rust: Add an alternative package for the master tip

based off of pull request #3084

pkgs/development/compilers/rust/head.nix

@@ -0,0 +1,73 @@
+{stdenv, fetchurl, fetchgit, which, file, perl, curl, python27, makeWrapper}:
+
+/* Rust's build process has a few quirks :
+
+- It requires some patched in llvm that haven't landed upstream, so it
+  compiles its own llvm. This might change in the future, so at some
+  point we may be able to switch to nix's llvm.
+
+- The Rust compiler is written is Rust, so it requires a bootstrap
+  compiler, which is downloaded during the build. To make the build
+  pure, we download it ourself before and put it where it is
+  expected. Once the language is stable (1.0) , we might want to
+  switch it to use nix's packaged rust compiler.
+
+*/
+
+with ((import ./common.nix) {inherit stdenv; version = "0.12.0-pre-7a25cf3f3"; });
+
+let snapshot = if stdenv.system == "i686-linux"
+      then "a5e1bb723020ac35173d49600e76b0935e257a6a"
+      else if stdenv.system == "x86_64-linux"
+      then "1a2407df17442d93d1c34c916269a345658045d7"
+      else if stdenv.system == "i686-darwin"
+      then "6648fa88e41ad7c0991a085366e36d56005873ca"
+      else if stdenv.system == "x86_64-darwin"
+      then "71b2d1dfd0abe1052908dc091e098ed22cf272c6"
+      else abort "no-snapshot for platform ${stdenv.system}";
+    snapshotDate = "2014-07-17";
+    snapshotRev = "9fc8394";
+    snapshotName = "rust-stage0-${snapshotDate}-${snapshotRev}-${platform}-${snapshot}.tar.bz2";
+
+in stdenv.mkDerivation {
+  inherit name;
+  inherit version;
+  inherit meta;
+
+  src = fetchgit {
+    url = https://github.com/rust-lang/rust;
+    rev = "7a25cf3f30fa5fae2e868fa910ecc850f5e9ee65";
+    sha256 = "1hx8vd4gn5plbdvr0zvdvqyw9x9r2vbmh112h2f5d2xxsf9p7rf1";
+  };
+
+  # We need rust to build rust. If we don't provide it, configure will try to download it.
+  snapshot = stdenv.mkDerivation {
+    name = "rust-stage0";
+    src = fetchurl {
+      url = "http://static.rust-lang.org/stage0-snapshots/${snapshotName}";
+      sha1 = snapshot;
+    };
+    dontStrip = true;
+    installPhase = ''
+      mkdir -p "$out"
+      cp -r bin "$out/bin"
+    '' + (if stdenv.isLinux then ''
+      patchelf --interpreter "${stdenv.glibc}/lib/${stdenv.gcc.dynamicLinker}" \
+               --set-rpath "${stdenv.gcc.gcc}/lib/:${stdenv.gcc.gcc}/lib64/" \
+               "$out/bin/rustc"
+    '' else "");
+  };
+
+  configureFlags = [ "--enable-local-rust" "--local-rust-root=$snapshot" ];
+
+  # The compiler requires cc, so we patch the source to tell it where to find it
+  patches = [ ./hardcode_paths.patch ./local_stage0.patch ];
+  postPatch = ''
+    substituteInPlace src/librustc/back/link.rs \
+      --subst-var-by "ccPath" "${stdenv.gcc}/bin/cc" \
+      --subst-var-by "arPath" "${stdenv.gcc.binutils}/bin/ar"
+  '';
+
+  buildInputs = [ which file perl curl python27 makeWrapper ];
+  enableParallelBuilding = true;
+}

pkgs/top-level/all-packages.nix

@@ -3289,7 +3289,8 @@ let
 
   roadsend = callPackage ../development/compilers/roadsend { };
 
-  rust = callPackage ../development/compilers/rust {};
+  rust       = callPackage ../development/compilers/rust {};
+  rustMaster = callPackage ../development/compilers/rust/head.nix {};
 
   sbclBootstrap = callPackage ../development/compilers/sbcl/bootstrap.nix {};
   sbcl = callPackage ../development/compilers/sbcl {