Improve coverage for reference type in various contexts

[anba]

Missing coverage encountered while implementing
tc39/ecma262#3307 in SpiderMonkey.

Ensure environment lookups are performed in the correct order:

• keyed-destructuring-property-reference-target-evaluation-order-with-bindings.js

Ensure delete super[elem] steps are correctly performed:

• delete/super-property-topropertykey.js
• delete/super-property-uninitialized-this.js

Ensure ToPropertyKey for computed property names in object literals correctly performed:

• object/computed-property-name-topropertykey-before-value-evaluation.js

Ensure GetSuperBase is executed before ToPropertKey:

• super/prop-expr-getsuperbase-before-topropertykey-*

Ensure GetThisBinding is executed first:

• super/prop-expr-uninitialized-this-*

[anba]

@linusg Do you need these flags because your implementation doesn't support these features? I'm asking because other files in the same directories are already omitting some flags. Unless it's necessary for some actual implementation, I'd prefer to omit flags for language features which were added years ago.

[linusg]

Personally I've never used the flags, IMO evergreen engines don't need them. A failure is a failure and filtering doesn't change that.

The comments are just for completeness, feel free to disregard them if the maintainers agree that we don't need to be strict about flags 👍

[ljharb]

We in fact do want every test to have flags for every feature, even ones added many years ago (we also want to avoid newer syntax when it's not strictly necessary for the test)

[anba]

No, that's not what's documented in features.txt.

[ljharb]

ok, but that's the current policy of the maintainers (and the existence of class and other <= ES2015 features should make it clear that the sentence at the top is nonexhaustive). I'll add to my list to update the wording in that document.

[anba]

Is this documented anywhere? For example #3196 (comment) and #3665 (comment) don't state that it's a strict requirement to name each and every feature.

[ljharb]

It's indeed not a strict requirement - but we still want everything to have them.

[ptomato]

I should nuance my position on the policy - All other things being equal I'd prefer to have exhaustive flags, but I also don't think we should be putting that burden on people who contribute tests, so I'd much rather pursue that via codemods.

[Ms2ger]

These are nasty. Thanks.

[Ms2ger]

One might assert that this method is called only once

[anba]

I think I'd prefer to not assert this, because otherwise V8 will have to skip this test, because V8 evaluates obj[key] += value as obj[key] = obj[key] + value, which evaluates ToPropertyKey(key) twice. And if we don't assert how many times ToPropertyKey(key) is evaluated, V8 is more likely to not skip this test, so there's maybe more incentive for V8 to fix their implementation to evaluate GetSuperBase before ToPropertyKey.