feature request for compile time assert to print message

[nbingham1]

spec {
assert()
}

needs to be able to print a given message. Maybe like this?

spec {
assert<EXPR, "print this message">()
}

[fangism]

I'd propose something like this:

spec {
   assert<EXPR, STRING>()
}

Right now, it is:

spec {
  assert<EXPR, EXPR, EXPR, ...>()
}

and it checks that all expressions are true. I wonder if I can come up with a poor-man's workaround...