[Issue 10965] New: Allow alias initializer as enum member to avoid counter reset

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=10965

           Summary: Allow alias initializer as enum member to avoid
                    counter reset
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: enhancement
          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> 2013-09-04 17:47:00 PDT ---
I've recently ran into a hard to track bug in my code:

-----
enum MouseAction
{
    press,

    release,

    /** Convenience - equal to $(D press). */
    click = press,

    double_click,  // oops, it's now equal to release!!
}

void main()
{
    static assert(MouseAction.release != MouseAction.double_click);  // fail
}
-----

Unfortunately the introduction of the convenience member ended up re-setting
the enum member init counter, which ended up making "double_click" equal the
value of "release".

To avoid such buggy code, but still allow these convenience members, I propose
we introduce member aliases as a new feature:

-----
enum MouseAction
{
    press,

    release,

    alias click = press,  // same as press, but does not reset the counter!

    double_click,  // equals release + 1
}

void main()
{
    static assert(MouseAction.release != MouseAction.double_click);  // ok
}
-----

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