> Typescript taught me that I actually don’t care about types and all I care about is the shape of data. Seconding leafario2 here, that's exactly what types do

> Typescript taught me that I actually don’t care about types and all I care about is the shape of data. Seconding leafario2 here, that's exactly what types do: They give guarantees about the shape of data. Maybe what you meant was you don't care whether an object is of type Customer or Supplier, as long as it has an element/field named address. That's called "structural typing" (as opposed to "nominal typing"). Few static type systems have structural typing, probably because in practice, you actually do care whether the object is a Customer or a Supplier, even if their fields have the same names. Rust, for example, is nominally typed, but you can define a trait "HasAddress" with a trait function "fn address(&self) -> &str" and implement it for Customer and Supplier, to simulate structural typing where you need it.