[mono.git] / mcs / mcs / expression.cs

//
// expression.cs: Expression representation for the IL tree.
//
// Author:
//   Miguel de Icaza (miguel@ximian.com)
//
// (C) 2001 Ximian, Inc.
//
namespace CIR {
        using System.Collections;
        using System.Diagnostics;
        using System;
        using System.Reflection;
        using System.Reflection.Emit;

        // <remarks>
        //   The ExprClass class contains the is used to pass the 
        //   classification of an expression (value, variable, namespace,
        //   type, method group, property access, event access, indexer access,
        //   nothing).
        // </remarks>
        public enum ExprClass {
                Invalid,
                
                Value, Variable, Namespace, Type,
                MethodGroup, PropertyAccess,
                EventAccess, IndexerAccess, Nothing, 
        }

        // <remarks>
        //   Base class for expressions
        // </remarks>
        public abstract class Expression {
                protected ExprClass eclass;
                protected Type      type;
                
                public Type Type {
                        get {
                                return type;
                        }

                        set {
                                type = value;
                        }
                }

                public ExprClass ExprClass {
                        get {
                                return eclass;
                        }

                        set {
                                eclass = value;
                        }
                }

                public abstract Expression Resolve (TypeContainer tc);
                public abstract void Emit (EmitContext ec);
                
                // <summary>
                //   Protected constructor.  Only derivate types should
                //   be able to be created
                // </summary>

                protected Expression ()
                {
                        eclass = ExprClass.Invalid;
                        type = null;
                }

                // 
                // Returns a fully formed expression after a MemberLookup
                //
                static Expression ExprClassFromMemberInfo (MemberInfo mi)
                {
                        if (mi is EventInfo){
                                return new EventExpr ((EventInfo) mi);
                        } else if (mi is FieldInfo){
                                return new FieldExpr ((FieldInfo) mi);
                        } else if (mi is PropertyInfo){
                                return new PropertyExpr ((PropertyInfo) mi);
                        } else if (mi is Type)
                                return new TypeExpr ((Type) mi);

                        return null;
                }
                
                //
                // FIXME: Probably implement a cache for (t,name,current_access_set)?
                //
                // FIXME: We need to cope with access permissions here, or this wont
                // work!
                //
                // This code could use some optimizations, but we need to do some
                // measurements.  For example, we could use a delegate to `flag' when
                // something can not any longer be a method-group (because it is something
                // else).
                //
                // Return values:
                //     If the return value is an Array, then it is an array of
                //     MethodInfos
                //   
                //     If the return value is an MemberInfo, it is anything, but a Method
                //
                //     null on error.
                //
                // FIXME: When calling MemberLookup inside an `Invocation', we should pass
                // the arguments here and have MemberLookup return only the methods that
                // match the argument count/type, unlike we are doing now (we delay this
                // decision).
                //
                // This is so we can catch correctly attempts to invoke instance methods
                // from a static body (scan for error 120 in ResolveSimpleName).
                // 
                protected static Expression MemberLookup (Report r, Type t, string name, bool same_type)
                {
                        MemberTypes mt =
                                // MemberTypes.Constructor |
                                MemberTypes.Event       |
                                MemberTypes.Field       |
                                MemberTypes.Method      |
                                MemberTypes.NestedType  |
                                MemberTypes.Property;
                        
                        BindingFlags bf =
                                BindingFlags.Public |
                                BindingFlags.Static |
                                BindingFlags.Instance;
                        
                        if (same_type)
                                bf |= BindingFlags.NonPublic;

                        
                        MemberInfo [] mi = t.FindMembers (mt, bf, Type.FilterName, name);

                        if (mi.Length == 1 && !(mi [0] is MethodInfo))
                                return Expression.ExprClassFromMemberInfo (mi [0]);

                        for (int i = 0; i < mi.Length; i++)
                                if (!(mi [i] is MethodInfo)){
                                        r.Error (-5, "Do not know how to reproduce this case: Methods and non-Method with the same name, report this please");
                                        
                                }

                        return new MethodGroupExpr (mi);
                }
                
                // <summary>
                //   Resolves the E in `E.I' side for a member_access
                //
                // This is suboptimal and should be merged with ResolveMemberAccess
                static Expression ResolvePrimary (TypeContainer tc, string name)
                {
                        int dot_pos = name.LastIndexOf (".");

                        if (tc.RootContext.IsNamespace (name))
                                return new NamespaceExpr (name);

                        if (dot_pos != -1){
                        } else {
                                Type t = tc.LookupType (name, false);

                                if (t != null)
                                        return new TypeExpr (t);
                        }

                        return null;
                }
                        
                static public Expression ResolveMemberAccess (TypeContainer tc, string name)
                {
                        Expression left_e;
                        int dot_pos = name.LastIndexOf (".");
                        string left = name.Substring (0, dot_pos);
                        string right = name.Substring (dot_pos + 1);

                        left_e = ResolvePrimary (tc, left);
                        if (left_e == null)
                                return null;

                        switch (left_e.ExprClass){
                        case ExprClass.Type:
                                return  MemberLookup (tc.RootContext.Report,
                                                      left_e.Type, right,
                                                      left_e.Type == tc.TypeBuilder);
                                
                        case ExprClass.Namespace:
                        case ExprClass.PropertyAccess:
                        case ExprClass.IndexerAccess:
                        case ExprClass.Variable:
                        case ExprClass.Value:
                        case ExprClass.Nothing:
                        case ExprClass.EventAccess:
                        case ExprClass.MethodGroup:
                        case ExprClass.Invalid:
                                tc.RootContext.Report.Error (-1000,
                                                             "Internal compiler error, should have " +
                                                             "got these handled before");
                                break;
                        }
                        
                        return null;
                }
                
        }

        public class Unary : Expression {
                public enum Operator {
                        Plus, Minus, Negate, BitComplement,
                        Indirection, AddressOf, PreIncrement,
                        PreDecrement, PostIncrement, PostDecrement
                }

                Operator   oper;
                Expression expr;
                
                public Unary (Operator op, Expression expr)
                {
                        this.oper = op;
                        this.expr = expr;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }

                        set {
                                expr = value;
                        }
                }

                public Operator Oper {
                        get {
                                return oper;
                        }

                        set {
                                oper = value;
                        }
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class Probe : Expression {
                string probe_type;
                Expression expr;
                Operator oper;

                public enum Operator {
                        Is, As
                }
                
                public Probe (Operator oper, Expression expr, string probe_type)
                {
                        this.oper = oper;
                        this.probe_type = probe_type;
                        this.expr = expr;
                }

                public Operator Oper {
                        get {
                                return oper;
                        }
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public string ProbeType {
                        get {
                                return probe_type;
                        }
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }
        
        public class Cast : Expression {
                string target_type;
                Expression expr;
                
                public Cast (string cast_type, Expression expr)
                {
                        this.target_type = target_type;
                        this.expr = expr;
                }

                public string TargetType {
                        get {
                                return target_type;
                        }
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                        set {
                                expr = value;
                        }
                }
                
                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class Binary : Expression {
                public enum Operator {
                        Multiply, Divide, Modulo,
                        Add, Substract,
                        ShiftLeft, ShiftRight,
                        LessThan, GreatherThan, LessOrEqual, GreatherOrEqual, 
                        Equal, NotEqual,
                        BitwiseAnd,
                        ExclusiveOr,
                        BitwiseOr,
                        LogicalAnd,
                        LogicalOr
                }

                Operator oper;
                Expression left, right;

                OpCode opcode, opcode_check;
                
                public Binary (Operator oper, Expression left, Expression right)
                {
                        this.oper = oper;
                        this.left = left;
                        this.right = right;
                }

                public Operator Oper {
                        get {
                                return oper;
                        }
                        set {
                                oper = value;
                        }
                }
                
                public Expression Left {
                        get {
                                return left;
                        }
                        set {
                                left = value;
                        }
                }

                public Expression Right {
                        get {
                                return right;
                        }
                        set {
                                right = value;
                        }
                }

                Expression ResolveOperator (Operator oper, Type l, Type r)
                {
                        //
                        // Step 1: Perform Operator Overload location
                        //

                        //
                        // Step 2: Default operations
                        //
                        switch (oper){
                        case Operator.Multiply:
                                opcode = OpCodes.Mul;
                                if (l == TypeManager.int32_type)
                                        opcode_check = OpCodes.Mul_Ovf;
                                else if (l == TypeManager.uint32_type)
                                        opcode_check = OpCodes.Mul_Ovf_Un;
                                else if (l == TypeManager.uint64_type) 
                                        opcode_check = OpCodes.Mul_Ovf_Un;
                                else if (l == TypeManager.int64_type) 
                                        opcode_check = OpCodes.Mul_Ovf;
                                else
                                        opcode_check = OpCodes.Mul;
                                break;
                        }

                        return this;
                }
                
                public override Expression Resolve (TypeContainer tc)
                {
                        left = left.Resolve (tc);
                        right = right.Resolve (tc);

                        if (left == null || right == null)
                                return null;
                                        
                        return ResolveOperator (oper, left.Type, right.Type);
                }

                public override void Emit (EmitContext ec)
                {
                        ILGenerator ig = ec.ig;

                        left.Emit (ec);
                        right.Emit (ec);

                        if (ec.CheckState)
                                ec.ig.Emit (opcode_check);
                        else
                                ec.ig.Emit (opcode);
                }
        }

        public class Conditional : Expression {
                Expression expr, trueExpr, falseExpr;
                
                public Conditional (Expression expr, Expression trueExpr, Expression falseExpr)
                {
                        this.expr = expr;
                        this.trueExpr = trueExpr;
                        this.falseExpr = falseExpr;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public Expression TrueExpr {
                        get {
                                return trueExpr;
                        }
                }

                public Expression FalseExpr {
                        get {
                                return falseExpr;
                        }
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class SimpleName : Expression {
                string name;
                
                public SimpleName (string name)
                {
                        this.name = name;
                }

                public string Name {
                        get {
                                return name;
                        }
                }

                //
                // Checks whether we are trying to access an instance
                // property, method or field from a static body.
                //
                Expression MemberStaticCheck (Report r, Expression e)
                {
                        if (e is FieldExpr){
                                FieldInfo fi = ((FieldExpr) e).FieldInfo;
                                
                                if (!fi.IsStatic){
                                        r.Error (120,
                                                 "An object reference is required " +
                                                 "for the non-static field `"+name+"'");
                                        return null;
                                }
                        } else if (e is MethodGroupExpr){
                                // FIXME: Pending reorganization of MemberLookup
                                // Basically at this point we should have the
                                // best match already selected for us, and
                                // we should only have to check a *single*
                                // Method for its static on/off bit.
                                return e;
                        } else if (e is PropertyExpr){
                                if (!((PropertyExpr) e).IsStatic){
                                        r.Error (120,
                                                 "An object reference is required " +
                                                 "for the non-static property access `"+
                                                 name+"'");
                                        return null;
                                }
                        }

                        return e;
                }
                
                //
                // 7.5.2: Simple Names. 
                //
                // Local Variables and Parameters are handled at
                // parse time, so they never occur as SimpleNames.
                //
                Expression ResolveSimpleName (TypeContainer tc)
                {
                        Expression e;
                        Report r = tc.RootContext.Report;

                        e = MemberLookup (tc.RootContext.Report, tc.TypeBuilder, name, true);
                        if (e != null){
                                if (e is TypeExpr)
                                        return e;
                                if ((tc.ModFlags & Modifiers.STATIC) != 0)
                                        return MemberStaticCheck (r, e);
                                else
                                        return e;
                        }

                        //
                        // Do step 3 of the Simple Name resolution.
                        //
                        // FIXME: implement me.
                        
                        return this;
                }
                
                //
                // SimpleName needs to handle a multitude of cases:
                //
                // simple_names and qualified_identifiers are placed on
                // the tree equally.
                //
                public override Expression Resolve (TypeContainer tc)
                {
                        if (name.IndexOf (".") != -1)
                                return ResolveMemberAccess (tc, name);
                        else
                                return ResolveSimpleName (tc);
                }

                public override void Emit (EmitContext ec)
                {
                }
        }
        
        public class LocalVariableReference : Expression {
                public readonly string Name;
                public readonly Block Block;
                
                public LocalVariableReference (Block block, string name)
                {
                        Block = block;
                        Name = name;
                        eclass = ExprClass.Variable;
                }

                public VariableInfo VariableInfo {
                        get {
                                return (VariableInfo) Block.GetVariableInfo (Name);
                        }
                }
                
                public override Expression Resolve (TypeContainer tc)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        Console.WriteLine ("Internal compiler error, LocalVariableReference should not be emitted");
                }
        }

        public class ParameterReference : Expression {
                public readonly Parameters Pars;
                public readonly String Name;
                public readonly int Idx;
                
                public ParameterReference (Parameters pars, int idx, string name)
                {
                        Pars = pars;
                        Idx  = idx;
                        Name = name;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }
        
        // <summary>
        //   Used for arguments to New(), Invocation()
        // </summary>
        public class Argument {
                public enum AType {
                        Expression,
                        Ref,
                        Out
                };

                public readonly AType Type;
                Expression expr;

                public Argument (Expression expr, AType type)
                {
                        this.expr = expr;
                        this.Type = type;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                public bool Resolve (TypeContainer tc)
                {
                        expr = expr.Resolve (tc);
                        return expr != null;
                }

                public void Emit (EmitContext ec)
                {
                        expr.Emit (ec);
                }
        }

        // <summary>
        //   Invocation of methods or delegates.
        // </summary>
        public class Invocation : Expression {
                public readonly ArrayList Arguments;
                Expression expr;
                MethodInfo method = null;
                
                //
                // arguments is an ArrayList, but we do not want to typecast,
                // as it might be null.
                //
                // FIXME: only allow expr to be a method invocation or a
                // delegate invocation (7.5.5)
                //
                public Invocation (Expression expr, ArrayList arguments)
                {
                        this.expr = expr;
                        Arguments = arguments;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }

                /// <summary>
                ///   Computes whether Argument `a' and the ParameterInfo `pi' are
                ///   compatible, and if so, how good is the match (in terms of
                ///   "better conversions" (7.4.2.3).
                ///
                ///   0   is the best possible match.
                ///   -1  represents a type mismatch.
                ///   -2  represents a ref/out mismatch.
                /// </summary>
                static int Badness (Argument a, ParameterInfo pi)
                {
                        if (pi.ParameterType == a.Expr.Type)
                                return 0;

                        // FIXME: Implement implicit conversions here.
                        // FIXME: Implement better conversion here.
                        
                        return -1;
                }

                // <summary>
                //   Find the Applicable Function Members (7.4.2.1)
                // </summary>
                static MethodInfo OverloadResolve (MethodGroupExpr me, ArrayList Arguments)
                {
                        ArrayList afm = new ArrayList ();
                        int best_match = 10000;
                        int best_match_idx = -1;
                        MethodInfo method = null;
                        
                        for (int i = me.Methods.Length; i > 0; ){
                                i--;
                                ParameterInfo [] pi = me.Methods [i].GetParameters ();

                                //
                                // Compute how good this is
                                //
                                if (pi.Length == Arguments.Count){
                                        int badness = 0;
                                        
                                        for (int j = Arguments.Count; j > 0;){
                                                int x;
                                                j--;

                                                Argument a = (Argument) Arguments [j];

                                                x = Badness (a, pi [j]);

                                                if (x < 0){
                                                        // FIXME: report nice error.
                                                } else
                                                        badness += x;
                                        }

                                        if (badness < best_match){
                                                best_match = badness;
                                                method = me.Methods [i];
                                                best_match_idx = i;
                                        }
                                }
                        }

                        if (best_match_idx == -1)
                                return null;
                        
                        return method;
                }

                        
                public override Expression Resolve (TypeContainer tc)
                {
                        //
                        // First, resolve the expression that is used to
                        // trigger the invocation
                        //
                        this.expr = expr.Resolve (tc);
                        if (this.expr == null)
                                return null;

                        if (!(this.expr is MethodGroupExpr)){
                                tc.RootContext.Report.Error (118,
                                       "Denotes an " + this.expr.ExprClass + " while a method was expected");
                                return null;
                        }

                        //
                        // Next, evaluate all the expressions in the argument list
                        //
                        if (Arguments != null){
                                for (int i = Arguments.Count; i > 0;){
                                        --i;
                                        Argument a = (Argument) Arguments [i];

                                        if (!a.Resolve (tc))
                                                return null;
                                }
                        }

                        method = OverloadResolve ((MethodGroupExpr) this.expr, Arguments);

                        if (method == null){
                                tc.RootContext.Report.Error (-6,
                                "Figure out error: Can not find a good function for this argument list");
                                return null;
                        }

                        Console.WriteLine ("Found a method! " + method);

                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        int top = Arguments.Count;

                        for (int i = 0; i < top; i++){
                                Argument a = (Argument) Arguments [i];

                                a.Emit (ec);
                        }

                        ec.ig.Emit (OpCodes.Call, (MethodInfo) method);
                }
        }

        public class New : Expression {

                public enum NType {
                        Object,
                        Array
                };

                public readonly NType     NewType;
                public readonly ArrayList Arguments;
                public readonly string    RequestedType;
                // These are for the case when we have an array
                public readonly string    Rank;
                public readonly ArrayList Indices;
                public readonly ArrayList Initializers;
                

                public New (string requested_type, ArrayList arguments)
                {
                        RequestedType = requested_type;
                        Arguments = arguments;
                        NewType = NType.Object;
                }

                public New (string requested_type, ArrayList exprs, string rank, ArrayList initializers)
                {
                        RequestedType = requested_type;
                        Indices       = exprs;
                        Rank          = rank;
                        Initializers  = initializers;
                        NewType       = NType.Array;
                }
                
                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class This : Expression {
                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class TypeOf : Expression {
                public readonly string QueriedType;
                
                public TypeOf (string queried_type)
                {
                        QueriedType = queried_type;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class SizeOf : Expression {
                public readonly string QueriedType;
                
                public SizeOf (string queried_type)
                {
                        this.QueriedType = queried_type;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        public class MemberAccess : Expression {
                public readonly string Identifier;
                Expression expr;
                
                public MemberAccess (Expression expr, string id)
                {
                        this.expr = expr;
                        Identifier = id;
                }

                public Expression Expr {
                        get {
                                return expr;
                        }
                }
                
                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }

        }

        // <summary>
        //   Nodes of type Namespace are created during the semantic
        //   analysis to resolve member_access/qualified_identifier/simple_name
        //   accesses.
        //
        //   They are born `resolved'. 
        // </summary>
        public class NamespaceExpr : Expression {
                public readonly string Name;
                
                public NamespaceExpr (string name)
                {
                        Name = name;
                        eclass = ExprClass.Namespace;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }

        // <summary>
        //   Fully resolved expression that evaluates to a type
        // </summary>
        public class TypeExpr : Expression {
                public TypeExpr (Type t)
                {
                        Type = t;
                        eclass = ExprClass.Type;
                }

                override public Expression Resolve (TypeContainer tc)
                {
                        return this;
                }

                override public void Emit (EmitContext ec)
                {
                        
                }
        }

        // <summary>
        //   Fully resolved expression that evaluates to a type
        // </summary>
        public class MethodGroupExpr : Expression {
                public readonly MethodInfo [] Methods;
                
                public MethodGroupExpr (MemberInfo [] mi)
                {
                        Methods = new MethodInfo [mi.Length];
                        mi.CopyTo (Methods, 0);
                        eclass = ExprClass.MethodGroup;
                }

                override public Expression Resolve (TypeContainer tc)
                {
                        return this;
                }

                override public void Emit (EmitContext ec)
                {
                        
                }
        }
        
        public class BuiltinTypeAccess : Expression {
                public readonly string AccessBase;
                public readonly string Method;
                
                public BuiltinTypeAccess (string type, string method)
                {
                        System.Console.WriteLine ("DUDE! This type should be fully resolved!");
                        AccessBase = type;
                        Method = method;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME: Implement;
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }


        //   Fully resolved expression that evaluates to a Field
        // </summary>
        public class FieldExpr : Expression {
                public readonly FieldInfo FieldInfo;

                public FieldExpr (FieldInfo fi)
                {
                        FieldInfo = fi;
                        eclass = ExprClass.Variable;
                }

                override public Expression Resolve (TypeContainer tc)
                {
                        // We are born in resolved state. 
                        return this;
                }

                override public void Emit (EmitContext ec)
                {
                        // FIXME: Assert that this should not be reached?
                }
        }
        
        // <summary>
        //   Fully resolved expression that evaluates to a Property
        // </summary>
        public class PropertyExpr : Expression {
                public readonly PropertyInfo PropertyInfo;
                public readonly bool IsStatic;
                
                public PropertyExpr (PropertyInfo pi)
                {
                        PropertyInfo = pi;
                        eclass = ExprClass.PropertyAccess;
                        IsStatic = false;
                                
                        MethodInfo [] acc = pi.GetAccessors ();

                        for (int i = 0; i < acc.Length; i++)
                                if (acc [i].IsStatic)
                                        IsStatic = true;
                }

                override public Expression Resolve (TypeContainer tc)
                {
                        // We are born in resolved state. 
                        return this;
                }

                override public void Emit (EmitContext ec)
                {
                        // FIXME: Implement.
                }
        }

        // <summary>
        //   Fully resolved expression that evaluates to a Property
        // </summary>
        public class EventExpr : Expression {
                public readonly EventInfo EventInfo;
                
                public EventExpr (EventInfo ei)
                {
                        EventInfo = ei;
                        eclass = ExprClass.EventAccess;
                }

                override public Expression Resolve (TypeContainer tc)
                {
                        // We are born in resolved state. 
                        return this;
                }

                override public void Emit (EmitContext ec)
                {
                        // FIXME: Implement.
                }
        }
        
        public class CheckedExpr : Expression {

                public readonly Expression Expr;

                public CheckedExpr (Expression e)
                {
                        Expr = e;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME : Implement !
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
                
        }

        public class UnCheckedExpr : Expression {

                public readonly Expression Expr;

                public UnCheckedExpr (Expression e)
                {
                        Expr = e;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME : Implement !
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
                
        }

                public class ElementAccess : Expression {

                public readonly ArrayList  Arguments;
                public readonly Expression Expr;

                public ElementAccess (Expression e, ArrayList e_list)
                {
                        Expr = e;
                        Arguments = e_list;
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME : Implement
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                        // FIXME : Implement !
                }

        }

        public class BaseAccess : Expression {

                public enum BaseAccessType {
                        Member,
                        Indexer
                };
                
                public readonly BaseAccessType BAType;
                public readonly string         Member;
                public readonly ArrayList      Arguments;

                public BaseAccess (BaseAccessType t, string member, ArrayList args)
                {
                        BAType = t;
                        Member = member;
                        Arguments = args;
                        
                }

                public override Expression Resolve (TypeContainer tc)
                {
                        // FIXME : Implement !
                        return this;
                }

                public override void Emit (EmitContext ec)
                {
                }
        }
}