D-Programming-Language/dmd — pull request #1119 by 9rnsr (2012-09-16 11:05:48+00:00)
Title: Issue 8589 - Incorrect conversion of function returning `typeof(null)` to function returning an array

http://d.puremagic.com/issues/show_bug.cgi?id=8589

Runtime representation of `typeof(null)` is same as `void*`, then delegate and dynamic array type should not be covariant with `typeof(null)`. It's limitation.