2 // const.cs: Constant declarations.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Marek Safar (marek.safar@seznam.cz)
8 // (C) 2001 Ximian, Inc.
12 namespace Mono.CSharp {
15 using System.Reflection;
16 using System.Reflection.Emit;
17 using System.Collections;
19 public interface IConstant
21 void CheckObsoleteness (Location loc);
23 Constant Value { get; }
26 public class Const : FieldMember, IConstant {
31 public const int AllowedModifiers =
38 public Const (DeclSpace parent, Expression constant_type, string name,
39 Expression expr, int mod_flags, Attributes attrs, Location loc)
40 : base (parent, constant_type, mod_flags, AllowedModifiers,
41 new MemberName (name, loc), attrs)
44 ModFlags |= Modifiers.STATIC;
47 protected override bool CheckBase ()
49 // Constant.Define can be called when the parent type hasn't yet been populated
50 // and it's base types need not have been populated. So, we defer this check
51 // to the second time Define () is called on this member.
52 if (Parent.PartialContainer.BaseCache == null)
54 return base.CheckBase ();
58 /// Defines the constant in the @parent
60 public override bool Define ()
62 // Because constant define can be called from other class
65 return FieldBuilder != null;
73 Type ttype = MemberType;
74 if (!IsConstantTypeValid (ttype)) {
75 Error_InvalidConstantType (ttype, Location);
80 ttype = TypeManager.GetElementType (ttype);
82 FieldAttributes field_attr = FieldAttributes.Static | Modifiers.FieldAttr (ModFlags);
83 // Decimals cannot be emitted into the constant blob. So, convert to 'readonly'.
84 if (ttype == TypeManager.decimal_type) {
85 field_attr |= FieldAttributes.InitOnly;
86 Parent.PartialContainer.RegisterFieldForInitialization (this);
88 field_attr |= FieldAttributes.Literal;
91 FieldBuilder = Parent.TypeBuilder.DefineField (Name, MemberType, field_attr);
93 TypeManager.RegisterConstant (FieldBuilder, this);
98 public static bool IsConstantTypeValid (Type t)
100 if (TypeManager.IsBuiltinOrEnum (t))
103 if (t.IsPointer || t.IsValueType)
106 if (TypeManager.IsGenericParameter (t))
113 /// Emits the field value by evaluating the expression
115 public override void Emit ()
117 if (!ResolveValue ())
120 if (value.Type == TypeManager.decimal_type) {
121 Decimal d = ((DecimalConstant)value).Value;
122 int[] bits = Decimal.GetBits (d);
123 object[] args = new object[] { (byte)(bits [3] >> 16), (byte)(bits [3] >> 31), (uint)bits [2], (uint)bits [1], (uint)bits [0] };
124 CustomAttributeBuilder cab = new CustomAttributeBuilder (TypeManager.decimal_constant_attribute_ctor, args);
125 FieldBuilder.SetCustomAttribute (cab);
128 FieldBuilder.SetConstant (value.GetTypedValue ());
134 public static void Error_ExpressionMustBeConstant (Location loc, string e_name)
136 Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
139 public static void Error_CyclicDeclaration (MemberCore mc)
141 Report.Error (110, mc.Location, "The evaluation of the constant value for `{0}' involves a circular definition",
142 mc.GetSignatureForError ());
145 public static void Error_ConstantCanBeInitializedWithNullOnly (Location loc, string name)
147 Report.Error (134, loc, "`{0}': the constant of reference type other than string can only be initialized with null",
151 public static void Error_InvalidConstantType (Type t, Location loc)
153 Report.Error (283, loc, "The type `{0}' cannot be declared const", TypeManager.CSharpName (t));
156 #region IConstant Members
158 public bool ResolveValue ()
165 Error_CyclicDeclaration (this);
166 // Suppress cyclic errors
167 value = New.Constantify (MemberType);
172 // TODO: IResolveContext here
173 EmitContext ec = new EmitContext (this, Parent, Location, null, MemberType, ModFlags);
174 value = initializer.ResolveAsConstant (ec, this);
180 value = value.ImplicitConversionRequired (MemberType, Location);
184 if (!MemberType.IsValueType && MemberType != TypeManager.string_type && !value.IsDefaultValue) {
185 Error_ConstantCanBeInitializedWithNullOnly (Location, GetSignatureForError ());
192 public Constant Value {
201 public class ExternalConstant : IConstant
206 public ExternalConstant (FieldInfo fi)
211 private ExternalConstant (FieldInfo fi, Constant value):
218 // Decimal constants cannot be encoded in the constant blob, and thus are marked
219 // as IsInitOnly ('readonly' in C# parlance). We get its value from the
220 // DecimalConstantAttribute metadata.
222 public static IConstant CreateDecimal (FieldInfo fi)
224 if (fi is FieldBuilder)
227 object[] attrs = fi.GetCustomAttributes (TypeManager.decimal_constant_attribute_type, false);
228 if (attrs.Length != 1)
231 IConstant ic = new ExternalConstant (fi,
232 new DecimalConstant (((System.Runtime.CompilerServices.DecimalConstantAttribute) attrs [0]).Value, Location.Null));
237 #region IConstant Members
239 public void CheckObsoleteness (Location loc)
241 ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (fi);
246 AttributeTester.Report_ObsoleteMessage (oa, TypeManager.GetFullNameSignature (fi), loc);
249 public bool ResolveValue ()
254 if (fi.DeclaringType.IsEnum) {
255 value = Expression.Constantify (fi.GetValue (fi), TypeManager.EnumToUnderlying (fi.FieldType));
256 value = new EnumConstant (value, fi.DeclaringType);
260 value = Expression.Constantify (fi.GetValue (fi), fi.FieldType);
264 public Constant Value {