GHCi becomes confused about IO type

{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE UndecidableInstances  #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE KindSignatures        #-}
{-# LANGUAGE TypeOperators         #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE GADTs           #-}
{-# LANGUAGE Rank2Types      #-}
import GHC.Prim (Constraint)

class    (c1 t, c2 t) => (:&:) (c1 :: * -> Constraint) (c2 :: * -> Constraint) (t :: *)
instance (c1 t, c2 t) => (:&:) c1 c2 t

data ColD c where
  ColD :: (c a) => a -> ColD c

app :: (forall a. (c a) => a -> b) -> ColD c -> b
app f (ColD x) = f x

q :: ColD (Show :&: Real)
q = ColD (1.2 :: Double)

In the interactive mode it's possible to confuse GHCi about IO type. It tries to show expression instread of executing it.

*Main> app print q

<interactive>:3:1:
    No instance for (Show (IO ())) arising from a use of `print'
    Possible fix: add an instance declaration for (Show (IO ()))
    In a stmt of an interactive GHCi command: print it

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	GHCi
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