Add #[must_use] to generated `as_` method.

[nitsky]

Generated as_ methods for enum variants do not have #[must_use], causing clippy to display an error.

[lnicola]

We had this and too many people complained. I don't think you should be enabling the pedantic ones anyway.

[nitsky]

Okay, closing. I like using clippy::pedantic because it helps enforce a consistent code style.

[lnicola]

It should probably be configurable.

Hello from someone who tried Tangram/ModelFox, BTW!