[GHC] #15562: `-XStrict -XNoStrict` is not neutral

[GHC]

#15562: `-XStrict -XNoStrict` is not neutral
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        Reporter:  hvr               |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.6.1
       Component:  Compiler          |              Version:  8.4.3
      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 hvr):

 Well, with the current semantics, automatically reordering your `LANGUAGE`
 pragmas can change the effective set of enabled extensions. So that's
 something IDEs and refactoring tools will hopefully be aware of.

 At least for now we have a simple heuristic such tooling can use to avoid
 changing the meaning of pragmas: groups of negative and positive pragmas
 do not commute. I.e. you are only allowed to reorder pragmas within a
 sequence of either positive or negative pragmas.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15562#comment:3>
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