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Auto merge of #103957 - JakobDegen:drop-retag, r=RalfJung

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Retag as FnEntry on `drop_in_place`

This commit changes the mir drop shim to always retag its argument as if it were a `&mut`.

cc rust-lang/unsafe-code-guidelines#373
This commit is contained in:
bors 2022-12-22 17:48:43 +00:00
commit cca80b9a81
10 changed files with 199 additions and 15 deletions
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17
compiler/rustc_const_eval/src/interpret/terminator.rs
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@ -119,11 +119,20 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
Drop { place, target, unwind } => {
let place = self.eval_place(place)?;
let ty = place.layout.ty;
trace!("TerminatorKind::drop: {:?}, type {}", place, ty);
let frame = self.frame();
let ty = place.ty(&frame.body.local_decls, *self.tcx).ty;
let ty = self.subst_from_frame_and_normalize_erasing_regions(frame, ty)?;
let instance = Instance::resolve_drop_in_place(*self.tcx, ty);
if let ty::InstanceDef::DropGlue(_, None) = instance.def {
// This is the branch we enter if and only if the dropped type has no drop glue
// whatsoever. This can happen as a result of monomorphizing a drop of a
// generic. In order to make sure that generic and non-generic code behaves
// roughly the same (and in keeping with Mir semantics) we do nothing here.
self.go_to_block(target);
return Ok(());
}
let place = self.eval_place(place)?;
trace!("TerminatorKind::drop: {:?}, type {}", place, ty);
self.drop_in_place(&place, instance, target, unwind)?;
}