Type inference regression in 3.7-beta

[leonovalex]

TypeScript Version: 3.7.0-beta

type O = { data: string };
type A = () => Promise<O[]>;
type B = () => Promise<O | undefined>;

const f = async (a: A, b: B) => {
    const [_a, _b] = await Promise.all([a(), b()]);
    return _b != null ? _b.data + _a.length : _a.length;
}

Expected behavior:
Compiles as in 3.6.3

Actual behavior:
Errors (Regression)

Playground Link:
https://www.typescriptlang.org/play/index.html?ts=3.7-Beta#code/C4TwDgpgBA8lC8UDeUAmBDY6BcUDOwATgJYB2A5lAL4DcAUKJFAIIJQAUAlAgHxQAKhAPYBbYnggAeGAG0Auj3qNoAITZdeA4WInSoAHygBXUqggAzMhFSK6dAMZDSBKObbo8IUvY44WAGigAI1wVbng+JDooGKhHZ2AoGQB9dEDkoLl3AHd0YkTBUXEIADp0ABty9hl0LkCgrjlOelioQghgI0JSKAyoAEJEUiNKqAB+XqCSjCwoAGpe9BLyiApgAAsoXFTl1fIN+iogA

Related Issues:

[jack-williams]

Duplicate of #33752

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.