[ZPT] [Weakness] "metal:fill-slot" and "metal:use-macro" not together

[Dieter Maurer]

Currently, ZPT refuse to have
"metal:fill-slot" and "metal:use-macro" together on one element.

This is unfortunate, because it is quite natural to
fill a slot with a macro call, as natural than pass an
expression (rather than a constant) as parameter to a function
call....

I do not see potential problems, too.
Please allow it.

Not being able to use the macro directly forces to
add spurious "tal:XXXX" elements. They make other
problems (see documentation message) and
make the template more difficult to understand.


Dieter