Utility Functions for Changing Effect Types in TypeScript

export namespace EffectUtility {
  /**
   * Changes the success type of the effect to the specified type.
   *
   * Suitable in cases where effect will succeed with one
   * of the specified success types.
   */
  export const withSuccessType = <S>() => <A extends S, E, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R> => self

  /**
   * Changes the error type of the effect to the specified type.
   * It will not throw a type error if effect has `never` error type.
   *
   * Suitable in cases where effect will either never fail or will
   * fail with one of the specified error types (including `never`).
   */
  export const withErrorType = <K>() => <A, E extends K, R>(self: Effect.Effect<A, E, R>): Effect.Effect<A, E, R> => self

  /**
   * Changes the error type of the effect to the specified type.
   * It will throw a type error if effect has `never` error type.
   *
   * Suitable in cases where effect will always fail with the specified
   * error type and the error type is not `never`.
   */
  export const withExplicitErrorType = <K>() => <A, E extends K & (K extends E ? unknown : never), R>(self: Effect.Effect<A, E, R> & (E extends K ? unknown : never)): Effect.Effect<A, K, R> => self

  /**
   * Changes the context type of the effect to the specified type.
   * It will throw a type error if context type does not match the specified type.
   *
   * Suitable in cases where effect will always require the specified context type.
   */
  export const withContextType = <C>() => <A, E, R extends C & (C extends R ? unknown : never)>(self: Effect.Effect<A, E, R> & (R extends C ? unknown : never)): Effect.Effect<A, E, C> => self
}