export declare function asDefined<T>(value: T | undefined, message?: string, details?: object): NonNullable<T>;
export declare function asInstanceofError<T>(value: T): Error;
export declare function isTrue(value: boolean, message?: string, details?: object): asserts value is true;
export declare function isFalse(value: boolean, message?: string, details?: object): asserts value is false;
export declare function isNever(_: never): never;
export declare function isInstanceofError<T>(value: T | Error): asserts value is Error;
export declare function isDefined<T>(value: T | undefined, message?: string, details?: object): asserts value is NonNullable<T>;
export declare function isUndefined<T>(value: T | undefined, message?: string, details?: object): asserts value is undefined;