code: function getPreciseType(propValue) {
          var propType = getPropType(propValue);
          if (propType === 'object') {
              if (propValue instanceof Date) {
                  return 'date';
              } else if (propValue instanceof RegExp) {
                  return 'regexp';
              }
          }
          return propType;
      }
docs: This handles more types than `getPropType`. Only used for error messages. Copied from React.PropTypes