IPFail.hs:6:18: error:
    • Could not deduce (Num Bool) arising from the literal ‘5’
      from the context: ?x::Int
        bound by the type signature for:
                   f0 :: (?x::Int) => () -> Bool
        at IPFail.hs:5:1-31
    • In the expression: 5
      In the expression: let ?x = 5 in ?x
      In an equation for ‘f0’: f0 () = let ?x = 5 in ?x