In both the 'increment' and 'decrement' countFn, we observer the
following pattern:
if /* some computation with n */ {
// ...
return n +- 1, nil
}
// ...
return /* 0 or 1 */, nil
But in the below case of the increment implementation, we violate this
example. Let's fix that be adhering to the above.
bbb8f5e485