If I have a transitive verb with one object, passivizing an active sentence is straightforward. For example, "te amo" becomes "(a me) amaris".
But how to passivize a verb that has two objects? For example, can "te rem doceo" be passivized into "tu rem doceris" or "te res docetur"? If only one of the objects can be turned into the subject of a passive clause, which one is it?
It seems to me that if either passivization is correct, a verb could have a subject, an object and an agent at the same time ("tu rem doceris a me"). I am under the impression that if I only have one object for a verb that could take two, I can passivize normally: "te doceo" becomes "doceris" and "rem doceo" becomes "res docetur".
I don't recall this issue being ever discussed in my Latin grammars.