It is dead code. It was added in
8e0946e8df as part of the repeated /
enforce-determinism feature, but that was removed in
8fdd156a65.
It is not good because it skips many fields. For testing purposes we
will soon want to add a new one that doesn't skip fields, but we want to
make sure making == sensitive to those fields won't change how Nix
works. Proving in this commit that the old version is dead code achieves
that.
862d16436b