I wouldn’t mind that, but I am the one who suggested it. If anyone has a compelling reason, you could offer the less-safe API as an escape hatch. But some form of recursive do notation has been around for a long time. mdo was added in GHC 6.0 (May 2003), deprecated in 6.12.1 (December 2009) when rec was added, and then resurrected in 7.6.1 (September 2012). So I think it’s safe to say they’ve settled in.
