YJIT: Avoid identity-based known-class guards for IO objects (#7911)

`IO#reopen` is very special in that it is able to change the class and
singleton class of IO instances. In its presence, it is not correct to
assume that IO instances has a stable class/singleton class and guard
by comparing identity.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/ruby/test_yjit.rb b/test/ruby/test_yjit.rb
index 6700e58176..115c1902f0 100644
--- a/test/ruby/test_yjit.rb
+++ b/test/ruby/test_yjit.rb
@@ -1277,6 +1277,18 @@ class TestYJIT < Test::Unit::TestCase
     RUBY
   end
 
+  def test_io_reopen_clobbering_singleton_class
+    assert_compiles(<<~RUBY, result: [:ok, :ok])
+      def $stderr.to_i = :i
+
+      def test = $stderr.to_i
+
+      [test, test]
+      $stderr.reopen($stderr.dup)
+      [test, test].map { :ok unless _1 == :i }
+    RUBY
+  end
+
   private
 
   def code_gc_helpers