fix(compiler-core): make ForIteratorExpression's returns property optional

[so1ve]

Upstream: vuejs/language-tools#4409

Usage here:

core/packages/compiler-core/src/transforms/vFor.ts

Lines 206 to 223 in 530d9ec

	const loop = createFunctionExpression(
	createForLoopParams(forNode.parseResult, [
	createSimpleExpression(`_cached`),
	]),
	)
	loop.body = createBlockStatement([
	createCompoundExpression([`const _memo = (`, memo.exp!, `)`]),
	createCompoundExpression([
	`if (_cached`,
	...(keyExp ? [` && _cached.key === `, keyExp] : []),
	` && ${context.helperString(
	IS_MEMO_SAME,
	)}(_cached, _memo)) return _cached`,
	]),
	createCompoundExpression([`const _item = `, childBlock as any]),
	createSimpleExpression(`_item.memo = _memo`),
	createSimpleExpression(`return _item`),
	])

shows that a ForIteratorExpression's returns property can be undefined, so changed the type definition to match the runtime result.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	90.8 kB	34.5 kB	31.1 kB
vue.global.prod.js	148 kB	53.7 kB	48 kB

Usages

Name	Size	Gzip	Brotli
createApp	50.8 kB	19.9 kB	18.1 kB
createSSRApp	54.1 kB	21.2 kB	19.3 kB
defineCustomElement	53.1 kB	20.6 kB	18.8 kB
overall	64.6 kB	24.9 kB	22.6 kB

[so1ve]

e2e failed 🤔

[sxzz]

Re-ran and passed now

[sodatea]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

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nuxt	✅ success	✅ success
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