Overlapping functionality: IFTI, templates, is-expressions

[Russell Lewis]

Jason House wrote:
> #2 I know from past discussions that C++ programmers hold this very near and
> dear to their heart.  Personally, it seems like a back door to long
> compilation times.  I don't have any problem with enforcing criteria for
> templates to be defined up front, but I'm certain others don't agree with
> me.  Does the loss of SFINAE make templates too close to generics?  I know
> C# will refuse to compile code if the up-front criteria for a generic type
> isn't specific enough.

To put a humorous twist on my SFINAE rant, let's consider this 
pseudo-program:

	Bag BuyGroceries(SHOPPING_LIST...)
	                ()
	{
		auto myCar = GetInCar!(CalcCargoSize!(SHOPPING_LIST));

		auto home = GetCurLocation();
		auto myBank = GetBank();
		auto store = GetStore();

		DriveTo(myCar, myBank);
		auto money = myBank.Withdraw(CalcCost!(SHOPPING_LIST));

		DriveTo(myCar, store);
		auto ret = Buy!(SHOPPING_LIST)(store);

		DriveTo(myCar, home);
		return ret;
	}

If you didn't have enough money in your bank account, then, because of 
SFINAE, the compiler would give you the following error message:

	program.d: 12: You do not own a car.