Type of awaited expression is not inferred correctly, works on 2.5.3

[RafaelSalguero]

TypeScript Version: 2.6.1
also tested and fails on 2.7.0
also tested and fails on 2.7.0-dev.20180119 (@next)

Code

type MyType<T> = {[K in keyof T]: string | true | PromiseLike<string | true> };
function MapObject<T, TOut>(value: T, map: <K extends keyof T>(value: T[K], key: K) => TOut) : {[K in keyof T] : TOut} {
 return null as any;
}

//MyFunction
//2.5.3 compiles
//2.6.1 do not compiles since ret variable is not compatible with the function return value
//@next do not compiles since ret variable is not compatible with the function return value
function MyFunction<T>(value: MyType<T>) : {[K in keyof T] : Promise<string | undefined>} {
 const a = MapObject(value, x => x);

 //B should be { [K in keyof T ]: Promise<string | undefined>}
 const b = MapObject(a, async x => {
 //myVal type:
 //(correct) 2.5.3: string | true
 //(incorrect) 2.6.1: { [K in keyof T]: MyType<T>[any] }[K]
 //(incorrect) @next: { [K in keyof T]: MyType<T>[any] }[K]
 const myVal = await x;
 
 //ret type should be string | undefined
 //(correct) 2.5.3: string | undefined 
 //(incorrect) 2.6.1: { [K in keyof T]: MyType<T>[any] }[K] | undefined
 //(incorrect) @next: { [K in keyof T]: MyType<T>[any] }[K] | undefined
 const ret = myVal === true ? undefined : myVal;
 
 return ret;
 })

 return b;
}

Expected behavior:
myVal variable inferred type to be string | true
ret variable inferred type to be string | undefined
The code should compile since the return value of the function type and the return expression is the same

Actual behavior:
myVal variable inferred type is { [K in keyof T]: MyType<T>[any] }[K]
ret variable inferred type is { [K in keyof T]: MyType<T>[any] }[K] | undefined
The code does not compile since the return type does not match the return expression

[mhegazy]

That is another instance for awaited higher order type operator. #17077 and #21613 attempted to get that done, but eventually failed.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.