Andrei Alexandrescu wrote:
Today D does not support contravariant arguments, but Walter told me once he'd be quite willing to implement them. It is definitely the right thing to do, but Walter would want to see a compelling example before getting to work.
The stumbling block to contravariant parameters (not arguments) is how it throws a monkey wrench into the overloading rules. The problem is deciding if a function overrides or overloads, when its parameter types are different.
The current rule is simple: if the parameter types are identical, it overrides. If they are not identical, it overloads.
