Notably these runtime costs only occur if you’re calling into another library. For calls within a given swift library, you don’t incur the runtime costs: size c

Notably these runtime costs only occur if you’re calling into another library. For calls within a given swift library, you don’t incur the runtime costs: size checks are elided (since size is known), calls can be inlined, generics are monomorphized… the costs only happen when you’re calling into code that the compiler can’t see.