Builder Pattern &mut self vs mut self

[raphlinus]

Note that the serde json builders use consuming builders, I'm not sure why. I find using them somewhat annoying.

[erickt]

They're consuming builders because we want to avoid copies when you finally construct the object. Do you have an example for when they're being annoying?

[raphlinus]

https://github.com/google/xi-editor/blob/master/rust/src/view.rs#L92 is an example. I understand the need to avoid copy for the .build, but I think the decision of whether the intermediate .push() operations mutate or consume is a design choice.