DIP 36: Rvalue References

[Diggory]

I realise I'm new here but this seems to be suggesting a whole 
load of changes and special cases for something that can be done 
in (IMHO) a much simpler way:

Why not simply make escaping a "ref" pointer an unsafe operation. 
The compiler should be able to detect this and report it without 
any changes to the syntax.

This should cover 99% of cases with no extra attributes required 
and no limitations on what you can do with a "ref" within the 
function. In the 1% of cases that a pointer needs to be escaped 
safely you can add an attribute (maybe "heap ref" or something, 
although perhaps some existing syntax could be used) that 
requires the input to have been allocated on the heap.

In the case that a stack variable is passed as a "heap ref" 
parameter the compiler can automatically promote it where 
possible, or if that's not possible, such as the variable being 
marked "scope" (existing meaning) then it should complain.

All values (including literals and temporaries) should then be 
able to be passed to a "ref const" parameter.

As far as I'm aware the only real purpose for R-value references 
is to implement move semantics. This could already be done using 
"ref in" syntax, as that makes no guarantees that the value is 
not going to be destroyed, only says that the value should be 
initialised prior to it being passed in. The only change would be 
to allow passing temporaries as "ref in".

To promise that the variable is not going to be modified "ref 
const" or "ref const in" can be used.