/**
 * Make an assertion that actual is not null or undefined.
 * If not then throw.
 *
 * @example Usage
 * ```ts ignore
 * import { assertExists } from "mod.ts";
 *
 * assertExists("something"); // Doesn't throw
 * assertExists(undefined); // Throws
 * ```
 *
 * @typeParam T The type of the actual value.
 * @param actual The actual value to check.
 * @param msg The optional message to include in the error if the assertion fails.
 */
export declare function assertExists<T>(
  actual: T,
  msg?: string,
): asserts actual is NonNullable<T>;