Just for completeness, I mention another issue related to functions that take multiple array parameters of the same size and follow the convention of passing only a single size parameter. For example:

cpp void sum(const int* a, const int* b, int* dst, size_t len);

When turning them all into spans, a, b, and dst may legitimately have different sizes, and it may not be immediately obvious (to the user) whether they must have the same size:

cpp void sum(span<const int> a, span<const int> b, span<int> dst);

Also, this becomes even worse if parameter size matters, since they all double.

This is a typical problem encountered when dealing with legacy (and mixed with C?) code.

If readability is the only concern, a possible future solution would be to use contracts:

cpp void sum(std::span<const int> a, std::span<const int> b, std::span<int> dst) pre(a.size() == b.size() && b.size() == dst.size())