Better typings for Promise.all(), like #31117

[jablko]

Fixes#22469
Fixes#28427
Fixes#31722

[msftclas]

All CLA requirements met.

[Luxcium]

as in my issue comment in #37526

Update

My problem is solved with the nightly version of typescript but I will leave it there in case it can be useful for something or someone

"typescript": "3.9.0-dev.20200324"

I have placed a copy of this resolved problem in #33055 and in #33707 hoping it can be helpful and not too spammy ...

Issue now fixed

I have a similar problem and I don't know if I should open a different issue ...

"typescript": "3.8.3"

// Promise.all(this.fork) take a T1[] where T1 is a Promise<number>// and return a Promise<T2[]> where T2 is a number// therefore T1 and T2 are not both «T»

exportclassMyMaybeList<T=any>{privateconstructor(values: T[]){this.values=values;}privatevalues: T[];// get =======================================================-| fork() |-====publicgetfork(): T[]{returnthis.values!=null ? this.values.slice() : [].slice();}// public =====================================================-| map() |-====publicmap<R=any>(fn: (val: T,index: number,array: T[])=>R): MyMaybeList<R>{returnMyMaybeList.of(...this.values.map(fn));}// static ======================================================-| of() |-====publicstaticof<TVal>(...val: TVal[]): MyMaybeList<TVal>{if(val==null||!val.length)returnnewMyMaybeList<TVal>([]);returnnewMyMaybeList<TVal>([...val]);}// async =====================================================-| will() |-====publicasyncwill/* <R> */()/* : Promise<MyMaybeList<R>> */{// Promise.all(this.fork) take a T1[] where T1 is Promise<number>// and return a Promise<T2[]> where T2 is a number// therefore T1 and T2 are not both «T»console.log(this.fork);constwillThen=Promise.all(this.fork);constthenWill=awaitwillThen;returnMyMaybeList.of(...thenWill);}}

constoneToTen=MyMaybeList.of(1,2,3,4,5,6,7,8,9,10);constpowersOneToTen=oneToTen.map(asyncval=>val*val);// "log->" powersOneToTen: MyMaybeList<Promise<number>>console.log(powersOneToTen);// "log->" awaitedList: MyMaybeList<Promise<number>>// instead of a -> MyMaybeList{Promise<number>}// in fact is a -> Promise{MyMaybeList<number>}constawaitedPowersOneToTen=powersOneToTen.will/* <unnknow> */();awaitedPowersOneToTen.then(awaitedList=>console.log(awaitedList));// Promise{<pending>} will resolve into ->console.log(awaitedPowersOneToTen);

/* // Promise.all(this.fork) take a T1[] where T1 is Promise<number> // and return a Promise<T2[]> where T2 is a number // therefore T1 and T2 are not both «T» // console.log(this.fork); will display same as console.log(powersOneToTen);// console.log(powersOneToTen); ->// "log->" powersOneToTen: MyMaybeList<Promise<number>>MyMaybeList{ values: [ Promise{1 }, Promise{4 }, Promise{9 }, Promise{16 }, Promise{25 }, Promise{36 }, Promise{49 }, Promise{64 }, Promise{81 }, Promise{100 } ]}// console.log(awaitedPowersOneToTen); ->// "log ->" awaitedPowersOneToTen: Promise<MyMaybeList<Promise<number>>>Promise{<pending>}// Promise{<pending>} will resolve into ->// awaitedPowersOneToTen.then(awaitedList => console.log(awaitedList)); ->// console.log(awaitedList) ->// "log->" awaitedList: MyMaybeList<Promise<number>>// instead of a -> MyMaybeList{Promise<number>}// in fact is a (should be) -> Promise{MyMaybeList<number>}MyMaybeList{ values: [ 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 ]}*/

[Luxcium]

Now that #37610 has reverted the awaited type I don't know what to do I have posted an example above but my real-life situation is as follow :

I was relying on this solution because I have a Promise<MaybeList<Promise<ISymbolSearchResult[]>>>
where MaybeList is an array abstraction so I am using promise.all to remove the inner Promise I don't know what to do now to avoid using as unknown as MaybeList<ISymbolSearchResult[]> inside of my async function (which should be returning the Promise<MaybeList<ISymbolSearchResult[]>> instead of the Promise<MaybeList<Promise<ISymbolSearchResult[]>>>)

[jakebailey]

All of the issues this PR links are closed; I think that this all was handled in 4.5 with Awaited.

I'm going to close this, but am happy to reopen if I'm mistaken.