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Use a helper to zip together parent and child captures for coroutine-closures

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This commit is contained in:
Michael Goulet 2024-04-09 11:11:17 -04:00
parent 5974fe87c4
commit 568703c4bd
3 changed files with 81 additions and 71 deletions
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78
compiler/rustc_mir_transform/src/coroutine/by_move_body.rs
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@ -71,7 +71,7 @@
use rustc_data_structures::unord::UnordMap;
use rustc_hir as hir;
use rustc_middle::hir::place::{PlaceBase, Projection, ProjectionKind};
use rustc_middle::hir::place::{Projection, ProjectionKind};
use rustc_middle::mir::visit::MutVisitor;
use rustc_middle::mir::{self, dump_mir, MirPass};
use rustc_middle::ty::{self, InstanceDef, Ty, TyCtxt, TypeVisitableExt};
@ -124,44 +124,10 @@ impl<'tcx> MirPass<'tcx> for ByMoveBody {
.tuple_fields()
.len();
let mut field_remapping = UnordMap::default();
let mut child_captures = tcx
.closure_captures(coroutine_def_id)
.iter()
.copied()
// By construction we capture all the args first.
.skip(num_args)
.enumerate()
.peekable();
// One parent capture may correspond to several child captures if we end up
// refining the set of captures via edition-2021 precise captures. We want to
// match up any number of child captures with one parent capture, so we keep
// peeking off this `Peekable` until the child doesn't match anymore.
for (parent_field_idx, parent_capture) in
tcx.closure_captures(parent_def_id).iter().copied().enumerate()
{
// Make sure we use every field at least once, b/c why are we capturing something
// if it's not used in the inner coroutine.
let mut field_used_at_least_once = false;
// A parent matches a child if they share the same prefix of projections.
// The child may have more, if it is capturing sub-fields out of
// something that is captured by-move in the parent closure.
while child_captures.peek().map_or(false, |(_, child_capture)| {
child_prefix_matches_parent_projections(parent_capture, child_capture)
}) {
let (child_field_idx, child_capture) = child_captures.next().unwrap();
// This analysis only makes sense if the parent capture is a
// prefix of the child capture.
assert!(
child_capture.place.projections.len() >= parent_capture.place.projections.len(),
"parent capture ({parent_capture:#?}) expected to be prefix of \
child capture ({child_capture:#?})"
);
let field_remapping: UnordMap<_, _> = ty::analyze_coroutine_closure_captures(
tcx.closure_captures(parent_def_id).iter().copied(),
tcx.closure_captures(coroutine_def_id).iter().skip(num_args).copied(),
|(parent_field_idx, parent_capture), (child_field_idx, child_capture)| {
// Store this set of additional projections (fields and derefs).
// We need to re-apply them later.
let child_precise_captures =
@ -192,7 +158,7 @@ impl<'tcx> MirPass<'tcx> for ByMoveBody {
),
};
field_remapping.insert(
(
FieldIdx::from_usize(child_field_idx + num_args),
(
FieldIdx::from_usize(parent_field_idx + num_args),
@ -200,18 +166,10 @@ impl<'tcx> MirPass<'tcx> for ByMoveBody {
needs_deref,
child_precise_captures,
),
);
field_used_at_least_once = true;
}
// Make sure the field was used at least once.
assert!(
field_used_at_least_once,
"we captured {parent_capture:#?} but it was not used in the child coroutine?"
);
}
assert_eq!(child_captures.next(), None, "leftover child captures?");
)
},
)
.collect();
if coroutine_kind == ty::ClosureKind::FnOnce {
assert_eq!(field_remapping.len(), tcx.closure_captures(parent_def_id).len());
@ -241,22 +199,6 @@ impl<'tcx> MirPass<'tcx> for ByMoveBody {
}
}
fn child_prefix_matches_parent_projections(
parent_capture: &ty::CapturedPlace<'_>,
child_capture: &ty::CapturedPlace<'_>,
) -> bool {
let PlaceBase::Upvar(parent_base) = parent_capture.place.base else {
bug!("expected capture to be an upvar");
};
let PlaceBase::Upvar(child_base) = child_capture.place.base else {
bug!("expected capture to be an upvar");
};
parent_base.var_path.hir_id == child_base.var_path.hir_id
&& std::iter::zip(&child_capture.place.projections, &parent_capture.place.projections)
.all(|(child, parent)| child.kind == parent.kind)
}
struct MakeByMoveBody<'tcx> {
tcx: TyCtxt<'tcx>,
field_remapping: UnordMap<FieldIdx, (FieldIdx, Ty<'tcx>, bool, &'tcx [Projection<'tcx>])>,