Uncaught compiler error: Block-scoped variable from import used before its declaration.

TypeScript Version: 2.4.0 / nightly (2.5.0-dev.201xxxxx)

Code

Input Typescript

namespace A {
    export namespace B {
        export class C {
            constructor()
            {
                console.log("Hello World");
            }
        }
    }
}

import myA_B = myA.B;
import myA = A;

new myA_B.C();

Output JavaScript from tsc

var A;
(function (A) {
    var B;
    (function (B) {
        var C = (function () {
            function C() {
                console.log("Hello World");
            }
            return C;
        }());
        B.C = C;
    })(B = A.B || (A.B = {}));
})(A || (A = {}));
var myA_B = myA.B;
var myA = A;
new myA_B.C();

Expected behavior:
Expected the typescript compiler error Block-scoped variable 'myA' used before its declaration.

Actual behavior:
Runtime error of Uncaught TypeError: Cannot read property 'B' of undefined

Comments
The typescript compiler will catch this if I use const or let keywords instead, so I expected the same error handling for import in this case.

My team prefers using import over const or let when we can for performance of not pulling in javascript code from external files when we are only referencing types.

Beginne damit, den gemeldeten TypeScript 2.4-Fall mit tsc zu reproduzieren und ihn mit der im Issue beschriebenen const- oder let-Variante zu vergleichen. Verfolge, wie der Compiler den Import-Alias und seinen referenzierten Namespace vor der Deklaration behandelt. Fertig ist die Arbeit, wenn der gemeldete Code die erwartete Diagnose zur Compile-Zeit erhält, statt JavaScript zu erzeugen, das zur Laufzeit fehlschlägt.