[GHC] #9023: Error when using empty record update on binary pattern synonym

[GHC]

#9023: Error when using empty record update on binary pattern synonym
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        Reporter:  Iceland_jack                 |            Owner:  cactus
            Type:  bug                          |           Status:  merge
        Priority:  normal                       |        Milestone:
       Component:  Compiler                     |          Version:  7.8.2
      Resolution:                               |         Keywords:
Operating System:  Linux                        |     Architecture:  x86
 Type of failure:  None/Unknown                 |       Difficulty:
       Test Case:  patsyn/should_compile/T9023  |  Unknown
        Blocking:                               |       Blocked By:
                                                |  Related Tickets:
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Changes (by simonpj):

 * status:  patch => merge
 * testcase:   => patsyn/should_compile/T9023


Comment:

 archblob: you successfully provoked me into looking into this, but your
 patch was I'm afraid utterly wrong!  The `[Type]` argument to
 `patSynInstArgTys` is positional: the order of the types in that list
 matters a lot! Moreover we need the instantiating types, not the free
 variables of the instantiating types.  So if it worked for you it was a
 fluke.

 But don't be discouraged!  There is plenty more to do.

 Austin: worth merging this to 7.8.3.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9023#comment:7>
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