[GHC] #11274: Confused type checker with typed holes and a missing instance (also panic)

[GHC]

#11274: Confused type checker with typed holes and a missing instance (also panic)
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        Reporter:  Xandaros          |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Compile-time      |            Test Case:
  crash                              |  typecheck/should_fail/T11274
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Changes (by simonpj):

 * testcase:   => typecheck/should_fail/T11274
 * status:  new => closed
 * resolution:   => fixed


Comment:

 This works in HEAD (and hence 8.0), but I've added a regression test.  We
 rightly get
 {{{
 T11274.hs:10:25: error:
     • No instance for (Eq Asd) arising from a use of ‘==’
     • In the expression: x == y
       In an equation for ‘missingInstance’: missingInstance x y = x == y
 }}}
 I have not tested 7.10.3, but I assume you are right about it failing
 there.

 Honestly, even if we release 7.10.4 I doubt we'll fix this bug on that
 branch -- it's not a show-stopper, and it'd be fresh work to do so.

 So I'll close this as fixed.  Thanks for reporting such a nice small case!

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11274#comment:2>
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