diff options
Diffstat (limited to 'compiler/rustc_trait_selection/src/traits/coherence.rs')
| -rw-r--r-- | compiler/rustc_trait_selection/src/traits/coherence.rs | 155 |
1 files changed, 102 insertions, 53 deletions
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index dcf5fd869..533fe32f7 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -6,8 +6,8 @@ use crate::infer::outlives::env::OutlivesEnvironment; use crate::infer::InferOk; -use crate::solve::inspect; use crate::solve::inspect::{InspectGoal, ProofTreeInferCtxtExt, ProofTreeVisitor}; +use crate::solve::{deeply_normalize_for_diagnostics, inspect}; use crate::traits::engine::TraitEngineExt; use crate::traits::query::evaluate_obligation::InferCtxtExt; use crate::traits::select::{IntercrateAmbiguityCause, TreatInductiveCycleAs}; @@ -20,15 +20,15 @@ use crate::traits::{ }; use rustc_data_structures::fx::FxIndexSet; use rustc_errors::Diagnostic; +use rustc_hir::def::DefKind; use rustc_hir::def_id::{DefId, LOCAL_CRATE}; use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, TyCtxtInferExt}; use rustc_infer::traits::{util, TraitEngine}; use rustc_middle::traits::query::NoSolution; -use rustc_middle::traits::solve::{Certainty, Goal}; +use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal}; use rustc_middle::traits::specialization_graph::OverlapMode; use rustc_middle::traits::DefiningAnchor; use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams}; -use rustc_middle::ty::print::with_no_trimmed_paths; use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt}; use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor}; use rustc_session::lint::builtin::COINDUCTIVE_OVERLAP_IN_COHERENCE; @@ -53,7 +53,7 @@ pub enum Conflict { pub struct OverlapResult<'tcx> { pub impl_header: ty::ImplHeader<'tcx>, - pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause>, + pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause<'tcx>>, /// `true` if the overlap might've been permitted before the shift /// to universes. @@ -100,7 +100,7 @@ pub fn overlapping_impls( let impl1_ref = tcx.impl_trait_ref(impl1_def_id); let impl2_ref = tcx.impl_trait_ref(impl2_def_id); let may_overlap = match (impl1_ref, impl2_ref) { - (Some(a), Some(b)) => drcx.args_refs_may_unify(a.skip_binder().args, b.skip_binder().args), + (Some(a), Some(b)) => drcx.args_may_unify(a.skip_binder().args, b.skip_binder().args), (None, None) => { let self_ty1 = tcx.type_of(impl1_def_id).skip_binder(); let self_ty2 = tcx.type_of(impl2_def_id).skip_binder(); @@ -245,7 +245,7 @@ fn overlap<'tcx>( let trait_ref = infcx.resolve_vars_if_possible(trait_ref); format!( "of `{}` for `{}`", - trait_ref.print_only_trait_path(), + trait_ref.print_trait_sugared(), trait_ref.self_ty() ) } @@ -273,7 +273,6 @@ fn overlap<'tcx>( causing the impls to overlap", infcx.resolve_vars_if_possible(failing_obligation.predicate) )); - lint }, ); } @@ -308,7 +307,13 @@ fn overlap<'tcx>( .iter() .any(|c| c.0.involves_placeholders()); - let impl_header = selcx.infcx.resolve_vars_if_possible(impl1_header); + let mut impl_header = infcx.resolve_vars_if_possible(impl1_header); + + // Deeply normalize the impl header for diagnostics, ignoring any errors if this fails. + if infcx.next_trait_solver() { + impl_header = deeply_normalize_for_diagnostics(&infcx, param_env, impl_header); + } + Some(OverlapResult { impl_header, intercrate_ambiguity_causes, involves_placeholder }) } @@ -329,7 +334,7 @@ fn equate_impl_headers<'tcx>( impl1.self_ty, impl2.self_ty, ), - _ => bug!("mk_eq_impl_headers given mismatched impl kinds"), + _ => bug!("equate_impl_headers given mismatched impl kinds"), }; result.map(|infer_ok| infer_ok.obligations).ok() @@ -360,15 +365,23 @@ fn impl_intersection_has_impossible_obligation<'a, 'cx, 'tcx>( let infcx = selcx.infcx; obligations.iter().find(|obligation| { - if infcx.next_trait_solver() { - infcx.evaluate_obligation(obligation).map_or(false, |result| !result.may_apply()) + let evaluation_result = if infcx.next_trait_solver() { + infcx.evaluate_obligation(obligation) } else { // We use `evaluate_root_obligation` to correctly track intercrate // ambiguity clauses. We cannot use this in the new solver. - selcx.evaluate_root_obligation(obligation).map_or( - false, // Overflow has occurred, and treat the obligation as possibly holding. - |result| !result.may_apply(), - ) + selcx.evaluate_root_obligation(obligation) + }; + + match evaluation_result { + Ok(result) => !result.may_apply(), + // If overflow occurs, we need to conservatively treat the goal as possibly holding, + // since there can be instantiations of this goal that don't overflow and result in + // success. This isn't much of a problem in the old solver, since we treat overflow + // fatally (this still can be encountered: <https://github.com/rust-lang/rust/issues/105231>), + // but in the new solver, this is very important for correctness, since overflow + // *must* be treated as ambiguity for completeness. + Err(_overflow) => false, } }) } @@ -396,8 +409,11 @@ fn impl_intersection_has_negative_obligation( ) -> bool { debug!("negative_impl(impl1_def_id={:?}, impl2_def_id={:?})", impl1_def_id, impl2_def_id); + // N.B. We need to unify impl headers *with* intercrate mode, even if proving negative predicates + // do not need intercrate mode enabled. let ref infcx = tcx.infer_ctxt().intercrate(true).with_next_trait_solver(true).build(); - let universe = infcx.universe(); + let root_universe = infcx.universe(); + assert_eq!(root_universe, ty::UniverseIndex::ROOT); let impl1_header = fresh_impl_header(infcx, impl1_def_id); let param_env = @@ -407,13 +423,25 @@ fn impl_intersection_has_negative_obligation( // Equate the headers to find their intersection (the general type, with infer vars, // that may apply both impls). - let Some(_equate_obligations) = + let Some(equate_obligations) = equate_impl_headers(infcx, param_env, &impl1_header, &impl2_header) else { return false; }; - plug_infer_with_placeholders(infcx, universe, (impl1_header.impl_args, impl2_header.impl_args)); + // FIXME(with_negative_coherence): the infcx has constraints from equating + // the impl headers. We should use these constraints as assumptions, not as + // requirements, when proving the negated where clauses below. + drop(equate_obligations); + drop(infcx.take_registered_region_obligations()); + drop(infcx.take_and_reset_region_constraints()); + + plug_infer_with_placeholders( + infcx, + root_universe, + (impl1_header.impl_args, impl2_header.impl_args), + ); + let param_env = infcx.resolve_vars_if_possible(param_env); util::elaborate(tcx, tcx.predicates_of(impl2_def_id).instantiate(tcx, impl2_header.impl_args)) .any(|(clause, _)| try_prove_negated_where_clause(infcx, clause, param_env)) @@ -458,7 +486,7 @@ fn plug_infer_with_placeholders<'tcx>( ), ) else { - bug!() + bug!("we always expect to be able to plug an infer var with placeholder") }; assert_eq!(obligations, &[]); ControlFlow::Continue(()) @@ -481,7 +509,7 @@ fn plug_infer_with_placeholders<'tcx>( ), ) else { - bug!() + bug!("we always expect to be able to plug an infer var with placeholder") }; assert_eq!(obligations, &[]); ControlFlow::Continue(()) @@ -515,7 +543,7 @@ fn plug_infer_with_placeholders<'tcx>( ), ) else { - bug!() + bug!("we always expect to be able to plug an infer var with placeholder") }; assert_eq!(obligations, &[]); } @@ -540,15 +568,11 @@ fn try_prove_negated_where_clause<'tcx>( return false; }; - // FIXME(with_negative_coherence): the infcx has region contraints from equating - // the impl headers as requirements. Given that the only region constraints we - // get are involving inference regions in the root, it shouldn't matter, but - // still sus. - // - // We probably should just throw away the region obligations registered up until - // now, or ideally use them as assumptions when proving the region obligations - // that we get from proving the negative predicate below. - let ref infcx = root_infcx.fork(); + // N.B. We don't need to use intercrate mode here because we're trying to prove + // the *existence* of a negative goal, not the non-existence of a positive goal. + // Without this, we over-eagerly register coherence ambiguity candidates when + // impl candidates do exist. + let ref infcx = root_infcx.fork_with_intercrate(false); let ocx = ObligationCtxt::new(infcx); ocx.register_obligation(Obligation::new( @@ -830,7 +854,7 @@ where } fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { - // Need to lazily normalize here in with `-Ztrait-solver=next-coherence`. + // Need to lazily normalize here in with `-Znext-solver=coherence`. let ty = match (self.lazily_normalize_ty)(ty) { Ok(ty) => ty, Err(err) => return ControlFlow::Break(OrphanCheckEarlyExit::NormalizationFailure(err)), @@ -967,8 +991,8 @@ where fn compute_intercrate_ambiguity_causes<'tcx>( infcx: &InferCtxt<'tcx>, obligations: &[PredicateObligation<'tcx>], -) -> FxIndexSet<IntercrateAmbiguityCause> { - let mut causes: FxIndexSet<IntercrateAmbiguityCause> = Default::default(); +) -> FxIndexSet<IntercrateAmbiguityCause<'tcx>> { + let mut causes: FxIndexSet<IntercrateAmbiguityCause<'tcx>> = Default::default(); for obligation in obligations { search_ambiguity_causes(infcx, obligation.clone().into(), &mut causes); @@ -977,11 +1001,11 @@ fn compute_intercrate_ambiguity_causes<'tcx>( causes } -struct AmbiguityCausesVisitor<'a> { - causes: &'a mut FxIndexSet<IntercrateAmbiguityCause>, +struct AmbiguityCausesVisitor<'a, 'tcx> { + causes: &'a mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>, } -impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> { +impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> { type BreakTy = !; fn visit_goal(&mut self, goal: &InspectGoal<'_, 'tcx>) -> ControlFlow<Self::BreakTy> { let infcx = goal.infcx(); @@ -998,26 +1022,53 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> { let Goal { param_env, predicate } = goal.goal(); - // For bound predicates we simply call `infcx.replace_bound_vars_with_placeholders` + // For bound predicates we simply call `infcx.instantiate_binder_with_placeholders` // and then prove the resulting predicate as a nested 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))) => { + Some(ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj))) + if matches!( + infcx.tcx.def_kind(proj.projection_ty.def_id), + DefKind::AssocTy | DefKind::AssocConst + ) => + { proj.projection_ty.trait_ref(infcx.tcx) } _ => return ControlFlow::Continue(()), }; + // Add ambiguity causes for reservation impls. + for cand in goal.candidates() { + if let inspect::ProbeKind::TraitCandidate { + source: CandidateSource::Impl(def_id), + result: Ok(_), + } = cand.kind() + { + if let ty::ImplPolarity::Reservation = infcx.tcx.impl_polarity(def_id) { + let message = infcx + .tcx + .get_attr(def_id, sym::rustc_reservation_impl) + .and_then(|a| a.value_str()); + if let Some(message) = message { + self.causes.insert(IntercrateAmbiguityCause::ReservationImpl { message }); + } + } + } + } + + // Add ambiguity causes for unknowable goals. let mut ambiguity_cause = None; for cand in goal.candidates() { // FIXME: boiiii, using string comparisions here sure is scuffed. - if let inspect::ProbeKind::MiscCandidate { name: "coherence unknowable", result: _ } = - cand.kind() + if let inspect::ProbeKind::MiscCandidate { + name: "coherence unknowable", + result: Ok(_), + } = cand.kind() { let lazily_normalize_ty = |ty: Ty<'tcx>| { let mut fulfill_cx = <dyn TraitEngine<'tcx>>::new(infcx); if matches!(ty.kind(), ty::Alias(..)) { - // FIXME(-Ztrait-solver=next-coherence): we currently don't + // FIXME(-Znext-solver=coherence): we currently don't // normalize opaque types here, resulting in diverging behavior // for TAITs. match infcx @@ -1038,25 +1089,23 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> { 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 (trait_desc, self_desc) = with_no_trimmed_paths!({ - let trait_desc = trait_ref.print_only_trait_path().to_string(); - let self_desc = self_ty - .has_concrete_skeleton() - .then(|| self_ty.to_string()); - (trait_desc, self_desc) - }); + let self_ty = self_ty.has_concrete_skeleton().then(|| self_ty); ambiguity_cause = Some(match conflict { Conflict::Upstream => { IntercrateAmbiguityCause::UpstreamCrateUpdate { - trait_desc, - self_desc, + trait_ref, + self_ty, } } Conflict::Downstream => { IntercrateAmbiguityCause::DownstreamCrate { - trait_desc, - self_desc, + trait_ref, + self_ty, } } }); @@ -1093,7 +1142,7 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a> { fn search_ambiguity_causes<'tcx>( infcx: &InferCtxt<'tcx>, goal: Goal<'tcx, ty::Predicate<'tcx>>, - causes: &mut FxIndexSet<IntercrateAmbiguityCause>, + causes: &mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>, ) { infcx.visit_proof_tree(goal, &mut AmbiguityCausesVisitor { causes }); } |