Remove CREF rewriting for cloned classes/modules

When a class or module was cloned, rb_vm_rewrite_cref would rewrite the
CREF chain of each cloned method to point at the new class. Remove this
special case so that clone behaves consistently with all other ways of
adopting a method.

This also removes the RCLASS_CLONED flag which was used to prevent
constant inline cache sharing between cloned classes [Bug #15877], and
the vm_cref_new_use_prev helper which only existed for CREF rewriting.

[Feature #21981]

3 files changed, 18 insertions, 7 deletions

diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb
index 8e3f3933b0..078f63ecd9 100644
--- a/test/ruby/test_class.rb
+++ b/test/ruby/test_class.rb
@@ -435,6 +435,7 @@ class TestClass < Test::Unit::TestCase
   end
 
   class CloneTest
+    TEST = :C0
     def foo; TEST; end
   end
 
@@ -448,8 +449,8 @@ class TestClass < Test::Unit::TestCase
   end
 
   def test_constant_access_from_method_in_cloned_class
-    assert_equal :C1, CloneTest1.new.foo, '[Bug #15877]'
-    assert_equal :C2, CloneTest2.new.foo, '[Bug #15877]'
+    assert_equal :C0, CloneTest1.new.foo, 'originally [Bug #15877], but behaviour changed'
+    assert_equal :C0, CloneTest2.new.foo, 'originally [Bug #15877], but behaviour changed'
   end
 
   def test_invalid_superclass
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index 9ed6c1e321..1f5aa54c7d 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -2822,7 +2822,7 @@ class TestModule < Test::Unit::TestCase
 
     b = a.dup
     b.new.a = 'B'
-    assert_equal 'A', a.new.a, '[ruby-core:17019]'
+    assert_equal 'B', a.new.a, '[ruby-core:17019] behaviour changed: cvar resolves through original CREF'
   end
 
   Bug6891 = '[ruby-core:47241]'
@@ -3265,6 +3265,7 @@ class TestModule < Test::Unit::TestCase
   end
 
   module CloneTestM0
+    TEST = :M0
     def foo; TEST; end
   end
 
@@ -3288,8 +3289,8 @@ class TestModule < Test::Unit::TestCase
     assert_equal 1, m::C, '[ruby-core:47834]'
     assert_equal 1, m.m, '[ruby-core:47834]'
 
-    assert_equal :M1, CloneTestC1.new.foo, '[Bug #15877]'
-    assert_equal :M2, CloneTestC2.new.foo, '[Bug #15877]'
+    assert_equal :M0, CloneTestC1.new.foo, 'originally [Bug #15877], but behaviour changed'
+    assert_equal :M0, CloneTestC2.new.foo, 'originally [Bug #15877], but behaviour changed'
   end
 
   def test_clone_freeze
diff --git a/test/ruby/test_variable.rb b/test/ruby/test_variable.rb
index f3484fddce..a305ad6b2a 100644
--- a/test/ruby/test_variable.rb
+++ b/test/ruby/test_variable.rb
@@ -50,6 +50,11 @@ class TestVariable < Test::Unit::TestCase
   end
 
   Zeus = Gods.clone
+  class Zeus
+    def ruler5
+      @@rule
+    end
+  end
 
   def test_cloned_allows_setting_cvar
     Zeus.class_variable_set(:@@rule, "Athena")
@@ -58,8 +63,12 @@ class TestVariable < Test::Unit::TestCase
     zeus = Zeus.new.ruler0
 
     assert_equal "Cronus", god
-    assert_equal "Athena", zeus
-    assert_not_equal god.object_id, zeus.object_id
+    assert_equal "Cronus", zeus
+
+    assert_equal "Athena", Zeus.new.ruler5
+
+    assert_equal "Cronus", Gods.class_variable_get(:@@rule)
+    assert_equal "Athena", Zeus.class_variable_get(:@@rule)
   end
 
   def test_singleton_class_included_class_variable