source: trunk/HeuristicLab.ExtLibs/HeuristicLab.NRefactory/5.5.0/NRefactory.CSharp-5.5.0/Parser/mcs/delegate.cs @ 15682

//
// delegate.cs: Delegate Handler
//
// Authors:
//     Ravi Pratap (ravi@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 Ximian, Inc (http://www.ximian.com)
// Copyright 2003-2009 Novell, Inc (http://www.novell.com)
// Copyright 2011 Xamarin Inc
//

using System;

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

namespace Mono.CSharp {

  //
  // Delegate container implementation
  //
  public class Delegate : TypeDefinition, IParametersMember
  {
    public FullNamedExpression ReturnType;
    readonly ParametersCompiled parameters;

    Constructor Constructor;
    Method InvokeBuilder;
    Method BeginInvokeBuilder;
    Method EndInvokeBuilder;

    static readonly string[] attribute_targets = new string [] { "type", "return" };

    public static readonly string InvokeMethodName = "Invoke";
    
    Expression instance_expr;
    ReturnParameter return_attributes;

    const Modifiers MethodModifiers = Modifiers.PUBLIC | Modifiers.VIRTUAL;

    const Modifiers AllowedModifiers =
      Modifiers.NEW |
      Modifiers.PUBLIC |
      Modifiers.PROTECTED |
      Modifiers.INTERNAL |
      Modifiers.UNSAFE |
      Modifiers.PRIVATE;

    public Delegate (TypeContainer parent, FullNamedExpression type, Modifiers mod_flags, MemberName name, ParametersCompiled param_list,
         Attributes attrs)
      : base (parent, name, attrs, MemberKind.Delegate)

    {
      this.ReturnType = type;
      ModFlags        = ModifiersExtensions.Check (AllowedModifiers, mod_flags,
                 IsTopLevel ? Modifiers.INTERNAL :
                 Modifiers.PRIVATE, name.Location, Report);
      parameters      = param_list;
      spec = new TypeSpec (Kind, null, this, null, ModFlags | Modifiers.SEALED);
    }

    #region Properties
    public TypeSpec MemberType {
      get {
        return ReturnType.Type;
      }
    }

    public AParametersCollection Parameters {
      get {
        return parameters;
      }
    }

    public FullNamedExpression TypExpression {
      get {
        return ReturnType;
      }
    }

    #endregion

    public override void Accept (StructuralVisitor visitor)
    {
      visitor.Visit (this);
    }

    public override void ApplyAttributeBuilder (Attribute a, MethodSpec ctor, byte[] cdata, PredefinedAttributes pa)
    {
      if (a.Target == AttributeTargets.ReturnValue) {
        if (return_attributes == null)
          return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);

        return_attributes.ApplyAttributeBuilder (a, ctor, cdata, pa);
        return;
      }

      base.ApplyAttributeBuilder (a, ctor, cdata, pa);
    }

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

    protected override bool DoDefineMembers ()
    {
      var builtin_types = Compiler.BuiltinTypes;

      var ctor_parameters = ParametersCompiled.CreateFullyResolved (
        new [] {
          new Parameter (new TypeExpression (builtin_types.Object, Location), "object", Parameter.Modifier.NONE, null, Location),
          new Parameter (new TypeExpression (builtin_types.IntPtr, Location), "method", Parameter.Modifier.NONE, null, Location)
        },
        new [] {
          builtin_types.Object,
          builtin_types.IntPtr
        }
      );

      Constructor = new Constructor (this, Constructor.ConstructorName,
        Modifiers.PUBLIC, null, ctor_parameters, Location);
      Constructor.Define ();

      //
      // Here the various methods like Invoke, BeginInvoke etc are defined
      //
      // First, call the `out of band' special method for
      // defining recursively any types we need:
      //
      var p = parameters;

      if (!p.Resolve (this))
        return false;

      //
      // Invoke method
      //

      // Check accessibility
      foreach (var partype in p.Types) {
        if (!IsAccessibleAs (partype)) {
          Report.SymbolRelatedToPreviousError (partype);
          Report.Error (59, Location,
            "Inconsistent accessibility: parameter type `{0}' is less accessible than delegate `{1}'",
            partype.GetSignatureForError (), GetSignatureForError ());
        }
      }

      var ret_type = ReturnType.ResolveAsType (this);
      if (ret_type == null)
        return false;

      //
      // We don't have to check any others because they are all
      // guaranteed to be accessible - they are standard types.
      //
      if (!IsAccessibleAs (ret_type)) {
        Report.SymbolRelatedToPreviousError (ret_type);
        Report.Error (58, Location,
              "Inconsistent accessibility: return type `" +
              ret_type.GetSignatureForError () + "' is less " +
              "accessible than delegate `" + GetSignatureForError () + "'");
        return false;
      }

      CheckProtectedModifier ();

      if (Compiler.Settings.StdLib && ret_type.IsSpecialRuntimeType) {
        Method.Error1599 (Location, ret_type, Report);
        return false;
      }

      VarianceDecl.CheckTypeVariance (ret_type, Variance.Covariant, this);

      var resolved_rt = new TypeExpression (ret_type, Location);
      InvokeBuilder = new Method (this, resolved_rt, MethodModifiers, new MemberName (InvokeMethodName), p, null);
      InvokeBuilder.Define ();

      //
      // Don't emit async method for compiler generated delegates (e.g. dynamic site containers)
      //
      if (!IsCompilerGenerated) {
        DefineAsyncMethods (resolved_rt);
      }

      return true;
    }

    void DefineAsyncMethods (TypeExpression returnType)
    {
      var iasync_result = Module.PredefinedTypes.IAsyncResult;
      var async_callback = Module.PredefinedTypes.AsyncCallback;

      //
      // It's ok when async types don't exist, the delegate will have Invoke method only
      //
      if (!iasync_result.Define () || !async_callback.Define ())
        return;

      //
      // BeginInvoke
      //
      ParametersCompiled async_parameters;
      if (Parameters.Count == 0) {
        async_parameters = ParametersCompiled.EmptyReadOnlyParameters;
      } else {
        var compiled = new Parameter[Parameters.Count];
        for (int i = 0; i < compiled.Length; ++i) {
          var p = parameters[i];
          compiled[i] = new Parameter (new TypeExpression (parameters.Types[i], Location),
            p.Name,
            p.ModFlags & Parameter.Modifier.RefOutMask,
            p.OptAttributes == null ? null : p.OptAttributes.Clone (), Location);
        }

        async_parameters = new ParametersCompiled (compiled);
      }

      async_parameters = ParametersCompiled.MergeGenerated (Compiler, async_parameters, false,
        new Parameter[] {
          new Parameter (new TypeExpression (async_callback.TypeSpec, Location), "callback", Parameter.Modifier.NONE, null, Location),
          new Parameter (new TypeExpression (Compiler.BuiltinTypes.Object, Location), "object", Parameter.Modifier.NONE, null, Location)
        },
        new [] {
          async_callback.TypeSpec,
          Compiler.BuiltinTypes.Object
        }
      );

      BeginInvokeBuilder = new Method (this,
        new TypeExpression (iasync_result.TypeSpec, Location), MethodModifiers,
        new MemberName ("BeginInvoke"), async_parameters, null);
      BeginInvokeBuilder.Define ();

      //
      // EndInvoke is a bit more interesting, all the parameters labeled as
      // out or ref have to be duplicated here.
      //

      //
      // Define parameters, and count out/ref parameters
      //
      ParametersCompiled end_parameters;
      int out_params = 0;

      foreach (Parameter p in Parameters.FixedParameters) {
        if ((p.ModFlags & Parameter.Modifier.RefOutMask) != 0)
          ++out_params;
      }

      if (out_params > 0) {
        Parameter[] end_params = new Parameter[out_params];

        int param = 0;
        for (int i = 0; i < Parameters.FixedParameters.Length; ++i) {
          Parameter p = parameters [i];
          if ((p.ModFlags & Parameter.Modifier.RefOutMask) == 0)
            continue;

          end_params [param++] = new Parameter (new TypeExpression (p.Type, Location),
            p.Name,
            p.ModFlags & Parameter.Modifier.RefOutMask,
            p.OptAttributes == null ? null : p.OptAttributes.Clone (), Location);
        }

        end_parameters = new ParametersCompiled (end_params);
      } else {
        end_parameters = ParametersCompiled.EmptyReadOnlyParameters;
      }

      end_parameters = ParametersCompiled.MergeGenerated (Compiler, end_parameters, false,
        new Parameter (
          new TypeExpression (iasync_result.TypeSpec, Location),
          "result", Parameter.Modifier.NONE, null, Location),
        iasync_result.TypeSpec);

      //
      // Create method, define parameters, register parameters with type system
      //
      EndInvokeBuilder = new Method (this, returnType, MethodModifiers, new MemberName ("EndInvoke"), end_parameters, null);
      EndInvokeBuilder.Define ();
    }

    public override void PrepareEmit ()
    {
      if (!Parameters.IsEmpty) {
        parameters.ResolveDefaultValues (this);
      }

      InvokeBuilder.PrepareEmit ();
      if (BeginInvokeBuilder != null) {
        BeginInvokeBuilder.PrepareEmit ();
        EndInvokeBuilder.PrepareEmit ();
      }
    }

    public override void Emit ()
    {
      base.Emit ();

      if (ReturnType.Type != null) {
        if (ReturnType.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
          return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);
          Module.PredefinedAttributes.Dynamic.EmitAttribute (return_attributes.Builder);
        } else if (ReturnType.Type.HasDynamicElement) {
          return_attributes = new ReturnParameter (this, InvokeBuilder.MethodBuilder, Location);
          Module.PredefinedAttributes.Dynamic.EmitAttribute (return_attributes.Builder, ReturnType.Type, Location);
        }

        ConstraintChecker.Check (this, ReturnType.Type, ReturnType.Location);
      }

      Constructor.ParameterInfo.ApplyAttributes (this, Constructor.ConstructorBuilder);
      Constructor.ConstructorBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);

      parameters.CheckConstraints (this);
      parameters.ApplyAttributes (this, InvokeBuilder.MethodBuilder);
      InvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);

      if (BeginInvokeBuilder != null) {
        BeginInvokeBuilder.ParameterInfo.ApplyAttributes (this, BeginInvokeBuilder.MethodBuilder);
        EndInvokeBuilder.ParameterInfo.ApplyAttributes (this, EndInvokeBuilder.MethodBuilder);

        BeginInvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
        EndInvokeBuilder.MethodBuilder.SetImplementationFlags (MethodImplAttributes.Runtime);
      }
    }

    protected override TypeSpec[] ResolveBaseTypes (out FullNamedExpression base_class)
    {
      base_type = Compiler.BuiltinTypes.MulticastDelegate;
      base_class = null;
      return null;
    }

    protected override TypeAttributes TypeAttr {
      get {
        return base.TypeAttr | TypeAttributes.Class | TypeAttributes.Sealed;
      }
    }

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

    //TODO: duplicate
    protected override bool VerifyClsCompliance ()
    {
      if (!base.VerifyClsCompliance ()) {
        return false;
      }

      parameters.VerifyClsCompliance (this);

      if (!InvokeBuilder.MemberType.IsCLSCompliant ()) {
        Report.Warning (3002, 1, Location, "Return type of `{0}' is not CLS-compliant",
          GetSignatureForError ());
      }
      return true;
    }


    public static MethodSpec GetConstructor (TypeSpec delType)
    {
      var ctor = MemberCache.FindMember (delType, MemberFilter.Constructor (null), BindingRestriction.DeclaredOnly);
      return (MethodSpec) ctor;
    }

    //
    // Returns the "Invoke" from a delegate type
    //
    public static MethodSpec GetInvokeMethod (TypeSpec delType)
    {
      var invoke = MemberCache.FindMember (delType,
        MemberFilter.Method (InvokeMethodName, 0, null, null),
        BindingRestriction.DeclaredOnly);

      return (MethodSpec) invoke;
    }

    public static AParametersCollection GetParameters (TypeSpec delType)
    {
      var invoke_mb = GetInvokeMethod (delType);
      return invoke_mb.Parameters;
    }

    //
    // 15.2 Delegate compatibility
    //
    public static bool IsTypeCovariant (ResolveContext rc, TypeSpec a, TypeSpec b)
    {
      //
      // For each value parameter (a parameter with no ref or out modifier), an 
      // identity conversion or implicit reference conversion exists from the
      // parameter type in D to the corresponding parameter type in M
      //
      if (a == b)
        return true;

      if (rc.Module.Compiler.Settings.Version == LanguageVersion.ISO_1)
        return false;

      if (a.IsGenericParameter && b.IsGenericParameter)
        return a == b;

      return Convert.ImplicitReferenceConversionExists (a, b);
    }

    public static string FullDelegateDesc (MethodSpec invoke_method)
    {
      return TypeManager.GetFullNameSignature (invoke_method).Replace (".Invoke", "");
    }
    
    public Expression InstanceExpression {
      get {
        return instance_expr;
      }
      set {
        instance_expr = value;
      }
    }
  }

  //
  // Base class for `NewDelegate' and `ImplicitDelegateCreation'
  //
  public abstract class DelegateCreation : Expression, OverloadResolver.IErrorHandler
  {
    bool conditional_access_receiver;
    protected MethodSpec constructor_method;
    protected MethodGroupExpr method_group;

    public bool AllowSpecialMethodsInvocation { get; set; }

    public override bool ContainsEmitWithAwait ()
    {
      var instance = method_group.InstanceExpression;
      return instance != null && instance.ContainsEmitWithAwait ();
    }

    public static Arguments CreateDelegateMethodArguments (ResolveContext rc, AParametersCollection pd, TypeSpec[] types, Location loc)
    {
      Arguments delegate_arguments = new Arguments (pd.Count);
      for (int i = 0; i < pd.Count; ++i) {
        Argument.AType atype_modifier;
        switch (pd.FixedParameters [i].ModFlags & Parameter.Modifier.RefOutMask) {
        case Parameter.Modifier.REF:
          atype_modifier = Argument.AType.Ref;
          break;
        case Parameter.Modifier.OUT:
          atype_modifier = Argument.AType.Out;
          break;
        default:
          atype_modifier = 0;
          break;
        }

        var ptype = types[i];
        if (ptype.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
          ptype = rc.BuiltinTypes.Object;

        delegate_arguments.Add (new Argument (new TypeExpression (ptype, loc), atype_modifier));
      }

      return delegate_arguments;
    }

    public override Expression CreateExpressionTree (ResolveContext ec)
    {
      MemberAccess ma = new MemberAccess (new MemberAccess (new QualifiedAliasMember ("global", "System", loc), "Delegate", loc), "CreateDelegate", loc);

      Arguments args = new Arguments (3);
      args.Add (new Argument (new TypeOf (type, loc)));

      if (method_group.InstanceExpression == null)
        args.Add (new Argument (new NullLiteral (loc)));
      else
        args.Add (new Argument (method_group.InstanceExpression));

      args.Add (new Argument (method_group.CreateExpressionTree (ec)));
      Expression e = new Invocation (ma, args).Resolve (ec);
      if (e == null)
        return null;

      e = Convert.ExplicitConversion (ec, e, type, loc);
      if (e == null)
        return null;

      return e.CreateExpressionTree (ec);
    }

    protected override Expression DoResolve (ResolveContext ec)
    {
      constructor_method = Delegate.GetConstructor (type);

      var invoke_method = Delegate.GetInvokeMethod (type);

      if (!ec.HasSet (ResolveContext.Options.ConditionalAccessReceiver)) {
        if (method_group.HasConditionalAccess ()) {
          conditional_access_receiver = true;
          ec.Set (ResolveContext.Options.ConditionalAccessReceiver);
        }
      }

      Arguments arguments = CreateDelegateMethodArguments (ec, invoke_method.Parameters, invoke_method.Parameters.Types, loc);
      method_group = method_group.OverloadResolve (ec, ref arguments, this, OverloadResolver.Restrictions.CovariantDelegate);

      if (conditional_access_receiver)
        ec.With (ResolveContext.Options.ConditionalAccessReceiver, false);

      if (method_group == null)
        return null;

      var delegate_method = method_group.BestCandidate;
      
      if (delegate_method.DeclaringType.IsNullableType) {
        ec.Report.Error (1728, loc, "Cannot create delegate from method `{0}' because it is a member of System.Nullable<T> type",
          delegate_method.GetSignatureForError ());
        return null;
      }   
      
      if (!AllowSpecialMethodsInvocation)
        Invocation.IsSpecialMethodInvocation (ec, delegate_method, loc);

      ExtensionMethodGroupExpr emg = method_group as ExtensionMethodGroupExpr;
      if (emg != null) {
        method_group.InstanceExpression = emg.ExtensionExpression;
        TypeSpec e_type = emg.ExtensionExpression.Type;
        if (TypeSpec.IsValueType (e_type)) {
          ec.Report.Error (1113, loc, "Extension method `{0}' of value type `{1}' cannot be used to create delegates",
            delegate_method.GetSignatureForError (), e_type.GetSignatureForError ());
        }
      }

      TypeSpec rt = method_group.BestCandidateReturnType;
      if (rt.BuiltinType == BuiltinTypeSpec.Type.Dynamic)
        rt = ec.BuiltinTypes.Object;

      if (!Delegate.IsTypeCovariant (ec, rt, invoke_method.ReturnType)) {
        Expression ret_expr = new TypeExpression (delegate_method.ReturnType, loc);
        Error_ConversionFailed (ec, delegate_method, ret_expr);
      }

      if (method_group.IsConditionallyExcluded) {
        ec.Report.SymbolRelatedToPreviousError (delegate_method);
        MethodOrOperator m = delegate_method.MemberDefinition as MethodOrOperator;
        if (m != null && m.IsPartialDefinition) {
          ec.Report.Error (762, loc, "Cannot create delegate from partial method declaration `{0}'",
            delegate_method.GetSignatureForError ());
        } else {
          ec.Report.Error (1618, loc, "Cannot create delegate with `{0}' because it has a Conditional attribute",
            TypeManager.CSharpSignature (delegate_method));
        }
      }

      var expr = method_group.InstanceExpression;
      if (expr != null && (expr.Type.IsGenericParameter || !TypeSpec.IsReferenceType (expr.Type)))
        method_group.InstanceExpression = new BoxedCast (expr, ec.BuiltinTypes.Object);

      eclass = ExprClass.Value;
      return this;
    }
    
    public override void Emit (EmitContext ec)
    {
      if (conditional_access_receiver)
        ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());

      if (method_group.InstanceExpression == null) {
        ec.EmitNull ();
      } else {
        var ie = new InstanceEmitter (method_group.InstanceExpression, false);
        ie.Emit (ec, method_group.ConditionalAccess);
      }

      var delegate_method = method_group.BestCandidate;

      // Any delegate must be sealed
      if (!delegate_method.DeclaringType.IsDelegate && delegate_method.IsVirtual && !method_group.IsBase) {
        ec.Emit (OpCodes.Dup);
        ec.Emit (OpCodes.Ldvirtftn, delegate_method);
      } else {
        ec.Emit (OpCodes.Ldftn, delegate_method);
      }

      ec.Emit (OpCodes.Newobj, constructor_method);

      if (conditional_access_receiver)
        ec.CloseConditionalAccess (null);
    }

    public override void FlowAnalysis (FlowAnalysisContext fc)
    {
      base.FlowAnalysis (fc);
      method_group.FlowAnalysis (fc);

      if (conditional_access_receiver)
        fc.ConditionalAccessEnd ();
    }

    void Error_ConversionFailed (ResolveContext ec, MethodSpec method, Expression return_type)
    {
      var invoke_method = Delegate.GetInvokeMethod (type);
      string member_name = method_group.InstanceExpression != null ?
        Delegate.FullDelegateDesc (method) :
        TypeManager.GetFullNameSignature (method);

      ec.Report.SymbolRelatedToPreviousError (type);
      ec.Report.SymbolRelatedToPreviousError (method);
      if (ec.Module.Compiler.Settings.Version == LanguageVersion.ISO_1) {
        ec.Report.Error (410, loc, "A method or delegate `{0} {1}' parameters and return type must be same as delegate `{2} {3}' parameters and return type",
          method.ReturnType.GetSignatureForError (), member_name,
          invoke_method.ReturnType.GetSignatureForError (), Delegate.FullDelegateDesc (invoke_method));
        return;
      }

      if (return_type == null) {
        ec.Report.Error (123, loc, "A method or delegate `{0}' parameters do not match delegate `{1}' parameters",
          member_name, Delegate.FullDelegateDesc (invoke_method));
        return;
      }

      ec.Report.Error (407, loc, "A method or delegate `{0} {1}' return type does not match delegate `{2} {3}' return type",
        return_type.GetSignatureForError (), member_name,
        invoke_method.ReturnType.GetSignatureForError (), Delegate.FullDelegateDesc (invoke_method));
    }

    public static bool ImplicitStandardConversionExists (ResolveContext ec, MethodGroupExpr mg, TypeSpec target_type)
    {
//      if (target_type == TypeManager.delegate_type || target_type == TypeManager.multicast_delegate_type)
//        return false;

      var invoke = Delegate.GetInvokeMethod (target_type);

      Arguments arguments = CreateDelegateMethodArguments (ec, invoke.Parameters, invoke.Parameters.Types, mg.Location);
      return mg.OverloadResolve (ec, ref arguments, null, OverloadResolver.Restrictions.CovariantDelegate | OverloadResolver.Restrictions.ProbingOnly) != null;
    }

    #region IErrorHandler Members

    bool OverloadResolver.IErrorHandler.AmbiguousCandidates (ResolveContext ec, MemberSpec best, MemberSpec ambiguous)
    {
      return false;
    }

    bool OverloadResolver.IErrorHandler.ArgumentMismatch (ResolveContext rc, MemberSpec best, Argument arg, int index)
    {
      Error_ConversionFailed (rc, best as MethodSpec, null);
      return true;
    }

    bool OverloadResolver.IErrorHandler.NoArgumentMatch (ResolveContext rc, MemberSpec best)
    {
      Error_ConversionFailed (rc, best as MethodSpec, null);
      return true;
    }

    bool OverloadResolver.IErrorHandler.TypeInferenceFailed (ResolveContext rc, MemberSpec best)
    {
      return false;
    }

    #endregion
  }

  //
  // Created from the conversion code
  //
  public class ImplicitDelegateCreation : DelegateCreation
  {
    Field mg_cache;

    public ImplicitDelegateCreation (TypeSpec delegateType, MethodGroupExpr mg, Location loc)
    {
      type = delegateType;
      this.method_group = mg;
      this.loc = loc;
    }

    //
    // Returns true when type is MVAR or has MVAR reference
    //
    public static bool ContainsMethodTypeParameter (TypeSpec type)
    {
      var tps = type as TypeParameterSpec;
      if (tps != null)
        return tps.IsMethodOwned;

      var ec = type as ElementTypeSpec;
      if (ec != null)
        return ContainsMethodTypeParameter (ec.Element);

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

      if (type.IsNested)
        return ContainsMethodTypeParameter (type.DeclaringType);

      return false;
    }
    
    bool HasMvar ()
    {
      if (ContainsMethodTypeParameter (type))
        return false;

      var best = method_group.BestCandidate;
      if (ContainsMethodTypeParameter (best.DeclaringType))
        return false;

      if (best.TypeArguments != null) {
        foreach (var ta in best.TypeArguments) {
          if (ContainsMethodTypeParameter (ta))
            return false;
        }
      }

      return true;
    }

    protected override Expression DoResolve (ResolveContext ec)
    {
      var expr = base.DoResolve (ec);
      if (expr == null)
        return ErrorExpression.Instance;

      if (ec.IsInProbingMode)
        return expr;

      //
      // Cache any static delegate creation
      //
      if (method_group.InstanceExpression != null)
        return expr;

      //
      // Cannot easily cache types with MVAR
      //
      if (!HasMvar ())
        return expr;

      //
      // Create type level cache for a delegate instance
      //
      var parent = ec.CurrentMemberDefinition.Parent.PartialContainer;
      int id = parent.MethodGroupsCounter++;

      mg_cache = new Field (parent, new TypeExpression (type, loc),
        Modifiers.STATIC | Modifiers.PRIVATE | Modifiers.COMPILER_GENERATED,
        new MemberName (CompilerGeneratedContainer.MakeName (null, "f", "mg$cache", id), loc), null);
      mg_cache.Define ();
      parent.AddField (mg_cache);

      return expr;
    }

    public override void Emit (EmitContext ec)
    {
      Label l_initialized = ec.DefineLabel ();

      if (mg_cache != null) {
        ec.Emit (OpCodes.Ldsfld, mg_cache.Spec);
        ec.Emit (OpCodes.Brtrue_S, l_initialized);
      }

      base.Emit (ec);

      if (mg_cache != null) {
        ec.Emit (OpCodes.Stsfld, mg_cache.Spec);
        ec.MarkLabel (l_initialized);
        ec.Emit (OpCodes.Ldsfld, mg_cache.Spec);
      }
    }
  }
  
  //
  // A delegate-creation-expression, invoked from the `New' class 
  //
  public class NewDelegate : DelegateCreation
  {
    public Arguments Arguments;

    //
    // This constructor is invoked from the `New' expression
    //
    public NewDelegate (TypeSpec type, Arguments Arguments, Location loc)
    {
      this.type = type;
      this.Arguments = Arguments;
      this.loc  = loc; 
    }

    protected override Expression DoResolve (ResolveContext ec)
    {
      if (Arguments == null || Arguments.Count != 1) {
        ec.Report.Error (149, loc, "Method name expected");
        return null;
      }

      Argument a = Arguments [0];
      if (!a.ResolveMethodGroup (ec))
        return null;

      Expression e = a.Expr;

      AnonymousMethodExpression ame = e as AnonymousMethodExpression;
      if (ame != null && ec.Module.Compiler.Settings.Version != LanguageVersion.ISO_1) {
        e = ame.Compatible (ec, type);
        if (e == null)
          return null;

        return e.Resolve (ec);
      }

      method_group = e as MethodGroupExpr;
      if (method_group == null) {
        if (e.Type.BuiltinType == BuiltinTypeSpec.Type.Dynamic) {
          e = Convert.ImplicitConversionRequired (ec, e, type, loc);
        } else if (!e.Type.IsDelegate) {
          e.Error_UnexpectedKind (ec, ResolveFlags.MethodGroup | ResolveFlags.Type, loc);
          return null;
        }

        //
        // An argument is not a method but another delegate
        //
        method_group = new MethodGroupExpr (Delegate.GetInvokeMethod (e.Type), e.Type, loc);
        method_group.InstanceExpression = e;
      }

      return base.DoResolve (ec);
    }
  }

  //
  // Invocation converted to delegate Invoke call
  //
  class DelegateInvocation : ExpressionStatement
  {
    readonly Expression InstanceExpr;
    readonly bool conditionalAccessReceiver;
    Arguments arguments;
    MethodSpec method;
    
    public DelegateInvocation (Expression instance_expr, Arguments args, bool conditionalAccessReceiver, Location loc)
    {
      this.InstanceExpr = instance_expr;
      this.arguments = args;
      this.conditionalAccessReceiver = conditionalAccessReceiver;
      this.loc = loc;
    }

    public override bool ContainsEmitWithAwait ()
    {
      return InstanceExpr.ContainsEmitWithAwait () || (arguments != null && arguments.ContainsEmitWithAwait ());
    }
    
    public override Expression CreateExpressionTree (ResolveContext ec)
    {
      Arguments args = Arguments.CreateForExpressionTree (ec, this.arguments,
        InstanceExpr.CreateExpressionTree (ec));

      return CreateExpressionFactoryCall (ec, "Invoke", args);
    }

    public override void FlowAnalysis (FlowAnalysisContext fc)
    {
      InstanceExpr.FlowAnalysis (fc);
      if (arguments != null)
        arguments.FlowAnalysis (fc);
    }

    protected override Expression DoResolve (ResolveContext ec)
    {   
      TypeSpec del_type = InstanceExpr.Type;
      if (del_type == null)
        return null;

      //
      // Do only core overload resolution the rest of the checks has been
      // done on primary expression
      //
      method = Delegate.GetInvokeMethod (del_type);
      var res = new OverloadResolver (new MemberSpec[] { method }, OverloadResolver.Restrictions.DelegateInvoke, loc);
      var valid = res.ResolveMember<MethodSpec> (ec, ref arguments);
      if (valid == null && !res.BestCandidateIsDynamic)
        return null;

      type = method.ReturnType;
      if (conditionalAccessReceiver)
        type = LiftMemberType (ec, type);

      eclass = ExprClass.Value;
      return this;
    }

    public override void Emit (EmitContext ec)
    {
      if (conditionalAccessReceiver) {
        ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ());
      }

      //
      // Invocation on delegates call the virtual Invoke member
      // so we are always `instance' calls
      //
      var call = new CallEmitter ();
      call.InstanceExpression = InstanceExpr;
      call.Emit (ec, method, arguments, loc);

      if (conditionalAccessReceiver)
        ec.CloseConditionalAccess (type.IsNullableType && type !=  method.ReturnType ? type : null);
    }

    public override void EmitStatement (EmitContext ec)
    {
      if (conditionalAccessReceiver) {
        ec.ConditionalAccess = new ConditionalAccessContext (type, ec.DefineLabel ()) {
          Statement = true
        };
      }

      var call = new CallEmitter ();
      call.InstanceExpression = InstanceExpr;
      call.EmitStatement (ec, method, arguments, loc);

      if (conditionalAccessReceiver)
        ec.CloseConditionalAccess (null);
    }

    public override System.Linq.Expressions.Expression MakeExpression (BuilderContext ctx)
    {
      return Invocation.MakeExpression (ctx, InstanceExpr, method, arguments);
    }
  }
}