isTFHeaded :: Type -> Bool
-- See Note [Verifying injectivity annotation], case 3.
isTFHeaded ty | Just ty' <- coreView ty
              = isTFHeaded ty'
isTFHeaded :: Type -> Bool
isTFHeaded ty | Just ty' <- coreView ty
              = isTFHeaded ty'
isTFHeaded ty | Just ty' <- coreView ty
              = isTFHeaded ty'