fix rep check clone error

core/src/main/java/com/alibaba/druid/sql/ast/statement/SQLCheck.java

@@ -60,7 +60,7 @@ public class SQLCheck extends SQLConstraintImpl implements SQLTableElement, SQLT
         super.cloneTo(x);
 
         if (expr != null) {
-            expr = expr.clone();
+            x.expr = expr.clone();
         }
 
         x.enforced = enforced;

core/src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlRepCheckTest.java

@@ -0,0 +1,41 @@
+package com.alibaba.druid.bvt.sql.mysql;
+
+import com.alibaba.druid.sql.repository.Schema;
+import com.alibaba.druid.sql.repository.SchemaObject;
+import com.alibaba.druid.sql.repository.SchemaRepository;
+import com.alibaba.druid.util.JdbcUtils;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class MySqlRepCheckTest {
+    final private SchemaRepository repository = new SchemaRepository(JdbcUtils.MYSQL);
+
+    public static void main(String[] args) {
+        MySqlRepCheckTest testRep = new MySqlRepCheckTest();
+        String schemaName = "test_db";
+        testRep.repository.setDefaultSchema(schemaName);
+        testRep.repository.console("CREATE TABLE `test_table` (\n" +
+                "  `id` int NOT NULL AUTO_INCREMENT,\n" +
+                "  `action_flag` smallint unsigned NOT NULL,\n" +
+                "  CONSTRAINT `chk_1` CHECK ((`action_flag` >= 0))\n" +
+                ") ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci");
+        Map<String, String> snapshot = testRep.snapshot();
+        System.out.println(snapshot.get(schemaName));
+    }
+
+    public Map<String, String> snapshot() {
+        Map<String, String> schemaDdls = new HashMap<String, String>();
+        for (Schema schema : repository.getSchemas()) {
+            StringBuffer data = new StringBuffer(4 * 1024);
+            for (String table : schema.showTables()) {
+                SchemaObject schemaObject = schema.findTable(table);
+                schemaObject.getStatement().output(data);
+                data.append("; \n");
+            }
+            schemaDdls.put(schema.getName(), data.toString());
+        }
+
+        return schemaDdls;
+    }
+}