Simplify trigger notifications in equality engine (#4921)

This is further work towards a centralized approach for equality engines.

This PR merges the eqNotifyTriggerEquality callback with the eqNotifyTriggerPredicate callback, and adds assertions that capture the current behavior. It furthermore makes addTriggerEquality private in equality engine and invoked as a special case of addTriggerPredicate. Note this PR does not impact the internal implementation of these methods in equality engine, which indeed is different.

There are two reasons to merge these callbacks:
(1) all theories implement exactly the same method for the two callbacks, whenever they implement both. It would be trivial to do something different (by case splitting on the kind of predicate that is being notified), and moreover it is not recommended they do anything other than immediately propagate the predicate (regardless of whether it is an equality).
(2) It leads to some confusion with eqNotifyTriggerTermEquality, which is invoked when two trigger terms are merged.

1 files changed, 1 insertions, 16 deletions

diff --git a/src/theory/strings/theory_strings.h b/src/theory/strings/theory_strings.h
index 500daac1f..da48ece90 100644
--- a/src/theory/strings/theory_strings.h
+++ b/src/theory/strings/theory_strings.h
@@ -126,28 +126,13 @@ class TheoryStrings : public Theory {
   class NotifyClass : public eq::EqualityEngineNotify {
   public:
    NotifyClass(TheoryStrings& ts) : d_str(ts), d_state(ts.d_state) {}
-   bool eqNotifyTriggerEquality(TNode equality, bool value) override
-   {
-     Debug("strings") << "NotifyClass::eqNotifyTriggerEquality(" << equality
-                      << ", " << (value ? "true" : "false") << ")" << std::endl;
-     if (value)
-     {
-       return d_str.propagate(equality);
-     }
-     else
-     {
-       // We use only literal triggers so taking not is safe
-       return d_str.propagate(equality.notNode());
-     }
-    }
     bool eqNotifyTriggerPredicate(TNode predicate, bool value) override
     {
       Debug("strings") << "NotifyClass::eqNotifyTriggerPredicate(" << predicate << ", " << (value ? "true" : "false") << ")" << std::endl;
       if (value) {
         return d_str.propagate(predicate);
-      } else {
-        return d_str.propagate(predicate.notNode());
       }
+      return d_str.propagate(predicate.notNode());
     }
     bool eqNotifyTriggerTermEquality(TheoryId tag,
                                      TNode t1,