Clippy lints / Complexity
Clippy lint · Complexity · checked with Clippy 0.1.99
clippy::borrowed_box: Checks for usage of &Box<T> anywhere in the code. Check the Box documentation for more information
What it meansChecks for usage of &Box<T> anywhere in the code. Check the Box documentation for more information. It is in the complexity group and warns by default.
Does it matter?
A &Box<T> parameter requires the function caller to box T first before passing it to a function. Using &T defines a concrete type for the parameter and generalizes the function, this would also auto-deref to &T at the function call site if passed a &Box<T>.
Code that does something simple in a complicated way. Warns by default.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
fn foo(bar: &Box<T>) { ... }
Write this instead
fn foo(bar: &T) { ... }
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::borrowed_box)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
borrowed_box = "allow"One run
cargo clippy -- -A clippy::borrowed-boxThe [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.
Clippy's own documentation
What it does
Checks for usage of &Box<T> anywhere in the code.
Check the Box documentation for more information.
Why is this bad?
A &Box<T> parameter requires the function caller to box T first before passing it to a function.
Using &T defines a concrete type for the parameter and generalizes the function, this would also
auto-deref to &T at the function call site if passed a &Box<T>.
Example
fn foo(bar: &Box<T>) { ... }
Better:
fn foo(bar: &T) { ... }
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- too_many_argumentsChecks for functions with too many parameters
- clone_on_copyusing `clone` on type `u64` which implements the `Copy` trait
- type_complexityChecks for types used in structs, parameters and let declarations above a certain complexity threshold
- bind_instead_of_mapChecks for usage of _.and_then(|x| Some(y)), _.and_then(|x| Ok(y)) or _.or_else(|x| Err(y))
- bool_comparisonChecks for expressions of the form x == true, x != true and order comparisons such as x < true (or vice versa) and suggest using the variable directly
- borrow_deref_refderef on an immutable reference
- bytes_count_to_lenusing long and hard to read `.bytes().count()`
- char_lit_as_u8Checks for expressions where a character literal is cast to u8 and suggests using a byte literal instead
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
Up next
Related lintclippy::too_many_argumentsChecks for functions with too many parametersRead it next →Did this answer your question?