/**
 * Deep equality with NaN-safety and cycle detection.
 *
 * - `NaN === NaN` is false in JavaScript, so the previous `Object.is`
 *   tail correctly handled that case but only at the leaf — a
 *   `[NaN, NaN]` pair compared element-by-element worked, but compound
 *   structures relied on the tail. The new shape preserves that.
 * - Circular references used to send isDeepEqual into infinite recursion
 *   (`a.self = a; isDeepEqual(a, a)` blew the stack). A WeakSet of
 *   already-visited objects breaks the cycle and treats two structurally
 *   identical cycles as equal.
 */
export declare function isDeepEqual(value1: any, value2: any, seen?: WeakMap<object, object>): boolean;