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  1. #include <iostream>
  2. #include <utility>
  3. #include <type_traits>
  4.  
  5. struct A {
  6.     int x;
  7.  
  8.     void a() {
  9.         std::cout << "an a! " << x << "\n";
  10.     }
  11. };
  12.  
  13. struct B {
  14.     double x;
  15.  
  16.     double b(double k) {
  17.         std::cout << "b! " << x << ", " << k << "\n";
  18.         return x - k;
  19.     }
  20.  
  21.     void b() {
  22.         std::cout << "b! " << x << ", ?\n";
  23.     }
  24. };
  25.  
  26. struct C {
  27.     A *_first__;
  28.     B *_second__;
  29.      C(A * _first__, B * _second__):_first__(_first__), _second__(_second__) {
  30.     } template < typename K, typename ... T > static auto _a_caller__(K * k, T && ... args)->decltype(k->a(std::forward < T > (args) ...)) {
  31.     return k->a(std::forward < T > (args)...);
  32.     }
  33.     template < typename...T > auto a(T &&...args)->decltype(_a_caller__(_first__, std::forward < T > (args)...)) {
  34.         return _a_caller__(_first__, std::forward < T > (args)...);
  35.     }
  36.     template < typename...T > auto a(T &&...args)->decltype(_a_caller__(_second__, std::forward < T > (args)...)) {
  37.         return _a_caller__(_second__, std::forward < T > (args)...);
  38.     }
  39.     template < typename K, typename...T > static auto _b_caller__(K * k, T && ... args)->decltype(k->b(std::forward < T > (args) ...)) {
  40.         return k->b(std::forward < T > (args)...);
  41.     }
  42.     template < typename...T > auto b(T &&...args)->decltype(_b_caller__(_first__, std::forward < T > (args)...)) {
  43.         return _b_caller__(_first__, std::forward < T > (args)...);
  44.     }
  45.     template < typename...T > auto b(T &&...args)->decltype(_b_caller__(_second__, std::forward < T > (args)...)) {
  46.         return _b_caller__(_second__, std::forward < T > (args)...);
  47.     }
  48. };
  49.  
  50. int main() {
  51.     A a {12};
  52.     B b {24};
  53.  
  54.     C c (&a, &b);
  55.  
  56.     c.a();
  57.     c.b();
  58.     std::cout << c.b(2445) << std::endl;
  59. }
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
prog.cpp: In instantiation of 'decltype (decltype (k->.a((forward<T>)(C::_a_caller__::args)...)) C::_a_caller__(((C*)0)->C::_first__, (forward<T>)(C::a::args)...)) C::a(T&& ...) [with T = {}, decltype (C::_a_caller__(((C*)0)->C::_first__, (forward<T>)(C::a::args)...)) = void]':
prog.cpp:56:9:   instantiated from here
prog.cpp:33:36: sorry, unimplemented: mangling overload
prog.cpp: In instantiation of 'decltype (decltype (k->.b((forward<T>)(C::_b_caller__::args)...)) C::_b_caller__(((C*)0)->C::_second__, (forward<T>)(C::b::args)...)) C::b(T&& ...) [with T = {}, decltype (C::_b_caller__(((C*)0)->C::_second__, (forward<T>)(C::b::args)...)) = void]':
prog.cpp:57:9:   instantiated from here
prog.cpp:45:36: sorry, unimplemented: mangling overload
prog.cpp: In instantiation of 'decltype (decltype (k->.b((forward<T>)(C::_b_caller__::args)...)) C::_b_caller__(((C*)0)->C::_second__, (forward<T>)(C::b::args)...)) C::b(T&& ...) [with T = {int}, decltype (C::_b_caller__(((C*)0)->C::_second__, (forward<T>)(C::b::args)...)) = double]':
prog.cpp:58:26:   instantiated from here
prog.cpp:45:36: sorry, unimplemented: mangling overload
stdout
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Standard output is empty
https://ideone.com/AlDoKA
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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