bjoernager/rust
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consider a loan escapes the function via applied member constraints

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This commit is contained in:
Rémy Rakic 2023-10-19 21:44:03 +00:00
parent c69bd9480a
commit fa45efaafb
2 changed files with 14 additions and 12 deletions
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21
compiler/rustc_borrowck/src/dataflow.rs
View file

@ -272,21 +272,28 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
loan_issued_at: Location, loan_issued_at: Location,
) { ) {
let sccs = self.regioncx.constraint_sccs(); let sccs = self.regioncx.constraint_sccs();
let universal_regions = self.regioncx.universal_regions();
let issuing_region_scc = sccs.scc(issuing_region); let issuing_region_scc = sccs.scc(issuing_region);
// We first handle the cases where the loan doesn't go out of scope, depending on the issuing // We first handle the cases where the loan doesn't go out of scope, depending on the issuing
// region's successors. // region's successors.
for scc in sccs.depth_first_search(issuing_region_scc) { for scc in sccs.depth_first_search(issuing_region_scc) {
// 1. Via member constraints // 1. Via applied member constraints
// //
// The issuing region can flow into the choice regions, and they are either: // The issuing region can flow into the choice regions, and they are either:
// - placeholders or free regions themselves, // - placeholders or free regions themselves,
// - or also transitively outlive a free region. // - or also transitively outlive a free region.
// //
// That is to say, if there are member constraints here, the loan escapes the function // That is to say, if there are applied member constraints here, the loan escapes the
// and cannot go out of scope. We can early return. // function and cannot go out of scope. We could early return here.
if self.regioncx.scc_has_member_constraints(scc) { //
return; // For additional insurance via fuzzing and crater, we verify that the constraint's min
// choice indeed escapes the function. In the future, we could e.g. turn this check into
// a debug assert and early return as an optimization.
for constraint in self.regioncx.applied_member_constraints(scc) {
if universal_regions.is_universal_region(constraint.min_choice) {
return;
}
} }
// 2. Via regions that are live at all points: placeholders and free regions. // 2. Via regions that are live at all points: placeholders and free regions.
@ -413,12 +420,12 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
let mut polonius_prec = PoloniusOutOfScopePrecomputer::new(body, regioncx); let mut polonius_prec = PoloniusOutOfScopePrecomputer::new(body, regioncx);
for (loan_idx, loan_data) in borrow_set.iter_enumerated() { for (loan_idx, loan_data) in borrow_set.iter_enumerated() {
let issuing_region = loan_data.region; let issuing_region = loan_data.region;
let issued_location = loan_data.reserve_location; let loan_issued_at = loan_data.reserve_location;
polonius_prec.precompute_loans_out_of_scope( polonius_prec.precompute_loans_out_of_scope(
loan_idx, loan_idx,
issuing_region, issuing_region,
issued_location, loan_issued_at,
); );
} }

5
compiler/rustc_borrowck/src/region_infer/mod.rs
View file

@ -2293,11 +2293,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
self.constraint_sccs.as_ref() self.constraint_sccs.as_ref()
} }
/// Returns whether the given SCC has any member constraints.
pub(crate) fn scc_has_member_constraints(&self, scc: ConstraintSccIndex) -> bool {
self.member_constraints.indices(scc).next().is_some()
}
/// Returns whether the given SCC is live at all points: whether the representative is a /// Returns whether the given SCC is live at all points: whether the representative is a
/// placeholder or a free region. /// placeholder or a free region.
pub(crate) fn scc_is_live_at_all_points(&self, scc: ConstraintSccIndex) -> bool { pub(crate) fn scc_is_live_at_all_points(&self, scc: ConstraintSccIndex) -> bool {