Is definition of Monad causing an uncallable function in Haskell

Question

I am playing with Monads in Haskell trying to get good at it. This piece of coded I tried to finish by writing the right sides of the definitions in the instantiation of the Trace Monad.

The function and the newtype I didn't provide, they were there as part of the exercise.

As you can see I get an error. I am not sure I understand the error.

I interpret the error as: The function show isn't declared for the type (Trace Integer) and it therefore can't use print on the provided input 2.

If this is a correct interpretation where did I then make the mistake, in the function call, or in the definition of the monad? And how to correct it?

newtype Trace a = T (a, String) --My comment: here we apparently don't have a constructor ?


instance Monad Trace where 
  (T p) >>= f = f (fst p)
  return x = T(x, mempty)

traceable :: String -> (t -> a) -> t -> Trace a
traceable name f = \x -> T(f x, name ++" called.")

OUTPUT:

ghci> traceable "customStr" (*2) 2

<interactive>:2:1: error:
    * No instance for (Show (Trace Integer))
        arising from a use of `print'
    * In a stmt of an interactive GHCi command: print it