subtyping_projections

compiler/rustc_const_eval/src/interpret/projection.rs

@@ -332,6 +332,7 @@ where
                 self.project_constant_index(base, offset, min_length, from_end)?
             }
             Subslice { from, to, from_end } => self.project_subslice(base, from, to, from_end)?,
+            Subtype(ty) => base.transmute(self.layout_of(ty)?, self)?,
         })
     }
 }