anchor.diff: -{ stdenv, fetchurl, boehmgc, libatomic_ops, pcre, libevent, libiconv, llvm_39, makeWrapper }:
  +{ stdenv, fetchurl, boehmgc, libatomic_ops, pcre, libevent, libiconv, llvm_4, makeWrapper }:
   
   stdenv.mkDerivation rec {
  -  version = "0.22.0";
  +  version = "0.23.0";
     name = "crystal-${version}-1";
     arch =
       {
  
positive.code:     install -Dm644 etc/completion.bash $out/share/bash-completion/completions/crystal
      install -Dm644 etc/completion.zsh $out/share/zsh/site-functions/_crystal
  
      install -Dm644 LICENSE $out/share/licenses/crystal/LICENSE
    '';
  
  
negative.code:     url = "https://github.com/crystal-lang/crystal/releases/download/${version}/crystal-${version}-1-${arch}.tar.gz";
      sha256 =
        {
          "x86_64-linux" = "0nhs7swbll8hrk15kmmywngkhij80x62axiskb1gjmiwvzhlh0qx";
          "i686-linux" = "03xp8d3lqflzzm26lpdn4yavj87qzgd6xyrqxp2pn9ybwrq8fx8a";
          "x86_64-darwin" = "1prz6c1gs8z7dgpdy2id2mjn1c8f5p2bf9b39985bav448njbyjz";
        }."${stdenv.system}" or (throw "system ${stdenv.system} not supported");
    };
  
    src = fetchurl {
      url = "https://github.com/crystal-lang/crystal/archive/${version}.tar.gz";
      sha256 = "05ymwmjkl1b4m888p725kybpiap5ag2vj8l07d59j02inm5r0rcv";
    };
  
    # crystal on Darwin needs libiconv to build
    buildInputs = [
      boehmgc libatomic_ops pcre libevent llvm_4 makeWrapper
    ] ++ stdenv.lib.optionals stdenv.isDarwin [
      libiconv
    ];
  