25 Feb
2016
25 Feb
'16
8 a.m.
2. to implement a language extension in GHC that allows source language to specify a certain instance will never be defined and a type error shall be thrown statically at any use site, or
How about a feature that allows GHC to warn whenever a certain instance is used? That way, if you don't like a certain instance, you can put {-# FORBIDINSTANCE Foldable ((,) a) #-} in your modules and get warnings whenever that instance is used.