replace unsafe ptr::write with deref-write, benchmarks show no difference

library/alloc/src/vec.rs

@@ -2086,11 +2086,8 @@ fn extend<I: IntoIterator<Item = T>>(&mut self, iter: I) {
             <Self as SpecExtend<T, I::IntoIter>>::spec_extend(self, iter.into_iter())
         } else {
             // if self has no allocation then use the more powerful from_iter specializations
-            let other = SpecFrom::from_iter(iter.into_iter());
-            // replace self, don't run drop since self was empty
-            unsafe {
-                ptr::write(self, other);
-            }
+            // and overwrite self
+            *self = SpecFrom::from_iter(iter.into_iter());
         }
     }
 
@@ -2544,11 +2541,8 @@ fn extend<I: IntoIterator<Item = &'a T>>(&mut self, iter: I) {
             self.spec_extend(iter.into_iter())
         } else {
             // if self has no allocation then use the more powerful from_iter specializations
-            let other = SpecFrom::from_iter(iter.into_iter());
-            // replace self, don't run drop since self was empty
-            unsafe {
-                ptr::write(self, other);
-            }
+            // and overwrite self
+            *self = SpecFrom::from_iter(iter.into_iter());
         }
     }