Auto merge of #54339 - cramertj:no-cx, r=aturon

Remove spawning from task::Context

r? @aturon

cc https://github.com/rust-lang-nursery/wg-net/issues/56

4 files changed, 9 insertions, 197 deletions

diff --git a/src/libcore/task/context.rs b/src/libcore/task/context.rs
deleted file mode 100644
index 5a29c8528ef..00000000000
--- a/src/libcore/task/context.rs
+++ /dev/null
@@ -1,98 +0,0 @@
-// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#![unstable(feature = "futures_api",
-            reason = "futures in libcore are unstable",
-            issue = "50547")]
-
-use fmt;
-use super::{Spawn, Waker, LocalWaker};
-
-/// Information about the currently-running task.
-///
-/// Contexts are always tied to the stack, since they are set up specifically
-/// when performing a single `poll` step on a task.
-pub struct Context<'a> {
-    local_waker: &'a LocalWaker,
-    spawner: &'a mut dyn Spawn,
-}
-
-impl<'a> fmt::Debug for Context<'a> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.debug_struct("Context")
-            .finish()
-    }
-}
-
-impl<'a> Context<'a> {
-    /// Create a new task `Context` with the provided `local_waker`, `waker`,
-    /// and `spawner`.
-    #[inline]
-    pub fn new(
-        local_waker: &'a LocalWaker,
-        spawner: &'a mut dyn Spawn,
-    ) -> Context<'a> {
-        Context { local_waker, spawner }
-    }
-
-    /// Get the `LocalWaker` associated with the current task.
-    #[inline]
-    pub fn local_waker(&self) -> &'a LocalWaker {
-        self.local_waker
-    }
-
-    /// Get the `Waker` associated with the current task.
-    #[inline]
-    pub fn waker(&self) -> &'a Waker {
-        unsafe { &*(self.local_waker as *const LocalWaker as *const Waker) }
-    }
-
-    /// Get the spawner associated with this task.
-    ///
-    /// This method is useful primarily if you want to explicitly handle
-    /// spawn failures.
-    #[inline]
-    pub fn spawner(&mut self) -> &mut dyn Spawn {
-        self.spawner
-    }
-
-    /// Produce a context like the current one, but using the given waker
-    /// instead.
-    ///
-    /// This advanced method is primarily used when building "internal
-    /// schedulers" within a task, where you want to provide some customized
-    /// wakeup logic.
-    #[inline]
-    pub fn with_waker<'b>(
-        &'b mut self,
-        local_waker: &'b LocalWaker,
-    ) -> Context<'b> {
-        Context {
-            local_waker,
-            spawner: self.spawner,
-        }
-    }
-
-    /// Produce a context like the current one, but using the given spawner
-    /// instead.
-    ///
-    /// This advanced method is primarily used when building "internal
-    /// schedulers" within a task.
-    #[inline]
-    pub fn with_spawner<'b, Sp: Spawn>(
-        &'b mut self,
-        spawner: &'b mut Sp,
-    ) -> Context<'b> {
-        Context {
-            local_waker: self.local_waker,
-            spawner,
-        }
-    }
-}
diff --git a/src/libcore/task/mod.rs b/src/libcore/task/mod.rs
index f51e5f7ce0e..95c9cca292f 100644
--- a/src/libcore/task/mod.rs
+++ b/src/libcore/task/mod.rs
@@ -14,12 +14,6 @@
 
 //! Types and Traits for working with asynchronous tasks.
 
-mod context;
-pub use self::context::Context;
-
-mod spawn;
-pub use self::spawn::{Spawn, SpawnErrorKind, SpawnObjError, SpawnLocalObjError};
-
 mod poll;
 pub use self::poll::Poll;
 
diff --git a/src/libcore/task/spawn.rs b/src/libcore/task/spawn.rs
deleted file mode 100644
index 58ee85d232b..00000000000
--- a/src/libcore/task/spawn.rs
+++ /dev/null
@@ -1,93 +0,0 @@
-// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#![unstable(feature = "futures_api",
-            reason = "futures in libcore are unstable",
-            issue = "50547")]
-
-use fmt;
-use future::{FutureObj, LocalFutureObj};
-
-/// Spawns tasks that poll futures to completion onto its associated task
-/// executor.
-///
-/// The term "task" refers to a kind of lightweight "thread". Task executors
-/// are responsible for scheduling the execution of tasks on operating system
-/// threads.
-pub trait Spawn {
-    /// Spawns a new task with the given future. The future will be polled until
-    /// completion.
-    ///
-    /// # Errors
-    ///
-    /// The executor may be unable to spawn tasks, either because it has
-    /// been shut down or is resource-constrained.
-    fn spawn_obj(
-        &mut self,
-        future: FutureObj<'static, ()>,
-    ) -> Result<(), SpawnObjError>;
-
-    /// Determines whether the executor is able to spawn new tasks.
-    ///
-    /// # Returns
-    ///
-    /// An `Ok` return means the executor is *likely* (but not guaranteed)
-    /// to accept a subsequent spawn attempt. Likewise, an `Err` return
-    /// means that `spawn` is likely, but not guaranteed, to yield an error.
-    #[inline]
-    fn status(&self) -> Result<(), SpawnErrorKind> {
-        Ok(())
-    }
-}
-
-/// Provides the reason that an executor was unable to spawn.
-pub struct SpawnErrorKind {
-    _hidden: (),
-}
-
-impl fmt::Debug for SpawnErrorKind {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        f.debug_tuple("SpawnErrorKind")
-            .field(&"shutdown")
-            .finish()
-    }
-}
-
-impl SpawnErrorKind {
-    /// Spawning is failing because the executor has been shut down.
-    pub fn shutdown() -> SpawnErrorKind {
-        SpawnErrorKind { _hidden: () }
-    }
-
-    /// Check whether this error is the `shutdown` error.
-    pub fn is_shutdown(&self) -> bool {
-        true
-    }
-}
-
-/// The result of a failed spawn
-#[derive(Debug)]
-pub struct SpawnObjError {
-    /// The kind of error
-    pub kind: SpawnErrorKind,
-
-    /// The future for which spawning inside a task was attempted
-    pub future: FutureObj<'static, ()>,
-}
-
-/// The result of a failed spawn
-#[derive(Debug)]
-pub struct SpawnLocalObjError {
-    /// The kind of error
-    pub kind: SpawnErrorKind,
-
-    /// The future for which spawning inside a task was attempted
-    pub future: LocalFutureObj<'static, ()>,
-}
diff --git a/src/libcore/task/wake.rs b/src/libcore/task/wake.rs
index d770536ef42..651db6356ba 100644
--- a/src/libcore/task/wake.rs
+++ b/src/libcore/task/wake.rs
@@ -123,6 +123,15 @@ impl LocalWaker {
         LocalWaker { inner }
     }
 
+    /// Converts this `LocalWaker` into a `Waker`.
+    ///
+    /// `Waker` is nearly identical to `LocalWaker`, but is threadsafe
+    /// (implements `Send` and `Sync`).
+    #[inline]
+    pub fn into_waker(self) -> Waker {
+        self.into()
+    }
+
     /// Wake up the task associated with this `LocalWaker`.
     #[inline]
     pub fn wake(&self) {