Reference parameter forwarding

@ARGS: --lib tests/lib When a function receives a &Struct (mutable reference) parameter and passes it to another function that also takes &Struct, the reference must be forwarded without dereferencing. This is P144.

use p144_entry;

fn main() {

box_set_val calls box_ensure(b) internally — forwarding the & param.

  b = Box { items: [] };
  box_set_val(b, 42);
  assert(b.items[0].val == 42, "P144: & forwarded — item set to 42");

Calling the inner function directly also works.

  b2 = Box { items: [] };
  box_ensure(b2);
  assert(len(b2.items) == 1, "ensure added one item");
  assert(b2.items[0].val == 0, "default val is 0");

Multiple forwards: ensure is idempotent.

  box_ensure(b2);
  assert(len(b2.items) == 1, "ensure idempotent");

Set a second value via box_set_val on a pre-populated box.

  b3 = Box { items: [] };
  b3.items += [Inner { val: 10 }];
  b3.items += [Inner { val: 0 }];
  box_set_val(b3, 99);
  assert(b3.items[0].val == 10, "existing item preserved");
  assert(b3.items[1].val == 99, "zero item replaced");
}