std.ArrayList: actaully memset to undefined in shrinkRetainingCapacity and clearRetainingCapacity

See ziglang#25810

Author: mateusz834

lib/std/array_list.zig

@@ -380,15 +380,15 @@ pub fn AlignedManaged(comptime T: type, comptime alignment: ?mem.Alignment) type
         /// Asserts that the new length is less than or equal to the previous length.
         pub fn shrinkRetainingCapacity(self: *Self, new_len: usize) void {
             assert(new_len <= self.items.len);
-            self.items.len = new_len;
             @memset(self.items[new_len..], undefined);
+            self.items.len = new_len;
         }
 
         /// Reduce length to 0.
         /// Invalidates all element pointers.
         pub fn clearRetainingCapacity(self: *Self) void {
-            self.items.len = 0;
             @memset(self.items, undefined);
+            self.items.len = 0;
         }
 
         /// Invalidates all element pointers.