"Arity decrease" warnings when compiling Haddock
I'm getting warnings of the form
WARNING: file compiler/GHC/Core/Op/Simplify/Utils.hs, line 1528 Arity decrease: lvl_s4yB 3 0 0 lvl_s4XI `cast` (Sym (N:Builder) :: (forall r. BuildStep r -> BuildStep r) ~R# Builder) Call stack: CallStack (from HasCallStack): callStackDoc, called at compiler/utils/Outputable.hs:1289:29 in ghc:Outputable warnPprTrace, called at compiler/GHC/Core/Op/Simplify/Utils.hs:1526:11 in ghc:GHC.Core.Op.Simplify.Utils
Having looked at
prepareRhs lately, I suspect it has to do that we don't transfer
arityInfo on to
sanitised_info in the
As I said in #17673 (comment 267431), we probably want to share the logic with WW, which doesn't have this weakness.