NixOS default.nix for compiling Nightly Rust using Mozilla overlay, also with a specific RustRegistry for specific date, to handle "version not found" issues. Doesn't actually work, so do not use.

default.nix

{
  pkgs ? (
  let
    pkgs = import <nixpkgs>;
    pkgs_ = (pkgs {});
    rustOverlay = (pkgs_.fetchFromGitHub {
      owner = "mozilla";
      repo = "nixpkgs-mozilla";
      rev = "1608d31f7e5b2415fb80b5d76f97c009507bc45f";
      sha256 = "0mznf82k7bxpjyvigxvvwpmi6gvg3b30l58z36x192q2xxv47v1k";
    });
  in (pkgs {
    overlays = [

      (import (builtins.toPath "${rustOverlay}/rust-overlay.nix"))

      (self: super: { rustRegistry = super.callPackage ./rust-packages.nix { }; }) # by adding the rustRegistry entry here in the overlay, the specific rustRegistry date / SHA will be used in the later overlays and compiles.

      (self: super:
      let
        # base = super.rustChannels.nightly;
        base = super.rustChannelOf { date = "2017-07-12"; channel = "nightly"; };
      in
      {
        rust = {
          rustc = base.rust;
          cargo = base.cargo;
        };
        rustPlatform = super.recurseIntoAttrs (super.makeRustPlatform {
          rustc = base.rust;
          cargo = base.cargo;
        });
      })
    ];
  }))
}:

  pkgs.rustPlatform.buildRustPackage rec {

    name = "thingname-${version}";
    version = "0.3";
    src = ./.;
    depsSha256 = "0pch039h4nqpdm5f0r6n1xskrmjrf01l0zj881pz4rl1iihdhqr5";
    buildInputs = [ pkgs.rustc pkgs.cargo pkgs.entr ];
    #... etc.
  }

rust-packages.nix

# Change the `name` and `rev`values to select specific dates/commit-SHAs that will be used to download a specific SHA / date to use for nix rust.

# This file defines the source of Rust / cargo's crates registry
#
# buildRustPackage will automatically download dependencies from the registry
# version that we define here. If you're having problems downloading / finding
# a Rust library, try updating this to a newer commit.

{ stdenv, fetchFromGitHub, git }:

stdenv.mkDerivation {
  name = "rustRegistry-2017-07-12";

  src = fetchFromGitHub {
    owner = "rust-lang";
    repo = "crates.io-index";
    rev = "727fb516b25dd4f9fff535a8e507cd3ed21a1d6e";
    sha256 = "1srzy7w0402s9hfp90lq7i245wlwqmmwir6qik3m4zkfq41ymhls";
    # rev = "de7301b4aa5a933658ab14dba972cc2cab77da1c";
    # sha256 = "0dyx5n789pkmvk7x876v8rnagzp7xc8r2iysj2b70vcsqdvidnax";
  };
  phases = [ "unpackPhase" "installPhase" ];
  installPhase = ''
    # For some reason, cargo doesn't like fetchgit's git repositories, not even
    # if we set leaveDotGit to true, set the fetchgit branch to 'master' and clone
    # the repository (tested with registry rev
    # 965b634156cc5c6f10c7a458392bfd6f27436e7e), failing with the message:
    #
    # "Target OID for the reference doesn't exist on the repository"
    #
    # So we'll just have to create a new git repository from scratch with the
    # contents downloaded with fetchgit...

    mkdir -p $out

    cp -r ./* $out/

    cd $out

    git="${git}/bin/git"

    $git init
    $git config --local user.email "example@example.com"
    $git config --local user.name "example"
    $git add .
    $git commit --quiet -m 'Rust registry commit'

    touch $out/touch . "$out/.cargo-index-lock"
  '';
}