[Haskell-beginners] Different behaviors between GHC 7.6.3 and 7.8.3

[Henk-Jan van Tuyl]

On Tue, 30 Sep 2014 17:33:51 +0200, Emilio De Camargo Francesquini  
<francesquini at gmail.com> wrote:

:
> GHCi, version 7.8.3: http://www.haskell.org/ghc/  :? for help
> Loading package ghc-prim ... linking ... done.
> Loading package integer-gmp ... linking ... done.
> Loading package base ... linking ... done.
> Prelude> let x = 3 + 4
> Prelude> :print x
> x = (_t1::Num a => a)
> Prelude> :force x
> x = _
> Prelude> print _t1
> ghc: panic! (the 'impossible' happened)
>   (GHC version 7.8.3 for x86_64-unknown-linux):
>     tcTyVarDetails a{tv atm} [tv]
>
> Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
>
>
> Is it really a bug or is it something I really shouldn't be doing?

It seems to me that _t1 is a temporary name, therefore it is not  
meaningful to print _t1; GHCi should give a message telling that _t1 is  
not defined, not a panic message. It is best to write a bug report for  
this.

Regards,
Henk-Jan van Tuyl


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