lib.types.pkgs: init

A nominal type.

lib/types.nix

@@ -476,6 +476,14 @@ rec {
       check = x: isDerivation x && hasAttr "shellPath" x;
     };
 
+    pkgs = addCheck
+      (unique { message = "A Nixpkgs pkgs set can not be merged with another pkgs set."; } attrs // {
+        name = "pkgs";
+        descriptionClass = "noun";
+        description = "Nixpkgs package set";
+      })
+      (x: (x._type or null) == "pkgs");
+
     path = mkOptionType {
       name = "path";
       descriptionClass = "noun";

nixos/doc/manual/development/option-types.section.md

@@ -99,6 +99,10 @@ merging is handled.
     problems.
     :::
 
+`types.pkgs`
+
+:   A type for the top level Nixpkgs package set.
+
 ### Numeric types {#sec-option-types-numeric}
 
 `types.int`