Found because I was implementing p4lang/p4-spec#1213 in my front-end (though there are still issues with the testsuite as p4c considers all directionless arguments as compile time know constants) and noticed pna.p4 was broken (p4lang/pna#110 is the fix there) .
Take:

extern void f(bit t);
action a(bit t)
{
  f(t);
}
control c(in bit t)
{
  apply {
    // f(t);
    a(t);
  }
}

The call into the action should be rejected even though a's t is a directionless argument, it should really be treated as an in argument.
A call to f inside c is correctly rejected while the call to a is accepted because actions directionless arguments are the same as an in direction.