message: Use `Iterator::try_fold` instead of `fold` when renaming terms
diff: @@ -556,16 +556,16 @@ impl<'arena, 'env> Context<'arena, 'env> {
  },
  };
  - spine.iter().fold(Ok(head_expr), |head_expr, elim| {
  + spine.iter().try_fold(head_expr, |head_expr, elim| {
  Ok(match elim {
  Elim::FunApp(plicity, arg_expr) => Term::FunApp(
  span,
  *plicity,
  - self.scope.to_scope(head_expr?),
  + self.scope.to_scope(head_expr),
  self.scope.to_scope(self.rename(meta_var, arg_expr)?),
  ),
  Elim::RecordProj(label) => {
  - Term::RecordProj(span, self.scope.to_scope(head_expr?), *label)
  + Term::RecordProj(span, self.scope.to_scope(head_expr), *label)
  }
  Elim::ConstMatch(branches) => {
  let mut branches = branches.clone();
  @@ -591,7 +591,7 @@ impl<'arena, 'env> Context<'arena, 'env> {
  Term::ConstMatch(
  span,
  - self.scope.to_scope(head_expr?),
  + self.scope.to_scope(head_expr),
  pattern_branches.into(),
  default_branch
  .map(|(name, expr)| (name, self.scope.to_scope(expr) as &_)),
  