subtyping_projections

3 files changed, 7 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 55f895f73b4..128999a5fd1 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -1075,6 +1075,8 @@ pub enum ProjectionElem<V, T> {
     /// Like an explicit cast from an opaque type to a concrete type, but without
     /// requiring an intermediate variable.
     OpaqueCast(T),
+
+    Subtype(T),
 }
 
 /// Alias for projections as they appear in places, where the base is a place
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 01c04f63890..f534f0f5f3c 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -111,6 +111,7 @@ impl<'tcx> PlaceTy<'tcx> {
             }
             ProjectionElem::Field(f, fty) => PlaceTy::from_ty(handle_field(&self, f, fty)),
             ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(handle_opaque_cast(&self, ty)),
+            ProjectionElem::Subtype(_) => PlaceTy::from_ty(self.ty),
         };
         debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
         answer
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 51ec6da1ac8..800c3f44da1 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1110,6 +1110,7 @@ macro_rules! visit_place_fns {
                     if ty != new_ty { Some(PlaceElem::OpaqueCast(new_ty)) } else { None }
                 }
                 PlaceElem::Deref
+                | PlaceElem::Subtype { .. }
                 | PlaceElem::ConstantIndex { .. }
                 | PlaceElem::Subslice { .. }
                 | PlaceElem::Downcast(..) => None,
@@ -1175,7 +1176,9 @@ macro_rules! visit_place_fns {
             location: Location,
         ) {
             match elem {
-                ProjectionElem::OpaqueCast(ty) | ProjectionElem::Field(_, ty) => {
+                ProjectionElem::OpaqueCast(ty)
+                | ProjectionElem::Subtype(ty)
+                | ProjectionElem::Field(_, ty) => {
                     self.visit_ty(ty, TyContext::Location(location));
                 }
                 ProjectionElem::Index(local) => {