2 // const.cs: Constant declarations.
5 // Miguel de Icaza (miguel@ximian.com)
6 // Marek Safar (marek.safar@seznam.cz)
8 // (C) 2001 Ximian, Inc.
13 // This is needed because the following situation arises:
15 // The FieldBuilder is declared with the real type for an enumeration
17 // When we attempt to set the value for the constant, the FieldBuilder.SetConstant
18 // function aborts because it requires its argument to be of the same type
21 namespace Mono.CSharp {
24 using System.Reflection;
25 using System.Reflection.Emit;
26 using System.Collections;
28 public class Const : FieldMember {
29 public Expression Expr;
32 bool resolved = false;
33 object ConstantValue = null;
35 bool in_transit = false;
37 public const int AllowedModifiers =
44 public Const (TypeContainer parent, Expression constant_type, string name,
45 Expression expr, int mod_flags, Attributes attrs, Location loc)
46 : base (parent, constant_type, mod_flags, AllowedModifiers,
47 new MemberName (name), null, attrs, loc)
50 ModFlags |= Modifiers.STATIC;
54 void dump_tree (Type t)
56 Console.WriteLine ("Dumping hierarchy");
58 Console.WriteLine (" " + t.FullName + " " +
59 (t.GetType ().IsEnum ? "yes" : "no"));
65 protected override bool CheckBase ()
67 // Constant.Define can be called when the parent type hasn't yet been populated
68 // and it's base types need not have been populated. So, we defer this check
69 // to the second time Define () is called on this member.
70 if (Parent.BaseCache == null)
72 return base.CheckBase ();
76 /// Defines the constant in the @parent
78 public override bool Define ()
80 // Make Define () idempotent, but ensure that the error check happens.
81 if (FieldBuilder != null)
82 return base.CheckBase ();
87 const_ec = new EmitContext (Parent, Location, null, MemberType, ModFlags);
89 Type ttype = MemberType;
91 ttype = TypeManager.GetElementType (ttype);
93 if (!TypeManager.IsBuiltinType(ttype) && (!ttype.IsSubclassOf(TypeManager.enum_type)) && !(Expr is NullLiteral)){
96 "Constant type is not valid (only system types are allowed)");
100 FieldAttributes field_attr = FieldAttributes.Static | Modifiers.FieldAttr (ModFlags);
101 // I don't know why but they emit decimal constant as InitOnly
102 if (ttype == TypeManager.decimal_type) {
103 field_attr |= FieldAttributes.InitOnly;
106 field_attr |= FieldAttributes.Literal;
109 FieldBuilder = Parent.TypeBuilder.DefineField (Name, MemberType, field_attr);
111 TypeManager.RegisterConstant (FieldBuilder, this);
117 // Changes the type of the constant expression `expr' to the Type `type'
118 // Returns null on failure.
120 public static Constant ChangeType (Location loc, Constant expr, Type type)
122 if (type == TypeManager.object_type)
127 // from the null type to any reference-type.
128 if (expr.Type == TypeManager.null_type && !type.IsValueType && !TypeManager.IsEnumType (type))
129 return NullLiteral.Null;
131 if (!Convert.ImplicitStandardConversionExists (Convert.ConstantEC, expr, type)){
132 Convert.Error_CannotImplicitConversion (loc, expr.Type, type);
136 // Special-case: The 0 literal can be converted to an enum value,
137 // and ImplicitStandardConversionExists will return true in that case.
138 if (expr.Type == TypeManager.int32_type && TypeManager.IsEnumType (type)){
139 if (expr is IntLiteral && ((IntLiteral) expr).Value == 0)
140 return new EnumConstant (expr, type);
143 object constant_value = TypeManager.ChangeType (expr.GetValue (), type, out fail);
145 Convert.Error_CannotImplicitConversion (loc, expr.Type, type);
148 // We should always catch the error before this is ever
149 // reached, by calling Convert.ImplicitStandardConversionExists
151 throw new Exception (
152 String.Format ("LookupConstantValue: This should never be reached {0} {1}", expr.Type, type));
156 if (type == TypeManager.int32_type)
157 retval = new IntConstant ((int) constant_value);
158 else if (type == TypeManager.uint32_type)
159 retval = new UIntConstant ((uint) constant_value);
160 else if (type == TypeManager.int64_type)
161 retval = new LongConstant ((long) constant_value);
162 else if (type == TypeManager.uint64_type)
163 retval = new ULongConstant ((ulong) constant_value);
164 else if (type == TypeManager.float_type)
165 retval = new FloatConstant ((float) constant_value);
166 else if (type == TypeManager.double_type)
167 retval = new DoubleConstant ((double) constant_value);
168 else if (type == TypeManager.string_type)
169 retval = new StringConstant ((string) constant_value);
170 else if (type == TypeManager.short_type)
171 retval = new ShortConstant ((short) constant_value);
172 else if (type == TypeManager.ushort_type)
173 retval = new UShortConstant ((ushort) constant_value);
174 else if (type == TypeManager.sbyte_type)
175 retval = new SByteConstant ((sbyte) constant_value);
176 else if (type == TypeManager.byte_type)
177 retval = new ByteConstant ((byte) constant_value);
178 else if (type == TypeManager.char_type)
179 retval = new CharConstant ((char) constant_value);
180 else if (type == TypeManager.bool_type)
181 retval = new BoolConstant ((bool) constant_value);
182 else if (type == TypeManager.decimal_type)
183 retval = new DecimalConstant ((decimal) constant_value);
185 throw new Exception ("LookupConstantValue: Unhandled constant type: " + type);
191 /// Looks up the value of a constant field. Defines it if it hasn't
192 /// already been. Similar to LookupEnumValue in spirit.
194 public bool LookupConstantValue (out object value)
197 value = ConstantValue;
202 Report.Error (110, Location,
203 "The evaluation of the constant value for `" +
204 Name + "' involves a circular definition.");
210 int errors = Report.Errors;
213 // We might have cleared Expr ourselves in a recursive definition
220 Expr = Expr.Resolve (const_ec);
225 if (errors == Report.Errors)
226 Report.Error (150, Location, "A constant value is expected");
231 Expression real_expr = Expr;
233 Constant ce = Expr as Constant;
235 UnCheckedExpr un_expr = Expr as UnCheckedExpr;
236 CheckedExpr ch_expr = Expr as CheckedExpr;
237 EmptyCast ec_expr = Expr as EmptyCast;
239 if ((un_expr != null) && (un_expr.Expr is Constant))
241 else if ((ch_expr != null) && (ch_expr.Expr is Constant))
243 else if ((ec_expr != null) && (ec_expr.Child is Constant))
244 Expr = ec_expr.Child;
245 else if (Expr is ArrayCreation){
246 Report.Error (133, Location, "Arrays can not be constant");
248 if (errors == Report.Errors)
249 Report.Error (150, Location, "A constant value is expected");
254 ce = Expr as Constant;
257 if (MemberType != real_expr.Type) {
258 ce = ChangeType (Location, ce, MemberType);
267 ConstantValue = ce.GetValue ();
269 if (MemberType.IsEnum){
271 // This sadly does not work for our user-defined enumerations types ;-(
274 ConstantValue = System.Enum.ToObject (
275 MemberType, ConstantValue);
276 } catch (ArgumentException){
279 ".NET SDK 1.0 does not permit to create the constant "+
280 " field from a user-defined enumeration");
284 if (ce is DecimalConstant) {
285 Decimal d = ((DecimalConstant)ce).Value;
286 int[] bits = Decimal.GetBits (d);
287 object[] args = new object[] { (byte)(bits [3] >> 16), (byte)(bits [3] >> 31), (uint)bits [2], (uint)bits [1], (uint)bits [0] };
288 CustomAttributeBuilder cab = new CustomAttributeBuilder (TypeManager.decimal_constant_attribute_ctor, args);
289 FieldBuilder.SetCustomAttribute (cab);
292 FieldBuilder.SetConstant (ConstantValue);
295 if (!TypeManager.RegisterFieldValue (FieldBuilder, ConstantValue))
296 throw new Exception ("Cannot register const value");
298 value = ConstantValue;
305 /// Emits the field value by evaluating the expression
307 public override void Emit ()
310 LookupConstantValue (out value);