Do not use `NaturalTransformation` in types of functions that do not preserve the structure

[klntsky]

04de80b introduced a change adding NaturalTransformation to types of functions such as slice, head, etc.

However, as stated in the docs, natural transformation should not manipulate the inner values.

[hdgarrood]

These functions don’t manipulate the inner values; they actually aren’t capable of doing so, because the type system prevents that. I think you are understanding “manipulate the inner values” in a different way to how it is meant there.

[klntsky]

OK.