failure_with: Difference btw positives and negatives

[kusnezoff-alexander]

What is the difference btw positives and negatives in the failure_with macro? When do I need to use negatives?

The documentation only talks about "positive"/"negative" Rules, but I can't find the place where it is defined what a "positive/negative" Rule is.

My guess:

• !e = negative Rule
• all other rules = positive Rule

I think it would be helpful to define what negative/positive Rules are in the docs at failure_with.