Failed with uncaught exception

Question

Hi,

After adding a the pre-condition below Code contracts crashes with the following message:

CodeContracts: RestWeb: Failed with uncaught exception: Should never happen
CodeContracts: RestWeb: Stack trace:    at Microsoft.Research.CodeAnalysis.OptimisticHeapAnalyzer`8.EdgeRenaming(Pair`2 edge, Boolean joinPoint)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.OptimisticHeapAnalyzer`8.ValueDriver`1.EdgeConversion(APC from, APC next, Boolean joinPoint, AState state)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.ForwardAnalysisSolver`2.PushState(APC pc, APC next, AState state)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.DFARoot`2.ComputeFixpoint()
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.ForwardDFA`2.Run(AState startState)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.AnalysisDriver`10.MDriver..ctor(Method method, AnalysisDriver`10 parent)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.AnalysisDriver`10.MethodDriver(Method method)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.AnalyzeNonIteratorMethodInternal(Method method)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.AnalyzeMethodInternal(Method method)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.AnalyzeMethod(Method method)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.AnalyzeAssembly(String assemblyName, Set`1 assembliesUnderAnalysis)
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.InternalAnalyze()
CodeContracts: RestWeb:    at Microsoft.Research.CodeAnalysis.Clousot.TypeBinder`8.Analyze()


The method causing this is the following (removing the comment from the top-precondition causes the crash)

 private static Node convertToNode(NodeRow nodeRow)
        {
            //Contract.Requires(nodeRow == null || (!string.IsNullOrEmpty(nodeRow.RowKey)));
            //We return null iff nodeRow == null
            Contract.Ensures((nodeRow == null) == (Contract.Result<Node>() == null));
            
            if (nodeRow == null)
            {
                return null;
            }

            Node.Builder builder = Node.CreateBuilder().
                        SetId(nodeRow.RowKey.ToNodeID()).
                        SetUserId(nodeRow.UserID.ToUserID()).
                        SetAvailability(nodeRow.Availability).
                        SetName(nodeRow.Name);

            return builder.Build();
        }