[actionview] [Fix rails#54966] Check choice type before calling .second to detect grouped_choices in Select helper

Author: lavoiesl

actionview/lib/action_view/helpers/tags/select.rb

@@ -37,7 +37,12 @@ def render
           #   [nil, []]
           #   { nil => [] }
           def grouped_choices?
-            !@choices.blank? && @choices.first.respond_to?(:second) && Array === @choices.first.second
+            return false if @choices.blank?
+
+            first_choice = @choices.first
+            return false unless first_choice.is_a?(Enumerable)
+
+            first_choice.second.is_a?(Array)
           end
       end
     end

actionview/test/template/form_options_helper_test.rb

@@ -537,6 +537,13 @@ def test_select
     )
   end
 
+  def test_select_with_class
+    assert_dom_equal(
+      "<select name=\"post[class]\" id=\"post_class\"><option value=\"Struct::Post\">Struct::Post</option></select>",
+      select(:post, :class, [Post])
+    )
+  end
+
   def test_select_without_multiple
     assert_dom_equal(
       "<select id=\"post_category\" name=\"post[category]\"></select>",