Make let variables fresh in each iteration of a for-loop.

test/mjsunit/harmony/block-for.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 84 matching lines @@
 // in a for-in statement with let variables.
 // TODO(ES6): properly activate extended mode
 assertThrows("function foo() { 'use strict'; for (let in {}) { } }", SyntaxError);
 assertThrows("function foo() { 'use strict'; for (let x = 3 in {}) { } }", SyntaxError);
 assertThrows("function foo() { 'use strict'; for (let x, y in {}) { } }", SyntaxError);
 assertThrows("function foo() { 'use strict'; for (let x = 3, y in {}) { } }", SyntaxError);
 assertThrows("function foo() { 'use strict'; for (let x, y = 4 in {}) { } }", SyntaxError);
 assertThrows("function foo() { 'use strict'; for (let x = 3, y = 4 in {}) { } }", SyntaxError);
 
 
-// In a normal for statement the iteration variable is not
+// In a normal for statement the iteration variable is
 // freshly allocated for each iteration.
 function closures1() {
   let a = [];
   for (let i = 0; i < 5; ++i) {
     a.push(function () { return i; });
   }
   for (let j = 0; j < 5; ++j) {
-    assertEquals(5, a[j]());
+    assertEquals(j, a[j]());
   }
 }
 closures1();
 
 
 function closures2() {
   let a = [], b = [];
   for (let i = 0, j = 10; i < 5; ++i, ++j) {
     a.push(function () { return i; });
     b.push(function () { return j; });
   }
   for (let k = 0; k < 5; ++k) {
-    assertEquals(5, a[k]());
-    assertEquals(15, b[k]());
+    assertEquals(k, a[k]());
+    assertEquals(k + 10, b[k]());
   }
 }
 closures2();
 
 
+function closure_in_for_init() {
+  let a = [];
+  for (let i = 0, f = function() { return i }; i < 5; ++i) {
+    a.push(f);
+  }
+  for (let k = 0; k < 5; ++k) {
+    assertEquals(0, a[k]());
+  }
+}
+closure_in_for_init();
+
+
+function closure_in_for_cond() {
+  let a = [];
+  for (let i = 0; a.push(function () { return i; }), i < 5; ++i) { }
+  for (let k = 0; k < 5; ++k) {
+    assertEquals(k, a[k]());
+  }
+}
+closure_in_for_next();
+
+
+function closure_in_for_next() {
+  let a = [];
+  for (let i = 0; i < 5; a.push(function () { return i; }), ++i) { }
+  for (let k = 0; k < 5; ++k) {
+    assertEquals(k + 1, a[k]());
+  }
+}
+closure_in_for_next();
+
+
 // In a for-in statement the iteration variable is fresh
 // for earch iteration.
 function closures3(x) {
   let a = [];
   for (let p in x) {
     a.push(function () { return p; });
   }
   let k = 0;
   for (let q in x) {
     assertEquals(q, a[k]());
     ++k;
   }
 }
 closures3({a : [0], b : 1, c : {v : 1}, get d() {}, set e(x) {}});