Add Alpha and Subst instances for NonEmpty
#62
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@byorgey We turned off CI for GHC 7.x last year, so |
we turned off CI for 7.x last year
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NonEmptyhas been inbasesince version 4.9, so accepting this PR probably requires changing the lower bound onbasein the.cabalfile as well as removing GHC 7.8 and 7.10 from thetested-withlist, OR including theNonEmptyinstances conditionally, via CPP. I'm not sure what your policy is on support for older versions ofbase/GHC so I'll leave that up to you!Especially with the additional warnings generated by GHC 9.8 for the use of partial functions like
head, it is nice to be able to useNonEmptywhen we statically know a list cannot be empty. For example, I was refactoring some code where I have a function definition that contains a list of clauses --- but in fact it should really be aNonEmptylist since every definition must have at least one clause. After making the refactoring, I ran into the lack ofAlphaandSubstinstances. I put in some derived orphan instances for the moment but figured it would be nice to send these upstream.