[GHC] #11990: Custom Type Error not getting triggered in the nested Type function call

[GHC]

#11990: Custom Type Error not getting triggered in the nested Type function call
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        Reporter:  magesh.b          |                Owner:  diatchki
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  8.0.1-rc3
      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 bgamari):

 For the record the patch in comment:3 was merged to `ghc-8.0` as
 23be8c99a411f846ae7668682259bcad2a507122.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11990#comment:8>
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