data A = A1 Int | A2 Int Int

Then if I want to do pattern matching and ignore the parameters I do:

    f (A1 _) = ..

    f (A2 _ _) = ...

But that's annoying; I need to remember how many parameters each one has!

Yesterday I learned I can just do this:

    f A1 {} = ...

    f A2 {} = ...

And GHC is happy.

Is this expected? Am I the last to learn about this trick?