śr., 2 mar 2022 o 13:18 Ville Voutilainen
<ville.voutilainen_at_[hidden]> napisał(a):
>
> On Wed, 2 Mar 2022 at 14:13, Maciej Cencora <m.cencora_at_[hidden]> wrote:
> > > > If you think I am wrong, then please show me how this mentioned issue
> > > > can be solved without a language level construct?
> > >
> > > Convention. Don't declare functions to take rvalue references if they
> > > don't move, or otherwise document
> > > such functions if they move only sometimes. That's what we do today,
> > > and I don't have much evidence
> > > of that being insurmountable.
> > Convention is not a solution, as it is optional, and it is not
> > automatically checkable.
>
> Yet it works. That suggests it's a solution.
Maybe it works for you, it certainly doesn't work for everyone, so no,
it is not a solution.

>
> > > > Also there is a problem of teachability, which I'm sure you are aware
> > > > of if you teached anyone about move-semantics:
> > > > - std::move does nothing,
> > >
> > > It does what it claims to do, it enables moving.
> > I don't see it being named 'std::enable_move', so it doesn't do what
> > it's name claims to do!
>
> I didn't say it does what its name claims, I said it does what it
> claims to do. It's a well-documented
> facility that's been there since C++11, it's relatively easy to
> explain how it works and how to use it,
> and after such explanations, the complaints about it
> not-really-moving-right-there tend to not come up,
> except from language lawyers.
It is nowhere near 'easy' to explain what it does. Move-semantics is
topic that always takes most of the time to
to explain to devs that learn C++11.

>
> > > ..while introducing fair amounts of different complexity.
> > Assuming we chose 'move' as a contextual keyword for such an
> > operation, a code like this :
> > X sink = move source;
> > // any use of 'source' now is an hard error
> > or
> > consume(move source);
> > // any use of 'source' now is an hard error
> >
> > is straightforward and intuitive. It always does what it claims to do,
> > no possibility of errors, no corner-cases.
> >
> > So what exactly this new fair amount of complexity would be?
>
> Well, it's yet another language facility that needs to be learned.
> That in and of itself if additional complexity.
Refusing to add a new feature, because every new feature adds
complexity, is absurd. If we applied this logic to anything, we
wouldn't have C++11 or even C++ at all.