// (46,24): error CS8165: Cannot return by reference a member of result of 'Test.Foo<Test.S1>(ref Test.S1)' because the argument passed to parameter 'arg' cannot be returned by reference
// (46,24): error CS8165: Cannot return by reference a member of result of 'Test.Goo<Test.S1>(ref Test.S1)' because the argument passed to parameter 'arg' cannot be returned by reference