roslyn: Warning AD0001 Analyzer 'Microsoft.CodeAnalysis.CSharp.RemoveUnusedParametersAndValues.CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer' threw an exception of type 'System.NullReferenceException'

Version Used: VS 2019 Preview 28508.105.d16.0 C# Tools 3.0.0-beta2-19055-10+15504ac30ab7b6f5bfedcdeee0a180915689f66f

Steps to Reproduce: I don’t have a repro yet. The following warnings are showing in my Error List


Severity	Code	Description	Project	File	Line	Suppression State	Detail Description
Warning	AD0001	Analyzer 'Microsoft.CodeAnalysis.CSharp.RemoveUnusedParametersAndValues.CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'.	Microsoft.CodeAnalysis.Converter		1	Active	Analyzer 'Microsoft.CodeAnalysis.CSharp.RemoveUnusedParametersAndValues.CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer' threw the following exception:
'Exception occurred with following context:
Compilation: Microsoft.CodeAnalysis.Converter
ISymbol: VisitSimpleArgument (Method)

System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.AnalysisData.OnWriteReferenceFound(ISymbol symbol, IOperation operation, Boolean maybeWritten)
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.Walker.OnReferenceFound(ISymbol symbol, IOperation operation)
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.Walker.VisitDeclarationPattern(IDeclarationPatternOperation operation)
   at Microsoft.CodeAnalysis.Operations.DeclarationPatternOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitPatternCaseClause(IPatternCaseClauseOperation operation)
   at Microsoft.CodeAnalysis.Operations.BasePatternCaseClauseOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitSwitchCase(ISwitchCaseOperation operation)
   at Microsoft.CodeAnalysis.Operations.BaseSwitchCaseOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitSwitch(ISwitchOperation operation)
   at Microsoft.CodeAnalysis.Operations.BaseSwitchOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitBlock(IBlockOperation operation)
   at Microsoft.CodeAnalysis.Operations.BaseBlockOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitConditional(IConditionalOperation operation)
   at Microsoft.CodeAnalysis.Operations.BaseConditionalOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.VisitArray[T](IEnumerable`1 operations)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.DefaultVisit(IOperation operation)
   at Microsoft.CodeAnalysis.Operations.OperationVisitor.VisitBlock(IBlockOperation operation)
   at Microsoft.CodeAnalysis.Operations.BaseBlockOperation.Accept(OperationVisitor visitor)
   at Microsoft.CodeAnalysis.Operations.OperationWalker.Visit(IOperation operation)
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.Walker.Visit(IEnumerable`1 operations, AnalysisData analysisData, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.Walker.AnalyzeOperationsAndUpdateData(IEnumerable`1 operations, AnalysisData analysisData, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.FlowAnalysis.SymbolUsageAnalysis.SymbolUsageAnalysis.Run(IOperation rootOperation, ISymbol owningSymbol, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.RemoveUnusedParametersAndValues.AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.AnalyzeUnusedValueAssignments(OperationBlockAnalysisContext context, Boolean isComputingUnusedParams, PooledHashSet`1 symbolUsageResultsBuilder, Boolean& hasBlockWithAllUsedSymbolWrites)
   at Microsoft.CodeAnalysis.RemoveUnusedParametersAndValues.AbstractRemoveUnusedParametersAndValuesDiagnosticAnalyzer.SymbolStartAnalyzer.BlockAnalyzer.AnalyzeOperationBlockEnd(OperationBlockAnalysisContext context)
   at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.<>c__55`2.<ExecuteBlockActions>b__55_1(ValueTuple`2 data)
   at Microsoft.CodeAnalysis.Diagnostics.AnalyzerExecutor.ExecuteAndCatchIfThrows_NoLock[TArg](DiagnosticAnalyzer analyzer, Action`1 analyze, TArg argument, Nullable`1 info)
-----
'.

Expected Behavior:

No AD0001 warnings

Actual Behavior:

About this issue

Original URL
State: closed
Created 5 years ago
Comments: 18 (11 by maintainers)

Commits related to this issue

Handle null value for `IDeclarationPatternOperation.DeclaredSymbol` https://github.com/dotnet/roslyn/commit/6224a5c2feb8c9096cf5765f3d8d2ded396e7e88#diff-b68aa1802251151217571a56d9bfd2b8R31 changed t... — committed to mavasani/roslyn by mavasani 5 years ago

Most upvoted comments

@mwpowellhtx The AD0001 message you pasted points to an exception in CSharpDiagnosticAnalyzerApiUsageAnalyzer, while this issue is about AD0001 in CSharpRemoveUnusedParametersAndValuesDiagnosticAnalyzer, the latter was first added in VS2019.

You should be able to resolve the AD0001 in CSharpDiagnosticAnalyzerApiUsageAnalyzer by applying the suggestion from https://github.com/dotnet/roslyn-analyzers/issues/2961#issuecomment-545438365

mavasani on Oct 23, 2019

@jnm2 The feature that required a breaking change to semantics of IDeclarationPatternOperation.DeclaredSymbol was checked in preview2, hence it only repros on preview2. You have few choices here:

Wait for a build that has https://github.com/dotnet/roslyn/pull/32293 - I believe that is preview3, but @jinujoseph to confirm.
Disable all diagnostic IDs reported by this analyzer, which is the following three:

        public const string ExpressionValueIsUnusedDiagnosticId = "IDE0058";
        public const string ValueAssignedIsUnusedDiagnosticId = "IDE0059";
        public const string UnusedParameterDiagnosticId = "IDE0060";

Suppress or filter out AD0001 from the error list.

mavasani on Jan 25, 2019