thesir.nix

let
  eval = (import <nixpkgs/lib/modules.nix> { inherit lib; }).evalModules;
  lib = (import <nixpkgs> {}).lib;

  module = with lib; with types; {
    options.option = mkOption {
      default = [ { a = "Foo"; b = "Baar"; } ];
      type = with types; listOf (submodule {
        options = {
          a = mkOption {};
          b = mkOption {};
          c = mkOption {};
        };
      });
    };
  };
in
  eval {
    modules = [
      module
    ];
  }