private bool IsUnusedParameterCandidate(IParameterSymbol parameter)
{
// Ignore certain special parameters/methods.
// Note that "method.ExplicitOrImplicitInterfaceImplementations" check below is not a complete check,
// as identifying this correctly requires analyzing referencing projects, which is not
// supported for analyzers. We believe this is still a good enough check for most cases so
// we don't have to bail out on reporting unused parameters for all public methods.
if (parameter.IsImplicitlyDeclared ||
parameter.Name == DiscardVariableName ||
parameter.ContainingSymbol is not IMethodSymbol method ||
method.IsImplicitlyDeclared ||
method.IsExtern ||
method.IsAbstract ||
method.IsVirtual ||
method.IsOverride ||
method.PartialImplementationPart != null ||
!method.ExplicitOrImplicitInterfaceImplementations().IsEmpty ||
method.IsAccessor() ||
method.IsAnonymousFunction() ||
_compilationAnalyzer.MethodHasHandlesClause(method) ||
_deserializationConstructorCheck.IsDeserializationConstructor(method))
{
return(false);
}
// Ignore parameters of record primary constructors since they map to public properties
// TODO: Remove this when implicit operations are synthesised: https://github.com/dotnet/roslyn/issues/47829
if (method.IsConstructor() &&
_compilationAnalyzer.IsRecordDeclaration(method.DeclaringSyntaxReferences.FirstOrDefault()?.GetSyntax()))
{
return(false);
}
// Ignore event handler methods "Handler(object, MyEventArgs)"
// as event handlers are required to match this signature
// regardless of whether or not the parameters are used.
if (_eventArgsTypeOpt != null &&
method.Parameters.Length == 2 &&
method.Parameters[0].Type.SpecialType == SpecialType.System_Object &&
method.Parameters[1].Type.InheritsFromOrEquals(_eventArgsTypeOpt))
{
return(false);
}
// Ignore flagging parameters for methods with certain well-known attributes,
// which are known to have unused parameters in real world code.
if (method.GetAttributes().Any(a => _attributeSetForMethodsToIgnore.Contains(a.AttributeClass)))
{
return(false);
}
// Methods used as delegates likely need to have unused parameters for signature compat.
if (_methodsUsedAsDelegates.ContainsKey(method))
{
return(false);
}
// Ignore special parameter names for methods that need a specific signature.
// For example, methods used as a delegate in a different type or project.
// This also serves as a convenient way to suppress instances of unused parameter diagnostic
// without disabling the diagnostic completely.
// We ignore parameter names that start with an underscore and are optionally followed by an integer,
// such as '_', '_1', '_2', etc.
if (parameter.IsSymbolWithSpecialDiscardName())
{
return(false);
}
// Don't report on valid GetInstance method of ICustomMarshaler.
// See https://docs.microsoft.com/dotnet/api/system.runtime.interopservices.icustommarshaler#implementing-the-getinstance-method
if (method is { MetadataName : "GetInstance", IsStatic : true, Parameters.Length : 1, ContainingType : { } containingType } methodSymbol&&
methodSymbol.Parameters[0].Type.SpecialType == SpecialType.System_String &&
containingType.AllInterfaces.Any((@interface, marshaler) => @interface.Equals(marshaler), _iCustomMarshaler))
{
return(false);
}
return(true);
}