In a modelling sense, its a classic many-to-many concern. The issue is that both ends are non-discrete.

On the Dialect side, there can be custom Dialects so a Type saying what Dialects it works for will necessarily miss any custom Dialects. E.g., say that someone writes a custom Dialect for the pgsql-ng JDBC driver. It is impossible for the Hibernate PostgresUUIDType to be able to report that in your suggested Type#getDialectForContribution.

And the same thing on the other side. There can be custom Types. A Dialect reporting its special Types will miss these custom Types in the same way described above.

In fact, the more I think about this TypeContributor is the solution to your request. And unless I hear a compelling argument otherwise, I will close this issue as such.