Do not specify explicit type parameters. Signatures with type parameters that cannot be inferred will be removed in v8.

[huan]

When we start using typed-emitter, the event name is string literal instead of string, which will run into The way fromEvent checks if the first argument passed is an emitter or not is incorrect

Minimum Reproducible Code

import { EventEmitter } from 'events'
import TypedEventEmitter  from 'typed-emitter'

import { fromEvent } from 'rxjs'

interface Events {
  foo: (n: number) => void
  bar: (s: string) => void
}

const TypedEmitter = EventEmitter as new () => TypedEventEmitter<Events>
const emitter = new TypedEmitter()

fromEvent(emitter, 'foo')
// Error: Type 'TypedEventEmitter<Events>' is not assignable to type 'JQueryStyleEventEmitter'.

Related Discussion

1. rxjs fromEvent compatibility rxjs fromEvent compatibility andywer/typed-emitter#9
2. Proposal: Statically typed fromEvent Proposal: Statically typed fromEvent ReactiveX/rxjs#4891
3. typed-emitter compatibility typed-emitter compatibility devanshj/rxjs-from-emitter#4

To be fixed.

Update June 1, 2021

With RxJS 7.1, we can remove any but still get unknown.

It seems that the fromEvent still not be able to infer from on/off.

Update Nov 7, 2021

Have sent a PR for fixing this issue to RxJS:

• fix(fromEvent): infer from Node.js EventEmitter with types ReactiveX/rxjs#6669

Related issues

• Infer class type from keyof class type microsoft/TypeScript#37384