@ElementTypesAreNonnullByDefault
class CompactHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMap<K, V> implements Serializable {
  /*
   * TODO: Make this a drop-in replacement for j.u. versions, actually drop them in, and test the
   * world. Figure out what sort of space-time tradeoff we're actually going to get here with the

           * -4294967296L = -9223372036854775808L!
           *
           * To be clear, this bug affects not the test's computation of the expected result but the
           * _actual prod code_. But it probably affects only unusual cases.
           */
          continue;
        }
        BigInteger expectedResult = valueOf(a).multiply(valueOf(b));