message: Add type signature comments
diff: @@ -470,6 +470,8 @@ impl Default for Context {
  let ty_s16 = RcTerm::from(Term::from(&*context.globals.ty_s16.clone()));
  let ty_s32 = RcTerm::from(Term::from(&*context.globals.ty_s32.clone()));
  let ty_s64 = RcTerm::from(Term::from(&*context.globals.ty_s64.clone()));
  +
  + // OffsetX : Pos -> Type
  let offset_ty = RcValue::from(Value::Pi(Scope::new(
  (Binder(FreeVar::fresh_unnamed()), Embed(pos_ty.clone())),
  RcValue::from(Value::Pi(Scope::new(
  @@ -477,6 +479,8 @@ impl Default for Context {
  universe0.clone(),
  ))),
  )));
  +
  + // Array : int {0 ..} -> Type -> Type
  let array_ty = RcValue::from(Value::Pi(Scope::new(
  (Binder(FreeVar::fresh_unnamed()), Embed(nat_ty.clone())),
  RcValue::from(Value::Pi(Scope::new(
  @@ -484,10 +488,14 @@ impl Default for Context {
  universe0.clone(),
  ))),
  )));
  +
  + // Reserved : Type -> Type
  let reserved_ty = RcValue::from(Value::Pi(Scope::new(
  (Binder(FreeVar::fresh_unnamed()), Embed(universe0.clone())),
  universe0.clone(),
  )));
  +
  + // Link : Pos -> int {0 ..} -> Type -> Type
  let link_ty = RcValue::from(Value::Pi(Scope::new(
  (Binder(FreeVar::fresh_unnamed()), Embed(pos_ty.clone())),
  RcValue::from(Value::Pi(Scope::new(
  