anchor.diff:  
   /* Cargo binary snapshot */
   
  -let snapshotDate = "2015-06-17";
  +let
  +  snapshotDate = "2016-01-31";
   in
   
   with ((import ./common.nix) {
  
positive.code: 
    src = fetchurl {
      url = "https://static-rust-lang-org.s3.amazonaws.com/cargo-dist/${snapshotDate}/${snapshotName}";
      sha1 = snapshotHash;
    };
  
    buildInputs = [ makeWrapper ];
  
negative.code:   version = "snapshot-${snapshotDate}";
  });
  
  let snapshotHashes =
    if stdenv.system == "x86_64-linux" then {
      sha1 = "4c03a3fd2474133c7ad6d8bb5f6af9915ca5292a";
      sha256 = "19jzx889bi21kq8mm33xysq0pcigsshh8rzzcfkyndmmp9hyc80r";
    } else
      throw "no snapshot for platform ${stdenv.system}";
  
    snapshotName = "cargo-nightly-${platform}.tar.gz";
  in
  
  stdenv.mkDerivation {
  