public Integer computeNext() {
            if (haveBeenCalled) {
              throw new AssertionError("Should not have been called again");
            } else {
              haveBeenCalled = true;
              sneakyThrow(new SomeCheckedException());
              throw new AssertionError(); // unreachable
            }
          }
        };

    // The first time, the sneakily-thrown exception comes out

            if (haveBeenCalled) {
              throw new AssertionError("Should not have been called again");
            } else {
              haveBeenCalled = true;
              sneakyThrow(new SomeCheckedException());
              throw new AssertionError(); // unreachable
            }
          }
        };

    // The first time, the sneakily-thrown exception comes out

            if (haveBeenCalled) {
              throw new AssertionError("Should not have been called again");
            } else {
              haveBeenCalled = true;
              sneakyThrow(new SomeCheckedException());
              throw new AssertionError(); // unreachable
            }
          }
        };

    // The first time, the sneakily-thrown exception comes out

      }
    }
    if (exception != null) {
      // Normally this is a RuntimeException that doesn't need sneakyThrow.
      // But theoretically we could see sneaky checked exception
      sneakyThrow(exception);
    }
  }

  /** Throws an undeclared checked exception. */
  private static void sneakyThrow(Throwable t) {
    class SneakyThrower<T extends Throwable> {

      }
    }
    if (exception != null) {
      // Normally this is a RuntimeException that doesn't need sneakyThrow.
      // But theoretically we could see sneaky checked exception
      sneakyThrow(exception);
    }
  }

  /** Throws an undeclared checked exception. */
  private static void sneakyThrow(Throwable t) {
    class SneakyThrower<T extends Throwable> {

    AbstractFuture<String> f = new AbstractFuture<String>() {};
    f.set("foo");
    f.addListener(() -> sneakyThrow(new SomeCheckedException()), directExecutor());
  }

  private static final class SomeCheckedException extends Exception {}

  /** Throws an undeclared checked exception. */
  private static void sneakyThrow(Throwable t) {
    class SneakyThrower<T extends Throwable> {