Code cleanup

[arcz]

This PR features various cleanup and simplifications in the entirety of code:

• Use OverloadedRecordDot as much as possible
• Use </> operator for path joining
• Use Sets instead of (NE)lists. This is good for generating random data as picking random elements from a large Set is way faster than lists
• Rewrite some complex one-liners to something that we can understand 😄
• Remove underscores from most of the structures and Template Haskell generated lenses. I think we can even go entirely without lenses as, in practice, we don't really do that much nested data manipulation and I'm not sure a few more lines of code are worth the added cost of knowing lenses. However, if we still find lenses useful, we should move on to a more modern solution such as generic-lens or optics-core in the future.

[ggrieco-tob]

Is this change correct? 🤔

[arcz]

Maybe is now matched earlier:

  -- save corpus
  case cfg._cConf._corpusDir of
    Nothing -> pure ()
    Just dir -> do
      saveTxs (dir </> "reproducers") (filter (not . null) $ (.testReproducer) <$> cpg._tests)
      saveTxs (dir </> "coverage") (snd <$> Set.toList cpg._corpus)

[ggrieco-tob]

NonEmpty has different properties than Set, so I'm not sure.

[arcz]

I wish there were a non-empty set, but Set is better for what we do here as we pick random elements and list/non-empty list has slow random access. We would need to convert lists to sets, that takes linear time which kills the performance during fuzzing.

[ggrieco-tob]

I'm getting this error when trying to save a corpus:

echidna-test: corpus-new/covered./1674496096/.txt: withFile: does not exist (No such file or directory)

[arcz]

Fixed. Apparently, I got confused by the variable names so fixed them too.