I have been updating the ghc-exactprint library for real world use cases on the about to be released GHC 9.2.1, and realised I need to be able to put an Anchor into every SrcSpan in the ParsedSource AST. I prepared !6854 to sort it out in master and turned to the problem of GHC 9.2.1, where I had missed the boat. And then I discovered that we have SrcSpan defined as data SrcSpan = RealSrcSpan !RealSrcSpan !(Maybe BufSpan) | UnhelpfulSpan !UnhelpfulSpanReason and the (Maybe BufSpan) is only used for attaching haddock comments after parsing. This means there is an isomorphism between the RealSrcSpan variant and an Anchor, which I take advantage of with the code in [1], by using the Maybe to encode the AnchorOperation and the BufSpan to encode the DeltaPos. And it struck me that perhaps we should make this a more official approach. The only problem is the detail of the BufSpan, to be able to play both roles cleanly. Alan [1] https://gist.github.com/alanz/5e262599ab79138606cdfcf3792ef635