warning: type parameter `U` goes unused in function definition
    --> src/tree/tree.rs:1155:24
     |
1155 |     fn get_subtree_size<U: SmallUnsigned>(&self, idx: usize) -> usize {
     |                        ^^^^^^^^^^^^^^^^^^ help: consider removing the parameter
     |
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_type_parameters
     = note: `#[warn(clippy::extra_unused_type_parameters)]` on by default

warning: `filter(..).map(..)` can be simplified as `filter_map(..)`
   --> src/tree/tree.rs:511:18
    |
511 |                   .filter(|n| n.is_some())
    |  __________________^
512 | |                 .map(|n| n.as_ref().unwrap())
    | |_____________________________________________^ help: try: `filter_map(|n| n.as_ref())`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#manual_filter_map
    = note: `#[warn(clippy::manual_filter_map)]` on by default

warning: replacing an `Option` with `None`
   --> src/tree/arena.rs:114:24
    |
114 |             let node = core::mem::replace(&mut self.vec[idx], None);
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider `Option::take()` instead: `self.vec[idx].take()`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#mem_replace_option_with_none
    = note: `#[warn(clippy::mem_replace_option_with_none)]` on by default

warning: duplicated attribute
   --> src/lib.rs:205:9
    |
205 | #![deny(missing_docs)]
    |         ^^^^^^^^^^^^
    |
note: first defined here
   --> src/lib.rs:201:43
    |
201 | #![cfg_attr(not(any(test, fuzzing)), deny(missing_docs))]
    |                                           ^^^^^^^^^^^^
help: remove this attribute
   --> src/lib.rs:205:9
    |
205 | #![deny(missing_docs)]
    |         ^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#duplicated_attributes
    = note: `#[warn(clippy::duplicated_attributes)]` on by default

warning: unused import: `macros::*`
   --> src/lib.rs:228:9
    |
228 | pub use macros::*;
    |         ^^^^^^^^^
    |
    = note: `#[warn(unused_imports)]` on by default