Error handling meeting summary

[Richard (Rikki) Andrew Cattermole]

On 26/07/2025 12:03 PM, Steven Schveighoffer wrote:
> On Friday, 25 July 2025 at 16:58:43 UTC, Richard (Rikki) Andrew 
> Cattermole wrote:
>> Hello all!
>>
>> We've had a meeting on how error handling should work in D.
>>
>> Approved work:
>>
>> - Finalisers are brought back to the baseline behaviour. They will not 
>> be rewritten to sequences in the frontend.
> 
> Can you explain this? The link isn't very explanatory for those who 
> don't understand the DMD codebase.
> 
> -Steve

Yeah sure.

Right now final statements are different behavior based upon if the 
trybody scope could throw an ``Exception`` class.

If they do not throw an ``Exception``, it will rewrite it so that it is 
a sequence: ``trybody; finalbody;``

Final statements are used for a lot of things, running destructors of 
structs, or ``scope(exit)`` for instance.

That's a problem, its half way between two cleanup strategies. Never run 
cleanup on throwing of an ``Error`` or always cleaning up when ``Error`` 
is thrown.

An example of this behavior is the following code, where the destructor 
will run:

```d
void do1() {
	assert(0);
}

void main()
{
     static struct S
     {
         ~this()
         {
             import std.stdio;
             writeln("destructor ran!");
         }
     }

     S s;
     do1;
}
```

Bringing this back to baseline behavior of no rewrites, means that we 
can pick which strategy people want to use.