capnp-rpc 0.8.3

// Copyright (c) 2013-2017 Sandstorm Development Group, Inc. and contributors
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

use futures::{Future};

pub struct AttachFuture<F, T> where F: Future {
    original_future: F,
    value: Option<T>,
}

impl <F, T> Future for AttachFuture<F, T>
    where F: Future,
{
    type Item = F::Item;
    type Error = F::Error;

    fn poll(&mut self) -> ::futures::Poll<Self::Item, Self::Error> {
        let result = self.original_future.poll();
        if let Ok(::futures::Async::Ready(_)) = result {
            self.value.take();
        }
        result
    }
}

pub trait Attach: Future {
    fn attach<T>(self, value: T) -> AttachFuture<Self, T>
        where Self: Sized
    {
        AttachFuture {
            original_future: self,
            value: Some(value),
        }
    }
}

impl <F> Attach for F where F: Future {}