Bug: [Vue warn] Non-function value encountered for default slot on stubbed teleport

[freakzlike]

Describe the bug
After update from 2.1.0 to 2.2.0, tests with stubs: { teleport: true } produce a warning:

[Vue warn]: Non-function value encountered for default slot. Prefer function slots for better performance.
  at <Teleport to="body" >
  at <Anonymous ref="VTU_COMPONENT" >
  at <VTUROOT>         

To Reproduce
Able to reproduce within VTU unit test

test-utils/tests/mountingOptions/global.stubs.spec.ts

Lines 514 to 531 in 6371349

	it('opts in to stubbing teleport ', () => {
	const Comp = {
	template: `<teleport to="body"><div id="content" /></teleport>`
	}
	const wrapper = mount(Comp, {
	global: {
	stubs: {
	teleport: true
	}
	}
	})
	expect(wrapper.html()).toBe(
	'<teleport-stub to="body">\n' +
	' <div id="content"></div>\n' +
	'</teleport-stub>'
	)
	})

Expected behavior
Not print a warning

Related information:

• @vue/test-utils version: 2.2.0
• Vue version: 3.2.41
• node version: 16.18.0
• npm (or yarn) version: pnpm@7.14.0

Additional context
I think this might come from the stubs refactoring and some previous special handling on the teleport child nodes, where they have been explicit passed as function:

test-utils/src/stubs.ts

Line 208 in 30e9c0c

() => children

[gabriellatavares]

i'm having the same issue

[FlorentGimaret]

I'm facing the same issue

[cexbrayat]

I have a hacky workaround that gets rid of the warning in #1833 but I'm not convinced this is the proper way.