Method references are not taken into account by proguard

I’m not sure whether it’s an issue of retrolambda itself or gradle-retrolambda

Background

Proguard seems to shrink methods, referenced as method references. See an example below:

public class AsyncTaskBuilder<Progress, Result> {

    public interface BackgroundWorkWithProgress<_Progress, _Result> {
        _Result execute(ProgressObserver<_Progress> progressObserver);
    }

    private BackgroundWorkWithProgress<Progress, Result> work;

    public AsyncTask<Void, Progress, Result> build() {

        return new AsyncTask<Void, Progress, Result>() {
            @Override
            protected Result doInBackground(Void... voids) {
                // this reference will not be taken into account by Proguard
                return work.execute(this::publishProgress);
            }

        };
    }
}

After building, the following error is shown:

:app:proguardRelease
Warning: com.github.retrolambda_methodref_repro.AsyncTaskBuilder$1$$Lambda$1: can't find referenced method 'void publishProgress(java.lang.Object[])' in library class android.os.AsyncTask
Warning: there were 1 unresolved references to library class members.
         You probably need to update the library versions.
         (http://proguard.sourceforge.net/manual/troubleshooting.html#unresolvedlibraryclassmember)
Exception while processing task 
java.io.IOException: Please correct the above warnings first.
    at proguard.Initializer.execute(Initializer.java:473)
    at proguard.ProGuard.initialize(ProGuard.java:233)
    at proguard.ProGuard.execute(ProGuard.java:98)
    at proguard.gradle.ProGuardTask.proguard(ProGuardTask.java:1074)
    at com.android.build.gradle.tasks.AndroidProGuardTask.doMinification(AndroidProGuardTask.java:139)
    at com.android.build.gradle.tasks.AndroidProGuardTask$1.run(AndroidProGuardTask.java:115)
    at com.android.builder.tasks.Job.runTask(Job.java:48)
    at com.android.build.gradle.tasks.SimpleWorkQueue$EmptyThreadContext.runTask(SimpleWorkQueue.java:41)
    at com.android.builder.tasks.WorkQueue.run(WorkQueue.java:227)
    at java.lang.Thread.run(Thread.java:745)

Full log is available at travis-ci

Sample android project

Simple android project (with 1 class), reproducing the issue can be found here: https://github.com/denis-itskovich/retrolambda-method-ref-repro

Related issues

The issue seems to be related to this retrolambda issue: https://github.com/orfjackal/retrolambda/issues/48

[sunny-chung]

Reproducible in an Android project with gradle-retrolambda 3.2.5 + retrolambda 2.3.0/2.4.0/2.5.0 gradle-retrolambda 3.5.0 + retrolambda 2.5.0,

apply plugin: ‘me.tatarka.retrolambda’ is put at the last.

This plugin was working at past time.

[ncruces]

Ignoring these warnings is enough to fix it:

-dontwarn **$$Lambda$*