interpret: more consistently use ImmTy in operators and casts

compiler/rustc_mir_transform/src/const_prop.rs

@@ -210,7 +210,7 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for ConstPropMachine<'mir, 'tcx>
         _bin_op: BinOp,
         _left: &ImmTy<'tcx>,
         _right: &ImmTy<'tcx>,
-    ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> {
+    ) -> InterpResult<'tcx, (ImmTy<'tcx>, bool)> {
         // We can't do this because aliasing of memory can differ between const eval and llvm
         throw_machine_stop_str!("pointer arithmetic or comparisons aren't supported in ConstProp")
     }