[Haskell-cafe] wildcards for type variables?

Occasionally I have a function with an unused argument, whose type I don't want to restrict. Thus: f :: _unused -> A -> B f _ a = b Since it's a little unusual, I try to make it clear that the type is intentionally ignored. But it makes me wonder, would it make sense to allow _ as a type variable name, with the same meaning as in pattern matching?