#575 info class forward returning error instead of empty list

[dzach]

[info class forward className methodName] returns an error "prefix argument list not available for this kind of method" when it is used on a methodName that has no forward defined for it.

The documentation states:
"info class forward class method
This subcommand returns the argument list for the method forwarding called method that is set on the class called class. "

So, one would expect to get an empty list if there is no forward defined for a class, since there is no other way of introspecting a class method for any forwards.
The error given cannot be remedied by the programmer, since there is nothing one can do but use an unecessary [catch] to avoid it. Not having a forward is not an error for a method.

An empty list would convey the same meaning with the error message, i.e. the unavailability of an argument list, but in a non-exceptional manner.

[dzach]

Or, should there be another way to enumerate a class's 'forwards', without being punished with an error?

[Donal K. Fellows]

Everything is as designed and documented, and there's consistency with [info class definition] which only applies to methods defined with 'method'.

Whether or not it should be an error is a separate matter. Converting to FRQ.