message: Fix misbound variable
diff: from_term Context Source (term Target).
  % Variables
  - from_term Context (core.local Index) (type' (stratified.local Int)) :-
  + from_term Context (core.local Index) (type' (stratified.local Index)) :-
  context.lookup_universe Context Index type'.
  - from_term Context (core.local Index) (term (stratified.local Int)) :-
  + from_term Context (core.local Index) (term (stratified.local Index)) :-
  context.lookup_universe Context Index term.
  % Annotated terms
  