Remove -XMonadFailDesugaring as per MFP
Summary
-XMonadFailDesugaring
should have been removed in 8.8 as per MFP#Transition.
Steps to reproduce
Enable -XMonadFailDesugaring
: it's accepted (having no effect).
Expected behavior
The extension is rejected -- as unknown or removed (not sure which one?).
Environment
- GHC version used: GHC HEAD, 8.10
Discussion
This is a follow-up on the discussion over ghc-steering-committee. Quoting @simonpj:
We were due to remove them in 8.8, as the proposal says under "Transitional Strategy" https://gitlab.haskell.org/haskell/prime/-/wikis/libraries/proposals/monad-fail But we failed to do so. Would someone like to make a ticket to do them?
What bothers me a bit is the User Guide's wording:
This extension is enabled by default since GHC 8.6.1, under the MonadFail Proposal (MFP).
This extension is temporary, and will be deprecated in a future release.
This sounds much far from removal than it's from MFP's plan.
Also, there's another action item there, which, probably deserves its own issue:
Control.Monad.Fail is now a redundant module that can be considered deprecated.