Remove errant return assignment (facebook#14164)

Oopsie!

This could have been avoided if our types were modeled correctly with
Flow (using a disjoint union).

Fuzz tester didn't catch it because it does not generate cases where
a Suspense component mounts with no children. I'll update it.

Author: acdlite

packages/react-reconciler/src/ReactFiberBeginWork.js

@@ -1242,7 +1242,7 @@ function updateSuspenseComponent(
     } else {
       // The current tree has not already timed out. That means the primary
       // children are not wrapped in a fragment fiber.
-      const currentPrimaryChild: Fiber = (current.child: any);
+      const currentPrimaryChild = current.child;
       if (nextDidTimeout) {
         // Timed out. Wrap the children in a fragment fiber to keep them
         // separate from the fallback children.
@@ -1256,7 +1256,6 @@ function updateSuspenseComponent(
           null,
         );
         primaryChildFragment.child = currentPrimaryChild;
-        currentPrimaryChild.return = primaryChildFragment;
 
         // Even though we're creating a new fiber, there are no new children,
         // because we're reusing an already mounted tree. So we don't need to

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

@@ -883,7 +883,44 @@ describe('ReactSuspense', () => {
 
       root.update(null);
       expect(root).toFlushWithoutYielding();
+      jest.advanceTimersByTime(1000);
+    });
+
+    it('#14162', () => {
+      const {lazy} = React;
+
+      function Hello() {
+        return <span>hello</span>;
+      }
+
+      async function fetchComponent() {
+        return new Promise(r => {
+          // simulating a delayed import() call
+          setTimeout(r, 1000, {default: Hello});
+        });
+      }
+
+      const LazyHello = lazy(fetchComponent);
+
+      class App extends React.Component {
+        state = {render: false};
+
+        componentDidMount() {
+          setTimeout(() => this.setState({render: true}));
+        }
+
+        render() {
+          return (
+            <Suspense fallback={<span>loading...</span>}>
+              {this.state.render && <LazyHello />}
+            </Suspense>
+          );
+        }
+      }
+
+      const root = ReactTestRenderer.create(null);
 
+      root.update(<App name="world" />);
       jest.advanceTimersByTime(1000);
     });
   });