Replace Extension type with (newtyped?) String

[guest]

Currently it is not possible to put extensions that Cabal does not know about in Cabal files. With GHC's -XFoo and --supported-extension flags there is no need for Cabal to maintain its own extension list, so this type should be replaced with either

type Extension = String

or

newtype Extension = Extension String

[duncan]

Discussion inconclusive.

[duncan]

I'm closing this. The original problem is fixed though not via the suggested solution. That is to say that Cabal does now let you list extensions in the .cabal file that Cabal does not know about and if ghc supports them then it'll work.

However we still want to maintain a registry of known semi-standardised extensions. Then the choice between using a newtyped String and an enumeration with an UnknownExtension String case is a more detailed question of API and implementation. If anyone feels strongly about the latter then they should present their arguments (and patches) in this ticket or a new ticket.

Alternatively if anyone feels strongly that Cabal should not maintain the registry of known semi-standardised extensions, then that's a discussion we should probably hold on the mailing list.