Do not raise exceptions in exception clauses
Non Breaking, Breaking
When an exception is raised in an exception clause, it greatly increases the difficulty of debugging.
When an exception is raised in a finally or fault clause, the new exception hides the active exception, if present. This makes the original error hard to detect and debug.
When an exception is raised in a filter clause, the runtime silently catches the exception, and causes the filter to evaluate to false. There is no way to tell the difference between the filter evaluating to false and an exception being throw from a filter. This makes it hard to detect and debug errors in the filter's logic.