AD0001: ArgumentNullException in SymbolicExecutionRunner

[martin-strecker-sonarsource]

For .NET reference assemblies, we see AD0001 that look like so:

CSC : warning AD0001: Analyzer 'SonarAnalyzer.Rules.CSharp.SymbolicExecutionRunner' threw an exception of type
 'SonarAnalyzer.SymbolicExecution.SymbolicExecutionException' with message 'Error processing method: get_Item
## Method file: C:\sonar-ci\Project\src\libraries\System.Collections.Immutable\ref\System.Collections.Immutable.cs
## Method line: 917,35 
## Inner exception: System.ArgumentNullException: Value cannot be null. (Parameter 'type')
##    at SonarAnalyzer.SymbolicExecution.Roslyn.ExceptionState..ctor(ITypeSymbol type)
##    at SonarAnalyzer.SymbolicExecution.Roslyn.RoslynSymbolicExecution.ThrownException(ExplodedNode node, ControlFlowBranchSemantics semantics)
##    at SonarAnalyzer.SymbolicExecution.Roslyn.RoslynSymbolicExecution.ProcessBranching(ExplodedNode node)+MoveNext() ##    at SonarAnalyzer.SymbolicExecution.Roslyn.RoslynSymbolicExecution.Execute()
##    at SonarAnalyzer.Rules.SymbolicExecutionRunnerBase.AnalyzeRoslyn(SonarAnalysisContext analysisContext, SonarSyntaxNodeReportingContext nodeContext, ISymbol symbol)'. 
[C:\sonar-ci\Project\src\libraries\System.Collections.Immutable\ref\System.Collections.Immutable.csproj]

Source: https://api.cirrus-ci.com/v1/task/6240477526097920/logs/build.log

The files in questions are the reference assemblies like this one:

https://github.com/dotnet/runtime/blob/main/src/libraries/System.Collections.Immutable/ref/System.Collections.Immutable.cs#L18

A possible root cause is throw null where null does not have a type, and therefore, ITypeSymbol is null.