There are multiple cases of optional-braces regions described using <<< in https://dotty.epfl.ch/docs/internals/syntax.html.

Unlike actual-braces-delimited regions, there is currently no reliable way to capture which Trivial (aka, Comment or Whitespace) tokens belong to each such region, which makes it very difficult, sometimes impossible to format comments.

Therefore, let's enclose all such regions which are currently described as List[...].