D-Programming-Language/phobos — pull request #599 by 9rnsr (2012-05-23 04:09:00+00:00)
Title: Issue 7348 & 8040 - null literal should be formatted as "null"

Issue 7348 - to!string(null) matches more than one template declaration
Issue 8040 - writeln(null) too

See my comment in bugzilla:
http://d.puremagic.com/issues/show_bug.cgi?id=7348#c11