[mono.git] / mcs / gmcs / typemanager.cs

//
// typemanager.cs: C# type manager
//
// Author: Miguel de Icaza (miguel@gnu.org)
//         Ravi Pratap     (ravi@ximian.com)
//
// Licensed under the terms of the GNU GPL
//
// (C) 2001 Ximian, Inc (http://www.ximian.com)
//
//

//
// We will eventually remove the SIMPLE_SPEEDUP, and should never change 
// the behavior of the compilation.  This can be removed if we rework
// the code to get a list of namespaces available.
//
#define SIMPLE_SPEEDUP

using System;
using System.IO;
using System.Globalization;
using System.Collections;
using System.Reflection;
using System.Reflection.Emit;
using System.Text;
using System.Text.RegularExpressions;
using System.Runtime.CompilerServices;
using System.Diagnostics;

namespace Mono.CSharp {

public class TypeManager {
        //
        // A list of core types that the compiler requires or uses
        //
        static public Type object_type;
        static public Type value_type;
        static public Type string_type;
        static public Type int32_type;
        static public Type uint32_type;
        static public Type int64_type;
        static public Type uint64_type;
        static public Type float_type;
        static public Type double_type;
        static public Type char_type;
        static public Type char_ptr_type;
        static public Type short_type;
        static public Type decimal_type;
        static public Type bool_type;
        static public Type sbyte_type;
        static public Type byte_type;
        static public Type ushort_type;
        static public Type enum_type;
        static public Type delegate_type;
        static public Type multicast_delegate_type;
        static public Type void_type;
        static public Type enumeration_type;
        static public Type array_type;
        static public Type runtime_handle_type;
        static public Type icloneable_type;
        static public Type type_type;
        static public Type ienumerator_type;
        static public Type ienumerable_type;
        static public Type idisposable_type;
        static public Type default_member_type;
        static public Type iasyncresult_type;
        static public Type asynccallback_type;
        static public Type intptr_type;
        static public Type monitor_type;
        static public Type runtime_field_handle_type;
        static public Type attribute_type;
        static public Type attribute_usage_type;
        static public Type dllimport_type;
        static public Type unverifiable_code_type;
        static public Type methodimpl_attr_type;
        static public Type marshal_as_attr_type;
        static public Type param_array_type;
        static public Type guid_attr_type;
        static public Type void_ptr_type;
        static public Type indexer_name_type;
        static public Type exception_type;
        static public Type invalid_operation_exception_type;
        static public object obsolete_attribute_type;
        static public object conditional_attribute_type;
        static public Type in_attribute_type;

        //
        // An empty array of types
        //
        static public Type [] NoTypes;
        static public TypeExpr [] NoTypeExprs;


        // 
        // Expressions representing the internal types.  Used during declaration
        // definition.
        //
        static public TypeExpr system_object_expr, system_string_expr; 
        static public TypeExpr system_boolean_expr, system_decimal_expr;
        static public TypeExpr system_single_expr, system_double_expr;
        static public TypeExpr system_sbyte_expr, system_byte_expr;
        static public TypeExpr system_int16_expr, system_uint16_expr;
        static public TypeExpr system_int32_expr, system_uint32_expr;
        static public TypeExpr system_int64_expr, system_uint64_expr;
        static public TypeExpr system_char_expr, system_void_expr;
        static public TypeExpr system_asynccallback_expr;
        static public TypeExpr system_iasyncresult_expr;
        static public TypeExpr system_valuetype_expr;

        //
        // This is only used when compiling corlib
        //
        static public Type system_int32_type;
        static public Type system_array_type;
        static public Type system_type_type;
        static public Type system_assemblybuilder_type;
        static public MethodInfo system_int_array_get_length;
        static public MethodInfo system_int_array_get_rank;
        static public MethodInfo system_object_array_clone;
        static public MethodInfo system_int_array_get_length_int;
        static public MethodInfo system_int_array_get_lower_bound_int;
        static public MethodInfo system_int_array_get_upper_bound_int;
        static public MethodInfo system_void_array_copyto_array_int;

        
        //
        // Internal, not really used outside
        //
        static Type runtime_helpers_type;
        
        //
        // These methods are called by code generated by the compiler
        //
        static public MethodInfo string_concat_string_string;
        static public MethodInfo string_concat_string_string_string;
        static public MethodInfo string_concat_string_string_string_string;
        static public MethodInfo string_concat_object_object;
        static public MethodInfo string_isinterneted_string;
        static public MethodInfo system_type_get_type_from_handle;
        static public MethodInfo object_getcurrent_void;
        static public MethodInfo bool_movenext_void;
        static public MethodInfo ienumerable_getenumerator_void;
        static public MethodInfo void_reset_void;
        static public MethodInfo void_dispose_void;
        static public MethodInfo void_monitor_enter_object;
        static public MethodInfo void_monitor_exit_object;
        static public MethodInfo void_initializearray_array_fieldhandle;
        static public MethodInfo int_getlength_int;
        static public MethodInfo delegate_combine_delegate_delegate;
        static public MethodInfo delegate_remove_delegate_delegate;
        static public MethodInfo int_get_offset_to_string_data;
        static public MethodInfo int_array_get_length;
        static public MethodInfo int_array_get_rank;
        static public MethodInfo object_array_clone;
        static public MethodInfo int_array_get_length_int;
        static public MethodInfo int_array_get_lower_bound_int;
        static public MethodInfo int_array_get_upper_bound_int;
        static public MethodInfo void_array_copyto_array_int;
        
        //
        // The attribute constructors.
        //
        static public ConstructorInfo object_ctor;
        static public ConstructorInfo cons_param_array_attribute;
        static public ConstructorInfo void_decimal_ctor_five_args;
        static public ConstructorInfo unverifiable_code_ctor;
        static public ConstructorInfo invalid_operation_ctor;
        
        // <remarks>
        //   Holds the Array of Assemblies that have been loaded
        //   (either because it is the default or the user used the
        //   -r command line option)
        // </remarks>
        static Assembly [] assemblies;

        // <remarks>
        //  Keeps a list of modules. We used this to do lookups
        //  on the module using GetType -- needed for arrays
        // </remarks>
        static Module [] modules;

        // <remarks>
        //   This is the type_cache from the assemblies to avoid
        //   hitting System.Reflection on every lookup.
        // </summary>
        static Hashtable types;

        // <remarks>
        //  This is used to hotld the corresponding TypeContainer objects
        //  since we need this in FindMembers
        // </remarks>
        static Hashtable typecontainers;

        // <remarks>
        //   Keeps track of those types that are defined by the
        //   user's program
        // </remarks>
        static ArrayList user_types;

        static PtrHashtable builder_to_declspace;

        // <remarks>
        //   Tracks the interfaces implemented by typebuilders.  We only
        //   enter those who do implement or or more interfaces
        // </remarks>
        static PtrHashtable builder_to_ifaces;

        // <remarks>
        //   Maps MethodBase.RuntimeTypeHandle to a Type array that contains
        //   the arguments to the method
        // </remarks>
        static Hashtable method_arguments;

        // <remarks>
        //   Maps PropertyBuilder to a Type array that contains
        //   the arguments to the indexer
        // </remarks>
        static Hashtable indexer_arguments;

        // <remarks>
        //   Maybe `method_arguments' should be replaced and only
        //   method_internal_params should be kept?
        // <remarks>
        static Hashtable method_internal_params;

        // <remarks>
        //  Keeps track of attribute types
        // </remarks>

        static Hashtable builder_to_attr;

        // <remarks>
        //  Keeps track of methods
        // </remarks>

        static Hashtable builder_to_method;

        struct Signature {
                public string name;
                public Type [] args;
        }

        public static void CleanUp ()
        {
                // Lets get everything clean so that we can collect before generating code
                assemblies = null;
                modules = null;
                types = null;
                typecontainers = null;
                user_types = null;
                builder_to_declspace = null;
                builder_to_ifaces = null;
                method_arguments = null;
                indexer_arguments = null;
                method_internal_params = null;
                builder_to_attr = null;
                builder_to_method = null;
                
                fields = null;
                references = null;
                negative_hits = null;
                attr_to_allowmult = null;
                builder_to_constant = null;
                fieldbuilders_to_fields = null;
                events = null;
                priv_fields_events = null;
                properties = null;
                
                TypeHandle.CleanUp ();
        }

        /// <summary>
        ///   A filter for Findmembers that uses the Signature object to
        ///   extract objects
        /// </summary>
        static bool SignatureFilter (MemberInfo mi, object criteria)
        {
                Signature sig = (Signature) criteria;

                if (!(mi is MethodBase))
                        return false;
                
                if (mi.Name != sig.name)
                        return false;

                int count = sig.args.Length;
                
                if (mi is MethodBuilder || mi is ConstructorBuilder){
                        Type [] candidate_args = GetArgumentTypes ((MethodBase) mi);

                        if (candidate_args.Length != count)
                                return false;
                        
                        for (int i = 0; i < count; i++)
                                if (candidate_args [i] != sig.args [i])
                                        return false;
                        
                        return true;
                } else {
                        ParameterInfo [] pars = ((MethodBase) mi).GetParameters ();

                        if (pars.Length != count)
                                return false;

                        for (int i = 0; i < count; i++)
                                if (pars [i].ParameterType != sig.args [i])
                                        return false;
                        return true;
                }
        }

        // A delegate that points to the filter above.
        static MemberFilter signature_filter;

        //
        // These are expressions that represent some of the internal data types, used
        // elsewhere
        //
        static void InitExpressionTypes ()
        {
                system_object_expr  = new TypeLookupExpression ("System.Object");
                system_string_expr  = new TypeLookupExpression ("System.String");
                system_boolean_expr = new TypeLookupExpression ("System.Boolean");
                system_decimal_expr = new TypeLookupExpression ("System.Decimal");
                system_single_expr  = new TypeLookupExpression ("System.Single");
                system_double_expr  = new TypeLookupExpression ("System.Double");
                system_sbyte_expr   = new TypeLookupExpression ("System.SByte");
                system_byte_expr    = new TypeLookupExpression ("System.Byte");
                system_int16_expr   = new TypeLookupExpression ("System.Int16");
                system_uint16_expr  = new TypeLookupExpression ("System.UInt16");
                system_int32_expr   = new TypeLookupExpression ("System.Int32");
                system_uint32_expr  = new TypeLookupExpression ("System.UInt32");
                system_int64_expr   = new TypeLookupExpression ("System.Int64");
                system_uint64_expr  = new TypeLookupExpression ("System.UInt64");
                system_char_expr    = new TypeLookupExpression ("System.Char");
                system_void_expr    = new TypeLookupExpression ("System.Void");
                system_asynccallback_expr = new TypeLookupExpression ("System.AsyncCallback");
                system_iasyncresult_expr = new TypeLookupExpression ("System.IAsyncResult");
                system_valuetype_expr  = new TypeLookupExpression ("System.ValueType");
        }

        static TypeManager ()
        {
                assemblies = new Assembly [0];
                modules = null;
                user_types = new ArrayList ();
                
                types = new Hashtable ();
                typecontainers = new Hashtable ();
                
                builder_to_declspace = new PtrHashtable ();
                builder_to_attr = new PtrHashtable ();
                builder_to_method = new PtrHashtable ();
                method_arguments = new PtrHashtable ();
                method_internal_params = new PtrHashtable ();
                indexer_arguments = new PtrHashtable ();
                builder_to_ifaces = new PtrHashtable ();
                
                NoTypes = new Type [0];
                NoTypeExprs = new TypeExpr [0];

                signature_filter = new MemberFilter (SignatureFilter);
                InitExpressionTypes ();
        }

        public static void HandleDuplicate (string name, Type t)
        {
                Type prev = (Type) types [name];
                TypeContainer tc = builder_to_declspace [prev] as TypeContainer;
                
                if (tc != null){
                        //
                        // This probably never happens, as we catch this before
                        //
                        Report.Error (-17, "The type `" + name + "' has already been defined.");
                        return;
                }
                
                tc = builder_to_declspace [t] as TypeContainer;
                if (tc != null){
                        Report.Warning (
                                        1595, "The type `" + name + "' is defined in an existing assembly;"+
                                        " Using the new definition from: " + tc.Location);
                } else {
                        Report.Warning (
                                        1595, "The type `" + name + "' is defined in an existing assembly;");
                }
                
                Report.Warning (1595, "Previously defined in: " + prev.Assembly.FullName);
                
                types.Remove (name);
                types.Add (name, t);
        }
        
        public static void AddUserType (string name, TypeBuilder t, TypeExpr[] ifaces)
        {
                try {
                        types.Add (name, t);
                } catch {
                        HandleDuplicate (name, t); 
                }
                user_types.Add (t);
                        
                if (ifaces != null)
                        builder_to_ifaces [t] = ifaces;
        }

        //
        // This entry point is used by types that we define under the covers
        // 
        public static void RegisterBuilder (TypeBuilder tb, TypeExpr [] ifaces)
        {
                if (ifaces != null)
                        builder_to_ifaces [tb] = ifaces;
        }
        
        public static void AddUserType (string name, TypeBuilder t, TypeContainer tc, TypeExpr [] ifaces)
        {
                builder_to_declspace.Add (t, tc);
                typecontainers.Add (name, tc);
                AddUserType (name, t, ifaces);
        }

        public static void AddDelegateType (string name, TypeBuilder t, Delegate del)
        {
                try {
                        types.Add (name, t);
                } catch {
                        HandleDuplicate (name, t);
                }
                
                builder_to_declspace.Add (t, del);
        }
        
        public static void AddEnumType (string name, TypeBuilder t, Enum en)
        {
                try {
                        types.Add (name, t);
                } catch {
                        HandleDuplicate (name, t);
                }
                builder_to_declspace.Add (t, en);
        }

        public static void AddUserInterface (string name, TypeBuilder t, Interface i, TypeExpr [] ifaces)
        {
                AddUserType (name, t, ifaces);
                builder_to_declspace.Add (t, i);
        }

        public static void AddMethod (MethodBuilder builder, MethodData method)
        {
                builder_to_method.Add (builder, method);
        }

        public static void RegisterAttrType (Type t, TypeContainer tc)
        {
                builder_to_attr.Add (t, tc);
        }

        /// <summary>
        ///   Returns the DeclSpace whose Type is `t' or null if there is no
        ///   DeclSpace for `t' (ie, the Type comes from a library)
        /// </summary>
        public static DeclSpace LookupDeclSpace (Type t)
        {
                return builder_to_declspace [t] as DeclSpace;
        }

        /// <summary>
        ///   Returns the TypeContainer whose Type is `t' or null if there is no
        ///   TypeContainer for `t' (ie, the Type comes from a library)
        /// </summary>
        public static TypeContainer LookupTypeContainer (Type t)
        {
                return builder_to_declspace [t] as TypeContainer;
        }
        
        public static IMemberContainer LookupMemberContainer (Type t)
        {
                if (t is TypeBuilder) {
                        IMemberContainer container = builder_to_declspace [t] as IMemberContainer;
                        if (container != null)
                                return container;
                }

                return TypeHandle.GetTypeHandle (t);
        }

        public static Interface LookupInterface (Type t)
        {
                return builder_to_declspace [t] as Interface;
        }

        public static Delegate LookupDelegate (Type t)
        {
                return builder_to_declspace [t] as Delegate;
        }

        public static Enum LookupEnum (Type t)
        {
                return builder_to_declspace [t] as Enum;
        }
        
        public static TypeContainer LookupAttr (Type t)
        {
                return (TypeContainer) builder_to_attr [t];
        }
        
        /// <summary>
        ///   Registers an assembly to load types from.
        /// </summary>
        public static void AddAssembly (Assembly a)
        {
                foreach (Assembly assembly in assemblies) {
                        if (a == assembly)
                                return;
                }

                int top = assemblies.Length;
                Assembly [] n = new Assembly [top + 1];

                assemblies.CopyTo (n, 0);
                
                n [top] = a;
                assemblies = n;
        }

        /// <summary>
        ///  Registers a module builder to lookup types from
        /// </summary>
        public static void AddModule (Module mb)
        {
                int top = modules != null ? modules.Length : 0;
                Module [] n = new Module [top + 1];

                if (modules != null)
                        modules.CopyTo (n, 0);
                n [top] = mb;
                modules = n;
        }

        static Hashtable references = new Hashtable ();
        
        //
        // Gets the reference to T version of the Type (T&)
        //
        public static Type GetReferenceType (Type t)
        {
                return t.MakeByRefType ();
        }

        static Hashtable pointers = new Hashtable ();

        //
        // Gets the pointer to T version of the Type  (T*)
        //
        public static Type GetPointerType (Type t)
        {
                string tname = t.FullName + "*";
                
                Type ret = t.Assembly.GetType (tname);
                
                //
                // If the type comes from the assembly we are building
                // We need the Hashtable, because .NET 1.1 will return different instance types
                // every time we call ModuleBuilder.GetType.
                //
                if (ret == null){
                        if (pointers [t] == null)
                                pointers [t] = CodeGen.Module.Builder.GetType (tname);
                        
                        ret = (Type) pointers [t];
                }

                return ret;
        }
        
        //
        // Low-level lookup, cache-less
        //
        static Type LookupTypeReflection (string name)
        {
                Type t;

                foreach (Assembly a in assemblies){
                        t = a.GetType (name);
                        if (t == null)
                                continue;

                        do {
                                TypeAttributes ta = t.Attributes & TypeAttributes.VisibilityMask;
                                if (ta == TypeAttributes.NotPublic ||
                                    ta == TypeAttributes.NestedPrivate ||
                                    ta == TypeAttributes.NestedAssembly ||
                                    ta == TypeAttributes.NestedFamANDAssem){
                                        
                                        //
                                        // In .NET pointers turn out to be private, even if their
                                        // element type is not
                                        //
                                        if (t.IsPointer){
                                                t = t.GetElementType ();
                                                continue;
                                        } else
                                                t = null;
                                } else {
                                        return t;
                                }
                        } while (t != null);
                }

                foreach (Module mb in modules) {
                        t = mb.GetType (name);
                        if (t != null) 
                                return t;
                }
                        
                return null;
        }

        static Hashtable negative_hits = new Hashtable ();
        
        //
        // This function is used when you want to avoid the lookups, and want to go
        // directly to the source.  This will use the cache.
        //
        // Notice that bypassing the cache is bad, because on Microsoft.NET runtime
        // GetType ("DynamicType[]") != GetType ("DynamicType[]"), and there is no
        // way to test things other than doing a fullname compare
        //
        public static Type LookupTypeDirect (string name)
        {
                Type t = (Type) types [name];
                if (t != null)
                        return t;

                t = LookupTypeReflection (name);
                if (t == null)
                        return null;

                types [name] = t;
                return t;
        }

        static readonly char [] dot_array = { '.' };

        /// <summary>
        ///   Returns the Type associated with @name, takes care of the fact that
        ///   reflection expects nested types to be separated from the main type
        ///   with a "+" instead of a "."
        /// </summary>
        public static Type LookupType (string name)
        {
                Type t;

                //
                // First lookup in user defined and cached values
                //

                t = (Type) types [name];
                if (t != null)
                        return t;

                // Two thirds of the failures are caught here.
                if (negative_hits.Contains (name))
                        return null;

                // Sadly, split takes a param array, so this ends up allocating *EVERY TIME*
                string [] elements = name.Split (dot_array);
                int count = elements.Length;

                for (int n = 1; n <= count; n++){
                        string top_level_type = String.Join (".", elements, 0, n);

                        // One third of the failures are caught here.
                        if (negative_hits.Contains (top_level_type))
                                continue;
                        
                        t = (Type) types [top_level_type];
                        if (t == null){
                                t = LookupTypeReflection (top_level_type);
                                if (t == null){
                                        negative_hits [top_level_type] = null;
                                        continue;
                                }
                        }
                        
                        if (count == n){
                                types [name] = t;
                                return t;
                        } 

                        //
                        // We know that System.Object does not have children, and since its the parent of 
                        // all the objects, it always gets probbed for inner classes. 
                        //
                        if (top_level_type == "System.Object")
                                return null;
                        
                        string newt = top_level_type + "+" + String.Join ("+", elements, n, count - n);
                        //Console.WriteLine ("Looking up: " + newt + " " + name);
                        t = LookupTypeReflection (newt);
                        if (t == null)
                                negative_hits [name] = null;
                        else
                                types [name] = t;
                        return t;
                }
                negative_hits [name] = null;
                return null;
        }

        /// <summary>
        ///   Computes the namespaces that we import from the assemblies we reference.
        /// </summary>
        public static void ComputeNamespaces ()
        {
                MethodInfo assembly_get_namespaces = typeof (Assembly).GetMethod ("GetNamespaces", BindingFlags.Instance|BindingFlags.NonPublic);

                //
                // First add the assembly namespaces
                //
                if (assembly_get_namespaces != null){
                        int count = assemblies.Length;

                        for (int i = 0; i < count; i++){
                                Assembly a = assemblies [i];
                                string [] namespaces = (string []) assembly_get_namespaces.Invoke (a, null);
                                foreach (string ns in namespaces){
                                        if (ns == "")
                                                continue;
                                        Namespace.LookupNamespace (ns, true);
                                }
                        }
                } else {
                        foreach (Assembly a in assemblies){
                                foreach (Type t in a.GetTypes ()){
                                        string ns = t.Namespace;

                                        // t.Namespace returns null for <PrivateImplDetails>
                                        if (ns == ""|| ns == null)
                                                continue;
                                        Namespace.LookupNamespace (ns, true);
                                }
                        }
                }
        }

        public static bool NamespaceClash (string name, Location loc)
        {
                if (Namespace.LookupNamespace (name, false) == null)
                        return false;

                Report.Error (519, loc, String.Format ("`{0}' clashes with a predefined namespace", name));
                return true;
        }

        /// <summary>
        ///   Returns the C# name of a type if possible, or the full type name otherwise
        /// </summary>
        static public string CSharpName (Type t)
        {
                return Regex.Replace (t.FullName, 
                        @"^System\." +
                        @"(Int32|UInt32|Int16|UInt16|Int64|UInt64|" +
                        @"Single|Double|Char|Decimal|Byte|SByte|Object|" +
                        @"Boolean|String|Void)" +
                        @"(\W+|\b)", 
                        new MatchEvaluator (CSharpNameMatch));
        }       
        
        static String CSharpNameMatch (Match match) 
        {
                string s = match.Groups [1].Captures [0].Value;
                return s.ToLower ().
                Replace ("int32", "int").
                Replace ("uint32", "uint").
                Replace ("int16", "short").
                Replace ("uint16", "ushort").
                Replace ("int64", "long").
                Replace ("uint64", "ulong").
                Replace ("single", "float").
                Replace ("boolean", "bool")
                + match.Groups [2].Captures [0].Value;
        }

        /// <summary>
        ///  Returns the signature of the method with full namespace classification
        /// </summary>
        static public string GetFullNameSignature (MemberInfo mi)
        {
                string n = mi.Name;
                if (n == ".ctor")
                        n = mi.DeclaringType.Name;
                
                return mi.DeclaringType.FullName.Replace ('+', '.') + '.' + n;
        }

        static public string GetFullName (Type t)
        {
                string name = t.FullName.Replace ('+', '.');

                DeclSpace tc = LookupDeclSpace (t);
                if ((tc != null) && tc.IsGeneric) {
                        TypeParameter[] tparam = tc.TypeParameters;

                        StringBuilder sb = new StringBuilder (name);
                        sb.Append ("<");
                        for (int i = 0; i < tparam.Length; i++) {
                                if (i > 0)
                                        sb.Append (",");
                                sb.Append (tparam [i].Name);
                        }
                        sb.Append (">");
                        return sb.ToString ();
                } else if (t.HasGenericArguments && !t.IsGenericInstance) {
                        Type[] tparam = t.GetGenericArguments ();

                        StringBuilder sb = new StringBuilder (name);
                        sb.Append ("<");
                        for (int i = 0; i < tparam.Length; i++) {
                                if (i > 0)
                                        sb.Append (",");
                                sb.Append (tparam [i].Name);
                        }
                        sb.Append (">");
                        return sb.ToString ();
                }

                return name;
        }

        /// <summary>
        ///   Returns the signature of the property and indexer
        /// </summary>
        static public string CSharpSignature (PropertyBuilder pb, bool is_indexer) 
        {
                if (!is_indexer) {
                        return GetFullNameSignature (pb);
                }

                MethodBase mb = pb.GetSetMethod (true) != null ? pb.GetSetMethod (true) : pb.GetGetMethod (true);
                string signature = GetFullNameSignature (mb);
                string arg = TypeManager.LookupParametersByBuilder (mb).ParameterDesc (0);
                return String.Format ("{0}.this[{1}]", signature.Substring (0, signature.LastIndexOf ('.')), arg);
        }

        /// <summary>
        ///   Returns the signature of the method
        /// </summary>
        static public string CSharpSignature (MethodBase mb)
        {
                string sig = "(";

                //
                // FIXME: We should really have a single function to do
                // everything instead of the following 5 line pattern
                //
                ParameterData iparams = LookupParametersByBuilder (mb);

                if (iparams == null)
                        iparams = new ReflectionParameters (mb);
                
                for (int i = 0; i < iparams.Count; i++) {
                        if (i > 0) {
                                sig += ", ";
                        }
                        sig += iparams.ParameterDesc(i);
                }
                sig += ")";

                return GetFullNameSignature (mb) + sig;
        }

        /// <summary>
        ///   Looks up a type, and aborts if it is not found.  This is used
        ///   by types required by the compiler
        /// </summary>
        static Type CoreLookupType (string name)
        {
                Type t = LookupTypeDirect (name);

                if (t == null){
                        Report.Error (518, "The predefined type `" + name + "' is not defined or imported");
                        Environment.Exit (0);
                }

                return t;
        }

        /// <summary>
        ///   Returns the MethodInfo for a method named `name' defined
        ///   in type `t' which takes arguments of types `args'
        /// </summary>
        static MethodInfo GetMethod (Type t, string name, Type [] args, bool is_private, bool report_errors)
        {
                MemberList list;
                Signature sig;
                BindingFlags flags = instance_and_static | BindingFlags.Public;

                sig.name = name;
                sig.args = args;
                
                if (is_private)
                        flags |= BindingFlags.NonPublic;

                list = FindMembers (t, MemberTypes.Method, flags, signature_filter, sig);
                if (list.Count == 0) {
                        if (report_errors)
                                Report.Error (-19, "Can not find the core function `" + name + "'");
                        return null;
                }

                MethodInfo mi = list [0] as MethodInfo;
                if (mi == null) {
                        if (report_errors)
                                Report.Error (-19, "Can not find the core function `" + name + "'");
                        return null;
                }

                return mi;
        }

        static MethodInfo GetMethod (Type t, string name, Type [] args, bool report_errors)
        {
                return GetMethod (t, name, args, false, report_errors);
        }

        static MethodInfo GetMethod (Type t, string name, Type [] args)
        {
                return GetMethod (t, name, args, true);
        }


        /// <summary>
        ///    Returns the ConstructorInfo for "args"
        /// </summary>
        static ConstructorInfo GetConstructor (Type t, Type [] args)
        {
                MemberList list;
                Signature sig;

                sig.name = ".ctor";
                sig.args = args;
                
                list = FindMembers (t, MemberTypes.Constructor,
                                    instance_and_static | BindingFlags.Public | BindingFlags.DeclaredOnly,
                                    signature_filter, sig);
                if (list.Count == 0){
                        Report.Error (-19, "Can not find the core constructor for type `" + t.Name + "'");
                        return null;
                }

                ConstructorInfo ci = list [0] as ConstructorInfo;
                if (ci == null){
                        Report.Error (-19, "Can not find the core constructor for type `" + t.Name + "'");
                        return null;
                }

                return ci;
        }

        public static void InitEnumUnderlyingTypes ()
        {

                int32_type    = CoreLookupType ("System.Int32");
                int64_type    = CoreLookupType ("System.Int64");
                uint32_type   = CoreLookupType ("System.UInt32"); 
                uint64_type   = CoreLookupType ("System.UInt64"); 
                byte_type     = CoreLookupType ("System.Byte");
                sbyte_type    = CoreLookupType ("System.SByte");
                short_type    = CoreLookupType ("System.Int16");
                ushort_type   = CoreLookupType ("System.UInt16");
        }
        
        /// <remarks>
        ///   The types have to be initialized after the initial
        ///   population of the type has happened (for example, to
        ///   bootstrap the corlib.dll
        /// </remarks>
        public static void InitCoreTypes ()
        {
                object_type   = CoreLookupType ("System.Object");
                value_type    = CoreLookupType ("System.ValueType");

                InitEnumUnderlyingTypes ();

                char_type     = CoreLookupType ("System.Char");
                string_type   = CoreLookupType ("System.String");
                float_type    = CoreLookupType ("System.Single");
                double_type   = CoreLookupType ("System.Double");
                char_ptr_type = CoreLookupType ("System.Char*");
                decimal_type  = CoreLookupType ("System.Decimal");
                bool_type     = CoreLookupType ("System.Boolean");
                enum_type     = CoreLookupType ("System.Enum");

                multicast_delegate_type = CoreLookupType ("System.MulticastDelegate");
                delegate_type           = CoreLookupType ("System.Delegate");

                array_type    = CoreLookupType ("System.Array");
                void_type     = CoreLookupType ("System.Void");
                type_type     = CoreLookupType ("System.Type");

                runtime_field_handle_type = CoreLookupType ("System.RuntimeFieldHandle");
                runtime_helpers_type = CoreLookupType ("System.Runtime.CompilerServices.RuntimeHelpers");
                default_member_type  = CoreLookupType ("System.Reflection.DefaultMemberAttribute");
                runtime_handle_type  = CoreLookupType ("System.RuntimeTypeHandle");
                asynccallback_type   = CoreLookupType ("System.AsyncCallback");
                iasyncresult_type    = CoreLookupType ("System.IAsyncResult");
                ienumerator_type     = CoreLookupType ("System.Collections.IEnumerator");
                ienumerable_type     = CoreLookupType ("System.Collections.IEnumerable");
                idisposable_type     = CoreLookupType ("System.IDisposable");
                icloneable_type      = CoreLookupType ("System.ICloneable");
                monitor_type         = CoreLookupType ("System.Threading.Monitor");
                intptr_type          = CoreLookupType ("System.IntPtr");

                attribute_type       = CoreLookupType ("System.Attribute");
                attribute_usage_type = CoreLookupType ("System.AttributeUsageAttribute");
                dllimport_type       = CoreLookupType ("System.Runtime.InteropServices.DllImportAttribute");
                methodimpl_attr_type = CoreLookupType ("System.Runtime.CompilerServices.MethodImplAttribute");
                marshal_as_attr_type = CoreLookupType ("System.Runtime.InteropServices.MarshalAsAttribute");
                param_array_type     = CoreLookupType ("System.ParamArrayAttribute");
                in_attribute_type    = CoreLookupType ("System.Runtime.InteropServices.InAttribute");

                //
                // Sigh. Remove this before the release.  Wonder what versions of Mono
                // people are running.
                //
                guid_attr_type        = LookupType ("System.Runtime.InteropServices.GuidAttribute");

                unverifiable_code_type= CoreLookupType ("System.Security.UnverifiableCodeAttribute");

                void_ptr_type         = CoreLookupType ("System.Void*");

                indexer_name_type     = CoreLookupType ("System.Runtime.CompilerServices.IndexerNameAttribute");

                exception_type        = CoreLookupType ("System.Exception");
                invalid_operation_exception_type = CoreLookupType ("System.InvalidOperationException");

                //
                // Attribute types
                //
                obsolete_attribute_type = CoreLookupType ("System.ObsoleteAttribute");
                conditional_attribute_type = CoreLookupType ("System.Diagnostics.ConditionalAttribute");

                //
                // When compiling corlib, store the "real" types here.
                //
                if (!RootContext.StdLib) {
                        system_int32_type = typeof (System.Int32);
                        system_array_type = typeof (System.Array);
                        system_type_type = typeof (System.Type);
                        system_assemblybuilder_type = typeof (System.Reflection.Emit.AssemblyBuilder);

                        Type [] void_arg = {  };
                        system_int_array_get_length = GetMethod (
                                system_array_type, "get_Length", void_arg);
                        system_int_array_get_rank = GetMethod (
                                system_array_type, "get_Rank", void_arg);
                        system_object_array_clone = GetMethod (
                                system_array_type, "Clone", void_arg);

                        Type [] system_int_arg = { system_int32_type };
                        system_int_array_get_length_int = GetMethod (
                                system_array_type, "GetLength", system_int_arg);
                        system_int_array_get_upper_bound_int = GetMethod (
                                system_array_type, "GetUpperBound", system_int_arg);
                        system_int_array_get_lower_bound_int = GetMethod (
                                system_array_type, "GetLowerBound", system_int_arg);

                        Type [] system_array_int_arg = { system_array_type, system_int32_type };
                        system_void_array_copyto_array_int = GetMethod (
                                system_array_type, "CopyTo", system_array_int_arg);

                        Type [] system_3_type_arg = {
                                system_type_type, system_type_type, system_type_type };
                        Type [] system_4_type_arg = {
                                system_type_type, system_type_type, system_type_type, system_type_type };

                        MethodInfo set_corlib_type_builders = GetMethod (
                                system_assemblybuilder_type, "SetCorlibTypeBuilders",
                                system_4_type_arg, true, false);

                        if (set_corlib_type_builders != null) {
                                object[] args = new object [4];
                                args [0] = object_type;
                                args [1] = value_type;
                                args [2] = enum_type;
                                args [3] = void_type;
                                
                                set_corlib_type_builders.Invoke (CodeGen.Assembly.Builder, args);
                        } else {
                                // Compatibility for an older version of the class libs.
                                set_corlib_type_builders = GetMethod (
                                        system_assemblybuilder_type, "SetCorlibTypeBuilders",
                                        system_3_type_arg, true, true);

                                if (set_corlib_type_builders == null) {
                                        Report.Error (-26, "Corlib compilation is not supported in Microsoft.NET due to bugs in it");
                                        return;
                                }

                                object[] args = new object [3];
                                args [0] = object_type;
                                args [1] = value_type;
                                args [2] = enum_type;
                                
                                set_corlib_type_builders.Invoke (CodeGen.Assembly.Builder, args);
                        }
                }

                system_object_expr.Type = object_type;
                system_string_expr.Type = string_type;
                system_boolean_expr.Type = bool_type;
                system_decimal_expr.Type = decimal_type;
                system_single_expr.Type = float_type;
                system_double_expr.Type = double_type;
                system_sbyte_expr.Type = sbyte_type;
                system_byte_expr.Type = byte_type;
                system_int16_expr.Type = short_type;
                system_uint16_expr.Type = ushort_type;
                system_int32_expr.Type = int32_type;
                system_uint32_expr.Type = uint32_type;
                system_int64_expr.Type = int64_type;
                system_uint64_expr.Type = uint64_type;
                system_char_expr.Type = char_type;
                system_void_expr.Type = void_type;
                system_asynccallback_expr.Type = asynccallback_type;
                system_iasyncresult_expr.Type = iasyncresult_type;
                system_valuetype_expr.Type = value_type;
        }

        //
        // The helper methods that are used by the compiler
        //
        public static void InitCodeHelpers ()
        {
                //
                // Now load the default methods that we use.
                //
                Type [] string_string = { string_type, string_type };
                string_concat_string_string = GetMethod (
                        string_type, "Concat", string_string);
                Type [] string_string_string = { string_type, string_type, string_type };
                string_concat_string_string_string = GetMethod (
                        string_type, "Concat", string_string_string);
                Type [] string_string_string_string = { string_type, string_type, string_type, string_type };
                string_concat_string_string_string_string = GetMethod (
                        string_type, "Concat", string_string_string_string);

                Type [] object_object = { object_type, object_type };
                string_concat_object_object = GetMethod (
                        string_type, "Concat", object_object);

                Type [] string_ = { string_type };
                string_isinterneted_string = GetMethod (
                        string_type, "IsInterned", string_);
                
                Type [] runtime_type_handle = { runtime_handle_type };
                system_type_get_type_from_handle = GetMethod (
                        type_type, "GetTypeFromHandle", runtime_type_handle);

                Type [] delegate_delegate = { delegate_type, delegate_type };
                delegate_combine_delegate_delegate = GetMethod (
                                delegate_type, "Combine", delegate_delegate);

                delegate_remove_delegate_delegate = GetMethod (
                                delegate_type, "Remove", delegate_delegate);

                //
                // Void arguments
                //
                Type [] void_arg = {  };
                object_getcurrent_void = GetMethod (
                        ienumerator_type, "get_Current", void_arg);
                bool_movenext_void = GetMethod (
                        ienumerator_type, "MoveNext", void_arg);
                void_reset_void = GetMethod (
                        ienumerator_type, "Reset", void_arg);
                void_dispose_void = GetMethod (
                        idisposable_type, "Dispose", void_arg);
                int_get_offset_to_string_data = GetMethod (
                        runtime_helpers_type, "get_OffsetToStringData", void_arg);
                int_array_get_length = GetMethod (
                        array_type, "get_Length", void_arg);
                int_array_get_rank = GetMethod (
                        array_type, "get_Rank", void_arg);
                ienumerable_getenumerator_void = GetMethod (
                        ienumerable_type, "GetEnumerator", void_arg);
                
                //
                // Int32 arguments
                //
                Type [] int_arg = { int32_type };
                int_array_get_length_int = GetMethod (
                        array_type, "GetLength", int_arg);
                int_array_get_upper_bound_int = GetMethod (
                        array_type, "GetUpperBound", int_arg);
                int_array_get_lower_bound_int = GetMethod (
                        array_type, "GetLowerBound", int_arg);

                //
                // System.Array methods
                //
                object_array_clone = GetMethod (
                        array_type, "Clone", void_arg);
                Type [] array_int_arg = { array_type, int32_type };
                void_array_copyto_array_int = GetMethod (
                        array_type, "CopyTo", array_int_arg);
                
                //
                // object arguments
                //
                Type [] object_arg = { object_type };
                void_monitor_enter_object = GetMethod (
                        monitor_type, "Enter", object_arg);
                void_monitor_exit_object = GetMethod (
                        monitor_type, "Exit", object_arg);

                Type [] array_field_handle_arg = { array_type, runtime_field_handle_type };
                
                void_initializearray_array_fieldhandle = GetMethod (
                        runtime_helpers_type, "InitializeArray", array_field_handle_arg);

                //
                // Array functions
                //
                int_getlength_int = GetMethod (
                        array_type, "GetLength", int_arg);

                //
                // Decimal constructors
                //
                Type [] dec_arg = { int32_type, int32_type, int32_type, bool_type, byte_type };
                void_decimal_ctor_five_args = GetConstructor (
                        decimal_type, dec_arg);
                
                //
                // Attributes
                //
                cons_param_array_attribute = GetConstructor (
                        param_array_type, void_arg);

                unverifiable_code_ctor = GetConstructor (
                        unverifiable_code_type, void_arg);

                //
                // InvalidOperationException
                //
                invalid_operation_ctor = GetConstructor (
                        invalid_operation_exception_type, void_arg);


                // Object
                object_ctor = GetConstructor (object_type, void_arg);

        }

        const BindingFlags instance_and_static = BindingFlags.Static | BindingFlags.Instance;

        /// <remarks>
        ///   This is the "old", non-cache based FindMembers() function.  We cannot use
        ///   the cache here because there is no member name argument.
        /// </remarks>
        public static MemberList FindMembers (Type t, MemberTypes mt, BindingFlags bf,
                                              MemberFilter filter, object criteria)
        {
                DeclSpace decl = (DeclSpace) builder_to_declspace [t];

                //
                // `builder_to_declspace' contains all dynamic types.
                //
                if (decl != null) {
                        MemberList list;
                        Timer.StartTimer (TimerType.FindMembers);
                        list = decl.FindMembers (mt, bf, filter, criteria);
                        Timer.StopTimer (TimerType.FindMembers);
                        return list;
                }

                //
                // We have to take care of arrays specially, because GetType on
                // a TypeBuilder array will return a Type, not a TypeBuilder,
                // and we can not call FindMembers on this type.
                //
                if (t.IsSubclassOf (TypeManager.array_type))
                        return new MemberList (TypeManager.array_type.FindMembers (mt, bf, filter, criteria));

                //
                // Since FindMembers will not lookup both static and instance
                // members, we emulate this behaviour here.
                //
                if ((bf & instance_and_static) == instance_and_static){
                        MemberInfo [] i_members = t.FindMembers (
                                mt, bf & ~BindingFlags.Static, filter, criteria);

                        int i_len = i_members.Length;
                        if (i_len == 1){
                                MemberInfo one = i_members [0];

                                //
                                // If any of these are present, we are done!
                                //
                                if ((one is Type) || (one is EventInfo) || (one is FieldInfo))
                                        return new MemberList (i_members);
                        }
                                
                        MemberInfo [] s_members = t.FindMembers (
                                mt, bf & ~BindingFlags.Instance, filter, criteria);

                        int s_len = s_members.Length;
                        if (i_len > 0 || s_len > 0)
                                return new MemberList (i_members, s_members);
                        else {
                                if (i_len > 0)
                                        return new MemberList (i_members);
                                else
                                        return new MemberList (s_members);
                        }
                }

                return new MemberList (t.FindMembers (mt, bf, filter, criteria));
        }


        /// <summary>
        ///   This method is only called from within MemberLookup.  It tries to use the member
        ///   cache if possible and falls back to the normal FindMembers if not.  The `used_cache'
        ///   flag tells the caller whether we used the cache or not.  If we used the cache, then
        ///   our return value will already contain all inherited members and the caller don't need
        ///   to check base classes and interfaces anymore.
        /// </summary>
        private static MemberList MemberLookup_FindMembers (Type t, MemberTypes mt, BindingFlags bf,
                                                            string name, int num_type_arguments,
                                                            out bool used_cache)
        {
                //
                // We have to take care of arrays specially, because GetType on
                // a TypeBuilder array will return a Type, not a TypeBuilder,
                // and we can not call FindMembers on this type.
                //
                if (t == TypeManager.array_type || t.IsSubclassOf (TypeManager.array_type)) {
                        used_cache = true;
                        return TypeHandle.ArrayType.MemberCache.FindMembers (
                                mt, bf, name, FilterWithClosure_delegate, null);
                }

                //
                // If this is a dynamic type, it's always in the `builder_to_declspace' hash table
                // and we can ask the DeclSpace for the MemberCache.
                //
                if (t is TypeBuilder) {
                        DeclSpace decl = (DeclSpace) builder_to_declspace [t];
                        MemberCache cache = decl.MemberCache;

                        //
                        // If this DeclSpace has a MemberCache, use it.
                        //

                        if (cache != null) {
                                used_cache = true;
                                return cache.FindMembers (
                                        mt, bf, name, FilterWithClosure_delegate, null);
                        }

                        // If there is no MemberCache, we need to use the "normal" FindMembers.

                        MemberList list;
                        Timer.StartTimer (TimerType.FindMembers);
                        list = decl.FindMembers (mt, bf | BindingFlags.DeclaredOnly,
                                                 FilterWithClosure_delegate, name);
                        Timer.StopTimer (TimerType.FindMembers);
                        used_cache = false;
                        return list;
                }

                //
                // This call will always succeed.  There is exactly one TypeHandle instance per
                // type, TypeHandle.GetTypeHandle() will either return it or create a new one
                // if it didn't already exist.
                //
                TypeHandle handle = TypeHandle.GetTypeHandle (t);

                used_cache = true;
                return handle.MemberCache.FindMembers (mt, bf, name, FilterWithClosure_delegate, null);
        }

        public static bool IsBuiltinType (Type t)
        {
                if (t == object_type || t == string_type || t == int32_type || t == uint32_type ||
                    t == int64_type || t == uint64_type || t == float_type || t == double_type ||
                    t == char_type || t == short_type || t == decimal_type || t == bool_type ||
                    t == sbyte_type || t == byte_type || t == ushort_type || t == void_type)
                        return true;
                else
                        return false;
        }

        //
        // This is like IsBuiltinType, but lacks decimal_type, we should also clean up
        // the pieces in the code where we use IsBuiltinType and special case decimal_type.
        // 
        public static bool IsCLRType (Type t)
        {
                if (t == object_type || t == int32_type || t == uint32_type ||
                    t == int64_type || t == uint64_type || t == float_type || t == double_type ||
                    t == char_type || t == short_type || t == bool_type ||
                    t == sbyte_type || t == byte_type || t == ushort_type)
                        return true;
                else
                        return false;
        }

        public static bool IsDelegateType (Type t)
        {
                if (t.IsGenericInstance)
                        t = t.GetGenericTypeDefinition ();

                if (t.IsSubclassOf (TypeManager.delegate_type))
                        return true;
                else
                        return false;
        }
        
        public static bool IsEnumType (Type t)
        {
                if (t == TypeManager.enum_type || t.IsSubclassOf (TypeManager.enum_type))
                        return true;
                else
                        return false;
        }
        public static bool IsBuiltinOrEnum (Type t)
        {
                if (IsBuiltinType (t))
                        return true;
                
                if (IsEnumType (t))
                        return true;

                return false;
        }

        //
        // Only a quick hack to get things moving, while real runtime support appears
        //
        public static bool IsGeneric (Type t)
        {
                DeclSpace ds = (DeclSpace) builder_to_declspace [t];

                return ds.IsGeneric;
        }

        public static int GetNumberOfTypeArguments (Type t)
        {
                DeclSpace tc = LookupDeclSpace (t);
                if (tc != null)
                        return tc.IsGeneric ? tc.CountTypeParameters : 0;
                else
                        return t.HasGenericArguments ? t.GetGenericArguments ().Length : 0;
        }

        public static Type[] GetTypeArguments (Type t)
        {
                DeclSpace tc = LookupDeclSpace (t);
                if (tc != null) {
                        if (!tc.IsGeneric)
                                throw new InvalidOperationException ();

                        TypeParameter[] tparam = tc.TypeParameters;
                        Type[] ret = new Type [tparam.Length];
                        for (int i = 0; i < tparam.Length; i++) {
                                ret [i] = tparam [i].Type;
                                if (ret [i] == null)
                                        throw new InternalErrorException ();
                        }

                        return ret;
                } else
                        return t.GetGenericArguments ();
        }

        public static bool CheckGeneric (Type t, int num_type_arguments)
        {
                if (num_type_arguments < 0)
                        return true;

                DeclSpace tc = LookupDeclSpace (t);

                if (tc != null) {
                        if (!tc.IsGeneric)
                                return num_type_arguments == 0;

                        if (num_type_arguments == 0)
                                return false;

                        if (num_type_arguments != tc.CountTypeParameters)
                                return false;
                } else {
                        if (!t.HasGenericArguments)
                                return num_type_arguments == 0;

                        if (num_type_arguments == 0)
                                return false;

                        if (num_type_arguments != t.GetGenericArguments ().Length)
                                return false;
                }

                return true;
        }
        
        //
        // Whether a type is unmanaged.  This is used by the unsafe code (25.2)
        //
        public static bool IsUnmanagedType (Type t)
        {
                if (IsBuiltinType (t) && t != TypeManager.string_type)
                        return true;

                if (IsEnumType (t))
                        return true;

                if (t.IsPointer)
                        return true;

                if (IsValueType (t)){
                        if (t is TypeBuilder){
                                TypeContainer tc = LookupTypeContainer (t);

                                foreach (Field f in tc.Fields){
                                        if (f.FieldBuilder.IsStatic)
                                                continue;
                                        if (!IsUnmanagedType (f.FieldBuilder.FieldType))
                                                return false;
                                }
                        } else {
                                FieldInfo [] fields = t.GetFields ();

                                foreach (FieldInfo f in fields){
                                        if (f.IsStatic)
                                                continue;
                                        if (!IsUnmanagedType (f.FieldType))
                                                return false;
                                }
                        }
                        return true;
                }

                return false;
        }
                
        public static bool IsValueType (Type t)
        {
                return t.IsGenericParameter || t.IsValueType;
        }
        
        public static bool IsInterfaceType (Type t)
        {
                Interface iface = builder_to_declspace [t] as Interface;

                if (iface != null)
                        return true;
                else
                        return false;
        }

        public static bool IsEqualGenericType (Type a, Type b)
        {
                if ((a is TypeBuilder) && a.IsGenericTypeDefinition && b.IsGenericInstance) {
                        //
                        // `a' is a generic type definition's TypeBuilder and `b' is a
                        // generic instance of the same type.
                        //
                        // Example:
                        //
                        // class Stack<T>
                        // {
                        //     void Test (Stack<T> stack) { }
                        // }
                        //
                        // The first argument of `Test' will be the generic instance
                        // "Stack<!0>" - which is the same type than the "Stack" TypeBuilder.
                        //
                        if (a != b.GetGenericTypeDefinition ())
                                return false;

                        Type[] aparams = a.GetGenericArguments ();
                        Type[] bparams = b.GetGenericArguments ();

                        if (aparams.Length != bparams.Length)
                                return false;

                        for (int i = 0; i < aparams.Length; i++)
                                if (!aparams [i].Equals (bparams [i]))
                                        return false;

                        return true;
                }

                return false;
        }

        public static bool IsEqual (Type a, Type b)
        {
                if (a.Equals (b))
                        return true;
                else
                        return IsEqualGenericType (a, b);
        }

        public static bool MayBecomeEqualGenericTypes (Type a, Type b)
        {
                if (a.IsGenericParameter) {
                        //
                        // If a is an array of a's type, they may never
                        // become equal.
                        //
                        while (b.IsArray) {
                                b = b.GetElementType ();
                                if (a.Equals (b))
                                        return false;
                        }

                        //
                        // If b is a generic parameter or an actual type,
                        // they may become equal:
                        //
                        //    class X<T,U> : I<T>, I<U>
                        //    class X<T> : I<T>, I<float>
                        // 
                        if (b.IsGenericParameter || !b.IsGenericInstance)
                                return true;

                        //
                        // We're now comparing a type parameter with a
                        // generic instance.  They may become equal unless
                        // the type parameter appears anywhere in the
                        // generic instance:
                        //
                        //    class X<T,U> : I<T>, I<X<U>>
                        //        -> error because you could instanciate it as
                        //           X<X<int>,int>
                        //
                        //    class X<T> : I<T>, I<X<T>> -> ok
                        //

                        Type[] bargs = GetTypeArguments (b);
                        for (int i = 0; i < bargs.Length; i++) {
                                if (a.Equals (bargs [i]))
                                        return false;
                        }

                        return true;
                }

                if (b.IsGenericParameter)
                        return MayBecomeEqualGenericTypes (b, a);

                //
                // At this point, neither a nor b are a type parameter.
                //
                // If one of them is a generic instance, let
                // MayBecomeEqualGenericInstances() compare them (if the
                // other one is not a generic instance, they can never
                // become equal).
                //

                if (a.IsGenericInstance || b.IsGenericInstance)
                        return MayBecomeEqualGenericInstances (a, b);

                //
                // If both of them are arrays.
                //

                if (a.IsArray && b.IsArray) {
                        if (a.GetArrayRank () != b.GetArrayRank ())
                                return false;
                        
                        a = a.GetElementType ();
                        b = b.GetElementType ();

                        return MayBecomeEqualGenericTypes (a, b);
                }

                //
                // Ok, two ordinary types.
                //

                return a.Equals (b);
        }

        //
        // Checks whether two generic instances may become equal for some
        // particular instantiation (26.3.1).
        //
        public static bool MayBecomeEqualGenericInstances (Type a, Type b)
        {
                if (!a.IsGenericInstance || !b.IsGenericInstance)
                        return false;
                if (a.GetGenericTypeDefinition () != b.GetGenericTypeDefinition ())
                        return false;

                Type[] aargs = GetTypeArguments (a);
                Type[] bargs = GetTypeArguments (b);

                if (aargs.Length != bargs.Length)
                        return false;

                for (int i = 0; i < aargs.Length; i++) {
                        if (MayBecomeEqualGenericTypes (aargs [i], bargs [i]))
                                return true;
                }

                return false;
        }

        //
        // Checks whether `type' is a subclass or nested child of `parent'.
        //
        public static bool IsSubclassOrNestedChildOf (Type type, Type parent)
        {
                do {
                        if ((type == parent) || type.IsSubclassOf (parent) ||
                            IsEqualGenericType (type, parent))
                                return true;

                        // Handle nested types.
                        type = type.DeclaringType;
                } while (type != null);

                return false;
        }

        //
        // Checks whether `type' is a nested child of `parent'.
        //
        public static bool IsNestedChildOf (Type type, Type parent)
        {
                if (type == parent)
                        return false;

                type = type.DeclaringType;
                while (type != null) {
                        if (type == parent)
                                return true;

                        type = type.DeclaringType;
                }

                return false;
        }

        //
        // Do the right thing when returning the element type of an
        // array type based on whether we are compiling corlib or not
        //
        public static Type GetElementType (Type t)
        {
                if (RootContext.StdLib)
                        return t.GetElementType ();
                else
                        return TypeToCoreType (t.GetElementType ());
        }

        /// <summary>
        ///   Returns the User Defined Types
        /// </summary>
        public static ArrayList UserTypes {
                get {
                        return user_types;
                }
        }

        public static Hashtable TypeContainers {
                get {
                        return typecontainers;
                }
        }

        static Hashtable attr_to_allowmult;

        public static void RegisterAttributeAllowMultiple (Type attr_type, bool allow)
        {
                if (attr_to_allowmult == null)
                        attr_to_allowmult = new PtrHashtable ();

                if (attr_to_allowmult.Contains (attr_type))
                        return;

                attr_to_allowmult.Add (attr_type, allow);
                               
        }

        public static bool AreMultipleAllowed (Type attr_type)
        {
                if (!(attr_type is TypeBuilder)) {
                        System.Attribute [] attrs = System.Attribute.GetCustomAttributes (attr_type);

                        foreach (System.Attribute tmp in attrs)
                                if (tmp is AttributeUsageAttribute) {
                                        return ((AttributeUsageAttribute) tmp).AllowMultiple;
                                }

                        return false;
                }
                
                if (attr_to_allowmult == null)
                        return false;

                return (bool) attr_to_allowmult [attr_type];
        }

        static Hashtable builder_to_constant;

        public static void RegisterConstant (FieldBuilder fb, Const c)
        {
                if (builder_to_constant == null)
                        builder_to_constant = new PtrHashtable ();

                if (builder_to_constant.Contains (fb))
                        return;

                builder_to_constant.Add (fb, c);
        }

        public static Const LookupConstant (FieldBuilder fb)
        {
                if (builder_to_constant == null)
                        return null;
                
                return (Const) builder_to_constant [fb];
        }
        
        /// <summary>
        ///   Gigantic work around for missing features in System.Reflection.Emit follows.
        /// </summary>
        ///
        /// <remarks>
        ///   Since System.Reflection.Emit can not return MethodBase.GetParameters
        ///   for anything which is dynamic, and we need this in a number of places,
        ///   we register this information here, and use it afterwards.
        /// </remarks>
        static public bool RegisterMethod (MethodBase mb, InternalParameters ip, Type [] args)
        {
                if (args == null)
                        args = NoTypes;
                                
                method_arguments.Add (mb, args);
                method_internal_params.Add (mb, ip);
                
                return true;
        }
        
        static public InternalParameters LookupParametersByBuilder (MethodBase mb)
        {
                if (! (mb is ConstructorBuilder || mb is MethodBuilder))
                        return null;
                
                if (method_internal_params.Contains (mb))
                        return (InternalParameters) method_internal_params [mb];
                else
                        throw new Exception ("Argument for Method not registered" + mb);
        }

        /// <summary>
        ///    Returns the argument types for a method based on its methodbase
        ///
        ///    For dynamic methods, we use the compiler provided types, for
        ///    methods from existing assemblies we load them from GetParameters,
        ///    and insert them into the cache
        /// </summary>
        static public Type [] GetArgumentTypes (MethodBase mb)
        {
                if (method_arguments.Contains (mb))
                        return (Type []) method_arguments [mb];
                else {
                        ParameterInfo [] pi = mb.GetParameters ();
                        int c = pi.Length;
                        Type [] types = new Type [c];
                        
                        for (int i = 0; i < c; i++)
                                types [i] = pi [i].ParameterType;

                        method_arguments.Add (mb, types);
                        return types;
                }
        }

        /// <summary>
        ///    Returns the argument types for an indexer based on its PropertyInfo
        ///
        ///    For dynamic indexers, we use the compiler provided types, for
        ///    indexers from existing assemblies we load them from GetParameters,
        ///    and insert them into the cache
        /// </summary>
        static public Type [] GetArgumentTypes (PropertyInfo indexer)
        {
                if (indexer_arguments.Contains (indexer))
                        return (Type []) indexer_arguments [indexer];
                else if (indexer is PropertyBuilder)
                        // If we're a PropertyBuilder and not in the
                        // `indexer_arguments' hash, then we're a property and
                        // not an indexer.
                        return NoTypes;
                else {
                        ParameterInfo [] pi = indexer.GetIndexParameters ();
                        // Property, not an indexer.
                        if (pi == null)
                                return NoTypes;
                        int c = pi.Length;
                        Type [] types = new Type [c];
                        
                        for (int i = 0; i < c; i++)
                                types [i] = pi [i].ParameterType;

                        indexer_arguments.Add (indexer, types);
                        return types;
                }
        }
        
        // <remarks>
        //  This is a workaround the fact that GetValue is not
        //  supported for dynamic types
        // </remarks>
        static Hashtable fields = new Hashtable ();
        static public bool RegisterFieldValue (FieldBuilder fb, object value)
        {
                if (fields.Contains (fb))
                        return false;

                fields.Add (fb, value);

                return true;
        }

        static public object GetValue (FieldBuilder fb)
        {
                return fields [fb];
        }

        static Hashtable fieldbuilders_to_fields = new Hashtable ();
        static public bool RegisterFieldBase (FieldBuilder fb, FieldBase f)
        {
                if (fieldbuilders_to_fields.Contains (fb))
                        return false;

                fieldbuilders_to_fields.Add (fb, f);
                return true;
        }

        //
        // The return value can be null;  This will be the case for
        // auxiliary FieldBuilders created by the compiler that have no
        // real field being declared on the source code
        //
        static public FieldBase GetField (FieldInfo fb)
        {
                return (FieldBase) fieldbuilders_to_fields [fb];
        }
        
        static Hashtable events;

        static public bool RegisterEvent (MyEventBuilder eb, MethodBase add, MethodBase remove)
        {
                if (events == null)
                        events = new Hashtable ();

                if (events.Contains (eb))
                        return false;

                events.Add (eb, new Pair (add, remove));

                return true;
        }

        static public MethodInfo GetAddMethod (EventInfo ei)
        {
                if (ei is MyEventBuilder) {
                        Pair pair = (Pair) events [ei];

                        return (MethodInfo) pair.First;
                } else
                        return ei.GetAddMethod ();
        }

        static public MethodInfo GetRemoveMethod (EventInfo ei)
        {
                if (ei is MyEventBuilder) {
                        Pair pair = (Pair) events [ei];

                        return (MethodInfo) pair.Second;
                } else
                        return ei.GetRemoveMethod ();
        }

        static Hashtable priv_fields_events;

        static public bool RegisterPrivateFieldOfEvent (EventInfo einfo, FieldBuilder builder)
        {
                if (priv_fields_events == null)
                        priv_fields_events = new Hashtable ();

                if (priv_fields_events.Contains (einfo))
                        return false;

                priv_fields_events.Add (einfo, builder);

                return true;
        }

        static public MemberInfo GetPrivateFieldOfEvent (EventInfo ei)
        {
                if (priv_fields_events == null)
                        return null;
                else
                        return (MemberInfo) priv_fields_events [ei];
        }
                
        static Hashtable properties;
        
        static public bool RegisterProperty (PropertyBuilder pb, MethodBase get, MethodBase set)
        {
                if (properties == null)
                        properties = new Hashtable ();

                if (properties.Contains (pb))
                        return false;

                properties.Add (pb, new Pair (get, set));

                return true;
        }

        static public bool RegisterIndexer (PropertyBuilder pb, MethodBase get,
                                            MethodBase set, Type[] args)
        {
                if (!RegisterProperty (pb, get,set))
                        return false;

                indexer_arguments.Add (pb, args);

                return true;
        }

        /// <summary>
        ///   Given an array of interface types, expand and eliminate repeated ocurrences
        ///   of an interface.  
        /// </summary>
        ///
        /// <remarks>
        ///   This expands in context like: IA; IB : IA; IC : IA, IB; the interface "IC" to
        ///   be IA, IB, IC.
        /// </remarks>
        public static TypeExpr[] ExpandInterfaces (TypeExpr [] base_interfaces)
        {
                ArrayList new_ifaces = new ArrayList ();
                
                foreach (TypeExpr iface in base_interfaces){
                        if (!new_ifaces.Contains (iface))
                                new_ifaces.Add (iface);
                        
                        TypeExpr [] implementing = iface.GetInterfaces ();
                        
                        foreach (TypeExpr imp in implementing){
                                if (!new_ifaces.Contains (imp))
                                        new_ifaces.Add (imp);
                        }
                }
                TypeExpr [] ret = new TypeExpr [new_ifaces.Count];
                new_ifaces.CopyTo (ret, 0);
                return ret;
        }
                
        static PtrHashtable iface_cache = new PtrHashtable ();
                
        /// <summary>
        ///   This function returns the interfaces in the type `t'.  Works with
        ///   both types and TypeBuilders.
        /// </summary>
        public static TypeExpr [] GetInterfaces (Type t)
        {
                
                TypeExpr [] cached = iface_cache [t] as TypeExpr [];
                if (cached != null)
                        return cached;
                
                //
                // The reason for catching the Array case is that Reflection.Emit
                // will not return a TypeBuilder for Array types of TypeBuilder types,
                // but will still throw an exception if we try to call GetInterfaces
                // on the type.
                //
                // Since the array interfaces are always constant, we return those for
                // the System.Array
                //
                
                if (t.IsArray)
                        t = TypeManager.array_type;
                
                if (t is TypeBuilder){
                        TypeExpr [] parent_ifaces;
                        
                        if (t.BaseType == null)
                                parent_ifaces = NoTypeExprs;
                        else
                                parent_ifaces = GetInterfaces (t.BaseType);
                        TypeExpr [] type_ifaces = (TypeExpr []) builder_to_ifaces [t];
                        if (type_ifaces == null)
                                type_ifaces = NoTypeExprs;

                        int parent_count = parent_ifaces.Length;
                        TypeExpr [] result = new TypeExpr [parent_count + type_ifaces.Length];
                        parent_ifaces.CopyTo (result, 0);
                        type_ifaces.CopyTo (result, parent_count);

                        iface_cache [t] = result;
                        return result;
                } else {
                        Type [] ifaces = t.GetInterfaces ();
                        if (ifaces.Length == 0)
                                return NoTypeExprs;

                        TypeExpr [] result = new TypeExpr [ifaces.Length];
                        for (int i = 0; i < ifaces.Length; i++)
                                result [i] = new TypeExpression (ifaces [i], Location.Null);
                        
                        iface_cache [t] = result;
                        return result;
                }
        }
        
        //
        // gets the interfaces that are declared explicitly on t
        //
        public static TypeExpr [] GetExplicitInterfaces (TypeBuilder t)
        {
                return (TypeExpr []) builder_to_ifaces [t];
        }
        
        /// <remarks>
        ///  The following is used to check if a given type implements an interface.
        ///  The cache helps us reduce the expense of hitting Type.GetInterfaces everytime.
        /// </remarks>
        public static bool ImplementsInterface (Type t, Type iface)
        {
                TypeExpr [] interfaces;

                //
                // FIXME OPTIMIZATION:
                // as soon as we hit a non-TypeBuiler in the interface
                // chain, we could return, as the `Type.GetInterfaces'
                // will return all the interfaces implement by the type
                // or its parents.
                //
                do {
                        interfaces = GetInterfaces (t);

                        if (interfaces != null){
                                foreach (TypeExpr i in interfaces){
                                        if (i.Type == iface)
                                                return true;
                                }
                        }
                        
                        t = t.BaseType;
                } while (t != null);
                
                return false;
        }

        static NumberFormatInfo nf_provider = CultureInfo.CurrentCulture.NumberFormat;

        // This is a custom version of Convert.ChangeType() which works
        // with the TypeBuilder defined types when compiling corlib.
        public static object ChangeType (object value, Type conversionType, out bool error)
        {
                IConvertible convert_value = value as IConvertible;
                
                if (convert_value == null){
                        error = true;
                        return null;
                }
                
                //
                // We must use Type.Equals() here since `conversionType' is
                // the TypeBuilder created version of a system type and not
                // the system type itself.  You cannot use Type.GetTypeCode()
                // on such a type - it'd always return TypeCode.Object.
                //
                error = false;
                try {
                        if (conversionType.Equals (typeof (Boolean)))
                                return (object)(convert_value.ToBoolean (nf_provider));
                        else if (conversionType.Equals (typeof (Byte)))
                                return (object)(convert_value.ToByte (nf_provider));
                        else if (conversionType.Equals (typeof (Char)))
                                return (object)(convert_value.ToChar (nf_provider));
                        else if (conversionType.Equals (typeof (DateTime)))
                                return (object)(convert_value.ToDateTime (nf_provider));
                        else if (conversionType.Equals (typeof (Decimal)))
                                return (object)(convert_value.ToDecimal (nf_provider));
                        else if (conversionType.Equals (typeof (Double)))
                                return (object)(convert_value.ToDouble (nf_provider));
                        else if (conversionType.Equals (typeof (Int16)))
                                return (object)(convert_value.ToInt16 (nf_provider));
                        else if (conversionType.Equals (typeof (Int32)))
                                return (object)(convert_value.ToInt32 (nf_provider));
                        else if (conversionType.Equals (typeof (Int64)))
                                return (object)(convert_value.ToInt64 (nf_provider));
                        else if (conversionType.Equals (typeof (SByte)))
                                return (object)(convert_value.ToSByte (nf_provider));
                        else if (conversionType.Equals (typeof (Single)))
                                return (object)(convert_value.ToSingle (nf_provider));
                        else if (conversionType.Equals (typeof (String)))
                                return (object)(convert_value.ToString (nf_provider));
                        else if (conversionType.Equals (typeof (UInt16)))
                                return (object)(convert_value.ToUInt16 (nf_provider));
                        else if (conversionType.Equals (typeof (UInt32)))
                                return (object)(convert_value.ToUInt32 (nf_provider));
                        else if (conversionType.Equals (typeof (UInt64)))
                                return (object)(convert_value.ToUInt64 (nf_provider));
                        else if (conversionType.Equals (typeof (Object)))
                                return (object)(value);
                        else 
                                error = true;
                } catch {
                        error = true;
                }
                return null;
        }

        //
        // This is needed, because enumerations from assemblies
        // do not report their underlyingtype, but they report
        // themselves
        //
        public static Type EnumToUnderlying (Type t)
        {
                if (t == TypeManager.enum_type)
                        return t;

                t = t.UnderlyingSystemType;
                if (!TypeManager.IsEnumType (t))
                        return t;
        
                if (t is TypeBuilder) {
                        // slow path needed to compile corlib
                        if (t == TypeManager.bool_type ||
                                        t == TypeManager.byte_type ||
                                        t == TypeManager.sbyte_type ||
                                        t == TypeManager.char_type ||
                                        t == TypeManager.short_type ||
                                        t == TypeManager.ushort_type ||
                                        t == TypeManager.int32_type ||
                                        t == TypeManager.uint32_type ||
                                        t == TypeManager.int64_type ||
                                        t == TypeManager.uint64_type)
                                return t;
                        throw new Exception ("Unhandled typecode in enum " + " from " + t.AssemblyQualifiedName);
                }
                TypeCode tc = Type.GetTypeCode (t);

                switch (tc){
                case TypeCode.Boolean:
                        return TypeManager.bool_type;
                case TypeCode.Byte:
                        return TypeManager.byte_type;
                case TypeCode.SByte:
                        return TypeManager.sbyte_type;
                case TypeCode.Char:
                        return TypeManager.char_type;
                case TypeCode.Int16:
                        return TypeManager.short_type;
                case TypeCode.UInt16:
                        return TypeManager.ushort_type;
                case TypeCode.Int32:
                        return TypeManager.int32_type;
                case TypeCode.UInt32:
                        return TypeManager.uint32_type;
                case TypeCode.Int64:
                        return TypeManager.int64_type;
                case TypeCode.UInt64:
                        return TypeManager.uint64_type;
                }
                throw new Exception ("Unhandled typecode in enum " + tc + " from " + t.AssemblyQualifiedName);
        }

        //
        // When compiling corlib and called with one of the core types, return
        // the corresponding typebuilder for that type.
        //
        public static Type TypeToCoreType (Type t)
        {
                if (RootContext.StdLib || (t is TypeBuilder))
                        return t;

                TypeCode tc = Type.GetTypeCode (t);

                switch (tc){
                case TypeCode.Boolean:
                        return TypeManager.bool_type;
                case TypeCode.Byte:
                        return TypeManager.byte_type;
                case TypeCode.SByte:
                        return TypeManager.sbyte_type;
                case TypeCode.Char:
                        return TypeManager.char_type;
                case TypeCode.Int16:
                        return TypeManager.short_type;
                case TypeCode.UInt16:
                        return TypeManager.ushort_type;
                case TypeCode.Int32:
                        return TypeManager.int32_type;
                case TypeCode.UInt32:
                        return TypeManager.uint32_type;
                case TypeCode.Int64:
                        return TypeManager.int64_type;
                case TypeCode.UInt64:
                        return TypeManager.uint64_type;
                case TypeCode.Single:
                        return TypeManager.float_type;
                case TypeCode.Double:
                        return TypeManager.double_type;
                case TypeCode.String:
                        return TypeManager.string_type;
                default:
                        if (t == typeof (void))
                                return TypeManager.void_type;
                        if (t == typeof (object))
                                return TypeManager.object_type;
                        if (t == typeof (System.Type))
                                return TypeManager.type_type;
                        return t;
                }
        }

        /// <summary>
        ///   Utility function that can be used to probe whether a type
        ///   is managed or not.  
        /// </summary>
        public static bool VerifyUnManaged (Type t, Location loc)
        {
                if (t.IsValueType || t.IsPointer){
                        //
                        // FIXME: this is more complex, we actually need to
                        // make sure that the type does not contain any
                        // classes itself
                        //
                        return true;
                }

                if (!RootContext.StdLib && (t == TypeManager.decimal_type))
                        // We need this explicit check here to make it work when
                        // compiling corlib.
                        return true;

                Report.Error (
                        208, loc,
                        "Cannot take the address or size of a variable of a managed type ('" +
                        CSharpName (t) + "')");
                return false;   
        }
        
        /// <summary>
        ///   Returns the name of the indexer in a given type.
        /// </summary>
        /// <remarks>
        ///   The default is not always `Item'.  The user can change this behaviour by
        ///   using the DefaultMemberAttribute in the class.
        ///
        ///   For example, the String class indexer is named `Chars' not `Item' 
        /// </remarks>
        public static string IndexerPropertyName (Type t)
        {
                if (t.IsGenericInstance)
                        t = t.GetGenericTypeDefinition ();

                if (t is TypeBuilder) {
                        if (t.IsInterface) {
                                Interface i = LookupInterface (t);

                                if ((i == null) || (i.IndexerName == null))
                                        return "Item";

                                return i.IndexerName;
                        } else {
                                TypeContainer tc = LookupTypeContainer (t);

                                if ((tc == null) || (tc.IndexerName == null))
                                        return "Item";

                                return tc.IndexerName;
                        }
                }
                
                System.Attribute attr = System.Attribute.GetCustomAttribute (
                        t, TypeManager.default_member_type);
                if (attr != null){
                        DefaultMemberAttribute dma = (DefaultMemberAttribute) attr;
                        return dma.MemberName;
                }

                return "Item";
        }

        public static void MakePinned (LocalBuilder builder)
        {
                //
                // FIXME: Flag the "LocalBuilder" type as being
                // pinned.  Figure out API.
                //
        }


        //
        // Returns whether the array of memberinfos contains the given method
        //
        public static bool ArrayContainsMethod (MemberInfo [] array, MethodBase new_method)
        {
                Type [] new_args = TypeManager.GetArgumentTypes (new_method);
                
                foreach (MethodBase method in array) {
                        if (method.Name != new_method.Name)
                                continue;

                        if (method is MethodInfo && new_method is MethodInfo)
                                if (((MethodInfo) method).ReturnType != ((MethodInfo) new_method).ReturnType)
                                        continue;

                        
                        Type [] old_args = TypeManager.GetArgumentTypes (method);
                        int old_count = old_args.Length;
                        int i;
                        
                        if (new_args.Length != old_count)
                                continue;
                        
                        for (i = 0; i < old_count; i++){
                                if (old_args [i] != new_args [i])
                                        break;
                        }
                        if (i != old_count)
                                continue;

                        return true;
                }
                
                return false;
        }
        
        //
        // We copy methods from `new_members' into `target_list' if the signature
        // for the method from in the new list does not exist in the target_list
        //
        // The name is assumed to be the same.
        //
        public static ArrayList CopyNewMethods (ArrayList target_list, MemberList new_members)
        {
                if (target_list == null){
                        target_list = new ArrayList ();

                        foreach (MemberInfo mi in new_members){
                                if (mi is MethodBase)
                                        target_list.Add (mi);
                        }
                        return target_list;
                }
                
                MemberInfo [] target_array = new MemberInfo [target_list.Count];
                target_list.CopyTo (target_array, 0);
                
                foreach (MemberInfo mi in new_members){
                        MethodBase new_method = (MethodBase) mi;
                        
                        if (!ArrayContainsMethod (target_array, new_method))
                                target_list.Add (new_method);
                }
                return target_list;
        }

        [Flags]
        public enum MethodFlags {
                IsObsolete = 1,
                IsObsoleteError = 1 << 1,
                ShouldIgnore = 1 << 2
        }

        static public bool IsGenericMethod (MethodInfo mb)
        {
                if (mb.DeclaringType is TypeBuilder) {
                        MethodData method = (MethodData) builder_to_method [mb];
                        if (method == null)
                                return false;

                        return method.GenericMethod != null;
                }

                return mb.IsGenericMethodDefinition;
        }
        
        //
        // Returns the TypeManager.MethodFlags for this method.
        // This emits an error 619 / warning 618 if the method is obsolete.
        // In the former case, TypeManager.MethodFlags.IsObsoleteError is returned.
        //
        static public MethodFlags GetMethodFlags (MethodBase mb, Location loc)
        {
                MethodFlags flags = 0;

                if (mb.DeclaringType is TypeBuilder){
                        MethodData method = (MethodData) builder_to_method [mb];
                        if (method == null) {
                                // FIXME: implement Obsolete attribute on Property,
                                //        Indexer and Event.
                                return 0;
                        }

                        return method.GetMethodFlags (loc);
                }

                if (mb.HasGenericParameters) {
                        MethodBase generic = mb.GetGenericMethodDefinition ();

                        return GetMethodFlags (generic, loc);
                }

                object [] attrs = mb.GetCustomAttributes (true);
                foreach (object ta in attrs){
                        if (!(ta is System.Attribute)){
                                Console.WriteLine ("Unknown type in GetMethodFlags: " + ta);
                                continue;
                        }
                        System.Attribute a = (System.Attribute) ta;
                        if (a.TypeId == TypeManager.obsolete_attribute_type){
                                ObsoleteAttribute oa = (ObsoleteAttribute) a;

                                string method_desc = TypeManager.CSharpSignature (mb);

                                if (oa.IsError) {
                                        Report.Error (619, loc, "Method `" + method_desc +
                                                      "' is obsolete: `" + oa.Message + "'");
                                        return MethodFlags.IsObsoleteError;
                                } else
                                        Report.Warning (618, loc, "Method `" + method_desc +
                                                        "' is obsolete: `" + oa.Message + "'");

                                flags |= MethodFlags.IsObsolete;

                                continue;
                        }
                        
                        //
                        // Skip over conditional code.
                        //
                        if (a.TypeId == TypeManager.conditional_attribute_type){
                                ConditionalAttribute ca = (ConditionalAttribute) a;

                                if (RootContext.AllDefines [ca.ConditionString] == null)
                                        flags |= MethodFlags.ShouldIgnore;
                        }
                }

                return flags;
        }
        
#region MemberLookup implementation
        
        //
        // Whether we allow private members in the result (since FindMembers
        // uses NonPublic for both protected and private), we need to distinguish.
        //
        static bool     closure_private_ok;

        //
        // Who is invoking us and which type is being queried currently.
        //
        static Type     closure_invocation_type;
        static Type     closure_qualifier_type;
        static int      closure_num_type_arguments;

        //
        // The assembly that defines the type is that is calling us
        //
        static Assembly closure_invocation_assembly;

        static internal bool FilterNone (MemberInfo m, object filter_criteria)
        {
                return true;
        }
        
        //
        // This filter filters by name + whether it is ok to include private
        // members in the search
        //
        static internal bool FilterWithClosure (MemberInfo m, object filter_criteria)
        {
                //
                // Hack: we know that the filter criteria will always be in the `closure'
                // fields. 
                //

                if ((filter_criteria != null) && (m.Name != (string) filter_criteria))
                        return false;

                if (m is Type)
                        return TypeManager.CheckGeneric ((Type) m, closure_num_type_arguments);

                if (((closure_qualifier_type == null) || (closure_qualifier_type == closure_invocation_type)) &&
                    (closure_invocation_type != null) && IsEqual (m.DeclaringType, closure_invocation_type))
                        return true;

                //
                // Ugly: we need to find out the type of `m', and depending
                // on this, tell whether we accept or not
                //
                if (m is MethodBase){
                        MethodBase mb = (MethodBase) m;
                        MethodAttributes ma = mb.Attributes & MethodAttributes.MemberAccessMask;

                        if (ma == MethodAttributes.Private)
                                return closure_private_ok ||
                                        IsEqual (closure_invocation_type, m.DeclaringType) ||
                                        IsNestedChildOf (closure_invocation_type, m.DeclaringType);

                        //
                        // FamAndAssem requires that we not only derivate, but we are on the
                        // same assembly.  
                        //
                        if (ma == MethodAttributes.FamANDAssem){
                                if (closure_invocation_assembly != mb.DeclaringType.Assembly)
                                        return false;
                        }

                        // Assembly and FamORAssem succeed if we're in the same assembly.
                        if ((ma == MethodAttributes.Assembly) || (ma == MethodAttributes.FamORAssem)){
                                if (closure_invocation_assembly == mb.DeclaringType.Assembly)
                                        return true;
                        }

                        // We already know that we aren't in the same assembly.
                        if (ma == MethodAttributes.Assembly)
                                return false;

                        // Family and FamANDAssem require that we derive.
                        if ((ma == MethodAttributes.Family) || (ma == MethodAttributes.FamANDAssem)){
                                if (closure_invocation_type == null)
                                        return false;

                                if (!IsSubclassOrNestedChildOf (closure_invocation_type, mb.DeclaringType))
                                        return false;

                                // Although a derived class can access protected members of its base class
                                // it cannot do so through an instance of the base class (CS1540).
                                if (!mb.IsStatic && (closure_invocation_type != closure_qualifier_type) &&
                                    (closure_qualifier_type != null) &&
                                    closure_invocation_type.IsSubclassOf (closure_qualifier_type))
                                        return false;

                                return true;
                        }

                        // Public.
                        return true;
                }

                if (m is FieldInfo){
                        FieldInfo fi = (FieldInfo) m;
                        FieldAttributes fa = fi.Attributes & FieldAttributes.FieldAccessMask;

                        if (fa == FieldAttributes.Private)
                                return closure_private_ok ||
                                        IsEqual (closure_invocation_type, m.DeclaringType) ||
                                        IsNestedChildOf (closure_invocation_type, m.DeclaringType);

                        //
                        // FamAndAssem requires that we not only derivate, but we are on the
                        // same assembly.  
                        //
                        if (fa == FieldAttributes.FamANDAssem){
                                if (closure_invocation_assembly != fi.DeclaringType.Assembly)
                                        return false;
                        }

                        // Assembly and FamORAssem succeed if we're in the same assembly.
                        if ((fa == FieldAttributes.Assembly) || (fa == FieldAttributes.FamORAssem)){
                                if (closure_invocation_assembly == fi.DeclaringType.Assembly)
                                        return true;
                        }

                        // We already know that we aren't in the same assembly.
                        if (fa == FieldAttributes.Assembly)
                                return false;

                        // Family and FamANDAssem require that we derive.
                        if ((fa == FieldAttributes.Family) || (fa == FieldAttributes.FamANDAssem)){
                                if (closure_invocation_type == null)
                                        return false;

                                if (!IsSubclassOrNestedChildOf (closure_invocation_type, fi.DeclaringType))
                                        return false;

                                // Although a derived class can access protected members of its base class
                                // it cannot do so through an instance of the base class (CS1540).
                                if (!fi.IsStatic && (closure_invocation_type != closure_qualifier_type) &&
                                    (closure_qualifier_type != null) &&
                                    closure_invocation_type.IsSubclassOf (closure_qualifier_type))
                                        return false;

                                return true;
                        }

                        // Public.
                        return true;
                }

                //
                // EventInfos and PropertyInfos, return true because they lack permission
                // informaiton, so we need to check later on the methods.
                //
                return true;
        }

        static MemberFilter FilterWithClosure_delegate = new MemberFilter (FilterWithClosure);
        static MemberFilter FilterNone_delegate = new MemberFilter (FilterNone);

        //
        // Looks up a member called `name' in the `queried_type'.  This lookup
        // is done by code that is contained in the definition for `invocation_type'
        // through a qualifier of type `qualifier_type' (or null if there is no qualifier).
        //
        // `invocation_type' is used to check whether we're allowed to access the requested
        // member wrt its protection level.
        //
        // When called from MemberAccess, `qualifier_type' is the type which is used to access
        // the requested member (`class B { A a = new A (); a.foo = 5; }'; here invocation_type
        // is B and qualifier_type is A).  This is used to do the CS1540 check.
        //
        // When resolving a SimpleName, `qualifier_type' is null.
        //
        // The `qualifier_type' is used for the CS1540 check; it's normally either null or
        // the same than `queried_type' - except when we're being called from BaseAccess;
        // in this case, `invocation_type' is the current type and `queried_type' the base
        // type, so this'd normally trigger a CS1540.
        //
        // The binding flags are `bf' and the kind of members being looked up are `mt'
        //
        // The return value always includes private members which code in `invocation_type'
        // is allowed to access (using the specified `qualifier_type' if given); only use
        // BindingFlags.NonPublic to bypass the permission check.
        //
        // Returns an array of a single element for everything but Methods/Constructors
        // that might return multiple matches.
        //
        public static MemberInfo [] MemberLookup (Type invocation_type, Type qualifier_type,
                                                  Type queried_type, int num_type_arguments,
                                                  MemberTypes mt, BindingFlags original_bf,
                                                  string name)
        {
                Timer.StartTimer (TimerType.MemberLookup);

                MemberInfo[] retval = RealMemberLookup (invocation_type, qualifier_type,
                                                        queried_type, num_type_arguments,
                                                        mt, original_bf, name);

                Timer.StopTimer (TimerType.MemberLookup);

                return retval;
        }

        static MemberInfo [] RealMemberLookup (Type invocation_type, Type qualifier_type,
                                               Type queried_type, int num_type_arguments,
                                               MemberTypes mt, BindingFlags original_bf,
                                               string name)
        {
                BindingFlags bf = original_bf;
                
                ArrayList method_list = null;
                Type current_type = queried_type;
                bool searching = (original_bf & BindingFlags.DeclaredOnly) == 0;
                bool skip_iface_check = true, used_cache = false;
                bool always_ok_flag = false;

                closure_invocation_type = invocation_type;
                closure_invocation_assembly = invocation_type != null ? invocation_type.Assembly : null;
                closure_qualifier_type = qualifier_type;

                closure_num_type_arguments = num_type_arguments;

                //
                // If we are a nested class, we always have access to our container
                // type names
                //
                if (invocation_type != null){
                        string invocation_name = invocation_type.FullName;
                        if (invocation_name.IndexOf ('+') != -1){
                                string container = queried_type.FullName + "+";
                                int container_length = container.Length;

                                if (invocation_name.Length > container_length){
                                        string shared = invocation_name.Substring (0, container_length);
                                
                                        if (shared == container)
                                                always_ok_flag = true;
                                }
                        }
                }
                
                do {
                        MemberList list;

                        //
                        // `NonPublic' is lame, because it includes both protected and
                        // private methods, so we need to control this behavior by
                        // explicitly tracking if a private method is ok or not.
                        //
                        // The possible cases are:
                        //    public, private and protected (internal does not come into the
                        //    equation)
                        //
                        if ((invocation_type != null) &&
                            ((invocation_type == current_type) ||
                             IsNestedChildOf (invocation_type, current_type)) ||
                            always_ok_flag)
                                bf = original_bf | BindingFlags.NonPublic;
                        else
                                bf = original_bf;

                        closure_private_ok = (original_bf & BindingFlags.NonPublic) != 0;

                        Timer.StopTimer (TimerType.MemberLookup);

                        list = MemberLookup_FindMembers (current_type, mt, bf, name,
                                                         num_type_arguments, out used_cache);

                        Timer.StartTimer (TimerType.MemberLookup);

                        //
                        // When queried for an interface type, the cache will automatically check all
                        // inherited members, so we don't need to do this here.  However, this only
                        // works if we already used the cache in the first iteration of this loop.
                        //
                        // If we used the cache in any further iteration, we can still terminate the
                        // loop since the cache always looks in all parent classes.
                        //

                        if (used_cache)
                                searching = false;
                        else
                                skip_iface_check = false;

                        if (current_type == TypeManager.object_type)
                                searching = false;
                        else {
                                current_type = current_type.BaseType;
                                
                                //
                                // This happens with interfaces, they have a null
                                // basetype.  Look members up in the Object class.
                                //
                                if (current_type == null)
                                        current_type = TypeManager.object_type;
                        }
                        
                        if (list.Count == 0)
                                continue;

                        //
                        // Events and types are returned by both `static' and `instance'
                        // searches, which means that our above FindMembers will
                        // return two copies of the same.
                        //
                        if (list.Count == 1 && !(list [0] is MethodBase)){
                                return (MemberInfo []) list;
                        }

                        //
                        // Multiple properties: we query those just to find out the indexer
                        // name
                        //
                        if (list [0] is PropertyInfo)
                                return (MemberInfo []) list;

                        //
                        // We found an event: the cache lookup returns both the event and
                        // its private field.
                        //
                        if (list [0] is EventInfo) {
                                if ((list.Count == 2) && (list [1] is FieldInfo))
                                        return new MemberInfo [] { list [0] };

                                // Oooops
                                return null;
                        }

                        //
                        // We found methods, turn the search into "method scan"
                        // mode.
                        //

                        method_list = CopyNewMethods (method_list, list);
                        mt &= (MemberTypes.Method | MemberTypes.Constructor);
                } while (searching);

                if (method_list != null && method_list.Count > 0) {
                        return (MemberInfo []) method_list.ToArray (typeof (MemberInfo));
                }
                //
                // This happens if we already used the cache in the first iteration, in this case
                // the cache already looked in all interfaces.
                //
                if (skip_iface_check)
                        return null;

                //
                // Interfaces do not list members they inherit, so we have to
                // scan those.
                // 
                if (!queried_type.IsInterface)
                        return null;

                if (queried_type.IsArray)
                        queried_type = TypeManager.array_type;
                
                TypeExpr [] ifaces = GetInterfaces (queried_type);
                if (ifaces == null)
                        return null;
                
                foreach (TypeExpr itype in ifaces){
                        MemberInfo [] x;

                        x = MemberLookup (null, null, itype.Type, num_type_arguments,
                                          mt, bf, name);
                        if (x != null)
                                return x;
                }
                                        
                return null;
        }

        //
        // This is used to extract properties and event declarations from a type
        //
        static MemberInfo [] SpecialContainerLookup (Type t, bool is_static)
        {
                BindingFlags bf = BindingFlags.DeclaredOnly | (is_static ? BindingFlags.Static : BindingFlags.Instance);

                bf |= BindingFlags.Public | BindingFlags.NonPublic;
                
                if (t is TypeBuilder) {
                        DeclSpace decl = (DeclSpace) builder_to_declspace [t];

                        return (MemberInfo []) decl.FindMembers (
                                MemberTypes.Property | MemberTypes.Event,
                                bf, FilterNone_delegate, null);
                } else {
                        return t.FindMembers (MemberTypes.Property | MemberTypes.Event,
                                              bf, FilterNone_delegate, null);

                }
        }
        
        public static bool IsSpecialMethod (MethodBase mb)
        {
                Type t = mb.DeclaringType;
                
                MemberInfo [] matches = TypeManager.SpecialContainerLookup (t, mb.IsStatic);
                if (matches == null)
                        return false;
                
                foreach (MemberInfo mi in matches){
                        if (mi is PropertyBuilder){
                                Pair p = (Pair) properties [mi];

                                if (p.First == mb || p.Second == mb)
                                        return true;
                        } else if (mi is PropertyInfo){
                                MethodInfo [] methods = ((PropertyInfo) mi).GetAccessors (true);
                                
                                foreach (MethodInfo m in methods){
                                        if (m == mb)
                                                return true;
                                }
                        } else if (mi is MyEventBuilder){
                                Pair p = (Pair) events [mi];

                                if (p.First == mb || p.Second == mb)
                                        return true;
                        } else if (mi is EventInfo){
                                EventInfo ei = ((EventInfo) mi);
                                
                                if (ei.GetAddMethod (true) == mb)
                                        return true;
                                
                                if (ei.GetRemoveMethod (true) == mb)
                                        return true;
                                
                                if (ei.GetRaiseMethod (true) == mb)
                                        return true;
                        }
                }

                //
                // Now check if it is an operator method
                //
                string s = mb.Name;

                if (s.StartsWith ("op_")){
                        foreach (string name in Unary.oper_names){
                                if (s == name)
                                        return true;
                        }

                        foreach (string name in Binary.oper_names){
                                if (s == name)
                                        return true;
                        }
                }
                
                return false;
        }
                
#endregion
        
}

/// <summary>
///   There is exactly one instance of this class per type.
/// </summary>
public sealed class TypeHandle : IMemberContainer {
        public readonly TypeHandle BaseType;

        readonly int id = ++next_id;
        static int next_id = 0;

        /// <summary>
        ///   Lookup a TypeHandle instance for the given type.  If the type doesn't have
        ///   a TypeHandle yet, a new instance of it is created.  This static method
        ///   ensures that we'll only have one TypeHandle instance per type.
        /// </summary>
        public static TypeHandle GetTypeHandle (Type t)
        {
                TypeHandle handle = (TypeHandle) type_hash [t];
                if (handle != null)
                        return handle;

                handle = new TypeHandle (t);
                type_hash.Add (t, handle);
                return handle;
        }
        
        public static void CleanUp ()
        {
                type_hash = null;
        }

        /// <summary>
        ///   Returns the TypeHandle for TypeManager.object_type.
        /// </summary>
        public static IMemberContainer ObjectType {
                get {
                        if (object_type != null)
                                return object_type;

                        object_type = GetTypeHandle (TypeManager.object_type);

                        return object_type;
                }
        }

        /// <summary>
        ///   Returns the TypeHandle for TypeManager.array_type.
        /// </summary>
        public static IMemberContainer ArrayType {
                get {
                        if (array_type != null)
                                return array_type;

                        array_type = GetTypeHandle (TypeManager.array_type);

                        return array_type;
                }
        }

        private static PtrHashtable type_hash = new PtrHashtable ();

        private static TypeHandle object_type = null;
        private static TypeHandle array_type = null;

        private Type type;
        private bool is_interface;
        private MemberCache member_cache;

        private TypeHandle (Type type)
        {
                this.type = type;
                if (type.BaseType != null)
                        BaseType = GetTypeHandle (type.BaseType);
                this.is_interface = type.IsInterface;
                this.member_cache = new MemberCache (this);
        }

        // IMemberContainer methods

        public string Name {
                get {
                        return type.FullName;
                }
        }

        public Type Type {
                get {
                        return type;
                }
        }

        public IMemberContainer Parent {
                get {
                        return BaseType;
                }
        }

        public bool IsInterface {
                get {
                        return is_interface;
                }
        }

        public MemberList GetMembers (MemberTypes mt, BindingFlags bf)
        {
                MemberInfo [] members;
                if (mt == MemberTypes.Event)
                        members = type.GetEvents (bf | BindingFlags.DeclaredOnly);
                else
                        members = type.FindMembers (mt, bf | BindingFlags.DeclaredOnly,
                                                    null, null);
                Array.Reverse (members);

                return new MemberList (members);
        }

        // IMemberFinder methods

        public MemberList FindMembers (MemberTypes mt, BindingFlags bf, string name,
                                       MemberFilter filter, object criteria)
        {
                return member_cache.FindMembers (mt, bf, name, filter, criteria);
        }

        public MemberCache MemberCache {
                get {
                        return member_cache;
                }
        }

        public override string ToString ()
        {
                if (BaseType != null)
                        return "TypeHandle (" + id + "," + Name + " : " + BaseType + ")";
                else
                        return "TypeHandle (" + id + "," + Name + ")";
        }
}

}