TypeScript Version: 2.3.2

Code

function fn(): void {}
export type MyType = number;

when compiled with a default tsconfig.json emits

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
function fn() {
}

Expected behavior:

It should not emit

Object.defineProperty(exports, "__esModule", { value: true });

if exports is not emitted in the compiled module.

Actual behavior:

Object.defineProperty(...) is emitted even if exports is not defined for the compiled module. When this code is loaded in a browser, it will throw an exception: Uncaught ReferenceError: exports is not defined.

If the MyType type declaration in the above code is not exported, then Object.defineProperty(...) is not emitted.