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add helper method for finding the one non-1-ZST field

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This commit is contained in:
Ralf Jung 2023-09-12 20:51:00 +02:00
parent e5fedceabf
commit 60091fe924
5 changed files with 49 additions and 89 deletions
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39
compiler/rustc_const_eval/src/interpret/terminator.rs
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@ -269,19 +269,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
match layout.ty.kind() {
ty::Adt(adt_def, _) if adt_def.repr().transparent() && may_unfold(*adt_def) => {
assert!(!adt_def.is_enum());
// Find the non-1-ZST field.
let mut non_1zst_fields = (0..layout.fields.count()).filter_map(|idx| {
let field = layout.field(self, idx);
if field.is_1zst() { None } else { Some(field) }
});
let first = non_1zst_fields.next().expect("`unfold_transparent` called on 1-ZST");
assert!(
non_1zst_fields.next().is_none(),
"more than one non-1-ZST field in a transparent type"
);
// Found it!
self.unfold_transparent(first, may_unfold)
// Find the non-1-ZST field, and recurse.
let (_, field) = layout.non_1zst_field(self).unwrap();
self.unfold_transparent(field, may_unfold)
}
// Not a transparent type, no further unfolding.
_ => layout,
@ -797,25 +787,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
_ => {
// Not there yet, search for the only non-ZST field.
// (The rules for `DispatchFromDyn` ensure there's exactly one such field.)
let mut non_zst_field = None;
for i in 0..receiver.layout.fields.count() {
let field = self.project_field(&receiver, i)?;
let zst = field.layout.is_1zst();
if !zst {
assert!(
non_zst_field.is_none(),
"multiple non-1-ZST fields in dyn receiver type {}",
receiver.layout.ty
);
non_zst_field = Some(field);
}
}
receiver = non_zst_field.unwrap_or_else(|| {
panic!(
"no non-1-ZST fields in dyn receiver type {}",
receiver.layout.ty
)
});
let (idx, _) = receiver.layout.non_1zst_field(self).expect(
"not exactly one non-1-ZST field in a `DispatchFromDyn` type",
);
receiver = self.project_field(&receiver, idx)?;
}
}
};