List reference assignments (PHP 7.3)
-----
<?php

list(&$v) = $x;
list('k' => &$v) = $x;
[&$v] = $x;
['k' => &$v] = $x;
-----
array(
    0: Stmt_Expression(
        expr: Expr_Assign(
            var: Expr_List(
                items: array(
                    0: ArrayItem(
                        key: null
                        value: Expr_Variable(
                            name: v
                        )
                        byRef: true
                        unpack: false
                    )
                )
            )
            expr: Expr_Variable(
                name: x
            )
        )
    )
    1: Stmt_Expression(
        expr: Expr_Assign(
            var: Expr_List(
                items: array(
                    0: ArrayItem(
                        key: Scalar_String(
                            value: k
                        )
                        value: Expr_Variable(
                            name: v
                        )
                        byRef: true
                        unpack: false
                    )
                )
            )
            expr: Expr_Variable(
                name: x
            )
        )
    )
    2: Stmt_Expression(
        expr: Expr_Assign(
            var: Expr_List(
                items: array(
                    0: ArrayItem(
                        key: null
                        value: Expr_Variable(
                            name: v
                        )
                        byRef: true
                        unpack: false
                    )
                )
            )
            expr: Expr_Variable(
                name: x
            )
        )
    )
    3: Stmt_Expression(
        expr: Expr_Assign(
            var: Expr_List(
                items: array(
                    0: ArrayItem(
                        key: Scalar_String(
                            value: k
                        )
                        value: Expr_Variable(
                            name: v
                        )
                        byRef: true
                        unpack: false
                    )
                )
            )
            expr: Expr_Variable(
                name: x
            )
        )
    )
)