Make function arguments optional

[ghost]

It's easy to forget, or convenient to leave out, the function argument when you're looking for e.g. List higher-order functions like all or filter. E.g. "List a -> Bool" when you mean "List a -> (a -> Bool) -> Bool". It'd be great, and would save some confusion when "List a -> Bool" doesn't return anything, to be able to leave the function argument out and for results with that signature to still be returned. The fact that it's a higher-order function is only a detail compared to what you're trying to do: List to Bool. Sure, when someone publishes an allTheSame function for List, it will show up with List a -> Bool, but not until then.

[ghost]

A better example is of trying to find foldl or foldr before you've seen its type signature before:
(a -> b -> b) -> b -> List a -> b is harder to come up with than List a -> b, which currently returns no results. This is copied from Slack: "What in Elm similar to reduce".

[klaftertief]

Would you expect some special keyword or symbol or do you think this should work automagically?
I thought a bit about this for some special cases. I expect performance penalties for a too generic solution.

[ghost]

I think this should work automagically, as I've been confused when List a -> Bool didn't return what I was expecting.