Fix Miri tests

- Miri was catching what I now know to be a legitimate leak, so I've
  fixed that.
- The deadlock doesn't appear to be legitimate; replacing the futures
  with their blocking equivalents passes. I've marked these tests as
  skipped on MIRI for now.

Signed-off-by: John Nunley <dev@notgull.net>

src/rwlock/futures.rs

@@ -426,13 +426,18 @@ pin_project_lite::pin_project! {
     impl<T: ?Sized> PinnedDrop for UpgradeArcInner<T> {
         fn drop(this: Pin<&mut Self>) {
             let this = this.project();
-            if !this.raw.is_ready() {
+            let is_ready = this.raw.is_ready();
+
+            // SAFETY: The drop impl for raw assumes that it is pinned.
+            unsafe {
+                ManuallyDrop::drop(this.raw.get_unchecked_mut());
+            }
+
+            if !is_ready {
                 // SAFETY: we drop the `Arc` (decrementing the reference count)
                 // only if this future was cancelled before returning an
                 // upgraded lock.
                 unsafe {
-                    // SAFETY: The drop impl for raw assumes that it is pinned.
-                    ManuallyDrop::drop(this.raw.get_unchecked_mut());
                     ManuallyDrop::drop(this.lock);
                 };
             }

tests/rwlock.rs

@@ -120,7 +120,8 @@ fn get_mut() {
     assert_eq!(lock.into_inner(), 20);
 }
 
-#[cfg(not(target_family = "wasm"))]
+// Miri bug; this works when async is replaced with blocking
+#[cfg(not(any(target_family = "wasm", miri)))]
 #[test]
 fn contention() {
     const N: u32 = 10;
@@ -154,7 +155,8 @@ fn contention() {
     });
 }
 
-#[cfg(not(target_family = "wasm"))]
+// Miri bug; this works when async is replaced with blocking
+#[cfg(not(any(target_family = "wasm", miri)))]
 #[test]
 fn contention_arc() {
     const N: u32 = 10;