Protect map from accessing illegal keys

Author: mgreter

ast.cpp

@@ -8,6 +8,8 @@
 namespace Sass {
   using namespace std;
 
+  static Null sass_null(Sass::Null(ParserState("null")));
+
   bool Compound_Selector::operator<(const Compound_Selector& rhs) const
   {
     To_String to_string;
@@ -587,5 +589,12 @@ namespace Sass {
     return result;
   }*/
 
+  Expression* Hashed::at(Expression* k) const
+  {
+    if (elements_.count(k))
+    { return elements_.at(k); }
+    else { return &sass_null; }
+  }
+
 }
 

ast.hpp

@@ -210,9 +210,10 @@ namespace Sass {
     size_t length() const                  { return list_.size(); }
     bool empty() const                     { return list_.empty(); }
     bool has(Expression* k) const          { return elements_.count(k) == 1; }
-    Expression* at(Expression* k) const    { return elements_.at(k); }
+    Expression* at(Expression* k) const;
     bool has_duplicate_key() const         { return duplicate_key_ != 0; }
     Expression* get_duplicate_key() const  { return duplicate_key_; }
+    const unordered_map<Expression*, Expression*> elements() { return elements_; }
     Hashed& operator<<(pair<Expression*, Expression*> p)
     {
       reset_hash();