protected override bool TryAnalyzeVariableDeclaration(TypeSyntax typeName, SemanticModel semanticModel, OptionSet optionSet, CancellationToken cancellationToken, out TextSpan issueSpan)
        {
            issueSpan = default(TextSpan);

            // If it is currently not var, explicit typing exists, return. 
            // this also takes care of cases where var is mapped to a named type via an alias or a class declaration.
            if (!typeName.IsTypeInferred(semanticModel))
            {
                return false;
            }

            if (typeName.Parent.IsKind(SyntaxKind.VariableDeclaration) &&
                typeName.Parent.Parent.IsKind(SyntaxKind.LocalDeclarationStatement, SyntaxKind.ForStatement, SyntaxKind.UsingStatement))
            {
                // check assignment for variable declarations.
                var variable = ((VariableDeclarationSyntax)typeName.Parent).Variables.First();
                if (!AssignmentSupportsStylePreference(variable.Identifier, typeName, variable.Initializer, semanticModel, optionSet, cancellationToken))
                {
                    return false;
                }
            }

            issueSpan = typeName.Span;
            return true;
        }
        protected override bool TryAnalyzeVariableDeclaration(TypeSyntax typeName, SemanticModel semanticModel, OptionSet optionSet, CancellationToken cancellationToken, out TextSpan issueSpan)
        {
            // If it is already var, return.
            if (typeName.IsTypeInferred(semanticModel))
            {
                issueSpan = default(TextSpan);
                return false;
            }

            var candidateReplacementNode = SyntaxFactory.IdentifierName("var");
            var candidateIssueSpan = typeName.Span;

            // If there exists a type named var, return.
            var conflict = semanticModel.GetSpeculativeSymbolInfo(typeName.SpanStart, candidateReplacementNode, SpeculativeBindingOption.BindAsTypeOrNamespace).Symbol;
            if (conflict?.IsKind(SymbolKind.NamedType) == true)
            {
                issueSpan = default(TextSpan);
                return false;
            }

            if (typeName.Parent.IsKind(SyntaxKind.VariableDeclaration) &&
                typeName.Parent.IsParentKind(SyntaxKind.LocalDeclarationStatement, SyntaxKind.ForStatement, SyntaxKind.UsingStatement))
            {
                var variableDeclaration = (VariableDeclarationSyntax)typeName.Parent;

                // implicitly typed variables cannot be constants.
                if ((variableDeclaration.Parent as LocalDeclarationStatementSyntax)?.IsConst == true)
                {
                    issueSpan = default(TextSpan);
                    return false;
                }

                var variable = variableDeclaration.Variables.Single();
                if (AssignmentSupportsStylePreference(
                        variable.Identifier, typeName, variable.Initializer.Value,
                        semanticModel, optionSet, cancellationToken))
                {
                    issueSpan = candidateIssueSpan;
                    return true;
                }
            }
            else if (typeName.IsParentKind(SyntaxKind.ForEachStatement))
            {
                issueSpan = candidateIssueSpan;
                return true;
            }

            issueSpan = default(TextSpan);
            return false;
        }