Resolved: How to explicitly import ‘Fn’ pattern from Test.QuickCheck?

Question:

Haskell’s Test.QuickCheck module exports pattern Fn, which I have been using.
When I import it with:
it works fine. However, when I import it with:
I get an error: Module ‘Test.QuickCheck’ does not export ‘Fn’. I have also tried import Test.QuickCheck (Fun(Fn)), but get a similar error doing that.
As mentioned, the blanket import works, but here my preference is to use explicit imports so that I can easily see where each imported term came from. Is it possible to import such ‘patterns’ explicitly?

Answer:

You can’t do import Test.QuickCheck (Fun(Fn)) because, although Fn does construct a Fun value, it is not actually one of the associated constructors of this type. Rather, it is a standalone pattern synonym. As such, you need the corresponding extension to explicitly import it:

If you have better answer, please add a comment about this, thank you!