tcfail153.hs:6:9: error:
    • Couldn't match expected type ‘Bool’ with actual type ‘a’
      ‘a’ is a rigid type variable bound by
        the type signature for:
          f :: forall a. a -> [a]
        at tcfail153.hs:5:1-13
    • In the first argument of ‘g’, namely ‘x’
      In the expression: g x
      In an equation for ‘f’:
          f x
            = g x
            where
                g y = if y then [] else [...]
    • Relevant bindings include
        x :: a (bound at tcfail153.hs:6:3)
        f :: a -> [a] (bound at tcfail153.hs:6:1)