In the current Language Guide, and Language Reference, this 5.7 accepted evolution is not documented. The reference manual uses the grammar production rule:
protocol-declaration → attributes? access-level-modifier? protocol protocol-name type-inheritance-clause? generic-where-clause? protocol-body
which does not include productions for this evolution. Using for example something like:
enum AnEnum<T,C:Collection<T>> { ...}
is a fairly common syntax usage. Given this, should this usage not be documented in these docs. I know there are many evolutions which are not reflected in the Language docs, I feel the simple ones should be; especially the production rules.