I'm fine that the assignment to C is verboten. I'd disallow
the
first assignments to and would like to know, why they are kept.
OK, now I get it. I'm not sure why they're allowed, either; I
guess that it's just because it's written with assignment syntax.
On second thought, it might be for cases where you have a struct
that, for example, wraps an int to trap overflows. You'd want a
transparent interface for that; the fact that the initializer for
C isn't accepted looks like a potential wrinkle in D's design.
The only reason I can see to restrict the areas in which the
conversion takes place is to prevent issues with function
overloading, so the compiler probably should allow your code.
This might be a good situation for an enhancement request.
