Fix this in a functional component for ShallowRenderer (#13144)

Author: koba04

src/ReactShallowRenderer.js

@@ -107,7 +107,11 @@ class ReactShallowRenderer {
 
         this._mountClassComponent(element, this._context);
       } else {
-        this._rendered = element.type(element.props, this._context);
+        this._rendered = element.type.call(
+          undefined,
+          element.props,
+          this._context,
+        );
       }
     }
 

src/__tests__/ReactShallowRenderer-test.js

@@ -1407,4 +1407,15 @@ describe('ReactShallowRenderer', () => {
     instance.setState(state => ({count: state.count + 1}));
     expect(log).toEqual(['render']);
   });
+
+  it('should not get this in a functional component', () => {
+    const logs = [];
+    function Foo() {
+      logs.push(this);
+      return <div>foo</div>;
+    }
+    const shallowRenderer = createRenderer();
+    shallowRenderer.render(<Foo foo="bar" />);
+    expect(logs).toEqual([undefined]);
+  });
 });