Expressions in isset()
-----
<?php
// This is legal.
isset(($a), (($b)));
// This is illegal, but not a syntax error.
isset(1 + 1);
-----
array(
    0: Stmt_Expression(
        expr: Expr_Isset(
            vars: array(
                0: Expr_Variable(
                    name: a
                )
                1: Expr_Variable(
                    name: b
                )
            )
        )
        comments: array(
            0: // This is legal.
        )
    )
    1: Stmt_Expression(
        expr: Expr_Isset(
            vars: array(
                0: Expr_BinaryOp_Plus(
                    left: Scalar_Int(
                        value: 1
                    )
                    right: Scalar_Int(
                        value: 1
                    )
                )
            )
        )
        comments: array(
            0: // This is illegal, but not a syntax error.
        )
    )
)