Using a special static property for type detecting (#4673)

Related issue: #4655

.eslintrc.js

@@ -3,7 +3,7 @@ const eslintrc = {
   env: {
     browser: true,
     node: true,
-    mocha: true,
+    jasmine: true,
     jest: true,
     es6: true,
   },

components/breadcrumb/Breadcrumb.tsx

@@ -89,8 +89,8 @@ export default class Breadcrumb extends React.Component<BreadcrumbProps, any> {
     } else if (children) {
       crumbs = React.Children.map(children, (element: any, index) => {
         warning(
-          element.type === BreadcrumbItem,
-          ' `BreadcrumbItem` is required as the wrapper of children element. '
+          element && element.type.__ANT_BREADCRUMB_ITEM,
+          'Breadcrumb only accetps Breadcrumb.Item as it\'s children'
         );
         return cloneElement(element, {
           separator,

components/breadcrumb/BreadcrumbItem.tsx

@@ -8,6 +8,8 @@ export interface BreadcrumbItemProps {
 }
 
 export default class BreadcrumbItem extends React.Component<BreadcrumbItemProps, any> {
+  static __ANT_BREADCRUMB_ITEM = true;
+
   static defaultProps = {
     prefixCls: 'ant-breadcrumb',
     separator: '/',

components/breadcrumb/__tests__/Breadcrumb.test.js

@@ -0,0 +1,19 @@
+import React from 'react';
+import { mount } from 'enzyme';
+import Breadcrumb from '../Breadcrumb';
+
+describe('Breadcrumb', () => {
+  it('warns on non-Breadcrumb.Item children', () => {
+    const MyCom = () => <div>foo</div>;
+    spyOn(console, 'error');
+    mount(
+      <Breadcrumb>
+        <MyCom />
+      </Breadcrumb>
+    );
+    expect(console.error.calls.count()).toBe(1);
+    expect(console.error.calls.argsFor(0)[0]).toContain(
+      'Breadcrumb only accetps Breadcrumb.Item as it\'s children'
+    );
+  });
+});