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Polonius: emit placeholder and known_subset facts, as inputs to the subset error computation

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This commit is contained in:
Remy Rakic 2019-11-19 16:58:09 +01:00
parent 4dd6292c3c
commit 7a3dca69bb
2 changed files with 32 additions and 0 deletions
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2
src/librustc_mir/borrow_check/nll/facts.rs
View file

@ -66,6 +66,7 @@ impl AllFactsExt for AllFacts {
wr.write_facts_to_path(self.[
borrow_region,
universal_region,
placeholder,
cfg_edge,
killed,
outlives,
@ -80,6 +81,7 @@ impl AllFactsExt for AllFacts {
initialized_at,
moved_out_at,
path_accessed_at,
known_subset,
])
}
Ok(())

30
src/librustc_mir/borrow_check/nll/mod.rs
View file

@ -209,6 +209,36 @@ pub(in crate::borrow_check) fn compute_regions<'cx, 'tcx>(
.universal_region
.extend(universal_regions.universal_regions());
populate_polonius_move_facts(all_facts, move_data, location_table, &body);
// Emit universal regions facts, and their relations, for Polonius.
//
// 1: universal regions are modeled in Polonius as a pair:
// - the universal region vid itself.
// - a "placeholder loan" associated to this universal region. Since they don't exist in
// the `borrow_set`, their `BorrowIndex` are synthesized as the universal region index
// added to the existing number of loans, as if they succeeded them in the set.
//
let borrow_count = borrow_set.borrows.len();
debug!(
"compute_regions: polonius placeholders, num_universals={}, borrow_count={}",
universal_regions.len(),
borrow_count
);
for universal_region in universal_regions.universal_regions() {
let universal_region_idx = universal_region.index();
let placeholder_loan_idx = borrow_count + universal_region_idx;
all_facts.placeholder.push((universal_region, placeholder_loan_idx.into()));
}
// 2: the universal region relations `outlives` constraints are emitted as
// `known_subset` facts.
for (fr1, fr2) in universal_region_relations.known_outlives() {
if fr1 != fr2 {
debug!("compute_regions: emitting polonius `known_subset` fr1={:?}, fr2={:?}", fr1, fr2);
all_facts.known_subset.push((*fr1, *fr2));
}
}
}
// Create the region inference context, taking ownership of the