vala/valanulltype.vala

   1 /* valanulltype.vala
   2  *
   3  * Copyright (C) 2007-2010  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  * The type of the null literal.
  27  */
  28 public class Vala.NullType : ReferenceType {
  29         public NullType (SourceReference? source_reference) {
  30                 this.nullable = true;
  31                 this.source_reference = source_reference;
  32         }
  33
  34         public override bool compatible (DataType target_type) {
  35                 if (CodeContext.get ().experimental_non_null) {
  36                         return target_type.nullable;
  37                 }
  38
  39                 if (!(target_type is PointerType) && (target_type is NullType || (target_type.data_type == null && !(target_type is GenericType)))) {
  40                         return true;
  41                 }
  42
  43                 /* null can be cast to any reference or array type or pointer type */
  44                 if (target_type is GenericType ||
  45                     target_type is PointerType ||
  46                     target_type.nullable ||
  47                     target_type.data_type.get_attribute ("PointerType") != null) {
  48                         return true;
  49                 }
  50
  51                 if (target_type.data_type.is_reference_type () ||
  52                     target_type is ArrayType ||
  53                     target_type is DelegateType) {
  54                         return true;
  55                 }
  56
  57                 /* null is not compatible with any other type (i.e. value types) */
  58                 return false;
  59         }
  60
  61         public override DataType copy () {
  62                 return new NullType (source_reference);
  63         }
  64
  65         public override bool is_disposable () {
  66                 return false;
  67         }
  68
  69         public override string to_qualified_string (Scope? scope = null) {
  70                 return "null";
  71         }
  72 }