Fix case of non-constant value for sygus sampling (#4051)

Fixes #4050.

diff --git a/src/theory/quantifiers/sygus_sampler.cpp b/src/theory/quantifiers/sygus_sampler.cpp
index 10af0d703a5af5c528323323d03fbe0129ae809b..d2c2a238019b6ece5b522483e7b6b6da3ed89680 100644 (file)
--- a/src/theory/quantifiers/sygus_sampler.cpp
+++ b/src/theory/quantifiers/sygus_sampler.cpp
@@ -713,8 +713,12 @@ Node SygusSampler::getSygusRandomValue(TypeNode tn,
       Trace("sygus-sample-grammar") << "...returned " << ret << std::endl;
       ret = Rewriter::rewrite(ret);
       Trace("sygus-sample-grammar") << "...after rewrite " << ret << std::endl;
-      Assert(ret.isConst());
-      return ret;
+      // A rare case where we generate a non-constant value from constant
+      // leaves is (/ n 0).
+      if(ret.isConst())
+      {
+        return ret;
+      }
     }
   }
   Trace("sygus-sample-grammar") << "...resort to random value" << std::endl;