Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::bool_assert_comparison: used `assert_eq!` with a literal bool
What it meansThis lint warns about boolean comparisons in assert-like macros. It is in the style group and warns by default.
What you see
warning: used `assert_eq!` with a literal bool --> main.rs:3:1 | 3 | assert_eq!("a".is_empty(), false); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#bool_assert_comparison = note: `#[warn(clippy::bool_assert_comparison)]` on by default help: replace it with `assert!(..)` | 3 - assert_eq!("a".is_empty(), false); 3 + assert!(!"a".is_empty()); |
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 is shorter to use the equivalent.
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
assert_eq!("a".is_empty(), false);
assert_ne!("a".is_empty(), true);
Write this instead
assert!(!"a".is_empty());
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::bool_assert_comparison)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
bool_assert_comparison = "allow"One run
cargo clippy -- -A clippy::bool-assert-comparisonThe [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 boolean comparisons in assert-like macros.
Why is this bad?
It is shorter to use the equivalent.
Example
assert_eq!("a".is_empty(), false);
assert_ne!("a".is_empty(), true);
Use instead:
assert!(!"a".is_empty());
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
- assertions_on_constantsChecks for assert!(true) and assert!(false) calls
- assign_op_patternmanual implementation of an assign operation
- blocks_in_conditionsChecks for if and match conditions that use blocks containing an expression, statements or conditions that use closures with blocks
- borrow_interior_mutable_constborrow of a named constant with interior mutability
- box_default`Box::new(_)` of default value
- builtin_type_shadowthis generic shadows the built-in type `u32`
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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