Dual number overloads fail with dual numbers with no partials.

[j-fu]

See the discussion in https://discourse.julialang.org/t/automatic-differentiation-of-function-using-linearproblem/136063

[ChrisRackauckas]

Dual numbers without partials are ill-formed. Is there a reason to actually support this?

[j-fu]

True, it probably doesn't make sense. But may be a clearer error message could be helpful.

[ChrisRackauckas]

Yeah, though it's not a super high priority since you're in super hardcore territory if you're using undefined lower level APIs of an autodiff library only intended for developers of the library... so that really is entering "buyer beware" territory.