Update rule hash implementation

src/compiler/rules/string.cpp

@@ -2,6 +2,7 @@
 #include "transition_map.h"
 
 using std::string;
+using std::hash;
 
 namespace tree_sitter  {
     namespace rules {
@@ -12,6 +13,10 @@ namespace tree_sitter  {
             return (other != NULL) && (other->value == value);
         }
                 
+        size_t String::hash_code() const {
+            return typeid(this).hash_code() ^ hash<string>()(value);
+        }
+        
         string String::to_string() const {
             return string("#<string '") + value + "'>";
         }