[Issue 6617] Two problems using enum lenghs

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=6617


Andrej Mitrovic <andrej.mitrovich at gmail.com> changed:

           What    |Removed                     |Added
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           Keywords|rejects-valid               |
                 CC|                            |andrej.mitrovich at gmail.com
           Severity|normal                      |enhancement


--- Comment #2 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2012-12-02 10:06:34 PST ---
(In reply to comment #0)
> This is a bug report. I have found two different problems while creating a
> fixed-sized array as long as the number members of an enum (DMD 2.055beta3)

All of these now work.

> In practice I think a length attribute for enums is handy to have (this is a
> low-priority enhacement request):
> enum Foo : size_t { A = 0, B = 1, C = 2 }
> void main() {
>     int[Foo.length] bar;
> }

The problem with this is that lookups also go to the base type of the enum, so:

struct T
{
    @property static size_t length() { return 0; }
}

enum Foo : T { a = T() }

void main()
{
    assert(Foo.length == 1);  // fails
}

We could instead provide a template in std.traits:

template EnumLength(E) if (is(E == enum))
{
    enum size_t EnumLength = EnumMembers!E.length;
}

void main()
{
    assert(EnumLength!Foo == 1);
}

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