content: /*
   * 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.calcite.sql.type;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.SqlOperatorBinding;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Strategy to infer the type of an operator call from the type of the operands
   * by using a series of {@link SqlReturnTypeInference} rules in a given order.
   * If a rule fails to find a return type (by returning NULL), next rule is tried
   * until there are no more rules in which case NULL will be returned.
   */
  public class SqlReturnTypeInferenceChain implements SqlReturnTypeInference {
    //~ Instance fields --------------------------------------------------------
  
    private final ImmutableList<SqlReturnTypeInference> rules;
  
    //~ Constructors -----------------------------------------------------------
  
    /**
     * Creates a SqlReturnTypeInferenceChain from an array of rules.
     *
     * <p>Package-protected.
     * Use {@link org.apache.calcite.sql.type.ReturnTypes#chain}.
     */
    SqlReturnTypeInferenceChain(SqlReturnTypeInference... rules) {
      checkArgument(rules.length > 1);
      this.rules = ImmutableList.copyOf(rules);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public @Nullable RelDataType inferReturnType(SqlOperatorBinding opBinding) {
      for (SqlReturnTypeInference rule : rules) {
        RelDataType ret = rule.inferReturnType(opBinding);
        if (ret != null) {
          return ret;
        }
      }
      return null;
    }
  }
  