Missing this reference for function declaration instead of fat arrow functions

[CSchulz]

TypeScript Version: 2.0.10 / 2.0.2 / 2.1.5

Code
http://plnkr.co/edit/ZQONYB5oaLhO8aVRaLjE?p=preview

    this.service.getData().subscribe(
      function(x) {
        this.data = x;
      });

    this.service.getData().subscribe(
      (x) => {
         this.data = x;
      });

// transpiled output
    App.prototype.ngOnInit = function () {
        this.service.getData().subscribe(function (x) {
            this.data = x;
        });
    };

    App.prototype.ngOnInit = function () {
        var _this = this;
        this.service.getData().subscribe(function (x) {
            _this.data = x;
        });
    };

Expected behavior:
It should make no difference between function or fat arrow function.

Actual behavior:
Missing this reference. var _this = this; for the function

// transpiled output
    App.prototype.ngOnInit = function () {
        var _this = this;
        this.service.getData().subscribe(function (x) {
            _this.data = x;
        });
    };

[sandersn]

There is a difference between function and =>, which is that function binds this and => does not. Can you explain which line of the transpiled output you expected to be different?

[CSchulz]

I think you mean the other way around, right? => binds this to a variable.

I have updated the description.

It seems it was a misunderstanding of fat arrow. I thought it is the same as function, just another way to write it.
https://basarat.gitbooks.io/typescript/content/docs/arrow-functions.html told me something else.

[sandersn]

Sorry, I was talking about the Javascript standard, not the code that Typescript emits. In Javascript,

function () {
  this;
  function () {
    this; // not the same as the outer this
  }
}

the two this references are different because function binds a fresh this that is basically an implicit parameter to the function. => does not:

function () {
  this;
  () => this; // SAME as outer this;
}

The _this = this that Typescript emits is a workaround since it has to emit function in old JS versions that don't have =>.