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kotlinlang

I was analysing Kotlin antlr grammar and I noticed few strange things.
I wonder if anyone could explain why were they implemented this way:
1. WS is "-&gt; channel(HIDDEN)", but NL is not.
2. Why fragment Hidden is needed?
3. Why fragment Hidden does not include NL?
I found that, how "?:" and "!!" depend on this weird definition, but wouldn't it be cleaner to define them as separate tokens?

(lexer grammar - <https://github.com/Kotlin/kotlin-spec/blob/release/grammar/src/main/antlr/KotlinLexer.g4>)

dunno about `?:`, but a prefix `!!bool` is legal, although pointless