[dmd-beta] rvalue references

[Andrei Alexandrescu]

On 4/16/12 4:21 PM, Michel Fortin wrote:
> Did you notice the "ref struct" proposal I made a while ago on the
> newsgroup? Basically you attach a flag to a struct declaration that'd
> cause that struct to be automatically passed by ref when used as a
> function argument. It's crude, but it'd be much less verbose than
> writing 'ref' or 'auto ref' everywhere.

Walter convinced me a while ago that transparent pass by ref is 
problematic. Consider:

struct S @pass_by_ref(true)
{
    ...
}

void fun(T)(T a, T b)
{
    ...
}

Inside fun, code is free to assume that &a != &b with quite important 
consequences. If calling fun(s, s) ends up aliasing the two names to the 
same thing, it will fail in difficult to figure ways.


Andrei