Widen intersections produced by spead expressions in object literals

[ahejlsberg]

TypeScript Version: 3.3.0-dev

Code

function test<T extends { a: string, b: string }>(obj: T): T {
    let { a, ...rest } = obj;
    return { a: 'hello', ...rest } as T;  // Error, but shouldn't be
}

Expected behavior:

No errors.

Actual behavior:

Error as shown above.

Playground Link:

https://www.typescriptlang.org/play/index.html#src=function%20test%3CT%20extends%20%7B%20a%3A%20string%2C%20b%3A%20string%20%7D%3E(obj%3A%20T)%3A%20T%20%7B%0D%0A%20%20%20%20let%20%7B%20a%2C%20...rest%20%7D%20%3D%20obj%3B%0D%0A%20%20%20%20return%20%7B%20a%3A%20'hello'%2C%20...rest%20%7D%20as%20T%3B%0D%0A%7D%0D%0A

Related Issues:

Found while investigating #28884.