opImplicitCast/opImplicitCastFrom

[Hxal]

So it seems they were supposed to get implemented but it never happened.
Were there difficulties in implementing them properly?

Implementing range checked numeric types would be my example of implicit casts' usefulness,
but I'm sure a lot of people desire them.

An invocation to:
void foo (intrange!(1,10) x);
currently needs to include a painful cast or constructor call.