2 Nov
2016
2 Nov
'16
11:40 a.m.
GHC Trac #12438 [1] exists because there's no Data instance for Const in base. I found this quite surprising, since we have Data instances for just about every other type combinator out there (Identity, Sum, Product, Compose, etc.), but not for Const. The fix for #12438 would be quite simple: I propose we add deriving instance (Data a, Data b) => Data (Const a b) to Data.Data in base. Any objections? Ryan S. ----- [1] https://ghc.haskell.org/trac/ghc/ticket/12438