[Haskell-beginners] What does 'impossible happened' mean?

[David McBride]

And I should say, you might try a newer ghc, they fix things all the time.
Stack is still on ghc 8.0.2, but newer snapshots are on 8.2.2.

On Mon, Dec 11, 2017 at 11:43 AM, David McBride <toad3k at gmail.com> wrote:

> It may be a bug in ghc.  It may be a bug in stack.  Not much you can do
> about it other than to report it.
>
> On Mon, Dec 11, 2017 at 11:39 AM, Baa <aquagnu at gmail.com> wrote:
>
>> Hello, List. I hit error:
>>
>>     ghc: panic! (the 'impossible' happened)
>>       (GHC version 8.0.2 for x86_64-unknown-linux):
>>         initTc: unsolved constraints
>>       WC {wc_insol = [W] spec_a86e :: t_a86d[tau:1] (CHoleCan: spec)}
>>
>>     Please report this as a GHC bug:  http://www.haskell.org/ghc/rep
>> ortabug
>>
>> what does it mean and how to fix it?
>>
>> PS. I only added template Haskell "call" in my test suite like
>>
>>   $(blahBlah something)
>>
>> The same call works fine in other modules and in GHCI. "stack build"
>> works too, but tests - no (last stack 1.6.1)
>>
>> ===
>> Best regards, Paul
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>>
>
>
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