
<interactive>:4:7: error:
    • Couldn't match type ‘m’ with ‘(,) a0’
      Expected: (a0, ((), Int))
        Actual: m ((), Int)
        ‘m’ is untouchable
          inside the constraints: ()
          bound by the inferred type of it :: ((), Int)
          at <interactive>:4:1-25
      ‘m’ is an interactive-debugger skolem
    • In the second argument of ‘($)’, namely ‘runStateT _result 0’
      In the expression: snd $ runStateT _result 0
      In an equation for ‘it’: it = snd $ runStateT _result 0