D-Programming-Language/phobos — pull request #1995 by monarchdodra (2014-03-11 11:31:33+00:00)
Title:  Fix issue 12347 - adjoin!SingleFun does not ... 

...return a tuple.

This is a change of behavior that can break code. But:

1. It now makes the function behave according to doc.
2. While in theory, this might break code, in practice, I suspect it actually fixing more code that was incorrectly handling single argument adjoin.