Auto-generated dependent comparison operators

A.pm

use AutoGen;
class A {
    has $.x;
    multi infix:<cmp>(A $a, A $b) is autogen {
        $a.x cmp $b.x;
    }
}

AutoGen.pm6

module AutoGen {
    my %names =
        cmp => <before after>,
        leg => <gt lt ge le eq>,
        '<=>' => ('>', '<', '>=', '<=', '==')
        ;

    multi trait_mod:<is>(&routine, :$autogen!) is export {
        my @ops = 
            sub ($a, $b) { routine($a, $b) == Increase },
            sub ($a, $b) { routine($a, $b) == Decrease },
            sub ($a, $b) { routine($a, $b) != Decrease },
            sub ($a, $b) { routine($a, $b) != Increase },
            sub ($a, $b) { routine($a, $b) == Same     },
            ;

        my $shortname = &routine.name.substr(7, *-1);
        for %names{$shortname}.list Z @ops -> $n, $o {
            my role named { has $.name };
            $o does named("infix:<$n>");
            for &routine.signature.params.kv -> $i, $p {
                nqp::bindattr(nqp::p6decont($o.signature.params[$i]),
                        Parameter, '$!nominal_type', $p.type);
            } 
            trait_mod:<is>(:export, $o);
        }
    }
}

shell.txt

$ ./perl6 -e 'use A; say A.new(x => 5) before A.new(x => 7)'
True
$ ./perl6 -e 'use A; say "a" before "b"'
===SORRY!===
CHECK FAILED:
Calling 'infix:<before>' will never work with argument types (str, str) (line 1)
    Expected: :(A $a, A $b)