- Removes closures and function calls for types that implement default:
```rust
// Change
let _my_str = get_str().unwrap_or(String::new);
// To
let _my_str = get_str().unwrap_or_default();
```
- Uses the `.cloned()/.copied()` methods where possible
- Use function pointer instead of simple closure
May improve performace, as closures generate more code, and this might
unlock some inlining opportunities.
