code: public PExp findExpression(PExp exp, int lineno)
  	{
  		try
  		{
  			return exp.apply(af.getExpExpressionFinder(), lineno);// FIXME: should we handle exceptions like this
  		} catch (AnalysisException e)
  		{
  			return null; // Most have none
  		}
  	}
docs: Find an expression starting on the given line. Single expressions just compare their location to lineno, but
  expressions with sub-expressions iterate over their branches.
  
  @param exp
  @param lineno
  The line number to locate.
  @return An expression starting on the line, or null.