rust-clippy/identity_conversion.rs at master · rust-lang/rust-clippy
https://github.com/rust-lang/rust-clippy/blob/master/clippy_lints/src/identity_conversion.rs
とりあえずこれ読むか……
github.comrust-lang/rust-clippyA bunch of lints to catch common mistakes and improve your Rust code - rust-lang/rust-clippy