Extension of my previous gist specialized for RxJS

better-rxjs-pipe.ts

type UnaryFunction<T, R> = (source: T) => R;

type Identity = <T>(source: T) => T;

type Pipe<T, L = void, R extends UnaryFunction<any, any>[] = []> =
    T extends []
        ? R
        : L extends void
            ? T extends [(_: infer P) => infer V, ...infer Rest]
                ? Pipe<Rest, V, [...R, UnaryFunction<P, V>]>
                : never[]
            : T extends [(_: L) => infer V, ...infer Rest]
                ? Pipe<Rest, V, [...R, UnaryFunction<L, V>]>
                : never[]
;

type Compose<A> =
    A extends []
        ? Identity
        : A extends [UnaryFunction<infer S, infer V>]
            ? UnaryFunction<S, V>
            : A extends [UnaryFunction<infer S, any>, ...UnaryFunction<any, any>[], UnaryFunction<any, infer V>]
                ? UnaryFunction<S, V>
                : never
;

type Valid<A> = A extends UnaryFunction<any, any>[] ? Pipe<A> extends never[] ? never[] : A : never[];

declare function pipe<A extends UnaryFunction<any, any>[]>(...fns: Valid<A>): Compose<Pipe<A>>;

pipe(
    (_: string) => 0,
    (_: number) => "",
    (_: string) => true,
);