This will deal with linking problems when rule attribute type is not the same
as the actual attribute type. It will not harm anyone as the transformation
after parse_rule will just pass-through the attribute because it will be the
same there. It will also do not alter rule_definition parsing so other usages
are still valid.
There is a mistake in `make_attribute` trait that leads to synthesization and
immediately throwing out an attribue, so rule context always was unused_type
when actual attribute is unused_type (added test for this case). Instead of
fixing `make_attribute` trait I just completely removed synthesization in
rule by removing `make_attribute` trait usage (the traits could be removed
after a simple change in 'action' parser). I think the change is better
than fixing the trait because it removes excessive attribute default
construction in every rule and makes rule almost free to use.
- there are only 2 variations now f() and f(ctx)
- added _attr(ctx) accessor for accessing the attribute
- added _where(ctx) accessor for accessing the iterator range
this, and in preparation for a unified call interface for actions as well as lazy args to e.g. eps(f)
