Unable to infer types from callback in bindCallback function for RxJS #22952
Description
Currently type inference is unable to provide useful type inference for functions such as RxJS's bindCallback.
I have a PR here (ReactiveX/rxjs#3480) that tries to add overloads to support the desired behavior, but when I test it, it does not infer types properly.
TypeScript Version: @latest as of this moment
Search Terms: callback type inference, wrapping node callbacks, variadic arguments
Code
export function bindCallback(callbackFunc: (callback: () => any) => any, scheduler?: SchedulerLike): () => Observable<void>;
export function bindCallback<R1>(callbackFunc: (callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): () => Observable<R1>;
export function bindCallback<R1, R2>(callbackFunc: (callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): () => Observable<[R1, R2]>;
export function bindCallback<R1, R2, R3>(callbackFunc: (callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): () => Observable<[R1, R2, R3]>;
export function bindCallback<A1>(callbackFunc: (arg1: A1, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<void>;
export function bindCallback<A1, R1>(callbackFunc: (arg1: A1, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<R1>;
export function bindCallback<A1, R1, R2>(callbackFunc: (arg1: A1, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<[R1, R2]>;
export function bindCallback<A1, R1, R2, R3>(callbackFunc: (arg1: A1, callback: (res1: R1, res2: R2, res3: R3) => any) => any, scheduler?: SchedulerLike): (arg1: A1) => Observable<[R1, R2, R3]>;
export function bindCallback<A1, A2>(callbackFunc: (arg1: A1, arg2: A2, callback: () => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<void>;
export function bindCallback<A1, A2, R1>(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<R1>;
export function bindCallback<A1, A2, R1, R2>(callbackFunc: (arg1: A1, arg2: A2, callback: (res1: R1, res2: R2) => any) => any, scheduler?: SchedulerLike): (arg1: A1, arg2: A2) => Observable<[R1, R2]>;
function foo(a: number, b: number, callback: (c: string, d: string) => any): any {
setTimeout(() => callback(a + '!', b + '!');
}
const source = bindCallback(foo)(1, 3);Expected behavior:
source should be Observable<[string, string]>
Actual behavior:
source is Observable<void>
Related Issues: