[GHC] #14252: ApplicativeDo: Add compiler message about irrefutable pattern matches and Monad constraints

[GHC]

#14252: ApplicativeDo: Add compiler message about irrefutable pattern matches and
Monad constraints
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        Reporter:  mutantmell        |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler          |              Version:  8.2.1
      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 simonpj):

 When you add warnings like this you end up needing another flag to
 suppress the warning.  What if the user says "No, I didn't to make the
 match irrefutable; quit bugging me".  And then a per-module suppression
 flag is a bit of a blunt instrument.

 I'm not sure what's best; it would be good to get feedback from
 `ApplicativeDo` users.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14252#comment:3>
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