Infer whether a variable is assigned

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index fd0dd2913eacd62897b64fa7af4b54461a773bdb..d5893fdcdac87b6b4304c60a5ada9788d1734e6c 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -452,11 +452,10 @@ void ParserTraits::CheckPossibleEvalCall(Expression* expression,
 }
 
 
-Expression* ParserTraits::MarkExpressionAsLValue(Expression* expression) {
-  VariableProxy* proxy = expression != NULL
-      ? expression->AsVariableProxy()
-      : NULL;
-  if (proxy != NULL) proxy->MarkAsLValue();
+Expression* ParserTraits::MarkExpressionAsAssigned(Expression* expression) {
+  VariableProxy* proxy =
+      expression != NULL ? expression->AsVariableProxy() : NULL;
+  if (proxy != NULL) proxy->set_is_assigned();
   return expression;
 }
 
@@ -1715,6 +1714,8 @@ void Parser::Declare(Declaration* declaration, bool resolve, bool* ok) {
       Expression* expression = NewThrowTypeError(
           "var_redeclaration", name, declaration->position());
       declaration_scope->SetIllegalRedeclaration(expression);
+    } else if (mode == VAR) {
+      var->set_maybe_assigned();
     }
   }