D-Programming-Language/phobos — pull request #844 by 9rnsr (2012-10-06 05:48:56+00:00)
Title: More fix for Issue 8705 - std.conv.to bug, from documentation

http://d.puremagic.com/issues/show_bug.cgi?id=8705

Mutable care is just necessary for value type, and doesn't need for key types.

---

@monarchdodra, how about this change?