4 files changed, 16 insertions, 7 deletions
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index 745949d3ff0..8d4028de90d 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -318,13 +318,14 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             PlaceRef { local, projection: [proj_base @ .., elem] } => match elem {
                 ProjectionElem::Deref
                 | ProjectionElem::Index(..)
-                | ProjectionElem::Subtype(..)
                 | ProjectionElem::ConstantIndex { .. }
                 | ProjectionElem::Subslice { .. } => {
                     PlaceRef { local, projection: proj_base }.ty(self.body, self.infcx.tcx)
                 }
                 ProjectionElem::Downcast(..) => place.ty(self.body, self.infcx.tcx),
-                ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(*ty),
+                ProjectionElem::Subtype(ty) | ProjectionElem::OpaqueCast(ty) => {
+                    PlaceTy::from_ty(*ty)
+                }
                 ProjectionElem::Field(_, field_type) => PlaceTy::from_ty(*field_type),
             },
         };
diff --git a/compiler/rustc_borrowck/src/places_conflict.rs b/compiler/rustc_borrowck/src/places_conflict.rs
index fcf45179b9d..777ebf0d438 100644
--- a/compiler/rustc_borrowck/src/places_conflict.rs
+++ b/compiler/rustc_borrowck/src/places_conflict.rs
@@ -243,13 +243,13 @@ fn place_components_conflict<'tcx>(
                 }
 
                 (ProjectionElem::Deref, _, Deep)
-                | (ProjectionElem::Subtype(_), _, _)
                 | (ProjectionElem::Deref, _, AccessDepth::Drop)
                 | (ProjectionElem::Field { .. }, _, _)
                 | (ProjectionElem::Index { .. }, _, _)
                 | (ProjectionElem::ConstantIndex { .. }, _, _)
                 | (ProjectionElem::Subslice { .. }, _, _)
                 | (ProjectionElem::OpaqueCast { .. }, _, _)
+                | (ProjectionElem::Subtype(_), _, _)
                 | (ProjectionElem::Downcast { .. }, _, _) => {
                     // Recursive case. This can still be disjoint on a
                     // further iteration if this a shallow access and
@@ -360,7 +360,6 @@ fn place_projection_conflict<'tcx>(
         (
             ProjectionElem::Index(..),
             ProjectionElem::Index(..)
-            | ProjectionElem::Subtype(..)
             | ProjectionElem::ConstantIndex { .. }
             | ProjectionElem::Subslice { .. },
         )
@@ -505,12 +504,12 @@ fn place_projection_conflict<'tcx>(
             debug!("place_element_conflict: DISJOINT-OR-EQ-SLICE-SUBSLICES");
             Overlap::EqualOrDisjoint
         }
-        (ProjectionElem::Subtype(_), _) => Overlap::EqualOrDisjoint,
         (
             ProjectionElem::Deref
             | ProjectionElem::Field(..)
             | ProjectionElem::Index(..)
             | ProjectionElem::ConstantIndex { .. }
+            | ProjectionElem::Subtype(_)
             | ProjectionElem::OpaqueCast { .. }
             | ProjectionElem::Subslice { .. }
             | ProjectionElem::Downcast(..),
diff --git a/compiler/rustc_borrowck/src/prefixes.rs b/compiler/rustc_borrowck/src/prefixes.rs
index 72c22d217b4..e9c9709bd1f 100644
--- a/compiler/rustc_borrowck/src/prefixes.rs
+++ b/compiler/rustc_borrowck/src/prefixes.rs
@@ -89,7 +89,9 @@ impl<'cx, 'tcx> Iterator for Prefixes<'cx, 'tcx> {
                             cursor = cursor_base;
                             continue 'cursor;
                         }
-                        ProjectionElem::Subtype(..) => continue 'cursor,
+                        ProjectionElem::Subtype(..) => {
+                            panic!("Subtype projection is not allowed before borrow check")
+                        }
                         ProjectionElem::Deref => {
                             // (handled below)
                         }
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 33687792701..a3724c391d2 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -621,7 +621,6 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                     span_mirbug_and_err!(self, place, "deref of non-pointer {:?}", base_ty)
                 }))
             }
-            ProjectionElem::Subtype(ty) => PlaceTy::from_ty(ty),
             ProjectionElem::Index(i) => {
                 let index_ty = Place::from(i).ty(self.body(), tcx).ty;
                 if index_ty != tcx.types.usize {
@@ -717,6 +716,14 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 }
                 PlaceTy::from_ty(fty)
             }
+            ProjectionElem::Subtype(_) => {
+                let guard = span_mirbug_and_err!(
+                    self,
+                    place,
+                    "ProjectionElem::Subtype shouldn't exist in borrowck"
+                );
+                PlaceTy::from_ty(Ty::new_error(tcx, guard))
+            }
             ProjectionElem::OpaqueCast(ty) => {
                 let ty = self.sanitize_type(place, ty);
                 let ty = self.cx.normalize(ty, location);