[GHC] #15044: Option to output instance resolution process

[GHC]

#15044: Option to output instance resolution process
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           Reporter:  lyxia          |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.2.2
           Keywords:                 |  Operating System:  Unknown/Multiple
  debug,typeclasses                  |
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Would it be possible to see what instances get picked by the constraint
 solver? For example, see coq's `Set Typeclass Debug.`.

 The following comment also shows what it might look like:
 https://www.reddit.com/r/haskell/comments/8cmn4i/algorithmically_scrapping_your_typeclasses/dxg8fes/

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/15044>
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