/**
 * Returns `true` if `value` is an instance of the class identified by `type` (and optionally `ctor`).
 *
 * @remarks
 * Performs three checks in order: `instanceof ctor`, `Symbol.hasInstance`, then constructor-name
 * comparison. The constructor-name fallback handles cross-realm cases where `instanceof` fails.
 *
 * @typeParam T - The expected instance type.
 * @param value - The value to test.
 * @param type - The constructor name to compare against when `instanceof` is unavailable.
 * @param ctor - Optional constructor to use for `instanceof` and `Symbol.hasInstance` checks.
 * @returns `true` when `value` is an instance of the class described by `type`/`ctor`.
 */
export declare const isInstanceOf: <T>(value: unknown, type: string, ctor?: new (...args: any[]) => T) => value is T;
/**
 * Returns `true` if `value` is an `Error` instance or satisfies the `Error` duck-type shape.
 *
 * @remarks
 * Returns `false` for `undefined` and `null` — the `Error` contract requires an actual instance.
 *
 * @param value - The value to test.
 * @returns `true` when `value` conforms to the `Error` shape.
 */
export declare const isError: (value: unknown) => value is Error;
/**
 * Type guard to check if a value is a plain object (not null, not array)
 * @param value - The value to check
 * @returns True if the value is a plain object, false otherwise
 */
export declare const isObject: (value: unknown) => value is {
    [key: string]: unknown;
};