Typescript Result like Rust

result.ts

export class Err<O, E extends Error> {
  readonly value: E

  constructor(value: E) {
    this.value = value
  }

  isOk(): this is Ok<O, E> {
    return false
  }

  isErr(): this is Err<O, E> {
    return true
  }

  unwrap(): never {
    throw this.value
  }

  unwrapOr<T>(defaultValue: T): T {
    return defaultValue
  }
}

export class Ok<O, E extends Error> {
  readonly value: O

  constructor(value: O) {
    this.value = value
  }

  isOk(): this is Ok<O, E> {
    return true
  }

  isErr(): this is Err<O, E> {
    return false
  }

  unwrap(): O {
    return this.value
  }

  unwrapOr<T>(_defaultValue: T): O {
    return this.value
  }
}

/**
 * A type that represents a result of a computation.
 * It can be either an `Ok` or an `Err`.
 *
 * @template O The type of the value if the computation is successful.
 * @template E The type of the error if the computation fails.
 */
export type Result<O, E extends Error> = Ok<O, E> | Err<O, E>

/**
 * A type that represents a result of a computation that returns a promise.
 * It can be either an `Ok` or an `Err`.
 *
 * @template O The type of the value if the computation is successful.
 * @template E The type of the error if the computation fails.
 */
export type PromiseResult<O, E extends Error> = Promise<Result<O, E>>

/**
 * Creates a new `Ok` result with the given value.
 *
 * @param value The value to wrap in the `Ok` result.
 * @returns A new `Ok` result with the given value.
 */
export const ok = <O, E extends Error>(value: O): Result<O, E> => {
  return new Ok(value)
}

/**
 * Creates a new `Err` result with the given value.
 *
 * @param value The value to wrap in the `Err` result.
 * @returns A new `Err` result with the given value.
 */
export const err = <O, E extends Error>(value: E): Result<O, E> => {
  return new Err(value)
}