bug#56400: Make setopt warn on type mismatch

[Stefan Kangas]

Severity: wishlist

Why not make `setopt' warn in case there is a type mismatch?
For example, in:

    (setopt tetris-buffer-width "hello")

But the type of `tetris-buffer-width' is natnum.

I think this would save users from shooting themselves in the foot.
If they are sure they want to do that, they can use `setq' or
`customize-set-variable' directly.