This DEV-only field was added in 836331ba5f69f2cc53b273ec073fae116db14302 by @sebmarkbage but it's not being used anymore to my knowledge.
const outerPropTypes = type.propTypes;
          if (outerPropTypes) {
            checkPropTypes(
              outerPropTypes,
              resolvedProps, 
              'prop',
              getComponentNameFromType(type),
            );
          }
        }
      }
      resolvedProps = resolveDefaultProps(type.type, resolvedProps);
      return updateMemoComponent(
        current,
        workInProgress,
        type,
        resolvedProps,
        updateLanes,
        renderLanes,
      );
    }
    case SimpleMemoComponent: {