`this` context inside directive functions are undefined, should be bound to definition object

[pocesar]

In Typescript, you can define a directive like this (since angular.directive doesn't support constructors like controller, service, etc):

module stuff {
  export class MyDirective implements ng.IDirective {
     restrict = 'A';
     constructor(public injectSome: ngSome.injectSome) {}
     link(){
        this.injectSome(); // this is undefined
     }
     static instance(){
       return ['injectSome', (injectSome) => new this(injectSome)];
     }
  }
  angular.module('stuff', []).directive('myDirective', MyDirective.instance());
}

the link, compile, template and templateUrl functions should be called within the directive definition object context. this will make constructors work as they should.

Typescript enforces good practices and modularization, so you can even test stuff decoupled from angular itself (through the classes definitions), don't ruin the fun for us :)

(also happening on filters)

[rodyhaddad]

I'm certain that compile, template and templateUrl get called with their this being the directive definition object (although a bit modified with default fields that weren't specified, like priority)

The exception is link which doesn't preserve its this because it's actually a simplified form of compile (see code).
I'm personally okay with creating an extra function just to preserve the context, for people using TypeScript or CoffeeScript.

Feel free to send a PR for review. There's always a higher chance of it landing if there's code ready to be merged

[pocesar]

@rodyhaddad check the PR for this issue

[wesleycho]

Given that #9306 landed, this issue can be closed.