Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC Commits: 35bf6f4b by Simon Jakobi at 2026-09-24T20:12:49-04:00 Remove stale specHeader bullet from Note [Don't make fillers for constraint types] The Note said that Specialise.specHeader also calls mkAbsentFiller. abfc224a27c removed that call: the specialiser no longer drops dead arguments at all, see Note [Do not drop dead args from specialisations] in GHC.Core.Opt.Specialise. Assisted-by: Claude Fable 5.1 - - - - - 1 changed file: - compiler/GHC/Core/Opt/WorkWrap/Utils.hs Changes: ===================================== compiler/GHC/Core/Opt/WorkWrap/Utils.hs ===================================== @@ -1367,13 +1367,8 @@ It's surprisingly subtle. application; see test `T27627f`. TL;DR: we play safe: we never make an absent filler for any /constraint-kinded/ type, -using `isPredTy` to decide. - - * `mkAbsentFiller` returns `Nothing` for any constraint type, so worker/wrapper - keeps the real argument. - - * `Specialise.specHeader` calls `mkAbsentFiller` too, so it likewise keeps the - dead dictionary argument rather than dropping it for a filler. +using `isPredTy` to decide: `mkAbsentFiller` returns `Nothing` for any constraint +type, so worker/wrapper keeps the real argument. Prior failed approaches View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/35bf6f4bcf06675565992725df62e837... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/35bf6f4bcf06675565992725df62e837... You're receiving this email because of your account on gitlab.haskell.org. Manage all notifications: https://gitlab.haskell.org/-/profile/notifications | Help: https://gitlab.haskell.org/help