4 files changed, 27 insertions, 5 deletions
diff --git a/src/libcore/ops/deref.rs b/src/libcore/ops/deref.rs
index 91a3d77e8b2..ff836f4aa69 100644
--- a/src/libcore/ops/deref.rs
+++ b/src/libcore/ops/deref.rs
@@ -177,3 +177,19 @@ pub trait DerefMut: Deref {
 impl<T: ?Sized> DerefMut for &mut T {
     fn deref_mut(&mut self) -> &mut T { *self }
 }
+
+/// Indicates that a struct can be used as a method receiver, without the
+/// `arbitrary_self_types` feature. This is implemented by stdlib pointer types like `Box<T>`,
+/// `Rc<T>`, `&T`, and `Pin<P>`.
+#[cfg_attr(not(stage0), lang = "receiver")]
+#[unstable(feature = "receiver_trait", issue = "0")]
+#[doc(hidden)]
+pub trait Receiver {
+    // Empty.
+}
+
+#[unstable(feature = "receiver_trait", issue = "0")]
+impl<T: ?Sized> Receiver for &T {}
+
+#[unstable(feature = "receiver_trait", issue = "0")]
+impl<T: ?Sized> Receiver for &mut T {}
diff --git a/src/libcore/ops/function.rs b/src/libcore/ops/function.rs
index c9591c3f57b..3b356b9a1e7 100644
--- a/src/libcore/ops/function.rs
+++ b/src/libcore/ops/function.rs
@@ -26,7 +26,7 @@
 /// is expected.
 ///
 /// Use `Fn` as a bound when you want to accept a parameter of function-like
-/// type and need to call it repeatedly and without mutating state (e.g. when
+/// type and need to call it repeatedly and without mutating state (e.g., when
 /// calling it concurrently). If you do not need such strict requirements, use
 /// [`FnMut`] or [`FnOnce`] as bounds.
 ///
@@ -72,6 +72,7 @@
     label="expected an `Fn<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
+#[must_use]
 pub trait Fn<Args> : FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -84,7 +85,7 @@ pub trait Fn<Args> : FnMut<Args> {
 ///
 /// `FnMut` is implemented automatically by closures which take mutable
 /// references to captured variables, as well as all types that implement
-/// [`Fn`], e.g. (safe) [function pointers][] (since `FnMut` is a supertrait of
+/// [`Fn`], e.g., (safe) [function pointers][] (since `FnMut` is a supertrait of
 /// [`Fn`]). Additionally, for any type `F` that implements `FnMut`, `&mut F`
 /// implements `FnMut`, too.
 ///
@@ -150,6 +151,7 @@ pub trait Fn<Args> : FnMut<Args> {
     label="expected an `FnMut<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
+#[must_use]
 pub trait FnMut<Args> : FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -163,7 +165,7 @@ pub trait FnMut<Args> : FnOnce<Args> {
 /// implements `FnOnce`, it can only be called once.
 ///
 /// `FnOnce` is implemented automatically by closure that might consume captured
-/// variables, as well as all types that implement [`FnMut`], e.g. (safe)
+/// variables, as well as all types that implement [`FnMut`], e.g., (safe)
 /// [function pointers][] (since `FnOnce` is a supertrait of [`FnMut`]).
 ///
 /// Since both [`Fn`] and [`FnMut`] are subtraits of `FnOnce`, any instance of
@@ -228,6 +230,7 @@ pub trait FnMut<Args> : FnOnce<Args> {
     label="expected an `FnOnce<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
+#[must_use]
 pub trait FnOnce<Args> {
     /// The returned type after the call operator is used.
     #[stable(feature = "fn_once_output", since = "1.12.0")]
diff --git a/src/libcore/ops/mod.rs b/src/libcore/ops/mod.rs
index edfa6df11ac..06740d2e4cd 100644
--- a/src/libcore/ops/mod.rs
+++ b/src/libcore/ops/mod.rs
@@ -27,7 +27,7 @@
 //! should have some resemblance to multiplication (and share expected
 //! properties like associativity).
 //!
-//! Note that the `&&` and `||` operators short-circuit, i.e. they only
+//! Note that the `&&` and `||` operators short-circuit, i.e., they only
 //! evaluate their second operand if it contributes to the result. Since this
 //! behavior is not enforceable by traits, `&&` and `||` are not supported as
 //! overloadable operators.
@@ -178,6 +178,9 @@ pub use self::bit::{BitAndAssign, BitOrAssign, BitXorAssign, ShlAssign, ShrAssig
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::deref::{Deref, DerefMut};
 
+#[unstable(feature = "receiver_trait", issue = "0")]
+pub use self::deref::Receiver;
+
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::drop::Drop;
 
diff --git a/src/libcore/ops/unsize.rs b/src/libcore/ops/unsize.rs
index 4d9a40a1b90..e86a392a2c8 100644
--- a/src/libcore/ops/unsize.rs
+++ b/src/libcore/ops/unsize.rs
@@ -93,7 +93,7 @@ impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}
 /// {}
 /// ```
 #[unstable(feature = "dispatch_from_dyn", issue = "0")]
-#[cfg_attr(not(stage0), lang = "dispatch_from_dyn")]
+#[lang = "dispatch_from_dyn"]
 pub trait DispatchFromDyn<T> {
     // Empty.
 }