lib/types.nix: small eval optimization (listToAttrs + mapAttrsToList -> mapAttrs)

lib/types.nix

@@ -284,8 +284,7 @@ rec {
             (mergeDefinitions (loc ++ [name]) elemType defs).optionalValue
           )
           # Push down position info.
-          (map (def: listToAttrs (mapAttrsToList (n: def':
-            { name = n; value = { inherit (def) file; value = def'; }; }) def.value)) defs)));
+          (map (def: mapAttrs (n: v: { inherit (def) file; value = v; }) def.value) defs)));
       getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["<name>"]);
       getSubModules = elemType.getSubModules;
       substSubModules = m: attrsOf (elemType.substSubModules m);