Use Pin for the 'don't move' requirement of ReentrantMutex.

The code in io::stdio before this change misused the ReentrantMutexes,
by calling init() on them and moving them afterwards. Now that
ReentrantMutex requires Pin for init(), this mistake is no longer easy
to make.

1 files changed, 20 insertions, 15 deletions

diff --git a/library/std/src/sys_common/remutex/tests.rs b/library/std/src/sys_common/remutex/tests.rs
index 9c686e579d7..88453ded2f9 100644
--- a/library/std/src/sys_common/remutex/tests.rs
+++ b/library/std/src/sys_common/remutex/tests.rs
@@ -1,4 +1,6 @@
+use crate::boxed::Box;
 use crate::cell::RefCell;
+use crate::pin::Pin;
 use crate::sync::Arc;
 use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 use crate::thread;
@@ -6,10 +8,11 @@ use crate::thread;
 #[test]
 fn smoke() {
     let m = unsafe {
-        let m = ReentrantMutex::new(());
-        m.init();
+        let mut m = Box::pin(ReentrantMutex::new(()));
+        m.as_mut().init();
         m
     };
+    let m = m.as_ref();
     {
         let a = m.lock();
         {
@@ -27,18 +30,19 @@ fn smoke() {
 #[test]
 fn is_mutex() {
     let m = unsafe {
-        let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
-        m.init();
-        m
+        // FIXME: Simplify this if Arc gets a Arc::get_pin_mut.
+        let mut m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
+        Pin::new_unchecked(Arc::get_mut_unchecked(&mut m)).init();
+        Pin::new_unchecked(m)
     };
     let m2 = m.clone();
-    let lock = m.lock();
+    let lock = m.as_ref().lock();
     let child = thread::spawn(move || {
-        let lock = m2.lock();
+        let lock = m2.as_ref().lock();
         assert_eq!(*lock.borrow(), 4950);
     });
     for i in 0..100 {
-        let lock = m.lock();
+        let lock = m.as_ref().lock();
         *lock.borrow_mut() += i;
     }
     drop(lock);
@@ -48,20 +52,21 @@ fn is_mutex() {
 #[test]
 fn trylock_works() {
     let m = unsafe {
-        let m = Arc::new(ReentrantMutex::new(()));
-        m.init();
-        m
+        // FIXME: Simplify this if Arc gets a Arc::get_pin_mut.
+        let mut m = Arc::new(ReentrantMutex::new(()));
+        Pin::new_unchecked(Arc::get_mut_unchecked(&mut m)).init();
+        Pin::new_unchecked(m)
     };
     let m2 = m.clone();
-    let _lock = m.try_lock();
-    let _lock2 = m.try_lock();
+    let _lock = m.as_ref().try_lock();
+    let _lock2 = m.as_ref().try_lock();
     thread::spawn(move || {
-        let lock = m2.try_lock();
+        let lock = m2.as_ref().try_lock();
         assert!(lock.is_none());
     })
     .join()
     .unwrap();
-    let _lock3 = m.try_lock();
+    let _lock3 = m.as_ref().try_lock();
 }
 
 pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>);