code: def _cor_compile(rule, var, val, result_class, key, compilation_list):
          
          compilation = compilation_list.get(key, None)
          if compilation:
              if isinstance(val, ListRule):
                  result = []
                  for itemv in val.value:
                      result.append(compilation['callback'](itemv))
  
                  val = compilation['listclass'](result)
              else:
                  val = compilation['callback'](val)
          return result_class(rule.operation, var, val)
docs: Actual compilation worker method.