/*
   * We have some considerable complexity in these create methods because of
   * Builder.buildKeepingLast(). The same Builder might be called with buildKeepingLast() and then
   * buildOrThrow(), or vice versa. So in particular, if we modify alternatingKeysAndValues to
   * eliminate duplicate keys (for buildKeepingLast()) then we have to ensure that a later call to

     * use `get(key) ?: defaultValue` instead of this method, anyway.
     */
    V result = get(key);
    // TODO(b/192579700): Use a ternary once it no longer confuses our nullness checker.
    if (result != null) {
      return result;
    } else {
      return defaultValue;
    }
  }

       *
       * (And I don't believe there's any situation in which we call x.combine(y) when x is a plain
       * ImmutableSet.Builder but y is an ImmutableSortedSet.Builder (or vice versa). Certainly
       * ImmutableSortedSet.Builder.combine() is written as if its argument will never be a plain
       * ImmutableSet.Builder: It casts immediately to ImmutableSortedSet.Builder.)
       */

      Sets.newSetFromMap(map);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  /** The 0-ary cartesian product is a single empty list. */
  public void testCartesianProduct_zeroary() {
    assertThat(Sets.cartesianProduct()).containsExactly(list());
  }

  /** A unary cartesian product is one list of size 1 for each element in the input set. */
  public void testCartesianProduct_unary() {