scope gazelle_addForbiddenBindingHelpers.

sclass #Blocker {
  S var, value; // value == null means don't change variable at all
  bool debug;
 
  *() {}
  *(S *var, S *value, bool *debug) {}
  
  SS get(SS map, LS tokC, LS tokI, RuleEngine2_MatchedRule matched) {
    if (map == null) null;
    if (value == null) {
      if (map.containsKey(var)) null;
    } else
      if (eqic(value, map.get(var))) null;
    ret map;
  }
}

sclass #TotalBlocker {
  SS get(SS map, LS tokC, LS tokI, RuleEngine2_MatchedRule matched) {
    if (nempty(map)) null;
    ret map;
  }
}

sclass #BlockAllExcept {
  Set<S> allowedVars;
  
  *() {}
  *(Set<S> *allowedVars) {}
  
  SS get(SS map, LS tokC, LS tokI, RuleEngine2_MatchedRule matched) {
    if (containsKeysExcept(map, allowedVars)) null;
    ret map;
  }
}

svoid gazelle_addForbiddenBindingHelpers(RuleEngine2 engine, O... _) {
  bool debug = boolPar debug(_) || boolPar forbiddenBindingsDebug(_);
  for (final RuleEngine2.Rule r : engine.rules) {
    for (Matches m : getJMatches_all("don't change * to *", r.comments))
      r.addMapMassager(new Blocker($1, $2, debug));
    for (Matches m : getJMatches_all("don't change *", r.comments))
      if (isQuoted(m.get(0)))
        r.addMapMassager(new Blocker($1, null, debug));
    if (cic(r.comments, "don't change anything"))
      r.addMapMassager(new TotalBlocker);
    S var = matchAny_firstGroup("only var is *", r.comments);
    if (var != null)
      r.addMapMassager(new BlockAllExcept(litciset(var)));
  }
}

end scope

Began life as a copy of #1021872