Nixpkgs use 2 different fix-points with unclear separation.

[nbp]

While looking in nixpkgs, I noticed that we use 2 different fix-point strategy, and the difference between the 2 is not clear. #10307 highlight that there is a problem with self and pkgs are almost interchangeable but it is not clear why replacing one by the other does not work.

The problem is more than likely coming from the stdenv overrides added by the mkOverrides function. The way this function is written would cause infinite loops if we were to use pkgs instead of pkgsOrig because the name of the properties are not known ahead.

The problem here is not much about having 2 self-reference fix-points, but mostly about the fact that the first stage (pkgsOrig = pkgsFun pkgs {};) does not have a proper meaning for the 2 self-references. In the first stage, pkgs is the overloaded set of packages, while self is the non overloaded set of packages.

These 2 self-references are extremely confusing since self and pkgs are used interchangeably to lookup dependencies within all-packages.nix, either by relying on with self; or on callPackage (pkgs).

I will recommend that we convert one to the other and make them explicit within all-packages.nix, such that we can give a clear meaning to the first stage (pkgsOrig) which is used to compute the stdenv.

cc @edolstra

[Mathnerd314]

I implemented this already in #9400, although it has a few other changes that should be split out.

[Mathnerd314]

And now #9400 is merged, so this can be closed.