The problem is less that the syntax exists and more that people are used to nominal typing so get confused with edge cases where structural typing departs from

The problem is less that the syntax exists and more that people are used to nominal typing so get confused with edge cases where structural typing departs from it. The type checker isn’t breaking any promises it made it’s just slightly different from people’s mental model of how types should work from experience of other languages. It’s just a different kettle of fish to learn.