🚀 go-pugleaf

Execution of Test.Do in the following sample module generates a 
"NIL dereference read " trap on Oberon/F at the line indicated 
although in Oberon for Windows V4, it works all fine. 

MODULE Test;

TYPE
	T0 = POINTER TO T0desc;
	T0desc = RECORD
		next: T0;
	END;
	
	T1 = POINTER TO T1desc;
	T1desc = RECORD(T0desc)
	END;
	
PROCEDURE Do*;
	VAR x: T1; next: T0;
BEGIN
	NEW(x);
	x :=  x.next(T1); (* a TRAP is generated here *)
END Do;

END Test.

It seems that type-guarding the pointer x.next which happens to 
have the value NIL at execution time causes the problem. Did 
anybody else encounter this problem before? 

I am using Oberon/F v 1.1 for Windows.

Thank you in advance for any hints. 

Martin Weiss
Applied Physics Faculty
University of Eindhoven
The Netherlands