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  1. #include <iostream>
  2.  
  3. struct foo1 { };
  4. struct foo2 { typedef int bar; };
  5.  
  6. template<typename T>
  7. class has_bar
  8. {
  9.     typedef char yes;
  10.     typedef struct { yes no_[2]; } no;
  11.  
  12.     static T make();
  13.  
  14.     template<typename U>
  15.     static yes check(U&&, typename U::bar*);
  16.     template<typename U>
  17.     static no check(U&&, ...);
  18.  
  19. public:
  20.     enum { value = sizeof(check(make(), nullptr)) == sizeof(yes) };
  21. };
  22.  
  23. int main()
  24. {
  25.     std::cout
  26.         << has_bar<foo1>::value << '\n'
  27.         << has_bar<foo2>::value << '\n';
  28. }
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https://ideone.com/dhK9A
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
secret

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