decorators.js

//while a **decorator** is what's used by Babel/Typescript:

import * as di from './annotations';

const Inject = (...dependencies) => {
  return (classDef) => {
    di.annotate(classDef,new di.Inject(dependencies))
  }
}

const Provide = (targetClassDef) => {
  return (classDef) => {
    di.annotate(classDef, new di.Provide(targetClassDef));
  }
}

export {Provide, Inject}

tldr.js

//angular2 (and di.js) use Annotations - *not* decorators.

//source of the DI.js *annotation* looks like: 
class Inject {
  constructor(...tokens) {
    this.tokens = tokens;
    this.isPromise = false;
    this.isLazy = false;
  }
}
//used like
@Inject(SomeDep)
class SomeServiceThing {
  constructor(someDep){
    
  }
}

//which in *traceur* compiles down to
function SomeServiceThing(someDep){}
SomeServiceThing.annotations = [new Inject(someDep)];