mcs/mcs/const.cs

   1 //
   2 // const.cs: Constant declarations.
   3 //
   4 // Author:
   5 //   Miguel de Icaza (miguel@ximian.com)
   6 //   Marek Safar (marek.safar@seznam.cz)
   7 //
   8 // Copyright 2001-2003 Ximian, Inc.
   9 // Copyright 2003-2008 Novell, Inc.
  10 //
  11
  12 #if STATIC
  13 using IKVM.Reflection;
  14 #else
  15 using System.Reflection;
  16 #endif
  17
  18 namespace Mono.CSharp {
  19
  20         public class Const : FieldBase
  21         {
  22                 const Modifiers AllowedModifiers =
  23                         Modifiers.NEW |
  24                         Modifiers.PUBLIC |
  25                         Modifiers.PROTECTED |
  26                         Modifiers.INTERNAL |
  27                         Modifiers.PRIVATE;
  28
  29                 public Const (TypeDefinition parent, FullNamedExpression type, Modifiers mod_flags, MemberName name, Attributes attrs)
  30                         : base (parent, type, mod_flags, AllowedModifiers, name, attrs)
  31                 {
  32                         ModFlags |= Modifiers.STATIC;
  33                 }
  34
  35                 /// <summary>
  36                 ///   Defines the constant in the @parent
  37                 /// </summary>
  38                 public override bool Define ()
  39                 {
  40                         if (!base.Define ())
  41                                 return false;
  42
  43                         if (!member_type.IsConstantCompatible) {
  44                                 Error_InvalidConstantType (member_type, Location, Report);
  45                         }
  46
  47                         FieldAttributes field_attr = FieldAttributes.Static | ModifiersExtensions.FieldAttr (ModFlags);
  48                         // Decimals cannot be emitted into the constant blob.  So, convert to 'readonly'.
  49                         if (member_type.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
  50                                 field_attr |= FieldAttributes.InitOnly;
  51                         } else {
  52                                 field_attr |= FieldAttributes.Literal;
  53                         }
  54
  55                         FieldBuilder = Parent.TypeBuilder.DefineField (Name, MemberType.GetMetaInfo (), field_attr);
  56                         spec = new ConstSpec (Parent.Definition, this, MemberType, FieldBuilder, ModFlags, initializer);
  57
  58                         Parent.MemberCache.AddMember (spec);
  59
  60                         if ((field_attr & FieldAttributes.InitOnly) != 0)
  61                                 Parent.PartialContainer.RegisterFieldForInitialization (this,
  62                                         new FieldInitializer (spec, initializer, this));
  63
  64                         if (declarators != null) {
  65                                 var t = new TypeExpression (MemberType, TypeExpression.Location);
  66                                 foreach (var d in declarators) {
  67                                         var c = new Const (Parent, t, ModFlags & ~Modifiers.STATIC, new MemberName (d.Name.Value, d.Name.Location), OptAttributes);
  68                                         c.initializer = d.Initializer;
  69                                         ((ConstInitializer) c.initializer).Name = d.Name.Value;
  70                                         c.Define ();
  71                                         Parent.PartialContainer.Members.Add (c);
  72                                 }
  73                         }
  74
  75                         return true;
  76                 }
  77
  78                 public void DefineValue ()
  79                 {
  80                         var rc = new ResolveContext (this);
  81                         ((ConstSpec) spec).GetConstant (rc);
  82                 }
  83
  84                 /// <summary>
  85                 ///  Emits the field value by evaluating the expression
  86                 /// </summary>
  87                 public override void Emit ()
  88                 {
  89                         var c = ((ConstSpec) spec).Value as Constant;
  90                         if (c.Type.BuiltinType == BuiltinTypeSpec.Type.Decimal) {
  91                                 Module.PredefinedAttributes.DecimalConstant.EmitAttribute (FieldBuilder, (decimal) c.GetValue (), c.Location);
  92                         } else {
  93                                 FieldBuilder.SetConstant (c.GetValue ());
  94                         }
  95
  96                         base.Emit ();
  97                 }
  98
  99                 public static void Error_InvalidConstantType (TypeSpec t, Location loc, Report Report)
 100                 {
 101                         if (t.IsGenericParameter) {
 102                                 Report.Error (1959, loc,
 103                                         "Type parameter `{0}' cannot be declared const", TypeManager.CSharpName (t));
 104                         } else {
 105                                 Report.Error (283, loc,
 106                                         "The type `{0}' cannot be declared const", TypeManager.CSharpName (t));
 107                         }
 108                 }
 109         }
 110
 111         public class ConstSpec : FieldSpec
 112         {
 113                 Expression value;
 114
 115                 public ConstSpec (TypeSpec declaringType, IMemberDefinition definition, TypeSpec memberType, FieldInfo fi, Modifiers mod, Expression value)
 116                         : base (declaringType, definition, memberType, fi, mod)
 117                 {
 118                         this.value = value;
 119                 }
 120
 121                 //
 122                 // This expresion is guarantee to be a constant at emit phase only
 123                 //
 124                 public Expression Value {
 125                         get {
 126                                 return value;
 127                         }
 128                 }
 129
 130                 //
 131                 // For compiled constants we have to resolve the value as there could be constant dependecies. This
 132                 // is needed for imported constants too to get the right context type
 133                 //
 134                 public Constant GetConstant (ResolveContext rc)
 135                 {
 136                         if (value.eclass != ExprClass.Value)
 137                                 value = value.Resolve (rc);
 138
 139                         return (Constant) value;
 140                 }
 141         }
 142
 143         public class ConstInitializer : ShimExpression
 144         {
 145                 bool in_transit;
 146                 readonly FieldBase field;
 147
 148                 public ConstInitializer (FieldBase field, Expression value, Location loc)
 149                         : base (value)
 150                 {
 151                         this.loc = loc;
 152                         this.field = field;
 153                 }
 154
 155                 public string Name { get; set; }
 156
 157                 protected override Expression DoResolve (ResolveContext unused)
 158                 {
 159                         if (type != null)
 160                                 return expr;
 161
 162                         var opt = ResolveContext.Options.ConstantScope;
 163                         if (field is EnumMember)
 164                                 opt |= ResolveContext.Options.EnumScope;
 165
 166                         //
 167                         // Use a context in which the constant was declared and
 168                         // not the one in which is referenced
 169                         //
 170                         var rc = new ResolveContext (field, opt);
 171                         expr = DoResolveInitializer (rc);
 172                         type = expr.Type;
 173
 174                         return expr;
 175                 }
 176
 177                 protected virtual Expression DoResolveInitializer (ResolveContext rc)
 178                 {
 179                         if (in_transit) {
 180                                 field.Compiler.Report.Error (110, expr.Location,
 181                                         "The evaluation of the constant value for `{0}' involves a circular definition",
 182                                         GetSignatureForError ());
 183
 184                                 expr = null;
 185                         } else {
 186                                 in_transit = true;
 187                                 expr = expr.Resolve (rc);
 188                         }
 189
 190                         in_transit = false;
 191
 192                         if (expr != null) {
 193                                 Constant c = expr as Constant;
 194                                 if (c != null)
 195                                         c = field.ConvertInitializer (rc, c);
 196
 197                                 if (c == null) {
 198                                         if (TypeSpec.IsReferenceType (field.MemberType))
 199                                                 Error_ConstantCanBeInitializedWithNullOnly (rc, field.MemberType, expr.Location, GetSignatureForError ());
 200                                         else if (!(expr is Constant))
 201                                                 Error_ExpressionMustBeConstant (rc, expr.Location, GetSignatureForError ());
 202                                         else
 203                                                 expr.Error_ValueCannotBeConverted (rc, expr.Location, field.MemberType, false);
 204                                 }
 205
 206                                 expr = c;
 207                         }
 208
 209                         if (expr == null) {
 210                                 expr = New.Constantify (field.MemberType, Location);
 211                                 if (expr == null)
 212                                         expr = Constant.CreateConstantFromValue (field.MemberType, null, Location);
 213                                 expr = expr.Resolve (rc);
 214                         }
 215
 216                         return expr;
 217                 }
 218
 219                 public override string GetSignatureForError ()
 220                 {
 221                         if (Name == null)
 222                                 return field.GetSignatureForError ();
 223
 224                         return field.Parent.GetSignatureForError () + "." + Name;
 225                 }
 226
 227                 public override object Accept (StructuralVisitor visitor)
 228                 {
 229                         return visitor.Visit (this);
 230                 }
 231         }
 232 }