Fix constant name of `Ractor::IsolationError` message

`dest` of `const_decl_path` is `NODE_COLON2` or `NODE_COLON3` in some cases.
For example, `B::C ||= [“Not ” + “shareable”]` passes `NODE_COLON2`
and `::C ||= [“Not ” + “shareable”]` passes `NODE_COLON3`.
This commit fixes `Ractor::IsolationError` message for such case.

```
# shareable_constant_value: literal
::C ||= ["Not " + "shareable"]

# Before
# => cannot assign unshareable object to C (Ractor::IsolationError)

# After
# => cannot assign unshareable object to ::C (Ractor::IsolationError)
```

1 files changed, 34 insertions, 0 deletions

diff --git a/test/ruby/test_parse.rb b/test/ruby/test_parse.rb
index b6d306352c..edf61db325 100644
--- a/test/ruby/test_parse.rb
+++ b/test/ruby/test_parse.rb
@@ -1568,6 +1568,40 @@ x = __ENCODING__
         ::B::C = ["Not " + "shareable"]
       end
     end;
+
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      assert_raise_with_message(Ractor::IsolationError, /unshareable object to ::C/) do
+        # shareable_constant_value: literal
+        ::C ||= ["Not " + "shareable"]
+      end
+    end;
+
+    assert_raise_separately(Ractor::IsolationError, /unshareable object to B::C/,
+                            "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      # shareable_constant_value: literal
+      B = Class.new
+      B::C ||= ["Not " + "shareable"]
+    end;
+
+    assert_separately([], "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      assert_raise_with_message(Ractor::IsolationError, /unshareable object to ::B::C/) do
+        # shareable_constant_value: literal
+        ::B = Class.new
+        ::B::C ||= ["Not " + "shareable"]
+      end
+    end;
+
+    assert_raise_separately(Ractor::IsolationError, /unshareable object to ...::C/,
+                            "#{<<~"begin;"}\n#{<<~'end;'}")
+    begin;
+      # shareable_constant_value: literal
+      B = Class.new
+      def self.expr; B; end
+      expr::C ||= ["Not " + "shareable"]
+    end;
   end
 
   def test_shareable_constant_value_nonliteral