code: @Override
  	public void undefinedSubExpression(String subExprName, String exprName) {
  		reporter.error(prefix(exprName), "Undefined subexpression <", subExprName, ">");
  	}
docs: /*
  (non-Javadoc)
  @see com.github.misberner.duzzt.DuzztDiagnosticListener#undefinedSubExpression(java.lang.String, java.lang.String)