2 // const.cs: Constant declarations.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Marek Safar (marek.safar@seznam.cz)
8 // Copyright 2001-2003 Ximian, Inc.
9 // Copyright 2003-2008 Novell, 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 CreateConstantReference (Location loc);
26 public class Const : FieldBase, IConstant {
27 protected Constant value;
32 public const int AllowedModifiers =
39 public Const (DeclSpace parent, FullNamedExpression type, string name,
40 Expression expr, int mod_flags, Attributes attrs, Location loc)
41 : base (parent, type, mod_flags, AllowedModifiers,
42 new MemberName (name, loc), attrs)
45 ModFlags |= Modifiers.STATIC;
48 protected override bool CheckBase ()
50 // Constant.Define can be called when the parent type hasn't yet been populated
51 // and it's base types need not have been populated. So, we defer this check
52 // to the second time Define () is called on this member.
53 if (Parent.PartialContainer.BaseCache == null)
55 return base.CheckBase ();
59 /// Defines the constant in the @parent
61 public override bool Define ()
63 // Because constant define can be called from other class
66 return FieldBuilder != null;
74 Type ttype = MemberType;
75 if (!IsConstantTypeValid (ttype)) {
76 Error_InvalidConstantType (ttype, Location, Report);
79 // If the constant is private then we don't need any field the
80 // value is already inlined and cannot be referenced
81 //if ((ModFlags & Modifiers.PRIVATE) != 0 && RootContext.Optimize)
84 FieldAttributes field_attr = FieldAttributes.Static | Modifiers.FieldAttr (ModFlags);
85 // Decimals cannot be emitted into the constant blob. So, convert to 'readonly'.
86 if (ttype == TypeManager.decimal_type) {
87 field_attr |= FieldAttributes.InitOnly;
89 field_attr |= FieldAttributes.Literal;
92 FieldBuilder = Parent.TypeBuilder.DefineField (Name, MemberType, field_attr);
93 TypeManager.RegisterConstant (FieldBuilder, this);
94 Parent.MemberCache.AddMember (FieldBuilder, this);
96 if ((field_attr & FieldAttributes.InitOnly) != 0)
97 Parent.PartialContainer.RegisterFieldForInitialization (this,
98 new FieldInitializer (FieldBuilder, initializer, this));
103 public static bool IsConstantTypeValid (Type t)
105 if (TypeManager.IsBuiltinOrEnum (t))
108 if (TypeManager.IsGenericParameter (t) || t.IsPointer)
111 return TypeManager.IsReferenceType (t);
115 /// Emits the field value by evaluating the expression
117 public override void Emit ()
119 if (!ResolveValue ())
122 if (FieldBuilder == null)
125 if (value.Type == TypeManager.decimal_type) {
126 FieldBuilder.SetCustomAttribute (CreateDecimalConstantAttribute (value));
128 FieldBuilder.SetConstant (value.GetTypedValue ());
134 public static CustomAttributeBuilder CreateDecimalConstantAttribute (Constant c)
136 PredefinedAttribute pa = PredefinedAttributes.Get.DecimalConstant;
137 if (pa.Constructor == null &&
138 !pa.ResolveConstructor (c.Location, TypeManager.byte_type, TypeManager.byte_type,
139 TypeManager.uint32_type, TypeManager.uint32_type, TypeManager.uint32_type))
142 Decimal d = (Decimal) c.GetValue ();
143 int [] bits = Decimal.GetBits (d);
144 object [] args = new object [] {
145 (byte) (bits [3] >> 16),
146 (byte) (bits [3] >> 31),
147 (uint) bits [2], (uint) bits [1], (uint) bits [0]
150 return new CustomAttributeBuilder (pa.Constructor, args);
153 public static void Error_ExpressionMustBeConstant (Location loc, string e_name, Report Report)
155 Report.Error (133, loc, "The expression being assigned to `{0}' must be constant", e_name);
158 public static void Error_CyclicDeclaration (MemberCore mc, Report Report)
160 Report.Error (110, mc.Location, "The evaluation of the constant value for `{0}' involves a circular definition",
161 mc.GetSignatureForError ());
164 public static void Error_ConstantCanBeInitializedWithNullOnly (Type type, Location loc, string name, Report Report)
166 Report.Error (134, loc, "A constant `{0}' of reference type `{1}' can only be initialized with null",
167 name, TypeManager.CSharpName (type));
170 public static void Error_InvalidConstantType (Type t, Location loc, Report Report)
172 if (TypeManager.IsGenericParameter (t)) {
173 Report.Error (1959, loc,
174 "Type parameter `{0}' cannot be declared const", TypeManager.CSharpName (t));
176 Report.Error (283, loc,
177 "The type `{0}' cannot be declared const", TypeManager.CSharpName (t));
181 #region IConstant Members
183 public bool ResolveValue ()
186 return value != null;
190 Error_CyclicDeclaration (this, Report);
191 // Suppress cyclic errors
192 value = New.Constantify (MemberType);
199 ResolveContext.Options opt = ResolveContext.Options.ConstantScope;
200 if (this is EnumMember)
201 opt |= ResolveContext.Options.EnumScope;
203 ResolveContext rc = new ResolveContext (this, opt);
204 value = DoResolveValue (rc);
208 return value != null;
211 protected virtual Constant DoResolveValue (ResolveContext ec)
213 Constant value = initializer.ResolveAsConstant (ec, this);
217 Constant c = value.ConvertImplicitly (MemberType);
219 if (TypeManager.IsReferenceType (MemberType))
220 Error_ConstantCanBeInitializedWithNullOnly (MemberType, Location, GetSignatureForError (), Report);
222 value.Error_ValueCannotBeConverted (ec, Location, MemberType, false);
228 public virtual Constant CreateConstantReference (Location loc)
233 return Constant.CreateConstant (value.Type, value.GetValue(), loc);
239 public class ExternalConstant : IConstant
244 public ExternalConstant (FieldInfo fi)
249 private ExternalConstant (FieldInfo fi, object value):
256 // Decimal constants cannot be encoded in the constant blob, and thus are marked
257 // as IsInitOnly ('readonly' in C# parlance). We get its value from the
258 // DecimalConstantAttribute metadata.
260 public static IConstant CreateDecimal (FieldInfo fi)
262 if (fi is FieldBuilder)
265 PredefinedAttribute pa = PredefinedAttributes.Get.DecimalConstant;
269 object[] attrs = fi.GetCustomAttributes (pa.Type, false);
270 if (attrs.Length != 1)
273 IConstant ic = new ExternalConstant (fi,
274 ((System.Runtime.CompilerServices.DecimalConstantAttribute) attrs [0]).Value);
279 #region IConstant Members
281 public void CheckObsoleteness (Location loc)
283 ObsoleteAttribute oa = AttributeTester.GetMemberObsoleteAttribute (fi);
288 AttributeTester.Report_ObsoleteMessage (oa, TypeManager.GetFullNameSignature (fi), loc, RootContext.ToplevelTypes.Compiler.Report);
291 public bool ResolveValue ()
296 value = fi.GetValue (fi);
300 public Constant CreateConstantReference (Location loc)
302 return Constant.CreateConstant (TypeManager.TypeToCoreType (fi.FieldType), value, loc);