React: custom validator for type of children

container.js

const {forEach} = React.Children;

class Child extends React.Component { /*…*/ }

class Container extends React.Component { /*…*/ }
Container.propTypes = {
  children: function(props, propName, componentName) {
    forEach(props[propName], (element) => {
      const {type} = element;
      if (type !== Child) {
        throw Error(`Invalid child for "${componentName}": "${type.displayName || type.name || type}"`);
      }
    });
  }
};