The following code demonstrates the problem. It is handy to be able to "apply" arguments to a function/closure, but these calls do not properly handle the presence of default arguments. def xx = { a, b, c = "default" -> println "a $a b $b c $c"; }; xx(1, 2, 3); xx([1, 2, 3]); z = [1, 2, 3]; xx(z); z = [1, 2]; xx(1, 2); xx(z); def yy (a, b, c = "default") { println "a $a b $b c $c"; }; yy(1, 2, 3); yy([1, 2, 3]); z = [1, 2, 3]; yy(z); z = [1, 2]; yy(1, 2); yy(z); This would make the following ambiguous: def zz (a, b = "default", c = "default") { println "a $a b $b c $c"; }; zz([1, 2, 3]); There needs to be a way, as with Java varargs, to indicate when an array is "an array of arguments" and when it is "an argument that is an array". The current, Java-like approach may not be the best. It would be nice to have an "apply" method on functions/closures that would explicitly take "an array of arguments", much like Scheme/JavaScript: def zz (a, b = "default", c = "default") { println "a $a b $b c $c"; }; zz([1, 2, 3]); // "a [1, 2, 3] b default c default" zz.apply([1,2,3]); // "a 1 b 2 c 3"