Larry wrote:

: Can I write that as:
: : sub factorial (Int $n:) {
:     return 1 when 0;
:     return $n * factorial $n;
:   }

As it stands right now, no.  Ordinary subs do not allow invocants.
Arguably, it'd be more consistent if ordinary subs always topicalized
their first argument.  (But blocks have to be handled differently
since they expect to see the outer binding of $_ unless the block itself
rebinds $_.)  On the other hand, it'd probably work if you threw a
"multi" in front of the "sub".

Can anyone think of a good reason not to topicalize the first arg
of ordinary subs these days?

Only that methods no longer topicalize their invocant...they now invocantize it.

Also it's not a good general solution. I can easily imagine situations where you want the second argument, or the last arg, to be the topic.

I still think it would be better to allow people to explicitly say what they 

    sub factorial (Int $n is topic) {
        return 1 when 0;
        return $n * factorial $n;


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