ThrowEx

[DiagnosticAnalyzer]
[ExportDiagnosticAnalyzer(DiagnosticId, LanguageNames.CSharp)]
public class DiagnosticAnalyzer : ISyntaxNodeAnalyzer<SyntaxKind>
{
    internal const string DiagnosticId = "DoNotThrowCaughtException";
    internal const string Description = "Do not throw back a caught exception like this.";
    internal const string MessageFormat = "Really? REALLY?!";
    internal const string Category = "Usage";
    internal static DiagnosticDescriptor Rule = new DiagnosticDescriptor(DiagnosticId, Description, MessageFormat, Category, DiagnosticSeverity.Warning);

    public ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics
    {
        get { return ImmutableArray.Create(Rule); }
    }

    public ImmutableArray<SyntaxKind> SyntaxKindsOfInterest
    {
        get { return ImmutableArray.Create(SyntaxKind.CatchDeclaration); }
    }

    public void AnalyzeNode(SyntaxNode node, SemanticModel semanticModel, Action<Diagnostic> addDiagnostic, CancellationToken cancellationToken)
    {
        var catchDeclaration = (CatchDeclarationSyntax)node;
        var catchDeclarationIdentifier = catchDeclaration.Identifier;
        var exceptionIdentifier = catchDeclarationIdentifier.Text;

        var throwStatements = catchDeclaration.Parent.DescendantNodes()
            .OfType<ThrowStatementSyntax>()
            .Where(c => c.Expression != null && c.Expression is IdentifierNameSyntax && ((IdentifierNameSyntax)c.Expression).Identifier.ValueText == exceptionIdentifier);

        foreach (var throwStatement in throwStatements)
        {
            addDiagnostic(Diagnostic.Create(Rule, throwStatement.GetLocation()));
        }
    }
}