Fix typo in introspection code

lib/graphql/introspection/schema_type.rb

@@ -27,35 +27,20 @@ def types
       end
 
       def query_type
-        permitted_root_type("query")
+        @context.types.query_root
       end
 
       def mutation_type
-        permitted_root_type("mutation")
+        @context.types.mutation_root
       end
 
       def subscription_type
-        permitted_root_type("subscription")
+        @context.types.subscription_root
       end
 
       def directives
         @context.types.directives
       end
-
-      private
-
-      def permitted_root_type(op_type)
-        case op_type
-        when "query"
-          @context.types.query_root
-        when "mutation"
-          @context.types.mutation_root
-        when "subcription"
-          @context.types.subscription_root
-        else
-          nil
-        end
-      end
     end
   end
 end

spec/graphql/subscriptions_spec.rb

@@ -340,6 +340,11 @@ def to_param
         end
       end
 
+      it "works with the introspection query" do
+        res = schema.execute("{ __schema { subscriptionType { name } } }")
+        assert_equal "Subscription", res["data"]["__schema"]["subscriptionType"]["name"]
+      end
+
       if in_memory_backend_class != FromDefinitionInMemoryBackend # No way to specify this when using IDL
         it "supports filtering in the subscription class" do
           query_str = "subscription($channel: Int) { filteredStream(channel: $channel) { message } }"