fix for-head duplication testing and replacement - fixes #162

lib/6to5/transformation/transformers/let-scoping.js

@@ -145,11 +145,25 @@ LetScoping.prototype.noClosure = function () {
 
   if (_.isEmpty(replacements)) return;
 
-  traverse(block, function (node, parent) {
+  var replace = function (node, parent) {
     if (!t.isIdentifier(node)) return;
     if (!t.isReferenced(node, parent)) return;
     node.name = replacements[node.name] || node.name;
-  });
+  };
+
+  var traverseReplace = function (node, parent) {
+    replace(node, parent);
+    traverse(node, replace);
+  };
+
+  var forParent = this.forParent;
+  if (forParent) {
+    traverseReplace(forParent.right, forParent);
+    traverseReplace(forParent.test, forParent);
+    traverseReplace(forParent.update, forParent);
+  }
+
+  traverse(block, replace);
 };
 
 /**
@@ -181,10 +195,23 @@ LetScoping.prototype.getInfo = function () {
     keys:        []
   };
 
+  var duplicates = function (id, key) {
+    var has = scope.parentGet(key);
+
+    if (has && has !== id) {
+      // there's a variable with this exact name in an upper scope so we need
+      // to generate a new name
+      opts.duplicates[key] = id.name = file.generateUid(key, scope);
+    }
+  };
+
   _.each(opts.declarators, function (declar) {
     opts.declarators.push(declar);
 
-    var keys = t.getIds(declar);
+    var keys = t.getIds(declar, true);
+    _.each(keys, duplicates);
+    keys = _.keys(keys);
+
     opts.outsideKeys = opts.outsideKeys.concat(keys);
     opts.keys = opts.keys.concat(keys);
   });
@@ -193,14 +220,7 @@ LetScoping.prototype.getInfo = function () {
     if (!isLet(declar)) return;
 
     _.each(t.getIds(declar, true), function (id, key) {
-      var has = scope.parentGet(key);
-
-      if (has && has !== id) {
-        // there's a variable with this exact name in an upper scope so we need
-        // to generate a new name
-        opts.duplicates[key] = id.name = file.generateUid(key, scope);
-      }
-
+      duplicates(id, key);
       opts.keys.push(key);
     });
   });

test/fixtures/transformation/let-scoping/exec-block-scoped/exec.js

@@ -0,0 +1,6 @@
+let x = 1;
+{
+  let x = 2;
+  assert.equal(x, 2);
+}
+assert.equal(x, 1);

test/fixtures/transformation/let-scoping/exec-for-loop-head/exec.js

@@ -0,0 +1,5 @@
+assert.equal((function(){
+  let a = 1;
+  for (let a = 0; a < 8; a++) {}
+  return a;
+}()), 1);