message: Document impls module
diff: +//! Futures and stream types used in the crate.
  use bytes::{Bytes, IntoBuf};
  use futures::{try_ready, Async, Future, Poll, Stream};
  use std::error;
  @@ -8,6 +9,7 @@ use crate::{Client, Connection, Error, Portal, Row, Statement, TlsConnect};
  #[cfg(feature = "runtime")]
  use crate::{MakeTlsConnect, Socket};
  +/// The future returned by `Client::cancel_query_raw`.
  #[must_use = "futures do nothing unless polled"]
  pub struct CancelQueryRaw<S, T>(pub(crate) proto::CancelQueryRawFuture<S, T>)
  where
  @@ -27,6 +29,7 @@ where
  }
  }
  +/// The future returned by `Client::cancel_query`.
  #[cfg(feature = "runtime")]
  #[must_use = "futures do nothing unless polled"]
  pub struct CancelQuery<T>(pub(crate) proto::CancelQueryFuture<T>)
  @@ -46,6 +49,7 @@ where
  }
  }
  +/// The future returned by `Config::connect_raw`.
  #[must_use = "futures do nothing unless polled"]
  pub struct ConnectRaw<S, T>(pub(crate) proto::ConnectRawFuture<S, T>)
  where
  @@ -67,6 +71,7 @@ where
  }
  }
  +/// The future returned by `Config::connect`.
  #[cfg(feature = "runtime")]
  #[must_use = "futures do nothing unless polled"]
  pub struct Connect<T>(pub(crate) proto::ConnectFuture<T>)
  @@ -88,6 +93,7 @@ where
  }
  }
  +/// The future returned by `Client::prepare`.
  #[must_use = "futures do nothing unless polled"]
  pub struct Prepare(pub(crate) proto::PrepareFuture);
  @@ -102,6 +108,7 @@ impl Future for Prepare {
  }
  }
  +/// The future returned by `Client::query`.
  #[must_use = "streams do nothing unless polled"]
  pub struct Query(pub(crate) proto::QueryStream<proto::Statement>);
  @@ -114,6 +121,7 @@ impl Stream for Query {
  }
  }
  +/// The future returned by `Client::bind`.
  #[must_use = "futures do nothing unless polled"]
  pub struct Bind(pub(crate) proto::BindFuture);
  @@ -130,6 +138,7 @@ impl Future for Bind {
  }
  }
  +/// The future returned by `Client::query_portal`.
  #[must_use = "streams do nothing unless polled"]
  pub struct QueryPortal(pub(crate) proto::QueryStream<proto::Portal>);
  @@ -142,6 +151,7 @@ impl Stream for QueryPortal {
  }
  }
  +/// The future returned by `Client::copy_in`.
  #[must_use = "futures do nothing unless polled"]
  pub struct CopyIn<S>(pub(crate) proto::CopyInFuture<S>)
  where
  @@ -165,6 +175,7 @@ where
  }
  }
  +/// The future returned by `Client::copy_out`.
  #[must_use = "streams do nothing unless polled"]
  pub struct CopyOut(pub(crate) proto::CopyOutStream);
  