nix/tests/functional/lang/eval-okay-attrs.nix

let {
  as = {
    x = 123;
    y = 456;
  }
  // {
    z = 789;
  }
  // {
    z = 987;
  };

  body =
    if as ? a then
      as.a
    else
      assert as ? z;
      as.z;
}