According to this comment: https://github.com/dlang/phobos/pull/5291#issuecomment-360929553There was no way to get a deprecation to work.When we can't get a deprecation to work, we face a hard decision -- actually break code right away, print lots of crappy errors, or just leave the bug unfixed.-Steve
Ah, that's unfortunate. Damned if you do, damned if you don't. I still don't agree with making a breaking change to Phobos.