Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::write_literal: This lint warns about the use of literals as write!/writeln! args
What it meansThis lint warns about the use of literals as write!/writeln! args. It is in the style group and warns by default.
Does it matter?
Using literals as writeln! args is inefficient (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary (i.e., just put the literal in the format string)
Code that works but is not idiomatic Rust. Warns by default.
How to fix it
Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.
Flagged
writeln!(buf, "{}", "foo");
Write this instead
writeln!(buf, "foo");
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::write_literal)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
write_literal = "allow"One run
cargo clippy -- -A clippy::write-literalThe [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.
Clippy's own documentation
What it does
This lint warns about the use of literals as write!/writeln! args.
Why is this bad?
Using literals as writeln! args is inefficient
(c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
(i.e., just put the literal in the format string)
Example
writeln!(buf, "{}", "foo");
Use instead:
writeln!(buf, "foo");
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
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- writeln_empty_stringThis lint warns when you use writeln!(buf, "") to print a newline
- wrong_self_conventionChecks 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: PrefixPostfixself takenself type as_none&self or &mut selfany from_nonenoneany into_noneselfany is_none&mut self or &self or noneany to__mut&mut selfany to_not _mutselfCopy to_not _mut&selfnot 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
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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