如何更新nix语言版本(builtins.langVersion)？

Question

我想在本地运行nixpkgs测试，我找到了本手册，但它不起作用

$ cd my/nixpkgs
$ nix-build --show-trace nixos/tests/login.nix
error: while evaluating the attribute ‘buildCommand’ of the derivation ‘vm-test-run-login’ at /home/bjorn/projects/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:148:11:
while evaluating the attribute ‘buildCommand’ of the derivation ‘nixos-test-driver-login’ at /home/bjorn/projects/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:148:11:
while evaluating the attribute ‘buildCommand’ of the derivation ‘nixos-vm’ at /home/bjorn/projects/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:148:11:
while evaluating the attribute ‘text’ of the derivation ‘run-nixos-vm’ at /home/bjorn/projects/nixpkgs/pkgs/stdenv/generic/make-derivation.nix:148:11:
while evaluating anonymous function at /home/bjorn/projects/nixpkgs/pkgs/build-support/closure-info.nix:9:1, called from /home/bjorn/projects/nixpkgs/nixos/modules/virtualisation/qemu-vm.nix:105:13:
assertion failed at /home/bjorn/projects/nixpkgs/pkgs/build-support/closure-info.nix:11:1

因为这个断言

assert builtins.langVersion >= 5;

如何更新langVersion？

$ nix-repl
Welcome to Nix version 1.11.16. Type :? for help.

nix-repl> builtins.langVersion
3

nix-repl>

Answer 1

如果您想在17.09上多呆一段时间，可以使用以下NixOS配置升级Nix：

{ pkgs, ... }: {
  nix.package = pkgs.nixUnstable;
}

否则，你可能更喜欢切换到18.03，而不是不稳定。如果你要使用不稳定，确保你使用的是不稳定的，而不是不稳定的。请参阅https://nixos.wiki/wiki/Nixpkgs#Channels

Answer 2

给大卫·格雷森

我不得不将nixos更新为不稳定(sudo nix-channel很重要)

sudo nix-channel --add https://nixos.org/channels/nixos-unstable nixos
sudo nixos-rebuild switch --upgrade
nix-instantiate --eval -E '(import <nixos> {}).lib.nixpkgsVersion'
nix-instantiate --eval -E 'builtins.langVersion'