Dot notation does some fancy magic behind the scenes.  Read more here:
https://twig.symfony.com/doc/2.x/templates.html

Something that was added in Twig 2.x, when using foo.bar, it will check
for a `hasBar` method on the underlying object if `bar` is not a property
of it.  In this case, `hasClass` is a method, but not one we intend to
ever call.  This syntax makes that clear to twig, I think.

See https://twig.symfony.com/doc/1.x/deprecated.html#macros

> As of Twig 2.0, macros imported in a file are not available in child
> templates anymore (via an include call for instance). You need to
> import macros explicitly in each file where you are using them.

The implemented/extended classes here were deprecated well before this
code was originally written in 2018, in
#426.

In any case, \Twig\Extension\GlobalsInterface is needed to for the
getGlobals() method to work now.
See https://twig.symfony.com/doc/2.x/advanced.html