Promises are not checked for null/undefined on assignment

[wkrueger]

TS version: 2.2.1
strict null checks on

Is this desired/expected behavior?

let p1: Promise<number|undefined> = Promise.resolve(undefined)
let p2: Promise<number>

p2 = p1
//no error. Expected "cannot assign number|undefined to number" 

[ahejlsberg]

Duplicate of #13513. We still thinking about the best way to resolve this issue.

[wkrueger]

thx!
applying the "branding" workaround for now, just found it from #9953

interface Promise<T> { __promiseBrand: T }