sub echo(Int:D: $x) {
    say $x.^name;
}

echo(3);

--output:--
===SORRY!=== Error while compiling /Users/7stud/raku_programs/b.raku
Can only use the : invocant marker in the signature for a method
at /Users/7stud/raku_programs/b.raku:14
------> sub echo(Int:D: $x⏏) {
    expecting any of:
        constraint