utils

export interface Placeholder<A = unknown, E = never, R = never> {
  readonly [PlaceholderTypeId]: {
    readonly _R: (_: never) => R
    readonly _E: (_: never) => E
    readonly _A: (_: never) => A
  }
}

export type Any<A = any> =
  | Placeholder<A, any, any>
  | Placeholder<A, never, any>
  | Placeholder<A>
  | Placeholder<A, any>
  | Effect.Effect<A, any, any>
  // Null/Undefined cannot be modified globally to make them placeholders
  | ([A] extends [null] ? null : never)
  | ([A] extends [undefined] ? undefined : never)

export type Context<T> = [T] extends [never]
  ? never
  : T extends Effect.Effect<infer _A, infer _E, infer R>
    ? R
    : T extends Placeholder<infer _A, infer _E, infer R>
      ? R
      : never

export type Error<T> = [T] extends [never]
  ? never
  : T extends Effect.Effect<infer _A, infer E, infer _R>
    ? E
    : T extends Placeholder<infer _A, infer E, infer _R>
      ? E
      : never

export type Success<T> = [T] extends [never]
  ? never
  : T extends Effect.Effect<infer A, infer _E, infer _R>
    ? A
    : T extends Placeholder<infer A, infer _E, infer _R>
      ? A
      : never

export declare const PlaceholderTypeId: typeof PlaceholderTypeId

export type PlaceholderTypeId = typeof PlaceholderTypeId