Don't crash on returning expressions that evaluate to void.
Don't crash on returning expressions that evaluate to void.

    Void should be a valid type -- it's useful in generics. For
    example:

        type set = std.htab(foo, void)

    should be valid.

8l/myrddin,oridb/mc,oridb/mc,oridb/mc,oridb/mc,8l/myrddin