anchor.diff:    ghcAndroidAarch32 = (extendHaskellPackages nixpkgsCross.android.aarch32.pkgs.haskell.packages.ghcHEAD).override {
       overrides = lib.foldr lib.composeExtensions (_: _: {}) [
         (optionalExtension enableExposeAllUnfoldings haskellOverlays.exposeAllUnfoldings)
  -      haskellOverlays.ghc-8_4
  +      haskellOverlays.ghc-head
         haskellOverlays.android
         haskellOverlays.loadSplices
       ];
  
positive.code:   ghcIosSimulator64 = (extendHaskellPackages nixpkgsCross.ios.simulator64.pkgs.haskell.packages.ghcHEAD).override {
      overrides = lib.foldr lib.composeExtensions (_: _: {}) [
        (optionalExtension enableExposeAllUnfoldings haskellOverlays.exposeAllUnfoldings)
        haskellOverlays.ghc-8_4
        haskellOverlays.ios
        haskellOverlays.loadSplices
      ];
  
negative.code:   ghcAndroidAarch64 = (extendHaskellPackages nixpkgsCross.android.aarch64.pkgs.haskell.packages.ghcHEAD).override {
      overrides = lib.foldr lib.composeExtensions (_: _: {}) [
        (optionalExtension enableExposeAllUnfoldings haskellOverlays.exposeAllUnfoldings)
        haskellOverlays.ghc-head
        haskellOverlays.android
        haskellOverlays.loadSplices
      ];
  