The hunit test suite has the following constraint: https://github.com/system-f/validation/blob/e0755caa5f01c02c97c4a77a43a0112c1705d9e3/validation.cabal#L102 When building with the test suite enabled, using lens 5.* is not possible, consequently, although it would work perfectly fine.
The hunit test suite has the following constraint:
validation/validation.cabal
Line 102 in e0755ca
When building with the test suite enabled, using lens 5.* is not possible, consequently, although it would work perfectly fine.