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;
  
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.type.SqlOperandTypeChecker;
  import org.apache.calcite.sql.type.SqlOperandTypeInference;
  import org.apache.calcite.sql.type.SqlReturnTypeInference;
  import org.apache.calcite.sql.type.SqlTypeName;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Placeholder for an unresolved function.
   *
   * <p>Created by the parser, then it is rewritten to proper SqlFunction by
   * the validator to a function defined in a Calcite schema.
   */
  public class SqlUnresolvedFunction extends SqlFunction {
    /**
     * Creates a placeholder SqlUnresolvedFunction for an invocation of a function
     * with a possibly qualified name. This name must be resolved into either
     * a builtin function or a user-defined function.
     *
     * @param sqlIdentifier        possibly qualified identifier for function
     * @param returnTypeInference  strategy to use for return type inference
     * @param operandTypeInference strategy to use for parameter type inference
     * @param operandTypeChecker   strategy to use for parameter type checking
     * @param paramTypes           array of parameter types
     * @param funcType             function category
     */
    public SqlUnresolvedFunction(
        SqlIdentifier sqlIdentifier,
        @Nullable SqlReturnTypeInference returnTypeInference,
        @Nullable SqlOperandTypeInference operandTypeInference,
        @Nullable SqlOperandTypeChecker operandTypeChecker,
        @Nullable List<RelDataType> paramTypes,
        SqlFunctionCategory funcType) {
      super(sqlIdentifier, returnTypeInference, operandTypeInference,
          operandTypeChecker, paramTypes, funcType);
    }
  
    /**
     * {@inheritDoc}T
     *
     * <p>The operator class for this function isn't resolved to the
     * correct class. This happens in the case of user defined
     * functions. Return the return type to be 'ANY', so we don't
     * fail.
     */
    @Override public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
      final RelDataTypeFactory typeFactory = opBinding.getTypeFactory();
      return typeFactory.createTypeWithNullability(
          typeFactory.createSqlType(SqlTypeName.ANY), true);
    }
  }
  