fix impersonator-property:application-mark propagation

Propagate the mark value only if it's on the current continuation
frame, as originally intended. Adjust the docs to clarify.

pkgs/racket-doc/scribblings/reference/chaperones.scrbl

@@ -221,9 +221,11 @@ If any @racket[prop] is @racket[impersonator-prop:application-mark] and if the
 associated @racket[prop-val] is a pair, then the call to @racket[proc]
 is wrapped with @racket[with-continuation-mark] using @racket[(car
 prop-val)] as the mark key and @racket[(cdr prop-val)] as the mark
-value. In addition, if @racket[continuation-mark-set-first] with
+value. In addition, if the immediate
-@racket[(car prop-val)] produces a value for the immediate
+continuation frame of the call to the impersonated procedure
-continuation frame of the call to the impersonated procedure, the value is
+includes a value for @racket[(car prop-val)]---that is, if
+@racket[call-with-immediate-continuation-mark] would produce a value
+for @racket[(car prop-val)] in the call's continuation---then the value is
 also installed as an immediate value for @racket[(car prop-val)] as a
 mark during the call to @racket[wrapper-proc] (which allows tail-calls
 of impersonators with respect to wrapping impersonators to be detected within

pkgs/racket-test-core/tests/racket/chaperone.rktl

@@ -1883,6 +1883,27 @@
         (f 42))
   (test '(#f #f) values msgs))
 
+;; Make sure that `impersonator-prop:application-mark'
+;; doesn't propagate for non-tail values:
+(let ()
+  (define msgs '())
+  (define (wrap f)
+    (chaperone-procedure
+     f
+     (λ (x)
+        (call-with-immediate-continuation-mark
+         'key
+         (λ (m)
+            (set! msgs (cons m msgs))
+            (values x))))
+     impersonator-prop:application-mark
+     (cons 'key 'skip-this-check)))
+  
+  (test 42
+        values
+        ((wrap (lambda (x) (+ ((wrap (lambda (x) x)) x) 0))) 42))
+  (test '(#f #f) values msgs))
+
 ;; ----------------------------------------
 
 ;; Check that supplying a procedure `to make-keyword-procedure' that 

racket/src/racket/src/fun.c

@@ -3691,7 +3691,7 @@ Scheme_Object *scheme_apply_chaperone(Scheme_Object *o, int argc, Scheme_Object
     app_mark = NULL;
 
   if (app_mark) {
-    v = scheme_extract_one_cc_mark(NULL, SCHEME_CAR(app_mark));
+    v = scheme_chaperone_get_immediate_cc_mark(SCHEME_CAR(app_mark), NULL);
     if (v) {
       scheme_push_continuation_frame(&cframe);
       scheme_set_cont_mark(SCHEME_CAR(app_mark), v);