Symbol.hasInstance and [[Get]] vs [[GetOwnProperty]]

[/#!/JoePea]

It seems like using [[Get]] for looking up `@@hasInstance` can be confusing
and requires devs to write extra code. For example, suppose we have the
following code:

```js
class A {
    static [Symbol.hasInstance] (obj) {
        return false
    }
}

class B extends A {}
class C extends B {}

let c = new C

console.log(c instanceof B) // false, but expected true!
console.log(c instanceof A) // false, as expected
```

The `c instanceof B` check (arguably unintuitively) fails. Defining a
`Symbol.hasInstance` method on a base class causes `instanceof` checks on
any subclasses to automatically fail unless the developer takes care to
write an ugly and fragile workaround:

```js
class A {
    static [Symbol.hasInstance](obj) {
        if (this === A) return false
        else return Function.prototype[Symbol.hasInstance].call(this, obj)
    }
}

class B extends A {}
class C extends B {}

let c = new C

console.log(c instanceof B) // true, as expected
console.log(c instanceof A) // false, as expected
```

That seems likely to introduce errors or headaches.

What if the lookup for `Symbol.hasInstance` on an object use
[[GetOwnProperty]]? Then the first version without the conditional checks
would not break subclasses.

*/#!/*JoePea
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