Latest Template Haskell Breaks Package

[Erik Hesselink]

Are you on a Mac? OS X switched to clang, which caused all kinds of
problems as GHC uses the C compiler as a C preprocessor, and clang
behaves differently from gcc.

Erik

On Tue, Dec 23, 2014 at 4:06 PM, Dominic Steinitz <dominic at steinitz.org> wrote:
> Hi Erik,
>
> Thank you very much. With that clue the compilation now doesn’t fail at that particular point.
>
> The bad news is it now fails to compile this module
>
> https://hackage.haskell.org/package/yarr-1.3.2/docs/src/Data-Yarr-Utils-Primitive.html#clampM%27
>
> with a parse error(!). Not only do I not have much experience with TH but this has now exposed my ignorance of CPP.
>
>> Data/Yarr/Utils/Primitive.hs:119:126: Parse error in pattern: con
>
> If I comment out the last four lines
>
>> PRIM_COMP_INST(Int, I#, (<=#), (>=#))
>> PRIM_COMP_INST(Char, C#, leChar#, geChar#)
>> PRIM_COMP_INST(Word, W#, leWord#, geWord#)
>> PRIM_COMP_INST(Double, D#, (<=##), (>=##))
>> PRIM_COMP_INST(Float, F#, leFloat#, geFloat#)
>
> then the module compiles but of course then the whole package does *not* compile.
>
> Did something change in 7.8.3 with regard to CPP (this code has not been modified for at least two years)?
>
> Thanks once again.
>
> Dominic Steinitz
> dominic at steinitz.org
> http://idontgetoutmuch.wordpress.com
>
> On 23 Dec 2014, at 13:42, Erik Hesselink <hesselink at gmail.com> wrote:
>
>> Hi Dominic,
>>
>> It looks like just a representation change: a TySynEqn is a data type
>> containing a [Type] and a Type, and those were the original two
>> arguments. So it looks like with a little bit of CPP, you could
>> support both versions. Something like
>>
>> #if MIN_VERSION_template_haskell(2,9,0)
>> ...
>> #else
>> ...
>> #endif
>>
>> In general, I think each major release of template haskell has quite
>> some breaking changes, but I don't know of any place where they're
>> enumerated. The GHC changelog only has a couple of high level bullet
>> points.
>>
>> Regards,
>>
>> Erik
>>
>> On Tue, Dec 23, 2014 at 2:20 PM, Dominic Steinitz <dominic at steinitz.org> wrote:
>>> I realise I should have sent this to the libraries list.
>>>
>>> Dominic Steinitz
>>> dominic at steinitz.org
>>> http://idontgetoutmuch.wordpress.com
>>>
>>> Begin forwarded message:
>>>
>>> From: Dominic Steinitz <dominic at steinitz.org>
>>> Subject: Latest Template Haskell Breaks Package
>>> Date: 23 December 2014 13:14:26 GMT
>>> To: Haskell-Cafe <haskell-cafe at haskell.org>
>>>
>>> Hello Fellow Haskellers,
>>>
>>> I have become a maintainer for yarr
>>> (https://hackage.haskell.org/package/yarr). This no longer compiles with
>>> ghc-7.8.3 because it specifies base == 4.6. Relaxing this to base >=4.6 &&
>>> <4.8 tells me I need a newer version of Template Haskell
>>>
>>> rejecting: template-haskell-2.7.0.0, 2.6.0.0, 2.5.0.0, 2.4.0.1, 2.4.0.0,
>>> 2.3.0.1, 2.3.0.0, 2.2.0.0 (conflict: yarr => template-haskell>=2.8 && <2.9)
>>>
>>>
>>> If I now relax the constraint for Template Haskell I get a compiler error as
>>> there has been a breaking change from Template Haskell 2.9 to 2.10.
>>>
>>> Data/Yarr/Utils/FixedVector/VecTuple.hs:45:16:
>>>    Couldn't match expected type ‘TypeQ -> Q Dec’
>>>                with actual type ‘Q Dec’
>>>    The function ‘tySynInstD’ is applied to three arguments,
>>>    but its type ‘Name -> TySynEqnQ -> DecQ’ has only two
>>>
>>>
>>> And indeed looking at the changes in
>>> http://git.haskell.org/packages/template-haskell.git/commitdiff/ccd7891c536b29b8bea96eb92520f46e21390e39
>>> I can see that the function in question has changed.
>>>
>>> -tySynInstD :: Name -> [TypeQ] -> TypeQ -> DecQ
>>> -tySynInstD tc tys rhs =
>>> +tySynInstD :: Name -> [TySynEqnQ] -> DecQ
>>> +tySynInstD tc eqns =
>>>
>>>
>>> Did I miss some announcement of this breaking change and the advice on what
>>> to do about it?
>>>
>>> If I did can someone please point me at the relevant document. If not then I
>>> feel sad and would be very grateful if someone could help me as I know very
>>> little about Template Haskell.
>>>
>>> Many thanks
>>>
>>> Dominic Steinitz
>>> dominic at steinitz.org
>>> http://idontgetoutmuch.wordpress.com
>>>
>>>
>>>
>>> _______________________________________________
>>> Libraries mailing list
>>> Libraries at haskell.org
>>> http://www.haskell.org/mailman/listinfo/libraries
>>>
>