setindex!! fails for ReverseDiff.jl in certain scenarios #24
Description
It seems the specializations introduced in #22 didn't quite solve the issues of "incorrect" hits to immutable setindex!.
Atm it's a bit unclear to me if this is a BangBang.jl issue or if it's a ReverseDiff.jl issue. Specifically, is setindex! supposed to be allowed for promote_type or whenever convert is available. Posting here for now.