(I am writing this here since I just created my first account just to comment on Jurgen's answer but i need 2 reputation to do that.)

Having worked with Rascal for a course at my university (which I am pretty sure Jurgen is also a professor at), I feel the urge to ask (related to the snippet taken from Jurgen's answer): what is the point of being able to see the actual error only by using the try catch? Why not just display it as an error directly? What is the point of having to take 10 steps just to find what exactly is wrong instead of just displaying it?

My second question is: even if there is a need for taking all the steps to achieve something simple, why not put it in a universal document, or some kind of FAQ, instead of people having through go through Github issues and Stack Overflow answers? Something to at least make it easier to find these things?

"It seems we have a constructor to work with. So what is going on? I stepped through the code of implode in Java to find out that the real reason was hidden by a bug in the backtracking part of implode. That's now fixed (see next continuous release on the update site).

The current, better, error message is:

rascal>try { implode(#AST::Build, x); } catch IllegalArgument (t, m) : println("<m> : <t>");
Cannot find a constructor for IdeFolder with name options and arity 3 for syntax type 'Options' : set(${TARGET_NAME}_IDE_FOLDER "test")

"