Why is this call to member function ambiguous?

Question

Consider this class:

class Base{
public:
    void func(double a) = delete;
    void func(int a) const {}
};

int main(){
    Base base;

    base.func(1);
           


        

Answer 1

When a function is overloaded, the overload resolution takes place first. The program is ill-formed if the deleted function is the best match and is selected.

Therefore, your program would produce the same error as the following, because there is an implicit conversion from int to double and the compiler does not know what function you intend to call:

class Base{
public:
    void func(double a) {}
    void func(int a) const {}
};