Make sure that names of temporaries do not clash with real variables.

R=mstarzinger@chromium.org
BUG=v8:2322

Review URL: https://codereview.chromium.org/11035054

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12668 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -4066,7 +4066,7 @@ class Internals {
   static const int kNullValueRootIndex = 7;
   static const int kTrueValueRootIndex = 8;
   static const int kFalseValueRootIndex = 9;
-  static const int kEmptySymbolRootIndex = 116;
+  static const int kEmptySymbolRootIndex = 117;
 
   static const int kJSObjectType = 0xaa;
   static const int kFirstNonstringType = 0x80;

src/heap.h

@@ -176,6 +176,7 @@ namespace internal {
   V(constructor_symbol, "constructor")                                   \
   V(code_symbol, ".code")                                                \
   V(result_symbol, ".result")                                            \
+  V(dot_for_symbol, ".for.")                                             \
   V(catch_var_symbol, ".catch-var")                                      \
   V(empty_symbol, "")                                                    \
   V(eval_symbol, "eval")                                                 \

src/parser.cc

@@ -2842,7 +2842,12 @@ Statement* Parser::ParseForStatement(ZoneStringList* labels, bool* ok) {
 
         // TODO(keuchel): Move the temporary variable to the block scope, after
         // implementing stack allocated block scoped variables.
-        Variable* temp = top_scope_->DeclarationScope()->NewTemporary(name);
+        Factory* heap_factory = isolate()->factory();
+        Handle<String> dot =
+            heap_factory->NewStringFromAscii(CStrVector(".for."));
+        Handle<String> tempstr = heap_factory->NewConsString(dot, name);
+        Handle<String> tempname = heap_factory->LookupSymbol(tempstr);
+        Variable* temp = top_scope_->DeclarationScope()->NewTemporary(tempname);
         VariableProxy* temp_proxy = factory()->NewVariableProxy(temp);
         ForInStatement* loop = factory()->NewForInStatement(labels);
         Target target(&this->target_stack_, loop);

src/scopes.h

@@ -189,7 +189,7 @@ class Scope: public ZoneObject {
   // Creates a new temporary variable in this scope.  The name is only used
   // for printing and cannot be used to find the variable.  In particular,
   // the only way to get hold of the temporary is by keeping the Variable*
-  // around.
+  // around.  The name should not clash with a legitimate variable names.
   Variable* NewTemporary(Handle<String> name);
 
   // Adds the specific declaration node to the list of declarations in

test/mjsunit/harmony/debug-blockscopes.js

@@ -376,7 +376,7 @@ listener_delegate = function(exec_state) {
                    debug.ScopeType.Global], exec_state);
   CheckScopeContent({x:'y'}, 0, exec_state);
   // The function scope contains a temporary iteration variable.
-  CheckScopeContent({x:'y'}, 1, exec_state);
+  CheckScopeContent({'.for.x':'y'}, 1, exec_state);
 };
 for_loop_1();
 EndTest();
@@ -401,7 +401,7 @@ listener_delegate = function(exec_state) {
   CheckScopeContent({x:3}, 0, exec_state);
   CheckScopeContent({x:'y'}, 1, exec_state);
   // The function scope contains a temporary iteration variable.
-  CheckScopeContent({x:'y'}, 2, exec_state);
+  CheckScopeContent({'.for.x':'y'}, 2, exec_state);
 };
 for_loop_2();
 EndTest();

test/mjsunit/regress/regress-2322.js

@@ -27,5 +27,10 @@
 
 // Flags: --harmony-scoping
 
+"use strict";
+
 assertThrows("'use strict'; for (let x in x);", ReferenceError);
 
+let s;
+for (let pppp in {}) {};
+assertThrows(function() { pppp = true }, ReferenceError);