equality-check.md

Command	Mean [s]	Min [s]	Max [s]
!isEmpty	3.304 ± 0.049	3.221	3.422
isEmpty == false	4.082 ± 0.511	3.235	4.551
isEmpty.isFalse	3.294 s ± 0.050	3.192	3.420

The data is collected by using hyperfine to run each case 100 times:

hyperfine --prepare 'rm -rf ./.build' --runs 100 'swift build'

Here's the implementation for isFalse:

public extension Bool {
  var isFalse: Bool {
      !self
  }
}