New language features need to make their way into IDE to be fully usable.
Name resolution happens with common user activities: goto, find usages, rename.
Would any of the new forms of overloading be easy to implement
Syntax-free name resolution in non-haskell AST parser (of Haskell files) may be tricky to implement. It would likely require more data to be stored, extra lookups and checks. This may slow IDEs down.
This is not to advocate a particular TDNR proposal. Rather, a reminder that new language features need to be implemented and may break working applications.