Been having a bit of a discussion in the Cafe... Just wondered what GHC specific issues would be involved with assuming all classes are closed. I am thinking that there is no real dis-advantage to considering all classes closed within their current context (IE all the imports to the current module). It seems to me that the argument about breaking code is wrong, as any changes to modules not imported into this module cannot have any affect on the code in this module. The only changes that can affect this module are changes to modules imported into this module - which of course can break things in many ways (like changing the type of a function)... In other words when the instances visible in a module change - all modules importing that module need to be recompiled (which is what happens when you use 'make' anyway). Can somebody either convince me their is a real problem with the 'closed' assumption, otherwise can GHC be changes to do this? Maybe an intermediate step would be to have a command line flag (-fall-closed ?) Keean.