2002-05-31 Rafael Teixeira <rafaelteixeirabr@hotmail.com>

[mono.git] / mcs / mbas / class.cs

//
// class.cs: Class and Struct handlers
//
// Author: Miguel de Icaza (miguel@gnu.org)
//
// Licensed under the terms of the GNU GPL
//
// (C) 2001 Ximian, Inc (http://www.ximian.com)
//
//

using System.Collections;
using System.Reflection;
using System.Reflection.Emit;
using System;
using System.Runtime.CompilerServices;
using System.Diagnostics.SymbolStore;

namespace Mono.CSharp {

        /// <summary>
        ///   This is the base class for structs and classes.  
        /// </summary>
        public class TypeContainer : DeclSpace {
                // Holds a list of classes and structures
                ArrayList types;

                // Holds the list of properties
                ArrayList properties;

                // Holds the list of enumerations
                ArrayList enums;

                // Holds the list of delegates
                ArrayList delegates;
                
                // Holds the list of constructors
                ArrayList instance_constructors;

                // Holds the list of fields
                ArrayList fields;

                // Holds a list of fields that have initializers
                ArrayList initialized_fields;

                // Holds a list of static fields that have initializers
                ArrayList initialized_static_fields;

                // Holds the list of constants
                ArrayList constants;

                // Holds the list of
                ArrayList interfaces;

                // Holds order in which interfaces must be closed
                ArrayList interface_order;
                
                // Holds the methods.
                ArrayList methods;

                // Holds the events
                ArrayList events;

                // Holds the indexers
                ArrayList indexers;

                // Holds the operators
                ArrayList operators;

                // The emit context for toplevel objects.
                EmitContext ec;
                
                //
                // Pointers to the default constructor and the default static constructor
                //
                Constructor default_constructor;
                Constructor default_static_constructor;

                //
                // Whether we have seen a static constructor for this class or not
                //
                bool have_static_constructor = false;
                
                //
                // This one is computed after we can distinguish interfaces
                // from classes from the arraylist `type_bases' 
                //
                string     base_class_name;

                ArrayList type_bases;

                // Attributes for this type
                protected Attributes attributes;

                // Information in the case we are an attribute type

                public AttributeTargets Targets = AttributeTargets.All;
                public bool AllowMultiple = false;
                public bool Inherited;

                //
                // The indexer name for this class
                //
                public string IndexerName;

                public TypeContainer (TypeContainer parent, string name, Location l)
                        : base (parent, name, l)
                {
                        string n;
                        types = new ArrayList ();

                        if (parent == null)
                                n = "";
                        else
                                n = parent.Name;

                        base_class_name = null;
                        
                        //Console.WriteLine ("New class " + name + " inside " + n);
                }

                public AdditionResult AddConstant (Const constant)
                {
                        AdditionResult res;
                        string name = constant.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;
                        
                        if (constants == null)
                                constants = new ArrayList ();

                        constants.Add (constant);
                        DefineName (name, constant);

                        return AdditionResult.Success;
                }

                public AdditionResult AddEnum (Mono.CSharp.Enum e)
                {
                        AdditionResult res;
                        string name = e.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        if (enums == null)
                                enums = new ArrayList ();

                        enums.Add (e);
                        DefineName (name, e);

                        return AdditionResult.Success;
                }
                
                public AdditionResult AddClass (Class c)
                {
                        AdditionResult res;
                        string name = c.Name;


                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        DefineName (name, c);
                        types.Add (c);

                        return AdditionResult.Success;
                }

                public AdditionResult AddStruct (Struct s)
                {
                        AdditionResult res;
                        string name = s.Name;
                        
                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        DefineName (name, s);
                        types.Add (s);

                        return AdditionResult.Success;
                }

                public AdditionResult AddDelegate (Delegate d)
                {
                        AdditionResult res;
                        string name = d.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        if (delegates == null)
                                delegates = new ArrayList ();
                        
                        DefineName (name, d);
                        delegates.Add (d);

                        return AdditionResult.Success;
                }

                public AdditionResult AddMethod (Method method)
                {
                        string name = method.Name;
                        Object value = defined_names [name];
                        
                        if (value != null && (!(value is Method)))
                                return AdditionResult.NameExists;

                        if (methods == null)
                                methods = new ArrayList ();

                        methods.Add (method);
                        if (value != null)
                                DefineName (name, method);

                        return AdditionResult.Success;
                }

                public AdditionResult AddConstructor (Constructor c)
                {
                        if (c.Name != Basename) 
                                return AdditionResult.NotAConstructor;

                        bool is_static = (c.ModFlags & Modifiers.STATIC) != 0;
                        
                        if (is_static){
                                have_static_constructor = true;
                                if (default_static_constructor != null){
                                        Console.WriteLine ("I have a static constructor already");
                                        Console.WriteLine ("   " + default_static_constructor);
                                        return AdditionResult.MethodExists;
                                }

                                default_static_constructor = c;
                        } else {
                                if (c.IsDefault ()){
                                        if (default_constructor != null)
                                                return AdditionResult.MethodExists;
                                        default_constructor = c;
                                }
                                
                                if (instance_constructors == null)
                                        instance_constructors = new ArrayList ();
                                
                                instance_constructors.Add (c);
                        }
                        
                        return AdditionResult.Success;
                }
                
                public AdditionResult AddInterface (Interface iface)
                {
                        AdditionResult res;
                        string name = iface.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;
                        
                        if (interfaces == null)
                                interfaces = new ArrayList ();
                        interfaces.Add (iface);
                        DefineName (name, iface);
                        
                        return AdditionResult.Success;
                }

                public AdditionResult AddField (Field field)
                {
                        AdditionResult res;
                        string name = field.Name;
                        
                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        if (fields == null)
                                fields = new ArrayList ();

                        fields.Add (field);
                        
                        if (field.Initializer != null){
                                if ((field.ModFlags & Modifiers.STATIC) != 0){
                                        if (initialized_static_fields == null)
                                                initialized_static_fields = new ArrayList ();

                                        initialized_static_fields.Add (field);

                                        //
                                        // We have not seen a static constructor,
                                        // but we will provide static initialization of fields
                                        //
                                        have_static_constructor = true;
                                } else {
                                        if (initialized_fields == null)
                                                initialized_fields = new ArrayList ();
                                
                                        initialized_fields.Add (field);
                                }
                        }
                        
                        DefineName (name, field);
                        return AdditionResult.Success;
                }

                public AdditionResult AddProperty (Property prop)
                {
                        AdditionResult res;
                        string name = prop.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        if (properties == null)
                                properties = new ArrayList ();

                        properties.Add (prop);
                        DefineName (name, prop);

                        return AdditionResult.Success;
                }

                public AdditionResult AddEvent (Event e)
                {
                        AdditionResult res;
                        string name = e.Name;

                        if ((res = IsValid (name)) != AdditionResult.Success)
                                return res;

                        if (events == null)
                                events = new ArrayList ();
                        
                        events.Add (e);
                        DefineName (name, e);

                        return AdditionResult.Success;
                }

                public AdditionResult AddIndexer (Indexer i)
                {
                        if (indexers == null)
                                indexers = new ArrayList ();

                        indexers.Add (i);

                        return AdditionResult.Success;
                }

                public AdditionResult AddOperator (Operator op)
                {
                        if (operators == null)
                                operators = new ArrayList ();

                        operators.Add (op);

                        return AdditionResult.Success;
                }

                public void RegisterOrder (Interface iface)
                {
                        if (interface_order == null)
                                interface_order = new ArrayList ();

                        interface_order.Add (iface);
                }
                
                public ArrayList Types {
                        get {
                                return types;
                        }
                }

                public ArrayList Methods {
                        get {
                                return methods;
                        }
                }

                public ArrayList Constants {
                        get {
                                return constants;
                        }
                }

                public ArrayList Interfaces {
                        get {
                                return interfaces;
                        }
                }
                
                public string Base {
                        get {
                                return base_class_name;
                        }
                }
                
                public ArrayList Bases {
                        get {
                                return type_bases;
                        }

                        set {
                                type_bases = value;
                        }
                }

                public ArrayList Fields {
                        get {
                                return fields;
                        }
                }

                public ArrayList InstanceConstructors {
                        get {
                                return instance_constructors;
                        }
                }

                public ArrayList Properties {
                        get {
                                return properties;
                        }
                }

                public ArrayList Events {
                        get {
                                return events;
                        }
                }
                
                public ArrayList Enums {
                        get {
                                return enums;
                        }
                }

                public ArrayList Indexers {
                        get {
                                return indexers;
                        }
                }

                public ArrayList Operators {
                        get {
                                return operators;
                        }
                }

                public ArrayList Delegates {
                        get {
                                return delegates;
                        }
                }
                
                public Attributes OptAttributes {
                        get {
                                return attributes;
                        }
                }
                
                public bool HaveStaticConstructor {
                        get {
                                return have_static_constructor;
                        }
                }
                
                public virtual TypeAttributes TypeAttr {
                        get {
                                return Modifiers.TypeAttr (ModFlags, this);
                        }
                }

                //
                // Emits the instance field initializers
                //
                public bool EmitFieldInitializers (EmitContext ec)
                {
                        ArrayList fields;
                        ILGenerator ig = ec.ig;
                        Expression instance_expr;
                        
                        if (ec.IsStatic){
                                fields = initialized_static_fields;
                                instance_expr = null;
                        } else {
                                fields = initialized_fields;
                                instance_expr = new This (Location.Null).Resolve (ec);
                        }

                        if (fields == null)
                                return true;
                        
                        foreach (Field f in fields){
                                Object init = f.Initializer;

                                Expression e;
                                if (init is Expression)
                                        e = (Expression) init;
                                else {
                                        string base_type = f.Type.Substring (0, f.Type.IndexOf ("["));
                                        string rank = f.Type.Substring (f.Type.IndexOf ("["));
                                        e = new ArrayCreation (base_type, rank, (ArrayList)init, f.Location);
                                }

                                Location l = f.Location;
                                FieldExpr fe = new FieldExpr (f.FieldBuilder, l);
                                fe.InstanceExpression = instance_expr;
                                Expression a = new Assign (fe, e, l);

                                a = a.Resolve (ec);
                                if (a == null)
                                        return false;

                                if (a is ExpressionStatement)
                                        ((ExpressionStatement) a).EmitStatement (ec);
                                else {
                                        throw new Exception ("Assign.Resolve returned a non ExpressionStatement");
                                }
                        }
                        
                        return true;
                }
                
                //
                // Defines the default constructors
                //
                void DefineDefaultConstructor (bool is_static)
                {
                        Constructor c;
                        int mods = 0;

                        c = new Constructor (Basename, Parameters.GetEmptyReadOnlyParameters (),
                                             new ConstructorBaseInitializer (null, new Location (-1)),
                                             new Location (-1));
                        
                        if (is_static)
                                mods = Modifiers.STATIC;

                        c.ModFlags = mods;

                        AddConstructor (c);
                        
                        c.Block = new Block (null);
                        
                }

                public void ReportStructInitializedInstanceError ()
                {
                        string n = TypeBuilder.FullName;
                        
                        foreach (Field f in initialized_fields){
                                Report.Error (
                                        573, Location,
                                        "`" + n + "." + f.Name + "': can not have " +
                                        "instance field initializers in structs");
                        }
                }

                struct TypeAndMethods {
                        public Type          type;
                        public MethodInfo [] methods;

                        // Far from ideal, but we want to avoid creating a copy
                        // of methods above.
                        public Type [][]     args;

                        //
                        // This flag on the method says `We found a match, but
                        // because it was private, we could not use the match
                        //
                        public bool []       found;
                }

                //
                // This array keeps track of the pending implementations
                // 
                TypeAndMethods [] pending_implementations;

                //
                // Returns a list of the abstract methods that are exposed by all of our
                // parents that we must implement.  Notice that this `flattens' the
                // method search space, and takes into account overrides.  
                //
                ArrayList GetAbstractMethods (Type t)
                {
                        ArrayList list = null;
                        bool searching = true;
                        Type current_type = t;
                        
                        do {
                                MemberInfo [] mi;
                                
                                mi = FindMembers (
                                        current_type, MemberTypes.Method,
                                        BindingFlags.Public | BindingFlags.Instance |
                                        BindingFlags.DeclaredOnly,
                                        virtual_method_filter, null);

                                if (current_type == TypeManager.object_type)
                                        searching = false;
                                else {
                                        current_type = current_type.BaseType;
                                        if (!current_type.IsAbstract)
                                                searching = false;
                                }

                                if (mi == null)
                                        continue;

                                int count = mi.Length;
                                if (count == 0)
                                        continue;

                                if (count == 1 && !(mi [0] is MethodBase))
                                        searching = false;
                                else 
                                        list = TypeManager.CopyNewMethods (list, mi);
                        } while (searching);

                        if (list == null)
                                return null;
                        
                        for (int i = 0; i < list.Count; i++){
                                while (list.Count > i && !((MethodInfo) list [i]).IsAbstract)
                                        list.RemoveAt (i);
                        }

                        if (list.Count == 0)
                                return null;

                        return list;
                }
                
                //
                // Registers the required method implementations for this class
                //
                // Register method implementations are either abstract methods
                // flagged as such on the base class or interface methods
                //
                public void RegisterRequiredImplementations ()
                {
                        Type [] ifaces = TypeBuilder.GetInterfaces ();
                        Type b = TypeBuilder.BaseType;
                        int icount = 0;

#if DEBUG
                        {
                                Type x = TypeBuilder;

                                while (x != null){
                                        Type [] iff = x.GetInterfaces ();
                                        Console.WriteLine ("Type: " + x.Name);
                                        
                                        foreach (Type tt in iff){
                                                Console.WriteLine ("  Iface: " + tt.Name);
                                        }
                                        x = x.BaseType;
                                }
                        }
#endif
                                        
                        icount = ifaces.Length;

                        //
                        // If we are implementing an abstract class, and we are not
                        // ourselves abstract, and there are abstract methods (C# allows
                        // abstract classes that have no abstract methods), then allocate
                        // one slot.
                        //
                        // We also pre-compute the methods.
                        //
                        bool implementing_abstract = (b.IsAbstract && !TypeBuilder.IsAbstract);
                        ArrayList abstract_methods = null;

                        if (implementing_abstract){
                                abstract_methods = GetAbstractMethods (b);
                                
                                if (abstract_methods == null)
                                        implementing_abstract = false;
                        }
                        
                        int total = icount +  (implementing_abstract ? 1 : 0);
                        if (total == 0)
                                return;

                        pending_implementations = new TypeAndMethods [total];
                        
                        int i = 0;
                        if (ifaces != null){
                                foreach (Type t in ifaces){
                                        MethodInfo [] mi;

                                        if (t is TypeBuilder){
                                                Interface iface;

                                                iface = TypeManager.LookupInterface (t);
                                                
                                                mi = iface.GetMethods ();
                                        } else
                                                mi = t.GetMethods ();

                                        int count = mi.Length;
                                        pending_implementations [i].type = t;
                                        pending_implementations [i].methods = mi;
                                        pending_implementations [i].args = new Type [count][];
                                        pending_implementations [i].found = new bool [count];

                                        int j = 0;
                                        foreach (MethodInfo m in mi){
                                                Type [] types = TypeManager.GetArgumentTypes (m);

                                                pending_implementations [i].args [j] = types;
                                                j++;
                                        }
                                        i++;
                                }
                        }

                        if (abstract_methods != null){
                                int count = abstract_methods.Count;
                                pending_implementations [i].methods = new MethodInfo [count];
                                
                                abstract_methods.CopyTo (pending_implementations [i].methods, 0);
                                pending_implementations [i].found = new bool [count];
                                pending_implementations [i].args = new Type [count][];
                                pending_implementations [i].type = TypeBuilder;
                                
                                int j = 0;
                                foreach (MemberInfo m in abstract_methods){
                                        MethodInfo mi = (MethodInfo) m;
                                        
                                        Type [] types = TypeManager.GetArgumentTypes (mi);
                                        
                                        pending_implementations [i].args [j] = types;
                                        j++;
                                }
                        }
                }

                /// <summary>
                ///   This function computes the Base class and also the
                ///   list of interfaces that the class or struct @c implements.
                ///   
                ///   The return value is an array (might be null) of
                ///   interfaces implemented (as Types).
                ///   
                ///   The @parent argument is set to the parent object or null
                ///   if this is `System.Object'. 
                /// </summary>
                Type [] GetClassBases (bool is_class, out Type parent, out bool error)
                {
                        ArrayList bases = Bases;
                        int count;
                        int start, j, i;

                        error = false;

                        if (is_class)
                                parent = null;
                        else
                                parent = TypeManager.value_type;

                        if (bases == null){
                                if (is_class){
                                        if (RootContext.StdLib)
                                                parent = TypeManager.object_type;
                                        else if (Name != "System.Object")
                                                parent = TypeManager.object_type;
                                } else {
                                        //
                                        // If we are compiling our runtime,
                                        // and we are defining ValueType, then our
                                        // parent is `System.Object'.
                                        //
                                        if (!RootContext.StdLib && Name == "System.ValueType")
                                                parent = TypeManager.object_type;
                                }

                                return null;
                        }

                        //
                        // Bases should be null if there are no bases at all
                        //
                        count = bases.Count;

                        if (is_class){
                                string name = (string) bases [0];
                                Type first = FindType (name);

                                if (first == null){
                                        error = true;
                                        return null;
                                }

                                if (first.IsClass){
                                        parent = first;
                                        start = 1;
                                } else {
                                        parent = TypeManager.object_type;
                                        start = 0;
                                }

                        } else {
                                start = 0;
                        }

                        Type [] ifaces = new Type [count-start];
                        
                        for (i = start, j = 0; i < count; i++, j++){
                                string name = (string) bases [i];
                                Type t = FindType (name);

                                if (t == null){
                                        error = true;
                                        return null;
                                }

                                if (is_class == false && !t.IsInterface){
                                        Report.Error (527, "In Struct `" + Name + "', type `"+
                                                      name +"' is not an interface");
                                        error = true;
                                        return null;
                                }
                                
                                if (t.IsSealed) {
                                        string detail = "";
                                        
                                        if (t.IsValueType)
                                                detail = " (a class can not inherit from a struct/enum)";
                                                        
                                        Report.Error (509, "class `"+ Name +
                                                      "': Cannot inherit from sealed class `"+
                                                      bases [i]+"'"+detail);
                                        error = true;
                                        return null;
                                }

                                if (t.IsClass) {
                                        if (parent != null){
                                                Report.Error (527, "In Class `" + Name + "', type `"+
                                                              name+"' is not an interface");
                                                error = true;
                                                return null;
                                        }
                                }
                                
                                ifaces [j] = t;
                        }

                        return ifaces;
                }
                
                //
                // Defines the type in the appropriate ModuleBuilder or TypeBuilder.
                //
                public override TypeBuilder DefineType ()
                {
                        Type parent;
                        Type [] ifaces;
                        bool error;
                        bool is_class;

                        if (TypeBuilder != null)
                                return TypeBuilder;
                        
                        if (InTransit)
                                return null;
                        
                        InTransit = true;
                        
                        if (this is Class)
                                is_class = true;
                        else
                                is_class = false;

                        ec = new EmitContext (this, Mono.CSharp.Location.Null, null, null, ModFlags);

                        ifaces = GetClassBases (is_class, out parent, out error); 
                        
                        if (error)
                                return null;

                        if (is_class && parent != null){
                                if (parent == TypeManager.enum_type ||
                                    (parent == TypeManager.value_type && RootContext.StdLib) ||
                                    parent == TypeManager.delegate_type ||
                                    parent == TypeManager.array_type){
                                        Report.Error (
                                                644, Location, "`" + Name + "' cannot inherit from " +
                                                "special class `" + TypeManager.CSharpName (parent) + "'");
                                        return null;
                                }
                        }

                        if (!is_class && TypeManager.value_type == null)
                                throw new Exception ();

                        TypeAttributes type_attributes = TypeAttr;

                        // if (parent_builder is ModuleBuilder) {
                        if (IsTopLevel){
                                ModuleBuilder builder = CodeGen.ModuleBuilder;
                                
                                //
                                // Structs with no fields need to have a ".size 1"
                                // appended
                                //

                                if (!is_class && Fields == null)
                                        TypeBuilder = builder.DefineType (Name,
                                                                          type_attributes,
                                                                          parent, 
                                                                          PackingSize.Unspecified, 1);
                                else
                                //
                                // classes or structs with fields
                                //
                                        TypeBuilder = builder.DefineType (Name,
                                                                          type_attributes,
                                                                          parent,
                                                                          ifaces);
                        } else {
                                TypeBuilder builder = Parent.TypeBuilder;
                                
                                //
                                // Structs with no fields need to have a ".size 1"
                                // appended
                                //
                                if (!is_class && Fields == null)
                                        TypeBuilder = builder.DefineNestedType (Basename,
                                                                                type_attributes,
                                                                                parent, 
                                                                                PackingSize.Unspecified);
                                else {
                                        //
                                        // classes or structs with fields
                                        //
                                        TypeBuilder = builder.DefineNestedType (Basename,
                                                                                type_attributes,
                                                                                parent,
                                                                                ifaces);
                                }
                        }

                        //
                        // Finish the setup for the EmitContext
                        //
                        ec.ContainerType = TypeBuilder;

                        TypeManager.AddUserType (Name, TypeBuilder, this, ifaces);

                        if (parent == TypeManager.attribute_type ||
                            parent.IsSubclassOf (TypeManager.attribute_type)) {
                                RootContext.RegisterAttribute (this);
                                TypeManager.RegisterAttrType (TypeBuilder, this);
                        } else
                                RootContext.RegisterOrder (this); 
                                
                        if (Interfaces != null) {
                                foreach (Interface iface in Interfaces)
                                        iface.DefineType ();
                        }
                        
                        if (Types != null) {
                                foreach (TypeContainer tc in Types)
                                        tc.DefineType ();
                        }

                        if (Delegates != null) {
                                foreach (Delegate d in Delegates)
                                        d.DefineType ();
                        }

                        if (Enums != null) {
                                foreach (Enum en in Enums)
                                        en.DefineType ();
                        }

                        InTransit = false;
                        return TypeBuilder;
                }


                /// <summary>
                ///   Defines the MemberCore objects that are in the `list' Arraylist
                ///
                ///   The `defined_names' array contains a list of members defined in
                ///   a base class
                /// </summary>
                static ArrayList remove_list = new ArrayList ();
                void DefineMembers (ArrayList list, MemberInfo [] defined_names)
                {
                        int idx;
                        
                        remove_list.Clear ();

                        foreach (MemberCore mc in list){
                                if (!mc.Define (this)){
                                        remove_list.Add (mc);
                                        continue;
                                }
                                                
                                if (defined_names == null)
                                        continue;

                                idx = Array.BinarySearch (defined_names, mc.Name, mif_compare);
                                if (idx < 0){
                                        if (RootContext.WarningLevel >= 4){
                                                if ((mc.ModFlags & Modifiers.NEW) != 0)
                                                        Warning_KewywordNewNotRequired (mc.Location, mc);
                                        }
                                        continue;
                                }

                                MemberInfo match = defined_names [idx];

                                if (match is PropertyInfo && ((mc.ModFlags & Modifiers.OVERRIDE) != 0))
                                        continue;

                                //
                                // If we are both methods, let the method resolution emit warnings
                                //
                                if (match is MethodBase && mc is MethodCore)
                                        continue; 
                                
                                if ((mc.ModFlags & Modifiers.NEW) == 0)
                                        Warning_KeywordNewRequired (mc.Location, defined_names [idx]);
                        }
                        
                        foreach (object o in remove_list)
                                list.Remove (o);
                        
                        remove_list.Clear ();
                }

                //
                // Defines the indexers, and also verifies that the IndexerNameAttribute in the
                // class is consisten.  Either it is `Item' or it is the name defined by all the
                // indexers with the `IndexerName' attribute.
                //
                // Turns out that the IndexerNameAttribute is applied to each indexer,
                // but it is never emitted, instead a DefaultName attribute is attached
                // to the class.
                //
                void DefineIndexers ()
                {
                        string class_indexer_name = null;
                        
                        foreach (Indexer i in Indexers){
                                string name;
                                
                                i.Define (this);

                                name = i.IndexerName;
                                if (class_indexer_name == null){
                                        class_indexer_name = name;
                                        continue;
                                }
                                
                                if (name == class_indexer_name)
                                        continue;
                                
                                Report.Error (
                                        668, "Two indexers have different names, " +
                                        " you should use the same name for all your indexers");
                        }
                        if (class_indexer_name == null)
                                class_indexer_name = "Item";
                        IndexerName = class_indexer_name;
                }
                
                /// <summary>
                ///   Populates our TypeBuilder with fields and methods
                /// </summary>
                public override bool Define (TypeContainer parent)
                {
                        MemberInfo [] defined_names = null;

                        if (RootContext.WarningLevel > 1){
                                Type ptype;

                                //
                                // This code throws an exception in the comparer
                                // I guess the string is not an object?
                                //
                                ptype = TypeBuilder.BaseType;
                                if (ptype != null){
                                        defined_names = FindMembers (
                                                ptype, MemberTypes.All & ~MemberTypes.Constructor,
                                                BindingFlags.Public | BindingFlags.Instance |
                                                BindingFlags.Static, null, null);

                                        Array.Sort (defined_names, mif_compare);
                                }
                        }
                        
                        if (constants != null)
                                DefineMembers (constants, defined_names);

                        if (fields != null)
                                DefineMembers (fields, defined_names);

                        if (this is Class){
                                if (instance_constructors == null){
                                        if (default_constructor == null)
                                                DefineDefaultConstructor (false);
                                }

                                if (initialized_static_fields != null &&
                                    default_static_constructor == null)
                                        DefineDefaultConstructor (true);
                        }

                        if (this is Struct){
                                //
                                // Structs can not have initialized instance
                                // fields
                                //
                                if (initialized_static_fields != null &&
                                    default_static_constructor == null)
                                        DefineDefaultConstructor (true);

                                if (initialized_fields != null)
                                        ReportStructInitializedInstanceError ();
                        }

                        RegisterRequiredImplementations ();

                        //
                        // Constructors are not in the defined_names array
                        //
                        if (instance_constructors != null)
                                DefineMembers (instance_constructors, null);
                
                        if (default_static_constructor != null)
                                default_static_constructor.Define (this);
                        
                        if (methods != null)
                                DefineMembers (methods, defined_names);

                        if (properties != null)
                                DefineMembers (properties, defined_names);

                        if (events != null)
                                DefineMembers (events, defined_names);

                        if (indexers != null) {
                                DefineIndexers ();
                        } else
                                IndexerName = "Item";

                        if (operators != null)
                                DefineMembers (operators, null);

                        if (enums != null)
                                DefineMembers (enums, defined_names);
                        
                        if (delegates != null)
                                DefineMembers (delegates, defined_names);

                        return true;
                }

                /// <summary>
                ///   Looks up the alias for the name
                /// </summary>
                public string LookupAlias (string name)
                {
                        if (Namespace != null)
                                return Namespace.LookupAlias (name);
                        else
                                return null;
                }
                
                /// <summary>
                ///   This function is based by a delegate to the FindMembers routine
                /// </summary>
                static bool AlwaysAccept (MemberInfo m, object filterCriteria)
                {
                        return true;
                }

                /// <summary>
                ///   This filter is used by FindMembers, and we just keep
                ///   a global for the filter to `AlwaysAccept'
                /// </summary>
                static MemberFilter accepting_filter;

                static bool IsVirtualFilter (MemberInfo m, object filterCriteria)
                {
                        if (!(m is MethodInfo))
                                return false;

                        return ((MethodInfo) m).IsVirtual;
                }
                
                /// <summary>
                ///   This filter is used by FindMembers, and it is used to
                ///   extract only virtual/abstract fields
                /// </summary>
                static MemberFilter virtual_method_filter;
                
                /// <summary>
                ///   A member comparission method based on name only
                /// </summary>
                static IComparer mif_compare;

                static TypeContainer ()
                {
                        accepting_filter = new MemberFilter (AlwaysAccept);
                        virtual_method_filter = new MemberFilter (IsVirtualFilter);
                        mif_compare = new MemberInfoCompare ();
                }
                
                /// <summary>
                ///   This method returns the members of this type just like Type.FindMembers would
                ///   Only, we need to use this for types which are _being_ defined because MS' 
                ///   implementation can't take care of that.
                /// </summary>
                //
                // FIXME: return an empty static array instead of null, that cleans up
                // some code and is consistent with some coding conventions I just found
                // out existed ;-)
                //
                //
                // Notice that in various cases we check if our field is non-null,
                // something that would normally mean that there was a bug elsewhere.
                //
                // The problem happens while we are defining p-invoke methods, as those
                // will trigger a FindMembers, but this happens before things are defined
                //
                // Since the whole process is a no-op, it is fine to check for null here.
                //
                public MemberInfo [] FindMembers (MemberTypes mt, BindingFlags bf,
                                                  MemberFilter filter, object criteria)
                {
                        ArrayList members = new ArrayList ();
                        bool priv = (bf & BindingFlags.NonPublic) != 0;

                        if (filter == null)
                                filter = accepting_filter; 
                        
                        if ((mt & MemberTypes.Field) != 0) {
                                if (fields != null) {
                                        foreach (Field f in fields) {
                                                if ((f.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;

                                                FieldBuilder fb = f.FieldBuilder;
                                                if (fb != null && filter (fb, criteria) == true)
                                                        members.Add (fb);
                                        }
                                }

                                if (constants != null) {
                                        foreach (Const con in constants) {
                                                if ((con.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;
                                                
                                                FieldBuilder fb = con.FieldBuilder;
                                                if (fb != null && filter (fb, criteria) == true)
                                                        members.Add (fb);
                                        }
                                }
                        }

                        if ((mt & MemberTypes.Method) != 0) {
                                if (methods != null) {
                                        foreach (Method m in methods) {
                                                if ((m.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;
                                                
                                                MethodBuilder mb = m.MethodBuilder;

                                                if (mb != null && filter (mb, criteria) == true)
                                                        members.Add (mb);
                                        }
                                }

                                if (operators != null){
                                        foreach (Operator o in operators) {
                                                if ((o.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;
                                                
                                                MethodBuilder ob = o.OperatorMethodBuilder;
                                                if (ob != null && filter (ob, criteria) == true)
                                                        members.Add (ob);
                                        }
                                }

                                if (properties != null){
                                        foreach (Property p in properties){
                                                if ((p.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;
                                                
                                                MethodBuilder b;

                                                b = p.GetBuilder;
                                                if (b != null && filter (b, criteria) == true)
                                                        members.Add (b);

                                                b = p.SetBuilder;
                                                if (b != null && filter (b, criteria) == true)
                                                        members.Add (b);
                                        }
                                }
                        }

                        if ((mt & MemberTypes.Event) != 0) {
                                if (events != null)
                                        foreach (Event e in events) {
                                                if ((e.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;

                                                MemberInfo eb = e.EventBuilder;
                                                if (eb != null && filter (eb, criteria) == true)
                                                        members.Add (e.EventBuilder);
                                        }
                        }
                        
                        if ((mt & MemberTypes.Property) != 0){
                                if (properties != null)
                                        foreach (Property p in properties) {
                                                if ((p.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;

                                                MemberInfo pb = p.PropertyBuilder;
                                                if (pb != null && filter (pb, criteria) == true) {
                                                        members.Add (p.PropertyBuilder);
                                                }
                                        }

                                if (indexers != null)
                                        foreach (Indexer ix in indexers) {
                                                if ((ix.ModFlags & Modifiers.PRIVATE) != 0)
                                                        if (!priv)
                                                                continue;

                                                MemberInfo ib = ix.PropertyBuilder;
                                                if (ib != null && filter (ib, criteria) == true) {
                                                        members.Add (ix.PropertyBuilder);
                                                }
                                        }
                        }
                        
                        if ((mt & MemberTypes.NestedType) != 0) {

                                if (Types != null)
                                        foreach (TypeContainer t in Types)  
                                                if (filter (t.TypeBuilder, criteria) == true)
                                                        members.Add (t.TypeBuilder);

                                if (Enums != null)
                                        foreach (Enum en in Enums)
                                                if (filter (en.TypeBuilder, criteria) == true)
                                                        members.Add (en.TypeBuilder);
                                
                        }

                        if ((mt & MemberTypes.Constructor) != 0){
                                if (instance_constructors != null){
                                        foreach (Constructor c in instance_constructors){
                                                ConstructorBuilder cb = c.ConstructorBuilder;

                                                if (cb != null)
                                                        if (filter (cb, criteria) == true)
                                                                members.Add (cb);
                                        }
                                }

                                if (default_static_constructor != null){
                                        ConstructorBuilder cb =
                                                default_static_constructor.ConstructorBuilder;
                                        
                                        if (filter (cb, criteria) == true)
                                                members.Add (cb);
                                }
                        }

                        //
                        // Lookup members in parent if requested.
                        //
                        if ((bf & BindingFlags.DeclaredOnly) == 0){
                                MemberInfo [] mi;

                                mi = FindMembers (TypeBuilder.BaseType, mt, bf, filter, criteria);
                                if (mi != null)
                                        members.AddRange (mi);
                        }
                        
                        int count = members.Count;
                        if (count > 0){
                                MemberInfo [] mi = new MemberInfo [count];
                                members.CopyTo (mi);
                                return mi;
                        }

                        return null;
                }

                public MemberInfo GetFieldFromEvent (EventExpr event_expr)
                {
                        EventInfo ei = event_expr.EventInfo;

                        foreach (Event e in events) { 

                                if (e.FieldBuilder == null)
                                        continue;
                                
                                if (Type.FilterName (e.FieldBuilder, ei.Name))
                                        return e.FieldBuilder;
                        }

                        return null;
                }

                public static MemberInfo [] FindMembers (Type t, MemberTypes mt, BindingFlags bf,
                                                         MemberFilter filter, object criteria)
                {
                        TypeContainer tc = TypeManager.LookupTypeContainer (t);

                        if (tc != null)
                                return tc.FindMembers (mt, bf, filter, criteria);
                        else
                                return t.FindMembers (mt, bf, filter, criteria);
                }

                //
                // FindMethods will look for methods not only in the type `t', but in
                // any interfaces implemented by the type.
                //
                public static MethodInfo [] FindMethods (Type t, BindingFlags bf,
                                                         MemberFilter filter, object criteria)
                {
                        return null;
                }

                /// <summary>
                ///   Whether the specified method is an interface method implementation
                /// </summary>
                ///
                /// <remarks>
                ///   If a method in Type `t' (or null to look in all interfaces
                ///   and the base abstract class) with name `Name', return type `ret_type' and
                ///   arguments `args' implements an interface, this method will
                ///   return the MethodInfo that this method implements.
                ///
                ///   This will remove the method from the list of "pending" methods
                ///   that are required to be implemented for this class as a side effect.
                /// 
                /// </remarks>
                public MethodInfo IsInterfaceMethod (Type t, string Name, Type ret_type, Type [] args,
                                                     bool clear)
                {
                        int arg_len = args.Length;

                        if (pending_implementations == null)
                                return null;

                        foreach (TypeAndMethods tm in pending_implementations){
                                if (!(t == null || tm.type == t))
                                        continue;

                                int i = 0;
                                foreach (MethodInfo m in tm.methods){
                                        if (m == null){
                                                i++;
                                                continue;
                                        }

                                        if (Name != m.Name){
                                                i++;
                                                continue;
                                        }

                                        if (ret_type != m.ReturnType){
                                                if (!((ret_type == null && m.ReturnType == TypeManager.void_type) ||
                                                      (m.ReturnType == null && ret_type == TypeManager.void_type)))
                                                {
                                                        i++;
                                                        continue;
                                                }
                                        }

                                        //
                                        // Check if we have the same parameters
                                        //
                                        if (tm.args [i].Length != arg_len){
                                                i++;
                                                continue;
                                        }

                                        int j, top = args.Length;
                                        bool fail = false;
                                        
                                        for (j = 0; j < top; j++){
                                                if (tm.args [i][j] != args[j]){
                                                        fail = true;
                                                        break;
                                                }
                                        }
                                        if (fail){
                                                i++;
                                                continue;
                                        }

                                        if (clear)
                                                tm.methods [i] = null;
                                        tm.found [i] = true;
                                        return m;
                                }

                                // If a specific type was requested, we can stop now.
                                if (tm.type == t)
                                        return null;
                        }
                        return null;
                }

                /// <summary>
                ///   C# allows this kind of scenarios:
                ///   interface I { void M (); }
                ///   class X { public void M (); }
                ///   class Y : X, I { }
                ///
                ///   For that case, we create an explicit implementation function
                ///   I.M in Y.
                /// </summary>
                void DefineProxy (Type iface, MethodInfo parent_method, MethodInfo iface_method,
                                  Type [] args)
                {
                        MethodBuilder proxy;

                        string proxy_name = iface.Name + "." + iface_method.Name;

                        proxy = TypeBuilder.DefineMethod (
                                proxy_name,
                                MethodAttributes.HideBySig |
                                MethodAttributes.NewSlot |
                                MethodAttributes.Virtual,
                                CallingConventions.Standard | CallingConventions.HasThis,
                                parent_method.ReturnType, args);

                        int top = args.Length;
                        ILGenerator ig = proxy.GetILGenerator ();

                        ig.Emit (OpCodes.Ldarg_0);
                        for (int i = 0; i < top; i++){
                                switch (i){
                                case 0:
                                        ig.Emit (OpCodes.Ldarg_1); break;
                                case 1:
                                        ig.Emit (OpCodes.Ldarg_2); break;
                                case 2:
                                        ig.Emit (OpCodes.Ldarg_3); break;
                                default:
                                        ig.Emit (OpCodes.Ldarg, i - 1); break;
                                }
                        }
                        ig.Emit (OpCodes.Call, parent_method);
                        ig.Emit (OpCodes.Ret);

                        TypeBuilder.DefineMethodOverride (proxy, iface_method);
                }
                
                /// <summary>
                ///   This function tells whether one of our parent classes implements
                ///   the given method (which turns out, it is valid to have an interface
                ///   implementation in a parent
                /// </summary>
                bool ParentImplements (Type iface_type, MethodInfo mi)
                {
                        MethodSignature ms;
                        
                        Type [] args = TypeManager.GetArgumentTypes (mi);
                        ms = new MethodSignature (mi.Name, mi.ReturnType, args);
                        MemberInfo [] list = FindMembers (
                                TypeBuilder.BaseType, MemberTypes.Method | MemberTypes.Property,
                                BindingFlags.Public | BindingFlags.Instance,
                                MethodSignature.method_signature_filter, ms);

                        if (list == null || list.Length == 0)
                                return false;
                        
                        DefineProxy (iface_type, (MethodInfo) list [0], mi, args);
                        return true;
                }
                
                /// <summary>
                ///   Verifies that any pending abstract methods or interface methods
                ///   were implemented.
                /// </summary>
                bool VerifyPendingMethods ()
                {
                        int top = pending_implementations.Length;
                        bool errors = false;
                        int i;
                        
                        for (i = 0; i < top; i++){
                                Type type = pending_implementations [i].type;
                                int j = 0;
                                
                                foreach (MethodInfo mi in pending_implementations [i].methods){
                                        if (mi == null)
                                                continue;

                                        if (type.IsInterface){
                                                if (ParentImplements (type, mi))
                                                        continue;
 
                                                string extra = "";
                                                
                                                if (pending_implementations [i].found [j])
                                                        extra = ".  (method might be private or static)";
                                                Report.Error (
                                                        536, Location,
                                                        "`" + Name + "' does not implement " +
                                                        "interface member `" +
                                                        type.FullName + "." + mi.Name + "'" + extra);
                                        } else {
                                                Report.Error (
                                                        534, Location,
                                                        "`" + Name + "' does not implement " +
                                                        "inherited abstract member `" +
                                                        type.FullName + "." + mi.Name + "'");
                                        }
                                        errors = true;
                                        j++;
                                }
                        }
                        return errors;
                }

                /// <summary>
                ///   Emits the values for the constants
                /// </summary>
                public void EmitConstants ()
                {
                        if (constants != null)
                                foreach (Const con in constants)
                                        con.EmitConstant (this);
                        return;
                }

                /// <summary>
                ///   Emits the code, this step is performed after all
                ///   the types, enumerations, constructors
                /// </summary>
                public void Emit ()
                {
                        if (instance_constructors != null)
                                foreach (Constructor c in instance_constructors)
                                        c.Emit (this);

                        if (default_static_constructor != null)
                                default_static_constructor.Emit (this);
                        
                        if (methods != null)
                                foreach (Method m in methods)
                                        m.Emit (this);

                        if (operators != null)
                                foreach (Operator o in operators)
                                        o.Emit (this);

                        if (properties != null)
                                foreach (Property p in properties)
                                        p.Emit (this);

                        if (indexers != null){
                                foreach (Indexer ix in indexers)
                                        ix.Emit (this);
                                
                                CustomAttributeBuilder cb = Interface.EmitDefaultMemberAttr (
                                        this, IndexerName, ModFlags, Location);
                                TypeBuilder.SetCustomAttribute (cb);
                        }
                        
                        if (fields != null)
                                foreach (Field f in fields)
                                        f.Emit (this);

                        if (events != null){
                                foreach (Event e in Events)
                                        e.Emit (this);
                        }

                        if (pending_implementations != null)
                                if (!VerifyPendingMethods ())
                                        return;
                        
                        Attribute.ApplyAttributes (ec, TypeBuilder, this, OptAttributes, Location);

                        //
                        // Check for internal or private fields that were never assigned
                        //
                        if (fields != null && RootContext.WarningLevel >= 3) {
                                foreach (Field f in fields) {
                                        if ((f.ModFlags & Modifiers.PUBLIC) != 0)
                                                continue;

                                        if (f.status == 0){
                                                Report.Warning (
                                                        169, f.Location, "Private field " +
                                                        MakeName (f.Name) + " is never used");
                                                continue;
                                        }

                                        //
                                        // Only report 649 on level 4
                                        //
                                        if (RootContext.WarningLevel < 4)
                                                continue;

                                        if ((f.status & Field.Status.ASSIGNED) != 0)
                                                continue;

                                        Report.Warning (
                                                649, f.Location,
                                                "Field " + MakeName (f.Name) + " is never assigned " +
                                                " to and will always have its default value");
                                }
                        }
                        
//                      if (types != null)
//                              foreach (TypeContainer tc in types)
//                                      tc.Emit ();
                }
                
                public override void CloseType ()
                {
                        try {
                                if (!Created){
                                        Created = true;
                                        TypeBuilder.CreateType ();
                                }
                        } catch (TypeLoadException){
                                //
                                // This is fine, the code still created the type
                                //
//                              Report.Warning (-20, "Exception while creating class: " + TypeBuilder.Name);
//                              Console.WriteLine (e.Message);
                        } catch {
                                Console.WriteLine ("In type: " + Name);
                                throw;
                        }
                        
                        if (Enums != null)
                                foreach (Enum en in Enums)
                                        en.CloseType ();

                        if (interface_order != null){
                                foreach (Interface iface in interface_order)
                                        iface.CloseType ();
                        }
                        
                        if (Types != null){
                                foreach (TypeContainer tc in Types)
                                        if (tc is Struct)
                                                tc.CloseType ();

                                foreach (TypeContainer tc in Types)
                                        if (!(tc is Struct))
                                                tc.CloseType ();
                        }

                        if (Delegates != null)
                                foreach (Delegate d in Delegates)
                                        d.CloseDelegate ();
                }

                public string MakeName (string n)
                {
                        return "`" + Name + "." + n + "'";
                }

                public void Warning_KeywordNewRequired (Location l, MemberInfo mi)
                {
                        Report.Warning (
                                108, l, "The keyword new is required on " + 
                                MakeName (mi.Name) + " because it hides `" +
                                mi.ReflectedType.Name + "." + mi.Name + "'");
                }

                public void Warning_KewywordNewNotRequired (Location l, MemberCore mc)
                {
                        Report.Warning (
                                109, l, "The member " + MakeName (mc.Name) + " does not hide an " +
                                "inherited member, the keyword new is not required");
                }
                
                public static int CheckMember (string name, MemberInfo mi, int ModFlags)
                {
                        return 0;
                }

                //
                // Performs the validation on a Method's modifiers (properties have
                // the same properties).
                //
                public bool MethodModifiersValid (int flags, string n, Location loc)
                {
                        const int vao = (Modifiers.VIRTUAL | Modifiers.ABSTRACT | Modifiers.OVERRIDE);
                        const int nv = (Modifiers.NEW | Modifiers.VIRTUAL);
                        bool ok = true;
                        string name = MakeName (n);
                        
                        //
                        // At most one of static, virtual or override
                        //
                        if ((flags & Modifiers.STATIC) != 0){
                                if ((flags & vao) != 0){
                                        Report.Error (
                                                112, loc, "static method " + name + "can not be marked " +
                                                "as virtual, abstract or override");
                                        ok = false;
                                }
                        }

                        if ((flags & Modifiers.OVERRIDE) != 0 && (flags & nv) != 0){
                                Report.Error (
                                        113, loc, name +
                                        " marked as override cannot be marked as new or virtual");
                                ok = false;
                        }

                        //
                        // If the declaration includes the abstract modifier, then the
                        // declaration does not include static, virtual or extern
                        //
                        if ((flags & Modifiers.ABSTRACT) != 0){
                                if ((flags & Modifiers.EXTERN) != 0){
                                        Report.Error (
                                                180, loc, name + " can not be both abstract and extern");
                                        ok = false;
                                }

                                if ((flags & Modifiers.VIRTUAL) != 0){
                                        Report.Error (
                                                503, loc, name + " can not be both abstract and virtual");
                                        ok = false;
                                }

                                if ((ModFlags & Modifiers.ABSTRACT) == 0){
                                        Report.Error (
                                                513, loc, name +
                                                " is abstract but its container class is not");
                                        ok = false;

                                }
                        }

                        if ((flags & Modifiers.PRIVATE) != 0){
                                if ((flags & vao) != 0){
                                        Report.Error (
                                                621, loc, name +
                                                " virtual or abstract members can not be private");
                                        ok = false;
                                }
                        }

                        if ((flags & Modifiers.SEALED) != 0){
                                if ((flags & Modifiers.OVERRIDE) == 0){
                                        Report.Error (
                                                238, loc, name +
                                                " cannot be sealed because it is not an override");
                                        ok = false;
                                }
                        }

                        return ok;
                }

                //
                // Returns true if `type' is as accessible as the flags `flags'
                // given for this member
                //
                static public bool AsAccessible (Type type, int flags)
                {
                        return true;
                }

                Hashtable builder_and_args;
                
                public bool RegisterMethod (MethodBuilder mb, InternalParameters ip, Type [] args)
                {
                        if (builder_and_args == null)
                                builder_and_args = new Hashtable ();
                        return true;
                }
        }

        public class Class : TypeContainer {
                // <summary>
                //   Modifiers allowed in a class declaration
                // </summary>
                public const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.ABSTRACT |
                        Modifiers.SEALED |
                        Modifiers.UNSAFE;

                public Class (TypeContainer parent, string name, int mod, Attributes attrs, Location l)
                        : base (parent, name, l)
                {
                        int accmods;

                        if (parent.Parent == null)
                                accmods = Modifiers.INTERNAL;
                        else
                                accmods = Modifiers.PRIVATE;

                        this.ModFlags = Modifiers.Check (AllowedModifiers, mod, accmods, l);
                        this.attributes = attrs;
                }

                //
                // FIXME: How do we deal with the user specifying a different
                // layout?
                //
                public override TypeAttributes TypeAttr {
                        get {
                                return base.TypeAttr | TypeAttributes.AutoLayout | TypeAttributes.Class;
                        }
                }
        }

        public class Struct : TypeContainer {
                // <summary>
                //   Modifiers allowed in a struct declaration
                // </summary>
                public const int AllowedModifiers =
                        Modifiers.NEW       |
                        Modifiers.PUBLIC    |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL  |
                        Modifiers.UNSAFE    |
                        Modifiers.PRIVATE;

                public Struct (TypeContainer parent, string name, int mod, Attributes attrs, Location l)
                        : base (parent, name, l)
                {
                        int accmods;
                        
                        if (parent.Parent == null)
                                accmods = Modifiers.INTERNAL;
                        else
                                accmods = Modifiers.PRIVATE;
                        
                        this.ModFlags = Modifiers.Check (AllowedModifiers, mod, accmods, l);

                        this.ModFlags |= Modifiers.SEALED;
                        this.attributes = attrs;
                        
                }

                //
                // FIXME: Allow the user to specify a different set of attributes
                // in some cases (Sealed for example is mandatory for a class,
                // but what SequentialLayout can be changed
                //
                public override TypeAttributes TypeAttr {
                        get {
                                return base.TypeAttr |
                                        TypeAttributes.SequentialLayout |
                                        TypeAttributes.Sealed |
                                        TypeAttributes.BeforeFieldInit;
                        }
                }
        }

        public abstract class MethodCore : MemberCore {
                public readonly Parameters Parameters;
                Block block;
                
                //
                // Parameters, cached for semantic analysis.
                //
                InternalParameters parameter_info;
                
                public MethodCore (string name, Parameters parameters, Location l)
                        : base (name, l)
                {
                        Name = name;
                        Parameters = parameters;
                }
                
                //
                //  Returns the System.Type array for the parameters of this method
                //
                Type [] parameter_types;
                public Type [] ParameterTypes (TypeContainer parent)
                {
                        if (Parameters == null)
                                return TypeManager.NoTypes;
                        
                        if (parameter_types == null)
                                parameter_types = Parameters.GetParameterInfo (parent);

                        return parameter_types;
                }

                public InternalParameters ParameterInfo
                {
                        get {
                                return parameter_info;
                        }

                        set {
                                parameter_info = value;
                        }
                }
                
                public Block Block {
                        get {
                                return block;
                        }

                        set {
                                block = value;
                        }
                }

                public CallingConventions GetCallingConvention (bool is_class)
                {
                        CallingConventions cc = 0;
                        
                        cc = Parameters.GetCallingConvention ();

                        if (is_class)
                                if ((ModFlags & Modifiers.STATIC) == 0)
                                        cc |= CallingConventions.HasThis;

                        // FIXME: How is `ExplicitThis' used in C#?
                        
                        return cc;
                }

                public void LabelParameters (EmitContext ec, Type [] parameters, MethodBase builder)
                {
                        //
                        // Define each type attribute (in/out/ref) and
                        // the argument names.
                        //
                        Parameter [] p = Parameters.FixedParameters;
                        int i = 0;
                        
                        MethodBuilder mb = null;
                        ConstructorBuilder cb = null;

                        if (builder is MethodBuilder)
                                mb = (MethodBuilder) builder;
                        else
                                cb = (ConstructorBuilder) builder;

                        if (p != null){
                                for (i = 0; i < p.Length; i++) {
                                        ParameterBuilder pb;
                                        
                                        if (mb == null)
                                                pb = cb.DefineParameter (
                                                        i + 1, p [i].Attributes, p [i].Name);
                                        else 
                                                pb = mb.DefineParameter (
                                                        i + 1, p [i].Attributes, p [i].Name);
                                        
                                        Attributes attr = p [i].OptAttributes;
                                        if (attr != null)
                                                Attribute.ApplyAttributes (ec, pb, pb, attr, Location);
                                }
                        }

                        if (Parameters.ArrayParameter != null){
                                ParameterBuilder pb;
                                Parameter array_param = Parameters.ArrayParameter;
                                
                                if (mb == null)
                                        pb = cb.DefineParameter (
                                                i + 1, array_param.Attributes,
                                                array_param.Name);
                                else
                                        pb = mb.DefineParameter (
                                                i + 1, array_param.Attributes,
                                                array_param.Name);
                                        
                                CustomAttributeBuilder a = new CustomAttributeBuilder (
                                        TypeManager.cons_param_array_attribute, new object [0]);
                                
                                pb.SetCustomAttribute (a);
                        }
                }
        }
        
        public class Method : MethodCore {
                public readonly string ReturnType;
                public MethodBuilder MethodBuilder;
                public readonly Attributes OptAttributes;

                MethodAttributes flags;

                /// <summary>
                ///   Modifiers allowed in a class declaration
                /// </summary>
                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.VIRTUAL |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.ABSTRACT |
                        Modifiers.UNSAFE |
                        Modifiers.EXTERN;

                //
                // return_type can be "null" for VOID values.
                //
                public Method (string return_type, int mod, string name, Parameters parameters,
                               Attributes attrs, Location l)
                        : base (name, parameters, l)
                {
                        ReturnType = return_type;
                        ModFlags = Modifiers.Check (AllowedModifiers, mod, Modifiers.PRIVATE, l);
                        OptAttributes = attrs;
                }

                //
                // Returns the `System.Type' for the ReturnType of this
                // function.  Provides a nice cache.  (used between semantic analysis
                // and actual code generation
                //
                Type type_return_type;
                
                public Type GetReturnType (TypeContainer parent)
                {
                        if (type_return_type == null)
                                type_return_type = RootContext.LookupType (
                                        parent, ReturnType, false, Location);
                        
                        return type_return_type;
                }

                void DuplicateEntryPoint (MethodInfo b, Location location)
                {
                        Report.Error (
                                17, location,
                                "Program `" + CodeGen.FileName +
                                "'  has more than one entry point defined: `" +
                                TypeManager.CSharpSignature(b) + "'");
                }

                void Report28 (MethodInfo b)
                {
                        if (RootContext.WarningLevel < 4) 
                                return;
                                
                        Report.Warning (
                                28, Location,
                                "`" + TypeManager.CSharpSignature(b) +
                                "' has the wrong signature to be an entry point");
                }

                public bool IsEntryPoint (MethodBuilder b, InternalParameters pinfo)
                {
                        if (b.ReturnType != TypeManager.void_type &&
                            b.ReturnType != TypeManager.int32_type)
                                return false;

                        if (pinfo.Count == 0)
                                return true;

                        if (pinfo.Count > 1)
                                return false;

                        Type t = pinfo.ParameterType(0);
                        if (t.IsArray &&
                            (t.GetArrayRank() == 1) &&
                            (t.GetElementType() == TypeManager.string_type) &&
                            (pinfo.ParameterModifier(0) == Parameter.Modifier.NONE))
                                return true;
                        else
                                return false;
                }       

                //
                // Creates the type
                //
                public override bool Define (TypeContainer parent)
                {
                        Type ret_type = GetReturnType (parent);
                        Type [] parameters = ParameterTypes (parent);
                        bool error = false;
                        MethodInfo implementing;
                        Type iface_type = null;
                        string iface = "", short_name;
                        bool explicit_impl = false;

                        // Check if the return type and arguments were correct
                        if (ret_type == null || parameters == null)
                                return false;
                        
                        if (!parent.MethodModifiersValid (ModFlags, Name, Location))
                                return false;

                        flags = Modifiers.MethodAttr (ModFlags);

                        //
                        // verify accessibility
                        //
                        if (!TypeContainer.AsAccessible (ret_type, ModFlags))
                                return false;

                        if (ret_type.IsPointer && !UnsafeOK (parent))
                                return false;
                        
                        foreach (Type partype in parameters){
                                if (!TypeContainer.AsAccessible (partype, ModFlags))
                                        error = true;
                                if (partype.IsPointer && !UnsafeOK (parent))
                                        error = true;
                        }

                        if (error)
                                return false;

                        //
                        // Verify if the parent has a type with the same name, and then
                        // check whether we have to create a new slot for it or not.
                        //
                        Type ptype = parent.TypeBuilder.BaseType;

                        // ptype is only null for System.Object while compiling corlib.
                        if (ptype != null){
                                MethodSignature ms = new MethodSignature (Name, null, parameters);
                                MemberInfo [] mi, mi_static, mi_instance;

                                mi_static = TypeContainer.FindMembers (
                                        ptype, MemberTypes.Method,
                                        BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static,
                                        MethodSignature.inheritable_method_signature_filter, ms);

                                mi_instance = TypeContainer.FindMembers (
                                        ptype, MemberTypes.Method,
                                        BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
                                        MethodSignature.inheritable_method_signature_filter,
                                        ms);

                                if (mi_instance != null && mi_instance.Length > 0){
                                        mi = mi_instance;
                                } else if (mi_static != null && mi_static.Length > 0)
                                        mi = mi_static;
                                else
                                        mi = null;

                                if (mi != null && mi.Length > 0){
                                        if (!CheckMethodAgainstBase (parent, flags, (MethodInfo) mi [0])){
                                                return false;
                                        }
                                } else {
                                        if ((ModFlags & Modifiers.NEW) != 0)
                                                WarningNotHiding (parent);

                                        if ((ModFlags & Modifiers.OVERRIDE) != 0){
                                                Report.Error (115, Location,
                                                              parent.MakeName (Name) +
                                                              " no suitable methods found to override");
                                        }
                                }
                        } else if ((ModFlags & Modifiers.NEW) != 0)
                                WarningNotHiding (parent);

                        //
                        // If we implement an interface, extract the interface name.
                        //

                        if (Name.IndexOf (".") != -1){
                                int pos = Name.LastIndexOf (".");
                                iface = Name.Substring (0, pos);

                                iface_type = RootContext.LookupType (parent, iface, false, Location);
                                short_name = Name.Substring (pos + 1);

                                if (iface_type == null)
                                        return false;

                                // Compute the full name that we need to export
                                Name = iface_type.FullName + "." + short_name;
                                explicit_impl = true;
                        } else
                                short_name = Name;

                        //
                        // Check if we are an implementation of an interface method or
                        // a method
                        //
                        implementing = parent.IsInterfaceMethod (
                                iface_type, short_name, ret_type, parameters, false);
                                
                        //
                        // For implicit implementations, make sure we are public, for
                        // explicit implementations, make sure we are private.
                        //
                        if (implementing != null){
                                //
                                // Setting null inside this block will trigger a more
                                // verbose error reporting for missing interface implementations
                                //
                                // The "candidate" function has been flagged already
                                // but it wont get cleared
                                //
                                if (iface_type == null){
                                        //
                                        // We already catch different accessibility settings
                                        // so we just need to check that we are not private
                                        //
                                        if ((ModFlags & Modifiers.PRIVATE) != 0)
                                                implementing = null;

                                        //
                                        // Static is not allowed
                                        //
                                        if ((ModFlags & Modifiers.STATIC) != 0)
                                                implementing = null;
                                } else {
                                        if ((ModFlags & (Modifiers.PUBLIC | Modifiers.ABSTRACT)) != 0){
                                                Report.Error (
                                                        106, Location, "`public' or `abstract' modifiers "+
                                                        "are not allowed in explicit interface declarations"
                                                        );
                                                implementing = null;
                                        }
                                }
                        }
                        
                        //
                        // If implementing is still valid, set flags
                        //
                        if (implementing != null){
                                if (implementing.DeclaringType.IsInterface)
                                        flags |= MethodAttributes.NewSlot;
                                
                                flags |=
                                        MethodAttributes.Virtual |
                                        MethodAttributes.HideBySig;

                                //
                                // clear the flag
                                //
                                parent.IsInterfaceMethod (
                                        iface_type, short_name, ret_type, parameters, true);
                        } 

                        Attribute dllimport_attr = null;
                        if (OptAttributes != null && OptAttributes.AttributeSections != null) {
                                foreach (AttributeSection asec in OptAttributes.AttributeSections) {
                                        if (asec.Attributes == null)
                                                continue;
                                        
                                        foreach (Attribute a in asec.Attributes)
                                                if (a.Name.IndexOf ("DllImport") != -1) {
                                                        flags |= MethodAttributes.PinvokeImpl;
                                                        dllimport_attr = a;
                                                }
                                }
                        }

                        //
                        // Finally, define the method
                        //

                        if ((flags & MethodAttributes.PinvokeImpl) != 0) {

                                if ((ModFlags & Modifiers.STATIC) == 0) {
                                        Report.Error (601, Location, "The DllImport attribute must be specified on " +
                                                      "a method marked 'static' and 'extern'.");
                                        return false;
                                }
                                
                                EmitContext ec = new EmitContext (
                                        parent, Location, null, GetReturnType (parent), ModFlags);
                                
                                MethodBuilder = dllimport_attr.DefinePInvokeMethod (
                                        ec, parent.TypeBuilder,
                                        Name, flags, ret_type, parameters);
                        } else {
                                MethodBuilder = parent.TypeBuilder.DefineMethod (
                                        Name, flags,
                                        GetCallingConvention (parent is Class),
                                        ret_type, parameters);

                                if (implementing != null && explicit_impl)
                                        parent.TypeBuilder.DefineMethodOverride (
                                                MethodBuilder, implementing);
                        }

                        if (MethodBuilder == null)
                                return false;

                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        ParameterInfo = new InternalParameters (parent, Parameters);

                        if (!TypeManager.RegisterMethod (MethodBuilder, ParameterInfo,
                                                         parameters)) {
                                Report.Error (
                                        111, Location,
                                        "Class `" + parent.Name + "' already contains a definition with " +
                                        " the same return value and parameter types for method `" +
                                        Name + "'");
                                return false;
                        }
                        
                        //
                        // This is used to track the Entry Point,
                        //
                        if (Name == "Main" &&
                            ((ModFlags & Modifiers.STATIC) != 0) && 
                            (RootContext.MainClass == null ||
                             RootContext.MainClass == parent.TypeBuilder.FullName)){
                                if (IsEntryPoint (MethodBuilder, ParameterInfo)) {
                                        if (RootContext.EntryPoint == null) {
                                                RootContext.EntryPoint = MethodBuilder;
                                                RootContext.EntryPointLocation = Location;
                                        } else {
                                                DuplicateEntryPoint (RootContext.EntryPoint, RootContext.EntryPointLocation);
                                                DuplicateEntryPoint (MethodBuilder, Location);
                                        }
                                } else                                  
                                        Report28(MethodBuilder);
                        }

                        return true;
                }

                //
                // Emits the code
                // 
                public void Emit (TypeContainer parent)
                {
                        ILGenerator ig;
                        EmitContext ec;

                        if ((flags & MethodAttributes.PinvokeImpl) == 0)
                                ig = MethodBuilder.GetILGenerator ();
                        else
                                ig = null;

                        ec = new EmitContext (parent, Location, ig, GetReturnType (parent), ModFlags);

                        if (OptAttributes != null)
                                Attribute.ApplyAttributes (ec, MethodBuilder, this, OptAttributes, Location);
                        

                        LabelParameters (ec, ParameterTypes (parent), MethodBuilder);
                        
                        //
                        // abstract or extern methods have no bodies
                        //
                        if ((ModFlags & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0){
                                if (Block != null){
                                        if ((ModFlags & Modifiers.ABSTRACT) != 0){
                                                Report.Error (
                                                        500, "Abstract method `" +
                                                        TypeManager.CSharpSignature (MethodBuilder) +
                                                        "' can not have a body");
                                        }
                                }
                                return;
                        }

                        //
                        // Handle destructors specially
                        //
                        // FIXME: This code generates buggy code
                        //
                        if (Name == "Finalize" && type_return_type == TypeManager.void_type)
                                EmitDestructor (ec);
                        else {
                                ISymbolWriter sw = CodeGen.SymbolWriter;

                                if ((sw != null) && (!Location.IsNull (Location))) {
                                        MethodToken token = MethodBuilder.GetToken ();
                                        sw.OpenMethod (new SymbolToken (token.Token));
                                        sw.SetMethodSourceRange (Location.SymbolDocument,
                                                                 Location.Row, 0,
                                                                 Block.EndLocation.SymbolDocument,
                                                                 Block.EndLocation.Row, 0);

                                        ec.EmitTopBlock (Block, Location);

                                        sw.CloseMethod ();
                                } else
                                        ec.EmitTopBlock (Block, Location);
                        }
                }

                void EmitDestructor (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;
                        
                        Label finish = ig.DefineLabel ();
                        bool old_in_try = ec.InTry;
                        Expression member_lookup;
                        
                        ig.BeginExceptionBlock ();
                        ec.InTry = true;
                        ec.ReturnLabel = finish;
                        ec.EmitTopBlock (Block, Location);
                        ec.InTry = old_in_try;
                        
                        ig.MarkLabel (finish);
                        bool old_in_finally = ec.InFinally;
                        ec.InFinally = true;
                        ig.BeginFinallyBlock ();
                        
                        member_lookup = Expression.MemberLookup (
                                ec, ec.ContainerType.BaseType, "Finalize",
                                MemberTypes.Method, Expression.AllBindingFlags, Location);

                        if (member_lookup != null){
                                MethodGroupExpr parent_destructor = ((MethodGroupExpr) member_lookup);
                                
                                ig.Emit (OpCodes.Ldarg_0);
                                ig.Emit (OpCodes.Call, (MethodInfo) parent_destructor.Methods [0]);
                        }
                        ec.InFinally = old_in_finally;
                        
                        ig.EndExceptionBlock ();
                        //ig.MarkLabel (ec.ReturnLabel);
                        ig.Emit (OpCodes.Ret);
                }
        }

        public abstract class ConstructorInitializer {
                ArrayList argument_list;
                ConstructorInfo parent_constructor;
                Location location;
                
                public ConstructorInitializer (ArrayList argument_list, Location location)
                {
                        this.argument_list = argument_list;
                        this.location = location;
                }

                public ArrayList Arguments {
                        get {
                                return argument_list;
                        }
                }

                public bool Resolve (EmitContext ec)
                {
                        Expression parent_constructor_group;
                        Type t;
                        
                        if (argument_list != null){
                                foreach (Argument a in argument_list){
                                        if (!a.Resolve (ec, location))
                                                return false;
                                }
                        }

                        if (this is ConstructorBaseInitializer)
                                t = ec.ContainerType.BaseType;
                        else
                                t = ec.ContainerType;
                        
                        parent_constructor_group = Expression.MemberLookup (
                                ec, t, ".ctor", 
                                MemberTypes.Constructor,
                                BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly,
                                location);
                        
                        if (parent_constructor_group == null){
                                Report.Error (1501, location,
                                       "Can not find a constructor for this argument list");
                                return false;
                        }
                        
                        parent_constructor = (ConstructorInfo) Invocation.OverloadResolve (ec, 
                                (MethodGroupExpr) parent_constructor_group, argument_list, location);
                        
                        if (parent_constructor == null){
                                Report.Error (1501, location,
                                       "Can not find a constructor for this argument list");
                                return false;
                        }
                        
                        return true;
                }

                public void Emit (EmitContext ec)
                {
                        ec.ig.Emit (OpCodes.Ldarg_0);
                        if (argument_list != null)
                                Invocation.EmitArguments (ec, null, argument_list);
                        ec.ig.Emit (OpCodes.Call, parent_constructor);
                }
        }

        public class ConstructorBaseInitializer : ConstructorInitializer {
                public ConstructorBaseInitializer (ArrayList argument_list, Location l) : base (argument_list, l)
                {
                }
        }

        public class ConstructorThisInitializer : ConstructorInitializer {
                public ConstructorThisInitializer (ArrayList argument_list, Location l) : base (argument_list, l)
                {
                }
        }
        
        public class Constructor : MethodCore {
                public ConstructorBuilder ConstructorBuilder;
                public ConstructorInitializer Initializer;
                public Attributes OptAttributes;

                // <summary>
                //   Modifiers allowed for a constructor.
                // </summary>
                const int AllowedModifiers =
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.STATIC |
                        Modifiers.UNSAFE |
                        Modifiers.PRIVATE;

                //
                // The spec claims that static is not permitted, but
                // my very own code has static constructors.
                //
                public Constructor (string name, Parameters args, ConstructorInitializer init, Location l)
                        : base (name, args, l)
                {
                        Initializer = init;
                }

                //
                // Returns true if this is a default constructor
                //
                public bool IsDefault ()
                {
                        if ((ModFlags & Modifiers.STATIC) != 0)
                                return  (Parameters.FixedParameters == null ? true : Parameters.Empty) &&
                                        (Parameters.ArrayParameter == null ? true : Parameters.Empty);
                        
                        else
                                return  (Parameters.FixedParameters == null ? true : Parameters.Empty) &&
                                        (Parameters.ArrayParameter == null ? true : Parameters.Empty) &&
                                        (Initializer is ConstructorBaseInitializer) &&
                                        (Initializer.Arguments == null);
                }

                //
                // Creates the ConstructorBuilder
                //
                public override bool Define (TypeContainer parent)
                {
                        MethodAttributes ca = (MethodAttributes.RTSpecialName |
                                               MethodAttributes.SpecialName);

                        Type [] parameters = ParameterTypes (parent);

                        if (parameters == null)
                                return false;
                        
                        if ((ModFlags & Modifiers.STATIC) != 0)
                                ca |= MethodAttributes.Static;
                        else {
                                if (parent is Struct && parameters.Length == 0){
                                        Report.Error (
                                                568, Location, 
                                                "Structs can not contain explicit parameterless " +
                                                "constructors");
                                        return false;
                                }
                                ca |= MethodAttributes.Public | MethodAttributes.HideBySig;
                        }

                        foreach (Type partype in parameters)
                                if (!TypeContainer.AsAccessible (partype, ModFlags))
                                        return false;

                        ConstructorBuilder = parent.TypeBuilder.DefineConstructor (
                                ca, GetCallingConvention (parent is Class), parameters);

                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        ParameterInfo = new InternalParameters (parent, Parameters);

                        if (!TypeManager.RegisterMethod (ConstructorBuilder, ParameterInfo, parameters)) {
                                Report.Error (
                                        111, Location,
                                        "Class `" +parent.Name+ "' already contains a definition with the " +
                                        "same return value and parameter types for constructor `" + Name
                                        + "'");
                                return false;
                        }

                        return true;
                }

                //
                // Emits the code
                //
                public void Emit (TypeContainer parent)
                {
                        ILGenerator ig = ConstructorBuilder.GetILGenerator ();
                        EmitContext ec = new EmitContext (parent, Location, ig, null, ModFlags, true);

                        if (parent is Class && ((ModFlags & Modifiers.STATIC) == 0)){
                                if (Initializer == null)
                                        Initializer = new ConstructorBaseInitializer (null, parent.Location);


                                //
                                // Spec mandates that Initializers will not have
                                // `this' access
                                //
                                ec.IsStatic = true;
                                if (!Initializer.Resolve (ec))
                                        return;
                                ec.IsStatic = false;
                        }

                        LabelParameters (ec, ParameterTypes (parent), ConstructorBuilder);
                        
                        //
                        // Classes can have base initializers and instance field initializers.
                        //
                        if (parent is Class){
                                if ((ModFlags & Modifiers.STATIC) == 0){
                                        parent.EmitFieldInitializers (ec);

                                        Initializer.Emit (ec);
                                }
                        }
                        
                        if ((ModFlags & Modifiers.STATIC) != 0)
                                parent.EmitFieldInitializers (ec);

                        Attribute.ApplyAttributes (ec, ConstructorBuilder, this, OptAttributes, Location);

                        ec.EmitTopBlock (Block, Location);
                }
        }

        //
        // Fields and Events both generate FieldBuilders, we use this to share 
        // their common bits.  This is also used to flag usage of the field
        //
        abstract public class FieldBase : MemberCore {
                public readonly string Type;
                public readonly Object Initializer;
                public readonly Attributes OptAttributes;
                public FieldBuilder  FieldBuilder;
                public Status status;

                [Flags]
                public enum Status : byte { ASSIGNED = 1, USED = 2 }

                //
                // The constructor is only exposed to our children
                //
                protected FieldBase (string type, int mod, int allowed_mod, string name,
                                     object init, Attributes attrs, Location loc)
                        : base (name, loc)
                {
                        Type = type;
                        ModFlags = Modifiers.Check (allowed_mod, mod, Modifiers.PRIVATE, loc);
                        Initializer = init;
                        OptAttributes = attrs;
                }
        }

        //
        // The Field class is used to represents class/struct fields during parsing.
        //
        public class Field : FieldBase {
                // <summary>
                //   Modifiers allowed in a class declaration
                // </summary>
                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.VOLATILE |
                        Modifiers.UNSAFE |
                        Modifiers.READONLY;

                public Field (string type, int mod, string name, Object expr_or_array_init,
                              Attributes attrs, Location loc)
                        : base (type, mod, AllowedModifiers, name, expr_or_array_init, attrs, loc)
                {
                }

                public override bool Define (TypeContainer parent)
                {
                        Type t = RootContext.LookupType (parent, Type, false, Location);
                        
                        if (t == null)
                                return false;

                        if (!TypeContainer.AsAccessible (t, ModFlags))
                                return false;

                        if (t.IsPointer && !UnsafeOK (parent))
                                return false;
                                
                        if (RootContext.WarningLevel > 1){
                                Type ptype = parent.TypeBuilder.BaseType;

                                // ptype is only null for System.Object while compiling corlib.
                                if (ptype != null){
                                        MemberInfo [] mi;
                                        
                                        mi = TypeContainer.FindMembers (
                                                ptype, MemberTypes.Method,
                                                BindingFlags.Public |
                                                BindingFlags.Static | BindingFlags.Instance,
                                                System.Type.FilterName, Name);
                                }
                        }

                        if ((ModFlags & Modifiers.VOLATILE) != 0){
                                if (!t.IsClass){
                                        if (TypeManager.IsEnumType (t))
                                                t = TypeManager.EnumToUnderlying (t);

                                        if (!((t == TypeManager.bool_type) ||
                                              (t == TypeManager.sbyte_type) ||
                                              (t == TypeManager.byte_type) ||
                                              (t == TypeManager.short_type) ||    
                                              (t == TypeManager.ushort_type) ||
                                              (t == TypeManager.int32_type) ||    
                                              (t == TypeManager.uint32_type) ||    
                                              (t == TypeManager.char_type) ||    
                                              (t == TypeManager.float_type))){
                                                Report.Error (
                                                        677, Location, parent.MakeName (Name) +
                                                        " A volatile field can not be of type `" +
                                                        TypeManager.CSharpName (t) + "'");
                                                return false;
                                        }
                                }
                        }
                        
                        FieldBuilder = parent.TypeBuilder.DefineField (
                                Name, t, Modifiers.FieldAttr (ModFlags));

                        TypeManager.RegisterFieldBase (FieldBuilder, this);
                        return true;
                }

                public void Emit (TypeContainer tc)
                {
                        EmitContext ec = new EmitContext (tc, Location, null,
                                                          FieldBuilder.FieldType, ModFlags);

                        Attribute.ApplyAttributes (ec, FieldBuilder, this, OptAttributes, Location);
                }
        }

        //
        // `set' and `get' accessors are represented with an Accessor.
        // 
        public class Accessor {
                //
                // Null if the accessor is empty, or a Block if not
                //
                public Block Block;

                public Accessor (Block b)
                {
                        Block = b;
                }
        }
                        
        public class Property : MemberCore {
                public readonly string Type;
                public Accessor Get, Set;
                public PropertyBuilder PropertyBuilder;
                public Attributes OptAttributes;
                public MethodBuilder GetBuilder, SetBuilder;

                //
                // The type, once we compute it.
                
                Type PropertyType;

                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.ABSTRACT |
                        Modifiers.UNSAFE |
                        Modifiers.EXTERN |
                        Modifiers.VIRTUAL;

                public Property (string type, string name, int mod_flags,
                                 Accessor get_block, Accessor set_block,
                                 Attributes attrs, Location loc)
                        : base (name, loc)
                {
                        Type = type;
                        ModFlags = Modifiers.Check (AllowedModifiers, mod_flags, Modifiers.PRIVATE, loc);
                        Get = get_block;
                        Set = set_block;
                        OptAttributes = attrs;
                }

                //
                // Checks our base implementation if any
                //
                bool CheckBase (MethodAttributes flags, TypeContainer parent)
                {
                        //
                        // Find properties with the same name on the base class
                        //

                        MemberInfo [] props;
                        MemberInfo [] props_static = TypeManager.MemberLookup (
                                parent.TypeBuilder, 
                                parent.TypeBuilder.BaseType,
                                MemberTypes.Property, BindingFlags.Public | BindingFlags.Static,
                                Name);

                        MemberInfo [] props_instance = TypeManager.MemberLookup (
                                parent.TypeBuilder, 
                                parent.TypeBuilder.BaseType,
                                MemberTypes.Property, BindingFlags.Public | BindingFlags.Instance,
                                Name);

                        //
                        // Find if we have anything
                        //
                        if (props_static != null && props_static.Length > 0)
                                props = props_static;
                        else if (props_instance != null && props_instance.Length > 0)
                                props = props_instance;
                        else
                                props = null;

                        //
                        // If we have something on the base.
                        if (props != null && props.Length > 0){
                                if (props.Length > 1)
                                        throw new Exception ("Should not happen");
                                
                                PropertyInfo pi = (PropertyInfo) props [0];

                                MethodInfo inherited_get = TypeManager.GetPropertyGetter (pi);
                                MethodInfo inherited_set = TypeManager.GetPropertySetter (pi);

                                MethodInfo reference = inherited_get == null ?
                                        inherited_set : inherited_get;
                                
                                if (reference != null)
                                        if (!CheckMethodAgainstBase (parent, flags, reference))
                                                return false;
                                
                        } else {
                                if ((ModFlags & Modifiers.NEW) != 0)
                                        WarningNotHiding (parent);
                                
                                if ((ModFlags & Modifiers.OVERRIDE) != 0){
                                        Report.Error (115, Location,
                                                      parent.MakeName (Name) +
                                                      " no suitable properties found to override");
                                        return false;
                                }
                        }
                        return true;
                }

                bool DefineMethod (TypeContainer parent, Type iface_type, string short_name,
                                   MethodAttributes flags, bool is_get)
                {
                        Type [] parameters = TypeManager.NoTypes;
                        MethodInfo implementing;
                        Type fn_type;
                        string name;

                        if (is_get){
                                fn_type = PropertyType;
                                name = "get_" + short_name;
                        } else {
                                name = "set_" + short_name;
                                parameters = new Type [1];
                                parameters [0] = PropertyType;
                                fn_type = TypeManager.void_type;
                        }

                        implementing = parent.IsInterfaceMethod (
                                iface_type, name, fn_type, parameters, false);

                        //
                        // For implicit implementations, make sure we are public, for
                        // explicit implementations, make sure we are private.
                        //
                        if (implementing != null){
                                //
                                // Setting null inside this block will trigger a more
                                // verbose error reporting for missing interface implementations
                                //
                                // The "candidate" function has been flagged already
                                // but it wont get cleared
                                //
                                if (iface_type == null){
                                        //
                                        // We already catch different accessibility settings
                                        // so we just need to check that we are not private
                                        //
                                        if ((ModFlags & Modifiers.PRIVATE) != 0)
                                                implementing = null;
                                        
                                        //
                                        // Static is not allowed
                                        //
                                        if ((ModFlags & Modifiers.STATIC) != 0)
                                                implementing = null;
                                } else {
                                        if ((ModFlags & (Modifiers.PUBLIC | Modifiers.ABSTRACT)) != 0){
                                                Report.Error (
                                                        106, Location, "`public' or `abstract' modifiers "+
                                                        "are not allowed in explicit interface declarations"
                                                        );
                                                implementing = null;
                                        }
                                }
                        }
                        
                        //
                        // If implementing is still valid, set flags
                        //
                        if (implementing != null){
                                //
                                // When implementing interface methods, set NewSlot.
                                //
                                if (implementing.DeclaringType.IsInterface)
                                        flags |= MethodAttributes.NewSlot;
                                
                                flags |=
                                        MethodAttributes.Virtual |
                                        MethodAttributes.HideBySig;

                                //
                                // clear the pending flag
                                //
                                parent.IsInterfaceMethod (
                                        iface_type, name, fn_type, parameters, true);
                        }

                        //
                        // If this is not an explicit interface implementation,
                        // clear implementing, as it is only used for explicit
                        // interface implementation
                        //
                        if (Name.IndexOf (".") == -1)
                                implementing = null;
                        
                        if (is_get){
                                GetBuilder = parent.TypeBuilder.DefineMethod (
                                        name, flags, PropertyType, null);
                                PropertyBuilder.SetGetMethod (GetBuilder);
                        
                                if (implementing != null)
                                        parent.TypeBuilder.DefineMethodOverride (
                                                GetBuilder, implementing);
                                
                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                InternalParameters ip = new InternalParameters (
                                        parent, Parameters.GetEmptyReadOnlyParameters ());
                                
                                if (!TypeManager.RegisterMethod (GetBuilder, ip, null)) {
                                        Report.Error (111, Location,
                                                      "Class `" + parent.Name +
                                                      "' already contains a definition with the " +
                                                      "same return value and parameter types as the " +
                                                      "'get' method of property `" + Name + "'");
                                        return false;
                                }
                        } else {
                                SetBuilder = parent.TypeBuilder.DefineMethod (
                                        name, flags, null, parameters);
                                
                                if (implementing != null)
                                        parent.TypeBuilder.DefineMethodOverride (
                                                SetBuilder, implementing);
                                
                                SetBuilder.DefineParameter (1, ParameterAttributes.None, "value"); 
                                PropertyBuilder.SetSetMethod (SetBuilder);

                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                Parameter [] parms = new Parameter [1];
                                parms [0] = new Parameter (Type, "value", Parameter.Modifier.NONE, null);
                                InternalParameters ip = new InternalParameters (
                                        parent, new Parameters (parms, null, Location));

                                if (!TypeManager.RegisterMethod (SetBuilder, ip, parameters)) {
                                        Report.Error (
                                                111, Location,
                                                "Class `" + parent.Name +
                                                "' already contains a definition with the " +
                                                "same return value and parameter types as the " +
                                                "'set' method of property `" + Name + "'");
                                        return false;
                                }
                        }

                        return true;
                }

                public override bool Define (TypeContainer parent)
                {
                        Type iface_type = null;
                        string short_name;
                        
                        if (!parent.MethodModifiersValid (ModFlags, Name, Location))
                                return false;

                        MethodAttributes flags = Modifiers.MethodAttr (ModFlags);
                        
                        flags |= MethodAttributes.HideBySig |
                                MethodAttributes.SpecialName;

                        // Lookup Type, verify validity
                        PropertyType = RootContext.LookupType (parent, Type, false, Location);
                        if (PropertyType == null)
                                return false;

                        // verify accessibility
                        if (!TypeContainer.AsAccessible (PropertyType, ModFlags))
                                return false;

                        if (PropertyType.IsPointer && !UnsafeOK (parent))
                                return false;
                        
                        if (!CheckBase (flags, parent))
                                return false;

                        //
                        // Check for explicit interface implementation
                        //
                        if (Name.IndexOf (".") != -1){
                                int pos = Name.LastIndexOf (".");
                                string iface = Name.Substring (0, pos);

                                iface_type = RootContext.LookupType (parent, iface, false, Location);
                                if (iface_type == null)
                                        return false;

                                short_name = Name.Substring (pos + 1);

                                // Compute the full name that we need to export.
                                Name = iface_type.FullName + "." + short_name;
                        } else
                                short_name = Name;

                        // FIXME - PropertyAttributes.HasDefault ?

                        PropertyAttributes prop_attr = PropertyAttributes.RTSpecialName |
                                                       PropertyAttributes.SpecialName;
                
                        PropertyBuilder = parent.TypeBuilder.DefineProperty (
                                Name, prop_attr, PropertyType, null);

                        if (Get != null)
                                if (!DefineMethod (parent, iface_type, short_name, flags, true))
                                        return false;
                        
                        if (Set != null)
                                if (!DefineMethod (parent, iface_type, short_name, flags, false))
                                        return false;
                        
                        //
                        // HACK for the reasons exposed above
                        //
                        if (!TypeManager.RegisterProperty (PropertyBuilder, GetBuilder, SetBuilder)) {
                                Report.Error (
                                        111, Location,
                                        "Class `" + parent.Name +
                                        "' already contains a definition for the property `" +
                                        Name + "'");
                                return false;
                        }

                        return true;
                }
                
                public void Emit (TypeContainer tc)
                {
                        ILGenerator ig;
                        EmitContext ec;

                        ec = new EmitContext (tc, Location, null, PropertyType, ModFlags);
                        Attribute.ApplyAttributes (ec, PropertyBuilder, this, OptAttributes, Location);
                        

                        //
                        // abstract or extern properties have no bodies
                        //
                        if ((ModFlags & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
                                return;

                        if (Get != null){
                                ig = GetBuilder.GetILGenerator ();
                                ec = new EmitContext (tc, Location, ig, PropertyType, ModFlags);
                                
                                ec.EmitTopBlock (Get.Block, Location);
                        }

                        if (Set != null){
                                ig = SetBuilder.GetILGenerator ();
                                ec = new EmitContext (tc, Location, ig, null, ModFlags);
                                
                                ec.EmitTopBlock (Set.Block, Location);
                        }
                }
        }


        /// </summary>
        ///  Gigantic workaround  for lameness in SRE follows :
        ///  This class derives from EventInfo and attempts to basically
        ///  wrap around the EventBuilder so that FindMembers can quickly
        ///  return this in it search for members
        /// </summary>
        public class MyEventBuilder : EventInfo {
                
                //
                // We use this to "point" to our Builder which is
                // not really a MemberInfo
                //
                EventBuilder MyBuilder;
                
                //
                // We "catch" and wrap these methods
                //
                MethodInfo raise, remove, add;

                EventAttributes attributes;
                Type declaring_type, reflected_type, event_type;
                string name;

                public MyEventBuilder (TypeBuilder type_builder, string name, EventAttributes event_attr, Type event_type)
                {
                        MyBuilder = type_builder.DefineEvent (name, event_attr, event_type);

                        // And now store the values in our own fields.
                        
                        declaring_type = type_builder;

                        reflected_type = type_builder;
                        
                        attributes = event_attr;
                        this.name = name;
                        this.event_type = event_type;
                }
                
                //
                // Methods that you have to override.  Note that you only need 
                // to "implement" the variants that take the argument (those are
                // the "abstract" methods, the others (GetAddMethod()) are 
                // regular.
                //
                public override MethodInfo GetAddMethod (bool nonPublic)
                {
                        return add;
                }
                
                public override MethodInfo GetRemoveMethod (bool nonPublic)
                {
                        return remove;
                }
                
                public override MethodInfo GetRaiseMethod (bool nonPublic)
                {
                        return raise;
                }
                
                //
                // These methods make "MyEventInfo" look like a Builder
                //
                public void SetRaiseMethod (MethodBuilder raiseMethod)
                {
                        raise = raiseMethod;
                        MyBuilder.SetRaiseMethod (raiseMethod);
                }

                public void SetRemoveOnMethod (MethodBuilder removeMethod)
                {
                        remove = removeMethod;
                        MyBuilder.SetRemoveOnMethod (removeMethod);
                }

                public void SetAddOnMethod (MethodBuilder addMethod)
                {
                        add = addMethod;
                        MyBuilder.SetAddOnMethod (addMethod);
                }

                public void SetCustomAttribute (CustomAttributeBuilder cb)
                {
                        MyBuilder.SetCustomAttribute (cb);
                }
                
                public override object [] GetCustomAttributes (bool inherit)
                {
                        // FIXME : There's nothing which can be seemingly done here because
                        // we have no way of getting at the custom attribute objects of the
                        // EventBuilder !
                        return null;
                }

                public override object [] GetCustomAttributes (Type t, bool inherit)
                {
                        // FIXME : Same here !
                        return null;
                }

                public override bool IsDefined (Type t, bool b)
                {
                        return true;
                }

                public override EventAttributes Attributes {
                        get {
                                return attributes;
                        }
                }

                public override string Name {
                        get {
                                return name;
                        }
                }

                public override Type DeclaringType {
                        get {
                                return declaring_type;
                        }
                }

                public override Type ReflectedType {
                        get {
                                return reflected_type;
                        }
                }

                public Type EventType {
                        get {
                                return event_type;
                        }
                }
        }
        
        public class Event : FieldBase {
                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.VIRTUAL |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.UNSAFE |
                        Modifiers.ABSTRACT;

                public readonly Block     Add;
                public readonly Block     Remove;
                public MyEventBuilder     EventBuilder;

                Type EventType;
                MethodBuilder AddBuilder, RemoveBuilder;
                
                public Event (string type, string name, Object init, int mod, Block add_block,
                              Block rem_block, Attributes attrs, Location loc)
                        : base (type, mod, AllowedModifiers, name, init, attrs, loc)
                {
                        Add = add_block;
                        Remove = rem_block;
                }

                public override bool Define (TypeContainer parent)
                {
                        if (!parent.MethodModifiersValid (ModFlags, Name, Location))
                                return false;

                        MethodAttributes m_attr = Modifiers.MethodAttr (ModFlags);
                        EventAttributes e_attr = EventAttributes.RTSpecialName | EventAttributes.SpecialName;

                        EventType = RootContext.LookupType (parent, Type, false, Location);
                        if (EventType == null)
                                return false;

                        if (!TypeContainer.AsAccessible (EventType, ModFlags))
                                return false;

                        if (EventType.IsPointer && !UnsafeOK (parent))
                                return false;

                        if (!EventType.IsSubclassOf (TypeManager.delegate_type)) {
                                Report.Error (66, Location, "'" + parent.Name + "." + Name +
                                              "' : event must be of a delegate type");
                                return false;
                        }
                        
                        Type [] parameters = new Type [1];
                        parameters [0] = EventType;

                        EventBuilder = new MyEventBuilder (parent.TypeBuilder, Name, e_attr, EventType);

                        if (Add == null && Remove == null){
                                FieldBuilder = parent.TypeBuilder.DefineField (
                                        Name, EventType, FieldAttributes.Private);
                                TypeManager.RegisterFieldBase (FieldBuilder, this);
                        }
                        
                        //
                        // Now define the accessors
                        //
                        string add_name = "add_" + Name;
                        
                        AddBuilder = parent.TypeBuilder.DefineMethod (
                                add_name, m_attr, null, parameters);
                        AddBuilder.DefineParameter (1, ParameterAttributes.None, "value");
                        EventBuilder.SetAddOnMethod (AddBuilder);
                        parent.IsInterfaceMethod (null, add_name, null, parameters, true);
                        
                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        Parameter [] parms = new Parameter [1];
                        parms [0] = new Parameter (Type, "value", Parameter.Modifier.NONE, null);
                        InternalParameters ip = new InternalParameters (
                                                            parent, new Parameters (parms, null, Location)); 
                        
                        if (!TypeManager.RegisterMethod (AddBuilder, ip, parameters)) {
                                Report.Error (111, Location,
                                              "Class `" + parent.Name + "' already contains a definition with the " +
                                              "same return value and parameter types for the " +
                                              "'add' method of event `" + Name + "'");
                                return false;
                        }

                        string remove_name = "remove_" + Name;
                        RemoveBuilder = parent.TypeBuilder.DefineMethod (
                                                            remove_name, m_attr, null, parameters);
                        RemoveBuilder.DefineParameter (1, ParameterAttributes.None, "value");
                        EventBuilder.SetRemoveOnMethod (RemoveBuilder);
                        parent.IsInterfaceMethod (null, remove_name, null, parameters, true);

                        //
                        // HACK because System.Reflection.Emit is lame
                        //

                        if (!TypeManager.RegisterMethod (RemoveBuilder, ip, parameters)) {
                                Report.Error (111, Location,    
                                              "Class `" + parent.Name + "' already contains a definition with the " +
                                              "same return value and parameter types for the " +
                                              "'remove' method of event `" + Name + "'");
                                return false;
                        }
                        
                        if (!TypeManager.RegisterEvent (EventBuilder, AddBuilder, RemoveBuilder)) {
                                Report.Error (111, Location,
                                        "Class `" + parent.Name +
                                        "' already contains a definition for the event `" +
                                        Name + "'");
                                return false;
                        }
                        
                        return true;
                }

                void EmitDefaultMethod (EmitContext ec, bool is_add)
                {
                        ILGenerator ig = ec.ig;
                        MethodInfo method = null;
                        
                        if (is_add)
                                method = TypeManager.delegate_combine_delegate_delegate;
                        else
                                method = TypeManager.delegate_remove_delegate_delegate;
                        
                        ig.Emit (OpCodes.Ldarg_0);
                        ig.Emit (OpCodes.Ldarg_0);
                        ig.Emit (OpCodes.Ldfld, (FieldInfo) FieldBuilder);
                        ig.Emit (OpCodes.Ldarg_1);
                        ig.Emit (OpCodes.Call, method);
                        ig.Emit (OpCodes.Castclass, EventType);
                        ig.Emit (OpCodes.Stfld, (FieldInfo) FieldBuilder);
                        ig.Emit (OpCodes.Ret);
                }

                public void Emit (TypeContainer tc)
                {
                        EmitContext ec;
                        ILGenerator ig;

                        ig = AddBuilder.GetILGenerator ();
                        ec = new EmitContext (tc, Location, ig, TypeManager.void_type, ModFlags);

                        if (Add != null)
                                ec.EmitTopBlock (Add, Location);
                        else
                                EmitDefaultMethod (ec, true);

                        ig = RemoveBuilder.GetILGenerator ();
                        ec = new EmitContext (tc, Location, ig, TypeManager.void_type, ModFlags);
                        
                        if (Remove != null)
                                ec.EmitTopBlock (Remove, Location);
                        else
                                EmitDefaultMethod (ec, false);

                        ec = new EmitContext (tc, Location, null, EventType, ModFlags);
                        Attribute.ApplyAttributes (ec, EventBuilder, this, OptAttributes, Location);
                        
                }
                
        }

        //
        // FIXME: This does not handle:
        //
        //   int INTERFACENAME [ args ]
        //
        // Only:
        // 
        // int this [ args ]
 
        public class Indexer : MemberCore {

                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.VIRTUAL |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.UNSAFE |
                        Modifiers.EXTERN |
                        Modifiers.ABSTRACT;

                public readonly string     Type;
                public readonly string     InterfaceType;
                public readonly Parameters FormalParameters;
                public readonly Accessor   Get, Set;
                public Attributes          OptAttributes;
                public MethodBuilder       GetBuilder;
                public MethodBuilder       SetBuilder;
                public PropertyBuilder PropertyBuilder;
                public Type IndexerType;
                public string IndexerName;
                EmitContext ec;

                public Indexer (string type, string int_type, int flags, Parameters parms,
                                Accessor get_block, Accessor set_block, Attributes attrs, Location loc)
                        : base ("", loc)
                {

                        Type = type;
                        InterfaceType = int_type;
                        ModFlags = Modifiers.Check (AllowedModifiers, flags, Modifiers.PRIVATE, loc);
                        FormalParameters = parms;
                        Get = get_block;
                        Set = set_block;
                        OptAttributes = attrs;
                }

                bool DefineMethod (TypeContainer parent, Type iface_type, 
                                   Type ret_type, string name,
                                   Type [] parameters, MethodAttributes attr, bool is_get)
                {
                        MethodInfo implementing;
                        bool is_implementation;
                        
                        implementing = parent.IsInterfaceMethod (
                                iface_type, name, ret_type, parameters, false);

                        is_implementation = implementing != null;
                        
                        //
                        // Setting null inside this block will trigger a more
                        // verbose error reporting for missing interface implementations
                        //
                        // The "candidate" function has been flagged already
                        // but it wont get cleared
                        //
                        if (implementing != null){
                                if (iface_type == null){
                                        //
                                        // We already catch different accessibility settings
                                        // so we just need to check that we are not private
                                        //
                                        if ((ModFlags & Modifiers.PRIVATE) != 0)
                                                implementing = null;
                                        
                                        //
                                        // Static is not allowed
                                        //
                                        if ((ModFlags & Modifiers.STATIC) != 0)
                                                implementing = null;
                                } else {
                                        if((ModFlags&(Modifiers.PUBLIC | Modifiers.ABSTRACT)) != 0){
                                                Report.Error (
                                                        106, Location,
                                                        "`public' or `abstract' modifiers are not "+
                                                        "allowed in explicit interface declarations"
                                                        );
                                                implementing = null;
                                        }
                                }
                        }
                        if (implementing != null){
                                //
                                // When implementing interface methods, set NewSlot.
                                //
                                if (implementing.DeclaringType.IsInterface)
                                        attr |= MethodAttributes.NewSlot;
                                
                                attr |=
                                        MethodAttributes.Virtual |
                                        MethodAttributes.HideBySig;

                                //
                                // clear the pending flag
                                //
                                parent.IsInterfaceMethod (
                                        iface_type, name, ret_type, parameters, true);
                        }

                        //
                        // If this is not an explicit interface implementation,
                        // clear implementing, as it is only used for explicit
                        // interface implementation
                        //
                        if (InterfaceType == null)
                                implementing = null;

                        if (is_get){
                                string meth_name = "get_" + IndexerName;
                                if (iface_type != null)
                                        meth_name = iface_type + ".get_" + IndexerName;
                                
                                GetBuilder = parent.TypeBuilder.DefineMethod (
                                        meth_name, attr, IndexerType, parameters);

                                if (implementing != null) 
                                        parent.TypeBuilder.DefineMethodOverride (
                                                GetBuilder, implementing);
                        } else {
                                string meth_name = "set_" + IndexerName;

                                if (iface_type != null)
                                        meth_name = iface_type + ".set_" + IndexerName;
                                
                                SetBuilder = parent.TypeBuilder.DefineMethod (
                                        meth_name, attr, null, parameters);
                                if (implementing != null)
                                        parent.TypeBuilder.DefineMethodOverride (
                                                SetBuilder, implementing);
                        }

                        return is_implementation;
                }
                        
                public override bool Define (TypeContainer parent)
                {
                        PropertyAttributes prop_attr =
                                PropertyAttributes.RTSpecialName |
                                PropertyAttributes.SpecialName;
                        bool error = false;
                        
                        IndexerType = RootContext.LookupType (parent, Type, false, Location);
                        Type [] parameters = FormalParameters.GetParameterInfo (parent);

                        // Check if the return type and arguments were correct
                        if (IndexerType == null || parameters == null)
                                return false;

                        if (!parent.MethodModifiersValid (ModFlags, InterfaceType == null ?
                                                          "this" : InterfaceType, Location))
                                return false;

                        //
                        // verify accessibility and unsafe pointers
                        //
                        if (!TypeContainer.AsAccessible (IndexerType, ModFlags))
                                return false;

                        if (IndexerType.IsPointer && !UnsafeOK (parent))
                                return false;

                        foreach (Type partype in parameters){
                                if (!TypeContainer.AsAccessible (partype, ModFlags))
                                        error = true;
                                if (partype.IsPointer && !UnsafeOK (parent))
                                        error = true;
                        }

                        if (error)
                                return false;
                        
                        Type iface_type = null;

                        if (InterfaceType != null){
                                iface_type = RootContext.LookupType (parent, InterfaceType, false, Location);
                                if (iface_type == null)
                                        return false;
                        } 

                        ec = new EmitContext (parent, Location, null, IndexerType, ModFlags);

                        IndexerName = Attribute.ScanForIndexerName (ec, OptAttributes);
                        if (IndexerName == null)
                                IndexerName = "Item";
                        
                        MethodAttributes attr = Modifiers.MethodAttr (ModFlags);

                        bool is_implementing = false;
                        
                        if (Get != null){
                                is_implementing = DefineMethod (
                                        parent, iface_type, IndexerType, "get_" + IndexerName,
                                        parameters, attr, true);
                                InternalParameters pi = new InternalParameters (parent, FormalParameters);
                                if (!TypeManager.RegisterMethod (GetBuilder, pi, parameters)) {
                                        Report.Error (111, Location,
                                                      "Class `" + parent.Name +
                                                      "' already contains a definition with the " +
                                                      "same return value and parameter types for the " +
                                                      "'get' indexer");
                                        return false;
                                }
                        }
                        
                        if (Set != null){
                                int top = parameters.Length;
                                Type [] set_pars = new Type [top + 1];
                                parameters.CopyTo (set_pars, 0);
                                set_pars [top] = IndexerType;

                                Parameter [] fixed_parms = FormalParameters.FixedParameters;

                                if (fixed_parms == null){
                                        throw new Exception ("We currently do not support only array arguments in an indexer");
                                        // BUG BUG BUG BUG BUG BUG BUG BUG BUG BUG
                                        // BUG BUG BUG BUG BUG BUG BUG BUG BUG BUG
                                        //
                                        // Here is the problem: the `value' parameter has
                                        // to come *after* the array parameter in the declaration
                                        // like this:
                                        // X (object [] x, Type value)
                                        // .param [0]
                                        //
                                        // BUG BUG BUG BUG BUG BUG BUG BUG BUG BUG
                                        // BUG BUG BUG BUG BUG BUG BUG BUG BUG BUG
                                        
                                }
                                
                                Parameter [] tmp = new Parameter [fixed_parms.Length + 1];


                                fixed_parms.CopyTo (tmp, 0);
                                tmp [fixed_parms.Length] = new Parameter (
                                        Type, "value", Parameter.Modifier.NONE, null);

                                Parameters set_formal_params = new Parameters (tmp, null, Location);
                                
                                is_implementing = DefineMethod (
                                        parent, iface_type, TypeManager.void_type,
                                        "set_" + IndexerName, set_pars, attr, false);

                                InternalParameters ip = new InternalParameters (parent, set_formal_params);
                                
                                if (!TypeManager.RegisterMethod (SetBuilder, ip, set_pars)) {
                                        Report.Error (
                                                111, Location,
                                                "Class `" + parent.Name + "' already contains a " +
                                                "definition with the " +
                                                "same return value and parameter types for the " +
                                                "'set' indexer");
                                        return false;
                                }
                        }

                        //
                        // Now name the parameters
                        //
                        Parameter [] p = FormalParameters.FixedParameters;
                        if (p != null) {
                                int i;
                                
                                for (i = 0; i < p.Length; ++i) {
                                        if (Get != null)
                                                GetBuilder.DefineParameter (
                                                        i + 1, p [i].Attributes, p [i].Name);

                                        if (Set != null)
                                                SetBuilder.DefineParameter (
                                                        i + 1, p [i].Attributes, p [i].Name);
                                }

                                if (Set != null)
                                        SetBuilder.DefineParameter (
                                                i + 1, ParameterAttributes.None, "value");
                                        
                                if (i != parameters.Length) {
                                        Parameter array_param = FormalParameters.ArrayParameter;
                                        SetBuilder.DefineParameter (i + 1, array_param.Attributes,
                                                                    array_param.Name);
                                }
                        }


                        //
                        // Only define the PropertyBuilder if we are not implementing
                        // an interface property.
                        //
                        if (!is_implementing){
                                PropertyBuilder = parent.TypeBuilder.DefineProperty (
                                        IndexerName, prop_attr, IndexerType, parameters);
                                TypeManager.RegisterProperty (PropertyBuilder, GetBuilder, SetBuilder);

                                if (GetBuilder != null)
                                        PropertyBuilder.SetGetMethod (GetBuilder);

                                if (SetBuilder != null)
                                        PropertyBuilder.SetSetMethod (SetBuilder);
                        }

                        return true;
                }

                public void Emit (TypeContainer tc)
                {
                        ILGenerator ig;

                        Attribute.ApplyAttributes (
                                ec, PropertyBuilder, this, OptAttributes, Location);

                        if ((ModFlags & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
                                return;
                        
                        if (Get != null){
                                ig = GetBuilder.GetILGenerator ();
                                ec = new EmitContext (tc, Location, ig, IndexerType, ModFlags);
                                
                                ec.EmitTopBlock (Get.Block, Location);
                        }

                        if (Set != null){
                                ig = SetBuilder.GetILGenerator ();
                                ec = new EmitContext (tc, Location, ig, null, ModFlags);
                                
                                ec.EmitTopBlock (Set.Block, Location);
                        }
                }
        }

        public class Operator : MemberCore {

                const int AllowedModifiers =
                        Modifiers.PUBLIC |
                        Modifiers.UNSAFE |
                        Modifiers.EXTERN |
                        Modifiers.STATIC;

                const int RequiredModifiers =
                        Modifiers.PUBLIC |
                        Modifiers.STATIC;

                public enum OpType : byte {

                        // Unary operators
                        LogicalNot,
                        OnesComplement,
                        Increment,
                        Decrement,
                        True,
                        False,

                        // Unary and Binary operators
                        Addition,
                        Subtraction,

                        UnaryPlus,
                        UnaryNegation,
                        
                        // Binary operators
                        Multiply,
                        Division,
                        Modulus,
                        BitwiseAnd,
                        BitwiseOr,
                        ExclusiveOr,
                        LeftShift,
                        RightShift,
                        Equality,
                        Inequality,
                        GreaterThan,
                        LessThan,
                        GreaterThanOrEqual,
                        LessThanOrEqual,

                        // Implicit and Explicit
                        Implicit,
                        Explicit
                };

                public readonly OpType OperatorType;
                public readonly string ReturnType;
                public readonly string FirstArgType;
                public readonly string FirstArgName;
                public readonly string SecondArgType;
                public readonly string SecondArgName;
                public readonly Block  Block;
                public Attributes      OptAttributes;
                public MethodBuilder   OperatorMethodBuilder;
                
                public string MethodName;
                public Method OperatorMethod;

                public Operator (OpType type, string ret_type, int flags, string arg1type, string arg1name,
                                 string arg2type, string arg2name, Block block, Attributes attrs, Location loc)
                        : base ("", loc)
                {
                        OperatorType = type;
                        ReturnType = ret_type;
                        ModFlags = Modifiers.Check (AllowedModifiers, flags, Modifiers.PUBLIC, loc);
                        FirstArgType = arg1type;
                        FirstArgName = arg1name;
                        SecondArgType = arg2type;
                        SecondArgName = arg2name;
                        Block = block;
                        OptAttributes = attrs;
                }

                string Prototype (TypeContainer parent)
                {
                        return parent.Name + ".operator " + OperatorType + " (" + FirstArgType + "," +
                                SecondArgType + ")";
                }
                
                public override bool Define (TypeContainer parent)
                {
                        int length = 1;
                        MethodName = "op_" + OperatorType;
                        
                        if (SecondArgType != null)
                                length = 2;
                        
                        Parameter [] param_list = new Parameter [length];

                        if ((ModFlags & RequiredModifiers) != RequiredModifiers){
                                Report.Error (
                                        558, Location, 
                                        "User defined operators `" +
                                        Prototype (parent) +
                                        "' must be declared static and public");
                                return false;
                        }

                        param_list[0] = new Parameter (FirstArgType, FirstArgName,
                                                       Parameter.Modifier.NONE, null);
                        if (SecondArgType != null)
                                param_list[1] = new Parameter (SecondArgType, SecondArgName,
                                                               Parameter.Modifier.NONE, null);
                        
                        OperatorMethod = new Method (ReturnType, ModFlags, MethodName,
                                                     new Parameters (param_list, null, Location),
                                                     OptAttributes, Mono.CSharp.Location.Null);
                        
                        OperatorMethod.Define (parent);

                        if (OperatorMethod.MethodBuilder == null)
                                return false;
                        
                        OperatorMethodBuilder = OperatorMethod.MethodBuilder;

                        Type [] param_types = OperatorMethod.ParameterTypes (parent);
                        Type declaring_type = OperatorMethodBuilder.DeclaringType;
                        Type return_type = OperatorMethod.GetReturnType (parent);
                        Type first_arg_type = param_types [0];

                        // Rules for conversion operators
                        
                        if (OperatorType == OpType.Implicit || OperatorType == OpType.Explicit) {
                                if (first_arg_type == return_type && first_arg_type == declaring_type){
                                        Report.Error (
                                                555, Location,
                                                "User-defined conversion cannot take an object of the " +
                                                "enclosing type and convert to an object of the enclosing" +
                                                " type");
                                        return false;
                                }
                                
                                if (first_arg_type != declaring_type && return_type != declaring_type){
                                        Report.Error (
                                                556, Location, 
                                                "User-defined conversion must convert to or from the " +
                                                "enclosing type");
                                        return false;
                                }
                                
                                if (first_arg_type == TypeManager.object_type ||
                                    return_type == TypeManager.object_type){
                                        Report.Error (
                                                -8, Location,
                                                "User-defined conversion cannot convert to or from " +
                                                "object type");
                                        return false;
                                }

                                if (first_arg_type.IsInterface || return_type.IsInterface){
                                        Report.Error (
                                                552, Location,
                                                "User-defined conversion cannot convert to or from an " +
                                                "interface type");
                                        return false;
                                }
                                
                                if (first_arg_type.IsSubclassOf (return_type) ||
                                    return_type.IsSubclassOf (first_arg_type)){
                                        Report.Error (
                                                -10, Location,
                                                "User-defined conversion cannot convert between types " +
                                                "that derive from each other");
                                        return false;
                                }
                        } else if (SecondArgType == null) {
                                // Checks for Unary operators
                                
                                if (first_arg_type != declaring_type){
                                        Report.Error (
                                                562, Location,
                                                "The parameter of a unary operator must be the " +
                                                "containing type");
                                        return false;
                                }
                                
                                if (OperatorType == OpType.Increment || OperatorType == OpType.Decrement) {
                                        if (return_type != declaring_type){
                                                Report.Error (
                                                        559, Location,
                                                        "The parameter and return type for ++ and -- " +
                                                        "must be the containing type");
                                                return false;
                                        }
                                        
                                }
                                
                                if (OperatorType == OpType.True || OperatorType == OpType.False) {
                                        if (return_type != TypeManager.bool_type){
                                                Report.Error (
                                                        215, Location,
                                                        "The return type of operator True or False " +
                                                        "must be bool");
                                                return false;
                                        }
                                }
                                
                        } else {
                                // Checks for Binary operators
                                
                                if (first_arg_type != declaring_type &&
                                    param_types [1] != declaring_type){
                                        Report.Error (
                                                563, Location,
                                                "One of the parameters of a binary operator must " +
                                                "be the containing type");
                                        return false;
                                }
                        }

                        return true;
                }
                
                public void Emit (TypeContainer parent)
                {
                        EmitContext ec = new EmitContext (parent, Location, null, null, ModFlags);
                        Attribute.ApplyAttributes (ec, OperatorMethodBuilder, this, OptAttributes, Location);

                        //
                        // abstract or extern methods have no bodies
                        //
                        if ((ModFlags & (Modifiers.ABSTRACT | Modifiers.EXTERN)) != 0)
                                return;
                        
                        OperatorMethod.Block = Block;
                        OperatorMethod.Emit (parent);
                }
        }

        //
        // This is used to compare method signatures
        //
        struct MethodSignature {
                public string Name;
                public Type RetType;
                public Type [] Parameters;
                
                /// <summary>
                ///    This delegate is used to extract methods which have the
                ///    same signature as the argument
                /// </summary>
                public static MemberFilter method_signature_filter;

                /// <summary>
                ///   This delegate is used to extract inheritable methods which
                ///   have the same signature as the argument.  By inheritable,
                ///   this means that we have permissions to override the method
                ///   from the current assembly and class
                /// </summary>
                public static MemberFilter inheritable_method_signature_filter;
                
                static MethodSignature ()
                {
                        method_signature_filter = new MemberFilter (MemberSignatureCompare);
                        inheritable_method_signature_filter = new MemberFilter (
                                InheritableMemberSignatureCompare);
                }
                
                public MethodSignature (string name, Type ret_type, Type [] parameters)
                {
                        Name = name;
                        RetType = ret_type;

                        if (parameters == null)
                                Parameters = TypeManager.NoTypes;
                        else
                                Parameters = parameters;
                }
                
                public override int GetHashCode ()
                {
                        return Name.GetHashCode ();
                }

                public override bool Equals (Object o)
                {
                        MethodSignature other = (MethodSignature) o;

                        if (other.Name != Name)
                                return false;

                        if (other.RetType != RetType)
                                return false;
                        
                        if (Parameters == null){
                                if (other.Parameters == null)
                                        return true;
                                return false;
                        }

                        if (other.Parameters == null)
                                return false;
                        
                        int c = Parameters.Length;
                        if (other.Parameters.Length != c)
                                return false;

                        for (int i = 0; i < c; i++)
                                if (other.Parameters [i] != Parameters [i])
                                        return false;

                        return true;
                }

                static bool MemberSignatureCompare (MemberInfo m, object filter_criteria)
                {
                        MethodInfo mi;

                        if (! (m is MethodInfo))
                                return false;

                        MethodSignature sig = (MethodSignature) filter_criteria;

                        if (m.Name != sig.Name)
                                return false;
                        
                        mi = (MethodInfo) m;

                        //
                        // we use sig.RetType == null to mean `do not check the
                        // method return value.  
                        //
                        if (sig.RetType != null)
                                if (mi.ReturnType != sig.RetType)
                                        return false;

                        Type [] args = TypeManager.GetArgumentTypes (mi);
                        Type [] sigp = sig.Parameters;

                        if (args.Length != sigp.Length)
                                return false;

                        for (int i = args.Length; i > 0; ){
                                i--;
                                if (args [i] != sigp [i])
                                        return false;
                        }
                        return true;
                }

                //
                // This filter should be used when we are requesting methods that
                // we want to override.
                //
                // This makes a number of assumptions, for example
                // that the methods being extracted are of a parent
                // class (this means we know implicitly that we are
                // being called to find out about members by a derived
                // class).
                // 
                static bool InheritableMemberSignatureCompare (MemberInfo m, object filter_criteria)
                {
                        if (MemberSignatureCompare (m, filter_criteria)){
                                MethodInfo mi = (MethodInfo) m;
                                MethodAttributes prot = mi.Attributes & MethodAttributes.MemberAccessMask;

                                // If only accessible to the current class.
                                if (prot == MethodAttributes.Private)
                                        return false;

                                // If only accessible to the defining assembly or 
                                if (prot == MethodAttributes.FamANDAssem ||
                                    prot == MethodAttributes.Assembly){
                                        if (m.DeclaringType.Assembly == CodeGen.AssemblyBuilder)
                                                return true;
                                        else
                                                return false;
                                }

                                // Anything else (FamOrAssembly and Public) is fine
                                return true;
                        }
                        return false;
                }
        }               
}