How can I use rustc unstable with rustPlatform.buildRustPackage? [Solved]

Hello! I am attempting to package the password manager software “bitwarden_rs”. This software requires the unstable release of Rust to compile. I would like to use rustPlatform.buildRustPackage due to its convenience, but I am not sure how to use it with unstable rustc. It appears that the version of rustc in nixos-unstable is 1.35.0 (Stable), so the following nix expression fails to compile the software.

with import (fetchTarball {};
rustPlatform.buildRustPackage rec {
	pname = "bitwarden_rs";
	version = "1.9.1";

	src = fetchFromGitHub {
		owner = "dani-garcia";
		repo = pname;
		rev = version;
		sha256 = "0jfb4b2lp2v01aw615lx0qj1qh73hyrbjn9kva7zqp74wcfw12gp";

	cargoSha256 = "1ffbg8giqq674zgji5iihiy36051yxypz8wij3fzygp3paj16wsk";

	nativeBuildInputs = [python3 cmake pkg-config openssl];

	buildInputs = [ sqlite ];

The documentation for builtRustPackage here does not mention anything about this.
This is my first attempt at nix packaging, so I may be missing something obvious.


I’m fairly certain that is already packaged.

Yup. Even has a module. See master/nixos/modules/services/security/bitwarden_rs

Wow! I have no idea how I missed that, but that solves my problem. Thank you.

Hi! I came up with the same question and find this thread. Even though it has been closed, I am still wondering on how do I make unstable rustc from mozilla-nixpkgs’ rust-overlay for another package that I’m working on, but still leverage from rustPlatform feature.

I think the answer didn’t solved the question in general and maybe the correct answer will help beginners in the future.

You can always pass an overlay when importing nixpkgs:

mozillaOverlay = builtins.fetchurl { url = ...; sha256 = ...; };
with import <nixpkgs> { overlays = [ mozillaOverlay ]; };

Another possibility is to create a new Rust platform using your preferred nightly version. E.g., you could create a function such as:

{ callPackage, fetchFromGitHub, makeRustPlatform }:

# The date of the nighly version to use.

  mozillaOverlay = fetchFromGitHub {
    owner = "mozilla";
    repo = "nixpkgs-mozilla";
    rev = "9f35c4b09fd44a77227e79ff0c1b4b6a69dff533";
    sha256 = "18h0nvh55b5an4gmlgfbvwbyqj91bklf1zymis6lbdh75571qaz0";
  mozilla = callPackage "${mozillaOverlay.out}/package-set.nix" {};
  rustNightly = (mozilla.rustChannelOf { inherit date; channel = "nightly"; }).rust;
in makeRustPlatform {
  cargo = rustNightly;
  rustc = rustNightly;

You can then use this function to create Rust platforms for a given nightly. E.g.:

  rustPlatform = callPackage ./rust-platform-nightly.nix {};
in (rustPlatform "2019-07-30").buildRustPackage rec {
  # ...

This is how to use danieldk’s way to make a platform.

	mozilla_rust_channel = ( nixpkgs.rustChannelOf rustVersion );

	new_rustc= mozilla_rust_channel.rust;

	new_cargo= mozilla_rust_channel.cargo;

		cargo = new_cargo ;

	new_buildRustPackage =nixpkgs.rustPlatform.buildRustPackage.override{ 
		cargo = new_cargo;
		rustc = new_rustc;
		fetchCargoTarball = new_fetchCargoTarball;

	new_rustcSrc = mozilla_rust_channel.rust-src;

	new_rustPlatform = {
		rust = {
			rustc = new_rustc;
			cargo = new_cargo;

		fetchCargoTarball = new_fetchCargoTarball; 
		buildRustPackage = new_buildRustPackage;
		rustcSrc = new_rustcSrc;

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It’s interesting you have to do all that to make it work. I am still using what I wrote in my post and it still works in CI.

Function to make a nightly Rust platform:

Used here:

But maybe I am not using what is necessary to trigger the error that you are encountering?

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For posterity: My earlier comment is effective now in