/**
 * Immutably assigns or adds (if it doesn't exist) the specified key and value to the input object
 *
 * @since v0.0.1
 * @category Object
 * @template {T} - The type of the input object
 * @param {T} obj - The object on which to assign the key
 * @param {TValues} values - The object with values to assign to the original object
 * @returns {T | TValues | T & TValues | object}
 * @example
 * assign({ x: 'x' }, { x: 'assign' }) //=> { x: 'assign' }
 * assign({ x: 'x' }, { y: 'assign' }) //=> { x: 'x', y: 'assign' }
 * assign({}, { x: 'assign' })         //=> { x: 'assign' }
 * assign(null, { x: 'assign' })       //=> { x: 'assign' }
 * assign([], { x: 'assign' })         //=> { x: 'assign' }
 */
export declare const assign: <T = Record<string, unknown>, TValues = Record<string, unknown>>(obj: T, values: TValues) => Record<string, unknown> | T | TValues | (T & TValues);