Trying Guix: A Nixer's impressions(tazj.in)

      buildGoDir() {
        local d; local cmd;
        cmd="$1"
        d="$2"
        . $TMPDIR/buildFlagsArray
        echo "$d" | grep -q "\(/_\|examples\|Godeps\|testdata\)" && return 0
        [ -n "$excludedPackages" ] && echo "$d" | grep -q "$excludedPackages" && return 0
        local OUT
        if ! OUT="$(go $cmd $buildFlags "''${buildFlagsArray[@]}" -v -p $NIX_BUILD_CORES $d 2>&1)"; then
          if ! echo "$OUT" | grep -qE '(no( buildable| non-test)?|build constraints exclude all) Go (source )?files'; then
            echo "$OUT" >&2
            return 1
          fi
        fi
        if [ -n "$OUT" ]; then
          echo "$OUT" >&2
        fi
        return 0
      }

        std::string rc = fmt(
                R"(_nix_shell_clean_tmpdir() { rm -rf %1%; }; )"s +
                (keepTmp ?
                    "trap _nix_shell_clean_tmpdir EXIT; "
                    "exitHooks+=(_nix_shell_clean_tmpdir); "
                    "failureHooks+=(_nix_shell_clean_tmpdir); ":
                    "_nix_shell_clean_tmpdir; ") +
                (pure ? "" : "[ -n \"$PS1\" ] && [ -e ~/.bashrc ] && source ~/.bashrc;") +
                "%2%"
                "dontAddDisableDepTrack=1;\n"
                + structuredAttrsRC +
                "\n[ -e $stdenv/setup ] && source $stdenv/setup; "
                "%3%"
                "PATH=%4%:\"$PATH\"; "
                "SHELL=%5%; "
                "set +e; "
                R"s([ -n "$PS1" -a -z "$NIX_SHELL_PRESERVE_PROMPT" ] && PS1='\n\[\033[1;32m\][nix-shell:\w]\$\[\033[0m\] '; )s"
                "if [ \"$(type -t runHook)\" = function ]; then runHook shellHook; fi; "
                "unset NIX_ENFORCE_PURITY; "
                "shopt -u nullglob; "
                "unset TZ; %6%"
                "shopt -s execfail;"
                "%7%",
                shellEscape(tmpDir),
                (pure ? "" : "p=$PATH; "),
                (pure ? "" : "PATH=$PATH:$p; unset p; "),
                shellEscape(dirOf(*shell)),
                shellEscape(*shell),
                (getenv("TZ") ? (string("export TZ=") + shellEscape(getenv("TZ")) + "; ") : ""),
                envCommand);