message: Remove unused subst method
diff: @@ -69,37 +69,6 @@ impl LocallyNameless for RcTerm {
  }
  impl RcTerm {
  - pub fn subst(&mut self, name: &Name, x: &RcTerm) {
  - *self = match *Rc::make_mut(&mut self.inner) {
  - Term::Ann(_, ref mut expr, ref mut ty) => {
  - expr.subst(name, x);
  - ty.subst(name, x);
  - return;
  - },
  - Term::Universe(_, _) => return,
  - Term::Var(_, Var::Free(ref n)) if n == name => x.clone(),
  - Term::Var(_, Var::Free(_)) | Term::Var(_, Var::Bound(_)) => return,
  - Term::Lam(_, ref mut lam) => {
  - lam.unsafe_binder
  - .inner
  - .as_mut()
  - .map(|param| param.subst(name, x));
  - lam.unsafe_body.subst(name, x);
  - return;
  - },
  - Term::Pi(_, ref mut pi) => {
  - pi.unsafe_binder.inner.subst(name, x);
  - pi.unsafe_body.subst(name, x);
  - return;
  - },
  - Term::App(_, ref mut fn_expr, ref mut arg_expr) => {
  - fn_expr.subst(name, x);
  - arg_expr.subst(name, x);
  - return;
  - },
  - };
  - }
  -
  fn visit_vars<F: FnMut(&Var<Name, Debruijn>)>(&self, on_var: &mut F) {
  match *self.inner {
  Term::Ann(_, ref expr, ref ty) => {
  