> Can I pass the same parameter to a macro as typed and untyped version?
If your _proc_ itself takes parameters of concrete types then passing it to a macro in two different parameters -- one typed, one untyped -- should work. Not a very clean solution, though. BTW: the _CellEditable_ "interface" and its "implementations" look like a use case for a user defined type class, how about making it a concept? Maybe manually checking types will not be necessary then.
