2023-10-30.md

SWG 2023-10-30

Meeting URL: https://meet.jit.si/StableHaskellMeetBiWeekly

Previous meeting notes

Agenda & Notes

New items to discuss

• Template Haskell issue

  • Perhpas related to this reinstallable base doc.
  • Saving this for when Ben is present.

• GHC2024 Proposal

  • Particularly welcome -XExplicitNameSpaces because the current situation is:
    • TypeOperators implies ExplicitNameSpaces
    • TypeOperators is in GHC2021; but ExplicitNameSpaces is not. Weird!
    • Principle: if X is in GHC202x then all of X's implications should be.
  • General question: would shifting from GHC2021 to GHC2024 break any code? E.g. -XLambdaCase would not.
  • But switching on MonoLocalBinds by default definitely will break code.
  • Would like a deprecation cycle with a warning -Wmono-local-binds: compiles with -XNoMonoLocalBinds, but emits a warning if a locally-bound value is used polymorphically. (Because then -XMonoLocalbinds will errror.) The warning could give the signature to add.

• Semantics of implications.

  • -XGADTs implies -XMonoLocalBinds.

  • If you say -XGADTs -XNoGADTs what is the effect on MonoLocalBinds.

    • Trevis: off
    • Mikolaj: would like this to switch MonoLocalBinds off.
    • Jappie: on [this is the correct answer]

  • More realistically, suppose -XGADTs and -XMonoLocalBinds were in GHC2024, and GHC2024 was the default language edition, and you say ghc -XNoGADTs.

    • Trevis: -XGHC2024 switches on all its implications "explicitly"; -XNoGADTs only switches off -XMonoLocalBinds "implicitly". And explicit wins.
    • Mikolaj: Now -XGADTs is not on, but -XGHC2024 is, and the latter is enough to keep -XMonoLocalBinds on. Reference counting!

  • Count votes: extension is on iff more -XWombat than -XNoWombat.

Short-Term Action Items From Previous

• None

In progress projects

Updates

• Extension lifecycle framework proposal

• Bulletin discussed previously

  • Previously holding the token: Chris

• GHC warning policy document as discussed previously

  • Previously holding the token: Chris

• Creating and maintaining a set of hlint rules to promote stability

  • Previously holding the token: Trevis
  • Opened issue asking if we can write rules for typeclasses.

Parked Action Items/Projects due to expected absence of token holder

New for next week

Action items

Discussion items