It seems that the following works (starting with c++20)

#include <array>

template<std::array arr1, std::array arr2>
constexpr auto bar() {  return std::make_pair(arr1.size(), arr2.size());  }

static_assert (bar<{3,1,4,1,5},{2,4}>() == std::make_pair(5,2));

int main() {}

It seems that the following works (starting with C++20)

#include <array>

template<std::array arr1, std::array arr2>
constexpr auto bar() {  return std::make_pair(arr1.size(), arr2.size());  }

static_assert (bar<{3,1,4,1,5},{2,4}>() == std::make_pair(5,2));

int main() {}

It seems that the following works

#include <array>

template<std::array arr1, std::array arr2>
constexpr auto bar() {  return std::make_pair(arr1.size(), arr2.size());  }

static_assert (bar<{3,1,4,1,5},{2,4}>() == std::make_pair(5,2));

int main() {}

It seems that the following works (starting with c++20)

#include <array>

template<std::array arr1, std::array arr2>
constexpr auto bar() {  return std::make_pair(arr1.size(), arr2.size());  }

static_assert (bar<{3,1,4,1,5},{2,4}>() == std::make_pair(5,2));

int main() {}