It was common practice in the past to just declare a port direction
and declare it as a vector in a subsequent type declaration. Versions
of the standard up to and including 1364-2005 include an example that
does this (e.g. 1364-2005 section 12.3.7). Users may have old or
third-party code that they can't or don't want to modify, so allow
the warning to be suppressed by including it in the anachronisms
category.
Cary R
Martin Whitaker