android/guava/src/com/google/common/cache/CacheBuilder.java
@SuppressWarnings("unchecked")
  <K1 extends K, V1 extends V> Weigher<K1, V1> getWeigher() {
    return (Weigher<K1, V1>) MoreObjects.firstNonNull(weigher, OneWeigher.INSTANCE);
  }
@SuppressWarnings("unchecked")
  <K1 extends K, V1 extends V> Weigher<K1, V1> getWeigher() {
    return (Weigher<K1, V1>) MoreObjects.firstNonNull(weigher, OneWeigher.INSTANCE);
  }
Make a safe contravariant cast now so we don't have to do it over and over.