public static ReadOnlyList <UnaryOperationSymbolNode> GetUnaryOperations()
{
Debug.Assert(frameworkVersion != null);
Debug.Assert(typeIdentifierMap != null);
unaryOperations ??= frameworkVersion.UnaryOperations
.Select(op => CreateUnaryOperationSymbolNode(op,
typeIdentifierMap,
frameworkVersion))
.MakeReadOnly();
return(unaryOperations.GetValueOrDefault());
}