interface Thenable<R> {
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>, onRejected?: (error: any) => U | Thenable<U>): Thenable<U>;
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>, onRejected?: (error: any) => void): Thenable<U>;
}

declare class Promise<R> implements Thenable<R> {
    constructor(callback: (resolve: (value?: R | Thenable<R>) => void, reject: (error?: any) => void) => void);
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>, onRejected?: (error: any) => U | Thenable<U>): Promise<U>;
    then<U>(onFulfilled?: (value: R) => U | Thenable<U>, onRejected?: (error: any) => void): Promise<U>;
    catch<U>(onRejected?: (error: any) => U | Thenable<U>): Promise<U>;
}