Presumably the template-haskell-2.3 package does not build with ghc-6.8
but fails to correctly specify the version of base or ghc that it
requires. If it did then we would have a better chance to get this
right.
Yes, this is certainly an issue in general with template-haskell-2.3. How do we fix this?
Another possible workaround...
If you avoid using the flag hack then the solver would not have to
choose so early which version of template-haskell to commit to and it
would be able to pick the right version later. Though then you need an
alternative method of finding which version of template-haskell you
ended up with. You could do it with some custom code in Setup.hs.
I don't mind using a different approach. How do I detect which version of template-haskell I'm using in Setup.lhs that is backwords compatible to Cabal 1.2? I would like to support both template-haskell-2.2 and -2.3 by deriving EMGM type representations for it, but the later has the 'Loc' datatype. So, I'm currently using the CPP flag to determine whether 'Loc' is available or not:
#ifdef TH_LOC_DERIVEREP
-- This type is only provided in template-haskell-2.3 (included with GHC 6.10)
-- and up.
$(derive ''Loc)
#endif
Thanks,
Sean