@function one-positional-arg($a,) {
  @return positional 1 $a;
}

@function two-positional-args($a, $b,) {
  @return positional 2 $a $b;
}

@function one-keyword-arg($a: a,) {
  @return keyword 1 $a;
}

@function two-keyword-args($a: a, $b: b,) {
  @return keyword 2 $a $b;
}

@function mixed-args($a, $b: b,) {
  @return keyword 2 $a $b;
}

.calls {
  one-positional-arg: one-positional-arg(a,);
  two-positional-args: two-positional-args(a,b,);
  one-keyword-arg: one-keyword-arg($a: z,);
  two-keyword-args: two-keyword-args($a: y,$b: z,);
  mixed-args: mixed-args(y, $b: z,);
}