throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override
  public @Nullable K ceilingKey(K key) {
    return delegate.ceilingKey(checkValid(key));
  }

  @Override
  public void clear() {
    delegate.clear();
  }

    this.delegate = delegate;
    for (E e : this) {
      checkValid(e);
    }
  }

  @Override
  public boolean add(E element) {
    return delegate.add(checkValid(element));
  }

  @Override
  public boolean addAll(Collection<? extends E> collection) {
    for (E e : collection) {
      checkValid(e);
    }
    return delegate.addAll(collection);
  }

  @Override

      throw new NullPointerException();
    }
    for (K k : keySet()) {
      checkValid(k);
    }
  }

  @Override
  public @Nullable Entry<K, V> ceilingEntry(K key) {
    return delegate.ceilingEntry(checkValid(key));
  }

  @Override
  public @Nullable K ceilingKey(K key) {
    return delegate.ceilingKey(checkValid(key));
  }

  @Override
  public void clear() {
    delegate.clear();
  }

    this.delegate = delegate;
    for (E e : this) {
      checkValid(e);
    }
  }

  @Override
  public boolean add(E element) {
    return delegate.add(checkValid(element));
  }

  @Override
  public boolean addAll(Collection<? extends E> collection) {
    for (E e : collection) {
      checkValid(e);
    }
    return delegate.addAll(collection);
  }

  @Override

	if err := f.checkValid("SetReadDeadline"); err != nil {
		return err
	}
	return f.pfd.SetReadDeadline(t)
}

// setWriteDeadline sets the write deadline.
func (f *File) setWriteDeadline(t time.Time) error {
	if err := f.checkValid("SetWriteDeadline"); err != nil {
		return err
	}
	return f.pfd.SetWriteDeadline(t)
}

// checkValid checks whether f is valid for use.

type rawConn struct {
	file *File
}

func (c *rawConn) Control(f func(uintptr)) error {
	if err := c.file.checkValid("SyscallConn.Control"); err != nil {
		return err
	}
	err := c.file.pfd.RawControl(f)
	runtime.KeepAlive(c.file)
	return err
}

func (c *rawConn) Read(f func(uintptr) bool) error {
	if err := c.file.checkValid("SyscallConn.Read"); err != nil {
		return err
	}
	err := c.file.pfd.RawRead(f)

		return 0, true, nil
	}

	var src *File
	switch v := r.(type) {
	case *File:
		src = v
	case fileWithoutWriteTo:
		src = v.File
	default:
		return 0, false, nil
	}

	if src.checkValid("ReadFrom") != nil {
		// Avoid returning the error as we report handled as false,
		// leave further error handling as the responsibility of the caller.
		return 0, false, nil
	}