RFC: moving forward with @nogc Phobos

[via Digitalmars-d]

On Wednesday, 1 October 2014 at 15:48:39 UTC, Oren Tirosh wrote:
> On Tuesday, 30 September 2014 at 19:10:19 UTC, Marc Schütz 
> wrote:
>> (I'll try to make a sketch on how this can be implemented in 
>> another post.)
>
> Do elaborate!

Here's an example implementation of what I have in mind (totally 
untested and won't compile because of `scope`):

http://wiki.dlang.org/User:Schuetzm/RC,_Owned_and_allocators

This is just a sketch to explain the general idea. Some things 
probably won't work as implemented, especially the disable 
postblit and opAssign() of Owned!T. I think it needs to implement 
implicit moving, otherwise one would have to call `release()` 
everywhere.

As in the other post, the function that produces the value 
returns Owned!T. The types don't require @unique however 
(although integration with DMD's idea of unique would still be 
useful).

Because of auto-borrowing via alias this, Owned!T and RC!T both 
can pass their payloads to functions that accept them by `scope`. 
The ref-count is not touched for borrowing.

Usage examples:

     Owned!string setExtension(in char[] path, in char[] ext);

     void saveFileAs(in char[] name) {
         import std.path: setExtension;
         import std.file: write;
         name.                    // scope const(char[])
             setExtension("txt"). // Owned!string
             write(data);
     }

     RC!string[] stringList;

     void addToGlobalList(scope RC!string s) {
         stringList ~= s;    // increments ref-count
     }

     RC!string foo;
     addToGlobalList(foo);   // borrowing doesn't change ref-count

     auto newFileName = "hello-world".setExtension("txt");
     auto tmp1 = newFileName;       // ERROR: cannot copy
     scope tmp2 = newFileName;      // OK, borrowing
     foo = newFileName;             // ERROR: cannot copy
     foo = newFileName.release();   // OK, move
     auto bar = newFileName.toRC(); // ditto