Looks like it's in Ubuntu's build:

  $ lsb_release -a
  No LSB modules are available.
  Distributor ID:	Ubuntu
  Description:	Ubuntu 12.04.3 LTS
  Release:	12.04
  Codename:	precise
  $ dpkg -l bash | tail -1
  ii  bash                              4.2-2ubuntu2.5               GNU Bourne Again SHell
  $ foo() { echo foo; }
  $ export -f foo
  $ env | grep BASH_FUNC
  BASH_FUNC_foo()=() {  echo foo

Is this a correct test?

Probably as of about 13:27 UTC yesterday, if I'm reading correctly here: https://bazaar.launchpad.net/~ubuntu-branches/ubuntu/precise...