RS.CLIPPY.WRONG_SELF_CONVENTION

Defining a method named with an established prefix (like \"into_\") that takes `self` with the wrong convention

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

What it does

Checks for methods with certain name prefixes or suffixes, and which do not adhere to standard conventions regarding how self is taken. The actual rules are:

Prefix	Postfix	`self` taken	`self` type
`as_`	none	`&self` or `&mut self`	any
`from_`	none	none	any
`into_`	none	`self`	any
`is_`	none	`&mut self` or `&self` or none	any
`to_`	`_mut`	`&mut self`	any
`to_`	not `_mut`	`self`	`Copy`
`to_`	not `_mut`	`&self`	not `Copy`

Note: Clippy doesn't trigger methods with to_ prefix in:

Traits definition. Clippy can not tell if a type that implements a trait is Copy or not.
Traits implementation, when &self is taken. The method signature is controlled by the trait and often &self is required for all types that implement the trait (see e.g. the std::string::ToString trait).

Clippy allows Pin<&Self> and Pin<&mut Self> if &self and &mut self is required.

Please find more info here: https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv

Why is this bad?

Consistency breeds readability. If you follow the conventions, your users won't be surprised that they, e.g., need to supply a mutable reference to a as_.. function.

Example

impl X {
    fn as_str(self) -> &\'static str {
        // ..
    }
}

Use instead:

impl X {
    fn as_str(&self) -> &\'static str {
        // ..
    }
}

Configuration

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

(default: true)