Method key

packages/effect/src/Optic.ts:523–523

* Focuses on a property of the current struct/tuple focus. * * **Details** * * - On a Lens, returns a Lens. * - On an Optional, returns an Optional. * - Does **not** work on union types (compile error). * * **Example** (Drilling into nested structs) * *

(
    this: Lens<S, A>,
    key: Key,
    ..._err: ForbidUnion<A, "cannot use `key` on a union type">
  )

   * ```
   */
  key<S, A extends object, Key extends keyof A>(
    this: Lens<S, A>,
    key: Key,
    ..._err: ForbidUnion<A, "cannot use `key` on a union type">