Code is unsafe in many places

[benjamingr]

Hey,

There are many places in the codebase that make unsafe assumptions about types passed in, for example code does stuff like:

  andThen(f: any): any {
    return new ResultAsync(
      this._promise.then((res) => {
        if (res.isErr()) {
          return new Err<never, E>(res.error)
        }

        const newValue = f(res.value)
        return newValue instanceof ResultAsync ? newValue._promise : newValue
      }),
    )

For application code this is fine but for library code of a base abstractions many many things can go wrong here - for example .then can throw for a promsie subclass, res.isErr can throw is something that passes as a result is passed, instanceof can fail across realms and so on.

I would consider either:

• Hardening the code
• Changing the strategy to wrap hardened code (like native promises) instead

[janglad]

As for the throwing: maybe I'm missing something but is this not what fromPromise() and fromThrowable() is for? If Neverthrow were to catch errors here, should it return it as an Err? If so how would that be typed?