final void addInitialException(Set<Throwable> seen) {
    checkNotNull(seen);
    if (!isCancelled()) {
      /*
       * requireNonNull is safe because:
       *
       * - This is a TrustedFuture, so tryInternalFastPathGetFailure will in fact return the failure
       *   cause if this Future has failed.
       *
       * - And this future *has* failed: This method is called only from handleException (through

    future.set("261");
    assertThat(future.tryInternalFastPathGetFailure()).isNull();
  }

  public void testTrustedGetFailure_failed() {
    SettableFuture<String> future = SettableFuture.create();
    Throwable failure = new Throwable();
    future.setException(failure);
    assertThat(future.tryInternalFastPathGetFailure()).isEqualTo(failure);
  }

    future.set("261");
    assertThat(future.tryInternalFastPathGetFailure()).isNull();
  }

  public void testTrustedGetFailure_failed() {
    SettableFuture<String> future = SettableFuture.create();
    Throwable failure = new Throwable();
    future.setException(failure);
    assertThat(future.tryInternalFastPathGetFailure()).isEqualTo(failure);
  }

      return requireNonNull(v);
    }
    if (future instanceof InternalFutureFailureAccess) {
      Throwable throwable =
          InternalFutures.tryInternalFastPathGetFailure((InternalFutureFailureAccess) future);
      if (throwable != null) {
        return new Failure(throwable);
      }
    }
    boolean wasCancelled = future.isCancelled();