IGNORED_ARG does not work anymore with ENUM

(this is for C++).


yields


Here's a simple repro:

```cpp
typedef enum E
{A,B,C} E;

void f(E e)
{
(void)e;
}

int main(void)
{
f(0);
f(A);
return 0;
}

```

Start by reproducing the reported C++ example with the enum E, functions f(0), and f(A), then trace the IGNORED_ARG handling for enum arguments. Compare the behavior of both calls and use the existing project tests, if relevant, to verify the corrected handling.

Written by the indexing model from the issue text.