17 Jul
2012
17 Jul
'12
8:21 p.m.
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 2.6.0.0 when 2.7.0.0 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.