TypeScript Version: 3.7.x-dev.201xxxxx

Search Terms:

PromiseLike await

Code

const promiseA = new Promise(resolve => {
  resolve(5);
})

async function main() {
  const a = await 5; // typescript will give warning 80007
  const b = await promiseA; // expected
  const c = await ({} as PromiseLike<number>); // The cast to PromiseLike silences 80007
}

Expected behavior:

There should be warning on the line with const c. I found this while using chai-as-promised. "await expect(promise).to.eventually.be(arg)" was throwing UnhandledPromiseRejectionWarning. Chai.PromisedAssertion is a PromiseLike and not a Promise (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/chai-as-promised/index.d.ts#L105) and it's not safe to use with await. But the type system hid that from me.

Actual behavior:

No warning.

Playground Link:

https://www.typescriptlang.org/play/index.html?ssl=10&ssc=2&pln=1&pc=1#code/MYewdgzgLgBADgJxAWwJYQKYEEYF4ZgYDuMACkmpgBQIYQgA2AbhngHwwDeAUDDLfWYYqAVgCUAbm4BfMd24BDCAE8wwGADMArmqipwMZAtRgqYrrxihIsBXhgKix2CKl9r0GACN7j5-Ap0bDcrcE91fD9UWCpOaQcIMkDMABlUAGsMAB4wLWQvDAQ2SXlpIA

Related Issues:

#35419