On Tuesday, 16 September 2014 at 06:27:59 UTC, Klaus wrote:
On Tuesday, 16 September 2014 at 03:05:57 UTC, Franz wrote:
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[]
writing
auto i = cast(I[]) c ~ cast(I[]) d;
is just a horrible way of shortcuting the static typing. You
write this thinking that i "has to be..." and then you complain
latter because the cast does not work.
D is a strongly typed lang. in your example you use "auto"
because your brain doesnt give you what the type of i has to
be, which is an error. D is not a scripting lang. You made a
wrong usage of "auto".
AFACIS there's nothing wrong with his use of casting. It's fine
here, because `I` is a base type of `C` and `D`. If it weren't
for the arrays, the cast wouldn't even be necessary. I think it's
a bug.
