eval.c: fix message as same as previous versions

* eval.c (rb_frozen_class_p): fix message for singleton class of
  class/module as same as previous versions.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47568 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

eval.c

@@ -412,8 +412,21 @@ rb_frozen_class_p(VALUE klass)
     if (OBJ_FROZEN(klass)) {
 	const char *desc;
 
-	if (FL_TEST(klass, FL_SINGLETON))
+	if (FL_TEST(klass, FL_SINGLETON)) {
 	    desc = "object";
+	    klass = rb_ivar_get(klass, id__attached__);
+	    if (!SPECIAL_CONST_P(klass)) {
+		switch (BUILTIN_TYPE(klass)) {
+		  case T_MODULE:
+		  case T_ICLASS:
+		    desc = "Module";
+		    break;
+		  case T_CLASS:
+		    desc = "Class";
+		    break;
+		}
+	    }
+	}
 	else {
 	    switch (BUILTIN_TYPE(klass)) {
 	      case T_MODULE:

test/ruby/test_class.rb

@@ -389,8 +389,12 @@ class TestClass < Test::Unit::TestCase
     obj = Object.new
     c = obj.singleton_class
     obj.freeze
-    assert_raise(RuntimeError, /frozen object/) {
+    assert_raise_with_message(RuntimeError, /frozen object/) {
       c.class_eval {def f; end}
     }
+    c = Class.new.freeze
+    assert_raise_with_message(RuntimeError, /frozen Class/) {
+      def c.f; end
+    }
   end
 end