Extra arguments passed to fixed arity function don't cause error

[Chris Eppstein]

This should be an error.

@mixin foo($a, $b) {
  .foo { #{$a}: $b; }
}
$args: (color, red, extra-arg, another-extra-arg);
@include foo($args...);

It should behave exactly like this:

@mixin foo($a, $b) {
  .foo { #{$a}: $b; }
}
@include foo(color, red, extra-arg, another-extra-arg);

Which raises:

Syntax error: Mixin foo takes 2 arguments but 4 were passed.
        on line 4 of standard input, in `foo'
        from line 4 of standard input
  Use --trace for backtrace.

[Chris Eppstein]

This behavior has existed for as long as the varargs feature. Deprecation will be required.

[Natalie Weizenbaum]

I'm moving this issue to the new Ruby Sass repository because it's specific to Ruby Sass's implementation.