1 files changed, 28 insertions, 0 deletions
diff --git a/tool/lrama/lib/lrama/grammar/code/no_reference_code.rb b/tool/lrama/lib/lrama/grammar/code/no_reference_code.rb
new file mode 100644
index 0000000000..6e614cc64a
--- /dev/null
+++ b/tool/lrama/lib/lrama/grammar/code/no_reference_code.rb
@@ -0,0 +1,28 @@
+module Lrama
+  class Grammar
+    class Code
+      class NoReferenceCode < Code
+        private
+
+        # * ($$) error
+        # * (@$) error
+        # * ($:$) error
+        # * ($1) error
+        # * (@1) error
+        # * ($:1) error
+        def reference_to_c(ref)
+          case
+          when ref.type == :dollar # $$, $n
+            raise "$#{ref.value} can not be used in #{type}."
+          when ref.type == :at # @$, @n
+            raise "@#{ref.value} can not be used in #{type}."
+          when ref.type == :index # $:$, $:n
+            raise "$:#{ref.value} can not be used in #{type}."
+          else
+            raise "Unexpected. #{self}, #{ref}"
+          end
+        end
+      end
+    end
+  end
+end