The proc with top-level env must be 'proc-closure'; fix #3871

src/vm.c

@@ -2019,9 +2019,16 @@ RETRY_TRY_BLOCK:
           if (!MRB_PROC_ENV_P(proc) || !MRB_ENV_STACK_SHARED_P(MRB_PROC_ENV(proc))) {
             goto L_BREAK_ERROR;
           }
-          if (MRB_PROC_ENV(proc)->cxt != mrb->c) {
+          else {
+            struct REnv *e = MRB_PROC_ENV(proc);
+
+            if (e == mrb->c->cibase->env && proc != mrb->c->cibase->proc) {
               goto L_BREAK_ERROR;
             }
+            if (e->cxt != mrb->c) {
+              goto L_BREAK_ERROR;
+            }
+          }
           while (mrb->c->eidx > mrb->c->ci->epos) {
             ecall_adjust();
           }