add a way to bend the type for register_value

specifically for factories, where we know the type of next_object even it is not specified

lib/risc/register_value.rb

@@ -21,12 +21,10 @@ module Risc
     # for an XX instance
     def initialize( reg , type , extra = {})
       extra = {} unless extra
-      raise "Not Hash #{extra}"  unless extra.is_a?(Hash)
-      type = Parfait.object_space.get_type_by_class_name(type) if type.is_a?(Symbol)
-      raise "No type #{reg}" unless type
-      @type = type
-      @symbol = reg
       @extra = extra
+      @symbol = reg
+      raise "Not Hash #{extra}"  unless extra.is_a?(Hash)
+      known_type(type)
     end
 
     def class_name
@@ -42,6 +40,16 @@ module Risc
       self
     end
 
+    # basically set the type with the given symbol. Symbol is resolved to type
+    # just like in constructor
+    # return self for chaining
+    def known_type( type )
+      type = Parfait.object_space.get_type_by_class_name(type) if type.is_a?(Symbol)
+      raise "No type #{type} for #{self}" unless type
+      @type = type
+      self
+    end
+
     # using the registers type, resolve the slot to an index
     # Using the index and the register, add a SlotToReg to the instruction
     def resolve_and_add(slot , compiler)