[GHC] #14802: panic! (the 'impossible' happened)

[GHC]

#14802: panic! (the 'impossible' happened)
-------------------------------------+-------------------------------------
        Reporter:  Ebanflo           |                Owner:  (none)
            Type:  bug               |               Status:  infoneeded
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.2
  (Debugging)                        |
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Description changed by Ebanflo:

Old description:

> I was debugging and tried to print a matrix but got the following error
> message:
>
> <interactive>:34:21: error:<interactive>: panic! (the 'impossible'
> happened)
>   (GHC version 8.0.2 for x86_64-unknown-linux):
>         No skolem info: a1_IhXR[rt]
>
> Has this been fixed in the newer version of ghc? If so, what's the
> fastest way to update?

New description:

 I was debugging and tried to print a matrix but got the following error
 message:

 <interactive>:34:21: error:<interactive>: panic! (the 'impossible'
 happened)
   (GHC version 8.0.2 for x86_64-unknown-linux):
         No skolem info: a1_IhXR[rt]

 UPDATE:

 I downloaded ghc 8.2.2, extracted, ran `./config` and then `make install`.
 Now when I run `ghc -v` it says
     Glasgow Haskell Compiler, Version 8.2.2, stage 2 booted by GHC version
 8.0.2
 But when I run `ghci` it says that it is version 8.0.2 and it gives the
 same 'impossible' error as I did before.

 I put the function I was debugging in a small file with the other
 functions that it depends on (sorry, I accidentally attached the same file
 twice). It would be very difficult to replicate the test cases I was
 working with without copying a lot more code. I tried running the function
 on a simple test case (some 3x4 matrix) and when I tried to print the
 helper variable desired (mat1) it said that the runtime type of mat1 could
 not be determined. This was fixed by giving the function `calc` a type
 signature. Indeed, when I put this type signature in my actual code, I was
 able to debug it without a problem.

 My biggest concern at this point is how to boot ghci 8.2.2 instead of
 8.0.2, and because of this I'm not sure whether or not what I've described
 here is a problem with 8.2.2 or just 8.0.2.

--

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14802#comment:2>
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