/mcs/mcs/generic.cs

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//
// generic.cs: Generics support
//
// Authors: Martin Baulig (martin@ximian.com)
//          Miguel de Icaza (miguel@ximian.com)
//          Marek Safar (marek.safar@gmail.com)
//
// Dual licensed under the terms of the MIT X11 or GNU GPL
//
// Copyright 2001, 2002, 2003 Ximian, Inc (http://www.ximian.com)
// Copyright 2004-2008 Novell, Inc
// Copyright 2011 Xamarin, Inc (http://www.xamarin.com)
//

using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

#if STATIC
using MetaType = IKVM.Reflection.Type;
using IKVM.Reflection;
using IKVM.Reflection.Emit;
#else
using MetaType = System.Type;
using System.Reflection;
using System.Reflection.Emit;
#endif

namespace Mono.CSharp {
	public enum Variance
	{
		//
		// Don't add or modify internal values, they are used as -/+ calculation signs
		//
		None			= 0,
		Covariant		= 1,
		Contravariant	= -1
	}

	[Flags]
	public enum SpecialConstraint
	{
		None		= 0,
		Constructor = 1 << 2,
		Class		= 1 << 3,
		Struct		= 1 << 4
	}

	public class SpecialContraintExpr : FullNamedExpression
	{
		public SpecialContraintExpr (SpecialConstraint constraint, Location loc)
		{
			this.loc = loc;
			this.Constraint = constraint;
		}

		public SpecialConstraint Constraint { get; private set; }

		protected override Expression DoResolve (ResolveContext rc)
		{
			throw new NotImplementedException ();
		}

		public override FullNamedExpression ResolveAsTypeOrNamespace (IMemberContext ec)
		{
			throw new NotImplementedException ();
		}
	}

	//
	// A set of parsed constraints for a type parameter
	//
	public class Constraints
	{
		SimpleMemberName tparam;
		List<FullNamedExpression> constraints;
		Location loc;
		bool resolved;
		bool resolving;
		
		public Constraints (SimpleMemberName tparam, List<FullNamedExpression> constraints, Location loc)
		{
			this.tparam = tparam;
			this.constraints = constraints;
			this.loc = loc;
		}

		#region Properties

		public List<FullNamedExpression> TypeExpressions {
			get {
				return constraints;
			}
		}

		public Location Location {
			get {
				return loc;
			}
		}

		public SimpleMemberName TypeParameter {
			get {
				return tparam;
			}
		}

		#endregion

		public static bool CheckConflictingInheritedConstraint (TypeParameterSpec spec, TypeSpec bb, IMemberContext context, Location loc)
		{
			if (spec.HasSpecialClass && bb.IsStruct) {
				context.Module.Compiler.Report.Error (455, loc,
					"Type parameter `{0}' inherits conflicting constraints `{1}' and `{2}'",
					spec.Name, "class", bb.GetSignatureForError ());

				return false;
			}

			return CheckConflictingInheritedConstraint (spec, spec.BaseType, bb, context, loc);
		}

		static bool CheckConflictingInheritedConstraint (TypeParameterSpec spec, TypeSpec ba, TypeSpec bb, IMemberContext context, Location loc)
		{
			if (ba == bb)
				return true;

			if (TypeSpec.IsBaseClass (ba, bb, false) || TypeSpec.IsBaseClass (bb, ba, false))
				return true;

			Error_ConflictingConstraints (context, spec, ba, bb, loc);
			return false;
		}

		public static void Error_ConflictingConstraints (IMemberContext context, TypeParameterSpec tp, TypeSpec ba, TypeSpec bb, Location loc)
		{
			context.Module.Compiler.Report.Error (455, loc,
				"Type parameter `{0}' inherits conflicting constraints `{1}' and `{2}'",
				tp.Name, ba.GetSignatureForError (), bb.GetSignatureForError ());
		}

		public void CheckGenericConstraints (IMemberContext context, bool obsoleteCheck)
		{
			foreach (var c in constraints) {
				if (c == null)
					continue;

				var t = c.Type;
				if (t == null)
					continue;

				if (obsoleteCheck) {
					ObsoleteAttribute obsolete_attr = t.GetAttributeObsolete ();
					if (obsolete_attr != null)
						AttributeTester.Report_ObsoleteMessage (obsolete_attr, t.GetSignatureForError (), c.Location, context.Module.Compiler.Report);
				}

				ConstraintChecker.Check (context, t, c.Location);
			}
		}

		//
		// Resolve the constraints types with only possible early checks, return
		// value `false' is reserved for recursive failure
		//
		public bool Resolve (IMemberContext context, TypeParameter tp)
		{
			if (resolved)
				return true;

			if (resolving)
				return false;

			resolving = true;
			var spec = tp.Type;
			List<TypeParameterSpec> tparam_types = null;
			bool iface_found = false;

			spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;

			for (int i = 0; i < constraints.Count; ++i) {
				var constraint = constraints[i];

				if (constraint is SpecialContraintExpr) {
					spec.SpecialConstraint |= ((SpecialContraintExpr) constraint).Constraint;
					if (spec.HasSpecialStruct)
						spec.BaseType = context.Module.Compiler.BuiltinTypes.ValueType;

					// Set to null as it does not have a type
					constraints[i] = null;
					continue;
				}

				var type = constraint.ResolveAsType (context);
				if (type == null)
					continue;

				if (type.Arity > 0 && ((InflatedTypeSpec) type).HasDynamicArgument ()) {
					context.Module.Compiler.Report.Error (1968, constraint.Location,
						"A constraint cannot be the dynamic type `{0}'", type.GetSignatureForError ());
					continue;
				}

				if (!context.CurrentMemberDefinition.IsAccessibleAs (type)) {
					context.Module.Compiler.Report.SymbolRelatedToPreviousError (type);
					context.Module.Compiler.Report.Error (703, loc,
						"Inconsistent accessibility: constraint type `{0}' is less accessible than `{1}'",
						type.GetSignatureForError (), context.GetSignatureForError ());
				}

				if (type.IsInterface) {
					if (!spec.AddInterface (type)) {
						context.Module.Compiler.Report.Error (405, constraint.Location,
							"Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
					}

					iface_found = true;
					continue;
				}


				var constraint_tp = type as TypeParameterSpec;
				if (constraint_tp != null) {
					if (tparam_types == null) {
						tparam_types = new List<TypeParameterSpec> (2);
					} else if (tparam_types.Contains (constraint_tp)) {
						context.Module.Compiler.Report.Error (405, constraint.Location,
							"Duplicate constraint `{0}' for type parameter `{1}'", type.GetSignatureForError (), tparam.Value);
						continue;
					}

					//
					// Checks whether each generic method parameter constraint type
					// is valid with respect to T
					//
					if (tp.IsMethodTypeParameter) {
						TypeManager.CheckTypeVariance (type, Variance.Contravariant, context);
					}

					var tp_def = constraint_tp.MemberDefinition as TypeParameter;
					if (tp_def != null && !tp_def.ResolveConstraints (context)) {
						context.Module.Compiler.Report.Error (454, constraint.Location,
							"Circular constraint dependency involving `{0}' and `{1}'",
							constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
						continue;
					}

					//
					// Checks whether there are no conflicts between type parameter constraints
					//
					// class Foo<T, U>
					//      where T : A
					//      where U : B, T
					//
					// A and B are not convertible and only 1 class constraint is allowed
					//
					if (constraint_tp.HasTypeConstraint) {
						if (spec.HasTypeConstraint || spec.HasSpecialStruct) {
							if (!CheckConflictingInheritedConstraint (spec, constraint_tp.BaseType, context, constraint.Location))
								continue;
						} else {
							for (int ii = 0; ii < tparam_types.Count; ++ii) {
								if (!tparam_types[ii].HasTypeConstraint)
									continue;

								if (!CheckConflictingInheritedConstraint (spec, tparam_types[ii].BaseType, constraint_tp.BaseType, context, constraint.Location))
									break;
							}
						}
					}

					if (constraint_tp.HasSpecialStruct) {
						context.Module.Compiler.Report.Error (456, constraint.Location,
							"Type parameter `{0}' has the `struct' constraint, so it cannot be used as a constraint for `{1}'",
							constraint_tp.GetSignatureForError (), tp.GetSignatureForError ());
						continue;
					}

					tparam_types.Add (constraint_tp);
					continue;
				}

				if (iface_found || spec.HasTypeConstraint) {
					context.Module.Compiler.Report.Error (406, constraint.Location,
						"The class type constraint `{0}' must be listed before any other constraints. Consider moving type constraint to the beginning of the constraint list",
						type.GetSignatureForError ());
				}

				if (spec.HasSpecialStruct || spec.HasSpecialClass) {
					context.Module.Compiler.Report.Error (450, constraint.Location,
						"`{0}': cannot specify both a constraint class and the `class' or `struct' constraint",
						type.GetSignatureForError ());
				}

				switch (type.BuiltinType) {
				case BuiltinTypeSpec.Type.Array:
				case BuiltinTypeSpec.Type.Delegate:
				case BuiltinTypeSpec.Type.MulticastDelegate:
				case BuiltinTypeSpec.Type.Enum:
				case BuiltinTypeSpec.Type.ValueType:
				case BuiltinTypeSpec.Type.Object:
					context.Module.Compiler.Report.Error (702, constraint.Location,
						"A constraint cannot be special class `{0}'", type.GetSignatureForError ());
					continue;
				case BuiltinTypeSpec.Type.Dynamic:
					context.Module.Compiler.Report.Error (1967, constraint.Location,
						"A constraint cannot be the dynamic type");
					continue;
				}

				if (type.IsSealed || !type.IsClass) {
					context.Module.Compiler.Report.Error (701, loc,
						"`{0}' is not a valid constraint. A constraint must be an interface, a non-sealed class or a type parameter",
						TypeManager.CSharpName (type));
					continue;
				}

				if (type.IsStatic) {
					context.Module.Compiler.Report.Error (717, constraint.Location,
						"`{0}' is not a valid constraint. Static classes cannot be used as constraints",
						type.GetSignatureForError ());
				}

				spec.BaseType = type;
			}

			if (tparam_types != null)
				spec.TypeArguments = tparam_types.ToArray ();

			resolving = false;
			resolved = true;
			return true;
		}

		public void VerifyClsCompliance (Report report)
		{
			foreach (var c in constraints)
			{
				if (c == null)
					continue;

				if (!c.Type.IsCLSCompliant ()) {
					report.SymbolRelatedToPreviousError (c.Type);
					report.Warning (3024, 1, loc, "Constraint type `{0}' is not CLS-compliant",
						c.Type.GetSignatureForError ());
				}
			}
		}
	}

	//
	// A type parameter for a generic type or generic method definition
	//
	public class TypeParameter : MemberCore, ITypeDefinition
	{
		static readonly string[] attribute_target = new string [] { "type parameter" };
		
		Constraints constraints;
		GenericTypeParameterBuilder builder;
		readonly TypeParameterSpec spec;

		public TypeParameter (int index, MemberName name, Constraints constraints, Attributes attrs, Variance variance)
			: base (null, name, attrs)
		{
			this.constraints = constraints;
			this.spec = new TypeParameterSpec (null, index, this, SpecialConstraint.None, variance, null);
		}

		//
		// Used by parser
		//
		public TypeParameter (MemberName name, Attributes attrs, Variance variance)
			: base (null, name, attrs)
		{
			this.spec = new TypeParameterSpec (null, -1, this, SpecialConstraint.None, variance, null);
		}
		
		public TypeParameter (TypeParameterSpec spec, TypeSpec parentSpec, MemberName name, Attributes attrs)
			: base (null, name, attrs)
		{
			this.spec = new TypeParameterSpec (parentSpec, spec.DeclaredPosition, spec.MemberDefinition, spec.SpecialConstraint, spec.Variance, null) {
				BaseType = spec.BaseType,
				InterfacesDefined = spec.InterfacesDefined,
				TypeArguments = spec.TypeArguments
			};
		}
		
		#region Properties

		public override AttributeTargets AttributeTargets {
			get {
				return AttributeTargets.GenericParameter;
			}
		}

		public Constraints Constraints {
			get {
				return constraints;
			}
			set {
				constraints = value;
			}
		}

		public IAssemblyDefinition DeclaringAssembly {
			get	{
				return Module.DeclaringAssembly;
			}
		}

		public override string DocCommentHeader {
			get {
				throw new InvalidOperationException (
					"Unexpected attempt to get doc comment from " + this.GetType ());
			}
		}

		bool ITypeDefinition.IsComImport {
			get {
				return false;
			}
		}

		bool ITypeDefinition.IsPartial {
			get {
				return false;
			}
		}

		public bool IsMethodTypeParameter {
			get {
				return spec.IsMethodOwned;
			}
		}

		bool ITypeDefinition.IsTypeForwarder {
			get {
				return false;
			}
		}

		public string Name {
			get {
				return MemberName.Name;
			}
		}

		public string Namespace {
			get {
				return null;
			}
		}

		public TypeParameterSpec Type {
			get {
				return spec;
			}
		}

		public int TypeParametersCount {
			get {
				return 0;
			}
		}

		public TypeParameterSpec[] TypeParameters {
			get {
				return null;
			}
		}

		public override string[] ValidAttributeTargets {
			get {
				return attribute_target;
			}
		}

		public Variance Variance {
			get {
				return spec.Variance;
			}
		}

		#endregion

		//
		// This is called for each part of a partial generic type definition.
		//
		// If partial type parameters constraints are not null and we don't
		// already have constraints they become our constraints. If we already
		// have constraints, we must check that they're the same.
		//
		public bool AddPartialConstraints (TypeDefinition part, TypeParameter tp)
		{
			if (builder == null)
				throw new InvalidOperationException ();

			var new_constraints = tp.constraints;
			if (new_constraints == null)
				return true;

			// TODO: could create spec only
			//tp.Define (null, -1, part.Definition);
			tp.spec.DeclaringType = part.Definition;
			if (!tp.ResolveConstraints (part))
				return false;

			if (constraints != null)
				return spec.HasSameConstraintsDefinition (tp.Type);

			// Copy constraint from resolved part to partial container
			spec.SpecialConstraint = tp.spec.SpecialConstraint;
			spec.Interfaces = tp.spec.Interfaces;
			spec.TypeArguments = tp.spec.TypeArguments;
			spec.BaseType = tp.spec.BaseType;
			
			return true;
		}

		public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
		{
			builder.SetCustomAttribute ((ConstructorInfo) ctor.GetMetaInfo (), cdata);
		}

		public void CheckGenericConstraints (bool obsoleteCheck)
		{
			if (constraints != null)
				constraints.CheckGenericConstraints (this, obsoleteCheck);
		}

		public TypeParameter CreateHoistedCopy (TypeSpec declaringSpec)
		{
			return new TypeParameter (spec, declaringSpec, MemberName, null);
		}

		public override bool Define ()
		{
			return true;
		}

		//
		// This is the first method which is called during the resolving
		// process; we're called immediately after creating the type parameters
		// with SRE (by calling `DefineGenericParameters()' on the TypeBuilder /
		// MethodBuilder).
		//
		public void Define (GenericTypeParameterBuilder type, TypeSpec declaringType, TypeContainer parent)
		{
			if (builder != null)
				throw new InternalErrorException ();

			// Needed to get compiler reference
			this.Parent = parent;
			this.builder = type;
			spec.DeclaringType = declaringType;
			spec.SetMetaInfo (type);
		}

		public void EmitConstraints (GenericTypeParameterBuilder builder)
		{
			var attr = GenericParameterAttributes.None;
			if (spec.Variance == Variance.Contravariant)
				attr |= GenericParameterAttributes.Contravariant;
			else if (spec.Variance == Variance.Covariant)
				attr |= GenericParameterAttributes.Covariant;

			if (spec.HasSpecialClass)
				attr |= GenericParameterAttributes.ReferenceTypeConstraint;
			else if (spec.HasSpecialStruct)
				attr |= GenericParameterAttributes.NotNullableValueTypeConstraint | GenericParameterAttributes.DefaultConstructorConstraint;

			if (spec.HasSpecialConstructor)
				attr |= GenericParameterAttributes.DefaultConstructorConstraint;

			if (spec.BaseType.BuiltinType != BuiltinTypeSpec.Type.Object)
				builder.SetBaseTypeConstraint (spec.BaseType.GetMetaInfo ());

			if (spec.InterfacesDefined != null)
				builder.SetInterfaceConstraints (spec.InterfacesDefined.Select (l => l.GetMetaInfo ()).ToArray ());

			if (spec.TypeArguments != null)
				builder.SetInterfaceConstraints (spec.TypeArguments.Select (l => l.GetMetaInfo ()).ToArray ());

			builder.SetGenericParameterAttributes (attr);
		}

		public override void Emit ()
		{
			EmitConstraints (builder);

			if (OptAttributes != null)
				OptAttributes.Emit ();

			base.Emit ();
		}

		public void ErrorInvalidVariance (IMemberContext mc, Variance expected)
		{
			Report.SymbolRelatedToPreviousError (mc.CurrentMemberDefinition);
			string input_variance = Variance == Variance.Contravariant ? "contravariant" : "covariant";
			string gtype_variance;
			switch (expected) {
			case Variance.Contravariant: gtype_variance = "contravariantly"; break;
			case Variance.Covariant: gtype_variance = "covariantly"; break;
			default: gtype_variance = "invariantly"; break;
			}

			Delegate d = mc as Delegate;
			string parameters = d != null ? d.Parameters.GetSignatureForError () : "";

			Report.Error (1961, Location,
				"The {2} type parameter `{0}' must be {3} valid on `{1}{4}'",
					GetSignatureForError (), mc.GetSignatureForError (), input_variance, gtype_variance, parameters);
		}

		public TypeSpec GetAttributeCoClass ()
		{
			return null;
		}

		public string GetAttributeDefaultMember ()
		{
			throw new NotSupportedException ();
		}

		public AttributeUsageAttribute GetAttributeUsage (PredefinedAttribute pa)
		{
			throw new NotSupportedException ();
		}

		public override string GetSignatureForDocumentation ()
		{
			throw new NotImplementedException ();
		}

		public override string GetSignatureForError ()
		{
			return MemberName.Name;
		}

		bool ITypeDefinition.IsInternalAsPublic (IAssemblyDefinition assembly)
		{
			return spec.MemberDefinition.DeclaringAssembly == assembly;
		}

		public void LoadMembers (TypeSpec declaringType, bool onlyTypes, ref MemberCache cache)
		{
			throw new NotSupportedException ("Not supported for compiled definition");
		}

		//
		// Resolves all type parameter constraints
		//
		public bool ResolveConstraints (IMemberContext context)
		{
			if (constraints != null)
				return constraints.Resolve (context, this);

			if (spec.BaseType == null)
				spec.BaseType = context.Module.Compiler.BuiltinTypes.Object;

			return true;
		}

		public override bool IsClsComplianceRequired ()
		{
			return false;
		}

		public new void VerifyClsCompliance ()
		{
			if (constraints != null)
				constraints.VerifyClsCompliance (Report);
		}

		public void WarningParentNameConflict (TypeParameter conflict)
		{
			conflict.Report.SymbolRelatedToPreviousError (conflict.Location, null);
			conflict.Report.Warning (693, 3, Location,
				"Type parameter `{0}' has the same name as the type parameter from outer type `{1}'",
				GetSignatureForError (), conflict.CurrentType.GetSignatureForError ());
		}
	}

	[System.Diagnostics.DebuggerDisplay ("{DisplayDebugInfo()}")]
	public class TypeParameterSpec : TypeSpec
	{
		public static readonly new TypeParameterSpec[] EmptyTypes = new TypeParameterSpec[0];

		Variance variance;
		SpecialConstraint spec;
		int tp_pos;
		TypeSpec[] targs;
		TypeSpec[] ifaces_defined;

		//
		// Creates type owned type parameter
		//
		public TypeParameterSpec (TypeSpec declaringType, int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
			: base (MemberKind.TypeParameter, declaringType, definition, info, Modifiers.PUBLIC)
		{
			this.variance = variance;
			this.spec = spec;
			state &= ~StateFlags.Obsolete_Undetected;
			tp_pos = index;
		}

		//
		// Creates method owned type parameter
		//
		public TypeParameterSpec (int index, ITypeDefinition definition, SpecialConstraint spec, Variance variance, MetaType info)
			: this (null, index, definition, spec, variance, info)
		{
		}

		#region Properties

		public int DeclaredPosition {
			get {
				return tp_pos;
			}
			set {
				tp_pos = value;
			}
		}

		public bool HasSpecialConstructor {
			get {
				return (spec & SpecialConstraint.Constructor) != 0;
			}
		}

		public bool HasSpecialClass {
			get {
				return (spec & SpecialConstraint.Class) != 0;
			}
		}

		public bool HasSpecialStruct {
			get {
				return (spec & SpecialConstraint.Struct) != 0;
			}
		}

		public bool HasAnyTypeConstraint {
			get {
				return (spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0 || ifaces != null || targs != null || HasTypeConstraint;
			}
		}

		public bool HasTypeConstraint {
			get {
				var bt = BaseType.BuiltinType;
				return bt != BuiltinTypeSpec.Type.Object && bt != BuiltinTypeSpec.Type.ValueType;
			}
		}

		public override IList<TypeSpec> Interfaces {
			get {
				if ((state & StateFlags.InterfacesExpanded) == 0) {
					if (ifaces != null) {
						if (ifaces_defined == null)
							ifaces_defined = ifaces.ToArray ();

						for (int i = 0; i < ifaces_defined.Length; ++i ) {
							var iface_type = ifaces_defined[i];
							var td = iface_type.MemberDefinition as TypeDefinition;
							if (td != null)
								td.DoExpandBaseInterfaces ();

							if (iface_type.Interfaces != null) {
								for (int ii = 0; ii < iface_type.Interfaces.Count; ++ii) {
									var ii_iface_type = iface_type.Interfaces [ii];
									AddInterface (ii_iface_type);
								}
							}
						}
					}

					//
					// Include all base type interfaces too, see ImportTypeBase for details
					//
					if (BaseType != null) {
						var td = BaseType.MemberDefinition as TypeDefinition;
						if (td != null)
							td.DoExpandBaseInterfaces ();

						if (BaseType.Interfaces != null) {
							foreach (var iface in BaseType.Interfaces) {
								AddInterface (iface);
							}
						}
					}

					if (ifaces_defined == null)
						ifaces_defined = ifaces == null ? TypeSpec.EmptyTypes : ifaces.ToArray ();

					state |= StateFlags.InterfacesExpanded;
				}

				return ifaces;
			}
		}

		//
		// Unexpanded interfaces list
		//
		public TypeSpec[] InterfacesDefined {
			get {
				if (ifaces_defined == null) {
					if (ifaces == null)
						return null;

					ifaces_defined = ifaces.ToArray ();
				}

				return ifaces_defined.Length == 0 ? null : ifaces_defined;
			}
			set {
				ifaces_defined = value;
				if (value != null && value.Length != 0)
					ifaces = new List<TypeSpec> (value);
			}
		}

		public bool IsConstrained {
			get {
				return spec != SpecialConstraint.None || ifaces != null || targs != null || HasTypeConstraint;
			}
		}

		//
		// Returns whether the type parameter is known to be a reference type
		//
		public new bool IsReferenceType {
			get {
				if ((spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
					return (spec & SpecialConstraint.Class) != 0;

				//
				// Full check is needed (see IsValueType for details)
				//
				if (HasTypeConstraint && TypeSpec.IsReferenceType (BaseType))
					return true;

				if (targs != null) {
					foreach (var ta in targs) {
						//
						// Secondary special constraints are ignored (I am not sure why)
						//
						var tp = ta as TypeParameterSpec;
						if (tp != null && (tp.spec & (SpecialConstraint.Class | SpecialConstraint.Struct)) != 0)
							continue;

						if (TypeSpec.IsReferenceType (ta))
							return true;
					}
				}

				return false;
			}
		}

		//
		// Returns whether the type parameter is known to be a value type
		//
		public new bool IsValueType {
			get {
				//
				// Even if structs/enums cannot be used directly as constraints
				// they can apear as constraint type when inheriting base constraint
				// which has dependant type parameter constraint which has been
				// inflated using value type
				//
				// class A : B<int> { override void Foo<U> () {} }
				// class B<T> { virtual void Foo<U> () where U : T {} }
				//
				if (HasSpecialStruct)
					return true;

				if (targs != null) {
					foreach (var ta in targs) {
						if (TypeSpec.IsValueType (ta))
							return true;
					}
				}

				return false;
			}
		}

		public override string Name {
			get {
				return definition.Name;
			}
		}

		public bool IsMethodOwned {
			get {
				return DeclaringType == null;
			}
		}

		public SpecialConstraint SpecialConstraint {
			get {
				return spec;
			}
			set {
				spec = value;
			}
		}

		//
		// Types used to inflate the generic type
		//
		public new TypeSpec[] TypeArguments {
			get {
				return targs;
			}
			set {
				targs = value;
			}
		}

		public Variance Variance {
			get {
				return variance;
			}
		}

		#endregion

		public string DisplayDebugInfo ()
		{
			var s = GetSignatureForError ();
			return IsMethodOwned ? s + "!!" : s + "!";
		}

		//
		// Finds effective base class. The effective base class is always a class-type
		//
		public TypeSpec GetEffectiveBase ()
		{
			if (HasSpecialStruct)
				return BaseType;

			//
			// If T has a class-type constraint C but no type-parameter constraints, its effective base class is C
			//
			if (BaseType != null && targs == null) {
				//
				// If T has a constraint V that is a value-type, use instead the most specific base type of V that is a class-type.
				// 
				// LAMESPEC: Is System.ValueType always the most specific base type in this case?
				//
				// Note: This can never happen in an explicitly given constraint, but may occur when the constraints of a generic method
				// are implicitly inherited by an overriding method declaration or an explicit implementation of an interface method.
				//
				return BaseType.IsStruct ? BaseType.BaseType : BaseType;
			}

			var types = targs;
			if (HasTypeConstraint) {
				Array.Resize (ref types, types.Length + 1);

				for (int i = 0; i < types.Length - 1; ++i) {
					types[i] = types[i].BaseType;
				}

				types[types.Length - 1] = BaseType;
			} else {
				types = types.Select (l => l.BaseType).ToArray ();
			}

			if (types != null)
				return Convert.FindMostEncompassedType (types);

			return BaseType;
		}

		public override string GetSignatureForDocumentation ()
		{
			var prefix = IsMethodOwned ? "``" : "`";
			return prefix + DeclaredPosition;
		}

		public override string GetSignatureForError ()
		{
			return Name;
		}

		//
		// Constraints have to match by definition but not position, used by
		// partial classes or methods
		//
		public bool HasSameConstraintsDefinition (TypeParameterSpec other)
		{
			if (spec != other.spec)
				return false;

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

			if (!TypeSpecComparer.Override.IsSame (InterfacesDefined, other.InterfacesDefined))
				return false;

			if (!TypeSpecComparer.Override.IsSame (targs, other.targs))
				return false;

			return true;
		}

		//
		// Constraints have to match by using same set of types, used by
		// implicit interface implementation
		//
		public bool HasSameConstraintsImplementation (TypeParameterSpec other)
		{
			if (spec != other.spec)
				return false;

			//
			// It can be same base type or inflated type parameter
			//
			// interface I<T> { void Foo<U> where U : T; }
			// class A : I<int> { void Foo<X> where X : int {} }
			//
			bool found;
			if (!TypeSpecComparer.Override.IsEqual (BaseType, other.BaseType)) {
				if (other.targs == null)
					return false;

				found = false;
				foreach (var otarg in other.targs) {
					if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
						found = true;
						break;
					}
				}

				if (!found)
					return false;
			}

			// Check interfaces implementation -> definition
			if (InterfacesDefined != null) {
				//
				// Iterate over inflated interfaces
				//
				foreach (var iface in Interfaces) {
					found = false;
					if (other.InterfacesDefined != null) {
						foreach (var oiface in other.Interfaces) {
							if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
								found = true;
								break;
							}
						}
					}

					if (found)
						continue;

					if (other.targs != null) {
						foreach (var otarg in other.targs) {
							if (TypeSpecComparer.Override.IsEqual (BaseType, otarg)) {
								found = true;
								break;
							}
						}
					}

					if (!found)
						return false;
				}
			}

			// Check interfaces implementation <- definition
			if (other.InterfacesDefined != null) {
				if (InterfacesDefined == null)
					return false;

				//
				// Iterate over inflated interfaces
				//
				foreach (var oiface in other.Interfaces) {
					found = false;
					foreach (var iface in Interfaces) {
						if (TypeSpecComparer.Override.IsEqual (iface, oiface)) {
							found = true;
							break;
						}
					}

					if (!found)
						return false;
				}
			}

			// Check type parameters implementation -> definition
			if (targs != null) {
				if (other.targs == null)
					return false;

				foreach (var targ in targs) {
					found = false;
					foreach (var otarg in other.targs) {
						if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
							found = true;
							break;
						}
					}

					if (!found)
						return false;
				}
			}

			// Check type parameters implementation <- definition
			if (other.targs != null) {
				foreach (var otarg in other.targs) {
					// Ignore inflated type arguments, were checked above
					if (!otarg.IsGenericParameter)
						continue;

					if (targs == null)
						return false;

					found = false;
					foreach (var targ in targs) {
						if (TypeSpecComparer.Override.IsEqual (targ, otarg)) {
							found = true;
							break;
						}
					}

					if (!found)
						return false;
				}				
			}

			return true;
		}

		public static TypeParameterSpec[] InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec[] tparams)
		{
			return InflateConstraints (tparams, l => l, inflator);
		}

		public static TypeParameterSpec[] InflateConstraints<T> (TypeParameterSpec[] tparams, Func<T, TypeParameterInflator> inflatorFactory, T arg)
		{
			TypeParameterSpec[] constraints = null;
			TypeParameterInflator? inflator = null;

			for (int i = 0; i < tparams.Length; ++i) {
				var tp = tparams[i];
				if (tp.HasTypeConstraint || tp.InterfacesDefined != null || tp.TypeArguments != null) {
					if (constraints == null) {
						constraints = new TypeParameterSpec[tparams.Length];
						Array.Copy (tparams, constraints, constraints.Length);
					}

					//
					// Using a factory to avoid possibly expensive inflator build up
					//
					if (inflator == null)
						inflator = inflatorFactory (arg);

					constraints[i] = (TypeParameterSpec) constraints[i].InflateMember (inflator.Value);
				}
			}

			if (constraints == null)
				constraints = tparams;

			return constraints;
		}

		public void InflateConstraints (TypeParameterInflator inflator, TypeParameterSpec tps)
		{
			tps.BaseType = inflator.Inflate (BaseType);

			var defined = InterfacesDefined;
			if (defined != null) {
				tps.ifaces_defined = new TypeSpec[defined.Length];
				for (int i = 0; i < defined.Length; ++i)
					tps.ifaces_defined [i] = inflator.Inflate (defined[i]);
			}

			var ifaces = Interfaces;
			if (ifaces != null) {
				tps.ifaces = new List<TypeSpec> (ifaces.Count);
				for (int i = 0; i < ifaces.Count; ++i)
					tps.ifaces.Add (inflator.Inflate (ifaces[i]));
			}

			if (targs != null) {
				tps.targs = new TypeSpec[targs.Length];
				for (int i = 0; i < targs.Length; ++i)
					tps.targs[i] = inflator.Inflate (targs[i]);
			}
		}

		public override MemberSpec InflateMember (TypeParameterInflator inflator)
		{
			var tps = (TypeParameterSpec) MemberwiseClone ();
			InflateConstraints (inflator, tps);
			return tps;
		}

		//
		// Populates type parameter members using type parameter constraints
		// The trick here is to be called late enough but not too late to
		// populate member cache with all members from other types
		//
		protected override void InitializeMemberCache (bool onlyTypes)
		{
			cache = new MemberCache ();

			//
			// For a type parameter the membercache is the union of the sets of members of the types
			// specified as a primary constraint or secondary constraint
			//
			if (BaseType.BuiltinType != BuiltinTypeSpec.Type.Object && BaseType.BuiltinType != BuiltinTypeSpec.Type.ValueType)
				cache.AddBaseType (BaseType);

			if (InterfacesDefined != null) {
				foreach (var iface_type in InterfacesDefined) {
					cache.AddInterface (iface_type);
				}
			}

			if (targs != null) {
				foreach (var ta in targs) {
					var b_type = ta.BaseType;
					if (b_type.BuiltinType != BuiltinTypeSpec.Type.Object && b_type.BuiltinType != BuiltinTypeSpec.Type.ValueType)
						cache.AddBaseType (b_type);

					var tps = ta as TypeParameterSpec;
					var ifaces = tps != null ? tps.InterfacesDefined : ta.Interfaces;

					if (ifaces != null) {
						foreach (var iface_type in ifaces) {
							cache.AddInterface (iface_type);
						}
					}
				}
			}
		}

		public bool IsConvertibleToInterface (TypeSpec iface)
		{
			if (Interfaces != null) {
				foreach (var t in Interfaces) {
					if (t == iface)
						return true;
				}
			}

			if (TypeArguments != null) {
				foreach (var t in TypeArguments) {
					if (((TypeParameterSpec) t).IsConvertibleToInterface (iface))
						return true;
				}
			}

			return false;
		}

		public static bool HasAnyTypeParameterTypeConstrained (IGenericMethodDefinition md)
		{
			var tps = md.TypeParameters;
			for (int i = 0; i < md.TypeParametersCount; ++i) {
				if (tps[i].HasAnyTypeConstraint) {
					return true;
				}
			}

			return false;
		}

		public static bool HasAnyTypeParameterConstrained (IGenericMethodDefinition md)
		{
			var tps = md.TypeParameters;
			for (int i = 0; i < md.TypeParametersCount; ++i) {
				if (tps[i].IsConstrained) {
					return true;
				}
			}

			return false;
		}

		public bool HasDependencyOn (TypeSpec type)
		{
			if (TypeArguments != null) {
				foreach (var targ in TypeArguments) {
					if (TypeSpecComparer.Override.IsEqual (targ, type))
						return true;

					var tps = targ as TypeParameterSpec;
					if (tps != null && tps.HasDependencyOn (type))
						return true;
				}
			}

			return false;
		}

		public override TypeSpec Mutate (TypeParameterMutator mutator)
		{
			return mutator.Mutate (this);
		}
	}

	public struct TypeParameterInflator
	{
		readonly TypeSpec type;
		readonly TypeParameterSpec[] tparams;
		readonly TypeSpec[] targs;
		readonly IModuleContext context;

		public TypeParameterInflator (TypeParameterInflator nested, TypeSpec type)
			: this (nested.context, type, nested.tparams, nested.targs)
		{
		}

		public TypeParameterInflator (IModuleContext context, TypeSpec type, TypeParameterSpec[] tparams, TypeSpec[] targs)
		{
			if (tparams.Length != targs.Length)
				throw new ArgumentException ("Invalid arguments");

			this.context = context;
			this.tparams = tparams;
			this.targs = targs;
			this.type = type;
		}

		#region Properties

		public IModuleContext Context {
			get {
				return context;
			}
		}

		public TypeSpec TypeInstance {
			get {
				return type;
			}
		}

		//
		// Type parameters to inflate
		//
		public TypeParameterSpec[] TypeParameters {
			get {
				return tparams;
			}
		}

		#endregion

		public TypeSpec Inflate (TypeSpec type)
		{
			var tp = type as TypeParameterSpec;
			if (tp != null)
				return Inflate (tp);

			var ac = type as ArrayContainer;
			if (ac != null) {
				var et = Inflate (ac.Element);
				if (et != ac.Element)
					return ArrayContainer.MakeType (context.Module, et, ac.Rank);

				return ac;
			}

			//
			// When inflating a nested type, inflate its parent first
			// in case it's using same type parameters (was inflated within the type)
			//
			TypeSpec[] targs;
			int i = 0;
			if (type.IsNested) {
				var parent = Inflate (type.DeclaringType);

				//
				// Keep the inflated type arguments
				// 
				targs = type.TypeArguments;

				//
				// When inflating imported nested type used inside same declaring type, we get TypeSpec
				// because the import cache helps us to catch it. However, that means we have to look at
				// type definition to get type argument (they are in fact type parameter in this case)
				//
				if (targs.Length == 0 && type.Arity > 0)
					targs = type.MemberDefinition.TypeParameters;

				//
				// Parent was inflated, find the same type on inflated type
				// to use same cache for nested types on same generic parent
				//
				type = MemberCache.FindNestedType (parent, type.Name, type.Arity);

				//
				// Handle the tricky case where parent shares local type arguments
				// which means inflating inflated type
				//
				// class Test<T> {
				//		public static Nested<T> Foo () { return null; }
				//
				//		public class Nested<U> {}
				//	}
				//
				//  return type of Test<string>.Foo() has to be Test<string>.Nested<string> 
				//
				if (targs.Length > 0) {
					var inflated_targs = new TypeSpec[targs.Length];
					for (; i < targs.Length; ++i)
						inflated_targs[i] = Inflate (targs[i]);

					type = type.MakeGenericType (context, inflated_targs);
				}

				return type;
			}

			// Nothing to do for non-generic type
			if (type.Arity == 0)
				return type;

			targs = new TypeSpec[type.Arity];

			//
			// Inflating using outside type arguments, var v = new Foo<int> (), class Foo<T> {}
			//
			if (type is InflatedTypeSpec) {
				for (; i < targs.Length; ++i)
					targs[i] = Inflate (type.TypeArguments[i]);

				type = type.GetDefinition ();
			} else {
				//
				// Inflating parent using inside type arguments, class Foo<T> { ITest<T> foo; }
				//
				var args = type.MemberDefinition.TypeParameters;
				foreach (var ds_tp in args)
					targs[i++] = Inflate (ds_tp);
			}

			return type.MakeGenericType (context, targs);
		}

		public TypeSpec Inflate (TypeParameterSpec tp)
		{
			for (int i = 0; i < tparams.Length; ++i)
				if (tparams [i] == tp)
					return targs[i];

			// This can happen when inflating nested types
			// without type arguments specified
			return tp;
		}
	}

	//
	// Before emitting any code we have to change all MVAR references to VAR
	// when the method is of generic type and has hoisted variables
	//
	public class TypeParameterMutator
	{
		readonly TypeParameters mvar;
		readonly TypeParameters var;
		readonly TypeParameterSpec[] src;
		Dictionary<TypeSpec, TypeSpec> mutated_typespec;

		public TypeParameterMutator (TypeParameters mvar, TypeParameters var)
		{
			if (mvar.Count != var.Count)
				throw new ArgumentException ();

			this.mvar = mvar;
			this.var = var;
		}

		public TypeParameterMutator (TypeParameterSpec[] srcVar, TypeParameters destVar)
		{
			if (srcVar.Length != destVar.Count)
				throw new ArgumentException ();

			this.src = srcVar;
			this.var = destVar;
		}

		#region Properties

		public TypeParameters MethodTypeParameters {
			get {
				return mvar;
			}
		}

		#endregion

		public static TypeSpec GetMemberDeclaringType (TypeSpec type)
		{
			if (type is InflatedTypeSpec) {
				if (type.DeclaringType == null)
					return type.GetDefinition ();

				var parent = GetMemberDeclaringType (type.DeclaringType);
				type = MemberCache.GetMember<TypeSpec> (parent, type);
			}

			return type;
		}

		public TypeSpec Mutate (TypeSpec ts)
		{
			TypeSpec value;
			if (mutated_typespec != null && mutated_typespec.TryGetValue (ts, out value))
				return value;

			value = ts.Mutate (this);
			if (mutated_typespec == null)
				mutated_typespec = new Dictionary<TypeSpec, TypeSpec> ();

			mutated_typespec.Add (ts, value);
			return value;
		}

		public TypeParameterSpec Mutate (TypeParameterSpec tp)
		{
			if (mvar != null) {
				for (int i = 0; i < mvar.Count; ++i) {
					if (mvar[i].Type == tp)
						return var[i].Type;
				}
			} else {
				for (int i = 0; i < src.Length; ++i) {
					if (src[i] == tp)
						return var[i].Type;
				}
			}

			return tp;
		}

		public TypeSpec[] Mutate (TypeSpec[] targs)
		{
			TypeSpec[] mutated = new TypeSpec[targs.Length];
			bool changed = false;
			for (int i = 0; i < targs.Length; ++i) {
				mutated[i] = Mutate (targs[i]);
				changed |= targs[i] != mutated[i];
			}

			return changed ? mutated : targs;
		}
	}

	/// <summary>
	///   A TypeExpr which already resolved to a type parameter.
	/// </summary>
	public class TypeParameterExpr : TypeExpression
	{
		public TypeParameterExpr (TypeParameter type_parameter, Location loc)
			: base (type_parameter.Type, loc)
		{
			this.eclass = ExprClass.TypeParameter;
		}
	}

	public class InflatedTypeSpec : TypeSpec
	{
		TypeSpec[] targs;
		TypeParameterSpec[] constraints;
		readonly TypeSpec open_type;
		readonly IModuleContext context;

		public InflatedTypeSpec (IModuleContext context, TypeSpec openType, TypeSpec declaringType, TypeSpec[] targs)
			: base (openType.Kind, declaringType, openType.MemberDefinition, null, openType.Modifiers)
		{
			if (targs == null)
				throw new ArgumentNullException ("targs");

			this.state &= ~SharedStateFlags;
			this.state |= (openType.state & SharedStateFlags);

			this.context = context;
			this.open_type = openType;
			this.targs = targs;

			foreach (var arg in targs) {
				if (arg.HasDynamicElement || arg.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
					state |= StateFlags.HasDynamicElement;
					break;
				}
			}

			if (open_type.Kind == MemberKind.MissingType)
				MemberCache = MemberCache.Empty;

			if ((open_type.Modifiers & Modifiers.COMPILER_GENERATED) != 0)
				state |= StateFlags.ConstraintsChecked;
		}

		#region Properties

		public override TypeSpec BaseType {
			get {
				if (cache == null || (state & StateFlags.PendingBaseTypeInflate) != 0)
					InitializeMemberCache (true);

				return base.BaseType;
			}
		}

		//
		// Inflated type parameters with constraints array, mapping with type arguments is based on index
		//
		public TypeParameterSpec[] Constraints {
			get {
				if (constraints == null) {
					constraints = TypeParameterSpec.InflateConstraints (MemberDefinition.TypeParameters, l => l.CreateLocalInflator (context), this);
				}

				return constraints;
			}
		}

		//
		// Used to cache expensive constraints validation on constructed types
		//
		public bool HasConstraintsChecked {
			get {
				return (state & StateFlags.ConstraintsChecked) != 0;
			}
			set {
				state = value ? state | StateFlags.ConstraintsChecked : state & ~StateFlags.ConstraintsChecked;
			}
		}

		public override IList<TypeSpec> Interfaces {
			get {
				if (cache == null)
					InitializeMemberCache (true);

				return base.Interfaces;
			}
		}

		public override bool IsExpressionTreeType {
			get {
				return (open_type.state & StateFlags.InflatedExpressionType) != 0;
			}
		}

		public override bool IsGenericIterateInterface {
			get {
				return (open_type.state & StateFlags.GenericIterateInterface) != 0;
			}
		}

		public override bool IsGenericTask {
			get {
				return (open_type.state & StateFlags.GenericTask) != 0;
			}
		}

		public override bool IsNullableType {
			get {
				return (open_type.state & StateFlags.InflatedNullableType) != 0;
			}
		}

		//
		// Types used to inflate the generic  type
		//
		public override TypeSpec[] TypeArguments {
			get {
				return targs;
			}
		}

		#endregion

		public override bool AddInterface (TypeSpec iface)
		{
			var inflator = CreateLocalInflator (context);
			iface = inflator.Inflate (iface);
			if (iface == null)
				return false;

			return base.AddInterface (iface);
		}

		public static bool ContainsTypeParameter (TypeSpec type)
		{
			if (type.Kind == MemberKind.TypeParameter)
				return true;

			var element_container = type as ElementTypeSpec;
			if (element_container != null)
				return ContainsTypeParameter (element_container.Element);

			foreach (var t in type.TypeArguments) {
				if (ContainsTypeParameter (t)) {
					return true;
				}
			}

			return false;
		}

		TypeParameterInflator CreateLocalInflator (IModuleContext context)
		{
			TypeParameterSpec[] tparams_full;
			TypeSpec[] targs_full = targs;
			if (IsNested) {
				//
				// Special case is needed when we are inflating an open type (nested type definition)
				// on inflated parent. Consider following case
				//
				// Foo<T>.Bar<U> => Foo<string>.Bar<U>
				//
				// Any later inflation of Foo<string>.Bar<U> has to also inflate T if used inside Bar<U>
				//
				List<TypeSpec> merged_targs = null;
				List<TypeParameterSpec> merged_tparams = null;

				var type = DeclaringType;

				do {
					if (type.TypeArguments.Length > 0) {
						if (merged_targs == null) {
							merged_targs = new List<TypeSpec> ();
							merged_tparams = new List<TypeParameterSpec> ();
							if (targs.Length > 0) {
								merged_targs.AddRange (targs);
								merged_tparams.AddRange (open_type.MemberDefinition.TypeParameters);
							}
						}
						merged_tparams.AddRange (type.MemberDefinition.TypeParameters);
						merged_targs.AddRange (type.TypeArguments);
					}
					type = type.DeclaringType;
				} while (type != null);

				if (merged_targs != null) {
					// Type arguments are not in the right order but it should not matter in this case
					targs_full = merged_targs.ToArray ();
					tparams_full = merged_tparams.ToArray ();
				} else if (targs.Length == 0) {
					tparams_full = TypeParameterSpec.EmptyTypes;
				} else {
					tparams_full = open_type.MemberDefinition.TypeParameters;
				}
			} else if (targs.Length == 0) {
				tparams_full = TypeParameterSpec.EmptyTypes;
			} else {
				tparams_full = open_type.MemberDefinition.TypeParameters;
			}

			return new TypeParameterInflator (context, this, tparams_full, targs_full);
		}

		MetaType CreateMetaInfo (TypeParameterMutator mutator)
		{
			//
			// Converts nested type arguments into right order
			// Foo<string, bool>.Bar<int> => string, bool, int
			//
			var all = new List<MetaType> ();
			TypeSpec type = this;
			TypeSpec definition = type;
			do {
				if (type.GetDefinition().IsGeneric) {
					all.InsertRange (0,
						type.TypeArguments != TypeSpec.EmptyTypes ?
						type.TypeArguments.Select (l => l.GetMetaInfo ()) :
						type.MemberDefinition.TypeParameters.Select (l => l.GetMetaInfo ()));
				}

				definition = definition.GetDefinition ();
				type = type.DeclaringType;
			} while (type != null);

			return definition.GetMetaInfo ().MakeGenericType (all.ToArray ());
		}

		public override ObsoleteAttribute GetAttributeObsolete ()
		{
			return open_type.GetAttributeObsolete ();
		}

		protected override bool IsNotCLSCompliant (out bool attrValue)
		{
			if (base.IsNotCLSCompliant (out attrValue))
				return true;

			foreach (var ta in TypeArguments) {
				if (ta.MemberDefinition.CLSAttributeValue == false)
					return true;
			}

			return false;
		}

		public override TypeSpec GetDefinition ()
		{
			return open_type;
		}

		public override MetaType GetMetaInfo ()
		{
			if (info == null)
				info = CreateMetaInfo (null);

			return info;
		}

		public override string GetSignatureForError ()
		{
			if (IsNullableType)
				return targs[0].GetSignatureForError () + "?";

			return base.GetSignatureForError ();
		}

		protected override string GetTypeNameSignature ()
		{
			if (targs.Length == 0 || MemberDefinition is AnonymousTypeClass)
				return null;

			return "<" + TypeManager.CSharpName (targs) + ">";
		}

		public bool HasDynamicArgument ()
		{
			for (int i = 0; i < targs.Length; ++i) {
				var item = targs[i];

				if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
					return true;

				if (item is InflatedTypeSpec) {
					if (((InflatedTypeSpec) item).HasDynamicArgument ())
						return true;

					continue;
				}

				if (item.IsArray) {
					while (item.IsArray) {
						item = ((ArrayContainer) item).Element;
					}

					if (item.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
						return true;
				}
			}

			return false;
		}

		protected override void InitializeMemberCache (bool onlyTypes)
		{
			if (cache == null) {
				var open_cache = onlyTypes ? open_type.MemberCacheTypes : open_type.MemberCache;

				// Surprisingly, calling MemberCache on open type could meantime create cache on this type
				// for imported type parameter constraints referencing nested type of this declaration
				if (cache == null)
					cache = new MemberCache (open_cache);
			}

			var inflator = CreateLocalInflator (context);

			//
			// Two stage inflate due to possible nested types recursive
			// references
			//
			// class A<T> {
			//    B b;
			//    class B {
			//      T Value;
			//    }
			// }
			//
			// When resolving type of `b' members of `B' cannot be 
			// inflated because are not yet available in membercache
			//
			if ((state & StateFlags.PendingMemberCacheMembers) == 0) {
				open_type.MemberCacheTypes.InflateTypes (cache, inflator);

				//
				// Inflate any implemented interfaces
				//
				if (open_type.Interfaces != null) {
					ifaces = new List<TypeSpec> (open_type.Interfaces.Count);
					foreach (var iface in open_type.Interfaces) {
						var iface_inflated = inflator.Inflate (iface);
						if (iface_inflated == null)
							continue;

						base.AddInterface (iface_inflated);
					}
				}

				//
				// Handles the tricky case of recursive nested base generic type
				//
				// class A<T> : Base<A<T>.Nested> {
				//    class Nested {}
				// }
				//
				// When inflating A<T>. base type is not yet known, secondary
				// inflation is required (not common case) once base scope
				// is known
				//
				if (open_type.BaseType == null) {
					if (IsClass)
						state |= StateFlags.PendingBaseTypeInflate;
				} else {
					BaseType = inflator.Inflate (open_type.BaseType);
				}
			} else if ((state & StateFlags.PendingBaseTypeInflate) != 0) {
				//
				// It can happen when resolving base type without being defined
				// which is not allowed to happen and will always lead to an error
				//
				// class B { class N {} }
				// class A<T> : A<B.N> {}
				//
				if (open_type.BaseType == null)
					return;

				BaseType = inflator.Inflate (open_type.BaseType);
				state &= ~StateFlags.PendingBaseTypeInflate;
			}

			if (onlyTypes) {
				sta…