Missing alternatives for types containing nested tuples

[sander2]

See the discussion in #5395.

Tl;dr: not all alternatives are created by the type generator when the type contains nested tuples.

[jacogr]

These are most-probably tricky without getting yourself into knots. And not getting into knots is why enums still have aka { Key: any }. Anyway, if this does become a problem immediately, we probably can also do a any solution inside the []'s as an interim stopgap like we do with enums.

(Although we know the "stopgap" will also last a while. Granted, I have not looked in ages, it could have been pure lazyness on my side at original implementation time...)