Swich identifiers to byte[]

* JAVA_STRING_TYPE and related change to IDENTIFIER
* TruffleRuby still uses java.lang.String

Fixes ruby#4009

Author: headius

templates/java/org/ruby_lang/prism/Loader.java.erb

@@ -1,4 +1,4 @@
-<%- string_type = Prism::Template::JAVA_STRING_TYPE -%>
+<%- string_type = Prism::Template::JAVA_IDENTIFIER_TYPE -%>
 package org.ruby_lang.prism;
 
 import java.lang.Short;
@@ -31,7 +31,7 @@ public class Loader {
         <%- if string_type == "String" -%>
         return new String(bytes, encodingCharset).intern();
         <%- else -%>
-        return null; // Must be implemented by subclassing Loader
+        return bytes; // Must be implemented by subclassing Loader
         <%- end -%>
     }
 
@@ -229,7 +229,7 @@ public class Loader {
     private <%= string_type %>[] loadConstants() {
         int length = loadVarUInt();
         if (length == 0) {
-            return Nodes.EMPTY_STRING_ARRAY;
+            return Nodes.EMPTY_IDENTIFIER_ARRAY;
         }
         <%= string_type %>[] constants = new <%= string_type %>[length];
         for (int i = 0; i < length; i++) {
@@ -395,7 +395,7 @@ public class Loader {
         int bufferPosition = buffer.position();
         int serializedLength = buffer.getInt();
         // Load everything except the body and locals, because the name, receiver, parameters are still needed for lazily defining the method
-        Nodes.DefNode lazyDefNode = new Nodes.DefNode(<%= base_params.join(", ") -%>, -bufferPosition, this, loadConstant(), loadOptionalNode(), (Nodes.ParametersNode) loadOptionalNode(), null, Nodes.EMPTY_STRING_ARRAY);
+        Nodes.DefNode lazyDefNode = new Nodes.DefNode(<%= base_params.join(", ") -%>, -bufferPosition, this, loadConstant(), loadOptionalNode(), (Nodes.ParametersNode) loadOptionalNode(), null, Nodes.EMPTY_IDENTIFIER_ARRAY);
         buffer.position(bufferPosition + serializedLength); // skip past the serialized DefNode
         return lazyDefNode;
     }

templates/java/org/ruby_lang/prism/Nodes.java.erb

@@ -1,4 +1,4 @@
-<%- string_type = Prism::Template::JAVA_STRING_TYPE -%>
+<%- string_type = Prism::Template::JAVA_IDENTIFIER_TYPE -%>
 package org.ruby_lang.prism;
 
 import java.lang.Override;
@@ -16,7 +16,7 @@ import java.util.Arrays;
 // @formatter:off
 public abstract class Nodes {
 
-    public static final <%= string_type %>[] EMPTY_STRING_ARRAY = {};
+    public static final <%= string_type %>[] EMPTY_IDENTIFIER_ARRAY = {};
 
     @Target(ElementType.FIELD)
     @Retention(RetentionPolicy.SOURCE)

templates/template.rb

@@ -12,7 +12,7 @@ module Template # :nodoc: all
     CHECK_FIELD_KIND = ENV.fetch("CHECK_FIELD_KIND", false)
 
     JAVA_BACKEND = ENV["PRISM_JAVA_BACKEND"] || "truffleruby"
-    JAVA_STRING_TYPE = JAVA_BACKEND == "jruby" ? "org.jruby.RubySymbol" : "String"
+    JAVA_IDENTIFIER_TYPE = JAVA_BACKEND == "truffleruby" ? "String" : "byte[]"
     INCLUDE_NODE_ID = !SERIALIZE_ONLY_SEMANTICS_FIELDS || JAVA_BACKEND == "jruby"
 
     COMMON_FLAGS_COUNT = 2
@@ -272,7 +272,7 @@ def call_seq_type
       end
 
       def java_type
-        JAVA_STRING_TYPE
+        JAVA_IDENTIFIER_TYPE
       end
     end
 
@@ -292,7 +292,7 @@ def call_seq_type
       end
 
       def java_type
-        JAVA_STRING_TYPE
+        JAVA_IDENTIFIER_TYPE
       end
     end
 
@@ -312,7 +312,7 @@ def call_seq_type
       end
 
       def java_type
-        "#{JAVA_STRING_TYPE}[]"
+        "#{JAVA_IDENTIFIER_TYPE}[]"
       end
     end