Embed Notice

@mcc The language feature was approved with https://github.com/rust-lang/rfcs/pull/3681, and documents that yeah, #[derive(Default)] will work if every field has a default value or itself implements Default.

From the RFC:

```
#[derive(Default)]
struct Pet {
name: Option<String>, // impl Default for Pet will use Default::default() for name
age: i128 = 42, // impl Default for Pet will use the literal 42 for age
}
```