checker/tests/nullness/java8inference/Issue4048.java

// Test case for issue #4048: https://tinyurl.com/cfissue/4048

// @skip-test until the issue is fixed

import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;

abstract class Issue4048 {
  @Nullable Number m1(List<? extends Number> numbers) {
    return getOnlyElement1(numbers);
  }

  abstract <T> @Nullable T getOnlyElement1(Iterable<T> values);

  @Nullable Number m2(List<? extends Number> numbers) {
    return getOnlyElement2(numbers);
  }

  abstract <T> @Nullable T getOnlyElement2(Iterable<? extends T> values);
}