Treat arguments to recursive functions as beta redexes

An argument to a recursive function would escape the scope of the function application when the recursive function definitions are unfolded. Therefore, such argument occurrences need not be considered for extensional equality / equality sharing.

This filter is mostly relevant for recursive functions that take a lambda expression as argument. Lambda expressions / arrays that occur in shared occurrences are checked for extensionality.

src/sat/smt/recfun_solver.cpp

@@ -333,6 +333,11 @@ namespace recfun {
         return found;
     }
 
+    bool solver::is_beta_redex(euf::enode* p, euf::enode* n) const {
+        return is_defined(p) || is_case_pred(p);
+    }
+
+
     bool solver::add_dep(euf::enode* n, top_sort<euf::enode>& dep) {
         if (n->num_args() == 0)
             dep.insert(n, nullptr);