Directly destructuring awaited generic collapses to any

New in 3.2.2(?) is this type mistake in baz() below. result should be destructured to having type string, but instead it is any even though the unabbreviated syntaxes work correctly.

type responseType = { result: string }

declare function post<T = responseType>(): Promise<T>;

async function foo() {
    const response = await post(); // response : responseType  OK
    const result = response.result; // result : string OK
}

async function bar() {
    const response = await post(); // response : responseType OK
    const { result } = response; // result : string OK
}

async function baz() {
    const { result } = await post(); // result : any !!!!!!!!!!!
}

Simpler repro

declare function post<T = { result: string }>(): T;

function bar() {
  const response = post();
  const { result } = response;
}

function baz() {
  const { result } = post();
  result.subst_r; // should be error
}

This is fixed in our latest nightlies, by #39081 (#38969 was a dupe of this, looks like)

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Directly destructuring awaited generic collapses to any #29414

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Directly destructuring awaited generic collapses to any #29414

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RyanCavanaugh commented on Jan 14, 2019

weswigham commented on Jul 8, 2020

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