DMD 2.100, bring ont he attribute soup

[Timon Gehr]

On 28.05.22 12:55, Nick Treleaven wrote:
> On Friday, 27 May 2022 at 21:09:49 UTC, deadalnix wrote:
>>> void f(scope T);
>>>
>>> T v = new T; // can be stack allocated
>>> f(v);
>>
>> I don't think this is a valid optimization, because DIP1000 cannot 
>> track indirections. Therefore, I could have an objects within the 
>> subgraph reachable from `v` which escape and which itself can reaches 
>> back to `v`.
> 
> Can you give an example? The following currently compiles:
> 
> ```d
> @safe @nogc:
> 
> class C {
>      C g() => this;
> }
> 
> //C f(C c); // error
> C f(scope C c); // OK
> //C f(scope C c) { return c.g; } // error
> 
> void main()
> {
>      scope c = new C(); // allocated on the stack, scope currently required
>      f(c);
> }
> ```
> 
> If I switch in the third version of `f`, I get an error with -dip1000:
> scopeclass.d(7): Error: scope variable `c` assigned to non-scope 
> parameter `this` calling scopeclass.C.g

```d
class D{
     C c;
}
class C {
     D d;
     int x=3;
     this(D d)@safe @nogc{
         d.c=this;
         this.d=d;
     }
}
C foo(D d)@nogc @safe{
     scope c = new C(d); // remove `scope` and program does not crash
     return c.d.c; // escape c
}
void main(){
     import std.stdio;
     writeln(foo(new D)); // segfault
}
```

Not sure if this was already in bugzilla, added it:

https://issues.dlang.org/show_bug.cgi?id=23145