exportdeclareconstnotDefined: <T>(x?: T | undefined) => x is undefined;
exportdeclareconstnotDef: <T>(x?: T | undefined) => x is undefined;
exportdeclareconstisDefined: <T>(x?: T | undefined) => x is T;
exportdeclareconstisDef: <T>(x?: T | undefined) => x is T;