EPA: Opt_KeepRawTokenStream is no longer used

Follow-up from !2418 (closed), see #19579

The flag Opt_KeepRawTokenStream is no longer used. It should be removed.

Is there a policy around deprecation, or can it just be removed?

added API annotations needs triage labels

mentioned in issue #19579

Given that this is exported from the GHC module, it would probably be best to give this a proper deprecation:

• Add a DEPRECATED pragma on the declaration
• Issue a warning when the flag is used
• Update its documentation to say that it is now a no-op
• Add a note to the release notes mentioning the deprecation

Then in 9.2 + 2 releases we drop the constructor.

added Ttask label and removed needs triage label

added GHC API label

Looking more closely at this, I see it is used, but it now functions as a flag to the lexer to retain the non-haddock comments, and still needs to be set if the exact print annotations are to be used.

So it has turned into something that is used, but is now named incorrectly.

I think it should be renamed to something like Opt_KeepComments.

Also, it makes sense for exposing it as a command line option, -dkeep-comments.

I notice there is also a parser flag for haddock comments, which appears to be in the parser flags only.

In fact, this is a parser flag only, perhaps it should be removed from DynFlags.

mentioned in commit d96e920b

mentioned in merge request !7979 (closed)

mentioned in commit f0203665

mentioned in commit 2d13702b

mentioned in commit d5a3c9a7

mentioned in commit 83c67f76

mentioned in commit bf5c251d

mentioned in commit 389759ce