Follow up from https://github.com/facebook/react/pull/11616.

Here's one I found. These two invariants:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L330-L343

are in a function that's behind a DEV block:

https://github.com/facebook/react/blob/7e7127387ba64f57299eaff8656542cea6fb3a2d/packages/react-reconciler/src/ReactFiberClassComponent.js#L447-L449

I don't think this is intentional, but need to verify.

There may be more. I'll use this issue to track while https://github.com/facebook/react/pull/11616 preserves existing behavior.
return null;
        }
      };
    });
    describe('elements', function() {
      describe('reconnecting different component implementations', function() {
        let ES6ClassComponent, PureComponent, bareElement;
        beforeEach(() => {
          
          ES6ClassComponent = class extends React.Component {
            render() {
              return <div id={this.props.id} />;
            }
          };
          PureComponent = props => <div id={props.id} />;
          bareElement = <div id="foobarbaz" />;
        });
        it('should reconnect ES6 Class to ES6 Class', () =>
          expectMarkupMatch(
            <ES6ClassComponent id="foobarbaz" />,
            <ES6ClassComponent id="foobarbaz" />,
          ));
        it('should reconnect Pure Component to ES6 Class', () =>
          expectMarkupMatch(
            <ES6ClassComponent id="foobarbaz" />,