[GHC] #12526: regression in type inference with respect to type families

[GHC]

#12526: regression in type inference with respect to type families
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        Reporter:  Lemming           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  highest           |            Milestone:  8.0.2
       Component:  Compiler (Type    |              Version:  8.1
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  10634             |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by Lemming):

 Replying to [comment:9 simonpj]:

 > Here is a yet simpler version of the problem

 Thank you for the simplification! I guess we can also drop the type
 parameters of `Signal` and `Causal`.

 For now I have solved the problem in my package by adding type signatures
 to the let binding.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12526#comment:11>
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