On Sunday, 10 March 2019 at 13:20:12 UTC, Sebastiaan Koppe wrote:
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() {}


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

It looks like a bug, a "reject-valid" one.
Try the same code with

    enum A = 0;

and it work, despite of B being still opaque. The problem may be related to the fact the enum A in the orginal code is opaque and has not type.

I've seen a related issue lately.

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