Re: Better handling of noncopyable objects and objects with this(this)

[via Digitalmars-d]

On Monday, 1 June 2015 at 14:20:46 UTC, Jonathan M Davis wrote:
On Monday, 1 June 2015 at 12:50:28 UTC, Marc Schütz wrote:
Also, object with destructors need to have more restrictions:
   S {
       ~this();
   }

   void foo() {
       S s;
       if(condition)
           bar(s);
       // <- should we run the destructor here?
   }

This can either be solved by making such cases non-eligible, 
or by "remembering" whether an object was moved using a hidden 
boolean variable. AFAIK the latter is incidentally the 
solution Rust chose.

Wouldn't the compiler just do something like

if(condition)
{
    bar(s); // Do a move; the destructor is run inside bar
    return;
}
else
{
    s.__dtor();
    return;
}

In which case, the destructor is always run in the right spot, 
and the compiler can guarantee that a move is done rather than 
a copy?

When this can be done, it's of course a good solution. But when 
there is additional code between the move and the destruction, it 
usually doesn't work:

    void foo() {
        S s;
        if(condition)
            bar(s);
        baz();
        // <- should we run the destructor here?
    }