Typesafe providers for Angular 2

safeProvide.ts

export class SafeToken<T> {
    constructor(private name: string){}

    toString() {
        return `Token ${this.name}`
    }
}

export function safeProvide<T>(token:SafeToken<T>) {

    return {
        useClass<U extends T>(Klass:{new(...args:any[]):U;}) {
            return {provide: token, useClass: Klass};
        },

        useValue<U extends T>(value:U) {
            return {provide: token, useValue: value};
        },

        useFactory<U extends T>(factory:(...args:any[]) => U) {
            return {provide: token, useFactory: factory};
        }
    };
}