Describe data type in English

td.cc

#include <iostream>
#include <cxxabi.h>

template <typename T> struct TypeDescriptor {};

// function
template <typename Ret, typename... Args>
std::ostream &operator<<(std::ostream &os,
                         const TypeDescriptor<Ret(Args...)> &td) {
  return os << "function returning " << TypeDescriptor<Ret>();
}

// pointer
template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T *> &td) {
  return os << "pointer to " << TypeDescriptor<T>();
}

// reference
template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T &> &td) {
  return os << "reference to " << TypeDescriptor<T>();
}

template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T &&> &td) {
  return os << "rvalue reference to " << TypeDescriptor<T>();
}

// array
template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T[]> &td) {
  return os << "array of " << TypeDescriptor<T>();
}

template <typename T>
std::ostream &operator<<(std::ostream &os,
                         const TypeDescriptor<const T[]> &td) {
  return os << "array of " << TypeDescriptor<const T>();
}

// array with size
template <typename T, size_t N>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T[N]> &td) {
  return os << "array (size " << N << ") of " << TypeDescriptor<T>();
}

template <typename T, size_t N>
std::ostream &operator<<(std::ostream &os,
                         const TypeDescriptor<const T[N]> &td) {
  return os << "array (size " << N << ") of " << TypeDescriptor<const T>();
}

// const
template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<const T> &td) {
  return os << "const-qualified " << TypeDescriptor<T>();
}

// terminal
template <typename T>
std::ostream &operator<<(std::ostream &os, const TypeDescriptor<T> &td) {
  int status;
  auto mname = typeid(T).name();
  auto name = abi::__cxa_demangle(typeid(T).name(), nullptr, nullptr, &status);
  if (status != 0) {
    return os << mname;
  }
  os << name;
  free(name);
  return os;
}

int main() {
  std::cerr << TypeDescriptor<int()>() << std::endl;
  std::cerr << TypeDescriptor<int[20]>() << std::endl;
  std::cerr << TypeDescriptor<int[]>() << std::endl;
  std::cerr << TypeDescriptor<const int>() << std::endl;
  std::cerr << TypeDescriptor<const int[]>() << std::endl;
  std::cerr << TypeDescriptor<int *>() << std::endl;
  std::cerr << TypeDescriptor<const int *>() << std::endl;
  std::cerr << TypeDescriptor<const int *const>() << std::endl;
  std::cerr << TypeDescriptor<const int &>() << std::endl;
  std::cerr << TypeDescriptor<int &&>() << std::endl;
  std::cerr << TypeDescriptor<const int(*())[10]>() << std::endl;
  std::cerr << TypeDescriptor<const int (*(*)())[10][9]>() << std::endl;
  std::cerr << TypeDescriptor<const char *>() << std::endl;
  std::cerr << TypeDescriptor<char *const>() << std::endl;
  std::cerr << TypeDescriptor<const char *const>() << std::endl;
  std::cerr << TypeDescriptor<const char[10]>() << std::endl;
  std::cerr << TypeDescriptor<const std::string[30]>() << std::endl;
}