On Monday, 10 December 2012 at 23:47:49 UTC, Walter Bright wrote:
We've debated this feature at length in various threads. It's under heavy use by some people. It does not break any existing code. I don't see any unresolved issue that should delay its incorporation.
Right now, holding it off won't break any code not relying on an unreleased version of the compiler. Releasing it, then having to make changes will break code though. There were plenty of discussions about UDA stuff that never really got fully resolved. For example, whether only specific types should be allowed to be used as annotations. These things should have been fully decided before UDA's were implemented, because otherwise we may end up with an inferior approach for the sake of not breaking code, or breaking code because a feature was not fully fleshed out before being released.
