Cleaned up alloc::sync::Weak Clone implementation

Since both return points (tail and early return) return the same
expression and the only difference is whether inner is available, the
code that does the atomic operations and checks on inner was moved into
the if body and the only return is at the tail. Original comments
preserved.

Author: JohnTheCoolingFan

alloc/src/sync.rs

@@ -2917,20 +2917,17 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Weak<T, A> {
     /// ```
     #[inline]
     fn clone(&self) -> Weak<T, A> {
-        let inner = if let Some(inner) = self.inner() {
-            inner
-        } else {
-            return Weak { ptr: self.ptr, alloc: self.alloc.clone() };
-        };
-        // See comments in Arc::clone() for why this is relaxed. This can use a
-        // fetch_add (ignoring the lock) because the weak count is only locked
-        // where are *no other* weak pointers in existence. (So we can't be
-        // running this code in that case).
-        let old_size = inner.weak.fetch_add(1, Relaxed);
-
-        // See comments in Arc::clone() for why we do this (for mem::forget).
-        if old_size > MAX_REFCOUNT {
-            abort();
+        if let Some(inner) = self.inner() {
+            // See comments in Arc::clone() for why this is relaxed. This can use a
+            // fetch_add (ignoring the lock) because the weak count is only locked
+            // where are *no other* weak pointers in existence. (So we can't be
+            // running this code in that case).
+            let old_size = inner.weak.fetch_add(1, Relaxed);
+
+            // See comments in Arc::clone() for why we do this (for mem::forget).
+            if old_size > MAX_REFCOUNT {
+                abort();
+            }
         }
 
         Weak { ptr: self.ptr, alloc: self.alloc.clone() }