Fix issue with const params in operand.rs

Author: varkor

src/librustc_mir/interpret/operand.rs

@@ -524,7 +524,8 @@ impl<'a, 'mir, 'tcx, M: Machine<'a, 'mir, 'tcx>> InterpretCx<'a, 'mir, 'tcx, M>
         layout: Option<TyLayout<'tcx>>,
     ) -> EvalResult<'tcx, OpTy<'tcx, M::PointerTag>> {
         let op = match val.val {
-            ConstValue::Param(_) | ConstValue::Infer(_) | ConstValue::Placeholder(_) => bug!(),
+            ConstValue::Param(_) => return err!(TooGeneric),
+            ConstValue::Infer(_) | ConstValue::Placeholder(_) => bug!(),
             ConstValue::ByRef(ptr, alloc) => {
                 // We rely on mutability being set correctly in that allocation to prevent writes
                 // where none should happen -- and for `static mut`, we copy on demand anyway.