anchor.diff:        { modules
         , specialArgs ? {}
         , shorthandOnlyDefinesConfig ? false
  +      , description ? null
   
           # Internal variable to avoid `_key` collisions regardless
           # of `extendModules`. Wired through by `evalModules`.
  
positive.code:               else if lhs.shorthandOnlyDefinesConfig == rhs.shorthandOnlyDefinesConfig
                then lhs.shorthandOnlyDefinesConfig
                else throw "A submoduleWith option is declared multiple times with conflicting shorthandOnlyDefinesConfig values";
            };
          };
        };
  
negative.code: 
          freeformType = base._module.freeformType;
  
          name = "submodule";
  
        in
        mkOptionType {
          inherit name;
          description =
            if description != null then description
            else freeformType.description or name;
          check = x: isAttrs x || isFunction x || path.check x;
          merge = loc: defs:
            (base.extendModules {
  