On Monday, 22 June 2015 at 13:23:47 UTC, Marc Schütz wrote:
On Monday, 22 June 2015 at 04:11:41 UTC, Andrei Alexandrescu
wrote:
Walter and I discussed what auto ref for templates should look
like and reached the conclusion that an approach based on
lowering would be best. I added a proposed lowering to
https://github.com/D-Programming-Language/dmd/pull/4717.
I have to concur with Manu's statement in the PR. IMO `auto
ref` (i.e. the status quo) is a hack introduced because of the
lack of usable `scope`. We shouldn't spread it to other parts
of the language, at least not for rvalue references. `scope
ref` is the perfect fit for those.
(There may still be a use for `auto ref` with the meaning "pass
this as efficiently as possible, I don't care whether it's a
reference or not", but I'm not convinced of that either.)
I'm afraid that I don't understand this. What on earth does scope
have to do with this issue? We need a way to indicate that a
parameter should accept both lvalues and rvalues. auto ref was
supposed to do that originally, but Walter misunderstood what
Andrei was proposing and implemented what we have now, which is
great for forwarding, but it doesn't solve the general case,
because it only works with templates. That means that if we want
that functionality we then need to either implement auto ref for
non-templated functions as originally intended, or we need to
come up with a new attribute which does that and which could be
used with both templated and non-templated functions (thus not
requiring the extra template bloat of the current auto ref
implementation with templates if all you want is to accept both
lvalues and rvalues, not have the refness of the argument
forwarded).
What on earth does _any_ of that have to do with scope?
Theoretically, scope indicates that a variable isn't supposed to
escape the function - whatever that really means (it's never
actually been defined outside of delegates, and even there, I'm
not sure that it's defined all that well). What does that have to
do with accepting lvalues or rvalues?
- Jonathan M Davis
