anchor.diff:      };
       foundation = fetch {
         repo = "swift-corelibs-foundation";
  -      sha256 = "06pbhb7wg4q5qgprhiyzbqy6hssga7xxjclhlh81gd6rvfd6bxvw";
  +      sha256 = "1bhrag63rmz41bg2g6ap01qrdpq37hislgf5hg6myy2v69q7mahx";
       };
       libdispatch = fetch {
         repo = "swift-corelibs-libdispatch";
  
positive.code:     };
      swift = fetch {
        repo = "swift";
        sha256 = "1flvr12bg8m4k44yq0xy9qrllv5rpxgxisjgbpakk5p3myfsx7ky";
      };
    };
  
  
negative.code: }:
  
  let
    v_base = "4.1.3";
    version = "${v_base}-RELEASE";
    version_friendly = "${v_base}";
  
    tag = "refs/tags/swift-${version}";
    fetch = { repo, sha256, fetchSubmodules ? false }:
  