- If the same name appears in multiple input lists with different types, an
- error is signalled; this error will quote the origins of a representative
- conflicting pair of arguments."
+ If the same name appears in multiple input lists with different types, a
+ continuable error is signalled.
+
+ The WHATFN function is given no arguments, and is expected to return a
+ file location (or other object convertible with `file-location'), and a
+ string (or other printable object) describing the site at which the
+ keyword argument lists are being merged or nil; a mismatch error will be
+ reported as being at the location returned by WHATFN, and the description
+ will be included in the error message. A nil WHATFN is equivalent to a
+ function which returns a nil location and description, though this is
+ considered poor practice.
+
+ The REPORTFN is given a single argument ARG, which is one of the
+ conflicting `argument' objects found in the REPORTFN's corresponding
+ argument list: the REPORTFN is expected to issue additional `info'
+ messages to help the user diagnose the problem. The (common) name of the
+ argument has already been reported. A nil REPORTFN is equivalent to one
+ which does nothing, though this is considered poor practice."