4 files changed, 39 insertions, 9 deletions
diff --git a/lib/psych.rb b/lib/psych.rb
index 16602ef..59f9712 100644
--- a/lib/psych.rb
+++ b/lib/psych.rb
@@ -218,13 +218,6 @@ module Psych
     @domain_types[key] = [key, block]
   end
 
-  def self.add_ruby_type type_tag, &block
-    warn "#{caller[0]}: add_ruby_type is deprecated, use add_domain_type" if $VERBOSE && !caller[0].start_with?(File.dirname(__FILE__))
-    domain = 'ruby.yaml.org,2002'
-    key = ['tag', domain, type_tag].join ':'
-    @domain_types[key] = [key, block]
-  end
-
   def self.remove_type type_tag
     @domain_types.delete type_tag
   end
@@ -241,6 +234,5 @@ module Psych
     attr_accessor :dump_tags
     attr_accessor :domain_types
   end
-
   # :startdoc:
 end
diff --git a/lib/psych/deprecated.rb b/lib/psych/deprecated.rb
index 093f145..b306b85 100644
--- a/lib/psych/deprecated.rb
+++ b/lib/psych/deprecated.rb
@@ -30,6 +30,26 @@ module Psych
     list.each(&block)
   end
 
+  def self.detect_implicit thing
+    warn "#{caller[0]}: detect_implicit is deprecated" if $VERBOSE
+    return '' unless String === thing
+    return 'null' if '' == thing
+    ScalarScanner.new.tokenize(thing).class.name.downcase
+  end
+
+  def self.add_ruby_type type_tag, &block
+    warn "#{caller[0]}: add_ruby_type is deprecated, use add_domain_type" if $VERBOSE
+    domain = 'ruby.yaml.org,2002'
+    key = ['tag', domain, type_tag].join ':'
+    @domain_types[key] = [key, block]
+  end
+
+  def self.add_private_type type_tag, &block
+    warn "#{caller[0]}: add_private_type is deprecated, use add_domain_type" if $VERBOSE
+    domain = 'x-private'
+    key = [domain, type_tag].join ':'
+    @domain_types[key] = [key, block]
+  end
 end
 
 class Object
diff --git a/lib/psych/visitors/to_ruby.rb b/lib/psych/visitors/to_ruby.rb
index bbbe9a8..e28ac7b 100644
--- a/lib/psych/visitors/to_ruby.rb
+++ b/lib/psych/visitors/to_ruby.rb
@@ -17,7 +17,7 @@ module Psych
         return result if @domain_types.empty? || !target.tag
 
         key = target.tag.sub(/^[!\/]*/, '').sub(/(,\d+)\//, '\1:')
-        key = "tag:#{key}" unless key.start_with?('tag:')
+        key = "tag:#{key}" unless key =~ /^(tag:|x-private)/
 
         if @domain_types.key? key
           value, block = @domain_types[key]
diff --git a/test/psych/test_deprecated.rb b/test/psych/test_deprecated.rb
index c93b36e..c2c8a97 100644
--- a/test/psych/test_deprecated.rb
+++ b/test/psych/test_deprecated.rb
@@ -163,5 +163,23 @@ module Psych
 
       assert_equal [["tag:ruby.yaml.org,2002:foo", "bar"]], types
     end
+
+    def test_detect_implicit
+      assert_equal '', Psych.detect_implicit(nil)
+      assert_equal '', Psych.detect_implicit(Object.new)
+      assert_equal '', Psych.detect_implicit(1.2)
+      assert_equal 'null', Psych.detect_implicit('')
+      assert_equal 'string', Psych.detect_implicit('foo')
+    end
+
+    def test_private_type
+      types = []
+      Psych.add_private_type('foo') { |*args| types << args }
+      Psych.load <<-eoyml
+- !x-private:foo bar
+      eoyml
+
+      assert_equal [["x-private:foo", "bar"]], types
+    end
   end
 end