C++ safe bool wrapper

Question

I'm trying to design a bool wrapper struct applying the safe bool idiom.
The classic implementation to solve this is pretty trivial: the skeleton could be something like this:

struct Bool final
{
  Bool() = default;

  Bool(bool value)
    : _value{value}
  {}

  explicit operator bool() const {
    return _value;
  }

private:
  bool _value{false};
};

The part I'm trying to improve is how Bool is constructed.
For example I want to avoid implicit narrowing by design:

Bool b1(45); // yields warnings, but it compiles
Bool b2{3};  // not ok by standard

I tried to hurt myself using templates, but without success.

How could I make it work?

Answer 1

You can achieve this by explicitly deleting all other constructors.

struct Bool final
{
    template<class T>
    Bool(T) = delete;

    Bool(bool value);
};