tcfail208.hs:4:19: error: [GHC-39999]
    • Could not deduce ‘Eq (m a)’ arising from a use of ‘==’
      from the context: (Monad m, Eq a)
        bound by the type signature for:
                   f :: forall (m :: * -> *) a. (Monad m, Eq a) => a -> m a -> Bool
        at tcfail208.hs:3:1-40
    • In the expression: return x == y
      In an equation for ‘f’: f x y = (return x == y)