According to the libSyntax documentation:
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:
But actually, both comments are bundled as `var`'s leading trivia.
You can test the code at https://swift-ast-explorer.kishikawakatsumi.com/ (screenshot attached).
By the way, in TypeScript, it seems to work as is: