[plt-scheme] Matching typed structs in untyped code

It would be nice if I could pattern match in untyped code on
structures defined in Typed Scheme code. Presently I get:

  match: Dot does not refer to a structure definition in: Dot

Using Typed Scheme for a couple of days has made me revert to my ML
days, and now I'm pattern matching everywhere. Oh, and the untyped
code is using classes, which I believe aren't yet supported by Typed
Scheme so I can't just rewrite it.

[I know there is a class form in Typed Scheme but it ain't documented.
I'm using MrEd. I suppose if I could extend the existing bindings to
MrEd to cover what I need. That does sound tedious...]

N.