// @module: commonjs // @filename: map.ts import { Observable } from "observable" (Observable.prototype).map = function() { } declare module "observable" { interface Observable { map(proj: (e:T) => U): Observable } namespace Observable { let someAnotherValue: number; } } // @filename: observable.d.ts declare module "observable" { class Observable { filter(pred: (e:T) => boolean): Observable; } namespace Observable { let someValue: number; } } // @filename: main.ts /// import { Observable } from "observable" import "./map"; let x: Observable; let y = x.map(x => x + 1);