Closes#718
We pass an extra `contents` parameter to the string callback function to
provide contextual information for autocomplete.
Because we support both string literals and simple interpolated strings,
we pass it through as a `std::string` value.
This is a breaking change
* Fixed unions of `nil` types displaying as `?`
* Internal normalization now handles class types which can make
previously failing (incorrectly) sub-typing checks to succeed
Closes#599
Not sure if these context definitions are distinct enough, but they work for my use cases.
I repurposed (a majority of) the existing unit tests for this, but if it should live in separate test cases let me know
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* Add autocomplete context to result
* Update tests
* Remove comments
* Fix expression context issues
JohnnyMorganz