In ObjectReferenceImpl.validateMethodInvocation() it is expected, that the method invoker is declared in a ClassType. However, this is not the case for default methods in interfaces in Java 8.

Following exception is thrown when invoking a default method of an interface via debugger:

java.lang.ClassCastException: com.sun.tools.jdi.InterfaceTypeImpl cannot be cast to com.sun.tools.jdi.ClassTypeImpl
   at com.sun.tools.jdi.ObjectReferenceImpl.validateMethodInvocation(ObjectReferenceImpl.java:328)
   at com.sun.tools.jdi.ObjectReferenceImpl.invokeMethod(ObjectReferenceImpl.java:381)

A project that can be used to reproduce this issue is attached. Stop on line 19 and evaluate "c.getId()".

Can be reproduced via jdb:
$ java -Xdebug -Xrunjdwp:transport=dt_socket,server=y,address=4567 -classpath build/classes interfacemethods.InterfaceMethods

$ jdb -attach 4567
main[1] stop at interfacemethods.InterfaceMethods:19
main[1] cont
Breakpoint hit: "thread=main", interfacemethods.InterfaceMethods.main(), line=19 bci=8

main[1] print c.getId()
java.lang.ClassCastException: com.sun.tools.jdi.InterfaceTypeImpl cannot be cast to com.sun.tools.jdi.ClassTypeImpl
 c.getId() = null