RS.CLIPPY.EXCESSIVE_NESTING

Checks for blocks nested beyond a certain threshold

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

What it does

Checks for blocks which are nested beyond a certain threshold.

Note: Even though this lint is warn-by-default, it will only trigger if a maximum nesting level is defined in the clippy.toml file.

Why is this bad?

It can severely hinder readability.

Example

An example clippy.toml configuration:

excessive-nesting-threshold = 3

// lib.rs
pub mod a {
    pub struct X;
    impl X {
        pub fn run(&self) {
            if true {
                // etc...
            }
        }
    }
}

Use instead:

// a.rs
fn private_run(x: &X) {
    if true {
        // etc...
    }
}

pub struct X;
impl X {
    pub fn run(&self) {
        private_run(self);
    }
}

// lib.rs
pub mod a;

Configuration

excessive-nesting-threshold: The maximum amount of nesting a block can reside in

(default: 0)