AliasAssign - is this a bug?

[Mathias LANG]

On Wednesday, 28 April 2021 at 00:29:46 UTC, Andrei Alexandrescu 
wrote:
> Is this a bug? If not, where is the mistake in the code?

Not a bug, since `static foreach` does not introduce a scope, 
you're trying to declare twice the same alias at the same scope, 
the compiler rightfully flags it.

> If so, what would be a workaround? Thanks!

Depends on what you want to do. Either use a different name, but 
it will fail as soon as you have more than one instantiation, or 
re-assign the alias:

```D
template AliasThisType(T) {
     alias A = AliasSeq!();
     static foreach (U; AliasSeq!(__traits(getMember, T, "xyz"))) {
         A = AliasSeq!(A, typeof(U)); // No more `alias` here
     }
     alias AliasThisType = A;
}
```