vala/valanullliteral.vala

   1 /* valanullliteral.vala
   2  *
   3  * Copyright (C) 2006-2010  Jürg Billeter
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2.1 of the License, or (at your option) any later version.
   9
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
  18  *
  19  * Author:
  20  *      Jürg Billeter <j@bitron.ch>
  21  */
  22
  23 using GLib;
  24
  25 /**
  26  * Represents a literal `null` in the source code.
  27  */
  28 public class Vala.NullLiteral : Literal {
  29         /**
  30          * Creates a new null literal.
  31          *
  32          * @param source reference to source code
  33          * @return       newly created null literal
  34          */
  35         public NullLiteral (SourceReference? source = null) {
  36                 source_reference = source;
  37         }
  38
  39         public override void accept (CodeVisitor visitor) {
  40                 visitor.visit_null_literal (this);
  41
  42                 visitor.visit_expression (this);
  43         }
  44
  45         public override string to_string () {
  46                 return "null";
  47         }
  48
  49         public override bool is_pure () {
  50                 return true;
  51         }
  52
  53         public override bool check (CodeContext context) {
  54                 if (checked) {
  55                         return !error;
  56                 }
  57
  58                 checked = true;
  59
  60                 value_type = new NullType (source_reference);
  61
  62                 return !error;
  63         }
  64
  65         public override void emit (CodeGenerator codegen) {
  66                 codegen.visit_null_literal (this);
  67
  68                 codegen.visit_expression (this);
  69         }
  70 }