On Monday, 22 June 2015 at 20:42:58 UTC, Daniel N wrote:
Considering we already have working 'Sealed references', why not simply allow rvalues for plain ref?
Please, please, no. That would be horrible. ref indicates an intention to mutate the argument, which makes no sense with rvalues. And if ref is used simply so that you can accept both rvalues and lvalues without copying lvalues, then there's zero indication in the function signature when the point of the ref is to actually set what's being passed in.
It works in C++ with const&, because you know that the function won't mutate the argument, but if you allow it with ref in general, then you stand no chance of being able to look at a function signature and deduce whether the function intends to mutate an argument or not. And even if Andrei wasn't so set against const ref that we could go that route in D as well, it wouldn't solve the problem either, because const in D is just too restrictive to use in many cases. We need a way to indicate that a parameter accepts both lvalues and rvalues without intending to mutate the argument but without actually guaranteeing it via const. And that does _not_ work with naked ref.
- Jonathan M Davis
