[GHC] #14685: Pragma to reset language extensions in module header

[GHC]

#14685: Pragma to reset language extensions in module header
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        Reporter:  mgsloan           |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.2
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by mgsloan):

 *Sigh* You think I didn't consider something like that?  When convenient,
 I strongly prefer to write code that is compatible with older versions of
 the tools we use, unless there is a strong reason to do otherwise.  I
 particularly appreciate it when others do the same.... :|

 With all prior versions, your suggestion would result in

 {{{
 foo.hs:1:16: error: unknown flag in  {-# OPTIONS_GHC #-} pragma: -X
 }}}

 With my proposal, it results in

 {{{
 foo.hs:1:1: warning: [-Wunrecognised-pragmas] Unrecognised pragma
 }}}

 That said, having `-X` mean the same thing would be consistent with `-i`
 and the like, so that could be considered.  I think that flag convention
 is really weird, but it is at least consistent.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14685#comment:2>
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