code: /*
   * 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.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.compiler.util;
  
  import org.apache.bcel.generic.Instruction;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.PUSH;
  import org.apache.xalan.xsltc.compiler.Constants;
  
  /**
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   */
  public final class VoidType extends Type {
      protected VoidType() {}
  
      public String toString() {
  	return "void";
      }
  
      public boolean identicalTo(Type other) {
  	return this == other;
      }
  
      public String toSignature() {
  	return "V";
      }
  
      public org.apache.bcel.generic.Type toJCType() {
  	return null;	// should never be called
      }
  
      public Instruction POP() {
          return NOP;
      }
  
      /**
       * Translates a void into an object of internal type <code>type</code>.
       * This translation is needed when calling external functions
       * that return void.
       *
       * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
       */
      public void translateTo(ClassGenerator classGen, MethodGenerator methodGen,
  			    Type type) {
  	if (type == Type.String) {
  	    translateTo(classGen, methodGen, (StringType) type);
  	}
  	else {
  	    ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
  					toString(), type.toString());
  	    classGen.getParser().reportError(Constants.FATAL, err);
  	}
      }
  
      /**
       * Translates a void into a string by pushing the empty string ''.
       *
       * @see	org.apache.xalan.xsltc.compiler.util.Type#translateTo
       */
      public void translateTo(ClassGenerator classGen, MethodGenerator methodGen,
  			    StringType type) {
  	final InstructionList il = methodGen.getInstructionList();
  	il.append(new PUSH(classGen.getConstantPool(), ""));
      }
  
      /**
       * Translates an external (primitive) Java type into a void.
       * Only an external "void" can be converted to this class.
       */
      public void translateFrom(ClassGenerator classGen, MethodGenerator methodGen,
  			      Class clazz) {
  	if (!clazz.getName().equals("void")) {
  	    ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
  					toString(), clazz.getName());
  	    classGen.getParser().reportError(Constants.FATAL, err);
  	}
      }
  }
  