`toggled` or `isFalse` property/method on bool for use with KeyPath APIs

Evolution Discussion
21

However, perhaps the right thing is to find a way to express an inversion of a KeyPath to a Bool instead of unnecessarily expanding Bool 's API.

I agree with your sentiment, however, such a solution escapes me. It looks like the key path code only deals with downcats.
swift/KeyPath.swift at main · apple/swift (github.com)](https://github.com/apple/swift/blob/main/stdlib/public/core/KeyPath.swift))

So, something like this may not work,

extension KeyPath where Value == Bool {
  var not: KeyPath<Root, Bool> {
    return <#...#>
  }
}