Segfault when casting array of Interface types

[Franz via Digitalmars-d-learn]

On Tuesday, 16 September 2014 at 03:03:16 UTC, Franz wrote:
> On Tuesday, 16 September 2014 at 02:21:42 UTC, rcor wrote:
>> I'm back for another round of "is this a bug, or am I doing 
>> something stupid?".
>>
>> C and D implement interface I, and I have an array of each. 
>> I'd like to combine these into one I[], but eventually I'd 
>> like to cast an element back to its original type.
>>
>> interface I {}
>> class C : I {}
>> class D : I {}
>>
>> void main() {
>>  C[] c = [new C, new C];
>>  D[] d = [new D, new D];
>>  auto i = cast(I[]) c ~ cast(I[]) d;
>>  assert(cast(C) i[0]); // segfault
>> }
>>
>> casting each array to I[] is fine, but casting an element back 
>> to C segfaults (even if it weren't a C, it should just return 
>> null, right?)
>
> look at what 's auto has created:
>
> import std.stdio;
>
> interface I {}
> class C : I {}
> class D : I {}
>
> void main() {
>   C[] c = [new C, new C];
>   D[] d = [new D, new D];
>   auto i = cast(I[]) c ~ cast(I[]) d;
>   writeln(typeof(i).stringof);
> }
>
> Your issue comme from auto.

i is a I[]