Issue: Function templates with auto ref parameters can’t be instantiated independently form a function call.

Technically, it makes sense, because the ref presence for auto ref parameters is determined by the value category of the argument. No argument → no value category → can’t determine ref presence. But that means, you can’t take the address of such a function template instance.

One way to solve this is to pass something to the template. In this enhancement issue I drafted the idea of passing ref, essentially as a 1-bit data token. The issue with that idea is that it can only work with auto ref T where T is a template type parameter.

The idea of today is allowing ref to carry a boolean value to tell if it’s there:

void f(ref{false} int x); // void f(int x)
void f(ref{true}  int x); // void f(ref int x)

That boolean can be inferred for templates:

void f(bool isRef)(ref{isRef} int x) {}

int x;
f(0); // f!false(0);
f(x); // f!true(x);
auto fp0 =

For variadics, the function can use a bool[] parameter:

void f(bool[] areRef, Ts...)(ref{areRef} Ts args)

int x;
f(0, x); // f!([false, true], int, int)(0, x);

Unfortunately, that can’t help with auto ref.