javac bug: dispatch to multiply inherited defenders

[Brian Goetz]

This test case fails to compile:

public class MultipleInheritanceTest extends DefenderTestCase {
     private interface A {
         public extension int get() default Implementations.one;
     }

     private interface B {
         public extension int get() default Implementations.one;
     }

     private static class X implements A, B { }

     public void testValidMI() {
         assertDefender(X.class, "get", new Class[] { }, 
Implementations.class, "one");
         X x = new X();
         assertEquals(1, x.get());        // @@@
         assertEquals(1, ((A) x).get());
         assertEquals(1, ((B) x).get());
     }
}

We get the error at the line marked // @@@

test-compile:
     [javac] Compiling 3 source files to 
/home/brian/work/mangler/trunk/defender/build/test-classes
     [javac] 
/home/brian/work/mangler/trunk/defender/test/src/junit/MultipleInheritanceTest.java:20: 
reference to get is ambiguous, both method get() in B and method get() in A match
     [javac]         assertEquals(1, x.get());
     [javac]                          ^


The static type of 'x' is 'X', which is a class that has a get() method.  That 
method happens to be inherited from both A and B, but their signatures and 
defaults are the same so they should be compatible methods.

The testValidMI() method should generate an invokevirtual and two 
invokeinterface invocations.