Fill positional arguments by name (Perl 6)

call-positional-by-name.pl

use v6;

sub t ($x, $y, :$label = 'sum') {
    say "$label: ", $x + $y;
}

sub namecall(&c, *@pos, *%named is rw) {
    my %name-to-idx;
    for &c.signature.params.kv -> $idx, $p {
        next if $p.named;
        my $name =  $p.name.substr(1);
        %name-to-idx{$name} = $idx;
    }
    my @seen;
    my @args;
    # map named to positional
    for %named.pairs -> $p {
        if %name-to-idx{$p.key}.defined {
            my $v  := $p.value;
            %named{$p.key}:delete;
            my $idx = %name-to-idx{$p.key};
            @args[$idx] := $v;
            @seen[$idx] = True;
        }
    }
    # fills the gaps
    for @seen.kv -> $idx, $there {
        unless $there {
            unless (@pos) {
                die "Too few arguments supplied!";
            }
            @args[$idx] := @pos.shift;
        }
    }

    @args.push: @pos;

    # call!
    c |@args, |%named;
}

namecall &t, 40, x => 2, label => 'bla';