Differences between javac and tycho-compiler-jdt (1.2.0)

Animal.java

public interface Animal<ID extends KeyOfAllBeings> extends Identifiable<KeyOfAllBeings> {
    @Override
    ID getKey();

    void setKey(ID item);
}

AnimalKey.java

public class AnimalKey extends KeyOfAllBeings {
    
}

BaseAnimal.java

public abstract class BaseAnimal implements Identifiable<KeyOfAllBeings>, Animal<AnimalKey> {

}

Elephant.java

public class Elephant extends BaseAnimal {
  
  private AnimalKey key;
  
  @Override
  public AnimalKey getKey() {
    return key;
  }
  
  @Override
  public void setKey(AnimalKey key) {
    this.key = key;
  }
}

Identifiable.java

public interface Identifiable<T extends Key> {
    T getKey();
}

Key.java

public class Key {

}

KeyOfAllBeings.java

public class KeyOfAllBeings extends Key {
}

Main.java

public class Main {

  public static void main(String[] args) {
    BaseAnimal baseAnimal = new Animal();
    
    // Both work on javac, but not ecj (at least not with tycho-compiler-jdt 1.2.0)
    AnimalKey key = baseAnimal.getKey();
    KeyOfAllBeings key2 = baseAnimal.getKey();
  }
}