```d struct UDA {} int foo() @UDA => 123; void main() { assert(foo() == 123); // error: undefined reference to '_D9onlineapp3fooFZi' } ``` The issue was originally reported as spec issue https://github.com/dlang/dlang.org/issues/4137 But I think it belongs here.