clippy::single_char_pattern: Checks for string methods that receive a single-character str as an argument, e.g., _.split("x")

_.split("x");

_.split('x');

[lints.clippy]
single_char_pattern = "warn"

#![warn(clippy::single_char_pattern)]

cargo clippy -- -W clippy::single-char-pattern

Clippy's own documentation

What it does

Checks for string methods that receive a single-character str as an argument, e.g., _.split("x").

Why is this bad?

While this can make a perf difference on some systems, benchmarks have proven inconclusive. But at least using a char literal makes it clear that we are looking at a single character.

Known problems

Does not catch multi-byte unicode characters. This is by design, on many machines, splitting by a non-ascii char is actually slower. Please do your own measurements instead of relying solely on the results of this lint.

Example

_.split("x");

Use instead:

_.split('x');

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

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• str_split_at_newlineChecks for usages of str.trim().split("\n") and str.trim().split("\r\n")

All 847 Clippy lints · Rust compiler errors · Cargo.toml checker