Support Haskell2010 as pragma

[jan-christiansen]

Haskell2010 is an official GHC extension (https://downloads.haskell.org/ghc/latest/docs/users_guide/exts/table.html) and used in yi-editor/yi (https://github.com/yi-editor/yi/blob/13fa0f7c598a115485572b66fed5bc3cf383d0ef/yi-core/src/Yi/PersistentState.hs#L5), for example. I suggest to support this extension by replacing

readExtension :: String -> Maybe Extension

with

readExtension :: String -> [Extension]

and yield default2010Extensions in the case of Haskell2010.

If this is fine, I will create a pull request.

[tomjaguarpaw]

Thanks. Perhaps we do have to do something about that, but I am somewhat surprised that this feature doesn't exist already. The authors would have been aware of Haskell2010. That makes me think there is a good reason it is omitted.

[jan-christiansen]

Good point, perhaps it is because languages are handled orthogonally to pragmas by Cabal and my approach is rather a hack to make the parser succeed : ) You are right, in my approach the parser would actually successfully parse NoHaskell2010 : ) As this should obviously not be allowed, adding support for language pragmas would require a larger refactor and explicitly handling language extensions.