Class inherits a class defined just below fails in js side but no error shown in ts side

[TadasPa]

TS:

class A extends B { }
class B { }
// no TS errors here

JS:

var A = (function (_super) {
        __extends(A, _super);
        function A() {
            _super.apply(this, arguments);
        }
        return A;
    })(B);
var B = (function () {
        function B() {
        }
        return B;
    })();

When "__extends(A, _super);" is called "_super" is not defined yet and it's prototype, of course. I guess TS side should complain or JS should be reordered.

[RyanCavanaugh]

There are about eleventybillion dupes on this but I thought we had fixed this already. Vlad says we can probably use isBlockScopedNameDeclaredBeforeUse to implement this very cheaply.

[drake7707]

Also see #4341

[mhegazy]

closing in favor of #5207