Remove copies (#8583)

src/qe/nlqsat.cpp

@@ -385,10 +385,9 @@ namespace qe {
             // They are sorted by size, so we project the largest variables first to avoid 
             // renaming variables. 
             for (unsigned i = vars.size(); i-- > 0;) {
-                new_result.reset();
                 ex.project(vars[i], result.size(), result.data(), new_result);
                 TRACE(qe, display_project(tout, vars[i], result, new_result););
-                result.swap(new_result);
+                result = std::move(new_result);
             }
             negate_clause(result);
         }