my favourite* thing about the Ruby parser is how the lexer state changes in a very complex context sensitive way based on which parse node you're in. * I actually hate it
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there are > 100 different sites in the ruby parser that change the lexer state.
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search for SET_LEX_STATE https://github.com/ruby/ruby/blob/v2_5_5/parse.y …
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Ruby just fundamentally isn’t context-free, yet we keep trying to use context-free tools to parse it.
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my gut feeling is that the context-sensitivity is a bit unnecessary. I understand that the exact parsing rules are tricky to express in CFG, but is it really that critical that foo / 1 #/ is parsed differently depending on whether foo is a local variable or not?
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