Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::single_char_add_str: Warns when using push_str/insert_str with a single-character string literal where push/insert with a char would work fine
What it meansWarns when using push_str/insert_str with a single-character string literal where push/insert with a char would work fine. It is in the style group and warns by default.
Does it matter?
It’s less clear that we are pushing a single character.
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
string.insert_str(0, "R");
string.push_str("R");
Write this instead
string.insert(0, 'R');
string.push('R');
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::single_char_add_str)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
single_char_add_str = "allow"One run
cargo clippy -- -A clippy::single-char-add-strThe [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
Warns when using push_str/insert_str with a single-character string literal
where push/insert with a char would work fine.
Why is this bad?
It’s less clear that we are pushing a single character.
Example
string.insert_str(0, "R");
string.push_str("R");
Use instead:
string.insert(0, 'R');
string.push('R');
Past names
- single_char_push_str
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
Related lints
- needless_returnunneeded `return` statement
- new_without_defaultChecks for public types with a pub fn new() -> Self method and no implementation of Default
- len_zeroChecks for getting the length of something via .len() just to compare to zero, and suggests using .is_empty() where applicable
- same_item_pushit looks like the same item is being pushed into this `Vec`
- self_named_constructorsconstructor `foo` has the same name as the type
- should_implement_traitChecks for methods that should live in a trait implementation of a std trait (see llogiq’s blog post for further information) instead of an inherent implementation
- single_component_path_importsthis import is redundant
- single_matchChecks for matches with a single arm where an if let will usually suffice. This intentionally does not lint if there are comments inside of the other arm, so as to allow the user to document why having another explicit pattern with an empty body is necessary, or because the comments need to be preserved for other reasons
- string_extend_charscalling `.extend(_.chars())`
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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