fix expander problem with set!

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

@@ -2100,6 +2100,19 @@
                                 m))))
                      m))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Make sure that `set!` works right in forced subform expansion:
+
+(let ()
+  (define (time-print-mixin t%)
+    (define start-time #f)
+    (class t%
+      (super-new)
+      (define/override (m)
+        (set! start-time 1)
+        (super m))))
+  (void time-print-mixin))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/racket/src/compenv.c

@@ -1799,7 +1799,7 @@ scheme_lookup_binding(Scheme_Object *find_id, Scheme_Comp_Env *env, int flags,
 	  if (SCHEME_FALSEP(val)) {
 	    /* Corresponds to a run-time binding (but will be replaced later
 	       through a renaming to a different binding) */
-            if (flags & SCHEME_OUT_OF_CONTEXT_LOCAL)
+            if (flags & (SCHEME_OUT_OF_CONTEXT_LOCAL | SCHEME_SETTING))
               return scheme_make_local(scheme_local_type, 0, 0);
             return NULL;
 	  }