import { mtp, tl } from '@mtcute/tl';
export declare function isPresent<T>(t: T | undefined | null | void): t is T;
/**
 * Returns a function that can be used to filter down objects
 * to the ones that have a specific value V under a key `k`.
 *
 * @example
 * ```ts
 * type File = { type: "image", imageUrl: string } | { type: "pdf", pdfUrl: string };
 * const files: File[] = [];
 *
 * const imageFiles = files.filter(file => file.type === "image");
 * files[0].type // In this case, TS will still treat it  as `"image" | "pdf"`
 *
 * const filesWithUrl = files.filter(hasValueKey("type", "image" as const));
 * files[0].type // TS will now know that this is "image"
 * files[0].imageUrl // TS will know this is present, because already it excluded the other union members.
 * ```
 */
export declare function hasValueAtKey<const K extends string | number | symbol, const V>(k: K, v: V): <T>(a: T & {
    [k in K]: unknown;
}) => a is T & {
    [k in K]: V;
};
export declare function assertTypeIs<T extends tl.TlObject, K extends T['_']>(context: string, obj: T, expected: K): asserts obj is tl.FindByName<T, K>;
export declare function assertTypeIsNot<T extends tl.TlObject, K extends T['_']>(context: string, obj: T, expectedNot: K): asserts obj is Exclude<T, tl.FindByName<T, K>>;
export declare function mtpAssertTypeIs<T extends mtp.TlObject, K extends T['_']>(context: string, obj: T, expected: K): asserts obj is mtp.FindByName<T, K>;
export declare function assertTrue(context: string, cond: boolean): asserts cond;
export declare function isTlRpcError(obj: unknown): obj is mtp.RawMt_rpc_error;