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Consider alias bounds when considering lliveness for alias types in NLL

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This commit is contained in:
Michael Goulet 2023-09-21 04:11:08 +00:00
parent 96c4dba794
commit 184d5ef107
3 changed files with 103 additions and 20 deletions
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97
compiler/rustc_borrowck/src/type_check/liveness/trace.rs
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@ -5,10 +5,13 @@ use rustc_index::interval::IntervalSet;
use rustc_infer::infer::canonical::QueryRegionConstraints;
use rustc_middle::mir::{BasicBlock, Body, ConstraintCategory, Local, Location};
use rustc_middle::traits::query::DropckOutlivesResult;
use rustc_middle::ty::{RegionVid, Ty, TyCtxt, TypeVisitable, TypeVisitableExt};
use rustc_middle::ty::{
self, RegionVid, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
};
use rustc_span::DUMMY_SP;
use rustc_trait_selection::traits::query::type_op::outlives::DropckOutlives;
use rustc_trait_selection::traits::query::type_op::{TypeOp, TypeOpOutput};
use std::ops::ControlFlow;
use std::rc::Rc;
use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
@ -601,34 +604,88 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
values::location_set_str(elements, live_at.iter()),
);
let tcx = typeck.tcx();
let borrowck_context = &mut typeck.borrowck_context;
// When using `-Zpolonius=next`, we want to record the loans that flow into this value's
// regions as being live at the given `live_at` points: this will be used to compute the
// location where a loan goes out of scope.
let num_loans = borrowck_context.borrow_set.len();
let mut value_loans = HybridBitSet::new_empty(num_loans);
let num_loans = typeck.borrowck_context.borrow_set.len();
let value_loans = &mut HybridBitSet::new_empty(num_loans);
tcx.for_each_free_region(&value, |live_region| {
let live_region_vid = borrowck_context.universal_regions.to_region_vid(live_region);
borrowck_context
.constraints
.liveness_constraints
.add_elements(live_region_vid, live_at);
// There can only be inflowing loans for this region when we are using
// `-Zpolonius=next`.
if let Some(inflowing) = inflowing_loans.row(live_region_vid) {
value_loans.union(inflowing);
struct MakeAllRegionsLive<'a, 'b, 'tcx> {
typeck: &'b mut TypeChecker<'a, 'tcx>,
live_at: &'b IntervalSet<PointIndex>,
value_loans: &'b mut HybridBitSet<BorrowIndex>,
inflowing_loans: &'b SparseBitMatrix<RegionVid, BorrowIndex>,
}
impl<'tcx> MakeAllRegionsLive<'_, '_, 'tcx> {
fn make_alias_live(&mut self, t: Ty<'tcx>) -> ControlFlow<!> {
let ty::Alias(_kind, alias_ty) = t.kind() else {
bug!();
};
let tcx = self.typeck.infcx.tcx;
let mut outlives_bounds = tcx
.item_bounds(alias_ty.def_id)
.iter_instantiated(tcx, alias_ty.args)
.filter_map(|clause| {
if let Some(outlives) = clause.as_type_outlives_clause()
&& outlives.skip_binder().0 == t
{
Some(outlives.skip_binder().1)
} else {
None
}
});
if let Some(r) = outlives_bounds.next()
&& !r.is_late_bound()
&& outlives_bounds.all(|other_r| {
other_r == r
})
{
r.visit_with(self)
} else {
t.super_visit_with(self)
}
}
});
}
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for MakeAllRegionsLive<'_, '_, 'tcx> {
type BreakTy = !;
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
if r.is_late_bound() {
return ControlFlow::Continue(());
}
let live_region_vid =
self.typeck.borrowck_context.universal_regions.to_region_vid(r);
self.typeck
.borrowck_context
.constraints
.liveness_constraints
.add_elements(live_region_vid, self.live_at);
// There can only be inflowing loans for this region when we are using
// `-Zpolonius=next`.
if let Some(inflowing) = self.inflowing_loans.row(live_region_vid) {
self.value_loans.union(inflowing);
}
ControlFlow::Continue(())
}
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
if !t.has_free_regions() {
ControlFlow::Continue(())
} else if let ty::Alias(..) = t.kind() {
self.make_alias_live(t)
} else {
t.super_visit_with(self)
}
}
}
value.visit_with(&mut MakeAllRegionsLive { typeck, live_at, value_loans, inflowing_loans });
// Record the loans reaching the value.
if !value_loans.is_empty() {
for point in live_at.iter() {
borrowck_context.live_loans.union_row(point, &value_loans);
typeck.borrowck_context.live_loans.union_row(point, value_loans);
}
}
}