public static BinaryExpression createVariableIsNotNullExpression(VariableExpression var) {
    return new BinaryExpression(
      var,
      Token.newSymbol(Types.COMPARE_NOT_EQUAL, -1, -1),
      new ConstantExpression(null));
  }
Turns an argument list obtained from AstUtil.getArguments() into an Object[] array
suitable to be passed to InvokerHelper or SpockRuntime. The main challenge is
to handle SpreadExpression's correctly.
spock-core/src/main/java/org/spockframework/compiler/AstUtil.java