entry.ts

// 実行方法
// $ tsc --module commonjs *.ts
// $ node entry.js

import Vector2 = require("./Vector2");
import Vector3 = require("./Vector3");

var a = new Vector2(0, 0);
console.log(a.toVector3(1));

var b = new Vector3(0, 0, 1);
console.log(b.toVector2());

result.txt

{ x: 0, y: 0, z: 1 }

/Users/omochi/temp/test5/Vector3.js:9
        return new Vector2(this.x, this.y);
               ^
TypeError: object is not a function
    at Vector3.toVector2 (/Users/omochi/temp/test5/Vector3.js:9:16)
    at Object.<anonymous> (/Users/omochi/temp/test5/entry.js:8:15)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3

Vector2.ts

import Vector3 = require("./Vector3");
class Vector2 {
	constructor(public x: number, public y: number){

	}
	toVector3(z: number): Vector3{
		return new Vector3(this.x, this.y, z);
	}
}
export = Vector2;

Vector3.ts

import Vector2 = require("./Vector2");
class Vector3 {
	constructor(public x: number, public y: number, public z: number){

	}
	toVector2(): Vector2 {
		return new Vector2(this.x, this.y);
	}
}
export = Vector3;