There are four levels of compiler diagnostic severity:
The first three levels correspond to condition classes which are
defined in the ANSI standard for Common Lisp and which have special
significance to the
These levels of compiler error severity occur when the compiler
handles conditions of these classes.
The fourth level of compiler error severity, note, corresponds
sb-ext:compiler-note, and is used for problems which are
too mild for the standard condition classes, typically hints about how
efficiency might be improved. The
compiler-note, is signalled when the compiler
deletes user-supplied code after proving that the code in question is
Future work for SBCL includes expanding this hierarchy of types to allow more fine-grained control over emission of diagnostic messages.
Root of the hierarchy of conditions representing information discovered by the compiler that the user might wish to know, but which does not merit a
style-warning(or any more serious condition).