Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::single_char_lifetime_names: single-character lifetime names are likely uninformative

What it meansChecks for lifetimes with names which are one character long. It is in the restriction group and off by default.

What you see

warning: single-character lifetime names are likely uninformative
 --> main.rs:3:22
  |
3 | struct DiagnosticCtx<'a> {
  |                      ^^
  |
  = help: use a more informative name
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#single_char_lifetime_names
  = note: requested on the command line with `-W clippy::single-char-lifetime-names`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

A single character is likely not enough to express the purpose of a lifetime. Using a longer name can make code easier to understand.

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

struct DiagnosticCtx<'a> {
    source: &'a str,
}

Write this instead

struct DiagnosticCtx<'src> {
    source: &'src str,
}

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
single_char_lifetime_names = "warn"

In code

#![warn(clippy::single_char_lifetime_names)]

One run

cargo clippy -- -W clippy::single-char-lifetime-names

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Restrictiongroup

allowdefault level

nofixed by cargo clippy --fix

1.60.0added in Rust

Clippy's own documentation

What it does

Checks for lifetimes with names which are one character long.

Why restrict this?

A single character is likely not enough to express the purpose of a lifetime. Using a longer name can make code easier to understand.

Known problems

Rust programmers and learning resources tend to use single character lifetimes, so this lint is at odds with the ecosystem at large. In addition, the lifetime’s purpose may be obvious or, rarely, expressible in one character.

Example

struct DiagnosticCtx<'a> {
    source: &'a str,
}

Use instead:

struct DiagnosticCtx<'src> {
    source: &'src str,
}

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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