Add docs, remove code, change subtyper code

2 files changed, 12 insertions, 9 deletions

diff --git a/compiler/rustc_mir_transform/src/add_subtyping_projections.rs b/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
index e51f4a2ff21..594bb9bf142 100644
--- a/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
+++ b/compiler/rustc_mir_transform/src/add_subtyping_projections.rs
@@ -7,13 +7,13 @@ use rustc_middle::ty::TyCtxt;
 
 pub struct Subtyper;
 
-pub struct SubTypeCheker<'a, 'tcx> {
+pub struct SubTypeChecker<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     patcher: MirPatch<'tcx>,
     local_decls: &'a IndexVec<Local, LocalDecl<'tcx>>,
 }
 
-impl<'a, 'tcx> MutVisitor<'tcx> for SubTypeCheker<'a, 'tcx> {
+impl<'a, 'tcx> MutVisitor<'tcx> for SubTypeChecker<'a, 'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx> {
         self.tcx
     }
@@ -25,28 +25,30 @@ impl<'a, 'tcx> MutVisitor<'tcx> for SubTypeCheker<'a, 'tcx> {
         location: Location,
     ) {
         let place_ty = place.ty(self.local_decls, self.tcx);
-        let rval_ty = rvalue.ty(self.local_decls, self.tcx);
+        let mut rval_ty = rvalue.ty(self.local_decls, self.tcx);
         if place_ty.ty != rval_ty {
+            // Not erasing this causes `Free Regions` errors in validator,
+            // when rval is `ReStatic`.
+            rval_ty = self.tcx.erase_regions_ty(rval_ty);
             let temp = self
                 .patcher
                 .new_temp(rval_ty, self.local_decls[place.as_ref().local].source_info.span);
-            let new_place =
-                Place::from(temp).project_deeper(&[ProjectionElem::Subtype(place_ty.ty)], self.tcx);
+            let new_place = Place::from(temp);
             self.patcher.add_assign(location, new_place, rvalue.clone());
-            let new_rval = Rvalue::Use(Operand::Move(new_place));
-            *rvalue = new_rval;
+            let subtyped =
+                new_place.project_deeper(&[ProjectionElem::Subtype(place_ty.ty)], self.tcx);
+            *rvalue = Rvalue::Use(Operand::Move(subtyped));
         }
     }
 }
 
 pub fn subtype_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let patch = MirPatch::new(body);
-    let mut checker = SubTypeCheker { tcx, patcher: patch, local_decls: &body.local_decls };
+    let mut checker = SubTypeChecker { tcx, patcher: patch, local_decls: &body.local_decls };
 
     for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
         checker.visit_basic_block_data(bb, data);
     }
-
     checker.patcher.apply(body);
 }
 
diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs
index 449bade3322..56bdc5a171a 100644
--- a/compiler/rustc_mir_transform/src/gvn.rs
+++ b/compiler/rustc_mir_transform/src/gvn.rs
@@ -306,6 +306,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> {
                 }
                 ProjectionElem::Downcast(name, index) => ProjectionElem::Downcast(name, index),
                 ProjectionElem::OpaqueCast(ty) => ProjectionElem::OpaqueCast(ty),
+                ProjectionElem::Subtype(ty) => ProjectionElem::Subtype(ty),
             };
             value = self.insert(Value::Projection(value, proj));
         }