Static rustc_lint_defs::builtin::SINGLE_USE_LIFETIMES

pub static SINGLE_USE_LIFETIMES: &'static Lint

The single_use_lifetimes lint detects lifetimes that are only used once.

Example

#![deny(single_use_lifetimes)]

fn foo<'a>(x: &'a u32) {}

{{produces}}

Explanation

Specifying an explicit lifetime like 'a in a function or impl should only be used to link together two things. Otherwise, you should just use '_ to indicate that the lifetime is not linked to anything, or elide the lifetime altogether if possible.

This lint is “allow” by default because it was introduced at a time when '_ and elided lifetimes were first being introduced, and this lint would be too noisy. Also, there are some known false positives that it produces. See RFC 2115 for historical context, and issue #44752 for more details.