Store rule metadata as a map, not a single number

Need to store more than just boolean values

src/compiler/rules/metadata.cc

@@ -6,9 +6,10 @@
 namespace tree_sitter  {
     using std::hash;
     using std::make_shared;
+    using std::map;
 
     namespace rules {
-        Metadata::Metadata(rule_ptr rule, MetadataValue value) : rule(rule), value(value) {}
+        Metadata::Metadata(rule_ptr rule, map<MetadataKey, int> values) : rule(rule), value(values) {}
 
         bool Metadata::operator==(const Rule &rule) const {
             auto other = dynamic_cast<const Metadata *>(&rule);
@@ -16,7 +17,12 @@ namespace tree_sitter  {
         }
 
         size_t Metadata::hash_code() const {
-            return hash<int>()(value);
+            size_t result = hash<size_t>()(value.size());
+            for (auto &pair : value) {
+                result ^= hash<int>()(pair.first);
+                result ^= hash<int>()(pair.second);
+            }
+            return result;
         }
 
         rule_ptr Metadata::copy() const {

src/compiler/rules/metadata.h

@@ -2,18 +2,19 @@
 #define COMPILER_RULES_METADATA_H_
 
 #include <string>
+#include <map>
 #include "compiler/rules/rule.h"
 
 namespace tree_sitter  {
     namespace rules {
         typedef enum {
-            NONE = 0,
-            START_TOKEN = 1,
-        } MetadataValue;
+            START_TOKEN,
+            PRECEDENCE
+        } MetadataKey;
 
         class Metadata : public Rule {
         public:
-            Metadata(rule_ptr rule, MetadataValue value);
+            Metadata(rule_ptr rule, std::map<MetadataKey, int> value);
 
             bool operator==(const Rule& other) const;
             size_t hash_code() const;
@@ -22,7 +23,7 @@ namespace tree_sitter  {
             void accept(Visitor *visitor) const;
 
             const rule_ptr rule;
-            const MetadataValue value;
+            const std::map<MetadataKey, int> value;
         };
     }
 }