16 Oct
2016
16 Oct
'16
3:34 p.m.
On Sun, 16 Oct 2016, Andrew Martin wrote:
Thanks for weighing in. It is possible to use cabal flags + CPP to work around this, although I don't like doing that for the reasons you would expect. I'm also not typically comfortable opening up an issue to ask a package maintainer to add a flag to enable conditional dependencies for instances.
Conditionally compiling instances into a package is not an option. If another package imports a certain version of your package it can expect the availability of all instances. There is no other way for a package to assert certain instances other than specifying the package version.