Editorial: Change some `X is Y` to `SameValue(X, Y) is *true*`

[jmdyck]

(apply editorial convention to recently-merged PR #3337)

[gibson042]

@jmdyck There's another instance in sec-weakref-execution:

           1. For each FinalizationRegistry _fg_ such that _fg_.[[Cells]] contains a Record _cell_ such that _cell_.[[WeakRefTarget]] is _value_, do
             1. Set _cell_.[[WeakRefTarget]] to ~empty~.
             1. Optionally, perform HostEnqueueFinalizationRegistryCleanupJob(_fg_).
-          1. For each WeakMap _map_ such that _map_.[[WeakMapData]] contains a Record _r_ such that _r_.[[Key]] is _value_, do
+          1. For each WeakMap _map_ such that _map_.[[WeakMapData]] contains a Record _r_ such that _r_.[[Key]] is not ~empty~ and SameValue(_r_.[[Key]], _value_) is *true*, do
             1. Set _r_.[[Key]] to ~empty~.
             1. Set _r_.[[Value]] to ~empty~.
           1. For each WeakSet _set_ such that _set_.[[WeakSetData]] contains _value_, do

[jmdyck]

@jmdyck There's another instance in sec-weakref-execution:

In more detail (for those who are wondering):

• The status quo _r_.[[Key]] is _value_ uses is rather than SameValue because (in this algorithm) _r_.[[Key]] can be ~empty~, and SameValue doesn't accept spec values.
• But we know that _S_ is "a set of objects and/or symbols", so _value_ is an Object or Symbol, i.e. it isn't ~empty~, so the is always fails when _r_.[[Key]] is ~empty~.
• So if we insert the test _r_.[[Key]] is not ~empty~ and ..., then after that, we're comparing an Object-or-Symbol with an Object-or-Symbol, for which SameValue is the editorial convention.

I.e., replace

_r_.[[Key]] is _value_

with

_r_.[[Key]] is not ~empty~ and SameValue(_r_.[[Key]], _value_)

as you suggest.

(I think the same reasoning applies to the is comparisons on steps 1.a and 1.b of that algorithm.)

While this is a valid replacement, I'm not sure it's an improvement. I'll put it in if the editors want it.

[syg]

While this is a valid replacement, I'm not sure it's an improvement. I'll put it in if the editors want it.

I'm leaning towards leaving the WeakRef execution stuff as is since explictly using is is more evocative (to me) of comparing identity, which is fitting for WeakRefs.