Clippy lints / Pedantic
Clippy lint · Pedantic · checked with Clippy 0.1.99
clippy::decimal_bitwise_operands: using decimal literal for bitwise operation
What it meansChecks for decimal literals used as bit masks in bitwise operations. It is in the pedantic group and off by default.
What you see
warning: using decimal literal for bitwise operation --> main.rs:3:9 | 3 | let a = 14 & 6; // Bit pattern is not immediately clear | ^^ | = help: use binary (0b1110), hex (0x000e), or octal (0o16) notation for better readability = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#decimal_bitwise_operands = note: `-W clippy::decimal-bitwise-operands` 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?
Using decimal literals for bit masks can make the code less readable and obscure the intended bit pattern. Binary, hexadecimal, or octal literals make the bit pattern more explicit and easier to understand at a glance.
Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.
How to fix it
Clippy does not fix this one automatically. Change the code by hand:
Flagged
let a = 14 & 6; // Bit pattern is not immediately clear
Write this instead
let a = 0b1110 & 0b0110;
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]
decimal_bitwise_operands = "warn"In code
#![warn(clippy::decimal_bitwise_operands)]One run
cargo clippy -- -W clippy::decimal-bitwise-operandsThe [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 decimal literals used as bit masks in bitwise operations.
Why is this bad?
Using decimal literals for bit masks can make the code less readable and obscure the intended bit pattern. Binary, hexadecimal, or octal literals make the bit pattern more explicit and easier to understand at a glance.
Example
let a = 14 & 6; // Bit pattern is not immediately clear
Use instead:
let a = 0b1110 & 0b0110;
From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.
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All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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