Following up from a discussion occurring now in Slack #clojure-spec. Lots more discussion there, check timestamp.
I found this very surprising. I've been using instrument during dev/repl-time (as recommended? distinguishing form test-time), but just learned that fspec isn't suitable for functions with side-effects due to the use of generators. I expected instrument to only instrument calls to vars, never to use the generators, and either 1) ignore fspec's details (easier) or 2) proxy the fn (many challenges here).
instrument has been very useful for dev (again, vs test), but not as useful as it could be if :ret and :fn were checked, and generators were never used.