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  1. #include <utility>
  2.  
  3. template<typename T>
  4. union _impl_itca_helper { T dummy; };
  5.  
  6. template<typename T>
  7. std::true_type _impl_itca (T, int,
  8.   decltype (
  9.     (std::declval<_impl_itca_helper<T>> () = std::declval<_impl_itca_helper<T>> ()),
  10.     int { }
  11.   ) = 0
  12. );
  13.  
  14. template<typename T, typename U>
  15. std::false_type _impl_itca (T, U);
  16.  
  17. template<typename T>
  18. using is_trivially_copy_assignable = decltype (
  19.   _impl_itca (std::declval<T> (), int { })
  20. );
  21.  
  22. int
  23. main (int argc, char *argv[])
  24. {
  25.   struct Obj1 { Obj1& operator= (Obj1 const&) = default; };
  26.   struct Obj2 { Obj1& operator= (Obj2 const&); };
  27.  
  28.   static_assert (
  29.     is_trivially_copy_assignable<Obj1>::value,
  30.     "Obj1 is not trivially copy assignable"
  31.   );
  32.  
  33.   static_assert (
  34.     is_trivially_copy_assignable<Obj2>::value,
  35.     "Obj2 is not trivially copy assignable"
  36.   );
  37. }
  38.  
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(int, char**)’:
prog.cpp:33:3: error: static assertion failed: Obj2 is not trivially copy assignable
   static_assert (
   ^
stdout
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Standard output is empty
https://ideone.com/SF6gIJ
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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