/** Asserts that value is `boolean` or `null | undefined`. Converts `Boolean` instance to `boolean`. */
export declare function expectBooleanOrNil(maybeBoolean: any): boolean;
/** Asserts that value is `number` or `null | undefined`. Converts `Number` instance to `number`. */
export declare function expectNumberOrNil(maybeNumber: any): number;
/** Asserts that value is `string` or `null | undefined`. Converts `String` instance to `string`. */
export declare function expectStringOrNil(maybeString: any): string;
/** Check if target is a promise */
export declare function isPromise<T = unknown>(target: unknown): target is Promise<T>;