Function fib

test/matchit/constexpr.cpp:4–14

using namespace matchit;

constexpr int32_t fib(int32_t n)
{
  assert(n >= 1);
  return match(n)(
      // clang-format off
        pattern | 1 = expr(1),
        pattern | 2 = expr(1),
        pattern | _ = [n] { return fib(n - 1) + fib(n - 2); }
      // clang-format on
  );
}

static_assert(fib(1) == 1);
static_assert(fib(2) == 1);