[GHC] #10143: Separate PprFlags (used by Outputable) from DynFlags

[GHC]

#10143: Separate PprFlags (used by Outputable) from DynFlags
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        Reporter:  ezyang            |                Owner:  ezyang
            Type:  task              |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.11
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #10961            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 I think your goal is this (taken from the top of the ticket).

 > At the moment, SDoc computations have full access to the entirety of
 DynFlags, despite only a minusculely small amount of the data structure
 being relevant to them.   This proposal is to split out a PprFlags
 structure which will be contained in a DynFlags, and contain dynamic flags
 JUST for pretty-printing.

 Is that your goal?  If so,seems a good goal.  But that seems to contradict
 your comment:11, where you say

 > If PprFlags is to be strictly about rendering, then SDocContext either
 needs to continue to have DynFlags in it, or needs to carry around the
 PlatformConstants, the general flags, and a **whole heap of other stuff
 from DynFlags**.

 My confusion is about whether it's true that `SDoc` computations need only
 a "miniscule" bit of `DynFlags`.  If true, then this project seems
 worthwhile. If false, not so worthwhile.

 I think the reason no one is being clear about whether this change is
 wanted or not is that there is confusion about what "this change" actually
 is.

 Could you, for example, list exactly the things you propose to put in
 `PprFlags`?  And what functions/data types change their signatures?
 Thanks

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10143#comment:15>
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