ATerm ph = ((ATermPlaceholder) t).getPlaceholder();
if (ph.getType() == ATerm.LIST) {
list = (ATermList) ph;
appl = (ATermAppl) list.elementAt(0);
String fieldId = appl.getAFun().getName();
appl = (ATermAppl) appl.getArgument(0);
String fieldType = appl.getAFun().getName();
loc.makeTail();
addField(fieldId, fieldType, loc);