if (length < 0) length= 0; return new Position(problem.getSourceStart(), length);
if (length < 0) return null;  return new Position(start, length);
			protected Position createPositionFromProblem(IProblem problem) {				int length= problem.getSourceEnd() - problem.getSourceStart() + 1;				if (length < 0) length= 0;				return new Position(problem.getSourceStart(), length);			}