Add lift to FunctionK

[andyscott]

Quick attempt at providing a lift method for FunctionK, by means of a macro.

In my local testing, this works for Free and other more complicated types if you've enabled some form of the SI-2712 fix.

Thoughts?

[andyscott]

Everything passes except some style assertions, such as using null.

[non]

Thanks!

Would you mind writing some Scaladoc to explain what the macro does, how to use it, etc.? I think it will be relatively hard for casual users to look at this and understand how to use it.

[codecov-io]

Current coverage is 91.72% (diff: 88.23%)

Merging #1352 into master will decrease coverage by 0.01%

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  Files           237        238     +1   
  Lines          3571       3588    +17   
  Methods        3505       3520    +15   
  Messages          0          0          
  Branches         65         67     +2   
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+ Hits           3276       3291    +15   
- Misses          295        297     +2   
  Partials          0          0          

Powered by Codecov. Last update 0408170...e819893

[kailuowang]

Thanks very much! I like the idea (yah! less boilerplate for Free) and the test and doc looks good to me, but I am not too qualified to reviewed the macro part, other than @non, maybe @fthomas ?

[andyscott]

Less boilerplate for Free was exactly what motivated me to write this! I am considering using free monads on a project where a number of people have worked minimally in Scala, so I've been crafting a demo project that minimizes as many "scary" concepts as possible.

[andyscott]

Do I need to fix the code coverage issues for this PR? I'm not entirely sure how I'd be able to provide coverage for some of the "internal" methods to the macro.

[non]

@andyscott I think it's fine -- I'm not sure if those error message can be hit, but I'm glad you're providing an error message in case someone does hit them.

LGTM 👍

[johnynek]

👍