[ractor] shareable_constant_value: literal makes constants shareable between ractors

language/fixtures/shareable_constant_value_magic_comment.rb

@@ -0,0 +1,9 @@
+# shareable_constant_value: literal
+
+A = [1, 2]
+H = {a: "a"}
+
+Ractor.new do
+  A
+  H
+en.take

language/ractor_spec.rb

@@ -0,0 +1,33 @@
+require_relative '../spec_helper'
+
+describe "Magic comments" do
+  ruby_version_is "3.0" do
+    it 'makes constants shareable between ractors' do
+      -> { ruby_exe(fixture(__FILE__, 'shareable_constant_value_magic_comment.rb'), options: '-W0')}.should_not raise_error
+    end
+
+    it 'makes constants shareable between ractors' do
+      a, b, c = Class.new.class_eval("#{<<~"begin;"}\n#{<<~'end;'}")
+      begin;
+        # shareable_constant_value: experimental_everything
+        A = [[1]]
+        # shareable_constant_value: none
+        B = [[2]]
+        # shareable_constant_value: literal
+        C = [["shareable", "constant#{nil}"]]
+        [A, B, C]
+      end;
+      Ractor.shareable?(a).should == true
+      Ractor.shareable?(b).should == false
+      Ractor.shareable?(c).should == true
+    end
+
+    it 'raises an error whenn shared constant is not a literal' do
+      -> { Class.new.class_eval("#{<<~"begin;"}\n#{<<~'end;'}", /unshareable expression/) }.should raise_error
+      begin;
+        # shareable_constant_value: literal
+        C = ["Not " + "shareable"]
+      end;
+    end
+  end
+end