rivo/Ary/IsReadonly.d.ts

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import type { Ary } from ".";
import type { Args, Fn } from "../HKT";
import type { AssertBool } from "../helpers";

/**
 * Check if an {@link Ary} (i.e., `Array` or `ReadonlyArray`) is readonly.
 *
 * Sig: `(a: Ary) => boolean`
 *
 * @example
 * ```typescript
 * type R1 = IsReadonly<string[]>;
 * //   ^?: false
 * type R2 = IsReadonly<readonly number[]>;
 * //   ^?: true
 * type R3 = IsReadonly<["foo", "bar"]>;
 * //   ^?: false
 * type R4 = IsReadonly<readonly [42, 1337, ...string[]]>;
 * //   ^?: true
 * ```
 */
export type IsReadonly<A extends Ary> = AssertBool<A extends unknown[] ? false : true>;

/**
 * [Fn] Check if an {@link Ary} (i.e., `Array` or `ReadonlyArray`) is readonly.
 *
 * Sig: `(a: Ary) => boolean`
 */
export default interface IsReadonlyFn extends Fn<[Ary], boolean> {
  def: ([a]: Args<this>) => IsReadonly<typeof a>;
}