Raise `TypeError` if the argument type is unsupported in `mrb_stat0`

mrbgems/mruby-io/src/file_test.c

@@ -42,14 +42,7 @@ extern struct mrb_data_type mrb_io_type;
 static int
 mrb_stat0(mrb_state *mrb, mrb_value obj, struct stat *st, int do_lstat)
 {
-  mrb_value tmp;
-  mrb_value io_klass, str_klass;
-
-  io_klass  = mrb_obj_value(mrb_class_get(mrb, "IO"));
-  str_klass = mrb_obj_value(mrb_class_get(mrb, "String"));
-
-  tmp = mrb_funcall(mrb, obj, "is_a?", 1, io_klass);
-  if (mrb_test(tmp)) {
+  if (mrb_obj_is_kind_of(mrb, obj, mrb_class_get(mrb, "IO"))) {
     struct mrb_io *fptr;
     fptr = (struct mrb_io *)mrb_get_datatype(mrb, obj, &mrb_io_type);
 
@@ -60,9 +53,7 @@ mrb_stat0(mrb_state *mrb, mrb_value obj, struct stat *st, int do_lstat)
     mrb_raise(mrb, E_IO_ERROR, "closed stream");
     return -1;
   }
-
-  tmp = mrb_funcall(mrb, obj, "is_a?", 1, str_klass);
-  if (mrb_test(tmp)) {
+  else {
     char *path = mrb_locale_from_utf8(mrb_string_value_cstr(mrb, &obj), -1);
     int ret;
     if (do_lstat) {
@@ -73,8 +64,6 @@ mrb_stat0(mrb_state *mrb, mrb_value obj, struct stat *st, int do_lstat)
     mrb_locale_free(path);
     return ret;
   }
-
-  return -1;
 }
 
 static int

mrbgems/mruby-io/test/file_test.rb

@@ -20,9 +20,8 @@ assert("FileTest.exist?") do
   assert_equal true,  FileTest.exist?(io), "io obj - exist"
   io.close
   assert_equal true, io.closed?
-  assert_raise IOError do
-    FileTest.exist?(io)
-  end
+  assert_raise(IOError) { FileTest.exist?(io) }
+  assert_raise(TypeError) { File.exist?($mrbtest_io_rfname.to_sym) }
 end
 
 assert("FileTest.file?") do