[es6] Handle conflicts for sloppy let

test/mjsunit/harmony/block-let-semantics-sloppy.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 67 matching lines @@
 TestAll('f(); let x; function f() { x++; }');
 TestAll('f(); const x = 1; function f() { return x; }');
 
 TestAll('f()(); let x; function f() { return function() { return x + 1; } }');
 TestAll('f()(); let x; function f() { return function() { x = 1; } }');
 TestAll('f()(); let x; function f() { return function() { x += 1; } }');
 TestAll('f()(); let x; function f() { return function() { ++x; } }');
 TestAll('f()(); let x; function f() { return function() { x++; } }');
 TestAll('f()(); const x = 1; function f() { return function() { return x; } }');
 
-// Use before initialization with a dynamic lookup.
-TestAll('eval("x + 1;"); let x;');
-TestAll('eval("x = 1;"); let x;');
-TestAll('eval("x += 1;"); let x;');
-TestAll('eval("++x;"); let x;');
-TestAll('eval("x++;"); let x;');
-TestAll('eval("x"); const x = 1;');
+for (var kw of ['let', 'const']) {
+  // Use before initialization with a dynamic lookup.
+  TestAll(`eval("x"); ${kw} x = 2;`);
+  TestAll(`eval("x + 1;"); ${kw} x = 2;`);
+  TestAll(`eval("x = 1;"); ${kw} x = 2;`);
+  TestAll(`eval("x += 1;"); ${kw} x = 2;`);
+  TestAll(`eval("++x;"); ${kw} x = 2;`);
+  TestAll(`eval("x++;"); ${kw} x = 2;`);
 
-// Use before initialization with check for eval-shadowed bindings.
-TestAll('function f() { eval("var y = 2;"); x + 1; }; f(); let x;');
-// TODO(arv): https://code.google.com/p/v8/issues/detail?id=4284
-// TestAll('function f() { eval("var y = 2;"); x = 1; }; f(); let x;');
-TestAll('function f() { eval("var y = 2;"); x += 1; }; f(); let x;');
-TestAll('function f() { eval("var y = 2;"); ++x; }; f(); let x;');
-TestAll('function f() { eval("var y = 2;"); x++; }; f(); let x;');
+  // Use before initialization with check for eval-shadowed bindings.
+  TestAll(`function f() { eval("var y = 2;"); x + 1; }; f(); ${kw} x = 2;`);
+  TestAll(`function f() { eval("var y = 2;"); x = 1; }; f(); ${kw} x = 2;`);
+  TestAll(`function f() { eval("var y = 2;"); x += 1; }; f(); ${kw} x = 2;`);
+  TestAll(`function f() { eval("var y = 2;"); ++x; }; f(); ${kw} x = 2;`);
+  TestAll(`function f() { eval("var y = 2;"); x++; }; f(); ${kw} x = 2;`);
+}
 
 // Test that variables introduced by function declarations are created and
 // initialized upon entering a function / block scope.
 function f() {
   {
     assertEquals(2, g1());
     assertEquals(2, eval("g1()"));
 
     // block scoped function declaration
     function g1() {
@@ skipping 66 matching lines @@
     }
     eval("1 + 1");
     return x + inner();
   }
 
   let x = 1;
   return middle();
 }
 
 assertEquals(2, outer());