fix handling of code compiled to ignore

When the compiler sees `(if #f A B)`, it compiles A in a throwaway
mode, but the throwaway mode need to produce a slightly more plausible
result than it was so that further throwaway transformation is not
confused.

pkgs/racket-pkgs/racket-test/tests/racket/optimize.rktl

@@ -3375,6 +3375,20 @@
         (call-with-continuation-prompt g p)
         (call-with-continuation-prompt g p)))
   
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Make sure the compiler isn't confused by
+;; throwaway internal-definition expansion:
+
+(test #t procedure?
+      (eval '(lambda (db)
+               (if #f
+                   (let ()
+                     (define matches
+                       (let loop ()
+                         (define s db)
+                         null))
+                     5)
+                   (void)))))
 
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 

racket/src/racket/src/compenv.c

@@ -1777,7 +1777,7 @@ scheme_lookup_binding(Scheme_Object *find_id, Scheme_Comp_Env *env, int flags,
               *_lexical_binding_id = val;
             }
 	    if (flags & SCHEME_DONT_MARK_USE)
-	      return scheme_make_local(scheme_local_type, 0, 0);
+	      return scheme_make_local(scheme_local_type, p+i, 0);
 	    else
 	      return (Scheme_Object *)get_frame_loc(frame, i, j, p, flags);
 	  }