Investigate uncovered differences between development and production

[gaearon]

Follow up from #11616.

Here's one I found. These two invariants:

react/packages/react-reconciler/src/ReactFiberClassComponent.js

Lines 330 to 343 in 7e71273

	if (state && (typeof state !== 'object' || isArray(state))) {
	invariant(
	false,
	'%s.state: must be set to an object or null',
	getComponentName(workInProgress),
	);
	}
	if (typeof instance.getChildContext === 'function') {
	invariant(
	typeof workInProgress.type.childContextTypes === 'object',
	'%s.getChildContext(): childContextTypes must be defined in order to ' +
	'use getChildContext().',
	getComponentName(workInProgress),
	);

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

react/packages/react-reconciler/src/ReactFiberClassComponent.js

Lines 447 to 449 in 7e71273

	if (__DEV__) {
	checkClassInstance(workInProgress);
	}

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

There may be more. I'll use this issue to track while #11616 preserves existing behavior.

[gaearon]

Here’s another difference: in development, putting a string ref on a functional component throws with:

Stateless function components cannot have refs.

but in production gives you:

Element ref was specified as a string but no owner was set.

[gaearon]

#11630