DynamicallyAccessedMembersAnalyzer errors - NullReferenceException and NotImplementedException

[JamesNK]

The DynamicallyAccessedMembersAnalyzer analyzer throws many errors when run on ASP.NET Core assemblies with trimming enabled.

PR that enables trimming analyzers - dotnet/aspnetcore#41021

Sample of errors:

43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.NoneOperation'.
43>CSC : warning AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'.

Also, in ASP.NET Core repo we have been using ILLink to provide warnings of trimming areas to fix. Enabling trim analyzers provides new warnings that weren't caught by ILLink. Is that expected?

e.g.

[JamesNK]

Raw log from a failing build: 54.txt

[agocke]

@sbomer could you take a look? Looks like some flow analysis walking is hitting NIE

[vitek-karas]

Re difference between analyzer/linker. The analyzer has better handling of more complex data flow like backward branches (loops), exceptions and lambdas/local functions. Depending on the situation it can produce warnings which the linker will not. It would be great if you could point us to these to validate. I would hope they're actually correct as much as possible.

And example of a pattern which the linker will not warn on:

Type type = typeof(Foo);
while (true)
{
    type.GetProperties ();  // IL2xxx - produced only by the analyzer 
                            // the reason is that the return value of GetSomeOtherUnannotatedType is being used in GetProperties
    type = GetSomeOtherUnannotatedType ();
}

Linker will currently not detect this situation.

[sbomer]

One NRE happens when visiting an assignment to a get-only property in a constructor, for example at https://github.com/dotnet/aspnetcore/blob/61506cd77e9f2c457afb27e487789585bea90264/src/Shared/Nullable/NullableAttributes.cs#L191. This causes a crash because the analyzer is incorrectly assuming that an assignment to a property means that it has a setter:

linker/src/ILLink.RoslynAnalyzer/DataFlow/LocalDataFlowVisitor.cs

Lines 105 to 106 in b9b72d1

	// A property assignment is really a call to the property setter.
	var setMethod = propertyRef.Property.SetMethod!;

The NIE happens for an assignment to a property where the LHS of the assignment is represented as a FlowCaptureReferenceOperation, which we don't handle. I assume it is represented as a FlowCaptureReference instead of a PropertyReference when the RHS has branches. Here's an example where this is hit - it also is an assignment to a set-only property, but I think this is a coincidence:
https://github.com/dotnet/aspnetcore/blob/61506cd77e9f2c457afb27e487789585bea90264/src/JSInterop/Microsoft.JSInterop/src/DotNetStreamReference.cs#L18

There's a second NRE because we visit generic instantiations for crefs in XML comments, where the generic argument might be a string representing a generic parameter. We try to access the ContainingSymbol which is null

linker/src/ILLink.RoslynAnalyzer/TrimAnalysis/GenericParameterValue.cs

Line 28 in b9b72d1

=> new string[] { GenericParameter.TypeParameterSymbol.Name, GenericParameter.TypeParameterSymbol.ContainingSymbol.GetDisplayName () };

and this causes a NRE in GetDisplayName. Example:
Example: https://github.com/dotnet/aspnetcore/blob/61506cd77e9f2c457afb27e487789585bea90264/src/JSInterop/Microsoft.JSInterop/src/IJSObjectReference.cs#L18

[JamesNK]

Another trimmed project I work on has started throwing NIE and NRE: grpc/grpc-dotnet#1667

The is the broken project: https://github.com/grpc/grpc-dotnet/blob/master/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj. Note that in repo the project isn't updated to net7.0 or have a .NET 7 SDK. You'll need to make changes to upgrade it.

Might be the same errors, but you should double-check.

Build log:

Command:
dotnet publish GrpcAspNetCoreServer.csproj -c Release -o /tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/perf/benchmarkapps/GrpcAspNetCoreServer/published /p:MicrosoftNETCoreAppPackageVersion=7.0.0-preview.4.22201.3 /p:MicrosoftAspNetCoreAppPackageVersion=7.0.0-preview.4.22201.3 /p:MicrosoftNETCoreApp50PackageVersion=7.0.0-preview.4.22201.3 /p:GenerateErrorForMissingTargetingPacks=false /p:MicrosoftNETPlatformLibrary=Microsoft.NETCore.App /p:RestoreNoCache=true --framework net7.0 --self-contained -r linux-x64 
Microsoft (R) Build Engine version 17.2.0-preview-22178-04+ce7523296 for .NET
Copyright (C) Microsoft Corporation. All rights reserved.

  Determining projects to restore...
  Restored /tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.Net.Common/Grpc.Net.Common.csproj (in 1.76 sec).
  Restored /tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/perf/benchmarkapps/GrpcAspNetCoreServer/GrpcAspNetCoreServer.csproj (in 2 sec).
  Restored /tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj (in 3.2 sec).
  You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
  You are using a preview version of .NET. See: https://aka.ms/dotnet-support-policy
/tmp/benchmarks-agent/benchmarks-server-1/wer2iulg.kmm/sdk/7.0.100-preview.4.22201.11/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(1113,5): warning NETSDK1179: One of '--self-contained' or '--no-self-contained' options are required when '--runtime' is used. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.Net.Common/Grpc.Net.Common.csproj]
/tmp/benchmarks-agent/benchmarks-server-1/wer2iulg.kmm/sdk/7.0.100-preview.4.22201.11/Sdks/Microsoft.NET.Sdk/targets/Microsoft.NET.Sdk.targets(1113,5): warning NETSDK1179: One of '--self-contained' or '--no-self-contained' options are required when '--runtime' is used. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
/root/.nuget/packages/microsoft.codeanalysis.netanalyzers/6.0.0/build/Microsoft.CodeAnalysis.NetAnalyzers.targets(591,5): warning : The .NET SDK has newer analyzers with version '7.0.0' than what version '6.0.0' of 'Microsoft.CodeAnalysis.NetAnalyzers' package provides. Update or remove this package reference. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.Net.Common/Grpc.Net.Common.csproj]
  Grpc.Net.Common -> /tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.Net.Common/bin/Release/net6.0/Grpc.Net.Common.dll
/root/.nuget/packages/microsoft.codeanalysis.netanalyzers/6.0.0/build/Microsoft.CodeAnalysis.NetAnalyzers.targets(591,5): warning : The .NET SDK has newer analyzers with version '7.0.0' than what version '6.0.0' of 'Microsoft.CodeAnalysis.NetAnalyzers' package provides. Update or remove this package reference. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
CSC : error AD0001: Analyzer 'ILLink.RoslynAnalyzer.DynamicallyAccessedMembersAnalyzer' threw an exception of type 'System.NotImplementedException' with message 'Microsoft.CodeAnalysis.Operations.FlowCaptureReferenceOperation'. [/tmp/benchmarks-agent/benchmarks-server-1/xgnmy1m2.pox/grpc-dotnet/src/Grpc.AspNetCore.Server/Grpc.AspNetCore.Server.csproj]
Exit code: 1

[JamesNK]

FYI I'm going to temporarily disable the analyzer in the dotnet/aspnetcore repo:

  <!-- Trim analyzers are automatically enabled by IsTrimming=true. They currently break when run on aspnetcore.
       Remove when trimming analyzers are fixed: https://github.com/dotnet/aspnetcore/issues/41016 -->
  <PropertyGroup>
    <EnableTrimAnalyzer Condition=" '$(EnableTrimAnalyzer)' == ''">false</EnableTrimAnalyzer>
  </PropertyGroup>

Let me know when you think the linker issues have been fixed. Once the changes have flowed through to aspnetcore I'll test reenabling them.

[agocke]

Sounds good, thanks. When that's done, we'll hopefully catch any new regressions during insertion.