diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/outlives')
5 files changed, 167 insertions, 27 deletions
diff --git a/compiler/rustc_infer/src/infer/outlives/components.rs b/compiler/rustc_infer/src/infer/outlives/components.rs index 6a9d40daa..38819e8ad 100644 --- a/compiler/rustc_infer/src/infer/outlives/components.rs +++ b/compiler/rustc_infer/src/infer/outlives/components.rs @@ -102,17 +102,17 @@ fn compute_components<'tcx>( compute_components(tcx, tupled_ty, out, visited); } - ty::Generator(_, ref args, _) => { + ty::Coroutine(_, ref args, _) => { // Same as the closure case - let tupled_ty = args.as_generator().tupled_upvars_ty(); + let tupled_ty = args.as_coroutine().tupled_upvars_ty(); compute_components(tcx, tupled_ty, out, visited); - // We ignore regions in the generator interior as we don't + // We ignore regions in the coroutine interior as we don't // want these to affect region inference } // All regions are bound inside a witness - ty::GeneratorWitness(..) => (), + ty::CoroutineWitness(..) => (), // OutlivesTypeParameterEnv -- the actual checking that `X:'a` // is implied by the environment is done in regionck. diff --git a/compiler/rustc_infer/src/infer/outlives/for_liveness.rs b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs new file mode 100644 index 000000000..398ac94ee --- /dev/null +++ b/compiler/rustc_infer/src/infer/outlives/for_liveness.rs @@ -0,0 +1,129 @@ +use rustc_middle::ty::{ + self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor, +}; + +use std::ops::ControlFlow; + +use crate::infer::outlives::test_type_match; +use crate::infer::region_constraints::VerifyIfEq; + +/// Visits free regions in the type that are relevant for liveness computation. +/// These regions are passed to `OP`. +/// +/// Specifically, we visit all of the regions of types recursively, except if +/// the type is an alias, we look at the outlives bounds in the param-env +/// and alias's item bounds. If there is a unique outlives bound, then visit +/// that instead. If there is not a unique but there is a `'static` outlives +/// bound, then don't visit anything. Otherwise, walk through the opaque's +/// regions structurally. +pub struct FreeRegionsVisitor<'tcx, OP: FnMut(ty::Region<'tcx>)> { + pub tcx: TyCtxt<'tcx>, + pub param_env: ty::ParamEnv<'tcx>, + pub op: OP, +} + +impl<'tcx, OP> TypeVisitor<TyCtxt<'tcx>> for FreeRegionsVisitor<'tcx, OP> +where + OP: FnMut(ty::Region<'tcx>), +{ + fn visit_binder<T: TypeVisitable<TyCtxt<'tcx>>>( + &mut self, + t: &ty::Binder<'tcx, T>, + ) -> ControlFlow<Self::BreakTy> { + t.super_visit_with(self); + ControlFlow::Continue(()) + } + + fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> { + match *r { + // ignore bound regions, keep visiting + ty::ReLateBound(_, _) => ControlFlow::Continue(()), + _ => { + (self.op)(r); + ControlFlow::Continue(()) + } + } + } + + fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + // We're only interested in types involving regions + if !ty.flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS) { + return ControlFlow::Continue(()); + } + + // FIXME: Don't consider alias bounds on types that have escaping bound + // vars. See #117455. + if ty.has_escaping_bound_vars() { + return ty.super_visit_with(self); + } + + match ty.kind() { + // We can prove that an alias is live two ways: + // 1. All the components are live. + // + // 2. There is a known outlives bound or where-clause, and that + // region is live. + // + // We search through the item bounds and where clauses for + // either `'static` or a unique outlives region, and if one is + // found, we just need to prove that that region is still live. + // If one is not found, then we continue to walk through the alias. + ty::Alias(kind, ty::AliasTy { def_id, args, .. }) => { + let tcx = self.tcx; + let param_env = self.param_env; + let outlives_bounds: Vec<_> = tcx + .item_bounds(def_id) + .iter_instantiated(tcx, args) + .chain(param_env.caller_bounds()) + .filter_map(|clause| { + let outlives = clause.as_type_outlives_clause()?; + if let Some(outlives) = outlives.no_bound_vars() + && outlives.0 == ty + { + Some(outlives.1) + } else { + test_type_match::extract_verify_if_eq( + tcx, + param_env, + &outlives.map_bound(|ty::OutlivesPredicate(ty, bound)| { + VerifyIfEq { ty, bound } + }), + ty, + ) + } + }) + .collect(); + // If we find `'static`, then we know the alias doesn't capture *any* regions. + // Otherwise, all of the outlives regions should be equal -- if they're not, + // we don't really know how to proceed, so we continue recursing through the + // alias. + if outlives_bounds.contains(&tcx.lifetimes.re_static) { + // no + } else if let Some(r) = outlives_bounds.first() + && outlives_bounds[1..].iter().all(|other_r| other_r == r) + { + assert!(r.type_flags().intersects(ty::TypeFlags::HAS_FREE_REGIONS)); + r.visit_with(self)?; + } else { + // Skip lifetime parameters that are not captures. + let variances = match kind { + ty::Opaque => Some(self.tcx.variances_of(*def_id)), + _ => None, + }; + + for (idx, s) in args.iter().enumerate() { + if variances.map(|variances| variances[idx]) != Some(ty::Variance::Bivariant) { + s.visit_with(self)?; + } + } + } + } + + _ => { + ty.super_visit_with(self)?; + } + } + + ControlFlow::Continue(()) + } +} diff --git a/compiler/rustc_infer/src/infer/outlives/mod.rs b/compiler/rustc_infer/src/infer/outlives/mod.rs index cb92fc6dd..0987915f4 100644 --- a/compiler/rustc_infer/src/infer/outlives/mod.rs +++ b/compiler/rustc_infer/src/infer/outlives/mod.rs @@ -9,6 +9,7 @@ use rustc_middle::ty; pub mod components; pub mod env; +pub mod for_liveness; pub mod obligations; pub mod test_type_match; pub mod verify; 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 fefa89595..6f973ee37 100644 --- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs +++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs @@ -44,7 +44,7 @@ pub fn extract_verify_if_eq<'tcx>( test_ty: Ty<'tcx>, ) -> Option<ty::Region<'tcx>> { assert!(!verify_if_eq_b.has_escaping_bound_vars()); - let mut m = Match::new(tcx, param_env); + let mut m = MatchAgainstHigherRankedOutlives::new(tcx, param_env); let verify_if_eq = verify_if_eq_b.skip_binder(); m.relate(verify_if_eq.ty, test_ty).ok()?; @@ -87,24 +87,32 @@ pub(super) fn can_match_erased_ty<'tcx>( // pointless micro-optimization true } else { - Match::new(tcx, param_env).relate(outlives_ty, erased_ty).is_ok() + MatchAgainstHigherRankedOutlives::new(tcx, param_env).relate(outlives_ty, erased_ty).is_ok() } } -struct Match<'tcx> { +struct MatchAgainstHigherRankedOutlives<'tcx> { tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>, pattern_depth: ty::DebruijnIndex, map: FxHashMap<ty::BoundRegion, ty::Region<'tcx>>, } -impl<'tcx> Match<'tcx> { - fn new(tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Match<'tcx> { - Match { tcx, param_env, pattern_depth: ty::INNERMOST, map: FxHashMap::default() } +impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> { + fn new( + tcx: TyCtxt<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> MatchAgainstHigherRankedOutlives<'tcx> { + MatchAgainstHigherRankedOutlives { + tcx, + param_env, + pattern_depth: ty::INNERMOST, + map: FxHashMap::default(), + } } } -impl<'tcx> Match<'tcx> { +impl<'tcx> MatchAgainstHigherRankedOutlives<'tcx> { /// Creates the "Error" variant that signals "no match". fn no_match<T>(&self) -> RelateResult<'tcx, T> { Err(TypeError::Mismatch) @@ -134,7 +142,7 @@ impl<'tcx> Match<'tcx> { } } -impl<'tcx> TypeRelation<'tcx> for Match<'tcx> { +impl<'tcx> TypeRelation<'tcx> for MatchAgainstHigherRankedOutlives<'tcx> { fn tag(&self) -> &'static str { "Match" } @@ -169,7 +177,9 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> { value: ty::Region<'tcx>, ) -> RelateResult<'tcx, ty::Region<'tcx>> { debug!("self.pattern_depth = {:?}", self.pattern_depth); - if let ty::RegionKind::ReLateBound(depth, br) = pattern.kind() && depth == self.pattern_depth { + if let ty::RegionKind::ReLateBound(depth, br) = pattern.kind() + && depth == self.pattern_depth + { self.bind(br, value) } else if pattern == value { Ok(pattern) diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs index 4279d0ab7..7f0a4717d 100644 --- a/compiler/rustc_infer/src/infer/outlives/verify.rs +++ b/compiler/rustc_infer/src/infer/outlives/verify.rs @@ -108,20 +108,20 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> { let alias_ty_as_ty = alias_ty.to_ty(self.tcx); // Search the env for where clauses like `P: 'a`. - let env_bounds = self - .approx_declared_bounds_from_env(alias_ty) - .into_iter() - .map(|binder| { - if let Some(ty::OutlivesPredicate(ty, r)) = binder.no_bound_vars() && ty == alias_ty_as_ty { - // Micro-optimize if this is an exact match (this - // occurs often when there are no region variables - // involved). - VerifyBound::OutlivedBy(r) - } else { - let verify_if_eq_b = binder.map_bound(|ty::OutlivesPredicate(ty, bound)| VerifyIfEq { ty, bound }); - VerifyBound::IfEq(verify_if_eq_b) - } - }); + let env_bounds = self.approx_declared_bounds_from_env(alias_ty).into_iter().map(|binder| { + if let Some(ty::OutlivesPredicate(ty, r)) = binder.no_bound_vars() + && ty == alias_ty_as_ty + { + // Micro-optimize if this is an exact match (this + // occurs often when there are no region variables + // involved). + VerifyBound::OutlivedBy(r) + } else { + let verify_if_eq_b = + binder.map_bound(|ty::OutlivesPredicate(ty, bound)| VerifyIfEq { ty, bound }); + VerifyBound::IfEq(verify_if_eq_b) + } + }); // Extend with bounds that we can find from the definition. let definition_bounds = |