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  1. #include <type_traits>
  2.  
  3. struct T2;
  4. struct T1 {
  5.     T1(){}
  6.     T1(int){}
  7.     operator T2();
  8. };
  9. struct T2 {
  10.     operator int() { return 0; }
  11. };
  12. struct T3 {
  13.     operator int() { return 0; }
  14. };
  15. T1::operator T2() { return T2(); }
  16.  
  17. using namespace std;
  18. using X = T1;
  19. using Y = T2;
  20. using Z = T3;
  21. int main()
  22. {
  23.  
  24.     true?T2():T3(); // int
  25.     static_assert(std::is_same<std::common_type_t<T2,
  26.                                                   T3>,
  27.                                int>::value,
  28.                   "Not int");
  29.  
  30.     true?T1():(true?T2():T3()); // T1
  31.     static_assert(std::is_same<std::common_type_t<T1,
  32.                                                   std::common_type_t<T2,
  33.                                                                      T3>>,
  34.                                T1>::value,
  35.                   "Not T1");
  36.  
  37.     // -----------------------------------------
  38.  
  39.     true?T1():T2(); // T2
  40.     static_assert(std::is_same<std::common_type_t<T1,
  41.                                                   T2>,
  42.                                T2>::value,
  43.                   "Not T2");
  44.  
  45.     true?(true?T1():T2()):T3(); // int
  46.     static_assert(std::is_same<std::common_type_t<std::common_type_t<T1,
  47.                                                                      T2>,
  48.                                                   T3>,
  49.                                int>::value,
  50.                   "Not int");
  51.  
  52.     // -----------------------------------------
  53.  
  54.     static_assert( is_same<common_type_t< X, common_type_t<Y,Z>    >,
  55.                            common_type_t<    common_type_t<X,Y>, Z > >::value,
  56.                     "Don't match");
  57. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp: In function 'int main()':
prog.cpp:54:5: error: static assertion failed: Don't match
     static_assert( is_same<common_type_t< X, common_type_t<Y,Z>    >,
     ^
stdout
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Standard output is empty
https://ideone.com/dwzCQO
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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