Clippy lints / Style
Clippy lint · Style · checked with Clippy 0.1.99
clippy::legacy_numeric_constants: usage of a legacy numeric constant
What it meansChecks for usage of <integer>::max_value(), std::<integer>::MAX, std::<float>::EPSILON, etc. It is in the style group and warns by default.
What you see
warning: usage of a legacy numeric constant --> main.rs:3:11 | 3 | let eps = std::f32::EPSILON; | ^^^^^^^^^^^^^^^^^ | = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#legacy_numeric_constants = note: `#[warn(clippy::legacy_numeric_constants)]` on by default help: use the associated constant instead | 3 - let eps = std::f32::EPSILON; 3 + let eps = f32::EPSILON; |
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?
All of these have been superseded by the associated constants on their respective types, such as i128::MAX. These legacy items may be deprecated in a future version of rust.
Code that works but is not idiomatic Rust. Warns by default.
How to fix it
Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:
Flagged
let eps = std::f32::EPSILON;
Write this instead
let eps = f32::EPSILON;
Turn it off, or on
Allow it where it does not fit your code, as narrowly as you can:
On one item
#[allow(clippy::legacy_numeric_constants)]
fn my_function() { /* ... */ }Whole crate (Cargo.toml)
[lints.clippy]
legacy_numeric_constants = "allow"One run
cargo clippy -- -A clippy::legacy-numeric-constantsThe [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.
Settings in clippy.toml
msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml
Clippy's own documentation
What it does
Checks for usage of <integer>::max_value(), std::<integer>::MAX,
std::<float>::EPSILON, etc.
Why is this bad?
All of these have been superseded by the associated constants on their respective types,
such as i128::MAX. These legacy items may be deprecated in a future version of rust.
Example
let eps = std::f32::EPSILON;
Use instead:
let eps = f32::EPSILON;
Configuration
-
msrv: The minimum rust version that the project supports. Defaults to therust-versionfield inCargo.toml(default:
current version)
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
- iter_nth_zeroChecks for the use of iter.nth(0)
- iter_skip_nextcalled `skip(..).next()` on an iterator
- just_underscores_and_digitsconsider choosing a more descriptive name
- len_without_is_emptyChecks for items that implement .len() but not .is_empty()
- let_and_returnreturning the result of a `let` binding from a block
All 847 Clippy lints · Rust compiler errors · Cargo.toml checker
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