Implicit conversion : const reference vs non-const reference vs non-reference

Question

Consider this code,

struct A {};
struct B {  B(const A&) {} };
void f(B)
{
    cout << \"f()\"<

        

Answer 1

I would like to hear reasons, rationale and reference(s) from the language specification

Is The Design and Evolution of C++ sufficient?

I made one serious mistake, though, by allowing a non-const reference to be initialized by a non-lvalue [comment by me: that wording is imprecise!]. For example:

void incr(int& rr) { ++rr; }

void g()
{
    double ss = 1;
    incr(ss);    // note: double passed, int expected
                 // (fixed: error in release 2.0)
}

Because of the difference in type the int& cannot refer to the double passed so a temporary was generated to hold an int initialized by ss's value. Thus, incr() modified the temporary, and the result wasn't reflected back to the calling function [emphasis mine].

Think about it: The whole point of call-by-reference is that the client passes things that are changed by the function, and after the function returns, the client must be able to observe the changes.