Here, the recursive call position(ch, n + 1) expands to s.position(ch, n + 1). This is important, since otherwise
we'd get lots of errors in particular for collective extension methods. We can do that since there is no way to
confuse with a non-extension call, which would be written extension_position(s)(ch, n + 1). Without the extension_
we'd not know in general whether the call we see was an extension call with implied prefix, or a non-extension call.
Читаю это и не могу понять "non-extension call, which would be written extension_position(s)(ch, n + 1)". Почему у нон экстеншна появляется префикс extension?