simple test case:
import std.stdio;
class C { int x; }
void foo(const(C)[] arg)
{
auto arg2 = arg.dup;
foreach(c; arg2) c.x = 5;
}
void main()
{
C[] arr;
arr ~= new C;
foo(arr);
writefln("%d", arr[0].x);
}
This compiles and outputs 5.
I believe dup should statically fail if the element type has any references in it and the type is const or invariant.
Likewise, I think idup should fail if the element type has any references in it. These properties are not supposed to be "you're on your own" territory IMO.
This is related to bug 1339
Comment #1 by schveiguy — 2009-11-24T20:02:10Z
I should clarify:
I think idup should fail if the element has any *non-immutable* references in it.
Note this leaves us with no ways to dup a const array with references in it! Should we have cdup? A workaround to both would be to always allow dup when an explicit cast is involved.
i.e.:
auto arg2 = cast(const(C)[])arg.dup;