internal SourceCustomEventSymbol(SourceMemberContainerTypeSymbol containingType, Binder binder, EventDeclarationSyntax syntax, DiagnosticBag diagnostics) :
            base(containingType, syntax, syntax.Modifiers, syntax.ExplicitInterfaceSpecifier, syntax.Identifier, diagnostics)
        {
            ExplicitInterfaceSpecifierSyntax interfaceSpecifier = syntax.ExplicitInterfaceSpecifier;
            SyntaxToken nameToken = syntax.Identifier;
            bool        isExplicitInterfaceImplementation = interfaceSpecifier != null;

            string aliasQualifierOpt;

            _name = ExplicitInterfaceHelpers.GetMemberNameAndInterfaceSymbol(binder, interfaceSpecifier, nameToken.ValueText, diagnostics, out _explicitInterfaceType, out aliasQualifierOpt);

            _type = BindEventType(binder, syntax.Type, diagnostics);

            var explicitlyImplementedEvent = this.FindExplicitlyImplementedEvent(_explicitInterfaceType, nameToken.ValueText, interfaceSpecifier, diagnostics);

            this.FindExplicitlyImplementedMemberVerification(explicitlyImplementedEvent, diagnostics);

            // The runtime will not treat the accessors of this event as overrides or implementations
            // of those of another event unless both the signatures and the custom modifiers match.
            // Hence, in the case of overrides and *explicit* implementations, we need to copy the custom
            // modifiers that are in the signatures of the overridden/implemented event accessors.
            // (From source, we know that there can only be one overridden/implemented event, so there
            // are no conflicts.)  This is unnecessary for implicit implementations because, if the custom
            // modifiers don't match, we'll insert bridge methods for the accessors (explicit implementations
            // that delegate to the implicit implementations) with the correct custom modifiers
            // (see SourceMemberContainerTypeSymbol.SynthesizeInterfaceMemberImplementation).

            // Note: we're checking if the syntax indicates explicit implementation rather,
            // than if explicitInterfaceType is null because we don't want to look for an
            // overridden event if this is supposed to be an explicit implementation.
            if (!isExplicitInterfaceImplementation)
            {
                // If this event is an override, we may need to copy custom modifiers from
                // the overridden event (so that the runtime will recognize it as an override).
                // We check for this case here, while we can still modify the parameters and
                // return type without losing the appearance of immutability.
                if (this.IsOverride)
                {
                    EventSymbol overriddenEvent = this.OverriddenEvent;
                    if ((object)overriddenEvent != null)
                    {
                        CopyEventCustomModifiers(overriddenEvent, ref _type, ContainingAssembly);
                    }
                }
            }
            else if ((object)explicitlyImplementedEvent != null)
            {
                CopyEventCustomModifiers(explicitlyImplementedEvent, ref _type, ContainingAssembly);
            }

            AccessorDeclarationSyntax addSyntax    = null;
            AccessorDeclarationSyntax removeSyntax = null;

            foreach (AccessorDeclarationSyntax accessor in syntax.AccessorList.Accessors)
            {
                switch (accessor.Kind())
                {
                case SyntaxKind.AddAccessorDeclaration:
                    if (addSyntax == null)
                    {
                        addSyntax = accessor;
                    }
                    else
                    {
                        diagnostics.Add(ErrorCode.ERR_DuplicateAccessor, accessor.Keyword.GetLocation());
                    }
                    break;

                case SyntaxKind.RemoveAccessorDeclaration:
                    if (removeSyntax == null)
                    {
                        removeSyntax = accessor;
                    }
                    else
                    {
                        diagnostics.Add(ErrorCode.ERR_DuplicateAccessor, accessor.Keyword.GetLocation());
                    }
                    break;

                case SyntaxKind.GetAccessorDeclaration:
                case SyntaxKind.SetAccessorDeclaration:
                    diagnostics.Add(ErrorCode.ERR_AddOrRemoveExpected, accessor.Keyword.GetLocation());
                    break;

                case SyntaxKind.UnknownAccessorDeclaration:
                    // Don't need to handle UnknownAccessorDeclaration.  An error will have
                    // already been produced for it in the parser.
                    break;

                default:
                    throw ExceptionUtilities.UnexpectedValue(accessor.Kind());
                }
            }

            _addMethod    = CreateAccessorSymbol(addSyntax, explicitlyImplementedEvent, aliasQualifierOpt, diagnostics);
            _removeMethod = CreateAccessorSymbol(removeSyntax, explicitlyImplementedEvent, aliasQualifierOpt, diagnostics);

            if (containingType.IsInterfaceType())
            {
                if (addSyntax == null && removeSyntax == null) //NOTE: AND - different error code produced if one is present
                {
                    // CONSIDER: we're matching dev10, but it would probably be more helpful to give
                    // an error like ERR_EventPropertyInInterface.
                    diagnostics.Add(ErrorCode.ERR_EventNeedsBothAccessors, this.Locations[0], this);
                }
            }
            else
            {
                if (addSyntax == null || removeSyntax == null)
                {
                    diagnostics.Add(ErrorCode.ERR_EventNeedsBothAccessors, this.Locations[0], this);
                }
            }

            _explicitInterfaceImplementations =
                (object)explicitlyImplementedEvent == null ?
                ImmutableArray <EventSymbol> .Empty :
                ImmutableArray.Create <EventSymbol>(explicitlyImplementedEvent);
        }
        internal SourceCustomEventSymbol(SourceMemberContainerTypeSymbol containingType, Binder binder, EventDeclarationSyntax syntax, DiagnosticBag diagnostics) :
            base(containingType, syntax, syntax.Modifiers, syntax.ExplicitInterfaceSpecifier, syntax.Identifier, diagnostics)
        {
            ExplicitInterfaceSpecifierSyntax interfaceSpecifier = syntax.ExplicitInterfaceSpecifier;
            SyntaxToken nameToken = syntax.Identifier;
            bool isExplicitInterfaceImplementation = interfaceSpecifier != null;

            string aliasQualifierOpt;
            _name = ExplicitInterfaceHelpers.GetMemberNameAndInterfaceSymbol(binder, interfaceSpecifier, nameToken.ValueText, diagnostics, out _explicitInterfaceType, out aliasQualifierOpt);

            _type = BindEventType(binder, syntax.Type, diagnostics);

            var explicitlyImplementedEvent = this.FindExplicitlyImplementedEvent(_explicitInterfaceType, nameToken.ValueText, interfaceSpecifier, diagnostics);

            // The runtime will not treat the accessors of this event as overrides or implementations
            // of those of another event unless both the signatures and the custom modifiers match.
            // Hence, in the case of overrides and *explicit* implementations, we need to copy the custom
            // modifiers that are in the signatures of the overridden/implemented event accessors.
            // (From source, we know that there can only be one overridden/implemented event, so there
            // are no conflicts.)  This is unnecessary for implicit implementations because, if the custom
            // modifiers don't match, we'll insert bridge methods for the accessors (explicit implementations 
            // that delegate to the implicit implementations) with the correct custom modifiers
            // (see SourceNamedTypeSymbol.ImplementInterfaceMember).

            // Note: we're checking if the syntax indicates explicit implementation rather,
            // than if explicitInterfaceType is null because we don't want to look for an
            // overridden event if this is supposed to be an explicit implementation.
            if (!isExplicitInterfaceImplementation)
            {
                // If this event is an override, we may need to copy custom modifiers from
                // the overridden event (so that the runtime will recognize it as an override).
                // We check for this case here, while we can still modify the parameters and
                // return type without losing the appearance of immutability.
                if (this.IsOverride)
                {
                    EventSymbol overriddenEvent = this.OverriddenEvent;
                    if ((object)overriddenEvent != null)
                    {
                        CopyEventCustomModifiers(overriddenEvent, ref _type, ContainingAssembly);
                    }
                }
            }
            else if ((object)explicitlyImplementedEvent != null)
            {
                CopyEventCustomModifiers(explicitlyImplementedEvent, ref _type, ContainingAssembly);
            }

            AccessorDeclarationSyntax addSyntax = null;
            AccessorDeclarationSyntax removeSyntax = null;
            foreach (AccessorDeclarationSyntax accessor in syntax.AccessorList.Accessors)
            {
                switch (accessor.Kind())
                {
                    case SyntaxKind.AddAccessorDeclaration:
                        if (addSyntax == null || addSyntax.Keyword.Span.IsEmpty)
                        {
                            addSyntax = accessor;
                        }
                        break;
                    case SyntaxKind.RemoveAccessorDeclaration:
                        if (removeSyntax == null || removeSyntax.Keyword.Span.IsEmpty)
                        {
                            removeSyntax = accessor;
                        }
                        break;
                }
            }

            _addMethod = CreateAccessorSymbol(addSyntax, explicitlyImplementedEvent, aliasQualifierOpt, diagnostics);
            _removeMethod = CreateAccessorSymbol(removeSyntax, explicitlyImplementedEvent, aliasQualifierOpt, diagnostics);

            if (containingType.IsInterfaceType())
            {
                if (addSyntax == null && removeSyntax == null) //NOTE: AND - different error code produced if one is present
                {
                    // CONSIDER: we're matching dev10, but it would probably be more helpful to give
                    // an error like ERR_EventPropertyInInterface.
                    diagnostics.Add(ErrorCode.ERR_EventNeedsBothAccessors, this.Locations[0], this);
                }
            }
            else
            {
                if (addSyntax == null || removeSyntax == null)
                {
                    diagnostics.Add(ErrorCode.ERR_EventNeedsBothAccessors, this.Locations[0], this);
                }
            }

            _explicitInterfaceImplementations =
                (object)explicitlyImplementedEvent == null ?
                    ImmutableArray<EventSymbol>.Empty :
                    ImmutableArray.Create<EventSymbol>(explicitlyImplementedEvent);
        }