gcc/testsuite/g++.dg/ext/is_convertible2.C

   1 // PR c++/106784
   2 // { dg-do compile { target c++20 } }
   3 // Adapted from <https://en.cppreference.com/w/cpp/types/is_convertible>.
   4
   5 #include <string>
   6 #include <string_view>
   7
   8 #define SA(X) static_assert((X),#X)
   9
  10 class E { public: template<class T> E(T&&) { } };
  11
  12 int main()
  13 {
  14     class A {};
  15     class B : public A {};
  16     class C {};
  17     class D { public: operator C() { return c; }  C c; };
  18
  19     SA(__is_convertible(B*, A*));
  20     SA(!__is_convertible(A*, B*));
  21     SA(__is_convertible(D, C));
  22     SA(!__is_convertible(B*, C*));
  23     SA(__is_convertible(A, E));
  24
  25     using std::operator "" s, std::operator "" sv;
  26
  27     auto stringify = []<typename T>(T x) {
  28         if constexpr (std::is_convertible_v<T, std::string> or
  29                       std::is_convertible_v<T, std::string_view>) {
  30             return x;
  31         } else {
  32             return std::to_string(x);
  33         }
  34     };
  35
  36     const char* three = "three";
  37
  38     SA(!__is_convertible(std::string_view, std::string));
  39     SA(__is_convertible(std::string, std::string_view));
  40
  41     auto s1 = stringify("one"s);
  42     auto s2 = stringify("two"sv);
  43     auto s3 = stringify(three);
  44     auto s4 = stringify(42);
  45     auto s5 = stringify(42.);
  46 }