//
// Author:
// Miguel de Icaza (miguel@ximian.com)
+// Marek Safar (marek.safar@seznam.cz)
//
// (C) 2001 Ximian, Inc.
//
public class NullType {
}
- //
- // The null Literal constant
- //
- public class NullLiteral : Constant {
- public NullLiteral (Location loc):
+
+ public class NullConstant : Constant
+ {
+ public NullConstant (Location loc):
base (loc)
{
eclass = ExprClass.Value;
+ type = TypeManager.null_type;
}
override public string AsString ()
return null;
}
- public override Expression DoResolve (EmitContext ec)
+ public override void Emit (EmitContext ec)
{
- type = TypeManager.null_type;
- return this;
+ ec.ig.Emit(OpCodes.Ldnull);
+ }
+
+ public override string ExprClassName {
+ get {
+ return GetSignatureForError ();
+ }
}
- public override void Emit (EmitContext ec)
+ public override string GetSignatureForError ()
{
- ec.ig.Emit (OpCodes.Ldnull);
+ return "null";
}
public override Constant Increment ()
throw new NotSupportedException ();
}
- public override bool IsDefaultValue {
- get {
- return true;
- }
+ public override bool IsDefaultValue
+ {
+ get { return true; }
}
- public override bool IsNegative {
- get {
- return false;
- }
+ public override bool IsNegative
+ {
+ get { return false; }
}
- public override bool IsZeroInteger {
+ public override bool IsNull {
get { return true; }
}
- public override string GetSignatureForError()
+ public override bool IsZeroInteger
{
- return "null";
+ get { return true; }
}
- public override void Error_ValueCannotBeConverted (Location loc, Type t, bool expl)
+ public override Constant ConvertExplicitly(bool inCheckedContext, Type target_type)
{
- Report.Error (37, loc, "Cannot convert null to `{0}' because it is a value type",
- TypeManager.CSharpName (t));
+ if (!TypeManager.IsValueType (target_type))
+ return new EmptyConstantCast (this, target_type);
+
+ return null;
}
- public override Constant ToType (Type type, Location loc)
+ public override Constant ConvertImplicitly (Type targetType)
{
- if (!type.IsValueType && !TypeManager.IsEnumType (type))
- return this;
+ if (!TypeManager.IsValueType (targetType))
+ return new EmptyConstantCast (this, targetType);
- return base.ToType (type, loc);
+ return null;
}
+ }
- public override Constant Reduce(EmitContext ec, Type target_type)
+ //
+ // Represents default(X) when result can be reduced to null
+ //
+ public class NullDefault : EmptyConstantCast
+ {
+ public NullDefault(Constant value, Type type)
+ : base (value, type)
{
- if (!TypeManager.IsValueType (target_type))
- return new NullCast (this, target_type);
+ }
- return null;
+ public override void Error_ValueCannotBeConverted (EmitContext ec, Location loc, Type target, bool expl)
+ {
+ base.Error_ValueCannotBeConverted (ec, loc, target, expl);
}
}
//
- // A null literal in a pointer context
+ // The null Literal constant
//
- public class NullPointer : NullLiteral {
- public static readonly NullLiteral Null;
+ public class NullLiteral : NullConstant {
+ public NullLiteral (Location loc):
+ base (loc)
+ {
+ }
+
+ public override Expression DoResolve (EmitContext ec)
+ {
+ type = TypeManager.null_type;
+ return this;
+ }
+
+ public override void Error_ValueCannotBeConverted (EmitContext ec, Location loc, Type t, bool expl)
+ {
+ if (TypeManager.IsGenericParameter (t)) {
+ Report.Error(403, loc,
+ "Cannot convert null to the type parameter `{0}' because it could be a value " +
+ "type. Consider using `default ({0})' instead", t.Name);
+ } else {
+ Report.Error(37, loc, "Cannot convert null to `{0}' because it is a value type",
+ TypeManager.CSharpName(t));
+ }
+ }
- static NullPointer ()
+ public override Constant ConvertImplicitly (Type targetType)
{
- Null = new NullPointer ();
+ if (targetType.IsPointer)
+ return new EmptyConstantCast (NullPointer.Null, targetType);
+
+ if (TypeManager.IsGenericParameter(targetType)) {
+ GenericConstraints gc = null;
+
+#if GMCS_SOURCE
+ gc = TypeManager.GetTypeParameterConstraints(targetType);
+#endif
+ if (gc != null && gc.IsReferenceType)
+ return new EmptyConstantCast (this, targetType);
+
+ return null;
+ }
+
+ return base.ConvertImplicitly(targetType);
}
+ }
+
+ //
+ // A null literal in a pointer context
+ //
+ public class NullPointer : NullLiteral {
+ public static readonly NullLiteral Null = new NullPointer ();
+
private NullPointer ():
base (Location.Null)
{
{
ILGenerator ig = ec.ig;
+ // TODO: why not use Ldnull instead ?
ig.Emit (OpCodes.Ldc_I4_0);
ig.Emit (OpCodes.Conv_U);
}
type = TypeManager.int32_type;
return this;
}
+
+ public override Constant ConvertImplicitly (Type type)
+ {
+ ///
+ /// The 0 literal can be converted to an enum value,
+ ///
+ if (Value == 0 && TypeManager.IsEnumType (type)) {
+ Constant c = ConvertImplicitly (TypeManager.EnumToUnderlying (type));
+ if (c == null)
+ return null;
+
+ return new EnumConstant (c, type);
+ }
+ return base.ConvertImplicitly (type);
+ }
+
}
public class UIntLiteral : UIntConstant {
return this;
}
+
+ public override void Error_ValueCannotBeConverted (EmitContext ec, Location loc, Type target, bool expl)
+ {
+ if (target == TypeManager.float_type) {
+ Error_664 (loc, "float", "f");
+ return;
+ }
+
+ if (target == TypeManager.decimal_type) {
+ Error_664 (loc, "decimal", "m");
+ return;
+ }
+
+ base.Error_ValueCannotBeConverted (ec, loc, target, expl);
+ }
+
+ static void Error_664 (Location loc, string type, string suffix)
+ {
+ Report.Error (664, loc,
+ "Literal of type double cannot be implicitly converted to type `{0}'. Add suffix `{1}' to create a literal of this type",
+ type, suffix);
+ }
}
public class DecimalLiteral : DecimalConstant {
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