> Whether or not a square is a rectangle in a Euclidian sense it is a normal thing to use a type system in this way. Why do I care about whether or not it's no

> Whether or not a square is a rectangle in a Euclidian sense it is a normal thing to use a type system in this way. Why do I care about whether or not it's normal way (for some people/languages) to use a type system in this way? I care about reality and having my types reflect it precisely. > Gives one pause about the value of type systems for correctness eh? I actually don't see how. It seems like you are saying "regardless of whether a square is a rectangle in reality, people (mis)use type systems to say this". Someone’s misuse of a tool doesn't call the tools value into question. Basically, I may not be able to model your exact relationships in the exact same way but I can model real world concrete things in the type-system which obtains the same or more flexibility and maintainability.