🐛 Bug: Added type should be Promise<boolean> not Promise<boolean> | boolean

[rubiesonthesky]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Expected

This function is not missing return types

	function navigateByUrl(url: string): Promise<boolean>;

	async function navigateTo(): Promise<boolean> {
		return await navigateByUrl("");
	}

Actual

However, it's "fixed" into this

       function navigateByUrl(url: string): Promise<boolean>;

	async function navigateTo(): Promise<boolean> | boolean {
		return await navigateByUrl("");
	}

Additional Info

See discussion https://github.com/JoshuaKGoldberg/TypeStat/pull/1481/files#r1545469119

tsconfig.json

{
	"files": ["actual.ts"]
}

typestat.json

{
	"fixes": {
		"incompleteTypes": true
	},
	"types": {
		"strictNullChecks": true
	}
}

The problem seems to lie when using await or other promise kinds. If function is marked as async, it would be safer to put all types inside Promise.