fix(xfunc ARRAY filter): update description and error message

Author: akinomyoga

completions/ARRAY

@@ -9,14 +9,17 @@
 #
 #     status 0 .... when the element should be preserved
 #     status 1 .... when the element should be removed
+#     status 2 .... when the usage of the predicate is wrong
 #     status 27 ... when the loop should be canceled.  All the remaining
 #                   elements will be preserved regardless of the presence of
 #                   option `-r'.
 #
-#   The other exit status will cancel the array filtering.  If this is an
-#   existing command name, the function is called with the value of the array
-#   element.  Otherwise, this shall be the shell command that tests the
-#   array-element value stored in the shell variable "value".
+#   The other exit status is reserved and cancel the array filtering with an
+#   error message, and the function returns with the exit status 2.  If this is
+#   an existing command name, the command is called with the value of the array
+#   element being specified as the first command argument.  Otherwise, this
+#   shall be a shell command that tests the array-element value stored in the
+#   environment variable "value".
 #
 # Options:
 #
@@ -134,7 +137,7 @@ _comp_xfunc_ARRAY_filter()
             27) break ;;
             *)
                 printf 'bash_completion: %s: %s\n' "$FUNCNAME" \
-                    "the filter condition broken '${_comp_local_pattype:+-$_comp_local_pattype }$2'" >&2
+                    "filter condition broken '${_comp_local_pattype:+-$_comp_local_pattype }$2'" >&2
                 return 2
                 ;;
         esac