If a Java method such as

public static void foo(Object... args) {}

is called from Jython as

foo(1, 2, [3,4])

The call should be valid and the argsthat gets passed to the Java method should be [1, 2, [3, 4]].

The current method checks the final arg to check if it's a sequence and assumes the varargs are already being passed as a list so the call fails. A similar call without the list (eg foo(1, 2, 3)) works as expected.

A similar bug (but the other way around) can be see by calling a Java method such as

static void foo(int[] a, int... b) {}

as

foo([1,2,3])

which should be valid, but needs an additional empty list added to fit the vararg signature.