1 files changed, 13 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/basic/letTDZEffectful.js b/js/src/jit-test/tests/basic/letTDZEffectful.js
new file mode 100644
index 000000000..62245d8c1
--- /dev/null
+++ b/js/src/jit-test/tests/basic/letTDZEffectful.js
@@ -0,0 +1,13 @@
+function assertThrowsReferenceError(f) {
+  var e = null;
+  try {
+    f();
+  } catch (ex) {
+    e = ex;
+  }
+  assertEq(e instanceof ReferenceError, true);
+}
+
+// TDZ is effectful, don't optimize out x.
+assertThrowsReferenceError(function () { x; let x; });
+assertThrowsReferenceError(function () { x; const x = undefined; });