export declare function merge<A extends object, B extends object, C extends object>(target: A, source: [B, C], options?: merge.Options): A & B & C;
export declare function merge<A extends object, B extends object, C extends object, D extends object>(target: A, source: [B, C, D], options?: merge.Options): A & B & C & D;
export declare function merge<A extends object, B extends object, C extends object, D extends object, E extends object>(target: A, source: [B, C, D, E], options?: merge.Options): A & B & C & D & E;
export declare function merge<A, B, C, D, F>(target: A, source: [B, C, D, F], options?: merge.Options): A & B & C & D & F;
export declare function merge<A extends object, B extends object>(target: A, source: B, options?: merge.Options): A & B;
/**
 * @namespace
 */
export declare namespace merge {
    type CallbackFn = (value: any, ctx: CallbackContext) => boolean;
    interface CallbackContext {
        source: any;
        target: any;
        key: string | symbol | number;
        path: string;
    }
    interface Options {
        /**
         * Optional variable that determines the depth of an operation or inclusion behavior.
         *
         * - If set to `true`, it enables a deep operation for only plain objects and arrays. Non-plain objects (class instances) are assigned by reference.
         * - If set to `'full'`, it enables a deep operation for all objects, including classes, excluding built-in objects.
         * - If assigned a `NodeCallback` function, it provides a custom callback mechanism for handling the operation.
         *
         * This variable can be used to define the level of depth or customization for a given process.
         * @default false
         */
        deep?: boolean | 'full' | CallbackFn;
        /**
         * Indicates whether symbol keys should be included.
         * If set to `true`, properties with symbol keys will be considered.
         * If `false` or `undefined`, symbol keys will be ignored.
         * @default true
         */
        symbolKeys?: boolean;
        /**
         * Specifies the behavior for merging arrays during a particular operation.
         *
         * When set to `true`, all array elements will be deeply merged, preserving all duplicates.
         * When set to `'unique'`, only unique elements will be preserved in the merged array.
         * If a callback function (`CallbackFn`) is provided, it determines the custom merging logic for the arrays.
         */
        mergeArrays?: boolean | 'unique' | CallbackFn;
        /**
         * Determines whether to retain pre-existing values.
         * If set to `true`, existing entities are preserved without modification.
         * If set to `false`, existing entities may be replaced or overridden by new ones.
         * Alternatively, can be assigned a callback function (`CallbackFn`) that dynamically resolves whether to keep existing entities based on custom logic.
         */
        keepExisting?: boolean | CallbackFn;
        /**
         * A boolean flag that determines whether property descriptors
         * should be copied when transferring properties from one object
         * to another.
         *
         * If set to true, both the value and descriptor metadata
         * (e.g., writable, configurable, enumerable) of a property
         * will be copied. If set to false or undefined, only the
         * property values will be copied, without preserving descriptor
         * details.
         *
         * This is typically used when needing to retain detailed control
         * over property attributes during object manipulation.
         */
        copyDescriptors?: boolean;
        /**
         * Ignores the source field if callback returns true
         */
        ignoreSource?: CallbackFn;
        /**
         * Ignore fields which values are "undefined"
         * @default true
         */
        ignoreUndefined?: boolean;
        /**
         * Ignore fields which values are "null"
         * @default false
         */
        ignoreNulls?: boolean;
        /**
         * Ignores both target and source field if callback returns true
         */
        filter?: CallbackFn;
    }
}