Regression in type inference for Promise.all()

[Tatamo]

TypeScript Version: 3.2.1 & 3.3.0-dev.20181201

Search Terms:
type inference, promise, tuple

Code

async function f(x: number): Promise<number>{
 return x + 1;
}

async function g(s: string): Promise<string>{
 return s + "\n";
}

async function h(): Promise<string> {
 const [a, b] = await Promise.all([f(1), g("x")]).catch(() => [null, null]);
 if (a === null || b === null) throw new Error();
 return b.trim();
}

Expected behavior:
no compile error, as in TS3.1

Actual behavior:

test.ts:12:12 - error TS2339: Property 'trim' does not exist on type 'string | number'.
 Property 'trim' does not exist on type 'number'.

12 return b.trim();
 ~~~~

In TS3.1:

a: number | null
b: string | null

In TS3.2:

a: string | number | null
b: string | number | null

Playground Link:
here
(Enable strictNullChecks to reproduce it)

Related Issues:

[Tatamo]

It looks like the problem of destructuring assignment with an union between tuple and Array types.
simplified code:

function f(): [number, string] | null[] { // when using [null, null] instead of null[], it works properly
 return Math.random() < 0.5 ? [1, "x"] : [null, null];
}

const [a, b] = f(); // a:string|number|null, b:string|number|null

[weswigham]

cc Daniel Rosenwasser (@DanielRosenwasser)