Throw a TypeError if RDATA is called on a non data holder.

Author: aardvark179

lib/truffle/truffle/cext.rb

@@ -1778,6 +1778,7 @@ def rb_tr_log_warning(message)
   end
 
   def RDATA(object)
+    raise TypeError unless Truffle::CExt.hidden_variable_get(object, :data_holder)
     RData.new(object)
   end