[Issue 22981] Another forward reference bug involving a string mixin

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22981

--- Comment #9 from Basile-z <b2.temp at gmx.com> ---
even better

```
enum E { e1 = S.a }

struct S
{
    E e;
    enum a = "string";
}   
```

> /tmp/temp_7F3BFB9249F0.d:6:14: Error: cannot implicitly convert expression `"string"` of type `string` to `int`

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