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.
