Function discriminators

packages/effect/src/internal/matcher.ts:398–427

(field: D)

/** @internal */
export const discriminators = <D extends string>(field: D) =>
<
  R,
  Ret,
  P extends
    & {
      readonly [Tag in Types.Tags<D, R> & string]?:
        | ((_: Extract<R, Record<D, Tag>>) => Ret)
        | undefined
    }
    & { readonly [Tag in Exclude<keyof P, Types.Tags<D, R>>]: never }
>(
  fields: P
) => {
  const predicate = makeWhen(
    (arg: any) => arg != null && arg[field] in fields,
    (data: any) => (fields as any)[data[field]](data)
  )

  return <I, F, A, Pr>(
    self: Matcher<I, F, R, A, Pr, Ret>
  ): Matcher<
    I,
    Types.AddWithout<F, Extract<R, Record<D, keyof P>>>,
    Types.ApplyFilters<I, Types.AddWithout<F, Extract<R, Record<D, keyof P>>>>,
    A | ReturnType<P[keyof P] & {}>,
    Pr,
    Ret
  > => (self as any).add(predicate)
}

/** @internal */
export const discriminatorsExhaustive: <D extends string>(