If a generic function is invoked with a combination of parameters for which there is no applicable method, GOOPS raises an error.
When an application invokes a generic function, and no methods at all
have been defined for that generic function, GOOPS calls the
no-method generic function. The default method calls
goops-error with an appropriate message.
When an application applies a generic function to a set of arguments,
and no methods have been defined for those argument types, GOOPS calls
the no-applicable-method generic function. The default method
calls goops-error with an appropriate message.
When a generic function method calls (next-method) to invoke the
next less specialized method for that generic function, and no less
specialized methods have been defined for the current generic function
arguments, GOOPS calls the no-next-method generic function. The
default method calls goops-error with an appropriate message.