Method references to private methods

[naixx]

Hi. The problem is:

{
  someObserable.finallyDo(this::myProblemMethod);
}

private void myProblemMethod(){}

The code is compiled and dexed to run on Davlik VM. But in runtime on an android device I get warnings and the method isn't called, of course.

 DexOpt: illegal method access (ca;.myProblemMethod ()V from (Fragment$$Lambda$1;)
 I/dalvikvm﹕ Could not find method myProblemMethod, referenced from method Fragment$$Lambda$1.call
VFY: unable to resolve virtual method 43525:

The code works as a lambda if myProblemMethod is package private, public, everything except private. The method can be called explicitly. But it doesn't work as a method reference. Warnings appear only once.

So, is it a problem, that retrolambda somehow processes references, so that dex excludes them from the build?

[luontola]

Thanks. I was able to reproduce it. I'll have a look at solving it soon, maybe tomorrow.

I'm guessing that this has something to do with how in Java 8 the lambda classes have some special handling to that they can call private methods of other classes. Retrolamdba should probably detect when a method reference targets a private method and make it package private.

[luontola]

This isn't a Dalvik specific problem, so I renamed the issue.

[naixx]

Great to hear, that the problem is identified!

[luontola]

Still one bug remains (seems to depend on JDK 8 build). Working on it...

[luontola]

The fix is included in Retrolambda 1.2.2. It should show up in Maven Central in a couple of hours.

[naixx]

Looks like magic, thanks!

[naixx]

Hello, @orfjackal !

After updating to the new version, I've catched a crash.

 @Test
    public void call_of_method_with_reference(){
        class InnerClass {
            void foo(){
                Runnable r = LambdaTest.this::privateVoidMethod;
                r.run();
            }
        }
        new InnerClass().foo();
        privateVoidMethod();
        assertThat(privateInstanceMethod(), is("foo"));
    }

The code structure is like this. I haven't checked it in a test.

[luontola]

Please submit a SSCCE. You example doesn't compile and I haven't managed to reproduce the problem.

[naixx]

@orfjackal ok, finally I managed to reproduce the problem.

void thisMethodIsAlsoReferenced() {
    Observable.from("foo").lift((Operator<String, String>) (subscriber) -> {
        Runnable ref = MyOuterClass.this::problemPrivateMethod; //we make a reference in an anonymous class
        ref.run();
        return subscriber;
    }).subscribe(s -> {
        L.e(s);
    });
    problemPrivateMethod(); //java.lang.NoSuchMethodError
}

Unfortunately, I can't reproduce the problem in tests.

[luontola]

Please make that example short and self contained (http://www.sscce.org/) so that I can run it. Or send the me .class files before and after processing that code with Retrolambda.

Does the problem happen with Oracle JVM or only Dalvik VM?