Re: DIP23 draft: Fixing properties redux

[Steven Schveighoffer]

On Tue, 05 Feb 2013 13:33:35 -0500, Andrei Alexandrescu  
<seewebsiteforem...@erdani.org> wrote:

Walter and I reviewed the discussion and had a long talk. We are very  
seriously considering banning the use of & against a ref result from a  
function (and actually ref parameters and even struct members in @safe  
code). One would still be able to take the address of a field in a class  
because that's assumed to live on the GC heap.

Back to the problem I stated, how does one do this:

ref A foo();

ref A bar();

A *a;

if(condition)
   a = &foo();
else
   a = &bar();

// use a for a few lines

I can see a possible solution but it's not pretty:

void processA(ref A a)
{
   // lines that deal with a here
}

if(condition)
  processA(foo());
else
  processA(bar());

But this kind of seems hacky.  Why should I have to declare a function  
just to keep a persistent reference to a return value for the scope of my  
function?  Not only is is awkward, there is a performance hit in that I  
have to call another function.

Note also that this doesn't fix memory issues:

struct S
{
  ref S self() {return this;}
}

ref S bad()
{
   S s;
   return s.self();
}

Which I believe would be valid still with your rules.

-Steve