Stack allocate lexical locals + hoist stack slots

test/mjsunit/es6/debug-blockscopes.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 480 matching lines @@
     debugger;
     let x = 1;
   }
 }
 
 listener_delegate = function(exec_state) {
   CheckScopeChain([debug.ScopeType.Block,
                    debug.ScopeType.Local,
                    debug.ScopeType.Script,
                    debug.ScopeType.Global], exec_state);
-  CheckScopeContent({}, 0, exec_state);
+  CheckScopeContent({x:undefined}, 0, exec_state);
 };
 uninitialized_1();
 EndTest();
+
+
+// Block scopes shadowing
+BeginTest("Block scopes shadowing 1");
+function shadowing_1() {
+  let i = 0;
+  {
+    let i = 5;
+    debugger;
+    assertEquals(27, i);
+  }
+  assertEquals(0, i);
+  debugger;
+  assertEquals(27, i);
+}
+
+listener_delegate = function (exec_state) {
+  exec_state.frame(0).evaluate("i = 27");
+}
+shadowing_1();
+EndTest();
+
+
+// Block scopes shadowing
+BeginTest("Block scopes shadowing 2");
+function shadowing_2() {
+  let i = 0;
+  {
+    let j = 5;
+    debugger;
+    assertEquals(27, j);
+  }
+  assertEquals(0, i);
+}
+
+listener_delegate = function (exec_state) {
+  exec_state.frame(0).evaluate("j = 27");
+}
+shadowing_2();
+EndTest();