Specify default type bound for returned values of a bound generic type

[bethebunny]

I have a bound generic type, eg.

  nb::class_<::mlir::Type>(m, "Type");

  nb::dict t_bounds;
  t_bounds["bound"] = nb::type<mlir::Type>();
  m.attr("T") = nb::type_var("T", **t_bounds);

  nb::class_<::mlir::Value>(m, "Value", nb::is_generic(),
                            nb::sig("class Value(typing.Generic[T])"))
  ...

I'd like for cases that return a Value instance that don't statically know their type to annotate the return as Value[Type]. This is then no longer considered a "raw generic" by typecheckers.

With a type caster I could configure this via the Name, but since type casters are generated for bound classes, how can I configure this?

[wjakob]

This is not supported by nanobind.