Why doesn't this rise an error? What is happenning here?

Question

struct A {
A(int) {}
};

void f(A) {}

int main() {
f(1);
return 0;
}

Answer 1

When you call F(1), the compiler looks for a way to convert the arguments you have passed into the function into the proper type. Since you have given a constructor for A that takes an int, the compiler has a way to convert the int literal 1 into an object of type A. It constructs an object of type A using the value 1. This is similar to how you can pass an int to something that requires a double, but the compiler will upcast the int.
https://code.sololearn.com/cvNW7YXzaOqz/?ref=app