value-type-issues.php

<?php

data class Vec {
    public function __construct(
        public $x,
        public $y,
    ) {}

    public mutating function double() {
        $this->x *= 2;
        $this->y *= 2;
    }

    public function print() {
        echo "Vec({$this->x}, {$this->y})\n";
    }
}

$vec = new Vec(1, 2);
$vec2 = $vec; // References the same object
$vec2->double(); // Needs to cause separation of $vec/$vec2.

data class Rect {
    public function __construct(
        public Vec $pos,
    ) {}
}

$rect = new Rect($vec);
$rect->pos->double();
// Needs to separate both $rect and pos. However, by the time we know we need to
// separate (on INIT_METHOD_CALL), we're already passed the FETCH_OBJ_R.
// Repeating the opcodes is not possible if the input to the fetch is a
// [TMP]VAR.