Add Parallel.parFoldMapA

[nigredo-tori]

Aka foldMapA hoisted through a Parallel.

[LukaJCB]

This is a great feature!

I wonder though if it would be easier to just place this method straight on the Foldable trait?

[nigredo-tori]

It would probably be easier (no extra syntax). I'm a bit out of the loop, though - is this the preferred way to do things at the moment? I put parFoldMapA on Parallel to keep it consistent with all the other par* functions, but I can put it on Foldable if you want.

[codecov-io]

Codecov Report

Merging #3147 into master will decrease coverage by 0.02%.
The diff coverage is 50%.

@@            Coverage Diff             @@
##           master    #3147      +/-   ##
==========================================
- Coverage   93.28%   93.25%   -0.03%     
==========================================
  Files         376      376              
  Lines        7323     7327       +4     
  Branches      195      199       +4     
==========================================
+ Hits         6831     6833       +2     
- Misses        492      494       +2

Flag	Coverage Δ
#scala_version_212	93.59% <50%> (-0.03%)	⬇️
#scala_version_213	90.92% <50%> (-0.03%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/syntax/parallel.scala	58.82% <0%> (-3.68%)	⬇️
core/src/main/scala/cats/Parallel.scala	84.84% <100%> (+0.47%)	⬆️

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[travisbrown]

This looks great, thanks @nigredo-tori!

I think it probably is best to keep this on Parallel for consistency. I've made a few comments, but not adding another BinCompatN trait is the only important one.

Would you mind adding a syntax test to SyntaxSuite as well?

[travisbrown]

Looks good to me, thanks!

[rossabaker]

I agree that it's in the right place where it is. Thanks!