message: Rename `Span::proceeds`
  This name is incorrect --- the span on which it's called is the subsequent span,
  not the preceeding one.
diff: @@ -253,7 +253,7 @@ impl Span {
  }
  }
  - pub fn proceeds<I: AsId>(&self, from: I) -> Result<(), PriorError> {
  + pub fn follows<I: AsId>(&self, from: I) -> Result<(), PriorError> {
  if let Some(ref inner) = self.inner {
  let from_id = from.as_id().ok_or(PriorError::NoPreceedingId)?;
  let inner = &inner.inner;
  