This ticket seems to have spec, spectests and implementation all blocking on each other. Meanwhile, a bit of discussion on #perl6 reveals that STD.pm6 acutally takes a stand; it checks whether there's a 'foo' sub declared if it encounters &foo at compile time.
Unfortunately, there's a bug in STD.pm6 such that exactly that check doesn't work at present. But that doesn't concern this ticket; the behavior reported in this ticket is decidedly not a bug. Rejecting ticket.
