string.c: no exception on dummy encoding

* string.c (str_compat_and_valid): as scrub does nothing for dummy
  encoding string now, incompatible encoding is not a matter.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53235 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 6 insertions, 0 deletions

diff --git a/test/ruby/test_m17n.rb b/test/ruby/test_m17n.rb
index 9f96652083..3a45f1f028 100644
--- a/test/ruby/test_m17n.rb
+++ b/test/ruby/test_m17n.rb
@@ -1642,6 +1642,12 @@ class TestM17N < Test::Unit::TestCase
                  scrub)
   end
 
+  def test_scrub_dummy_encoding
+    s = "\u{3042}".encode("iso-2022-jp")
+    assert_equal(s, s.scrub)
+    assert_equal(s, s.force_encoding("iso-2022-jp").scrub("?"))
+  end
+
   def test_scrub_bang
     str = "\u3042\u3044"
     assert_same(str, str.scrub!)