shrinkAfun :: ShrinkAcc acc -> PreOpenAfun acc aenv t -> PreOpenAfun acc aenv t
shrinkAfun s afun =
  case afun of
    Abody b     -> Abody (s b)
    Alam f      -> Alam (shrinkAfun s f)
shrinkAfun :: ShrinkAcc acc -> PreOpenAfun acc aenv t -> PreOpenAfun acc aenv t
shrinkAfun s afun =
  case afun of
    Abody b     -> Abody (s b)
    Alam f      -> Alam (shrinkAfun s f)
shrinkAfun s afun =
  case afun of
    Abody b     -> Abody (s b)
    Alam f      -> Alam (shrinkAfun s f)