anchor.diff:  , python, libconfig, lit, gdb, unzip, darwin, bash
   , callPackage, makeWrapper, targetPackages
   , bootstrapVersion ? false
  -, version ? "1.8.0"
  -, ldcSha256 ? "0zswjlibj8zcdj06nn09jjhbd99chsa5f4kps8xifzgrpgsa28g4"
  +, version ? "1.10.0"
  +, ldcSha256 ? "0wc3vlblsz4qdwa9ay9plv9nvfd07zj2byqqffaa4a5gvjwf5dlr"
   }:
   
   let
  
positive.code: 
      makeFlags = [ "DMD=$DMD" ];
  
      doCheck = true;
  
      checkPhase = ''
        # Build and run LDC D unittests.
  
negative.code: 
    # Need to test Phobos in a fixed-output derivation, otherwise the
    # network stuff in Phobos would fail if sandbox mode is enabled.
    #
    # Disable tests on Darwin for now because of
    # https://github.com/NixOS/nixpkgs/issues/41099
    # https://github.com/NixOS/nixpkgs/pull/36378#issuecomment-385034818
    ldcUnittests = if (!bootstrapVersion && !stdenv.hostPlatform.isDarwin) then
      stdenv.mkDerivation rec {
        name = "ldcUnittests-${version}";
  
        enableParallelBuilding = ldcBuild.enableParallelBuilding;
        preferLocalBuild = true;
        inputString = ldcBuild.outPath;
        outputHashAlgo = "sha256";
        outputHash = builtins.hashString "sha256" inputString;
  
        src = ldcBuild.src;
  
        postUnpack = ldcBuild.postUnpack;
  
        postPatch = ldcBuild.postPatch;
  
        nativeBuildInputs = ldcBuild.nativeBuildInputs
  
        ++ [
          ldcBuild
        ];
  
        buildInputs = ldcBuild.buildInputs;
  
        preConfigure = ''
          cmakeFlagsArray=( "-DINCLUDE_INSTALL_DIR=$out/include/dlang/ldc"
                            "-DCMAKE_BUILD_TYPE=Release"
                            "-DCMAKE_SKIP_RPATH=ON"
                            "-DBUILD_SHARED_LIBS=OFF"
                            "-DLDC_WITH_LLD=OFF"
                            # Xcode 9.0.1 fixes that bug according to ldc release notes
                            "-DRT_ARCHIVE_WITH_LDC=OFF"
                            "-DD_COMPILER=${ldcBuild.out}/bin/ldmd2"
                          )
        '';
  
        postConfigure = ldcBuild.postConfigure;
  
        makeFlags = ldcBuild.makeFlags;
  
        buildCmd = if bootstrapVersion then
          "ctest -V -R \"build-druntime-ldc-unittest|build-phobos2-ldc-unittest\""
        else
          "make -j$NIX_BUILD_CORES DMD=${ldcBuild.out}/bin/ldc2 phobos2-test-runner phobos2-test-runner-debug";
  
        testCmd = if bootstrapVersion then
          "ctest -j$NIX_BUILD_CORES --output-on-failure -E \"dmd-testsuite|lit-tests|ldc2-unittest|llvm-ir-testsuite\""
        else
          "ctest -j$NIX_BUILD_CORES --output-on-failure -E \"dmd-testsuite|lit-tests|ldc2-unittest\"";
  
        buildPhase = ''
            ${buildCmd}
            ln -s ${ldcBuild.out}/bin/ldmd2 $PWD/bin/ldmd2
            ${testCmd}
        '';
  
        installPhase = ''
            echo -n $inputString > $out
        '';
      }
    else
      "";
  
  in
  
  