There's also a peculiarity however: the condition type will be
presented as SIMPLE-FILE-ERROR in these new implementations which
doesn't actually exist in the condition system, but it's actually
FILE-ERROR, with SIMPLE- prefixed. I forgot the exact reason for this,
but Juanjo once explained it to me and I could search my archives if
Simple errors carry an explanatory message, file errors do not; for this reason most errors signaled by ECL are mixins of simple-error and some more fundamental class.
In principle the fact that the condition is signaled as a descendent of file-error and not a file-error instance should not be a problem, provided the user does not assume unspecified behavior.