Clippy lints / Pedantic
Clippy lint · Pedantic · checked with Clippy 0.1.99
clippy::redundant_closure_for_method_calls: redundant closure
What it meansChecks for closures which only invoke a method on the closure argument and can be replaced by referencing the method directly. It is in the pedantic group and off by default.
What you see
warning: redundant closure --> main.rs:3:15 | 3 | Some('a').map(|s| s.to_uppercase()); | ^^^^^^^^^^^^^^^^^^^^ help: replace the closure with the method itself: `char::to_uppercase` | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#redundant_closure_for_method_calls = note: `-W clippy::redundant-closure-for-method-calls` implied by `-W clippy::pedantic`
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?
It’s unnecessary to create the closure.
Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.
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
Some('a').map(|s| s.to_uppercase());
Write this instead
Some('a').map(char::to_uppercase);
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]
redundant_closure_for_method_calls = "warn"In code
#![warn(clippy::redundant_closure_for_method_calls)]One run
cargo clippy -- -W clippy::redundant-closure-for-method-callsThe [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
Checks for closures which only invoke a method on the closure argument and can be replaced by referencing the method directly.
Why is this bad?
It’s unnecessary to create the closure.
Example
Some('a').map(|s| s.to_uppercase());
may be rewritten as
Some('a').map(char::to_uppercase);
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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- missing_errors_docChecks the doc comments of publicly visible functions that return a Result type and warns if there is no # Errors section
- must_use_candidateChecks for public functions that have no #[must_use] attribute, but return something not already marked must-use, have no mutable arg and mutate no statics
- pub_underscore_fieldsChecks whether any field of the struct is prefixed with an _ (underscore) and also marked pub (public)
- range_minus_oneChecks for inclusive ranges where 1 is subtracted from the upper bound, e.g., x..=(y-1)
- range_plus_oneChecks for exclusive ranges where 1 is added to the upper bound, e.g., x..(y+1)
- redundant_elseredundant else block
- ref_as_ptrreference as raw pointer
- ref_binding_to_referenceChecks for ref bindings which create a reference to a reference
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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