Template alias that evaluates to the type used for representing a static rank.

This results in a substitution failure if Rank < 0 (in particular, if Rank == dynamic_rank).

If this is used to specify a default value for a function parameter, e.g.: StaticOrDynamicRank<Rank> rank = StaticRank<Rank>(), the effect is that the parameter is required if Rank == dynamic_rank, but optional otherwise.