On 12/5/2014 3:59 PM, deadalnix wrote:
On Friday, 5 December 2014 at 21:32:53 UTC, Walter Bright wrote:
I don't believe this is correct. Rvalues can be assigned, just like:
__gshared int x;
{ int i; x = i; }
i's scope ends at the } but it can still be assigned to x.
It work even better when i has indirections.
I understand what you're driving at, but only a scoped rvalue would not be
copyable.
The DIP say nothing about scoped rvalue having different behavior
than non scoped ones.
Can you propose some new wording?
I originally had scope only apply to ref, but that made
having scoped classes
impossible.
Promoting scoped class on stack is an ownership problem, and out
of scope (!). It make sense to allow it as an optimization.
Problem is, lifetime goes to infinite after indirection, so I'm
not sure what the guarantee is.
The guarantee is there will be no references to the class instance after the
scoped class goes out of scope.
Through use of that view. I see it as follow:
- When unconsumed owner goes out of scope, it can (must ?) be
free automatically.
- scope uses do not consume.
- When the compiler see a pair of alloc/free, it can promote on
stack.
That is a much more useful definition as it allow for stack
promotion after inlining:
class FooBuilder {
Foo build() { return new Foo(); }
}
class Foo {}
void bar() {
auto f = new FooBuilder().build();
// Use f and do not consume...
}
This can be reduced in such a way no allocation happen at all.
Yes, but I think the proposal allows for that.
I cause everything reached through the view to be scope and
obliviate the need for things like &(*e) having special meaning.
Are you suggesting transitive scope?
For rvalues, yes. Not for lvalues.
I don't think that is workable.
