AliasSeq in UDA

[Sebastiaan Koppe]

The compiler complains about `cannot form tuple of tuples` 
whenever I try to put an AliasSeq in a UDA and try to use it.

You would expect the compiler to expand it. Is this a bug?

---

import std.meta;

enum A; enum B;

@AliasSeq!(A,B) // <-- Error: cannot form tuple of tuples
struct Foo {}

pragma(msg, __traits(getAttributes, Foo)); // <- must be present 
(error happens only when queried)

void main() {}

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link to run.dlang.io: 
https://run.dlang.io/gist/cd5cd94d8ce5327e8a7d5ad77f1d15b8