> ... I'm reasoning more about the shape of the data than the actual type implementing it, and that to me is closer to a value than a type. The shape of the da

> ... I'm reasoning more about the shape of the data than the actual type implementing it, and that to me is closer to a value than a type. The shape of the data is its type. You have been reasoning about types all this time. Check out https://en.wikipedia.org/wiki/Structural_type_system https://en.wikipedia.org/wiki/Structural_type_system