Automatic Boxing and Unboxing of Primitive Values about boa

[jasonwilliams]

V8 representation of primitive values:
https://cs.chromium.org/chromium/src/v8/src/objects/js-objects.h?rcl=fe77d58a6a3cd9385454aa0bc29330ec668e293a&l=1236-1252

Unboxing in Spidermonkey:
https://searchfox.org/mozilla-central/source/js/src/vm/JSObject.cpp#4198-4220

ChakraCore:
https://github.com/microsoft/ChakraCore/blob/4565a28e899322e364ee1a204f1e1a6c17aa5269/lib/Runtime/Language/JavascriptConversion.cpp#L221-L265

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SpiderMonkey js::getProperty()
https://searchfox.org/mozilla-central/rev/928742d3ea30e0eb4a8622d260041564d81a8468/js/src/vm/Interpreter.cpp#4438-4493
Spidermonkey have a js::getProperty method which checks if a JSValue is a primitive, if it is it will get the proto of its object equivalent and use that.

They also cache this value so it can be used again, but the cache never gets cleared.
https://searchfox.org/mozilla-central/source/js/src/vm/GlobalObject.h#207-211

This is quite a different approach from V8 who create wrapper objects and use them

[jasonwilliams]

Fixed by jasonwilliams#86