Make mainBody inline about kotlin-argparser HOT 2 CLOSED

Good idea!

One gotcha with this: if you only return from (an inline version of) mainBody's lambda sometimes, it's fine, but if you do it on every code path you start getting errors like:

Kotlin: 'Nothing' return type needs to be specified explicitly
Kotlin: This function must return a value of type Nothing

This is because returning from main in every code path of mainBody means that mainBody's return type is now Nothing (as it always exits prematurely), and the type of main is the same as mainBody in the typical usage.

A workaround (which also works right now, BTW) is to use a qualified return:

return@mainBody

This returns from mainBody, rather than from main, but in the typical usage that's pretty much the same thing.

Another work around is to write something like this:

fun main(args: Array<String>) {
    mainBody {
        ...
        return
    }
}

instead of:

fun main(args: Array<String>) = mainBody {
        ...
        return
    }

This decouples the type from mainBody's lambda from main, so Kotlin is happy.

from kotlin-argparser.

Thank you for that detailed answer!

I think using return@mainBody is a fine solution.

from kotlin-argparser.