What "first" & "second" are referring to is inconsistent

[iiYese]

This example shows just one instance of this. .with::<&X>().set_second_name("$x") being synonymous with .with_first_name::<&X>("$x") is confusing. In the prior "second" is referring to the name of second part of the pair but in the later "first" is referring to the type parameter not the name of the second part of the pair.