Feedback on this proposal was light but positive. The Language Steering Group agrees that the proposed extracting() operations, which return rebased-to-zero subsequences of various span and buffer pointer types, are generally useful and are worth providing uniformly across all of those types. Therefore, we have accepted this proposal.
Thanks to everybody who participated in the review!
The original write-up of SE-0488 also defined the extracting() operations on the Slice types of unsafe buffer pointers. However, those operations were not implemented, and as we are approaching the one year deadline before unimplemented parts of a proposal expire, the author has updated the proposal to shrink it to fit what has actually been implemented.
If those operations end up being desirable, they may be pitched anew.