rtti cast

[BCS]

terranium wrote:
> BCS Wrote:
> 
> 
>>In most cases forgetting to check the cast return will result in an 
>>seg-v from a dereferenced null because you almost always use it as the 
> 
> 
> In most cases... almost always... When an invalid cast occurs,

it is not an error.

Thinking about it, I can't recall ever casting to a derived type where a 
failed cast was an indication of a bug. In the few times I have done it, 
it has always been in the context of "if a is'a B then" (and not just in 
the code but in the proper function of the program as well).


>>Having the "bad cast" -> null is very handy when you don't known if the 
>>cast will be good. It mean you can test it without invoking the 
>>exception system and all the overhead that entails.
> 
> 
> maybe in this case we need some syntax sugar, not a silent cast?

a little sugar for the other way might be even handier

// not tested
template Force_Cast(T)
{
	T Force_Cast(U)(U u)
	{
		static assert(is(U : T), "cant cast from " ~
			U.stringof ~ " to " ~ T.stringof);

		if(auto t = cast(T)u)
			return t;
		else
			throw new
			InvalidCastException("failed cast from " ~
			U.stringof ~ " to " ~ T.stringof);
	}
}