for the current goal, do not use any impl candidates diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index 8558520897b..8b55f84bccc 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -29,6 +29,7 @@ use crate::infer::outlives::env::OutlivesEnvironment; use crate::infer::InferOk; use crate::solve::inspect::{InspectGoal, ProofTreeInferCtxtExt, ProofTreeVisitor}; use crate::solve::{deeply_normalize_for_diagnostics, inspect}; +use crate::traits::query::evaluate_obligation::InferCtxtExt; use crate::traits::select::IntercrateAmbiguityCause; use crate::traits::{ util, FulfillmentErrorCode, NormalizeExt, Obligation, ObligationCause, PredicateObligation, @@ -624,14 +625,13 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> { // at ambiguous goals, as for others the coherence unknowable candidate // was irrelevant. match goal.result() { - Ok(Certainty::Maybe(_)) => {} Ok(Certainty::Yes) | Err(NoSolution) => return, + Ok(Certainty::Maybe(_)) => {} } - let Goal { param_env, predicate } = goal.goal(); - // For bound predicates we simply call `infcx.enter_forall` // and then prove the resulting predicate as a nested goal. + let Goal { param_env, predicate } = goal.goal(); let trait_ref = match predicate.kind().no_bound_vars() { Some(ty::PredicateKind::Clause(ty::ClauseKind::Trait(tr))) => tr.trait_ref, Some(ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj))) @@ -645,7 +645,11 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> { _ => return, }; - // Add ambiguity causes for reservation impls. + if trait_ref.references_error() { + return; + } + + let mut candidates = goal.candidates(); for cand in goal.candidates() { if let inspect::ProbeKind::TraitCandidate { source: CandidateSource::Impl(def_id), @@ -664,78 +668,68 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> { } } - // Add ambiguity causes for unknowable goals. - let mut ambiguity_cause = None; - for cand in goal.candidates() { - if let inspect::ProbeKind::TraitCandidate { - source: CandidateSource::CoherenceUnknowable, - result: Ok(_), - } = cand.kind() - { - let lazily_normalize_ty = |mut ty: Ty<'tcx>| { - if matches!(ty.kind(), ty::Alias(..)) { - let ocx = ObligationCtxt::new(infcx); - ty = ocx - .structurally_normalize(&ObligationCause::dummy(), param_env, ty) - .map_err(|_| ())?; - if !ocx.select_where_possible().is_empty() { - return Err(()); - } - } - Ok(ty) - }; + // We also look for unknowable candidates. In case a goal is unknowable, there's + // always exactly 1 candidate. + let Some(cand) = candidates.pop() else { + return; + }; - infcx.probe(|_| { - match trait_ref_is_knowable(infcx, trait_ref, lazily_normalize_ty) { - Err(()) => {} - Ok(Ok(())) => warn!("expected an unknowable trait ref: {trait_ref:?}"), - Ok(Err(conflict)) => { - if !trait_ref.references_error() { - // Normalize the trait ref for diagnostics, ignoring any errors if this fails. - let trait_ref = - deeply_normalize_for_diagnostics(infcx, param_env, trait_ref); - - let self_ty = trait_ref.self_ty(); - let self_ty = self_ty.has_concrete_skeleton().then(|| self_ty); - ambiguity_cause = Some(match conflict { - Conflict::Upstream => { - IntercrateAmbiguityCause::UpstreamCrateUpdate { - trait_ref, - self_ty, - } - } - Conflict::Downstream => { - IntercrateAmbiguityCause::DownstreamCrate { - trait_ref, - self_ty, - } - } - }); - } - } - } - }) - } else { - match cand.result() { - // We only add an ambiguity cause if the goal would otherwise - // result in an error. - // - // FIXME: While this matches the behavior of the - // old solver, it is not the only way in which the unknowable - // candidates *weaken* coherence, they can also force otherwise - // successful normalization to be ambiguous. - Ok(Certainty::Maybe(_) | Certainty::Yes) => { - ambiguity_cause = None; - break; - } - Err(NoSolution) => continue, + let inspect::ProbeKind::TraitCandidate { + source: CandidateSource::CoherenceUnknowable, + result: Ok(_), + } = cand.kind() + else { + return; + }; + + let lazily_normalize_ty = |mut ty: Ty<'tcx>| { + if matches!(ty.kind(), ty::Alias(..)) { + let ocx = ObligationCtxt::new(infcx); + ty = ocx + .structurally_normalize(&ObligationCause::dummy(), param_env, ty) + .map_err(|_| ())?; + if !ocx.select_where_possible().is_empty() { + return Err(()); } } - } + Ok(ty) + }; - if let Some(ambiguity_cause) = ambiguity_cause { - self.causes.insert(ambiguity_cause); - } + infcx.probe(|_| { + let conflict = match trait_ref_is_knowable(infcx, trait_ref, lazily_normalize_ty) { + Err(()) => return, + Ok(Ok(())) => { + warn!("expected an unknowable trait ref: {trait_ref:?}"); + return; + } + Ok(Err(conflict)) => conflict, + }; + + // It is only relevant that a goal is unknowable if it would have otherwise + // failed. + let non_intercrate_infcx = infcx.fork_with_intercrate(false); + if non_intercrate_infcx.predicate_may_hold(&Obligation::new( + infcx.tcx, + ObligationCause::dummy(), + param_env, + predicate, + )) { + return; + } + + // Normalize the trait ref for diagnostics, ignoring any errors if this fails. + let trait_ref = deeply_normalize_for_diagnostics(infcx, param_env, trait_ref); + let self_ty = trait_ref.self_ty(); + let self_ty = self_ty.has_concrete_skeleton().then(|| self_ty); + self.causes.insert(match conflict { + Conflict::Upstream => { + IntercrateAmbiguityCause::UpstreamCrateUpdate { trait_ref, self_ty } + } + Conflict::Downstream => { + IntercrateAmbiguityCause::DownstreamCrate { trait_ref, self_ty } + } + }); + }); } } diff --git a/compiler/rustc_type_ir/src/solve/mod.rs b/compiler/rustc_type_ir/src/solve/mod.rs index 96c939a898b..96998d2ec9f 100644 --- a/compiler/rustc_type_ir/src/solve/mod.rs +++ b/compiler/rustc_type_ir/src/solve/mod.rs @@ -58,7 +58,7 @@ pub enum Reveal { All, } -#[derive(Debug, Clone, Copy)] +#[derive(Debug, Clone, Copy, PartialEq, Eq)] pub enum SolverMode { /// Ordinary trait solving, using everywhere except for coherence. Normal, diff --git a/tests/ui/coherence/normalize-for-errors.next.stderr b/tests/ui/coherence/normalize-for-errors.next.stderr index 634a10b7a14..44952dc1944 100644 --- a/tests/ui/coherence/normalize-for-errors.next.stderr +++ b/tests/ui/coherence/normalize-for-errors.next.stderr @@ -7,7 +7,7 @@ LL | LL | impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)` | - = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `(MyType,)` in future versions + = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions error: aborting due to 1 previous error diff --git a/tests/ui/coherence/normalize-for-errors.rs b/tests/ui/coherence/normalize-for-errors.rs index 4188389a3ad..c17bb766b5b 100644 --- a/tests/ui/coherence/normalize-for-errors.rs +++ b/tests/ui/coherence/normalize-for-errors.rs @@ -18,6 +18,6 @@ impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {} //~^ ERROR conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, //~| NOTE conflicting implementation for `(Box<(MyType,)>, //~| NOTE upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions -//[next]~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `(MyType,)` in future versions +//[next]~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions fn main() {} |