c++variadic-templatestype-traitsconditional-compilationparameter-pack

deduced conflicting types for parameter 'T' (<const int &> vs. <int>)

I have a class Base and MyFunc templates with parameter packs.

I have a class Derived, which specifies a const T& type in the parameter pack.

template <typename... T>
class Base {};

template <typename... T>
void MyFunc(Base<T...>, T... t) {}

class Derived : public Base<const int&> {};

void Test() { MyFunc(Derived(), 1); }

This yields the error:

no matching function for call to 'MyFunc'
deduced conflicting types for parameter 'T' (<const int &> vs. <int>)

How can I make this work so that I can use const T& in the parameter pack?

Solution

  • Make one type non deducible

    template <typename... Ts>
void MyFunc(Base<Ts...>, std::type_identity_t<Ts>... ts) {}

    or, possibly, if appropriate, make 2 parameter packs:

    template <typename... Ts, typename... Us>
void MyFunc(Base<Ts...>, Us&&... us) {}