refactor a bit for upcoming delegations

must get method to be private
more tell, not ask

test/mom/instruction/helper.rb

@@ -2,6 +2,11 @@ require_relative '../helper'
 
 module Mom
   class CompilerMock
+    # resolve a symbol to a type. Allowed symbols are :frame , :receiver and arguments
+    # which return the respective types, otherwise nil
+    def resolve_type( name )
+        return nil
+    end
     def use_reg( type )
       Risc.tmp_reg(type , nil)
     end