Remove unused macros (#610)

* replace async-macros with internals only

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* clean up MaybeDone

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* inline futures_core::ready

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

* remove big commented blob

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

Cargo.toml

@@ -38,7 +38,6 @@ docs = ["attributes", "unstable"]
 unstable = ["default", "broadcaster"]
 attributes = ["async-attributes"]
 std = [
-  "async-macros",
   "crossbeam-utils",
   "futures-core",
   "futures-io",
@@ -51,7 +50,6 @@ std = [
 
 [dependencies]
 async-attributes = { version = "1.1.1", optional = true }
-async-macros = { version = "2.0.0", optional = true }
 async-task = { version = "1.0.0", optional = true }
 broadcaster = { version = "0.2.6", optional = true, default-features = false, features = ["default-channels"] }
 crossbeam-channel = { version = "0.4.0", optional = true }

src/future/future/join.rs

@@ -1,6 +1,6 @@
 use std::pin::Pin;
 
-use async_macros::MaybeDone;
+use crate::future::MaybeDone;
 use pin_project_lite::pin_project;
 
 use crate::task::{Context, Poll};

src/future/future/race.rs

@@ -1,7 +1,7 @@
 use std::future::Future;
 use std::pin::Pin;
 
-use async_macros::MaybeDone;
+use crate::future::MaybeDone;
 use pin_project_lite::pin_project;
 
 use crate::task::{Context, Poll};

src/future/future/try_join.rs

@@ -1,6 +1,6 @@
 use std::pin::Pin;
 
-use async_macros::MaybeDone;
+use crate::future::MaybeDone;
 use pin_project_lite::pin_project;
 
 use crate::task::{Context, Poll};

src/future/future/try_race.rs

@@ -1,6 +1,6 @@
 use std::pin::Pin;
 
-use async_macros::MaybeDone;
+use crate::future::MaybeDone;
 use pin_project_lite::pin_project;
 
 use crate::task::{Context, Poll};

src/future/maybe_done.rs

@@ -0,0 +1,79 @@
+//! A type that wraps a future to keep track of its completion status.
+//!
+//! This implementation was taken from the original `macro_rules` `join/try_join`
+//! macros in the `futures-preview` crate.
+
+use std::future::Future;
+use std::mem;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use futures_core::ready;
+
+/// A future that may have completed.
+#[derive(Debug)]
+pub(crate) enum MaybeDone<Fut: Future> {
+    /// A not-yet-completed future
+    Future(Fut),
+
+    /// The output of the completed future
+    Done(Fut::Output),
+
+    /// The empty variant after the result of a [`MaybeDone`] has been
+    /// taken using the [`take`](MaybeDone::take) method.
+    Gone,
+}
+
+impl<Fut: Future> MaybeDone<Fut> {
+    /// Create a new instance of `MaybeDone`.
+    pub(crate) fn new(future: Fut) -> MaybeDone<Fut> {
+        Self::Future(future)
+    }
+
+    /// Returns an [`Option`] containing a reference to the output of the future.
+    /// The output of this method will be [`Some`] if and only if the inner
+    /// future has been completed and [`take`](MaybeDone::take)
+    /// has not yet been called.
+    #[inline]
+    pub(crate) fn output(self: Pin<&Self>) -> Option<&Fut::Output> {
+        let this = self.get_ref();
+        match this {
+            MaybeDone::Done(res) => Some(res),
+            _ => None,
+        }
+    }
+
+    /// Attempt to take the output of a `MaybeDone` without driving it
+    /// towards completion.
+    #[inline]
+    pub(crate) fn take(self: Pin<&mut Self>) -> Option<Fut::Output> {
+        unsafe {
+            let this = self.get_unchecked_mut();
+            match this {
+                MaybeDone::Done(_) => {}
+                MaybeDone::Future(_) | MaybeDone::Gone => return None,
+            };
+            if let MaybeDone::Done(output) = mem::replace(this, MaybeDone::Gone) {
+                Some(output)
+            } else {
+                unreachable!()
+            }
+        }
+    }
+}
+
+impl<Fut: Future> Future for MaybeDone<Fut> {
+    type Output = ();
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let res = unsafe {
+            match Pin::as_mut(&mut self).get_unchecked_mut() {
+                MaybeDone::Future(a) => ready!(Pin::new_unchecked(a).poll(cx)),
+                MaybeDone::Done(_) => return Poll::Ready(()),
+                MaybeDone::Gone => panic!("MaybeDone polled after value taken"),
+            }
+        };
+        self.set(MaybeDone::Done(res));
+        Poll::Ready(())
+    }
+}

src/future/mod.rs

@@ -63,5 +63,7 @@ cfg_default! {
 
 cfg_unstable! {
     pub use into_future::IntoFuture;
+    pub(crate) use maybe_done::MaybeDone;
     mod into_future;
+    mod maybe_done;
 }

src/task/mod.rs

@@ -121,10 +121,9 @@ cfg_std! {
     #[doc(inline)]
     pub use std::task::{Context, Poll, Waker};
 
-    #[doc(inline)]
-    pub use async_macros::ready;
-
+    pub use ready::ready;
     pub use yield_now::yield_now;
+    mod ready;
     mod yield_now;
 }
 

src/task/ready.rs

@@ -0,0 +1,4 @@
+/// Extracts the successful type of a `Poll<T>`.
+///
+/// This macro bakes in propagation of `Pending` signals by returning early.
+pub use futures_core::ready;