LambdaMetaFactory::metafactory on a
REF_invokeSpecial implementation method should behave as if
invokespecial instruction unless it's a private method in the caller class.
The integration of JEP 371 Hidden Classes (JDK-8238358) introduced a regression in JDK 15. The LambdaMetaFactory implementation was enhanced to generate hidden implementation classes that are nestmates (JEP 181: Nest-Based Access Control) of the caller, nest-host, class.
Such nestmates class that invoke private methods on the nest host should use
REF_invokeInterface. However, the LambdaMetaFactory implementation incorrectly applied that to non-private (public, protected and package private) methods which should be invoked with
Fix the implementation to convert REF_invokeSpecial to REF_invokeVirtual/REF_invokeInterface only if the implementation method is a private method of the caller class.
No specification change.