D hackers requested. Dancing around postblit.

[IgorStepanov via Digitalmars-d]

On Wednesday, 5 November 2014 at 20:01:59 UTC, Adam D. Ruppe 
wrote:
> If you're willing to make it @system or @trusted, you can just 
> copy the data and call postblit manually:
>
> extern(C) @safe int printf(in char*);
>
> struct S {
>         ~this() { printf("dtor\n"); }
>         this(this) { printf("postblit\n"); }
>
>         @disable S opAssign(S s);
> }
>
> S[] data;
> void emplace(Struct)(ref Struct val, size_t i) {
>         // just blit the struct contents over
>         // (same thing normal assign does anyway)
>         (cast(ubyte*)&(data[i]))[0 .. Struct.sizeof] = 
> (cast(ubyte*)&val)[0 ..  Struct.sizeof];
>         // call postblit
>         data[i].__postblit();
> }
>
> void main() {
>         data.length = 1;
>         S s;
>
>         emplace(s, 0);
> }
>
>
>
> Since it is a template, attribute inference should take care of 
> nothrow, etc.

It was my first try :(
data[i].__postblit();
calls the user-defined postblit and only it.

struct Sx {
          ~this() { printf("dtor\n"); }
          this(this) { printf("postblit\n"); }

          @disable S opAssign(S s);
}

struct S
{
    Sx s;
}

data[i].__postblit(); //error: S hasn't __postblit member, but it 
need the postblit call for Sx
typeid(S).postblit(&data[i]) works as needed, but doesn't save 
postblit attributes.