New operator overloading syntax. Was: Does std.bigint compile

[bearophile]

Don:
> http://www.dsource.org/projects/phobos/browser/trunk/docsrc/operatoroverloading.dd

It says:
223 	    logical negation operator. More obscurely absent is a unary operator
224 	    to convert to a bool result.
...
234 	if (e)   =>  if (e.opCast!(bool))
235 	if (!e)  =>  if (!e.opCast!(bool))
...
238 	    $(P etc., whenever a bool result is expected. This only happens, however, for
239 	    instances of structs. Class references are converted to bool by checking to
240 	    see if the class reference is null or not.

I have asked for this several times, but I didn't know that was accepted :-)
So if you change a class into a struct or the opposite, you have to be careful of changing all such points where the boolean value is asked for.
What does it happen if this semantics is extended to class instances too? I guess this is an unthinkable change.

Bye,
bearophile