__rvalue and Move Semantics first draft - aliasing problem/danger

[Richard (Rikki) Andrew Cattermole]

On 10/11/2024 11:44 AM, Walter Bright wrote:
> Timon mentioned the related problem with:
> 
> |callee(__rvalue s, __rvalue s); |
> 
> where s would be destroyed twice. This isn't always detectable:

Break it down into an IR:

```
a = __rvalue(s)
b = __rvalue(s)
callee(a, b)
```

This is what type state analysis sees at an IR level.

```
// s must be >=initialized
a = s
// s is reachable which is < initialied

// s must be >= initialized, ERROR
b = s
```

We don't need to solve type state analysis here ;)

But it does tell us, that as a language feature it is dependent upon it, 
to be working correctly, so can't be turned on until then.