Regression with call()

[lunelson]

The following code was working correctly up until one of the last minor bumps.

@function apply($args) { @return call($args...); }
@function foo($a, $b, $c){ @return $a $b $c; }

.fntest {
  output: call(foo,1,2,3);
  output: apply(foo 1 2 3);
}

Returned correctly, as late as v3.3.4:

.fntest {
  output: 1 2 3;
  output: 1 2 3; }

now with v3.3.6 returns:

.fntest {
  output: 1 2 3;
  output: foo 1 2 3...(); }

[mgreter]

Probably a duplicate of #2034