1. A token owns all of its trailing trivia up to, but not including, the next newline character.
2. Looking backward in the text, a token owns all of the leading trivia up to and including the first contiguous sequence of newlines characters.
The following code should have leading / trailing trivias as follows:
let x =1// This should be "1"'s trailing trivia/// This should be `var`'s leading triviavar y =2
But actually, both comments are bundled as `var`'s leading trivia.