Regression with `await` type extraction in strict mode

[ulrichb]

TypeScript Version: 3.6.0-dev.20190807 (worked up to 3.6.0-dev.20190804)

Search Terms: await type promise

Code

const containsPromises: unique symbol = Symbol();

type DeepPromised<T> =
 { [containsPromises]?: true } &
 {
 [TKey in keyof T]: T[TKey] | DeepPromised<T[TKey]> | Promise<DeepPromised<T[TKey]>>
 };

async function fun<T>(deepPromised: DeepPromised<T>) {

 const deepPromisedWithIndexer:
 DeepPromised<{ [name: string]: {} | null | undefined }> = deepPromised;

 for (const value of Object.values(deepPromisedWithIndexer)) {

 const awaitedValue = await value;

 if (awaitedValue)
 await fun(awaitedValue);
 }
}

(Compile with --strict!)

Expected behavior:
No compile error as in TS 3.5.3.

Actual behavior:

TypeScriptIssueNext.ts:21:23 - error TS2345: Argument of type '{} | ({ [containsPromises]?: true | undefined; } & {})' is not assignable to parameter of type 'DeepPromised<{ [containsPromises]?: undefined; }>'.
 Types of property '[containsPromises]' are incompatible.
 Type 'true | undefined' is not assignable to type '(true & Promise<never>) | undefined'.
 Type 'true' is not assignable to type '(true & Promise<never>) | undefined'.

21 await fun(awaitedValue);
 ~~~~~~~~~~~~

Playground Link: Here
BTW: Please update the libs in the playground, Object.values() (ES2017) isn't available.

Related Issues: -

[ahejlsberg]

Simpler repro:

type Deep<T> = { [K in keyof T]: T[K] | Deep<T[K]> };

declare function foo<T>(dp: Deep<T>): T;
declare let xx: { a: string | undefined };

foo(xx); // Error