Re:GHC 8.0.1 is available
by johncolanduoni on Sunday May 22, 2016 @08:56AM
(#11748430)
Idris[1] already has a working system for this, and it's type system is more complicated (it has much more support for dependent typing). It allows this principle for regular function names as well.
That would need very careful design to work well with type inference, I suppose?