[GHC] #9637: Type level programming needs an error function

[GHC]

#9637: Type level programming needs an error function
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        Reporter:  augustss          |                Owner:
            Type:  feature request   |               Status:  closed
        Priority:  normal            |            Milestone:  8.0.1
       Component:  Compiler          |              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:  #9180, #9636      |  Differential Rev(s):  Phab:D1236
       Wiki Page:                    |
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Comment (by Lemming):

 I just want to add: The Helium people also thought about customizing error
 messages:
 See Heeren, Hage, Swierstra on
 [http://www.staff.science.uu.nl/~hage0101/scriptingthetypeinferencer.pdf
 Scripting the Type Inference Process].

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9637#comment:14>
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