TypeScript Class: TypeScript types by structure(, not inheritance?)

sample.ts

class Hoge{
	constructor(public x:number,public y:number){}
}

class Fuga{
	constructor(x:number,y:number){}
	x:number;
	y:number;
}
function f(v:Fuga){
	console.log(v.x+":"+v.y);
}

var h = new Hoge(10,29);
f(h);