public static IMember GetReturnValueFromAnnotation(ExpressionEval eval, Expression annotation)
{
if (eval == null || annotation == null)
{
return(null);
}
var annotationType = eval.GetTypeFromAnnotation(annotation, LookupOptions.All);
if (annotationType.IsUnknown())
{
return(null);
}
// Annotations are typically types while actually functions return
// instances unless specifically annotated to a type such as Type[T].
// TODO: try constructing argument set from types. Consider Tuple[_T1, _T2] where _T1 = TypeVar('_T1', str, bytes)
var t = annotationType.CreateInstance(ArgumentSet.Empty(annotation, eval));
// If instance could not be created, such as when return type is List[T] and
// type of T is not yet known, just use the type.
var instance = t.IsUnknown() ? (IMember)annotationType : t;
return(instance);
}