Object spread not checking for strictNullChecks

[thitemple]

TypeScript Version: 2.2.1

Code

type Movie = {
	title: string;
	yearReleased: number;
}

const m = { title: "The Matrix", yearReleased: 1999 };
const x: Movie = { ...m, title: undefined };

Expected behavior:
When strictNullChecks = true it should not allow for title = undefined
Actual behavior:
It does not raise an error and I can have an object with a required property undefined.
It does work if I try to set null to title, the compiler will raise an error

[mprobst]

Similar, but might be a different bug:

const x: {a: number}|null = null;
const y = {...x};

With strictNullChecks, this should complain about x being possibly null at the spread location (in ES6 or with downlevelIteration this also gives a TypeError).

[mhegazy]

With strictNullChecks, this should complain about x being possibly null at the spread location (in ES6 or with downlevelIteration this also gives a TypeError).

The semantics of object spread allows for skipping null and undefined values, see https://github.com/tc39/proposal-object-rest-spread/blob/master/Spread.md. It is meant to follow the Object.assign semantics.

The __assign polyfill handles that accordingly.

[mprobst]

@mhegazy sorry, incorrect example, and I found that the usage site I ran into actually used ! (so, self inflicted pain...).

[sandersn]

Fix is up at #15938