diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/outlives/obligations.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/obligations.rs | 170 |
1 files changed, 123 insertions, 47 deletions
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs index ad052f58c..6ca884799 100644 --- a/compiler/rustc_infer/src/infer/outlives/obligations.rs +++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs @@ -68,12 +68,14 @@ use crate::infer::{ }; use crate::traits::{ObligationCause, ObligationCauseCode}; use rustc_data_structures::undo_log::UndoLogs; +use rustc_hir::def_id::DefId; use rustc_hir::def_id::LocalDefId; +use rustc_middle::mir::ConstraintCategory; use rustc_middle::ty::subst::GenericArgKind; -use rustc_middle::ty::{self, Region, Ty, TyCtxt, TypeVisitable}; +use rustc_middle::ty::{self, Region, SubstsRef, Ty, TyCtxt, TypeVisitable}; use smallvec::smallvec; -impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { +impl<'tcx> InferCtxt<'tcx> { /// Registers that the given region obligation must be resolved /// from within the scope of `body_id`. These regions are enqueued /// and later processed by regionck, when full type information is @@ -92,12 +94,14 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { sub_region: Region<'tcx>, cause: &ObligationCause<'tcx>, ) { + debug!(?sup_type, ?sub_region, ?cause); let origin = SubregionOrigin::from_obligation_cause(cause, || { infer::RelateParamBound( cause.span, sup_type, match cause.code().peel_derives() { - ObligationCauseCode::BindingObligation(_, span) => Some(*span), + ObligationCauseCode::BindingObligation(_, span) + | ObligationCauseCode::ExprBindingObligation(_, span, ..) => Some(*span), _ => None, }, ) @@ -161,7 +165,8 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { let outlives = &mut TypeOutlives::new(self, self.tcx, ®ion_bound_pairs, None, param_env); - outlives.type_must_outlive(origin, sup_type, sub_region); + let category = origin.to_constraint_category(); + outlives.type_must_outlive(origin, sup_type, sub_region, category); } } @@ -178,7 +183,7 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { outlives_env.param_env, ); - self.resolve_regions_and_report_errors(generic_param_scope, outlives_env) + self.err_ctxt().resolve_regions_and_report_errors(generic_param_scope, outlives_env) } } @@ -205,6 +210,7 @@ pub trait TypeOutlivesDelegate<'tcx> { origin: SubregionOrigin<'tcx>, a: ty::Region<'tcx>, b: ty::Region<'tcx>, + constraint_category: ConstraintCategory<'tcx>, ); fn push_verify( @@ -247,19 +253,19 @@ where /// - `origin`, the reason we need this constraint /// - `ty`, the type `T` /// - `region`, the region `'a` + #[instrument(level = "debug", skip(self))] pub fn type_must_outlive( &mut self, origin: infer::SubregionOrigin<'tcx>, ty: Ty<'tcx>, region: ty::Region<'tcx>, + category: ConstraintCategory<'tcx>, ) { - debug!("type_must_outlive(ty={:?}, region={:?}, origin={:?})", ty, region, origin); - assert!(!ty.has_escaping_bound_vars()); let mut components = smallvec![]; push_outlives_components(self.tcx, ty, &mut components); - self.components_must_outlive(origin, &components, region); + self.components_must_outlive(origin, &components, region, category); } fn components_must_outlive( @@ -267,21 +273,25 @@ where origin: infer::SubregionOrigin<'tcx>, components: &[Component<'tcx>], region: ty::Region<'tcx>, + category: ConstraintCategory<'tcx>, ) { for component in components.iter() { let origin = origin.clone(); match component { Component::Region(region1) => { - self.delegate.push_sub_region_constraint(origin, region, *region1); + self.delegate.push_sub_region_constraint(origin, region, *region1, category); } Component::Param(param_ty) => { self.param_ty_must_outlive(origin, region, *param_ty); } + Component::Opaque(def_id, substs) => { + self.opaque_must_outlive(*def_id, substs, origin, region) + } Component::Projection(projection_ty) => { self.projection_must_outlive(origin, region, *projection_ty); } Component::EscapingProjection(subcomponents) => { - self.components_must_outlive(origin, &subcomponents, region); + self.components_must_outlive(origin, &subcomponents, region, category); } Component::UnresolvedInferenceVariable(v) => { // ignore this, we presume it will yield an error @@ -308,17 +318,69 @@ where ); let generic = GenericKind::Param(param_ty); - let verify_bound = self.verify_bound.generic_bound(generic); + let verify_bound = self.verify_bound.param_bound(param_ty); self.delegate.push_verify(origin, generic, region, verify_bound); } - #[tracing::instrument(level = "debug", skip(self))] + #[instrument(level = "debug", skip(self))] + fn opaque_must_outlive( + &mut self, + def_id: DefId, + substs: SubstsRef<'tcx>, + origin: infer::SubregionOrigin<'tcx>, + region: ty::Region<'tcx>, + ) { + self.generic_must_outlive( + origin, + region, + GenericKind::Opaque(def_id, substs), + def_id, + substs, + true, + |ty| match *ty.kind() { + ty::Opaque(def_id, substs) => (def_id, substs), + _ => bug!("expected only projection types from env, not {:?}", ty), + }, + ); + } + + #[instrument(level = "debug", skip(self))] fn projection_must_outlive( &mut self, origin: infer::SubregionOrigin<'tcx>, region: ty::Region<'tcx>, projection_ty: ty::ProjectionTy<'tcx>, ) { + self.generic_must_outlive( + origin, + region, + GenericKind::Projection(projection_ty), + projection_ty.item_def_id, + projection_ty.substs, + false, + |ty| match ty.kind() { + ty::Projection(projection_ty) => (projection_ty.item_def_id, projection_ty.substs), + _ => bug!("expected only projection types from env, not {:?}", ty), + }, + ); + } + + #[instrument(level = "debug", skip(self, filter))] + fn generic_must_outlive( + &mut self, + origin: infer::SubregionOrigin<'tcx>, + region: ty::Region<'tcx>, + generic: GenericKind<'tcx>, + def_id: DefId, + substs: SubstsRef<'tcx>, + is_opaque: bool, + filter: impl Fn(Ty<'tcx>) -> (DefId, SubstsRef<'tcx>), + ) { + // An optimization for a common case with opaque types. + if substs.is_empty() { + return; + } + // This case is thorny for inference. The fundamental problem is // that there are many cases where we have choice, and inference // doesn't like choice (the current region inference in @@ -337,16 +399,15 @@ where // These are guaranteed to apply, no matter the inference // results. let trait_bounds: Vec<_> = - self.verify_bound.projection_declared_bounds_from_trait(projection_ty).collect(); + self.verify_bound.declared_region_bounds(def_id, substs).collect(); debug!(?trait_bounds); // Compute the bounds we can derive from the environment. This // is an "approximate" match -- in some cases, these bounds // may not apply. - let mut approx_env_bounds = - self.verify_bound.projection_approx_declared_bounds_from_env(projection_ty); - debug!("projection_must_outlive: approx_env_bounds={:?}", approx_env_bounds); + let mut approx_env_bounds = self.verify_bound.approx_declared_bounds_from_env(generic); + debug!(?approx_env_bounds); // Remove outlives bounds that we get from the environment but // which are also deducible from the trait. This arises (cc @@ -360,14 +421,8 @@ where // If the declaration is `trait Trait<'b> { type Item: 'b; }`, then `projection_declared_bounds_from_trait` // will be invoked with `['b => ^1]` and so we will get `^1` returned. let bound = bound_outlives.skip_binder(); - match *bound.0.kind() { - ty::Projection(projection_ty) => self - .verify_bound - .projection_declared_bounds_from_trait(projection_ty) - .all(|r| r != bound.1), - - _ => panic!("expected only projection types from env, not {:?}", bound.0), - } + let (def_id, substs) = filter(bound.0); + self.verify_bound.declared_region_bounds(def_id, substs).all(|r| r != bound.1) }); // If declared bounds list is empty, the only applicable rule is @@ -384,23 +439,11 @@ where // the problem is to add `T: 'r`, which isn't true. So, if there are no // inference variables, we use a verify constraint instead of adding // edges, which winds up enforcing the same condition. - let needs_infer = projection_ty.needs_infer(); - if approx_env_bounds.is_empty() && trait_bounds.is_empty() && needs_infer { - debug!("projection_must_outlive: no declared bounds"); - - for k in projection_ty.substs { - match k.unpack() { - GenericArgKind::Lifetime(lt) => { - self.delegate.push_sub_region_constraint(origin.clone(), region, lt); - } - GenericArgKind::Type(ty) => { - self.type_must_outlive(origin.clone(), ty, region); - } - GenericArgKind::Const(_) => { - // Const parameters don't impose constraints. - } - } - } + let needs_infer = substs.needs_infer(); + if approx_env_bounds.is_empty() && trait_bounds.is_empty() && (needs_infer || is_opaque) { + debug!("no declared bounds"); + + self.substs_must_outlive(substs, origin, region); return; } @@ -430,9 +473,10 @@ where .all(|b| b == Some(trait_bounds[0])) { let unique_bound = trait_bounds[0]; - debug!("projection_must_outlive: unique trait bound = {:?}", unique_bound); - debug!("projection_must_outlive: unique declared bound appears in trait ref"); - self.delegate.push_sub_region_constraint(origin, region, unique_bound); + debug!(?unique_bound); + debug!("unique declared bound appears in trait ref"); + let category = origin.to_constraint_category(); + self.delegate.push_sub_region_constraint(origin, region, unique_bound, category); return; } @@ -441,19 +485,51 @@ where // projection outlive; in some cases, this may add insufficient // edges into the inference graph, leading to inference failures // even though a satisfactory solution exists. - let generic = GenericKind::Projection(projection_ty); - let verify_bound = self.verify_bound.generic_bound(generic); + let verify_bound = self.verify_bound.projection_opaque_bounds( + generic, + def_id, + substs, + &mut Default::default(), + ); debug!("projection_must_outlive: pushing {:?}", verify_bound); self.delegate.push_verify(origin, generic, region, verify_bound); } + + fn substs_must_outlive( + &mut self, + substs: SubstsRef<'tcx>, + origin: infer::SubregionOrigin<'tcx>, + region: ty::Region<'tcx>, + ) { + let constraint = origin.to_constraint_category(); + for k in substs { + match k.unpack() { + GenericArgKind::Lifetime(lt) => { + self.delegate.push_sub_region_constraint( + origin.clone(), + region, + lt, + constraint, + ); + } + GenericArgKind::Type(ty) => { + self.type_must_outlive(origin.clone(), ty, region, constraint); + } + GenericArgKind::Const(_) => { + // Const parameters don't impose constraints. + } + } + } + } } -impl<'cx, 'tcx> TypeOutlivesDelegate<'tcx> for &'cx InferCtxt<'cx, 'tcx> { +impl<'cx, 'tcx> TypeOutlivesDelegate<'tcx> for &'cx InferCtxt<'tcx> { fn push_sub_region_constraint( &mut self, origin: SubregionOrigin<'tcx>, a: ty::Region<'tcx>, b: ty::Region<'tcx>, + _constraint_category: ConstraintCategory<'tcx>, ) { self.sub_regions(origin, a, b) } |