T22742.hs:7:17: error: [GHC-83865]
    • Couldn't match kind ‘GHC.Types.BoxedRep’ with ‘f a’
      Expected kind ‘TYPE (f a b)’, but ‘()’ has kind ‘*’
    • In the second argument of ‘T’, namely ‘()’
      In the type signature: f :: T @(f a b) () -> ()