Empty unit name declaration is valid according to the original implementation in NEURON:

i.e.

UNITS 
{
                   () = (millivolt)
}

is accepted now. Note the empty bracket on the left where there should be a name. Similarly, function declarations like the below are now also accepted:

FUNCTION ssCB(kdf(), kds()) (mM) 
{
}

Above behaviour was implemented in #3 in order to pass the fail existing ModelDB files.

When we will have semantic analysis pass for error checking, we can add a check to see if there is an empty unit definition like above and then error / throw exception. This way, parsing will be successful but the semantic analysis will be a "proper" place to do such checking.