Destroying structs (literally)

[via Digitalmars-d]

On Friday, 29 August 2014 at 19:01:51 UTC, Andrei Alexandrescu 
wrote:
> On 8/29/14, 3:53 AM, "Marc Schütz" <schuetzm at gmx.net>" wrote:
>> Jacob Carlborg just recently brought this up in another 
>> thread. Isn't it
>> kind of consensus that calling a destructor from the GC is not 
>> a good
>> idea because of the restrictions that apply in this context? 
>> Andrei even
>> wanted to deprecate destructors for classes because of this. 
>> Maybe a
>> better direction would be to separate the concepts of 
>> destruction and
>> finalization, and introduce two kinds of "destructors" for 
>> them.
>
> I think we need to stay with what we have. Adding a distinct 
> kind of destructor might be interesting. -- Andrei

Our idea was that an additional destructor (let's call it a 
finalizer) would be helpful because it is backward compatible. 
The compiler could make some validity checks on it, at the least 
make it nothrow, maybe @nogc (but I believe we can relax this 
restriction), pure (?). Disallowing access to references (because 
they could pointer to already destroyed objects) is unfortunately 
not feasible, because we can't distinguish GC pointers from other 
ones. To avoid the need for code duplication, finalizers could 
always be called implicitly by destructors (assuming everything 
that is allowed in finalizers is also permitted in destructors).

Calling destructors from the GC could later be phased out. It is 
technically not a breaking change, because there never was a 
guarantee that they'd be called anyway.