Exception class instead of struct

src/SymbolTable.hh

@@ -204,6 +204,7 @@ public:
     //! Was the previous declaration done with the same symbol type ?
     const bool same_type;
 
+  public:
     AlreadyDeclaredException(string name_arg, bool same_type_arg) : name(name_arg),
 								    same_type(same_type_arg)
     {