Only `sortedValues()` compares a container’s elements. Where should `Element: Comparable`…

Only `sortedValues()` compares a container’s elements. Where should `Element: Comparable` usually go?

1. On `sortedValues()` or a constrained extension containing it.
2. On the entire container declaration in every case.
3. Nowhere; cast every element to Comparable at runtime.
4. On every caller that reads the container count.