/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.spark.sql.catalyst.analysis.resolver

/**
 * Represents the kind of alias being processed. This is used by [[AliasResolver]] to inform
 * the [[LateralColumnAliasRegistry]] whether an alias was explicitly written by the user
 * (e.g., `SELECT a AS b`) or implicitly generated during resolution of an [[UnresolvedAlias]],
 * so that the registry can apply the correct scoping rules for lateral column alias references.
 */
object AliasKind extends Enumeration {
  type AliasKind = Value

  /**
   * Explicit alias created by the user (e.g., SELECT a AS b).
   */
  val Explicit: Value = Value

  /**
   * Implicit alias generated automatically (e.g., from UnresolvedAlias).
   */
  val Implicit: Value = Value
}
