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, 12 insertions, 8 deletions

diff --git a/src/theory/uf/equality_engine.cpp b/src/theory/uf/equality_engine.cpp
index 643029b05..5ccda1dc2 100644
--- a/src/theory/uf/equality_engine.cpp
+++ b/src/theory/uf/equality_engine.cpp
@@ -1704,11 +1704,11 @@ void EqualityEngine::addTriggerEquality(TNode eq) {
 
   // If they are equal or disequal already, no need for the trigger
   if (areEqual(eq[0], eq[1])) {
-    d_notify.eqNotifyTriggerEquality(eq, true);
+    d_notify.eqNotifyTriggerPredicate(eq, true);
     skipTrigger = true;
   }
   if (areDisequal(eq[0], eq[1], true)) {
-    d_notify.eqNotifyTriggerEquality(eq, false);
+    d_notify.eqNotifyTriggerPredicate(eq, false);
     skipTrigger = true;
   }
 
@@ -1726,8 +1726,12 @@ void EqualityEngine::addTriggerEquality(TNode eq) {
 }
 
 void EqualityEngine::addTriggerPredicate(TNode predicate) {
-  Assert(predicate.getKind() != kind::NOT
-         && predicate.getKind() != kind::EQUAL);
+  Assert(predicate.getKind() != kind::NOT);
+  if (predicate.getKind() == kind::EQUAL)
+  {
+    // equality is handled separately
+    return addTriggerEquality(predicate);
+  }
   Assert(d_congruenceKinds.tst(predicate.getKind()))
       << "No point in adding non-congruence predicates";
 
@@ -1997,8 +2001,8 @@ void EqualityEngine::propagate() {
                 d_deducedDisequalityReasons.push_back(EqualityPair(original, d_falseId));
               }
               storePropagatedDisequality(THEORY_LAST, lhsId, rhsId);
-              if (!d_notify.eqNotifyTriggerEquality(triggerInfo.d_trigger,
-                                                    triggerInfo.d_polarity))
+              if (!d_notify.eqNotifyTriggerPredicate(triggerInfo.d_trigger,
+                                                     triggerInfo.d_polarity))
               {
                 d_done = true;
               }
@@ -2007,8 +2011,8 @@ void EqualityEngine::propagate() {
           else
           {
             // Equalities are simple
-            if (!d_notify.eqNotifyTriggerEquality(triggerInfo.d_trigger,
-                                                  triggerInfo.d_polarity))
+            if (!d_notify.eqNotifyTriggerPredicate(triggerInfo.d_trigger,
+                                                   triggerInfo.d_polarity))
             {
               d_done = true;
             }