Implement Eq and Hash for GreenTokenData

[hurryabit]

GreenToken implements all traits required to use it as the key type of a hash map. It also implements Borrow<GreenTokenData>. Thus is would be nice if GreenTokenData also implemented Eq and Hash such that the result of SyntaxToken::green could be used for lookups in such a hash map without additional overhead in terms of syntax or runtime.

[matklad]

Consider if you might want to intern GreenTokens&Nodes, and use pointer-equality and identity instead of content hashing

[hurryabit]

Thanks for your quick response.

That's basically what I'm doing. I'm still prototyping and wanted to use the GreenTokens as the keys of my interning table instead of putting an interner into the lexer.

I just realised that the GreenNodeBuilder already does interning but it's unclear to me how to leverage that for a lookup table with the current API.