public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            var document = context.Document;
            var position = context.Position;
            var cancellationToken = context.CancellationToken;

            var showSpeculativeT = await document.IsValidContextForDocumentOrLinkedDocumentsAsync(
                (doc, ct) => ShouldShowSpeculativeTCompletionItemAsync(doc, position, ct),
                cancellationToken).ConfigureAwait(false);

            if (showSpeculativeT)
            {
                var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
                var filterSpan = this.GetTextChangeSpan(text, position);

                const string T = nameof(T);
                context.AddItem(new CompletionItem(this, T, filterSpan, descriptionFactory: null, glyph: Glyph.TypeParameter));
            }
        }
        public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            var document = context.Document;
            var position = context.Position;
            var cancellationToken = context.CancellationToken;

            var tree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);

            if (tree.IsInNonUserCode(position, cancellationToken))
            {
                return;
            }

            var targetToken = tree
                .FindTokenOnLeftOfPosition(position, cancellationToken)
                .GetPreviousTokenIfTouchingWord(position);

            if (targetToken.IsKind(SyntaxKind.AliasKeyword) && targetToken.Parent.IsKind(SyntaxKind.ExternAliasDirective))
            {
                var compilation = await document.Project.GetCompilationAsync(cancellationToken).ConfigureAwait(false);
                var aliases = compilation.ExternalReferences.SelectMany(r => r.Properties.Aliases).ToSet();

                if (aliases.Any())
                {
                    var root = await tree.GetRootAsync(cancellationToken).ConfigureAwait(false);
                    var usedAliases = root.ChildNodes().OfType<ExternAliasDirectiveSyntax>()
                        .Where(e => !e.Identifier.IsMissing)
                        .Select(e => e.Identifier.ValueText);

                    aliases.RemoveRange(usedAliases);
                    aliases.Remove(MetadataReferenceProperties.GlobalAlias);

                    var text = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
                    var filterSpan = CompletionUtilities.GetTextChangeSpan(text, position);

                    foreach (var alias in aliases)
                    {
                        context.AddItem(new CompletionItem(this, alias, filterSpan, glyph: Glyph.Namespace));
                    }
                }
            }
        }
        public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            var document = context.Document;
            var position = context.Position;
            var cancellationToken = context.CancellationToken;

            // the provider might be invoked in non-interactive context:
            Workspace ws;
            SourceText sourceText = await document.GetTextAsync(cancellationToken).ConfigureAwait(false);
            if (Workspace.TryGetWorkspace(sourceText.Container, out ws))
            {
                var workspace = ws as InteractiveWorkspace;
                if (workspace != null)
                {
                    var window = workspace.Engine.CurrentWindow;
                    var tree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);

                    if (ShouldDisplayCommandCompletions(tree, position, cancellationToken))
                    {
                        var filterSpan = await this.GetTextChangeSpanAsync(document, position, cancellationToken).ConfigureAwait(false);

                        IInteractiveWindowCommands commands = window.GetInteractiveCommands();
                        if (commands != null)
                        {
                            foreach (var command in commands.GetCommands())
                            {
                                foreach (var commandName in command.Names)
                                {
                                    string completion = GetCompletionString(commandName);
                                    context.AddItem(new CompletionItem(
                                        this, completion, filterSpan, c => Task.FromResult(command.Description.ToSymbolDisplayParts()), glyph: Glyph.Intrinsic));
                                }
                            }
                        }
                    }
                }
            }
        }
        public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            var document = context.Document;
            var position = context.Position;
            var cancellationToken = context.CancellationToken;

            if (document != null && document.SourceCodeKind == SourceCodeKind.Interactive)
            {
                // the provider might be invoked in non-interactive context:
                Workspace ws;
                if (Workspace.TryGetWorkspace(document.GetTextAsync(cancellationToken).WaitAndGetResult(cancellationToken).Container, out ws))
                {
                    var workspace = ws as InteractiveWorkspace;
                    if (workspace != null)
                    {
                        var window = workspace.Engine.CurrentWindow;
                        var tree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);

                        if (tree.IsBeforeFirstToken(position, cancellationToken) &&
                            tree.IsPreProcessorKeywordContext(position, cancellationToken))
                        {
                            var filterSpan = await this.GetTextChangeSpanAsync(document, position, cancellationToken).ConfigureAwait(false);

                            IInteractiveWindowCommands commands = window.GetInteractiveCommands();
                            if (commands != null)
                            {
                                foreach (var command in commands.GetCommands())
                                {
                                    foreach (var commandName in command.Names)
                                    {
                                        context.AddItem(new CompletionItem(
                                            this, commandName, filterSpan, c => Task.FromResult(command.Description.ToSymbolDisplayParts()), glyph: Glyph.Intrinsic));
                                    }
                                }
                            }
                        }
                    }
                }
            }
        }
        public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            var document = context.Document;
            var position = context.Position;
            var options = context.Options;
            var cancellationToken = context.CancellationToken;

            var span = new TextSpan(position, length: 0);
            var semanticModel = await document.GetSemanticModelForSpanAsync(span, cancellationToken).ConfigureAwait(false);
            var syntaxTree = semanticModel.SyntaxTree;

            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
            var semanticFacts = document.GetLanguageService<ISemanticFactsService>();

            if (syntaxFacts.IsInNonUserCode(syntaxTree, position, cancellationToken) ||
                semanticFacts.IsPreProcessorDirectiveContext(semanticModel, position, cancellationToken))
            {
                return;
            }

            if (!syntaxTree.IsRightOfDotOrArrowOrColonColon(position, cancellationToken))
            {
                return;
            }

            var node = syntaxTree.FindTokenOnLeftOfPosition(position, cancellationToken)
                                 .GetPreviousTokenIfTouchingWord(position)
                                 .Parent;

            if (node.Kind() != SyntaxKind.ExplicitInterfaceSpecifier)
            {
                return;
            }

            // Bind the interface name which is to the left of the dot
            var name = ((ExplicitInterfaceSpecifierSyntax)node).Name;

            var symbol = semanticModel.GetSymbolInfo(name, cancellationToken).Symbol as ITypeSymbol;
            if (symbol?.TypeKind != TypeKind.Interface)
            {
                return;
            }

            var members = semanticModel.LookupSymbols(
                position: name.SpanStart,
                container: symbol)
                    .Where(s => !s.IsStatic)
                    .FilterToVisibleAndBrowsableSymbols(options.GetOption(CompletionOptions.HideAdvancedMembers, semanticModel.Language), semanticModel.Compilation);

            // We're going to create a entry for each one, including the signature
            var namePosition = name.SpanStart;

            var text = await syntaxTree.GetTextAsync(cancellationToken).ConfigureAwait(false);
            var textChangeSpan = CompletionUtilities.GetTextChangeSpan(text, position);

            foreach (var member in members)
            {
                var displayText = member.ToMinimalDisplayString(semanticModel, namePosition, s_signatureDisplayFormat);
                var insertionText = displayText;

                context.AddItem(new SymbolCompletionItem(
                    this,
                    displayText,
                    insertionText: insertionText,
                    filterSpan: textChangeSpan,
                    position: position,
                    symbols: new List<ISymbol> { member },
                    context: CSharpSyntaxContext.CreateContext(document.Project.Solution.Workspace, semanticModel, position, cancellationToken),
                    rules: ItemRules.Instance));
            }
        }
        public override async Task ProduceCompletionListAsync(CompletionListContext context)
        {
            try
            {
                var document = context.Document;
                var position = context.Position;
                var options = context.Options;
                var cancellationToken = context.CancellationToken;

                var tree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
                if (tree.IsInNonUserCode(position, cancellationToken))
                {
                    return;
                }

                var token = tree.FindTokenOnLeftOfPosition(position, cancellationToken);
                if (token.IsMandatoryNamedParameterPosition())
                {
                    return;
                }

                var typeInferenceService = document.GetLanguageService<ITypeInferenceService>();

                var span = new TextSpan(position, 0);
                var semanticModel = await document.GetSemanticModelForSpanAsync(span, cancellationToken).ConfigureAwait(false);
                var type = typeInferenceService.InferType(semanticModel, position,
                    objectAsDefault: true,
                    cancellationToken: cancellationToken);

                // If we have a Nullable<T>, unwrap it.
                if (type.OriginalDefinition.SpecialType == SpecialType.System_Nullable_T)
                {
                    type = type.GetTypeArguments().FirstOrDefault();

                    if (type == null)
                    {
                        return;
                    }
                }

                if (type.TypeKind != TypeKind.Enum)
                {
                    type = GetCompletionListType(type, semanticModel.GetEnclosingNamedType(position, cancellationToken), semanticModel.Compilation);
                    if (type == null)
                    {
                        return;
                    }
                }

                if (!type.IsEditorBrowsable(options.GetOption(CompletionOptions.HideAdvancedMembers, semanticModel.Language), semanticModel.Compilation))
                {
                    return;
                }

                // Does type have any aliases?
                ISymbol alias = await type.FindApplicableAlias(position, semanticModel, cancellationToken).ConfigureAwait(false);

                var displayService = document.GetLanguageService<ISymbolDisplayService>();
                var displayText = alias != null
                    ? alias.Name
                    : displayService.ToMinimalDisplayString(semanticModel, position, type);

                var workspace = document.Project.Solution.Workspace;
                var text = await semanticModel.SyntaxTree.GetTextAsync(cancellationToken).ConfigureAwait(false);
                var textChangeSpan = CompletionUtilities.GetTextChangeSpan(text, position);

                var item = new CompletionItem(
                    this,
                    displayText: displayText,
                    filterSpan: textChangeSpan,
                    descriptionFactory: CommonCompletionUtilities.CreateDescriptionFactory(workspace, semanticModel, position, alias ?? type),
                    glyph: (alias ?? type).GetGlyph(),
                    preselect: true,
                    rules: ItemRules.Instance);

                context.AddItem(item);
            }
            catch (Exception e) when (FatalError.ReportUnlessCanceled(e))
            {
                throw ExceptionUtilities.Unreachable;
            }
        }