message: Make CallStack function pub(crate)
  Summary: The struct is `pub(crate)`, more clear this way.
diff: @@ -176,7 +176,7 @@ impl<'v> CallStack<'v> {
  /// The location at the top of the stack. May be `None` if
  /// either there the stack is empty, or the top of the stack lacks location
  /// information (e.g. called from Rust).
  - pub fn top_location(&self) -> Option<FileSpan> {
  + pub(crate) fn top_location(&self) -> Option<FileSpan> {
  if self.count == 0 {
  None
  } else {
  @@ -184,7 +184,7 @@ impl<'v> CallStack<'v> {
  }
  }
  - pub fn to_diagnostic_frames(&self) -> Vec<Frame> {
  + pub(crate) fn to_diagnostic_frames(&self) -> Vec<Frame> {
  // The first entry is just the entire module, so skip it
  self.stack[1..self.count].map(CheapFrame::to_frame)
  }
  