modify the type of return value (mrb_bool => mrb_value).

src/symbol.c

@@ -72,25 +72,30 @@ mrb_intern_str(mrb_state *mrb, mrb_value str)
   return mrb_intern2(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
 }
 
-mrb_bool
+mrb_value
 mrb_cstr_interned(mrb_state *mrb, const char *name)
 {
   return mrb_interned(mrb, name, strlen(name));
 }
 
-mrb_bool
+mrb_value
 mrb_interned(mrb_state *mrb, const char *name, size_t len)
 {
   khash_t(n2s) *h = mrb->name2sym;
   symbol_name sname;
+  khiter_t k;
 
   sname.len = len;
   sname.name = name;
 
-  return (kh_get(n2s, h, sname) != kh_end(h)) ? TRUE : FALSE;
+  k = kh_get(n2s, h, sname);
+  if (k != kh_end(h)) {
+    return mrb_symbol_value(kh_value(h, k));
+  }
+  return mrb_nil_value();
 }
 
-mrb_bool
+mrb_value
 mrb_str_interned(mrb_state *mrb, mrb_value str)
 {
   return mrb_interned(mrb, RSTRING_PTR(str), RSTRING_LEN(str));