SFINAE Constructors [duplicate]

Answer 1

One way to fix this is to add extra , typename=void arguments so that none of the overloads has the same number of template parameters.

Answer 2

Use a non-type template parameter instead:

template <class Integer,
    std::enable_if_t<std::is_integral<Integer>::value, int> = 0>
T(Integer n) {
    // ...
}

template <class Float,
    std::enable_if_t<std::is_floating_point<Float>::value, int> = 0>
T(Float n) {
    // ...
}

This works because the compiler has to substitute the first template parameter before it can determine the type of the value parameter.