private static IImmutableList<IParameterSymbol> GetUnusedParameters(BaseMethodDeclarationSyntax declaration, IMethodSymbol methodSymbol,
SemanticModel semanticModel)
{
var usedParameters = new HashSet<IParameterSymbol>();
SyntaxNode[] bodies;
if (declaration.IsKind(SyntaxKind.MethodDeclaration))
{
var methodDeclararion = (MethodDeclarationSyntax)declaration;
bodies = new SyntaxNode[] { methodDeclararion.Body, methodDeclararion.ExpressionBody };
}
else
{
var constructorDeclaration = (ConstructorDeclarationSyntax)declaration;
bodies = new SyntaxNode[] { constructorDeclaration.Body, constructorDeclaration.Initializer };
}
foreach (var body in bodies.Where(b => b != null))
{
usedParameters.UnionWith(GetUsedParameters(methodSymbol.Parameters, body, semanticModel));
}
var unusedParameter = methodSymbol.Parameters.Except(usedParameters);
if (methodSymbol.IsExtensionMethod)
{
unusedParameter = unusedParameter.Except(new[] { methodSymbol.Parameters.First() });
}
return unusedParameter.Except(usedParameters).ToImmutableArray();
}
private static void ReportOnDeadParametersAtEntry(BaseMethodDeclarationSyntax declaration, IMethodSymbol methodSymbol,
IImmutableList<IParameterSymbol> noReportOnParameters, SyntaxNodeAnalysisContext context)
{
if (!declaration.IsKind(SyntaxKind.MethodDeclaration) ||
declaration.Body == null)
{
return;
}
var excludedParameters = noReportOnParameters;
if (methodSymbol.IsExtensionMethod)
{
excludedParameters = excludedParameters.Add(methodSymbol.Parameters.First());
}
excludedParameters = excludedParameters.AddRange(methodSymbol.Parameters.Where(p => p.RefKind != RefKind.None));
var candidateParameters = methodSymbol.Parameters.Except(excludedParameters);
if (!candidateParameters.Any())
{
return;
}
IControlFlowGraph cfg;
if (!ControlFlowGraph.TryGet(declaration.Body, context.SemanticModel, out cfg))
{
return;
}
var lva = LiveVariableAnalysis.Analyze(cfg, methodSymbol, context.SemanticModel);
var liveParameters = lva.GetLiveIn(cfg.EntryBlock).OfType<IParameterSymbol>();
ReportOnUnusedParameters(declaration, candidateParameters.Except(liveParameters).Except(lva.CapturedVariables), MessageDead,
context, isRemovable: false);
}