Const ref and rvalues again...

[martin]

On Monday, 5 November 2012 at 08:01:57 UTC, Jonathan M Davis 
wrote:
> auto ref's current semantics can't possibly work with 
> non-templated functions,
> and it's clear that there are good reasons for keeping auto ref 
> as it is now
> for templates. So, either we make it work with non-templated 
> functions with
> different (albeit similar) semantics, or we need a new 
> attribute for doing what
> we want to do with non-templated functions.

I agree that the current auto ref semantics are only useful for 
templates since "auto ref T" is replaced by either a reference 
(ref T for lvalues) or a value (T for rvalues), two very 
different things.
I don't know how auto ref for templates is currently implemented, 
i.e., if, given a function

void foo(T)(auto ref T x, auto ref T y) {}

the compiler would instantiate the template max 2^2 times for 
each used type T to cover all lvalue/rvalue combinations for x 
and y. In that case, treating a non-templated function

void foo(auto ref MyStruct x, auto ref MyStruct y) {}

as implicit template (without template parameters) would be a 
viable option imho, i.e.,

void foo()(auto ref MyStruct x, auto ref MyStruct y) {}

If that kind of auto-templating is not what we want, I'd 
definitely opt for allowing rvalues as "in ref" parameters to 
keep things simple.