No compile error thrown when `this` referenced before call to `super` completes

TypeScript Version:

1.8.9

Code JSFiddle: https://jsfiddle.net/kitsonk/fs9t96ep/ TS Playground: http://goo.gl/X7cgvV

class A {
    constructor(fn: () => void) {
        fn.call(this);
    }
    foo: string = 'foo';
}

class B extends A {
    constructor() {
        super(() => {
            console.log(this);
        });
    }
    bar: string = 'bar';
}

const b = new B();

Expected behavior: Typescript should guard against the use of this as the call to super has not completed. Thus it should not compile.

Actual behavior: Typescript compiles this successfully. It works fine when the target is set to es5 but breaks the browser when target is set to es6. Error is: VM89:55 Uncaught ReferenceError: this is not defined

[zemlanin]

One more case (https://gist.github.com/zemlanin/a306e8498d05c923cac405c047014029):

// this.ts
class A {
    constructor(protected cb: () => void) { }
}

class Greeter extends A {
    constructor() {
        // ^ there should be `var _this = this;`
        super(() => { this })
    }
}

// compiled_with_ts2_0_10.js
var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
var A = (function () {
    function A(cb) {
        this.cb = cb;
    }
    return A;
}());
var Greeter = (function (_super) {
    __extends(Greeter, _super);
    function Greeter() {
        var _this = this;
        // ^ there should be `var _this = this;`
        _super.call(this, function () { _this; });
    }
    return Greeter;
}(A));

// compiled_with_ts2_1_1.js
var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
var A = (function () {
    function A(cb) {
        this.cb = cb;
    }
    return A;
}());
var Greeter = (function (_super) {
    __extends(Greeter, _super);
    function Greeter() {
        return
        // ^ there should be `var _this = this;`
        _super.call(this, function () { _this; }) || this;
    }
    return Greeter;
}(A));

[kitsonk]

Just a note on this, the emit in master (TS 2.1) now breaks these examples in ES5 at run-time, so this now has parity. It still does not warn you that it is invalid.

Given:

class A {
    constructor(fn: () => void) {
        fn.call(this);
    }
    foo: string = 'foo';
}

class B extends A {
    constructor() {
        super(() => {
            console.log(this);
        });
    }
    bar: string = 'bar';
}

The emit is…

Version 2.1.0-dev.20161103

var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
var A = (function () {
    function A(fn) {
        this.foo = 'foo';
        fn.call(this);
    }
    return A;
}());
var B = (function (_super) {
    __extends(B, _super);
    function B() {
        var _this = _super.call(this, function () {
            console.log(_this);
        }) || this;
        _this.bar = 'bar';
        return _this;
    }
    return B;
}(A));

Version 2.0.6

var __extends = (this && this.__extends) || function (d, b) {
    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
    function __() { this.constructor = d; }
    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
var A = (function () {
    function A(fn) {
        this.foo = 'foo';
        fn.call(this);
    }
    return A;
}());
var B = (function (_super) {
    __extends(B, _super);
    function B() {
        var _this = this;
        _super.call(this, function () {
            console.log(_this);
        });
        this.bar = 'bar';
    }
    return B;
}(A));