I'm not sure if #%variable-reference is supposed to be unsafe or not (it's not mentioned in the documentation), but it looks like an attempt to get the location of an identifier that is neither top-level nor module-level results in a hard crash:
=== #lang racket/base (define (go) (define foo 3) (#%variable-reference foo)) (go) _________________________ Racket Developers list: http://lists.racket-lang.org/dev