fixing tests for shifting constants into slots

lib/risc/instructions/reg_to_slot.rb

@@ -15,6 +15,7 @@ module Risc
 
   # Produce a RegToSlot instruction.
   # From and to are registers or symbols that can be transformed to a register by resolve_to_register
+  #     (which are precisely the symbols :message or :new_message. or a register)
   # index resolves with resolve_to_index.
   def self.reg_to_slot( source , from_reg , to , index )
     from = resolve_to_register from_reg

lib/risc/register_value.rb

@@ -86,7 +86,7 @@ module Risc
     return instance_name unless instance_name.is_a? Symbol
     real_name = clazz_name.to_s.split('_').last.capitalize.to_sym
     clazz = Parfait.object_space.get_class_by_name(real_name)
-    raise "Class name not given #{real_name}" unless clazz
+    raise "Class name not given #{real_name} #{clazz_name} #{instance_name}" unless clazz
     index = clazz.instance_type.variable_index( instance_name )
     raise "Instance name=#{instance_name} not found on #{real_name}:#{clazz.instance_type}" unless index.is_a?(Numeric)
     return index #  the type word is at index 0, but type is a list and starts at 1 == type