resolved upstream merge conflicts

6 files changed, 42 insertions, 33 deletions

diff --git a/src/libstd/sync/mod.rs b/src/libstd/sync/mod.rs
index 642b284c6c7..e12ef8d9eda 100644
--- a/src/libstd/sync/mod.rs
+++ b/src/libstd/sync/mod.rs
@@ -18,7 +18,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 #[stable(feature = "rust1", since = "1.0.0")]
-pub use alloc_crate::arc::{Arc, Weak};
+pub use alloc_crate::sync::{Arc, Weak};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::sync::atomic;
 
diff --git a/src/libstd/sync/mpsc/mod.rs b/src/libstd/sync/mpsc/mod.rs
index 2dd3aebe610..02a96b01cca 100644
--- a/src/libstd/sync/mpsc/mod.rs
+++ b/src/libstd/sync/mpsc/mod.rs
@@ -689,7 +689,7 @@ impl<T> UnsafeFlavor<T> for Receiver<T> {
 /// only one [`Receiver`] is supported.
 ///
 /// If the [`Receiver`] is disconnected while trying to [`send`] with the
-/// [`Sender`], the [`send`] method will return a [`SendError`]. Similarly, If the
+/// [`Sender`], the [`send`] method will return a [`SendError`]. Similarly, if the
 /// [`Sender`] is disconnected while trying to [`recv`], the [`recv`] method will
 /// return a [`RecvError`].
 ///
@@ -1638,7 +1638,7 @@ impl<T: Send> error::Error for SendError<T> {
         "sending on a closed channel"
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         None
     }
 }
@@ -1681,7 +1681,7 @@ impl<T: Send> error::Error for TrySendError<T> {
         }
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         None
     }
 }
@@ -1709,7 +1709,7 @@ impl error::Error for RecvError {
         "receiving on a closed channel"
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         None
     }
 }
@@ -1742,7 +1742,7 @@ impl error::Error for TryRecvError {
         }
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         None
     }
 }
@@ -1783,7 +1783,7 @@ impl error::Error for RecvTimeoutError {
         }
     }
 
-    fn cause(&self) -> Option<&error::Error> {
+    fn cause(&self) -> Option<&dyn error::Error> {
         None
     }
 }
diff --git a/src/libstd/sync/mpsc/select.rs b/src/libstd/sync/mpsc/select.rs
index 9310dad9172..a7a284cfb79 100644
--- a/src/libstd/sync/mpsc/select.rs
+++ b/src/libstd/sync/mpsc/select.rs
@@ -93,7 +93,7 @@ pub struct Handle<'rx, T:Send+'rx> {
     next: *mut Handle<'static, ()>,
     prev: *mut Handle<'static, ()>,
     added: bool,
-    packet: &'rx (Packet+'rx),
+    packet: &'rx (dyn Packet+'rx),
 
     // due to our fun transmutes, we be sure to place this at the end. (nothing
     // previous relies on T)
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index 3b4904c98e8..e5a410644b9 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -150,7 +150,7 @@ unsafe impl<T: ?Sized + Send> Sync for Mutex<T> { }
 /// [`lock`]: struct.Mutex.html#method.lock
 /// [`try_lock`]: struct.Mutex.html#method.try_lock
 /// [`Mutex`]: struct.Mutex.html
-#[must_use]
+#[must_use = "if unused the Mutex will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct MutexGuard<'a, T: ?Sized + 'a> {
     // funny underscores due to how Deref/DerefMut currently work (they
@@ -227,7 +227,7 @@ impl<T: ?Sized> Mutex<T> {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn lock(&self) -> LockResult<MutexGuard<T>> {
         unsafe {
-            self.inner.lock();
+            self.inner.raw_lock();
             MutexGuard::new(self)
         }
     }
@@ -454,7 +454,7 @@ impl<'a, T: ?Sized> Drop for MutexGuard<'a, T> {
     fn drop(&mut self) {
         unsafe {
             self.__lock.poison.done(&self.__poison);
-            self.__lock.inner.unlock();
+            self.__lock.inner.raw_unlock();
         }
     }
 }
diff --git a/src/libstd/sync/once.rs b/src/libstd/sync/once.rs
index 6fd8b6a5bba..10282ecb658 100644
--- a/src/libstd/sync/once.rs
+++ b/src/libstd/sync/once.rs
@@ -73,16 +73,17 @@ use thread::{self, Thread};
 /// A synchronization primitive which can be used to run a one-time global
 /// initialization. Useful for one-time initialization for FFI or related
 /// functionality. This type can only be constructed with the [`ONCE_INIT`]
-/// value.
+/// value or the equivalent [`Once::new`] constructor.
 ///
 /// [`ONCE_INIT`]: constant.ONCE_INIT.html
+/// [`Once::new`]: struct.Once.html#method.new
 ///
 /// # Examples
 ///
 /// ```
-/// use std::sync::{Once, ONCE_INIT};
+/// use std::sync::Once;
 ///
-/// static START: Once = ONCE_INIT;
+/// static START: Once = Once::new();
 ///
 /// START.call_once(|| {
 ///     // run initialization here
@@ -148,9 +149,9 @@ struct Waiter {
 
 // Helper struct used to clean up after a closure call with a `Drop`
 // implementation to also run on panic.
-struct Finish {
+struct Finish<'a> {
     panicked: bool,
-    me: &'static Once,
+    me: &'a Once,
 }
 
 impl Once {
@@ -180,10 +181,10 @@ impl Once {
     /// # Examples
     ///
     /// ```
-    /// use std::sync::{Once, ONCE_INIT};
+    /// use std::sync::Once;
     ///
     /// static mut VAL: usize = 0;
-    /// static INIT: Once = ONCE_INIT;
+    /// static INIT: Once = Once::new();
     ///
     /// // Accessing a `static mut` is unsafe much of the time, but if we do so
     /// // in a synchronized fashion (e.g. write once or read all) then we're
@@ -217,9 +218,13 @@ impl Once {
     ///
     /// [poison]: struct.Mutex.html#poisoning
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn call_once<F>(&'static self, f: F) where F: FnOnce() {
+    pub fn call_once<F>(&self, f: F) where F: FnOnce() {
         // Fast path, just see if we've completed initialization.
-        if self.state.load(Ordering::SeqCst) == COMPLETE {
+        // An `Acquire` load is enough because that makes all the initialization
+        // operations visible to us. The cold path uses SeqCst consistently
+        // because the performance difference really does not matter there,
+        // and SeqCst minimizes the chances of something going wrong.
+        if self.state.load(Ordering::Acquire) == COMPLETE {
             return
         }
 
@@ -248,10 +253,10 @@ impl Once {
     /// ```
     /// #![feature(once_poison)]
     ///
-    /// use std::sync::{Once, ONCE_INIT};
+    /// use std::sync::Once;
     /// use std::thread;
     ///
-    /// static INIT: Once = ONCE_INIT;
+    /// static INIT: Once = Once::new();
     ///
     /// // poison the once
     /// let handle = thread::spawn(|| {
@@ -274,9 +279,13 @@ impl Once {
     /// INIT.call_once(|| {});
     /// ```
     #[unstable(feature = "once_poison", issue = "33577")]
-    pub fn call_once_force<F>(&'static self, f: F) where F: FnOnce(&OnceState) {
+    pub fn call_once_force<F>(&self, f: F) where F: FnOnce(&OnceState) {
         // same as above, just with a different parameter to `call_inner`.
-        if self.state.load(Ordering::SeqCst) == COMPLETE {
+        // An `Acquire` load is enough because that makes all the initialization
+        // operations visible to us. The cold path uses SeqCst consistently
+        // because the performance difference really does not matter there,
+        // and SeqCst minimizes the chances of something going wrong.
+        if self.state.load(Ordering::Acquire) == COMPLETE {
             return
         }
 
@@ -298,9 +307,9 @@ impl Once {
     // currently no way to take an `FnOnce` and call it via virtual dispatch
     // without some allocation overhead.
     #[cold]
-    fn call_inner(&'static self,
+    fn call_inner(&self,
                   ignore_poisoning: bool,
-                  init: &mut FnMut(bool)) {
+                  init: &mut dyn FnMut(bool)) {
         let mut state = self.state.load(Ordering::SeqCst);
 
         'outer: loop {
@@ -389,7 +398,7 @@ impl fmt::Debug for Once {
     }
 }
 
-impl Drop for Finish {
+impl<'a> Drop for Finish<'a> {
     fn drop(&mut self) {
         // Swap out our state with however we finished. We should only ever see
         // an old state which was RUNNING.
@@ -431,10 +440,10 @@ impl OnceState {
     /// ```
     /// #![feature(once_poison)]
     ///
-    /// use std::sync::{Once, ONCE_INIT};
+    /// use std::sync::Once;
     /// use std::thread;
     ///
-    /// static INIT: Once = ONCE_INIT;
+    /// static INIT: Once = Once::new();
     ///
     /// // poison the once
     /// let handle = thread::spawn(|| {
@@ -452,9 +461,9 @@ impl OnceState {
     /// ```
     /// #![feature(once_poison)]
     ///
-    /// use std::sync::{Once, ONCE_INIT};
+    /// use std::sync::Once;
     ///
-    /// static INIT: Once = ONCE_INIT;
+    /// static INIT: Once = Once::new();
     ///
     /// INIT.call_once_force(|state| {
     ///     assert!(!state.poisoned());
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index f7fdedc0d21..e3db60cff84 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -94,7 +94,7 @@ unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
 /// [`read`]: struct.RwLock.html#method.read
 /// [`try_read`]: struct.RwLock.html#method.try_read
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,
@@ -115,7 +115,7 @@ unsafe impl<'a, T: ?Sized + Sync> Sync for RwLockReadGuard<'a, T> {}
 /// [`write`]: struct.RwLock.html#method.write
 /// [`try_write`]: struct.RwLock.html#method.try_write
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,