/// <summary>
 /// Return true if the given type is valid as a calling convention modifier type.
 /// </summary>
 internal static bool IsCallingConventionModifier(NamedTypeSymbol modifierType)
 {
     Debug.Assert(modifierType.ContainingAssembly is not null || modifierType.IsErrorType());
     return((object?)modifierType.ContainingAssembly == modifierType.ContainingAssembly?.CorLibrary &&
            modifierType.Arity == 0 &&
            modifierType.Name != "CallConv" &&
            modifierType.Name.StartsWith("CallConv", StringComparison.Ordinal) &&
            modifierType.IsCompilerServicesTopLevelType());
 }