Function auto return type

Question

Why does it work with ternary operator but not with classic if approach?

template <class T, class F>
auto smaller(T a, F b)
{
return(a<b ? a:b); //this works

if(a<b) //this does not
return a; // Error:
else // inconsistent deduction
return b; // for auto return type
}
int main(void)
{
cout << smaller(4,5.2) << endl;
cout << smaller(6,5.2) << endl;
return 0;
}

Answer 1

It works with ternary operator because a and b are implicitly converted into the common arithmetic type. There are rules for second operands and third operands conversion, you can read here:

https://docs.microsoft.com/en-us/cpp/cpp/conditional-operator-q?view=vs-2019