D-Programming-Language/dmd — pull request #1276 by 9rnsr (2012-11-10 13:07:55+00:00)
Title: Appendix for Issue 6652

From the coment: http://d.puremagic.com/issues/show_bug.cgi?id=4090#c15

By the interaction of fix 4090 and 6652, useless warning has been reported.
If *implicit ref* foreach key doesn't have a mutable type, warning is not necessary.