anchor.diff:      let callPackage = newScope self ; in rec {
         inherit callPackage coq;
         coqPackages = self;
  +
  +      contribs = recurseIntoAttrs
  +        (callPackage ../development/coq-modules/contribs {});
   
         autosubst = callPackage ../development/coq-modules/autosubst {};
         bignums = if lib.versionAtLeast coq.coq-version "8.6"
  
positive.code: { lib, callPackage, newScope
  , gnumake3
  , ocamlPackages_3_12_1
  , ocamlPackages_4_02
  
negative.code:       paco = callPackage ../development/coq-modules/paco {};
        QuickChick = callPackage ../development/coq-modules/QuickChick {};
        ssreflect = callPackage ../development/coq-modules/ssreflect { };
      };
  
    filterCoqPackages = coq:
      lib.filterAttrsRecursive
      (_: p:
        let pred = p.compatibleCoqVersions or (_: true);
        in pred coq.coq-version
  