The GHC Steering Commitee has accepted [proposal #669](https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0669-extension-categorization.md) which categorizes the stability of various language extensions. The categorisations should be documented in the User's Guide, and where an extension has been deprecated it should be warned about by `-Wdeprecated-flags`. @telser You previously indicated willingness to work on the documentation aspect of this, is that still the case? And do you expect to be able to make progress on the next round of classifications? (EDIT: I realise now that the latter is in progress at https://github.com/ghc-proposals/ghc-proposals/pull/738.)