console.info(fnc()); // this is fine
console.info(new Cls()); //TypeError: Cls is not a constructor
function fnc(){
  return "value"
}
class Cls {
  constructor(){
    //...
  }
}

// one.ts
import {Two} from "./two"
class One {
  static two = new One();
}
// two.ts
import {One} from "./one"
class One {
  static two = new One(); //TypeError: One is not a function 
}
//main.ts
import {One} from "./one"
import {Two} from "./two"
console.info(One.two) 
console.info(Two.one)

// cached.ts
export function Cached(target,key,desc){
    var initializer = desc.get;
    desc.get = function(){
        return Object.defineProperty(this,key,{
            value:initializer()
        })[key];
    };
    return desc;
}
// one.ts
import {Cached} from "./cached";
import {Two} from "./two";
export class One {
    @Cached
    static get two():Two{
        return new Two()
    }
}
// two.ts
import {Cached} from "./cached";
import {One} from "./one";
export class Two {
    @Cached
    static get one():One{
        return new One();
    }
}
//main.ts
import {One} from "./one"
import {Two} from "./two"
console.info(One.two) 
console.info(Two.one)

function Model(target){}
function Collection(target){}
function Field(target:any,key:any,desc?:any):any{
    var type:any = Reflect.getMetadata("design:type",target,key);
    document.write(`<pre>${target.constructor.name}.${key} : ${type?type.name:"<span style='color: red'>UNDEFINED ?</span>"}</pre>`);
}

@Model
export class User {
    @Field id:String;
    @Field name:String;
    @Field projects:Projects; // Project Is not defined yet
}

@Collection
export class Users extends Array<User> {}

@Model
export class Project {
    @Field id:String;
    @Field name:String;
    @Field author:User;
    @Field contributors:Users; // Users will not be defined 
                               // if we will change definition order
}

@Collection
export class Projects extends Array<Project>{}