Re: RCArray is unsafe

[Walter Bright via Digitalmars-d]

On 3/1/2015 7:44 AM, "Marc =?UTF-8?B?U2Now7x0eiI=?= <schue...@gmx.net>" wrote:
A weakness of the same kind affects DIP25, too. The core of the problem is
borrowing (ref return as in DIP25), combined with manual (albeit hidden) memory
management. An example to illustrate:
     struct T {
         void doSomething();
     }
     struct S {
         RCArray!T array;
     }
     void main() {
         auto s = S(RCArray!T([T()])); // s.array's refcount is now 1
         foo(s, s.array[0]);           // pass by ref
     }
     void foo(ref S s, ref T T) {
         s.array = RCArray!T([]);      // drop the old s.array
         t.doSomething();              // oops, t is gone
     }

The trouble seems to happen when there are two references to the same object 
passed to a function. I.e. there can be only one "borrowed" ref at a time.

I'm thinking this could be statically disallowed in @safe code.