opDispatch and compile time parameters

[Timon Gehr via Digitalmars-d]

On 10/19/2015 09:57 PM, Adam D. Ruppe wrote:
> On Monday, 19 October 2015 at 19:53:14 UTC, Andrei Alexandrescu wrote:
>> struct A {
>>     int[] x = new int[10];
>> }
>>
>> void main() {
>>     import std.stdio;
>>     A a;
>>     a.x[1] = 42;
>>     writeln(a.x);
>> }
>>
>> Looks like a bona fide runtime array to me.
>
> It is still in the static data segment. Try this:
>
>
> struct A {
>      int[] x = new int[10];
> }
>
> void main() {
>      import std.stdio;
>      A a;
>      a.x[1] = 42;
>      writeln(a.x);
>
>      A a2;
>      writeln(a2.x);
>
>      assert(a.ptr is a2.ptr); // passes
> }
>
>
> The `new int[10]` is done at compile time and the pointer it produces is
> put into the .init for the struct. So the same pointer gets blitted over
> to ALL instances of `A`, meaning they alias the same data (until the
> slice gets reallocated by append or whatever).

This is the worst part:

class C{
     int[] x=[1,2,3];
}

void main(){
     auto mut=new C;
     auto imm=new immutable(C);
     assert(imm.x[0]==1);
     mut.x[0]=2;
     assert(imm.x[0]==2);
}