`AsyncIterableX#pipe` completely ignores types.

[jeengbe]

IxJS version: 7.0.0

Code to reproduce: https://codesandbox.io/p/sandbox/typescript-playground-export-forked-9jmsj9?workspaceId=ws_TdkXAMqyc14LovZfzuJaP6

import { AsyncIterableX, from } from "ix/asynciterable";
import { tap } from "ix/asynciterable/operators";
import {
  MonoTypeOperatorAsyncFunction,
  MonoTypeOperatorFunction,
} from "ix/interfaces";
import { IterableX } from "ix/iterable";

declare const sync: IterableX<number>;
declare const async: AsyncIterableX<number>;
declare const syncOp: MonoTypeOperatorFunction<string>;
declare const asyncOp: MonoTypeOperatorAsyncFunction<string>;

sync.pipe(syncOp);
//        ~~~~~~ Errors, as it should
async.pipe(asyncOp);
//         ^^^^^^^ No error!

// Demo, will crash at runtime
from([1, 2, 3]).pipe(tap((val: string) => val.length));

Expected behavior: The function signature should prevent piping an AsyncIterable<number> into an operator that expects string. The attached code demonstrates how this could end up bad.

Actual behavior: According to TS, the expression is a-ok for async iterables. Note that it works as intended for sync iterables.

Additional information:

[trxcllnt]

Thanks for the report, this definitely seems odd. What version of typescript are you using?

Minor annoyance in that the sync.pipe() call is decaying to the WritableStream case:

No overload matches this call.
  The last overload gave the following error.
    Argument of type 'MonoTypeOperatorFunction<string>' is not assignable to parameter of type 'WritableStream'.ts(2769)

But at least TS is inferring the OperatorFunction<T, R> correctly:

In the AsyncIterable case, it's decaying to OperatorAsyncFunction<any, any>, and I'm not sure why:

We've been through a few TS upgrades since these signatures were written, there may be a better way to write this now. I'll investigate.