From 0caccdf9f79d39d6b0a1d385aec995b75c3cb9ba Mon Sep 17 00:00:00 2001
From: Xidorn Quan <me@upsuper.org>
Date: Sun, 26 Apr 2020 16:08:42 +1000
Subject: [PATCH 1/2] Implement Fn traits for Rc and Arc

---
 src/liballoc/rc.rs   | 23 +++++++++++++++++++++++
 src/liballoc/sync.rs | 23 +++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/src/liballoc/rc.rs b/src/liballoc/rc.rs
index 2f9505ec79ffa..dc8801fe8b461 100644
--- a/src/liballoc/rc.rs
+++ b/src/liballoc/rc.rs
@@ -1436,6 +1436,29 @@ impl<T: ?Sized> fmt::Pointer for Rc<T> {
     }
 }
 
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> FnOnce<A> for Rc<F> {
+    type Output = <F as FnOnce<A>>::Output;
+
+    extern "rust-call" fn call_once(self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(&*self, args)
+    }
+}
+
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> FnMut<A> for Rc<F> {
+    extern "rust-call" fn call_mut(&mut self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(self, args)
+    }
+}
+
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> Fn<A> for Rc<F> {
+    extern "rust-call" fn call(&self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(self, args)
+    }
+}
+
 #[stable(feature = "from_for_ptrs", since = "1.6.0")]
 impl<T> From<T> for Rc<T> {
     fn from(t: T) -> Self {
diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs
index 19d289c87fd9f..c88b8865e650c 100644
--- a/src/liballoc/sync.rs
+++ b/src/liballoc/sync.rs
@@ -2066,6 +2066,29 @@ impl<T: ?Sized + Hash> Hash for Arc<T> {
     }
 }
 
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> FnOnce<A> for Arc<F> {
+    type Output = <F as FnOnce<A>>::Output;
+
+    extern "rust-call" fn call_once(self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(&*self, args)
+    }
+}
+
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> FnMut<A> for Arc<F> {
+    extern "rust-call" fn call_mut(&mut self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(self, args)
+    }
+}
+
+#[stable(feature = "rc_fn", since = "1.45.0")]
+impl<A, F: Fn<A> + ?Sized> Fn<A> for Arc<F> {
+    extern "rust-call" fn call(&self, args: A) -> Self::Output {
+        <F as Fn<A>>::call(self, args)
+    }
+}
+
 #[stable(feature = "from_for_ptrs", since = "1.6.0")]
 impl<T> From<T> for Arc<T> {
     fn from(t: T) -> Self {

From 0cb80ab265f389f054f1f3ee08026596cfd9e6c4 Mon Sep 17 00:00:00 2001
From: Xidorn Quan <me@upsuper.org>
Date: Sun, 10 May 2020 10:18:32 +1000
Subject: [PATCH 2/2] Add tests for Fn impl of Rc and Arc

---
 src/liballoc/rc/tests.rs   | 20 ++++++++++++++++++++
 src/liballoc/sync/tests.rs | 20 ++++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/src/liballoc/rc/tests.rs b/src/liballoc/rc/tests.rs
index 56788bb56d550..d847948559082 100644
--- a/src/liballoc/rc/tests.rs
+++ b/src/liballoc/rc/tests.rs
@@ -434,3 +434,23 @@ fn test_array_from_slice() {
     let a: Result<Rc<[u32; 2]>, _> = r.clone().try_into();
     assert!(a.is_err());
 }
+
+#[test]
+fn test_fn() {
+    fn apply_fn_once<T>(v: T, f: impl FnOnce(T)) {
+        f(v)
+    }
+    fn apply_fn_mut<T>(v: T, mut f: impl FnMut(T)) {
+        f(v)
+    }
+    fn apply_fn<T>(v: T, f: impl Fn(T)) {
+        f(v)
+    }
+
+    let x = RefCell::new(0);
+    let f = Rc::new(|v: i32| *x.borrow_mut() += v);
+    apply_fn_once(1, f.clone());
+    apply_fn_mut(2, f.clone());
+    apply_fn(4, f.clone());
+    assert_eq!(*x.borrow(), 7);
+}
diff --git a/src/liballoc/sync/tests.rs b/src/liballoc/sync/tests.rs
index edc2820ee22f1..f4319dabf7ef5 100644
--- a/src/liballoc/sync/tests.rs
+++ b/src/liballoc/sync/tests.rs
@@ -490,3 +490,23 @@ fn test_array_from_slice() {
     let a: Result<Arc<[u32; 2]>, _> = r.clone().try_into();
     assert!(a.is_err());
 }
+
+#[test]
+fn test_fn() {
+    fn apply_fn_once<T>(v: T, f: impl FnOnce(T)) {
+        f(v)
+    }
+    fn apply_fn_mut<T>(v: T, mut f: impl FnMut(T)) {
+        f(v)
+    }
+    fn apply_fn<T>(v: T, f: impl Fn(T)) {
+        f(v)
+    }
+
+    let x = Mutex::new(0);
+    let f = Arc::new(|v: i32| *x.lock().unwrap() += v);
+    apply_fn_once(1, f.clone());
+    apply_fn_mut(2, f.clone());
+    apply_fn(4, f.clone());
+    assert_eq!(*x.lock().unwrap(), 7);
+}