[turbofan] Fix broken dynamic TDZ check for let and const.

test/mjsunit/regress/regress-4388.js

Index: test/mjsunit/regress/regress-4388.js
diff --git a/test/mjsunit/regress/regress-4388.js b/test/mjsunit/regress/regress-4388.js
new file mode 100644
index 0000000000000000000000000000000000000000..908bcccb4e0ed4614223b77908a94897e42df533
--- /dev/null
+++ b/test/mjsunit/regress/regress-4388.js
@@ -0,0 +1,35 @@
+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --turbo-filter=test*
+
+// Tests that TurboFan emits a dynamic hole-check for the temporal dead zone at
+// a non-initializing assignments to a {let} variable.
+function test_hole_check_for_let(a) {
+  'use strict';
+  { switch (a) {
+      case 0: let x;
+      case 1: x = 9;
+    }
+  }
+}
+assertDoesNotThrow("test_hole_check_for_let(0)");
+assertThrows("test_hole_check_for_let(1)", ReferenceError);
+%OptimizeFunctionOnNextCall(test_hole_check_for_let)
+assertThrows("test_hole_check_for_let(1)", ReferenceError);
+
+// Tests that TurboFan emits a dynamic hole-check for the temporal dead zone at
+// a non-initializing assignments to a {const} variable.
+function test_hole_check_for_const(a) {
+  'use strict';
+  { switch (a) {
+      case 0: const x = 3;
+      case 1: x = 2;
+    }
+  }
+}
+assertThrows("test_hole_check_for_const(0)", TypeError);
+assertThrows("test_hole_check_for_const(1)", ReferenceError);
+%OptimizeFunctionOnNextCall(test_hole_check_for_const)
+assertThrows("test_hole_check_for_const(1)", ReferenceError);