2001-10-07 Miguel de Icaza <miguel@ximian.com>

[mono.git] / mcs / mcs / 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;

namespace CIR {
        
        public class TypeContainer : DeclSpace {
                protected int mod_flags;

                // 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 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 the methods.
                ArrayList methods;

                // Holds the events
                ArrayList events;

                // Holds the indexers
                ArrayList indexers;

                // Holds the operators
                ArrayList operators;

                // Maps MethodBuilders to Methods
                static Hashtable method_builders_to_methods;
                
                //
                // 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 is the namespace in which this typecontainer
                // was declared.  We use this to resolve names.
                //
                Namespace my_namespace;
                
                //
                // This one is computed after we can distinguish interfaces
                // from classes from the arraylist `type_bases' 
                //
                string     base_class_name;

                TypeContainer parent;
                ArrayList type_bases;

                //
                // This behaves like a property ;-)
                //
                public readonly RootContext RootContext;

                // Attributes for this type
                protected Attributes attributes;

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

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

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

                public AdditionResult AddConstant (Constant 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 (CIR.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;

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

                        constructors.Add (c);

                        bool is_static = (c.ModFlags & Modifiers.STATIC) != 0;
                        
                        if (is_static)
                                have_static_constructor = true;

                        if (c.IsDefault ()) {
                                if (is_static)
                                        default_static_constructor = c;
                                else
                                        default_constructor = 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 TypeContainer Parent {
                        get {
                                return parent;
                        }
                }

                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 int ModFlags {
                        get {
                                return mod_flags;
                        }
                }

                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 Constructors {
                        get {
                                return 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 Namespace Namespace {
                        get {
                                return my_namespace;
                        }

                        set {
                                my_namespace = value;
                        }
                }

                // 
                // root_types contains all the types.  All TopLevel types
                // hence have a parent that points to `root_types', that is
                // why there is a non-obvious test down here.
                //
                public bool IsTopLevel {
                        get {
                                if (parent != null){
                                        if (parent.Parent == null)
                                                return true;
                                }
                                return false;
                        }
                }
                        
                public bool HaveStaticConstructor {
                        get {
                                return have_static_constructor;
                        }
                }
                
                public virtual TypeAttributes TypeAttr {
                        get {
                                return Modifiers.TypeAttr (mod_flags, this);
                        }
                }

                //
                // Emits the instance field initializers
                //
                public bool EmitFieldInitializers (EmitContext ec, bool is_static)
                {
                        ArrayList fields;
                        ILGenerator ig = ec.ig;
                        
                        if (is_static)
                                fields = initialized_static_fields;
                        else
                                fields = initialized_fields;

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

                                if (init is Expression){
                                        Expression e = (Expression) init;

                                        e = e.Resolve (this);
                                        if (e == null)
                                                return false;

                                        if (!is_static)
                                                ig.Emit (OpCodes.Ldarg_0);
                                        
                                        e.Emit (ec);

                                        if (is_static)
                                                ig.Emit (OpCodes.Stsfld, f.FieldBuilder);
                                        else
                                                ig.Emit (OpCodes.Stfld, f.FieldBuilder);
                                }
                        }

                        return true;
                }

                //
                // Defines the default constructors
                //
                void DefineDefaultConstructor (bool is_static)
                {
                        Constructor c;
                        int mods = 0;

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

                        c.ModFlags = mods;      
                }

                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");
                        }
                }

                public void RegisterRequiredImplementations ()
                {
                        Type [] ifaces = TypeBuilder.GetInterfaces ();
                        Type b = TypeBuilder.BaseType;
                        
                        if (ifaces != null)
                                SetRequiredInterfaces (ifaces);

                        if (b.IsAbstract){
                                MemberInfo [] abstract_methods;

                                abstract_methods = FindMembers (
                                        TypeBuilder.BaseType,
                                        MemberTypes.Method, BindingFlags.Public,
                                        abstract_method_filter, null);

                                if (abstract_methods != null){
                                        MethodInfo [] mi = new MethodInfo [abstract_methods.Length];

                                        abstract_methods.CopyTo (mi, 0);
                                        RequireMethods (mi, b);
                                }
                        }
                        
                }

                static object MakeKey (MethodBase mb)
                {
                        if (mb is MethodBuilder || mb is ConstructorBuilder)
                                return mb.ReflectedType.FullName + ":" + mb;
                        else
                                return mb.MethodHandle.ToString ();
                }
                
                //
                // Populates our TypeBuilder with fields and methods
                //
                public void Populate ()
                {
                        if (Constants != null){
                                foreach (Constant c in Constants)
                                        c.EmitConstant (RootContext, this);
                        }

                        if (Fields != null){
                                foreach (Field f in Fields)
                                        f.Define (this);
                        } else if (this is Struct){
                                //
                                // FIXME: Add a dummy field, because it is currently
                                // not possible with the reflection API to tell the size
                                // of a structure
                                //
                                TypeBuilder.DefineField ("Dummy", TypeManager.sbyte_type,
                                                         FieldAttributes.Static | FieldAttributes.Private);
                        }

                        if (this is Class){
                                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 ();
                        
                        ArrayList remove_list = new ArrayList ();

                        if (constructors != null || methods != null ||
                            properties != null || operators != null){
                                if (method_builders_to_methods == null)
                                        method_builders_to_methods = new Hashtable ();
                        }
                        
                        if (constructors != null){
                                foreach (Constructor c in constructors){
                                        MethodBase builder = c.Define (this);
                                        
                                        if (builder == null)
                                                remove_list.Add (c);
                                        else
                                                method_builders_to_methods.Add (MakeKey (builder), c);
                                }

                                foreach (object o in remove_list)
                                        constructors.Remove (o);
                                
                                remove_list.Clear ();
                        } 

                        if (Methods != null){
                                foreach (Method m in methods){
                                        MethodBase key = m.Define (this);

                                        //
                                        // FIXME:
                                        // The following key is not enoug
                                        // class x { public void X ()  {} }
                                        // class y : x { public void X () {}}
                                        // fails
                                        
                                        if (key == null)
                                                remove_list.Add (m);
                                        else
                                                method_builders_to_methods.Add (MakeKey (key), m);
                                }
                                foreach (object o in remove_list)
                                        methods.Remove (o);
                                
                                remove_list.Clear ();
                        }

                        if (Properties != null) {
                                foreach (Property p in Properties)
                                        p.Define (this);
                        }

                        if (Enums != null) {
                                foreach (Enum e in Enums)
                                        e.Define (this);
                        }

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

                        if (Indexers != null) {
                                foreach (Indexer i in Indexers)
                                        i.Define (this);
                        }

                        if (Operators != null) {
                                foreach (Operator o in Operators) {
                                        o.Define (this);
                                        
                                        method_builders_to_methods.Add (
                                                MakeKey (o.OperatorMethodBuilder), o.OperatorMethod);
                                }
                        }

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

                //
                // the `mb' must be a MethodBuilder or a
                // ConstructorBuilder, we return the method that
                // defines it.
                // 
                static public MethodCore LookupMethodByBuilder (MethodBase mb)
                {
                        return (MethodCore) method_builders_to_methods [MakeKey (mb)];
                }
                
                public Type LookupType (string name, bool silent)
                {
                        return RootContext.LookupType (this, name, silent);
                }

                //
                // This function is based by a delegate to the FindMembers routine
                //
                static bool AlwaysAccept (MemberInfo m, object filterCriteria)
                {
                        return true;
                }
                
                //
                static bool IsAbstractMethod (MemberInfo m, object filter_criteria)
                {
                        MethodInfo mi = (MethodInfo) m;

                        return mi.IsAbstract;
                }

                // This filter is used by FindMembers, and we just keep
                // a global for the filter to `AlwaysAccept'
                //
                static MemberFilter accepting_filter;
                
                // <summary>
                //    This delegate is a MemberFilter used to extract the 
                //    abstact methods from a type.  
                // </summary>
                static MemberFilter abstract_method_filter;

                static TypeContainer ()
                {
                        abstract_method_filter = new MemberFilter (IsAbstractMethod);
                        accepting_filter = new MemberFilter (AlwaysAccept);
                }
                
                // <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>
                public MemberInfo [] FindMembers (MemberTypes mt, BindingFlags bf,
                                                  MemberFilter filter, object criteria)
                {
                        ArrayList members = new ArrayList ();

                        if (filter == null)
                                filter = accepting_filter; 
                        
                        if ((mt & MemberTypes.Field) != 0 && Fields != null) {
                                foreach (Field f in Fields) {
                                        if (filter (f.FieldBuilder, criteria) == true)
                                                members.Add (f.FieldBuilder);
                                }
                        }

                        if ((mt & MemberTypes.Method) != 0) {
                                if (Methods != null){
                                        foreach (Method m in Methods) {
                                                MethodBuilder mb = m.MethodBuilder;

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

                                if (Operators != null){
                                        foreach (Operator o in Operators) {
                                                MethodBuilder ob = o.OperatorMethodBuilder;

                                                if (filter (ob, criteria) == true)
                                                        members.Add (ob);
                                        }
                                }
                        }

                        // FIXME : This ain't right because EventBuilder is not a
                        // MemberInfo. What do we do ?
                        
                        if ((mt & MemberTypes.Event) != 0 && Events != null) {
                                //foreach (Event e in Events) {
                                //      if (filter (e.EventBuilder, criteria) == true)
                                //              mi [i++] = e.EventBuilder;
                                //}
                        }

                        if ((mt & MemberTypes.Property) != 0 && Properties != null) {
                                foreach (Property p in Properties) {
                                        if (filter (p.PropertyBuilder, criteria) == true)
                                                members.Add (p.PropertyBuilder);
                                }
                        }
                        
                        if ((mt & MemberTypes.NestedType) != 0 && Types != null) {
                                foreach (TypeContainer t in Types) { 
                                        if (filter (t.TypeBuilder, criteria) == true)
                                                members.Add (t.TypeBuilder);
                                }
                        }

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

                Hashtable pending_implementations;
                
                // <summary>
                //   Requires that the methods in `mi' be implemented for this
                //   class
                // </summary>
                public void RequireMethods (MethodInfo [] mi, object data)
                {
                        if (pending_implementations == null)
                                pending_implementations = new Hashtable ();

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

                                pending_implementations.Add (
                                        new MethodSignature 
                                                (m.Name, m.ReturnType, types), data);
                        }
                }

                // <summary>
                //   Used to set the list of interfaces that this typecontainer
                //   must implement.
                // </summary>
                //
                // <remarks>
                //   For each element exposed by the type, we create a MethodSignature
                //   struct that we will label as `implemented' as we define the various
                //   methods.
                // </remarks>
                public void SetRequiredInterfaces (Type [] ifaces)
                {
                        foreach (Type t in ifaces){
                                MethodInfo [] mi;

                                if (t is TypeBuilder){
                                        Interface iface = RootContext.TypeManager.LookupInterface (t);

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

                                RequireMethods (mi, t);
                        }
                }

                // <summary>
                //   If a method with name `Name', return type `ret_type' and
                //   arguments `args' implements an interface, this method will
                //   return true.
                //
                //   This will remove the method from the list of "pending" methods
                //   that are required to be implemented for this class as a side effect.
                // 
                // </summary>
                public bool IsInterfaceMethod (string Name, Type ret_type, Type [] args)
                {
                        MethodSignature query;

                        if (pending_implementations == null)
                                return false;

                        query = new MethodSignature (Name, ret_type, args);

                        if (pending_implementations.Contains (query)){
                                pending_implementations.Remove (query);
                                return true;
                        }

                        return false;
                }

                // <summary>
                //   Verifies that any pending abstract methods or interface methods
                //   were implemented.
                // </summary>
                void VerifyPendingMethods ()
                {
                        int pending = 0;
                        
                        foreach (object m in pending_implementations){
                                DictionaryEntry de = (DictionaryEntry) m;
                                Type t = (Type) de.Value;
                                pending++;

                                MethodSignature method = (MethodSignature) de.Key;

                                if (t.IsInterface)
                                        Report.Error (
                                                536, Location,
                                                "`" + Name + "' does not implement interface member `" +
                                                t.FullName + "." + method.Name + "'");
                                else
                                        Report.Error (
                                                534, Location,
                                                "`" + Name + "' does not implement inherited abstract " +
                                                "member `" + t.FullName + "." + method.Name + "'");
                        }
                }
                
                // <summary>
                //   Emits the code, this step is performed after all
                //   the types, enumerations, constructors
                // </summary>
                public void Emit ()
                {
                        if (Constructors != null)
                                foreach (Constructor c in Constructors)
                                        c.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 (pending_implementations != null)
                                VerifyPendingMethods ();
                }

                string MakeName (string n)
                {
                        return "`" + Name + "." + n + "'";
                }
                
                public static int CheckMember (string name, MemberInfo mi, int ModFlags)
                {
                        return 0;
                }
        }

        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;

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

                        if (parent.Parent == null)
                                accmods = Modifiers.INTERNAL;
                        else
                                accmods = Modifiers.PRIVATE;
                        
                        this.mod_flags = Modifiers.Check (AllowedModifiers, mod, accmods);
                        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;
                        }
                }
        }

        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.PRIVATE;

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

                        this.mod_flags |= 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 class MethodCore {
                public readonly Parameters Parameters;
                public readonly string Name;
                public int ModFlags;
                Block block;
                public readonly Location Location;
                
                //
                // Parameters, cached for semantic analysis.
                //
                InternalParameters parameter_info;
                
                public MethodCore (string name, Parameters parameters, Location l)
                {
                        Name = name;
                        Parameters = parameters;
                        Location = l;
                }
                
                //
                //  Returns the System.Type array for the parameters of this method
                //
                Type [] parameter_types;
                public Type [] ParameterTypes (TypeContainer parent)
                {
                        if (Parameters == null)
                                return null;
                        
                        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 class Method : MethodCore {
                public readonly string     ReturnType;
                public MethodBuilder MethodBuilder;
                public readonly Attributes OptAttributes;

                // <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.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);
                        OptAttributes = attrs;
                }

                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;

                        if (mi.ReturnType != sig.RetType)
                                return false;

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

                        //
                        // FIXME: remove this assumption if we manage to
                        // not enter a null as a the Parameters in TypeManager's 
                        // MethodBase to Type argument mapper.
                        //
                        if (args == null){
                                if (sigp != null)
                                        return false;
                                else
                                        return true;
                        } else if (sigp == null)
                                return false;
                        
                        if (args.Length != sigp.Length)
                                return false;

                        for (int i = args.Length; i > 0; ){
                                i--;
                                if (args [i] != sigp [i])
                                        return false;
                        }
                        return true;
                }
                
                // <summary>
                //    This delegate is used to extract methods which have the
                //    same signature as the argument
                // </summary>
                static MemberFilter method_signature_filter;
                
                static Method ()
                {
                        method_signature_filter = new MemberFilter (MemberSignatureCompare);
                }
                
                //
                // 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 = parent.LookupType (ReturnType, false);
                        
                        return type_return_type;
                }

                void WarningNotHiding (TypeContainer parent)
                {
                        Report.Warning (
                                109, Location,
                                "The member `" + parent.Name + "." + Name + "' does not hide an " +
                                "inherited member.  The keyword new is not required");
                                                           
                }

                string MakeName (TypeContainer parent)
                {
                        return "`" + parent.Name + "." + Name + "'";
                }

                string MethodBaseName (MethodBase mb)
                {
                        return "`" + mb.ReflectedType.Name + "." + mb.Name + "'";
                }
                
                bool CheckMethod (TypeContainer parent, MemberInfo [] mi)
                {
                        MethodInfo mb = (MethodInfo) mi [0];

                        if ((ModFlags & (Modifiers.NEW | Modifiers.OVERRIDE)) == 0){
                                Report.Warning (
                                        108, Location, "The keyword new is required on " + 
                                        MakeName (parent) + " because it hides `" +
                                        mb.ReflectedType.Name + "." +
                                        mb.Name + "'");
                        }

                        if (mb.IsVirtual || mb.IsAbstract){
                                if ((ModFlags & (Modifiers.NEW | Modifiers.OVERRIDE)) == 0){
                                        Report.Warning (
                                                114, Location, MakeName (parent) + 
                                                "hides inherited member " + MethodBaseName (mb) +
                                                ".  To make the current member override that " +
                                                "implementation, add the override keyword, " +
                                                "otherwise use the new keyword");
                                }
                                
                        }

                        return true;
                }
                
                //
                // Creates the type
                // 
                public MethodBuilder Define (TypeContainer parent)
                {
                        Type ret_type = GetReturnType (parent);
                        Type [] parameters = ParameterTypes (parent);
                        MethodAttributes flags;
                        bool error = 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, ret_type, parameters);
                                MemberInfo [] mi;
                                
                                mi = TypeContainer.FindMembers (
                                        ptype, MemberTypes.Method,
                                        BindingFlags.Public, method_signature_filter,
                                        ms);

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

                        //
                        // If we implement an interface, then set the proper flags.
                        //
                        flags = Modifiers.MethodAttr (ModFlags);

                        if (parent.IsInterfaceMethod (Name, ret_type, parameters))
                                flags |= MethodAttributes.Virtual;

                        //
                        // Catch invalid uses of virtual and abtract modifiers
                        //
                        const int va = (Modifiers.VIRTUAL | Modifiers.ABSTRACT);
                        const int nv = (Modifiers.NEW | Modifiers.VIRTUAL);

                        if ((ModFlags & va) == va){
                                if ((ModFlags & va) == va){
                                        Report.Error (
                                                503, Location, "The abstract method " +
                                                MakeName (parent) + "can not be marked virtual");
                                        error = true;
                                }
                        }

                        if ((ModFlags & Modifiers.ABSTRACT) != 0){
                                if ((parent.ModFlags & Modifiers.ABSTRACT) == 0){
                                        Report.Error (
                                                513, Location, MakeName (parent) +
                                                " is abstract but its container class is not");
                                        error = true;
                                }
                        }

                        if ((ModFlags & va) != 0 && ((ModFlags & Modifiers.PRIVATE) != 0)){
                                Report.Error (
                                        621, Location, MakeName (parent) +
                                        " virtual or abstract members can not be private");
                                error = true;
                        }

                        if ((ModFlags & Modifiers.OVERRIDE) != 0 && ((ModFlags & nv) != 0)){
                                Report.Error (
                                        113, Location, MakeName (parent) +
                                        "marked as override cannot be marked as new or virtual");
                                error = true;
                        }

                        if (error)
                                return null;
                        
                        //
                        // Finally, define the method
                        //
                        
                        MethodBuilder = parent.TypeBuilder.DefineMethod (
                                Name, flags,
                                GetCallingConvention (parent is Class),
                                ret_type, parameters);

                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        TypeManager.RegisterMethod (MethodBuilder, parameters);
                        
                        ParameterInfo = new InternalParameters (parameters);

                        //
                        // This is used to track the Entry Point,
                        //
                        // FIXME: Allow pluggable entry point, check arguments, etc.
                        //
                        if (Name == "Main"){
                                if ((ModFlags & Modifiers.STATIC) != 0){
                                        parent.RootContext.EntryPoint = MethodBuilder;
                                }
                        }
                        
                        //
                        // Define each type attribute (in/out/ref) and
                        // the argument names.
                        //
                        Parameter [] p = Parameters.FixedParameters;
                        if (p != null){
                                int i;
                                
                                for (i = 0; i < p.Length; i++)
                                        MethodBuilder.DefineParameter (
                                                i + 1, p [i].Attributes, p [i].Name);

                                if (i != parameters.Length)
                                        Console.WriteLine ("Implement the type definition for params");
                        }

                        return MethodBuilder;
                }

                //
                // Emits the code
                // 
                public void Emit (TypeContainer parent)
                {
                        ILGenerator ig = MethodBuilder.GetILGenerator ();
                        EmitContext ec = new EmitContext (parent, ig);
                        
                        ec.EmitTopBlock (Block);
                }
        }

        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 (TypeContainer tc)
                {
                        Expression parent_constructor_group;
                        
                        if (argument_list != null){
                                for (int i = argument_list.Count; i > 0; ){
                                        --i;

                                        Argument a = (Argument) argument_list [i];
                                        if (!a.Resolve (tc))
                                                return false;
                                }
                        }

                        parent_constructor_group = Expression.MemberLookup (
                                tc,
                                tc.TypeBuilder.BaseType, ".ctor", false,
                                MemberTypes.Constructor,
                                BindingFlags.Public | BindingFlags.Instance);

                        if (parent_constructor_group == null){
                                Console.WriteLine ("Could not find a constructor in our parent");
                                return false;
                        }
                        
                        parent_constructor = (ConstructorInfo) Invocation.OverloadResolve (tc, 
                                (MethodGroupExpr) parent_constructor_group, argument_list, location);
                        
                        if (parent_constructor == null)
                                return false;
                        
                        return true;
                }

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

                // <summary>
                //   Modifiers allowed for a constructor.
                // </summary>
                const int AllowedModifiers =
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.STATIC |
                        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 ()
                {
                        return  (Parameters == null ? true : Parameters.Empty) &&
                                (Initializer is ConstructorBaseInitializer) &&
                                (Initializer.Arguments == null);
                }

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

                        Type [] parameters = ParameterTypes (parent);

                        if (parent is Struct && parameters == null){
                                Report.Error (
                                        568, Location, 
                                        "Structs can not contain explicit parameterless constructors");
                                return null;
                        }

                        if ((ModFlags & Modifiers.STATIC) != 0)
                                ca |= MethodAttributes.Static;

                        ConstructorBuilder = parent.TypeBuilder.DefineConstructor (
                                ca, GetCallingConvention (parent is Class),
                                parameters);
                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        TypeManager.RegisterMethod (ConstructorBuilder, parameters);

                        ParameterInfo = new InternalParameters (parameters);

                        return ConstructorBuilder;
                }

                //
                // Emits the code
                //
                public void Emit (TypeContainer parent)
                {
                        if (parent is Class){
                                if (Initializer == null)
                                        Initializer = new ConstructorBaseInitializer (null, parent.Location);
                                if (!Initializer.Resolve (parent))
                                        return;
                        }

                        ILGenerator ig = ConstructorBuilder.GetILGenerator ();
                        EmitContext ec = new EmitContext (parent, ig);

                        //
                        // Classes can have base initializers and instance field initializers.
                        //
                        if (parent is Class){
                                if ((ModFlags & Modifiers.STATIC) == 0)
                                        Initializer.Emit (ec);
                                parent.EmitFieldInitializers (ec, false);
                        }
                        
                        if ((ModFlags & Modifiers.STATIC) != 0)
                                parent.EmitFieldInitializers (ec, true);

                        ec.EmitTopBlock (Block);
                }
        }
        
        public class Field {
                public readonly string Type;
                public readonly Object Initializer;
                public readonly string Name;
                public readonly int    ModFlags;
                public readonly Attributes OptAttributes;
                public FieldBuilder  FieldBuilder;
                
                
                // <summary>
                //   Modifiers allowed in a class declaration
                // </summary>
                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.READONLY;

                public Field (string type, int mod, string name, Object expr_or_array_init, Attributes attrs)
                {
                        Type = type;
                        ModFlags = Modifiers.Check (AllowedModifiers, mod, Modifiers.PRIVATE);
                        Name = name;
                        Initializer = expr_or_array_init;
                        OptAttributes = attrs;
                }

                public void Define (TypeContainer parent)
                {
                        Type t = parent.LookupType (Type, false);

                        if (t == null)
                                return;
                        
                        FieldBuilder = parent.TypeBuilder.DefineField (
                                Name, t, Modifiers.FieldAttr (ModFlags));
                }
        }

        public class Property {
                
                public readonly string Type;
                public readonly string Name;
                public readonly int    ModFlags;
                public Block           Get, Set;
                public PropertyBuilder PropertyBuilder;
                public Attributes OptAttributes;
                MethodBuilder GetBuilder, SetBuilder;
                

                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.ABSTRACT |
                        Modifiers.VIRTUAL;
                
                public Property (string type, string name, int mod_flags, Block get_block, Block set_block, Attributes attrs)
                {
                        Type = type;
                        Name = name;
                        ModFlags = Modifiers.Check (AllowedModifiers, mod_flags, Modifiers.PRIVATE);
                        Get = get_block;
                        Set = set_block;
                        OptAttributes = attrs;
                }

                public void Define (TypeContainer parent)
                {

                        MethodAttributes method_attr = Modifiers.MethodAttr(ModFlags);
                                        
                        // FIXME - PropertyAttributes.HasDefault ?

                        PropertyAttributes prop_attr = PropertyAttributes.RTSpecialName |
                                                       PropertyAttributes.SpecialName;
                
                
                        Type tp = parent.LookupType (Type, false);
                        Type [] parameters = new Type [1];
                        parameters [0] = tp;

                        PropertyBuilder = parent.TypeBuilder.DefineProperty(Name, prop_attr, tp, null);
                                        
                        if (Get != null)
                        {
                                GetBuilder = parent.TypeBuilder.DefineMethod (
                                        "get_" + Name, method_attr, tp, null);
                                PropertyBuilder.SetGetMethod (GetBuilder);
                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                TypeManager.RegisterMethod (GetBuilder, null);
                        }
                        
                        if (Set != null)
                        {
                                SetBuilder = parent.TypeBuilder.DefineMethod (
                                        "set_" + Name, method_attr, null, parameters);
                                SetBuilder.DefineParameter (1, ParameterAttributes.None, "value"); 
                                PropertyBuilder.SetSetMethod (SetBuilder);
                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                TypeManager.RegisterMethod (SetBuilder, parameters);
                        }
                        
                }

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

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

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

        public class Event {
                
                const int AllowedModifiers =
                        Modifiers.NEW |
                        Modifiers.PUBLIC |
                        Modifiers.PROTECTED |
                        Modifiers.INTERNAL |
                        Modifiers.PRIVATE |
                        Modifiers.STATIC |
                        Modifiers.VIRTUAL |
                        Modifiers.SEALED |
                        Modifiers.OVERRIDE |
                        Modifiers.ABSTRACT;

                public readonly string    Type;
                public readonly string    Name;
                public readonly Object    Initializer;
                public readonly int       ModFlags;
                public readonly Block     Add;
                public readonly Block     Remove;
                public EventBuilder       EventBuilder;
                public Attributes         OptAttributes;
                
                public Event (string type, string name, Object init, int flags, Block add_block, Block rem_block,
                              Attributes attrs)
                {
                        Type = type;
                        Name = name;
                        Initializer = init;
                        ModFlags = Modifiers.Check (AllowedModifiers, flags, Modifiers.PRIVATE);  
                        Add = add_block;
                        Remove = rem_block;
                        OptAttributes = attrs;
                }

                public void Define (TypeContainer parent)
                {
                        MethodAttributes m_attr = Modifiers.MethodAttr (ModFlags);

                        EventAttributes e_attr = EventAttributes.RTSpecialName | EventAttributes.SpecialName;
                        
                        MethodBuilder mb;

                        Type t = parent.LookupType (Type, false);
                        Type [] parameters = new Type [1];
                        parameters [0] = t;
                        
                        EventBuilder = parent.TypeBuilder.DefineEvent (Name, e_attr, t);
                        
                        if (Add != null) {
                                mb = parent.TypeBuilder.DefineMethod ("add_" + Name, m_attr, null,
                                                                      parameters);
                                mb.DefineParameter (1, ParameterAttributes.None, "value");
                                EventBuilder.SetAddOnMethod (mb);
                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                TypeManager.RegisterMethod (mb, parameters);
                        }

                        if (Remove != null) {
                                mb = parent.TypeBuilder.DefineMethod ("remove_" + Name, m_attr, null,
                                                                      parameters);
                                mb.DefineParameter (1, ParameterAttributes.None, "value");
                                EventBuilder.SetRemoveOnMethod (mb);

                                //
                                // HACK because System.Reflection.Emit is lame
                                //
                                TypeManager.RegisterMethod (mb, parameters);
                        }
                }
                
        }

        public class Indexer {

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

                public readonly string     Type;
                public readonly string     InterfaceType;
                public readonly Parameters FormalParameters;
                public readonly int        ModFlags;
                public readonly Block      Get;
                public readonly Block      Set;
                public Attributes          OptAttributes;
                public MethodBuilder GetMethodBuilder;
                public MethodBuilder SetMethodBuilder;
                

                public Indexer (string type, string int_type, int flags, Parameters parms,
                                Block get_block, Block set_block, Attributes attrs)
                {

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

                public void Define (TypeContainer parent)
                {
                        MethodAttributes attr = Modifiers.MethodAttr (ModFlags);
                        
                        Type ret_type = parent.LookupType (Type, false);
                        Type [] parameters = FormalParameters.GetParameterInfo (parent);

                        GetMethodBuilder = parent.TypeBuilder.DefineMethod (
                                "get_Item", attr, ret_type, parameters);
                        SetMethodBuilder = parent.TypeBuilder.DefineMethod (
                                "set_Item", attr, ret_type, parameters);

                        //
                        // HACK because System.Reflection.Emit is lame
                        //
                        TypeManager.RegisterMethod (GetMethodBuilder, parameters);
                        TypeManager.RegisterMethod (SetMethodBuilder, parameters);

                        Parameter [] p = FormalParameters.FixedParameters;

                        if (p != null) {
                                int i;
                                
                                for (i = 0; i < p.Length; ++i) {
                                        GetMethodBuilder.DefineParameter (i + 1, p [i].Attributes, p [i].Name);
                                        SetMethodBuilder.DefineParameter (i + 1, p [i].Attributes, p [i].Name);
                                }
                                
                                if (i != parameters.Length)
                                        Console.WriteLine ("Implement type definition for params");
                        }

                }
                
        }

        public class Operator {

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

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

                public enum OpType {

                        // Unary operators
                        Negate,
                        BitComplement,
                        Increment,
                        Decrement,
                        True,
                        False,

                        // Unary and Binary operators
                        Addition,
                        Subtraction,
                        
                        // 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 int    ModFlags;
                public readonly Block  Block;
                public Attributes      OptAttributes;
                public MethodBuilder   OperatorMethodBuilder;
                public Location        Location;
                
                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)
                {
                        OperatorType = type;
                        ReturnType = ret_type;
                        ModFlags = Modifiers.Check (AllowedModifiers, flags, Modifiers.PUBLIC);
                        FirstArgType = arg1type;
                        FirstArgName = arg1name;
                        SecondArgType = arg2type;
                        SecondArgName = arg2name;
                        Block = block;
                        OptAttributes = attrs;
                        Location = loc;
                }

                string Prototype (TypeContainer parent)
                {
                        return parent.Name + ".operator " + OperatorType + " (" + FirstArgType + "," +
                                SecondArgType + ")";
                }
                
                public void 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");
                        }

                        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),
                                                     OptAttributes, Location.Null);
                        
                        OperatorMethod.Define (parent);
                        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");
                                
                                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");
                                
                                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");
                                
                                if (first_arg_type.IsInterface || return_type.IsInterface)
                                        Report.Error (-9, Location,
                                               "User-defined conversion cannot convert to or from an interface type");   
                                
                                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"); 
                                
                        } 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");
                                
                                
                                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");
                                        
                                }
                                
                                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");
                                }
                                
                        } 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");
                        }
                        
                
                        
                }
                
                public void Emit (TypeContainer parent)
                {
                        OperatorMethod.Block = Block;
                        OperatorMethod.Emit (parent);
                }
                

        }

        //
        // This is used to compare method signatures
        //
        struct MethodSignature {
                public string Name;
                public Type RetType;
                public Type [] Parameters;
                
                public MethodSignature (string name, Type ret_type, Type [] parameters)
                {
                        Name = name;
                        RetType = ret_type;
                        Parameters = parameters;

                        if (parameters != null){
                                if (parameters.Length == 0)
                                        Parameters = null;
                        } 
                }
                
                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;
                }
        }               
}