TypeScript error: Initializer of instance member variable cannot reference identifier declared in the constructor.

In a TypeScript application we are building, we have code similar to the following:

	public processAllOrders = () => {
	system.log("process orders");
	var that = this;
	all([
	this.processOrder(),
	this.processPayment()
	]).then(function (results) {
	that.Orders=results;
	system.log("All orders processed!");
	});
	};

view raw processAllOrders.ts hosted with ❤ by GitHub

However when we try to run this, TypeScript complains with the following error message:

Error      19           Initializer of instance member variable 'processAllOrders' cannot reference identifier 'that' declared in the constructor.             

I think it’s a bug in TypeScript as I don’t see any reason why this shouldn’t work.