usesOfFA :: UsesOfAcc acc -> Idx aenv a -> PreOpenFun acc env aenv f -> Int
usesOfFA s idx fun =
  case fun of
    Body e      -> usesOfEA s idx e
    Lam f       -> usesOfFA s idx f
usesOfFA :: UsesOfAcc acc -> Idx aenv a -> PreOpenFun acc env aenv f -> Int
usesOfFA s idx fun =
  case fun of
    Body e      -> usesOfEA s idx e
    Lam f       -> usesOfFA s idx f
usesOfFA s idx fun =
  case fun of
    Body e      -> usesOfEA s idx e
    Lam f       -> usesOfFA s idx f