if ($enum instanceof BackedEnum) doesn't infer BackedEnum type

[GromNaN]

BackedEnum always have the properties name and value. In the context of a method attribute with a type, using instanceof BackedEnum doesn't infer the type.

function fun(OperatorInterface $operator) :string|int
{
    if ($operator instanceof BackedEnum) {
        // $operator is OperatorInterface&BackedEnum
        // but psalm triggers NoInterfaceProperties error
        return $operator->value;
    }

    // ...
}

https://psalm.dev/r/48ec6feed1

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/48ec6feed1

<?php

interface Operator {}

enum Foo: string implements Operator
{
    case bar = 'bar';
}

function fun(Operator $operator) :string|int
{
    if ($operator instanceof BackedEnum) {
        // $operator is Operator&BackedEnum but psalm triggers NoInterfaceProperties error
        return $operator->value;
    }
    
    return '';
}

function fun1(BackedEnum $operator) :string|int
{
    return $operator->value;
}

Psalm output (using commit 3c90054):

ERROR: NoInterfaceProperties - 14:16 - Interfaces cannot have properties