Fix Arc:into_inner behavior

Author: EFanZh

library/alloc/src/raw_rc.rs

@@ -598,6 +598,20 @@ impl<T, A> RawWeak<T, A> {
     {
         Self::new_zeroed_in::<STRONG_COUNT>(A::default())
     }
+
+    unsafe fn assume_init_into_inner<R>(mut self) -> T
+    where
+        A: Allocator,
+        R: RcOps,
+    {
+        unsafe {
+            let result = self.ptr.read();
+
+            self.drop_unchecked::<R>();
+
+            result
+        }
+    }
 }
 
 impl<T, A> RawWeak<[T], A> {
@@ -1001,14 +1015,7 @@ impl<T, A> RawRc<T, A> {
         R: RcOps,
     {
         unsafe {
-            match self.try_unwrap::<R>() {
-                Ok(value) => Some(value),
-                Err(mut rc) => {
-                    rc.drop::<R>();
-
-                    None
-                }
-            }
+            R::dec_strong(&self.strong_count()).then(|| self.weak.assume_init_into_inner::<R>())
         }
     }
 
@@ -1019,7 +1026,7 @@ impl<T, A> RawRc<T, A> {
     {
         unsafe {
             if R::lock_strong_count(self.strong_count()) {
-                Ok(RawUniqueRc::from_weak(self.weak).into_inner::<R>())
+                Ok(self.weak.assume_init_into_inner::<R>())
             } else {
                 Err(self)
             }
@@ -1893,20 +1900,6 @@ impl<T, A> RawUniqueRc<T, A> {
     {
         unsafe { Self::from_weak_with_value(RawWeak::new_uninit::<0>(), value) }
     }
-
-    pub unsafe fn into_inner<R>(mut self) -> T
-    where
-        A: Allocator,
-        R: RcOps,
-    {
-        unsafe {
-            let result = ptr::read(self.as_ref());
-
-            self.weak.drop_unchecked::<R>();
-
-            result
-        }
-    }
 }
 
 impl<T, A> AsRef<T> for RawUniqueRc<T, A>