mcs/mcs/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 : FieldBase {
  28                 public Expression Expr;
  29                 EmitContext const_ec;
  30
  31                 bool resolved = false;
  32                 object ConstantValue = null;
  33                 Type type;
  34
  35                 bool in_transit = false;
  36
  37                 public const int AllowedModifiers =
  38                         Modifiers.NEW |
  39                         Modifiers.PUBLIC |
  40                         Modifiers.PROTECTED |
  41                         Modifiers.INTERNAL |
  42                         Modifiers.PRIVATE;
  43
  44                 public Const (Expression constant_type, string name, Expression expr, int mod_flags,
  45                               Attributes attrs, Location loc)
  46                         : base (constant_type, mod_flags, AllowedModifiers, name, null, attrs, loc)
  47                 {
  48                         Expr = expr;
  49                 }
  50
  51                 public FieldAttributes FieldAttr {
  52                         get {
  53                                 return FieldAttributes.Literal | FieldAttributes.Static |
  54                                         Modifiers.FieldAttr (ModFlags) ;
  55                         }
  56                 }
  57
  58 #if DEBUG
  59                 void dump_tree (Type t)
  60                 {
  61                         Console.WriteLine ("Dumping hierarchy");
  62                         while (t != null){
  63                                 Console.WriteLine ("   " + t.FullName + " " +
  64                                         (t.GetType ().IsEnum ? "yes" : "no"));
  65                                 t = t.BaseType;
  66                         }
  67                 }
  68 #endif
  69
  70                 /// <summary>
  71                 ///   Defines the constant in the @parent
  72                 /// </summary>
  73                 public override bool Define (TypeContainer parent)
  74                 {
  75                         type = parent.ResolveType (Type, false, Location);
  76
  77                         if (type == null)
  78                                 return false;
  79
  80                         const_ec = new EmitContext (parent, Location, null, type, ModFlags);
  81
  82                         Type ttype = type;
  83                         while (ttype.IsArray)
  84                             ttype = TypeManager.GetElementType (ttype);
  85
  86                         if (!TypeManager.IsBuiltinType (ttype) &&
  87                             (!ttype.IsSubclassOf (TypeManager.enum_type))) {
  88                                 Report.Error (
  89                                         -3, Location,
  90                                         "Constant type is not valid (only system types are allowed)");
  91                                 return false;
  92                         }
  93
  94                         Type ptype = parent.TypeBuilder.BaseType;
  95
  96                         if (ptype != null) {
  97                                 MemberList list = TypeContainer.FindMembers (
  98                                         ptype, MemberTypes.Field, BindingFlags.Public,
  99                                         System.Type.FilterName, Name);
 100
 101                                 if (list.Count == 0)
 102                                         if ((ModFlags & Modifiers.NEW) != 0)
 103                                                 WarningNotHiding (parent);
 104
 105                         } else if ((ModFlags & Modifiers.NEW) != 0)
 106                                 WarningNotHiding (parent);
 107
 108                         FieldBuilder = parent.TypeBuilder.DefineField (Name, type, FieldAttr);
 109
 110                         TypeManager.RegisterConstant (FieldBuilder, this);
 111
 112                         return true;
 113                 }
 114
 115                 //
 116                 // Changes the type of the constant expression `expr' to the Type `type'
 117                 // Returns null on failure.
 118                 //
 119                 public static Constant ChangeType (Location loc, Constant expr, Type type)
 120                 {
 121                         bool fail;
 122
 123                         // from the null type to any reference-type.
 124                         if (expr is NullLiteral && !type.IsValueType && !TypeManager.IsEnumType (type))
 125                                 return NullLiteral.Null;
 126
 127                         if (!Convert.ImplicitStandardConversionExists (expr, type)){
 128                                 Convert.Error_CannotImplicitConversion (loc, expr.Type, type);
 129                                 return null;
 130                         }
 131
 132                         object constant_value = TypeManager.ChangeType (expr.GetValue (), type, out fail);
 133                         if (fail){
 134                                 Convert.Error_CannotImplicitConversion (loc, expr.Type, type);
 135
 136                                 //
 137                                 // We should always catch the error before this is ever
 138                                 // reached, by calling Convert.ImplicitStandardConversionExists
 139                                 //
 140                                 throw new Exception (
 141                                                      String.Format ("LookupConstantValue: This should never be reached {0} {1}", expr.Type, type));
 142                         }
 143
 144                         Constant retval;
 145                         if (type == TypeManager.int32_type)
 146                                 retval = new IntConstant ((int) constant_value);
 147                         else if (type == TypeManager.uint32_type)
 148                                 retval = new UIntConstant ((uint) constant_value);
 149                         else if (type == TypeManager.int64_type)
 150                                 retval = new LongConstant ((long) constant_value);
 151                         else if (type == TypeManager.uint64_type)
 152                                 retval = new ULongConstant ((ulong) constant_value);
 153                         else if (type == TypeManager.float_type)
 154                                 retval = new FloatConstant ((float) constant_value);
 155                         else if (type == TypeManager.double_type)
 156                                 retval = new DoubleConstant ((double) constant_value);
 157                         else if (type == TypeManager.string_type)
 158                                 retval = new StringConstant ((string) constant_value);
 159                         else if (type == TypeManager.short_type)
 160                                 retval = new ShortConstant ((short) constant_value);
 161                         else if (type == TypeManager.ushort_type)
 162                                 retval = new UShortConstant ((ushort) constant_value);
 163                         else if (type == TypeManager.sbyte_type)
 164                                 retval = new SByteConstant ((sbyte) constant_value);
 165                         else if (type == TypeManager.byte_type)
 166                                 retval = new ByteConstant ((byte) constant_value);
 167                         else if (type == TypeManager.char_type)
 168                                 retval = new CharConstant ((char) constant_value);
 169                         else if (type == TypeManager.bool_type)
 170                                 retval = new BoolConstant ((bool) constant_value);
 171                         else
 172                                 throw new Exception ("LookupConstantValue: Unhandled constant type: " + type);
 173
 174                         return retval;
 175                 }
 176
 177                 /// <summary>
 178                 ///  Looks up the value of a constant field. Defines it if it hasn't
 179                 ///  already been. Similar to LookupEnumValue in spirit.
 180                 /// </summary>
 181                 public bool LookupConstantValue (out object value)
 182                 {
 183                         if (resolved) {
 184                                 value = ConstantValue;
 185                                 return true;
 186                         }
 187
 188                         if (in_transit) {
 189                                 Report.Error (110, Location,
 190                                               "The evaluation of the constant value for `" +
 191                                               Name + "' involves a circular definition.");
 192                                 value = null;
 193                                 return false;
 194                         }
 195
 196                         in_transit = true;
 197                         int errors = Report.Errors;
 198
 199                         //
 200                         // We might have cleared Expr ourselves in a recursive definition
 201                         //
 202                         if (Expr == null){
 203                                 value = null;
 204                                 return false;
 205                         }
 206
 207                         Expr = Expr.Resolve (const_ec);
 208
 209                         in_transit = false;
 210
 211                         if (Expr == null) {
 212                                 if (errors == Report.Errors)
 213                                         Report.Error (150, Location, "A constant value is expected");
 214                                 value = null;
 215                                 return false;
 216                         }
 217
 218                         Constant ce = Expr as Constant;
 219                         if (ce == null){
 220                                 UnCheckedExpr un_expr = Expr as UnCheckedExpr;
 221                                 CheckedExpr ch_expr = Expr as CheckedExpr;
 222
 223                                 if ((un_expr != null) && (un_expr.Expr is Constant))
 224                                         Expr = un_expr.Expr;
 225                                 else if ((ch_expr != null) && (ch_expr.Expr is Constant))
 226                                         Expr = ch_expr.Expr;
 227                                 else if (Expr is ArrayCreation) {
 228                                         ArrayCreation ac = (ArrayCreation) Expr;
 229
 230                                         Expr = ac.TurnIntoConstant ();
 231                                         if (Expr == null){
 232                                                 Report.Error (150, Location, "A constant value is expected");
 233                                                 value = null;
 234                                                 return false;
 235                                         }
 236                                 } else {
 237                                         if (errors == Report.Errors)
 238                                                 Report.Error (150, Location, "A constant value is expected");
 239                                         value = null;
 240                                         return false;
 241                                 }
 242                         }
 243
 244                         if (type != ce.Type) {
 245                                 ce = ChangeType (Location, ce, type);
 246                                 if (ce == null){
 247                                         value = null;
 248                                         return false;
 249                                 }
 250                                 Expr = ce;
 251                         }
 252                         ConstantValue = ce.GetValue ();
 253
 254                         if (type.IsEnum){
 255                                 //
 256                                 // This sadly does not work for our user-defined enumerations types ;-(
 257                                 //
 258                                 try {
 259                                         ConstantValue = System.Enum.ToObject (
 260                                                 type, ConstantValue);
 261                                 } catch (ArgumentException){
 262                                         Report.Error (
 263                                                 -16, Location,
 264                                                 ".NET SDK 1.0 does not permit to create the constant "+
 265                                                 " field from a user-defined enumeration");
 266                                 }
 267                         }
 268
 269                         FieldBuilder.SetConstant (ConstantValue);
 270
 271                         if (!TypeManager.RegisterFieldValue (FieldBuilder, ConstantValue))
 272                                 throw new Exception ("Cannot register const value");
 273
 274                         value = ConstantValue;
 275                         resolved = true;
 276                         return true;
 277                 }
 278
 279
 280                 /// <summary>
 281                 ///  Emits the field value by evaluating the expression
 282                 /// </summary>
 283                 public override void Emit (TypeContainer parent)
 284                 {
 285                         object value;
 286                         LookupConstantValue (out value);
 287                         base.Emit (parent);
 288                 }
 289         }
 290 }
 291
 292