Nested destructuring does not narrow dependent parameters

[Fireboltofdeath]

Bug Report

🔎 Search Terms

destructuring destructured dependent parameters nested control flow analysis

🕗 Version & Regression Information

• This changed between versions 4.5.5 and 4.6

⏯ Playground Link

Playground link with relevant code

💻 Code

declare const Tuple: [true, string] | [false, number];
const [[val1, val2]] = [Tuple];
if (val1) {
	val2 // string | number
}

🙁 Actual behavior

TypeScript does not correctly narrow val2 when narrowing val1 if it's in any type of nested destructuring.

🙂 Expected behavior

I expect it to behave the same as directly destructuring the object.

[jtbandes]

Is this the same issue?

type T = { path: ['one'], value: string } | { path: ['two'], value: number }

function foo(payload: T) {
  if (payload.path[0] === 'one') {
    payload.value  // string | number, should be just string
  }
}

[Fireboltofdeath]

This issue is referring to the control flow analysis of destructured unions so I don't believe this is related to that issue.