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Give precendence to regions from member constaints when inferring concrete types.

This commit is contained in:
Camille GILLOT 2022-11-14 21:24:18 +00:00
parent b552965a93
commit b37feca804
4 changed files with 46 additions and 18 deletions

View file

@ -11,6 +11,7 @@ use std::ops::Index;
/// Compactly stores a set of `R0 member of [R1...Rn]` constraints,
/// indexed by the region `R0`.
#[derive(Debug)]
pub(crate) struct MemberConstraintSet<'tcx, R>
where
R: Copy + Eq,
@ -31,6 +32,7 @@ where
}
/// Represents a `R0 member of [R1..Rn]` constraint
#[derive(Debug)]
pub(crate) struct NllMemberConstraint<'tcx> {
next_constraint: Option<NllMemberConstraintIndex>,

View file

@ -128,6 +128,7 @@ pub struct RegionInferenceContext<'tcx> {
/// adds a new lower bound to the SCC it is analyzing: so you wind up
/// with `'R: 'O` where `'R` is the pick-region and `'O` is the
/// minimal viable option.
#[derive(Debug)]
pub(crate) struct AppliedMemberConstraint {
/// The SCC that was affected. (The "member region".)
///

View file

@ -1,4 +1,4 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
use rustc_data_structures::vec_map::VecMap;
use rustc_hir::def_id::LocalDefId;
use rustc_hir::OpaqueTyOrigin;
@ -63,17 +63,21 @@ impl<'tcx> RegionInferenceContext<'tcx> {
opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, (OpaqueHiddenType<'tcx>, OpaqueTyOrigin)>,
) -> VecMap<LocalDefId, OpaqueHiddenType<'tcx>> {
let mut result: VecMap<LocalDefId, OpaqueHiddenType<'tcx>> = VecMap::new();
let member_constraints: FxHashMap<_, _> = self
.member_constraints
.all_indices()
.map(|ci| (self.member_constraints[ci].key, ci))
.collect();
debug!(?member_constraints);
for (opaque_type_key, (concrete_type, origin)) in opaque_ty_decls {
let substs = opaque_type_key.substs;
debug!(?concrete_type, ?substs);
let mut subst_regions = vec![self.universal_regions.fr_static];
let universal_substs = infcx.tcx.fold_regions(substs, |region, _| {
if let ty::RePlaceholder(..) = region.kind() {
// Higher kinded regions don't need remapping, they don't refer to anything outside of this the substs.
return region;
}
let vid = self.to_region_vid(region);
let to_universal_region = |vid, subst_regions: &mut Vec<_>| {
trace!(?vid);
let scc = self.constraint_sccs.scc(vid);
trace!(?scc);
@ -94,10 +98,33 @@ impl<'tcx> RegionInferenceContext<'tcx> {
infcx.tcx.lifetimes.re_static
}
}
});
};
subst_regions.sort();
subst_regions.dedup();
// Start by inserting universal regions from the member_constraint choice regions.
// This will ensure they get precedence when folding the regions in the concrete type.
if let Some(&ci) = member_constraints.get(&opaque_type_key) {
for &vid in self.member_constraints.choice_regions(ci) {
to_universal_region(vid, &mut subst_regions);
}
}
debug!(?subst_regions);
// Next, insert universal regions from substs, so we can translate regions that appear
// in them but are not subject to member constraints, for instance closure substs.
let universal_substs = infcx.tcx.fold_regions(substs, |region, _| {
if let ty::RePlaceholder(..) = region.kind() {
// Higher kinded regions don't need remapping, they don't refer to anything outside of this the substs.
return region;
}
let vid = self.to_region_vid(region);
to_universal_region(vid, &mut subst_regions)
});
debug!(?universal_substs);
debug!(?subst_regions);
// Deduplicate the set of regions while keeping the chosen order.
let subst_regions = subst_regions.into_iter().collect::<FxIndexSet<_>>();
debug!(?subst_regions);
let universal_concrete_type =
infcx.tcx.fold_regions(concrete_type, |region, _| match *region {
@ -108,8 +135,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
.unwrap_or(infcx.tcx.lifetimes.re_erased),
_ => region,
});
debug!(?universal_concrete_type, ?universal_substs);
debug!(?universal_concrete_type);
let opaque_type_key =
OpaqueTypeKey { def_id: opaque_type_key.def_id, substs: universal_substs };