[GHC] #13443: Typeclass resolution errors quite puzzling

[GHC]

#13443: Typeclass resolution errors quite puzzling
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        Reporter:  tomjaguarpaw      |                Owner:  (none)
            Type:  feature request   |               Status:  new
        Priority:  normal            |            Milestone:  8.4.1
       Component:  Compiler (Type    |              Version:  8.0.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Poor/confusing    |  Unknown/Multiple
  error message                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by dfeuer):

 * failure:  None/Unknown => Poor/confusing error message
 * milestone:   => 8.4.1


Comment:

 I think it would be very useful to offer this as an option. Turning it on
 by default could be quite harmful, however, as context reduction can take
 many steps (thousands or more in type-heavy code) and we don't want to use
 a ton of memory unnecessarily. One option might be to let users set a
 particular maximum depth to report. Another (maybe?) could be to add a
 feature a bit like `HasCallStack` at the type level.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13443#comment:1>
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