Fix another corner case of datatypes+PBE (#2938)

2 files changed, 34 insertions, 16 deletions

diff --git a/src/theory/quantifiers/sygus/sygus_unif_io.cpp b/src/theory/quantifiers/sygus/sygus_unif_io.cpp
index 7d51ec43a..207aa4c8e 100644
--- a/src/theory/quantifiers/sygus/sygus_unif_io.cpp
+++ b/src/theory/quantifiers/sygus/sygus_unif_io.cpp
@@ -458,25 +458,26 @@ void SubsumeTrie::getLeavesInternal(const std::vector<Node>& vals,
     {
       int new_status = status;
       bool success = true;
-      // if the current value is true, we must consider the value of this child
+      // If the current value is true, then this is a relevant point.
+      // We must consider the value of this child.
       if (curr_val_true)
       {
-        if (status != 0)
+        if (it->first.isNull())
         {
-          if (it->first.isNull())
-          {
-            // The value of this child is unknown on this point, hence we
-            // ignore it.
-            success = false;
-          }
-          else
+          // The value of this child is unknown on this point, hence we
+          // do not recurse
+          success = false;
+        }
+        else if (status != 0)
+        {
+          // if the status is not zero (indicating that we have a mix of T/F),
+          // then we must compute the new status.
+          Assert(it->first.getType().isBoolean());
+          Assert(it->first.isConst());
+          new_status = (it->first.getConst<bool>() ? 1 : -1);
+          if (status != -2 && new_status != status)
           {
-            Assert(it->first.getType().isBoolean());
-            new_status = (it->first.getConst<bool>() ? 1 : -1);
-            if (status != -2 && new_status != status)
-            {
-              new_status = 0;
-            }
+            new_status = 0;
           }
         }
       }
diff --git a/src/theory/quantifiers/sygus/sygus_unif_io.h b/src/theory/quantifiers/sygus/sygus_unif_io.h
index 5d38ba827..fced29871 100644
--- a/src/theory/quantifiers/sygus/sygus_unif_io.h
+++ b/src/theory/quantifiers/sygus/sygus_unif_io.h
@@ -218,7 +218,24 @@ class SubsumeTrie
                        int status,
                        bool checkExistsOnly,
                        bool checkSubsume);
-  /** helper function for above functions */
+  /** helper function for above functions
+   *
+   * This adds to v[-1], v[0], v[1] the children of the trie that occur
+   * along paths that contain only false (v[-1]), a mix of true/false (v[0]),
+   * and only true (v[1]) values for respectively for relevant points.
+   *
+   * vals/pol is used to determine the relevant points, which impacts which
+   * paths of the trie to traverse on this call.
+   * In particular, all points such that (pol ? vals[index] : !vals[index])
+   * are relevant.
+   *
+   * Paths that contain an unknown value for any relevant point are not
+   * traversed. In the larger picture, this ensures that terms are not used in a
+   * way such that their unknown value is relevant to the overall behavior of
+   * a synthesis solution.
+   *
+   * status holds the current value of v (0,1,-1) that we will be adding to.
+   */
   void getLeavesInternal(const std::vector<Node>& vals,
                          bool pol,
                          std::map<int, std::vector<Node>>& v,