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#include <memory>
 
template <typename Op, typename T>
struct base { };
 
template <typename Mode, typename T>
struct derived { };
 
template <typename T>
struct derived<int, T> : public base<int, T> { };
 
template <typename D, typename T>
void fun(std::unique_ptr<base<D, T>>) { }
 
int main() {
	auto d = std::make_unique<derived<int, double>>();
	fun(std::move(d));
}

prog.cpp: In function 'int main()':
prog.cpp:17:18: error: no matching function for call to 'fun(std::remove_reference<std::unique_ptr<derived<int, double>, std::default_delete<derived<int, double> > >&>::type)'
  fun(std::move(d));
                  ^
prog.cpp:17:18: note: candidate is:
prog.cpp:13:6: note: template<class D, class T> void fun(std::unique_ptr<base<D, T> >)
 void fun(std::unique_ptr<base<D, T>>) { }
      ^
prog.cpp:13:6: note:   template argument deduction/substitution failed:
prog.cpp:17:18: note:   mismatched types 'base<D, T>' and 'derived<int, double>'
  fun(std::move(d));
                  ^
prog.cpp:17:18: note:   'std::unique_ptr<derived<int, double>, std::default_delete<derived<int, double> > >' is not derived from 'std::unique_ptr<base<D, T> >'

Standard output is empty