diff --git a/lib/risc/builder.rb b/lib/risc/builder.rb
index 26b5b54b..2e210da9 100644
--- a/lib/risc/builder.rb
+++ b/lib/risc/builder.rb
@@ -24,6 +24,27 @@ module Risc
       @source_used = false
     end
 
+    # Infer the type from a symbol. In the simplest case the symbol is the class name.
+    # But in building, sometimes variations are needed, so next_message or caller work
+    # too (and both return "Message")
+    # A general "_reg"/"_obj"/"_const" or "_tmp" at the end of the name will be removed
+    # An error is raised if the symbol/object can not be inferred
+    def infer_type( name )
+      as_string = name.to_s
+      parts = as_string.split("_")
+      if( ["reg" , "obj" , "tmp" , "self" , "const", "1" , "2"].include?( parts.last ) )
+        parts.pop
+        as_string = parts.join("_")
+      end
+      as_string = "word" if as_string == "name"
+      as_string = "message" if as_string == "next_message"
+      as_string = "message" if as_string == "caller"
+      sym = as_string.camelise.to_sym
+      clazz = Parfait.object_space.get_class_by_name(sym)
+      raise "Not implemented/found object #{name}:#{sym}" unless clazz
+      return clazz.instance_type
+    end
+
     def if_zero( label )
       @source_used = true
       add_code Risc::IsZero.new(@source , label)
diff --git a/test/risc/test_builder2.rb b/test/risc/test_builder2.rb
new file mode 100644
index 00000000..1b56fc79
--- /dev/null
+++ b/test/risc/test_builder2.rb
@@ -0,0 +1,51 @@
+require_relative "../helper"
+
+module Risc
+  class TestBuilderInfer < MiniTest::Test
+
+    def setup
+      Parfait.boot!(Parfait.default_test_options)
+      Risc.boot!
+      method = FakeCallable.new
+      @compiler = Risc::MethodCompiler.new( method, SlotMachine::Label.new( "source_name", "return_label") )
+      @builder  = @compiler.builder(method)
+    end
+    def test_list
+      assert_equal :List , @builder.infer_type(:list).class_name
+    end
+    def test_name
+      assert_equal :Word , @builder.infer_type(:name).class_name
+    end
+    def test_word
+      assert_equal :Word , @builder.infer_type(:word).class_name
+    end
+    def test_caller
+      assert_equal :Message , @builder.infer_type(:caller).class_name
+    end
+    def test_caller_reg
+      assert_equal :Message , @builder.infer_type(:caller_reg).class_name
+    end
+    def test_caller_tmp
+      assert_equal :Message , @builder.infer_type(:caller_tmp).class_name
+    end
+    def test_caller_obj
+      assert_equal :Message , @builder.infer_type(:caller_obj).class_name
+    end
+    def test_caller_const
+      assert_equal :Message , @builder.infer_type(:caller_const).class_name
+    end
+    def test_caller_self
+      assert_equal :Message , @builder.infer_type(:caller_self).class_name
+    end
+    def test_caller_1
+      assert_equal :Message , @builder.infer_type(:caller_1).class_name
+    end
+    def test_message
+      assert_equal :Message , @builder.infer_type(:message).class_name
+    end
+    def test_next_message
+      assert_equal :Message , @builder.infer_type(:next_message).class_name
+    end
+
+  end
+end