DMD 2.100, bring ont he attribute soup

[rikki cattermole]

On 27/05/2022 5:06 PM, Walter Bright wrote:
> On 5/26/2022 8:07 PM, rikki cattermole wrote:
>> I want lifetime checks to work,
> 
> So do I. But nobody has figured out how to make this work without 
> strongly impacting the programmer.

I did come up with a design, but I'm not convinced it is entirely doable.

I explained this to Timon earlier today (so have examples).

Its basically making all memory objects (as in C definition), in 
reference to other memory objects, and tieing their lifetime to them.

My worked example:

```d
int[] array = [1, 2, 3]; // ownership: []
// arg ownership: [] (not ref/out)
// return ownership: [first argument] -> [array]
int* got = func(array); // ownership: [array]

int* func(int[] source) {
   int[] slice = source[1 .. 2]; // ownership: [source]
   int* ptr = &slice[0]; // ownership: [slice, source] -> [source]
   return ptr; // ownership: [ptr] -> [source]
}
```

A question Timon came up with that I answered:

```d
int[][] func(int[] a, int[] b){
     return [a,b];
}
```

(for return value): ``// ownership: [first argument, second argument]``

This ticks a lot of the boxes I'm using as preferable acceptance criteria:

1. Inferred for anything non-virtual
2. Nothing outlives its owner
3. Fairly straight forward to understand

But yeah none of this is easy to resolve.

On that note, an issue I have found to have in practice is[0]. I haven't 
been bothered to report it, but at least this shouldn't require going 
back to the drawing board ;) #dbugfix

[0] https://issues.dlang.org/show_bug.cgi?id=23142