[GHC] #14273: Typed holes' "valid substitutions" suggestions are oblivious to type class constraints

[GHC]

#14273: Typed holes' "valid substitutions" suggestions are oblivious to type class
constraints
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        Reporter:  RyanGlScott       |                Owner:  Tritlo
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler (Type    |              Version:  8.3
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #9091, #9479      |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by vanto):

 I said in old tickets that Typed Holes should not be enabled by
 default in the compiler. It does not make sense to activate it by
 default. At most it will only be an additional help but not a wonder
 and has shown so far that Typed Holes gives us more worry than
 clarity because of the errors (or warning) returned by the compiler.
 In this attitude the author is not wrong. I agree with him, because in
 some circumstances Typed Holes does not make sense. As for the
 usefulness of Typed Holes, his help is not miraculous. in all cases,
 Typed Holes should not be enabled by default. Take a look in Miranda,
 there is no Typed Holes and everything goes very well. Sometimes when one
 wants to do too well one does too badly. So Typed Holes in Haskell, why
 not? Provided you do not activate it by default!

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14273#comment:12>
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