Deduction in template functions with few args (C++17)

I have few instances of one template function. Each of them sequentially executes each of given lambdas, accompanying them with specific messages. When I do that with one lambda, everything works fine, but when I try to add more than one, I get

note: candidate template ignored: deduced conflicting types for parameter 'Task'

from Clang. Here is my code:

template <class Task>
void doTasks(Task task1) {   //works fine
    if (std::__is_invocable<Task>::value) {
        std::cout << "doing first task" << endl;
        task1;
    }
}

template <class Task>
void doTasks(Task task1, Task task2) { //deduced conflicting types
    if (std::__is_invocable<Task>::value) {
        std::cout << "doing first task" << endl;
        task1();
        std::cout << "doing second task" << endl;
        task2();
    }
}

int main(){
    doTasks([&] (){std::cout << "1" << endl;}); 

    doTasks([&] (){std::cout << "1" << endl;},
            [&] (){std::cout << "2" << endl;}); 
  
    return 0; 
}

What’s wrong with it? How can I deal with my problem?

Sorry if it’s a stupid question, I’m some kind of a beginner in C++ and may not understand some template nuances.

>Solution :

The lambdas are of different types. You need to add another template parameter for the second one:

#include <type_traits> // for the proper `std::invocable`

template <class Task, class AnotherTask>
void doTasks(Task task1, AnotherTask task2) {
    if constexpr (std::is_invocable_v<Task> && std::is_invocable_v<AnotherTask>) {
        std::cout << "doing first task\n";
        task1();
        std::cout << "doing second task\n";
        task2();
    }
}

Note: Since it’s C++17, you can also use constexpr if to deal with the if at compile time only.

Demo