• d-bugmail puremagic.com (38/38) Feb 08 2020 https://issues.dlang.org/show_bug.cgi?id=20569

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=20569

          Issue ID: 20569
           Summary: [DIP1000] allow taking the address of a `scope` struct
                    field if it has no indirections
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: safe
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: ag0aep6g gmail.com

This came up in the forum:
https://forum.dlang.org/post/r1lkbt$2vmk$1 digitalmars.com

As far as I can tell, this can be allowed without compromising safety:

----
void main()  safe
{
    static struct S
    {
        int value;
        int* pointer;
    }

    /* explicit `scope`: */
    scope S s1;
    scope int* p1 = &s1.value; /* Error: cannot take address of scope local */

    /* inferred `scope`: */
    int x;
    S s2 = S(0, &x);
    int* p2 = &s2.value; /* Error: cannot take address of scope local */
}
----

The `scope` on `s1` and `s2` really just applies to the `pointer` field. It can
be ignored for the `value` field.

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