Avoided redefinition. Who requires this?

[shinyaohtani]

on my macOS, this conflicts

[lava]

On a linux system this appears to be necessary, e.g. this doesn't compile for me:

#include <cstdint>

template<typename T>
struct foo {
  foo() = delete;
};

template<>
struct foo<unsigned long long> {};

int main() {
  foo<uint64_t> f;
  return 0;
}

I'm told on Windows it leads to a warning, so it looks like some research is required to come up with a solution that works on all platforms.