fix local-expand on module body with phase-2 binding

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

@@ -981,6 +981,30 @@
            (syntax-local-lift-require ''m (datum->syntax stx '(x)))))
   (eval '(m)))
 
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Check that local-expanding module body
+;; doesn't pollute future expansion with
+;; bindings in any phase (such as phase 2)
+
+(module check-defn-le-lang racket
+   (provide
+    (except-out (all-from-out racket) #%module-begin)
+    (rename-out [module-begin #%module-begin]))
+
+   (define-syntax (module-begin stx)
+     (syntax-case stx ()
+       ((_ . bs)
+        (local-expand
+         #'(#%module-begin . bs)
+         'module-begin null)))))
+
+(module check-defn-le-module 'check-defn-le-lang
+   (require (for-meta 2 racket/base))
+   (define x 0)
+   (begin-for-syntax
+     (begin-for-syntax
+       (define y 2))))
+  
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 (report-errs)

racket/src/racket/src/module.c

@@ -8340,9 +8340,11 @@ static Scheme_Object *do_module_begin(Scheme_Object *orig_form, Scheme_Comp_Env
 
     if (rec[drec].depth == -2) {
       /* This was a local expand. Flush definitions, because the body expand may start over. */
-      flush_definitions(env->genv);
+      Scheme_Env *f_genv = env->genv;
-      if (env->genv->exp_env)
+      while (f_genv) {
-        flush_definitions(env->genv->exp_env);
+        flush_definitions(f_genv);
+        f_genv = f_genv->exp_env;
+      }
     }
 
     p = SCHEME_STX_CAR(form);