RS.CLIPPY.BOX_COLLECTION

Usage of `Box<Vec<T>>`, vector elements are already on the heap

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: box_collection. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for usage of Box<T> where T is a collection such as Vec anywhere in the code. Check the Box documentation for more information.

Why is this bad?

Collections already keeps their contents in a separate area on the heap. So if you Box them, you just add another level of indirection without any benefit whatsoever.

Example

struct X {
    values: Box<Vec<Foo>>,
}

Better:

struct X {
    values: Vec<Foo>,
}

Past names

box_vec

Configuration

avoid-breaking-exported-api: Suppress lints whenever the suggested change would cause breakage for other crates.

(default: true)