The proposed functionality is useful and much safer than the current workarounds, which require extensive use of unsafe APIs to obtain similar performance. I participated in the pitch thread and I'm very happy with how the proposal turned out. The main remaining sharp edge is the inout initializedCount, which is easy to misuse by forgetting to set it on some return path, but there doesn't seem to be an alternative that preserves the other useful aspects like rethrows (see the pitch thread for details). These methods are clearly labelled as unsafe, so I think having this sharp edge is acceptable.