[m-dev.] Repeated type variables in existentially quantified data constructors

[Julien Fischer]

Hi,

I assume the fact that the frontend accepts existentially quantified
data constructors
with repeated type variables is an oversight, e.g.

    :- type process_unit
         ---> some [T, T] process_unit(T)

The above type causes all four of our code generators to abort.

Julien.