In JS, constructor functions without property assignments aren't recognised as classes

[mjbvz]

TypeScript Version: 2.5.1

Code

For the JS:

function Foo() {
	this.init();
}

Foo.prototype.init = function () {
	// code
}

const a = new Foo();
a.init()

Expected behavior:
In the function Foo, this is the type of Foo and you can run go to definition on this.init

Actual behavior:
this is any. go to definition does not work on this.init but does on a.init

[AlCalzone]

I believe I'm running into a similar issue:

function Foo() {
	if (!(this instanceof Foo)) return new Foo();
	
	this.method1 = (abc) => {
		console.log(abc);
	};
	this.method1();

	this.method2 = () => {
		this.method1();
	};
}

method1 and method2 are correctly detected as properties of Foo:

However, inside the constructor and the methods, this is any and so is this.method1. Thus calling method1 with no parameters is not detected as an error.