RS.CLIPPY.DERIVABLE_IMPLS

Manual implementation of the `Default` trait which is equal to a derive

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

What it does

Detects manual std::default::Default implementations that are identical to a derived implementation.

Why is this bad?

It is less concise.

Example

struct Foo {
    bar: bool
}

impl Default for Foo {
    fn default() -> Self {
        Self {
            bar: false
        }
    }
}

Use instead:

#[derive(Default)]
struct Foo {
    bar: bool
}

Known problems

Derive macros sometimes use incorrect bounds in generic types and the user defined impl may be more generalized or specialized than what derive will produce. This lint can't detect the manual impl has exactly equal bounds, and therefore this lint is disabled for types with generic parameters.

Configuration

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml

(default: current version)