[GHC] #13936: initTc: unsolved constraints

[GHC]

#13936: initTc: unsolved constraints
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           Reporter:  junkbondtrader  |             Owner:  (none)
               Type:  bug             |            Status:  new
           Priority:  normal          |         Milestone:
          Component:  Compiler        |           Version:  8.0.2
           Keywords:                  |  Operating System:  Windows
       Architecture:  x86_64 (amd64)  |   Type of failure:  None/Unknown
          Test Case:                  |        Blocked By:
           Blocking:                  |   Related Tickets:
Differential Rev(s):                  |         Wiki Page:
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 {{{
 Prelude> lucky (7.0 :: Num)
 ghc.exe: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-unknown-mingw32):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] lucky_afgR :: t_afgQ[tau:1] (CHoleCan: lucky)
         [W] lucky_afhl :: t_afhk[tau:1] (CHoleCan: lucky)}

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 {{{#!hs
 lucky :: Num -> String
 lucky 7 = "LUCKY NUMBER SEVEN!"
 lucky x = "Sorry, you're out of luck, pal!"
 }}}

 I believe that above function declaration doesn't actually make sense, but
 it caused a panic that asked for a bug report so I'm doing it. Apologies
 for my newness :)

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13936>
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