T16456.hs:7:7: error:
    • Found hole: _ :: T Int
    • In an equation for ‘foo’: foo = _
    • Relevant bindings include foo :: T Int (bound at T16456.hs:7:1)
      Valid hole fits include
        foo :: T Int (bound at T16456.hs:7:1)
        MkT :: forall {k} (p :: k). T p
          with MkT @Int
          (defined at T16456.hs:4:12)