Substitution Failure Is Not An Error (SFINAE)

Ran into a lot on my day-to-day work at Tesla, and a little bit at NVIDIA.

Substitution Failure Is Not An Error (SFINAE) applies during overload resolution of templates.

There’s enable_if

SFINAE states that when substituting the deduced type for the template parameter fails, the specialization is discarded from the overload set instead of causing a compile error.

This piece of code is very hard to underestand for me, from GXF repo

template <class T>
struct AddRvalueReference {
 private:
  template <class U> static constexpr TypeIdentity<U&&> Test(void*);
  template <class U> static constexpr TypeIdentity<U>   Test(...);
 public:
    using type = typename decltype(Test<T>(nullptr))::type;
};

Resources

• https://federico-busato.github.io/Modern-CPP-Programming/11.Templates_II.pdf