Fix Arc Clone

Author: ThePuzzlemaker

src/arc-clone.md

@@ -55,7 +55,7 @@ machines) incrementing the reference count at once. This is what we'll do.
 
 It's pretty simple to implement this behaviour:
 ```rust,ignore
-if old_rc >= isize::MAX {
+if old_rc >= isize::MAX as usize {
     std::process::abort();
 }
 ```
@@ -77,9 +77,9 @@ impl<T> Clone for Arc<T> {
         let inner = unsafe { self.ptr.as_ref() };
         // Using a relaxed ordering is alright here as knowledge of the original
         // reference prevents other threads from wrongly deleting the object.
-        inner.rc.fetch_add(1, Ordering::Relaxed);
+        let old_rc = inner.rc.fetch_add(1, Ordering::Relaxed);
 
-        if old_rc >= isize::MAX {
+        if old_rc >= isize::MAX as usize {
             std::process::abort();
         }
 

src/arc-final.md

@@ -46,16 +46,14 @@ impl<T> Deref for Arc<T> {
     }
 }
 
-use std::sync::atomic::Ordering;
-
 impl<T> Clone for Arc<T> {
     fn clone(&self) -> Arc<T> {
         let inner = unsafe { self.ptr.as_ref() };
         // Using a relaxed ordering is alright here as knowledge of the original
         // reference prevents other threads from wrongly deleting the object.
-        inner.rc.fetch_add(1, Ordering::Relaxed);
+        let old_rc = inner.rc.fetch_add(1, Ordering::Relaxed);
 
-        if old_rc >= isize::MAX {
+        if old_rc >= isize::MAX as usize {
             std::process::abort();
         }