Occurs in Fiber with multiple instances of the React package (which can't share current owner).
// 
              break;
            }
          }
        }
        // 
        // 
        // 
        case FunctionalComponent: {
          const Component = returnFiber.type;
          invariant(
            false,
            '%s(...): Nothing was returned from render. This usually means a ' +
              'return statement is missing. Or, to render nothing, ' +
              'return null.',
            Component.displayName || Component.name || 'Component',
          );
        }
      }
    }
    // 
    return deleteRemainingChildren(returnFiber, currentFirstChild);
  }
  return reconcileChildFibers;
}
exports.reconcileChildFibers = ChildReconciler(true, true);
exports.reconcileChildFibersInPlace = ChildReconciler(false, true);
exports.mountChildFibersInPlace = ChildReconciler(false, false);
exports.cloneChildFibers = function(
  current: Fiber | null,