diff options
Diffstat (limited to '')
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/components.rs | 17 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/env.rs | 66 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/mod.rs | 2 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/obligations.rs | 170 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/test_type_match.rs | 15 | ||||
| -rw-r--r-- | compiler/rustc_infer/src/infer/outlives/verify.rs | 117 |
6 files changed, 246 insertions, 141 deletions
diff --git a/compiler/rustc_infer/src/infer/outlives/components.rs b/compiler/rustc_infer/src/infer/outlives/components.rs index b2d7f4a66..14ee9f051 100644 --- a/compiler/rustc_infer/src/infer/outlives/components.rs +++ b/compiler/rustc_infer/src/infer/outlives/components.rs @@ -3,8 +3,9 @@ // RFC for reference. use rustc_data_structures::sso::SsoHashSet; +use rustc_hir::def_id::DefId; use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; -use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitable}; +use rustc_middle::ty::{self, SubstsRef, Ty, TyCtxt, TypeVisitable}; use smallvec::{smallvec, SmallVec}; #[derive(Debug)] @@ -45,6 +46,8 @@ pub enum Component<'tcx> { // them. This gives us room to improve the regionck reasoning in // the future without breaking backwards compat. EscapingProjection(Vec<Component<'tcx>>), + + Opaque(DefId, SubstsRef<'tcx>), } /// Push onto `out` all the things that must outlive `'a` for the condition @@ -120,6 +123,17 @@ fn compute_components<'tcx>( out.push(Component::Param(p)); } + // Ignore lifetimes found in opaque types. Opaque types can + // have lifetimes in their substs which their hidden type doesn't + // actually use. If we inferred that an opaque type is outlived by + // its parameter lifetimes, then we could prove that any lifetime + // outlives any other lifetime, which is unsound. + // See https://github.com/rust-lang/rust/issues/84305 for + // more details. + ty::Opaque(def_id, substs) => { + out.push(Component::Opaque(def_id, substs)); + }, + // For projections, we prefer to generate an obligation like // `<P0 as Trait<P1...Pn>>::Foo: 'a`, because this gives the // regionck more ways to prove that it holds. However, @@ -168,7 +182,6 @@ fn compute_components<'tcx>( ty::Float(..) | // OutlivesScalar ty::Never | // ... ty::Adt(..) | // OutlivesNominalType - ty::Opaque(..) | // OutlivesNominalType (ish) ty::Foreign(..) | // OutlivesNominalType ty::Str | // OutlivesScalar (ish) ty::Slice(..) | // ... diff --git a/compiler/rustc_infer/src/infer/outlives/env.rs b/compiler/rustc_infer/src/infer/outlives/env.rs index b2decd64f..33543135d 100644 --- a/compiler/rustc_infer/src/infer/outlives/env.rs +++ b/compiler/rustc_infer/src/infer/outlives/env.rs @@ -2,6 +2,7 @@ use crate::infer::free_regions::FreeRegionMap; use crate::infer::{GenericKind, InferCtxt}; use crate::traits::query::OutlivesBound; use rustc_data_structures::fx::FxIndexSet; +use rustc_data_structures::transitive_relation::TransitiveRelationBuilder; use rustc_middle::ty::{self, ReEarlyBound, ReFree, ReVar, Region}; use super::explicit_outlives_bounds; @@ -51,23 +52,49 @@ pub struct OutlivesEnvironment<'tcx> { region_bound_pairs: RegionBoundPairs<'tcx>, } +/// Builder of OutlivesEnvironment. +#[derive(Debug)] +struct OutlivesEnvironmentBuilder<'tcx> { + param_env: ty::ParamEnv<'tcx>, + region_relation: TransitiveRelationBuilder<Region<'tcx>>, + region_bound_pairs: RegionBoundPairs<'tcx>, +} + /// "Region-bound pairs" tracks outlives relations that are known to /// be true, either because of explicit where-clauses like `T: 'a` or /// because of implied bounds. pub type RegionBoundPairs<'tcx> = FxIndexSet<ty::OutlivesPredicate<GenericKind<'tcx>, Region<'tcx>>>; -impl<'a, 'tcx> OutlivesEnvironment<'tcx> { - pub fn new(param_env: ty::ParamEnv<'tcx>) -> Self { - let mut env = OutlivesEnvironment { +impl<'tcx> OutlivesEnvironment<'tcx> { + /// Create a builder using `ParamEnv` and add explicit outlives bounds into it. + fn builder(param_env: ty::ParamEnv<'tcx>) -> OutlivesEnvironmentBuilder<'tcx> { + let mut builder = OutlivesEnvironmentBuilder { param_env, - free_region_map: Default::default(), + region_relation: Default::default(), region_bound_pairs: Default::default(), }; - env.add_outlives_bounds(None, explicit_outlives_bounds(param_env)); + builder.add_outlives_bounds(None, explicit_outlives_bounds(param_env)); - env + builder + } + + #[inline] + /// Create a new `OutlivesEnvironment` without extra outlives bounds. + pub fn new(param_env: ty::ParamEnv<'tcx>) -> Self { + Self::builder(param_env).build() + } + + /// Create a new `OutlivesEnvironment` with extra outlives bounds. + pub fn with_bounds( + param_env: ty::ParamEnv<'tcx>, + infcx: Option<&InferCtxt<'tcx>>, + extra_bounds: impl IntoIterator<Item = OutlivesBound<'tcx>>, + ) -> Self { + let mut builder = Self::builder(param_env); + builder.add_outlives_bounds(infcx, extra_bounds); + builder.build() } /// Borrows current value of the `free_region_map`. @@ -79,6 +106,18 @@ impl<'a, 'tcx> OutlivesEnvironment<'tcx> { pub fn region_bound_pairs(&self) -> &RegionBoundPairs<'tcx> { &self.region_bound_pairs } +} + +impl<'tcx> OutlivesEnvironmentBuilder<'tcx> { + #[inline] + #[instrument(level = "debug")] + fn build(self) -> OutlivesEnvironment<'tcx> { + OutlivesEnvironment { + param_env: self.param_env, + free_region_map: FreeRegionMap { relation: self.region_relation.freeze() }, + region_bound_pairs: self.region_bound_pairs, + } + } /// Processes outlives bounds that are known to hold, whether from implied or other sources. /// @@ -86,11 +125,8 @@ impl<'a, 'tcx> OutlivesEnvironment<'tcx> { /// contain inference variables, it must be supplied, in which /// case we will register "givens" on the inference context. (See /// `RegionConstraintData`.) - pub fn add_outlives_bounds<I>( - &mut self, - infcx: Option<&InferCtxt<'a, 'tcx>>, - outlives_bounds: I, - ) where + fn add_outlives_bounds<I>(&mut self, infcx: Option<&InferCtxt<'tcx>>, outlives_bounds: I) + where I: IntoIterator<Item = OutlivesBound<'tcx>>, { // Record relationships such as `T:'x` that don't go into the @@ -106,6 +142,10 @@ impl<'a, 'tcx> OutlivesEnvironment<'tcx> { self.region_bound_pairs .insert(ty::OutlivesPredicate(GenericKind::Projection(projection_b), r_a)); } + OutlivesBound::RegionSubOpaque(r_a, def_id, substs) => { + self.region_bound_pairs + .insert(ty::OutlivesPredicate(GenericKind::Opaque(def_id, substs), r_a)); + } OutlivesBound::RegionSubRegion(r_a, r_b) => { if let (ReEarlyBound(_) | ReFree(_), ReVar(vid_b)) = (r_a.kind(), r_b.kind()) { infcx @@ -122,7 +162,9 @@ impl<'a, 'tcx> OutlivesEnvironment<'tcx> { // system to be more general and to make use // of *every* relationship that arises here, // but presently we do not.) - self.free_region_map.relate_regions(r_a, r_b); + if r_a.is_free_or_static() && r_b.is_free() { + self.region_relation.add(r_a, r_b) + } } } } diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs index 2a085288f..2d19d1823 100644 --- a/compiler/rustc_infer/src/infer/outlives/mod.rs +++ b/compiler/rustc_infer/src/infer/outlives/mod.rs @@ -9,7 +9,7 @@ pub mod verify; use rustc_middle::traits::query::OutlivesBound; use rustc_middle::ty; -#[instrument(level = "debug", skip(param_env))] +#[instrument(level = "debug", skip(param_env), ret)] pub fn explicit_outlives_bounds<'tcx>( param_env: ty::ParamEnv<'tcx>, ) -> impl Iterator<Item = OutlivesBound<'tcx>> + 'tcx { 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) } diff --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs index 772e297b7..a5c21f0fb 100644 --- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs +++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs @@ -34,7 +34,7 @@ use crate::infer::region_constraints::VerifyIfEq; /// like are used. This is a particular challenge since this function is invoked /// very late in inference and hence cannot make use of the normal inference /// machinery. -#[tracing::instrument(level = "debug", skip(tcx, param_env))] +#[instrument(level = "debug", skip(tcx, param_env))] pub fn extract_verify_if_eq<'tcx>( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, @@ -71,7 +71,7 @@ pub fn extract_verify_if_eq<'tcx>( } /// True if a (potentially higher-ranked) outlives -#[tracing::instrument(level = "debug", skip(tcx, param_env))] +#[instrument(level = "debug", skip(tcx, param_env))] pub(super) fn can_match_erased_ty<'tcx>( tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, @@ -110,7 +110,7 @@ impl<'tcx> Match<'tcx> { /// Binds the pattern variable `br` to `value`; returns an `Err` if the pattern /// is already bound to a different value. - #[tracing::instrument(level = "debug", skip(self))] + #[instrument(level = "debug", skip(self))] fn bind( &mut self, br: ty::BoundRegion, @@ -174,7 +174,14 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> { #[instrument(skip(self), level = "debug")] fn tys(&mut self, pattern: Ty<'tcx>, value: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>> { - if pattern == value { Ok(pattern) } else { relate::super_relate_tys(self, pattern, value) } + if let ty::Error(_) = pattern.kind() { + // Unlike normal `TypeRelation` rules, `ty::Error` does not equal any type. + self.no_match() + } else if pattern == value { + Ok(pattern) + } else { + relate::super_relate_tys(self, pattern, value) + } } #[instrument(skip(self), level = "debug")] diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs index c7d7ef40d..f470b2eb8 100644 --- a/compiler/rustc_infer/src/infer/outlives/verify.rs +++ b/compiler/rustc_infer/src/infer/outlives/verify.rs @@ -2,11 +2,10 @@ use crate::infer::outlives::components::{compute_components_recursive, Component use crate::infer::outlives::env::RegionBoundPairs; use crate::infer::region_constraints::VerifyIfEq; use crate::infer::{GenericKind, VerifyBound}; -use rustc_data_structures::captures::Captures; use rustc_data_structures::sso::SsoHashSet; use rustc_hir::def_id::DefId; -use rustc_middle::ty::subst::{GenericArg, Subst}; -use rustc_middle::ty::{self, EarlyBinder, OutlivesPredicate, Ty, TyCtxt}; +use rustc_middle::ty::GenericArg; +use rustc_middle::ty::{self, EarlyBinder, OutlivesPredicate, SubstsRef, Ty, TyCtxt}; use smallvec::smallvec; @@ -38,25 +37,13 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { Self { tcx, region_bound_pairs, implicit_region_bound, param_env } } - /// Returns a "verify bound" that encodes what we know about - /// `generic` and the regions it outlives. - pub fn generic_bound(&self, generic: GenericKind<'tcx>) -> VerifyBound<'tcx> { - let mut visited = SsoHashSet::new(); - match generic { - GenericKind::Param(param_ty) => self.param_bound(param_ty), - GenericKind::Projection(projection_ty) => { - self.projection_bound(projection_ty, &mut visited) - } - } - } - - fn param_bound(&self, param_ty: ty::ParamTy) -> VerifyBound<'tcx> { - debug!("param_bound(param_ty={:?})", param_ty); - + #[instrument(level = "debug", skip(self))] + pub fn param_bound(&self, param_ty: ty::ParamTy) -> VerifyBound<'tcx> { // Start with anything like `T: 'a` we can scrape from the // environment. If the environment contains something like // `for<'a> T: 'a`, then we know that `T` outlives everything. let declared_bounds_from_env = self.declared_generic_bounds_from_env(param_ty); + debug!(?declared_bounds_from_env); let mut param_bounds = vec![]; for declared_bound in declared_bounds_from_env { let bound_region = declared_bound.map_bound(|outlives| outlives.1); @@ -65,6 +52,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { param_bounds.push(VerifyBound::OutlivedBy(region)); } else { // This is `for<'a> T: 'a`. This means that `T` outlives everything! All done here. + debug!("found that {param_ty:?} outlives any lifetime, returning empty vector"); return VerifyBound::AllBounds(vec![]); } } @@ -72,6 +60,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { // Add in the default bound of fn body that applies to all in // scope type parameters: if let Some(r) = self.implicit_region_bound { + debug!("adding implicit region bound of {r:?}"); param_bounds.push(VerifyBound::OutlivedBy(r)); } @@ -103,41 +92,31 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { /// the clause from the environment only applies if `'0 = 'a`, /// which we don't know yet. But we would still include `'b` in /// this list. - pub fn projection_approx_declared_bounds_from_env( + pub fn approx_declared_bounds_from_env( &self, - projection_ty: ty::ProjectionTy<'tcx>, + generic: GenericKind<'tcx>, ) -> Vec<ty::Binder<'tcx, ty::OutlivesPredicate<Ty<'tcx>, ty::Region<'tcx>>>> { - let projection_ty = GenericKind::Projection(projection_ty).to_ty(self.tcx); + let projection_ty = generic.to_ty(self.tcx); let erased_projection_ty = self.tcx.erase_regions(projection_ty); self.declared_generic_bounds_from_env_for_erased_ty(erased_projection_ty) } - /// Searches the where-clauses in scope for regions that - /// `projection_ty` is known to outlive. Currently requires an - /// exact match. - pub fn projection_declared_bounds_from_trait( + #[instrument(level = "debug", skip(self, visited))] + pub fn projection_opaque_bounds( &self, - projection_ty: ty::ProjectionTy<'tcx>, - ) -> impl Iterator<Item = ty::Region<'tcx>> + 'cx + Captures<'tcx> { - self.declared_projection_bounds_from_trait(projection_ty) - } - - pub fn projection_bound( - &self, - projection_ty: ty::ProjectionTy<'tcx>, + generic: GenericKind<'tcx>, + def_id: DefId, + substs: SubstsRef<'tcx>, visited: &mut SsoHashSet<GenericArg<'tcx>>, ) -> VerifyBound<'tcx> { - debug!("projection_bound(projection_ty={:?})", projection_ty); - - let projection_ty_as_ty = - self.tcx.mk_projection(projection_ty.item_def_id, projection_ty.substs); + let generic_ty = generic.to_ty(self.tcx); // Search the env for where clauses like `P: 'a`. - let env_bounds = self - .projection_approx_declared_bounds_from_env(projection_ty) + let projection_opaque_bounds = self + .approx_declared_bounds_from_env(generic) .into_iter() .map(|binder| { - if let Some(ty::OutlivesPredicate(ty, r)) = binder.no_bound_vars() && ty == projection_ty_as_ty { + if let Some(ty::OutlivesPredicate(ty, r)) = binder.no_bound_vars() && ty == generic_ty { // Micro-optimize if this is an exact match (this // occurs often when there are no region variables // involved). @@ -147,21 +126,19 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { VerifyBound::IfEq(verify_if_eq_b) } }); - // Extend with bounds that we can find from the trait. - let trait_bounds = self - .projection_declared_bounds_from_trait(projection_ty) - .map(|r| VerifyBound::OutlivedBy(r)); + let trait_bounds = + self.declared_region_bounds(def_id, substs).map(|r| VerifyBound::OutlivedBy(r)); // see the extensive comment in projection_must_outlive let recursive_bound = { let mut components = smallvec![]; - let ty = self.tcx.mk_projection(projection_ty.item_def_id, projection_ty.substs); - compute_components_recursive(self.tcx, ty.into(), &mut components, visited); + compute_components_recursive(self.tcx, generic_ty.into(), &mut components, visited); self.bound_from_components(&components, visited) }; - VerifyBound::AnyBound(env_bounds.chain(trait_bounds).collect()).or(recursive_bound) + VerifyBound::AnyBound(projection_opaque_bounds.chain(trait_bounds).collect()) + .or(recursive_bound) } fn bound_from_components( @@ -193,7 +170,18 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { match *component { Component::Region(lt) => VerifyBound::OutlivedBy(lt), Component::Param(param_ty) => self.param_bound(param_ty), - Component::Projection(projection_ty) => self.projection_bound(projection_ty, visited), + Component::Opaque(did, substs) => self.projection_opaque_bounds( + GenericKind::Opaque(did, substs), + did, + substs, + visited, + ), + Component::Projection(projection_ty) => self.projection_opaque_bounds( + GenericKind::Projection(projection_ty), + projection_ty.item_def_id, + projection_ty.substs, + visited, + ), Component::EscapingProjection(ref components) => { self.bound_from_components(components, visited) } @@ -291,30 +279,6 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { /// } /// ``` /// - /// then this function would return `'x`. This is subject to the - /// limitations around higher-ranked bounds described in - /// `region_bounds_declared_on_associated_item`. - fn declared_projection_bounds_from_trait( - &self, - projection_ty: ty::ProjectionTy<'tcx>, - ) -> impl Iterator<Item = ty::Region<'tcx>> + 'cx + Captures<'tcx> { - debug!("projection_bounds(projection_ty={:?})", projection_ty); - let tcx = self.tcx; - self.region_bounds_declared_on_associated_item(projection_ty.item_def_id) - .map(move |r| EarlyBinder(r).subst(tcx, projection_ty.substs)) - } - - /// Given the `DefId` of an associated item, returns any region - /// bounds attached to that associated item from the trait definition. - /// - /// For example: - /// - /// ```rust - /// trait Foo<'a> { - /// type Bar: 'a; - /// } - /// ``` - /// /// If we were given the `DefId` of `Foo::Bar`, we would return /// `'a`. You could then apply the substitutions from the /// projection to convert this into your namespace. This also @@ -334,17 +298,20 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { /// /// This is for simplicity, and because we are not really smart /// enough to cope with such bounds anywhere. - fn region_bounds_declared_on_associated_item( + pub fn declared_region_bounds( &self, - assoc_item_def_id: DefId, + def_id: DefId, + substs: SubstsRef<'tcx>, ) -> impl Iterator<Item = ty::Region<'tcx>> { let tcx = self.tcx; - let bounds = tcx.item_bounds(assoc_item_def_id); + let bounds = tcx.item_bounds(def_id); + trace!("{:#?}", bounds); bounds .into_iter() .filter_map(|p| p.to_opt_type_outlives()) .filter_map(|p| p.no_bound_vars()) .map(|b| b.1) + .map(move |r| EarlyBinder(r).subst(tcx, substs)) } /// Searches through a predicate list for a predicate `T: 'a`. |