From df668b9fb960855ca1483ea520862c1eb8184d25 Mon Sep 17 00:00:00 2001 From: Ali MJ Al-Nasrawy Date: Mon, 3 Oct 2022 12:14:48 +0300 Subject: [PATCH] simplify applying closure requirements Don't use `ConstraintCategory::ClosureBounds`! Set the category and the span for the promoted constraints to that of the original constraint earlier than before. This eliminates the need for `closure_bounds_mapping`. --- .../rustc_borrowck/src/constraints/graph.rs | 1 + .../rustc_borrowck/src/constraints/mod.rs | 3 + compiler/rustc_borrowck/src/nll.rs | 2 - .../src/region_infer/dump_mir.rs | 3 +- .../rustc_borrowck/src/region_infer/mod.rs | 146 ++---------------- .../src/type_check/constraint_conversion.rs | 75 +++++++-- compiler/rustc_borrowck/src/type_check/mod.rs | 96 +++--------- .../src/type_check/relate_tys.rs | 1 + ...tion-two-region-trait-bound-closure.stderr | 7 +- 9 files changed, 97 insertions(+), 237 deletions(-) diff --git a/compiler/rustc_borrowck/src/constraints/graph.rs b/compiler/rustc_borrowck/src/constraints/graph.rs index 609fbc2bc15..385f153174c 100644 --- a/compiler/rustc_borrowck/src/constraints/graph.rs +++ b/compiler/rustc_borrowck/src/constraints/graph.rs @@ -163,6 +163,7 @@ fn next(&mut self) -> Option { span: DUMMY_SP, category: ConstraintCategory::Internal, variance_info: VarianceDiagInfo::default(), + from_closure: false, }) } else { None diff --git a/compiler/rustc_borrowck/src/constraints/mod.rs b/compiler/rustc_borrowck/src/constraints/mod.rs index df04128135b..9d9c4abb0aa 100644 --- a/compiler/rustc_borrowck/src/constraints/mod.rs +++ b/compiler/rustc_borrowck/src/constraints/mod.rs @@ -96,6 +96,9 @@ pub struct OutlivesConstraint<'tcx> { /// Variance diagnostic information pub variance_info: VarianceDiagInfo<'tcx>, + + /// If this constraint is promoted from closure requirements. + pub from_closure: bool, } impl<'tcx> fmt::Debug for OutlivesConstraint<'tcx> { diff --git a/compiler/rustc_borrowck/src/nll.rs b/compiler/rustc_borrowck/src/nll.rs index 08fdd28eb01..4e0205f8d43 100644 --- a/compiler/rustc_borrowck/src/nll.rs +++ b/compiler/rustc_borrowck/src/nll.rs @@ -242,7 +242,6 @@ pub(crate) fn compute_regions<'cx, 'tcx>( mut liveness_constraints, outlives_constraints, member_constraints, - closure_bounds_mapping, universe_causes, type_tests, } = constraints; @@ -264,7 +263,6 @@ pub(crate) fn compute_regions<'cx, 'tcx>( universal_region_relations, outlives_constraints, member_constraints, - closure_bounds_mapping, universe_causes, type_tests, liveness_constraints, diff --git a/compiler/rustc_borrowck/src/region_infer/dump_mir.rs b/compiler/rustc_borrowck/src/region_infer/dump_mir.rs index fe5193102f9..cc945099952 100644 --- a/compiler/rustc_borrowck/src/region_infer/dump_mir.rs +++ b/compiler/rustc_borrowck/src/region_infer/dump_mir.rs @@ -74,8 +74,7 @@ fn for_each_constraint( let mut constraints: Vec<_> = self.constraints.outlives().iter().collect(); constraints.sort_by_key(|c| (c.sup, c.sub)); for constraint in &constraints { - let OutlivesConstraint { sup, sub, locations, category, span, variance_info: _ } = - constraint; + let OutlivesConstraint { sup, sub, locations, category, span, .. } = constraint; let (name, arg) = match locations { Locations::All(span) => { ("All", tcx.sess.source_map().span_to_embeddable_string(*span)) diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs index 0e7f243bcf3..6782fc0665f 100644 --- a/compiler/rustc_borrowck/src/region_infer/mod.rs +++ b/compiler/rustc_borrowck/src/region_infer/mod.rs @@ -6,10 +6,9 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_data_structures::graph::scc::Sccs; use rustc_errors::Diagnostic; -use rustc_hir::def_id::{DefId, CRATE_DEF_ID}; +use rustc_hir::def_id::CRATE_DEF_ID; use rustc_hir::CRATE_HIR_ID; use rustc_index::vec::IndexVec; -use rustc_infer::infer::canonical::QueryOutlivesConstraint; use rustc_infer::infer::outlives::test_type_match; use rustc_infer::infer::region_constraints::{GenericKind, VarInfos, VerifyBound, VerifyIfEq}; use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin}; @@ -19,9 +18,7 @@ }; use rustc_middle::traits::ObligationCause; use rustc_middle::traits::ObligationCauseCode; -use rustc_middle::ty::{ - self, subst::SubstsRef, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitable, -}; +use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, TypeVisitable}; use rustc_span::Span; use crate::{ @@ -89,10 +86,6 @@ pub struct RegionInferenceContext<'tcx> { /// `member_region_scc`. member_constraints_applied: Vec, - /// Map closure bounds to a `Span` that should be used for error reporting. - closure_bounds_mapping: - FxHashMap, Span)>>, - /// Map universe indexes to information on why we created it. universe_causes: FxHashMap>, @@ -265,10 +258,6 @@ pub(crate) fn new( universal_region_relations: Frozen>, outlives_constraints: OutlivesConstraintSet<'tcx>, member_constraints_in: MemberConstraintSet<'tcx, RegionVid>, - closure_bounds_mapping: FxHashMap< - Location, - FxHashMap<(RegionVid, RegionVid), (ConstraintCategory<'tcx>, Span)>, - >, universe_causes: FxHashMap>, type_tests: Vec>, liveness_constraints: LivenessValues, @@ -310,7 +299,6 @@ pub(crate) fn new( rev_scc_graph: None, member_constraints, member_constraints_applied: Vec::new(), - closure_bounds_mapping, universe_causes, scc_universes, scc_representatives, @@ -1804,18 +1792,6 @@ pub(crate) fn cannot_name_placeholder(&self, r1: RegionVid, r2: RegionVid) -> bo } } - pub(crate) fn retrieve_closure_constraint_info( - &self, - constraint: OutlivesConstraint<'tcx>, - ) -> Option<(ConstraintCategory<'tcx>, Span)> { - match constraint.locations { - Locations::All(_) => None, - Locations::Single(loc) => { - self.closure_bounds_mapping[&loc].get(&(constraint.sup, constraint.sub)).copied() - } - } - } - /// Finds a good `ObligationCause` to blame for the fact that `fr1` outlives `fr2`. pub(crate) fn find_outlives_blame_span( &self, @@ -1921,6 +1897,7 @@ pub(crate) fn find_constraint_paths_between_regions( span: p_c.definition_span, category: ConstraintCategory::OpaqueType, variance_info: ty::VarianceDiagInfo::default(), + from_closure: false, }; handle_constraint(constraint); } @@ -2066,31 +2043,12 @@ pub(crate) fn best_blame_constraint( // Classify each of the constraints along the path. let mut categorized_path: Vec> = path .iter() - .map(|constraint| { - let (category, span, from_closure, cause_code) = - if constraint.category == ConstraintCategory::ClosureBounds { - if let Some((category, span)) = - self.retrieve_closure_constraint_info(*constraint) - { - (category, span, true, ObligationCauseCode::MiscObligation) - } else { - ( - constraint.category, - constraint.span, - false, - ObligationCauseCode::MiscObligation, - ) - } - } else { - (constraint.category, constraint.span, false, cause_code.clone()) - }; - BlameConstraint { - category, - from_closure, - cause: ObligationCause::new(span, CRATE_HIR_ID, cause_code), - variance_info: constraint.variance_info, - outlives_constraint: *constraint, - } + .map(|constraint| BlameConstraint { + category: constraint.category, + from_closure: constraint.from_closure, + cause: ObligationCause::new(constraint.span, CRATE_HIR_ID, cause_code.clone()), + variance_info: constraint.variance_info, + outlives_constraint: *constraint, }) .collect(); debug!("categorized_path={:#?}", categorized_path); @@ -2274,92 +2232,6 @@ fn new(universe: ty::UniverseIndex, rv_origin: RegionVariableOrigin) -> Self { } } -pub trait ClosureRegionRequirementsExt<'tcx> { - fn apply_requirements( - &self, - tcx: TyCtxt<'tcx>, - closure_def_id: DefId, - closure_substs: SubstsRef<'tcx>, - ) -> Vec>; -} - -impl<'tcx> ClosureRegionRequirementsExt<'tcx> for ClosureRegionRequirements<'tcx> { - /// Given an instance T of the closure type, this method - /// instantiates the "extra" requirements that we computed for the - /// closure into the inference context. This has the effect of - /// adding new outlives obligations to existing variables. - /// - /// As described on `ClosureRegionRequirements`, the extra - /// requirements are expressed in terms of regionvids that index - /// into the free regions that appear on the closure type. So, to - /// do this, we first copy those regions out from the type T into - /// a vector. Then we can just index into that vector to extract - /// out the corresponding region from T and apply the - /// requirements. - fn apply_requirements( - &self, - tcx: TyCtxt<'tcx>, - closure_def_id: DefId, - closure_substs: SubstsRef<'tcx>, - ) -> Vec> { - debug!( - "apply_requirements(closure_def_id={:?}, closure_substs={:?})", - closure_def_id, closure_substs - ); - - // Extract the values of the free regions in `closure_substs` - // into a vector. These are the regions that we will be - // relating to one another. - let closure_mapping = &UniversalRegions::closure_mapping( - tcx, - closure_substs, - self.num_external_vids, - closure_def_id.expect_local(), - ); - debug!("apply_requirements: closure_mapping={:?}", closure_mapping); - - // Create the predicates. - self.outlives_requirements - .iter() - .map(|outlives_requirement| { - let outlived_region = closure_mapping[outlives_requirement.outlived_free_region]; - - match outlives_requirement.subject { - ClosureOutlivesSubject::Region(region) => { - let region = closure_mapping[region]; - debug!( - "apply_requirements: region={:?} \ - outlived_region={:?} \ - outlives_requirement={:?}", - region, outlived_region, outlives_requirement, - ); - ( - ty::Binder::dummy(ty::OutlivesPredicate( - region.into(), - outlived_region, - )), - ConstraintCategory::BoringNoLocation, - ) - } - - ClosureOutlivesSubject::Ty(ty) => { - debug!( - "apply_requirements: ty={:?} \ - outlived_region={:?} \ - outlives_requirement={:?}", - ty, outlived_region, outlives_requirement, - ); - ( - ty::Binder::dummy(ty::OutlivesPredicate(ty.into(), outlived_region)), - ConstraintCategory::BoringNoLocation, - ) - } - } - }) - .collect() - } -} - #[derive(Clone, Debug)] pub struct BlameConstraint<'tcx> { pub category: ConstraintCategory<'tcx>, diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs index d5bfc2f5208..88be80c0b55 100644 --- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs +++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs @@ -1,10 +1,10 @@ -use rustc_infer::infer::canonical::QueryOutlivesConstraint; +use rustc_hir::def_id::DefId; use rustc_infer::infer::canonical::QueryRegionConstraints; use rustc_infer::infer::outlives::env::RegionBoundPairs; use rustc_infer::infer::outlives::obligations::{TypeOutlives, TypeOutlivesDelegate}; use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound}; use rustc_infer::infer::{self, InferCtxt, SubregionOrigin}; -use rustc_middle::mir::ConstraintCategory; +use rustc_middle::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory}; use rustc_middle::ty::subst::GenericArgKind; use rustc_middle::ty::TypeFoldable; use rustc_middle::ty::{self, TyCtxt}; @@ -38,6 +38,7 @@ pub(crate) struct ConstraintConversion<'a, 'tcx> { locations: Locations, span: Span, category: ConstraintCategory<'tcx>, + from_closure: bool, constraints: &'a mut MirTypeckRegionConstraints<'tcx>, } @@ -64,6 +65,7 @@ pub(crate) fn new( span, category, constraints, + from_closure: false, } } @@ -81,12 +83,62 @@ pub(super) fn convert_all(&mut self, query_constraints: &QueryRegionConstraints< } self.constraints.member_constraints = tmp; - for query_constraint in outlives { - self.convert(query_constraint); + for (predicate, constraint_category) in outlives { + // At the moment, we never generate any "higher-ranked" + // region constraints like `for<'a> 'a: 'b`. At some point + // when we move to universes, we will, and this assertion + // will start to fail. + let predicate = predicate.no_bound_vars().unwrap_or_else(|| { + bug!("query_constraint {:?} contained bound vars", predicate,); + }); + + self.convert(predicate, *constraint_category); } } - fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) { + /// Given an instance of the closure type, this method instantiates the "extra" requirements + /// that we computed for the closure. This has the effect of adding new outlives obligations + /// to existing region variables in `closure_substs`. + #[instrument(skip(self), level = "debug")] + pub fn apply_closure_requirements( + &mut self, + closure_requirements: &ClosureRegionRequirements<'tcx>, + closure_def_id: DefId, + closure_substs: ty::SubstsRef<'tcx>, + ) { + // Extract the values of the free regions in `closure_substs` + // into a vector. These are the regions that we will be + // relating to one another. + let closure_mapping = &UniversalRegions::closure_mapping( + self.tcx, + closure_substs, + closure_requirements.num_external_vids, + closure_def_id.expect_local(), + ); + debug!(?closure_mapping); + + // Create the predicates. + let backup = (self.category, self.span, self.from_closure); + self.from_closure = true; + for outlives_requirement in &closure_requirements.outlives_requirements { + let outlived_region = closure_mapping[outlives_requirement.outlived_free_region]; + let subject = match outlives_requirement.subject { + ClosureOutlivesSubject::Region(re) => closure_mapping[re].into(), + ClosureOutlivesSubject::Ty(ty) => ty.into(), + }; + + self.category = outlives_requirement.category; + self.span = outlives_requirement.blame_span; + self.convert(ty::OutlivesPredicate(subject, outlived_region), self.category); + } + (self.category, self.span, self.from_closure) = backup; + } + + fn convert( + &mut self, + predicate: ty::OutlivesPredicate, ty::Region<'tcx>>, + constraint_category: ConstraintCategory<'tcx>, + ) { debug!("generate: constraints at: {:#?}", self.locations); // Extract out various useful fields we'll need below. @@ -94,17 +146,7 @@ fn convert(&mut self, query_constraint: &QueryOutlivesConstraint<'tcx>) { tcx, region_bound_pairs, implicit_region_bound, param_env, .. } = *self; - // At the moment, we never generate any "higher-ranked" - // region constraints like `for<'a> 'a: 'b`. At some point - // when we move to universes, we will, and this assertion - // will start to fail. - let ty::OutlivesPredicate(k1, r2) = - query_constraint.0.no_bound_vars().unwrap_or_else(|| { - bug!("query_constraint {:?} contained bound vars", query_constraint,); - }); - - let constraint_category = query_constraint.1; - + let ty::OutlivesPredicate(k1, r2) = predicate; match k1.unpack() { GenericArgKind::Lifetime(r1) => { let r1_vid = self.to_region_vid(r1); @@ -188,6 +230,7 @@ fn add_outlives( sub, sup, variance_info: ty::VarianceDiagInfo::default(), + from_closure: self.from_closure, }); } diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs index 3c1c3ab45ce..3d9e08b4ca7 100644 --- a/compiler/rustc_borrowck/src/type_check/mod.rs +++ b/compiler/rustc_borrowck/src/type_check/mod.rs @@ -27,7 +27,7 @@ use rustc_middle::mir::*; use rustc_middle::ty::adjustment::PointerCast; use rustc_middle::ty::cast::CastTy; -use rustc_middle::ty::subst::{GenericArgKind, SubstsRef, UserSubsts}; +use rustc_middle::ty::subst::{SubstsRef, UserSubsts}; use rustc_middle::ty::visit::TypeVisitable; use rustc_middle::ty::{ self, Binder, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, Dynamic, @@ -61,7 +61,7 @@ region_infer::values::{ LivenessValues, PlaceholderIndex, PlaceholderIndices, RegionValueElements, }, - region_infer::{ClosureRegionRequirementsExt, TypeTest}, + region_infer::TypeTest, type_check::free_region_relations::{CreateResult, UniversalRegionRelations}, universal_regions::{DefiningTy, UniversalRegions}, Upvar, @@ -144,7 +144,6 @@ pub(crate) fn type_check<'mir, 'tcx>( liveness_constraints: LivenessValues::new(elements.clone()), outlives_constraints: OutlivesConstraintSet::default(), member_constraints: MemberConstraintSet::default(), - closure_bounds_mapping: Default::default(), type_tests: Vec::default(), universe_causes: FxHashMap::default(), }; @@ -585,7 +584,6 @@ fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Locatio let all_facts = &mut None; let mut constraints = Default::default(); let mut type_tests = Default::default(); - let mut closure_bounds = Default::default(); let mut liveness_constraints = LivenessValues::new(Rc::new(RegionValueElements::new(&promoted_body))); // Don't try to add borrow_region facts for the promoted MIR @@ -597,10 +595,6 @@ fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Locatio &mut constraints, ); mem::swap(&mut this.cx.borrowck_context.constraints.type_tests, &mut type_tests); - mem::swap( - &mut this.cx.borrowck_context.constraints.closure_bounds_mapping, - &mut closure_bounds, - ); mem::swap( &mut this.cx.borrowck_context.constraints.liveness_constraints, &mut liveness_constraints, @@ -653,18 +647,6 @@ fn sanitize_promoted(&mut self, promoted_body: &'b Body<'tcx>, location: Locatio .add_element(region, location); } } - - if !closure_bounds.is_empty() { - let combined_bounds_mapping = - closure_bounds.into_iter().flat_map(|(_, value)| value).collect(); - let existing = self - .cx - .borrowck_context - .constraints - .closure_bounds_mapping - .insert(location, combined_bounds_mapping); - assert!(existing.is_none(), "Multiple promoteds/closures at the same location."); - } } fn sanitize_projection( @@ -941,9 +923,6 @@ pub(crate) struct MirTypeckRegionConstraints<'tcx> { pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>, - pub(crate) closure_bounds_mapping: - FxHashMap, Span)>>, - pub(crate) universe_causes: FxHashMap>, pub(crate) type_tests: Vec>, @@ -2562,6 +2541,7 @@ fn add_reborrow_constraint( span: location.to_locations().span(body), category, variance_info: ty::VarianceDiagInfo::default(), + from_closure: false, }); match mutbl { @@ -2679,62 +2659,22 @@ fn prove_closure_bounds( substs: SubstsRef<'tcx>, location: Location, ) -> ty::InstantiatedPredicates<'tcx> { - if let Some(ref closure_region_requirements) = tcx.mir_borrowck(def_id).closure_requirements - { - let closure_constraints = QueryRegionConstraints { - outlives: closure_region_requirements.apply_requirements( - tcx, - def_id.to_def_id(), - substs, - ), - - // Presently, closures never propagate member - // constraints to their parents -- they are enforced - // locally. This is largely a non-issue as member - // constraints only come from `-> impl Trait` and - // friends which don't appear (thus far...) in - // closures. - member_constraints: vec![], - }; - - let bounds_mapping = closure_constraints - .outlives - .iter() - .enumerate() - .filter_map(|(idx, constraint)| { - let ty::OutlivesPredicate(k1, r2) = - constraint.0.no_bound_vars().unwrap_or_else(|| { - bug!("query_constraint {:?} contained bound vars", constraint,); - }); - - match k1.unpack() { - GenericArgKind::Lifetime(r1) => { - // constraint is r1: r2 - let r1_vid = self.borrowck_context.universal_regions.to_region_vid(r1); - let r2_vid = self.borrowck_context.universal_regions.to_region_vid(r2); - let outlives_requirements = - &closure_region_requirements.outlives_requirements[idx]; - Some(( - (r1_vid, r2_vid), - (outlives_requirements.category, outlives_requirements.blame_span), - )) - } - GenericArgKind::Type(_) | GenericArgKind::Const(_) => None, - } - }) - .collect(); - - let existing = self - .borrowck_context - .constraints - .closure_bounds_mapping - .insert(location, bounds_mapping); - assert!(existing.is_none(), "Multiple closures at the same location."); - - self.push_region_constraints( + if let Some(ref closure_requirements) = tcx.mir_borrowck(def_id).closure_requirements { + constraint_conversion::ConstraintConversion::new( + self.infcx, + self.borrowck_context.universal_regions, + self.region_bound_pairs, + self.implicit_region_bound, + self.param_env, location.to_locations(), - ConstraintCategory::ClosureBounds, - &closure_constraints, + DUMMY_SP, // irrelevant; will be overrided. + ConstraintCategory::Boring, // same as above. + &mut self.borrowck_context.constraints, + ) + .apply_closure_requirements( + &closure_requirements, + def_id.to_def_id(), + substs, ); } diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs index 4f2dc263bf5..94d51032866 100644 --- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs +++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs @@ -136,6 +136,7 @@ fn push_outlives( span: self.locations.span(self.type_checker.body), category: self.category, variance_info: info, + from_closure: false, }, ); } diff --git a/src/test/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr b/src/test/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr index 0195a693e5f..1260a656c98 100644 --- a/src/test/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr +++ b/src/test/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr @@ -167,7 +167,7 @@ LL | | T: Anything<'b, 'b>, = note: defining type: two_regions::<'_#1r, T> error: lifetime may not live long enough - --> $DIR/projection-two-region-trait-bound-closure.rs:87:29 + --> $DIR/projection-two-region-trait-bound-closure.rs:87:5 | LL | fn two_regions<'a, 'b, T>(cell: Cell<&'a ()>, t: T) | -- -- lifetime `'b` defined here @@ -175,9 +175,12 @@ LL | fn two_regions<'a, 'b, T>(cell: Cell<&'a ()>, t: T) | lifetime `'a` defined here ... LL | with_signature(cell, t, |cell, t| require(cell, t)); - | ^^^^^^^^^^^^^^^^^^^^^^^^^^ closure body requires that `'b` must outlive `'a` + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'b` must outlive `'a` | = help: consider adding the following bound: `'b: 'a` + = note: requirement occurs because of the type `Cell<&'_#8r ()>`, which makes the generic argument `&'_#8r ()` invariant + = note: the struct `Cell` is invariant over the parameter `T` + = help: see for more information about variance note: external requirements --> $DIR/projection-two-region-trait-bound-closure.rs:97:29