try..catch..pass..finally Was: DMD 0.148 - scope guard

[Walter Bright]

"S. Chancellor" <dnewsgr at mephit.kicks-ass.org> wrote in message 
news:du376e$1fbf$2 at digitaldaemon.com...
> Something like this would be equivalent?
>
> Transaction abc()
> {
> Foo f;
>     Bar b;
>     Def d;
> Auto scoped = new Scoper();  //scoped.exit() can be called by the 
> destructor.  We won't add a finally block.
>
> try {
> scoped.failures ~= void delegate () { dofoo_unwind(f); }
>     f = dofoo();
>
> scoped.failures ~= void delegate () { dobar_unwind(b); }
> b = dobar();
>
> scoped.success()
> } catch (Exception o) {
> scoped.failed()
> throw o;
> }
>
> return Transaction(f, b, d);
> }

Should be:
     f = dofoo();
     scoped.failures ~= void delegate () { dofoo_unwind(f); }
etc. Other than that, it looks like it'll work, but it's a lot more code 
than on_scope. You also need to be sure that the delegates don't refer to 
any variables declared inside the try block, as those variables no longer 
exist in the catch block - and the compiler can't catch that error. This 
isn't a problem with on_scope.