[Issue 9125] mixin + textual import = order of declaration dependence

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=9125

Dennis <dkorpel at live.nl> changed:

           What    |Removed                     |Added
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                 CC|                            |dkorpel at live.nl

--- Comment #3 from Dennis <dkorpel at live.nl> ---
Can be reduced to:
```
immutable int a = b;
mixin("immutable int b = 3;");
```

Output as of 2.083:
Error: undefined identifier b

It compiles when swapping the two lines or when removing the mixin and directly
putting the declaration in the code.

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