[GHC] #14489: GHC panic from emacs haskell mode

[GHC]

#14489: GHC panic from emacs haskell mode
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           Reporter:  ggoetz         |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Compiler       |           Version:  8.0.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Hello,

 I encountered a ghc panic while going through one of the chapters from
 "Haskell Programming from first principles".
 The following error message is reported from flycheck checker from
 src/Main.hs in the attached files:

 {{{
 Suspicious state from syntax checker haskell-stack-ghc: Flycheck checker
 haskell-stack-ghc returned non-zero exit code 1, but its output contained
 no errors: [1 of 2] Compiling Morse            ( [some
 path]/haskell_programming/ch14/morse/src/Morse.hs,
 /var/folders/2s/c4mvtf0x5_b4d9gf18r65wwh0000gn/T/flycheck-haskell-ghc-
 cache90097PyL/Morse.o )
 [2 of 2] Compiling Main             (
 /var/folders/2s/c4mvtf0x5_b4d9gf18r65wwh0000gn/T/flycheck90097c8R/Main.hs,
 /var/folders/2s/c4mvtf0x5_b4d9gf18r65wwh0000gn/T/flycheck-haskell-ghc-
 cache90097PyL/Main.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-apple-darwin):
         initTc: unsolved constraints
   WC {wc_insol =
         [W] convertLine_a2Ml :: t_a2Mk[tau:1] (CHoleCan: convertLine)}

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


 Try installing a more recent version of haskell-stack-ghc, and please open
 a bug report if the issue persists in the latest release.  Thanks!
 }}}

 Stack upgrade reports "Skipping binary upgrade, you are already running
 the most recent version". I'm not entirely sure whether this should be
 reported or not (I can't say I know what I'm doing...), so I'm reporting
 it just in case.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14489>
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