Use prepared accessors to retrieve Data fields

Data types are initialized with a set of accessors for the
requested fields, which allows caching those accessors and
avoiding costly hash lookups for future accesses. Due to a bug in
how these accessors are initialized, parent and subclasses may
have a different view of how those fields are stored in the object.

Here, the cached accessors are iterated, but then not used to read
the field. This results in a second field being created for the
subclass, in a different order from definition time. Using the
original accessor here accesses the correct field.

Fixes jruby#9241.

Note that there's other problems with the data layout inside a Data
type and other fixes will be needed to clean up how these accessors
are allocated and shared with subclasses.

Author: headius

core/src/main/java/org/jruby/RubyData.java

@@ -123,7 +123,7 @@ public static void initialize(ThreadContext context, IRubyObject self, IRubyObje
             String keyString = toSymbol(context, k).idString();
             VariableAccessor variableAccessor = variableAccessors.get(keyString);
             if (variableAccessor != null) {
-                selfObj.setInternalVariable(keyString, v);
+                variableAccessor.set(self, v);
             } else {
                 RubyArray unknownKeywords = unknownKeywordsPtr[0];
                 if (unknownKeywords == null) {