[GHC] #15272: Handle implied flags more intuitively

[GHC]

#15272: Handle implied flags more intuitively
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        Reporter:  tdammers          |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.8.1
       Component:  Compiler          |              Version:  8.4.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Other             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #14963            |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by tdammers):

 Replying to [comment:1 nomeata]:
 > Hmm, would that still lead to the desired outcome if the user specifies
 `-fdefer-type-errors -fno-defer-type-holes`?
 >
 > Currently, I expect that after this, `defer-type-holes` is disabled.
 >
 > Under your scheme, it seems that `-fno-defered-type-holes` does not
 actually affect the list of ''explicit flags'' (because there is no
 `Opt_DeferTypeHoles` to undo), but then when we calculate the set of
 ''explicit flags'' `Opt_DeferTypeErrors` will imply `Opt_DeferTypeHoles`,
 and that flag will be enabled – against the user’s intention, I presume?

 Ah, you're right, that would still be a problem. Essentially though,
 asking for `-fdefer-type-errors -fno-defer-type-holes` is kind of an
 impossible request. Hmm.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15272#comment:3>
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