checker/tests/nullness/Issue3681.java

// Test case for isse #3681: https://tinyurl.com/cfissue/3681

// @below-java11-jdk-skip-test
package org.jro.tests.checkerfwk.utils;

public class Issue3681 {
  interface PartialFunction<T, R> {
    R apply(T t);

    boolean isDefinedAt(T value);
  }

  interface Either<L, R> {
    R get();

    boolean isRight();
  }

  public static <L, R> PartialFunction<Either<L, R>, R> createKeepRight() {
    return new PartialFunction<>() {

      @Override
      public R apply(final Either<L, R> either) {
        return either.get();
      }

      @Override
      public boolean isDefinedAt(final Either<L, R> value) {
        return value.isRight();
      }
    };
  }

  public static <L, R>
      PartialFunction<Either<L, ? extends R>, ? extends R> createRCovariantKeepRight() {
    return new PartialFunction<>() {

      @Override
      public R apply(final Either<L, ? extends R> either) {
        return either.get();
      }

      @Override
      public boolean isDefinedAt(final Either<L, ? extends R> value) {
        return value.isRight();
      }
    };
  }
}