---

yaml
---
r: 178954
b: refs/heads/master
c: 706be5b
h: refs/heads/master
v: v3

Author: bors

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: d0e82a68a9bf32eff2509e9f2579c5aa0fc61e92
+refs/heads/master: 706be5ba1f65ede0ffe095df8fa79706cbb562c8
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: ac134f7ca435551964996ee88319241cd3c7c110
 refs/heads/try: ccf8fedf1cffcb8f6f3581d53d220039e192fe77

trunk/src/liballoc/rc.rs

@@ -160,6 +160,7 @@ use core::option::Option::{Some, None};
 use core::ptr::{self, PtrExt};
 use core::result::Result;
 use core::result::Result::{Ok, Err};
+use core::intrinsics::assume;
 
 use heap::deallocate;
 
@@ -769,12 +770,34 @@ trait RcBoxPtr<T> {
 
 impl<T> RcBoxPtr<T> for Rc<T> {
     #[inline(always)]
-    fn inner(&self) -> &RcBox<T> { unsafe { &(**self._ptr) } }
+    fn inner(&self) -> &RcBox<T> {
+        unsafe {
+            // Safe to assume this here, as if it weren't true, we'd be breaking
+            // the contract anyway.
+            // This allows the null check to be elided in the destructor if we
+            // manipulated the reference count in the same function.
+            if cfg!(not(stage0)) { // NOTE remove cfg after next snapshot
+                assume(!self._ptr.is_null());
+            }
+            &(**self._ptr)
+        }
+    }
 }
 
 impl<T> RcBoxPtr<T> for Weak<T> {
     #[inline(always)]
-    fn inner(&self) -> &RcBox<T> { unsafe { &(**self._ptr) } }
+    fn inner(&self) -> &RcBox<T> {
+        unsafe {
+            // Safe to assume this here, as if it weren't true, we'd be breaking
+            // the contract anyway.
+            // This allows the null check to be elided in the destructor if we
+            // manipulated the reference count in the same function.
+            if cfg!(not(stage0)) { // NOTE remove cfg after next snapshot
+                assume(!self._ptr.is_null());
+            }
+            &(**self._ptr)
+        }
+    }
 }
 
 #[cfg(test)]