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  1. #include <string>
  2. #include <iostream>
  3.  
  4. template <class T, class Factory> class add_ctor {
  5.     public:
  6.         add_ctor() : obj(Factory()) {
  7.         }
  8.         T* operator->() {
  9.             return obj;
  10.         }
  11.     private:
  12.         T* obj;
  13. };
  14.  
  15. class A {
  16.     public:
  17.         std::string v;
  18.         static A createOne();
  19.     private:
  20.         A();
  21. };
  22. A A::createOne() {
  23.     A a;
  24.     a.v = "Hello!";
  25.     return a;
  26. }
  27.  
  28. int main() {
  29.     // this should work:
  30.     add_ctor<A, decltype(&A::createOne)> added_a;
  31.     std::cout << added_a->v << "\n";
  32.  
  33.     // this should error:
  34.     //A non_added_a;
  35.     //std::cout << non_added_a.v << "\n";
  36.     return 0;
  37. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
prog.cpp: In constructor 'add_ctor<T, Factory>::add_ctor() [with T = A, Factory = A (*)()]':
prog.cpp:30:42:   instantiated from here
prog.cpp:6:35: error: cannot convert 'A (*)()' to 'A*' in initialization
stdout 
Standard output is empty
https://ideone.com/lRKAey
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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