iri/-ur-

[Lavrentivs]

What is the difference between

Scimus copias advenitas iri.

and

Scimus copias adventuras esse.

?

[adrianus]

"Adventas iri" is passive but "advenio" is intransitive. However, you can use an impersonal construction, as in "copiis adventum iri" = "supplies/forces are going/about to arrive [it is about to be arrived to the supplies/forces]", with "copiis" in the dative.
Passivâ voce est "adventas iri". Advenio autem verbum intransitivum, at dicitur quidem "adventum iri" impersonaliter cum dativo casu.

amatus -a -um iri = "to be going to be loved"
amaturus -a -um esse = "to be going to love"

[adrianus]

Antecessor autem eius, Alan Greenspan (photographemate a laeva monstratur), qui annis 1987-2006 argentariae Fed praeerat, cum diurnariis loquendo non excludit possibilitatem alteram phasin recessionis (cuius prima scilicet phasis evenit annis 2008-09) mox adventum iri.

I found this. Am I making a mistake? Or rather, isn't this author wrong?
Hoc inveni. Errone tunc? Immò, nonnè errat auctor huius loci?

[Lavrentivs]

Why dative? Should it not be accusative?

[Lavrentivs]

In that case, let me change my quæstion:

What is the difference between

Scimus copias adventum iri.

and

Scimus copias adventuras esse.

? I mean: is it merely a matter of præference which one chooses or is there some semantic nuance?

[adrianus]

IWhat is the difference between

Scimus copias adventum iri.

and

Scimus copias adventuras esse.

? I mean: is it merely a matter of præference which one chooses or is there some semantic nuance?

I believe that "Scimus copias adventum iri" is grammatically wrong. And I believe there is no difference between "Scimus copiis adventum iri" and "Scimus copias adventuras esse". Others might confirm or correct this.
Soloecismum credo primum esse et nullum discrimen exstare inter "Scimus copiis adventum iri" et "Scimus copias adventuras esse". Alii approbent corrigantve.

[Lavrentivs]

Sorry, I'm a bit slow, but I think I get it now: supine + iri is passive and -ur- esse is active. And I suppose you meant the dative to be agentis.

[adrianus]

Indeed. You know that impersonal means that the subject is an empty "it", so if an agent is mentioned with an impersonal, it's an indirect agent (dative) or also ablative (according to this source, http://openlibrary.org/books/OL7182349M/A_study_of_the_impersonal_passive_of_the_ventum_est_type).

Ita. Scis quid velit dicere "impersonaliter" vocabulum: vacuum est subjectum; tunc, si explicitum quod agit per constructionem impersonalem indirectum dativo agentis casu sit vel ablativo, secundum fontem suprà citatum.