function observeNewline(
  state: LayoutState,
  current: PreviewToken,
  frameDepth: int,
) -> LayoutState {
  let pipeContinues = previousIs(state.previous, "pipe") &&
    patternContinuesAt(state.pattern, frameDepth)
  let frame = topFrame(state.frames)
  if frame.mode == LayoutMode.Separator && frame.hasItem &&
    lastTokenKind(state.output) != "separator" && !previousIsTrailing(state.previous) &&
    !pipeContinues {
    match state.pending {
      case Some(_) => ()
      case None => return LayoutState {
        ...state,
        pending: Some(current),
      }
    }
  }
  state
}