How do I use `__rvalue` expression on a struct property?

[Manu]

FWIW; user code shouldn't contain __rvalue directly.
You can define a move function like:
   ref T move(T)(ref T value) __rvalue => value;

Then you can do:
  T x = var.move;  // move construction

`forward` can be implemented similarly.

On Thu, 24 Apr 2025 at 18:26, Jiten Devlani via Digitalmars-d <
digitalmars-d at puremagic.com> wrote:

> I'm exploring the new `__rvalue` expressions, and got stuck while
> creating a move constructor for a container(non-copyable) with a
> non-copyable container property.
>
> ```d
> import core.stdc.stdio : printf;
> import core.memory : pureMalloc, pureFree;
> struct S {
>      @("mallocd") ubyte[] p;
>      this() @disable;
>      this(this) @disable;
>      this(ubyte[] p) @nogc @trusted nothrow {
>          printf("Base constructor!\n");
>          this.p = p;
>      }
>
>      this(S rhs) @nogc @trusted nothrow {
>          printf("Move constructor!\n");
>          p = rhs.p;
>          rhs.p = null;
>      }
>
>      ~this() pure @nogc @trusted nothrow {
>          if (p) {
>              pureFree(p.ptr);
>              p = null;
>          }
>      }
> }
>
> struct Container {
>      S s;
>      this() @disable;
>      this(this) @disable;
>      this(S s) @nogc @trusted nothrow {
>          this.s = __rvalue(s);
>      }
>
>      this(Container rhs) @nogc @trusted nothrow {
>          this.s = __rvalue(rhs.s);
>      }
> }
> ```
>
> Above code results in compilation error:
> ```
> <source>(35): Error: struct `example.S` is not copyable because
> it has a disabled postblit
>          this.s = __rvalue(rhs.s);
> ```
>
> I've looked into the language reference but could not find a way
> to move a property of a rvalue object instance.
>
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