//// [extension.ts] interface I { x; } interface I { y; } declare module M { export class C { public p:number; } } declare module M { export extension class C { public pe:string; } } var c=new M.C(); c.pe; c.p; var i:I; i.x; i.y; //// [extension.js] var c = new M.C(); c.pe; c.p; var i; i.x; i.y;