Fix React.lazy(forwardRef) (facebook#13446)

* Fix React.lazy(forwardRef)

* Forbid bad typeof

.eslintrc.js

@@ -41,6 +41,7 @@ module.exports = {
     'quotes': [ERROR, 'single', {avoidEscape: true, allowTemplateLiterals: true }],
     'space-before-blocks': ERROR,
     'space-before-function-paren': OFF,
+    'valid-typeof': [ERROR, {requireStringLiterals: true}],
 
     // React & JSX
     // Our transforms set this automatically

packages/react-reconciler/src/ReactFiberLazyComponent.js

@@ -33,7 +33,7 @@ export function readLazyComponentType<T>(thenable: Thenable<T>): T {
               // resolved value itself.
               const defaultExport = (resolvedValue: any).default;
               resolvedValue =
-                typeof defaultExport !== undefined && defaultExport !== null
+                defaultExport !== undefined && defaultExport !== null
                   ? defaultExport
                   : resolvedValue;
             } else {

packages/react-reconciler/src/__tests__/ReactSuspense-test.internal.js

@@ -72,7 +72,7 @@ describe('ReactSuspense', () => {
 
   function Text(props) {
     ReactNoop.yield(props.text);
-    return <span prop={props.text} />;
+    return <span prop={props.text} ref={props.hostRef} />;
   }
 
   function AsyncText(props) {
@@ -1600,6 +1600,41 @@ describe('ReactSuspense', () => {
       }).toWarnDev('    in Text (at **)\n' + '    in Foo (at **)');
       expect(ReactNoop.getChildren()).toEqual([div(span('A'), span('B'))]);
     });
+
+    it('supports class and forwardRef components', async () => {
+      const LazyClass = lazy(() => {
+        class Foo extends React.Component {
+          render() {
+            return <Text text="Foo" />;
+          }
+        }
+        return Promise.resolve(Foo);
+      });
+
+      const LazyForwardRef = lazy(() => {
+        const Bar = React.forwardRef((props, ref) => (
+          <Text text="Bar" hostRef={ref} />
+        ));
+        return Promise.resolve(Bar);
+      });
+
+      const ref = React.createRef();
+      ReactNoop.render(
+        <Placeholder fallback={<Text text="Loading..." />}>
+          <LazyClass />
+          <LazyForwardRef ref={ref} />
+        </Placeholder>,
+      );
+      expect(ReactNoop.flush()).toEqual(['Loading...']);
+      expect(ReactNoop.getChildren()).toEqual([]);
+      expect(ref.current).toBe(null);
+
+      await LazyClass;
+      await LazyForwardRef;
+      expect(ReactNoop.flush()).toEqual(['Foo', 'Bar']);
+      expect(ReactNoop.getChildren()).toEqual([span('Foo'), span('Bar')]);
+      expect(ref.current).not.toBe(null);
+    });
   });
 
   it('does not call lifecycles of a suspended component', async () => {