[Issue 19917] unions should require that all members are `= void` initialised

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19917

--- Comment #2 from Manu <turkeyman at gmail.com> ---
Okay... well take this as the enhancement request that it is ;)
That existing rule you describe is unintuitive and terrible. Users should
specify `= void` on every member except one of their choosing. You can't
possibly go wrong then, and there's also zero magic rules in the compiler that
need to be explained under that arrangement.

--