import { Promised } from "./utils";
declare global {
    interface Generator<T = unknown, TReturn = any, TNext = unknown> {
        /**
         * Returns the first element of a sequence.
         * @returns The first element in the specified sequence.
         */
        first(): T;
        /**
         * Returns the first element of a sequence, or undefined if the sequence contains no elements.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the specified sequence, or undefined if the sequence is empty.
         */
        first(allow_empty: "or-default"): T | undefined;
        /**
         * Returns the first element in a sequence that satisfies a specified condition.
         * @param predicate A function to test each element for a condition.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first(predicate: (item: T) => boolean): T;
        /**
         * Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
         * @param predicate A function to test each element for a condition.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first(predicate: (item: T) => boolean, allow_empty: "or-default"): T | undefined;
        /**
         * Returns the first element in a sequence that matches the type specified in the type checker.
         * @param predicate A function to test each element for a type.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first<TRes extends T>(predicate: (item: T) => item is TRes): TRes;
        /**
         * Returns the first element of the sequence that matches the type specified in the type checker or a default value if no such element is found.
         * @param predicate A function to test each element for a type.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first<TRes extends T>(predicate: (item: T) => item is TRes, allow_empty: "or-default"): TRes | undefined;
    }
    interface AsyncGenerator<T = unknown, TReturn = any, TNext = unknown> {
        /**
         * Returns the first element of a sequence.
         * @returns The first element in the specified sequence.
         */
        first(): Promise<T>;
        /**
         * Returns the first element of a sequence, or undefined if the sequence contains no elements.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the specified sequence, or undefined if the sequence is empty.
         */
        first(allow_empty: "or-default"): Promise<T | undefined>;
        /**
         * Returns the first element in a sequence that satisfies a specified condition.
         * @param predicate A function to test each element for a condition.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first(predicate: (item: T) => Promised<boolean>): Promise<T>;
        /**
         * Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
         * @param predicate A function to test each element for a condition.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first(predicate: (item: T) => Promised<boolean>, allow_empty: "or-default"): Promise<T | undefined>;
        /**
         * Returns the first element in a sequence that matches the type specified in the type checker.
         * @param predicate A function to test each element for a type.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first<TRes extends T>(predicate: (item: T) => item is TRes): Promise<TRes>;
        /**
         * Returns the first element of the sequence that matches the type specified in the type checker or a default value if no such element is found.
         * @param predicate A function to test each element for a type.
         * @param allow_empty Specify that the sequence may be empty.
         * @returns The first element in the sequence that passes the test in the specified predicate function.
         */
        first<TRes extends T>(predicate: (item: T) => item is TRes, allow_empty: "or-default"): Promise<TRes | undefined>;
    }
}