[Issue 10917] New: scope ref should be allowed

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10917

           Summary: scope ref should be allowed
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: andrej.mitrovich at gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2013-08-28 15:22:18 PDT ---
-----
void foo(scope int* val) { }  // ok
void bar(scope ref int val) { }  // error

void main()
{
    int x;
    foo(&x);  // ok
    bar(x);
}
-----

'scope ref int' is almost the same thing as 'scope int*', except that 'ref'
cannot be null, and 'ref' is simpler to use in code since a user can copy by
value with the assignment syntax instead of having to dereference the pointer
first.

Note that addresses can be extracted from both pointers and references:

-----
int* ptr;

void foo(scope int* val)
{
    ptr = val;  // disallowed once scope is properly implemented
}

void bar(/*scope*/ ref int val)
{
    ptr = &val;  // equivalent to &main.x
}

void main()
{
    int x;
    foo(&x);
    bar(x);
}
-----

So scope ref is very much useful to have.

And yeah, I realize scope does practically nothing in the compiler right now
(e.g.
http://forum.dlang.org/thread/rbgssjrzdcmbhxyhwlak@forum.dlang.org#post-mailman.391.1348770797.5162.digitalmars-d-learn:40puremagic.com).

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