Promise<void> should work like void

[DetachHead]

Bug Report

🔎 Search Terms

promise void

🕗 Version & Regression Information

4.5.0-dev.20211021

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const foo: (fn: () => Promise<void>) => void

//error: Type 'Promise<number>' is not assignable to type 'Promise<void>'.
foo(async () => 1)

🙁 Actual behavior

error: Type 'Promise<number>' is not assignable to type 'Promise<void>'.

🙂 Expected behavior

a function that returns a Promise for a non-null value should be assignable to a function that returns Promise<void> because that's the purpose of void. see https://github.com/Microsoft/TypeScript/wiki/FAQ#why-are-functions-returning-non-void-assignable-to-function-returning-void

[MartinJohns]

Duplicate of #44201 / #12871. Used search terms: promise void in:title