TypeHole.hs

GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
Prelude> let f x y = x + y
Prelude> f 2 _w
{-
<interactive>:5:5:
    Found hole ‘_w’ with type: a
    Where: ‘a’ is a rigid type variable bound by
               the inferred type of it :: a at <interactive>:5:1
    Relevant bindings include it :: a (bound at <interactive>:5:1)
    In the second argument of ‘f’, namely ‘_w’
    In the expression: f 2 _w
    In an equation for ‘it’: it = f 2 _w
-}