mcs/mbas/const.cs

   1 //
   2 // const.cs: Constant declarations.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //
   7 // (C) 2001 Ximian, Inc.
   8 //
   9 //
  10
  11 //
  12 // This is needed because the following situation arises:
  13 //
  14 //     The FieldBuilder is declared with the real type for an enumeration
  15 //
  16 //     When we attempt to set the value for the constant, the FieldBuilder.SetConstant
  17 //     function aborts because it requires its argument to be of the same type
  18 //
  19
  20 namespace Mono.CSharp {
  21
  22         using System;
  23         using System.Reflection;
  24         using System.Reflection.Emit;
  25         using System.Collections;
  26
  27         public class Const : MemberCore {
  28                 public readonly string ConstantType;
  29                 public Expression Expr;
  30                 public Attributes  OptAttributes;
  31                 public FieldBuilder FieldBuilder;
  32
  33                 object ConstantValue = null;
  34                 Type type;
  35
  36                 public const int AllowedModifiers =
  37                         Modifiers.NEW |
  38                         Modifiers.PUBLIC |
  39                         Modifiers.PROTECTED |
  40                         Modifiers.INTERNAL |
  41                         Modifiers.PRIVATE;
  42
  43                 public Const (string constant_type, string name, Expression expr, int mod_flags,
  44                               Attributes attrs, Location loc)
  45                         : base (name, loc)
  46                 {
  47                         ConstantType = constant_type;
  48                         Name = name;
  49                         Expr = expr;
  50                         ModFlags = Modifiers.Check (AllowedModifiers, mod_flags, Modifiers.PRIVATE, loc);
  51                         OptAttributes = attrs;
  52                 }
  53
  54                 public FieldAttributes FieldAttr {
  55                         get {
  56                                 return FieldAttributes.Literal | FieldAttributes.Static |
  57                                         Modifiers.FieldAttr (ModFlags) ;
  58                         }
  59                 }
  60
  61 #if DEBUG
  62                 void dump_tree (Type t)
  63                 {
  64                         Console.WriteLine ("Dumping hierarchy");
  65                         while (t != null){
  66                                 Console.WriteLine ("   " + t.FullName + " " +
  67                                         (t.GetType ().IsEnum ? "yes" : "no"));
  68                                 t = t.BaseType;
  69                         }
  70                 }
  71 #endif
  72
  73                 /// <summary>
  74                 ///   Defines the constant in the @parent
  75                 /// </summary>
  76                 public override bool Define (TypeContainer parent)
  77                 {
  78                         type = RootContext.LookupType (parent, ConstantType, true, Location);
  79
  80                         if (type == null)
  81                                 return false;
  82
  83                         if (!TypeManager.IsBuiltinType (type) &&
  84                             (!type.IsSubclassOf (TypeManager.enum_type))) {
  85                                 Report.Error (
  86                                         -3, Location,
  87                                         "Constant type is not valid (only system types are allowed)");
  88                                 return false;
  89                         }
  90
  91                         Type ptype = parent.TypeBuilder.BaseType;
  92
  93                         if (ptype != null) {
  94                                 MemberInfo [] mi = TypeContainer.FindMembers (
  95                                         ptype, MemberTypes.Field, BindingFlags.Public,
  96                                         Type.FilterName, Name);
  97
  98                                 if (mi == null || mi.Length == 0)
  99                                         if ((ModFlags & Modifiers.NEW) != 0)
 100                                                 WarningNotHiding (parent);
 101
 102                         } else if ((ModFlags & Modifiers.NEW) != 0)
 103                                 WarningNotHiding (parent);
 104
 105                         FieldBuilder = parent.TypeBuilder.DefineField (Name, type, FieldAttr);
 106
 107                         TypeManager.RegisterConstant (FieldBuilder, this);
 108
 109                         return true;
 110                 }
 111
 112                 /// <summary>
 113                 ///  Looks up the value of a constant field. Defines it if it hasn't
 114                 ///  already been. Similar to LookupEnumValue in spirit.
 115                 /// </summary>
 116                 public object LookupConstantValue (EmitContext ec)
 117                 {
 118                         if (ConstantValue != null)
 119                                 return ConstantValue;
 120
 121                         Expr = Expr.Resolve (ec);
 122
 123                         if (Expr == null) {
 124                                 Report.Error (150, Location, "A constant value is expected");
 125                                 return null;
 126                         }
 127
 128                         if (!(Expr is Constant)) {
 129                                 Report.Error (150, Location, "A constant value is expected");
 130                                 return null;
 131                         }
 132
 133                         ConstantValue = ((Constant) Expr).GetValue ();
 134
 135                         if (type != Expr.Type) {
 136                                 try {
 137                                         ConstantValue = TypeManager.ChangeType (ConstantValue, type);
 138                                 } catch {
 139                                         Expression.Error_CannotConvertImplicit (Location, Expr.Type, type);
 140                                         return null;
 141                                 }
 142
 143                                 if (type == TypeManager.int32_type)
 144                                         Expr = new IntConstant ((int) ConstantValue);
 145                                 else if (type == TypeManager.uint32_type)
 146                                         Expr = new UIntConstant ((uint) ConstantValue);
 147                                 else if (type == TypeManager.int64_type)
 148                                         Expr = new LongConstant ((long) ConstantValue);
 149                                 else if (type == TypeManager.uint64_type)
 150                                         Expr = new ULongConstant ((ulong) ConstantValue);
 151                                 else if (type == TypeManager.float_type)
 152                                         Expr = new FloatConstant ((float) ConstantValue);
 153                                 else if (type == TypeManager.double_type)
 154                                         Expr = new DoubleConstant ((double) ConstantValue);
 155                                 else if (type == TypeManager.string_type)
 156                                         Expr = new StringConstant ((string) ConstantValue);
 157                                 else if (type == TypeManager.short_type)
 158                                         Expr = new ShortConstant ((short) ConstantValue);
 159                                 else if (type == TypeManager.ushort_type)
 160                                         Expr = new UShortConstant ((ushort) ConstantValue);
 161                                 else if (type == TypeManager.sbyte_type)
 162                                         Expr = new SByteConstant ((sbyte) ConstantValue);
 163                                 else if (type == TypeManager.byte_type)
 164                                         Expr = new ByteConstant ((byte) ConstantValue);
 165                                 else if (type == TypeManager.char_type)
 166                                         Expr = new CharConstant ((char) ConstantValue);
 167                                 else if (type == TypeManager.bool_type)
 168                                         Expr = new BoolConstant ((bool) ConstantValue);
 169                         }
 170
 171                         if (type.IsEnum){
 172                                 //
 173                                 // This sadly does not work for our user-defined enumerations types ;-(
 174                                 //
 175                                 try {
 176                                         ConstantValue = System.Enum.ToObject (
 177                                                 type, ConstantValue);
 178                                 } catch (ArgumentException){
 179                                         Report.Error (
 180                                                 -16, Location,
 181                                                 ".NET SDK 1.0 does not permit to create the constant "+
 182                                                 " field from a user-defined enumeration");
 183                                 }
 184                         }
 185
 186                         FieldBuilder.SetConstant (ConstantValue);
 187
 188                         if (!TypeManager.RegisterFieldValue (FieldBuilder, ConstantValue))
 189                                 return null;
 190
 191                         return ConstantValue;
 192                 }
 193
 194
 195                 /// <summary>
 196                 ///  Emits the field value by evaluating the expression
 197                 /// </summary>
 198                 public void EmitConstant (TypeContainer parent)
 199                 {
 200                         EmitContext ec = new EmitContext (parent, Location, null, type, ModFlags);
 201                         LookupConstantValue (ec);
 202
 203                         return;
 204                 }
 205         }
 206 }
 207
 208