[Haskell-cafe] Fwd: hackage compile failure with QuickCheck 2.5

Ross Paterson ross at soi.city.ac.uk
Wed Jul 18 02:21:04 CEST 2012

On Wed, Jul 18, 2012 at 12:14:12AM +0100, Antoine Latter wrote:
> Cabal doesn't play well with version constraints on the template-haskell
> package - it doesn't know it can't reinstall template-haskell.
> The workaround is to figure out why QuickCheck has version constraints on
> template-haskell and solve that problem in the QuickCheck package a different
> way - perhaps with CPP conditonal compilation macros - and then remove the
> problematic version constraints.

QuickCheck's constraint is template-haskell >= 2.4, which doesn't explain
why cabal wanted to install when was already present.

Also, I'd expect --avoid-reinstalls to stop it reinstalling anything,
but apparently it doesn't do that with the modular solver.

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