CppCoreGuidelines T.68 为避免混淆，在模板中用 {} 不要用 ()

template<typename T, typename U>
void f(T t, U u)
{
    T v1(T(u));    // mistake: oops, v1 is a function not a variable
    T v2{u};       // clear:   obviously a variable
    auto x = T(u); // unclear: construction or cast?
}

f(1, "asdf"); // bad: cast from const char* to int