Supporting feature tests directly

Kyle Simpson getify at
Tue Mar 24 22:44:20 UTC 2015

I should stress that while my original proposal (linked earlier in thread) mentions some of the "hard" ES6 cases (like TCO), my focus is not on creating feature tests for ES6. ES6 has sailed. Any feature we could possibly conceive here is quite unlikely to land in a browser before that browser gets all (or at least most) of the ES6 stuff that one might be wanting to test for.

My goal is for us to stop adding features to JS that aren't practically feature testable. I would strenuously desire to have something like `Reflect.supports(..)` (of whatever bikeshedded form) in ES2016 along with any new conceived features. That goes a thousand times more if we invent new syntax (we likely are) or new untestable semantics (like TCO).

Of course, if we had `Reflect.supports(..)` now, it'd be amazingly helpful in detecting TCO, which I would dearly love. But that's not the goal. I don't think we need to muddy the waters about what the ES6 feature tests would be. At least not for now.

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