Struct with default ctor (Was: [dmd-beta] dmd 2.064 beta take 2)

[Maxim Fomin]

On Saturday, 18 May 2013 at 18:41:49 UTC, Walter Bright wrote:
> On 5/18/2013 12:30 AM, deadalnix wrote:
>> On Saturday, 18 May 2013 at 07:14:29 UTC, Walter Bright wrote:
>>> What default would you use for non-null pointers?
>>
>> Compile time error as a default sound like a nice option. 
>> Probably too late now,
>> but that is where most language are going now, and having done 
>> quite a lot of
>> java myself, I can guarantee you that it make sense.
>
> D has that:
>
>    @disable this();
>
> which is not the same thing as allowing default constructors. 
> See:
>
> http://d.puremagic.com/issues/show_bug.cgi?id=10102

struct S
{
    int a;
    @disable this();
    this(int) { a = 1; }
    ~this() { assert(a !is 0); }
}

enum E : S { A = S.init }

union U
{
    S s;
    this(this) { assert (s.a !is 0); }
    ~this() { assert (s.a !is 0); }
}

void foo(out S s, out E e, out U u) { }

void main()
{
    S[] arr;
    arr.length = 5; // compiles
    E[] e;
    e.length = 5; // compiles
    S[1] x = (S[1]).init; // compiles
    U[] u;
    u.length = 5; //compiles
    foo(arr[0], e[0], u[0]); // compiles
}

@disable this(); commitments are cheap.