I just wrote a long comment on #174 about associated values in conjunction with field offsets that I think provides a potentially-compelling reason to have field offsets.

@Zoxc for what it's worth here is a possible implementation of an intrusive linked list without needing field offsets. It does require a helper trait, but I think this trick should work for many cases where field offsets would be useful.

BTW, RFCs should not be rebased or amended; any changes should be made with new commits.

This should probably be postponed until #56 or something like that lands in order to provide greater motivation.

I believe that the broad goal here is to provide better support for 'intrusive' data structures, which Rust is currently weak at. It's not clear that this is the design to solve that problem, and @pcwalton has some ideas for designing intrusive data structures without changing the language.

offsetof is certainly a potentially useful operator, and for that the keyword is already reserved.

Closing. Thank you.