feat: raise "assignment similar to the default"

[Malix-Labs]

Is your feature request related to a problem? Please describe.

Relying on sane defaults might be desirable for some users

And explicitly assigning a key to a value already being its default is not relying on that sane default

Example:

module

{ lib, ... }:
{
  options.key = lib.mkOption { };

  config.key = lib.mkDefault "value";
}

consumer (explicitly and redundantly assigning its default value)

{
  key = "value";
}

Hence, it might be interesting to raise (info / warn) when an assignment is similar to the default

Describe the solution you'd like

Raise (info / warn) when an assignment is similar to the default

module

{ lib, ... }:
{
  options.key = lib.mkOption { };

  config.key = lib.mkDefault "value";
}

consumer (explicitly and redundantly assigning its default value)

{
  key = "value"; # INFO / WARN: key `key` assignment `"value"` similar to its default
}

Describe alternatives you've considered

No response

Additional context

• Provide the default value for options #693 (the internal defaults evaluation will be shared)