Automatic Boxing and Unboxing of Primitive Values

[jasonwilliams]

As spotted in jasonwilliams#13 (comment) string methods on string literals won't work because automatic Boxing and Unboxing is not supported in Boa yet. This is something we'll need to think about adding, it could be worth seeing how spidermonkey or V8 do this

[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