/// <summary>
        /// A symbol requires a documentation comment if it was explicitly declared and
        /// will be visible outside the current assembly (ignoring InternalsVisibleTo).
        /// Exception: accessors do not require doc comments.
        /// </summary>
        private static bool RequiresDocumentationComment(Symbol symbol)
        {
            Debug.Assert((object)symbol != null);

            if (symbol.IsImplicitlyDeclared || symbol.IsAccessor())
            {
                return false;
            }

            while ((object)symbol != null)
            {
                switch (symbol.DeclaredAccessibility)
                {
                    case Accessibility.Public:
                    case Accessibility.Protected:
                    case Accessibility.ProtectedOrInternal:
                        symbol = symbol.ContainingType;
                        break;
                    default:
                        return false;
                }
            }

            return true;
        }
        /// <summary>
        /// Compile documentation comments on the symbol and write them to the stream if one is provided.
        /// </summary>
        public override void DefaultVisit(Symbol symbol)
        {
            _cancellationToken.ThrowIfCancellationRequested();

            if (symbol.IsImplicitlyDeclared || symbol.IsAccessor())
            {
                return;
            }

            if (_filterTree != null && !symbol.IsDefinedInSourceTree(_filterTree, _filterSpanWithinTree))
            {
                return;
            }

            bool isPartialMethodDefinitionPart = symbol.IsPartialDefinition(); // CONSIDER: ignore this if isForSingleSymbol?
            if (isPartialMethodDefinitionPart)
            {
                MethodSymbol implementationPart = ((MethodSymbol)symbol).PartialImplementationPart;
                if ((object)implementationPart != null)
                {
                    Visit(implementationPart);
                }
            }

            DocumentationMode maxDocumentationMode;
            ImmutableArray<DocumentationCommentTriviaSyntax> docCommentNodes;
            if (!TryGetDocumentationCommentNodes(symbol, out maxDocumentationMode, out docCommentNodes))
            {
                // If the XML in any of the doc comments is invalid, skip all further processing (for this symbol) and 
                // just write a comment saying that info was lost for this symbol.
                string message = ErrorFacts.GetMessage(MessageID.IDS_XMLIGNORED, CultureInfo.CurrentUICulture);
                WriteLine(string.Format(CultureInfo.CurrentUICulture, message, symbol.GetDocumentationCommentId()));
                return;
            }

            // If there are no doc comments, then no further work is required (other than to report a diagnostic if one is required).
            if (docCommentNodes.IsEmpty)
            {
                if (maxDocumentationMode >= DocumentationMode.Diagnose && RequiresDocumentationComment(symbol))
                {
                    // Report the error at a location in the tree that was parsing doc comments.
                    Location location = GetLocationInTreeReportingDocumentationCommentDiagnostics(symbol);
                    if (location != null)
                    {
                        _diagnostics.Add(ErrorCode.WRN_MissingXMLComment, location, symbol);
                    }
                }
                return;
            }

            _cancellationToken.ThrowIfCancellationRequested();

            bool reportParameterOrTypeParameterDiagnostics = GetLocationInTreeReportingDocumentationCommentDiagnostics(symbol) != null;

            string withUnprocessedIncludes;
            bool haveParseError;
            HashSet<TypeParameterSymbol> documentedTypeParameters;
            HashSet<ParameterSymbol> documentedParameters;
            ImmutableArray<CSharpSyntaxNode> includeElementNodes;
            if (!TryProcessDocumentationCommentTriviaNodes(
                    symbol,
                    isPartialMethodDefinitionPart,
                    docCommentNodes,
                    reportParameterOrTypeParameterDiagnostics,
                    out withUnprocessedIncludes,
                    out haveParseError,
                    out documentedTypeParameters,
                    out documentedParameters,
                    out includeElementNodes))
            {
                return;
            }

            if (haveParseError)
            {
                // If the XML in any of the doc comments is invalid, skip all further processing (for this symbol) and 
                // just write a comment saying that info was lost for this symbol.
                string message = ErrorFacts.GetMessage(MessageID.IDS_XMLIGNORED, CultureInfo.CurrentUICulture);
                WriteLine(string.Format(CultureInfo.CurrentUICulture, message, symbol.GetDocumentationCommentId()));
                return;
            }

            // If there are no include elements, then there's nothing to expand.
            if (!includeElementNodes.IsDefaultOrEmpty)
            {
                _cancellationToken.ThrowIfCancellationRequested();

                // NOTE: we are expanding include elements AFTER formatting the comment, since the included text is pure
                // XML, not XML mixed with documentation comment trivia (e.g. ///).  If we expanded them before formatting,
                // the formatting engine would have trouble determining what prefix to remove from each line.
                TextWriter expanderWriter = isPartialMethodDefinitionPart ? null : _writer; // Don't actually write partial method definition parts.
                IncludeElementExpander.ProcessIncludes(withUnprocessedIncludes, symbol, includeElementNodes,
                    _compilation, ref documentedParameters, ref documentedTypeParameters, ref _includedFileCache, expanderWriter, _diagnostics, _cancellationToken);
            }
            else if (_writer != null && !isPartialMethodDefinitionPart)
            {
                // CONSIDER: The output would look a little different if we ran the XDocument through an XmlWriter.  In particular, 
                // formatting inside tags (e.g. <__tag___attr__=__"value"__>) would be normalized.  Whitespace in elements would
                // (or should) not be affected.  If we decide that this difference matters, we can run the XDocument through an XmlWriter.
                // Otherwise, just writing out the string saves a bunch of processing and does a better job of preserving whitespace.
                Write(withUnprocessedIncludes);
            }

            if (reportParameterOrTypeParameterDiagnostics)
            {
                _cancellationToken.ThrowIfCancellationRequested();

                if (documentedParameters != null)
                {
                    foreach (ParameterSymbol parameter in GetParameters(symbol))
                    {
                        if (!documentedParameters.Contains(parameter))
                        {
                            Location location = parameter.Locations[0];
                            Debug.Assert(location.SourceTree.ReportDocumentationCommentDiagnostics()); //Should be the same tree as for the symbol.

                            // NOTE: parameter name, since the parameter would be displayed as just its type.
                            _diagnostics.Add(ErrorCode.WRN_MissingParamTag, location, parameter.Name, symbol);
                        }
                    }
                }

                if (documentedTypeParameters != null)
                {
                    foreach (TypeParameterSymbol typeParameter in GetTypeParameters(symbol))
                    {
                        if (!documentedTypeParameters.Contains(typeParameter))
                        {
                            Location location = typeParameter.Locations[0];
                            Debug.Assert(location.SourceTree.ReportDocumentationCommentDiagnostics()); //Should be the same tree as for the symbol.

                            _diagnostics.Add(ErrorCode.WRN_MissingTypeParamTag, location, typeParameter, symbol);
                        }
                    }
                }
            }
        }
        /// <returns>False if no further checks are required (because they would be cascading).</returns>
        private bool VisitTypeOrMember(Symbol symbol, Compliance compliance)
        {
            SymbolKind symbolKind = symbol.Kind;

            System.Diagnostics.Debug.Assert(
                symbolKind == SymbolKind.NamedType ||
                symbolKind == SymbolKind.Field ||
                symbolKind == SymbolKind.Property ||
                symbolKind == SymbolKind.Event ||
                symbolKind == SymbolKind.Method);
            System.Diagnostics.Debug.Assert(!symbol.IsAccessor());

            if (!CheckForDeclarationWithoutAssemblyDeclaration(symbol, compliance))
            {
                return false; // Don't cascade from this failure.
            }

            bool isCompliant = IsTrue(compliance);
            bool isAccessibleOutsideAssembly = IsAccessibleOutsideAssembly(symbol);

            if (isAccessibleOutsideAssembly)
            {
                if (isCompliant)
                {
                    CheckName(symbol);
                    CheckForCompliantWithinNonCompliant(symbol);
                    CheckReturnTypeCompliance(symbol);

                    if (symbol.Kind == SymbolKind.NamedType)
                    {
                        CheckMemberDistinctness((NamedTypeSymbol)symbol);
                    }
                }
                else if (GetDeclaredOrInheritedCompliance(symbol.ContainingAssembly) == Compliance.DeclaredTrue && IsTrue(GetInheritedCompliance(symbol)))
                {
                    CheckForNonCompliantAbstractMember(symbol);
                }
            }
            else if (IsDeclared(compliance))
            {
                this.AddDiagnostic(ErrorCode.WRN_CLS_MeaninglessOnPrivateType, symbol.Locations[0], symbol);
                return false; // Don't cascade from this failure.
            }

            if (isCompliant)
            {
                // Independent of accessibility.
                CheckForAttributeWithArrayArgument(symbol);
            }

            // These checks are independent of accessibility and compliance.
            if (symbolKind == SymbolKind.NamedType)
            {
                NamedTypeSymbol type = (NamedTypeSymbol)symbol;
                if (type.TypeKind == TypeKind.Delegate)
                {
                    MethodSymbol method = type.DelegateInvokeMethod;
                    CheckForMeaninglessOnParameter(method.Parameters);
                    CheckForMeaninglessOnReturn(method);
                }
            }
            else if (symbolKind == SymbolKind.Method)
            {
                MethodSymbol method = (MethodSymbol)symbol;
                CheckForMeaninglessOnParameter(method.Parameters);
                CheckForMeaninglessOnReturn(method);
            }
            else if (symbolKind == SymbolKind.Property)
            {
                PropertySymbol property = (PropertySymbol)symbol;
                CheckForMeaninglessOnParameter(property.Parameters);
            }

            // All checks that apply to inaccessible symbols are performed by this method.
            return isAccessibleOutsideAssembly;
        }
        /// <remarks>
        /// NOTE: Dev11 behavior - First, it ignores arity,
        /// which seems like a good way to disambiguate symbols (in particular,
        /// CLS Rule 43 says that the name includes backtick-arity).  Second, it
        /// does not consider two members with identical names (i.e. not differing
        /// in case) to collide.
        /// </remarks>
        private void CheckSymbolDistinctness(Symbol symbol, string symbolName, MultiDictionary<string, Symbol>.ValueSet sameNameSymbols)
        {
            Debug.Assert(sameNameSymbols.Count > 0);
            Debug.Assert(symbol.Name == symbolName);

            bool isMethodOrProperty = symbol.Kind == SymbolKind.Method || symbol.Kind == SymbolKind.Property;

            foreach (Symbol other in sameNameSymbols)
            {
                if (other.Name != symbolName && !(isMethodOrProperty && other.Kind == symbol.Kind))
                {
                    // TODO: Shouldn't we somehow reference the conflicting member?  Dev11 doesn't.
                    this.AddDiagnostic(ErrorCode.WRN_CLS_BadIdentifierCase, symbol.Locations[0], symbol);
                    return;
                }
            }

            if (!isMethodOrProperty)
            {
                return;
            }

            foreach (Symbol other in sameNameSymbols)
            {
                // Note: not checking accessor signatures, but checking accessor names.
                ErrorCode code;
                if (symbol.Kind == other.Kind &&
                    !symbol.IsAccessor() &&
                    !other.IsAccessor() &&
                    TryGetCollisionErrorCode(symbol, other, out code))
                {
                    this.AddDiagnostic(code, symbol.Locations[0], symbol);
                    return;
                }
                else if (other.Name != symbolName)
                {
                    // TODO: Shouldn't we somehow reference the conflicting member?  Dev11 doesn't.
                    this.AddDiagnostic(ErrorCode.WRN_CLS_BadIdentifierCase, symbol.Locations[0], symbol);
                    return;
                }
            }
        }
        /// <remarks>
        /// NOTE: Dev11 behavior - First, it ignores arity,
        /// which seems like a good way to disambiguate symbols (in particular,
        /// CLS Rule 43 says that the name includes backtick-arity).  Second, it
        /// does not consider two members with identical names (i.e. not differing
        /// in case) to collide.
        /// </remarks>
        private void CheckSymbolDistinctness(Symbol symbol, IEnumerable<Symbol> sameNameSymbols)
        {
            System.Diagnostics.Debug.Assert(sameNameSymbols != null);
            System.Diagnostics.Debug.Assert(System.Linq.Enumerable.Any(sameNameSymbols));

            bool isMethodOrProperty = symbol.Kind == SymbolKind.Method || symbol.Kind == SymbolKind.Property;

            foreach (Symbol other in sameNameSymbols)
            {
                if (other.Name != symbol.Name && !(isMethodOrProperty && other.Kind == symbol.Kind))
                {
                    // TODO: Shouldn't we somehow reference the conflicting member?  Dev11 doesn't.
                    this.AddDiagnostic(ErrorCode.WRN_CLS_BadIdentifierCase, symbol.Locations[0], symbol);
                    return;
                }
            }

            if (!isMethodOrProperty)
            {
                return;
            }

            foreach (Symbol other in sameNameSymbols)
            {
                // Note: not checking accessor signatures, but checking accessor names.
                ErrorCode code;
                if (symbol.Kind == other.Kind &&
                    !symbol.IsAccessor() &&
                    !other.IsAccessor() &&
                    TryGetCollisionErrorCode(symbol, other, out code))
                {
                    this.AddDiagnostic(code, symbol.Locations[0], symbol);
                    return;
                }
                else if (symbol.Name != other.Name)
                {
                    // TODO: Shouldn't we somehow reference the conflicting member?  Dev11 doesn't.
                    this.AddDiagnostic(ErrorCode.WRN_CLS_BadIdentifierCase, symbol.Locations[0], symbol);
                    return;
                }
            }
        }