Autocompletion and Diagnostics for `self`

[Ryokune]

Is your feature request related to a problem? Please describe.
Would be nice to have. Currently, I maintain a flake that uses flake parts and import tree, and I access imports via self.nixosModules.foo self.nixosModules.myService etc.
Ex:

... modules/hosts/myHost:
flake.nixosConfigurations.myHost = inputs.nixpkgs.lib.nixosSystem {
  modules = [
    self.nixosModules.someModule
  ]
}

... flake.nix:
outputs =
    inputs@{ self, ... }:
    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
      imports = [
        (inputs.import-tree ./modules)
      ];
      debug = true;
    };

Currently by how things are I could mistype something, or access an invalid attribute eg: self.invalid.module and nixd won't catch it via diagnostics. But i am unsure if this is just a misconfiguration on my end.

Additional context
Using hercules-ci:flake-parts and vic:import-tree in a project.