[racket] A safe version of unsafe-struct-ref [for Whalesong]

Is it possible to implement unsafe-struct-ref using safe constructs only?

The reason behind this peculiar question, is that I am porting racket/match
to Whalesong. The match compiler uses various unsafe constructs that Whalesong
doesn't implement. It is straightforward to replace, say,
unsafe-vector-ref with vector-ref.

But unsafe-struct-ref ?

It is okay to use all tricks in the book in phase 1 (Whalesong has
restrictions in phase 0 only).

/Jens Axel