2009-07-20 Jb Evain <jbevain@novell.com>

[mcs.git] / mcs / attribute.cs

//
// attribute.cs: Attribute Handler
//
// Author: Ravi Pratap (ravi@ximian.com)
//         Marek Safar (marek.safar@seznam.cz)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
//
// Copyright 2001-2003 Ximian, Inc (http://www.ximian.com)
// Copyright 2003-2008 Novell, Inc.
//

using System;
using System.Diagnostics;
using System.Collections;
using System.Collections.Specialized;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
using System.Security; 
using System.Security.Permissions;
using System.Text;
using System.IO;

namespace Mono.CSharp {

        /// <summary>
        ///   Base class for objects that can have Attributes applied to them.
        /// </summary>
        public abstract class Attributable {
                /// <summary>
                ///   Attributes for this type
                /// </summary>
                protected Attributes attributes;

                public Attributable (Attributes attrs)
                {
                        if (attrs != null)
                                OptAttributes = attrs;
                }

                public Attributes OptAttributes 
                {
                        get {
                                return attributes;
                        }
                        set {
                                attributes = value;

                                if (attributes != null) {
                                        attributes.AttachTo (this);
                                }
                        }
                }

                /// <summary>
                /// Use member-specific procedure to apply attribute @a in @cb to the entity being built in @builder
                /// </summary>
                public abstract void ApplyAttributeBuilder (Attribute a, CustomAttributeBuilder cb, PredefinedAttributes pa);

                /// <summary>
                /// Returns one AttributeTarget for this element.
                /// </summary>
                public abstract AttributeTargets AttributeTargets { get; }

                public abstract IResolveContext ResolveContext { get; }

                public abstract bool IsClsComplianceRequired ();

                /// <summary>
                /// Gets list of valid attribute targets for explicit target declaration.
                /// The first array item is default target. Don't break this rule.
                /// </summary>
                public abstract string[] ValidAttributeTargets { get; }
        };

        public class Attribute : Expression
        {
                //
                // Wraps owner resolve context, the owner is an attribute
                // parent and the rest is exactly same
                //
                struct AttributeResolveContext : IResolveContext
                {
                        readonly IResolveContext rc;

                        public AttributeResolveContext (IResolveContext rc)
                        {
                                this.rc = rc;
                        }

                        #region IResolveContext Members

                        public DeclSpace DeclContainer {
                                get {
                                        DeclSpace ds = rc as DeclSpace;
                                        if (ds == null)
                                                return rc.DeclContainer;

                                        return ds;
                                }
                        }

                        public bool IsInObsoleteScope {
                                get { return rc.IsInObsoleteScope; }
                        }

                        public bool IsInUnsafeScope {
                                get { return rc.IsInUnsafeScope; }
                        }

                        public DeclSpace GenericDeclContainer {
                                get { return rc.GenericDeclContainer; }
                        }

                        #endregion
                }

                public readonly string ExplicitTarget;
                public AttributeTargets Target;

                // TODO: remove this member
                public readonly string    Name;
                public readonly Expression LeftExpr;
                public readonly string Identifier;

                Arguments PosArguments;
                Arguments NamedArguments;

                bool resolve_error;
                readonly bool nameEscaped;

                // It can contain more onwers when the attribute is applied to multiple fiels.
                protected Attributable[] owners;

                static readonly AttributeUsageAttribute DefaultUsageAttribute = new AttributeUsageAttribute (AttributeTargets.All);
                static Assembly orig_sec_assembly;
                public static readonly object[] EmptyObject = new object [0];

                // non-null if named args present after Resolve () is called
                PropertyInfo [] prop_info_arr;
                FieldInfo [] field_info_arr;
                object [] field_values_arr;
                object [] prop_values_arr;
                object [] pos_values;

                static PtrHashtable usage_attr_cache;
                // Cache for parameter-less attributes
                static PtrHashtable att_cache;

                public Attribute (string target, Expression left_expr, string identifier, Arguments[] args, Location loc, bool nameEscaped)
                {
                        LeftExpr = left_expr;
                        Identifier = identifier;
                        Name = LeftExpr == null ? identifier : LeftExpr + "." + identifier;
                        if (args != null) {
                                PosArguments = args [0];
                                NamedArguments = args [1];                              
                        }
                        this.loc = loc;
                        ExplicitTarget = target;
                        this.nameEscaped = nameEscaped;
                }

                public Attribute Clone ()
                {
                        Attribute a = new Attribute (ExplicitTarget, LeftExpr, Identifier, null, loc, nameEscaped);
                        a.PosArguments = PosArguments;
                        a.NamedArguments = NamedArguments;
                        return a;
                }

                static Attribute ()
                {
                        Reset ();
                }

                public static void Reset ()
                {
                        usage_attr_cache = new PtrHashtable ();
                        att_cache = new PtrHashtable ();
                }

                public virtual void AttachTo (Attributable owner)
                {
                        if (this.owners == null) {
                                this.owners = new Attributable[1] { owner };
                                return;
                        }

                        // When the same attribute is attached to multiple fiels
                        // we use this extra_owners as a list of owners. The attribute
                        // then can be removed because will be emitted when first owner
                        // is served
                        Attributable[] new_array = new Attributable [this.owners.Length + 1];
                        owners.CopyTo (new_array, 0);
                        new_array [owners.Length] = owner;
                        this.owners = new_array;
                        owner.OptAttributes = null;
                }

                void Error_InvalidNamedArgument (NamedArgument name)
                {
                        Report.Error (617, name.Name.Location, "`{0}' is not a valid named attribute argument. Named attribute arguments " +
                                      "must be fields which are not readonly, static, const or read-write properties which are " +
                                      "public and not static",
                              name.Name.Value);
                }

                void Error_InvalidNamedArgumentType (NamedArgument name)
                {
                        Report.Error (655, name.Name.Location,
                                "`{0}' is not a valid named attribute argument because it is not a valid attribute parameter type",
                                name.Name.Value);
                }

                public static void Error_AttributeArgumentNotValid (Location loc)
                {
                        Report.Error (182, loc,
                                      "An attribute argument must be a constant expression, typeof " +
                                      "expression or array creation expression");
                }
                
                static void Error_TypeParameterInAttribute (Location loc)
                {
                        Report.Error (
                                -202, loc, "Can not use a type parameter in an attribute");
                }

                public void Error_MissingGuidAttribute ()
                {
                        Report.Error (596, Location, "The Guid attribute must be specified with the ComImport attribute");
                }

                public void Error_MisusedExtensionAttribute ()
                {
                        Report.Error (1112, Location, "Do not use `{0}' directly. Use parameter modifier `this' instead", GetSignatureForError ());
                }

                /// <summary>
                /// This is rather hack. We report many emit attribute error with same error to be compatible with
                /// csc. But because csc has to report them this way because error came from ilasm we needn't.
                /// </summary>
                public void Error_AttributeEmitError (string inner)
                {
                        Report.Error (647, Location, "Error during emitting `{0}' attribute. The reason is `{1}'",
                                      TypeManager.CSharpName (Type), inner);
                }

                public void Error_InvalidSecurityParent ()
                {
                        Error_AttributeEmitError ("it is attached to invalid parent");
                }

                Attributable Owner {
                        get {
                                return owners [0];
                        }
                }

                protected virtual TypeExpr ResolveAsTypeTerminal (Expression expr, IResolveContext ec, bool silent)
                {
                        return expr.ResolveAsTypeTerminal (ec, silent);
                }

                Type ResolvePossibleAttributeType (string name, bool silent, ref bool is_attr)
                {
                        IResolveContext rc = new AttributeResolveContext (Owner.ResolveContext);

                        TypeExpr te;
                        if (LeftExpr == null) {
                                te = ResolveAsTypeTerminal (new SimpleName (name, Location), rc, silent);
                        } else {
                                te = ResolveAsTypeTerminal (new MemberAccess (LeftExpr, name), rc, silent);
                        }

                        if (te == null)
                                return null;

                        Type t = te.Type;
                        if (TypeManager.IsSubclassOf (t, TypeManager.attribute_type)) {
                                is_attr = true;
                        } else if (!silent) {
                                Report.SymbolRelatedToPreviousError (t);
                                Report.Error (616, Location, "`{0}': is not an attribute class", TypeManager.CSharpName (t));
                        }
                        return t;
                }

                /// <summary>
                ///   Tries to resolve the type of the attribute. Flags an error if it can't, and complain is true.
                /// </summary>
                void ResolveAttributeType ()
                {
                        bool t1_is_attr = false;
                        Type t1 = ResolvePossibleAttributeType (Identifier, true, ref t1_is_attr);

                        bool t2_is_attr = false;
                        Type t2 = nameEscaped ? null :
                                ResolvePossibleAttributeType (Identifier + "Attribute", true, ref t2_is_attr);

                        if (t1_is_attr && t2_is_attr) {
                                Report.Error (1614, Location, "`{0}' is ambiguous between `{0}' and `{0}Attribute'. " +
                                              "Use either `@{0}' or `{0}Attribute'", GetSignatureForError ());
                                resolve_error = true;
                                return;
                        }

                        if (t1_is_attr) {
                                Type = t1;
                                return;
                        }

                        if (t2_is_attr) {
                                Type = t2;
                                return;
                        }

                        if (t1 == null && t2 == null)
                                ResolvePossibleAttributeType (Identifier, false, ref t1_is_attr);
                        if (t1 != null)
                                ResolvePossibleAttributeType (Identifier, false, ref t1_is_attr);
                        if (t2 != null)
                                ResolvePossibleAttributeType (Identifier + "Attribute", false, ref t2_is_attr);

                        resolve_error = true;
                }

                public virtual Type ResolveType ()
                {
                        if (Type == null && !resolve_error)
                                ResolveAttributeType ();
                        return Type;
                }

                public override string GetSignatureForError ()
                {
                        if (Type != null)
                                return TypeManager.CSharpName (Type);

                        return LeftExpr == null ? Identifier : LeftExpr.GetSignatureForError () + "." + Identifier;
                }

                public bool HasSecurityAttribute {
                        get {
                                PredefinedAttribute pa = PredefinedAttributes.Get.Security;
                                return pa.IsDefined && TypeManager.IsSubclassOf (type, pa.Type);
                        }
                }

                public bool IsValidSecurityAttribute ()
                {
                        return HasSecurityAttribute && IsSecurityActionValid (false);
                }

                static bool IsValidArgumentType (Type t)
                {
                        if (t.IsArray)
                                t = TypeManager.GetElementType (t);

                        return t == TypeManager.string_type ||
                                TypeManager.IsPrimitiveType (t) ||
                                TypeManager.IsEnumType (t) ||
                                t == TypeManager.object_type ||
                                t == TypeManager.type_type;
                }

                void ApplyModuleCharSet ()
                {
                        if (Type != PredefinedAttributes.Get.DllImport)
                                return;

                        if (!RootContext.ToplevelTypes.HasDefaultCharSet)
                                return;

                        const string CharSetEnumMember = "CharSet";
                        if (NamedArguments == null) {
                                NamedArguments = new Arguments (1);
                        } else {
                                foreach (NamedArgument a in NamedArguments) {
                                        if (a.Name.Value == CharSetEnumMember)
                                                return;
                                }
                        }
                        
                        NamedArguments.Add (new NamedArgument (new LocatedToken (loc, CharSetEnumMember),
                                Constant.CreateConstant (typeof (CharSet), RootContext.ToplevelTypes.DefaultCharSet, Location)));
                }

                public CustomAttributeBuilder Resolve ()
                {
                        if (resolve_error)
                                return null;

                        resolve_error = true;

                        if (Type == null) {
                                ResolveAttributeType ();
                                if (Type == null)
                                        return null;
                        }

                        if (Type.IsAbstract) {
                                Report.Error (653, Location, "Cannot apply attribute class `{0}' because it is abstract", GetSignatureForError ());
                                return null;
                        }

                        ObsoleteAttribute obsolete_attr = AttributeTester.GetObsoleteAttribute (Type);
                        if (obsolete_attr != null) {
                                AttributeTester.Report_ObsoleteMessage (obsolete_attr, TypeManager.CSharpName (Type), Location);
                        }

                        if (PosArguments == null && NamedArguments == null) {
                                object o = att_cache [Type];
                                if (o != null) {
                                        resolve_error = false;
                                        return (CustomAttributeBuilder)o;
                                }
                        }

                        Attributable owner = Owner;
                        DeclSpace ds = owner.ResolveContext as DeclSpace;
                        if (ds == null)
                                ds = owner.ResolveContext.DeclContainer;
                        
                        EmitContext ec = new EmitContext (owner.ResolveContext, ds, ds,
                                Location, null, typeof (Attribute), ds.ModFlags, false);
                        ec.IsAnonymousMethodAllowed = false;

                        ConstructorInfo ctor = ResolveConstructor (ec);
                        if (ctor == null) {
                                if (Type is TypeBuilder && 
                                    TypeManager.LookupDeclSpace (Type).MemberCache == null)
                                        // The attribute type has been DefineType'd, but not Defined.  Let's not treat it as an error.
                                        // It'll be resolved again when the attached-to entity is emitted.
                                        resolve_error = false;
                                return null;
                        }

                        ApplyModuleCharSet ();

                        CustomAttributeBuilder cb;
                        try {
                                // SRE does not allow private ctor but we want to report all source code errors
                                if (ctor.IsPrivate)
                                        return null;

                                if (NamedArguments == null) {
                                        cb = new CustomAttributeBuilder (ctor, pos_values);

                                        if (pos_values.Length == 0)
                                                att_cache.Add (Type, cb);

                                        resolve_error = false;
                                        return cb;
                                }

                                if (!ResolveNamedArguments (ec)) {
                                        return null;
                                }

                                cb = new CustomAttributeBuilder (ctor, pos_values,
                                                prop_info_arr, prop_values_arr,
                                                field_info_arr, field_values_arr);

                                resolve_error = false;
                                return cb;
                        }
                        catch (Exception) {
                                Error_AttributeArgumentNotValid (Location);
                                return null;
                        }
                }

                protected virtual ConstructorInfo ResolveConstructor (EmitContext ec)
                {
                        if (PosArguments != null)
                                PosArguments.Resolve (ec);

                        MethodGroupExpr mg = MemberLookupFinal (ec, ec.ContainerType,
                                Type, ConstructorInfo.ConstructorName, MemberTypes.Constructor,
                                BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly,
                                Location) as MethodGroupExpr;

                        if (mg == null)
                                throw new NotImplementedException ();

                        mg = mg.OverloadResolve (ec, ref PosArguments, false, Location);
                        if (mg == null)
                                return null;
                        
                        ConstructorInfo constructor = (ConstructorInfo)mg;
                        if (PosArguments == null) {
                                pos_values = EmptyObject;
                                return constructor;
                        }

                        AParametersCollection pd = TypeManager.GetParameterData (constructor);

                        if (!PosArguments.GetAttributableValue (ec, out pos_values))
                                return null;

                        // Here we do the checks which should be done by corlib or by runtime.
                        // However Zoltan doesn't like it and every Mono compiler has to do it again.
                        PredefinedAttributes pa = PredefinedAttributes.Get;
                        if (Type == pa.Guid) {
                                try {
                                        new Guid ((string)pos_values [0]);
                                }
                                catch (Exception e) {
                                        Error_AttributeEmitError (e.Message);
                                        return null;
                                }
                        }

                        if (Type == pa.AttributeUsage && (int)pos_values [0] == 0) {
                                Report.Error (591, Location, "Invalid value for argument to `System.AttributeUsage' attribute");
                                return null;
                        }

                        if (Type == pa.IndexerName || Type == pa.Conditional) {
                                string v = pos_values [0] as string;
                                if (!Tokenizer.IsValidIdentifier (v) || Tokenizer.IsKeyword (v)) {
                                        Report.Error (633, PosArguments [0].Expr.Location,
                                                "The argument to the `{0}' attribute must be a valid identifier", GetSignatureForError ());
                                        return null;
                                }
                        }

                        if (Type == pa.MethodImpl && pos_values.Length == 1 &&
                                pd.Types [0] == TypeManager.short_type &&
                                !System.Enum.IsDefined (typeof (MethodImplOptions), pos_values [0].ToString ())) {
                                Error_AttributeEmitError ("Incorrect argument value.");
                                return null;
                        }

                        return constructor;
                }

                protected virtual bool ResolveNamedArguments (EmitContext ec)
                {
                        int named_arg_count = NamedArguments.Count;

                        ArrayList field_infos = new ArrayList (named_arg_count);
                        ArrayList prop_infos  = new ArrayList (named_arg_count);
                        ArrayList field_values = new ArrayList (named_arg_count);
                        ArrayList prop_values = new ArrayList (named_arg_count);

                        ArrayList seen_names = new ArrayList (named_arg_count);
                        
                        foreach (NamedArgument a in NamedArguments) {
                                string name = a.Name.Value;
                                if (seen_names.Contains (name)) {
                                        Report.Error (643, a.Name.Location, "Duplicate named attribute `{0}' argument", name);
                                        continue;
                                }                       
        
                                seen_names.Add (name);

                                a.Resolve (ec);

                                Expression member = Expression.MemberLookup (
                                        ec.ContainerType, Type, name,
                                        MemberTypes.All,
                                        BindingFlags.Public | BindingFlags.Instance | BindingFlags.Static,
                                        Location);

                                if (member == null) {
                                        member = Expression.MemberLookup (ec.ContainerType, Type, name,
                                                MemberTypes.All, BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Static,
                                                Location);

                                        if (member != null) {
                                                Report.SymbolRelatedToPreviousError (member.Type);
                                                Expression.ErrorIsInaccesible (Location, member.GetSignatureForError ());
                                                return false;
                                        }
                                }

                                if (member == null){
                                        Expression.Error_TypeDoesNotContainDefinition (Location, Type, name);
                                        return false;
                                }
                                
                                if (!(member is PropertyExpr || member is FieldExpr)) {
                                        Error_InvalidNamedArgument (a);
                                        return false;
                                }

                                if (a.Expr is TypeParameterExpr){
                                        Error_TypeParameterInAttribute (Location);
                                        return false;
                                }

                                ObsoleteAttribute obsolete_attr;

                                if (member is PropertyExpr) {
                                        PropertyInfo pi = ((PropertyExpr) member).PropertyInfo;

                                        if (!pi.CanWrite || !pi.CanRead || pi.GetGetMethod ().IsStatic) {
                                                Report.SymbolRelatedToPreviousError (pi);
                                                Error_InvalidNamedArgument (a);
                                                return false;
                                        }

                                        if (!IsValidArgumentType (member.Type)) {
                                                Report.SymbolRelatedToPreviousError (pi);
                                                Error_InvalidNamedArgumentType (a);
                                                return false;
                                        }

                                        object value;
                                        if (!a.Expr.GetAttributableValue (ec, member.Type, out value))
                                                return false;

                                        PropertyBase pb = TypeManager.GetProperty (pi);
                                        if (pb != null)
                                                obsolete_attr = pb.GetObsoleteAttribute ();
                                        else
                                                obsolete_attr = AttributeTester.GetMemberObsoleteAttribute (pi);

                                        prop_values.Add (value);
                                        prop_infos.Add (pi);
                                        
                                } else {
                                        FieldInfo fi = ((FieldExpr) member).FieldInfo;

                                        if (fi.IsInitOnly || fi.IsStatic) {
                                                Error_InvalidNamedArgument (a);
                                                return false;
                                        }

                                        if (!IsValidArgumentType (member.Type)) {
                                                Report.SymbolRelatedToPreviousError (fi);
                                                Error_InvalidNamedArgumentType (a);
                                                return false;
                                        }

                                        object value;
                                        if (!a.Expr.GetAttributableValue (ec, member.Type, out value))
                                                return false;

                                        FieldBase fb = TypeManager.GetField (fi);
                                        if (fb != null)
                                                obsolete_attr = fb.GetObsoleteAttribute ();
                                        else
                                                obsolete_attr = AttributeTester.GetMemberObsoleteAttribute (fi);

                                        field_values.Add (value);                                       
                                        field_infos.Add (fi);
                                }

                                if (obsolete_attr != null && !Owner.ResolveContext.IsInObsoleteScope)
                                        AttributeTester.Report_ObsoleteMessage (obsolete_attr, member.GetSignatureForError (), member.Location);
                        }

                        prop_info_arr = new PropertyInfo [prop_infos.Count];
                        field_info_arr = new FieldInfo [field_infos.Count];
                        field_values_arr = new object [field_values.Count];
                        prop_values_arr = new object [prop_values.Count];

                        field_infos.CopyTo  (field_info_arr, 0);
                        field_values.CopyTo (field_values_arr, 0);

                        prop_values.CopyTo  (prop_values_arr, 0);
                        prop_infos.CopyTo   (prop_info_arr, 0);

                        return true;
                }

                /// <summary>
                ///   Get a string containing a list of valid targets for the attribute 'attr'
                /// </summary>
                public string GetValidTargets ()
                {
                        StringBuilder sb = new StringBuilder ();
                        AttributeTargets targets = GetAttributeUsage (Type).ValidOn;

                        if ((targets & AttributeTargets.Assembly) != 0)
                                sb.Append ("assembly, ");

                        if ((targets & AttributeTargets.Module) != 0)
                                sb.Append ("module, ");

                        if ((targets & AttributeTargets.Class) != 0)
                                sb.Append ("class, ");

                        if ((targets & AttributeTargets.Struct) != 0)
                                sb.Append ("struct, ");

                        if ((targets & AttributeTargets.Enum) != 0)
                                sb.Append ("enum, ");

                        if ((targets & AttributeTargets.Constructor) != 0)
                                sb.Append ("constructor, ");

                        if ((targets & AttributeTargets.Method) != 0)
                                sb.Append ("method, ");

                        if ((targets & AttributeTargets.Property) != 0)
                                sb.Append ("property, indexer, ");

                        if ((targets & AttributeTargets.Field) != 0)
                                sb.Append ("field, ");

                        if ((targets & AttributeTargets.Event) != 0)
                                sb.Append ("event, ");

                        if ((targets & AttributeTargets.Interface) != 0)
                                sb.Append ("interface, ");

                        if ((targets & AttributeTargets.Parameter) != 0)
                                sb.Append ("parameter, ");

                        if ((targets & AttributeTargets.Delegate) != 0)
                                sb.Append ("delegate, ");

                        if ((targets & AttributeTargets.ReturnValue) != 0)
                                sb.Append ("return, ");

#if NET_2_0
                        if ((targets & AttributeTargets.GenericParameter) != 0)
                                sb.Append ("type parameter, ");
#endif                  
                        return sb.Remove (sb.Length - 2, 2).ToString ();
                }

                /// <summary>
                /// Returns AttributeUsage attribute based on types hierarchy
                /// </summary>
                static AttributeUsageAttribute GetAttributeUsage (Type type)
                {
                        AttributeUsageAttribute ua = usage_attr_cache [type] as AttributeUsageAttribute;
                        if (ua != null)
                                return ua;

                        Class attr_class = TypeManager.LookupClass (type);
                        PredefinedAttribute pa = PredefinedAttributes.Get.AttributeUsage;

                        if (attr_class == null) {
                                if (!pa.IsDefined)
                                        return new AttributeUsageAttribute (0);

                                object[] usage_attr = type.GetCustomAttributes (pa.Type, true);
                                ua = (AttributeUsageAttribute)usage_attr [0];
                                usage_attr_cache.Add (type, ua);
                                return ua;
                        }

                        Attribute a = null;
                        if (attr_class.OptAttributes != null)
                                a = attr_class.OptAttributes.Search (pa);

                        if (a == null) {
                                if (attr_class.TypeBuilder.BaseType != TypeManager.attribute_type)
                                        ua = GetAttributeUsage (attr_class.TypeBuilder.BaseType);
                                else
                                        ua = DefaultUsageAttribute;
                        } else {
                                ua = a.GetAttributeUsageAttribute ();
                        }

                        usage_attr_cache.Add (type, ua);
                        return ua;
                }

                AttributeUsageAttribute GetAttributeUsageAttribute ()
                {
                        if (pos_values == null)
                                // TODO: It is not neccessary to call whole Resolve (ApplyAttribute does it now) we need only ctor args.
                                // But because a lot of attribute class code must be rewritten will be better to wait...
                                Resolve ();

                        if (resolve_error)
                                return DefaultUsageAttribute;

                        AttributeUsageAttribute usage_attribute = new AttributeUsageAttribute ((AttributeTargets)pos_values [0]);

                        object field = GetPropertyValue ("AllowMultiple");
                        if (field != null)
                                usage_attribute.AllowMultiple = (bool)field;

                        field = GetPropertyValue ("Inherited");
                        if (field != null)
                                usage_attribute.Inherited = (bool)field;

                        return usage_attribute;
                }

                /// <summary>
                /// Returns custom name of indexer
                /// </summary>
                public string GetIndexerAttributeValue ()
                {
                        if (pos_values == null)
                                // TODO: It is not neccessary to call whole Resolve (ApplyAttribute does it now) we need only ctor args.
                                // But because a lot of attribute class code must be rewritten will be better to wait...
                                Resolve ();

                        if (resolve_error)
                                return null;

                        return pos_values [0] as string;
                }

                /// <summary>
                /// Returns condition of ConditionalAttribute
                /// </summary>
                public string GetConditionalAttributeValue ()
                {
                        if (pos_values == null)
                                // TODO: It is not neccessary to call whole Resolve (ApplyAttribute does it now) we need only ctor args.
                                // But because a lot of attribute class code must be rewritten will be better to wait...
                                Resolve ();

                        if (resolve_error)
                                return null;

                        return (string)pos_values [0];
                }

                /// <summary>
                /// Creates the instance of ObsoleteAttribute from this attribute instance
                /// </summary>
                public ObsoleteAttribute GetObsoleteAttribute ()
                {
                        if (pos_values == null)
                                // TODO: It is not neccessary to call whole Resolve (ApplyAttribute does it now) we need only ctor args.
                                // But because a lot of attribute class code must be rewritten will be better to wait...
                                Resolve ();

                        if (resolve_error)
                                return null;

                        if (pos_values == null || pos_values.Length == 0)
                                return new ObsoleteAttribute ();

                        if (pos_values.Length == 1)
                                return new ObsoleteAttribute ((string)pos_values [0]);

                        return new ObsoleteAttribute ((string)pos_values [0], (bool)pos_values [1]);
                }

                /// <summary>
                /// Returns value of CLSCompliantAttribute contructor parameter but because the method can be called
                /// before ApplyAttribute. We need to resolve the arguments.
                /// This situation occurs when class deps is differs from Emit order.  
                /// </summary>
                public bool GetClsCompliantAttributeValue ()
                {
                        if (pos_values == null)
                                // TODO: It is not neccessary to call whole Resolve (ApplyAttribute does it now) we need only ctor args.
                                // But because a lot of attribute class code must be rewritten will be better to wait...
                                Resolve ();

                        if (resolve_error)
                                return false;

                        return (bool)pos_values [0];
                }

                public Type GetCoClassAttributeValue ()
                {
                        if (pos_values == null)
                                Resolve ();

                        if (resolve_error)
                                return null;

                        return (Type)pos_values [0];
                }

                public bool CheckTarget ()
                {
                        string[] valid_targets = Owner.ValidAttributeTargets;
                        if (ExplicitTarget == null || ExplicitTarget == valid_targets [0]) {
                                Target = Owner.AttributeTargets;
                                return true;
                        }

                        // TODO: we can skip the first item
                        if (((IList) valid_targets).Contains (ExplicitTarget)) {
                                switch (ExplicitTarget) {
                                case "return": Target = AttributeTargets.ReturnValue; return true;
                                case "param": Target = AttributeTargets.Parameter; return true;
                                case "field": Target = AttributeTargets.Field; return true;
                                case "method": Target = AttributeTargets.Method; return true;
                                case "property": Target = AttributeTargets.Property; return true;
                                }
                                throw new InternalErrorException ("Unknown explicit target: " + ExplicitTarget);
                        }
                                
                        StringBuilder sb = new StringBuilder ();
                        foreach (string s in valid_targets) {
                                sb.Append (s);
                                sb.Append (", ");
                        }
                        sb.Remove (sb.Length - 2, 2);
                        Report.Error (657, Location, "`{0}' is not a valid attribute location for this declaration. " +
                                "Valid attribute locations for this declaration are `{1}'", ExplicitTarget, sb.ToString ());
                        return false;
                }

                /// <summary>
                /// Tests permitted SecurityAction for assembly or other types
                /// </summary>
                protected virtual bool IsSecurityActionValid (bool for_assembly)
                {
                        SecurityAction action = GetSecurityActionValue ();

                        switch (action) {
                        case SecurityAction.Demand:
                        case SecurityAction.Assert:
                        case SecurityAction.Deny:
                        case SecurityAction.PermitOnly:
                        case SecurityAction.LinkDemand:
                        case SecurityAction.InheritanceDemand:
                                if (!for_assembly)
                                        return true;
                                break;

                        case SecurityAction.RequestMinimum:
                        case SecurityAction.RequestOptional:
                        case SecurityAction.RequestRefuse:
                                if (for_assembly)
                                        return true;
                                break;

                        default:
                                Error_AttributeEmitError ("SecurityAction is out of range");
                                return false;
                        }

                        Error_AttributeEmitError (String.Concat ("SecurityAction `", action, "' is not valid for this declaration"));
                        return false;
                }

                System.Security.Permissions.SecurityAction GetSecurityActionValue ()
                {
                        return (SecurityAction)pos_values [0];
                }

                /// <summary>
                /// Creates instance of SecurityAttribute class and add result of CreatePermission method to permission table.
                /// </summary>
                /// <returns></returns>
                public void ExtractSecurityPermissionSet (ListDictionary permissions)
                {
                        Type orig_assembly_type = null;

                        if (TypeManager.LookupDeclSpace (Type) != null) {
                                if (!RootContext.StdLib) {
                                        orig_assembly_type = Type.GetType (Type.FullName);
                                } else {
                                        string orig_version_path = Environment.GetEnvironmentVariable ("__SECURITY_BOOTSTRAP_DB");
                                        if (orig_version_path == null) {
                                                Error_AttributeEmitError ("security custom attributes can not be referenced from defining assembly");
                                                return;
                                        }

                                        if (orig_sec_assembly == null) {
                                                string file = Path.Combine (orig_version_path, Driver.OutputFile);
                                                orig_sec_assembly = Assembly.LoadFile (file);
                                        }

                                        orig_assembly_type = orig_sec_assembly.GetType (Type.FullName, true);
                                        if (orig_assembly_type == null) {
                                                Report.Warning (-112, 1, Location, "Self-referenced security attribute `{0}' " +
                                                                "was not found in previous version of assembly");
                                                return;
                                        }
                                }
                        }

                        SecurityAttribute sa;
                        // For all non-selfreferencing security attributes we can avoid all hacks
                        if (orig_assembly_type == null) {
                                sa = (SecurityAttribute) Activator.CreateInstance (Type, pos_values);

                                if (prop_info_arr != null) {
                                        for (int i = 0; i < prop_info_arr.Length; ++i) {
                                                PropertyInfo pi = prop_info_arr [i];
                                                pi.SetValue (sa, prop_values_arr [i], null);
                                        }
                                }
                        } else {
                                // HACK: All security attributes have same ctor syntax
                                sa = (SecurityAttribute) Activator.CreateInstance (orig_assembly_type, new object[] { GetSecurityActionValue () } );

                                // All types are from newly created assembly but for invocation with old one we need to convert them
                                if (prop_info_arr != null) {
                                        for (int i = 0; i < prop_info_arr.Length; ++i) {
                                                PropertyInfo emited_pi = prop_info_arr [i];
                                                // FIXME: We are missing return type filter
                                                // TODO: pi can be null
                                                PropertyInfo pi = orig_assembly_type.GetProperty (emited_pi.Name);

                                                object old_instance = TypeManager.IsEnumType (pi.PropertyType) ?
                                                        System.Enum.ToObject (pi.PropertyType, prop_values_arr [i]) :
                                                        prop_values_arr [i];

                                                pi.SetValue (sa, old_instance, null);
                                        }
                                }
                        }

                        IPermission perm;
                        perm = sa.CreatePermission ();
                        SecurityAction action = GetSecurityActionValue ();

                        // IS is correct because for corlib we are using an instance from old corlib
                        if (!(perm is System.Security.CodeAccessPermission)) {
                                switch (action) {
                                case SecurityAction.Demand:
                                        action = (SecurityAction)13;
                                        break;
                                case SecurityAction.LinkDemand:
                                        action = (SecurityAction)14;
                                        break;
                                case SecurityAction.InheritanceDemand:
                                        action = (SecurityAction)15;
                                        break;
                                }
                        }

                        PermissionSet ps = (PermissionSet)permissions [action];
                        if (ps == null) {
                                if (sa is PermissionSetAttribute)
                                        ps = new PermissionSet (sa.Unrestricted ? PermissionState.Unrestricted : PermissionState.None);
                                else
                                        ps = new PermissionSet (PermissionState.None);

                                permissions.Add (action, ps);
                        } else if (!ps.IsUnrestricted () && (sa is PermissionSetAttribute) && sa.Unrestricted) {
                                ps = ps.Union (new PermissionSet (PermissionState.Unrestricted));
                                permissions [action] = ps;
                        }
                        ps.AddPermission (perm);
                }

                public object GetPropertyValue (string name)
                {
                        if (prop_info_arr == null)
                                return null;

                        for (int i = 0; i < prop_info_arr.Length; ++i) {
                                if (prop_info_arr [i].Name == name)
                                        return prop_values_arr [i];
                        }

                        return null;
                }

                //
                // Theoretically, we can get rid of this, since FieldBuilder.SetCustomAttribute()
                // and ParameterBuilder.SetCustomAttribute() are supposed to handle this attribute.
                // However, we can't, since it appears that the .NET 1.1 SRE hangs when given a MarshalAsAttribute.
                //
#if !NET_2_0
                public UnmanagedMarshal GetMarshal (Attributable attr)
                {
                        UnmanagedType UnmanagedType;
                        if (!RootContext.StdLib || pos_values [0].GetType () != typeof (UnmanagedType))
                                UnmanagedType = (UnmanagedType) System.Enum.ToObject (typeof (UnmanagedType), pos_values [0]);
                        else
                                UnmanagedType = (UnmanagedType) pos_values [0];

                        object value = GetFieldValue ("SizeParamIndex");
                        if (value != null && UnmanagedType != UnmanagedType.LPArray) {
                                Error_AttributeEmitError ("SizeParamIndex field is not valid for the specified unmanaged type");
                                return null;
                        }

                        object o = GetFieldValue ("ArraySubType");
                        UnmanagedType array_sub_type = o == null ? (UnmanagedType) 0x50 /* NATIVE_MAX */ : (UnmanagedType) o;

                        switch (UnmanagedType) {
                        case UnmanagedType.CustomMarshaler: {
                                MethodInfo define_custom = typeof (UnmanagedMarshal).GetMethod ("DefineCustom",
                                        BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
                                if (define_custom == null) {
                                        Report.RuntimeMissingSupport (Location, "set marshal info");
                                        return null;
                                }
                                
                                object [] args = new object [4];
                                args [0] = GetFieldValue ("MarshalTypeRef");
                                args [1] = GetFieldValue ("MarshalCookie");
                                args [2] = GetFieldValue ("MarshalType");
                                args [3] = Guid.Empty;
                                return (UnmanagedMarshal) define_custom.Invoke (null, args);
                        }
                        case UnmanagedType.LPArray: {
                                object size_const = GetFieldValue ("SizeConst");
                                object size_param_index = GetFieldValue ("SizeParamIndex");

                                if ((size_const != null) || (size_param_index != null)) {
                                        MethodInfo define_array = typeof (UnmanagedMarshal).GetMethod ("DefineLPArrayInternal",
                                                BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
                                        if (define_array == null) {
                                                Report.RuntimeMissingSupport (Location, "set marshal info");
                                                return null;
                                        }
                                
                                        object [] args = new object [3];
                                        args [0] = array_sub_type;
                                        args [1] = size_const == null ? -1 : size_const;
                                        args [2] = size_param_index == null ? -1 : size_param_index;
                                        return (UnmanagedMarshal) define_array.Invoke (null, args);
                                }
                                else
                                        return UnmanagedMarshal.DefineLPArray (array_sub_type);
                        }
                        case UnmanagedType.SafeArray:
                                return UnmanagedMarshal.DefineSafeArray (array_sub_type);

                        case UnmanagedType.ByValArray:
                                FieldBase fm = attr as FieldBase;
                                if (fm == null) {
                                        Error_AttributeEmitError ("Specified unmanaged type is only valid on fields");
                                        return null;
                                }
                                return UnmanagedMarshal.DefineByValArray ((int) GetFieldValue ("SizeConst"));

                        case UnmanagedType.ByValTStr:
                                return UnmanagedMarshal.DefineByValTStr ((int) GetFieldValue ("SizeConst"));

                        default:
                                return UnmanagedMarshal.DefineUnmanagedMarshal (UnmanagedType);
                        }
                }

                object GetFieldValue (string name)
                {
                        int i;
                        if (field_info_arr == null)
                                return null;
                        i = 0;
                        foreach (FieldInfo fi in field_info_arr) {
                                if (fi.Name == name)
                                        return GetValue (field_values_arr [i]);
                                i++;
                        }
                        return null;
                }

                static object GetValue (object value)
                {
                        if (value is EnumConstant)
                                return ((EnumConstant) value).GetValue ();
                        else
                                return value;                           
                }
                
#endif

                public CharSet GetCharSetValue ()
                {
                        return (CharSet)System.Enum.Parse (typeof (CharSet), pos_values [0].ToString ());
                }

                public bool HasField (string fieldName)
                {
                        if (field_info_arr == null)
                                return false;

                        foreach (FieldInfo fi in field_info_arr) {
                                if (fi.Name == fieldName)
                                        return true;
                        }

                        return false;
                }

                public bool IsInternalMethodImplAttribute {
                        get {
                                if (Type != PredefinedAttributes.Get.MethodImpl)
                                        return false;

                                MethodImplOptions options;
                                if (pos_values[0].GetType () != typeof (MethodImplOptions))
                                        options = (MethodImplOptions)System.Enum.ToObject (typeof (MethodImplOptions), pos_values[0]);
                                else
                                        options = (MethodImplOptions)pos_values[0];

                                return (options & MethodImplOptions.InternalCall) != 0;
                        }
                }

                public LayoutKind GetLayoutKindValue ()
                {
                        if (!RootContext.StdLib || pos_values [0].GetType () != typeof (LayoutKind))
                                return (LayoutKind)System.Enum.ToObject (typeof (LayoutKind), pos_values [0]);

                        return (LayoutKind)pos_values [0];
                }

                public object GetParameterDefaultValue ()
                {
                        return pos_values [0];
                }

                public override bool Equals (object obj)
                {
                        Attribute a = obj as Attribute;
                        if (a == null)
                                return false;

                        return Type == a.Type && Target == a.Target;
                }

                public override int GetHashCode ()
                {
                        return base.GetHashCode ();
                }

                /// <summary>
                /// Emit attribute for Attributable symbol
                /// </summary>
                public void Emit (ListDictionary allEmitted)
                {
                        CustomAttributeBuilder cb = Resolve ();
                        if (cb == null)
                                return;

                        AttributeUsageAttribute usage_attr = GetAttributeUsage (Type);
                        if ((usage_attr.ValidOn & Target) == 0) {
                                Report.Error (592, Location, "The attribute `{0}' is not valid on this declaration type. " +
                                              "It is valid on `{1}' declarations only",
                                        GetSignatureForError (), GetValidTargets ());
                                return;
                        }

                        try {
                                foreach (Attributable owner in owners)
                                        owner.ApplyAttributeBuilder (this, cb, PredefinedAttributes.Get);
                        }
                        catch (Exception e) {
                                Error_AttributeEmitError (e.Message);
                                return;
                        }

                        if (!usage_attr.AllowMultiple && allEmitted != null) {
                                if (allEmitted.Contains (this)) {
                                        ArrayList a = allEmitted [this] as ArrayList;
                                        if (a == null) {
                                                a = new ArrayList (2);
                                                allEmitted [this] = a;
                                        }
                                        a.Add (this);
                                } else {
                                        allEmitted.Add (this, null);
                                }
                        }

                        if (!RootContext.VerifyClsCompliance)
                                return;

                        // Here we are testing attribute arguments for array usage (error 3016)
                        if (Owner.IsClsComplianceRequired ()) {
                                if (PosArguments != null)
                                        PosArguments.CheckArrayAsAttribute ();
                        
                                if (NamedArguments == null)
                                        return;

                                NamedArguments.CheckArrayAsAttribute ();
                        }
                }

                private Expression GetValue () 
                {
                        if (PosArguments == null || PosArguments.Count < 1)
                                return null;

                        return PosArguments [0].Expr;
                }

                public string GetString () 
                {
                        Expression e = GetValue ();
                        if (e is StringConstant)
                                return ((StringConstant)e).Value;
                        return null;
                }

                public bool GetBoolean () 
                {
                        Expression e = GetValue ();
                        if (e is BoolConstant)
                                return ((BoolConstant)e).Value;
                        return false;
                }

                public Type GetArgumentType ()
                {
                        TypeOf e = GetValue () as TypeOf;
                        if (e == null)
                                return null;
                        return e.TypeArgument;
                }

                public override Expression CreateExpressionTree (EmitContext ec)
                {
                        throw new NotSupportedException ("ET");
                }

                public override Expression DoResolve (EmitContext ec)
                {
                        throw new NotImplementedException ();
                }

                public override void Emit (EmitContext ec)
                {
                        throw new NotImplementedException ();
                }
        }
        

        /// <summary>
        /// For global attributes (assembly, module) we need special handling.
        /// Attributes can be located in the several files
        /// </summary>
        public class GlobalAttribute : Attribute
        {
                public readonly NamespaceEntry ns;

                public GlobalAttribute (NamespaceEntry ns, string target, 
                                        Expression left_expr, string identifier, Arguments[] args, Location loc, bool nameEscaped):
                        base (target, left_expr, identifier, args, loc, nameEscaped)
                {
                        this.ns = ns;
                        this.owners = new Attributable[1];
                }
                
                public override void AttachTo (Attributable owner)
                {
                        if (ExplicitTarget == "assembly") {
                                owners [0] = CodeGen.Assembly;
                                return;
                        }
                        if (ExplicitTarget == "module") {
                                owners [0] = RootContext.ToplevelTypes;
                                return;
                        }
                        throw new NotImplementedException ("Unknown global explicit target " + ExplicitTarget);
                }

                void Enter ()
                {
                        // RootContext.ToplevelTypes has a single NamespaceEntry which gets overwritten
                        // each time a new file is parsed.  However, we need to use the NamespaceEntry
                        // in effect where the attribute was used.  Since code elsewhere cannot assume
                        // that the NamespaceEntry is right, just overwrite it.
                        //
                        // Precondition: RootContext.ToplevelTypes == null

                        if (RootContext.ToplevelTypes.NamespaceEntry != null)
                                throw new InternalErrorException (Location + " non-null NamespaceEntry");

                        RootContext.ToplevelTypes.NamespaceEntry = ns;
                }

                protected override bool IsSecurityActionValid (bool for_assembly)
                {
                        return base.IsSecurityActionValid (true);
                }

                void Leave ()
                {
                        RootContext.ToplevelTypes.NamespaceEntry = null;
                }

                protected override TypeExpr ResolveAsTypeTerminal (Expression expr, IResolveContext ec, bool silent)
                {
                        try {
                                Enter ();
                                return base.ResolveAsTypeTerminal (expr, ec, silent);
                        }
                        finally {
                                Leave ();
                        }
                }

                protected override ConstructorInfo ResolveConstructor (EmitContext ec)
                {
                        try {
                                Enter ();
                                return base.ResolveConstructor (ec);
                        }
                        finally {
                                Leave ();
                        }
                }

                protected override bool ResolveNamedArguments (EmitContext ec)
                {
                        try {
                                Enter ();
                                return base.ResolveNamedArguments (ec);
                        }
                        finally {
                                Leave ();
                        }
                }
        }

        public class Attributes {
                public readonly ArrayList Attrs;

                public Attributes (Attribute a)
                {
                        Attrs = new ArrayList ();
                        Attrs.Add (a);
                }

                public Attributes (ArrayList attrs)
                {
                        Attrs = attrs;
                }

                public void AddAttributes (ArrayList attrs)
                {
                        Attrs.AddRange (attrs);
                }

                public void AttachTo (Attributable attributable)
                {
                        foreach (Attribute a in Attrs)
                                a.AttachTo (attributable);
                }

                public Attributes Clone ()
                {
                        ArrayList al = new ArrayList (Attrs.Count);
                        foreach (Attribute a in Attrs)
                                al.Add (a.Clone ());

                        return new Attributes (al);
                }

                /// <summary>
                /// Checks whether attribute target is valid for the current element
                /// </summary>
                public bool CheckTargets ()
                {
                        foreach (Attribute a in Attrs) {
                                if (!a.CheckTarget ())
                                        return false;
                        }
                        return true;
                }

                public Attribute Search (PredefinedAttribute t)
                {
                        foreach (Attribute a in Attrs) {
                                if (a.ResolveType () == t)
                                        return a;
                        }
                        return null;
                }

                /// <summary>
                /// Returns all attributes of type 't'. Use it when attribute is AllowMultiple = true
                /// </summary>
                public Attribute[] SearchMulti (PredefinedAttribute t)
                {
                        ArrayList ar = null;

                        foreach (Attribute a in Attrs) {
                                if (a.ResolveType () == t) {
                                        if (ar == null)
                                                ar = new ArrayList ();
                                        ar.Add (a);
                                }
                        }

                        return ar == null ? null : ar.ToArray (typeof (Attribute)) as Attribute[];
                }

                public void Emit ()
                {
                        CheckTargets ();

                        ListDictionary ld = Attrs.Count > 1 ? new ListDictionary () : null;

                        foreach (Attribute a in Attrs)
                                a.Emit (ld);

                        if (ld == null || ld.Count == 0)
                                return;

                        foreach (DictionaryEntry d in ld) {
                                if (d.Value == null)
                                        continue;

                                foreach (Attribute collision in (ArrayList)d.Value)
                                        Report.SymbolRelatedToPreviousError (collision.Location, "");

                                Attribute a = (Attribute)d.Key;
                                Report.Error (579, a.Location, "The attribute `{0}' cannot be applied multiple times",
                                        a.GetSignatureForError ());
                        }
                }

                public bool Contains (PredefinedAttribute t)
                {
                        return Search (t) != null;
                }
        }

        /// <summary>
        /// Helper class for attribute verification routine.
        /// </summary>
        sealed class AttributeTester
        {
                static PtrHashtable analyzed_types;
                static PtrHashtable analyzed_types_obsolete;
                static PtrHashtable analyzed_member_obsolete;
                static PtrHashtable analyzed_method_excluded;
                static PtrHashtable fixed_buffer_cache;

                static object TRUE = new object ();
                static object FALSE = new object ();

                static AttributeTester ()
                {
                        Reset ();
                }

                private AttributeTester ()
                {
                }

                public static void Reset ()
                {
                        analyzed_types = new PtrHashtable ();
                        analyzed_types_obsolete = new PtrHashtable ();
                        analyzed_member_obsolete = new PtrHashtable ();
                        analyzed_method_excluded = new PtrHashtable ();
                        fixed_buffer_cache = new PtrHashtable ();
                }

                public enum Result {
                        Ok,
                        RefOutArrayError,
                        ArrayArrayError
                }

                /// <summary>
                /// Returns true if parameters of two compared methods are CLS-Compliant.
                /// It tests differing only in ref or out, or in array rank.
                /// </summary>
                public static Result AreOverloadedMethodParamsClsCompliant (AParametersCollection pa, AParametersCollection pb) 
                {
                        Type [] types_a = pa.Types;
                        Type [] types_b = pb.Types;
                        if (types_a == null || types_b == null)
                                return Result.Ok;

                        if (types_a.Length != types_b.Length)
                                return Result.Ok;

                        Result result = Result.Ok;
                        for (int i = 0; i < types_b.Length; ++i) {
                                Type aType = types_a [i];
                                Type bType = types_b [i];

                                if (aType.IsArray && bType.IsArray) {
                                        Type a_el_type = TypeManager.GetElementType (aType);
                                        Type b_el_type = TypeManager.GetElementType (bType);
                                        if (aType.GetArrayRank () != bType.GetArrayRank () && a_el_type == b_el_type) {
                                                result = Result.RefOutArrayError;
                                                continue;
                                        }

                                        if (a_el_type.IsArray || b_el_type.IsArray) {
                                                result = Result.ArrayArrayError;
                                                continue;
                                        }
                                }

                                if (aType != bType)
                                        return Result.Ok;

                                const Parameter.Modifier out_ref_mod = (Parameter.Modifier.OUTMASK | Parameter.Modifier.REFMASK);
                                if ((pa.FixedParameters[i].ModFlags & out_ref_mod) != (pb.FixedParameters[i].ModFlags & out_ref_mod))
                                        result = Result.RefOutArrayError;
                        }
                        return result;
                }

                /// <summary>
                /// This method tests the CLS compliance of external types. It doesn't test type visibility.
                /// </summary>
                public static bool IsClsCompliant (Type type) 
                {
                        if (type == null)
                                return true;

                        object type_compliance = analyzed_types[type];
                        if (type_compliance != null)
                                return type_compliance == TRUE;

                        if (type.IsPointer) {
                                analyzed_types.Add (type, FALSE);
                                return false;
                        }

                        bool result;
                        if (type.IsArray) {
                                result = IsClsCompliant (TypeManager.GetElementType (type));
                        } else if (TypeManager.IsNullableType (type)) {
                                result = IsClsCompliant (TypeManager.GetTypeArguments (type) [0]);
                        } else {
                                result = AnalyzeTypeCompliance (type);
                        }
                        analyzed_types.Add (type, result ? TRUE : FALSE);
                        return result;
                }        
        
                /// <summary>
                /// Returns IFixedBuffer implementation if field is fixed buffer else null.
                /// </summary>
                public static IFixedBuffer GetFixedBuffer (FieldInfo fi)
                {
                        // Fixed buffer helper type is generated as value type
                        if (TypeManager.IsReferenceType (fi.FieldType))
                                return null;

                        FieldBase fb = TypeManager.GetField (fi);
                        if (fb != null) {
                                return fb as IFixedBuffer;
                        }
                        
                        if (TypeManager.GetConstant (fi) != null)
                                return null;

                        object o = fixed_buffer_cache [fi];
                        if (o == null) {
                                PredefinedAttribute pa = PredefinedAttributes.Get.FixedBuffer;
                                if (!pa.IsDefined)
                                        return null;

                                if (!fi.IsDefined (pa.Type, false)) {
                                        fixed_buffer_cache.Add (fi, FALSE);
                                        return null;
                                }
                                
                                IFixedBuffer iff = new FixedFieldExternal (fi);
                                fixed_buffer_cache.Add (fi, iff);
                                return iff;
                        }

                        if (o == FALSE)
                                return null;

                        return (IFixedBuffer)o;
                }

                public static void VerifyModulesClsCompliance ()
                {
                        Module[] modules = GlobalRootNamespace.Instance.Modules;
                        if (modules == null)
                                return;

                        // The first module is generated assembly
                        for (int i = 1; i < modules.Length; ++i) {
                                Module module = modules [i];
                                if (!GetClsCompliantAttributeValue (module, null)) {
                                        Report.Error (3013, "Added modules must be marked with the CLSCompliant attribute " +
                                                      "to match the assembly", module.Name);
                                        return;
                                }
                        }
                }

                public static Type GetImportedIgnoreCaseClsType (string name)
                {
                        foreach (Assembly a in GlobalRootNamespace.Instance.Assemblies) {
                                Type t = a.GetType (name, false, true);
                                if (t == null)
                                        continue;

                                if (IsClsCompliant (t))
                                        return t;
                        }
                        return null;
                }

                static bool GetClsCompliantAttributeValue (ICustomAttributeProvider attribute_provider, Assembly a) 
                {
                        PredefinedAttribute pa = PredefinedAttributes.Get.CLSCompliant;
                        if (!pa.IsDefined)
                                return false;

                        object[] cls_attr = attribute_provider.GetCustomAttributes (pa.Type, false);
                        if (cls_attr.Length == 0) {
                                if (a == null)
                                        return false;

                                return GetClsCompliantAttributeValue (a, null);
                        }
                        
                        return ((CLSCompliantAttribute)cls_attr [0]).IsCompliant;
                }

                static bool AnalyzeTypeCompliance (Type type)
                {
                        type = TypeManager.DropGenericTypeArguments (type);
                        DeclSpace ds = TypeManager.LookupDeclSpace (type);
                        if (ds != null) {
                                return ds.IsClsComplianceRequired ();
                        }

                        if (TypeManager.IsGenericParameter (type))
                                return true;

                        return GetClsCompliantAttributeValue (type, type.Assembly);
                }

                /// <summary>
                /// Returns instance of ObsoleteAttribute when type is obsolete
                /// </summary>
                public static ObsoleteAttribute GetObsoleteAttribute (Type type)
                {
                        object type_obsolete = analyzed_types_obsolete [type];
                        if (type_obsolete == FALSE)
                                return null;

                        if (type_obsolete != null)
                                return (ObsoleteAttribute)type_obsolete;

                        ObsoleteAttribute result = null;
                        if (TypeManager.HasElementType (type)) {
                                result = GetObsoleteAttribute (TypeManager.GetElementType (type));
                        } else if (TypeManager.IsGenericParameter (type))
                                result = null;  // TODO: throw new NotSupportedException ()
                        else if (TypeManager.IsGenericType (type) && !TypeManager.IsGenericTypeDefinition (type)) {
                                return GetObsoleteAttribute (TypeManager.DropGenericTypeArguments (type));
                        } else {
                                DeclSpace type_ds = TypeManager.LookupDeclSpace (type);

                                // Type is external, we can get attribute directly
                                if (type_ds == null) {
                                        PredefinedAttribute pa = PredefinedAttributes.Get.Obsolete;
                                        if (pa.IsDefined) {
                                                object[] attribute = type.GetCustomAttributes (pa.Type, false);
                                                if (attribute.Length == 1)
                                                        result = (ObsoleteAttribute) attribute[0];
                                        }
                                } else {
                                        result = type_ds.GetObsoleteAttribute ();
                                }
                        }

                        // Cannot use .Add because of corlib bootstrap
                        analyzed_types_obsolete [type] = result == null ? FALSE : result;
                        return result;
                }

                /// <summary>
                /// Returns instance of ObsoleteAttribute when method is obsolete
                /// </summary>
                public static ObsoleteAttribute GetMethodObsoleteAttribute (MethodBase mb)
                {
                        IMethodData mc = TypeManager.GetMethod (mb);
                        if (mc != null) 
                                return mc.GetObsoleteAttribute ();

                        // compiler generated methods are not registered by AddMethod
                        if (mb.DeclaringType is TypeBuilder)
                                return null;

                        MemberInfo mi = TypeManager.GetPropertyFromAccessor (mb);
                        if (mi != null)
                                return GetMemberObsoleteAttribute (mi);

                        mi = TypeManager.GetEventFromAccessor (mb);
                        if (mi != null)
                                return GetMemberObsoleteAttribute (mi);

                        return GetMemberObsoleteAttribute (mb);
                }

                /// <summary>
                /// Returns instance of ObsoleteAttribute when member is obsolete
                /// </summary>
                public static ObsoleteAttribute GetMemberObsoleteAttribute (MemberInfo mi)
                {
                        object type_obsolete = analyzed_member_obsolete [mi];
                        if (type_obsolete == FALSE)
                                return null;

                        if (type_obsolete != null)
                                return (ObsoleteAttribute)type_obsolete;

                        if ((mi.DeclaringType is TypeBuilder) || TypeManager.IsGenericType (mi.DeclaringType))
                                return null;

                        PredefinedAttribute pa = PredefinedAttributes.Get.Obsolete;
                        if (!pa.IsDefined)
                                return null;

                        ObsoleteAttribute oa = System.Attribute.GetCustomAttribute (mi, pa.Type, false)
                                as ObsoleteAttribute;
                        analyzed_member_obsolete.Add (mi, oa == null ? FALSE : oa);
                        return oa;
                }

                /// <summary>
                /// Common method for Obsolete error/warning reporting.
                /// </summary>
                public static void Report_ObsoleteMessage (ObsoleteAttribute oa, string member, Location loc)
                {
                        if (oa.IsError) {
                                Report.Error (619, loc, "`{0}' is obsolete: `{1}'", member, oa.Message);
                                return;
                        }

                        if (oa.Message == null || oa.Message.Length == 0) {
                                Report.Warning (612, 1, loc, "`{0}' is obsolete", member);
                                return;
                        }
                        Report.Warning (618, 2, loc, "`{0}' is obsolete: `{1}'", member, oa.Message);
                }

                public static bool IsConditionalMethodExcluded (MethodBase mb, Location loc)
                {
                        object excluded = analyzed_method_excluded [mb];
                        if (excluded != null)
                                return excluded == TRUE ? true : false;

                        PredefinedAttribute pa = PredefinedAttributes.Get.Conditional;
                        if (!pa.IsDefined)
                                return false;

                        ConditionalAttribute[] attrs = mb.GetCustomAttributes (pa.Type, true)
                                as ConditionalAttribute[];
                        if (attrs.Length == 0) {
                                analyzed_method_excluded.Add (mb, FALSE);
                                return false;
                        }

                        foreach (ConditionalAttribute a in attrs) {
                                if (loc.CompilationUnit.IsConditionalDefined (a.ConditionString)) {
                                        analyzed_method_excluded.Add (mb, FALSE);
                                        return false;
                                }
                        }

                        analyzed_method_excluded.Add (mb, TRUE);
                        return true;
                }

                /// <summary>
                /// Analyzes class whether it has attribute which has ConditionalAttribute
                /// and its condition is not defined.
                /// </summary>
                public static bool IsAttributeExcluded (Type type, Location loc)
                {
                        if (!type.IsClass)
                                return false;

                        Class class_decl = TypeManager.LookupDeclSpace (type) as Class;

                        // TODO: add caching
                        // TODO: merge all Type bases attribute caching to one cache to save memory
                        PredefinedAttribute pa = PredefinedAttributes.Get.Conditional;
                        if (class_decl == null && pa.IsDefined) {
                                object[] attributes = type.GetCustomAttributes (pa.Type, false);
                                foreach (ConditionalAttribute ca in attributes) {
                                        if (loc.CompilationUnit.IsConditionalDefined (ca.ConditionString))
                                                return false;
                                }
                                return attributes.Length > 0;
                        }

                        return class_decl.IsExcluded ();
                }

                public static Type GetCoClassAttribute (Type type)
                {
                        TypeContainer tc = TypeManager.LookupInterface (type);
                        PredefinedAttribute pa = PredefinedAttributes.Get.CoClass;
                        if (tc == null) {
                                if (!pa.IsDefined)
                                        return null;

                                object[] o = type.GetCustomAttributes (pa.Type, false);
                                if (o.Length < 1)
                                        return null;
                                return ((System.Runtime.InteropServices.CoClassAttribute)o[0]).CoClass;
                        }

                        if (tc.OptAttributes == null)
                                return null;

                        Attribute a = tc.OptAttributes.Search (pa);
                        if (a == null)
                                return null;

                        return a.GetCoClassAttributeValue ();
                }
        }

        public class PredefinedAttributes
        {
                // Core types
                public readonly PredefinedAttribute ParamArray;
                public readonly PredefinedAttribute Out;

                // Optional types
                public readonly PredefinedAttribute Obsolete;
                public readonly PredefinedAttribute DllImport;
                public readonly PredefinedAttribute MethodImpl;
                public readonly PredefinedAttribute MarshalAs;
                public readonly PredefinedAttribute In;
                public readonly PredefinedAttribute IndexerName;
                public readonly PredefinedAttribute Conditional;
                public readonly PredefinedAttribute CLSCompliant;
                public readonly PredefinedAttribute Security;
                public readonly PredefinedAttribute Required;
                public readonly PredefinedAttribute Guid;
                public readonly PredefinedAttribute AssemblyCulture;
                public readonly PredefinedAttribute AssemblyVersion;
                public readonly PredefinedAttribute ComImport;
                public readonly PredefinedAttribute CoClass;
                public readonly PredefinedAttribute AttributeUsage;
                public readonly PredefinedAttribute DefaultParameterValue;
                public readonly PredefinedAttribute OptionalParameter;

                // New in .NET 2.0
                public readonly PredefinedAttribute DefaultCharset;
                public readonly PredefinedAttribute TypeForwarder;
                public readonly PredefinedAttribute FixedBuffer;
                public readonly PredefinedAttribute CompilerGenerated;
                public readonly PredefinedAttribute InternalsVisibleTo;
                public readonly PredefinedAttribute RuntimeCompatibility;
                public readonly PredefinedAttribute DebuggerHidden;
                public readonly PredefinedAttribute UnsafeValueType;

                // New in .NET 3.5
                public readonly PredefinedAttribute Extension;

                //
                // Optional types which are used as types and for member lookup
                //
                public readonly PredefinedAttribute DefaultMember;
                public readonly PredefinedAttribute DecimalConstant;
                public readonly PredefinedAttribute StructLayout;
                public readonly PredefinedAttribute FieldOffset;

                public static PredefinedAttributes Get = new PredefinedAttributes ();

                private PredefinedAttributes ()
                {
                        ParamArray = new PredefinedAttribute ("System", "ParamArrayAttribute");
                        Out = new PredefinedAttribute ("System.Runtime.InteropServices", "OutAttribute");

                        Obsolete = new PredefinedAttribute ("System", "ObsoleteAttribute");
                        DllImport = new PredefinedAttribute ("System.Runtime.InteropServices", "DllImportAttribute");
                        MethodImpl = new PredefinedAttribute ("System.Runtime.CompilerServices", "MethodImplAttribute");
                        MarshalAs = new PredefinedAttribute ("System.Runtime.InteropServices", "MarshalAsAttribute");
                        In = new PredefinedAttribute ("System.Runtime.InteropServices", "InAttribute");
                        IndexerName = new PredefinedAttribute ("System.Runtime.CompilerServices", "IndexerNameAttribute");
                        Conditional = new PredefinedAttribute ("System.Diagnostics", "ConditionalAttribute");
                        CLSCompliant = new PredefinedAttribute ("System", "CLSCompliantAttribute");
                        Security = new PredefinedAttribute ("System.Security.Permissions", "SecurityAttribute");
                        Required = new PredefinedAttribute ("System.Runtime.CompilerServices", "RequiredAttributeAttribute");
                        Guid = new PredefinedAttribute ("System.Runtime.InteropServices", "GuidAttribute");
                        AssemblyCulture = new PredefinedAttribute ("System.Reflection", "AssemblyCultureAttribute");
                        AssemblyVersion = new PredefinedAttribute ("System.Reflection", "AssemblyVersionAttribute");
                        ComImport = new PredefinedAttribute ("System.Runtime.InteropServices", "ComImportAttribute");
                        CoClass = new PredefinedAttribute ("System.Runtime.InteropServices", "CoClassAttribute");
                        AttributeUsage = new PredefinedAttribute ("System", "AttributeUsageAttribute");
                        DefaultParameterValue = new PredefinedAttribute ("System.Runtime.InteropServices", "DefaultParameterValueAttribute");
                        OptionalParameter = new PredefinedAttribute ("System.Runtime.InteropServices", "OptionalAttribute");

                        DefaultCharset = new PredefinedAttribute ("System.Runtime.InteropServices", "DefaultCharSetAttribute");
                        TypeForwarder = new PredefinedAttribute ("System.Runtime.CompilerServices", "TypeForwardedToAttribute");
                        FixedBuffer = new PredefinedAttribute ("System.Runtime.CompilerServices", "FixedBufferAttribute");
                        CompilerGenerated = new PredefinedAttribute ("System.Runtime.CompilerServices", "CompilerGeneratedAttribute");
                        InternalsVisibleTo = new PredefinedAttribute ("System.Runtime.CompilerServices", "InternalsVisibleToAttribute");
                        RuntimeCompatibility = new PredefinedAttribute ("System.Runtime.CompilerServices", "RuntimeCompatibilityAttribute");
                        DebuggerHidden = new PredefinedAttribute ("System.Diagnostics", "DebuggerHiddenAttribute");
                        UnsafeValueType = new PredefinedAttribute ("System.Runtime.CompilerServices", "UnsafeValueTypeAttribute");

                        Extension = new PredefinedAttribute ("System.Runtime.CompilerServices", "ExtensionAttribute");

                        DefaultMember = new PredefinedAttribute ("System.Reflection", "DefaultMemberAttribute");
                        DecimalConstant = new PredefinedAttribute ("System.Runtime.CompilerServices", "DecimalConstantAttribute");
                        StructLayout = new PredefinedAttribute ("System.Runtime.InteropServices", "StructLayoutAttribute");
                        FieldOffset = new PredefinedAttribute ("System.Runtime.InteropServices", "FieldOffsetAttribute");
                }

                public void Initialize ()
                {
                        foreach (FieldInfo fi in GetType ().GetFields (BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly)) {
                                ((PredefinedAttribute) fi.GetValue (this)).Resolve (true);
                        }
                }

                public static void Reset ()
                {
                        Get = new PredefinedAttributes ();
                }
        }

        public class PredefinedAttribute
        {
                Type type;
                CustomAttributeBuilder cab;
                ConstructorInfo ctor;
                readonly string ns, name;

                public PredefinedAttribute (string ns, string name)
                {
                        this.ns = ns;
                        this.name = name;
                }

                public static bool operator == (Type type, PredefinedAttribute pa)
                {
                        return type == pa.type;
                }

                public static bool operator != (Type type, PredefinedAttribute pa)
                {
                        return type != pa.type;
                }

                public ConstructorInfo Constructor {
                        get { return ctor; }
                }

                public override int GetHashCode ()
                {
                        return base.GetHashCode ();
                }

                public override bool Equals (object obj)
                {
                        throw new NotSupportedException ();
                }

                public void EmitAttribute (ConstructorBuilder builder)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public void EmitAttribute (MethodBuilder builder)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public void EmitAttribute (FieldBuilder builder)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public void EmitAttribute (TypeBuilder builder)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public void EmitAttribute (AssemblyBuilder builder)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public void EmitAttribute (ParameterBuilder builder, Location loc)
                {
                        if (ResolveBuilder ())
                                builder.SetCustomAttribute (cab);
                }

                public bool IsDefined {
                        get { return type != null && type != typeof (PredefinedAttribute); }
                }

                public bool Resolve (bool canFail)
                {
                        if (type != null) {
                                if (IsDefined)
                                        return true;
                                if (canFail)
                                        return false;
                        }

                        type = TypeManager.CoreLookupType (ns, name, Kind.Class, !canFail);
                        if (type == null) {
                                type = typeof (PredefinedAttribute);
                                return false;
                        }

                        return true;
                }

                bool ResolveBuilder ()
                {
                        if (cab != null)
                                return true;

                        //
                        // Handle all parameter-less attributes as optional
                        //
                        if (!Resolve (true))
                                return false;

                        ConstructorInfo ci = TypeManager.GetPredefinedConstructor (type, Location.Null, Type.EmptyTypes);
                        if (ci == null)
                                return false;

                        cab = new CustomAttributeBuilder (ci, new object[0]);
                        return true;
                }

                public bool ResolveConstructor (Location loc, params Type[] argType)
                {
                        if (ctor != null)
                                throw new InternalErrorException ("Predefined ctor redefined");

                        if (!Resolve (false))
                                return false;

                        ctor = TypeManager.GetPredefinedConstructor (type, loc, argType);
                        return ctor != null;
                }

                public Type Type {
                        get { return type; }
                }
        }
}