[GHC] #9880: ghc crashes on th splices in instance context

[GHC]

#9880: ghc crashes on th splices in instance context
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        Reporter:  Philonous         |                Owner:
            Type:  bug               |               Status:  closed
        Priority:  normal            |            Milestone:
       Component:  Documentation     |              Version:  7.8.3
      Resolution:  fixed             |             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 mentheta):

 Replying to [comment:2 goldfire]:
 > The behavior you see -- that error -- is what I'd expect.
 >
 > I had a brief go at implementing local declaration splices but soon
 realized that implementing this involves quite a bit of replumbing. The
 splices would have to break up mutually-recursive groups within class,
 instance, and `let` declarations, and that would require changes to
 several bits of HsSyn. So, I settled for just fixing the panic and waiting
 for someone to scream loudly that they need this feature.

 Hello goldfire,

 I've just run into the situation where I hoped `Q [Dec]` would have worked
 in a let binding, and it did not. I don't yet intend to scream, however, I
 am curious; Is there any Trac ticket in particular I could subscribe to,
 where I can follow any potential development on the implementation for
 supporting declaration splices in let bindings?

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9880#comment:7>
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