Implicit conversion of struct to bool for if (s) operation ?

[Adam D. Ruppe via Digitalmars-d-learn]

On Monday, 6 June 2016 at 15:23:50 UTC, chmike wrote:
> I would like an implicit conversion of Info to bool that return 
> false if category_ is null so that I can write

add:

bool opCast(T : bool)() {
    return whatever;
}

to the struct and it should work.