Re: [GHC] #13461: Panic on compile of file with a hole and nothing else

20 Mar 2017

      #13461: Panic on compile of file with a hole and nothing else
-------------------------------------+-------------------------------------
        Reporter:  Tritlo            |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.0.2
  checker)                           |
      Resolution:                    |             Keywords:
Operating System:  MacOS X           |         Architecture:  x86_64
                                     |  (amd64)
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Old description:
...
The example is very simple, just:
{{{
test :: Int -> Int
test = _
}}}
which produces the panic:
{{{
[1 of 1] Compiling Main             ( manyIdsTest.hs, manyIdsTest.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.2 for x86_64-apple-darwin):
        initTc: unsolved constraints
  WC {wc_insol = [W] __awc :: t_awb[tau:1] (CHoleCan: _)}
}}}
New description:

 The example is very simple, just:

 {{{
 test :: Int -> Int
 test = _
 }}}

 which produces the panic:

 {{{
 [1 of 1] Compiling Main             ( manyIdsTest.hs, manyIdsTest.o )
 ghc: panic! (the 'impossible' happened)
   (GHC version 8.0.2 for x86_64-apple-darwin):
         initTc: unsolved constraints
   WC {wc_insol = [W] __awc :: t_awb[tau:1] (CHoleCan: _)}
 }}}

 I suspect that there might be a missing case when there is nothing else in
 scope.

--

Comment (by Tritlo):

 Replying to [ticket:13461 Tritlo]:
...
The example is very simple, just:
{{{
test :: Int -> Int
test = _
}}}
which produces the panic:
{{{
[1 of 1] Compiling Main             ( manyIdsTest.hs, manyIdsTest.o )
ghc: panic! (the 'impossible' happened)
  (GHC version 8.0.2 for x86_64-apple-darwin):
      initTc: unsolved constraints
  WC {wc_insol = [W] __awc :: t_awb[tau:1] (CHoleCan: _)}
}}}
--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13461#comment:2
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