T3950.hs:16:13: error: [GHC-18872]
    • Couldn't match kind ‘* -> *’ with ‘*’
      When matching types
        w :: (* -> * -> *) -> *
        Sealed :: (* -> *) -> *
      Expected: w (Id p)
        Actual: Sealed (Id p0 x0)
    • In the first argument of ‘Just’, namely ‘rp'’
      In the expression: Just rp'
      In an equation for ‘rp’:
          rp _
            = Just rp'
            where
                rp' :: Sealed (Id p x)
                rp' = undefined
    • Relevant bindings include
        rp :: Bool -> Maybe (w (Id p)) (bound at T3950.hs:16:1)