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