Support obj.clone(freeze: true) for freezing clone

This freezes the clone even if the receiver is not frozen.  It
is only for consistency with freeze: false not freezing the clone
even if the receiver is frozen.

Because Object#clone is now partially implemented in Ruby and
not fully implemented in C, freeze: nil must be supported to
provide the default behavior of only freezing the clone if the
receiver is frozen.

This requires modifying delegate and set, to set freeze: nil
instead of freeze: true as the keyword parameter for
initialize_clone.  Those are the two libraries in stdlib that
override initialize_clone.

Implements [Feature #16175]

1 files changed, 9 insertions, 3 deletions

diff --git a/spec/ruby/core/kernel/clone_spec.rb b/spec/ruby/core/kernel/clone_spec.rb
index f20ea618b5..1bbef64f85 100644
--- a/spec/ruby/core/kernel/clone_spec.rb
+++ b/spec/ruby/core/kernel/clone_spec.rb
@@ -37,11 +37,17 @@ describe "Kernel#clone" do
     o3.frozen?.should == true
   end
 
-  it 'takes an option to copy freeze state or not' do
-    @obj.clone(freeze: true).frozen?.should == false
+  ruby_version_is '2.8' do
+    it 'takes an freeze: true option to frozen copy' do
+      @obj.clone(freeze: true).frozen?.should == true
+      @obj.freeze
+      @obj.clone(freeze: true).frozen?.should == true
+    end
+  end
+
+  it 'takes an freeze: false option to not return frozen copy' do
     @obj.clone(freeze: false).frozen?.should == false
     @obj.freeze
-    @obj.clone(freeze: true).frozen?.should == true
     @obj.clone(freeze: false).frozen?.should == false
   end