Use getOrElse in NonEmptyList#last

[PeterPerhac]

seems like someone re-implemented Option's getOrElse inside NonEmptyList. Delegate to Option#getOrElse instead

[codecov-io]

Codecov Report

Merging #3168 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3168      +/-   ##
==========================================
- Coverage   93.04%   93.04%   -0.01%     
==========================================
  Files         376      376              
  Lines        7374     7373       -1     
  Branches      209      209              
==========================================
- Hits         6861     6860       -1     
  Misses        513      513

Flag	Coverage Δ
#scala_version_212	93.34% <100%> (-0.01%)	⬇️
#scala_version_213	90.63% <100%> (-0.01%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/data/NonEmptyList.scala	98.7% <100%> (-0.01%)	⬇️

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[joroKr21]

It could be an optimization.

[travisbrown]

I'm not sure this is the reason for the original implementation, but getOrElse takes a Function0 argument, and before Scala 2.12 that meant that the pattern matching version was one allocation lighter. In this case now it's just an extra synthetic method and my guess is the two are probably close to the same.

Neither of those versions are going to be anywhere close to if (tail.isEmpty) head else tail.last, which actually does still avoid an allocation on 2.12+, but I don't think it matters much here.

[djspiewak]

This is somewhat defensible as an optimization, but as @travisbrown pointed out, both of them are quite slow compared to the if/else equivalent. I don't see any problem with the simplification.