Auto merge of #95576 - DrMeepster:box_erasure, r=oli-obk

Remove dereferencing of Box from codegen

Through #94043, #94414, #94873, and #95328, I've been fixing issues caused by Box being treated like a pointer when it is not a pointer. However, these PRs just introduced special cases for Box. This PR removes those special cases and instead transforms a deref of Box into a deref of the pointer it contains.

Hopefully, this is the end of the Box<T, A> ICEs.

1 files changed, 12 insertions, 1 deletions

diff --git a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
index 8d16c5f22c3..c0b0cc3c591 100644
--- a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
+++ b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
@@ -410,7 +410,18 @@ where
     fn open_drop_for_box(&mut self, adt: ty::AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> BasicBlock {
         debug!("open_drop_for_box({:?}, {:?}, {:?})", self, adt, substs);
 
-        let interior = self.tcx().mk_place_deref(self.place);
+        // drop glue is sent straight to codegen
+        // box cannot be directly dereferenced
+        let unique_ty = adt.non_enum_variant().fields[0].ty(self.tcx(), substs);
+        let nonnull_ty =
+            unique_ty.ty_adt_def().unwrap().non_enum_variant().fields[0].ty(self.tcx(), substs);
+        let ptr_ty = self.tcx().mk_imm_ptr(substs[0].expect_ty());
+
+        let unique_place = self.tcx().mk_place_field(self.place, Field::new(0), unique_ty);
+        let nonnull_place = self.tcx().mk_place_field(unique_place, Field::new(0), nonnull_ty);
+        let ptr_place = self.tcx().mk_place_field(nonnull_place, Field::new(0), ptr_ty);
+        let interior = self.tcx().mk_place_deref(ptr_place);
+
         let interior_path = self.elaborator.deref_subpath(self.path);
 
         let succ = self.box_free_block(adt, substs, self.succ, self.unwind);