Remove implicit conversion using `to_str` method; fix #3854

We have added internal convenience method `__to_str` which
does string type check.

The issue #3854 was fixed but fundamental flaw of lack of stack
depth check along with fibers still remains. Use `MRB_GC_FIXED_ARENA`
for workaround.

1 files changed, 6 insertions, 33 deletions

diff --git a/src/kernel.c b/src/kernel.c
index 195594d6b..ce9cd1d44 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -746,6 +746,7 @@ basic_obj_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym id, int pub)
 {
   return mrb_respond_to(mrb, obj, id);
 }
+
 /* 15.3.1.3.43 */
 /*
  *  call-seq:
@@ -765,45 +766,16 @@ basic_obj_respond_to(mrb_state *mrb, mrb_value obj, mrb_sym id, int pub)
 static mrb_value
 obj_respond_to(mrb_state *mrb, mrb_value self)
 {
-  mrb_value mid;
   mrb_sym id, rtm_id;
-  mrb_bool priv = FALSE, respond_to_p = TRUE;
-
-  mrb_get_args(mrb, "o|b", &mid, &priv);
-
-  if (mrb_symbol_p(mid)) {
-    id = mrb_symbol(mid);
-  }
-  else {
-    mrb_value tmp;
-    if (mrb_string_p(mid)) {
-      tmp = mrb_check_intern_str(mrb, mid);
-    }
-    else {
-      tmp = mrb_check_string_type(mrb, mid);
-      if (mrb_nil_p(tmp)) {
-        tmp = mrb_inspect(mrb, mid);
-        mrb_raisef(mrb, E_TYPE_ERROR, "%S is not a symbol", tmp);
-      }
-      tmp = mrb_check_intern_str(mrb, tmp);
-    }
-    if (mrb_nil_p(tmp)) {
-      respond_to_p = FALSE;
-    }
-    else {
-      id = mrb_symbol(tmp);
-    }
-  }
-
-  if (respond_to_p) {
-    respond_to_p = basic_obj_respond_to(mrb, self, id, !priv);
-  }
+  mrb_bool priv = FALSE, respond_to_p;
 
+  mrb_get_args(mrb, "n|b", &id, &priv);
+  respond_to_p = basic_obj_respond_to(mrb, self, id, !priv);
   if (!respond_to_p) {
     rtm_id = mrb_intern_lit(mrb, "respond_to_missing?");
     if (basic_obj_respond_to(mrb, self, rtm_id, !priv)) {
       mrb_value args[2], v;
-      args[0] = mid;
+      args[0] = mrb_symbol_value(id);
       args[1] = mrb_bool_value(priv);
       v = mrb_funcall_argv(mrb, self, rtm_id, 2, args);
       return mrb_bool_value(mrb_bool(v));
@@ -873,6 +845,7 @@ mrb_init_kernel(mrb_state *mrb)
   mrb_define_method(mrb, krn, "to_s",                       mrb_any_to_s,                    MRB_ARGS_NONE());    /* 15.3.1.3.46 */
   mrb_define_method(mrb, krn, "__case_eqq",                 mrb_obj_ceqq,                    MRB_ARGS_REQ(1));    /* internal */
   mrb_define_method(mrb, krn, "__to_int",                   mrb_to_int,                      MRB_ARGS_NONE()); /* internal */
+  mrb_define_method(mrb, krn, "__to_str",                   mrb_to_str,                      MRB_ARGS_NONE()); /* internal */
 
   mrb_define_method(mrb, krn, "class_defined?",             mrb_krn_class_defined,           MRB_ARGS_REQ(1));