Statically check for assignments to const in harmony mode.

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 8a47fb9bede5fcd80e89e010334f1e0ccad414b7..05ce9cabfd13b006d935984c60b176fc485fcf0f 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -2689,6 +2689,7 @@ Expression* Parser::ParseAssignmentExpression(bool accept_IN, bool* ok) {
     // Assignment to eval or arguments is disallowed in strict mode.
     CheckStrictModeLValue(expression, "strict_lhs_assignment", CHECK_OK);
   }
+  MarkAsUsedAsLValue(expression);
 
   Token::Value op = Next();  // Get assignment operator.
   int pos = scanner().location().beg_pos;
@@ -2922,6 +2923,7 @@ Expression* Parser::ParseUnaryExpression(bool* ok) {
       // Prefix expression operand in strict mode may not be eval or arguments.
       CheckStrictModeLValue(expression, "strict_lhs_prefix", CHECK_OK);
     }
+    MarkAsUsedAsLValue(expression);
 
     int position = scanner().location().beg_pos;
     return new(zone()) CountOperation(isolate(),
@@ -2957,6 +2959,7 @@ Expression* Parser::ParsePostfixExpression(bool* ok) {
       // Postfix expression operand in strict mode may not be eval or arguments.
       CheckStrictModeLValue(expression, "strict_lhs_prefix", CHECK_OK);
     }
+    MarkAsUsedAsLValue(expression);
 
     Token::Value next = Next();
     int position = scanner().location().beg_pos;
@@ -4315,6 +4318,15 @@ Handle<String> Parser::ParseIdentifierName(bool* ok) {
 }
 
 
+void Parser::MarkAsUsedAsLValue(Expression* expression) {
+  VariableProxy* lhs = expression != NULL
+      ? expression->AsVariableProxy()
+      : NULL;
+
+  if (lhs != NULL) lhs->MarkAsUsedAsLValue();
+}
+
+
 // Checks LHS expression for assignment and prefix/postfix increment/decrement
 // in strict mode.
 void Parser::CheckStrictModeLValue(Expression* expression,